Modification mechanism and performance of polyurethane modified asphalt

To solve the problems such as poor storage stability, easy segregation and aging for polymer modified asphalt, the polyurethane (PU) was used to chemically modify the asphalt. The PU modified asphalt was prepared. The Fourier transform infrared spectroscopy (FTIR) test, dynamic thermomechanical analysis (DMA) test and differential scanning calorimetry (DSC) test were conducted to analyze the modification mechanism of PU modified asphalt. The performances of PU modified asphalt, SBS modified asphalt and 70# base asphalt were evaluated by the Brookfield rotary viscosity test, dynamic shear rheological (DSR) test, low-temperature bending beam rheological (BBR) test, rotating thin film oven test (RTFOT), and ultraviolet aging test. Research result shows that the disk sawtooth agitator can expose the active group well in the asphalt, and make the PU achieve better modification effect. There are mainly two reactions in the PU modified asphalt. One is the reaction between the isocyanate and polyol to form carbamate, the other is the addition reaction between the isocyanate and aromatic compounds in the asphalt. The high-temperature Brookfield viscosity of PU modified asphalt is higher than that of SBS modified asphalt at the same temperature. The rutting factor of PU modified asphalt at 64℃ is about 6 times of that of SBS modified asphalt, showing that its high-temperature performance is excellent. The penetration ratio of PU modified asphalt before to after RTFOT reaches 85%. The softening point change scope of PU modified asphalt is 0.5℃, showing that its thermal oxygen aging resistance is excellent. In the ultraviolet aging test, the change scopes of softening point and penetration of PU modified asphalt are 1℃-4℃ and 0.1-0.3 mm, respectively, indicating that its ultraviolet aging resistance is excellent. © 2019, Editorial Department of Journal of Traffic and Transportation Engineering. All right reserved.