Autoclaved steel slag coarse aggregate

A large-scale utilization of steel slag as an aggregate in green concrete industry has been hindered by steel slag’s inherent volume instability. This study presents a volume stability modification procedure to develop autoclaved steel slag aggregates (ASA), investigating ASA’s characteristics and the performance of concrete made with ASA. A total of seven concrete mixes with varying ASA and original steel slag aggregate (OSA) substitution ratios (0%, 30%, 50%, 70%, 100%) was assessed for expansibility, mechanical properties (i.e. compressive strength, splitting tensile strength, axial compression behavior), and durability performance under wetting and drying cycles. The study shows that autoclaving treatments significantly changed the characteristics of steel slag aggregates: the f-CaO content, water absorption, and crushing value were reduced by 84%, 41%, and 22%, respectively. Concrete containing ASA demonstrated lower workability, higher apparent density, greater values in both compressive and splitting tensile strength, and satisfactory durability performance under wetting and drying cycles compared to natural aggregate concrete (NAC). An optimal ASA replacement ratio of 50% led to enhancements in compressive strength, split tensile strength, and elastic modulus by 33.2%, 24.4%, and 20%, respectively, while reducing compression toughness by 16%. Overall, this study introduced a feasible approach for utilizing steel slag to produce high-quality aggregates for green concrete application.