Computational multiscale modelling of thermally induced dehydration of blended hardened cement paste

A multiscale model able to describe the dehydration behaviour in terms of mass loss, porosity increase and Young's modulus degradation of blended cement pastes at elevated temperatures is proposed. The cement composition and the heating rate are the input of the model. Known stoichiometric chemical dehydration formulas and kinetics of each hardened cement constituent are used to predict the water release and the porosity of the blended hardened cement paste at elevated temperatures. Based on these submodels, micromechanics homogenisation methods (Mori–Tanaka and Self-Consistent schemes) are employed to determine the Young's modulus. The model is extensively validated using nine experimental data sets (measurements of mass loss, porosity, Young's modulus). Finally, the model based analysis shows that adding carbonate decreases and fly ash, silica fume and blast furnace slag increases the explosive spalling risk of blended hardened cement pastes.