INFLUENCES OF DIFFERENT IONS FOR HYDRATED CALCIUM SILICATES UNDER AUTOCLAVED CONDITION

摘要

autoclaved concrete products and autoclaved silicate products have been widely used in civil engineering,such as pretensioned spun concrete piles,autoclaved aerated concrete blocks and others. Hydrated calcium silicate has been studied for the major constituent of compressive strength of autoclaved silicate products. This text reviews types of hydrated calcium silicate and influences of different ions for hydrated calcium silicate under autoclaved condition,and focuses on the effect of aluminium,sulfur and alkali metal ions. This text thinks,with the alkalinity descend under autoclaved condition,hydrogarnet breaks down into two kinds of Al-substituted calcium silicate hydrates. One of Al-substituted calcium silicate hydrate is fibriform hydrate when a small quantity of Ca2* and a mass of silicate anions were released from the autoclaved materials,and another of the Al-substituted calcium silicate hydrates grows high alkalinity hydrate and could form well crystallized tobermorite when a mass of hydrogarnet is broken down. [SO4] could enter into calcium silicate hydrate during autoclaved. But the amount of [SO4] replacing [SiO4] depends on the kinds and amount of calcium silicate hydrate. The alkali ions could accelerate hydrothermal reaction rate because of the slowly sustained alkali ions leaching. Because Al-bearing phase,sulfate and alkali inevitably widely exist in autoclaved materials,and these ions have important influences for structure or performance of calcium silicate hydrate,studying the mechanism and improving the performance of autoclaved products based on this are necessary and important for wide application of autoclaved products.