Influence of Firing Temperature on the Physicochemical, Thermomechanical and Microstructural Properties of the Yansoki Kaolininic Clays Douala Cameroon: A Preliminary Performance Investigation.

The present work evaluated the thermomechanical performance of three natural kaolinitic clays Arg-G, Arg-V and Arg-Y sampled in an inking zone of the Yansoki locality in the Douala sub-basin. The clay raw materials were characterized by standard methods (XRF, XRD, SEM/EDX and TGA/DSC). Physical and thermomechanical tests were carried out and the influence of parameters such as: water absorption, compressive strength, flexural strength, bulk density, linear shrinkage and mass loss were examined. Chemical characterizations showed that the materials are rich in silica (34.05-50.55%), alumina (17.68-23.98%) and hematite (1.55-11.22%). Mineralogical analysis of the clays revealed three main mineralogical phases: quartz kaolinite and illite. The clays showed stacked platelet and pseudo-hexagonal microstructures revealing the presence of predominantly kaolinite in the Arg-G (Si/Al ˂ 1) clay than the other Arg-V and Arg-Y (Si/Al ˃ 1). The clays physically presented a sandy-clay texture with relatively high plasticity indices Arg-G (49.20%), Arg-V (23.40%) and Arg-Y (21.70%) respectively. Thermomechanical properties indicated that the gradual increase in bulk density and linear shrinkage, in contrast to the decrease in water absorption, are indicative of the mineralogical transformations taking place during firing. Compressive and flexural strengths increased gradually with temperature, reflecting a thermomechanical improvement of the fired products in line with the chemical and mineralogical composition of the clays studied. The improvements in thermal and thermomechanical properties observed are the result of mineralogical transformations such as trydimite, cristobalite, metakaolin, spinel, mullite, and silica glass during calcination. The results of this study highlighted the high ceramic performance of clays from the Yansoki locality in the Douala sub-basin.