Influence of silicate depolymerisation on the polycondensation reaction with hydroxoaluminate in alkaline aqueous solution

Abstract

The polycondensation reaction between silicate and hydroxoaluminate in alkaline aqueous solution has been experimentally studied. The time required for the solution to transform to a gel was measured to determine the reaction rate. The addition of alkali hydroxide to the silicate solution was found to strongly accelerate the subsequent reaction of silicate with hydroxoaluminate. The results indicate that the acceleration was caused by depolymerisation of the oligosilicates contained in the water glass, which was used as the source of soluble silicates. The course of oligosilicate depolymerisation in aqueous alkaline solution was experimentally observed by measuring the electrical conductivity of the solution.