Synergistic use of industrial solid wastes to prepare belite-rich sulphoaluminate cement and its feasibility use in repairing materials

Abstract

This paper investigated the feasibility of belite-rich sulphoaluminate cement prepared from Bayer red mud, blast furnace slag, steel slag, flue gas desulfurization and carbide slag on synergistic theory. X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) were used to analyze the phase composition of clinkers and determine the optimum calcination temperature and holding time. The influence of gypsum content on the performance of clinker was studied by compressive strength test. The properties of synthetic cement were characterized by XRD, SEM-EDS, isothermal calorimetry, and mechanical test. The results showed that the optimum calcination temperature and holding time of synthesis cement were 1300 °C and 60 min, respectively. The formed phases in the clinkers were ye'elimite (10 wt% C4A3Ŝ), larnite (60 wt% β-C2S), brownmillerite (9 wt% C4AF), and mayenite (21 wt% C12A7). The main hydration products were ettringite. The compressive strength of synthetic cement in 28 d was 29.3 MPa when gypsum content is 20 wt%. The total hydration heat output of synthetic cement was lower than ordinary Portland cement (OPC) and sulphoaluminate cement (SAC), and its early hydration behavior was better than that of SAC and OPC at the initial 11.8 h and 58.6 h, respectively. And the test showed that the belite-rich sulphoaluminate cement is feasible in the application of repair materials.