Interior Humidity of Concrete under Dry-Wet Cycles

The dry-wet cycle is one of the aggressive environmental conditions suffered by concrete. This paper focuses on the experimental study and theoretical simulation of water distribution in normal- and high-strength concrete through dry-wet cycles. The experimental results show that under dry-wet cycles, the variation in the interior humidity of concrete occurs mainly within a certain depth from the drying/wetting face. This depth is called the influencing depth under dry-wet cycles. The interior relative humidity of concrete within the influencing region periodically changes under dry-wet cycles. As concrete undergoes wetting, a fast rise in interior humidity occurs in a short time, and finally the relative humidity reaches approximately 100%. By contrast, as concrete undergoes drying, the interior relative humidity does not drop immediately, but in a more gradual manner. In the modeling, a model taking both cement hydration and moisture diffusion into account synchronously is used to simulate the moisture distribution in concrete under dry-wet cycles. A comparison between model and experimental results concludes that the model can predict the moisture distribution in concrete, as well as its variations, through dry-wet cycles. DOI: 10.1061/(ASCE)MT.1943-5533.0000382. (C) 2012 American Society of Civil Engineers.