Isotropic material for moisture transport based on Bazant and Najjar - BazantNajjarMoisture

is a special case of Eq. (237), valid under the assumption that the slope of the sorption isotherm is linear, i.e. the moisture capacity is constant. In Eq. (235), is the relative humidity and is the humidity-dependent diffusivity approximated by

where is the diffusivity at saturation (typical value for concrete mmday), is the dimensionless ratio of diffusivity at low humidity to diffusivity at saturation (typical value ), is the humidity ``in the middle'' of the transition between low and high diffusivity (typical value ), and is dimensionless exponent (high values of , e.g. 12, lead to a rapid transition between low and high diffusivity). Optionally, it is possible to specify the moisture capacity. This property is not needed for solution of the diffusion equation (235), but it is needed if the computed change of relative humidity is transformed into water content loss (mass of lost water per unit volume).

The model parameters are summarized in Tab. 54.

2018-01-02