Hot-Mix Asphalt Cracking Potential Prediction from Binder Rheological Parameters

This study provides insights into the complexities of asphalt binder modifications and their effect on hot-mix asphalt (HMA) cracking potential. Binder rheological parameters were used to predict HMA cracking potential, in particular, the flexibility index (FI) of the Illinois Flexibility Index Test. An experimental program was developed to assess HMA cracking potential from binder characteristics. Various binder types, including binders modified with polymer softener, were considered. Rheological tests were conducted on binders at short- and long-term aging conditions. The Illinois FI test was conducted on mixes produced with the tested binders. Binder rheology parameters and corresponding FI results were analyzed statistically. Multilinear regressions were used to develop predictive models linking binder rheological parameters (independent variables) to HMA FI (dependent variable). The HMA FI was successfully predicted using binder and mix parameters available to contractors to allow binder selection. The binder rheology parameters are creep stiffness at 60 s ( S ) and rate of stress relaxation at 60 s ( m ), and the mix characteristics are binder content, asphalt binder replacement, and number of design gyrations ( N gyr ). The models were developed for short- and long-term aged HMA. Three uncertainty categories for predicted FI from binder rheology parameters are introduced. The categories are associated with binder selection for acceptance based on potential cracking risk.