Effect of water loss during curing on hydration reaction and hydrates conversion in calcium aluminate cement-bonded castables
摘要
Free water available in calcium aluminate cement (CAC)-bonded castables is crucial for the hydration of CAC and the conversion of hydration products in the curing and drying processes, as both the hydration and conversion reactions are dissolution–precipitation reactions. To elucidate the effect of different levels of free water loss upon the hydration of CAC, the conversion of hydration products and the mechanical strength of the CAC-bonded castables, the CAC-bonded castables were subjected to sealed and unsealed curing conditions at 50 °C and drying at 110 °C. The results demonstrate that the fast removal of free water during unsealed curing would hinder the conversion from 2CaO·Al2O3·8H2O to 3CaO·Al2O3·6H2O and consequently prevent the deterioration of strength. As a comparison, although sealed-cured samples have less water loss and high degree of hydration of CAC, they still show lower strength than the unsealed samples after curing. The following drying process further accelerates the hydration of residual calcium aluminate clinkers for both the sealed and unsealed samples, but still does not favor the conversion from 2CaO·Al2O3·8H2O to 3CaO·Al2O3·6H2O in the unsealed-cured samples.