Properties of Debadib Evaporates (Northern Tunisia) for Potential Use in Industrial Fields

Gypsum is widely distributed in Tunisia occurring in the formation of Triassic age. The gypsum deposit of Mellegue is the alabastine type with a little of the porphyroblast type and contains traces of clay minerals and calcite. It is a moderately strong rock in terms of its unconfined compressive strength of 16 Mpa and tensile strength of 3.35 Mpa. Triaxial testing values indicated an apparent cohesion of 10 Mpa and an angle of friction of 26°. The gypsum studied had a percentage of SO3 of 41.71% and a percentage of CaO of 32.9%. All the samples had low densities according to the International Association of Engineering Geology (IAEG) classification and exhibited a moderate porosity whether effective or absolute. The gypsum proved to be moderately strong when tested in unconfined compression and tensile strength. Thermal analysis indicated a total weight loss of 20.27% and the whiteness index about 90%. This proved a high degree of whiteness. The time of setting can be considered short and medium, which is quite favorable for industrial application compared with other gypsum deposits currently operated.

Technological Characterization and Industrial Application of Tunisian Clays from Makthar Area (Central Tunisia) in the Ceramic Industry

This study focused on the geochemical, mineralogical and technological characterization of clays in Makthar area (Central of Tunisia) of Cretaceous-Paleogene. Its aims are to identify and promote use in the field of ceramics industry. The result of the mineralogical analysis of clays showed a dominance of illite with a percentage higher than 65%, of kaolinite and smectite with percentages of 15%. Geochemical analysis of the major elements of clay showed a SiO2 content exceeding 29% and a percentage of Al2O3 higher than 7.5%. The Fe2O3 percentage was ranging from 3% to 8%. The percentage of CaO was between 22.5% and 28% while that of K2O is 4%. The percentages of SO4, MgO and NaO2 were in very small fractions. Granulometric and microgranulometric analysis showed that the clay fraction (<2 μm) varies from 30% to 37%. The plasticity index showed the plasticity character of clays which presented a specific surface area ranging from 112 m2/g to 178 m2/g reflecting illite dominance. Drying behavior indicated that clay mixture had a drying shrinkage less than 7%, while the firing shrinkage didn’t exceed 2% giving the possibility of clay using in the ceramics field.

Effects of Lizardite Addition on Technological Properties of Forsterite- monticellite Rich Ceramics Prepared from Natural Magnesite and Dolomite

Lizardite rich peridotite has never been used to prepare ceramic specimens,especially in Morocco.For this raison,potential use of naturally abundant lizarditic material from the Rif domain,as a supply for ceramic industry,has been evaluated.The effects of lizardite addition to magnesite and dolomite mixtures on the thermomechanical properties of the calcined ceramics were also detailed.To achieve this target,natural lizardite,magnesite and dolomite samples were collected in ultrabasic Beni Bousra massif.Those raw samples were used for the synthesis of a forsterite-monticellite rich ceramics.Both raw and sintered samples were characterized by x-ray diffraction,scanning electron microscope and fourier transform infrared.The obtained results showed that both magnesite and dolomite were mainly composed of MgCO_(3) and CaCO_(3).In contrast,lizardite sample showed high amounts of SiO_(2),MgO and Fe2O_(3).An increased amount of lizardite in the initial mixtures enhanced mechanical and dimensional properties of the prepared ceramic specimens,and subsequently,the production of ceramics with the required technological properties.Thus,the preparation of Moroccan lizardite-based ceramics is technically feasible,economically justifiable and socially desirable due to the contribution to the economic growth of the raw materials sector,especially ceramic industry.