Moisture characterization of cementitious material properties: Assessment of water vapor sorption isotherm and permeability variation with ages

The water vapor adsorption desorption isotherm and the water vapor permeability of cementitious materials were experimentally evaluated in this study according to the evolving nature of the microstructure of this type of material due to their hardening over time (7 days and 28 days). For getting a constant microstructure during measurements, it was necessary to stop hydration. The cement arresting hydration technique was chosen based on a comparative study on various methods known in literature. Results show that the suitable method is immersion under air vacuum in acetone bath for 7 days, followed by drying in an air vacuum for 3 days (without acetone). Using adsorption and desorption isotherms allowed identifying the moisture storage capacity. This parameter varies according to the relative humidity and material age. Moreover, the range where the relative humidity values are important (saturation zone RH > 90%) was investigated by means of retention water measurements using the membrane extraction method. The results obtained show an important gap of water content from 90% of RH to saturation step. Consequently, the water vapor permeability tests highlight the evolution of this coefficient according to material age and its formulation.