The construction of infrastructures such as dams requires a stable ground for the foundations to lay on, which also have to be protected from erosion deriving from groundwater exposure. One way to achieve this is to grout the rock fractures present in the bedrock using cement. However, the continuous flow of groundwater will, over time, cause the deterioration of the grout by dissolving and mobilising the mineral phases resulting from the hydration process. This study aims to determine the variations in porosity and hydraulic conductivity induced by the dissolution of portlandite present in the grout under the influence of groundwater flow.