Performance of eggshell powder and steel slag as cementitious and fine aggregate replacements in concrete

Abstract This study investigates the synergistic use of eggshell powder (EP) and steel slag (SS) as sustainable partial replacements for cement and fine aggregate (manufactured sand) in concrete, with the goal of enhancing mechanical performance while promoting eco-friendly construction practices through waste material utilization. In the experimental program, 10% eggshell powder was used as a cement substitute, and steel slag was incorporated as a fine aggregate replacement at 20%, 40%, and 60% levels. The mechanical properties of concrete—including compressive strength, split tensile strength, and flexural strength—were evaluated across various curing periods (7, 28, 56, and 90 days). Results showed that concrete containing 10% EP achieved mechanical properties nearly equivalent to the control mix (without EP). Moreover, when combined with up to 60% steel slag, the mix exhibited notable improvements in all measured strengths compared to both the control and other replacement levels. A scanning electron microscopic (SEM) analysis confirmed the positive microstructural development in the optimized mix, supporting the mechanical performance improvements. The combination of 10% eggshell powder and up to 60% steel slag offers a promising sustainable solution for improving concrete’s mechanical properties while utilizing industrial and agricultural waste materials. The study provides a valuable pathway toward greener and more durable concrete formulations.