Predicting Ca(OH) 2 content and chemical shrinkage of hydrating cement pastes using analytical approach

Abstract

A semiempirical model is proposed to predict the evolution of chemical shrinkage and Ca(OH) 2 content of cement paste at early age of hydration. The model is based on chemical equations and cement compound hydration rates. Chemical shrinkage and Ca(OH) 2 amount are computed using the stoichiometric results of the hydration reactions considered in the model and the density of hydration products and reactants. The model validation is conducted by comparison between computed and experimental results achieved on ordinary cement pastes with different water-to-cement (w/c) ratios (0.25, 0.30, 0.35 and 0.40) cured at 10, 20, 30, 40 and 50 °C, respectively. Hydration degree and Ca(OH) 2 content are determined using the thermogravimetric analysis (TGA) and chemical shrinkage evolution using a gravimetric method. The comparison reveals a good consistency between modelled and experimental data at early age of hydration.