Effect of the expanded perlite dose on the fire performance of gypsum plasters

Gypsum plasters are often used in buildings to provide passive protection against fire. This paper studies the fire behaviour of lightweight plasters containing moderate and high doses of expanded perlite. A propane flame was used to study the heat transmission through the plaster from the exposed side to the back side (2 cm thickness) using an IR camera. The microstructural and mineralogical variations induced by fire were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) using micro-perforated lids to improve the resolution (separation) of endothermic peaks of gypsum and bassanite. The exposed side of the plasters was drastically affected by fire regardless the concen-tration of perlite. However, important differences were found in the non-exposed side depending on the used amount of perlite. The greatest alteration was observed for high doses of perlite (6.5 % w/w) followed by control samples (0 % w/w). By contrast, using moderate doses of perlite (2.0 % w/w) the plasters showed excellent fire performance and CaSO4 2H2O was well preserved. The results suggest that the incorporation of lightweight materials to plasters should be carefully adjusted to ensure appropriate fire protection.