Abstract: In order to promote the low-carbon and resource utilization of steel slag, steel slag combined with ground blast furnace slag, desulfurized gypsum and a small amount of cement were used to prepare steel slag solid waste cementitious materials. The effect of early CO₂ curing on the properties of steel slag solid waste cementitious materials was studied by compressive strength, product composition, microstructure, volume stability and soundness analysis. The results show that the compressive strength and linear expansion rate of steel slag solid waste cementitious materials under early CO₂curing are lower than those non-carbonation curing. Under early CO₂ curing, when the steel slag content (40%~45%, mass fraction) is low and the ground blast furnace slag content (32%~35%, mass fraction) is high, the early compressive strength of steel slag solid waste cementitious material is high, up to 14 MPa. When the steel slag content (55%~60%, mass fraction) is high, the late compressive strength of steel slag solid waste cementitious materials is high. Under early CO₂ curing, the steel slag solid waste cementitious materials undergo carbonization reaction to form CaCO₃ crystals, which fill the pores and compact the microstructure. Some CaCO₃ participates in the hydration reaction in the later stage to form single carbon hydrated calcium carboaluminate. The steel slag solid waste cementitious materials with high steel slag content (>55%, mass fraction) and low desulfurized gypsum content (<15%, mass fraction) have lower linear expansion rate and autoclave expansion rate, and improve volume stability.

Key words: steel slag, solid waste cementitious material, compressive strength, soundness, early CO₂ curing