Study on desorption characteristics of water vapor in fly ash concrete materials

In this paper, water vapor desorption tests are carried out on water-saturated concrete materials with different water-binder ratios and fly ash content. The desorption parameters are analyzed using the adsorption curve analysis method, which enables the acquisition of desorption characteristics for concrete materials. By utilizing the desorption isothermal curve, the desorption rate is calculated and further analysis is conducted on the influence of water-binder ratio and fly ash content on this rate. The results indicate that the desorption and activation energy for water vapor desorption in concrete materials is higher than the adsorption energy at the first layer, suggesting that removing water vapor from inner pore walls is more challenging than its adsorption. The amount of water vapor released from concrete materials follows a power function over time, as does the rate of desorption. Under conditions of relatively low ambient humidity, an increase in the water-binder ratio leads to a decrease in the rate of desorption. Conversely, under relatively high ambient humidity, an increase in the water-binder ratio results in an increased rate of desorption.