Ceramic behaviour of some kaolins from Cauquenes Province (VII Region of Maule, Chile)

This study was focused on the properties of ceramic clays from Chile, a country with an important local ceramic industry. Four deposits with industrial applications were studied. The kaolins come from Cauquenes Province in the VII Region of Chile. The chemical and mineralogical composition of clays was determined by X-ray fluorescence (XRD) and X-ray diffraction (XRD). Also, the plasticity index (PI) was measured for each sample. Test samples were prepared by pressing and firing at 800–1150 °C. Linear contraction (LC), water absorption capacity (WAC) and thermodilatometric analysis (TDA) were done to characterize the fired clays. The clays deposits studied were highly plastic kaolins with very high contents of unaltered kaolinite. A considerable decrease in the WAC coinciding with the beginning of vitrification was observed between 1050 and 1100 °C. At 1150 °C, the porosity of the tile bodies decreased significantly. The studied clays seem to be easily adaptable to a correct dry pressing ceramic process.