Chlorellestadite (Synth): Formation, Structure, and Carbonate Substitution during Synthesis of Belite Clinker from Wastes in the Presence of CaCl2 and CO2

The synthesis of low-temperature belite (C2S) clinker from wastes autoclaved aerated concrete and limestone was studied in the presence CaCl2 as a mineralizing agent. Synthetic chlorellestadite (SCE; Ca10(SiO4)3(SO4)3Cl2) forms experiments at temperatures between 700 1200 °C. Samples were investigated by X-ray diffraction Raman spectroscopy. In general, amount SCE depends mainly on sulfate content to lesser extent temperature. At lower formation, non-stoichiometric seems crystallize monoclinic symmetry similar hydroxylellestadite. Rietveld refinements revealed chlorine calcium vacancies. spectroscopy proved partial substitution CO32− groups ellestadites formed 800 °C 900 air. Incorporation CO3 results shorter unit cell parameters smaller volume CO3−apatite. low temperatures, coexists with spurrite intermixed very fine nm scale. above air, ellestadite is carbonate-free 1000 loss starts all samples.