Study of the pozzolanicity of two clays from Kindia (Guinea) with a view to their use in the formulation of hydraulic binder

Ce travail présente, dans un premier temps, les résultats d’essais de pouzzolanicité de deux variétés d’argile, codifiées respectivement ABD et ARD, prélevées à Débélé. Dans un second temps, les propriétés physiques des mortiers obtenus à partir de ces deux argiles par substitution du ciment au taux de 20 % sont présentées et discutés. Le comportement mécanique des mortiers manifeste des variations acceptables avec des masses volumiques apparentes comprises entre 1,800 et 2,090 g/cm3. Les résistances mécaniques restent inférieures à celle du mortier témoin pour les hybrides à base d’argiles brutes, mais celles des hybrides à base d’argiles calcinées sont supérieures à celle du mortier témoin au-delà du 28ème. Ces résultats attestent le caractère pouzzolanique des argiles de Débélé et constituent une contribution pour leur valorisation dans la formulation des liants hydrauliques.This work presents, firstly, the results of pozzolanicity tests on two varieties of clay, codified respectively ABD and ARD, taken at Débélé. In a second step, the physical properties of the mortars obtained from these two clays by substitution of cement at a rate of 20% are presented and discussed. The mechanical behaviour of the mortars shows acceptable variations with apparent densities between 1.800 and 2.090 g/cm3. The mechanical resistance is lower than that of the control mortar for hybrids based on raw clays, but those of hybrids based on calcined clays are higher than that of the control mortar beyond the 28th. These results attest to the pozzolanic character of the Débélé clays and constitute a contribution to their valorisation in the formulation of hydraulic binder

Etude de la pouzzolanicité de deux argiles de Kindia (Guinée) en vue de leur utilisation dans la formulation de liant hydraulique

This work presents, firstly, the results of pozzolanicity tests on two varieties of clay, codified respectively ABD and ARD, taken at Débélé. In a second step, the physical properties of the mortars obtained from these two clays by substitution of cement at a rate of 20% are presented and discussed. The mechanical behaviour of the mortars shows acceptable variations with apparent densities between 1.800 and 2.090 g/cm3. The mechanical resistance is lower than that of the control mortar for hybrids based on raw clays, but those of hybrids based on calcined clays are higher than that of the control mortar beyond the 28th. These results attest to the pozzolanic character of the Débélé clays and constitute a contribution to their valorisation in the formulation of hydraulic bindersCe travail présente, dans un premier temps, les résultats d’essais de pouzzolanicité de deux variétés d’argile, codifiées respectivement ABD et ARD, prélevées à Débélé. Dans un second temps, les propriétés physiques des mortiers obtenus à partir de ces deux argiles par substitution du ciment au taux de 20 % sont présentées et discutés. Le comportement mécanique des mortiers manifeste des variations acceptables avec des masses volumiques apparentes comprises entre 1,800 et 2,090 g/cm3. Les résistances mécaniques restent inférieures à celle du mortier témoin pour les hybrides à base d’argiles brutes, mais celles des hybrides à base d’argiles calcinées sont supérieures à celle du mortier témoin au-delà du 28ème. Ces résultats attestent le caractère pouzzolanique des argiles de Débélé et constituent une contribution pour leur valorisation dans la formulation des liants hydrauliques

Extraction of ferruginous compounds and gibbsite from kaolinic clay materials

Bull. Chem. Soc. Ethiop., 4(2), 105-113 (1990)

Étude de quelques matériaux argileux du site de Lembo (Cameroun) (minéralogie, comportement au frittage et analyse des propriétés d élasticité)

L étude de l aptitude de quelques matières premières argileuses prélevées sur le site de Lembo (Cameroun) pour la fabrication de produits céramiques de grande diffusion a constitué l objectif de cette thèse. Pour cela, leur composition minéralogique a été préalablement déterminée par recoupement des résultats issus de différentes techniques de caractérisation. L étude de l évolution en fonction de la température du module d Young de l échantillon présentant une densification par écoulement d un flux visqueux à T<1200C a ensuite été réalisée en y associant des hypothèses sur la distribution des phases présentes. La forte augmentation de ce module observée lorsque la proportion volumique de mullite croît de seulement 4,7% entre 1150 et 1200C a pu être reliée à un changement de connectivité des aiguilles de mullite et des grains de quartz, qui passent de l état d inclusions rigides isolées et noyées dans une matrice plus souple à un sous-réseau rigide percolant. La bonne tenue mécanique de cet échantillon après traitement thermique a ainsi été mise en évidence.The objective of this work was to study the ability of some clay raw materials from Lembo site (Cameroon) for the manufacture of wide diffusion ceramics. In this respect, their mineralogical composition has been determined by using different characterization techniques. The study of the evolution on heating of Young s modulus of the sample which undergoes densification by viscous flow at T<1200C has then been achieved by using hypotheses on phases distribution. The strong increase of this modulus observed when the mullite volume proportion increases of only 4.7% between 1150 and 1200C has been related to a microstructural transition: the connectivity of mullite needles and quartz grains changes from rigid isolated inclusions in a softer matrix to a rigid percolating subnetwork. The good mechanical strength of the sample after thermal treatment has been therefore brought to light.LIMOGES-BU Sciences (870852109) / SudocLIMOGES-ENSCI (870852305) / SudocSudocFranceF

[Properties of porous ceramics from two Cameroonian clays mixed with sawdust] : Elaboration de céramiques poreuses à base de sciure de bois et de deux argiles du Cameroun

International audienceSawdust was mixed with two clays in a weight ratio varying from 1 to 10 %. Both clays are kaolinitic, but one named MY45g contains a few quantity of fine quartz (9.4 wt. %) and the second denoted BEAC a larger quantity of large size quartz (27.2 wt. %). Samples were shaped and fired between 1200 and 1350°C. At 1000°C, sawdust is reduced to a very small quantity of ashes, containing only SiO2 and Al2O3 oxides. During sintering the densification rate increases with the amount of sawdust, up to 15 % (MY45g) and 3,5 % (BEAC). This phenomenon is due to the increase of inter-connected large pores within the volume, but also to the role of a 3D network of large grains especially with BEAC. The addition of sawdust to clays leads to porous and insulating quality products, without changing the maximum temperature in service. However, the amount of sawdust must stay below 5 wt. % to avoid the excessive reduction of the mechanical strength

Effect of Porogenic Agent Type and Firing Temperatures on Properties of Low-Cost Microfiltration Membranes from Kaolin

International audienc

Surface modification of smecticte clay induced by non-thermal gliding arc plasma at atmospheric pressure

Smectite clay from Sabga (west-Cameroon) was treated in aqueous suspension by gliding arc plasma to modify its surface properties. The evolution of the modifications was followed with the exposure time and post-discharge duration using Fourier transformed infra red spectroscopy and scanning electron microscopy. X-ray diffraction and nitrogen physisorption analyses were also performed to evaluate if both crystalline and textural properties of the material are affected by the treatment. The results obtained show that the plasma treatment causes the breakdown of structural bounds at the clay surface and induces the formation of new hydroxyl groups (Si–OH and Al–OH) on the clay edges. Crystallinity, sheet structure and textural properties are not significantly affected by the plasma treatment. However, it should be noted that an intensive treatment of the clay lowers the pH of the suspension, which subsequently induces an acid attack of the clay. In such case, the specific surface area of the clay increases. This study demonstrates that gliding arc plasma treatments can be used to activate clay minerals for environmental application

Talc as raw material for cementitious products formulation

International audienceThis study reports the characterization of a talc from Cameroon as a possible source material for cement formulation. To that end, the talc sample was characterized and mixed with a solution of sodium polyphosphate to formulate the cementitious products. Addition of magnesia (MgO) was done to analyze the effect of available MgO on the products. Fourier transform infrared, X-rays diffraction, linear shrinkage, compressive strength and scanning electron microscopy were used to analyze the products. The compressive strength increased with addition of MgO and the linear shrinkage decreased. All the analyses indicate that talc is a raw material of interest in cementitious products formulation; however, the inclusion of the MgO is a key factor for a better performance of the products