Hydration behavior and cementitious properties of steel slag: From an early age to a long-term

In China, steel slag as a solid waste caused land occupation and environmental pollution, and its utilization ratio is relatively low. To increase the utilization field and ratio of steel slag, hydration behavior and cementitious properties of three types of steel slag were investigated and compared based on test results from an early age to a long-term via multiple techniques. Experimental results suggested that steel slag showed a strong latent hydraulic activity at a later age, and the mechanical strength of steel slag paste specimens (w/b=0.3) could reach 15 MPa at 360 days. Cementitious properties of steel slag were primally depended on the hydration of calcium silicate (C3S and C2S), calcium aluminate (ferrite), glassy phase in steel slag, especially for calcium silicate. The sum amount of calcium silicate in used steel slag was approximately from 21% to 28%, and the amount of C2S was significantly greater than that of C3S. The hydration of C2S and glassy phase resulted in the continuous increase in bound water content of steel slag, and a certain content of C2S still existed in pastes at 360 days. The mechanical strength of steel slag pastes markedly increased at a later age due to more hydrates formed in the microstructure.