chapter 4 - road construction 1.ppt - author | the uthm...

Chapter 4ROAD CONSTRUCTION

1HIGHWAY ENGINEERING BFC31802

� ROAD CONSTRUCTION PROCESS

- Site Investigation, Earthworks, Mass Haul Diagram,

- Preparation of subgrade, sub-base, base

What you will be

learning from this

chapter …

SUB-TOPICS:

HIGHWAY ENGINEERING BFC31802

2

� ASPHALT PAVEMENT CONSTRUCTION (FLEXIBLE)

- Preparation of bituminous coat: prime & tack coat

- Paving a binder & wearing coarse.

� CONCRETE PAVEMENT CONSTRUCTION (RIGID)

- Form, joints, concrete mix, curing, joint awing

� QUALITY ASSURANCE IN PAVEMENT CONSTRUCTION

SITE INVESTIGATIONSITE INVESTIGATIONSITE INVESTIGATIONSITE INVESTIGATION

Site investigation is carried in most cases as a preliminary to new works.

The reasons for site investigation are given below:

• Investigation of defects of existing roads

3

• Investigation of defects of existing roads

• Investigation to the safety of existing works.

• Investigation relating to the suitability and availability of materials for constructional purposes.



Investigation of defects of existing roads

This type of investigation is necessary to establish the cause of the failure and to provide information indicative of remedy.

4

Measurements and observations of the structure are taken to indicate whether or not the ground conditions are involved.

This investigation will reveal the level of ground water and the true state of sub-strata.



Investigation to the safety of existing works

To investigate existing works and decide whether the latter will adversely be affected by changes in ground conditions.

Existing works may be affected by the following:

• excavations may reduced ground support• tunneling or mining which may cause subsidence

5

• tunneling or mining which may cause subsidence• vibrations ( eg. from piling operation) which may cause fractures• extra load created by new works may overload stratum supportingexisting works

• soil movement due to heat induced by proximity to plantinstallations.

• ground water lowering• disturbed drainage path may cause flooding and instability ofslopes.



Investigation relating to the suitability and availability of materials for constructional purposes

There are two quite different problems with the mass movement of earth:

(1) Disposal

6

(1) Disposal- e.g. in the case of spoil from cuts

(2) Acquisition- e.g for large fill projects such as reclaimation

In both cases however, investigation is necessary toestablish the quantity and suitability of the soil for the purpose for which it is to be used.


ROAD CONSTRUCTION PROCESS

� ROUTE SURVEY

� SITE INVESTIGATION


� SITE CLEARANCE

� EARTHWORKS


� SUBGRADE COMPACTION AND LEVELLING

� ESTABLISHING THE FORMATION LEVEL


�SUB-BASE CONSTRUCTION


�BASE CONSTRUCTION


� APPLYING OF PRIME COAT

� LAYING OF BINDER COURSE


� APPLYING OF TACK COAT

� LAYING OF WEARING COURSE

ROAD IS COMPLETED.


EARTHWORKS

This process consists of clearing, grubbing and stripping in road construction

area. It also includes the demolition and disposal of soils to a formation level

(top of the sub grade).

Activity Work Description Measurement

Cutting, removal and disposal of

everything above ground level

including object overhanging the

All stumps and roots be removed to a

depth of not less than 0.3 m below the

propose road.

14

Clearing

including object overhanging the

area to be cleared

Levelling of obsolete dikes,

terraces, ditches

propose road.

This requirement also usually holds in

embankment areas where the height of

the feel not less than about 1.5 m.

In embankment section when the

embankment height is to be more than

1.5 m, tree and stump may be left in

place and cut off at ground level or at a

height of 75-150 mm above the existing

ground surface.

Grubbing

Removal and disposal of surface

vegetation, roots, underground

parts of the structure and other

obstruction

Stripping Removal topsoil or stockpiling


EARTHWORKS

Excavation- Excavation increases the volume of material.

- It is therefore necessary to use a bulking factor to determine the volume of material that will be created by excavation.

Bulking factor is defined as:

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Bulking Factor = Volume after Excavation / Volume before Excavation

Similarly a shrinkage factor is defined for the compaction of a soil at it's final destination:

Shrinkage Factor = Volume after Compaction / Volume before Excavation


EARTHWORKS

Earthmoving Equipment

Bulldozer - This is used primarily for pushing soil. Vehicles

are generally tracked and require large amounts of

traction. Many bulldozers incorporate hydraulic

attachments at the rear for breaking up soil and rock. The

best known of the vehicles.

Drag Line - This vehicle allows excavation below it's own

Bulldozer

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Drag Line - This vehicle allows excavation below it's own

level. It is essentially a bucket on the end of a jib and is

used solely for bulk excavation as it is relatively

uncontrolled.

Dump Truck - These are wheeled vehicles and as such are

able to move much faster. This is offset by a lack of

traction and dump trucks are always the first to get stuck.

They are used for transferring material from one part of

the site to another.

Drag Line

Dump Truck


EARTHWORKS

Earthmoving Equipment

Shovels - These again are normally wheeled vehicles and

are used to fill up the dump trucks. Typically they take 2-3

loads to fill an average dump truck.

Hydraulic Excavators - These can be either wheeled or

tracked and are used again to excavate below truck level.

Shovel

Excavator

17

tracked and are used again to excavate below truck level.

They have a very small capacity and are extremely

flexible.

Grader - Used to level out deposited fill, ready for

compaction.

Rollers - There are many different types of roller and they

are used for compaction. Different types include vibratory,

sheepsfoot and grid. Vibratory are the most common as

they have effectively double the effect.

Grader

RollerHIGHWAY ENGINEERING BFC31802

MASS HAUL DIAGRAM

o Minimize material waste or borrow.

o A plot of cumulative volume of soil against distance along the road.

o Cut volumes - positive and fill volumes - negative.


MASS HAUL DIAGRAM

A rising curve - increasing volume (cut).

A maximum point - end of a cut.

A falling curve - decreasing volume (fill).

A minimum point - the end of a fill.

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Areas at the end of the diagram - waste


MASS HAUL DIAGRAM

Calculation of Cross Sectional Area

The first stage - cut or fill sectional areas at different points along the road.

For a cut or fill on horizontal ground

Assuming a cut such as the one above, the cross sectional area is given by:

1

20

Area =

= hb + nh2

= h(b + nh)

+ )(

2

12 nhhhb


MASS HAUL DIAGRAM

For a cut or fill on sloping ground

Assuming a cut such as the one above, the cross sectional area is found firstly by

calculating WL and WG:

WL = nhb

S

+

2

21

WL =

WG =

Thus Area =

nS +

2

nS

nhb

S

−

+

2

n

bWW

n

bh

GL

4)(

22

12

−+

+


MASS HAUL DIAGRAM

Example Calculation

The table below shows ground levels and formation levels for a proposed road construction.

Embankments are to be built with side slopes of 1:2.5 and cuttings with slopes of 1:3.0. The

embankment crest width and cutting base width is 13m. It may be assumed that the ground

is horizontal across the section.


(a) Construct a Mass Haul diagram for the project given the following:

Bulking Factor = 0.8

Shrinkage Factor = 1.0


MASS HAUL DIAGRAM

0

10000

20000

30000

40000

50000

Cu

mu

lati

ve

vo

lum

e (

cu

bic

me

ter)

24

-90000

-80000

-70000

-60000

-50000

-40000

-30000

-20000

-10000

0

0

10

0

20

0

30

0

40

0

50

0

60

0

70

0

80

0

90

0

10

00

11

00

12

00

13

00

14

00

15

00

Chainange (m)

Cu

mu

lati

ve

vo

lum

e (

cu

bic

me

ter)


MASS HAUL DIAGRAM

10000

20000

30000

40000

50000

Cu

mu

lati

ve

vo

lum

e (

cu

bic

me

ter)

(b) A river breaks up the project at chainage 1160m. Calculate the volumes of

waste material and borrow for this scenarios:

(i) Material cannot be moved across the river

150 280 500 740 1160 1280

25

-90000

-80000

-70000

-60000

-50000

-40000

-30000

-20000

-10000

0

10000

0

10

0

20

0

30

0

40

0

50

0

60

0

70

0

80

0

90

0

10

00

11

00

12

00

13

00

14

00

15

00

Chainange (m)

Cu

mu

lati

ve

vo

lum

e (

cu

bic

me

ter)

Fill Cut Cut Fill Fill Fill Cut


Distance (m) 150 130 220 240 420 120 220

Cut (m3) 15,000 36,000 49,000

Fill (m3) 15,000 36,000 68,000 11,000

Haul (m3) 15,000 36,000 11,000

Borrow (m3) 68,000

River

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Borrow (m3) 68,000

Waste (m3) 38,000

Borrow = 68,000 m3

Waste = 38,000 m3


MASS HAUL DIAGRAM

10000

20000

30000

40000

50000

Cu

mu

lati

ve

vo

lum

e (

cu

bic

me

ter)

(b) A river breaks up the project at chainage 1160m. Calculate the volumes of

waste material and borrow for this scenarios:

(ii) A Bailey bridge is constructed allowing material to be transported across the river

150 280 500 740 1280

27

-90000

-80000

-70000

-60000

-50000

-40000

-30000

-20000

-10000

0

10000

0

10

0

20

0

30

0

40

0

50

0

60

0

70

0

80

0

90

0

10

00

11

00

12

00

13

00

14

00

15

00

Chainange (m)

Cu

mu

lati

ve

vo

lum

e (

cu

bic

me

ter)

Fill Cut Cut Fill Fill Fill Cut


Distance (m) 150 130 220 240 540 220

Cut (m3) 15,000 36,000 49,000

Fill (m3) 15,000 36,000 79,000

Haul (m3) 15,000 36,000 49,000

Borrow (m3) 30,000

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Borrow (m3) 30,000

Waste (m3)

Borrow = 30,000 m3

Waste = 0 m3


SUBGRADE PREPARATION

�The subgrade is the in-situ material upon which the pavement structure is placed.

�Increasing the load-bearing capacity of the subgrade - improve pavement load-bearing capacity – increasing pavement strength and performance.

�Greater subgrade structural capacity - thinner (but not excessively thin) and more economical pavement structures.

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�The finished subgrade should meet elevations, grades and slopes specified in the contract plans.



Subgrade Performance

A subgrade’s performance generally depends on two interrelated characteristics:

(1) Load bearing capacity

- The subgrade must be able to support loads transmitted from the pavement structure.

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pavement structure.

- This load bearing capacity is often affected by degree of compaction, moisture content, and soil type.

- A subgrade that can support a high amount of loading without excessive deformation is considered good.

(2) Volume changes

- Most soils undergo some amount of volume change when exposed to excessive moisture.



Improving Subgrade Performance

Poor subgrade should be avoided if possible, but when it is necessary to build over weak soils there are several methods used to improved subgrade performance:

(1) Removal and replacement (over-excavation)

Poor subgrade soil can simply be removed and replaced with higher quality fill

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(2) Stabilization with a cementitious or asphaltic binder

The addition of an appropriate binder (such as lime, portland cement or emulsified asphalt) can increase subgrade stiffness and/or reduce swelling tendencies.

(3) Additional base layers

- These layers spread pavement loads over a larger subgrade area

- When designing pavements for poor subgrades the temptation may be to just design a thicker section with more base material because the thicker section will satisfy most design equations.



Good Practices in Subgrade Preparation

(1) Ensure the compacted subgrade is able to support construction traffic

If the subgrade ruts excessively under construction traffic it may cause premature pavement rutting and will result in variable paving thicknesses.

(2) Remove all debris, large rocks, vegetation and topsoil from the area to be paved

These items either do not compact well or cause non-uniform compaction

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These items either do not compact well or cause non-uniform compaction and mat thickness.

(3) Treat the subgrade under the area to be paved with an approved herbicide

This will prevent or at least retard future vegetation growth, which could affect subgrade support or lead directly to pavement failure.


SUB-BASE AND BASE CONSTRUCTION

Sub-BaseMaterial

i. Natural or prepared aggregate comprising crushed rock

ii. Weathered or fragmented rock

iii. Gravel or crushed gravel

iv. Sand

v. Mixture from any materials above

Requirement

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Requirement

- small portion of plastic or non-plastic fines

- free from vegetative or other organic matter, clay

- Physical and mechanical characteristic – comply to JKR/SPJ/1988:

Liquid limit < 35 %

Plasticity index in the range of 4 to 10

Aggregate Crushing Value < 35

Gradation – Table 4.2



B.S Sieve

Size

% Passing by Weight

A B C D E F

50.0 mm 100 100 - - - -

Table 4.2: Gradation Limits for Sub-base Material


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50.0 mm

25.0 mm

9.50 mm

4.75 mm

2.00 mm

425 µm

75 µm

100

-

30-65

25-55

15-40

8-20

2-8

100

79-95

40-75

30-60

20-45

15-30

5-20

-

100

50-85

35-65

25-50

15-30

5-20

-

100

60-100

50-85

40-70

25-45

5-20

-

100

-

55-100

40-100

20-50

5-20

-

100

-

70-100

55-100

30-70

8-25

Method of construction

- shaped and compacted

- uniform moisture content – prevent seperation

- compaction not less than 95 % of MDD – BS1377 (Compaction Test 4.5 kg rammer method)

- Pattern of compaction – longitudinal direction


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- Pattern of compaction – longitudinal direction

- From outer edge – center

- Superelevation – from lower to higher edge

- Final surface – must : required shape, superelevation, levels and grade within the tolerence



Base Material

i. Crushed aggregate or gravel

ii. Mix of crushed and natural aggregate

Generally - hard, durable, clean and free from clay

Requirement

Physical and mechanical characteristic – comply to JKR/SPJ/1988

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- Plasticity index < 6

- Flakiness index < 30

- Aggregate Crushing Value < 30

- > 80 % particle retained 4.75 mm sieve – had fractured face

- Soundness test < 12 %

- CBR value > 80 %

- Gradation – Table 4.3


Method of construction (refer to sub-base except the thickness preparation)

B.S Sieve Size % Passing by Weight

A B

50.0 mm

37.5 mm

28.5 mm

100

95-100

-

100

85-100

70-100

Table 4.3: Gradation Limits For Crushed Aggregate Roadbase


28.5 mm

20.0 mm

10.0 mm

5.0 mm

2.36 µm

2.00 µm

600 µm

425 µm

75 µm

-

60-80

40-60

25-40

15-30

-

8-22

-

0-8

70-100

60-90

40-65

30-55

-

20-40

-

10-25

2-10HIGHWAY ENGINEERING

BFC3180238

The method of base construction processes refer to themethod of construction for sub-base except for thethickness specification.


Sub-base and Base construction

ASPHALT PAVEMENT CONSTRUCTION

Pavements constructed without adequate surface

preparation may not meet smoothness specifications,

Before a pavement is placed, the surface to be

paved must be prepared.


preparation may not meet smoothness specifications,

may not bond to the existing pavement (in the case of

overlays) or may fail because of inadequate subgrade

support.

BITUMINOUS COATSBITUMINOUS COATSBITUMINOUS COATSBITUMINOUS COATS

Prime Coats

� A cutback or emulsion asphalt. According to Asphalt Institute (2001):

(i) Fill the surface voids and protect the subbase from weather.

(ii) Stabilize the fines and preserve the subbase material.

(iii) Promote bonding to the subsequent pavement layers.


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� Carried out – dry, warm weather – final surface essentially dry

� Left undisturbed – 24 hours after application

� Rate of application:

-range 0.9 to 2.3 litre/m2

- temperature

cutback bitumen – 50 C to 70 C during spraying

emulsion – 25 C to 45 C during spraying


Tack Coats

� Thin bituminous liquid asphalt, emulsion or cutback

� Between HMA pavement lifts to promote bonding

� Need an adequate bonding – for good result

� Material – emulsion bitumen – rapid setting



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� Material – emulsion bitumen – rapid setting

� Rate and temperature of applications:

- range 0.19 to 0.38 litres/m2

- temperature of the bitumen - 25 C to 45 C


SURFACE DRESSING

� Cleaning of the surface

� Binder used – penetration graded bitumen, cutback or emulsion

� Aggregate – from the screed

� It must clean, hard, dry, tough, sound and angular


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� It must clean, hard, dry, tough, sound and angular


ASPHALTIC CONCRETE

Aggregate used in the mixture MUST:

� Aggregate Crushing Value < 30

� Soundness Test < 12 %

� Flakiness index < 30



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� Flakiness index < 30

� Water absorption < 2 %

� Polished stone value > 40 (wearing course)

� Gradation and mixture – Comply JKR/SPJ/1988 (Table 4.4, 4.5

� Mixture analysis – Comply JKR/SPJ/1988 (Table 4.6)


Laying the Asphaltic Concrete

� Compacted thickness – twice of nominal aggregate size of the mixture.

� Proper laying – avoid the irregularities and segregation of the mix

Compaction Measurement



45

Compaction Measurement

� Compaction – reduce the volume of air in HMA

� Expressed as “percent of air voids”

� Determine by the ratio of density of specimen with density of “Theoretical Maximum Density”

� Factor affecting compaction (refer Module)


COMPACTION

Compaction is the process by which the volume of air in an Hot Mix Asphalt (HMA) mixture is reduced by using external forces to reorient the constituent aggregate particles into a more closely spaced arrangement.

Compaction is the greatest determining factor in dense graded pavement



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Compaction is the greatest determining factor in dense graded pavement performance.

Inadequate compaction results in a pavement with decreased stiffness, reduced fatigue life, accelerated aging/decreased durability, rutting, raveling, and moisture damage.





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Compaction Equipment

There are three basic pieces of equipment available for HMA compaction:

(1) Paver screed

(2) Steel wheeled roller

(3) Pneumatic tire roller.


48

Paver Screed Steel Wheel Roller Pneumatic Tire RollerHIGHWAY ENGINEERING

BFC31802

RIGID PAVEMENT CONSTRUCTION

• Need to be done carefully and precisely to meet

- structural strength

- structural smoothness

• Follow the sequences

a. Subgrade

b. Subbase (sometimes – 75 to 150 mm)

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b. Subbase (sometimes – 75 to 150 mm)

c. Placing of form

d. Mixing of Concrete

- batch dry – outside from the site

- in-situ, mixed with water

- for central location – straight away mix with

water and transport to the site


• Placing and finishing

- Used ordinary concrete work machines

- Pavement surface – check for the

irregularities

• Joint sawing

• Curing – wet curing ( 1 to 3 days)

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• Curing – wet curing ( 1 to 3 days)


QUALITY ASSURANCE IN PAVEMENT CONSTRUCTION

Quality assurance

Planned and systematic actions

Most efficient, economical, and satisfactory manner possible.

Involves continued evaluation of the activities of planning, design, development of plans and specifications, advertising and awarding of contracts, construction, and maintenance, and the interactions of these

3 KEYS COMPONENT

51

activities

Quality control

To assess production and construction processes- control the level of quality being produced in the end product.

Includes sampling and testing


Independent assurance

A management tool that requires a third party, not directly responsible for process control or

acceptance, to provide an independent assessment of the product and/or the reliability of

test results obtained from process control and acceptance testing.

The results of independent assurance tests should not be used as a basis of product

acceptance

Acceptance

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Sampling, testing, and the assessment of test results to determine whether or not the quality

of produced material or construction is acceptable in terms of the specifications.

.


chapter 4 - road construction 1.ppt - author | the uthm...

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