Evaluation the mechanism of moisture damage of asphalt mixtures with using thermodynamic and mix design parameters

Moisture damage in asphalt mixtures is defined as loss in strength and durability in present of water. Lack of relationship between distress mechanism in the laboratory and field, lack of measurement of effective properties of materials and their role, lack of modification solution, and other deficiencies of these methods have motivated researchers to present more appropriate experimental methods based on the properties of materials and asphalt mixtures, which could have a determining role in the occurrence of moisture-induced distress. Thus, the present research tries to present a model for predicting moisture sensitivity of asphalt mixtures based on thermodynamic parameters and characteristics of mix design of asphalt mixtures, which could predict the performance of an asphalt mixture against moisture based on the mentioned parameters.Results of this study demonstrated that using antistripping additives can generally improve the performance of asphalt mixtures against moisture; but, type and percent of these additives must be determined considering type of aggregate, type of asphalt binder, and properties of asphalt binder-aggregate mixture. Moreover, based on the presented statistical analyses, the results represented that the parameters of cohesion free energy and adhesion free energy of aggregate-asphalt binder in dry conditions, wettability of aggregate by asphalt binder, specific surface area of aggregates, and apparent film thickness of asphalt binder on the aggregate surface as well as free energy of system during antistripping event and permeability of asphalt mixture considerably influenced the occurrence of moisture damage directly and reversely, respectively.