Analysis of the compressive strength development of concrete considering the interactions between hydration and drying

After removing the formwork, concrete is exposed to environmental air and dries. Due to the interactions between hydration and drying, the strength development of outdoor air-cured concrete is different from that of water-cured concrete or seal-cured concrete. This paper proposes a numerical procedure to evaluate the interactions among cement hydration, moisture diffusion, and compressive strength development. First, by using a desorption isotherm considering the degree of hydration of cement, the relative humidity reduction due to self desiccation is calculated. Second, a moisture diffusion equation considering the microstructure evolution of concrete is proposed. A hydration model considering the local relative humidity is also put forward. Third, by combining the hydration model with the moisture diffusion model, the individual degree of hydration with varying concrete depths is calculated. Using the individual degree of hydration at different depths, the average degree of hydration is calculated. The compressive strength is evaluated using the average degree of hydration.