Influencing factors of reserve time and the rheological properties of thermosetting polyurethane-modified asphaltOA

Thermosetting polyurethane‑modified asphalt(PUMA)undergoes an irreversible curing reaction,which means any improper handling during construction cannot be corrected.This study investigates the effects of hard segment content,isocyanate index,polyurethane(PU)content,and temperature on the viscosity of PUMA and proposes a method for regulating its reserve time.Based on viscosity‑temperature profiles,a viscosity growth model was established to predict the evolution of PUMA viscosity with temperature and time.The results indicate that temperature exerts the most pronounced effect on the reserve time of thermosetting PUMA.Moreover,the developed viscosity growth model under different temperatures enables the prediction of PUMA reserve time.As PU content increases,the microstructure of PUMA evolves from a dispersed to a continuous phase.When the PU content exceeds 30%,a continuous crosslinked network forms,imparting excellent thermal resistance and elastic recovery at high temperatures.Furthermore,high PU content enhances the low‑temperature flexibility of PUMA.These findings provide valuable insights for optimizing the application of PUMA materials in pavement engineering.