Study of Eco-Friendly Belite-Calcium Sulfoaluminate Cements Obtained from SpecialWastes

Belite-calcium sulfoaluminate (BCSA) cements are special binders obtained from non-Portland clinkers; they have become increasingly more important due to their environmental impact during the manufacturing process compared to Portland cements, such as lower energy consumption and CO2 emissions. The aim of this paper was to assess the possible use of titanogypsum (T) and water potabilization sludge (W) to reduce the amount of natural raw materials (natural gypsum and clay, respectively) used in the production of BCSA cements. Three BCSA clinker generating raw mixes, containing T and/orW, and a reference mix based only on natural materials (limestone, clay, bauxite and natural gypsum) were heated in an electric furnace at temperatures ranging from 1200 to 1350 C. Quantitative X-ray diraction (XRD) analysis of the burnt products showed high conversion of reactants towards the main hydraulically active BCSA clinkers components (C2S and C4A3$), particularly at temperatures of 1300 and 1350 C. Isothermal calorimetric measurements, differential thermal–thermogravimetric and XRD analyses as well as porosimetric measurements showed that all BCSA cements, from mixing the clinkers (at optimum temperatures) with commercial anhydrite, exhibited similar hydration behavior.