Synthesis use of coal gasification slag to prepare belite sulphoaluminate cementitious material and its hydration characteristics study

Coal gasification slag, rich in SiO2, Al2O3, Fe2O3, and other components, with high pozzolanic activity, is a potential high-quality raw material for cement preparation. In this paper, coal gasification slag (CGS), carbide slag (CS), alumina oxide powder (AP), and flue gas desulfurization (FGD) gypsum are synergized to explore the key technical parameters for preparing coal gasification slag-based sulphoaluminate cement (CGS-SAC) clinker. The physical and chemical reactions of raw materials during the heating process are analyzed using Thermogravimetry-differential scanning calorimetry (TG-DSC) and free calcium oxide test. X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterize the microstructure of cement clinker and hydration products. Fourier transform infrared spectroscopy (FTIR) is used to evaluate the evolution of functional groups in clinker. Uniaxial compressive strength (UCS) tests and isothermal calorimetry evaluate the hydration characteristics of cement. The results show that it is feasible to prepare sulphoaluminate cement using solid waste, such as CGS, and the utilization rate of solid waste is up to 90 %. Under the conditions of a calcination temperature of 1280 degrees C, a calcination duration of 60 minutes, and a gypsum proportion of 12 %, the sulphoaluminate cement produced has the best performance, and the compressive strength of the net cement paste specimens can reach 16.23 MPa and 26.83 MPa at the curing age of 3 and 28 days, respectively. The produced cement is hydrated more rapidly in 72 hours, and the cumulative hydration calorific value is 135 J/g in 72 hours, which shows a lower hydration exothermic property. The results of this study provide a reference for the resource utilization of CGS.