Physico-chemical and geotechnical characterization of Bargou clays (Northwestern Tunisia): application on traditional ceramics

Abstract

The Lower Aptian clays of the Drija formation (Jebel Bargou-Siliana, Tunisia) have been studied for their use in the ceramic industry. The physico-chemical characterization and advanced technological tests were carried out on two samples, Bargou 1 and Bargou 2 using many analytical methods. The samples indicate that these clays can be considered as a non-refractory material. The X-ray diffraction mineralogical analysis on whole rock and clay fractions reveals the presence of phyllitic minerals (illite, kaolinite, and interstratified illite/smectite). Associated minerals are mainly represented by dolomite, calcite, quartz and feldspar, and occasionally gypsum. The chemical analysis of major elements reveals a moderate level in Al2O3 (10–18%) and SiO2 (36–64%) with a SiO2:Al2O3 ratio that can reach level 3 and a low CaO content. The plasticity index of the samples, cut from the Drija formation, shows that they are low plastic clays (l2% < IP < 15%). The drying curves of various samples show that the clay materials have a quick drying behavior since they have a relatively low drying shrinkage. The tested briquettes, fired at different temperatures of 950, 1050, and 1100 °C, remain flat without deformations or defects; they are of red brick color. These briquettes show a high mechanical resistance to flexion and a good sound. The results obtained show that the Drija formation clays of Lower Aptian from the Bargou region can be directly used in the manufacture of tiles.