Innovative utilization of carbonated steel slag in low-carbon cement system containing metakaolin and wollastonite

The utilization of carbonated steel slag (CSS) in cement systems is crucial for enhancing sustainability and significantly reducing CO2 emissions. This study explores the innovative integration of CSS into a low-carbon cement system incorporating metakaolin and wollastonite. CSS demonstrates rapid carbonation, achieving a 15.5 % CO2 uptake within 30 min. The incorporation of CSS affects cement hydration by delaying its onset and reducing compressive strength. Despite a reduction in strength compared to Ordinary Portland Cement (OPC), substituting CSS for wollastonite in the blend maintains 87 % of the compressive strength of the control group (MW-50) at 90 days, while also achieving substantial reductions in clinker content. Replacing metakaolin with CSS significantly lowers compressive strength to approximately 21 MPa at 90 days, indicating the essential role of metakaolin in the hydration process. Although the early compressive strength of the blended system is lower than OPC, at 28 days, MW-50 and MW-50 (W100) reach 88 % and 80 % of OPC's strength, respectively. These findings highlight the potential of CSS in sustainable construction, demonstrating that even with a slight reduction in strength, the use of CSS can lead to significant reductions in cement usage and CO2 emissions, making it a viable option for more environmentally friendly construction practices.