Using the CEMHYD3D and ELAS3D microstructure and property models, the leaching from cement paste of the phases CH, AFm, and AFt was numerically simulated. Leaching effects on capillary porosity, connected capillary porosity fraction, and Young's modulus were computed and analysed for six cements, at three different water-to-cement ratios and with and without 7.7 % silica fume addition. The results clearly show that CH dissolution strongly increases capillary porosity and its connected fraction and significantly decreases the Young's modulus value. A reduction of more than 50 % in Young's modulus was found, in good agreement with experiment. These increase and reduction rates depend on the initial CH content and consequently on water-to-cement ratio and silica fume addition. The system with silica fume had a higher residual elastic modulus value due to the lower initial CH content. For the six cement pastes, the fractional reduction in elastic modulus increases with the water-to-cement ratio. As far as the two other hydrates, AFm and Aft, are concerned, their dissolution causes a much lower increase in capillary porosity and decrease in Young's modulus because their initial volume fraction is much lower than that of CH. Finally, an empirical equation relating elastic modulus to capillary porosity was developed using the numerical results.
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