Synergistic aging resistance of calcium sulfate whiskers and polyurethane in asphalt binders: Microscale mechanisms and rheological perspectives

Polyurethane is commonly used to modify asphalt for improved strength and toughness, while it is prone to degradation from thermal oxidative and ultraviolet aging during service. This study investigates the incorporation of whisker materials to enhance the aging resistance of polyurethane-modified asphalt, exploring their synergistic effects and underlying mechanisms. The results show that the network structure formed by whisker-reinforced polyurethane effectively inhibits the degradation of polyurethane during the aging process of modified asphalt. This is reflected in smaller molecular weight changes and reduced morphological alterations caused by asphaltene aggregation, thereby mitigating the degree of asphalt aging. Chemical aging indexes indicate that whisker-reinforced polyurethane-modified asphalt exhibits significantly improved aging resistance, with reductions of up to 76.97 % under ultraviolet aging and 51.16 % under thermal-oxidative aging compared with base asphalt. Rheological aging index results further reveal that whiskers enhance the resistance of polyurethane to thermo-oxidative and ultraviolet aging across different temperature domains, effectively delaying asphalt aging. However, excessive whisker content negatively impacts aging resistance at low temperatures. This research elucidates the fundamental mechanism for designing durable polyurethane-modified asphalt, thereby establishing a framework for sustainable asphalt pavement construction.