Influence of variable intensity ultraviolet on the performance of SBS modified asphalt

Previous scholars studied UV aged asphalt performance under constant UV intensity. This study proposed a method of UV aged asphalt based on the time-varying UV intensity, which is more capable of realistically simulating the UV aging of asphalt under natural conditions. The softening point, viscosity, and DSR tests were used to analyze changes in conventional and rheological properties of UV aged asphalt and compared them with RTFO (Rolling Thin-Film Oven) aged asphalt. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM) tests were analyzed for the microscopic characteristics. The aging index was also used to evaluate the percentage of asphalt aging attributable to each UV aging cycle. The results show that the softening point is more susceptible to UV radiation, with UV-6 cycles exceeding the softening point increment of RTFO. On the contrary, the viscosity is more susceptible to thermo-oxidative aging, and the viscosity increment of RTFO is 39.3 % higher than that of UV-12 cycles. Based on DSR's test results, the rutting factor magnitude of RTFO was between 9 and 12 UV aging cycles The phase angle results indicate that thermo-oxidative aging is more likely to convert asphalt to elastomer than RTFO asphalt. UV aging process of asphalt produced sulfinyl and, carbonyl and other polar functional groups, asphalt intermolecular forced to enhance the production of a harder oxidation layer, the asphalt surface began to appear cracks. As aging time increases, the cracks become longer and deeper. Practical image recognition technology can identify the areas of the cracks. The crack area follows a linear pattern during cycles 3-9, while the growth rate slows down during cycles 9-12.