Nondestructive acoustic emission test to evaluate thermal damage in asphalt concrete materials

This study presents an acoustic emission (AE)-based approach to assess low-temperature cracking behavior of asphalt concrete materials, in which thermally induced damage within asphalt concrete is continuously monitored and evaluated when the material is exposed to decreasing temperatures from 20°C to approximately −50°C. Results of three different asphalt mixtures at three different aging levels (unaged [TANK], Short-term Aged [RTFO], Long-term Aged [PAV]) are presented. Two AE characteristic temperatures, i.e., the embrittlement temperature and the temperature corresponding to the maximum energy event, were sensitive to asphalt type as well as oxidative aging levels of the asphalt concrete materials. Low-temperature cracking performance of asphalt concrete materials was found to be better than what their low-temperature performance grades (PGLTs) suggest. X-ray microtomography (micro-CT) visualization of thermal damage within asphalt concrete showed the formation of microcracks in the mastic along with debondings at the interface of aggregates and mastic.