The P2P Initiative: Performance-based Specs for Concrete

NRMCA Continuing Education Series

© National Ready Mixed Concrete Association All 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-Performance Concrete High-Strength Concrete Self- Consolidating Concrete

Improved Quality Systems

Testing Labs Product Development 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

Air Water Cement

Paste

Air Water Cement

w/cm alone does not control strength

8000 7000 6000 5000 4000 3000 2000 Mix 1 Mix 2 Mix 3 1000 0 0.40

0.45

0.5

0.55

0.6

Water-Cementitious Ratio (w/cm) 0.70

Source: ACI 211

w/cm alone does not control permeability

8000 7000 6000 5000 4000 3000 2000 1000 0 Portland cement SCM1 SCM2 Ternary Blend 0.70

0.55

0.45

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   Most concrete does not require prescriptive criteria

Classes of Concrete for the Project

Class 1 Application Slabs and beams 2 3 4 Exposure None Columns Footings None Slabs on grade, Foundation walls Freeze/Thaw, Deicing Chemicals, Sulfate (severe) Sulfate (severe) Strength, f’ 4,000 psi 5,000 psi 4,500 psi c 4,500 psi Class 1 and 2 strength is governed by structural design requirements Class 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)

Class 1 2 3 4 App.

Slabs and beams Columns Footings Exp.

None None Slabs on grade, Foundation walls Freeze/Thaw, Deicing Chemicals, Sulfate (severe) Sulfate (severe) ƒ΄ c Table 2.12 Concrete Mixtures Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight 4,000 psi 5,000 psi 4,500 psi 4,500 psi 3/4” 3/4” 1 1 1/2” 1/2” N/A N/A N/A 2 2 5-1/2 % 2 3 N/A N/A 0.45

0.45

Cement itious Materials Admix.

See section 2.5 A See section 2.5 A See section 2.5 D See section 2.5 D Limits on cement 4 , fly ash, slag, and silica fume 5 No calcium chloride admixtures Limits on hydraulic cement 4 No calcium chloride admixtures Max. water sol. Cl ion in conc., % by wt of cement 1.00

1.00

0.15

0.30

  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)

Class 1 2 App.

Exp.

Slabs and beams Columns None None ƒ΄ c 4,000 psi 5,000 psi Table 2.12 Concrete Mixtures Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement itious Materials 3/4” 3/4” N/A N/A 2 2 N/A N/A Admix.

See section 2.5 A See section 2.5 D See section 2.5 A See section 2.5 D Max. water sol. Cl ion in conc., % by wt of cement 1.00

1.00

     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)

Class 3 App.

Exp.

Slabs on grade Foundation walls Freeze/Thaw, Deicing Chemicals, Sulfate (severe) ƒ΄ c Table 2.12 Concrete Mixtures Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement itious Materials 4,500 psi 1 1/2” 5-1/2 % 3 0.45

Admix.

Limits on cement 4 , fly ash, slag, and silica fume 5 No calcium chloride admixtures Max. water sol. Cl ion in conc., % by wt of cement 0.15

    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)

Class 4 App.

Exp.

Footings Sulfate (severe) ƒ΄ c 4,500 psi

Table 2.12 Concrete Mixtures

Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement itious Materials 1 1/2” N/A 2 0.45

Admix.

Limits on cement 4 No calcium chloride admixtures Max. water sol. Cl ion in conc., % by wt of cement 0.30

  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 yd 3 of concrete, nor less than once for each 5000 ft 2 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