Valorization of Steel Slag and Granite Powder for sustainable hot mix asphalt production

The growing demand for sustainable pavement materials has led to the increased use of industrial by-products in asphalt mixtures. This study explores the combined use of steel slag (SS) as a fine aggregate (20–100% replacement) and granite powder (GP) as a mineral filler in hot mix asphalt (HMA). Twelve different mixture combinations were evaluated to assess the mechanical performance, moisture resistance, and microstructural characteristics. The mixtures were characterized through Marshall stability, indirect tensile strength (ITS), tensile strength ratio (TSR), and scanning electron microscopy (SEM) analyses. The results reveal that incorporating SS significantly affects mixture performance, with both stability and moisture resistance improving as SS content increases up to 40% replacement. Beyond this point, a gradual decline in performance is observed. Mixtures containing GP filler demonstrated superior strength and durability compared to those using conventional stone dust filler, indicating enhanced binder-filler interaction. The mixture with 40% SS and GP achieved the highest values for Marshall stability, ITS, and TSR, reflecting improved structural integrity and resistance to moisture damage. Two-way ANOVA analysis confirmed that the interaction between SS replacement level and filler type significantly impacts mixture performance, with moderate to large effect sizes noted for several parameters. Overall, the findings suggest that optimizing the use of SS and GP can enhance the mechanical and durability characteristics of asphalt mixtures. • SS and GP were evaluated as sustainable HMA modifiers. • SS replacement upto 40% improved stability and moisture resistance • GP enhanced strength compared with conventional stone dust • 40% SS with GP showed the highest ITS and TSR among all mix designs. • SEM confirmed improved interlocking and bonding in modified mixtures.