Effect mechanism of steel slag on CO2 capture in hydraulic lime

Steel slag (SS) inhibits the early hydration of cement, limiting its application in cement-based materials. In this study, SS was used to prepare hydraulic lime (HL), and the effect of SS on CO2 capture in HL was investigated. SS inhibited the carbonation of HL in the early stages but promoted carbonation in the later stages. Adding more than 10% SS inhibited the formation of hydration products, and the reduction of hydration products inhibited the carbonation product content, increased the porosity of the hydration mortar, promoted the later stage carbonation rate, and reduced the compressive strength. The carbonation area and captured CO2 content of the mortars in SS-HL increased exponentially with an increasing carbonation curing age. With an increasing SS content, the carbonation area and the degree of CO2 capture decreased then increased after 1 day and after 3 days of accelerated carbonation curing, respectively.