Carbonation and hydration behavior of EAF and BOF steel slag binders

In this study, the carbonation and hydration behavior of electrical arc furnace (EAF) slag and basic oxygen furnace (BOF) slag were examined. Steel slag is a latent hydraulic material. Its early strength can be activated by carbonation reaction. The carbonated steel slag can be used as a binder to replace Portland cement in the fabrication of building products. It was found that steel slag could develop a compressive strength of 20 MPa in EAF slag and 36 MPa in EAF–BOF hybrid slag after a combination of carbonation and hydration. Higher calcium silicate content and longer carbonation time could result in a higher compressive strength. The activated steel slag binders were composed of calcium carbonates intermingled with calcium silicate hydrates, forming a particle reinforced composite material. It was the calcium silicate content in raw slag, rather than the CaO content, that determined the extent of carbonation activation. Replacing Portland cement with steel slag could help preserve natural resources, reduce the embodied energy and promote carbon utilization in building products.