Evaluation of Superpave Mixtures with High RAP Content

The Kansas Department of Transportation (KDOT) is currently evaluating Superpave mixture performance with higher percentage of reclaimed asphalt pavement (RAP) materials. Hamburg Wheel Tracking Device (HWTD) tests were done on Superpave mixes with high RAP content sampled from a number projects across the state. Each mixture was subjected to 20,000 repetitions or 20-mm rut depth, which ever came first. The HWTD test results were also correlated with the volumetric parameters and other potentially significant factors. The analysis results showed that the rutting performance was significantly affected by the asphalt source, and binder grade regardless of RAP content. The surface mixes with higher percentage of recycled asphalt material (RAP) were not significantly susceptible to rutting compared to the mixes with moderate percentage of RAP material. Volumetric mix design parameters of these mixture, except voids in mineral aggregate (VMA), were not significant in determining rutting performance. The rut depth decreased with increasing percent VMA for the mixes with moderate percentage (25%) of RAP materials.