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Nzeugang Nzeukou A.,Laboratory of Clays | Nzeugang Nzeukou A.,Laboratory of Alterology and Engineering Geology | Fagel N.,Laboratory of Clays | Njoya A.,University of Dschang | And 4 more authors.
Applied Clay Science | Year: 2013

Alluvial clays from four localities along the Sanaga River (Center Cameroon) were studied by physico-chemical, mineralogical and technological characterization in order to assess their suitability as ceramic raw materials. The chemical compositions indicated that SiO2 (65-70%) and Al2O3 (12-15%) are major elements while Fe2O3 is less (4-7%). Kaolinite, quartz and feldspar are the main minerals. Particle size distribution and chemical composition are indicative of "plastic red clays" belonging to heavy sandy clays group. Their medium to high plasticity is suitable for fired earth and fine ceramics products. Pressed samples were fired at temperatures ranging between 900 and 1100°C for coarse ceramic products. Linear shrinkage, flexural strength and water absorption indicated that the clays from one site (Mbandjock) are good for brick making. Clays from the three other localities present poor technological properties (higher shrinkage and cracks), they need degreasers before use as ceramic raw materials. Although water absorption and flexural strength parameters are good for all the studied samples, firing shrinkage needs to be improved. © 2013 Elsevier B.V.

Fongang R.T.T.,University of Yaounde I | Pemndje J.,Local Materials Promotion Authority MIPROMALO | Lemougna P.N.,Local Materials Promotion Authority MIPROMALO | Melo U.C.,Local Materials Promotion Authority MIPROMALO | And 5 more authors.
Energy and Buildings | Year: 2015

Inorganic polymer cement paste was used as cleaner binder for the design of lightweight matrices as insulating envelopes and panels in building and construction industries. Sponge-like structure with a homogeneously distributed pore network, low density and low thermal conductivity permitted to classify the geopolymer-wood fiber composites promising clean insulating materials. Matrices with the density ∼0.79 g/cm3, bi-axial four-point flexural strength of ∼4 MPa presented thermal conductivity between 0.2 and 0.3 W/(m K). The possibility of substituting the sodium silicate with rice ash-NaOH system and the efficiency of the matrices to constitute an effective tortuous road for the thermal gradient improved the sustainability and quality of this new class of products. The pores network and the microstructure approximated by a spatial periodic geometry suggested a "macro transport" mechanism to explain the movement of heat across the matrix of light geopolymer composite. © 2015 Elsevier B.V. All rights reserved.

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