Proposal of an empirical relationship for moisture storage function of concrete

In this paper an empirical mathematical relationship for concrete's moisture storage function is proposed. Most of the simple relationships that are used in hygrothermal models for the approximation of building materials' moisture storage functions cannot provide a very satisfactory estimation for concrete. In this paper, an empirical function, having three branches, is formulated to express concrete's moisture storage function and to be used in hygrothermal calculations. The formulation of this relationship is analytically presented. The proposed expression can be adjusted to a type of concrete when only the values of free saturation moisture content (relative humidity 100 %) and of moisture content corresponding to 80% air relative humidity are known for this concrete.