Properties of Thermosetting Polyurethane/Nano-TiO2 Composite-Modified Asphalt and Its Mixtures

This study prepared a composite-modified asphalt to address the challenges of asphalt pavement aging and cracking caused by elevated temperatures and ultraviolet (UV) radiation. The composite includes thermosetting polyurethane (TPU) and nano-TiO2. The fundamental physical properties and rheological behavior of the composite-modified asphalt were evaluated using standard tests for physical properties and high- and low-temperature rheology. The UV aging resistance of the modified asphalt was assessed by evaluating rheological performance parameters. The microstructure and modification mechanism of the composite-modified asphalt were analyzed using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Road performance of the composite-modified asphalt mixture was evaluated using rutting tests, beam bending tests, and other performance tests. SEM analysis showed that when the nano-TiO2 content exceeded 2%, nano-TiO2 aggregation occurred. Rheological and UV aging tests indicated that the composite-modified asphalt with 10% TPU and 2% nano-TiO2 showed optimal UV aging resistance. After 6 days of aging at 60°C, the complex modulus aging index (CMAI) at 64°C decreased by 67.55%. Additionally, the creep recovery rate (R) under a stress of 3.2 kPa increased by 26.59 times, and the creep rate (m) at –18°C improved by 6.95%. The dynamic stability (DS) of the asphalt mixture at 60°C increased by a factor of 2.05, with improved low-temperature cracking resistance and water stability.