Prediction of Hot Mix Asphalt Stability Using the Superpave Gyratory Compactor

A method is developed to assess hot mix asphalt (HMA) stability during compaction in the mix design process, and prior to conducting further expensive and time consuming testing. The method consists of a mathematical derivation, and an experimental procedure to determine a new stability index, referred to as the contact energy index (CEI). The CEI reflects the ability of the aggregate structure to develop contacts among the particles when subjected to shear stresses. The stability of HMA increases with an increase in CEI. The sensitivity of the CEI to changes in mix components is evaluated by analyzing asphalt mixes that differ in their nominal maximum aggregate size, aggregate gradation, source of aggregate, percent of natural sand, and asphalt content. In addition, the CEI is compared with mechanical properties of a number of asphalt mixes. The results show that the CEI captures the influence of changes in mix constituents on mix stability, and has very good correlation with the mechanical properties.