Mathematical expression of water diffusivity coefficient in cementitious materials based on a novel adsorption isotherm
By Hideyuki Utsumi
Concrete Research and Technology
Vol.20, No.2, May. 2009 (Issue 50)
- Synopsis:
- A mathematical expression of the diffusivity coefficients for the vapor and liquid phase of water in cementitious materials has been developed that depends on the adsorption amount. This expression has been formulated based on a thermodynamic equation of the state by which to express the progress of the water adsorption phenomenon in pore spaces, and uses the new adsorption isotherm reflecting the characterictics of the pore size distribution of cementitious materials. This expression enables one to express quantitatively the influence produced by the change of temperature and pore size distribution on the diffusivity coefficients of each phase. The analysis results show a valid correlation with the previous studies, and clarifies that the principal factors of the water transfer phenomenon change from the vapor phase transfer to the liquid phase transfer with the increase of the amount of adsorption.
- Keywords:
- diffusivity, water transfer, water adsorption isotherm, pore size distribution, cementitious matelials
