Production of belite–calcium sulfoaluminate cements from various waste materials to boost their environmentally friendly features

This study investigates the incorporation of marble and waste brick powders, water potabilisation sludge and red titanogypsum into the raw meal for the production of a belite–calcium sulfoaluminate (BCSA) clinker. A reference clinker was prepared using conventional raw materials, limestone, clay, bauxite, and natural gypsum. Clinkers were synthesised in a laboratory electric furnace at temperatures ranging from 1200°C to 1350°C and characterised by X-ray diffraction (XRD) and X-ray fluorescence analyses. BCSA cements were produced by blending the optimised clinkers with natural anhydrite at a calcium sulfate-to-ye’elimite molar ratio of 2. The hydration behaviour of the cements was assessed at various curing times using conduction calorimetry, XRD, differential thermal and thermogravimetric analysis, mercury intrusion porosimetry and thermodynamic modelling. Mechanical performance was assessed by compressive strength testing and dimensional stability assessments. Both BCSA cements exhibited comparable mineralogy and strength development. The waste-derived cement showed slightly accelerated early hydration and higher cumulative heat release, with ettringite forming as the main early hydration product. Total porosity decreased with curing time, and both cements reached similar compressive strengths, increasing by approximately 20% between 56 and 90 days.