Laboratory research on physical–chemical composite modified asphalt and its mixture

To further improve the asphalt performance, polyurethane (PU) prepolymer and SBS were used in this paper to prepare modified asphalt through physical–chemical composite modification. The physical performance and rheological properties of the modified asphalt was tested to evaluate the improving effect. And the asphalt mixtures performance was evaluated. The results indicated that the physical–chemical composite modification could significantly improve the physical performance and rheological properties with the recommended dosage of 5% SBS and 4% PU prepolymer. The modified asphalt exhibited excellent rutting resistance and elasticity recovery and good cracking resistance. In the composite modification process, PU could improve the compatibility of the modified asphalt system, which in turn improved the mechanical performance and storage stability. The PU-SBS composite modified asphalt mixture had good high-temperature and low-temperature performance, and moisture damage resistance. These results provided valuable theoretical insights for further research and application of physical–chemical composite modified asphalt.