Composition and Ceramic Properties of Carbonate-Bearing: Illitic Clays from North-Eastern Tunisia

The Aptian clays of Jebel Ressas (north-east of Tunisia) have been studied for their use in ceramic industry. At first, mineralogical, chemical, physical, and thermal analyses of these clays are given. Indeed, illite is the main mineral (60–65 wt%) but other minerals; quartz, kaolinite, interstratified illite/smectite, calcite and feldspar, are present in small quantities. Next, this study reveals that the average amounts of silica and potassium are 51.57 and 3.35 wt%, respectively. The percentage of potassium is also quite high, suggesting the presence of illite. The amount of alumina is in average of 19.01 wt%. The contents of lime and iron vary between 5 and 8 wt%. The grain size data indicate a silt-dominated assemblage. The plasticity test shows a medium value (PI= 16–20 wt%). The firing shrinkage and the expansion are limited. The absence of expansible minerals in these clays explains why the plasticity and the linear shrinkage are limited. Finally, two mixtures M1 and M2 prepared from these clays show that ceramic properties respect the norm and the industrial tests confirm that these clays could be used in manufacturing of bricks and earthenware tiles.