Study of the binary CaCO3-SiO2 system by quantatitative DTA

Solid-state reactions in the CaCO₃-SiO₂ system with different mass ratios (CaCO₃:SiO₂=from 10.2 to 110) were studied by means of thermogravimetry, quantitative DTA and high-temperature X-ray diffraction up to 1500 °C.It was found that not CaCO₃, but CaO reacted with SiO₂. The rate of decarboxylation increased and the temperature of formation of silicate phases decreased significantly with increasing silica content. Only mono- and dicalcium silicates could be detected as solid-state reaction products. Above 1400 °C, an intensive melting process took place; the amount of silica had no clear effect on its temperature range.Quantitative DTA and X-ray diffraction data proved that, below 1000 °C, not only the decarboxylation process, but also silicate formation must be taken into consideration.