Research on the Rheological Performance of Fast-Melting SBS-Modified Asphalt under Complex Environmental Factors

Currently, fast-melting SBS (Styrene-Butadiene-Styrene)-modified asphalt is widely used in pavements. However, in practical applications, complex environmental factors accelerate the deterioration of asphalt material properties, significantly affecting the service life of roads during their operational period. This study aims to examine the effects of complex environmental factors, including thermal oxidation, ultraviolet radiation, and various concentrations of salt solutions, on the high and low-temperature rheological properties of fast-melting SBS-modified asphalt (abbreviated as SBS-T-modified asphalt). Pressure aging–ultraviolet aging coupling and pressure aging–ultraviolet aging different concentration salt solution coupling were selected as the aging groups to simulate complex environmental conditions. Additionally, base asphalt and pressure-aged asphalt were used as control groups. The rheological properties of SBS-T-modified asphalt were evaluated using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The results indicate that multiple-factor coupling aging reduces both the high-temperature and low-temperature performance of SBS-T-modified asphalt compared to single-factor aging, although the impact on rheological properties is not consistent across all conditions. After the combined effects of UV aging and pressure aging, the rutting resistance and high-temperature performance of SBS-T-modified asphalt are most severely impacted. However, when coupled with salt-solution aging, the rutting resistance of SBS-T-modified asphalt improves, with the complex modulus increasing by approximately 30%. This indicates that the presence of the salt solution enhances the high-temperature performance of the asphalt. An analysis of the low-temperature rheological properties of SBS-T-modified asphalt based on Burgers model shows that the low-temperature rheological performance of SBS-T-modified asphalt worsens under three-factor coupling aging compared to two-factor or single-factor aging, leading to poorer crack resistance. Notably, after adding salt solutions, the thermal sensitivity of SBS-T-modified asphalt increases significantly, with the ΔTc value decreasing approximately sixfold for every 2% increase in salt concentration.