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
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 Source: ACI 211
w/cm alone does not control permeability 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 ClassApplicationExposureStrength, f’ c 1Slabs and beamsNone4,000 psi 2ColumnsNone5,000 psi 3 Slabs on grade, Foundation walls Freeze/Thaw, Deicing Chemicals, Sulfate (severe) 4,500 psi 4FootingsSulfate (severe)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.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
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 ClassApp.Exp.ƒ΄ c Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement- itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement 1 Slabs and beams None 4,000 psi 3/4”N/A 2 N/A See section 2.5 A See section 2.5 D 1.00 2ColumnsNone 5,000 psi 3/4”N/A 2 N/A See section 2.5 A See section 2.5 D 1.00 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 cement 4, fly ash, slag, and silica fume 5 No calcium chloride admixtures 0.15 4Footings Sulfate (severe) 4,500 psi 1-1/2”N/A 2 0.45 Limits on hydraulic cement 4 No calcium chloride admixtures 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) Table 2.12 Concrete Mixtures ClassApp.Exp.ƒ΄ c Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement- itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement 1 Slabs and beams None4,000 psi3/4”N/A 2 N/A See section 2.5 A See section 2.5 D 1.00 2ColumnsNone5,000 psi3/4”N/A 2 N/A See section 2.5 A See section 2.5 D 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) Table 2.12 Concrete Mixtures ClassApp.Exp.ƒ΄ c Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement- itious Materials Admix. 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 cement 4, fly ash, slag, and silica fume 5 No calcium chloride admixtures 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) Table 2.12 Concrete Mixtures ClassApp.Exp.ƒ΄ c Nom. Max. Agg. Size 1 Air Content Max. w/cm by weight Cement- itious Materials Admix. Max. water sol. Cl ion in conc., % by wt of cement 4Footings Sulfate (severe) 4,500 psi 1-1/2”N/A 2 0.45 Limits on cement 4 No calcium chloride admixtures 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/P2Pwww.nrmca.org/P2P Download Example Specification Download P2P Articles Download Research Studies