Thermal behaviour of ceramics obtained from the kaolinitic clays of Terra Alta, Catalonia, Spain

Abstract The thermal properties and evolution of mineralogy colour kaolinitic clay from the Terra Alta region were studied. these materials consists mainly kaolinite (13–27 mass%) quartz (48–86 mass%). Minor illite, hematite, K -feldspar calcite also occur. linear expansion absorption curves used to predict optimal firing temperature raw clays. During firing, 1100 °C water decreases steeply, due an increase in liquid phase, which penetrates into pores close porosity. At this temperature, shrinkage increases progressively. fired clays are composed quartz, cristobalite mullite, with minor hematite rutile. Mullite starts appear at 1050–1100 °C. SEM observations show that porosity temperature. measured bricks different temperatures. lightness, L *, is lower test pieces respect natural This varies according content, being white reddish samples.