Scrutinizing Gypsum Board Thermal Performance at Dehydration Temperatures

This article investigates the thermal performance of gypsum boards in the dehydration temperature region, where pronounced chemical reactivity is anticipated. Gypsum board samples were gradually heated up to 300°C, using a low heating rate. Temperature measurements at pre-selected board locations indicated three distinct stages of gypsum dehydration; free moisture evaporation, transformation of calcium sulfate dihydrate to calcium sulfate hemi-hydrate and of calcium sulfate hemi-hydrate to calcium sulfate anhydrate. Physical properties of the gypsum board sample, that is density, specific heat, and thermal conductivity, were measured as a function of the dehydration temperature range. Results suggested that the thermal conductivity of the calcium anhydrate sulfate is higher than that of the hemi-hydrate, despite the fact that gypsum porosity increases during the dehydration process. Based on the experimental results, correlations for the thermal conductivity and the dehydration energy as a function of the mass loss during the dehydration process and the initial water content of the gypsum board, respectively, were obtained.