Creating Circularity in the Production of Sustainable Concrete by Unlocking the Potential Applications of Steel Slags as Coarse Aggregates

The global construction sector seeks to use sustainable materials to reduce its environmental footprint. In this direction, steel manufacturing by-products like electric arc furnace slag (EAFS), basic oxygen furnace slag (BOFS), and induction furnace slag (IFS) present a viable alternative to natural aggregates, offering environmental and cost benefits. These slags are underutilized resources with transformative potential for concrete and other applications, potentially reducing carbon emissions by up to 60 kg CO2 per metric ton of concrete. This review article critically examines the properties, applications, and challenges associated with steel slag coarse aggregates (SSCA) in concrete, highlighting key characteristics through ternary plots and whisker diagrams, which depict each slag’s variability, median values, and outlier ranges, making it an invaluable repository for researchers. The compositional analysis through these visualization tools demonstrates that BOFS is CaO-rich, EAFS has a balanced CaO-SiO2-FeO composition, whereas IFS is FeO-dominant. This study also clearly depicts different slag replacement ratios with optimal dosage varying from 50% to 75%, enhancing compressive strength by 10–20%, chloride and sulphate resistance by 30%, and fire resistance up to 1,200°C. The performance of steel slag-based concrete with more than 75% replacement level showed higher porosity and poor interlocking. Challenges like volumetric instability due to free CaO/MgO and workability loss can be mitigated through pretreatment and adding supplementary cementitious materials (SCMs), making a viable alternative to conventional concrete. The environmental benefits are substantial, as life cycle assessment (LCA) studies reveal that steel slag concrete has a 30%–40% lower environmental impact than conventional concrete, demonstrating its potential for reducing the construction industry’s carbon footprint. Looking toward future developments, nanoengineered SSCA composites present even better prospects for enhanced performance and sustainability. Combined with the proven environmental advantages, these advanced applications position steel slag utilization as a key strategy for achieving sustainable development goals (SDGs) 9, 11, and 12, driving toward circularity and sustainable concrete innovation.