Assessment of the variability of moisture transfer properties of High Performance Concrete from a multi-stage drying experiment

This article aims to assess the characterisation of the water vapour desorption process and its variability under site conditions. It presents a probabilistic approach allowing the assessment of the distribution laws for the water vapour desorption isotherms (WVDI) and the moisture diffusion coefficient. These two parameters were evaluated from multistage drying experiment. For each stage, the analysis of the equilibrium state allows the determination of WVDI whereas the analysis of the desiccation kinetic makes possible the evaluation of the moisture diffusion coefficient. In order to have a representative variability, the study was carried out on two different High Performance Concretes (HPC) during a large-scale construction: overall, more than 300 specimens were tested. Results indicate that Gaussian distribution can be used for modelling the statistical variability of desorption isotherm while log-normal distribution is more appropriate for describing the variability of moisture diffusion coefficient. Furthermore, whatever the concrete, the coefficient of variation on the water content at equilibrium remain very similar.