Mineralogical and Physical Changes during Sintering of Plastic Red Clays from Sanaga Swampy Valley, Cameroon

Abstract

The sintering behavior and mechanical properties of four alluvial clays sampled from the Sanaga River (sampling sites: Nanga-Eboko, Mbandjock, Batschenga, and Ebebda), central region of Cameroon were investigated. Specimens were shaped by cold pressing and fired between 850 and 1100°C. X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy were used to monitor microstructural modifications and thermal phase transformations. Linear shrinkage, density, open/closed porosity, and water absorption were used to assess the effects of firing cycle on the mechanical properties of the fired compacts. The results showed that between 850 and 1050°C the mineralogical phases are mainly quartz and feldspar. Mullite, spinel, and cristoballite appear at 1100°C together with viscous phases. The values of apparent density (2.62–2.76 g/cm3), open porosity, and flexural strength (3–30 MPa) of the brown compacts suggest the possible use of these clays for earthenware ceramics such as building bricks, roof and floor tiles.