PREDICTION OF WATER SORPTIVITY IN CEMENT-BASED MATERIALS

The capillary absorption of water by unsaturated cement-based material is the main cause of degradation of the structures subjecting to an aggressive environment since water often acts as the transporting medium for damaging contaminants. It is well known that the capillarity coefficient and sorptivity are two important parameters to characterize the water absorption of porous materials. Generally, the former is used to describe the penetration depth or height of water transport, which must be measured by special and advanced equipment. In contrast, the sorptivity represents the relationship between cumulative volume of water uptake and the square root of the elapsed time, which can be easily measured by the gravimetric method in a normal laboratory condition. In the current paper, an analytical method is developed to build up a bridge between these two parameters, with the purpose that the sorptivity or the gravimetric method can be used to predict the penetration depth of water absorption. Additionally, a new model to account for the dependence of sorptivity on initial water content of the material is developed in order to fit the in situ condition. Water sorptivity of concrete is also analyzed with help of this model in terms of the mesoscale of concrete. The comparison of predicted results by the analytical method with experimental data or numerical calculation results, as well as some previous models, validates the feasibility of the methods presented in the current paper.