Influence of CaO reactivity on the formation of low-base calcium silicate hydrates

The influence of CaO reactivity on the formation of calcium silicate hydrates in the CaO-SiO2onH2O-H2O system has been determined when the CaO/SiO2molar ratio was equal to 0.83 and 1.0. In a pure CaO-SiO2onH2O-H2O system, with CaO/SiO2 = 0.83, C-S-H (I) is rather stable, and at 175 °C, even after 72 h, only partially recrystallizes into 1.13 nm tobermorite. Meanwhile, in the mixtures with less reactive CaO (96%), the stoichiometric composition (CaO/SiO2) of products of the synthesis varies from 0.66 to 0.83. When the CaO/SiO2 molar ratio in the initial mixture is equal to 1.0, the CaO reactivity has a significant effect on the composition of products forming in hydrothermal conditions. The products of the syntheses were characterized by X-ray diffraction analysis, simultaneous thermal analysis and Fourier transform infrared spectroscopy.