Synthesis and characterization of high belite sulfoaluminate cement through rich alumina fly ash and desulfurization gypsum

The objective of this study was the preparation and characterization of high belite sulfoaluminate cement (HBSC) from industrial residues. HBSC promises eco-friendly building materials with great mechanical performance at earlier ages than Ordinary Portland Cement (OPC). Preliminary results show the formation of main phase dicalcium silicate (C2S) and ye'elimite (C4A3$) at 1250°C, as determined by X-ray diffraction (XRD), are promising. The formation of minerals in the clinker was analyzed by differential scanning calorimetry-thermogravimetry (DSC-TG). Likewise, Scanning electron microscope (SEM) and XRD were used to carry out the analysis of the micro-structural and hydration products. The main HBSC hydration products, Ettringite and amorphous Al(OH)3, were formed in the early stages; however, during the later stages, monosulfate and Strätlingite were formed. Isothermal conduction calorimetry measurements indicate that hydration properties of the cements are comparable to OPC; the total hydration heat after 3 days was 438 J/g. The optimum compressive strength values of the mortars after 1-,3-,7-, and 28-days were 24.9 MPa, 33.2 MPa, 35.6MPa and 52.8 MPa which can meet the requirement of special structures.