Study of the Vapour Phase Diffusivity in Hardened Cement Pastes Based on Water Adsorption Isotherms

Abstract

The characteristics of moisture diffusivity, which change depending on the water content, were examined based on the water adsorption isotherms of hardened cement pastes optimized by the BSB model. The maximum value of moisture diffusivity occurs in the monolayer adsorption state, regardless of material age or water cement ratio, and it decreases as the amount of monolayer adsorption increases. The mechanism of moisture diffusivity in hardened cement pastes can be split into two factors. One addresses the interaction effects between the surface of specimens and moisture becoming the driving force of adsorption before the monolayer adsorption state is reached. The other addresses the geometrical effects related to the diffusion pathway in the adsorbed state beyond the monolayer adsorption state.