Effect of Dry–Wet and Freeze–Thaw Repeated Cycles on Water Resistance of Steel Slag Asphalt Mixture

Abstract

As an attractive substitute of natural aggregate for asphalt mixture, steel slag raises many concerns on the water resistance of steel slag asphalt mixture in frozen and wet areas, due to the special interaction between steel slag and asphalt. This study aims to investigate the deterioration process of water resistance for asphalt mixture with different steel slag contents in dry–wet and freeze–thaw cycles environments. The Marshall immersion test and indirect tensile test were conducted, and the residual stability and tensile strength ratio (TSR) were measured to characterize the water resistance of the steel slag asphalt mixture. Furthermore, dry–wet and freeze–thaw repeated cycling conditions were designed to simulate the effect of actual environments on the long-term water resistance of asphalt pavement. Finally, the microstructures of the aggregate–asphalt interface area were observed, and the enhancement mechanism of the steel slag replacement in asphalt mixture was revealed. Results show that steel slag asphalt mixture exhibits significant resistance to water damage. With the increase in dry–wet or freeze–thaw repeated cycles, the water resistance of steel slag asphalt mixture rapidly deteriorates first and then tends to be stable, and there is a limit state of water damage. In dry–wet repeated cycles condition, the asphalt mixture with 50% steel slag content has a better water resistance, while the asphalt mixture with 100% steel slag content has a better water resistance under freeze–thaw repeated cycles condition. The interface phase structure of steel slag asphalt mixture is stable and dense, where the asphalt mortar evenly and tightly wraps the steel slag and forms a certain penetration depth. The enhancement mechanism of steel slag with asphalt mainly includes the physical anchoring effect and the chemical adhesion effect.