Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” WHRP Project HMA Fatigue and Low Temperature Properties to Support MEPDG Ramon Bonaquist, Ph.D., P.E. Advanced Asphalt Technologies, LLC
“Engineering Services for the Asphalt Industry” Outline Objectives Approach Major Findings Conclusions and Recommendations
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” 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.
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Approach Collect and analyze low temperature compliance and strength data on 16 mixtures using AASHTO T322
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Mixtures WHRP Project , Wisconsin Mixture Characterization Using the SPT on Historical Aggregate Structures
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Binder Low Temperature Grade
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Compliance Master Curve 100 sec Indirect Tensile Creep Tests at 0, -10, and -20 ºC Compute compliance Shift into master curve
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” 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
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” LTSRESS Master Curve
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” LTSTRESS Thermal Stress
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Analysis of Variance Compliance
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Graphically
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Equation to Estimate Compliance
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Errors Using Only Binder Grade
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Effect on Thermal Stresses
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Grade Model Thermal Stresses
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” MEPDG Estimated Compliance
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Effect of Errors on Stresses
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Tensile Strength
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Analysis of Variance
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” MEPDG Estimated Strength
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” VFA Effect
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Coefficient of Thermal Contraction Estimated From Volumetric Properties and Typical Values for Asphalt Cement and Aggregate As Important as Compliance in Stress Calculation
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Effect of Thermal Coefficient Can be similar to one grade
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” 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
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” 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
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” 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
Advanced Asphalt Technologies, LLC “Engineering Services for the Asphalt Industry” Questions/Discussion Ramon Bonaquist Advanced Asphalt Technologies, LLC 108 Powers Court, Suite 100 Sterling, VA