Water Transport Behavior of Concrete: Boundary Condition and Water Influential Depth

Abstract

In this study, water transport in concrete was investigated using an environmental simulation test system, and the boundary conditions of water transport on the concrete surface are proposed in this paper. The water influential depth in concrete was deduced by analyzing the influence of several factors. Moreover, a numerical simulation method was proposed to analyze the influence of wind speed on the mass transfer coefficient and water distribution in concrete. Results indicated that the water distribution and transport process can be represented by the finite difference method and Fick’s diffusion law, but the corresponding water diffusion coefficient of Fick’s diffusion law differs between the wetting and drying processes. In addition, numerical simulation showed that environmental relative humidity can be considered the interface relative humidity when the value of wind speed multiplied by critical time exceeds a certain value. A good relationship between the equilibrium time ratio and influence factors (i.e., water-to-cement ratio, initial water saturation of the concrete, and environmental water saturation degree imposed on the concrete surface) manifested in terms of an exponential function. Furthermore, the water influential depth in concrete and the square root of the wetting time had a linear relationship.