Sustainable utilization of steel slag in asphalt pavement: Three-dimensional deformation characterization and environmental performance assessment

Steel slag (SS) has been widely investigated as an alternative aggregate for sustainable asphalt pavement. However, comprehensive characterization of deformation evolution and quantitative evaluation of structural stability remain challenging for steel slag asphalt mixture (SSAM). This study investigates the high-temperature deformation behavior and environmental performance of asphalt mixtures incorporating four types of SS at different replacement levels. The chemical composition and surface characteristics of SS aggregates were characterized, while wheel tracking tests and three-dimensional laser scanning were conducted to capture the deformation evolution under high-temperature loading. The results indicate that SS exhibits significantly different chemical and morphological characteristics from basalt aggregate, with higher alkalinity and rougher surface textures. Increasing SS content effectively improves rutting resistance, and the maximum dynamic stability reaches 12,987 cycles/mm. Based on the three-dimensional deformation field, the settlement-heave ratio V r and volumetric deformation stability index V D S I were proposed to quantitatively describe deformation redistribution and stability characteristics. The established nonlinear model using these indicators achieved an R 2 value of 0.908, indicating that the proposed indicators effectively characterize variations in the comprehensive deformation response. Furthermore, carbon emissions assessment and leaching tests demonstrate that SS utilization can reduce carbon emissions while maintaining environmental safety. This study provides a three-dimensional evaluation approach for understanding deformation characteristics and promoting the sustainable application of SSAM.