Polymerization of alkaline-calcium-silicate hydrates obtained by interaction between alkali–silica solutions and calcium compounds. A 29Si nuclear magnetic resonance study

Abstract

Alkali–silica solutions containing varying amounts of silica and alkali ions have been prepared. Solids were obtained by interaction of these solutions with calcium hydroxide, calcium chloride or calcium sulphate. A 29Si nuclear magnetic resonance study has been carried out on these products during the initial and final stages of the synthesis. Three major kinds of solids appear in the CaO–Na2O(K2O)–SiO2 phase diagram; a chain-like nanocrystalline solid, a plate-like amorphous solid, and a three-dimensional amorphous network solid. A relationship between the initial system (i.e., the initial solution) and the final system (i.e., the solid plus the residual solution) is established. The solid is found to have a higher degree of polymerization than the initial solution while the residual solution is mearly an alkali–silica solution without calcium ions.