Multiscale Cracking Resistance and Enhancement Mechanisms of Steel Slag–Rubber Asphalt under Thermooxidative–UV Aging

The study examines the impact of thermooxidative–ultraviolet (UV) aging on the low-temperature cracking properties of steel slag–rubber asphalt mixes (CR-SMA). The semicircular bending (SCB) test and digital image correlation (DIC) technique were used to analyze the displacement and strain fields of the basalt–rubber asphalt (CR-BMA) and CR-SMA during loading. The cracking characteristics of the two mixes were analyzed using measures like balanced cracking index (BCI) and J-integral, and the horizontal strain release energy (JE) is proposed as a new metric to evaluate the cracking resistance of asphalt mixes. When evaluating the low-temperature cracking characteristics of asphalt mixtures, the new indexes JE show a strong correlation with the macroscopic cracking indexes BCI and J integral. To better reflect the magnitude of strain energy released from the specimens in stress cracking, it is important to observe and analyze the changes in the strain and displacement fields during the loading of the two asphalt mixtures. After aging, both modified asphalt mixtures showed a decrease in the energy released by strain and cracking resistance. However, CR-SMA exhibited better crack and aging resistance than CR-BMA under the same conditions. It provides a theoretical basis for the choice of pavement materials in cold regions.