Rheological and microscopic characterization and correlation analysis of asphalt under high-intensity ultraviolet radiation

The lower radiation intensity (2–20 W/m2) was widely used for asphalt ultraviolet (UV) aging. The effect of high-intensity radiation on asphalt properties and microscopic morphology is unknown. This study investigated the rheological behavior, microscopic characterization, and correlation analysis of SBS modified asphalt under high-intensity UV radiation. Rheological properties tests encompassed temperature sweep (TS), multiple stress creep recovery (MSCR), and frequency sweep (FS). Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Gel Permeation Chromatography (GPC) tests were performed to reveal the microscopic characterization. In the early stages of UV aging, the rutting factor of asphalt was increased. The increment decreased as the UV aging time increased. The UV aging process did not alter the temperature sensitivity of asphalt. The complex shear modulus was influenced by UV radiation duration and loading frequency. Extended exposure to high-intensity UV radiation resulted in the formation of microcracks on the surface of the asphalt. The maximum molecular weight of the UV-aged asphalt was higher than that of the original asphalt. The degraded SBS modifier deteriorated the homogeneity of asphalt. The sulfoxide aging index, carbonyl aging index, number-average molecular weight (Mn), weight average molecular weight (Mw), and polymer dispersity index (PDI) presented a better correlation with rheological behavior indexes. The correlation between small molecule size (SMS), medium molecule size (MMS), and large molecule size (LMS) with rutting factor and complex shear modulus was poor. It was worth mentioning that the correlation between the MSCR test results and microscopic performance indicators was the best. Especially for the recovery rate and Jnr at 3.2 kPa, the mean absolute value of the correlation coefficient was 0.953.