Drying Kinetics of Building Materials: Brief Theory and Experimental Evaluation

Abstract

The effect of moisture in buildings is normally related with damage, which may occur due to the presence of moisture itself or due to its evaporation. The drying process plays an important role in the available moisture, both inside the material or at its surface. This paper presents the results of an experimental evaluation of the drying kinetics, considering both surface and bulk moisture transfer. Two different specimens were used: External Thermal Insulation Composite Systems (ETICS) to study surface moisture transfer and Autoclaved Cellular Concrete (ACC) to analyse the bulk moisture transfer. For both samples the drying kinetics was assessed considering different environment conditions (air temperature and humidity). Five different first-order kinetics models, available in the literature, were adjusted to describe the drying process and estimate the equilibrium moisture content of ETICS and ACC.The results point that Logarithmic and Midilli models allow the best fit and that the drying time constant is strongly affected by the moisture transfer phenomenon (at surface or bulk) and by the drying air conditions. It was also estimated the apparent molecular diffusion coefficient for ACC and its variation with temperature.