Accelerated testing for studying pavement design and performance (FY 99)

The objectives of the project described in this report are to perform the experimental work and associated data acquisition/data processing for the research study entitled "Rut Resistance of Superpave Mixtures Containing River Sands." The goal of the research is to compare the rut resistance of Superpave mixtures in which different percentages of river sands have been used. The work described in this report deals with the experimental aspects of the research study. This mainly entails the applications of realistic wheel/axle load cycles to large-scale full-depth pavement slabs in controlled thermal conditions. The experiment was conducted at the Kansas Accelerated Testing Laboratory at Kansas State University. The experimental work also includes monitoring and measuring the degree of rutting of the asphalt surface and recording the states of strains, soil pressure, and temperature gradients in and below the pavement slabs being tested. Four mixes were tested in this experiment. These are denoted as follows: (Mix 1) a standard Kansas Department of Transportation Marshall-type mix, BM-2C; (Mix 2) a Superpave mix SM-2A with 20% sand; (Mix 3) a Superpave mix SM-2A with 30% sand; and (Mix 4) a Superpave mix SM-2A with 15% sand. By comparing the final rutting at the end of 80,000 load repetitions of a dual tandem axle of 150 kN (34 kips), it was observed that, except for the mix with 30% sand, Superpave mixes show less rutting than the Marshall mix. The best performing mix of all the four sections tested is Mix 2, indicating that 20% is the optimum sand content in these Superpave mixes. On the other hand, 30% is the worst sand content and resulted in the most rutting (unacceptable, more than one inch).