Aging characteristics and microscopic mechanisms of SBS asphalt based on coupled light-heat-water aging

To further evaluate the effects of intensive ultraviolet (UV) radiation, high temperature, and high humidity on the macro- and micro-scale aging characteristics of styrene-butadiene-styrene (SBS) asphalt, a light-heat-water (LHW) coupled aging test was developed to simulate the multi-factor coupled aging effect. Variation patterns of the chemical composition, micro-structure, and micro-mechanical properties of SBS asphalt were investigated under various aging conditions via micro nano testing technology. Then, the influences of UV radiation, temperature, and water on the aging characteristics of SBS asphalt were evaluated to further reveal the LHW-coupled aging mechanism. The results indicated that the coupled aging effects had a significant impact on physical, micro-structure, and micro-mechanical properties. Both the residual penetration ratio and residual ductility ratio of SBS asphalt after coupled aging increased compared with those after UV aging, whereas the softening point increment and viscosity aging index decreased, demonstrating that spray and dewing had a certain inhibitory effect on the UV aging of asphalt. Due to the variation of the SARA fraction, the carbonyl index, sulfoxide index, and large molecules content of SBS asphalt gradually increased with aging, whereas the butadiene index decreased. The micro-structure and micro-mechanical behavior of SBS asphalt before and after aging are quantitatively evaluated using the height difference, adhesive force, and surface roughness.The average height difference of catana phase showed an increasing trend with aging, while the average adhesion force and surface roughness of SBS asphalt gradually decreased. The analysis of micro results showed that UV radiation aging alone caused more severe micro-structural damage to the SBS asphalt compared to the coupled aging. This study offers a more comprehensive understanding of the coupled aging process of SBS asphalt in plateau regions using multiscale approaches.