Preparation and characterization of cementitious materials based on sulfuric-acid-activated coal gasification coarse slag

Coal gasification slag (CGS) is the alumino-silicate solid waste discharged by chilling during coal gasification that causes serious environmental pollution. According to its physical and chemical properties, CGS is mainly used in carbon ash separation, brick making, aluminum-silicon extraction, and ceramics, but some problems remain, such as the low utilization rate of inorganic components and unstable product performance. In view of the above problems, a new method of preparing CGS based low-carbon cementitious material by mechanical and chemical activation of protic acid and dehydration reconstruction was proposed in this work, and sulfuric acid activated cementitious material was prepared by coal gasification coarse slag (CGCS) as raw material. The effects of the sulfuric acid content and concentration and the curing temperature and time on the properties of cementitious materials were studied. The hydration mechanism of the samples was analyzed through scanning electron microscopy, nuclear magnetic resonance, X-ray diffraction, and thermogravimetric analysis. Results show that CGCS could be activated by sulfuric acid to improve its cementitious activity. After activating 65 % concentration of sulfuric acid and curing at 80 °C for 2 days, a gel material with a compressive strength of 25.84 MPa could be formed.