Research Progress on the Deterioration Law and Mechanism of Asphalt and Mixture Properties Under the Coupling Influence of Salt and Environment

Salt sprinkling is an efficient approach for melting snow accumulated on roads. However, salt erosion and complex environmental conditions have adverse effects on asphalt pavements. This review clarifies the influence of salt on the conventional performance indicators, rheology, and microscopic morphology of asphalt. Further, this review analyzes the variation laws of road performance and the internal structure of mixtures and investigates the mechanism of deterioration in mixture performance. The results reveal that the process of salt erosion of asphalt is mainly a physical reaction:in particular, the light components of asphalt become heavier, sulfoxide index increases, and asphalt hardens, leading to better high-temperature and anti-aging performance and deteriorated low-temperature and fatigue performance. The combined effect of salt and external environment deteriorates the engineering performance of the asphalt mixture. However, adding fibers, slaked lime, and other materials to the asphalt mixture can improve this performance. Notably, crystallization and expansion pressures lead to an increase in the scale and average diameter of voids in asphalt mixtures. Additionally, lower surface tensions and higher permeability coefficients enable the salt solution to better permeate the asphalt-aggregate interface compared to water, destroying the asphalt-aggregate adhesion properties and resulting in performance degradations. Given the current research results, it is necessary to combine the computed tomography technology with numerical simulations to evaluate the diffusion models of Cl-, SO42-, etc. Overall, an asphalt-aggregate interface model in salt solutions must be established based on the molecular dynamics theory, and the mechanism of deterioration in mixture performance must be analyzed from a molecular perspective. © 2023 Cailiao Daobaoshe/ Materials Review. All rights reserved.