Industrial Potentiality of Alluvial Clays Deposits from Cameroon: Influence of Lateritic Clayey Admixture for Fired Bricks Production
The cartography and characterization of an alluvial clay deposit from Ebebda (Central region of Cameroon) were carried out in order to assess its suitability for the production of fired clay bricks. The clayey area investigated is ~ 50,000 m2 with an average thickness of the exploitable layer of 2.2 m, suggesting a deposit of about ~2.2 × 105 tonnes of clay. Mineralogy, physico-chemical and thermal analyses as well as firing properties were performed on representative clay samples. Kaolinite and quartz are the major minerals associated to illite. Upon heating to 900℃ - 1200℃, the linear shrinkage varies from 1.5% to 15%, the water absorption from 1.5% to 24% and the bending strength from 2 to 12 MPa. The admixture of lateritic clays (widely available) at 50%, 60%, 70% and 80% allow to decrease the shrinkage and bending strength, and to increase the water absorption. Overall, properties were satisfying the requirement for fired brick with 70% of laterite in the mixture.
Anthropogenic geomorphic change as a potential generator of renewable geologic resources in the humid Pampa of Argentina
Abstract The nature and amount of sediments in various lakes, intermittent swampy areas and river sectors in the humid Pampa (Buenos Aires Province, Argentina) were analysed. The aim was to determine whether recent sediments in such environments could serve as an alternative resource to the brick industry, for minimising the current, high environmental impact of soil mining. Sediment sequences were obtained, and the thicknesses of the upper sediment layers, corresponding to the suballuvial (approx. 1400–700 years BP) and alluvial (approx. 250 years BP to present) were determined. Sediment samples were collected and analysed for grain size and Atterberg limits. Suitable sediments were then selected to determine the optimal brick materials and their technical properties. Similarly, control bricks were prepared with ceramic pastes of local industries. The results show that the quality of the former is similar or superior to that of the latter. The initial estimates of the available resource indicate a long-term supply for the industry. Estimates of the current sedimentation rates indicate that resource renewal might occur at a rate comparable to current consumption. The sedimentation rates have increased significantly in the past two centuries – more so in the past few decades (the Anthropocene?) – with increasing human modification of geomorphic processes. If the results presented here are confirmed, a highly sustainable model can be implemented in the brick industry.
Dissolution of kaolinites and accumulation of iron oxides in lateritic-ferruginous nodules: mineralogical and microstructural transformations
In-situ geochemical and structural microanalysis of non-disturbed samples of laterite and mineralogical identifications of microsamples demonstrate an orderly succession of mineralogical and structural transformations. These transformations result in the formation of Fe-nodules. They start from a micaceous phase whose micropores are occupied by hematite. Because the source of iron is external to micas this hematite corresponds to an absolute accumulation (in the meaning of Brewer, 1964). The following transformations constitute a succession of three mineral phases corresponding to relative accumulations with the removal of some components and in-situ reutilization of residual materials. 
 
(1) Phase of Fe-kaolinite accumulation during which the structures inherited from micas are preserved. 
 
(2) Phase of Al-hematite accumulation resulting from a dissolution of Fe-kaolinite, with development of pedoplasma and vesicular porosity. 
 
(3) Phase of accumulation of more or less aluminous goethite which ultimately results in the crystallization of geodes at the borders of voids.