Abstract
AbstractThe structure and behaviour of two gypsum composites after exposition to elevated temperatures were investigated. The silica sand and fine basalt aggregate were used as solid fillers. The changes in structure and composition at temperatures from 50 to 1,000°C were investigated by scanning electron microscopy and X-ray diffraction together with the size and strength of the samples and their pore size distribution. The structure of gypsum matrix changed significantly at 1,000°C in both composites, while the aggregate particles were not changed. It was found that even if the silica sand is considered as less suitable filler at high temperatures because of its volume changes, the gypsum with sand performed better than gypsum with basalt at the highest temperatures, because the shrinkage of the gypsum matrix was compensated by the increase in the volume of aggregate. The final volume change at 1,000°C was 3.5% in composite with silica sand and 6.8% in composite with basalt. The residual compressive strength of both composites was about 9.4%. No cracks appeared in the samples and no spalling was observed.
Highlights
Calcined gypsum (CaSO4·0.5H2O) is considered to be good fire-resistant material and it is often used as a fire protection for other, less resistant materials as a steel orIt was found that even after heating to 1,000°C the gypsum samples maintained their integrity and they preserved some residual strength [3,4]
The silica sand is generally not considered suitable for these purposes, because even if it is chemically stable under 1,000°C, it exhibits significant volume changes at temperatures
It can be seen that the contact between sand particles and gypsum paste in GS composite was disrupted at 600°C, which corresponds with the phase transformation and first volume change of silica sand
Summary
Calcined gypsum (CaSO4·0.5H2O) is considered to be good fire-resistant material and it is often used as a fire protection for other, less resistant materials as a steel or. Common nonporous fillers are not used in the gypsum products very often, because the gypsum does not shrink at normal temperatures [7]. These fillers can reduce the volume changes of gypsum at higher temperatures. The silica sand is generally not considered suitable for these purposes, because even if it is chemically stable under 1,000°C, it exhibits significant volume changes at temperatures. The influence of two types of fine solid aggregates (silica sand and basalt) on the behaviour and structure of gypsum composites exposed to the high temperatures was studied. The gypsum composites were heated up to 1,000°C, and their structure and properties were investigated and compared to each other
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