Moisture Susceptibility of Asphalt Mixture Subjected to Chloride-Based Deicing Salt Solutions under Simulated Environmental Conditions

Chloride-based deicing salts are considered to be cost-effective and highly efficient in ensuring safe and efficient roadway and/or aircraft operation during snowy pavement conditions. However, it brings inevitable detrimental effects on the asphalt pavement. This study seeks to elucidate the influence of deicing salt type, concentration, and exposed environment on moisture susceptibility of an asphalt mixture. Immersion Marshall stability testing and freezing-thawing splitting tensile testing were employed to evaluate the moisture susceptibility of the asphalt mixture under drying-wetting and freezing-thawing cycling. Two types of compound deicing agents and three concentrations of 3%, 10%, and 20% of each salt were used to examine and compare their degrees of deterioration on the asphalt mixture. Statistical analysis was performed to establish the relationship between key indicators of moisture susceptibility and the main factors of the asphalt mixture. Microstructure analysis was carried out to elucidate the effects of those factors on the moisture susceptibility of the asphalt mixture using x-ray diffraction (XRD) analysis and scanning electron microscope (SEM) observation. Test results indicated that the moisture susceptibility of the asphalt mixture was greatly influenced by the salt concentration and conditioned drying-wetting (D/W) or freezing-thawing (F/T) cycles. With the increase of D/W or F/T cycles, the Marshall stability, Marshall modulus, and splitting tensile strength decreased while the flow value increased. The 3% salt concentration showed a significant effect on moisture susceptibility, followed by 10% and then 20%. The proposed models can effectively predict the key indicators of moisture susceptibility with high correlation coefficients over 0.9. As confirmed by the microstructural analyses, the deterioration of the asphalt mixture under simulated environmental conditions was attributed to decreased asphalt-aggregate adhesion from water ingress, salt crystallization, and/or ice formation pressure.