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.