Densification Behaviour of a Red Firing Tunisian Triassic Clay

Abstract

Investigations were undertaken to assess the thermal modification in clay products from Triassic sedimentary deposits. This study deals with the mineralogical, physico-chemical, thermal analysis and faience making attributes of representative Triassic clay in the south-Eastern Tunisia. The data collected from these techniques show that illite and kaolinite are the major clay phases. The accessory minerals detected in powdered rock are; quartz, dolomite and hematite. The faience samples were dried pressed and sintered at temperatures ranging from 850 to 11501150°C.The densification was measured by three parameters: firing shrinkage, water absorption, and resistance to the inflection. The development of resistance to the inflection and reduction in water absorption on samples products from this Triassic clay material was noticed at elevated temperatures due to enhanced vitrification. Large amount of iron oxides shows rapid vitrification and fusion during firing. Higher proportions of finer particles in the raw material also favour vitrification due to the good compaction of samples during moulding, this is has a positive influence on resistance of fired samples. Given the mineralogy and physicochemical characteristics of this clay could be used for the manufacture of faience ceramic.