Application of Waste Cooking Oil–Steel Slag in Dry Process Preparation of Rubber Asphalt Mixtures

This study explores using steel slag as a substitute for natural aggregates and waste cooking oil in the dry-mixing rubber asphalt mixture. First, the feasibility of steel slag as a replacement for aggregate was analyzed using scanning electron microscopy observation. Then, the oil-stone ratio of the dry-mixing rubber asphalt mixture with varying steel slag contents was determined based on Marshall test results. Furthermore, the optimal dosage of waste cooking oil as a rubber activator was evaluated to enhance the performance of the dry-mixing steel slag rubber asphalt mixture. The working mechanism of steel slag as a substitute for natural aggregate and waste oil in the rubber asphalt mixture was analyzed through rutting, immersion Marshall and freeze-thaw splitting, low-temperature beam bending tests, and scanning electron microscopy (SEM). The testing results show that the performance of the dry-mixing steel slag rubber asphalt mixture with waste cooking oil is better than the mixture without waste cooking oil. The asphalt thoroughly penetrates into the surface porous of the steel slag, potentially improving the adhesion between the asphalt and steel slag. The optimal combination for the dry-mixing rubber asphalt mixture is a 50% substitution rate for steel slag and a 4∶1 ratio of rubber powder to waste cooking oil, providing a reference for transforming resource utilization in road construction.