CHARACTERIZATION OF ALGERIAN DD3 KAOLIN

The objective of this work is a structural and microstructural characterization of Algerian kaolin in order to valorize these local raw materials, and to elaborate refractory bricks from DD3 kaolin. The DD3 kaolin of Djebbel Debbagh-Guelma located in the North-East of Algeria has been characterized by means of X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermal analysis (DTA/TGA). The hydrothermal rock contains mainly 41% silica, 35% alumina, 17% of fire loss and small amounts of MnO, CaO and Fe2O3. X-ray analysis of DD3 kaolin shows the presence of the clay minerals which are kaolinite or halloysite as main phaseas well as the minor phases of muscovite and todorokite. Differential thermal analysis scan reveals the existence of several endothermic and exothermic peaks in the temperature range (50-1000)°C. The first endothermic peak at about 80°C can be attributed to the release of interstitial water in the kaolinite [2SiO2 Al2O3 2H2O]. The dehydroxylation to metakaolinite (Al2O3 2SiO2) occurs between 400 and 500°C. The exothermic peak at 995°C can be ascribed to the metakaolinite restructuring. The thermo-gravimetric analysis curve shows that the mass loss between 400 and 800°C is about 14%. The SEM observations show a needle-like form structure with an entanglement in all the directions of the halloysite.