Drying behaviour of calcium silicate

•Calcium silicate has an atypical drying behaviour.•The second drying stage shows an intermediate platform in the temperature course.•A detailed 3D drying model explains the drying behaviour.•During drying, the dried out top acts as a thermal insulation layer.

Nowadays, the hygrothermal performance of the building envelope is often evaluated using HAM (heat, air and moisture) models. These models can be used to predict the hygrothermal response of the building envelope and can assist in reducing the risk of any moisture-related damage (e.g. decrease of thermal insulation value due to wetting, interstitial condensation, etc.). At the same time it is important to understand the physical mechanisms of wetting and drying of building materials. Experimental research can contribute to a better understanding of these mechanisms.In this paper the focus lies on the wetting and drying phenomena occurring in building materials. One specific material is highlighted: calcium silicate. Calcium silicate is an inorganic, hygroscopic and capillary active insulation material, which is often used in interior thermal insulations systems. The paper describes a drying experiment in which a calcium silicate sample dries out starting from saturation. The experiments showed that calcium silicate has an atypical drying behaviour: during the second drying phase an intermediate plateau was observed in the temperature course. Numerical simulations performed with a recently developed CFD–HAM model were compared with the experimental results and were used to explain the experimental observations.