Preparation Process Optimization of Polyurethane Prepolymer Modified Asphalt Binder Based on Response Surface Methodology and Its Rheological Behaviors

ABSTRACT To explore the preparation process and rheological behaviors of polyurethane prepolymer (PUP) modified asphalt binder, based on response surface methodology (RSM), the interactive influence of preparation process parameters on the conventional properties of PUP‐modified asphalt binder was analyzed, and its optimal preparation process parameter was first recommended. Then, following the preparation process parameters, the effects of PUP dosage on the conventional indexes, toughness, storage stability, and viscosity of asphalt binder were investigated, and the optimal PUP dosage was determined. Finally, the rheological behaviors of PUP‐modified asphalt binder were illustrated via dynamic shear rheological (DSR) test. Results displayed that the preparation process parameters overall had a remarkable and interactive influence on the penetration, softening point, and ductility of PUP‐modified asphalt binder, and its optimal preparation method was suggested as follows: unit‐preparation weight, shear rate, shear temperature, and shear time were approximately 420–430 g, 3450–3500 r/min, 145°C–150°C, and 30–35 min, respectively. The addition of PUP enhanced the high‐temperature performance and low‐temperature toughness of asphalt binder while weakening its storage stability. However, the incorporation of PUP with appropriate proportions can ensure the storage stability of asphalt binder satisfied the specification requirement. Synthetically considering the conventional indexes, toughness, storage stability, and viscosity of PUP‐modified asphalt binder, the optimal PUP dosage was suggested to be 6% – 10%. The high‐temperature deformation resistance of PUP‐modified asphalt binder increased with the growing loading frequency, and the modified asphalt binder with 8% PUP content exhibited superior resistance to deformation at a high‐temperature situation. When the loading stress exceeded 1000 Pa, the viscoelastic structure of PUP‐modified asphalt binder changed, and when the stress reached approximately 1530.8 Pa, the PUP‐modified asphalt binder began to yield.