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WHRP Project 0092-10-07 HMA Fatigue and Low Temperature Properties to Support MEPDG

WHRP Project 0092-10-07 HMA Fatigue and Low Temperature Properties to Support MEPDG. Ramon Bonaquist, Ph.D., P.E. Advanced Asphalt Technologies, LLC. Outline. Objectives Approach Major Findings Conclusions and Recommendations. Objectives.

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WHRP Project 0092-10-07 HMA Fatigue and Low Temperature Properties to Support MEPDG

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  1. WHRP Project 0092-10-07 HMA Fatigue and Low Temperature Properties to Support MEPDG Ramon Bonaquist, Ph.D., P.E. Advanced Asphalt Technologies, LLC

  2. Outline • Objectives • Approach • Major Findings • Conclusions and Recommendations

  3. Objectives • Establish a range of tensile strength and creep compliance properties for representative Wisconsin mixtures • Provide recommendations for using the measured mechanical properties in the MEPDG • Evaluate the thermal fracture resistance of Wisconsin mixtures and recommend appropriate specification changes if warranted.

  4. Approach • Collect and analyze low temperature compliance and strength data on 16 mixtures using AASHTO T322

  5. Mixtures WHRP Project 0092- 0092-08-06, Wisconsin Mixture Characterization Using the SPT on Historical Aggregate Structures

  6. Binder Low Temperature Grade

  7. Compliance Master Curve • 100 sec Indirect Tensile Creep Tests at 0, -10, and -20 ºC • Compute compliance • Shift into master curve

  8. LTSTRESS • Excel workbook • Developed by D. Christensen for Northeast Center for Excellence in Pavement Technology • Funded by FHWA when implementing Superpave IDT equipment • Computes compliance • Shifts to form master curve • Simplified thermo-viscoelastic stress analysis • Critical cracking temperature

  9. LTSRESS Master Curve

  10. LTSTRESS Thermal Stress

  11. Analysis of Variance Compliance

  12. Graphically

  13. Equation to Estimate Compliance

  14. Errors Using Only Binder Grade

  15. Effect on Thermal Stresses

  16. Grade Model Thermal Stresses

  17. MEPDG Estimated Compliance

  18. Effect of Errors on Stresses

  19. Tensile Strength

  20. Analysis of Variance

  21. MEPDG Estimated Strength

  22. VFA Effect

  23. Coefficient of Thermal Contraction • Estimated From Volumetric Properties and Typical Values for Asphalt Cement and Aggregate • As Important as Compliance in Stress Calculation

  24. Effect of Thermal Coefficient Can be similar to one grade

  25. Conclusions • Compliance can be estimated based on continuous grade of binder • Low temperature tensile strength not a function of binder grade, aggregate source, design traffic level • MEPDG Level 3 estimates of compliance and strength have significant errors for WI mixtures • Coefficient of thermal contraction as important as compliance in thermal stress analysis

  26. Recommendations • Use compliance equation to estimate compliance as a function of binder continuous grade. • Input this in MEPDG analysis as Level 1 data • Tables provided to assist with analysis • Use tensile strength of 430 psi in analysis

  27. Recommendations • Consider measuring coefficient of thermal contraction on these mixtures • As important as binder grade in stress calculations • Glass Transition Test at UW-Madison • IDT instrumentation approach developed by Christensen • No adjustments to WI mixtures recommended • Select correct binder grade considering changes caused by RAP or RAS

  28. Questions/Discussion Ramon Bonaquist Advanced Asphalt Technologies, LLC 108 Powers Court, Suite 100 Sterling, VA 20166 703-444-4200 aatt@erols.com

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