Degradation behaviors of asphalt concrete under chloride erosion-freeze-thaw cycles: Insights into microstructure evolution and mechanical property correlation

Chloride-based de-icing salts contribute to significant asphalt pavement damage through erosion-freeze-thaw cycles (EFTC) action despite effective in snow and ice removal in winter. However, microstructure characteristics degradation and correlation between them and mechanical property of asphalt pavement under salt EFTC needs to be systematically discussed further. This study investigates the mechanical property deterioration of asphalt concrete using splitting strength based on the viscoelastic and damage mechanics. The splitting strength decreases with higher concentrations or longer exposure under the action of salt solution and salt fog, with damage increasing logarithmically over time. X-ray CT image and microstructure analysis showed the porosity, pore number, and connectivity increased while average pore diameter decreased with time. Local pores complexity due to the generation of excess new pores might result in increased tortuosity of asphalt concretes. These variations are more pronounced under salt fog action. Pearson correlation analysis highlighted average pore diameter as most correlated with mechanical properties, while connectivity showed weaker correlation. And the correlation between mechanical property and microstructure is mainly related to the stress concentration effects. These findings are expected to improve the design and maintenance of asphalt pavements for longer service life in cold regions.