The P2P Initiative:Performance-based Specs for Concrete

NRMCA Continuing Education Series

© National Ready Mixed Concrete AssociationAll rights reserved

Announcement

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.

Introduction

Continuing education for engineers and architects Length of Presentation: 1 Hour Architects Earn 1 LU Engineers Earn 1 PDH NRMCA is an AIA/CES Registered Provider Records kept on file with NRMCA and AIA/CES Records

Outline

What is the P2P Initiative? What is a Prescriptive Specification? What is a Performance Specification? What are the Benefits of P2P? What Activities are Underway? How to Specify Concrete using Current Codes?

What is the P2P Initiative?

Stands for Prescription-to-Performance Initiative of the ready mixed industry through the NRMCA Coordinated by P2P Steering Committee under the

NRMCA Research, Engineering and Standards Committee

Members include technical representatives, product suppliers, contractors, engineers, and architects

Why Performance?

Shifting Expertise to Concrete Producers Reduce Conflicts in Specifications Identify Roles and Responsibilities Controlling Construction Cost (through optimization) Meet Greater Demands on the Product (through

innovation) Improving Quality Systems Training and Certification Programs

Construction Cost Savings of P2P

Innovative construction means and methods Improved construction schedules More efficient structural designs Simplified specifications and submittal process Optimized mix designs

Innovative Technologies

High-Strength Concrete

High-Performance Concrete

Self- Consolidating Concrete

Improved Quality Systems

Product Development

Testing Labs

Material Handling

NRMCA Training and Certifications

Plant and Truck Certification Plant Manager Certification Concrete Technologist Certifications Certified Delivery Professional (drivers) Concrete Certified Sales Professional Under development

Concrete technologist responsible for performance mixes Concrete producer certification based on quality system

P2P Goals

Allow performance specifications as an alternative to current prescriptive specifications

Leverage expertise of all parties to improve quality and reliability of concrete construction

Assist architects/engineers to address concrete specifications in terms of functional requirements

Allow flexibility on the details of concrete mixtures and construction means and methods

Better establish roles and responsibilities based on expertise Continue to elevate the performance level of the ready mixed

concrete industry Foster innovation and advance new technology at a faster pace

What is a Prescriptive Specification?

Details mixture proportions and construction means and methods

Do not always cover intended performance May conflict with intended performance

Example: Low w/c for durability could increase thermal and shrinkage cracking

Requirements are generally not directly enforceable Producer held responsible for performance and defects,

even though he lacks the freedom to make changes Prevents mixture optimization for performance No incentive for quality control / batch uniformity

Prescriptive Specification

Intended Performance Placing/Finishing Strength Min Shrinkage Resistance To:

Freeze-Thaw Corrosion Sulfate attack ASR Cracking Abrasion

Prescriptive Criteria Slump Max w/cm ratio Min cement content Min/max air Min/Max pozzolans/slag Blended cements Aggregate grading Source Limitations Chloride Limits

Prescriptive Specification

Intended Performance Placing/Finishing Strength Min Shrinkage Resistance To:

Freeze-Thaw Corrosion Sulfate attack ASR Cracking Abrasion

Prescriptive Criteria Slump Max w/cm ratio Min cement content Min/max air Min/Max pozzolans/slag Blended cements Aggregate grading Source Limitations Chloride Limits

Some prescriptive criteria are required by code but many are not

Prescriptive Specification Example

w/c ratio = 0.40 Min. cement = 600 pcy Strength = 3500 psi No SCM Aggregate grading 8 – 18% No reactive aggregate Low alkali cement Shrinkage = 0.04% max

No cracking No curling Slump 5 ± 1 inch Setting time 4 ± 0.5 hrs Max temp 85° F Impermeable Uniform color

Example: Water Cement Ratio

Cement

Water

Air

Cement

Water

Air

Paste

w/cm alone does not control strength

0

1000

2000

3000

4000

5000

6000

7000

8000

0.40 0.45 0.5 0.55 0.6 0.70

Water-Cementitious Ratio (w/cm)

Co

mp

ress

ive

Str

eng

th,

psi

Mix 1

Mix 2

Mix 3

Source: ACI 211

w/cm alone does not control permeability

0

1000

2000

3000

4000

5000

6000

7000

8000

0.70 0.55 0.45

Ch

arg

e P

as

se

d,

Co

ulo

mb

s

Portland cement

SCM1

SCM2

Ternary Blend

Water-Cementitious Ratio (w/cm)

Source: ACI 232, 233, 234

What is a Performance Specification?

Performance requirements of concrete Hardened state for Service (meeting owner’s requirements) Plastic state for Constructability (meeting the contractor’s

requirements) Focus on performance and function Assignment of responsibility Flexibility to adjust mixture ingredients and proportions to

achieve consistent performance Changes in weather conditions Changes in materials

Measurable and enforceable Defined test methods and acceptance criteria

How would it work?

Qualification requirements would be established for producers

Performance criteria would be specified by the A/E Contractor would partner with producer to establish

constructability criteria Submittal will demonstrate compliance with specified

requirements Compliance through pre-qualification tests and limited

jobsite acceptance tests

Who Benefits from P2P?

Owners Engineers/Architects Concrete Contractors Concrete Producers

Benefits to Owners from P2P

Improved quality Improved performance Reduced construction time Reduced cost Higher confidence in concrete construction Innovative solutions

Benefits to Engineers/Architects

Focus on function rather than composition Strength, Durability, Shrinkage, etc.

Simplified submittal review Improved product consistency Reduced conflict with contractor/producer Reduced risk

Producer responsible for concrete mix design

Innovative solutions

Benefits to the Contractors

Improved communication / coordination Constructability requirements addressed Predictable performance Innovate on construction means and methods

Benefits to Concrete Producers

Eliminates conflicts in specifications Improved clarity in what needs to be furnished Encourages innovation Rewards investment in quality control Allows optimization of mixtures for performance Allows adjustment of materials/proportions to

compensate for changes in materials and weather Provide innovative products

What are the Challenges?

Acceptance of Change Trust / Credibility Knowledge Level (training) Reference Codes and Specifications

Prescriptive limitations

Measurement and Testing Reliability of existing tests Reliability of jobsite tests

What Activities are Underway?

Communication Engineers, Architects, Contractors, and Producers Articles and presentations

Developing Producer Quality System / Qualifications Developing Model Spec / Code Revisions

Look at model codes from other countries (Canada, Europe, Australia) Look at similar initiatives in the US (FHWA and DOTs)

Documenting Case Studies Conducting Research

Test Methods for Performance Quantifying differences between prescriptive and performance mixes

Delivering Training Programs

How to Specify Concrete Using Current Codes

Objective: Minimize prescriptive requirements Comply with ACI 318 Chapter 3, 4 and 5 Example: 3 story concrete building with first level parking

Structural slabs, beams, and columns Slabs-on-grade (parking) Foundation walls Footings Freezing and thawing (with deicing chemicals) Soils contain sulfates (severe)

Unusual to have freeze-thaw and sulfate exposure Items in are comments Most concrete does not require prescriptive criteria

Yellow

Classes of Concrete for the Project

Class Application Exposure Strength, f’c

1 Slabs and beams None 4,000 psi

2 Columns None 5,000 psi

3Slabs on grade,

Foundation walls

Freeze/Thaw,

Deicing Chemicals,

Sulfate (severe)

4,500 psi

4 Footings Sulfate (severe) 4,500 psi

Class 1 and 2 strength is governed by structural design requirementsClass 3 and 4 strength is governed by durability requirements

Part 1 - General

1.1 RELATED DOCUMENTS 1.2 SUMMARY 1.3 DEFINITIONS 1.4 SUBMITTALS 1.5 QUALITY ASSURANCE 1.6 DELIVERY, STORAGE, AND HANDLING

Submittals

Submit field or laboratory test records for each class of concrete to demonstrate concrete will meet: Required average compressive strength Other specified requirements in section 2.12

Test data should meet the following requirements Test data from concrete supplied from the same production

facilities proposed for the work Test data from concrete mixtures containing similar materials

proposed for the work

Submittals (cont’d)

Submit properties of mix design for each class of concrete including: Specified compressive strength, ƒ΄c Documentation of strength test results indicating the standard deviation Required average compressive strength, ƒ΄cr Average compressive strength of proposed mixture Placement method Slump or slump flow Air content Density w/cm ratio Maximum aggregate size Sources and designations of ingredient materials

Some properties will be specified and others will be selected by producer and contractor

Slump is one example. Slump should not be specified but selected by the contractor and producer since this is means and methods

Submittals (cont’d)

Submit documentation indicating installer, manufacturer, and testing agency meet the qualifications specified in Section 1.5 Quality Assurance.

Quality Assurance

Installer Qualifications: On-site supervisor of the finishing crew who qualified as ACI Certified

Concrete Flatwork Technician for flatwork placing and finishing.

Flatwork finisher certification is important for constructing slabs General standard of care of concrete construction is addressed in

this certification program

Quality Assurance (cont’d)

Manufacturer Qualifications: NRMCA Certified Ready Mixed Concrete Production Facility NRMCA Concrete Technologist Level 2

NRMCA certified concrete production facilities demonstrate compliance with requirements of ASTM C 94

Includes an annual certification of delivery vehicles The NRMCA Concrete Technologist Level 2 Certification validates

personnel’s knowledge of fundamentals of concrete technology including mixture proportioning.

Certification is obtained by passing a 90 minute exam administered by NRMCA with ACI Grade 1 Field Testing Technician Certification as the prerequisite.

Details available at www.nrmca.org/certifications .

Quality Assurance (cont’d)

Testing Agency Qualifications: Meet the requirements of ASTM C 1077. Field testing: ACI Concrete Field Testing Technician Grade I. Lab testing: ACI Concrete Strength Testing Technician or ACI Concrete

Laboratory Testing Technician – Grade I. Test results for the purpose of acceptance shall be certified by a

registered design professional employed with the Testing Agency.

Concrete testing is very sensitive to the way specimens are collected, cured, and tested. Proper field and lab procedures are essential to achieving meaningful results.

Quality Assurance (cont’d)

Pre Installation Conference: Require representatives of each entity directly concerned with cast-in-

place concrete to attend, including: Architect Structural Engineer Contractor Installer (Concrete Contractor) Pumping Contractor Manufacturer (Ready-mixed concrete producer) Independent testing agency

NRMCA and American Society of Concrete Contractors has a document titled Checklist for the Concrete Pre-Construction Conference that can be used as a guide

Part 2 - Products

2.1 MANUFACTURERS 2.2 FORMING MATERIALS 2.3 STEEL REINFORCEMENT 2.4 REINFORCEMENT ACCESSORIES 2.5 CONCRETE MATERIALS 2.6 WATERSTOPS 2.7 VAPOR RETARDERS 2.8 FLOOR AND SLAB TREATEMENTS 2.9 CURING MATERIALS 2.10 RELATED MATERIALS 2.11 REPAIR MATERIALS 2.12 CONCRETE MIXTURES

Concrete Materials

Cementitious Materials: Use materials meeting the following requirements with limitations

specified in Section 2.12. Hydraulic Cement: ASTM C 150 or ASTM C 1157 or ASTM C 595 Fly Ash: ASTM C 618 Slag: ASTM C 989 Silica Fume: ASTM C 1240

Avoid listing brand names for most materials in this section if a standard for the product already exists.

Many existing standards are performance-based. Avoid limiting the type or quantities of cementitious materials that

can be used unless required for certain performance attributes as listed in Section 2.12 Concrete Mixtures.

Concrete Materials (cont’d)

Normalweight Aggregate: ASTM C 33 Water: ASTM C 1602 Fibers: ASTM C 1116

Concrete Materials (cont’d)

Chemical Admixtures: Air Entraining: ASTM C 260 Water reducing, accelerating and retarding: ASTM C 494 Admixtures for flowing concrete: ASTM C 1017 Admixtures with no standard designation shall be used only with the

permission of the design professional when its use for specific properties is required.

Avoid limiting the type of admixtures that can be used unless there is a specific reason (eg. Chloride based admixtures for corrosion).

Consider specifying or allowing the use of admixtures which do not have a specific ASTM designation with appropriate documentation indicating beneficial use to concrete properties.

These include colors, viscosity modifying admixtures, hydration stabilizing admixtures, pumping aids, anti-freeze admixtures, etc.

Concrete Mixtures

Prepare design mixtures for each class of concrete on the basis of field test data or laboratory trial mixtures, or both according to ACI 318, Chapter 5.

Design mixtures shall meet the requirements listed in Table 2.12.

Concrete Mixtures (cont’d)

Table 2.12 Concrete Mixtures

Class App. Exp. ƒ΄c

Nom. Max. Agg. Size1

Air Content

Max. w/cm

by weight

Cement-itious

MaterialsAdmix.

Max. water sol. Cl ion in conc., % by

wt of cement

1Slabs and

beamsNone

4,000 psi

3/4” N/A2 N/ASee section

2.5 A

See section

2.5 D1.00

2 Columns None5,000 psi

3/4” N/A2 N/ASee section

2.5 A

See section

2.5 D1.00

3

Slabs on grade,

Foundation walls

Freeze/Thaw,Deicing

Chemicals,Sulfate (severe)

4,500 psi

1-1/2” 5-1/2 %3 0.45

Limits on cement4,

fly ash, slag, and silica

fume5

No calcium chloride

admixtures0.15

4 FootingsSulfate (severe)

4,500 psi

1-1/2” N/A2 0.45Limits on hydraulic cement4

No calcium chloride

admixtures0.30

Provide a schedule of concrete classes of the structure including a description of exposure.

Provide limits on materials based on Chapter 3 and 4 of ACI 318

Concrete Mixtures (cont’d)

Table 2.12 Concrete Mixtures

Class App. Exp. ƒ΄c

Nom. Max. Agg. Size1

Air Content

Max. w/cm by weight

Cement-itious

MaterialsAdmix.

Max. water sol. Cl ion in conc., % by

wt of cement

1Slabs and

beamsNone 4,000 psi 3/4” N/A2 N/A

See section 2.5 A

See section 2.5 D

1.00

2 Columns None 5,000 psi 3/4” N/A2 N/ASee section

2.5 ASee section

2.5 D1.00

Few limits on materials for class 1 and 2 since durability is not a concern No maximum water-cement ratio or minimum cement content Compressive strength based on structural design requirements Maximum aggregate size controlled by ACI 318 – 3.3 Aggregates

1/5 narrowest dimension of forms 1/3 slab depth 3/4 minimum clear spacing between reinforcement (governs)

Maximum chloride ions controlled by ACI 318 – 4.4 for corrosion protection of reinforcement that will be dry or protected from moisture in service

Concrete Mixtures (cont’d)

Table 2.12 Concrete Mixtures

Class App. Exp. ƒ΄c

Nom. Max. Agg. Size1

Air Content

Max. w/cm

by weight

Cement-itious

MaterialsAdmix.

Max. water sol. Cl ion in conc., % by

wt of cement

3

Slabs on grade

Foundation walls

Freeze/Thaw,Deicing

Chemicals,Sulfate (severe)

4,500 psi

1-1/2” 5-1/2 %3 0.45

Limits on cement4, fly ash,

slag, and silica fume5

No calcium chloride

admixtures0.15

Class 3 concrete is exposed to freeze-thaw, deicing chemicals, and severe sulfates Compressive strength, air content, maximum w/cm based on ACI 318 4.2 Freezing

and thawing exposure. Limits on SCMs based on ACI 318 4.2.3 for concrete exposed to deicing chemicals:

Fly ash, 25% max Slag, 50% max Silica fume, 10% max Total of fly ash, slag, and silica fume, 50% max Total of fly ash and silica fume, 35% max

Limits on cement type, calcium chloride admixtures, strength, and w/cm are based on ACI 318 4.3 Sulfate exposure.

Type V cement must be used

Concrete Mixtures (cont’d)

Table 2.12 Concrete Mixtures

Class App. Exp. ƒ΄c

Nom. Max. Agg. Size1

Air Content

Max. w/cm by weight

Cement-itious

MaterialsAdmix.

Max. water sol. Cl ion in conc., % by

wt of cement

4 FootingsSulfate (severe)

4,500 psi

1-1/2” N/A2 0.45Limits on cement4

No calcium chloride

admixtures0.30

Class 4 concrete is exposed to severe sulfates Compressive strength, cement type, maximum w/cm, and restriction

on using calcium chloride admixtures are based on ACI 318 4.3 – Sulfate exposure Type V cement must be used

PART 3 - Execution

3.1 FORMWORK 3.2 EMBEDDED ITEMS 3.3 REMOVING AND REUSING FORMS 3.4 SHORES AND RESHORES 3.5 VAPOR RETARDERS 3.6 STEEL REINFORCEMENT 3.7 JOINTS 3.8 WATERSTOPS 3.9 CONCRETE PLACEMENT 3.10 FINISHING FORMED SURFACES 3.11 FINISHING FLOORS AND SLABS 3.12 MISCELLANEOUS CONCRETE ITEMS 3.13 CONCRETE PROTECTING AND CURING 3.14 LIQUID FLOOR TREATEMENTS 3.15 JOINT FILLING 3.16 CONCRETE SURFACE REPAIRS 3.17 FIELD QUALITY ASSURANCE

Concrete Placement

Measure, batch, mix, deliver, and provide delivery ticket for each batch of concrete in accordance with ASTM C 94. Do not add water to concrete during delivery or during

placement. Water is permitted to be added to a batch of concrete at the

project site before placement of the batch begins provided that the amount of water added does not exceed the allowed amount indicated on the delivery ticket.

Field Quality Assurance

Testing: Owner shall engage a qualified testing agency to perform concrete field tests and prepare test reports.

Concrete Field Tests: Concrete Test Samples: Samples for concrete tests shall be

taken in accordance with ASTM C 172.

Field Quality Assurance (cont’d)

Compressive Strength Tests on concrete: Samples shall be taken not less than once per day, nor less than once for each 150 yd3 of concrete, nor less than once for each 5000 ft2 surface area for slabs or walls. Acceptance based on standard cured cylinders in accordance with ASTM C 31

and tested at 28 days in accordance with ASTM C 39. Strength test results are the average of two specimens. Tests of slump, air content, temperature and density shall be made and

recorded with the strength test results.

Consider testing at 56 or 90 days for high volumes of SCMs. Average of two cylinders represent a strength test result by ACI 318 If a 7 day test is specified for informational purposes (not acceptance),

clearly indicate that in the specification. The installer and manufacturer may choose to make additional cylinders for

field cured specimens to monitor early age strength for form removal and reshoring.

Field cured specimens are typically not recognized for acceptance.

Field Quality Assurance (cont’d)

Strength of each concrete class shall be deemed satisfactory: The average of three consecutive compressive-strength tests

equals or exceeds specified compressive strength Any individual compressive-strength test result does not fall

below specified compressive strength by more than 500 psi.

When compressive strength tests indicate low strength, follow procedure in ACI 318 chapter 5.6.4 Investigation of low-strength test results

Field Quality Assurance (cont’d)

Air Content: ASTM C 231. Air content tests shall be performed on concrete at least at the same

frequency as compressive strength testing. The provisions of ASTM C 94 shall apply for acceptance of air content

of concrete.

Only use air content as an acceptance criterion if there is an air content requirement

ACI 318 establishes an air content tolerance of ±1.5% ASTM C 94 permits a jobsite adjustment if the air content is low Allows for retesting prior to rejecting concrete

Field Quality Assurance (cont’d)

Slump: ASTM C 143; one test when concrete is sampled for strength tests.

Temperature: ASTM C 1064; one test when concrete is sampled for strength tests.

Density: ASTM C 138; one test when concrete is sampled for strength tests.

Test results shall be reported to architect, engineer, concrete producer, and concrete contractor within 48 hours of testing.

Recap

Comply with ACI 318 Place limits on materials in concrete based on the

exposure of the concrete. Plan to propose changes to ACI 318 Chapter 4 –

Durability Requirements to allow performance-based alternatives

Plan to develop model performance-based specifications based on the new provisions

Additional Information

Visit www.nrmca.org/P2P Download Example Specification Download P2P Articles Download Research Studies