The role of deicing salts on the non-linear moisture diffusion coeffcient of cementitious materials during drying

Abstract

The drying of cementitious materials is of interest in volume change (i.e., shrinkage) research. However, the movement of water due to drying and wetting also plays a significant role in many durability related problems (e.g., corrosion, alkali silica reactivity, freezing and thawing). Many factors can influence the drying and wetting process in concrete including: pore structure, environmental conditions, and liquid properties. This paper describes the influence of the liquid properties on the drying process. Specifically, this work examines the non-linear moisture diffusion coefficient that is used in a differential equation that describes drying. This paper describes how the non-linear moisture diffusion coefficient is influenced by the presence of deicing salts solutions. The relationship between the equilibrium relative humidity and the solution properties is also discussed in this paper. A higher degree of saturation was observed for the samples containing deicing salt solutions, as compared to the plain samples at any given humidity. The presence of deicing salt causes a shift of the non-linear moisture diffusion coefficient as a function of relative humidity. The non-linear moisture diffusion coefficient curves have near zero rates of drying at low relative humidity with a rapid increase in drying rate as the relative humidity is increased (especially near the equilibrium relative humidity) followed by diffusion coefficient of 0 between RHeq and 100% RH.