Epoxy steel slag asphalt mixture: Achieving breakthrough in pavement performance and efficient waste resource utilization

To address the key technical challenges of poor volume stability and insufficient moisture resistance that hinder the large-scale application of steel slag asphalt mixtures (SSAM), an innovative approach was proposed by incorporating epoxy asphalt (EA) into SSAM (EASSAM). Through a systematic investigation that entirely omitted the pretreatment of steel slag (SS), the effects of epoxy system (ES) content and SS replacement ratio on mixture performance were thoroughly examined, and the enhancement mechanisms were revealed through microstructural characterization. Meanwhile, a life cycle assessment was conducted to quantitatively evaluate the economic and environmental benefits of EASSAM. The results showed that increasing the ES content improved both the pavement performance and the long-term volume stability of EASSAM. The mixture with 20 wt% ES and 100 % replacement of natural coarse aggregates with SS (EA20SS100AM) demonstrated outstanding comprehensive performance and was recommended for summer construction to accelerate traffic opening. ES effectively infiltrated the porous surface of SS, forming a dense coating layer and enhancing the adhesion between asphalt and aggregates, thereby effectively inhibiting performance deterioration and heavy metal leaching caused by moisture intrusion. Over the life cycle, EA20SS100AM achieved a 19.5 % reduction in annualized costs and a 42.1 % decrease in carbon emissions compared to commonly used SBS-modified asphalt mixtures. These research outcomes offer a practical technical solution for the large-scale utilization of SS resources while supporting reductions in natural aggregate extraction and promoting sustainable transportation infrastructure development with significant environmental, economic, and social benefits.