Study of the long-term water stability of asphalt mixtures containing steel slag aggregate

Abstract

This article aims to elucidate the long-term water stability of a steel slag asphalt mixture. Both chemical composition and physical morphology of the steel slag were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), the Vickers hardness test and mercury injection testing. Methods of testing wet-dry (W–D) cycles and freeze-thaw (F–T) cycles were designed, and corresponding indices were proposed. The immersion rutting test was conducted to explore the variation in rutting depth, and consequently, the long-term dynamic water coefficient Kl was proposed to analyze the resistance to dynamic water flushing. A regression model was used to analyze the relationship between steel slag content and long-term water stability. Finally, the long-term corrosion characteristics of the steel slag asphalt mixture were analyzed by SEM. The results show that the addition of steel slag can improve the long-term water stability of the asphalt mixture. The water stability of the steel slag asphalt mixture declines with increasing W–D and F–T cycles. The degradation trend becomes gentle after 6 W–D cycles. The attenuation of the water stability of the mixture slows after 15 F–T cycles. The long-term water stability of the steel slag asphalt mixture was evaluated by comparing the residual stability after 6 W–D cycles (MS6) and the tensile strength ratio (TSR) of the steel slag asphalt mixture after 15 F–T cycles (TSR15). The Kl value of the steel slag asphalt mixture first increases and then decreases with increasing steel slag content, and the best effect in terms of long-term dynamic water corrosion resistance is observed for a 30% steel slag asphalt mixture. The SEM results show that, for steel slag asphalt mixture water damage, the steel slag hydrates and produces microcracking on the surface.