Cliff Ashcroft


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Presentation on Rubber Pavements presented at the CalAPA Fall Asphalt Pavement Conference Oct. 24, 2013 in Sacramento, Calif.

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  • Cliff Ashcroft

    1. 1. CalAPA Conference Sacramento, CA October 24, 2013 Asphalt Rubber Revolution By Cliff Ashcroft President Rubber Pavements Association
    2. 2. If you think you know everything about asphalt rubber pavements? Think again! Major changes in California regarding AR pavements.
    3. 3. Asphalt Rubber History Asphalt Rubber Chip Seal (SAM) A R Chip Seal Interlayer (SAMI) AZ Open-Graded Hot Mix CA Dense-Graded Hot Mix Gap-Graded Hot Mix 1960 1970 1980 1990 2000 2010
    4. 4. Definition of Asphalt Rubber  Uses a minimum of 20 +/- 2 % crumb rubber  Uses 10 mesh (2mm) crumb rubber  Reacts/interacts crumb rubber for a minimum of 45 min. at elevated temperatures  Modifies original properties of asphalt cement  Only crumb rubber binder with an ASTM definition and extensive research background
    5. 5. What is Asphalt Rubber Binder?  It is a NON PRORIATARY recipe specification  A blend of recycled tire rubber, asphalt and extender oil  Reacted at high temperatures to significantly modify the asphalt  Result is a unique product – asphalt rubber binder  AR has a 45 year proven performance history
    6. 6. How is Asphalt Rubber produced? Specialized equipment and binder blended on-site High shear blender for mixing crumb rubber with asphalt and modifier Reaction tank with adequate agitation to assure proper reaction All materials are metered-in
    7. 7. Asphalt Rubber Blending Schematic Asphalt Storage Tank Heat Tank Binder Pumped to Plant Crumb Rubber High Shear Blender Reaction Vessel
    8. 8. Heater Blender Rubber Weigh Hopper
    9. 9. Reaction Vessel Reaction Vessel Augers and Direct Fire Heating
    10. 10. Computer Controlled Accurately Measures Materials During Production
    11. 11. Components of the Asphalt Rubber Binder Crumb rubber modifier (CRM) Asphalt cement Asphalt modifier
    12. 12. Paving Asphalt PG 64-16 and PG 58-22 asphalt (80 +/- 2 %) Conform to Section 92 “Asphalts” of the Standard Specifications
    13. 13. Asphalt Rubber Binder Properties Cone penetration Resilience Field softening point Viscosity
    14. 14. Factors Affecting Binder Properties Asphalt cement Amount of crumb rubber Gradation of crumb rubber Reaction time and temperature
    15. 15. High Viscosity 20 % CRM
    16. 16. Asphalt Rubber Conv. & Other Mod. Asphalts
    17. 17. 22,937,600 rubber particles per ton of mix help fight cracking
    18. 18. Key to asphalt rubber is high viscosity and reduced aging properties. 13 Year Old Asphalt Rubber Chip Seal
    19. 19. Where have Asphalt Rubber strategies been used successfully? AR Hot Mix AR Chip Seals 22 yrs. old 15 yrs. old AR AR Cape Seals Multi-layer Strategies 20 yrs. old 10 yrs. old
    20. 20. Asphalt Rubber Specifications Rubberized hot mix asphalt Type “G” Type “O” Type “O-HB” Asphalt rubber chip seal Asphalt rubber cape seal Multi-layer systems
    21. 21. What are the major changes in California (Caltrans) regarding specifications for AR pavements?
    22. 22. Changes in AR Pavements in California Changes in Caltrans specifications  New Superpave specifications  Some changes made to Section 39 Changes in testing requirements  Gyratory compactor  Hamburg wheel tracking  Moisture sensitivity, minimum dry and wet strengths Changes in acceptance requirements Changes in measuring  MPQP
    23. 23. Changes in Specifications New Superpave specification developed by Caltrans with major changes to RHMA requirements (will be finalized in July 2014) Some changes also made to Section 39 in standard specifications New specs have new requirements for RHMA Laboratory mix design Field mix acceptance
    24. 24. Changes in Mix Design Testing Increase in minimum binder content to 7.5 % by total weight of mix (move from min. 7.0% to 8.1% by dry weight of aggregate) However, no change in the minimum void requirements or aggregate grading requirements - makes this especially difficult
    25. 25. Changes in Mix Design Testing  AASHTO T-312 gyratory compactor now required for compaction during mix design (National Standard from SHRP)  Move away from Hveem kneading compactor  New compaction method in California for all mixes, labs have very little experience  Contractor’s/labs need to familiarize themselves with new method  New method allows variable compaction to achieve mix voids requirements (N design 50-150 gyrations and can increase pressure to 825 kPa)
    26. 26. Gyratory Compactor
    27. 27. Changes in Mix Design Testing AASHTO T-324 (modified) Hamburg testing requirement Maximum rut depth requirement of 0.5 inch on field produced mixes  Rut depth - minimum number of passes (15,000 to 25,000) depending on type and grade of asphalt (PG 58, 64 or 70)  Inflection point - minimum number of passes (10,000 to 15,000) depending on type on grade of asphalt (PG 58, 64 or 70)
    28. 28. Hamburg Wheel Tracking Device
    29. 29. Changes in Mix Design Testing AASHTO T-283 (modified) Moisture Induced Damage Test requirement Minimum dry strength of 110 psi on field produced material Minimum wet strength of 84 psi on field produced material Freeze thaw cycle required
    30. 30. Changes in Acceptance Binder content tolerance changed from +/- 0.5% to - 0.4% +0.5% In-place mix density requirements changed from 91-97% relative density to 92-97% Air voids requirement in field changed from +/2% to +/- 1.5%
    31. 31. Changes in Measuring New requirements for AR in the Materials Plant Quality Program (MPQP) New requirements for weights and measures for AR blending and production New recording requirements New reporting requirements Asphalt rubber MPQP requirements are different from other types of binder production
    32. 32. Use of Warm Mix Technology in RHMA Contractor now has the option to use warm mix technology (WMA) in asphalt rubber hot mix. WMA will help offset low temperature placement problems WMA will aid in the compaction process
    33. 33. WMA Benefits to Contractor Reduced worker exposure to fumes Decreased emissions at HMA plant Savings in energy Easier permitting Extended haul distances Lower odor/fumes Improved thin lift capabilities Expanded season
    34. 34. What to Expect in the Future  Performance Grade (PG) AR specification  Sub-Task Group formed under CT/Industry Rock Products Committee to work on development of a PG specification for asphalt rubber - 3 year work plan  Draft specification developed by Industry  Initial round robin testing conducted through the PCCAS to determine feasibility of using Dynamic Shear Rheometer (DSR) for testing AR binders  Very successful –results indicate DSR can be used for testing AR binders  Second round robin planned for early next year
    35. 35. AB 513 (FRAZIER) Establishes the rubberized asphalt concrete (RAC) market development act. Requires CalRecycle to award grants to California Cities, Counties, and regional park districts. Requires grants provide $2 for every 12 lbs. of crumb rubber used in a paving project. Limited to road rehabilitation, not chip seal projects which use less crumb rubber.
    36. 36. AB 513 (FRAZIER) Background on why this bill is needed. CalRecycle collects $40 million annually for its tire fund from the fee on sale of new tires. Of all the programs to divert tires from landfills, RAC grants have had the most success. Environmental groups support RAC because it is considered the highest and best use of tire recycling. Most California Cities and Counties are strapped for money and even though life cycle costs for RAC are less than conventional asphalt, local governments look for up front savings.
    37. 37. AB 513 (FRAZIER)  Conventional asphalt is cheaper up front. Unless they can get grants, they usually repave with conventional asphalt)  The RAC grants are so popular in California that this past year $3 million was allocated for them but there were almost $10 million in qualified grant applications from cities and counties.  Governor Jerry Brown signed AB 513 on October 3, 2013.  Net result to industry is $7,000,000 +
    38. 38. How do you get your bang for your buck using Asphalt Rubber design?
    39. 39. Reflection Crack Retardation Equivalencies (ft.) HMA RHMA-G RHMA-G Over SAMI-R 0.15 0.10 -- 0.20 0.10 -- 0.25 0.15 -- 0.30 0.15 -- 0.35 0.15 or 0.20a 0.10 or 0.15a 0.45 0.15/0.15 HMA 0.20 a. Depending on crack width and base conditions
    40. 40. 3-Layer AR Cape Seal San Leandro Original AR Chip Seal Microsurfacing as Leveling Slurry/Micro Surfacing
    41. 41. Randolph Avenue Costa Mesa, CA
    42. 42. Costa Mesa 20 years old 37mm ARHM-GG ARCS 25mm AC
    43. 43. Whittier 20 years old 37mm ARHMGG ARCS 25mm AC
    44. 44. Advantages of Asphalt Rubber Pavement Strategies 50% reduced thickness application Initial savings Increased fatigue resistance Reduced oxidation Reduced construction time Increased safety Savings in energy and natural resources Lower maintenance cost
    45. 45. Thank You Questions?