Investigation on the moisture resistance and mechanism of asphalt concrete using metallurgical solid waste as anti-stripping agent

The sustainable transition of the steel industry is constrained by the limited utilization of metallurgical solid waste (MSW); however, its potential cementitious activity enables its application as anti-stripping agent in asphalt pavement, thereby significantly promoting its utilization. This study investigates the feasibility of employing multiple-MSW including steel slag (SS), flue gas desulfurization ash (FGDA) and granulated blast furnace slag (GBFS) as anti-stripping agent in asphalt concrete. The physicochemical properties of FGDA, SS and GBFS were first characterized, and then the MSWs were mixed to produce the solid-waste-based anti-stripping agent (SWA). Then, simulated water-vapor erosion was conducted on the SWA modified asphalt mortar. Rheological properties, surface free energy, and chemical functional groups of the asphalt mortar were evaluated respectively. Finally, the water-damage resistance of asphalt concrete with SWA was further assessed. The results indicate that SWA contains abundant alkaline minerals and exhibits potential hydration activity; the finer particle size of which enhances compatibility with asphalt. The addition of SWA within asphalt increases the compactness and mechanical performance of asphalt mortar. Compared with limestone powder (LP) asphalt mortar, SWA asphalt mortar exhibits superior rheological properties at high temperature, demonstrating better rutting resistance. SWA enhanced the adhesion work between asphalt and aggregate, also decreased the peeling rate, which confirms the interfacial reinforcement effect of SWA. The water-resistance performance of SWA-modified asphalt concrete has been markedly improved. After replacing LP with SWA in the asphalt-mastic mixture, RSM and TSR increase by 14.2% and 9.0%, respectively, while Cantabro mass loss decreases by 5.0%. Based on the performance comparisons, SWA can be used as an anti-stripping agent to enhance the water-resistance of asphalt concrete and thereby extend the service life of the road.