Study on the Dynamic Performance of PU and SBS-Modified Asphalt Mixtures with Dense Gradation

A polyurethane (PU) mixture with excellent strength is regarded as an alternative to a modified asphalt mixture, but characteristic analysis on them is lacking. In this paper, the dynamic modulus of PU- and SBS-modified asphalt mixtures with the same gradation, aggregate type, and binder content was investigated and compared in terms of dynamic and viscoelastic properties. Compared with the SBS-modified asphalt mixture, the PU mixture with an extremely high dynamic modulus and reduced phase angle at high temperatures had lower temperature sensitivity, which allowed it to resist high-temperature deformation. While the phase angle did not show a statistically significant correlation, the dynamic modulus between the two mixtures did. The dynamic modulus and phase angle values of the PU mixture showed relatively small deviations and could be fitted to produce acceptable master curves, which exhibited obvious differences compared to those of the SBS-modified asphalt mixture. The PU mixture exhibited elastic properties during the test temperature range and, since its thermal rheological property is much smaller than that of the SBS-modified asphalt mixture, it is closer to viscoelastic material. This study provides an understanding of the PU mixture’s dynamic and viscoelastic properties, as well as material information for pavement design and performance prediction with PU mixture layers.