聚氨酯前驱体基化学改性沥青及其改性机理

The research and application of the eco-friendly and durable materials are of great significance to realize the sustainable development of road engineering. The preparation of modified asphalt with Polyurethane-precursor-based Reactive Modifier (PRM) with isocyanate as the active functional group shows significant values in environmental protection and performance improvement. The cross-scale (micro-meso-macro) characterization method was used to clarify the modification mechanism of PRM in detail. Compared with SBS modified asphalt, the rheological mechanical properties and thermal-oxidative aging resistance of PRM modified asphalt were characterized, and the road performance of PRM modified asphalt mixture was evaluated. The results show that there are obvious chemical changes in the modification process with PRM. Based on the urethane and urea functional groups formed in the modification process, the covalent crosslinking network structure based on the presence of asphaltene components can be established in asphalt. This process not only promotes the selective aggregation of asphalt fractions and the reconfiguration of asphaltenes, but also increases the surface free energy of asphalt, so as to obtain a more stable internal structure. The temperature sensitivity of PRM modified asphalt is lower than that of base asphalt, showing good resistance to high-temperature permanent deformation, fatigue damage, low-temperature cracking and thermal-oxidative aging. Compared with the SBS modified asphalt, PRM has obvious advantages in improving high-temperature performance, fatigue resistance and thermal-oxidative aging resistance of asphalt. Besides, it is expected to reduce the production temperature of modified asphalt to 140℃-150℃. Combined with the test results of pavement performance of asphalt mixture, PRM modified asphalt mixture with 2.5% concentration shows equivalent low-temperature performance as well as better high-temperature performance and water stability as SBS modified asphalt mixture with 4% concentration. PRM has significant advantages in improving pavement performance of asphalt mixture.