Influence of calcium hydroxide dissolution on the transport properties of hydrated cement systems

Calcium hydroxide is one of the main reaction products resulting from the hydration of Portland cement with water. It is also one of the more soluble phases found in hydrated cement systems. The influence of calcium hydroxide dissolution and its effect on the diffusion properties of hydrated cement pastes were investigated using the NIST CEMHYD3D cement hydration and microstructure development model. The results of these simulations were implemented in another numerical model called STADIUM. This latter model can be used to predict the transport of ions in unsaturated porous systems. Numerical simulations clearly indicate that calcium hydroxide dissolution contributes to a marked increase in the porosity of the hydrated cement paste. This increase in porosity has a detrimental influence on the material transport properties. The results yielded by the numerical simulations are in good agreement with data of calcium leaching experiments performed in deionized water.