Effects of temperature and carbonation curing on the mechanical properties of steel slag-cement binding materials

In this study, 30% of cement was replaced by steel slag to prepare cementitious material, additionally, higher temperature and carbonation curing were investigated to study the effects of curing conditions on the mechanical properties of steel slag-cement binding materials. The hydration degree of the steel slag cementitious material was analysed by XRD and TG-DTG. Characterization of the hydration products and the changes in the cementitious material morphology was investigated using SEM and EDS. The results showed that the best curing condition was 60 °C combined with carbonization for 7 h. The 3 d, 7 d, 28 d flexural compressive strengths were greater compared with that of standard curing. The compressive strength increased by 63.94% at 3 d, 25.55% at 7 d, and 11.79% at 28 d. The cementitious material surface produced a dense shell layer of CaCO3 after carbonation curing, and the particle size of the CaCO3 was 1–8 μm. The dense shell can effectively prevent the occurrence of dissolution erosion of cement-based materials, and the shell can improve the durability of the cementitious material. The fine CaCO3 particles provide nucleation points for the hydration of C3S, accelerate the hydration of C3S, and create a micro-aggregate effect, which enhances the compactness of the cementitious material.