Study on the heat-moisture transfer in concrete under real environment

Surplus water inside a concrete other than moisture that is used for hydration of the cement affects the physical properties of the concrete (modulus of elasticity, compressive strength, drying shrinkage, and creep) by drying. Changes in temperature and humidity inside a concrete has correlation with the movement speed and reaction rate of deterioration factors such as carbon dioxide and chloride ions. Though the prediction of temperature and humidity inside a concrete is an important research field, there are not enough research achievements about it due to difficulties in measurement. In this study, comparison was performed between temperature and relative humidity inside the concrete and meteorological data for exposure environment through measurement at the site for two years. Surface temperature of the concrete (depth 1 cm) was measured higher by 6 °C during the summers, while it was measured lower by 2 °C during the winters due to solar radiation, wind, and radiation cooling. As for relative humidity, change was large in the depth of 1 cm, while more than 85% was maintained in the depth of 10 cm. A heat-moisture coupling model was prepared using FEM for the test results. With the coupling model, temperature could be predicted with a high degree of accuracy. However, daily changes of the humidity could not be simulated with the model. It might be because ink bottle effect and hysteresis effect could not be reflected as a form developed from the macroscopic model based on the partial differential equation. Yet, the proposed model could predict average relative humidity changes capable of evaluating long-term durability evaluation.