Low-temperature characteristics and microstructure of asphalt under complex aging conditions

In order to study the low-temperature characteristics and microstructure of asphalt under complex aging conditions, ductility test and BBR test were used to study the effects of temperature, aging degree on the low-temperature performance of 90# asphalt and SBS modified asphalt. In addition, the changes of the apparent morphology and microstructure indexes of the two asphalt after aging were observed by the atomic force microscopy (AFM) and Fourier Infrared Spectroscopy (FTIR). The results showed that with the increasing aging degree, the ductility of the two asphalts decreased but the low-temperature critical temperature increased. After short-term aging, the ductility of SBS modified asphalt was always higher than that of 90# asphalt under the same conditions, yet its critical temperature was lower than that of 90# asphalt. As the temperature dropped, the relaxation time gradually increased, and the dissipation energy ratio declined. Furthermore, there were bee-shaped structures with light alternating with dark on the surface of the asphalt. Besides, the increasing aging degree resulted in a decrease in the number of bee-shaped structures, but a more dispersed distribution. During the aging process, the –CH2- and –CH3- contents of SBS modified asphalt changed, and the area ratio at 1376 cm−1 gradually increased after long-term aging and water aging, and reached the minimum after UV aging. In addition, after short-term aging, the SBS modifier degraded at 966 cm−1, destroying the effect of the modifier, and inducing a gradual reduction in its peak area ratio. The above results indicate that SBS modified asphalt has better plastic deformation ability and stronger anti-aging ability. Moreover, ultraviolet radiation has a much larger impact on the low-temperature crack resistance of asphalt than thermal oxidative aging and water aging. Furthermore, the aging mechanism of moisture on the two asphalt is different.