Research on Aging Characteristics and Interfacial Adhesion Performance of Polyurethane-Modified Asphalt

Polyurethane (PU) owing to its superior physicochemical properties, is considered an ideal modifier for asphalt. To enhance the mechanical performance and service durability of asphalt pavements, PU-modified asphalts with varying dosages were prepared and systematically evaluated through a combination of laboratory experiments and molecular dynamics simulations. Aging tests, rheological and thermodynamic analyses, mechanical property evaluations, and asphalt–aggregate interfacial adhesion energy calculations were conducted to elucidate the modification mechanism, aging resistance, and interfacial behavior. The results showed that PU incorporation markedly improved rutting resistance at high temperatures and flexibility at low temperatures, thereby enhancing the load-bearing capacity of asphalt. Under ultraviolet and long-term aging conditions, PU-modified asphalts exhibited significantly lower performance degradation than base asphalt, highlighting their superior anti-aging properties. At the molecular level, PU adsorbed light fractions and formed a cross-linked network, reducing the free volume fraction while enhancing mechanical strength and deformation resistance. Additionally, PU substantially increased asphalt–aggregate adhesion energy, strengthening interfacial bonding. However, excessive PU content led to molecular aggregation and partial phase separation, compromising system stability. These findings provide theoretical insights and practical guidance for the optimal design and engineering application of PU-modified asphalt.