MICROSTRUCTURE OF GYPSUM PASTE AT ELEVATED TEMPERATURES

ABSTRACT

Gypsum paste was subjected to the temperatures up to 1000 °C and its microstructure was investigated by SEM microscopy. The volume and mass changes were also measured and the bulk density, porosity and residual strength were determined. After heating to the 1000 °C the structure of paste changed substantially, as can be seen in the micrographs. The structure of heated material is denser and the anhydrite crystals are bigger. The volume of the samples decreased more than 50%. The bulk density increased by 20%, while the porosity decreased correspondingly. The compressive strength firstly decreased to 17% at 100 °C, but after heating to 1000 °C it increased again to the initial value.

Keywords: gypsum, high temperature, SEM, microstructure