Effect of salt on hygroscopic properties of cement mortar

Abstract

It is widely known that coastal buildings are eroded by salt, and hygroscopic performance of the building materials significantly affects the building energy consumption. Therefore, for buildings in marine atmospheric zones, it is necessary to explore the impact of salt on the hygroscopic properties of cement mortar. In this study, cement mortar specimens with different salt contents were prepared to measure their hygroscopic properties at different humidity levels, and acquire the regulation of equilibrium moisture content with changes in the salt content and relative humidity. In addition, based on a variety of commonly used adsorption formulae, combined with the influencing factors of salt content proposed in this study, a hygroscopic fitting formula for salt-containing materials was established. The experimental results revealed the following: the higher the salt content, the longer the stability time; the maximum increase in moisture absorption occurred in the early stage of the experiment, which gradually decreased and tended to be stable in the later stage; at any level of relative humidity, the equilibrium moisture content of the specimen increased with an increase in the salt content, and the promoting effect could be enhanced by more than three-fold; furthermore, the maximum moisture content appeared under conditions of high salt and high humidity. In addition, the fitting formula based on the BET formula and salt influence factor had a good fitting effect, and the goodness of fit could reach 0.98.