Evaluation of Simple Performance Tests on HMA Mixtures from the South Central United States (9-558-1)

A wide variety of hot mix asphalt (HMA) materials and mixture designs were obtained from the six states in the south central region of the United States. Three additional mixtures were designed and proquced in the laboratory to provide modified mixtures in this project. All mixtures were characterized using the three simple performance tests (dynamic modulus, flow number, and flow time), Superpave shear test - frequency sweep at constant height (SST -FSCH), and the Asphalt Pavement Analyzer (AP A) as a torture test. The Hamburg wheel-tracking device (HWTD) was also conducted on selected mixtures. Objectives included the following: evaluate applicability of current test procedures and equipment for measuring HMA mixture properties with particular emphasis on complex modulus; provide state departments of transportation in the south central United States familiarity with the proposed IE*I parameter; generate information on performance of selected HMA mixtures with the new tests; extend the application of the protocols to gap-graded (e.g., stone mastic asphalt or Texas department of transportation coarse matrix high binder) mixtures; compare results from IE*I test results with other established tests (e.g., SST -FSCH, AP A); evaluate specially designed HMA mixtures which may exhibit low dynamic modulus but high recovery of strains (i.e., HMA containing a highly polymermodified soft asphalt, e.g., PG 64-40). A limited study was conducted to characterize the cracking potential of the selected mixtures using parameters from the indirect creep test in addition to the dynamic modulus test parameters. Results showed that flow number value and flow time slope correlated better with laboratory rutting (AP A and HWTD) than dynamic modulus. The correlations,ofIE*1 or IG*I with APA were better at lower frequencies than at higher frequencies. Flow time slope, flow number value, IE*lfsin at 1 Hz, flow number slope, and flow time value were among the best five correlations both with HWTD and the AP A rut depths.