Macro-Micro Aging Mechanisms and Correlation Analysis of Asphalt Under Light-Heat-Oxygen Coupling Action

To investigate the macroscopic and microscopic aging mechanisms of asphalt under combined light, heat, and oxygen exposure in southwestern China, four aging schemes were designed and tested on three base asphalts. Chemical changes-components, elements, and functional groups-were characterized by SARA and elemental analyses, and FTIR. High- and low-temperature rheological properties were measured via MSCR and BBR tests, and the gray correlation method linked microscopic mechanisms to macroscopic performance. The results show that coupled aging causes bond breakage and dehydrogenation, with recombined small molecules increasing the asphaltene content. Dehydrogenated bonds combine with oxygen to form polar functional groups, increasing chain stiffness and restricting internal rotation. Macroscopically, high-temperature performance improves while low-temperature performance degrades. Carbonyl and sulfoxide indices serve as effective aging indicators. Correlation analysis identifies functional group changes as the most significant factor affecting rheological decay. Engineering implications are as follows: oxygen-containing polar groups enhance chemical stability but accelerate low-temperature performance loss; thus, their evolution should be monitored in high-radiation, high-temperature regions to mitigate premature cracking.