Enhancing strength and sustainability of concrete with steel slag aggregate

This study investigates the transformation of steel slag, a by-product of the steel industry, into a sustainable construction material by substituting it for natural aggregates in concrete mixtures. To this end, we have conducted an experimental program that evaluated 28 mix designs, along with a control mix based on natural aggregates, cement, silica fume, and chemical admixtures, to assess the effects of replacing natural aggregates with steel slag. Some mixes also incorporated different fiber types to enhance performance. The study assessed the mechanical and physical properties of both fresh and hardened concrete to evaluate the overall effects of these alterations. Furthermore, thermogravimetry-differential thermal analysis (TG-DTA) and X-ray diffraction (XRD) were employed to characterize the mineralogical composition and thermal behavior of the concrete mixes. To further validate the compressive strength improvements and quantify data variability, a statistical analysis was conducted. The results revealed that concrete mixtures utilizing steel slag demonstrated substantial enhancements in compressive strength, with four mixtures featuring complete replacement of natural aggregates achieving more than 1.7 times the strength of control mix. The inclusion of fibers further enhanced performance in terms of crack resistance and post-cracking behavior. The TG-DTA and XRD analyses revealed that the steel slag promotes additional hydration and the formation of calcium silicate hydrate, resulting in a denser microstructure. Furthermore, the statistical analyses confirmed that these improvements are statistically significant, highlighting the potential of steel slag and fiber reinforcement to enhance both the fresh and hardened properties of concrete. The current study demonstrated that steel slag can fully replace natural aggregates while enhancing concrete performance, offering a sustainable solution for both construction material sourcing and industrial waste management.