Characterization of the Tensile Properties and Nanoscale Phase Structures of Modified Asphalts and Their Aging Behavior

This study focuses on exploring tensile properties and nanoscale phase structures of different modified asphalts, and their aging behavior. For this, one virgin asphalt and three modified asphalts, namely, 4% SBS-modified asphalt, 2% SBS and 20% crumb rubber (CR) composite asphalt, and 4% SBS and 2%TiO₂ composite asphalt, were prepared and investigated using the force-ductility test and atomic force microscopy (AFM). Also, detailed experiments of short-term (STA) and long-term (LTA) aging were conducted to obtain aged asphalt specimens. The results showed that a ductile fracture was found for the three modified asphalts. However, for the activation energy, SBS asphalt and SBS&TiO₂ asphalt were 2.87 times and 3.31 times that of SBS&CR asphalt, respectively. This demonstrates that the activation of the SBS polymer phase requires more energy during the stretching process when the rubber powder is not present. SBS&CR asphalt and SBS&TiO₂ asphalt showed better tensile properties and aging resistance in terms of the quantitative results of tensile property indicators, indicated by a larger value of fracture ductility, tensile compliance, and the toughness ratio under the same aging condition. According to the AFM results, SBS modifier had little effect on the phase structure of virgin asphalt, while TiO₂ modifier increased the number of bee phases and made their distribution more uniform, indicating the formation of a more stable phase structure system. This may contribute to its better tensile properties and aging resistance. Moreover, TiO₂ molecules inhibited the aggregation behavior of polar molecules during the aging process, which led to a reduction in surface roughness. By comparison, the effect of aging on the phase structure of SBS&CR asphalt was more significant among the three modified asphalts. This result can be attributed to the interaction between rubber powder particles and asphalt.