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Guide for Construction of

Concrete Pavements Reported by ACI Committee 325

American Concrete Institute Always advancing

Licensed to: Florida Suncoast Chapter


First Printing August 2015

ISBN: 978-1-942727-31-6

Guide for Construction of Concrete Pavements

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ACI 325.9R-15

Guide for Construction of Concrete Pavements Reported by ACI Committee 325

David W. Pittman, Chair

David J. Akers

Richard 0. Albright

William L. Arent

Jamshid M. Armaghani

Bob J. Banka

Donald L. Brogna

Neeraj J. Buch

Archie F. Carter

Tim Cost

Juan Pablo Covarrubias

Mohamed Nasser Darwish

Norbert J. Delatte

W. Charles Greer

Jerry A. Holland

Mark K. Kaler

Gary L. Mitchell

Paul E. Mueller

Jon I. Mullarky

Kamran M. Nemati

Kelly Nix

Nigel K. Parkes

Steven A. Ragan

David Newton Richardson

John W. Roberts

The primary focus of this guide is pavement construction. Modern

slipform paving techniques and time-proven formed construction

procedures are highlighted. Quality control, quality assurance, and

construction inspection, as well as the environmental, economic,

and societal benefits of concrete pavement, are also presented.

This guide briefly reviews all aspects of concrete pavement

construction for highways and, to some extent, local roads, streets,

and airfields. Intended for field and office personnel, this guide

provides a background on design issues that relate to construction

and reviews material selection.

Note that the materials, processes, quality control measures, and

inspections described in this guide should be tested, monitored, or

performed as applicable only by individuals holding the appro

priate ACI certifications or equivalent.

Keywords: concrete pavement; concrete pavement construction; concrete

paving; fixed-form paving; paving materials; slipforrn paving; sustainability.

ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

Jack A. Scott

Sanjaya P. Senadheera

Kieran G. Sharp

Terry W. Shennan

Alex Hak-Chul Shin

W. James Wilde

Gergis W. William

James M. Willson

Dan G. Zollinger

Kurt D. Smith

Tim James Smith

Anthony M. Sorcic

Shiraz D. Tayabji

Samuel S. Tyson

Suneel N. Vanikar

Consulting Members Michael I. Darter

Starr D. Kohn*

John L. Rice

Raymond S. Rollings

Don J. Wade *Deceased

CONTENTS

CHAPTER 1 -INTRODUCTION AND SCOPE, p. 2 1 . 1-Introduction, p. 2

1 .2-Scope, p. 2

CHAPTER 2-ACRONYMS AND DEFINITIONS, p. 2 2 . 1-Acronyms, p. 2

2.2-Definitions, p. 3

CHAPTER 3-DESIGN ISSUES RELATING TO CONSTRUCTION, p. 3

3 . 1-Introduction, p. 3

3 .2-Design principles, p. 3 3 .3-Current design procedures, p. 4

3 .4-Critical design inputs for construction, p. 4 3 .5-Pavement design considerations, p. 9

3 .6-City streets, p. 1 0 3 .7-Drainage issues, p . 1 2

CHAPTER 4-MATERIAL SELECTION, p. 1 2

4. 1-Introduction, p . 1 2 4.2-Foundation materials, p . 1 2 4.3-Pavement concrete materials, p . 1 3

4.4-Reinforcement, dowels, and tie bars, p . 26 4.5-Joint sealants and fillers, p. 27

4.6-Curing materials, p. 27

ACI 325.9R-15 supersedesACI325.9R-91 and was adopted and published August 2015.

Copyright© 2015, American Concrete Institute.

All rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic or

mechanical device, printed, written, or oral, or recording for sound or visual reproduc

tion or for use in any knowledge or retrieval system or device, unless permission in

writing is obtained from the copyright proprietors.

CaCiJ Licensed to: Florida Suncoast Chapter

2 GUIDE FOR CONSTRUCTION OF CONCRETE PAVEMENTS (ACI 325.9R-15)

CHAPTER 5-CONSTRUCTION, p. 27 5. 1-Foundation preparation, p. 27 5 .2-Production, placing, consolidation, and finishing

concrete pavement, p. 28 5 .3-Curing and enhancing characteristics of concrete, p. 3 1

5 .4-Installation of joints and reinforcement, p . 32

5 .5-Dowels and tie bars, p. 35 5 .6-Placing embedded reinforcement, p. 36 5 .7-Texturing, p. 37

5 .8-Tolerances, p. 43 5 .9-Extreme weather conditions, p. 45

5 . 1 0-0pening to traffic, p . 45 5 . 1 1-Quality control/quality assurance, p. 46

5 . 12-Construction inspection, p. 50

CHAPTER 6-SUSTAINABILITY, p. 52 6. 1-Introduction, p. 52 6.2-Sustainable concrete pavements, p. 52

6.3-Societal benefits of concrete pavement, p. 53

6.4-Environmental benefits of concrete pavement, p. 53 6.5-Economic benefits of concrete pavement, p. 55

6.6-Conclusion, p. 55

CHAPTER 7-REFERENCES, p . 55 Authored documents, p. 58

CHAPTER 1-INTRODUCTION AND SCOPE

1.1 -1 ntroduction In the United States, concrete pavements have been built

for over a century. The first street constructed with concrete

was built in Bellefontaine, OH, in 1 89 1 ; a portion of which, built in 1 893, still remains in service. Concrete pave

ments make up an integral part of the national primary and secondary highway system, farm-to-market road system,

city streets, parking lots, and airport runways. Historically,

concrete pavements have exhibited a higher initial cost than asphalt pavements, but recent construction and market

forces have narrowed that gap. Moreover, the longer service

life and lower maintenance costs associated with concrete

make it a very attractive and sustainable paving material.

1.2-Scope This guide briefly discusses the construction of hydraulic

cement concrete pavements for highways, streets, local

roads, and airfields. Design issues are presented in the

context of their impact on construction. Today, the slipform method of paving is preferred for roadway construction.

This modern construction method is capable of producing

a sustainable, high-quality, smooth pavement that can be placed quickly and economically. This guide will focus on

pavement constructed using slipform methods; however, where appropriate, formed pavement construction practices

are also discussed. This guide is intended to serve as a reference for field

project management, inspectors, and construction personnel

by providing background information, illustrations of best practice, and information helpful in solving day-to-day

jobsite problems. Designers and specification writers will

also find the guide helpful in preparing contract documents and selecting construction methods that assure quality

construction under normal jobsite conditions using established and proven practices. Regardless of the type of equip

ment used, quality construction depends, in large measure,

on the skill of crews involved in the construction process and quality of materials used.

CHAPTER 2-ACRONYMS AND DEFINITIONS

2.1 -Acronyms AAR: alkali-aggregate reactivity ABS: anti-lock braking system

ACR: alkali-carbonate reactivity ADTT: average daily truck traffic

ASR: alkali-silica reaction ATB: asphalt-treated base

BPN: British Pendulum Number BPI: British Pendulum Tester CBR: California bearing ratio

COTE: coefficient of thermal expansion

CPX: close proximity

CRCP: Continuously reinforced concrete pavement

CT meter: circular texture meter CTB: cement-treated base

CTE: coefficient of thermal expansion

DF tester: dynamic friction tester EAC: exposed aggregate concrete

EICM: Enhanced Integrated Climatic Model

EOT: early-opening-to-traffic

FN: friction number FWD: falling weight deflectometer

GPR: ground-penetrating radar HPC: high-performance concrete

HRWR: high-range water reducers HRWRA: high-range water-reducing admixture

IFI: international friction index IRI: international roughness index JPCP: jointed plain concrete pavement

JRCP: jointed reinforced concrete pavement

LCA: life cycle assessment LCB: lean concrete base

LOI: loss on ignition LIE: load transfer efficiency

LWAS : lightweight aggregate sand

M-E: mechanistic-empirical

MIT: magnetic imaging tomography MOR: modulus of rupture

MPD: mean profile depth MID: mean texture depth

NCHRP: National Cooperative Highway Research Program

NDT: nondestructive testing

NGCS: next-generation concrete surface

OBSI: On-board sound intensity PCC: portland cement concrete PI: plasticity index

QA: quality assurance

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GUIDE FOR CONSTRUCTION OF CONCRETE PAVEMENTS (ACI 325.9R-15) 3

QC: quality control

R-value: resistance value SE: sand equivalent

SN: skid number SPL: sound pressure level

SSD: saturated surface-dry

VPD: vehicles per day VPM: vibrations per minute

2.2-Definitions ACI provides a comprehensive list of definitions though

an online resource, "ACI Concrete Terminology," http:// www.concrete.org/store/productdetail.aspx ?ItemiD=CT 1 3 .

Definitions provided herein complement that resource.

dowel-mechanical devices (such as bars or plates) placed across a joint to transfer vertical load while allowing

the joint to open and close. drainage-interception and removal of water from, on, or

under an area or roadway. equivalent single-axle loads (ESAL)-number of equiv

alent 80 kN ( 1 8 kip) single-axle loads used to combine

mixed traffic into a single design traffic parameter for thick

ness design according to the methodology described in the AASHTO design guide (AASHTO 1 993) .

falling weight deftectometer-device in which electronic sensors measure the deflection of the pavement as a result of

an impact load of known magnitude; results can be used to

estimate the elastic moduli of sub grade and pavement layers and the load transfer across joints and cracks.

internal curing-a method to supply water throughout

a freshly placed cementitious mixture using reservoirs, via

prewetted lightweight aggregates, that readily release water as needed for hydration or to replace moisture lost through

evaporation or self-desiccation. jointed plain concrete pavement-hydraulic cement

concrete pavement system characterized by short joint

spacing and no distributed reinforcing steel in the slab, with or without dowels.

jointed reinforced concrete pavements-hydraulic

cement concrete pavement system containing dowels, char

acterized by long joint spacing and distributed reinforcing

steel in the slab to control crack widths. load transfer device-mechanical means designed to

transfer wheel loads across a joint. pavement structure-combination of subbase, base,

rigid slab, and other layers designed to work together to

provide uniform, lasting support for imposed traffic loads and distribution of loads to subgrade.

pavement surface friction-the retarding force devel

oped at the tire-pavement interface that resists longitudinal

sliding when braking forces are applied to the vehicle tires (Dahir and Gramling 1 990; AASHTO 2008b ).

shoulder-portion of the roadway contiguous and parallel

with the traveled way provided to accommodate stopped or

errant vehicles for maintenance or emergency use, or to give lateral support to the subbase and some edge support to the

pavement, and to aid surface drainage and moisture control of the underlying material.

soil support value-index characterizing the relative

ability of a soil or aggregate mixture to support traffic loads imposed through flexible and rigid pavement structures.

stabilization-the modification of soil or aggregate layers by incorporating materials that will increase load-bearing

capacity, stiffness, and resistance to weathering or displace

ment, and decrease swell potential.

CHAPTER 3-DESIGN ISSUES RELATING TO

CONSTRUCTION

3.1-lntroduction The overall goal of pavement design is to create a struc

ture that is reliable, economical, constructible, and maintain

able throughout its design life while meeting or exceeding

the needs of the traveling public, taxpayers, and owning

agencies (FHWA 2012). In general, the pavement structure should be able to support the expected level of traffic and

resist weathering until the next scheduled rehabilitation or

reconstruction.

3.2-Design principles 3.2.1 Introduction-Design and construction of the

roadbed is key to the long-term performance of any pave

ment structure. A layer of materials that provides a foundation for the riding surface characterizes a roadbed. For

concrete pavements, the foundation is typically composed

of a base layer on top of the subgrade soil. Proper care and attention should be paid to design and construction of

the subgrade and base layers to ensure structural capacity,

stability, uniformity, durability, and smoothness of any

concrete pavement over its design life. Concrete pavement slabs constructed over the subgrade should have adequate

strength and durability to endure exposure to traffic loadings and environmental effects (ACPA 2007).

3.2.2 Slab characteristics-Pavement concrete typically

has a 28-day flexural strength ranging from 550 to 750 psi (3 .8 to 5.2 MPa) or greater, and an elastic modulus ranging

from 4 to 6 million psi (28,000 to 4 1 ,000 MPa), which helps to provide a high degree of rigidity. This rigidity enables

concrete pavements to distribute loads over large areas of

the supporting layers. As a result, the stresses on the layers beneath the pavement slab are low.

3.2.3 Influence of foundation strength on pavement thickness-The degree of support provided by the foundation

for a concrete pavement structure is typically quantified in

terms of the modulus of subgrade reaction, or the k-value. The magnitude of increase in the k-value from the inclusion

of base layers in the design of pavements depends on the

material type. Normal variations in estimated subgrade or composite k-values would not appreciably affect pavement

thickness for a typical range of k-values ( 1 00 to 500 psi/in. [27 to 136 MPa/m]). It is not economical to over-design the

base layers for the sole purpose of increasing the k-value, as

adequate structural designs can be achieved by other means (for example, increasing the slab thickness or concrete

strength) (ACPA 2007).

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3.2.4 Influence of foundation stiffness on stresses and strains in concrete pavement slabs-If a concrete pavement is placed either directly on the subgrade or on any number

of base layers, the properties of these foundation layers will directly influence the stresses and strains in the concrete

slabs and, in tum, will have an impact on the long-term

performance of the pavement structure. If a concrete slab is in complete contact with the foundation, a stiffer support

will result in reduced deflections and, thus, reduced stresses

under heavy loads. Stiffer support systems, however, will increase deflections and stresses under environmental effects

(thermal curling and moisture warping). If a concrete pavement is constructed on a very rigid foundation, the founda

tion might not conform to the shape of the slab and a signifi

cant increase in curling stresses can result. Higher curling stresses have a more damaging impact

when the concrete is relatively young and has not developed the strength required to resist cracking. If the stiffness

of the base becomes too great, the curling stresses in the slab will increase, and the potential for midpanel cracking

will also increase. The thicker the base layer is, the greater

the increase in the support stiffness. The pavement design engineer should recognize that base thickness and stiffness are important properties in the foundation design process

(ACPA 2007). 3.2.5 Drainage-Drainage is one of the most important

factors in pavement design. Water enters the pavement

structure either by surface infiltration through cracks, joints, pavement surfaces, and shoulders; or as groundwater from

a high water table, aquifers, and localized springs. Where

water is trapped within the pavement structure due to inad

equate drainage, it reduces the strength of the pavement and subgrade, and also generates high hydrodynamic pres

sures that might pump out fine material under the pavement, resulting in loss of support. Aggregates used for drainage

purposes should satisfy filter requirements. They should be fine enough to prevent the adjacent soil from migrating into

them, but coarse enough to carry water with no significant

resistance (Huang 2004). In many ways, the pavements built

in the United States today, particularly those on interstate

highways and routes, are less vulnerable to the detrimental

effects of excessive moisture than pavements built in the past because of features such as widened concrete slabs, doweled

joints, stabilized base layers, and higher-quality aggregates.

Still, at sites with wet climates and poorly draining soils,

the need for a subsurface drainage system should be consid

ered. This is particularly true for pavement designs likely vulnerable to moisture-related distress, such as undoweled

concrete pavements on untreated aggregate base layers.

3.3-Current design procedures 3.3.1 PCA design methodology-The Portland Cement

Association (PCA) thickness-design procedure for concrete

highways and streets (PCA 1 984) can be applied to jointed

plain concrete pavement (JPCP), jointed reinforced concrete pavement (JRCP), and continually reinforced concrete pave

ment (CRCP). The PCA concrete pavement design procedure evaluates a candidate pavement design with respect to two

potential failure modes: fatigue and erosion. The procedure was developed using the results of finite element analyses of stresses induced in concrete pavements by joint, edge,

and comer loading. The analyses onsiders the degree ofload transfer provided by dowels or aggregate interlock and the

degree of edge support provided by a concrete shoulder. The

PCA procedure, like the 1 993 AASHTO procedure, employs

the "composite" k concept in which the design k is a func

tion of the subgrade soil k, base thickness, and base type (granular or cement-treated) (Huang 2004; Hall 2000).

3.3.2 AASHTO design methodology-The AASHTO

design methodology is the most commonly used rigid pavement design method in the United States (AASHTO 1 993). It is based on the empirical equations obtained from the

AASHO Road Test, with modifications based on theory and experience. The empirical model for the performance of the

JPCP and JRCP sections in the main loops of the AASHO Road Test predicts the log of the number of axle load appli

cations (log W) as a function of the slab thickness, axle type

(single or tandem) and weight, and terminal serviceability (Highway Research Board (HRB) 1 962). This original

model applies only to the designs, traffic conditions, climate,

subgrade, and materials of the AASHO Road Test. It has been modified and extended to allow for the estimation of

allowable axle load applications to a given terminal serviceability level for conditions of concrete strength, subgrade

k-value, and concrete elastic modulus different than those of

the AASHO Road Test. The AASHTO design methodology has also been extended to accommodate the conversion of

mixed axle loads to equivalent single axle loads (ESALs) of

1 8 kip (80 kN) through the use of load equivalency factors

(Huang 2004; Hall 2000). 3.3.3 Mechanistic-empirical (M-E) design method

ology-The M-E design procedure uses mechanistic pavement responses such as stress, strain, and deflection; relates them to performance indicators such as cracking, faulting,

and roughness; and calibrates them against the field data.

The axle load spectra data, rather than ESALs, are used in

this design procedure; climatic effects are also considered. An incremental damage concept is used in the M-E design

procedure, where the damage is computed monthly and

accumulated. The design life is divided into monthly increments and specific materials properties, traffic, and climatic

data are used for each increment. The performance criteria considered are joint faulting and transverse cracking for

JPCP, punchouts for CRCP, and the international roughness

index (IRI) for both pavement types; JRCP is not included in the design methodology. Designs that meet the appro

priate performance criteria at a chosen level of reliability

are considered feasible from structural and functional standpoints and can be further considered for other evaluations

such as life cycle cost analysis and environmental impacts (NCHRP 2004; AASHTO 2008a).

3.4-Critical design inputs for construction 3.4.1 General-The key input parameters in any concrete

pavement design procedure related to construction are outlined (3.4. 1 . 1 through 3 .4 . 1 .3) .



Table 3.4.1 .1 -Subgrade soil types and approximate support values (ACI 330R)

Type of soil Support k, psi/in. (kPa/mm)

Fine-grained soils in which silt and Low 75 to 1 20 (20 to 32)

clay-size particles predominate

Sands and sand-gravel mixtures with Medium 1 30 to 1 70 (35 to 46)

moderate amounts of silt and clay

Sand and sand-gravel mixtures High 1 80 to 220 (49 to 60)

relatively free of plastic fines

3.4.1 .1 Subgrade-Although the k-value of the founda

tion (natural soil and embankment) can be measured by plate-bearing tests, it is usually estimated from correlations

with soil type, soil strength measures such as the California bearing ratio (CBR), or by back-calculation from deflection

testing on existing pavements (Table 3.4. 1 . 1 ). The k-value

is the primary subgrade design variable for concrete pavements (ACPA 2007) .

3.4.1 .2 Base and subbase-A base course provides a stable platform for construction of concrete slab, improves the

smoothness achieved in the paving of the slab, could serve

as a drainage layer, and protects the foundation from frost penetration. Some types of bases also significantly reduce

bending stresses and deflections in the slab and improve load

transfer at joints and cracks. The estimated elastic modulus of the base, its erodibility, its potential for friction and bond

with the concrete slab, and its drainability are factors considered in characterizing the support to the concrete slab and

the quality of subsurface drainage (ACPA 2007).

3.4.1 .3 Concrete material properties-For the purpose of

pavement thickness design, concrete is characterized by its flexural strength as well as its modulus of elasticity. Concrete

flexural strength is usually characterized by the 28-day

modulus of rupture (MOR) from third-point loading tests of beams, or it may be estimated from compressive strengths

(Eq. (3 .5 .3 .3)) . The corresponding elastic modulus E can also be measured, but is usually estimated from strength

data. In addition to its strength and stiffness, durability of

concrete mixture is important to the long-term performance of the pavement (Hall 2000).

3.4.2 Subgrade considerations 3.4.2.1 Load-bearing capaciry-Design methods were

devised based on tests that provided an index number related

to soil strength that was most commonly considered to represent the shear strength. Some of these test methods and their

associated index values are discussed in this section (ACPA 2007).

3.4.2.1.1 California-bearing ratio (CBR) test-The CBR

test measures the force required to penetrate a soil surface

by a circular piston with a 3 in.2 ( 1 9 cm2) piston area. The index (CBR) value is the percent of an established reference

value for 0. 1 and 0.2 in. (2 .5 and 5 .0 mm) penetration. The reference value of 1 00 was originally considered to repre

sent the resistance of a well-graded crushed stone. Methods of preparing specimens and conducting the test are given in

AASHTO T l 93 and ASTM D 1 883 .

3.4.2.1.2 Resistance value (R-value) test-The R-value test is a measure of the material stiffuess by way of resis

tance to plastic flow. This laboratory test was developed as

Califomia bearing ratio R Soil support value

2.5 to 3.5 10 to 22 2.3 to 3 . 1

4.5 to 7 .5 29 to 41 3 .5 to 4.9

8.5 to 12 45 to 52 5 .3 to 6 . 1

an improved CBR test. Samples are prepared to represent the worst-case scenario during testing and are confined

on all sides in the testing apparatus, resulting in a triaxial state of stress. The R-value is the ratio of the vertical load

applied to the resultant lateral pressures. Standard R-value

test methods are described in AASHTO T 190 and ASTM D2844/D2844M.

3.4.2.1.3 Resilient modulus of subgrade soil-The stiffness, as an estimate of the modulus of elasticity, E, is

measured by this test. The modulus of elasticity is the ratio

of stress applied to the strain produced for a slowly applied load. The resilient modulus is the stress divided by the strain

for a rapidly applied load. The standard resilient modulus test is given in AASHTO T307.

3.4.2.1.4 Modulus of subgrade reaction (k-value)-This

bearing test, conducted in the field, provides an index to rate the support provided by a soil layer directly beneath the

concrete slab. Most concrete pavement design is based on

the k-value, as used in the Westergaard ( 1 933) equations. The k-value is defined as the reaction of the subgrade per

unit area of deformation and is typically given in psi/in.

(kg/cm3). Details on conducting the plate-bearing field tests

are given in AASHTO T22 1 and T222 or in ASTM D 1 1 95/ D l l 95M (repetitive test) and D l l 96/D l l 96M (no repetitive test). The elastic k-value (ke), as determined from the repeti

tive plate-bearing test (ASTM D l l95/D l l 95M) is a higher value because it considers only the elastic deformation in the

k-value computation.

Because of slow productivity in conducting plate-bearing

tests and their relatively high costs and labor intensiveness, very few agencies routinely conduct them. Instead, most

agencies obtain k-values through correlations with other

properties or through the back calculation of deflection data using the falling weight deflectometer (FWD). The use of

the FWD enables collection of a large number of data points

that can help evaluate the subgrade variability over a project.

3.4.2.1.5 Cone penetrometer-A cone penetrometer is a device used to measure the strength of in-place soil. The test results can be used to estimate the soil shear strength, CBR,

and k-value. Because these tests are rapid and essentially

nondestructive, they are ideally suited for on-site construction, and testing over large areas can evaluate uniformity. The

penetrometer is driven into the ground at either a constant rate or by dropping a specific hammer over a given distance. The measured values (load needed to drive the penetrometer

or blow counts per unit of depth) are then correlated to CBR, shear strength, or soil modulus value. Profiles of the changes

in soil strengths across the project area can be obtained by plotting the load or blow counts versus depth. This can be



used to check the depth of stabilization and to find soft or stiff layers.

3.4.2.2 Volume stability 3.4.2.2.1 Introduction-It is essential to quantify the

expansion and shrinkage of soils as the overall volume

change, or differential volume changes from point-to-point,

can result in serious damage to a pavement structure, particularly in areas where soils remain relatively dry until wetted

by an infrequent rainy period. Tests used to quantify poten

tial volume stability issues are discussed in the following sections (ACPA 2007). ASTM D4829 gives an expansive

index of soils and, based on the test results, evaluates soils from very low to very high expansion potential.

3.4.2.2.2 California-bearing ratio and R-value testsExpansion tests are usually conducted in conjunction with

the CBR and R-value tests. In both instances, the test specimen is compacted to a predetermined density at proper moisture content in a mold and a supply of water is made

available. Surcharges, equal to the weight of the cover mate

rial that will overlay the soil in the ultimate pavement structure, are applied to the top of the specimen. The expansion

that occurs during a given soaking period is measured as the

change in length of the specimen. The pressure exerted by the expanding soil can be measured by means of a calibrated restraining gauge.

3.4.2.2.3 Sand equivalent (SE) tests-The SE test is a

rapid field-testing method to detect the presence of unde

sirable clay-like materials in soils and aggregate materials. This method tends to magnify the volume of clay present

in a sample in proportion to its detrimental effects. Details on this test method are given in AASHTO T l 76 and ASTM

D24 1 9. Natural sand and crushed stone have SE values of approximately 80, whereas very expansive clays have values

ranging from 0 to 5 . 3.4.3 Subgrade strength and working platform-Due

to the ability of a concrete pavement to spread loads over large areas, the highest subgrade stresses will normally occur during the construction phase of a concrete pave

ment or the base layer. Once in place, the base layer and the concrete pavement protect the subgrade from high-stress

contact by loads. Thus, the required strength of a subgrade

is typically dictated by providing a stable working platform to construct successive layers. Research performed by the

Wisconsin Department of Transportation has concluded

that a minimum CBR value of 6 in the top 24 in. (6 1 0 mm)

of subgrade provides an adequate working platform while

limiting subgrade rutting under construction traffic to 0.5 in.

( 1 3 mm) or less (Crovetti and Schabelski 2002). Compacting the subgrade to a density that provides an

adequate working platform for construction equipment

will provide adequate subgrade strength for the in-service

concrete pavement. The AASHTO T099 field test is recommended to characterize a subgrade for acceptance. State

departments of transportation recommend values ranging

from 84 to 100 percent, but a value of 95 percent is most often specified and thus is recommended for most applica

tions (ACPA 2005).

3.4.4 Obtaining uniform support-For a subgrade to

provide a reasonably uniform support, the four major causes of nonuniformity should be addressed (ACPA 2007):

1) Expansive soils 2) Frost-susceptible soils

3) Wet soils 4) Pumping 3.4.4.1 Expansive soils-Expansive soils change volume

with changes in moisture content. Expansive soils that can

swell enough to cause problems are clays with a plasticity

index (PI) greater than approximately 25 (ASTM D43 1 8).

Experience has indicated that volume changes of clays with a medium to low degree of expansion (PI less than 25) are

not a significant concern for concrete pavements, especially if selective construction grading operations are performed,

such as cross-hauling and blending of soil types to minimize

or eliminate abrupt changes in soil character along the alignment. Experience has also indicated, however, that uncon

trolled shrinkage and swelling of expansive soils can lead to increased stresses in concrete pavements due to nonuniform

support, which accelerates pavement deterioration and nega

tively impacts pavement smoothness.

Construction-related factors that can further aggravate performance issues related to expansive soils include:

a) Compacting expansive soils where they are too dry, resulting in the possibility that the soil will absorb moisture

and expand after the subgrade is prepared.

b) Placing a pavement on a sub grade with widely varying moisture contents, allowing differential volume change of

the soil to take place along the road alignment.

c) Creating nonuniform support by ignoring abrupt

changes between soil types with different capacities for volume change along the road alignment. The volume

change that could occur with potentially expansive soils depends on several factors, including:

1 . The moisture variation that will take place in the

subgrade throughout the year or from year to year, dictated by the climate. Generally, the pavement will

protect the grade to a certain degree and reduce moisture variation in an underlying subgrade, as long as the

soil is not capable of drawing water from below through

capillary suction. 2. The effect of weight of the soil, base layer(s), and the

pavement above the expansive soil. Tests indicate that surcharge loads can reduce soil swell (Holtz and Gibbs

1 956).

d) Moisture and density conditions of the expansive soil during paving.

e) Knowledge of the interrelationships between these

factors leads to the selection of economical and effective control methods.

3.4.4.2 Frost action-Frost action is a phenomenon that occurs in the winter and early spring in northern climates.

All surface soils undergo a certain amount of frost action,

the magnitude of which depends on the prevailing local climate and precipitation level. Frost action can be divided

into two phases: 1) freezing of soil water; and 2) thawing of soil water.



For pavements, frost action is a major concern where either

the freezing phase is accompanied by noticeable heaving of

the road surface or the thawing phase is accompanied by

noticeable softening of the roadbed. Frost heave is defined as the surface distortion caused by

volume expansion within the soil or pavement structure,

where water freezes and ice lenses form within the freezing zone. Ice lenses are formed when moisture, diffused within

soil highly susceptible to capillary action, accumulates in a

localized zone; ice initially accumulates within small collocated pores, wedging the soil apart, causing frost heave.

Frost-susceptible soils are subgrade or subbase materials in

which segregated ice will form, causing frost heave, under the required conditions of moisture supply and temperature.

Note that design considerations for controlling frost heave are not necessarily identical to those for controlling subgrade

softening. For example, a soil with high frost-heave potential will not necessarily exhibit the maximum amount of subgrade softening. Field investigations have shown that

frost damage due to frost heave, in the form of differential

frost heave, has affected performance more than subgrade

softening.

Subgrade softening due to frost action is not a major concern for subgrade design, as uniform support is more

important than strength. Subgrade softening, however, can aggravate pumping in pavements that are constructed

without adequately addressing pumping potential. Frost

design for concrete pavements is concerned with providing uniform subgrade conditions. This is achieved by elimi

nating the moisture conditions that lead to objectionable

differential frost heave, which occur where subgrade soils

vary abruptly from non-frost-susceptible to highly frostsusceptible silts, at cut-fill transitions or at silt pockets, and

where groundwater is close to the surface or water-bearing strata are encountered.

3.4.4.3 Wet soils-Wet soils can be encountered during

construction for reasons ranging from a naturally high water table, seasonal rainfall, or changes in drainage conditions

due to construction. Regardless of the cause, in-place wet soils should be addressed before the base layer(s) or the

concrete pavement is constructed over the subgrade.

The simplest ways to mitigate the problems due to wet soils are to construct drains before construction or to let the

subgrade dry out prior to constructing a base or concrete pavement on the subgrade. Construction and scheduling

constraints, however, may make these solutions no longer

feasible. The other procedures fall into three categories : 1 . Enhancement-A method of removing excess mois

ture in wet soils by providing drainage via trenches or toe

drains at the lowest point(s), compacting the subgrade using heavy equipment that forces the excess moisture out of the subgrade, or adjusting the moisture content through chemical modification.

2. Reinforcement/separation-A method of removing

excess water by using geosynthetics. Geosynthetics are thin, pliable sheets of textile material of varying permeability.

The effectiveness of geosynthetics depends on the type; the

intended function, such as filtration, separation, or reinforce

ment; in-place soil conditions; and installation techniques . 3 . Substitution-A method of removing excess water by

removing unsuitable, unstable, or excessively wet soils and replacing it with borrow material, or by covering the wet

soil with suitable material to develop necessary uniformity and stability.

3.4.4.4 Pumping resistance-Pumping is the forceful

displacement of a mixture of soil and water through slab

joints, cracks, and pavement edges. Continued, uncontrolled pumping will eventually displace enough soil to result in the

loss of uniform support, leaving the slab corners and ends unsupported. This nonuniform support condition results in

premature cracking at slab corners and pavement roughness

in the form of faulted transverse joints. In the worst case, loads deflect concrete slabs enough to pump water and fine

soil particles through joints and onto the surface of the pavement, where visible stains become evident.

For pumping to occur, these conditions should be present:

a) Significant slab deflections due to heavy loads, poor load transfer at joints, or both

b) Presence of water between the pavement and the

subgrade or base layer c) Presence of a fine-grained subgrade or erodible base

material The subgrade materials most prone to pumping are high

p lasticity silts and clays. Unstabilized (granular) base mate

rials prone to pumping are generally those with 1 5 percent or more fines passing through the No. 200 (75 11m) sieve.

The two most effective factors for mitigating pumping are using doweled transverse pavement joints and properly graded base courses. Using nonerodible or stabilized bases can mitigate pumping. Unstabilized bases meeting

AASHTO M 1 55 requirements will effectively prevent

pumping in pavements carrying even the highest traffic

volumes, assuming that other design features are appropri

ately selected. Using a properly graded base (stabilized or unstabilized) eliminates the fines that will go into suspen

sion, whereas using dowels eliminates rapid differential deflection caused by frequent heavy loads.

3.4.5 Base/subbase considerations-The base for a

concrete pavement is the untreated or treated granular layer constructed on the prepared subgrade and upon which the

concrete slab is placed. A base layer provides benefits to both the construction and performance of concrete pavements.

From the construction perspective, the base layer provides a

stable working platform for construction equipment, which enables the contractor to provide a smoother pavement and

achieve a more consistent pavement thickness than might be

possible if constructing directly over the sub grade. From the performance perspective, the base layer provides uniform

support to the pavement and prevents pumping of fines. Secondary benefits are their help in controlling volume

changes for expansive or frost-susceptible soils and reducing

excessive differential frost heave. A base layer can also be used as a drainage layer; however, a careful balance between

drainability and stability should be achieved. Base thickness for road and highway pavements is usually in the range of



4 to 6 in. ( 1 02 to 150 mm). In addition, granular subbase or

select material up to 24 in. (600 mm) is sometimes used over weak sub grades or to provide frost protection.

The tendency in recent years has been to use the terms "subbase" and "base" interchangeably in reference to a

single layer between the slab and sub grade. If another layer,

such as lower-quality gravel or a filter layer separates the base from the subgrade, this second layer is referred to as

the subbase.

3.4.5.1 Types of bases-Various types of bases have been successfully used under concrete pavements. These include

unstabilized (granular) bases, and stabilized (treated) bases that include cement-stabilized bases (cement-treated or lean

concrete), asphalt-treated bases, and fly ash or lime-treated

bases (ACPA 2007). Regardless of the specific base considerations, the best

results are obtained by: a) Selecting base materials that will not contribute to

excessive pavement deflections under service loads and will

remain stable over the design life. b) Treating the base to ensure that it does not cause exces

sive friction or induce bonding to pavement slabs. c) Specifying gradation or material controls that will

ensure consistent quality. l . Unstabilized (granular) bases-Unstabilized (gran

ular) bases are the most common type of base for road

ways and highways. If designed and constructed prop

erly, unstabilized bases make an excellent support layer for concrete pavements for all types of roadways and

highways. Their primary advantage is their relatively low cost compared to stabilized bases.

As a minimum, an unstabilized base should meet the requirements ofAASHTO M l 47 (AASHTO M l 55 may

be used if pumping is a major concern). These factors define materials that are composed of a good unstabi

lized base:

i. Maximum particle size of no more than one-third of the base thickness

ii. Less than 1 5 percent passing the No. 200 (75 J.tm) sieve

iii. Plasticity index of 6 or less

iv. Liquid limit of25 or less v. Los Angeles abrasion resistance (AASHTO T096

or ASTM C l 3 l /C l 3 1M) of 50 percent or less vi. Target permeability of 1 50 to 350 ft/day ( 45 to

1 07 m/day)

The principal criterion for creating a good unstabilized base is to limit the amount of fines passing the No. 200

(75 J.tm) sieve. Too many fines will result in the base

holding water more readily, which increases the potential for erosion and pumping. 2. Stabilized bases-Stabilized bases generally refer

to base materials that are bound by either portland or

blended cement or asphalt binders. Stabilized bases fall

into three categories: cement-treated, lean concrete, and asphalt-treated.

Compared with unstabilized bases, stabilized bases provide a higher degree of support to the pavement

slabs (that is, a higher k-value). They can significantly

reduce slab stresses and improve load transfer at pavement joints, especially for pavements with undoweled

joints and plain concrete slabs (Colley and Humphrey 1 967; Henrichs et al. 1 989; Ioannides and Korovesis

1 990). Their relatively high stiffness and potential

bonding can, however, increase curling stresses in the slab, which can reduce the service life if not accounted

for in the design process, usually by using shorter joint

spacing. 3. Cement stabilized bases-Cement stabilized bases

fall into two categories: 1) cement-treated base (CTB); and 2) lean concrete base (LCB). Fly ash or slag cement can be included in either a CTB or LCB.

Cement-treated bases have a much drier consistency, contain less cement, and are best controlled using

compaction or density requirements rather than strength requirements. Because a CTB layer is best controlled

using compaction or density requirements, common

requirements are a level of compaction between 96 and 1 00 percent of the maximum density (determined

by AASHTO T l 34 or ASTM D558). Although there is

typically no strength requirement on CTB, targeting a 7-day compressive strength from 300 to 800 psi (2. 1 to 5 .5 MPa) assures long-term durability (Halsted et al.

2007). Cement-treated bases typically require approxi

mately 2 to 5 percent cement by weight. The granular

material typically has no more than approximately 35

percent passing the No. 200 (75 J.tm) sieve-a PI of 10

or less. A maximum particle size of 0.75 to 1 in. ( 1 9 to 25 mm) is preferable to permit accurate grading of the

base material. Lean concrete bases contain more cement and water

than CTBs, but they contain less cement than conventional concrete. Lean concrete has the same appearance

and consistency as conventional concrete, and can be

placed using conventional paving equipment. For a lean concrete base, typical specifications require a 7 -day

compressive strength from 750 to 1 200 psi (5 .2 to 8.3 MPa) and an air content of 4.0 to 1 2.0 percent. The air

content of an LCB may be used to prevent exceeding the maximum strength as well as for freezing-and-thawing

resistance. 4. Asphalt-treated bases (ATB)-The design criteria

for asphalt-treated soils and aggregate combinations

focus on compaction, stability, and gradation param

eters. An asphalt coating on granular material provides a membrane, which prevents the infiltration of water

and thereby reduces the tendency of the material to

lose strength in the presence of water. Because asphalttreated bases rely on adhesion to bind aggregate parti

cles together, stripping is a primary concern. Stripping is defined as the separation of the asphalt binder from

the aggregate surface resulting in destabilization of the base.

The following design/material considerations are advis

able for using asphalt-treated bases:



i. Asphalt-treated base may use a lower grade of

asphalt binder than is required for asphalt surfaces ii. A binder content of 4 to 4.5 percent is considered

typical for ATB

iii. Durability of aggregates is an important require

ment for ATB. The maximum aggregate size is typically 3/4 in. ( 1 9 mm)

iv. Aggregates meeting moderate soundness requirements and a maximum freezing-and-thawing

weight loss, in water, of 10 percent and a loss in wateralcohol solution of up to 45 percent according to

AASHTO T 1 03 may be considered adequate 3.4.5.2 When to use a base-Base layers are appropriate

if a stable and uniform construction platform will benefit

construction; if the combination of sub grade soil type, water

availability, and high-speed, heavy traffic are at a level conducive to cause pumping and associated distresses; or both. Therefore, a base layer is required for heavily traveled

pavements, particularly those with a large amount of truck

traffic. Pavements for slow-moving trucks or light-traffic pave

ments, such as residential streets, secondary roads, and

parking lots, are not necessarily prone to the development of pumping. Factors to consider include:

a) Traffic-Pavement designers often use the rule-of

thumb that a pavement expected to carry 50 trucks or fewer per day does not require a base layer to prevent pumping.

The American Concrete Pavement Association recommends that pavements designed to carry less than 1 million 1 8 kip

(80 kN) equivalent single axial loads (ESALs) over their

service life do not require base layers to prevent pumping

(ACPA 2007). b) Natural drainage-A subgrade soil that is naturally

free-draining typically will not pump as the water percolates through the subgrade and does not remain under the pavement where it can transport fines in suspension. Pavements

can be built directly on natural subgrade soils with this character as long as the soil is satisfactory in other critical regards, such as frost action or expansion (ACPA 2007).

c) Qualified subgrade soils-Subgrade soils with less

than 45 percent passing a No. 200 (75 �m) sieve and with a

PI of 6 or less are adequate for moderate volumes of heavy truck traffic without the use of a base layer. In these cases, it is advisable to use doweled joints to prevent differential

deflections at slab joints (ACPA 2007).

Note that increasing the thickness of concrete pavement

slabs is not an acceptable measure to prevent pumping.

Without proper preventive measures, pumping can occur even in the thickest of pavements (ACPA 2007).

3.5-Pavement design considerations 3.5.1 Sub grade support-The ability to provide uniform

support conditions is the most important property required from a subgrade layer. The major causes of nonuniform

support conditions, which include expansive soils, differential frost heave, pumping, and wet soils, have been discussed

in detail in previous sections.

3.5.2 Base friction-Concrete slabs continually move

throughout their life due to shrinkage, thermal effects, and moisture gradients. If the slab moves, any bonding between

the slab and base develops resisting forces. These forces can lead to the development of restraint cracking. High friction

between the concrete pavement and the underlying base

layer is, therefore, not desirable. Also, as stiffness of the base increases, friction between the base and pavement slab

increases. This in turn induces higher tensile stresses within

the slab, which increases the probability of cracking. Stiffer bases by themselves do not lead to less contact with the slab

unless curling or warping is occurring. The potential for bonding between concrete and the base layer can be mini

mized with the application of a bond breaker (ACPA 2007).

3.5.3 Concrete materials 3.5.3.1 Durability-Concrete pavements should be able

to resist environmental effects such as temperature changes, freezing-and-thawing cycling, and the action of deicing

chemicals in northern climates. Under these conditions, it

is essential that the mixture have a low water-cementitious materials ratio (w/cm), adequate cement, sufficient amount

of entrained air, and an adequate curing period. The amount

of air entrainment needed for concrete resistant to freezing and thawing varies with maximum aggregate size and expo

sure conditions. The recommended amount of entrained air is given in ACI 2 1 1 . 1 .

In addition to making the hardened concrete pavement

resistant to freezing and thawing, recommended amounts of entrained air improve the properties of the concrete while it

is still in the plastic state by reducing segregation, increasing

workability without adding additional water, and reducing

bleeding. Aggregate selected for paving should be resistant to

freezing-and-thawing deterioration (D-cracking) and not prone to alkali-silica reaction (ASR). Aggregates that meet

the requirements of state highway departments for concrete

paving should be acceptable in most cases. Type F fly ash, as well as other supplementary cementitious materials such as

slag cement, can be used as effective mineral admixtures to help prevent deterioration due to ASR. High concentration

of soil sulfates can also cause premature failure of concrete

pavements. For high-sulfate soils that may be in contact with concrete pavement, recommendations of ACI 20 1 .2R should be followed (ACI 325 . 1 2R).

3.5.3.2 Coefficient of thermal expansion (COTE)-The

COTE is a measure of expansion of material or contrac

tion with temperature. The COTE of concrete is approximately 3 .3 to 5 .5 �EI°F (8 to 1 2 �EfOC). Because aggregate

comprises approximately 70 percent of the concrete, aggre

gate type has the greatest influence on the COTE of concrete. Although the COTE is not featured in earlier design

methods (for example, PCA [ 1 984] ; AASHTO [ 1 993]), it is a major design input in the most recent M-E procedure

available from AASHTO (2008b ). The importance of the use

of COTE in design is discussed in the following (NCHRP 2004) :

a) The magnitude of curling stresses caused by temperature differences along the cross section of the pavement



slab is very sensitive to the COTE of concrete. Under

certain conditions, curling stresses comprise approximately 50 percent or more of the critical stresses experienced by

a loaded pavement slab and, thus, affect slab cracking and CRCP punchouts, which is the area enclosed by two closely

spaced transverse cracks, a short longitudinal crack, and the edge of the pavement or a longitudinal joint. The COTE,

therefore, plays an important role in optimizing JPCP joint

design, CRCP reinforcement, and in accurately computing

pavement stresses and joint and crack load transfer efficiency (LTE).

b) It is an important factor in designing joint sealant reservoirs and in selecting joint sealant materials.

c) The COTE is also critical in affecting the cracking

width and spacing in CRCP over the entire design life; the crack width directly affects the crack LTE, which is the key

factor in punchout development. 3.5.3.3 Strength-Whereas loads applied to concrete pave

ments generate both compressive and flexural stresses in the

slabs, it is the flexural stresses that are more critical, as the service loads can induce flexural stresses that may exceed

the flexural strength of the slab. Because the strength of

concrete is much lower in tension than in compression, the MOR is often used in concrete pavement thickness design. The MOR test is performed according to ASTM C78/C78M

(third-point loading).

Concrete strength is a function of the amount and type

of cementitious material, the w!cm, and the air content of hardened concrete. The aggregates used should be clean to

ensure good aggregate-to-paste bond and should conform

to the quality requirements of ASTM C33/C33M, ASTM

C330/C330M, or the quality requirements established by the state departments of transportation for concrete pavement.

Regardless of when the pavement is opened to traffic, the strength should be checked to verify that the design strength

has been achieved.

Design methods are generally based on the results of the third-point loading test. Because the required thickness for

pavement design changes approximately 0.5 in. ( 1 3 mm) for a 70 psi (0.5 MPa) change in MOR, knowledge of flexural

strength is essential for economic design. MOR values for

28- or 90-day strengths are normally used in design. The use of 90-day strengths could be justified because of the limited

loadings that pavements receive before this early age and could be considered as the long-term design strength. If

the facility is not opened to traffic for a long period, later

strengths can be used, but the designer should be aware of earlier environment and construction loadings that may

and flexural (MOR) strengths is not readily established, an

approximate relationship between them is given to facilitate these purposes by the formula

MOR = a(fconc0·5fc'0·5 (ACI 209R) (3 .5 .3 .3)

where '¥cone is the concrete unit weight, and a1 varies from 0.6 to 1 .0 for units of psi (0.0 1 2 to and 0.20 for units of MPa). If desired, correlations between flexural and compressive

strength can be developed for specific mixtures. The strength of concrete should not be exceeded by environmentallyinduced stresses such as curling and warping, which may

be critical during the first three days after placement (ACI 325 . 1 2R).

3.5.3.4 Shrinkage-Drying shrinkage ofhardened concrete is an important factor that governs the performance of port

land cement concrete (PCC) pavements. Drying shrinkage affects the crack development in CRCP as well as long-term

performance ofload transfer across the cracks. For JPCP, the

primary effect of drying shrinkage is slab warping caused by differential shrinkage due to moisture gradient along the

thickness of the pavement slab, which leads to increased

cracking potential (NCHRP 2004; AASHTO 2008a). Drying shrinkage-related inputs in AASHTO (2008b)

include: a) Ultimate shrinkage-Shrinkage strain that PCC will

experience upon prolonged exposure to drying conditions

(40 percent relative humidity). Equations to estimate ultimate shrinkage are available AASHTO (2008b ). Ultimate

shrinkage at the termination of the AASHTO T l 60 test (at

64 weeks) can also be used. b) Time to develop 50 percent of ultimate shrinkage

Unless more reliable information is available, a value of 35

days (recommended by ACI 209R) i s recommended to be used for the time required to develop 50 percent of ultimate

shrinkage strains. If the AASHTO T l 60 test method is used

to estimate the shrinkage in the laboratory, the time required to develop 5 percent of the shrinkage refers the number of

days to reach half of the ultimate shrinkage after the specimen has been removed from a completely soaked condition.

c) Anticipated amount of reversible shrinkage-Refers

to the reversible shrinkage strain upon rewetting of PCC. A value of 50 percent is recommended unless more reliable

information is available. d) Mean monthly relative humidity data-Data provided

by the Enhanced Integrated Climatic Model (EICM) from

the weather station data.

cause pavement stresses that could exceed the early-age 3.6-City streets

strength of concrete. Under normal conditions, concrete 3.6.1 Introduction-Design and construction of pave-that has an MOR of 550 to 700 psi (3 .8 to 4.8 MPa) is most ments for city streets should entail both long service life and

economical. low maintenance. To ensure that these concrete pavements

While the design of concrete pavement is generally based will serve our needs into the future, it is important that all on the tensile strength of concrete, as represented by the design and construction aspects be incorporated.

flexural strength, it is more common to use compressive Concrete pavement performs well for city streets because strength testing in the field for quality-control acceptance of its durability while being continuously subjected to traffic

purposes and in the laboratory for mixture design purposes. and, in some cases, severe weather conditions. Because of Although a useful correlation between compressive (fc') its relatively high stiffness, concrete pavements spread the

cCiC"iJ American Concrete Institute- Copyrighted© Material- www.concrete.org Licensed to: Florida Suncoast Chapter


imposed loads over large areas of the subgrade and are

capable of resisting deformation caused by passing vehicles. Concrete pavements exhibit high wear resistance along with

providing a light-reflective surface that improves driver visibility.

3.6.2 Pavement types-The most common type of concrete for streets and other low-volume roads is JPCP. This type of pavement does not contain reinforcement and may or may

not have dowels at transverse joints. Cracking is controlled

by short joint spacing. Aggregate interlock at these joints

will help transfer the load across the joint and could help

mitigate faulting. Pavements that contain dowels at the transverse joints are used to provide additional load transfer

and prevent faulting.

Jointed reinforced concrete pavement can be used when joint spacing is greater than needed to effectively control

shrinkage cracking. Distributed steel reinforcement is used to control the opening of intermediate cracks between joints.

The sole function of distributed steel reinforcement is to hold together the fracture faces if cracks form.

3.6.3 Intersections-Concrete intersections offer long life,

reduction in maintenance costs, high reflectivity at lighted

intersections, high and durable skid-resistant surfaces, and the elimination of washboarding and rutting, which is a common problem associated with asphalt.

The volume of traffic at an intersection can be up to double that of either street. Where light traffic intersects

heavy traffic, a thickness for heavy traffic is adequate. In the case where heavy traffic is in both directions, an additional

1 in. (25 mm) of thickness is required. The following indicated thicknesses are generally accepted for intersections: 6

in. ( 1 50 mm) for passenger cars and light trucks; 8 in. (203 mm) for moderate volumes of heavy trucks and buses; and

9 or 10 in. (225 or 250 mm) for industrial traffic and high volumes of heavy trucks. Concrete pavements should cover

at least the entire functional area of the intersection. Addi

tionally, the subgrade where trucks and buses are anticipated should contain a thin, well-compacted, granular subbase.

3.6.4 Basis of pavement thickness design-Pavement design methods are discussed in 3 .3 of this guide. Methods

used for streets and low-volume roads should have been

validated and calibrated by road tests, pavement studies, and surveys of pavement performance that included thin

section, low-volume applications. The most commonly used methods are the AASHTO design guide, which was devel

oped from performance data obtained at the AASHO road

test (AASHTO 1 993); and the Portland Cement Association (PCA) design procedure, which is based on pavement

resistance to fatigue and deflection effects on the subgrade (PCA 1 984). The PCA procedure is recommended for use

in instances of overload conditions. These thickness design

methods can be used for plain or reinforced pavements because the presence or lack of distributed reinforcement has

no significant effect on loaded slab behavior as it pertains to

thickness design. 3.6.5 Street classification and traffic-Comprehensive

traffic studies made within city boundaries can supply data for the design of municipal pavements. A practical approach

is to establish a street classification system. Streets of similar

character may have similar traffic densities and axle-load intensities. The street classifications used in this guide are discussed in 3.6.5 . 1 through 3.6.5 .6 (ACI 325. 12R).

3.6.5.1 Light residential-These are short streets in subdi

visions and may dead end with a turnaround. Light resi

dential streets serve traffic to and from a few houses (20 to 30). Traffic volumes are low-less than 200 vehicles

per day (VPD) with two to four two-axle, six-tire trucks

(and heavier) in two directions (excluding two-axle, fourtire trucks). Trucks using these streets will generally have

a maximum tandem axle load of 34 kip ( 1 50 kN) and an 1 8 kip (80 kN) maximum single-axle load. Garbage trucks

and buses most frequently constitute the overloads on those

types of streets. 3.6.5.2 Residential-These streets carry the same type

of traffic as light residential streets but serve more houses (up to 300), including those on dead-end streets. Traffic

generally consists of vehicles serving the homes plus an

occasional heavy truck. Traffic volumes range from 200 to 1 000 VPD with average daily truck traffic (ADTT) of 1 0 to

50. Maximum loads for these streets are 22 kip (98 kN) for

single axles and 34 kip ( 1 50 kN) for tandem axles. Thicker pavement sections may be required on established bus routes

in residential areas. 3.6.5.3 Collector-Collectors serve several subdivisions

and may be several miles long. They may be bus routes and

serve truck movements to and from an area even though they are not through-routes. Traffic volumes vary from

1 000 to 8000 VPD with ADTT of approximately 50 to 500.

Trucks using these streets generally have a 26 kip ( 1 1 5 kN)

maximum single-axle load and a 44 kip (200 kN) maximum tandem-axle load.

3.6.5.4 Business-Business streets carry movements through commercial areas from expressways, arterials, or

both. They carry nearly as much traffic as arterials; however,

the percentage of trucks and axle weights generally tends to be less. Business streets are frequently congested and speeds

are slow due to high traffic volumes, but with a low (400 to 700) ADTT; average traffic volumes vary from 1 1 ,000 to

1 7,000 VPD. Maximum loads are similar to collector streets.

3.6.5.5 Arterials-Arterials bring traffic to and from expressways and serve major movements of traffic within

and through metropolitan areas not served by expressways. Truck and bus routes and state- and federal-numbered routes

are usually on arterials. For design purposes, arterials are

divided into minor arterial and major arterial, depending on traffic capacity and type. A minor arterial may have fewer

travel lanes and carry less volume of total traffic, but the

percentage of heavy trucks may be greater than that on a six-lane major arterial. Minor arterials carry 4000 to 1 5 ,000

VPD with a 300 to 600 ADTT. Major arterials carry approximately 4000 to 30,000 VPD with a 700 to 1 500 ADTT. Maximum loads for minor arterials are 26 kip ( 1 1 5 kN) for

single axles and 44 kip (200 kN) for tandem axles. Major arterials have maximum loads of 30 kip ( 1 30 kN) for single axles and 52 kip (230 kN) for tandem axles.


1 2 GUIDE FOR CONSTRUCTION OF CONCRETE PAVEMENTS (ACI 325.9R-15)

3.6.5.6 Industrial-Industrial streets provide access to

industrial areas or parks. Total traffic volume may be in

the lower range but the percentage of heavy axle loads is

high. Typical VPD are approximately 2000 to 4000 with 300 to 800 ADTT. Truck volumes are not much different than

the business class; however, the maximum axle loads are

heavier-30 kip ( 1 33 kN) for single axles and 52 kip (230 kN) for tandem axles.

3.6.6 Thickness determination for streets-Proper selec

tion of the slab thickness is a crucial element of a concrete pavement design. Inadequate thickness will lead to cracking

and premature loss of serviceability. Suggested thickness for the design of low-volume concrete roads is found in ACI 325. 12R.

Small changes in concrete thickness or an increase in concrete strength can have a significant effect on pavement

fatigue life. For this reason, tolerances on pavement thickness are important.

For overloaded traffic and cases related to variable support

conditions that may require the use of dowel bars at the joints, thickness designs should be developed using the PCA procedure (PCA 1 984).

3.6. 7 Utilities-Many times during the construction of new subdivisions and commercial properties, utilities will

be placed in the right-of-way of the pavement area. This is mainly done to accommodate maintenance and additions to

the utility system. Present and future needs should be evaluated and provisions made for them. Careful planning in the

laying of these utilities can avoid the unnecessary task of

removal of existing concrete pavements for work on utilities.

3.6.8 Integral curbs and gutters-Integral curbs are

constructed with the pavement in a single operation with all concrete work being done simultaneously. They can be

constructed using forms or slipform pavers. Curbs and gutters provide many benefits to concrete

streets. They confine pavement structures, outline the edges

of pavements, provide easily definable borders between traveled and untraveled surfaces, and help to contain low

speed traffic within the edges of the pavements. Pavement life can be extended through the added thick

ness given to edges of concrete pavements by integral curbs.

These curbs increase strength and stiffness and reduce deflections induced by traffic loads.

3.6.9 Street widths-Street widths vary according to the traffic that the street is designed to carry. In normal cases,

the minimum recommended width is 25 ft (7 .6 m) with a maximum transverse slope of 2 percent. Traffic lanes are customarily 1 0 to 1 2 ft (3 to 3 .6 m) wide. Due to driver

safety, lane widths over 1 2 ft (3.6 m) are not recommended

because experience has shown that some drivers will attempt to pass on wider, single lanes.

Typically, lane widths of 1 2 ft (3.6 m) are used to accommodate buses. Locations for bus lanes may be either at the

curb or in the median. With curb-side bus lanes, bicyclists

and right turners are usually permitted. Median lanes are normally located on wide boulevards and are less likely to be

congested by other traffic. Parking lanes along the curb are usually 7 to 8 ft (2 to 2.5 m) wide. In areas where passenger

vehicles are the norm, a lane width of 7 ft (2 m) is recom

mended and those lanes, which should accommodate trucks, a width of 8 ft (2.5 m) is recommended. On major streets,

parking lanes are 1 0 to 12 ft (3 to 3 .6 m) wide and they can also be used as travel or turning lanes. For those streets

where parking is prohibited, an extra 2 ft (0.6 m) of width

is generally provided along the curb as nontraveled space.

3.7-Drainage issues 3.7.1 Cross slopes-Because a concrete surface maintains

its shape, flatter grades (but typically at least 2 percent for

most high-volume facilities) can be used to provide adequate surface drainage. This minimizes the amount of earthwork

during construction and may result in a greater spacing of

inlets. Cross slopes (or crowns) built into concrete pavements

provide for draining the water from the surface rapidly. Generally, a minimum slope of 1 percent is recommended.

Slopes greater than 1 percent can be used provided they are

consistent with road safety and drivability of the vehicles using them. For paved sections constructed between and

abutting buildings, the type of center drain or inverted crown

used in alleys may be best. The design should be for uniform slopes toward the center of not less than 1 percent.

3. 7.2 Integral curbs and gutters-Curbs and gutters collect water from crowned pavements and convey it to points of

collection. This also allows for a reduction of water, which

would otherwise penetrate underneath the pavement. It is important that the aprons have adequate hydraulic capacity

to carry runoff from most rainstorms. Making aprons wider

reduces the opportunity for rainwater to move down through

joints between curbs and pavements. In areas where there are storm sewers, the flow in gutters

is diverted through inlets built into the curbs and gutters. In areas where the rains are infrequent, the inlets may only be

gaps in the curb to allow the runoff to exist. Inlets, which

are more or less anchored in place, should be isolated from

curbs and gutters.

CHAPTER 4-MATERIAL SELECTION

4.1-lntroduction All materials used in concrete pavements should be

furnished from supply sources approved before shipments are started and used only so long as the materials continue to

meet the requirements of the contract documents. The basis

of approval of such sources should be the ability to consistently produce materials of the quality and in the quantity

required. Unless local conditions such as quality, cost, and

general availability indicate a need for modification, materials should meet the standard specifications of the governing

agency or those listed in 4.2.

4.2-Foundation materials

4.2.1 Subgrade soil-Subgrade is the underlying surface of soil over which the pavement will be constructed. The

required pavement thickness and performance of the pavement will depend in large part on the strength and unifor-



Table 4.2.1-lmprovements in modulus of subgrade reaction k* (ACI 330R)

Subgrade k-value, psi/in. Subbase thickness

(kPa/mm) 4 in. ( 1 00 mm) 6 in. ( 1 50 mm) 9 in. (225 mm) 12 in. (300 mm)

Granular aggregate subbase

50 ( 1 4) 65 in. ( 1 625 mm) 75 in. ( 1 875 mm) 85 in. (2 125 mm) 1 1 0 in. (2750 mm)

100 (27) 1 30 in. (3250 mm) 1 40 in. (3500 mm) 160 in. (4000 mm) 1 90 in. (4750 mm)

200 (54) 220 in. (5500 mm) 230 in. (5750 mm) 270 in. (6750 mm) 320 in. (8000 mm)

300 (8 1 ) 320 in. (8000 mm) 330 in. (8250 mm) 370 in. (9250 mm) 430 in. ( 1 0,750 mm)

Cement-treated subbase

50 ( 1 4) 1 70 in. (4250 mm) 230 in. (5750 mm) 3 1 0 in. (7750 mm) 390 in. (9750 mm)

1 00 (27) 280 in. (7000 mm) 400 in. ( 10,000 mm) 520 in. ( 1 3,000 mm) 640 in. ( 1 6,000 mm)

200 (54) 470 in. ( 1 1 ,750 mm) 640 in. ( 1 6,000 mm) 830 in. (20,750 mm) -

Other treated subbase

50 ( 1 4) 85 in. (2 1 25 mm) 1 1 5 in. (2875 mm) 1 70 in. (4250 mm) 2 1 5 in. (5375 mm)

1 00 (27) 1 75 in. (4375 mm) 2 1 0 in. (5250 mm) 270 in. (6750 mm) 325 in. (8 1 25 mm)

200 (54) 280 in. (7000 mm) 3 1 5 in. (7875 mm) 360 in. (9000 mm) 400 in. ( 1 0,000 mm)

300 (8 1 ) 350 in. (8750 mm) 385 in. (9625 mm) 420 in. (I 0,500 mm) 490 in. ( 12,250 mm)

mity of the subgrade. Preliminary information on the engineering properties of the soil at a particular project site can

be obtained from the U.S. Department of Agriculture soil

survey maps or geotechnical investigations conducted for adjacent roads or buildings; however, for final design of the

pavement structure, soil conditions and subgrade properties

should be determined by appropriate soil testing. Refer to 3 .4.2 for a discussion of properties and tests used to charac

terize subgrade soils. Uniform subgrade support is the goal of proper site prepa

ration. The designer can require grading operations to blend

soil types to improve uniformity. Properties of the sub grade

soil can be improved by compaction, stabilization, and moisture control.

Although the typical values of k for various subgrade soil

types and moisture conditions are given in Table 3 .4. 1 . 1 ,

they should be considered as a guide only. Low-strength

subgrades can be stabilized to upgrade the support rating listed in Table 3 .4. 1 . 1 . Where granular subbase materials are

used, there may be a moderate increase in the modulus of

subgrade reactions, or k-values that can be incorporated in the thickness design. The suggested increase in k-values for

design purposes is shown in Table 4.2. 1 . Usually, it is not economical to use a granular subbase for the sole purpose

of increasing k-values or reducing the concrete pavement

thickness. 4.2.2 Subbase material-As discussed in 3 .4.3 , a subbase

is a layer of select material placed under a concrete slab

primarily for bearing uniformity, pumping control, and erosion resistance. The select material may be unbound or

stabilized. It is more important, however, that the subbase be well drained to prevent excess pore pressure to resist

pumping-induced erosion than to achieve a greater stiffness

in the overall pavement. The subbase serves many important purposes, and in some

cases is used to provide a stable surface for construction expediency. This could be applicable in wet-freeze climates where

the use of a stabilized subbase is recommended; water can easily collect under a slab due to freezing-and-thawing action.

A contractor may find it advantageous to use a subbase

or a stabilized subgrade to provide a more stable working

platform during construction. Although subbases are not

generally used for local streets and roads, they can be effective in controlling erosion of the subgrade materials where

traffic conditions warrant such measures. Subbase materials

include untreated, treated, and drainable material.

4.2.3 Base-Unlike asphalt pavement systems, it is not

always necessary that concrete highway pavements have both a base and subbase layer. Airfield pavements handling

heavy aircraft loads often have both a base and a subbase

(Kohn et al. 2003). Base materials include untreated, treated,

and drainable materials.

4.3-Pavement concrete materials 4.3.1 Introduction-Concrete mixtures for paving should

be proportioned following accepted proportioning proce

dures. The concrete should be designed to produce the specified strength, provide adequate durability, rideability,

and skid resistance. The mixture should provide adequate

workability so that it can be efficiently placed, finished, and textured with the equipment the contractor will use. Paving mixtures should use the largest nominal maximum size aggregate consistent with the requirements for placing the

concrete. This will minimize shrinkage cracking, enhance

load transfer, and produce the most economical concrete.

Mixtures with excessive natural fine aggregates should be avoided, as these mixtures tend to increase water demand

and the potential for uncontrolled shrinkage cracking. Construction of a test section, using the production equip

ment and paving train to be used on the actual job is also recommended.

4.3.2 Strength and durability-Because concrete strength

is a function of the type and amount of cementitious mate

rial (hydraulic cement plus supplementary cementitious materials), the completeness of the hydration, and the water-cementitious materials ratio (w/cm) selected for the

mixture, water-reducing admixtures, or internal curing also

can be used to increase strength while maintaining sufficient workability of the fresh mixture. Internal curing can



improve strength at 3, 7, 28, and 90 days, and improve dura

bility and the interfacial transition zone, as well as reduce cracking, permeability, and warping. Detailed information

on hydraulic cements and supplementary cementitious materials are found in ACI 225R, 232. 1 R, 233R, and 234R.

Aggregates should be clean to provide good aggregate-to

paste bond and should conform to the quality requirements of ASTM C33/C33M. Cubical-shaped coarse aggregates have been shown to increase flexural strength. Air entrain

ment is a critical item in concrete durability. Curing also ensures proper strength gain and durable concrete pavement.

Mixtures designed for high early strength can be provided if the pavement should be used by construction equipment or

opened to traffic earlier than normal (4 to 24 hours). Regard

less of when the pavement is opened to traffic, the concrete strength should be checked to verify that the design strength

has been achieved. For concrete pavement applications, flexural strength is

used by most design procedures as the most direct indicator

of load capacity. Flexural strength values indicate the tensile strength at the bottom of the slab where wheel loads induce

tensile stresses (ACI 325. 1 1R). Flexural strength tests from

ASTM C78/C78M are very sensitive to the beam fabricating

and testing procedures. Many agencies realize this short

coming and use compressive strength tests (ASTM C39/ C39M) to evaluate concrete for acceptance and opening

(ACI 325. 1 1 R). While design of concrete pavement is

generally based on the tensile strength of the concrete, as represented by the flexural strength, it may be useful to use

compressive-strength testing in the field for quality-control

acceptance purposes and in the laboratory for mixture design

purposes. Refer to 3 .5 .3 .3 for a useful correlation between compressive strength and flexural strength.

If desired, however, a specific flexural-to-compressive

strength correlation can be developed for specific mixtures.

The strength of the concrete should not be exceeded by envi

ronmentally-induced stresses (curling and warping), which may be critical during the first 72 hours after placement.

4.3.3 Concrete materials-Concrete can be described as a paste (cement and water) binding together aggregate

particles. Paving concrete in common use today makes use

of supplementary cementitious materials (SCMs), chemical admixtures, and air entrainment to improve the prop

erties of the paste and hardened concrete. Future use may include high-performance concrete (HPC) using materials

for internal curing to improve durability and viscosity-modifying admixtures to improve extrusion properties for slipform paving applications. Aggregates make a major contri

bution to the properties and performance of paving concrete.

Aggregates are usually local materials and include a wide variety of rock types as well as recycled materials.

During construction, other materials such as dowel bars, tie bars, and reinforcement may be incorporated into the

pavement system. Other materials such as joint sealants,

evaporation retarders, and curing materials are also used

in the construction process. All these materials affect the construction process and the long-term performance of a concrete pavement. The following sections of this chapter

describe these materials and the influences they have on

the construction process as well as the performance of the pavement.

4.3.3.1 Cementitious materials-Hydraulic cement is the most important component of the concrete paste. Cement

combines with water (thus the term "hydraulic cement") to

form the paste, which gives the concrete initial workability, and then reacts to harden and bind aggregate particles

together.

There are several types of hydraulic cement, but portland cement, which is cement meeting the requirements of ASTM

C l 50/C l 50M or AASHTO M085, is the most widely used hydraulic cement. Intergrinding produces blended hydraulic cements or blended cement with supplementary cementi

tious materials. ASTM C595/C595M or AASHTO M240 is used to specify blended cements. ASTM C 1 1 57 /C 1 1 57M

is a performance specification for hydraulic cement. Portland cements meeting the ASTM C 1 50/C 1 50M Type I and

Type II requirements are the most common cements used

in paving applications (Table 4.3.3 . 1 ). Type III cement is commonly used for patching and may be used in mixtures

for fast-track paving. Type IV is a low-heat-of-hydration

cement, but it has been largely replaced in modern mixtures by incorporating supplementary cementitious materials. Type V cements are used in areas where soils have high

sulfate concentrations. The manufacture of hydraulic cement

clinker releases carbon dioxide into the atmosphere, so envi

ronmental responsibility dictates that procedures and materials should be used in the concrete mixture that minimizes

the clinker content of concrete. The use of blended cements and ASTM C l l 57/C l l 57M general-purpose and moderate

sulfate-resistant cements is growing in some areas of the

country.

4.3.3.1.1 Portland cement-Portland cement is hydraulic cement that meets the chemical composition and physical

property requirements of ASTM C l 50/C l 50M or AASHTO

M085. The fundamental difference between portland cement types is the chemical composition and physical properties.

These specifications cover five major types of portland cement; however, not all types may be available in any given

geographic area. While the standard specifications contain

requirements for air-entraining portland cements and Type

IV low-heat cements, other technologies have replaced

these cement products and they are generally not available in the United States. ASTM C l 50/C l 50M cautions that "in advance of specifying the use of cement other than Type I,"

the specifier should "determine whether the proposed type of cement is, or can be made, available."

The cement type or types to be used should conform to

the requirements of the contract documents and those of the specified ASTM or AASHTO standards. Even though cements from different sources meet the requirements of the same specification, there may be subtle differences that

might impact concrete performance or compatibility with

SCMs and admixtures used in the concrete mixture. For this reason, many agencies specify that all cement used in

a given approved mixture should be from the same source. In the event that its use from more than one source is antici-



Table 4.3.3.1 -Hydraulic cement types

Types

Resistance to

Cement General Moderate heat of High early Low heat of Moderate sulfate High sulfate alkali-silica reac-

specification purpose hydration strength hydration resistance resistance tivity (ASR)

Portland cements

ASTM C l 50/C l 50M Type I Type II(MH) Type III Type IV Type II Type V Low alkali option

AASHTO M85

Blended hydraulic IS(x)

cements IP(x)

IS( <70)(MH) IP(x)(LH)

IS(<70)(MS) IS( <70)(HS) Low reactivity

ASTM C595/C595M IP(x)(MH) IP(x)(MS) IP(HS) option

AASHTO M240 IT(Ax)(By)

Performance

hydraulic cements GU MH HE LH MS HS Option R

ASTM C l l 57/

C l l 57M

Note: IS = Type IS (portland blast-furnace slag cement); IP = Type IP (portland-pozzolan cement); IT = Type IT (ternary blend); GU = Type GU (hydraulic cement for general

construction); HE = Type HE (high early strength); MS = Type MS (moderate sulfate resistance); HS = Type HS (high sulfate resistance); MH = Type MH (moderate heat of hydra

tion); and LH = Type LH (low heat of hydration).

pated, mixture designs for each source to be used should be developed and submitted for approval.

The term "Type 1/II portland cement" is a frequently used and misunderstood term. Type 1/II is not an actual ASTM designation, but instead denotes that the cement being repre

sented has a C3A content of 8 percent or less and meets all

of the requirements of both ASTM C l 50/C l 50M Type I and Type II. This is particularly helpful to the concrete producer

who has limited silo storage capacity, and for whom the ability to inventory a single cement that meets both ASTM

C 1 50/C 1 50M Type I and Type II specifications in one silo is

a convenience. "Type II modified" is another term frequently

misunderstood. The word "modified" can mean modified by such characteristics as lower alkali content, coarser fine

ness, or significantly lower C3A content. If the term "Type

II modified" is used, the purchaser should request that the manufacturer define the modification employed to ensure

that the product is appropriate for the intended application. The speed with which a concrete mixture sets and develops

strength is a result of the hydration characteristics of a

particular combination of cement, supplementary cementitious materials, and admixtures. Cements play a major role

in setting, strength gain, and heat generation. These properties depend on the interaction of the individual chemical

compounds in the cement, SCMs, and admixtures used (ACI 225R).

Finely ground cements, such as Type III cement, have

increased surface areas, which allows for more cement

contact with mixing water. This additional contact results in cement that hydrates faster and generates more heat from

the hydration process. Due to the higher fineness of Type III cement (which provides a much greater surface area for

the hydration reaction), early strength normally develops

faster than other types of portland cement. Type III has been successfully used in cold weather and selective fast-track

paving operations and in pavement patching. Due to the faster hydration reaction associated with Type

III cement, early setting of the concrete mixture should be

expected. The materials engineer and contractor should be

aware of this. Tests should be conducted using the same

cement that the contractor will use in construction. With proper proportioning, concretes using Type I or Type

II portland cement also can produce adequate characteristics

for accelerated-concrete paving. To develop adequate early

strength, concrete made from these cements will usually

require either accelerating admixtures or low water-cement ratios (w/c), dense graded aggregate proportions, and the use

of curing as an adjunct to standard external curing.

4.3.3.1.2 Blended cement-Blended hydraulic cements are usually made by grinding portland-cement clinker with

calcium sulfate (gypsum) and a quantity of a suitable reac

tive material such as slag cement, fly ash, silica fume, or

raw or calcined natural pozzolan. They may also be made by blending the finely ground ingredients. For specifica

tion purposes, portland and blended hydraulic cements are designated by type depending on their chemical composition

and properties. The availability of a given type of cement can vary widely among geographical regions. The use of

blended cements, though presently small, is growing in

response to needs for use in concrete requiring special properties, conservation of energy, and raw materials.

The use of silica fume in blended cements has also attracted interest. Typically, the properties of cements containing

silica fume as a blending material may be expected to be the

same as if the silica fume were added separately. As with any blended cement, there will be a loss in flexibility in mixture

proportioning with respect to the exact amount of silica

fume in a given concrete mixture. ASTM C595/C595M applies to blended cements that are

intended for use in general concrete construction. AASHTO M240 is the equivalent AASHTO specification. Blended

cements covered by these specifications are Type IS (port

land blast furnace slag cement) and Type IP (portland

pozzolan cement). The percentage of slag or pozzolan in the

product is expressed by a whole number based on the mass of the final blended product. The percentage is designated by

adding the suffix (x) to the type designation. Additionally,

these blended cements may have special properties such as air-entraining cement (A), moderate sulfate resistance (MS),



moderate heat of hydration (MH), and low heat of hydra

tion (LH). These special properties will be specified by adding the suffix (A), (MS), (MH), or (LH) to the blended

type designation. Type IT designates a ternary blend with (Ax) and (By) indicating the percentage of the A and B SCM

components of the blend.

4.3.3.1.3 Performance cement-Performance-based cements provide an option to the standard prescriptive-based

cements such as those of ASTM C l 50/C l 50M and ASTM

C595/C595M. These cements can provide equal perfor

mance to many of the standard cements used on previous

work. Many of the performance-based cements produced today are more environmentally friendly and require less

energy to produce.

ASTM C 1 1 57 /C 1 1 57M classifies cements based on specific requirements for general use, high early strength,

resistance to attack by sulfates, and heat of hydration. Optional requirements are provided for the property of low

reactivity with alkali-silica-reactive aggregates (ASTM

C 1 1 57 /C 1 1 57M). This specification covers six basic types of cements and is: Type GU (hydraulic cement for general

construction), Type HE (high early strength), Type MS

(moderate sulfate resistance), Type HS (high sulfate resistance), Type MH (moderate heat of hydration), and Type LH

(low heat of hydration). There is no equivalent AASHTO specification for performance-based cement.

4.3.3.2 Special-purpose cements-In addition to portland

and blended cements, other cements may be available for use in pavements.

4.3.3.2.1 Rapid-hardening hydraulic cements-Rapidhardening hydraulic cements are similar in composition

to other blended cements, except that they are specially formulated with functional additions to provide design

strengths in approximately 3 to 12 hours. Regular blended cements normally provide design strengths in 7 to 28 days.

Very-early-strength blended cements can be used in the

same application as portland and blended cement. They are usually used in applications where early-strength develop

ment is highly beneficial, such as in repair applications or accelerated paving applications. ASTM C 1 600/C 1 600M

provides performance requirements for four categories of

rapid hardening hydraulic cements: a) Type URH-Ultra rapid hardening, for use where ultra

high early strength is desired b) Type VRH-Very rapid hardening, for use where very

high early strength is desired c) Type MRH-Medium rapid hardening, for use where

midrange rapid hardening, high early strength is desired d) Type GRH-General rapid hardening, for use if the

higher strength property of Type VRH or Type MRH cement

is not required

4.3.3.2.2 Magnesium phosphate cements-Magnesium phosphate cements are rapid hardening, non-portland

cements that are primarily used in highway and airport pave

ment repairs. They may be two-part cements consisting of a dry powder and a phosphoric acid liquid with which the

powder should be mixed, or they may be one-component products to which only water is added.

4.3.3.2.3 Expansive cement-Paving applications for

expansive or shrinkage-compensating cements covered by ASTM C845 are very limited. Some agencies have used

them in bridge decks and pavement patching applications. These cements are designed to expand a small amount

during the first few days of hydration to offset the effects

of later drying shrinkage. They are used to reduce cracking resulting from drying shrinkage, and to cause stressing of

reinforcing steel. Shrinkage-compensating cements manu

factured in the United States depend on the formation of a higher-than-usual amount of ettringite during hydra

tion of the cement to cause the expansion. The expansive ingredient-an anhydrous calcium sulfoaluminate-can be

purchased separately. Magnesium oxide or calcium oxide,

which are used in Europe and Japan, can also be used as expansive agents.

4.3.4 Supplementary cementitious materials-Supplementary cementitious materials (SCMs) are materials that,

if used in conjunction with portland or blended cement, contribute to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both. In the past, the term

"mineral admixture" was used to refer to these materials, but

because of the large quantities of these materials used in modern concrete, this term has fallen out of favor.

Several types of SCMs can be used in pavement concrete. These materials have gained popularity over the years due to

the desirable concrete properties that result from their use,

and sustainability issues. In particular, SCMs have shown to improve the durability of concrete through a variety of

mechanisms. Some SCMs are incorporated in blended

cements discussed in 3 .2.2, but they are also introduced as

a separately hatched material at the concrete mixing plants. Supplementary cementitious materials are classified into

four primary groups : 1 ) Fly ash (ASTM C6 1 8)

2) Slag cement (ASTM C989/C989M)

3) Silica fume (ASTM C l 240) 4) Natural pozzolan-volcanic ash and calcined clays

(ASTM C6 1 8) 4.3.4.1 Fly ash-Fly ash-a by-product of coal combus

tion from electric power plants-became available in large

quantities in the 1 930s. Initially, fly ash was used as a partial mass or volume replacement of portland cement, which is

the expensive cementing component in concrete. However, as the use of fly ash increased, the potential for improved

properties of concrete containing fly ash was recognized. Fly ash is now used in concrete for many reasons, including

improvements in workability of fresh concrete, reduction in temperature rise during initial hydration, improved resis

tance to sulfate attack, reduced expansion due to alkali-silica reaction (ASR), reduced cost, and other contributions to the

durability and strength of hardened concrete.

The commonly used specification for fly ash, ASTM

C6 1 8, establishes two classifications: Class C and Class

F, both of which are used in concrete pavements. Used in paving concrete, fly ash will lower water demand, improve

workability, and increase long-term concrete strength. All fly ashes display pozzolanic properties, but some Type C ashes



possess varying degrees of cementitious value without the

addition of calcium hydroxide or portland cement because they contain some lime. Type F has the added benefit

of minimizing the effects of ASR, but has less cementitious value to contribute to the hydraulic reaction. Fly ash

containing higher levels of calcium (typically classified as Type C) usually comes from sub-bituminous and lignite coals, whereas fly ash containing lower levels of calcium

(typically classified as Type F) comes from bituminous or

anthracite coals.

Fly ash in concrete makes efficient use of the products of hydration of portland cement: 1) solutions of calcium and alkali hydroxide, which are released into the pore structure

of the paste, then combine with the silica in the fly ash, and

form a cementing medium similar to that formed by the portland cement; and 2) the heat generated by hydration of

portland cement is an important factor in initiating the reaction of the fly ash. In properly cured concrete containing

fly ash, fly-ash reaction products fill in the spaces between

hydrating cement particles, thus lowering the concrete permeability to water and aggressive chemicals. The slower

hydration reaction rate of many fly ashes compared to port

land cement limits the amount of early heat generation and

the detrimental early temperature rise in massive structures.

Properly proportioned fly ash mixtures impart properties to concrete that may not be achievable through the use of port

land cement alone.

4.3.4.1.1 Effects of fly ash on properties of fresh concreteUsing fly ash in a concrete mixture can impact the work

ability, bleeding characteristics, set time, finishing character

istics, heat generation characteristics, and air entrained in the

fresh concrete. These effects can be helpful or detrimental to pavement construction depending on project requirements.

4.3.4.1 .1 .1 Workability-The absolute volume of cement plus fly ash normally exceeds that of cement in similar

concrete mixtures not containing fly ash. While it depends on

the proportions used, this increase in paste volume produces a concrete with improved plasticity and better cohesiveness

(Lane 1 983). In addition, the increase in the volume of fines from fly ash can compensate for deficient aggregate fines.

The generally spherical shape of fly ash particles normally

permits the water in the concrete to be reduced for a given workability (Brown 1 980) . Ravina ( 1 984) reported on a

Class F fly ash that reduced the rate of slump loss compared to non-fly ash concrete in hot-weather conditions. Fly ash

particles vary in size from less than 1 J.lm to more than 1 00

J.lm, with the typical particle size measuring under 20 J.lm (Mehta 1 984), the smaller size favorably influencing work

ability and density.

4.3.4.1 . 1.2 Bleeding-Using fly ash in air-entrained and non-air-entrained concrete mixtures usually reduces

bleeding by providing greater surface area of solid particles and a lower water content for a given workability.

4.3.4.1 . 1.3 Time of setting-The use of fly ash may extend

the time of setting of concrete if the portland cement content is reduced. Jawed and Skalny ( 1 98 1 ) found that Class F fly

ashes retarded early C3S hydration. Grutzeck et a!. ( 1 985) also found retardation with Class C fly ash. The setting

characteristics of concrete are influenced by ambient and

concrete temperature, cement type, source, content, fineness, water content of the paste, water-soluble alkalis, use and

dosages of other admixtures, the amount of fly ash, and the

fineness and chemical composition of the fly ash (Plowman and Cabrera 1 984) . If these factors are given proper consid

eration in the concrete mixture proportioning, an acceptable

time of setting can usually be obtained. The actual effect of a given fly ash on time of setting may be determined by testing if a precise determination is needed or by observation if a

less precise determination is acceptable.

4.3.4.1.1.4 Finishability-Where fly ash concrete has a

longer time of setting than concrete without fly ash, such mixtures should be finished at a later time than mixtures

without fly ash. Failure to do so could lead to premature finishing, which can seal the bleed water under the top

surface, creating a plane of weakness. Longer times of

setting may increase the probability of plastic shrinkage cracking or surface crusting under conditions of high evapo

ration rates . Using very wet mixtures containing fly ash with significant amounts of very light unburned coal particles or

cenospheres can cause these particles to migrate upward

and collect at the surface, which may lead to an unacceptable appearance. Some situations are encountered where the

addition of fly ash results in stickiness and consequent diffi

culties in finishing. In such cases, the concrete may have too much fine material or too high an air content.

4.3.4.1 .1 .5 Temperature rise-The heat generated during cement hydration has an important bearing on the rate of

strength development and on early stress development due

to differential volume change in concrete. The rate of hydra

tion and heat generation depends on the quantity, fineness, and type of cement; mass of the structure; method of place

ment; temperature of the concrete at the time of placement;

and curing temperature. Using fly ash as a portion of the cementitious material in concrete can reduce the temperature

rise. As the amount of portland cement is reduced, the heat of hydration of the concrete is generally reduced (Mather

1 974). However, some Class C fly ashes do contribute to

early temperature rise in concrete (Dunstan 1 984). When heat of hydration is of critical concern, the proposed concrete

mixture should be tested for temperature rise. 4.3.4.1 .1 .6 Air entrainment-The use of fly ash in air

entrained concrete will generally require a change in the

dosage rate of the air-entraining admixture. Some fly ashes

with loss on ignition (LOI) values of less than 3 percent require no appreciable increase in air-entraining admixture

dosage. Some Class C fly ashes may reduce the amount of air-entraining admixture required, particularly for those with significant water-soluble alkalis in the fly ash (Pistilli 1983). To maintain constant air content, admixture dosages should

usually be increased, depending on the carbon content as

indicated by LOI, fineness, and amount of organic material in the fly ash. When using a fly ash with a high LOI, more

frequent testing of air content at the point of placement is desirable to maintain proper control of air content in the

concrete. Required air-entraining admixture dosages may increase with an increase in the coarse fractions of a fly ash.



Adjustments should be made as necessary in the admixture

dosage to provide concrete with the desired air content at the point of placement.

Meininger ( 1 98 1 ) and Gebler and Klieger ( 1 983) have shown that there appears to be a relationship between the

required dosage of air-entraining admixture to obtain the

specified air content and the loss of air in fly ash concrete

with prolonged mixing or agitation prior to placement. Those fly ashes that require a higher admixture dosage tend

to suffer more air loss in fresh concrete. When this problem is suspected, air tests should be made as the concrete is

placed to measure the magnitude of the loss in air and to provide information necessary to properly adjust the dosage

level for adequate air content at the time of placement.

The loss of air depends on a number of factors, such as properties and proportions of fly ash, cement, and fine

aggregate; duration of mixing; and type of air-entraining

admixture used (Gaynor 1 980; Meininger 1 98 1 ). Neutral

ized vinsol resin air-entraining admixtures did not perform well with fly ashes having high LOI values. For a given

fly ash, the most stable air content was achieved with the cement-fine-aggregate combinations that had the highest

air-entraining admixture requirement. However, a change in fly ash that requires a higher admixture dosage to obtain the

specified air content is more likely to cause loss of air if the

mixture is agitated or manipulated for a period of time. High LOI of fly ash is often, but not always, an indicator

of the likelihood of air-loss problems; so far, the problem seems to be confined to the lower-CaO, Class F fly ashes.

The foam-index test (ACI 233R) is a rapid test that can be used to check successive shipments of fly ash to detect a

change in the required dosage of air-entraining admixture in concrete.

4.3.4.1.2 Effects of fly ash on properties of hardened concrete-The hardened properties of concrete are also

affected by the use of fly ash in the mixture. These effects

may improve or have a detrimental impact on the long-term performance of the pavement.

4.3.4.1 .2.1 Compressive strength and rate of strength gain-Strength at any given age and rate of strength gain of

concrete are affected by the characteristics of the particular fly ash, the cement with which it is used, and their propor

tions in the concrete. Compared with concrete without fly ash, concrete containing a typical Class F fly ash may develop lower strength at 7 days of age or before if tested

at room temperature (Abdun-Nur 1 96 1 ). If equivalent 3- or

7-day strength is desired, it may be possible to provide the desired strength by using accelerators or water reducers, or

by changing the mixture proportions (Swamy et a!. 1 983).

After the rate of strength contribution of portland cement slows, the continued pozzolanic activity of fly ash contrib

utes to increased strength gain at later ages, provided moisture is available to continue the hydration reactions (refer

to 4.6 and 5.3 for further information on curing) being a

reliable method; therefore, concrete containing fly ash with equivalent or lower strength at early ages may have equiva

lent or higher strength at later ages than concrete without fly ash. Other tests, comparing concrete with and without fly ash

showed significantly higher performance for the concrete

containing fly ash at ages up to 1 0 years (Mather 1965). Class C fly ashes often exhibit a higher rate of reaction at

early ages than Class F fly ashes, and typically give very good strength results at 28 days as well. In fact, Cook ( 1 98 1 )

reported that some Class C fly ashes were as effective as

portland cement on an equivalent-mass basis. However, certain Class C fly ashes may not show the later-age strength

gain typical of Class F fly ashes. Changes in cement source

may change concrete strengths with Class F fly ash as much as 20 percent. Cements with alkali contents of 0.60 percent

Na20 equivalent or more typically perform better with fly ash for strength measured beyond 28 days.

4.3.4.1 .2.2 Modulus of elasticity-Lane and Best ( 1 982)

report that the modulus of elasticity of Class F fly ash concrete is somewhat lower at early ages and slightly higher

at later ages than similar concretes without fly ash. Cain ( 1 979) concluded that cement and aggregate characteristics

will have a greater effect on modulus of elasticity than the use of fly ash.

4.3.4.1.2.3 Abrasion resistance-Compressive strength,

curing, finishing, and aggregate properties are the major

factors controlling the abrasion resistance of concrete (ACI 201 .2R; 2 1 0R). At equal compressive strengths, properly finished and cured concretes with and without fly ash will

exhibit essentially equal resistance to abrasion. 4.3.4.1 .2.4 Resistance to freezing and thawing-The resis

tance to damage from freezing and thawing of concrete made with or without fly ash depends on the adequacy of the air

void system, the soundness of the aggregates, age, maturity

of the cement paste, and moisture condition of the concrete

(Larson 1 964). Use care proportioning mixtures to ensure

that the concrete has adequate strength when first exposed

to cyclic freezing and thawing-that is, approximately 3500 psi (24 MPa) or more. When compared on this basis in prop

erly air-entrained concrete, investigators found no signifi

cant difference in the resistance to freezing and thawing of concretes with and without fly ash (Lane and Best [ 1 982]

for Class F fly ash; Majko and Pistilli [ 1 984] for Class C fly ash).

4.3.4.1.2.5 Permeability and corrosion protectionThrough its pozzolanic properties, fly ash chemically combines with calcium hydroxide and water to produce

desirable hydration products (C-S-H), thus reducing the risk of leaching calcium hydroxide. Additionally, the long-term

reaction of fly ash improves the pore structure of concrete to

reduce the ingress of chloride ions. As a result ofthe improved pore structure, permeability is reduced (Manmohan and

Mehta 198 1 ). Despite concerns that the pozzolanic action

of fly ash could reduce the pH of concrete, researchers have found that an alkaline environment, very similar to that in

concrete without fly ash, remains to preserve the passivity of steel reinforcement (Ho and Lewis 1 983) .

4.3.4.1 .2.6 Reduction of expansion caused by ASR-The

reaction between the siliceous glass in fly ash and the alkali hydroxides in the portland-cement paste consumes alkalis,

which reduces their availability for expansive reactions

with reactive aggregates . The use of adequate amounts of



some fly ashes can reduce the amount of aggregate reaction

and reduce or eliminate harmful expansion of the concrete. Often, the amount of fly ash necessary to prevent damage due

to alkali-aggregate reaction will be more than the optimum amount necessary for improvement in strength and work

ability properties of concrete. Particular replacement levels

of some high-alkali fly ashes increase the problem of ASR and higher replacement levels of the same fly ash reduce the

problem of ASR. The pessimum level of a particular fly ash

is an important consideration for selecting mixture proportions using potentially reactive aggregates.

4.3.5 Slag cement 4.3.5.1 Introduction-Blast-furnace slag is a nonmetallic

product, consisting essentially of silicates and aluminosili

cates of calcium and of other bases that is developed in a molten condition simultaneously with iron in a blast furnace.

Slag cement is the glassy granular material formed where molten blast-furnace slag is rapidly chilled, such as by

immersion in water. The composition of blast-furnace slag is

determined by that of the ores, fluxing stone, and impurities

in the coke charged into the blast furnace. Typically, silicon,

calcium, aluminum, magnesium, and oxygen constitute 95

percent or more of the blast-furnace slag. A discussion of the basic principles of slag cement hydra

tion makes it possible to identify the primary factors that,

in practice, will influence the effectiveness of the uses of slag cement in concrete and mortar. The factors determining

cementitious properties are: a) Chemical composition of the slag cement and portland

cement

b) Alkali ion concentration in the reacting system

c) Glass content of the slag cement d) Fineness of the slag cement and the portland cement

e) Temperature during the early phases of the hydration process

4.3.5.2 Proportioning with slag cement-The propor

tion of slag cement in a concrete mixture will depend on the purposes for which the concrete is to be used, curing

temperature, grade (activity) of the slag cement, and portland cement or other activator. In most cases, slag cements

have been used in proportions of25 to 70 percent by mass of

the total cementitious material. Other considerations that determine the proportion of slag

cement could include the requirements for permeability, temperature rise control, time of setting and finishing, sulfate

resistance, and the control of expansion due to ASR.

4.3.5.3 Environmental considerations-Use of slag cement in concrete and mortar is an environmentally sound

and efficient use of existing resources. The use of slag

cement has several benefits, including reduced energy, reduced greenhouse gas emissions, and reduced virgin raw

materials. Recognizing the positive environmental impacts of using slag cement, the Environmental Protection Agency

(EPA) actively encourages the expanded use of slag cement.

4.3.5.4 Effects on properties of fresh concrete 4.3.5.4.1 Workability-Fulton ( 1 974) investigated work

ability in great detail and suggested that a cementitious matrix containing slag cements exhibited greater workability

due to the increased paste content and increased cohesiveness of the paste. Wood ( 1 9 8 1 ) reported that the workability and placeability of concrete containing slag cement was

improved where compared with concrete containing no slag cement.

4.3.5.4.2 Time of setting-Delays in setting time can be

expected if more than 25 percent slag cement is used as a replacement for portland cement in concrete mixtures. The

degree to which the setting time is affected depends on the

temperature of the concrete, amount of slag cement used, w/ em, and characteristics of the portland cement (Fulton 1974).

The amount of portland cement is also important. Hogan and Meuse! ( 1 9 8 1 ) found that for 50 percent slag cement, the

initial setting time is increased 0.5 to 1 hour at 23°C (73°F);

little if any change was found above 29°C (85°F). Although significant retardation has been observed at low

temperatures, the addition of conventional accelerators, such as calcium chloride or nonchloride accelerating admixtures,

can reduce or eliminate this effect. Because the amount of

portland cement in a mixture usually determines setting characteristics, reducing the slag cement-portland cement

ratio may be considered in cold weather.

4.3.5.4.3 Bleeding-Bleeding capacity and bleeding rate of concrete are influenced by a number of factors, including the ratio of the surface area of solids to the unit volume of

water, air content, subgrade conditions, and concrete thick

ness. When slag cements are used, bleeding characteris

tics can be estimated depending on the fineness of the slag cement compared with that of the portland cement, and

the combined effect of the two cementitious materials. For

slag cement that is finer than portland cement and is substi

tuted on an equal-mass basis, bleeding may be reduced; conversely, for slag cement that is coarser, the rate and

amount of bleeding may increase. 4.3.5.4.4 Slump-Meusei and Rose ( 1 983) indicated

that concrete containing slag cement at 50 percent substitution yielded slump loss equal to that of concrete without slag cement. Experiences in the United Kingdom indicated

reduced slump loss, particularly where the portland cement used in the blend, exhibited rapid slump loss such as that

caused by false-set characteristics of the cement (Lea 197 1 ) .

4.3.5.5 Effects on properties of hardened concrete and mortar

4.3.5.5.1 Strength-Compressive and flexural strength gain characteristics of concrete containing slag cement can

vary over a wide range. The extent to which slag cement affects strength depends on the slag activity index of the

particular slag cement and the fraction in which it is used in

the mixture. The activity index is the ratio of the compres

sive strength of a mortar cube made with a 50 percent slag cement blend to that of a mortar cube made with a refer

ence cement. Compared with portland-cement concrete, the use of Grade 1 20 slag cement typically results in reduced

strength at early ages ( 1 to 3 days) and increased strength at later ages (7 days and beyond) (Hogan and Meuse! 198 1 ). The use of Grade 1 00 slag cement results in lower strengths

at early ages ( 1 to 2 1 days) but equal or greater strength at later ages. Grade 80 slag cement typically gives reduced



strength at early ages, although, by the 28th day, the strength

may be equivalent to or slightly higher than a 1 00 percent portland cement mixture.

4.3.5.5.2 Modulus of rupture (MOR)-Of particular interest is the effect of slag cement for concrete that is

tested for flexural strength MOR. If comparisons are made

between concrete with and without slag cement, where the slag cement is used at proportions designed for greatest

strength, the blends generally yield higher MOR at ages

beyond 7 days (Fulton 1 974; Malhotra 1 980; Hogan and Meusel 198 1 ).

This is believed to be a result of the increased density of the paste and improved bond at the aggregate-paste interface.

4.3.5.5.3 Creep and shrinkage-Published data on creep

and shrinkage of concrete containing slag cement indicate somewhat conflicting results for comparison with concrete

containing only portland cement. These differences are

likely to be affected by differences in maturity and char

acteristics of the portland cement from which the concrete

specimens were made. Overall, the published information suggests that drying shrinkage is similar in portland-cement

concrete and concrete containing slag cement.

4.3.5.5.4 Color-Slag cement is considerably lighter in

color than most portland cement and will produce a lighter

color in concrete after curing. In certain operations, up to 30 percent slag cement has been used to replace white portland

cement without a noticeable color difference in the cured

product. 4.3.5.5.5 Permeability-The use of slag cement in

hydraulic structures is well documented. The permeability

of mature concrete containing slag cement is much lower

than that of concrete not containing slag cement (Hooton and Emery 1 990; Roy 1 989; Rose 1 987) . As the slag cement

content is increased, permeability of the concrete decreases. 4.3.5.5.6 Resistance to sulfate attack-Partial replacement

of portland cement with slag cement improves the sulfate

resistance of concrete. High resistance to sulfate attack has been demonstrated where the slag cement proportion exceeds 50 percent of the total cementitious material where Type II cements was used (Hogan and Meusel 1 98 1 ) .

4.3.5.5. 7 Reduction of expansion due to alkali-silica reaction-The use of slag cement as a partial replacement for portland cement is known to reduce the potential expansion

of concrete due to ASR (Bakker 1 980; Hogan and Meuse! 1 98 1 ) .

Results of tests using slag cement as a partial replacement

for high-alkali cement with aggregate known to exhibit alkali-silica and alkali-carbonate reactions were reported

by Soles et a!. ( 1 989). After 2 years of observation, the slag

cement blends were found to be effective in reducing expansion, but the reduction was less than that found with the lowalkali cement. Used in combination with high-alkali cement, blends of 50 percent slag cement appear to be effective in

reducing the potential of A SR.

4.3.5.5.8 Resistance to freezing and thawing-Many studies related to freezing-and-thawing resistance have

been made using concrete containing slag cement. Results of these studies generally indicate that where concrete

made with slag cement (ASTM C989/C989M) was tested in comparison with Type I and Type II cements, they are

the same (Fulton 1974; Klieger and Isbemer 1 967; Mather 1 957).

4.3.5.5.9 Resistance to deicing chemicals-Although

some laboratory tests with Type IS cement indicate less

resistance to deicing salts, many researchers have found, in field exposure, little difference compared with concrete not containing slag cement (Klieger and Isberner 1 967). Similar

results were reported using blends of 50 percent slag cement and 50 percent portland cement (Hogan and Meuse! 1 98 1 ),

or slag cement percentages in excess of 35 percent (Afrani and Rogers 1 994) .

4.3.5.6 Silica fume

4.3.5.6.1 Introduction-Silica fume-a by-product of the ferrosilicon industry-is a highly pozzolanic material

that is used to enhance mechanical and durability properties of concrete. Silica fume is a very fine noncrystalline

silica (more than 95 percent of the particles are less than 1

11m) produced in electric arc furnaces as a by-product of the production of elemental silicon or alloys containing silicon. Silica fume can be added directly to concrete as an individual

ingredient or in a blend of portland cement and silica fume. In the United States, silica fume is used predominantly to

produce concrete with greater resistance to chloride penetration for applications such as parking structures, bridges, and

bridge decks. Silica fume is normally not used in paving

applications because of cost and availability of other supplementary cementitious materials. It has been used in curb and

gutter applications to improve durability and by the U.S.

military for roads and airfields in the Middle East since the

mid- 1 990s. Silica fume was initially viewed as a cement replacement

material, but currently the most important reason for its use is

the production of high-performance concrete, where adding silica fume provides enhancements in concrete properties.

In this role, silica fume has been used to produce concrete with enhanced compressive strength and very high levels of durability.

Because of the fineness of the material, adding silica fume

to concrete mixtures usually increases water demand. To

produce high-performance, durable concrete, it is necessary to maintain (or decrease) the w/cm. Consequently, high

range water-reducing admixtures (HRWRAs), sometimes combined with water-reducing admixtures (WRAs), are

used to obtain the required performance and workability.

Silica-fume concrete will be more cohesive than ordinary concrete; consequently, a somewhat higher slump will

normally be required to maintain the same apparent degree

of workability. 4.3.5.6.2 Effects of silica fume on properties of fresh

concrete 4.3.5.6.2.1 Color-Most silica fumes range from light to

dark gray. Because Si02 is colorless, the color is determined

by the nonsilica components, which typically include carbon and iron oxide.

In general, the higher the carbon content, the darker the silica fume. Silica fume is typically used in amounts between



5 and 10 percent by mass of the total cementitious material (Kosmatka et al. 2002).

4.3.5.6.2.2 Water demand-The water demand of concrete

containing silica fume increases with increasing amounts of silica fume (Carette and Malhotra 1 983 ; Scali et al. 1 987) .

Primarily, the high surface area of the silica fume causes this

increase. To achieve a maximum improvement in strength and durability, silica-fume concrete should contain a WRA,

HRWRA, or both. The dosage of the HRWRA will depend

on the amount of silica fume and the type of HRWRA used (Jahren 1 983).

4.3.5.6.2.3 Workability-Fresh concrete containing silica

fume is more cohesive and less prone to segregation than

concrete without silica fume. As the silica fume content is

increased, the concrete becomes sticky. 4.3.5.6.2.4 Slump loss-The presence of silica fume by

itself will not significantly change the rate of slump loss of a given concrete mixture. The slump loss of silica-fume

concrete will be determined by the presence and character

istics of a WRA or HRWRA, or by any of the other factors

that affect slump loss of any concrete, such as high cement

temperature, high concrete temperature, or failure to account

for aggregate moisture correctly. Trial batches conducted at conditions simulating the concrete placing environment

using project materials are recommended to establish slumploss characteristics for a particular situation.

4.3.5.6.2.5 Time of setting-Experience indicates that

the time of setting is not significantly affected by the use of silica fume by itself. The chemical admixtures typically

used in silica-fume concrete may affect the time of setting of

the concrete. Practical control of the time of setting may be

achieved by using appropriate chemical admixtures. 4.3.5.6.2.6 Segregation-Concrete containing silica fume

normally does not segregate appreciably because of the fineness of the silica fume and the use of HRWRA. Segregation

can occur in many types of concrete, including those (with

or without silica fume) with excessive slump, improper proportioning, improper handling, or prolonged vibration. The use of silica fume will not overcome poor handling or

consolidation practices.

4.3.5.6.2.7 Bleeding and plastic shrinkage-Concrete

containing silica fume shows significantly reduced bleeding. As silica fume dosage is increased, bleeding will be reduced. This effect is caused primarily by the high surface area of

the silica fume to be wetted; there is very little free water left

in the mixture for bleeding (Grutzeck et al. 1 982) . Plastic

shrinkage cracks occur if the rate of water evaporation from the concrete surface exceeds the rate at which water appears

at the surface due to bleeding, or if water is lost into the

subgrade. Because silica-fume concrete exhibits significantly reduced bleeding, the potential for plastic-shrinkage

cracking is increased. 4.3.5.6.2.8 Air entrainment-The dosage of air-entraining

admixture to produce a required volume of air in concrete

usually increases with increasing amounts of silica fume. Typically, the increase in air-entraining admixture will be

approximately 1 25 to 1 50 percent of that used in similar concrete without silica fume. This increase is attributed to

the very high surface area of silica fume and possibly to the effect of carbon where the latter is present (Carette and Malhotra 1983) .

4.3.5.6.3 Effects of silica fume on mechanical properties of concrete-The effects of silica fume on the properties of

hardened concrete can be directly related to the physical and chemical mechanisms by which silica fume functions. The primary changes in the concrete are in pore structure, cement

paste-aggregate transition zone, and chemical composition,

particularly the content of calcium hydroxide and alkalinity of the pore solution.

Many of the improvements in mechanical properties appear to be related to improvements in bond strength

between the paste and aggregate. Therefore, the influence

of the aggregate properties on the mechanical properties of concrete becomes more important in silica-fume concrete.

The size, durability, and engineering properties (strength, modulus of elasticity, Poisson's ratio) become important

factors to consider in selecting the appropriate aggregate for

the concrete. 4.3.5.6.4 Effects of silica fume on durability of concrete

Durability is a complex subject, and a number of mechanisms

can be involved in the degradation of concrete, concerning

both the transport of substances into and out of concrete

and the effect of these substances on the concrete. The most important reason for using silica fume is its contribution to

improved durability in concrete. Overall, silica fume can

improve the durability of conventional concrete by: a) Reducing rates of transport of aggressive fluids through

the pore structure b) Reducing the rate of chloride-ion ingress

c) Providing equal or improved resistance to freezing and thawing, as well as to deicer scaling

d) Improving chemical attack resistance e) Improving erosion and abrasion resistance f) Providing similar fire resistance

g) Improving resistance to deleterious expansion due to ASR

h) Improving sulfate resistance i) Increasing electrical resistivity

4.3.5.6.5 Silica-fume concrete and cracking-Silica-fume

concrete is usually high strength and has a low w!cm. Such concrete can be susceptible to two basic types of cracking.

First, there is early-age cracking relating to the material itself and to construction practices. This form of cracking is

reasonably well understood, and appears to be controlled by

adopting appropriate construction practices. Second, there is later-age cracking that is apparently related to performance

under load. This form of cracking is not well understood.

4.3.5.7 Natural pozzolans-Volcanic ash and calcined

clays exhibit pozzolanic properties and have been used in

construction for centuries. These materials, termed "natural pozzolan," are specified using ASTM C61 8. In North

America, natural pozzolan has been used in public works

construction since the early part of the twentieth century. Volcanic ash is available in the western part of the United

States, but the most common natural pozzolans are calcined clay, calcined shale, and metakaolin. To make metakaolin,



high-purity kaolin clay is calcined at a low temperature. The

product is ground to a particle size of 1 to 2 micrometers. Metakaolin is used in special applications where concrete

having a very low permeability or very high strength is needed. Typical addition rates are approximately 1 0 percent

of the cement mass.

4.3.6 Water-Water quality is a concern because chemicals in it, even in very small amounts, sometimes change the

setting time of the mixture on the long-term performance

of the concrete. Almost any drinkable water can be used to make concrete. Treated city water (tap water) from almost

all major cities in the United States and Canada are suitable for making concrete. Some water that is not drinkable

most notably, recycled water from concrete production

and other industrial processes-is used for mixing water. ASTM C 1602/C 1 602M provides detailed requirements for

mixing water and provides procedures for testing water to ensure that it is suitable for use. Compressive strength of

concrete made with the nonpotable source proposed for the

job must not be less than 90 percent of the strength of the same concrete made with potable or distilled water and the

time of set must be no more than 1 hour earlier to 1 hour and

30 minutes later than the comparison concrete. If water from concrete production is recycled, the density of the recycled

water must be monitored daily. ASTM C 1 602/C 1 602M also contains maximum concentration requirements for chlo

rides, sulfate, alkalis, and total solids.

4.3. 7 Chemical admixtures 4.3.7.1 Introduction-Admixtures are typically used to

modify the properties of concrete so that it will be more suit

able for a particular purpose. Their use to obtain desirable

characteristics should be based on appropriate evaluation of their effects on specific combinations of materials and on

economic considerations. Air-entraining and water-reducing admixtures are commonly used in concrete for paving.

Consult ACI 2 1 2.3R if considering admixture use in

concrete. Experience records on use of specific admixture

with concreting materials commonly used in the area should also be considered. If admixtures are required by the general specifications, or permitted by the engineer, they should

conform to the appropriate specifications:

a) ASTM C260/C260M; AASHTO M 1 54 (air-entraining admixtures)

b) ASTM C494/C494M; AASHTO M 1 94 (waterreducing/set-controlling admixtures)

c) ASTM D98; AASHTO M 1 44 (calcium chloride)

NCHRP Report 578 (Nagi et a!. 2007) contains helpful information on the use and selection of air-entraining

admixtures.

Air-entraining admixtures should be used to improve durability and workability. Water-reducing admixtures may reduce total water content and w!cm, thus increasing compressive strength, flexural strength, and durability, and

decreasing permeability, shrinkage, and creep. Some admix

tures accelerate the time of setting of concrete, permitting earlier finishing, removal of forms, and opening of lanes

to traffic, as well as reduce the time of protection from freezing during cold weather. Others can retard the time of

setting of concrete where rapid setting is undesirable. Many

retarding admixtures accelerate strength gain once initial set is attained.

Admixtures are tested for one or more reasons: 1 ) Determination of their compliance with specifications

2) Evaluation of the effect of admixture on the proper

ties of concrete to be produced with job materials under the anticipated ambient conditions and construction procedures

3) Determination of the uniformity of product

Although ASTM tests afford a valuable screening procedure for selection of admixtures, continuing use of admix

tures in production of concrete should be preceded by testing that allows observation and measurement of the performance of the chemical admixture under concrete plant

operating conditions in combination with concrete-making materials then in use. Uniformity of results is as important as

the average result with respect to each significant property of the admixture or the concrete.

Although specifications deal primarily with the influence

of admixtures on standard properties of fresh and hardened concrete, the concrete supplier, contractor, and owner of

the construction project are interested in other features of

concrete construction. Of primary concern may be workability, placing and finishing qualities, and early strength

development. These additional features are often of great importance when determining the selection and dosage rate

of an admixture.

4.3.7.2 Cost effectiveness-Economic evaluation of any given admixture should be based on the results obtained

with the particular concrete in question under conditions simulating those expected on the job. This is highly desir

able because the results obtained are influenced by the characteristics of the cement, supplementary cementitious mate

rials and aggregate, as well as their relative proportions, temperature, humidity, and curing conditions.

Water-reducing and set-retarding admixtures permit

placement of large volumes of concrete over extended periods, thereby minimizing the need for forming, placing,

and joining separate units. Accelerating admixtures reduce finishing and forming costs.

4.3.7.3 Other considerations-Careful attention should be

given to the instructions provided by the manufacturer of the admixture. The effects of an admixture should be evaluated

as possible by use with the particular materials and conditions of use intended. Such an evaluation is particularly

important if: 1 ) the admixture has not been used previously

with the particular combination of materials; 2) special types of cement are specified; 3) more than one admixture is to

be used; and 4) mixing and placing is done at temperatures

well outside generally recommended concreting temperature ranges.

Furthermore, note that: 1 ) a change in type or source of cement or amount of cement, or a modification of aggregate

grading or mixture proportions, may be desirable; 2) many

admixtures affect more than one property of concrete, sometimes adversely affecting desirable properties; 3) the effects

of some admixtures are significantly modified by such factors as water content and cement content of the mixture,



by aggregate type and grading, and by type and length of mixing.

Admixtures that modify the properties of fresh concrete

can cause problems through early stiffening or undesirable retardation that prolong the time of setting. The cause of

abnormal setting behavior should be determined through

studies of how such admixtures affect the cement to be used; early stiffening often is caused by changes in the

rate of reaction between C3A and sulfate. Retardation can

be caused by an overdose of admixture or by a lowering of ambient temperature, both of which delay the hydration of

the calcium silicates.

Table 4.3.8-Typical natural aggregate properties

Property Natural aggregate

Particle shape and texture Well rounded, smooth (gravels) to

angular and rough (crushed stone)

Absorption capacity 0.8 to 3 .7 percent

Specific gravity 2.4 to 2.9

L.A. abrasion test mass loss 15 to 3 0 percent

Sodium sulfate soundness mass 7 to 21 percent

loss

Magnesium sulfate soundness 4 to 7 percent

mass loss

Chloride content 0 to 2 lb/yd3 (0 to 1 .2 kg/m3)

4.3.8 Aggregates-Aggregates for pavement concrete procedures consider the proportions of coarse and fine should conform to the quality requirements of ASTM C33/ aggregates without specifying the combined or total grading. C33M, or applicable state department of transportation spec- Consequently, concrete producers draw aggregate from two ifications. If lightweight aggregate sand (LWAS) is specified stockpiles at the plant site: one for coarse aggregate and one for internal curing, aggregates for pavement concrete should for fine aggregate. To improve aggregate grading, additional conform to the quality requirements of ASTM C33/C33M intermediate sizes of material (blend sizes) at the plant site and C330/C330M, considering that the minus 1 00 and 200 during project construction may be required. sizes of ASTM C330/C330M material are pozzolanic in Grading data indicate the relative composition of aggre-action. For evaluating potential reactivity of an aggregate, gate by particle size. Sieve analyses of source stockpiles methods are provided in the appendix of ASTM C33/C33M. are necessary to characterize the materials . The best use of Following the recommendations in ACI 20 1 .2R can reduce such data is to calculate the individual proportions of each the danger of aggregate-alkali reactivity distress. aggregate stockpile in the mixture to obtain the designed

A number of recycled and industrial by-product mate- combined-aggregate grading. Well-graded mixtures gener-rials (RIBMs) are becoming attractive for use in pavement ally have a uniform distribution of aggregates on each construction from a sustainability perspective. Some of sieve. An optimum combined-aggregate grading efficiently these materials include recycled concrete aggregate, recy- uses locally available materials to fill the major voids in cled asphalt pavement (RAP), air-cooled blast-furnace slag the concrete to reduce the need for mortar. One approach (ACBFS), steel furnace slag, and foundry sand. However, to evaluate the combined-aggregate grading is to assess the these materials possess properties that are different from percentage of aggregates retained on each sieve (Shilstone natural aggregates, so they should be adequately charac- and Shilstone 2002) . A grading that approaches the shape of terized and carefully evaluated before incorporating into a bell curve on a standard grading chart indicates an optimal a construction project. In general, recycled materials to be distribution, as shown in Fig. 4.3 .8 . 1 (a). Blends that leave a used as aggregate for pavement concrete should meet the deficiency of aggregates retained in the No. 8 through No. same requirements as virgin aggregate materials, unless the 30 (2.36 through 0.6 mm) sieves are gap-graded mixtures, lower-quality recycled material is used in the lower layer of shown in Fig. 4 .3 . 8 . 1 (b). a two-course pavement. There is a definite relationship between aggregate grading

Laboratory tests on aggregates depend on the poten- and concrete strength, workability, and long-term durability. tial modes of deterioration, but should include absorption, Intermediate-size aggregates fill voids typically occupied specific gravity, abrasion resistance, and soundness; some by less-dense cement paste and thereby optimize concrete typical values are given in Table 4.3.8 . More detailed infor- density. Increasing concrete density in this manner results in: mation can be found in ACI 22 1 . 1R. a) Reduced mixing water demand and improved strength

4.3.8.1 Gradation-The desired gradation limits for the because less mortar is necessary to fill space between project should be stipulated, along with permissible day- aggregates to-day variations within the specification limits. To avoid b) Increased durability through reduced avenues for water segregation, coarse aggregates should be furnished in at penetration in the hardened concrete least two separate sizes, with the separation at the 0.75 in. c) Better workability and mobility because large aggre-( 1 9 mm) sieve if combined material graded from No. 4 to gate particles do not bind in contact with other large particles 1 - 1 12 in. (4.75 to 37.5 mm) nominal maximum size (or 2 under the dynamics of finishing and vibration in. [50 mm] maximum size) is specified, and at the 1 in. (25 d) Less edge slump because of increased particle-to-mm) sieve if combined material graded from No. 4 to 2 in. particle contact (4.75 to 50 mm) nominal maximum size (or 2- 1 /2 in. [63 Well-graded aggregates also influence workability and mm] maximum size) is specified. If the nominal maximum ease the placing, consolidating, and finishing of concrete. size of coarse aggregate is 1 in. (25 mm) or less, such separa- While engineers traditionally look at the slump test as a tion is not necessary. measure of workability, it does not necessarily reflect that

Consideration of grading and aggregate particle shape characteristic of concrete. Slump evaluates only the fluidity may optimize early and long-term concrete strength. Typical of a single concrete batch and provides a relative measure

American Concrete Institute- Copyrighted© Material- www.concrete.org cCiC'iJ Licensed to: Florida Suncoast Chapter


� �

Individual Percent Retained

18 ,--,,-.-.. �--,--,---:--:--:--:--:�======� 16

14

12

10

25

20

15

10

' '

50mm = 2" 37.5mm = 1-1/2" 25.0mm = 1 " 19.0mm = 3/4" 12.5mm = 1/2" 9.50mm = 318" 4.75mm = #4 2.36mm = #8 1.18mm =#16 0.600mm = #30 0.300mm = #50 0.150mm = #100 0.075mm = #200

H , r: ::=:: :-r ' : :

: : 1-1ir l_31_· •• -1;-2" l'--.. l._-.. ,i,----,-i.1::-6 -:::#3::-0 ---:.;;;50:--;#;;;;10:;;-0 -;.;;;;20;;;-0 -------2.. 1.. lis" Sieve Size

(a) well graded

Individual Percent Retained

#16 #30 #50 #100 #200 1" Sieve Size

(b) gap graded

50mm = 2" 37.5mm = 1-1/2" 25.0mm = 1 " 19.0mm = 314" 12.5mm = 1/2" 9.50mm = 318" 4.75mm = #4 2.36mm = #8 1.18mm = #16 0.600mm = #30 0.300mm = #50 0.150mm = #100 0.075mm = #200

Fig. 4.3. 8. 1-Well graded versus gap graded (Missouri Department of Transportation (MoDOT) 2005).

of fluidity between separate concrete batches of the same

mixture proportions. Concrete with a well-graded aggregate often will be much

more workable at a low slump than a gap-graded mixture

at a higher slump. A well-graded aggregate may change

concrete slump by 3- 1/2 in. (90 mm) over a similar gapgraded mixture. This is because approximately 540 to 650

lb/yd3 (320 to 3 85 kg/m3) less water is necessary to main

tain mixture consistency than is necessary with gap grading (Shilstone and Shilstone 2002).

AlthoughASTM C33/C33M and C330/C330M are acceptable specifications, Table 5 .4 . 1 in ACI 302. 1 R-96 recom

mends preferred grading specifications for the toppings for

Class 7 floors. These gradations limit the amount of material passing the No. 50 and No. 1 00 (300 and 1 50 �m) sieves

to reduce the amount of cement paste needed. However, ACI 302. 1 R-96 cautions that where fine aggregates contain

minimum percentages of material passing the No. 50 and No. 1 00 (300 and 1 50 �m) sieves, the likelihood of excessive bleeding is increased and limitations on water content

of the mixture become increasingly important. Natural sand

is preferred to manufactured sand (which can increase the harshness of the mixture and make it very difficult to work);

the gradation indicated in Table 5 .4. 1 in ACI 302 . 1 R-96 will

minimize water demand. For lightweight fine aggregates

(governed by ASTM C330/C330M), the material passing

the No. 1 00 and No. 200 ( 1 50 and 300 �m) are usually

pozzolanic in nature and improve the characteristics of the

concrete. The use of large aggregate is generally desired for lower

water demand and shrinkage reduction. However, it is

important to recognize the overall gradation of all the aggregate. According to ACI 302. 1 R-96, gradations requiring

between 8 and 1 8 percent for large top-size aggregates (such as 1 - 1 /2 in. [37.5 mm]) or 8 and 22 percent for smaller topsize aggregates (such as 1 in. or 0.75 in. [25 or 1 9 mm])

retained on each sieve below the top size and above the No. 1 00 ( 1 50 �m) sieve have proven to be satisfactory in

reducing water demand while providing good workability. It is recommended that the ideal range for No. 30 and No.

50 ( 600 and 300 �m) sieves be 8 to 1 5 percent retained on

each, and often, a third aggregate is required to achieve this gradation.

Typically, 0 to 4 percent retained on the top size sieve and 1 .5 to 5.0 percent on the No. 1 00 ( 1 50 �m) sieve will be a

well-graded mixture. This particle size distribution is appro

priate for round or cubically shaped particles in the No. 4

through No. 1 6 (4.75 mm through 1 . 1 9 mm) sieve sizes. If the available aggregates for these sizes are slivered, sharp,

or elongated, 4 to 8 percent retained on any single sieve is a reasonable compromise. Mixture proportions should be

adjusted where individual aggregate grading varies during

the course of the work.

4.3.8.2 Particle shape and texture-The shape and texture

of aggregate particles impact concrete properties. Sharp and

rough particles generally produce less-workable mixtures than rounded and smooth particles with the same w/cm. Particle shape and texture are important to the response of

the concrete to vibration, especially in the intermediate sizes.

The bond strength between aggregate and cement mortar improves as aggregate texture becomes rougher. The improved bond will improve concrete flexural strength, and

is the result of increased mechanical interlock. Concrete

mixtures containing natural coarse aggregates and natural sands are easily consolidated, and cube-shaped crushed

aggregates are also more easily consolidated than flat or elongated aggregate. The good mobility allows concrete to

flow easily around the baskets, chairs, and reinforcing bars,

and is ideal for pavements.

Flat or elongated intermediate and large aggregates can cause mixture problems. These shapes generally require more mixing water or fine aggregate for workability and,

consequently, result in a lower concrete flexural strength,

unless more cementitious materials are added. Allowing no more than 1 5 percent flat or elongated aggregate by weight of

the total aggregate is advisable. Use ASTM D479 1 to determine the maximum quantity of flat or elongated particles.

4.3.8.3 Durability 4.3.8.3.1 Alkali-aggregate reactivity-In many parts of

the world, precautions should be taken to avoid excessive

expansion due to alkali-aggregate reactivity (AAR) in many types of concrete construction. Alkali-aggregate reactivity



may involve siliceous aggregates (such as ASR) or carbonate

aggregates (alkali-carbonate reactivity [ACR]); failure to take precautions may result in progressive deterioration,

requiring costly repair and rehabilitation of concrete structures to maintain their intended function. Extensive knowl

edge is available regarding the mechanisms of the reactions,

the aggregate constituents that may react deleteriously, and precautions that can be taken to avoid resulting distress. As

a result of extensive research, concrete structures can now

be designed and built with a high degree of assurance that excessive expansion due to AAR will not occur and cause

progressive degradation of the concrete. 4.3.8.3.2 Alkali-silica reactiviry-Alkali-silica reactivity

was first recognized in a California concrete pavement by

Stanton ( 1 940) of the California State Division of Highways. Stanton's early laboratory work demonstrated that

expansion and cracking resulted if certain combinations of high-alkali cement and aggregate were combined in mortar

bars stored in containers at very high relative humidity. Two

important conclusions were drawn from this work: 1 ) Expansions resulting from ASR in damp mortar bars

were negligible where alkali levels in cement were less than

0.60 percent, expressed as equivalent sodium oxide (percent Na20e = percent Na20 + 0.658 percent K20).

2) The partial replacement of high-alkali cement with a

suitable pozzolanic material prevented excessive expan

sions. Replacement of a portion or all of a normalweight,

nonreactive sand with lightweight (expanded shale) sand can reduce the ASR in concretes containing a known, reac

tive, normalweight coarse aggregate (Boyd et a!. 2000).

Thus, foundations for the engineering control of the reac

tion were developed. Test methods currently in use to determine potential for expansive reactivity, particularly in the United States, were derived primarily from work carried

out in the 1 940s. However, recent research efforts in several

countries indicate a promise of newer, more reliable tests to

identify potentially deleteriously reactive cement-aggregate combinations. Common aggregates that could be susceptible

to ASR include chert, shale, and rhyolite. 4.3.8.3.3 Alkali-carbonate reactiviry-Alkali-carbonate

reactivity was identified as causing a type of progressive

deterioration of concrete by Swenson ( 1 957) of the National Research Council of Canada. He found that an alkali

sensitive reaction had developed in concrete containing argillaceous calcite dolomite aggregate that appeared to

be different than the ASR. Because rock susceptible to this

type of reaction is relatively rare and often unacceptable for use as concrete aggregate for other reasons, reported occur

rences of deleterious ACR in actual structures are relatively

few. The only area where it appears to have developed to any great extent is in southern Ontario, Canada, in the vicinities

of Kingston and Cornwall. Isolated occurrences in concrete structures have been found in the United States in Indiana,

Kentucky, Tennessee, and Virginia. So-called alkali-dolo

mite reactions involving dolomitic limestone and dolostones have also been recognized in China (Tang et a!. 1 996) . Addi

tional information on AAR and ways to mitigate it can be found in ACI 2 1 1 . 1 .

4.3.8.4 D-cracking-D-cracks are a series of cracks in

concrete near and roughly parallel to joints, edges, and structural cracks. D-cracking is commonly associated with

distress due to freezing and thawing of critically saturated

aggregate particles in concrete pavements. Three conditions are necessary for D-cracking to occur:

a) The aggregate should be susceptible to D-cracking;

such aggregates that have weakened planes and deleterious pore size

b) Pavement joints are poorly drained, making moisture available

c) The pavement should be subj ect to freezing and thawing

D-cracking can be prevented by using nonporous aggregate or reducing the top size of the aggregate (Schwartz 1 987).

4.3.8.5 Recycled aggregates-Disposal of exiting concrete pavements is often a problem faced on many pavement

reconstruction projects. Recycling concrete, as an aggregate product, is encouraged by the Federal Highway Adminis

tration (FHWA 2002) Policy Memorandum and is common

practice by many public and private organizations. Removed concrete pavement can be processed into aggregate product

for use as granular or stabilized base, subbase, or shoulder

materials. It can also be processed into aggregate material used for bedding, backfill, granular embankment, and

aggregate for asphalt or hydraulic-cement concrete. Specific guidelines for use of recycled concrete pavement as aggre

gate in hydraulic-cement concrete pavement can be found in

FHWA Technical Advisory T 5040.37 (FHWA 2007a). In general, the recycled materials used for concrete paving

projects should meet the same quality requirements normally

used for virgin aggregates. Although recycling demonstrates

good environmental stewardship and can reduce the cost of a paving project, economic and environmental costs are

different for each project. 4.3.9 Rapid-setting concrete mixtures 4.3.9.1 Introduction-For the most part, early-opening-to

traffic (EOT) concrete is composed of the same constituents as normal paving concrete. Coarse and fine aggregates are

blended with hydraulic cement, water, and admixtures to produce a stiff but moldable mass that hardens by hydration.

In the resulting stone-like mass, the aggregates have been

bound together by the hydration products formed through chemical reactions between the water and cement. Air is

also entrapped, entrained, or both, typically making up 5 to 7 percent of the total mixture volume (NCHRP 2005).

The emerging technology is to use HPC, with a wlcm of 0.33 to 0.43 , usually at ±0.38 . This is an opportunity for the contractor using internal curing to place the concrete in

service sooner.

4.3.9.2 Cement-ASTM C l 50/C l 50M Types I, II, or III portland cement can produce successful accelerated paving

mixtures. Certain ASTM C595/C595M blended cements, ASTM C l 1 57/C l 1 57M cements, rapid-setting hydraulic

cements meeting ASTM C l 600/C l 600M, and several

proprietary cements that develop high early strengths can also be useful for accelerated paving applications. Not

every portland cement will gain strength rapidly, however, and testing is necessary to confirm the applicability of



each cement. The materials engineer and contractor should

be aware of these phenomena in testing mixtures and trial batches. Tests should be conducted using the same cement

that the contractor will use in construction. 4.3.9.3 Cement factor-The cement factor (or cement

content) of EOT concrete is typically much higher than that

used in conventional paving concrete. These high cement factors contribute to increased paste porosity, as reflected in

an increase in percent of permeable voids, absorption, and

sorptivity. Further, the increase in paste volume increases the amount of shrinkage, potentially producing more cracking

and reducing durability of the mixture. This suggests that increasing cement content will not necessarily improve the

early or long-term strength of the EOT concrete. Instead,

other methods of increasing early strength, such as lowering the w/c and internal curing, are likely to be more effective. Therefore, mixtures with lower cement contents, as well as those with corresponding higher aggregate volumes, should

be investigated for use in EOT concrete (NCHRP 2005).

4.3.9.4 w/cm-Decreasing the w!cm of the mixture (over the range of 0.43 to 0.33) will increase the various measures

of strength at all ages of testing, decrease absorption, and

improve paste homogeneity with no observed disadvantages other than increasing autogenous shrinkage, as long as

workability is maintained. It is therefore advantageous both from the perspective of strength gain and durability to use a w/

em at or below 0.40 for 6- to 8-hour EOT concrete mixtures,

although a slightly higher w/cm appears to be acceptable for 20- to 24-hour EOT concrete mixtures.

4.3.9.5 Accelerating admixtures-Accelerating admixtures, which are also called accelerators (Type C or E) in

AASHTO M 1 94 are common in EOT concrete, profoundly affecting strength gain and, potentially, durability. Although

calcium chloride is the most common accelerator used in concrete, it promotes corrosion of embedded steel and could have other adverse impacts on concrete durability. Calcium

nitrite is the most common nonchloride accelerator used in concrete (NCHRP 2005).

4.3.9.6 Water reducer-Water reducers (AASHTO M 1 94 Type A, Type E, and Type F) are often used in 6- to 8-hour

EOT concrete mixtures and occasionally 20- to 24-hour EOT

concrete mixtures to assist in producing workable concrete at low w/cm. The use of the Type F HRWRs may negatively

impact the air-void system parameters, creating a network of rather large bubbles with insufficient spacing factors, thus

compromising the freezing-and-thawing performance of the

concrete (Whiting and Nagi 1 998). Various water-reducing admixtures are available for use in EOT concrete; it is

impossible to categorize their interaction with other concrete

constituents. However, the final selection of the waterreducing admixture should be done only after testing the job

mixture, including evaluation of the impact on both strength and durability characteristics. This testing is of particular

importance if HRWRs are being considered, as difficulties

have been reported in obtaining satisfactory air void systems in mixtures containing Type F HRWRs (NCHRP 2005).

4.3.9.7 Coarse aggregate-The type of coarse aggregate used affects concrete density and coefficient of thermal

expansion (CTE). The coarse aggregate can also impact

some strength properties of the mixtures and scaling resistance. Thus, care should be exercised in selecting coarse

aggregate that will provide both the desired strength and the durability properties (NCHRP 2005).

4.4-Reinforcement, dowels, and tie bars The desired types of reinforcing steel and accessories

should be specified in accordance with the following appli

cable specifications. 4.4.1 Steel wire fabric reinforcement-Steel wire fabric

reinforcement should conform to ASTM A1064 or ASTM A884/ A884M.

4.4.2 Bar mats (ASTM A l84/AJ84M)-Member size and

spacing should be shown on the plans. All intersections of longitudinal and transverse bars should be securely wired,

clipped, or welded together in the plant of the steel supplier. 4.4.3 Reinforcing bars-Reinforcing bars should conform

to the requirements of one of the standard specifications:

a) ASTM A6 1 5/A6 15M, Grade 40, or Grade 60 b) ASTM A996/A996M

c) ASTM A775/A775M and ASTM A934/A934M specify

materials, surface preparation procedures, and coating requirements for protective epoxy coatings

d) ASTM A955/ A955M specifies requirements for stainless steel materials.

Guidance for the use of fiber-reinforced concrete can be found in ACI 544. 1R.

4.4.4 Surface condition-Reinforcing steel should be free

from dirt, oil, paint, grease, or other organic materials that

may adversely affect or reduce bond with the concrete. Rust,

mill scale, or a combination of both should be considered acceptable provided the minimum dimensions, weight, and

physical properties of a hand-wire-brushed test specimen are not less than the applicable ASTM specification requirements (refer to ASTM A6 1 5/ A6 1 5M, for example).

4.4.5 Tie bars-Tie bars should be deformed steel bars conforming to the requirements of the governing specifica

tions for reinforcing bars except that only grades of steel bars should be used that can be bent and restraightened

without damage if this procedure is indicated. Tie bars may

be inserted in the fresh concrete, placed on chairs ahead of the paver, or drilled into the slab after paving (the latter

case being when separate pavings are made, such as a tied shoulder that is added later).

4.4.6 Dowels--{ASTM A61 5/A6 1 5M) Dowels should

be plain bars conforming to the requirements of the specifications for plain round bars. Dowels should not be burred,

roughened, or deformed out of round in such a manner as to

hinder slippage in the concrete. If expansion caps are used for expansion joints, they should cover the ends of the dowels for

not less than 2 in. (50 mm) or more than 3 in. (75 mm). Caps should be closed at one end, and should provide for adequate expansion and not interfere with proper load transfer. It

should be of such rigid design that the closed end will not collapse during construction. Epoxy coatings are commonly

applied for corrosion protection, although plastic coatings are occasionally used. In addition, several alternative dowel



Table 4.5-Joint sealants and filler materials

Material type Properties Material Common specification

Four types, performance specification ASTM D6690

Field molded Hot applied Elastomeric

Jet-fuel resistant Fed Spec SS-S- 16 14A

Field molded Cold applied

Single component silicone ASTM D5893/05893M

Jet-blast resistant Fed Spec SS-S-200E

Preformed Compression seal Preformed polychloroprene elastomeric seal ASTM 02628

Lubricant for installing compression seals ASTM 02835

Preformed expansion joint Bituminous ASTM 0994/0994M

Filler Preformed expansion joint Nonextruded and resilient bituminous ASTM 0 1 75 1

Preformed joint filler Sponge, rubber, cork, and recycled PVC ASTM D 1 752

bar materials that are either noncorrodible (for example,

fiber reinforced polymer) or have a high resistance to corrosion (for example, stainless steel) are being used by a few

agencies in severe exposure conditions.

4.4.6.1 New developments in load transfer-In addition to round steel bars, there are a number of new materials and

dowel configurations available that may offer some advantages over the traditional round dowel. Elliptical dowels,

plate dowel bars, and tapered plate dowel bars provide

increased bearing surface with a smaller steel cross section and improved joint opening characteristics. Fiberglass-rein

forced polymer dowels can offer adequate load transfer and rider comfort in joints while reducing issues with corrosion.

These dowels are beneficial in areas where metal dowels

would interfere with pavement performance, such as toll booth sensors. Alternative dowels should be designed and

selected to provide equivalent performance to the standard

round dowel size and spacing for a typical pavement thick

ness or for the specific performance criteria of the designer. 4.4. 7 Chairs-Chairs, which are used to support rein

forcing steel, dowels, or tie bars on subbases, should be of adequate strength and designed to resist displacement or

deformation before and during concrete placing. On loose

or sandy bases, chairs should have base plates such that they do not sink into the subgrade under steel or concrete load.

4.4.8 Stakes-Stakes used to support expansion joint fillers should be metal. Their length and stiffness should

be adequate to keep the fillers in proper position during

concrete placement.

4.5-Joint sealants and fillers

Joint sealants are installed in concrete pavements to prevent the entry of water and solid foreign materials into

joints. Joint fillers help to exclude water and debris from the

joint and provide support for sealants applied to the exposed surface; however, sealants should be capable of minimizing

the amount of water that enters the pavement structure and keeping incompressible material out of the joint (FHWA

1 990) . Many types of sealants are available, but the materials fall into one of four general categories; 1 ) mastic; 2)

field-molded thermoplastics; 3) field-molded thermoset

ting materials; and 4) preformed compression seals. Table 4.5 provides an overview of materials and commonly used

specifications. The recommendations found in ACPA ( 1991 ,

1 995) should be consulted for more details on the selection

and use of sealants and fillers.

4.6-Curing materials The specifications should stipulate the type or types

of curing material to be used and require conformance to

the appropriate specification. The general requirements of curing practice as recommended by ACI 308R should be followed.

4.6.1 Burlap-Burlap should be made from jute or keaf

and at the time of use, be in good condition, and be free

from holes, dirt, clay, or any substance that interferes with its absorptive quality. It should not contain any substance that

would have a deleterious effect on the concrete. Additional details can be found in AASHTO M 1 82. Burlap that will not

absorb water readily if dipped or sprayed and that weighs

less than 7 oz/yd2 (240 g/m2) clean and dry should not be used. Burlap made into mats should be handled with care to

avoid marring the finished surface of the concrete.

4.6.2 Waterproof paper and impermeable sheets-Water

proof paper and impermeable sheets should conform to the water retention requirements of ASTM C 1 7 1 .

4.6.3 Liquid membrane-forming compounds-Liquid

membrane-forming compounds should conform to the requirements of ASTM C309. Type 2, white-pigmented

curing compound, is generally preferred for concrete pavements. Type 1 , clear or translucent, and Type 3, light gray

pigmented, are also used.

4.6.4 Fogging-Where there is little or no wind or adequate protection with screens, fogging provides excel

lent protection against surface drying if applied properly and frequently and where the air temperature is well above

freezing. Its primary purpose is to increase the humidity of

the air and reduce the rate of evaporation (ACI 308R). 4.6.5 Internal curing-Internal curing is not a replacement

of burlap, fogging, waterproof paper, or liquid membrane,

but as an adjunct to them, because they do not adequately

supply water into the interior of the concrete and do not

supply water for hydration in low-w/c mixtures. Because it is widely distributed throughout the concrete, lightweight

aggregate sand can supply water to the cement particles

that are not sufficiently hydrated by the mixing water or the external curing water.

CHAPTER 5-CONSTRUCTION

5.1 -Foundation preparation 5.1.1 Introduction-Performance of a concrete pave

ment system is highly dependent on the construction of the



subgrade, subbase, and base layers. Delatte (2008) points

out that there is nothing more expensive than a cheap foundation. The construction team should recognize that the

goal in building the foundation is to insure that the pavement substructure will provide the characteristics the

designer assumed would support the pavement surface. If drainage, uniform strength, or other properties are not

achieved, the long-term performance of the pavement will

be compromised.

5.1.2 Grade preparation-Construction of the subgrade begins with clearing and grubbing, which is the removal of all trees, shrubs, and stumps, along the route. All vegeta

tion should be removed and hauled to a disposal site. Topsoil

removed from the construction area is often stockpiled for

reuse in vegetated areas constructed along the route. Organic

material and poor soil should not be buried in deep fills

where settlement could cause pavement failure. Variations from subgrade materials expected at the site shown in the

construction documents should be reported to the design

agency. Subgrade soils should be compacted at moisture contents and to densities that will ensure stable and uniform

support for the pavement. In areas where there is an abrupt

change in soil type, cross hauling and mixing of soils is often used to achieve uniform support conditions. In cut-and-fill

areas, the better soil types should be placed in the top of the subgrade. Extremely poor soils can be treated with cement,

lime, or replaced with better soil.

The agency and contractor should have contingency plans

in the event that unsuitable soils are encountered during

subgrade preparation. Options include removing unsatisfac

tory material and replacing it with suitable material from

nearby areas, soil stabilization, removing undesirable soil and replacing it with crushed stone, and placing a geogrid

and 10 in. (250 mm) lift of crushed stone over soft areas (Delatte 2008).

Embankments are placed in uniform layers and compacted

to the density specified in the contract documents. Optimum moisture content and maximum dry density for compac

tion can be specified using either the standard proctor test (ASTM D698) or the modified proctor test (ASTM D l 557).

Additional information on subgrade compaction for specific

soil types can be found in Delatte (2008). Special techniques and precautions to control expansive soils and frost heave

can be found in ACPA (2007). 5.1.3 Subbase and base-Terminology relating to subbase

and base used in other types of pavements, airport construc

tion, and concrete highway construction can be confusing. Concrete highways usually have a single layer of subbase

under the concrete pavement. Subbases and bases can be

constructed using untreated, cement-treated, lean-treated, asphalt-treated, and permeable bases. Detailed information

on the construction of each subbase or base type is found in ACPA (2007). Whatever type is used, the final layer under

the concrete surface should be uniform in strength, smooth,

and provide the characteristics assumed by the designer and contained in the job specifications.

5.2-Production, placing, consol idation, and finishing concrete pavement

5.2.1 Introduction-Quality concrete pavement can be constructed using a variety of methods. Today, large paving projects are built using slipform paving machines and

concrete produced at a dedicated site production facility.

Smaller jobs may use concrete from commercial concrete plants and use simple formed construction techniques. The

following section on production applies equally to site and

commercial production roadways, as shown in Fig. 5.2. 1 . Construction discussion will focus on slipform methods,

and information on formed paving construction will be presented.

5.2.2 Concrete production

5.2.2.1 Handling and storing materials-Aggregates should be handled and stored in a manner that minimizes

segregation, degradation, contamination, or mixing different kinds and sizes. A preferred method of stockpiling coarse

aggregates to minimize segregation is construction of the

stockpile in successive horizontal layers not more than 6 ft (2 m) thick, with each layer completed over the entire stock

pile area before the next is started. Successive lifts should

not be allowed to cascade over lower lifts. Radial stacking conveyors can be a great source of segregation. The drop

from the conveyor should be minimized. Stacker discharge should be used to build a windrow, which is then leveled

before the next stockpile lift is added. If operation of hauling

equipment on a stockpile is necessary, boards should cover all ramps and runways on the stockpile, or rubber-tired

vehicles should be used to minimize degradation. Rejected

material can be reprocessed and returned to the stockpile,

provided the reprocessed materials meet the applicable specifications. Use care in removing the aggregates from

the stockpiles to prevent segregation. Information about stockpiling in specific situations is found in ACI 304R and 22 1 . 1R.

Frozen aggregates or aggregates containing frozen lumps

should be thawed before use. Aggregate moisture content

should be reasonably uniform when delivered to the mixer. Wetting of dry aggregates prior to hatching will affect

cooling by evaporation and can, if carefully done, mini

mize moisture variations and reduce excessive absorption of mixing water. Fine aggregates, including those produced

or manipulated by hydraulic methods, should be allowed to drain for at least 1 2 hours before use. Stockpiles, or cars

and barges equipped with seep holes, are considered to offer

suitable opportunity for drainage.

If lightweight aggregate sand is used, it should be saturated surface-dry (SSD) when hatched into the concrete

mixer. It is appropriate to have it delivered to the batch plant

in such condition and to use sprinklers to maintain it at SSD. The hatching sequence should be to batch the lightweight

aggregate sand (LWAS) along with a sizable part of the

water before other ingredients are hatched.

5.2.2.2 Storage of cementitious materials-Cementitious materials should be stored in closed, watertight facilities. If

cement and SCMs are stored in adjacent silos, the common wall should be a double wall with a void that is inspectable



Fig. 5.2. 1-Concrete production plant (courtesy of Jon Mullarky).

between the two storage units. A control system should be in

place to prevent accidental discharge of the wrong material into silos.

5.2.2.3 Storage of admixtures-Admixtures should be stored out of the sun and protected from freezing. Control

systems should be in place to prevent contamination by

discharge from the wrong admixture into a storage tank. 5.2.2.4 Concrete production facilities-Characteristics

and requirements of concrete hatching plants are covered

in more detail in ACI 301 , ASTM C94/C94M, and the

NRMCA Concrete Production Facility Certification Checklist (NRMCA 20 1 5). This guide highlights areas of specific

concern to the contractor and inspection personnel on a

concrete pavement project. Because of the large volumes of concrete consumed in a paving project, most paving plants

are large-volume central mixing plants. Most are highly automated, with the entire hatching cycle controlled by a

computer. Lockouts prevent charging if the material in the

weigh hatcher is out of tolerance. Short mixing times are a necessity. Stationary mixers are able to produce accept

ably uniform concrete in a mixing time between 30 and 90 seconds. If mixer performance information is not available,

ASTM C94/C94M requires a mixing time of 1 minute for

the first yard of capacity plus 1 5 seconds for each additional yard of capacity, that is, a mixer rated as 4 yd3 (3 m3) would

require a mixing time of 1 minute, 45 seconds (ASTM C94/ C94M).

5.2.2.5 Delivery units-Freshly mixed concrete can be

delivered to the paver in truck mixers, agitating units or in non-agitating equipment such as dump trucks. ASTM C94/

C94M requires that the bodies of non-agitating equipment

be smooth, watertight metal containers. Covers are required for protection against inclement weather. Non-agitating

equipment should be capable of delivering concrete to the paving site in a thoroughly mixed and uniform mass, and

discharged with a satisfactory degree of uniformity (ASTM

C94/C94M).

5.2.3 Slipform paving-Slipform paving is a continuous extrusion process used to place, form, consolidate, and finish

concrete pavement. The paving train may include a placer/

spreader, slipform paver, and equipment to texture the pavement surface and apply curing compound. Slipform paving

is most appropriate for larger jobs that require high production rates. Particular characteristics of slipform paving

include (FHWA1996) :

a) Uses low-slump concrete-Low-slump concrete is

necessary so that the fresh concrete is able to hold its shape once the slipform paver has passed. Typically, concrete with

slumps from 1 to 3 in. (0 to 75 mm) are used.

b) High productivity-Large jobs generally require high production rates to maintain schedules and produce a high

quality pavement. Slipform paving production rates are typically in the range of 85 to 450 yd3/h (65 to 1 00 m3/h) for

mainline paving. Paving speed is normally between 1 and 8 ft/min (0.30 and 2.44 m/min) with an optimum speed of 3 to

6 ft/min (0.9 1 and 1 .83 m/min). Airport paving could require

higher production rates. c) Smooth riding surface-Automation and computer

control allow slipform pavers to produce very smooth riding surfaces with international roughness index (IRI) values on

the order of 65 to 75 in./mile ( 1 000 mm/krn).

This section presents concrete placement, consolidation, finishing, and curing as it is typically done in slipform

paving. Most often, on large paving jobs, these steps are

accomplished by three pieces of equipment: 1 ) the placer/ spreader (used for rough placement); 2) the concrete paver,

which is used for final placement, consolidation, and initial finishing; and 3) texturing and curing machines. On smaller

jobs, the placer/finisher may not be included in the paving

train. These machines usually travel together in a series down the length of the project.

5.2.3.1 Placer/spreader-Although not always used, placer/spreaders (Fig. 5.2.3 . 1 ) are common. They place

a metered supply of concrete in front of the paver using a

series of conveyor belts, augers, plows, and strikeoff devices.



Fig. 5.2.3 .1-Placer/spreader (courtesy of University of Washington).

Using a placer/spreader allows the contractor to receive material from transport vehicles, and to place a uniform

amount of concrete in front of the entire paver width, while

minimizing segregation. 5.2.3.2 Paver-The paver performs screeding, consoli

dation, and initial finishing. A typical track-mounted, selfpropelled paver operates at speeds between 3 and 8 ft/min

( I and 2.5 m/min) (FHWA 1 996). The paving machine

obtains line and grade information from a variety of sources, depending on the specific job. Normally, sensors riding

on a string line or wire are used, but sensors on accurately

trimmed foundations or existing pavement may also be used.

Modern electronic positioning systems are also finding use to accurately guide pavers. Some pavers are equipped to posi

tion reinforcing steel if used, and insert dowel bars and tie bars. Figure 5 .2.3.2 shows the basic slipform paving process

as it occurs underneath the paver. First, an auger, plow or

hopper, and strike-off plate spreads and maintains a constant surcharge of concrete above the conforming plate level.

Vibrators consolidate the concrete. The conforming plate

(also called the profile pan) and finishing screed level off the slab at the correct elevation and provide initial finishing.

The remainder of this section describes this process in more detail.

5.2.3.3 Screeding-Slipform pavers, shown in Fig.

5 .2.3 .3 , first use an auger or plow to perform any final mate

rial spreading, and then strike off the concrete at the correct elevation using a simple strike-off plate, or screed.

5.2.3.4 Consolidation-After screeding, the paver consol

idates the fresh concrete using a series of vibrators. Typically, the most effective vibrator position is after the strike

off mechanism at the final slab elevation. Depending on

mixture design and slab depth, vibrators are usually set in

the 6000 to 7000 vibrations per min (VPM) range. Vibrators are positioned next to one another such that their influence

zone overlap is approximately 2 to 3 in. (50 to 75 mm) at normal paver speed (FHWA 1 996). Gap-graded mixtures

could require excessive vibration to consolidate. This exces

sive vibration has been found to cause segregation in some pavements. Excessive slump can also be the cause of segre-

Concrete

Fig. 5.2.3.2-Schematic of slipform paver (courtesy of GOMACO Corp.).

Fig. 5.2.3.3-Slipform side form and profile pan (courtesy of University of Washington).

gation. Each vibrator in the paver has an effective radius of

action over which consolidation occurs; as a minimum, this

is the distance from the vibrator to the top and bottom of the slab. Note that this zone of influence will also be exerted

both ahead and behind the vibrator. A 1 5 in. (38 1 mm) vibrator spacing is effective in most

paving applications. Thinner pavement sections may require

tighter vibrator spacing. Vibrator diameters typically range from 2.25 to 3 in. (58 to 76 mm), with larger top-size aggre

gates possibly requiring the use of larger-diameter vibrators. The vibrator spacing is established during the initial setup

of a paver for a specific project. This spacing cannot be

adjusted during the paving operation. Vibrator banks can be adjusted for height while paving and the VPM of individual

vibrators can be adjusted while paving as well.

5.2.3.5 Initial .finishing-Initial finishing is accomplished by extruding concrete through a moving form made up of

the base course (bottom), the side forms (vertical edges of the paver), and the conforming plate (profile pan). Extruding

concrete through the resulting rectangular shape provides the

final slab dimensions and also serves to imbed larger aggregate particles below the surface, which results in a smooth

finish. Some pavers are also equipped with a hydraulic tamper bar located just behind the vibrators, although a

tamper may not be necessary on many jobs. Although it

forces the coarse aggregate away from the surface to make finishing easier, it can also create a mortar-rich surface layer

that could scale or craze (FHWA 1996; Kohn et a!. 2003).

(ciCIJ American Concrete Institute- Copyrighted© Material- www.concrete.org Licensed to: Florida Suncoast Chapter


Usually, a tamper is not necessary with a well-designed concrete mixture; however, it may be helpful with finishing a harsh, low-slump mixture.

Any hand finishing, as needed, occurs just behind the profile pan and is usually accomplished using a straight

edge, simple floats, or both (FHWA 1 996; Kohn et a!. 2003) .

Proper mixture proportioning and paving train operation should result in a minimum of hand finishing. Micro texturing

is usually accomplished by dragging a section of burlap or

artificial turf behind the paver, as shown in Fig. 5 .2.3 .5 . 5.2.3.6 Texturing and curing machines-Texturing and

curing machines follow the paver; texturing machines are

used to impart texture to the newly paved surface. The tined

rake provides macrotexture necessary to prevent hydro

planing. Although the tining device shown in Fig. 5 .2.3.6 is part of the curing machine, a separate tining machine could

be required if the tining operation delays curing application. Microtexture, which provides braking support, is created

with a turf or burlap drag. Refer to 5 .7.4 for additional information on various concrete pavement surface textures.

Curing is typically done once finishing of an area is

complete and the original wet sheen has nearly disappeared.

On tined pavements, curing is usually specified to occur in two passes, one forward and one in reverse, to ensure both sides of the texture ridges are coated with curing membrane.

5.2.4 Fixed-formed paving-Fixed-form paving requires

the use of wooden or metal side forms that are set up along

the perimeter of the pavement before paving. These side forms are used to hold fresh hydraulic-cement concrete in

place at the proper grade and alignment until it sets and hardens. The following are some general guidance for using

forms (FHWA 1 996): a) Form depth should be equal to concrete slab thickness.

This way, slab elevation can be tightly controlled out to and including the edges.

b) Forms should not move during placement and initial set

of the concrete. c) The top of the form should be straight and true. Speci

fications vary, but generally anything more than 0. 1 2 in. (3

mm) every 10 ft (3 m) is considered excessive.

d) Form ends should be able to lock together. If not, they

could come apart when subject to the hydraulic pressure imposed by the fresh portland-cement concrete (PCC).

e) Forms should be staked as needed so that they do not move during the placement and initial setting of concrete.

f) Forms should be cleaned and oiled before use. Dirty,

unlubricated forms will cause surface defects in the slab sides and could stick to the slab during removal.

g) Curves less than approximately 1 00 ft (30 m) in radius

should be done with flexible forms (for example, wood) or curved metal forms. Above 1 00 ft (30 m), straight 1 0 ft (3 m)

long metal forms can be used to form a sufficiently smooth curve.

5.2.5 Finishing-Finishing is required to close the surface

and correct any minor deficiencies. This initial process is accomplished during strike-off with a screeding device riding

on top of the forms. Hand screeds can be used on small jobs, but on most fixed form paving projects, a vibrating screed

Fig. 5.2.3.5-Turf drag (courtesy of University of Washington).

Fig. 5.2.3. 6-Tining machine (courtesy of University of Washington).

or roller screed are recommended. Internal vibration could

be required to achieve proper consolidation throughout the thickness of the pavement. Immediately following the

strike-off, the concrete surface should be leveled with a bull

float or scraping straightedge. The surface should be finished no more than necessary to remove irregularities. The use of

hand or power floats and trowels is not necessary and is not

recommended, as it may result in surface scaling. Working in conjunction with finishing includes texturing the road

surface to provide for skid resistance, noise mitigation, and

friction resistance. Texturing can be accomplished through a number of means including diamond grinding, transverse

or longitudinal tining, and drag texturing, which is accomplished by dragging a piece of burlap or artificial turf, as

discussed in 5.2.3.6.

5.3-Curing and enhancing characteristics of concrete

5.3.1 Introduction-Curing of concrete is essential

to provide strength and durability to the pavement. For

instance, it has been shown that concrete that is air-cured for 3 days followed by 25 days of moist curing has an 1 1 percent

lower compressive strength than concrete moist-cured for the entire 28 days. (Richardson 1 99 1 ). Durability require

ments include abrasion resistance, freezing-and-thawing and

deicer resistance, and low shrinkage and cracking. Moreover,



effective curing can also help reduce the magnitude of built

in curling. Built-in curling develops due to the presence of a temperature gradient at the time of initial set of the concrete

and can have a large effect on concrete pavement performance (Eisenmann and Leykauf 1 990; Hiller et al. 2004) .

5.3.1 .1 Membrane curing-Immediately after the water

film has disappeared from the finished surface of the concrete pavement, the surface should be uniformly coated

with liquid membrane curing material by a suitable means of

an approved mechanical spray machine at the rate of not less than 1 gal/ 1 50 ft2 (1 L/3 .7 m2) of surface area, or as recom

mended by the manufacturer. Curing compounds should comply with ASTM C309 or ASTM C 1 3 1 5 . Compound

can be clear, translucent, or pigmented. White-pigmented

compounds are usually recommended for hot, sunny weather conditions to reflect solar radiation. To ensure uniform

consistency and dispersion of the pigment in the curing material, it should be agitated in the supply container imme

diately before transfer to the distributor and kept thoroughly

agitated during application. The curing machine should recirculate and continually mix the curing compound during

application. Irregular areas or sections of pavement where

the use of a mechanical spraying machine is impracticable may be sprayed with approved hand-spraying equipment.

The sides of the pavement slab should be coated immediately after removal of forms. Any areas of the coating that

are damaged within the specified curing period should be

immediately repaired. 5.3.1.2 Monomolecular coatings-This type of membrane

coating material is desirable to retard surface evaporation

under adverse drying conditions. These coatings are not a

substitute for membrane curing materials. 5.3.1.3 Cotton mats or burlap-If specified, the surface

and edges of the pavement should be entirely covered with mats. Prior to being placed, mats should be saturated thor

oughly with water. Mats should be placed so as to cause

them to remain in intimate contact with the surface, but should not be placed until the surface has hardened suffi

ciently to prevent marring. They should be maintained fully wetted and in position for the specified curing period.

5.3.1.4 Waterproof paper-If specified, as soon as the pavement has hardened sufficiently to prevent marring of the surface, the pavement should be entirely covered with

waterproof paper. The paper units should be lapped 12 in. (300 mm). The waterproof paper should be sufficiently wide

to overlap and completely cover the sides of the slab after

the forms have been removed, unless additional strips of paper are furnished for curing the sides. The curing paper

should be placed and maintained in intimate contact with the

surface and sides of the pavement during the curing period. Damaged curing paper, which cannot be effectively patched

or repaired, should be discarded. Curing paper should be placed only on a moist surface. If the surface appears dry,

a spray fine enough to prevent damage to the fresh concrete

should wet it. 5.3.1.5 White polyethylene sheeting-If specified, the

surface and sides of the pavement should be entirely covered with white polyethylene sheeting. It should be placed while

the surface ofthe concrete is still moist. If the surface appears

dry, it should be wetted with a fine spray before the sheeting is placed. Adjacent sheets should be lapped 1 8 in. (460 mm).

The sheeting should be weighted to keep it in contact with

the pavement surface and should be large enough to extend beyond the pavement edge, and completely cover the sides

of the slab after the forms have been removed. The poly

ethylene sheeting should remain in place for the duration of the curing period. A minimum polyethylene thickness of 4

mils ( 1 mm) should be specified. Special insulating sheeting materials are sometimes used for cold weather or fast-track

paving. 5.3.1 .6 Curing of saw cuts-Saw cuts in pavement being

cured should be protected from rapid drying. This is often

accomplished with twisted paper or fiber cords or ropes, gummed polyethylene strips, or an application of curing

compound after sawing.

5.4-lnstallation of joints and reinforcement 5.4.1 General-Joints are placed in concrete pavements

to control the location of cracks and, in some instances,

provide relief for expansion due to temperature and moisture

changes. Information on joint sealants is found in several references (ACPA 1 99 1 , 1 995; Kahn et al. 2003). All longi

tudina1 and transverse joints should conform to the details and positions shown on the plans. Plans and specifications

should be explicit as to location and type of joints at ramp

entrances and intersections, and where normal spacing is altered due to end-of-day or emergency construction joints.

All transverse joints should be constructed in line for the

full pavement width. Faces of joints should be normal to the

surface pavement. 5.4.1 .1 Riding surface-Special care should be taken to

prevent uneven riding surfaces at formed joints. If edging is required or permitted, a 1 0 ft (3 m) straightedge should be used to ensure that displaced concrete does not result in high

spots. Exercise special care when using joint forming inserts, as they may result in high spots if not placed properly.

5.4.1.2 Keyways-Keyways, a tongue and groove type of configuration between abutting slabs, are sometimes

used in longitudinal joints to help maintain alignment and

reduce deflections. Although commonly used at one time, many agencies have gone away from their use because of

performance issues. In particular, the use of keyways in pavements less than 8 in. (203 mm) thick is discouraged,

as they create a potential for cracking in the joint. If speci

fied, the keyway should be accurately formed by material

of sufficient strength to ensure a full keyway and accurate

alignment. An example keyway is presented in Fig. 5 .4. 1 .2.

5.4.2 Longitudinal joints 5.4.2.1 Weakened plane joints-Longitudinal weak

ened plane joints can be formed in the concrete by sawing. Exercise care to ensure that the depth of cut is adequate to prevent random cracking, usually approximately one-third

of the slab depth. If required, a second, widening cut will be done later to create the reservoir for the joint sealant; the

depth and width of that cut will depend on the sealant type being used. If unsealed joints are specified, the depth of the



0.2d

_.L_l_ O.Sd

---1 l--0.1d

f

Fig. 5. 4. 1 .2-Example keyway (FHWA 1990).

d

initial saw cut is generally the same as for a sealed joint, but the width is controlled by the saw blade. Figure 5 .4.2. 1 shows a typical longitudinal joint, along with a transverse

contraction joint and dowel bar assembly. 5.4.2.1 . 1 Sawing-The timing of the joint sawing operation

will vary depending on the mixture design and curing condi

tions, but generally should be done from 4 to 1 2 hours after paving. The goal is for the saw-cut timing to be late enough

to avoid raveling of the new concrete, but soon enough so

that random cracking does not occur. Where cracking has occurred at or within a few feet of the proposed joint loca

tion, sawing that individual joint should be omitted. Whatever the sawing method-diamond blades, wet abrasive

blades, or dry abrasive blades-care should be exercised to

saw the joints as soon as possible without causing excessive raveling.

5.4.2.2 Construction joints-Longitudinal construc

tion joints, which are joints between lanes that are placed

separately, can be formed with either the slipform methods or standard steel forms. In these cases, the new concrete

slabs are generally paved right up against the existing slabs

without a filler material. The existing slab may have been placed with a keyway, but again, these are not commonly

used anymore. If permitted by the specifications, tie bars can be bent against the form during casting of the first lane, and

then bent out for insertion into the adjacent lane. Generally, Grade 40 (Grade 280) steel and reinforcing bar with flex

ible epoxy coatings produced under ASTM A775/A775M are more tolerant to bending. The use of smaller size bars at a closer spacing could also mitigate bending problems. The

problem can be alleviated by use a 60-degree bend initially,

and then a straightening 60-degree bend to produce a skewed but adequate tie bar arrangement, as shown in Fig. 5 .4.2.2.

Joint hook bolts are not recommended. Equip slipform pavers with a suitable device for the installation of tie bars,

or provide other approved means of holding the lanes in

contact. 5.4.3 Isolation or expansion joints-Isolation or expansion

joints should be placed between all structures and features such as catch basins and manholes projecting through, into,

or against the pavement. They should not be used as part

of regularly spaced transverse or longitudinal joints. Unless otherwise indicated on the plans, expansion joints should be not less than 0.25 in. (6 mm) wide. Expansion joint fillers

should be firmly held in place and not dislodged so that

Fig. 5.4.2. 1-Showing details of a longitudinal joint, a transverse contraction joint, and a dowel bar assembly.

concrete cannot enter the expansion space at bottom, sides, or top. In addition, most expansion joints should be doweled

or should be thickened to reduce joint deflections. 5.4.3.1 Transverse expansion joints-Transverse expan

sionjoints should be constructed at right angles to the center

line of the pavement, unless otherwise required, and should extend the full width of the pavement. In new construction,

expansion joints are constructed or formed and not sawed. 5.4.3.1 .1 Expansion joints at bridge ends-Bridge ends

should be protected from excessive pressures due to pave

ment expansion by the installation of ample width expansion joints in the pavement near ends of bridges.

5.4.3.1 .2 Expansion joints where dowels are used-These

joints should be formed by securely staking in place approved

load transfer devices, which consist of welded assemblies of dowels, supporting and spacing devices, and joint filler. The

filler may be the premolded type, redwood board, or other approved material. The filler should extend downward to the

bottom of the slab, and unless otherwise prescribed, the top

edge should be held approximately 0.5 in. ( 1 3 mm) below the finished surface of the pavement. A removable channel

can be used to protect the top edge of the filler while the

concrete is being placed. The joint assemblies should be protected against damage until they are installed in the work.

Joint assemblies damaged during transportation, by careless handling, or while in storage should be replaced or repaired

and should not be used until they have been approved by the

engineer. 5.4.3.1.3 Joint filler-The designated joint filler for the

expansion joint should be punched or drilled to the exact diameter and at the location of the dowels. It should be

furnished in lengths equal to the width of one lane. Where

more than one length is used in a joint, the abutting ends of the filler should be held in alignment. The supporting assembly should furnish positive support of the filler in a

position normal to the surface.

5.4.4 Transverse weakened plane contraction jointsTransverse groove or weakened plane contraction joints should be constructed in the same manner as provided for

weakened plane longitudinal joints, except that some type

of load transfer may need to be provided where expected traffic volume and the magnitude of the loads will be heavy.



Face of keyway

� I ,, I

300� No. 5 tie bar bent 60°

1 and concealed in keyway

I � I I I ,, I '

Tie bar straightened and

� ready for placement of

adjacent lane

Note: Most No. 4 bars can be bent

goo and straightened without

breaking. Many No.5 bars cannot be

bent up to goo

Fig. 5. 4.2.2-Method for minimizing breakage of tie bars that are bent into keyways and restraightened.

In this case, it is recommended that smooth dowels or other

load transfer devices be provided. Although a few heavily

traveled pavements without dowels have been marginally

successful where high-quality bases were employed, such as cement or asphalt stabilized, dowel bars are recommended

for most pavements subjected to heavy traffic (as evidenced by slabs that are greater than 8 in. [250 mm]) .

A positive marking system should be used to assure that sawed or tooled grooves are over the midlengths of the dowels. Saw cuts are recommended to be one-third of the

slab thickness. Timing of the sawing operation is critical,

and should be done as soon as the slab can be cut without

excessive raveling. In the event that cracking occurs before or during joint sawing, the location where the crack occurred

should be skipped; it may be necessary to begin a saw-cutting process in which every third or fourth transverse joint is

cut to relieve stress and the potential for random cracking,

followed by cutting of intermediate joints. This saw-cutting scenario may be needed when adverse curing conditions are

encountered.

5.4.5 Transverse construction joints-Transverse construction joints should be made at the end of each day or where

interruptions occur in the concreting operation. Weather conditions should govern the length of delays that are consid

ered cause for requiring the setting of a joint. A 30-minute delay could be considered a reasonable limit during hot, dry,

windy weather; up to an hour or more may be tolerated if

conditions are less severe. Concrete mixtures that contain SCMs or high-early-strength mixtures could alter setting

time and, therefore, should be considered when establishing

construction joints. A bulkhead of the proper shape and dimensions is staked in place to form transverse construction

joints. Dowel bars are used in transverse construction joints

to establish load transfer between the just-placed slab and the next placement. Transverse construction joints should not be formed to make a slab less than 10 ft (3 m) long. If

sufficient concrete is not available to place a slab at least 1 0

ft (3 m) long, the construction joint should be formed at the preceding transverse joint location. The spacing of subse-

quent transverse joints should be measured from the trans

verse contraction joints last placed.

5.4.6 Joint sealing-Despite the long-standing practice to seal all concrete pavement joints to prevent water and

incompressibles from entering, and although research into

this topic is still ongoing, some owners/agencies no longer

require this practice under certain conditions. These agencies

omit sealing of joints in their newly constructed, doweled concrete pavements and some specialty concrete pavement

types where erosion of the subbase is not a concern. An

example is undoweled bonded concrete overlays of asphalt pavements. It is therefore important to review the contract

documents carefully and understand jointing details for each project. The blade width must match the width required by

the design (ACPA 20 10) .

If joints are not sealed, agencies essentially just make use of the initial saw cut with no further widening or installa

tion of sealant material; the width of the joint is approximately 0. 1 2 in. (3 mm). A 2009 Tech Brief (FHWA 2009b)

reports no significant difference in performance of sealed and unsealed saw-cut joints where compared in terms of

blowups and pressure damage, joint faulting, joint spalling,

and joint sealant damage for pavements less than approximately 8 to 1 0 years old; long-term performance capabili

ties, however, are unknown.

In the event that joint sealing is performed, guidance for

selecting proper joint shape factors and joint sealants can be found in several documents (ACPA 1 99 1 , 1 995 ; Smith and Hall 2001 ) . The shape factor, which is the ratio of the sealant

width W to the sealant depth D (Fig. 5 .4.6), is important to

the performance of field-molded sealants such as rubber

ized asphalt and silicone (Smith and Hall 200 1) . A backer rod--commonly a closed-cell polyethylene or polyurethane

foam-is often used to achieve the desired shape factor and

to prevent three-sided adhesion of the sealant to the joint walls.

If joints are to be sealed, it is generally preferred to seal

them before opening the facility to traffic. Joint openings

should be thoroughly cleaned of all foreign matter before

the sealing material is placed. All contact faces of joints should be cleaned to remove loose material and surface dry if hot-poured or silicone materials are used. Sealing material

should be installed in the joint openings to conform to the

details shown on the plans. The installation should be done

in such a manner that the material would not be spilled on the exposed surfaces of the concrete. The sealant should be

kept below the pavement surface so that compression of the

joint does not cause the seal to squeeze up to the surface. Any excess material on the surface of the concrete pavement

should be removed immediately and the pavement surface cleaned.

5.4.6.1 Poured joint sealants-Poured joint sealing mate

rials should not be placed if temperatures are such as to prevent proper installation. Manufacturer recommendations

can be useful in preparing specification limits. 5.4.6.2 Preformed joint materials-Where preformed joint

material such as neoprene preformed compression sealant is used, the uncompressed width of such joint material should



1/8 to 1/4 in Recess

Fig. 5.4. 6-Cross section of transverse joint sealant installation (Smith and Hall 2001).

Fig. 5.4. 6.2-Machine used for installation of preformed neoprene contraction joint strip. The material and reel are not pictured. Machine is self-propelled and capable of

installation of the strip with little length change.

be properly balanced with the joint opening, which in tum

should be of a width consistent with the length of the slab and temperature ranges expected. The installation device

should ensure that the preformed material is not stretched more than allowed by job specifications (typically 1 to 3

percent) during insertion in the joint opening because the

result of such stretching could be a drastic shortening of the useful life of the material. The seal and the installation lubri

cant should conform to ASTM D2628 and ASTM D2835 .

Figure 5 .4.6.2 shows a machine used to install preformed joint material.

5.4.6.3 Edge seals-Edge seals, which are shown in Fig.

5 .4.6.3, are sometimes specified. They can be useful for

preventing water infiltration. Because such systems exhib

ited varying degrees of success, their use should be based

on experience. 5.4.6.4 Compatibility of materials-Some jointing mate

rials are incompatible and should not be used in direct

contact with each other without an inert divider. Some bitu

minous materials, for example, should not be in contact with a joint seal of the two-component, polysulfide type. They

can be separated with a neoprene tape or other relatively inert material.

5.5-Dowels and tie bars 5.5.1 Dowels-Dowel bars, which should be sized consis

tent with slab depth and design requirements, are placed at

mid-depth of the slab. Proper horizontal and vertical alignment should be assured by either approved dowel assembly

devices or by approved machine placement in contraction

joints and assembly devices, or dowel sleeves in construc

tion joints. Good consolidation of concrete around the dowels is essential to satisfactory performance.

5.5.2 Dowel coating-The free or unbonded end of each dowel should be coated with a debonding agent. Common

de bonding agents include a thin layer of grease or oil, a wax

based curing compound, or commercial corrosion inhibitor/

debonding agent applied at the fabrication facility. In any

case, an excessive coating should be avoided, as this can cause excessive movement in the dowel. The free ends of

the dowel bars for expansion joints should be provided with

dowel caps. Consider also other types of coatings or dowel sleeves for the purpose of preventing bond, corrosion, or

both. Epoxy-coated dowels should conform to AASHTO M254.

3/4 X 3/4 in. SAWED OR FORMED G ROOVE, SLIGHTLY OVERFILLED

3 in. SURFACE COU RSE (if required)

4 in. SUBBASE

Fig. 5.4. 6.3-A method sometimes used to prevent entrance of water between pavement and asphalt shoulder. (Note: 1 in. = 25.4 mm.)



5.5.3 Installation of dowel assemblies 5.5.3.1 Dowel baskets-Dowel assemblies should be put

in place on prepared subbase or subgrade. Transverse dowel

assemblies should be placed at right angles to the centerline of the pavement except where otherwise detailed on the

plans. Doweled joints required or permitted to be set at angles

other than normal to the centerline require careful detailing and installation to assure freedom of movement. Dowels

should be securely held in the required position. On widened

curves, the longitudinal center joint should be placed so that it will be equidistant from the edges of the slab. Joints should be set to the required line and grade and should be securely held in the required position by stakes, an approved

installing device, or other approved method (5 .4). Dowels

should be installed in a way that prevents concrete pressure from disturbing their alignment. If joints are constructed a

lane at a time, there should be no offsets between joints of adjacent slabs. Dowel bars should be checked for position

and alignment as soon as the joint assembly is staked in

place on the subgrade or subbase, and it should be ensured that the assembly is adequately staked and firmly supported. An FHWA Report (Yu and Khazanovich 2005) found that

increasing dowel basket pins from four per basket, just at

the comers, to I 0 per basket and every other dowel, virtually eliminated occurrences of basket misalignment greater than 5/8 in. ( 1 5 mm). Any joint not firmly supported should be reset. Wires or bars used to hold assemblies in position

for shipment should be cut before concrete is placed if they could cause restraint to early shrinkage of new concrete.

Studies indicate that the forces required to break basket

assembly wire welds are much lower than typical concrete

shrinkage forces and baskets may be left uncut. However, leaving wires uncut can cause interference with some elec

tromagnetic dowel location devices (5.7.3). 5.5.3.2 Installation of dowels with dowel bar inserter

Dowel bar inserters are mechanical devices located on the

slipform paving machine that will pick up a dowel and vibrate it into the wet concrete as the machine passes over.

This eliminates the need for baskets. Depth variance is typically not a problem, but dowels should still be checked for

proper alignment and skew tolerances. If the dowels are

not properly vibrated, there is also the possibility of poor concrete consolidation on top of the dowel and surface

depressions over the dowel. 5.5.3.3 Dowel location-Nondestructive testing can

be used to verify and document the dowel location in the

finished slab. Two common methods are ground-penetrating radar (GPR) and magnetic tomography devices. Magnetic

tomography devices use magnetic fields to accurately locate

load-transfer dowels in the concrete joint. This nondestructive test device has been tested extensively by a number of

departments of transportation (DOTs). Key advantages of this technology over GPR devices are its use in inclement

weather and on green concrete. Key disadvantages are that

the device readings can be affected by other metal in the joint, such as dowel basket frames and tie wires. Additional

information on this technology is provided by Yu and Khazanovich (2005).

Dowel basket frames can affect the accuracy of the scan,

showing a 6 and 7 percent less reported depth and increasing sensitivity to side shift, respectively. These errors can both be adjusted with software and calibration of the unit. Transport ties should be cut to prevent invalid results or consis

tently located relative to dowels so that they can be filtered

out with software. Scan devices can locate dowels within a limited range of

concrete depth and misalignments. Consult device manufac

turer data for other possible location limitations or installation requirements.

5.6-Piacing embedded reinforcement 5.6.1 General-If steel reinforcement for jointed pave

ments is used, it should consist of welded deformed or welded plain wire fabric or bar mats in accordance with 4.3 . 1

and 4 .3 .2. The surface condition of the steel with respect to foreign matter and rust should conform to the requirements

in 4.3.4. The width of the fabric sheets, rolls, or bar mats

should be such that, where properly placed in the work, the extreme longitudinal members of the sheet or mat will be

located not less than 2 in. (50 mm) or more than 6 in. ( 1 50

mm) from the edges of the slab. The length of fabric sheets or bar mats should be as shown on the plans and such that,

where properly placed in the work, the reinforcement will clear all transverse contraction joints by not less than 6 in.

( 1 50 mm) as measured from the center of the joint to the

ends of the longitudinal members of the sheet or mat. The steel fabric or bar mats should be lapped as shown on the

plans and securely tied together to prevent displacement,

particularly from being pulled by the paving train.

5.6.2 Bar reiiiforcement-Reinforcing bar assemblies shown on the plans should show the bars firmly fastened

together at all intersections. Adjacent ends should lap not less than 30 diameters, or 1 6 in. (400 mm) (refer to 5 .6.5).

Where bars are fabricated into mat form by positive welding

at all intersections, the laps for longitudinal bars should be a minimum of 30 diameters. If the mat pattern is such that the edge longitudinal bars or the end transverse bars of the mats overlap, the lap should be made so that the bars overlap each

other by at least 2 in. (50 mm).

5.6.3 Two-lift installation-If reinforced concrete is placed in two lifts, as shown in Fig. 5.6.3, the initial layer should be

uniformly struck off at a depth not less than 2 in. (50 mm) below the finished surface nor greater than mid-depth of slab

below the proposed surface of the pavement, and the rein

forcement placed thereon. The concrete should be struck off across the entire width of the placement and over a sufficient

length to permit the sheet or mat of reinforcement to be laid

full length on the concrete in its final position without further manipulation of the reinforcement. The balance of the required concrete should be placed after the reinforcement

is in place. The first course of struck-off concrete should not

be exposed particularly during hot, windy weather. A reason

able maximum exposure time is 30 minutes. The positioning of the reinforcement during concrete operations should be

checked and, if necessary, corrected.



Fig. 5. 6.3-Mesh installations on two-course pavement, employing forms. Mesh cart towed by spreader.

5.6.4 Single-course placement-For concrete that is placed in a single course, wire fabric sheets or bar mats

may be laid in proper horizontal alignment on the full depth of struck-off concrete and machine vibrated or tamped to

proper elevation. Care should be exercised that the installing

machines are designed and adjusted so that they will not leave cleavage planes over steel members nor drag the sheets

or mats from their proper position. At each transverse joint, a check should be made to ensure proper clearance between mesh ends and the joint.

5.6.5 Continuously reinforced pavement-Where continu

ously reinforced concrete pavement is specified, steel in the

quantity, fabrication, and grade shown on the plans should be installed so that the reinforcement will have a minimum surface cover of 2 in. (50 mm) from top and the longitudinal

members will not fall below the mid-depth ofthe slab, unless otherwise specified or shown on the plans. All highway agen

cies that currently construct continually reinforced concrete

pavement (CRCP) use transverse steel that is first placed on supports on the base/subbase. This is followed by placement

of the longitudinal steel bars that are tied or clipped to the

transverse steel at specified locations (FHWA 2009a). Figure 5.6.5 shows longitudinal bars resting on transverse bars in a

CRCP construction project.

Lap splices for individual bars, prefabricated bar mats, or welded deformed or welded plain wire fabric mats or rolls

are usually designated on plans and should be carefully checked in the work. The importance of adequate laps and

proper placement cannot be overemphasized. The danger of

failure at splices at early ages can be minimized by arranging

the splices in a skewed or staggered pattern from one pavement edge to the other. Splice lengths should be shown on

the plans or specifications and should not be less than 30

diameters, or less than 16 in. (400 mm). 5.6.6 Location of reinforcement-Use a gauge to deter

mine the location of the reinforcement in pavement. Insertion to the depth of the reinforcing location will indicate its

positioning in the fresh concrete.

Fig. 5. 6.5-Bar on chairs, spliced, for single course slip

form operation.

5. 7-Texturing 5.7.1 Purpose of texturing-Texturing of the concrete

pavement surface is performed to provide adequate surface friction to meet the safety demands of the roadway, partic

ularly under wet conditions. Pavement surface texture, however, also influences many other functional attributes

of the pavement, including tire-pavement noise, which is

increasingly becoming a critical concern in many urban areas; hydroplaning, which affects vehicle handling and

braking; splash and spray, which can significantly reduce

visibility; and rolling resistance, which can affect fuel consumption (FHWA 2005a; AASHTO 2008b ). Ideally, an

optimum pavement surface texture is desired that economically provides adequate surface friction while also consid

ering these other factors.

The importance of texturing pavements cannot be overstated. Research indicates that approximately 14 percent of all crashes and 1 9 percent of all fatal crashes occur in wet

weather, and that 70 percent of all wet-weather crashes could

be prevented with improved pavement surface texture and friction (Larson et al. 2008). Other research shows that up

to I 0 percent of wet-weather crashes are caused by reduced

visibility due to splash and spray, especially at night, and that between 1 5 and 35 percent of wet-weather crashes involve

skidding (Larson et al. 2008). With over 30,000 fatalities and

2.3 million injuries per year occurring on national highways, significant reductions in the aforementioned percentages

brought about by effective texturing can save countless lives

and greatly reduce injuries.

5.7.2 Terminology-Pavement surface texture is defined as regular deviations of a pavement surface from a true

planar surface (AASHTO 2008b). As shown in Fig. 5 .7 .2a,

these deviations occur at three distinct levels of scale: I ) microtexture; 2) macrotexture; and 3 ) megatexture. Each of these deviations is defined by the wavelength and peakto-peak amplitude of its components (PIARC 1 987), with

American Concrete Institute - Copyrighted© Material- www.concrete.org (ciCiJ Licensed to: Florida Suncoast Chapter


Roughness/Uneven

Reference Length

Short stre tch

of I"Oad

Tire

Road-Tire

Contact Area Amplification ca. 5 times

/\ Single hiJ>ping

ca. = circa (approximately) Fig. 5. 7.2a-Schematics of micro texture, macro texture, and mega texture through various

amplification magnitudes (AASHTO 2008b).

microtexture and macrotexture most important to the safety and comfort aspects of a pavement.

Microtexture is the fine-scale roughness contributed in

most cases by the fine aggregate (sand) in the concrete mortar (ACPA 2000). Technically, it is the texture defined by wave

lengths of 0.04 to 20 mils (0.00 1 to 0.5 mm) and vertical

amplitudes less than 8 mils (0.2 mm) (AASHTO 2008b ). Because microtexture cannot be measured at highway

speeds, surrogate indicators are used. For example, the portable British Pendulum Tester (BPT) (ASTM E303) can

evaluate micro texture in the laboratory or field, based on the

British Pendulum Number (BPN) . The Dynamic Friction

Tester (DF Tester) (ASTM E 1 9 1 1 ) is a portable device that can be used to measure friction at various speeds, with low

speed (commonly 1 2.5 mph [20 kph]) values considered

most representative of microtexture and correlating well

with BPN (Larson et al. 2008) . Macrotexture refers to texture with wavelengths of0.02 to

2 in. (0.5 to 5 1 mm) and vertical amplitudes ranging between 5 and 800 mils (0. 1 and 20 mm) (PIARC 1 987). It is most

commonly produced through small channels, grooves, or indentations that are intentionally formed or cut in the pave

ment surface to allow water to escape from beneath vehicle tires. Concrete pavements constructed for speeds of 50 mph

(80 kph) or greater generally require effective macrotex

ture to increase available friction, reduce the potential for hydroplaning, and decrease the amount of splash and spray (Hibbs and Larson 1 996). Characteristics of certain macro

textures, however, can result in increased tire-pavement noise emissions.

Macrotexture can be assessed using a number of different methods. Traditionally, it has been determined using the

sand patch test (Texas Department of Transportation (DOT)

1 999), in which a known volume of sand, now glass beads, is spread out uniformly over the pavement surface (Snyder

2006). The mean texture depth (MTD) is then calculated by dividing the known volume of glass beads by the area of the

roughly circular spread using the average of four diameters.

The mean profile depth (MPD) is a measurement parameter derived from laser-based systems that collect detailed

Coefficient of Friction

0 (fi·ee rolling)

Peak friction

Intermittent sliding

Full ------.....!!"'::!!.di�ng friction I I I I I I I I I v Critical slip I I I I Increased Braking �

Tire Slip, %

100 (fully-locked)

Fig. 5. 7.2b-Pavement friction versus tire slip (AASHTO

2008b).

surface elevation profile data. The laser-based systems include the portable, stationary Circular Texture Meter (CT

Meter) and various high-speed texture profilers. Strongly

correlated equations have been developed to convert MPD values into estimates of MTD.

Pavement surface friction is defined as the retarding force developed at the tire-pavement interface that resists longitu

dinal sliding when braking forces are applied to the vehicle

tires (Dahir and Gramling 1 990; AASHTO 2008b ). Whereas adequate surface friction generally exists on dry pavements,

the presence of water reduces the direct contact between the

pavement surface and the tire, thereby reducing the available friction.

The amount of friction available depends on the degree of braking, which results in a relative difference in speed

between the circumference of the rotating tire and the pave

ment at the tire-pavement interface. This relative difference

in speed is referred to as slip speed. Where the tire is rolling

free (no braking), the slip speed is zero and the coefficient of friction is low, as seen in Fig. 5 .7 .2b (AASHTO 2008b). As

braking is increased, the slip speed increases to a level equal

to the vehicle speed where the tire is fully locked (that is, full sliding). Maximum or peak friction typically occurs where

the slip speed is between 10 and 20 percent of the vehicle



speed. Vehicles with an anti-lock braking system (ABS) are

designed to apply the brakes on and off (that is, pump the brakes) repeatedly, such that the slip is held near the peak

friction (Hall et al. 2009b ) . Pavement surface friction can be measured using a number

of different methods and equipment, with the locked-wheel

tester the most commonly used device in the United States (Hall et al. 2009b). In this procedure, which is described in

ASTM E274/E274M, a specified amount of water is applied

to a dry pavement in front of the test tire of the friction tester while the tester is towed down the road at a certain speed, typically 40 mph (64 kph). The test tire is then fully locked and the friction between the locked tire and the wetted pave

ment surface is measured. Two types of test tires can be used in this test, either a: 1) ribbed, or treaded, tire conforming

to ASTM E501 ; or 2) smooth, or bald, tire conforming to

ASTM E524. The ribbed tire is more sensitive to, and thus more indicative of, pavement microtexture while the smooth

tire is more sensitive to pavement macrotexture.

Surface friction is generally expressed in terms of a friction number (FN), commonly referred to as a skid number

(SN). Friction numbers represent the average coefficient of

friction measured across a test interval. It is computed as 1 00 times the force required to slide the locked tire at the stated speed, which is usually 40 mph (64 kph), divided by the effective wheel load (Henry 2000). The reporting values

range from 0 to 100, with 0 representing no friction and 1 00

representing complete friction.

Friction number values are generally designated by the

speed at which the test is conducted and by the type of tire

used in the test (Hall et al. 2009b ). For example, FN40R = 36

indicates a friction value of 36, as measured at a test speed of 40 mph (64 kph) and with a ribbed (R) tire. Similarly,

FN50S = 29 indicates a friction value of 29, as measured at a test speed of 50 mph (8 1 kph) and with a smooth (S) tire.

Ideally, FN40R values in the range of 30 to 40 or FN40S

values in the range of 28 to 35 are targeted for major highways, which are interstate highways and other roads with

design speeds of more than 40 mph (64 kph). Lower friction numbers are generally acceptable for low-speed and low

volume pavements with daily traffic less than 3000 vehicles

per day (VPD) (Hoerner et al. 2003). As part of an international effort to harmonize the friction

indexes produced by the different friction testing methods, an international friction index (IFI) was developed in the

1 990s (Hall et al. 2009b). The IFI (ASTM E 1 960), which is

composed of a friction number F(60) and a speed constant SP, provides a method of incorporating simultaneous measure

ments of friction and macrotexture into a single index repre

sentative of frictional characteristics of the pavement (Henry 2000). In this way, friction tests performed using different

equipment or at different speeds can be compared on a common basis. The details of computing IFI are found in

ASTM E 1 960 and in AASHTO (2008b ) .

5.7.3 Noise-In recent years, highway noise has become a critical issue, particularly on high-volume roadways in

urban settings. Highway noise emissions, which can be generated by the vehicle powertrain or by the tire-pavement

interaction, are not only irritating to those living adjacent to

the roadways, but also can be bothersome to roadway users. In the case of tire-pavement interactions, there are number

of factors that play a role in the generation and enhancement of noise, including tire design, size, condition, and loading;

vehicle speed; pavement surface texture; and porosity.

Sound is typically expressed in terms of sound pressure level (SPL) (Hall et al. 2009a) . Human hearing is not

equally sensitive to sound of all frequencies, however, and

one way to try to account for this is through the application of weighting filters (Sandberg and Ejsmont 2002). One filter

that is commonly considered to correspond fairly well with the human perception of sounds is the A filter (Bernhard

and Wayson 2005). The unit of measure is the A-weighted

decibel or dB( A).

Two common methods of measuring tire-pavement noise

at the source are the close-proximity (CPX) and on-board sound intensity (OBSI) methods. The CPX method, which

has been used in Europe for many years, uses sound pressure

microphones to measure average dB( A) at 0.3 to 1 .6 ft (0. 1 to 0 .5 m) from a reference tire in an enclosed, sound-absorbing

trailer (Hall et al. 2009a). The method is relatively inexpen

sive, fast, and done at roadway speeds so it does not require closing of the roadway; moreover, the device can be used to

continuously document the noise characteristics, including variability, of long portions of highway. The OBSI method

was originally developed in the 1 980s and has been used in

the United States since 2000 for conducting tire-pavement noise evaluations (Hall et al. 2009a). Microphones that are

mounted next to the tire of the test vehicle measure the rate

of energy flow through a unit area, which, integrated over

the area, provides sound pressure. Interior vehicle noise measurement entails the continuous

measurement of noise inside the test vehicle as it travels along a road at a specified speed (Hall et al. 2009a). While

beyond the scope of this document, details of the measure

ment procedure are available from SAE International (2000).

5.7.4 Texturing methods-A number of different texturing techniques are available for imparting texture to new (plastic) or existing (hardened) concrete pavements. A summary of

these techniques are provided in Table 5 .7 .4, with several example illustrations shown in Fig. 5 .7 .4.

Most early surface texturing methods commonly used

shallow texturing methods such as a broom or a burlap drag finish, both of which provide a quiet ride but do not typi

cally contain sufficient macrotexture for friction needed at

high speeds. By the mid- 1 970s, many agencies had adopted transverse tining as the standard for new concrete pavement

construction on high-speed roadways, although often still

preceded with a burlap drag to create microtexture. California was one notable exception, as they adopted longitu

dinal tining, and also pioneered the use of diamond grinding and grooving as a way of restoring texture to existing pave

ments. Beginning in the late 1 990s as noise issues began to

emerge as a critical issue in parts of the country, some agencies began investigating alternative texturing methods such

as random and skewed transverse tining, exposed aggregate



Table 5.7.4-Concrete pavement surface texturing techniques (AASHTO 2008a)

Mixture/texture

Application type Description Macrotexture depth

A long bristled broom is mechanically or manually dragged over the concrete

Broom drag surface in either the longitudinal or transverse direction. Texture properties are Typically ranges from 8 to 1 6

(longitudinal or controlled by adjusting the broom angle, bristle properties (length, strength, mils (0.2 to 0.4 mm)

transverse) density), and delay behind the paver. Uniform striations approximately 0.06 to 0 . 12

in . ( 1 .5 to 3.0 mm) deep are produced by this method.

One or two layers of moistened coarse burlap sheeting are dragged over the concrete

surface following placement. Texture properties are controlled by raising/lowering

Burlap drag the support boom and adjusting the delay following concrete placement. This Typically ranges from 8 to 1 6

(longitudinal) method produces uniform 0.06 to 0 . 1 2 in. ( 1 .5 to 3 .0 mm) deep striations in the mils (0.2 to 0.4 mm)

surface, and is often done prior to other texturing methods (for example, transverse

tining).

An inverted section of artificial turf is dragged longitudinally over a concrete Typically ranges from 8 to 16

Artificial surface following placement. Texture properties are controlled by raising/lowering mils (0.2 to 0.4 mm), but a

turf drag the support boom, adding weight to the turf, and delaying application to allow deep texture (minimum depth

(longitudinal) surface hardening. This method produces uniform 0.06 to 0 . 1 2 in. ( 1 .5 to 3.0 mm) of 0.04 in. [ 1 .0 mm]) has

deep surface striations. been achieved

New concrete or A mechanical assembly drags a wire comb of tines (- 5 in. [ 1 27 mm ] long and I 0 ft

concrete overlay [3 m] wide) behind the paver (and usually following a burlap or turf drag). Texture

Longitudinal properties are controlled by the tine angle, tine length, tine spacing, and delay for Typically ranges from 1 5 to

tine surface curing. Grooves from 0 . 1 2 to 0.25 in. (3 to 6 mm) deep and 0 . 12 in. (3 mm) 40 mils (0.4 to 1 .0 mm)

wide are produced by this method, typically spaced at 0.75 in. ( 1 9 mm). Typically

preceded by a drag texture.

Accomplished using methods similar to longitudinal tining; however, the

mechanical assembly drags the wire comb perpendicular to the paving direction. Typically ranges from 1 5 to

Transverse tine Variations include skewing the tines 9 to 14 degrees from perpendicular, and 40 mils (0.4 to 1 .0 mm)

using random or uniform tine spacing from 0.5 to 1 .5 in. ( 1 2 to 38 mm). Typically

preceded by a drag texture.

A self-propelled grinding machine with a grinding head of gang-mounted diamond

sawing blades removes 0. 1 2 to 0.75 in. (3 to 1 9 mm) of cured concrete surface,

Diamond leaving a corduroy-type surface. Blades are typically 0.08 to 0. 16 in. (2 to 4 mm) Typically ranges from 30 to

grinding wide and spaced 0. 1 8 to 0.25 in. (4.5 to 6 mm) apart, leaving 0.08 to 0 . 16 in. (2

(longitudinal) to 4 mm) high ridges. This method is most commonly used to restore surface 50 mils (0.7 to 1 .2 mm)

characteristics of existing pavements; however, in recent years, it has been used to

enhance the surface qualities of new PCC pavements or PCC overlays.

The EAC texturing technique is usually applied to a pavement composed of two

Exposed layers (Hibbs and Larson 1 996): a top layer between 1 .6 and 2.8 in. (40 and 70 mm)

New concrete or thick and a much thicker bottom layer. A set retarder is applied to the wet concrete Typically exceeds 0.035 in.

concrete overlay aggregate

surface and the surface protected for curing. After 1 2 to 24 hours, the unset mortar is (0.9 mm) concrete (EAC)

removed to a depth of0.04 to 0.08 in. (I to 2 mm) using a power broom. The large-

diameter aggregate is exposed by this process, leaving a unifonn surface.

Gap-graded, small-diameter aggregate are combined with cement, polymers, and

water to form a drainable surface layer (typically 8 in. [200 mm] thick). That surface Typically exceeds 0.04 in.

Porous PCC layer is bonded to the underlying wet or dry dense concrete layer. Texture properties ( l mm)

are controlled by aggregate sizes and gradations. Air voids range from 15 to 25

percent.

Next- The NGCS is produced by first performing a flush grind of the surface, followed

generation by a second grinding operation that imparts 0 . 1 2 to 0.25 in. (3 to 6 mm) wide

concrete longitudinal grooves into the pavement on 0.38 to 0.75 in. ( 10 to 1 9 mm) spacing.

surface The resulting manufactured surface maintains good frictional qualities and low

(NGCS) noise levels.

Retexturing of Diamond Refer to diamond grinding above.

existing concrete grinding

pavement (longitudinal)

An automated machine hurls recycled round steel abrasive material at the

pavement surface, abrading the surface and removing the mortar and sand particles Typically ranges from 25 to

Shot abrading surrounding the coarse aggregate to a depth of up to 0.25 in. (6 mm). Texture 50 mils (0.6 to 1 .2 mm)

properties are controlled by adjusting the steel abrasive material velocity and

approach angle and by modi tying the forward equipment speed.

Longitudinal A self-propelled grooving machine saws longitudinal grooves in the road surface

diamond approximately 0. 1 2 to 0.25 in. (3 to 6 mm) deep and spaced 0.5 to 1 . 5 in. ( 1 3 to 38 Typically ranges from 35 to

grooving mm) apart. This method adds macrotexture for drainage but relies on the original 55 mils (0.9 to 1 .4 mm)

surface for microtexture.

NGCS Refer to NGCS above



New construction

Diamond grinding Diamond grooving

Fig. 5. 7.4-Examples of common texturing methods (Hoerner and Smith 2002).



surfaces, and more recently, the NGCS for both new and

existing pavements. A considerable amount of research has been conducted

in the last several years to identify optimal surface textures

that first, effectively address safety, and second, address

other needs such as reduced noise. An example of safety is

adequate friction and minimized hydroplaning potential. A detailed process for selecting concrete pavement textures to

satisfy friction and noise criteria at the project level has been

developed and is presented in NCHRP Report 634 (Hall et al. 2009a).

Following are some of the key design and construction considerations associated with the use of the different

textures listed in Table 5 .7 .4.

5.7.4.1 Texturing new concrete surfaces 5. 7.4.1 .1 Broom, burlap, and turf drag textures-Because

of their relatively shallow textures, friction levels associated with drag textures are often inadequate for use on high

speed roadways. Although the FHWA recommends that

burlap drag textures be used only for roadways with posted speeds less than 50 mph (80 kph), but include broom and

turf drag textures for use on roadways with posted speeds

greater than 50 mph (80 kph) if their safety performance can be demonstrated (FHWA 2005b ). The Minnesota DOT is one

agency that employs the use of an artificial turf drag texture on high-speed roadways, requiring minimum texture depths

above 0.04 in. ( 1 .0 mm) and the use of a polish-resistant

aggregate (Izevbekhai and Watson 2008). Analyses of crash data on roadways constructed before and after the move to

artificial turf drag indicated no difference in the number of wet-weather crashes or in the crash rates (Izevbekhai and

Watson 2008). Noise levels for these textures typically range from

moderately low to moderately high (Hall et al. 2009a). Because drag textures result in a mortar fraction as the

wearing surface, it is imperative that the mortar be durable,

especially in heavy traffic and severe climates (Rasmussen et al. 2008). Durability is enhanced through the use of low

water-cementitious materials ratio (w!cm) and supplementary cementitious materials like fly ash, as well as proper

curing techniques. 5.7.4.2 Longitudinal tining-Use of longitudinal tining

has grown significantly in the last decade, largely because

it is quieter than transverse tining. Some research suggests, however, that longitudinal tining exhibits slightly lower

friction (7 to 14 percent lower) than transverse tining (Ahammed and Tighe 2008). Current recommendations call

for straight and uniform grooves spaced 0.75 in. ( 1 9 mm) apart, and with nominal dimensions of0. 12 x 0. 1 2 in. (3 x 3

mm) (FHWA 2005b).

Like drag textures, the mortar fraction of the concrete serves as the wearing surface for this texture and should, therefore, be very durable. However, the mixture should

strike a balance in the w!c so that that it is not too dry at

the time of tining, which results in rough, poorly defined groove shapes or insufficient groove depths; or too wet,

which results in slumped or closed-off grooves (Rasmussen et al. 2008). Because weather conditions can also impact

workability of the mixture, tining operators should monitor

texturing characteristics closely and make proper adjustments in response to site conditions (Hall et al. 2009a).

5. 7 .4.3 Transverse tining-Transverse tining is the most

commonly used surface texturing method for new high-speed

(50 mph [80 kph] or greater) concrete pavements. While

generally providing good overall friction, recent research has shown that this texture generates increased tire-pave

ment noise and that specific configurations-for example,

uniformly spaced grooves-produce objectionable levels of whine. To reduce noise emissions, the FHWA (2005b)

and others (Hall et al. 2009a; Rasmussen et al. 2008) have recommended narrower and deeper grooves, shorter groove

spacing (<0.75 in. [ 1 9 mm]), and randomly spaced grooves.

Current FHWA recommendations for random tine spacing are (FHWA 2005b):

a) For 0.5 in. ( 1 3 mm) average spacing: 0.39/0.55/0.63/0.43/0.39/0.5 110.59/0.63/0.43/0.39/0.83/0.5 1

/0.39 in. ( 10114116/ l l / 10/131 151 16/1 1110/2 11 13/10 mrn). b) For 1 in. (25 mm) average spacing: 0.94/ 1 .06/0.9 1/1 .22/0.83/1 .34 in. (24/27/23/3 1 /2 1 134 mrn). The same considerations regarding mixture characteris-

tics for longitudinal tining also apply to transverse tining. However, because the transverse tining operation is less continuous than longitudinal tining, greater variability in surface textures could be produced, making it imperative

that greater attention be given to keeping the tining process

synchronized with the paving and finishing operations (Hall et al. 2009a).

5.7.4.4 Diamond grinding-Diamond grinding of newly

placed concrete pavements can be conducted to help achieve

a high level of friction, but high-quality, polish-resistant aggregates are critical. Furthermore, diamond grinding

produces some of the lowest noise levels among all concrete pavement surface textures (Hall et al. 2009a).

Used as a texturing technique for new concrete pavements,

recognize that grinding generally reduces slab thickness by 0. 1 9 to 0.25 in. (4 to 6 mm), and that reduction may affect

the fatigue performance of pavement (Hall et al. 2009a). Slight increases in design slab thickness or concrete strength

might be needed to offset that effect. 5.7.4.5 Exposed aggregate concrete (EAC) pavement-An

EAC pavement is created by removing the surface mortar of

the concrete to expose hard and polish-resistant aggregates . Although there is limited experience with EAC pavements

in the United States, the European experience is significant.

Studies there have indicated that EAC is capable of providing

high levels of friction and low levels of noise if properly

designed (high-polish-resistant aggregate) and constructed

(strong durable mortar and proper level of macrotexture)

(Hall et al. 2009a). The EAC pavement is often used as part of a two-lift pave

ment construction system. In a two-lift system, two separate

pavers are used to first place a thicker, less expensive layer of

concrete (7 to 8 in. [ 1 77 to 203 mm]) followed immediately with a thinner layer of concrete (2 to 3 in. [5 1 to 7 6 mm]) in a wet-on-wet construction process. This system allows for the optimization of construction materials. In a typical two-lift



system, the top layer should consist of 30 percent siliceous

sand (size < 0.04 in. [ 1 mm]) and 70 percent high-quality chips (size between 0. 1 6 and 0.32 in. [4 and 8 mm]), and

that the bottom layer consist of less expensive yet durable aggregate having a maximum aggregate size of 1 .25 in. (32

mm) (Hibbs and Larson 1 996).

5. 7 .4.6 Porous concrete pavement-Porous concrete pavements are in the experimental stage in the United States, with

most recent applications restricted to low-traffic, light-load

roadways. Full-scale construction experiences from other countries-for example, in Belgium and Japan-indicate

generally good friction and noise characteristics, but some durability and clogging problems associated with the surface

openness (ACI 522R; Sandberg and Ejsmont 2002).

5.7.4.7 Next-generation concrete surface-The NGCS is a new surface texture that consist of uniform profile design

with essentially only negative texture; that is, there are no fins that protrude up (Scofield 2009). The NGCS can be

constructed using either a single- or double-pass opera

tion, in which a flush grinding of the surface is followed by grinding that creates longitudinal grooves in the surface that

are 0. 1 2 in. (3 mm) wide by 0 . 12 to 0 . 1 9 in. (3 to 5 mm) deep

and spaced 0.5 to 0.625 in. ( 1 3 to 1 6 mm) apart. To date, the NGCS has been constructed on 1 3 pavement

projects in nine states. Early analyses indicate that the NGCS is exhibiting lower noise levels than adjacent projects using

conventional diamond grinding (Scofield 2009). The friction

levels, however, are slightly lower for the NGCS sections. These values, however, are not expected to change signifi

cantly over time, unlike a diamond-ground surface where

the texture can wear down.

As noted previously, the micro texture of a concrete pavement surface is usually provided by the fine aggregate (sand)

component of the concrete mixture. As such, a minimum of 25 percent of the fine aggregate should be siliceous material

that is resistant to wearing and polishing (Snyder 2006). In

situations where diamond-ground surfaces, EAC surfaces, or porous concrete mixtures are used, the microtexture is

provided by the coarse aggregate fraction of the mixture. For good long-term friction, the selected coarse aggregate

should have high polishing resistance.

5.7.5 Existing concrete surfaces 5.7.5.1 Diamond grinding-If used as a retexturing

technique, the primary considerations associated with the long-term effectiveness of diamond grinding are: 1 ) the

polish resistance, which is the susceptibility of the aggre

gate to abrasion; and 2) the hardness of the coarse aggregate contained in the existing concrete. Polish-susceptible

aggregates will exhibit more rapidness in friction and more

significant increases in noise over time that, depending on

the degree of susceptibility, could impact the cost effectiveness of the procedure. Furthermore, the hardness of the aggregate and the depth of cut can affect the speed and costs

of the diamond grinding operations. 5.7.5.2 Diamond-grooved concrete-Like diamond

grinding, however, the speed of grooving operations is

affected by the hardness of the aggregate and depth of cut. Recent testing of diamond-grooved pavements shows that

high levels of friction can be achieved with this texture (Hall

et al. 2009a). 5. 7 .5.3 Shot-abraded concrete-This technique, in which

steel shot is propelled at the concrete surface at high velocity, has seen limited application in the United States. If used,

determine the characteristics of the coarse aggregate and

mortar in the existing concrete pavement to ensure that this texture will provide adequate long-term friction and noise

characteristics. 5. 7.6 Texturing procedures-The type of texturing to

be applied to a pavement project is generally specified by

the owner agency. On large production jobs, the texture is applied during the paving process with a separate texture

machine following the paver; on smaller jobs, texture can be

provided manually. Regardless of which type of texturing is used, there are several aspects critical to obtaining an effec

tive surface texture. Some of these are described as follows (Wiegand et al. 2005 ; Rasmussen et al. 2008) :

a) A consistent concrete mixture is essential to achieving

the desired surface texture. Significant variations between batches could result in textures of varying depths.

b) If used, wet burlap or artificial turf drag should be done

the full width of the pavement and should impart a uniform texture in a single pass. Additional weight may need to be added to the drag material to obtain the desired texture.

The artificial turf drag may need to be regularly cleaned or

replaced throughout the day so as not to leave buildup on the

slab surface. The drag should have sufficient length so that at least 3 to 4 ft ( 1 to 1 .2 m) are in contact with the pavement

surface.

c) Brooming may be conducted for smaller projects or on

irregular areas in place of other methods. The broom shall be drawn transversely across the pavement with adjacent

strokes slightly overlapping. d) If conducted, tining should be performed just after the

water sheen has disappeared from the pavement surface,

and to the specified dimensions for the tine groove spacing, width, and depth. Generally speaking, for wetter concrete, less pressure is needed to obtain the required texture and the

overall elevation of the tining machine is lowered, whereas

for drier concrete, more pressure is needed and the overall

elevation of the tining machine is raised. The most appropriate elevation will depend on the concrete mixture and

prevailing environmental conditions. Individual tines should be regularly inspected and kept clean to avoid uneven appli

cation of the texture to the surface. The texture equipment

should be operated at a consistent speed to promote overall uniformity.

Table 5.7.6 provides a checklist for consideration during

the texturing process.

5.8-Tolerances 5.8.1 Introduction-Tolerances are extremely important in

concrete pavement construction. Specified tolerances help to

ensure that assumptions made by the pavement designer are

fulfilled. They help the contractor in achieving quality and economy, and ensure that the pavement user needs are met. Tolerance requirements vary with the use of the pavement,



Table 5.7.6-Concrete pavement texturing checklist (Rasmussen et al. 2008)

Component Item

Ensure consistent and uniform mixture design in terms of:

Mixture design/ - Gradation

mixture proportioning - Paste volume

- Mortar volume

Preconstruction

- Ensure that the drag provides full paving width coverage

- Ensure that the drag has adequate longitudinal length so that at least 3 to 4 ft (1 to 1 .2 m) are in contact with the

pavement surface

Drag textures - Ensure that adequate ballast (sand, gravel, reinforcing bar, lumber) is available to weight the drag down

(burlap, artificial drag) - Ensure that the drag is clean and that replacement drag materials are available

Construction

- Moisten drag material before initiating the texturing process

- Add ballast as needed to achieve the desired texture

- Remove excess buildup of mortar as necessary

- Replace drag material as necessary to ensure the desired texture is achieved

Preconstruction

- Ensure that the tines are in good condition (straight and free of mortar buildup)

Tine textures - Ensure the tine spacing meets the specifications and that the tines are the same length

Construction (transverse, longitudinal)

- Commence lining just after the water sheen has disappeared from the surface

- Operate the texture equipment at a consistent speed

- Adjust tine angle, length, and downward pressure to achieve the desired texture

type of pavement, and service expectations. City streets where

traffic speeds are low do not need the same surface charac

teristics as highways carrying high-speed traffic. While plain and conventionally reinforced pavements may benefit from

excess thickness, continually reinforced concrete pavements

constructed thicker than the design reduce the percentage of steel in the pavement cross section, which can lead to early

pavement failure. This section discusses tolerance require

ments for various features of concrete pavements. 5.8.2 Thickness-An extensive study by Kim and

McCullough (2002) recommends that concrete pavement

thickness tolerances be dependent on design thickness and

the linearly proportional relationship between the tolerance

and the design thickness used. This study and many state

agencies allow deficiencies of up to 2 percent of specified pavement thickness to receive full unit price, while thick

ness deficiencies of 5 percent or 0.5 in. ( 1 3 mm) receive severe reductions in payment and may require removal and

replacement.

5.8.3 Dowel bars-Dowel bar location and orientation impact joint performance and service life of the pave

ment. The tolerance allowed for dowel bars varies among specifying agencies. In addition, the types of specification,

method, or end result will also affect the wording of specifi

cations. ACI 1 1 7, if incorporated in the contract documents, imposes tolerances for horizontal deviation of dowel bars:

a) Placement of dowels: ± 1 .25 in. (32 mm)

b) Alignment of dowels, relative to centerline of pavement: - 1 8 in. (457 mm) or less projection: ±0.25 in. (6 mm)

- Greater than 1 8 in. (457 mm) projection: not established

Additional guidance on dowel bar alignment tolerances

is available elsewhere (FHWA 2007b; Khazanovich et a!. 2009). Table 5 .8 .3 summarizes the guidance from FHWA

(2007b).

Table 5.8.3-Typical dowel location tolerance (FHWA 2007b)

Misalignment Acceptance criteria Rejection criteria

Horizontal and vertical 5/8 in. ( 1 5 mm) or less I in. (25 mm) + over

rotation (skew) in 1 8 in. (450 mm) 1 8 in. (450 mm)

2 in. (50 mm) or less 2 in. (50 mm) + for an

Longitudinal shift for a 18 in. (450 mm) 18 in. (450 mm) dowel

dowel

Midslab + I in. (25 Cover less than 3 in.

Depth (75 mm) or saw-cut mm)

depth

As previously noted, new nondestructive testing technology such as magnetic imaging tomography (MIT) scan

ning devices allow evaluation of the dowel bar position and alignment shortly after the concrete has reached its initial set,

if desired (5 .5 .3 .3) . This allows the contractor and owner to know if the pavement is meeting specification requirements and if adjustments are needed to the equipment and placing

techniques before too much pavement has been placed.

Some agencies require trial sections of pavement to be placed to verify that the equipment can place dowel bars in

accordance with the specification. For quality control, it is possible to randomly check joints

during the construction process to ensure the dowel bar

position and alignment meet the specification requirements (Lane and Kazmierowski 2008).

5.8.4 Joints-ACI 330R recommends the following tolerances:

a) Contraction joint depth (d = slab thickness): = + 1 14 in. (6 mm), -0 in.

b) Joint width: = + 1 1 16 in. (3 mm), -0 in.

5.8.5 Surface characteristics-Tolerances for surface

characteristics can be found in the FHWA and AASHTO literature and depend on the property specified and the

American Concrete Institute- Copyrighted© Material - www.concrete.org Licensed to: Florida Suncoast Chapter


measuring device. FHWA (2005a) reports the following

information for IRI measured using a lightweight profiler. On transverse tined surfaces, where three repeat runs were

obtained with lightweight profilers, the difference between the maximum and minimum IRI of the three runs was 3 . 8

in./mile (0.06 m/km). In longitudinally tined surfaces,

however, this value was much higher and ranged from 3 .8 to 5 .7 in./mile (0.06 to 0.09 m/km). Because of the interaction between the laser sensor and the longitudinal tining, the IRI

obtained on longitudinally tined surfaces is less repeatable than that obtained on transverse tined surfaces.

The short-interval IRI repeatability over 9 ft ( 1 5 m) segment lengths for transverse tined surfaces showed that

the average difference in IRI between the maximum and

minimum IRI obtained from three repeat runs ranged from 5 . 7 to 7 in./mile (0.09 to 0. 1 1 m/km). These results for a

longitudinal tined surface ranged from 7.6 to 1 5 .6 in./mile (0. 1 2 to 0.25 m/km). The computation of the IRI over the

entire section showed the repeat runs with very close IRI

values due to compensation effects that cause the IRI differences occurring within short intervals to cancel out. These

results indicate that implementing an IRI-based specification

that relies on short-interval IRI (for example, 49 ft [ 1 5 m]) is not practical for pavements that have longitudinal tining.

5.9-Extreme weather conditions 5.9.1 Cold weather-Concrete can be placed safely without

damage from freezing in cold climates if certain precautions are taken. During cold weather, the concrete mixture and its

temperature should be adapted to the construction proce

dure and ambient weather conditions. Adequate equipment

and preparations should be provided for heating concrete materials and protecting concrete during freezing or near

freezing weather. All concrete materials and all reinforcement, forms, fillers, and ground with which concrete is to

come in contact should be free from frost. Frozen materials

or materials containing ice should not be used. Cold weather curing should provide protection from freezing without

overlooking the primary goal of retaining moisture for the time necessary to bring cement hydration to an acceptable

point. Polyethylene sheets covered with hay or straw serve

both purposes. Refer to ACI 306R and ACI 306. 1 . The temperature of fresh concrete should be above W°C (50°F).

The curing period for cold weather concrete is longer than

the standard period for external curing due to reduced rate of

strength gain. Compressive strength of concrete cured and

maintained at woe (50°F) is expected to gain strength half as quickly as concrete cured at 23°C (73°F).

Further recommendations for cold weather concreting can

be found in ACI 306R. 5.9.2 Hot weather-Hot weather conditions adversely

influence concrete quality primarily by accelerating the rate of moisture loss and rate of cement hydration that occurs

at higher temperatures (Kosmatka et a!. 2002). During hot

weather, proper attention should be given to ingredients, production methods, handling, placing, protection, and

curing to prevent excessive concrete temperatures or water evaporation that could impair required strength or service-

ability of the pavement. Curing in hot weather requires addi

tional attention, sometimes placing at night or using internal curing. Because strength gain in hot weather is faster, the

curing period may be reduced. Further recommendations for hot weather concreting can be found in ACI 305R.

5.9.3 Rain-Heavy rain or hail striking concrete pave

ment that has not gained final set can cause serious surface damage. Good practice and many specifications require the

contractor to have sufficient plastic sheeting available at the

job site to help protect, or minimize the damage to, freshly placed pavement in the event of unanticipated rain or hail. If a sudden rain event occurs, the contractor should quickly

cover the most recent placement with plastic sheeting and

should not try to soak up water from the concrete surface.

After the event, the surface will need to be inspected to determine if any remedial action is required (ACPA 2003).

5.10-0pening to traffic

5.10.1 Opening to traffic and construction traffic limitations-General guidance on the allowance of construction traffic on the newly constructed pavement is summarized as follows.

a) The finished pavement should be protected against damage from the construction operations and traffic until

final acceptance. b) The pavement shall attain a strength sufficient (5 . 1 0.2)

to carry traffic without being damaged before hauling equip

ment or concrete mixer trucks are allowed on the pavement. c) The transverse and longitudinal joints should be sealed

or otherwise protected before any construction traffic is

permitted.

d) Rapid-strength-gain concrete mixtures may be specified to provide earlier opening of the pavement.

e) Other construction equipment, such as subgrade planers

and concrete finishing machines, can be permitted to ride on

the edges of previously constructed pavement slabs when

the concrete has attained strength sufficient to withstand damage. All edges of slabs should be protected from damage.

f) Pavements carrying construction equipment traffic should be kept clean. Spillage of material or concrete should

be removed immediately after occurrence.

Traffic should be excluded from the pavement by erecting and maintaining barricades and signs until the concrete

strength is sufficient. Any portion of a pavement damaged by traffic, construc

tion equipment, or other causes prior to final acceptance

by the engineer should be repaired or replaced by and at the expense of the contractor by approved procedures and

methods.

5.10.2 Criteria for opening to traffic-Various criteria for opening to a variety of traffic types are used. Most methods

are empirically based and involve a minimum time requirement, a minimum strength requirement, or some combina

tion of both. Alternatively, there is a rational method avail

able that is based on fatigue life consumption for various types of construction equipment and public traffic. Tables of

minimum required flexural strengths have been published. A simplified version is shown in Table 5 . 1 0.2. The advantage



Table 5.10.2-Minimum recommended flexural strengths for opening to traffic

Construction traffic'!

Thickness, in. (mm) Flexural strength, psi

(MPa)

<5 (<1 25) 570 (3.9)

6 ( 1 50) 460 (3.2)

7 ( 1 75) 340 (2.3)

8 (200) 300 (2. 1 )

� 1 0 (>50) 300 (2. 1 ) * Assumes 50 passes of a fully loaded veh1cle.

Public traffic t1

Flexural strength, psi

(MPa)

570

540

450

330

300

1Assumes 500 one-way equivalent single axle load (ESAL) repetitions between time

of opening and time concrete reaches design strength.

:Assumes modulus ofsubgrade reaction of 100 psi/in. (27 MPa/m).

of this method is that opening times can be reduced from

the typical arbitrary time limits if the minimum required strength has been attained.

5.10.3 Determination of flexural strength-There are

several methods for determination of the flexural strength necessary for determining the time to open pavements to

traffic. There are two categories: 1 ) testing of actual concrete specimens made at the job site and cured in a similar manner to the pavement; and 2) nondestructive testing (NDT)

methods of estimation of flexural strength. Actual specimens made and cured at the jobsite are typically either beams or

cylinders. If cylinders are to be used, then a correlation

between compressive strength and flexural strength would have to be developed with job materials prior to the start of

production.

One method of determination of opening strength by use

of strength specimens is to cast three or more sets of specimens from each placement unit that exceeds 50 yd2 (42 m2).

The specimens should be cured in a similar manner to the slab. At a given time, test one specimen from each set and

average the results to establish a test value. If the test value is not sufficient to meet the aforementioned opening strength

criteria, test a second set and so forth until the criteria has been met.

Nondestructive methods of estimation of flexural strength

include maturity, pulse velocity, pullout, and break off.

The emphasis in recent years has centered on the maturity method. In any case, the NDT method would have to be

correlated to flexural strength prior to construction.

5.10.4 Maturity method-The maturity method is based on the premise that the strength of a given concrete mixture

can be expressed as a function of time and temperature· thus concrete maturity can be used to estimate strength. Th:re ar� several expressions of maturity. The two most common are

the Arrhenius and the Nurse-Saul. Both methods have their advantages. The most commonly used one in the United

States is Nurse-Saul because of its simplicity. The expression is

M = L[(T- 7;,)(M)] (5. 1 0.4)

where T is the concrete temperature, °F (°C); T0 is the

temperature below which concrete will show no increase in

strength with time (typically 50 or 32°F [ 1 0 or 0°C]); and Llt is the curing time, days.

The advantages of the maturity method over cylinder or

beam testing are: 1) more accurate representation of the

actual conditions in the slab; 2) less cumbersome equipment at the jobsite; 3) elimination of casting and handling test

specimens; 4) acquisition of continuous curing condition

data throughout the entire process; and 5) strength determination can be made at an earlier age.

The maturity testing process is relatively simple and straightforward. As shown in Fig. 5 . 1 0.4, it essentially consists of two steps: 1 ) development of the maturity cali

bration curve; and 2) measurement of the maturity of the in-place concrete. From this information, the strength of the

in-place concrete can be monitored and assessed. Development of the maturity calibration curve is done

prior to job startup, and will be unique to the specific

mixture design. Any change in materials or mixture design

will require the development of a new calibration curve. In

the process, sets of concrete specimens are cast and tested at different ages, as shown in Fig. 5 . 1 0.4. The elapsed time

and temperature are also recorded, and the maturity-versus

strength curve is developed. During construction, maturity sensors are inserted into the

slab. There are two basic varieties of sensors: thermocouple

wire and self-contained data loggers. Maturity data can be collected in one of three ways: 1 ) digital thermometers can

be momentarily attached to the embedded thermocouple wire and discrete readings of temperature taken, and then,

knowing elapsed time, maturity can be calculated; 2) an external data logger can be attached to the thermocouples,

then temperature and time are recorded continuously and �aturity automatically calculated and recorded; and 3) an

mternal data logger can be inserted into the concrete and

continuous readings taken, then downloaded to a device at any time. Then, by use of the previously developed matu

rity-strength relationship, the strength of the slab can be estimated. This strength can then be compared to minimum

criteria, such as in Table 5 . 1 0.2, to determine ifthe pavement

can be opened to traffic. Methods for maturity testing are found in ASTM C 1 074.

5.11 -Quality control/qual ity assurance 5.1L1 General-Quality control (QC) includes actions

taken by the paving contractor and material supplier to s�ccessfully control the construction and material produc

tiOn process such that the final product (the pavement) is, at

the very least, within specifications and preferably will func�ion at an optimum level. To assist in controlling the process,

mspection and testing is performed by the contractor and material supplier. The contractor should proactively react to

process changes before quality is compromised.

Quality assurance (QA) includes the actions taken by the

owner ofthe project to assure that the QC operation is properly

functioning and that the test results of the QC operation represent the test result population of the pavement being tested.

Thus, to assist in assurance of the functionality of the QC operation, inspection and testing is performed by the owner.



Step 1 . Develop maturity curve for concre·te mixture Strength Tos.ts �lop Maturity Curve

F1 1-2 1-3 jjj M1 5 >< M2 .5! .. .. u.. M3 0 g! c C2 C3 ·;;; Ill

I ..

Step 2. Measure maturity of in-place concrete

.t

MatYrity M ICI" or Hllndhold Rood r

Tbormocouple or E:r�•l:>oddod Mieropmceum

Fig 5. 1 0.4-Maturity testing process (A CPA 2002).

The type of QC/QA program required to establish that

the as-produced concrete and the as-built pavement meet the requirements of the specification will depend on the nature and size of the project. On small jobs, only a limited

amount of sampling and testing can be justified, but on

major work, it is important to use a QC/QA program based on statistical concepts. The program should require that the

paving contractor, the concrete producer, and other material

suppliers be responsible for product quality control, and that

the owner be responsible for acceptance. Material accep

tance and payment is based on: 1 ) the pavement meeting

the specification requirements; 2) the contractor following

the approved QC plan; and 3) there is favorable comparison between the QC test results of the contractor and the QA test

results of the owner such that the QC test results can be used to compute pay factors. Because it is difficult and costly to

replace defective concrete, and because suitable tests do not yet exist that can fully define the required properties

of concrete after hardening, the owner may wish to elect to

sample and test the as-produced freshly mixed concrete prior to incorporation in the work, or to sample and test any of the

constituent materials. Such tests by the owner for acceptance purposes should not relieve the contractor of his responsi

bilities for product control. Guidelines for developing QC/ QA programs can be found in ACI 1 2 1 R, 22 1 . 1 R, 3 1 1 .4R, 3 1 1 . 5, and 3 1 1 . 1 R.

5.11.2 Sampling-Samples of materials on which the

acceptance or rejection of material is based should be carefully taken in accordance with prescribed procedures.

Samples for inspection or preliminary tests should be required of the producer. The sample should be represen

tative of the condition of interest. The as-produced condi

tion samples should be taken at the production facility, the concrete plant (aggregate) or in front of the paver (concrete),

and behind the paver. The as-placed hardened state concrete sampling and testing should be performed on the hardened

slab. As a general rule, the frequency of sampling should be greater at the start of a project.

The importance of proper sampling cannot be overempha

sized. No amount of care and accuracy in subsequent testing will provide correct information if the samples are carelessly

taken and not representative of the material sampled. Procedures should be set up for gathering samples in a manner that

provides the maximum possible information on the average

characteristics, plus the nature and extent of variability of materials. Poor sampling and testing procedures could result

in costly overdesign, rejection or removal of acceptable

material, acceptance of objectionable material, and unnecessary production process adjustments.

5.11.2.1 Methods-Methods of sampling materials and the

proper size of samples for various tests are often stipulated in the test methods. Sample sizes must be adequate for all tests to be conducted. Procedures for obtaining samples of materials can be found in applicable ASTM and AASHTO

standards for the given material.

5.11.2.1.1 Aggregate sampling-Proper sampling procedures are outlined in ASTM D75/D75M. Three alternate

types of sampling are in use: 1 ) belt; 2) stockpile; and 3) truck/rail car/barge. Belt sampling can be of the on-belt or

belt-discharge variety. It is difficult to obtain a representative

sample from stockpiles. If it is necessary to do so, the procedure can be optimized by use of a loader to sample and build

a minimum stockpile. All samples will have to be reduced

to the proper testing size using proper splitting methods as outlined in ASTM C702/C702M.

5.11.2.1.2 Plastic concrete sampling-Recommended concrete sampling procedures from ASTM C94/C94M

include either sampling off the sub grade or subbase in front

of the paver or from the discharge chute of a concrete truck.

If taken in front of the paver, the sample should be taken from five spots, being careful not to contaminate the concrete with subgrade or subbase material. A second acceptable method



is to sample directly from the discharge chute of a concrete

truck. In this case, the sampling container should be passed directly through the entire discharge stream, or the chute

should be directly discharged into a sample receptacle such as a wheelbarrow. The composite sample should consist of at

least two portions taken from the middle portion of the load. At least I yd3 (0.76 m3) of material should be discharged before the sampling begins. Regardless of sampling method,

after the composite sample has been taken, the material

should be thoroughly mixed in the sample receptacle. In some contract specifications, samples for air content

are taken behind the paver to obtain a truer measurement

in the slab. To avoid the necessity of sampling every time behind the paver, typical scenarios may entail sampling once

in the morning and once in the afternoon, both in front of and

behind the paver. From this, a correction factor for air loss

through the paver can be determined. Thereafter, samples can be taken in front of the paver, with the air loss adjust

ment factor applied.

5.11.2.1.3 Coring-Cores are cut from pavements to assess thickness, strength, or both. Various agencies have

significantly different methods of preparing the cores prior

to testing, thus the inspector needs to be familiar with the particular specifications in place for the project. Coring is discussed in more detail in 5 . 1 1 .3 . 1 . 1 and 5 . 1 1 .3 . 1 .4.

5.11.3 Test methods-Materials should be tested in accor

dance with methods referred to in the appropriate contract

specifications or other recognized standard procedures. The most commonly specified QC/QA material test

methods include those for aggregate, plastic concrete, and

hardened concrete. For aggregate, the gradation, delete

rious material, and moisture content are the most important properties to be tested during the construction process. For

plastic concrete, typical tests include slump; air content; and under certain circumstances, temperature and unit weight.

Casting strength specimens, such as cylinders and beams, is

also recommended. Additionally, concrete maturity is useful for estimation of strength gain to assist in the determination

of criteria for opening to traffic. Thickness and maturity are

discussed in 5 . 1 0.

Specimens for flexural strength tests to be used as the basis

for the laboratory proportioning of concrete mixtures should be molded and cured in accordance with ASTM C l92/

C 1 92M and tested in accordance with ASTM C78/C78M. For projects where it is desirable to use compressive

strength testing as the basis for job control, companion

compressive cylinders should also be made during the mixture proportioning phase. These cylinders should be molded and cured in accordance with ASTM C l 92/C l 92M

and tested in accordance with ASTM C39/C39M to establish the correlation between the flexural and compressive

strengths. The correlation should be based on a range of strengths as a function of w/cm.

5.11.3.1 Strength tests of field concrete

5.11.3.1.1 Strength test specimens-For material acceptance, either compressive or flexural specimens should be

made in the field and cured in accordance with the standard laboratory curing section in ASTM C3 1/C3 1 M. Flexural

specimens should be tested in accordance with ASTM C78/

C78M. Compressive specimens should be tested in accordance with ASTM C39/C39M.

Some state agencies, in an effort to base acceptance on

a performance specification strategy, determine compressive strength from 4 in. ( 1 02 mm) drilled cores from the slab

tested at 28 days. Coring is performed and testing done in accordance with AASHTO T024 and T022, respectively.

5.11 .3.1.2 Testing frequency-If the contract documents

include provisions for a statistically-based quality level analysis program, then a sampling/testing program involving requirements for both QC and QA will be outlined. A lot/ sublot system will most likely be established, and sampling

and testing intervals established for both concrete and

aggregate. Typically, the project will be divided into lots, and random sampling will be specified. The results will

be used in a method of payment based on percent within

limits or some similar strategy. Typically, a lot may be one

day of production, and the lot may be divided into four to

six sublots, with each sublot being tested for strength (cast cylinders or beams) and perhaps slab thickness from drilled

cores. Thickness is determined in accordance with AASHTO

T l48 . Specimens should be prepared in sufficient numbers to

assure job control-once per sublot with a minimum of not less than once per 5000 ft2 ( 460 m2). Minimum QA

frequency might be once per lot, where a lot may be defined

as a day of production. More elaborate testing programs can be developed using the methods described in ACI 2 1 4R.

5.1L3.1.3 Acceptance criteria-Whether compressive or

flexural strengths are used for acceptance, the acceptance

criteria should allow occasional low tests. Low strength results from standard-cured specimens should be evaluated in accordance with ACI 3 1 8- 1 1 , Section 5 .7 .4. 1 . Concrete

proportions should be considered adequate if the average of

any three consecutive tests equals or exceeds the specified

strength and no one test falls more than 500 psi (3 .5 MPa)

low in compression or 75 psi (0.5 MPa) low in flexure. The mixture should be reproportioned in the event of compressive or flexural strengths failing to meet the second criteria.

5.1L3.1.4 Tests of in-place concrete-In the event of low

compressive test results, core testing of in-place concrete should be conducted in accordance with ASTM C42/C42M

and evaluated in accordance with ACI 3 1 8 . Core testing has also been used for the primary strength evaluation in QC/

QA projects. Beams sawed from the pavement should not be

used to evaluate in-place concrete strength. 5.1L4 Job control acceptance criteria-Acceptance

criteria for each type of test can take one of several forms, as

shown in the following sections. The concept of action limits or threshold values may be included in the contract docu

ments. The limits are intended to alert the contractor that the process is in danger of becoming out of control, and steps

should be taken to correct the situation. The use of statistical

control charts can be beneficial in detection and analysis of process or material changes.

5.11.5 Aggregate testing-To assure concrete uniformity

in terms of consistency and quality, aggregates should be



tested with a frequency consistent with the production rate. Typically, specifications call for monitoring of gradation; deleterious materials; moisture content; and in certain cases,

absorption and specific gravity. 5.11.5.1 Gradation-The gradation of all aggregate frac

tions should be closely monitored using the sieve analysis

procedures ofASTM C l 36/C l36M. 5.11.5.1.1 Testing frequency-Typical recommended QC

sampling frequency is twice per day, and not less than once

per 7500 yd2 (6275 m2). Quality assurance frequency would be a minimum of once per week.

5.11.5.1.2 Acceptance criteria-Traditionally, aggregate gradation is assessed for each aggregate fraction (for

example, coarse and fine aggregate) by checking the percent

retained or passing on specified sieves and comparing the result to a plus/minus limit within which the gradation should

stay. For concrete aggregate, an alternative to this would be to use a total gradation concept such as some version of the

Shilstone Coarseness and Workability Factor Chart (Shil

stone and Shilstone 2002). With this method, once the gradation is established, the position on the chart is limited in its

movement by certain allowable amounts. If the point starts

to stray too far, then either the proportions or the gradations of the fractions will have to be adjusted.

5.11.5.2 Deleterious material-Deleterious material, such as clay, lumps, shale, and soft aggregate, should be tested in

accordance with the governing specifications, such as ASTM

C33/C33M. Note that military airfield pavement specifications have special deleterious materials requirements.

5.11.5.2.1 Testing frequency-Typical recommended QC

sampling frequency is twice per day, or not less than once

per 7500 yd2 (6275 m2). Quality assurance typical frequency would be once per 2 days.

5.11 .5.2.2 Acceptance criteria-Some agency specifications will divide deleterious materials into several categories

and assign maximum allowable limits to each.

5.11.5.3 Moisture content-Aggregate should be tested for moisture content so that batch weights can be adjusted to

maintain the specified mixture design. 5.11.5.3.1 Testing frequency-Typical recommended QC

sampling frequency is twice per day. It is good practice to

determine aggregate moisture content before the first batch of the day and continue QC testing frequently until stock

pile moisture has stabilized. Quality assurance minimum frequency is once per 2 days.

5.11.5.3.2 Acceptance criteria-If the moisture varies by

more than 0.5 percent, the batch weight settings should be adjusted.

5.11.5.4 Absorption and specific gravity-The bulk

specific gravity in a saturated surface-dry condition and

the absorption of coarse aggregate should be determined in

accordance with ASTM C l 27. The bulk specific gravity in a saturated surface-dry condition and the absorption of fine

aggregate should be determined in accordance with ASTM

C l 28. Testing frequency is on the order of once per 7500 yd2

(6275 m2) of concrete.

5.11.6 Fresh concrete tests

5.11.6.1 Air content-The air content of plastic concrete

may be determined in accordance with standard methods of test for air content: 1 ) gravimetric (ASTM C l 38/C l 38M);

2) volumetric (ASTM C l 73/C l 73M); or 3) pressure

(ASTM C23 1/C23 1M). The pressure meter method is the most commonly used in practice. For concretes made with blast-furnace slag aggregate, lightweight aggregate, or other

vesicular porous aggregates, the volumetric method should be used.

5.11.6.1.2 Testing frequency-Air content testing should be performed on the first batch of each day, whenever the

consistency seems to vary, and whenever strength specimens

are cast. Thus, typical recommended QC testing frequency is once per sublot and at least once per 5000 ftz (460 m2).

Quality assurance testing frequency should be at least once per lot (day). Additional monitoring of air content for process

control can also be done at the batch plant. 5.11.6.1.3 Acceptance criteria-Various agencies

approach acceptance criteria differently. One method is to

place an interval around a target value, typically ±0.5 to 1 .5 percent. Another approach is to use a minimum tolerance of

0.5 percent below the minimum specified level. The levels

will have been established based on the aggregate size used

in the mixture and the environmental exposure conditions. 5.11.6.2 Consistency (slump)-Slump is usually deter

mined in accordance with ASTM C l43/C l43M.

5.11.6.2.1 Testing frequency-Slump testing should be

performed on the first batch of each day, whenever the consistency seems to vary, whenever strength specimens are cast,

and whenever air content tests are performed. Thus, typical

recommended QC testing frequency is once per sublot, and

at least once per 5000 ft2 ( 460 m2). Quality assurance testing frequency should be at least once per lot (day).

5.11.6.2.2 Acceptance criteria-Typical target slumps are 3 to 4 in. (76 to 1 02 mm). ASTM C94/C94M details two

alternate acceptance limits: if the not-to-exceed method is

employed, the tolerance is - 1 .5 in. (-38 mm) for concrete

with a slump equal to or less than 3 in. (76 mm), and -2.5 in. ( -63 mm) for slump greater than 3 in. (76 mm). For the alternate method-for example, the not-to-exceed situation-the

recommendation is ±0.5 in. ( 1 3 mm) for equal to or less than 2 in. (5 1 mm) slump, ± 1 in. (25 mm) for slump 2 to 4 in. (5 1 to 1 02 mm), or ± 1 .5 in. (38 mm) for slump greater than 4 in. ( 1 02 mm)

5.11.6.3 Temperature-Temperature testing should be

conducted in accordance with ASTM C 1 064/C 1 064M.

5.11.6.3.1 Testing frequency-The necessary frequency of temperature testing varies with the criticality of the situ

ation. Extremes in weather and sensitivity of temperature

to the construction operation, such as prevention of plastic shrinkage cracks, dictate frequency of testing.

5.11.6.3.2 Acceptance criteria-Typical specifications

limit the maximum temperature to 90°F (32°C) (85°F [29°C] for bridge decks and 90°F [32°C] for heated concrete) and

minimum temperatures to 40 to 55°F (5 to 1 3 °C), depending on section thickness.

5.11.6.4 Unit weight-It is recommended that the unit

weight of the plastic concrete should be tested as a check for



several factors, such as batch-to-batch uniformity and yield.

Unit weight testing should be conducted in accordance with ASTM C 1 3 8/C 1 38M.

5.11.6.4.1 Testing frequency-Typical recommended sampling frequency is once per sublot and at least once

per 5000 ft2 ( 460 m2) . Quality assurance testing frequency

should be at least once per lot (day). 5.11 .6.5 Visual inspection-The goal of the inspection

program is to assure a smooth, dense, homogeneous, and

durable pavement with adequate strength. To that end, the pavement should meet certain visual criteria. These should

include no apparent edge slumping within 6 in. ( 1 50 mm) of

the pavement edge, no honeycombing at the edge, a well

defined and continuous radius along the edges of the concrete

along form lines and expansion and construction joints, no visible tool marks, a proper surface texture, all concrete removed from the top of the joint filler, and all excess joint

filler material removed. The concrete surface and exposed

edges should be covered and cured in accordance with the

project specifications. 5.11 .6.6 Straightedging-A smooth surface is important to

the functional performance of the pavement. For projects not

suited for equipment profiling using the lightweight profiler (5 .8 .5), all segments ofthe slab should be straightedged with

a tolerance of 1 /8 in. in 10 ft (3 mm in 3 m) by testing with a 1 0 ft (3 m) straightedge on lines 5 ft ( 1 .5 m) apart parallel

with the centerline of the pavement.

5.11 .6. 7 Thickness-Slab thickness testing can be obtained in several ways. One method entails placing 1 2 in. (305 mm)

square plates at certain intervals-for example, 200 ft ( 6 1

m)-and probing through the plastic concrete to measure the

slab thickness. A more traditional method involves coring,

which is discussed in 5 . 1 1 .2 . 1 .3 . Although several nonde

structive testing technologies, such as GPR or impact echo, can be used to estimate slab thickness, these are not accurate

enough to be used for acceptance.

Magnetic tomography equipment (5 .5 .3 .3) can also be used to assess slab thickness, provided that metal target

plates are first placed on the base course prior to paving.

5.1 2-Construction inspection 5.12.1 General-Sampling frequencies and testing

methods for QC/QA have been presented in 5 . 1 1 and

pertain to compliance of materials with specifications or for computing pay factors. This section pertains to observing an

operation or examination of a product to determine if it is

satisfactory. These additional inspection items may include field testing, although some inspection involves visual eval

uation with results that are not measurable.

5.12.2 Construction inspection items 5.12.2.1 Alignment and elevation-Setting and protec

tion of forms and stringlines is necessary for achieving proper surface elevations and pavement thicknesses. Once

proper elevation control has been set, the stringline eleva

tion should be checked prior to trimming and paving. Cross section elevation can be verified by stretching a stringline

transversely and checking the profile at several places across the roadway width.

It is suggested that tolerances for fine grading are no more

than 0.25 in. (6 mm) above or 0.5 in. ( 1 3 mm) below the specified design grade (ACI 330R).

5.12.2.2 Subgrade-Uniform subgrade support is the goal of proper site preparation. The designer may require grading operations to blend soil types to improve uniformity. Prop

erties of the subgrade soil can be improved by compaction, stabilization, and moisture control.

5.12.2.3 Subgrade, subbase, and base compactionSubgrade soils should be compacted to a minimum of 95 percent of ASTM D698 Method C maximum standard

proctor density. Some specifications may require the use of the modified proctor test (ASTM D 1 557) .The optimum

moisture, as determined in ASTM D698, can be used as a

reference point in determination of the proper moisture content at which a particular soil type should be compacted.

For instance, expansive soils should be compacted at moisture contents 1 to 3 percent above optimum moisture

content. In-place field density tests should be conducted at a

frequency of at least one test per 2000 yd2 ( 1 670 m2) of area per 6 in. ( 1 50 mm) lift with a minimum frequency of three

per lift. Acceptable methods of field density testing include:

ASTM D6938 (nuclear), D 1 556/D l 556M (sand cone), D2 1 67 (rubber balloon), and D2937 (drive tube) . Quality

control/QA of granular subbases and base materials typically entails meeting specifications for density, thickness,

gradation, deleterious materials, and PI. Material should

be sampled from the roadway after placement but prior to compaction. Sample locations should be random in nature.

A pair of random numbers should be generated for each

sampling location-one for longitudinal offset and one for

transverse offset. Typical minimum density and thickness testing frequency

for QC is one test per 1000 tons (907 tonnes) (minimum one per day). For QA, frequency is one test per 4000 tons (3628

tonnes) (minimum one per project). Minimum compacted

in-place field density should be 1 00 percent maximum standard proctor density (ASTM D698). The thickness should be

no less than 0.5 in. ( 1 3 mm) deficient from the plan thickness. Quality control gradation and deleterious materials testing

frequency is one test per 2000 tons ( 1 8 1 4 tonnes) (minimum one per day). Gradations should fall within the limits set in

the specifications for each control sieve. For QA, frequency is one test per 8000 tons (7256 tonnes) (minimum one per

project). The PI should be checked at a minimum frequency

of once per 1 0,000 tons (9070 tonnes) (minimum one per day) and once per 40,000 tons (36,280 tonnes) (minimum once per project) for QC and QA, respectively.

Proof rolling of the foundation surface prior to concrete

placement is often required to identify any soft spots. In the event that a soft area is discovered, the area should be stabi

lized or removed and replaced with material compacted to

the required density prior to concrete placement. 5.12.2.4 String line-The stringline or trackline grade

should be checked periodically before and during the paving operation against survey stakes for alignment and grade. The

string should be held firmly in the bracket; uniformly taut;



and free from kinks, bends, and obstructions (Kohn et a!.

2003). 5.12.2.5 Form setting-The subgrade under the forms

should be compacted, cut to grade, and tamped to furnish uniform support to the forms. Enough form pins or stakes

should be used to resist lateral movement. All forms should be cleaned and oiled as necessary to obtain neat edges on the slab. Lines and grades of forms should be checked immedi

ately before concrete placement and preferably after form

riding equipment has been moved along the forms (ACI 330R).

5.12.2.6 Tie bar placement-Tie bar inspection should include verification of proper bar length, diameter, grade of

steel, spacing, alignment, depth, and freedom from contami

nation and cracking (4.4, 5.5, and 5 .6) welded deformed or welded plain wire fabric.

5.12.2. 7 Reinforcement placement-Reinforcement should be checked for proper elevation, support of the steel,

and lapping. If sheets of welded deformed or welded plain

wire fabric are used, the sheets should be managed to prevent them from pushing together and upward, shifting horizontally, or portions protruding vertically. The inspection of the

reinforcement should include verification of proper bar or wire diameter, grade of steel, and spacing (4.4, 5.5, and 5 .6).

5.12.2.8 Dowel placement-Dowel bar inspection should include verification of proper bar length, diameter, spacing,

vertical and horizontal alignment, depth, condition, and bond

breaker (4.4, 5.5, and 5 .6). Prepaving inspection and verification can be accomplished by traditional manual methods.

Post-paving methods include the use of nondestructive scan

ning devices. These devices have been shown to be accu

rate within certain parameters, such as dowel depth, vertical misalignment, horizontal misalignment, whether dowels are

epoxy-coated, and whether the dowel baskets transport ties have been cut.

5.12.2.9 Concrete production-Refer to 5 .2 for informa

tion about concrete production. The plant inspector should verify that the plant is in good operating condition, the speci

fied materials are being hatched, scales are being checked as specified, and that aggregate moisture tests are being

conducted.

5.12.2.10 Concrete placement-The subgrade should be uniformly moist with no standing water. If the concrete is

placed in hot, dry, or windy conditions, the subgrade should be lightly dampened with water in advance of concrete

placement. All concrete handling operations should mini

mize segregation to maintain the integrity of the concrete. Concrete should be deposited as uniformly as possible ahead

of the paving equipment and as close to its final position as

possible so as to require a minimum of rehandling. If slip

form equipment is used, the concrete should be of proper

consistency to prevent excessive edge slump (refer to 5 .2 and ACI 330R).

5.12.2.11 Concrete consolidation-Concrete can be struck off and consolidated by using a laser screed, mechanical

paving machine, vibrating screed, or a straightedge after

consolidating with a hand-held vibrator. Screeds should be sufficiently rigid so that they do not sag between the form

lines or ride up over a stiff mixture. They should also be adjustable to produce any specified crown (ACI 330R). Vibrator frequency can be checked with hand-held devices or by observing the paving machine monitor. For well-propor

tioned mixtures, a frequency of 8000 VPM is commonly

recommended. However, for over-sanded mixtures, the

frequency should be reduced to a range between 5000 to 8000 VPM to avoid harming the air void system (Taylor et

a!. 2006) (refer to 5 .2).

5.12.2.12 Concrete finishing-Proper finishing should result in a concrete surface that is dense, smooth, and

durable. Excessive manipulation of the surface should be avoided because a surplus of mortar, water, and soft

materials can be brought to the surface. Hand floating and

straightedging should not be used accept to correct localized surface unevenness.

Edge slump should not exceed 3/8 in. (9 .5 mm) in 1 00 percent of slipformed pavement, and 0.25 in. (4.75 mm) in

8 5 percent of the pavement.

5.12.2.13 Surface texturing-Refer to 5 .2 and 5 .7 for more information about surface texturing.

5.12.2.14 Joint sawing-Typically, joints produced using

conventional processes are made within 4 to 1 2 hours after the slab has been finished in an area--4 hours in hot weather

to 1 2 hours in cold weather. For early-entry dry-cut saws, the waiting period will typically vary from 1 hour in hot weather

to 4 hours in cold weather after completing the finishing of

the slab in that joint location. The depth of saw cut using a conventional saw should be one-third of the slab depth or a

minimum of 1 in. (25 mm), whichever is greater. The depth

of a saw-cut using an early-entry dry-cut saw should be 1

in. (25 mm) minimum for pavement depths up to 9 in. (225 mm). This recommendation assumes that the early-entry

dry-cut saw is used within the time constraints noted previously (ACI 330R). Prior to sawing, the position of the saw

cut should be verified.

Because paving is typically done during the day, this means sawing may occur at night. Thus, adequate lighting

should be planned. Generally, each joint should be sawed in order, but occasionally sawing of alternating joints may

be required under severe conditions where random cracking

may otherwise result. Note, however, that this could lead to excessive opening of some joints due to differing slab

sizes. Damaged curing compound areas should be resprayed (Kohn et a!. 2003) (refer to 5 .4).

5.12.2.15 Joint cleaning and installation-Information

pertaining to joint cleaning and installation is contained in 4.5 and 5 .4.

5.12.2.16 Joint sealing-If joint sealing is required, the

joints should be thoroughly cleaned and the sealing materials installed without overfilling, in accordance with the

manufacturer's instructions, before the pavement is opened to traffic (ACI 330R). Additional information about joint

sealing is found in 4.4, 4.5, and 5 .4.

5.12.2.17 Concrete curing-Exterior curing can be accomplished by water curing or sealing the exposed surface.

Water curing methods include ponding or immersion; fog spraying or sprinkling; saturated burlap; cotton mats and



rugs; wet earth, sand, or sawdust; and straw or hay. Sealing

can be accomplished using spray-on curing compounds, plastic film, and reinforced paper. With the exception of

saw cuts that will be widened, saw-cut joints should also be cured. These methods are described in more detail in ACI

308R. Use of spray-on membrane curing compound is the

most widely used pavement curing method. Application of

white-pigmented membrane-forming curing compounds

meeting ASTM C309 or ASTM C 1 3 1 5 (Type II) should

follow the normal curing procedure recommended by the manufacturer. Two applications at 90 degrees offset can be

required on windy days (ACI 330R). Application of curing compound by a power-driven machine straddling the slab is

preferred so that the spray will be uniformly applied. The

use of hand-operated pressure sprayers should be limited to odd slab shapes and widths and surfaces exposed by removal of forms (Department of Defense 2004). Additional information is found in 5 .3 .

5.12.2.18 Surface grinding-A suggested surface texture

test method is ASTM E965 . The test locations could be the same locations as for strength and thickness determination. The results should show a minimum texture depth specified

in the contract documents. All testing should be completed

no later than the day following placement.

CHAPTER 6-SUSTAINABILITY

6.1 -lntroduction Sustainability is defined by the United Nations General

Assembly as "meeting the needs of the present without

compromising the ability of future generations to meet

their own needs" (United Nations General Assembly 1 987). Concrete is one of the most widely used building materials

on earth because of its utility and durability. Despite the wide use of concrete for structures and infrastructure, there is

criticism about concrete, specifically for cement production.

The process of converting lime, iron, silica, and alumina into portland cement is very energy-intensive and produces large

amounts of carbon dioxide (C02). C02 is considered a major cause of global climate change, which is a driving force

in the sustainability movement. Two strategies are used to reduce the energy and C02 emissions associated with the production of portland cement. First, the cement industry is

improving the efficiency and expanding the fuels that can be used in their production processes so that energy require

ments are reduced. Second, more common is the use of

supplementary cementitious materials (SCMs), maximizing the coarse aggregate quantities in a concrete mixture, and

using locally abundant and recycled coarse aggregates that

have low energy and C02 footprints. Additional information on the latter item is discussed later, with expanded discus

sion on the cement production provided as follows.

The total energy use by the U.S. cement industry has decreased 16 percent between 1 997 and 2007. To reduce the

fuel load required to heat the cement kiln, the manufacturing process now captures the heat produced during calcining and

preheats the raw materials before they enter the kiln. Old tires and other flammable materials known as alternate fuels

are used to heat the kiln along with renewable fuels such as

biomass. While C02 is liberated during cement production, U.S. and Canadian plants contribute only approximately 1 .5

to 1 .5 8 percent of the total North American man-made C02. By comparison, transportation accounts for approximately

25 percent of the total man-made C02• The fuels used to

obtain the temperature necessary to break down the limestone in the kilns are currently high-emissions intensity fuels

such as coal and petroleum coke because they are relatively

inexpensive. Although there is not a great deal more that can be done to economically increase the energy efficiency of

the kilns, there is a possibility of decreasing the amount of fossil fuels used in kilns and reducing the amount of raw

material that needs to be heated and transformed to make

each ton (tonne) of cement. Four methods are being pursued to reduce the cement industry energy and C02 footprints:

a) Improving the energy efficiency of manufacturing operations

b) Substituting alternative (waste-derived) and renewable

(biomass) energy sources for fossil fuels used in the manufacturing process

c) Substituting SCM for clinker in the production of

blended cements and other cement products and lime addition to cement at the mill to reduce C02 and the energy

required to produce the cement d) Undertaking long-term research and development on

less C02-intensive cementing materials and manufacturing

operations In addition, exposed concrete surfaces carbonate over

time, reabsorbing up to 46 percent of the originally produced

C02 based on the amount of cement in the mixture. Where

old concrete is removed and crushed for reuse as base or recycled concrete aggregate, the newly exposed surfaces

increase the absorption of C02 from the atmosphere.

6.2-Sustainable concrete pavements

The inherent durability and longevity of concrete make

it a prime sustainable construction material. Concrete pavements can reach the ultimate in sustainability through continuing coordination of design, materials, and construc

tion practices.

Highway construction, which accounts for 30 percent of the total cement use in the United States, can become a

major contributor toward better sustainability (PCA 2008). The contribution of concrete pavement to sustainability can

be measured based on its inherent durability (longevity) and

low maintenance. Long-lived pavements conserve the local aggregate resources and decrease the need for new cementi

tious materials, thus reducing the amount of C02 produced

and the amount of energy consumed. Several examples of long-life pavements that are still in service include:

a) Court St., Bellefontaine, OH - built in 1 893

b) 7th St., Calumet, MI - built in 1 906 c) Cemetery Road, Eddyville, lA - built in 1908

d) Central Ave., Urbana, IL - built in 1 9 1 9

Each of these pavements has performed well beyond their

original design life.



A study of Interstate highways in Illinois highlighted the durability of concrete pavements (Gharaibeh et a!. 1 997). Jointed reinforced concrete pavement (10 in. [250 mrn]

thick) had an average life of 24 years, a maximum age of 40 years, and an average traffic rate of 1 6.6 million equiva

lent single axial loads (ESALs). Continuously reinforced

concrete pavement 9 in. (225 mm) thick had an average life of 26.3 years at an average traffic rate of 28.5 million ESALs. These pavements had a 20-year design life but had

carried from 1 .6 to 7 .8 times their design traffic. Hundreds of Illinois streets are over 50 years old with some in excess

of 80 years. A section of l- 10 in San Bernardino, CA, was constructed

in 1 946 as part of then Route 66 and later incorporated into the

interstate system. It was diamond ground in 1 965 to correct joint spalling and faulting. Subsequent grindings were done

in 1 984 and 1 997. The originally designed 20-year pavement now carries 240,000 vehicles per day (VPD).

6.2.1 Sustainable design and materials-Materials that have been used to meet 28-day concrete test results are being improved through optimizing combinations so that 90-day

results might well become the basis for design engineers to

use. The 90-day characteristics can reduce the amount of cement used in a yard of concrete and the amount of concrete

used in certain applications (Roberts 2005).

With the need to reduce the amount of cement in concrete mixture, those materials that will enhance concrete charac

teristics in 90 days are ones that can improve all characteristics of the mortar and concrete in place. These include: a)

hydration of a maximum amount ofthe cement and cementi

tious materials; b) increasing the early-age strength (less than

3 days) (Bentz 2007; Geiker et a!. 2004; Roberts 2004, 2005) to withstand strain (Mack 2006); c) significantly increasing

the later-age strength (greater than 90 days); d) reducing the permeability (Hoff 2003); e) reducing the shrinkage (both drying and autogenous) (Jensen and Hansen 200 1 ; Philleo

1 99 1 ) and cracking (Cusson and Hoogeveen 2006); and f) reducing the warping (Ya and Hansen 2008).

6.2.2 High-performance concrete (HPC) as sustainability option-One approach to optimizing these wanted charac

teristic improvements and simultaneously contribute to the

sustainability of concrete pavements is through the use of

HPC. High-performance concrete uses SCMs, admixtures, higher-quality materials, internal curing, and improved construction methods to produce concrete pavements that

are more durable and offer longer life than pavements

constructed with traditional materials and methods. 6.2.3 Improvement of pavement base and subgrade

Concrete from reconstructed pavements and returned

concrete can both be crushed and reused as a base course or subgrade improvement. Returned concrete is concrete that is

not used in the construction project and returned to the plant.

6.3-Societal benefits of concrete pavement

Concrete pavement has many social benefits, which enhances it as a smart choice for the pavement-riding surface, including:

a) Improved nighttime visibility-The light color of concrete pavement results in better nighttime visibility for motorists. Concrete reflects more light from vehicles and

street lamps, thus better illuminating potential hazards. Reducing the number of fixtures or reducing the wattage of

lamps by one-third can attain an equal level of illumination.

Lamp fixtures can be maintained at the usual spacing on the pavement to provide improved illumination.

b) Decreased potential for hydroplaning-Rigid concrete

pavement does not rut, so the potential for hydroplaning is

reduced. Concrete pavement can be textured to create a long

lasting, textured surface for good skid resistance. Concrete pavements can be grooved to help carry rainwater away

from the road surface, thereby improving the tire pavement

interface and traction. c) Improved safety due to reduced maintenance-The

longer pavement life contributes to safety by reducing the amount of maintenance work and reducing the number of

work zones. This not only improves traffic flow, but also

increases safety for highway workers.

6.4-Environmental benefits of concrete pavement

Concrete pavement has many environmental benefits including:

6.4.1 Fuel savings and associated emission reductionsDue to the rigid nature of concrete, heavier vehicles create

less deflection and, therefore, require less fuel to operate

on concrete pavement. Research by the National Research Council of Canada (Taylor and Patton 2006) shows fuel

savings for heavy trucks ranging from 0.8 to 6.9 percent

when the trucks operated on concrete pavement. This means

that less fossil fuel is consumed, thereby decreasing vehicle operating costs and emissions such as C02, NOx, and S02.

Table 6.4. 1 shows the fuel savings results and related dollar and emission savings from building a 62 mile ( 1 00 km)

typical major arterial highway carrying 20,000 VPD (with

1 5 percent trucks). Pavement roughness and fuel consumption studies at

MIT's Concrete Sustainability Hub, using FHWA Long

term pavement performance (LTPP) data predicts that pave

ment roughness alone contributes to the consumption of an

additional 30,000 gal./mile (70,000 Llkm) for the representative pavement section used in the MIT study (Greene et a!. 20 1 3).

6.4.2 Low-energy-use footprint-Life cycle assessment

(LCA) research by the Athena Institute revealed that over a 5 0-year period, the energy used to construct, maintain, and rehabilitate an asphalt highway is substantially higher than

that of an equivalent concrete pavement structure (Athena

Institute 2006). For the pavement structures analyzed in

the report, energy use was 2.3 to 5 .2 times more for asphalt pavement structures than their equivalent concrete pavement structures. Unlike the binder used in asphalt pavement (liquid

bitumen), the binder used in concrete pavement (cement/

water paste) is not a form of feedstock energy and, therefore, greatly decreases the energy footprint of a concrete pave

ment. Life cycle assessments conducted by MIT resulted in the conclusion that "For a high traffic volume highway,



Table 6.4.1-Annual potential savings and emission reductions for typical major arterial highway

(Cement Association of Canada (CAC) 2007)

Results based on driving on rigid concrete versus

flexible asphalt pavements

Minimum Average Maximum

Sl units 0.8% 3 .85% 0.06%

Total fuel 377,000 1 8 1 ,000 3 ,249,000

savings (L)

Total dollar 338,000 1 ,625,000 2,9 1 2,000

savings ($)

Total C02

equivalent 1 039 6000 8960

reductions

(tonnes)

Total NOx

reductions 12 57 1 0 1

(tonnes)

Total S02 reduc-2 7 1 3

tion (tonnes)

Results based on driving on rigid concrete versus

u.s. flexible asphalt pavements

Customary Minimum Average Maximum

units 0.8% 3.85% 0.06%

Total fuel 1 00,000 480,000 860,000

savings (gal . )

Total dollar 338,000 1 ,625,000 2,9 12,000

savings ($)

Total C02

equivalent 1 145 5500 9875

reductions (tons)

Total NOx 1 3 62.4 1 1 1 .8

reductions (tons)

Total S02 1 . 7 7.9 14 . 1

reduction (tons)

potentially greater fuel efficiency of vehicles driving on concrete pavements could lead to significantly lower life

cycle carbon emissions compared to an asphalt pavement."

(Ochsendorf 201 0).

6.4.3 Longer service life-Concrete pavement lasts longer and requires less maintenance over its lifetime than other

pavement materials. Its rigid nature provides a stable surface

that will not rut, washboard, or undergo plastic deformation.

This translates into safe highways that require less maintenance, with less disruption for the traveling public and commercial truckers.

6.4.4 Reduced aggregate requirement-Compared to

layered pavement systems, rigid concrete pavement requires

thinner granular bases because it distributes vehicle weight more evenly over a larger area. In most cases, up to 50

percent less granular material is required to build a founda

tion for a concrete highway, reducing both costs and the use of scarce resources. Additionally, less hauling of granular

material results in significant fuel savings and an associated reduction in emissions.

6.4.5 Reusable/recyclable and extended life-Concrete

pavement is a very versatile construction material that can be reused through restoration techniques such as full-depth repairs, dowel bar retrofitting, and diamond grinding to

restore the pavement to an almost new state and increase its

useful life for many years. Concrete pavement is also 1 00

percent recyclable and provides cost-effective reconstruc

tion options if the pavement has served its useful life, such as use as road base or aggregate for new concrete pavement.

6.4.6 Use of industrial by-products-A common practice in concrete mixture designs is to use industrial by-products

known as supplementary cementitious materials (SCMs)

to replace a portion of the portland cement in the concrete mixture. As mentioned previously in this document, the

three most commonly used SCMs are fly ash (coal burning

by-product), slag cement (steel manufacturing by-product),

and silica fume (by-product from making silicon or ferrosilicon alloy). Using these products in the appropriate quantities can improve the durability, permeability, and strength of

concrete pavement, as well as decrease the energy and C02 footprint of concrete. Fly ash and slag cement also increase

the workability of concrete mixtures and can be used to mitigate potential alkali-aggregate reactivity problems.

6.4.7 Reduces urban heat island effect-Large cities can be several degrees warmer than outlying areas in the summer

due to the heat absorbed by dark-surfaced pavements. This

temperature increase, known as urban heat island effect,

can be reduced by using material, such as concrete pave

ment, that is lighter colored and has better reflective proper

ties. As urban areas decrease their tree cover, increase the

number of flat roofs (especially dark roofs), and increase the amount of dark pavement, urban areas are typically up to

9°F (5°C) warmer. Concrete pavement has a lighter color

(greater reflectivity) that more readily reflects solar radia

tion, keeping the ambient air cooler for a potential energy savings of $2 billion in the United States (Akbari 2005).

6.4.8 Pervious pavements-Pervious pavements have been around for some time and can be constructed of concrete or and other pavement materials. Efforts to reduce storm water run-off and pollution have brought more of a focus on this

technology as an environmentally friendly way to pave roads

and parking areas. Pervious concrete pavements, also known

as no-fines or porous concrete, are composed of specially graded coarse aggregates, cementitious materials, admixtures, and water. They could also contain fibers and little

to no fines. Mixing these products in a carefully controlled process creates a paste that forms a thick coating around

aggregate particles and creates a pavement with interconnected voids on the order of 1 2 to 35 percent. This provides

a pavement that is highly permeable with drainage rates in

the range of 22 to 1 66 gal. per min per yd2 ( 1 00 to 750 liters per min per m2), reducing storm runoff and minimizing the

amount of pollutants such as car oil, anti-freeze, and other

automobile fluids that are contained in captured stormwater.

By allowing the rainfall to percolate into the ground, soil chemistry and biology are allowed to naturally treat the

polluted water (Traynor 2009). This also allows for reduc

tion in stormwater retention areas, saving in land acquisition and construction costs. These pavements also recharge

groundwater, reducing the need to water trees and shrubs in the paved areas. The light-colored pavement surface is also a solution to the heat island effect.

American Concrete Institute - Copyrighted© Material- www.concrete.org Licensed to: Florida Suncoast Chapter


Table 6.5-Diesel fuel used during construction

(ACPA 2007)

Diesel fuel used during construction, gal./mile

Asphalt pavement Low Average High

Production 6468 8981 1 2,936

Hauling (0 to 10 miles) 1 035 1 220 1 257

Placing 222 5 1 7 739

Asphalt total 7725 1 0,7 1 8 1 4,932

Concrete pavement Low Average High

Production 293 548 880

Hauling (0 to 10 miles) 645 939 1 ,3 1 0

Placing 254 430 606

Concrete total 1 1 93 1 9 1 6 2796

6.4.9 Recycled aggregate benefits-Use of recycled aggregates in concrete and foundations for concrete pavements is

discussed earlier in this document (4.3.8.5). Use of recycled materials reduces the need to mine virgin aggregate material,

and could reduce the energy required to produce and haul

aggregates to the paving job site.

6.5-Economic benefits of concrete pavement As previously shown, properly designed and constructed

concrete pavements have potential lives well beyond their

design. Long-lived pavements ( 40 years plus design) carry a minimal additional cost with greater benefits derived from

their longer life. Aggregate resources in many areas are being

depleted. Building concrete pavements that only require a

diamond grind once or twice during their service life greatly extends the local aggregate resources. Also, concrete pave

ments require much less maintenance than other pavements.

Table 6.5 summarizes the savings realized during pavement construction, which are largely due to concrete most

commonly being constructed in a single lift and less subgrade excavation work being required.

6.6-Conclusion The many aforementioned benefits show why concrete

pavement is a sustainable choice. It can receive an even greater sustainability rating if optimizing materials, design,

and construction. The carbon footprint of concrete pavement can actually be reduced to zero if considering opera

tional effects such as truck fuel savings and light reflectance.

Reduced frequency of maintenance procedures and lengthening the pavement life cycle also make concrete pavement

a sustainable choice.

CHAPTER ?-REFERENCES ACI committee documents and documents published by

other organizations are listed first by document number, full title, and year of publication followed by authored documents listed alphabetically.

American Association of State Highway and Transportation

Officials

AASHTO M085-12-Standard Specification for Portland

Cement AASHTO M l 44- 14-Standard Specification for Calcium

Chloride AASHTO M l 47-65-Standard Specification for Mate

rials for Aggregate and Soil-Aggregate Subbase, Base, and

Surface Courses AASHTO M l 54- 1 2-Standard Specification for Air

Entraining Admixtures for Concrete AASHTO M l 55-87-Standard Specification for Granular

Material to Control Pumping under Concrete Pavement AASHTO M l 82-05-Standard Specification for Burlap

Cloth Made from Jute or Kenaf and Cotton Mats AASHTO M l 94- 1 3-Standard Specification for Chem

ical Admixtures for Concrete AASHTO M240- l l-Standard Specification for Blended

Hydraulic Cement AASHTO M254-06-Standard Specification for Corro

sion-Resistant Coated Dowel Bars AASHTO T022- 14-Standard Method of Test for

Compressive Strength of Cylindrical Concrete Specimens

AASHTO T024-07-Standard Method of Test for

Obtaining and Testing Drilled Cores and Sawed Beams of Concrete

AASHTO T096-02-Standard Method of Test for Resis

tance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine

AASHTO T099- l 0-Standard Method of Test for Moisture-Density Relations of Soils Using a 2.5-kg (5.5-lb)

Rammer and a 305-mm ( 12-in.) Drop

AASHTO T l 03-08-Standard Method of Test for Soundness of Aggregates by Freezing and Thawing

AASHTO T l 34-05-Standard Method of Test for Mois

ture-Density Relations of Soil-Cement Mixtures

AASHTO T l 48-07-Standard Method of Test for Measuring Length of Drilled Concrete Cores

AASHTO T l 60-09-Standard Method of Test for Length

Change of Hardened Hydraulic Cement Mortar and Concrete

AASHTO T l 76-08-Standard Method of Test for Plastic

Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test

AASHTO T l 90- 14-Standard Method of Test for Resistance R-Value and Expansion Pressure of Compacted Soils

AASHTO T l 93- 1 3-Standard Method of Test for the

California Bearing Ratio AASHTO T22 1 -90-Standard Method of Test for Repeti

tive Static Plate Load Tests of Soils and Flexible Pavement

Components for Use in Evaluation and Design of Airport and Highway Pavements

AASHTO T222-8 1-Standard Method of Test for Nonre

petitive Static Plate Load Test of Soils and Flexible Pavement Components for Use in Evaluation and Design of

Airport and Highway Pavements AASHTO T307-99-Standard Method of Test for Deter

mining the Resilient Modulus of Soils and Aggregate Materials

American Concrete Institute



ACI 1 1 7- 1 0-Specification for Tolerances for Concrete

Construction and Materials and Commentary ACI 1 2 1R-08-Guide for Concrete Construction Quality

Systems in Conformance with ISO 900 1 ACI 20 1 .2R-08-Guide to Durable Concrete

ACI 209R-92(08}-Prediction of Creep, Shrinkage, and

Temperature Effects in Concrete Structures ACI 2 1 0R-93(08)-Erosion of Concrete in Hydraulic

Structures

ACI 2 1 1 . 1 -9 1 (09)-Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass Concrete

ACI 2 1 2.3R- 1 0-Report on Chemical Admixtures for Concrete

ACI 2 14R- 1 1-Guide to Evaluation of Strength Test

Results of Concrete ACI 22 1 . 1 R-98(08)-Report on Alkali-Aggregate

Reactivity ACI 225R-99(09)-Guide to the Selection and Use of

Hydraulic Cements ACI 232. 1 R- 1 2-Use of Raw or Processed Natural

Pozzolans in Concrete ACI 233R-03(1 1 )-Slag Cement in Concrete and Mortar

ACI 234R-06-Guide for the Use of Silica Fume m Concrete

ACI 3 0 1 - 1 0-Specifications for Structural Concrete ACI 302. 1 R-96-Guide for Concrete Floor and Slab

Construction

ACI 304R-00(09)-Guide for Measuring, Mixing, Trans-

porting, and Placing Concrete

ACI 305R- 1 0-Guide to Hot Weather Concreting

ACI 306R-1 0-Guide to Cold Weather Concreting

ACI 306. 1 -90(02)-Standard Specification for Cold Weather Concreting

ACI 308R-0 1 (08)-Guide to Curing Concrete ACI 3 1 1 . 1 R-07-ACI Manual of Concrete Inspection

(SP-2) (Synopsis)

ACI 3 1 1 .4R-05-Guide for Concrete Inspection ACI 3 1 1 .5-04-Guide for Concrete Plant Inspection and

Testing of Ready-Mixed Concrete ACI 3 1 8- 1 1-Building Code Requirements for Structural

Concrete and Commentary

ACI 325. 1 1 R-0 1-Accelerated Techniques for Concrete Paving

ACI 325 . 1 2R-02-Guide for Design of Jointed Concrete pavements for Streets and Local Roads

ACI 330R-08-Guide for Design and Construction of Concrete Parking Lots

ACI 522R- 1 0-Report on Pervious Concrete

ACI 544. 1 R-96(09}-Report on Fiber Reinforced

Concrete

ASTM International ASTM A 1 84/A1 84M-06(20 1 1 )-Standard Specifica

tion for Welded Deformed Steel Bar Mats for Concrete Reinforcement

ASTM A6 1 5/A61 5M- 14-Standard Specification for

Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement

ASTM A775/A775M-07(2014)-Standard Specification for Epoxy-Coated Steel Reinforcing Bars

ASTM A884/A884M-14-Standard Specification for Epoxy-Coated Steel Wire and Welded Wire Reinforcement

ASTM A934/A934M-14-Standard Specification for

Epoxy-Coated Prefabricated Steel Reinforcing Bars

ASTM A955/A955M- 1 5-Standard Specification for

Deformed and Plain Stainless-Steel Bars for Concrete

Reinforcement

ASTM A996/A996M- 14-Standard Specification for Rail-Steel and Axle-Steel Deformed Bars for Concrete Reinforcement

ASTM C3 1/C3 1 M- 1 2-Standard Practice for Making and Curing Concrete Test Specimens in the Field

ASTM C33/C33M-1 3-Standard Specification for

Concrete Aggregates

ASTM C39/C39M- 14-Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens

ASTM C42/C42M- 1 3-Standard Test Method for

Obtaining and Testing Drilled Cores and Sawed Beams of Concrete

ASTM C78/C78M- 1 0-Standard Test Method for Flex

ural Strength of Concrete (Using Simple Beam with ThirdPoint Loading)

ASTM C94/C94M- 14-Standard Specification for

Ready-Mixed Concrete ASTM C 127- 1 5-Standard Test Method for Density,

Relative Density (Specific Gravity), and Absorption of Coarse Aggregate

ASTM C 1 28- 1 5-Standard Test Method for Relative Density (Specific Gravity) and Absorption ofFine Aggregate

ASTM C 1 3 1/C 1 3 1 M- 14-Standard Test Method for Resistance to Degradation of Small-Size Coarse Aggregate

by Abrasion and Impact in the Los Angeles Machine ASTM C 1 36/C 1 36M- 14-Standard Test Method for

Sieve Analysis of Fine and Coarse Aggregates

ASTM C 1 3 8/C 1 3 8M-14-Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric)

of Concrete ASTM C 143/C 143M- 12-Standard Test Method of

Slump of Hydraulic-Cement Concrete ASTM C 1 5 0/C 1 50M- 1 2-Standard Specification for

Portland Cement

ASTM C 1 7 1 -07-Standard Specification for Sheet Materials for Curing Concrete

ASTM C 1 73/C 1 73M- 14-Standard Test Method for

Air Content of Freshly Mixed Concrete by the Volumetric Method

ASTM C 1 92/C 1 92M- 14-Standard Practice for Making

and Curing Concrete Test Specimens in the Laboratory ASTM C23 1/C23 1 M- 1 4-Standard Test Method for Air

Content of Freshly Mixed Concrete by the Pressure Method ASTM C260/C260M- 1 0-Standard Specification for Air

Entraining Admixtures for Concrete ASTM C309- l l-Standard Specification for Liquid

Membrane-Forming Compounds for Curing Concrete ASTM C330/C330M- 14-Standard Specification for

Lightweight Aggregates for Structural Concrete



ASTM C494/C494M-1 3-Standard Specification for

Chemical Admixtures for Concrete ASTM C595/C595M-1 4-Standard Specification for

Blended Hydraulic Cements ASTM C6 1 8- 1 2-Standard Specification for Coal Fly Ash

and Raw or Calcined Natural Pozzolan for Use in Concrete ASTM C702/C702M- l l-Standard Practice for Reducing

Samples of Aggregate to Testing Size ASTM C845-04-Standard Specification for Expansive

Hydraulic Cement ASTM C989/C989M-1 4-Standard Specification for

Slag Cement for Use in Concrete and Mortars ASTM C l 064/C l 064M- 1 2-Standard Test Method for

Temperature of Freshly Mixed Hydraulic-Cement Concrete ASTM C l 074- 1 1-Standard Practice for Estimating

Concrete Strength by the Maturity Method

ASTM C l l 57/C 1 1 57M- 1 1-Standard Performance Specification for Hydraulic Cement

ASTM C l 240- 14-Standard Specification for Silica

Fume Used in Cementitious Mixtures ASTM C 1 3 15 - 1 1-Standard Specification for Liquid

Membrane-Forming Compounds Having Special Properties

for Curing and Sealing Concrete ASTM C 1 600/C l 600M- 1 1-Standard Specification for

Rapid Hardening Hydraulic Cement ASTM C 1602/C 1 602M-1 2-Standard Specification for

Mixing Water Used in the Production of Hydraulic Cement

Concrete ASTM D75/D75M- 1 4-Standard Practice for Sampling

Aggregates ASTM D98-05(20 1 3)-Standard Specification for

Calcium Chloride ASTM D558- l l -Standard Test Methods for Moisture

Density (Unit Weight) Relations of Soil-Cement Mixtures ASTM D698- 1 2-Standard Test Methods for Laboratory

Compaction Characteristics of Soil Using Standard Effort

( 1 2 400 ft-lbf/ft3 (600 kN-m/m3)) ASTM D994/D994M- 1 1-Standard Specification for

Preformed Expansion Joint Filler for Concrete (Bituminous Type)

ASTM D 1 1 95/D l 1 95M-09-Standard Test Method for Repetitive Static Plate Load Tests of Soils and Flexible

Pavement Components, for Use in Evaluation and Design of

Airport and Highway Pavements ASTM D 1 1 96/D 1 1 96M- 1 2-Standard Test Method for

Nonrepetitive Static Plate Load Tests of Soils and Flexible

Pavement Components, for Use in Evaluation and Design of Airport and Highway Pavements

ASTM D 1 556/D1 556M- 1 5-Standard Test Method for

Density and Unit Weight of Soil in Place by the Sand-Cone Method

ASTM D 1 557-1 2-Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (56,000 ft-lbf/ft3 (2,700 kN-m/m3))

ASTM D l 75 1 -04(201 3)-Standard Specification for Preformed Expansion Join Filler for Concrete Paving and

Structural Construction (Nonextruding and Resilient Bituminous Types)

ASTM D l 7 52-04(20 13 )-Standard Specification for

Preformed Sponge Rubber Cork and Recycled PVC Expansion Join Fillers for Concrete Paving and Structural

Construction ASTM D l 883- 14-Standard Test Method for CBR (Cali

fornia Bearing Ratio) of Laboratory-Compacted Soils ASTM D2 1 67 -08-Standard Test Method for Density and

Unit Weight of Soil in Place by the Rubber Balloon Method ASTM D24 19-14-Standard Test Method for Sand

Equivalent Value of Soils and Fine Aggregate ASTM D2628-9 1 (20 1 1 )-Standard Specification for

Preformed Polychloroprene Elastomeric Joint Seals for

Concrete Pavements ASTM D2835-89(20 1 2)-Standard Specification for

Lubricant for Installation of Preformed Compression Seals in Concrete Pavements

ASTM D2844/D2844M- 1 3-Standard Test Method for

Resistance R-Value and Expansion Pressure of Compacted Soils

ASTM D2937-1 0-Standard Test Method for Density of Soil in Place by the Drive-Cylinder Method

ASTM D43 1 8- 1 0-Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils

ASTM D479 1 - 1 0-Standard Test Method for Flat Parti

cles, Elongated Particles, or Flat and Elongated Particles in

Coarse Aggregate ASTM D4829- 1 1-Standard Test Method for Expansion

Index of Soils ASTM D5893/D5893M- 1 0-Standard Specification for

Cold Applied, Singe Component, Chemically Curing Sili

cone Joint Sealant for Portland Cement Concrete Pavements

ASTM D6690- 1 2-Standard Specification for Joint and Crack Sealants, Hot Applied, for Concrete and Asphalt

Pavements ASTM D6938- 1 0-Standard Test Method for In-Place

Density and Water Content of Soil and Soil-Aggregate by

Nuclear Methods (Shallow Depth) ASTM E274/E274M- 1 1-Standard Test Method for Skid

Resistance of Paved Surfaces Using a Full-Scale Tire

ASTM E303-93(2008)-Standard Test Method for Measuring Surface Frictional Properties Using the British

Pendulum Tester ASTM E50 1 -08-Standard Specification for Standard

Rib Tire for Pavement Skid-Resistance Tests ASTM E524-08-Standard Specification for Standard

Smooth Tire for Pavement Skid-Resistance Tests

ASTM E965-96(2006)-Standard Test Method for

Measuring Pavement Macrotexture Depth Using a Volumetric Technique

ASTM E 1 9 1 1 -09-Standard Test Method for Measuring Paved Surface Frictional Properties Using the Dynamic

Friction Tester

ASTM E 1 960-07(20 1 1 )-Standard Practice for Calculating International Friction Index of a Pavement Surface

Federal Specifications



SS-S-200E-Federal Specification: Sealants, Joint, Two

Component, Jet-Blast-Resistant, Cold-Applied, for Portland Cement Concrete Pavement ( 1 5-Aug- 1984)

SS-S- 1 6 1 4A-Federal Specification, Sealants, Joint, Jet-Fuel-Resistant, Hot-Applied, for Portland Cement and

Tar Concrete Payments ( 1 5-Aug- 1984)

Authored documents AASHTO, 1 993, Guide for Design of Pavement Struc

tures, fourth edition, American Association of State Highway and Transportation Officials, Washington, DC, 700 pp.

AASHTO, 2008a, Guide for Pavement Friction, first edition, American Association of State Highway and Trans

portation Officials, Washington, DC, 88 pp.

AASHTO, 2008b, Mechanistic-Empirical Pavement Design Guide, Interim Edition-A Manual of Practice, American Association of State Highway and Transportation Officials, Washington, DC, 2 1 2 pp.

Abdun-Nur, E., 1 96 1 , "Fly Ash in Concrete, an Evalua

tion," Bulletin No. 284, Highway Research Board. Washington, DC, 1 3 8 pp.

ACPA, 1 99 1 , "Design and Construction of Joints for

Concrete Highways," Technical Bulletin TB-OIO. O D, American Concrete Pavement Association, Rosemont, IL.

ACPA, 1 995, "Joint and Crack Sealing and Repair for Concrete Pavements," Technical Bulletin TB012P, Amer

ican Concrete Pavement Association, Rosemont, IL.

ACPA, 2000, "Concrete Pavement Surface Textures,"

Special Report No. SR902P, American Concrete Pavement

Association, Rosemont, IL.

ACPA, 2002, "Maturity Testing of Concrete Pavements: Applications and Benefits," IS257P, American Concrete Pavement Association, Rosemont, IL.

ACPA, 2003, "How to Handle Rained-On Concrete Pavements," R&T Update, Concrete Pavement Research & Technology, Number 4.04, American Concrete Pavement Asso

ciation, Rosemont, IL, Apr., 4 pp.

ACPA, 2005, "Making the Grade - Grade Prepara

tion is Important in Achieving Pavement Performance," R&T Update, Concrete Pavement Research & Technology,

Number 6.02, American Concrete Pavement Association, Rosemont, Apr., 4 pp.

ACPA, 2007, "Conserving Fuel in the Road-QD023P,"

American Concrete Pavement Association, Rosemont, IL. ACPA, 20 1 0, "Concrete Pavement Field Reference:

Paving," Engineering Bulletin EB23 8P, American Concrete

Pavement Association, Rosemont, IL, 1 50 pp. Afrani, 1. , and Rogers, C., 1 994, "The Effects of Different

Cementing Materials and Curing on Concrete Scaling,"

Cement, Concrete and Aggregates, V. 1 6, No. 2, Dec., pp. 1 32- 1 39. doi: 1 0 . 1 520/CCA1 029 1 J

Ahammed, M. A., and Tighe, S. L., 2008, "Pavement Surface Mixture, Texture, and Skid Resistance: A Factorial

Analysis," Proceedings of the 2008 Airfield and Highway Pavements Conference, American Society of Civil Engineers, Bellevue, WA, Oct. 1 5- 1 8, pp. 370-384.

Akbari, H., 2005, "Energy Saving Potentials and Air

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Athena Institute, 2006, "A Life Cycle Perspective on Concrete and Asphalt Roadways: Embodied Primary Energy

and Global Warming Potential," Athena Institute, Ottawa,

ON, Canada, Sept., 68 pp. Bakker, R. F. M., 1 980, "On the Cause of Increased

Resistance of Concrete Made from Blast-Furnace Cement

to Alkali Reaction and to Sulfate Corrosion," thesis, Rheinisch-Westfalische Technische Hochschule, 1 1 8 pp.

Bentz, D. P. , 2007, "Internal Curing of High-Performance Blended Cement Mortars," ACI Materials Journal, V. 1 04, No. 4, July-Aug., pp. 408-4 14.

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va ri ety of con crete reso u rces. As a vol u nteer m e m be r-d riven o rg a n izati o n ,

A C I i nvites p a rtners h ips a n d welcomes a l l con crete professi o n a l s who w i s h to

be part of a res pected, connected, soc i a l g ro u p that provides a n op portu n ity

for p rofessio n a l g rowth, n etwo rking a nd e nj oy m e nt.

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