Measurement of linear thermal expansion coefficient of alkali-activated aluminosilicate composites up to 1000 °C

The effect of high temperatures up to 1000 °C on the length changes of two alkali-activated aluminosilicate composites, one of them with quartz sand aggregates, the second with electrical porcelain, is analyzed in the paper. The thermal strain vs. temperature functions of both materials are found to increase monotonically in the whole temperature range studied so that the thermal expansion mismatch (the gel undergoes thermal shrinkage, the aggregates expand with increasing temperature) results in positive values of the apparent linear thermal expansion coefficient. The composite material with electrical porcelain aggregates exhibits a more desired thermomechanical behavior which is a consequence of the better high-temperature thermal stability of electrical porcelain as compared to quartz. In a comparison with Portland-cement based composites, the linear thermal expansion coefficient of both studied aluminosilicates is substantially lower in the whole temperature range of 20–1000 °C.