The One-Dimensional Moisture Transport Model for Concrete Under Dry–Wet Cycles

This study proposes a novel analytical model to predict one-dimensional moisture transport in concrete under cyclic drying and wetting conditions. The framework distinguishes between two physical mechanisms: diffusion-driven evaporation during drying and capillary-driven suction during wetting. Governing equations for weight loss and gain are derived for each respective phase. During the drying phase, weight loss follows a linear relationship with the square root of time, allowing the diffusion coefficient to be determined via evaporation tests. For the wetting phase, a modified sorptivity approach is employed, incorporating an error-function baseline to account for residual moisture. A calibration coefficient of ε is utilized to correct for varying conditions between standard water suction tests and environmental wetting, particularly for air-entrained concrete characterized by larger capillary volumes and complex tortuosity. Experimental validation was conducted on concrete with varying water-to-cement ratios. The model demonstrated excellent agreement with experimental data, maintaining relative errors below 10% for standard mixes. While higher-porosity samples exhibited greater scatter due to “water traps” and complex pore structures, the model effectively captured cumulative moisture trends over multiple cycles. This framework provides a robust tool for assessing the durability of concrete structures in unsheltered environments.