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03 rita leahy

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Presentation delivered by Rita Leahy of CalAPA at the California Asphalt Pavement Association Spring Conference April 25, 2013 in Ontario, CA.

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03 rita leahy

  1. 1.  Superior Performing Asphalt Pavement Product of SHRP –●Strategic Highway Research Program 1989 – 1993 $150 Million $50 Million on ASPHALT!
  2. 2. Materials SelectionDesign Aggregate StructureDesign Binder ContentMoisture Sensitivity
  3. 3.  Level 1 (Volumetric) Mix Design●Materials Selection►Aggregate consensus properties►PG asphalt binder specification
  4. 4.  Level 1 (Volumetric) Mix Design●Design Aggregate Structure and DesignAsphalt Binder Content►Using Superpave Gyratory Compactor(SGC)
  5. 5. 7-Day Maximum Air Temp (°C)Traffic(106 ESALs)< 39 39 – 40 41 - 42 43 - 44< 0.3 68 74 78 820.3 – 1 76 83 88 931 – 3 86 95 100 1053 – 10 96 106 113 11910 – 30 109 121 128 13530 – 100 126 139 146 153> 100 142 158 165 1727 Traffic Categories x 4 Climate Regimes= 28 Compaction Levels!
  6. 6.  Level 1 (Volumetric) Mix Design●Moisture Sensitivity Evaluation►AASHTO T-283 (Modified Lottman)
  7. 7.  Superpave Level 2/3 Mix Design●Performance-Based Mix Tests►Superpave Shear Tester▪Rutting & Fatigue►Indirect Tensile Tester▪Low temp cracking●Performance Prediction Models
  8. 8.  Observations with implementation●Reduce Ndesign for base mixes●Reduce the number of traffic levels●Ndesign yielding low binder contents●Constructability problematic●Reduce Ndesign for low volume roads
  9. 9. ESAL(106) Ninitial Ndesign Nmax< 0.3 6 50 750.3 to <3 7 75 1153 to <30 8 100 160≥30 9 125 205Based on independent work by NCAT and Asphalt Institute4 Compaction Levels!
  10. 10.  Revised Ndesign Table● Lower compaction►Higher binder content  better durability►Aggregate structure (coarse, gap-gradedmixes to finer, dense-graded mixes) reduced permeability WMA
  11. 11.  RAP and RAS●Increased use in recent years (noprovisions for using RAP in originalSuperpave mix designs) Moisture Sensitivity●Still AASHTO T283●Greater reliance on other tests –Hamburg Wheel Tracking Test
  12. 12.  Performance Testing● Simple Shear Tester (SST)● AMPT (Asphalt Mixture Performance Tester)►Flow Number for Rutting►Dynamic Modulus for Stiffness►Cyclic Fatigue● Flexural Beam Fatigue Performance Prediction● MEPDG? CalME?
  13. 13.  Volumetric Mix Design● Reduced Ndesign Levels● Coarser to Finer Mixes● Higher Binder Contents● AASHTO T283 and/or Hamburg● RAP, RAS & WMA Performance Testing Performance Prediction

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