Rheological Properties and Microscopic Mechanism of Rock Asphalt Composite Modified Asphalt with Consideration of Aging Effect

In order to investigate the rheological properties and microscopic mechanism of rock asphalt composite modified asphalt considering the aging effect, the frequency scanning test and time scanning test using dynamic shear rheometer (DSR) were conducted to analyze the viscoelastic characteristics and fatigue properties of rock asphalt/SBS composite modified asphalt (R/SMA), rock asphalt/crumb rubber composite modified asphalt (R/CMA), rock asphalt modified asphalt (RAMA) and SBS modified asphalt (SBSMA). The microstructure, modification mechanism and aging mechanism of the modified asphalts were studied by fluorescence microscopy (FM) and Fourier transform infrared spectroscopy (FTIR). The results showed that R/CMA exhibited good shear deformation resistance at high temperatures. Thermal oxygen and pressure aging reduced the frequency sensitivity of the R/SMA sample with 5% rock asphalt and 2% SBS and the compatibility of its system were improved. The R/CMA with high rock asphalt content showed poor structural stability and system compatibility after aging. The composite modified asphalts in this study generally had better fatigue resistance after short-term aging, while the fatigue resistance of SBSMA and RAMA was significantly improved after the long-term aging. Under different aging conditions, the R/CMA added 5% rock asphalt and 18% crumb rubber modifier presented excellent fatigue performance. The fluorescence microscopy test results indicated that the surface of the R/SMA with 5% rock asphalt and 2% SBS was flat and smooth. Without destroy the three-dimensional continuous network structure of the SBS, the addition of 5% rock asphalt improved the stability of the spatial network structure, and thus improved the shear deformation resistance of the SBSMA. There are grooves and protrusions on the surface of the R/CMA, and the discrete spherical particles of rock asphalt and irregular linear or reticular rubber powder particles were dispersed in asphalt phase independently, in which the local network structure of the R/CMA with 5% rock asphalt and 18% crumb rubber was the most significant in the all modified asphalts. The FTIR test results indicated that R/SMA presented a physically modification that inhe-rited the characteristics of both SBSMA and RAMA. The R/CMA showed a physical-chemically modification that was dominated by physical modification and supplemented by chemical modification. Based on comprehensively analyzing the functional indexes and aging indexes, the crumb rubber modifier presented superior inhibition effect on the formation of carbonyl and sulfoxide compounds than the SBS modifier, which meant the R/CMA with 5% rock asphalt and 18% crumb rubber exhibited better anti-aging properties than the R/SMA with 5% rock asphalt and 2% SBS