Effect of Salt Freeze-Thaw Cycle on Crack Resistance of Steel Slag Rubber Powder Modified Asphalt Mixture

To study the crack resistance of steel slag crumb rubber modified asphalt mixture (CR-steel slag) under salt freeze-thaw cycles, we selected styrene-butadiene-styrene (SBS)-steel slag and CR-basalt as the reference group. The relationship between CR-steel slag interfacial adhesion properties and crack resistance under salt freeze-thaw (FT) cycles was investigated through semicircular bending (SCB), pull-out, and contact angle tests. The results show that the salt FT will accelerate the process of micro-cracks in the mixture to macro-cracks. With the increase of FT cycles, the crack resistance will gradually deteriorate, and significant damage will occur in the mixture at 15 freeze-thaw cycles. The mutation point of freeze-thaw times will move forward in different degrees under the action of salt solution. At the same time, with the increase of salt solution concentration, its anticracking performance first decreases and then increases, reaching an extreme value of 8%. The magnitude of the crack resistance of the three asphalt mixtures is CR-steel slag > SBS-steel slag > CR-basalt. The macroscopic cracking index of asphalt mixtures has an excellent positive correlation with the matching index, and the matching index model has sufficient accuracy in evaluating the cracking resistance of three asphalt mixtures under the action of salt freeze-thaw cycles. Based on the surface energy theory to evaluate the crack resistance of the mixture from a microscopic perspective, combined with macroscopic evaluation indexes, the evaluation results are accurate and more reliable.