Analysis of Rutting Performance Impacting Factors in HMA Overlay Mixture Design

It is reasonable to assume that hot-mix asphalt (HMA) overlay rutting occurs only in HMA overlay(s) because of rutting from the existing pavement, if any, most of which had already occurred before the HMA overlay(s) was placed. So, this paper focuses only on the HMA overlay itself. Many factors—such as the asphalt binder grade, the aggregate gradation, the types of aggregates, the volumetric parameters of the mixtures, etc.—potentially influence the HMA rutting performance when designing an HMA overlay mix. In this paper, a Hamburg Wheel Tracking Test (HWTT) device is employed in order to evaluate the rutting performance of HMA overlay mixes in terms of the rut depth at specified wheel passes. An experimental design is developed to cover the different combinations of aggregates, gradations, and asphalt binder types. Through extensive laboratory tests and statistical analyses, the most significant impacting factors were identified. The corresponding HWTT rut depth prediction models were developed with high R2 values (>0.80). With these models and established rut depth criteria, the maximum allowable asphalt content that can be used without causing rutting problems was estimated for different overlay mixes. Furthermore, the models and estimated maximum allowable asphalt content were preliminarily verified by performance data of the National Center for Asphalt Technology test track sections and WesTrack test sections.