Elaboration and thermal study of iron-phosphorus-substituted dicalcium silicate phase

In the present work, we examine the simultaneous effect of iron and phosphorus additions on the calcium carbonate decomposition in CaCO₃, SiO₂, Fe₂O₃ and P₂O₅ mixtures at the molar ratio CaCO₃/SiO₂=2. The formation of the dicalcium silicate Ca₂SiO₄ is also studied. The temperatures of the decarbonation and the enthalpy evolution during the heating of the mixtures are measured. The additions of Fe₂O₃ and P₂O₅ oxides decrease the onset temperature of the CaCO₃ decomposition. The energy consumption of decarbonation at about 835 °C is lowered when the dopant concentrations increase. Synthesized solid solutions are analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The free-lime quantity is determined by chemical analysis. The mineralogical analysis at room temperature of the products of the reaction shows the presence of iron-phosphorus-doped β, α′ and α-C₂S modifications.