Experimental investigations of the viscoelastic and damage behaviors of hot-mix asphalt in compression

In this paper, the characteristic behaviors of hot-mix asphalt (HMA) in compression are studied by using concepts from the viscoelastic continuum damage (VECD) modeling approach. Temperature and frequency sweep tests with and without confining pressure were performed to determine the linear viscoelastic properties of HMA. The analysis of these tests showed that HMA exhibits significant and reversible stress-hardening behavior. This behavior was subsequently modeled by using a model developed from similar efforts for granular materials. To prove the importance of considering this characteristic behavior, constant crosshead rate tests were performed and analyzed with and without stress hardening. The VECD analysis framework was utilized for this purpose. When stress-hardening behavior was taken into account, it was found that microdamage-induced softening occurred over a range of temperatures from 5°C to 55°C. This finding suggests that microdamage may be significant for conditions in which HMA rutting is a primary concern. It also suggests that the mechanisms of microcrack-induced damage and stress-induced hardening must be investigated to accurately model the global behavior of HMA in compression.