XONOTLITE-TYPE CALCIUM SILICATE AND ITS PREPARATION

摘要

PURPOSE:To prepare a xonotlite-type calcium silicate having high crystallinity, by adding powdery lime material stepwise to a powder silicate material to effect the multi-stage batch-wise hydrothermal reaction, while specifying the ratio of CaO/SiO2 in the first-stage reaction. CONSTITUTION:A powdery silicate material is subjected to the hydrothermal reaction with a powdery lime material at a CaO/SiO2 molar ratio of 0.9-1.5. The above reaction is carried out batchwise in multistages by dividing the powdery lime material into two or more parts, and adding the material stepwise to the system. The molar ratio of CaO/SiO2 in the first-stage reaction is selected to be =0.6, and the reaction is carried out usually at 40-200 deg.C for 3-10hr. The process yields a xonotlite-type calcium silicate having collected acicular crystal form, high crystallinity, improved physical properties such as chemical resistance as formed article, and high specific surface area in powdery state.