Study on Polyurethane Properties and Road Performance of Polyurethane Rubber Particle Mixture

Poroelastic road surface (PERS) presents a promising solution for recycling waste tires and mitigating tire-pavement noise. However, the wide variety of polyurethane (PU) formulations makes it challenging to select appropriate binders for road applications. This study investigates the properties of PU binders with varying isocyanate indexes and evaluates the performance of polyurethane rubber particle mixture (PRPM). The curing characteristics, mechanical properties, and aging resistance of three PU binders were assessed through measurements of gel time, viscosity, hardness, tensile strength, and aging tests. Additionally, the road performance of PRPM and porous asphalt (PA) mixtures was evaluated using laboratory tests. The results indicate that decreasing the isocyanate index extends gel time and reduces viscosity, whereas elevated temperatures lower initial viscosity and enhance workability, albeit at the cost of accelerated curing. A higher isocyanate index enhances the tensile strength and hardness of PU but reduces its elongation at break. The tensile property development patterns of the three PU binders are consistent: approximately 90% of the final tensile strength is achieved after 3 days of curing, followed by slower strength gain, and curing is nearly complete after 7 days. Under aging conditions, the tensile properties of all three PUs exhibit an initial improvement followed by subsequent deterioration. Increasing the isocyanate index enhances the resistance of PU to thermal-oxidative and ultraviolet aging. PRPM outperforms PA mixture in high-temperature rutting resistance, raveling resistance, and low-temperature cracking resistance, though it exhibits inferior water stability. Raising the isocyanate index improves high-temperature performance, water stability, and raveling resistance of PRPM, yet compromises its low-temperature performance. PU-2 is recommended as the optimal binder due to its balanced performance. This study provides insights for the rational selection and application of PU binders in PERS.