Performance-Based Moisture Susceptibility Evaluation of Warm-Mix Asphalt Concrete through Laboratory Tests

Abstract

This study used the cyclic direct tension test, indirect tensile strength test, and Hamburg wheel tracking device (HWTD) test to evaluate the moisture susceptibility of warm-mix asphalt (WMA) mixtures. The stripped areas that were quantified by digital imaging analysis were derived from the cyclic direct tension, indirect tensile strength, and HWTD tests and were compared with the mechanical properties of the mixtures to identify sensitive moisture susceptibility indicators. These methods were applied to a Superpave® 9.5-mm hot-mix asphalt mixture and five corresponding WMA mixtures that used the following technologies: (a) Evotherm 3G that contained a chemical additive, (b) foaming, (c) WMA-A that contained a chemical additive and was under development, (d) WMA-B that contained an organic additive and was under development, and (e) WMA-C that also contained an organic additive (different from that used in WMA-B) and was under development. Fatigue life ratios obtained from the simplified viscoelastic continuum damage model combined with layered viscoelastic analyses were determined to be the most sensitive indicators for moisture susceptibility. The stripping infection points derived from the HWTD tests also showed good sensitivity to moisture conditioning; however, each stripping infection point was affected by the permanent deformation characteristics of a given mixture as well as its moisture susceptibility; therefore, the observation was inconclusive.