Prediction of relative permeabilities and water vapor diffusion reduction factor for cement-based materials

Relative permeabilities and water vapor diffusion reduction factor coefficients are essential data regarding the modeling of moisture transport and hence the prediction of structure lifetimes. The dependency of these parameters on the humidity history and the chemical evolutions of the material limits their experimental measurement since tests are long to carry out. For cement-based materials, the most usual approach for the calculation of relative permeabilities is the one developed for soils by Van Genuchten, requiring calibration on experimental water retention curves. Moreover, the model involves a pore network connectivity factor, the value of which varies from one author to another. The water vapor diffusion reduction factor is often calculated via Millington's semi-empirical model. This paper presents new methods for calculating transport factors based on physical and statistical considerations associated with a pore network model developed for the prediction of water sorption isotherms.