André Njoya

Smectite clay from the Sabga deposit (Cameroon): mineralogical and physicochemical properties

Abstract The physicochemical and mineralogical characterization of the <250 mm particlesize fraction from six clay-rich samples from the Sabga deposit (north-west, Cameroon) were carried out to evaluate their potential applications. The major clay mineral is dioctahedral smectite and minor kaolinite is present in three of the clay samples. Cristobalite, feldspars, ilmenite and heulandite are accessory minerals. Application of the Greene-Kelly test revealed that the smectite present is montmorillonite. The chemical composition (wt.%) of the bulk clays consists of (66-70%) SiO2, (13-16%) Al2O3 and (2-7%) Fe2O3. Physico-chemical characterization of the clays showed that the cation exchange capacity (CEC) and the specific surface area range from 38 to 46 meq/100 g and from 33 to 90 m2/g respectively. The physical and chemical properties are fully compatible with potential uses in environmental applications. After purification and chemical modification, these materials could also be used in refining edible oil as adsorbent, waste water treatment and wine technology.

Characterization of clay deposits of Nanga-Eboko (Central Cameroon): Suitability in the production of building materials

Abstract Clayey deposits of Nanga-Eboko (central Cameroon) were studied to assess their potential as building materials. Characterization was performed using XRD, FTIR, XRF, DTA/DTG and firing testing. Clays appear as discontinuous pockets with the same textural characteristics in three villages located on both sides of the Sanaga River. The average thickness of the exploitable layer is about 3m. The estimated tonnage ~7−17 x 105 m3 can supply a brick industry of great importance. SiO2 (~70%), Al2O3 (~15%) and Fe2O3 (~4%) are the predominant oxides of the natural clays. Quartz (~55%), kaolinite (~33%), illite (~5%) and K-feldspar (~4%) are major minerals. Clays are not suitable for building construction due to their fine-grained size and high plasticity properties. Firing properties of bricks (950 and 1050ºC) are good despite the high shrinkage values. Therefore the addition of ‘‘degreasers’’ is recommended to control shaping and drying.

The Ndop plain clayey materials (Bamenda area – NW Cameroon): Mineralogical, geochemical, physical characteristics and properties of their fired products

Abstract The physicochemical, mineralogical and technological properties of clayey materials from the Ndop plain (NW Cameroon) have been investigated, for their ceramic applications. The clayey materials have mixed facies with colour ranging from brown, grey, mottled and yellowish brown. The thickness of the exploitable clay layer is more than 5 m. Their mineralogical constituents are quartz, kaolinite, illite and feldspars, with kaolinite as major clay mineral. Based on the geochemistry, their source rocks might be felsic, with a mafic rock inference. These materials display high percentage in fine particles and high Atterberg limits. For all the firing temperatures, flexural strength (1.2–11 MPa), water absorption (8.03–24.27%), linear shrinkage (2.10%), weight loss (4.88–16.54%) and bulk density (1.57–2.03 g/cm3) indicate good ceramic properties for firing samples between 900 and 1100 °C. Most of the fired test bricks show a brick red colour with good to very good cohesion. The studied clays were thus, suitable as raw materials for roof tiles, light weight blocks and hollow bricks; however, mixing of high clayey and highly silty materials could improve the quality of the products.

Occurrences of kaolin in Koutaba (west Cameroon): Mineralogical and physicochemical characterization for use in ceramic products

Abstract Thirty clay samples collected from three hills in Koutaba (west Cameroon) were characterized in order to evaluate their potential use as raw materials for ceramics. After preliminary mineralogical identification by X-ray diffraction, three representative samples from the three different hills, referred to hereafter as K1M, K2M and K3M, were selected for further investigation by X-ray fluorescence, plasticity, granularity and thermogravimetric analysis. The main clay minerals are kaolinite (32-51%) and illite (up to 12%). Additional major phases are quartz (32-52%), goethite (6-7%) and feldspars (0-4%). The chemical composition showed variable amounts of SiO2 (60-72%), Al2O3 (15-20%) and Fe2O3 (1-9%), in accordance with the quartz abundance in all of the samples studied. The particle-size distribution showed a large proportion of silty fraction (64-88%) with moderate sandy (9-19%) and clayey fractions ( < 5% for K2M, 12% for K1M and 20% for K3M). All of the clays showed moderate plasticity-index values (8-11%). Because of these characteristics, K1M and K3M may be suitable for use in common bricks and hollow ceramic products. Sieving or the addition of ball clays is recommended to increase the plasticity of sample K2M for use in common bricks.