Preparation Process and Performance Evaluation of Polyurethane-Modified Asphalt and Its Mixtures

To overcome the limitations of traditional asphalt in terms of high-temperature rutting resistance, low-temperature cracking resistance, and control of construction temperature, a self-developed polyether-based polyurethane (PU) was employed to modify matrix asphalt in this study. The optimal preparation process was systematically investigated, and the performance of the modified asphalt was comprehensively evaluated. Orthogonal experiments were conducted to optimize the shear parameters, and the results showed that shear time was the critical factor affecting the modification effect. The optimal conditions were determined as 145°C, 30 min, and 3,000 r/min. The high- and low-temperature performance of the modified asphalt was assessed using the dynamic shear rheology (DSR) and bending beam rheology (BBR) tests, respectively. The microstructural modification mechanism was analyzed by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The dispersion of PU within the asphalt was examined via fluorescence microscopy (FM). The pavement performance of the PU-modified asphalt was then validated. The results demonstrated that PU modification significantly enhanced asphalt properties based on the rutting factor (G*/sinδ) and the glass transition temperature (Tg). FTIR analysis confirmed the chemical reactions between PU and polar groups in the asphalt, forming crosslinked structures that enhance asphalt stability. Moreover, compared with styrene-butadiene-styrene (SBS)-modified asphalt, the use of PU-modified asphalt reduced construction temperatures, thereby improving energy efficiency. Compared with matrix asphalt, PU-modified asphalt achieved superior deformation resistance at high temperatures and improved flexibility at low temperatures.