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The P2P Initiative – Focus on Innovation and Quality

The P2P Initiative – Focus on Innovation and Quality. © National Ready Mixed Concrete Association All rights reserved. Announcement.

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The P2P Initiative – Focus on Innovation and Quality

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  1. The P2P Initiative – Focus on Innovationand Quality © National Ready Mixed Concrete Association All rights reserved

  2. 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.

  3. Introduction • Continuing education for engineers and architects • Length of Presentation: 1 Hours • Architects Earn 1 LUs • Engineers Earn 1 PDHs • NRMCA is an AIA/CES Registered Provider • Records kept on file with NRMCA and AIA/CES Records

  4. What is the P2P Initiative? • Prescription-to-Performance • An alternative to current prescriptive specifications • An initiative of the concrete industry • Spearheaded by the NRMCA

  5. 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 • Elevate the performance level and quality of ready mixed concrete • Foster innovation and advance new technology at a faster pace

  6. What is a prescriptive Specification? • Do not always cover intended performance • May conflict with intended performance • Limits competitive bidding • No incentive for quality control • Not in the owner’s best interest

  7. Prescriptive Specification Intended Performance • Placing/Finishing • Strength • Max Shrinkage • Resistance To: • Freeze-Thaw • Deicer scaling • Corrosion • Sulfate attack • ASR • Cracking • Abrasion Typical Criteria • Slump • Max w/cm ratio • Min cement content • Min/max air • Min/Max pozzolans/slag • Blended cements • Aggregate grading • Source Limitations • Chloride Limits

  8. Water-cement Ratio Air Air Water Water Paste Cement Cement

  9. Does w/c alone control strength?

  10. Does w/c alone control permeability?

  11. What is a Performance Specification? • Focus on performance and function • Flexibility to adjust mixture ingredients and proportions to achieve consistent performance • Measurable and enforceable

  12. Benefits to the Owner • Improved quality • Improved performance • Reduced construction time • Reduced cost • Higher confidence in concrete construction

  13. Benefits to the Engineer/Architect • Focus on function rather than composition • Strength, Durability, Shrinkage, etc. • Simplified submittal review • Improved product consistency • Reduced conflict with contractor/producer • Reduced risk – contractor and producer are responsible for performance

  14. Benefits to the Contractor • Improved communication/coordination • Constructability requirements addressed • Predictable performance • Innovate on construction means and methods

  15. Benefits to the Producer • Eliminates conflicts and improves clarity in specifications • Encourages innovation and rewards investment in quality control • Allows optimization of mixtures for performance • Allows adjustment of materials/proportions to compensate for material or ambient conditions variations

  16. 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

  17. 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

  18. Lab Study Demonstrating Advantages of Performance Specification • Case 1: Real Floor Specification from a Major Owner • Case 2: Typical HPC Bridge Deck Specification • Case 3: ACI 318 Chapter 4 Code – prescriptive durability provisions

  19. Fresh Concrete Tests • Fresh Concrete Properties • Slump: ASTM 143 • Air Content: ASTM C 231 • Density: ASTM C 138 • Temperature: ASTM C 1064 • Initial Setting Time (Case 1): ASTM C 403 • Finishability (Case 1): Subjective rating (5=Excellent to 1=Poor) • Segregation (Case 1): Cylinders vibrated, density of top and bottom half compared

  20. Hardened Concrete Tests • Compressive Strength, ASTM C 39 • Length Change, ASTM C 157

  21. Durability Tests • Rapid Chloride Permeability Test (RCPT), ASTM C 1202 • Rapid Migration Test (RMT), AASHTO TP 64 • Sorptivity, ASTM C 1585 • Bulk Diffusion, ASTM C 1556

  22. Case 1 - Concrete Floor Specification Specified by Contractor

  23. Experimental Program (5 concrete mixtures) • One control (prescriptive) and 4 performance mixtures FS-1: CM = 611, w/cm = 0.49, 8-18% aggregate FS-2: CM = 517, w/cm = 0.57, 8-18% aggregate FS-3: CM = 530, 20% FA, w/cm = 0.57, 8-18% aggregate FS-4: CM = 530, 20% FA with binary aggregates, w/cm = 0.53, #467 stone aggregate FS-5: CM = 530, 20% SL, 15% FA with binary aggregates, w/cm = 0.54, #467 stone aggregate

  24. Combined Aggregate Grading of FS Mixtures

  25. Compressive Strength and Setting Time

  26. Segregation & Shrinkage • Segregation Index: Difference in the coarse aggregate content was consistently about 20% except for Mixture FS-5 which was about 15% • Shrinkage: All mixtures except FS-5 had 28 day shrinkage < 0.020%

  27. All 5 concrete mixtures had a rating above 4.5 indicating excellent finishability Slab Finishability Test

  28. Durability

  29. Summary – Floor Slab Mixtures • All performance mixtures met performance requirements except Mixture FS-5 • Strength over-design factor, limiting w/cm increased cement contents • Use of SCMs was beneficial • Continuous aggregate grading mixtures did not impact performance • Performance mixtures had substantial material costs savings

  30. Case 2 - HPC Bridge Deck Specification Specified by Contractor

  31. Experimental Program (4 mixtures) • One control (prescriptive) and 3 performance mixtures BR-1: C = 550, Class F FA = 105, SF = 50; Total = 705 BR-2: C = 426, Class F FA = 150, SF = 24; Total = 600 BR-3: C = 300, SL = 300; Total = 600 BR-4: C = 426, Class F FA = 150, UFFA = 34; Total = 612 • w/cm=0.39 for all mixtures except 0.36 for Mix 4

  32. Strength • Compressive Strength: 28 day strengths were much higher than specified (6800 to 8970 psi)

  33. RCPT (ASTM C 1202), RMT (AASHTO TP 64)

  34. Rapid Migration Test • FHWA Performance Grade (AASHTO TP 64) • Grade 1: RCPT = 2000 to 3000; RMT = 0.024 to 0.034 • Grade 2: RCPT = 800 to 2000; RMT = 0.012 to 0.024 • Grade 3: RCPT < 800; RMT < 0.012

  35. Drying Shrinkage (ASTM C 157)

  36. Summary – HPC Bridge Deck Mixtures • All performance mixtures met performance requirements • Performance mixtures had similar or better performance than Prescriptive mixtures • Drying shrinkage, workability (stickiness), HRWR dosage, strength, RCPT, RMT • Performance mixtures had substantial material cost savings

  37. Case 3 - ACI 318 Chapter 4 Prescriptive durability provisions • Objective: Determine if w/cm is the best measure for durability (permeability).

  38. Experimental Program (4 mixtures) • One control (prescriptive) and 3 performance mixtures 318-1: 750 lbs Portland cement mixture 318-2: CM = 700; 25% FA (1.16% less paste) 318-3: CM = 564; 25% FA (7.24% less paste) 318-4: Same as #3 but yield adjusted largely by coarse aggregate • w/cm = 0.42 • Slump = 3.75” – 6.5”; Air = 4.1% to 7.4%

  39. At same w/cm=0.42 Results

  40. Summary – ACI 318 Mixtures • Code limitations on w/cm are no guarantee for high durability concrete • Considerable advances in the use of SCMs and chemical admixtures • Code durability provisions should be performance based

  41. Conclusions • Prescriptive specs do not assure performance • Performance mixtures achieved equal or better performance • Great opportunity for mixture optimization • Producers compete on their knowledge, resources • ACI 318 durability provisions needs to change

  42. ACI 318 Chapter 4 Restructuring • Exposure Category F – Exposure to freezing and thawing cycles • Exposure Category S – Exposure to water-soluble sulfates • Exposure Category P – Conditions that require low permeability concrete • Exposure Category C – Conditions that require additional corrosion protection of reinforcement

  43. Exposure to freezing and thawing cycles

  44. Exposed to water-soluble sulfates

  45. Conditions that require low permeability concrete

  46. Conditions that require additional corrosion protection of reinforcement

  47. Requirements for Concrete - Exposure Class F

  48. Table 4.4.1—Total Air Content for Concrete Exposed to Cycles of Freezing and Thawing

  49. Table 4.4.2—Requirements for Concrete Subject to Deicing Exposure Class F3

  50. Requirements for Concrete - Exposure Class S

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