Effect of thermochemical high-temperature reconstruction on mechanical properties and activity of stainless steel slag

The low activity of stainless steel slag (SSS), primarily attributed to its high γ-C₂S and low C₃S content, impedes its effective utilisation. A thermochemical high-temperature reconstruction method using lime and bauxite as tempering agents to regulate the mineral phase was investigated in this work. Through an array of tests and analytical techniques, including compressive strength tests, activity index evaluation, X-ray diffraction, scanning electron microscopy and hydration heat analysis, the impacts of the calcium/silicon mass (CSM) ratio and the sintering temperature on the mechanical properties and activity of reconstituted SSS mortar were examined. It was found that, at a CSM ratio of 4.2 and a sintering temperature of 1290°C, the reconstructed slag demonstrated optimal mechanical properties and activity, yielding compressive strengths of 43.69 MPa and 62.58 MPa at 7 days and 28 days, respectively, with remarkable 28-day activity index of 143.49%. The proposed thermochemical high-temperature reconstruction method ingeniously employs high temperature to increase the content of C₃S while rapid cooling prevents alteration of the C₂S crystalline structure. This innovation significantly enhanced the mechanical properties and activity of the SSS, offering promising avenues to increase its utilisation rate.