Effect of EAF Slag on the Performance of Wollastonite Mixes Inspired by CO₂ Curing Technology

Replacement of cement with electric arc furnace (EAF) slag at higher volumes causes volumetric expansion; therefore, such blends are not recommended in concrete production. In this study, the effect of this slag on the performance and microstructure of mortar samples based on wollastonite (CaSiO₃) was examined. The samples were cured in a CO₂-rich environment, resulting in the formation of non-expansive products, including aragonite, calcite, and traces of tobermorite in the microstructure. The addition of slag above 20% affected the workability and strength developments. However, the formation of pores above 100 nm reduced with increasing slag content to 60%, highlighting the beneficial effect of slag when used in higher volumes. EAF slag contains a higher amount of Fe₂O₃ which limits its disposal at landfills, but its increased use in the production of CO₂ gas-cured wollastonite concrete can reduce the environmental burdens caused by the Portland cement and steel manufacturing industries.