Laboratory Evaluation of Hot Mix Asphalt Mixtures Incorporating Steel Slag as a Full Replacement for Coarse Aggregate

Abstract

The use of industrial by-products in road construction requires a thorough understanding of their physical and mechanical characteristics and their influence on asphalt mixture performance. This study presents a comprehensive laboratory evaluation of the feasibility of using Electric Arc Furnace Steel Slag (EAFS) produced by the Libyan Iron and Steel Company in Misurata as a full replacement for the natural coarse aggregate retained on the No. 4 sieve in dense-graded hot mix asphalt (HMA). Routine physical, mechanical, and chemical tests were conducted on both conventional aggregates and EAFS to assess their suitability for asphalt mixture production. Two asphalt mixtures were designed using the Marshall mix design method: a conventional control mixture and an EAFS mixture in which the coarse aggregate was completely replaced with steel slag. The optimum bitumen content (OBC), volumetric properties, and Marshall characteristics of both mixtures were evaluated and compared. The results showed that the use of EAFS increased the optimum bitumen content from 4.7% to 5.0%, increased the bulk density from 2.37 to 2.47 g/cm³, and improved the values of VMA and VFB. Conversely, the Marshall stability decreased from 1760 to 1600 kg, while the flow value decreased slightly from 2.78 to 2.66 mm. Despite these changes, all measured properties remained within the specified standard limits. The findings indicate that Electric Arc Furnace Steel Slag can be successfully utilized as a full replacement for natural coarse aggregate in hot mix asphalt, providing satisfactory volumetric and mechanical performance while promoting the sustainable utilization of industrial by-products and conserving natural aggregate resources.