Evaluating Rut Resistance of Hot Mix Asphalt with the Gyratory Testing Machine and Asphalt Pavement Analyzer

Rutting has been identified as one of the primary distresses in asphalt pavements. Rutting in Hot Mix Asphalt (HMA) mixtures can be attributed to a lack of interlocking of aggregate structure, insufficient bonding between aggregate and asphalt binder, or both. In the present study, efforts have been made to identify the contributions of aggregate structure and asphalt binder to the rutting characteristics of a densegraded surface HMA mixture. Coarse gravels at five different angularity levels were used to produce mixtures with similar aggregate gradations. Three different asphalt binders were used to make mixtures for laboratory rut evaluation. The United States Army Corps of Engineers' Gyratory Testing Machine (GTM) was employed to evaluate the aggregate structures, whereas the Asphalt Pavement Analyzer (APA) was selected to characterize the overall rut resistance of asphalt mixtures. The results from this study indicated that asphalt content significantly affected the GTM's capability to evaluate the stability of aggregate structures in asphalt mixtures, while the APA was able to capture the overall rutting properties of HMA mixtures. At temperatures close to binder's upper grade temperature, aggregate structure played a critical role for the rut resistance of HMA mixtures, whereas at temperatures below binder's upper grade temperature, the stiffness of asphalt binder played a more important role in the rut resistance of asphalt mixtures evaluated in this study.