Abstract: At the molar ratio of CaO to SiO₂ of 1, with calcium hydroxide and sodium silicate,   calcium silicate hydrate was synthesized at 50, 100, 170℃, respectively. The results show that temperature favors the formation of calcium silicate hydrate with perfect structure. When calcium silicate hydrate reacts with caustic solution, the decomposition rate of calcium silicate hydrate increases with the increasing caustic concentration and decreases with the raising synthesis temperature and the prolongation of reaction time. The decomposition rate is all less than 1.2% in caustic solution, and XRD pattern of the residue after reaction with caustic solution is found as the same as that of original calcium silicate hydrate,  which indicates the stable existence of calcium silicate hydrate in caustic solution. When reacted with soda solution, the decomposition rate increases with the increasing soda concentration and reaction time, while decreases with the synthesis temperature. The decomposition rate is more than 2% because CaO•SiO₂•H₂O(CSH(Ⅰ)),  except Ca₅(OH)₂Si₆O₁₆•4H₂O and Ca₆Si₆O₁₇(OH)₂, is decomposed. So the synthesis temperature and soda concentration should be controlled in the pr, ocess of transformation of sodium aluminosilicate hydrate into calcium silicate hydrate.

Key words:  calcium silicate hydrate; reaction behavior; soda solution