Model for Predicting Moisture Susceptibility of Asphalt Mixtures Based on Material Properties

Many studies and experiments have investigated the effective parameters, mechanisms, and methods of preventing moisture damage to asphalt mixtures. These experiments presented only a numerical index, in which the performance of asphalt mixture against moisture. Due to the lack of relationship between the damage mechanism in the laboratory and the field conditions, measurement of the material properties and their role, and corrective solution, it seems necessary to present more appropriate methods based on the characteristics of the asphalt mixture which are determinative in the occurrence of moisture damage. This study provides a model for prediction of moisture susceptibility of asphalt mixtures using thermodynamic parameters and mixing design properties. Twenty-four combinations of asphalt mixtures were investigated using three types of aggregates and additives and two types of base bitumen. The components of surface free energy (SFE) for bitumen and aggregate were measured using the sessile drop (SD) method and the universal sorption device (USD), respectively. The modified Lottman test method was used to predict the field performance of asphalt mixtures resistance to moisture damage. The results obtained from the prediction show that the SFE of cohesion (CE), the SFE of bitumen–aggregate adhesion (AE), the specific surface area of aggregates (SSA), and apparent asphalt film thickness (AFT) parameters directly affect the resistance to moisture damage, whereas the energy released by the system during stripping [debonding energy (DE)] and the permeability of asphalt mixtures (PA) inversely affect the strength. DE and SSA had the greatest effect on decreasing and increasing the strength of asphalt mixture against moisture, respectively.