The microstructure and repeat creep property of modified asphalt under the salt freezing cycle

In order to investigate the changes performance of pavement materials under the snow melting salt, the dynamic shear rheometer (DSR) was used to study repeat creep property of SBS (styrene-butadiene-styrene blockcopolymer) modified asphalt and rubber powder modified asphalt in Inner Mongolia region, and the atomic force microscope (AFM) was used to observe microstructure, the micro structure and the rheological properties of the two kinds of asphalt were compared and analysed after salt freezing cycles. AFM tests indicate that there are some "bee" structures in SBS modified asphalt, and the quality and size of "bee" structures change after freeze-thaw cycles; But there is not "bee" structures in rubber modified asphalt. At the same time, there is little change in microstructure before and after freeze-thaw cycles. DSR test results show that the ratio of transient strain to unloading instantaneous strain (ε_P/ε_L) of SBS modified asphalt and rubber powder modified asphalt increases at the beginning of the loading and then reach a steady state after a certain number of loading cycles. The ε_P/ε_L of SBS modified asphalt reduces and the ε_P/ε_L of rubber powder modified asphalt does not change after freeze-thaw cycles. Burgers model was used to fitting the parameter G_v. The G_v of SBS modified asphalt reduces, while it is increased for the rubber powder modified asphalt after freeze-thaw cycles. And the G_v of asphalt after water freezing has little difference from that after salt freezing. Rubber powder modified asphalt has better high temperature performance.