University of California Pavement Research Center

Although Caltrans has utilized the Hveem mix design process for hot mix asphalt for decades, it is currently implementing the Superpave mix design procedure, and is interested in including performance-related tests for mix design and quality assurance. Performance-related tests are also used for Caltrans mechanistic-empirical (ME) pavement design. This report includes descriptions of current performance-related tests and alternatives, including tests using the Asphalt Mixture Performance Tester (AMPT) device for permanent deformation, stiffness and fatigue, and other alternatives to the flexural beam and repeated shear tests currently used for ME characterization by Caltrans. The tests are compared for mixture design and quality assurance, and for characterization for ME design in terms of the usefulness of the results, and the difficulty and time required to obtain results. The report also presents an evaluation of the effects on mix properties for Hveem versus Superpave mix designs and the results of ME simulation of the effects on pavement performance for rutting and cracking. The results indicate that there is potential to use the unconfined Repeated Load Triaxial (RLT) test as a substitute for the repeated shear at constant height (RSCH) test for mix design and quality assurance, and to use the confined or unconfined RLT for ME characterization. However, the preliminary results regarding use of shift factors to convert results from RLT to RSCH to enable application to previously calibrated models needs more comprehensive evaluation. The results indicate that the direct tension (DT) test offers no advantages over flexural beam testing for ME fatigue characterization, and that the fracture energy index and fracture toughness parameters from the Semicircular Beam (SCB) Test may be useful for quality assurance and mix design. Results indicated that the Indirect Tension Test (IDT) did not correlate with flexural fatigue life. Results for the Hamburg Wheel-Track Testing (HWTT) indicated poor correlation with the RSCH for rutting potential.