HYDRATION AND EARLY MECHANICAL PERFORMANCE OF BELITE SULFOALUMINATE CEMENT CONTAINING MgAl2O4 FROM SOLID WASTE

This study dealt with the use of gold tailings, red mud, bauxite, desulfurised gypsum and high magnesium limestone as the raw materials in the production of a belite sulfoaluminate cement clinker containing MgAl2O4. The hydration and early mechanical properties of this cement were characterised by isothermal calorimetry, a mechanical test, X-ray diffraction and a thermal analysis. The results showed that the optimal calcination temperature to obtain a satisfactory clinker strength was 1350 celcius and the corresponding 1, 3 and 7-day strengths were 27.7, 45.8 and 54.3 MPa, respectively. The initial and final setting times of the cements range between 20 and 31 minutes. The cements had the characteristics of rapid hardening and the main hydration products were AFt, AFm and AH3. The total hydration heat release of this cement within the first 50 hours was only 158 J center dot g-1, which could effectively avoid the generation of internal cracks in the cement and has the potential to be applied to large concrete projects. Furthermore, the MgAl2O4 mineral phase was inert in the belite sulfoaluminate cement and did not participate in the hydration reaction, which eliminates the disadvantage of MgO in the cement systems and potentially increases the use of high magnesium limestone in cement production.