Caractérisation minéralogique, géochimiques et valorisation en céramique des matériaux argileux de Ngat, Mbalmayo, sud-Cameroun

Abstract

The study is being carried out in the locality of Ngat, at an average altitude of 680 m and located on the South Cameroon plateau. It includes a fundamental section on the petrology of clay materials and an applied section on their possible use as a raw material for brick production. In the latter part, Ilomba wood ash processed in the town of Ngoumou was used to improve the technological characteristics of these materials. Physico-chemical analyses were carried out at the Science Department of the University of Yaoundé I and at MIPROMALO. The mineralogy and geochemistry of the material powders were determined by X-ray diffractograms and X-ray fluorescence (Lausane, Switzerland), respectively. Trace elements and rare earths were determined by mass spectrometry (Geosciences Laboratory, Canada). Ceramic testing was carried out at MIPROMALO and at the Inorganic Chemistry Department of the University of Yaoundé I. Morphological results indicate that the overall color of the material is yellow, with variable thicknesses ranging from 10 to 160 cm. Physico-chemically, particle size analysis confirms their clayey nature, with clay proportions ranging from 25.13 to 61.15 %. This fraction is followed by the sandy fraction (23.51 - 60.18 %), giving these materials a clayey sandy, clayey-muddy and sandy-muddy texture. Atterberg limits give these materials low to medium plasticity. Organic matter (0.58 - 1.70%) and cation exchange capacity (14.75 - 16.06 meq/100g soil) are low. The Ngat materials consist mainly of quartz and kaolinite, with minor amounts of goethite, anatase and gibbsite. Geochemical data confirm the dominance of silicate minerals, with abundant silica (62.34-80.73%) and alumina (9.09-19.13%). Iron content is low (1.81-6.26%). TiO2 content averages 1.39%. Alkali and alkaline-earth contents are less than unit. The sum of flux oxides is low, below 2.5%. Cr, V, Zr, Rb and Ba contents are the highest. The sum of rare earths varies between 60 and 105 ppm. Correlations between silica and other major elements are negative. Rare earth normalization against chondrite values shows pronounced negative Eu anomalies. On the ceramic side, specimens were fired at several temperature levels (800, 900, 1000 and 1100°C). The mineralogy of the fired specimens consists of quartz, anatase, hematite and mullite. Linear shrinkage values are low (.0 - 7.30%). Water absorption varies between 11 and 23%. Flexural strength is moderate, ranging from 1.25 to 12.17 MPa. To improve the technological characteristics of these materials, Ilomba wood ash was added at various percentages. The addition of ash (10 %) shows values between 5.7 and 10.83% for linear shrinkage, 15.01 and 22.95% for water absorption and 6.8 to 7.44 MPa for flexural strength. ceramic properties of these materials. Ngat materials are ideal for the production of fired bricks for use in the construction industry.