Vincent Laurent ONANA

2026Journal article

Assessment of CBR of granite-derived lateritic gravels using machine-learning models with derived parameters

Willy Passy Mvindi Mvindi, Aloys Thierry Ndzié Mvindi, Hervé Nyassa Ohandja, Ghislain Nguentchou Tchanfa, Danielle Léa Mebouinz, Sylvie Désirée Noa Tang and 1 more

Arabian Journal of Geosciences

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2026Journal articleOpen access

Laboratory-to-field geotechnical suitability assessment of granular lateritic materials-crushed rock aggregate mixture for tropical pavements

Arnaud Ngo’o Ze, Jean Francis Lobe Bille, Hervé Nyassa Ohandja, Hermann Dimitri NgeuadjeuNgandou, Benjamin Atanne, Aloys Thierry Ndzié Mvindi and 1 more

Discover Civil Engineering

Granular lateritic materials (GLM), widely used in tropical regions for their availability and low cost, often exhibit high variability and inadequate bearing capacity to satisfy pavement design requirements. Nevertheless, their local abundance makes them a cost-effective option when properly improved. This study evaluates the suitability and structural performance of a granular lateritic materials–crushed rock aggregates mixture for pavement layers through laboratory characterization and in-situ measurements. A 75/25 mixture of GLM and crushed rock aggregates (CRA) was formulated and tested. Laboratory investigations included compaction, California Bearing Ratio (CBR), Micro-Deval, and Los Angeles abrasion (LAA) tests, while field performance was assessed using in-situ compaction control and deflection measurements. Results show that GLM are suitable for subbase applications (MDD = 2.094 g/cm³; CBR = 36%), whereas CRA meets base layer requirements with high mechanical resistance (Micro-Deval < 15; LAA < 45; CBR ≥ 60%). The combined material exhibited good homogeneity after nine mixing cycles. Field implementation achieved compaction degrees ≥ 98 ± 2% and low characteristic deflection (D90 ≈ 80/100 mm), indicating adequate stiffness under traffic loading. Differences between laboratory and field values remained limited (ΔMDD ≈ 0.043 g/cm³; ΔCBR ≈ 8%), confirming the reliability of the proposed mixture. These findings demonstrate that a properly designed GLM–CRA mixture provides a durable, cost-effective, and sustainable alternative for tropical pavements, promoting the efficient use of locally available materials.

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2025Journal articleOpen access

Enhancement of geotechnical properties of lateritic gravels from metamorphic rocks in Cameroon with quicklime to improve road construction material quality

Arnaud Ngo’o Ze, Roger Firmin Donald Ntouala, Jean Francis Lobe Bille, Christophe Enock Embom, Vincent Laurent Onana, Robert Medjo Eko and 1 more

Discover Civil Engineering

Lateritic gravels are commonly used in road construction due to their favourable geotechnical properties, which can be enhanced with additives like quicklime. This study conducted geological, microstructural, and geotechnical analyses on medium-grade metamorphic rock-derived lateritic gravels (MS-DLG) and low-grade metamorphic rock-derived lateritic gravels (CS-DLG) to evaluate the impact of the genesis of lateritic gravels and quicklime addition on their geotechnical characteristics for road construction purposes. Pavement design using these materials was evaluated with Alizé III software. The results indicated that both materials are primarily composed of non-swelling minerals. CS-DLG exhibited higher plasticity (Plasticity Index, PI = 34%), a lower California Bearing Ratio (CBR = 42%), and greater compressive strength (UCS = 1.75 MPa) compared to MS-DLG, which had a PI of 27%, a CBR of 49%, and a UCS of 1.45 MPa. Despite silica/sesquioxides ratios favoring base layer applications, both materials can effectively serve as sub-base layers for pavements designed for all traffic volumes. After 7 days of curing, MS-DLG modified with 2 to 4% quicklime showed improved compaction and suitability for base layers, achieving a CBR exceeding 160%, while CS-DLG remained below this threshold. Both materials were found suitable for semi-rigid pavement structures supporting T2 traffic. For T3 traffic, MS-DLG with 2 to 4% quicklime met acceptable standards, while CS-DLG required a higher proportion of 4 to 6% quicklime for similar performance. Thus, quicklime-modified MS-DLG is more suitable for road construction than CS-DLG.

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2024Journal articleOpen access

Assessment of crushed rock aggregates addition to granular lateritic materials in sub-Saharan extensive urbanization context (Yaoundé Cameroon) for road construction purposes

Aloys Thierry Ndzié Mvindi, Jean Francis Lobe Bille, Arnaud Ngo’o Ze, Christophe Enock Embom, Emmanuel Tsoyi À Koung, Michèle Stella Ngono Mbenti Emvana and 1 more

Discover Civil Engineering

Abstract Granular lateritic materials (GLM) suitability for road construction after the addition of crushed rock aggregates (CRA) in the sub-Saharan extensive urbanization context was evaluated. The urbanization rate was made by using Landsat7 and Landsat8 radar images. The studied materials were subject to petrographic description and geotechnical analysis. The urbanized surface in the Yaoundé area increased by 41.88% from 2004 to 2020. The studied rock are gneisses composed of quartz, garnet, biotite, pyroxene, and feldspars. The gneisses obtained CRA have fines content of less than 10%, maximum dry density value of more than 2.00 g/cm 3 , good bearing capacity (CBR = 88%), and excellent mechanical characteristics (Los Angeles < 40%). This recommend their use as base course for low to medium volume traffic pavements. Gneisses-derived GLM, less load-bearing (CBR = 39 to 42%) than CRA, have limited behaviour in road construction and can be used as sub-base for all volume traffics. Their use in base courses requires prior treatment. CRA addition to these GLM result in the plasticity index decrease and compaction parameters improvement. CBR values increase shows a perfect correlation (R 2 > 0.90) with the addition of CRA. Litho-stabilised materials (CBR ≥ 60%) can be used as base course for low-volume trafficked pavements. The addition of a CRA percentage greater than or equal to 25% is efficient for the optimization of their use. By reducing the amount of quarry aggregates, the improved material could be an economical alternative for road projects. This reduces and controls the haulage of materials within crowded urban area.

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2023Journal article

Mineralogical, geochemical, and geotechnical features of lateritic soils from termite mounds in two contrasting savannah areas (central Cameroon) as raw materials for brick making

Jean-Marc Kessoum Adamou, Roger Firmin Donald Ntouala, Estelle Ndome Effoudou, Marie Thérèse Nanga Bineli, Arnaud Ngo’o Ze, Gouban Hamadjida and 1 more

Heliyon

Termite mound soils (TMS) from humid savannah (HS) and dry savannah (DS) were evaluated as raw materials for compressed earth bricks (CEB) and fired bricks. Mineralogy and major elements geochemistry were performed by X-Ray Diffraction and X-Ray Fluorescence, respectively. Physico-mechanical characteristics of unfired and fired bricks at 900, 950, 1000, 1050, and 1100 °C after 7 curing days were evaluated. The studied TMS are made up of quartz, muscovite, anatase, kaolinite, hematite, and goethite. Illite is present in humid savannah while in DS gibbsite appears. These materials are rich in SiO 2 (58.96–61.79 wt%), Al 2 O 3 (16.93–18.78 wt%), and Fe 2 O 3 (7.41–10.33 wt%). The TMS from both HS and DS are sandy clay. Those from DS are silty (13%) than those from HS (<5.7%). Termite mound materials in DS are moderately plastic, while those in HS are highly plastic. Flexural strength values vary between 2.20 and 2.38 MPa for unfired bricks and between 2.41 and 3.26 MPa for fired bricks, respectively at 1100 and 1050 °C. Compressive strength values are ranged from 2.01 to 3.50 MPa for unfired bricks and 2.44 (1100 °C) to 11.08 MPa (1050 °C), with the best values in the DS area. Water absorption and linear shrinkage values are less than 25% and 5%, respectively, in the studied fired and unfired bricks. The physical and mechanical properties of unfired and fired bricks show that the studied TMS can be used for dense brick manufacturing. Materials from dry savannah exhibit better characteristics as construction materials due to relatively high weathering intensity leading to a spread-out particle size distribution, sintering, which promotes densification by reducing the porosity, and the conversion of metakaolinite into primary mullite upon temperature increase.

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2021Journal articleOpen access

Characteristics of Kaolinitic Raw Materials from the Lokoundje River (Kribi, Cameroon) for Ceramic Applications

Paul‐Désiré Ndjigui, Jean Aimé Mbey, Soureiyatou Fadil-Djenabou, Vincent Laurent Onana, Élie Constantin Bayiga, Christophe Enock Embom and 1 more

Applied Sciences

Eight kaolinitic materials from the Lokoundje River at Kribi were sampled and investigated for their physical, chemical, mineralogical and thermal characteristics in order to evaluate their potential suitability as raw materials in ceramics. The Lokoundje kaolinitic materials are clayey to silty clayey and are predominantly composed of kaolinite and quartz. The alkali (Na2O + K2O) content ranges between 1 and 2.5 wt.%; these low values do not favor vitrification of the ceramics but may be improved through flux amendment. The presence of goethite in some samples limits their utilization in white ceramics. The minerals content, color, metallic sound, cohesion, linear shrinkage, flexural strength, bulk density, water absorption and microstructure were determined. The XRD data reveal that kaolinite and goethite were transformed, respectively, into mullite and hematite. The colors of the fired products are characteristic of their mineral assemblage. The metallic sound is indicative of low vitrification which is confirmed by the presence of cracks due to low flux contents. The cohesion is good to very good, due to the abundance of kaolinite. The physicomechanical properties increase with temperature as well as densification. The geochemical data show that the Lokoundje alluvial clays are suitable for the manufacture of white stoneware tiles.

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2019Journal article

Mineralogy and preliminary assessment of the potential uses of alluvial clays from Batouri (Eastern-Cameroon)

Vincent Laurent Onana, Roger FD Ntouala, Jean Aimé Mbey, Arnaud Ngo’o Ze, Véronique Kamgang Kabeyene, Georges Emmanuel Ekodeck

Cerâmica

Abstract This study aimed at assessing the potential uses of alluvial clayey materials from Batouri. Their mineralogical, chemical and some physicomechanical characteristics are presented with some characteristics of fired bricks at 900, 950, 1000, 1050 and 1100 °C. The raw materials consisted of kaolinite, quartz, K-feldspars, anatase, and goethite. The phases formed during the firing process were mullite, quartz, hematite, and anatase. The linear shrinkage increased with firing temperature and remained <12% while water absorption decreased and remained <25%. Flexural strength increased due to the formation of dense phases (especially mullite) and, except for one sample, was at least 2 MPa. The SEM micrographs showed cracks that accounted for overall moderate mechanical responses. For firing above 1000 °C, the flexural strength of the three samples makes them usable as raw materials for roofing tiles manufacturing if the convenient amendment is done. The overall properties highlighted that all the studied materials are usable for brick manufacturing.

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2015Journal article

Caractérisation géotechnique des argiles alluviales de la vallée du Nyong (Cameroun)

Philippe Samba Assomo, Vincent Laurent Onana, Roger Firmin Ntouala, Ndome Priso, Armand Ekoumou Abomo, Véronique Beyala Kamgang Kabeyene

La region d’Akonolinga (Centre-Sud du Cameroun) appartient au bassin versant du Nyong. Des investigations y ont ete menees dans l’objectif de mettre en valeur la matiere premiere argileuse. Trois puits ont ete fonces dans la vallee du Nyong. Les echantillons recoltes ont permis la determination des parametres physiques et mineralogiques. Les resultats obtenus montrent que les parametres physiques sont influences par la presence de l’eau, la granulometrie est fine et confondue avec une consistance moyenne. La composition mineralogique revele que les argiles sont de type kaolinitique associees aux mineraux de quartz. Ces proprietes sont exploitables dans plusieurs domaines d’utilisabilite en geotechnique notamment en ceramique.

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2015Journal articleOpen access

Geotechnical, chemical and mineralogical evaluation of lateritic soils in humid tropical area (Mfou, Central-Cameroon): Implications for road construction

Brice Tchakam Kamtchueng, Vincent Laurent Onana, Wilson Y. Fantong, Akira Ueda, Roger FD Ntouala, Michel HD Wongolo and 4 more

International Journal of Geo-Engineering

Increased cost associated with the used of high quality materials have led to the need for local soils to be used in civil engineering works. In this paper, geo-chemical approaches coupled with conventional geotechnical techniques has been used to investigate vertical and lateral peculiar engineering index properties (EIP) of micaschist derived soils from Mfou, Central-Cameroon for their uses in road construction. The X-ray diffraction (XRD) analysis conducted on the soils indicated the absence of swelling clays. The main mineral phases were quartz, kaolinite, goethite, magnetite and chlorite. Geo-chemical results show that the investigated soils are “true laterites” made up of 41 wt.% of Fe 2 O 3 , 35 wt.% of SiO 2 , 21 wt.% of Al 2 O 3 , 1.17 wt.% of K 2 O and 0.05 wt.% of CaO. The results of geotechnical tests suggest that the upper clayey layer (UCL) and bottom mottled clayey layer (MCL) of the weathering profiles are poorly graded soils with EIP (fines particles (FP) of 61 and 63%, plasticity index (PI) of 30 and 31%, Californian Bearing Ratio (CBR) at 95% of 21 and 19%), which do not allow their use as raw materials in road construction whereas, intermediate nodular layer (INL) are well graded soils having EIP (FP of 26%, PI of 26% and CBR of 39%) that meet the specification required for sub-base materials for light traffic roads. The relatively high sesquioxyde present in these residual soils may act as cementing agent, thereby making the compacted soils relatively brittle. The direct shear test results show that the soils have high bearing capacity (cohesion of 62 Kpa and 27.2° angle of internal friction) making them to be useful in slope stability and shallow foundation design. The comparison of the studied soils with some lateritic soils in Sub-Saharan Africa indicates that i) genesis and climatic conditions are potentials factors that influence EIP of lateritic soils, ii) lateritic soils developed under semi-arid conditions exhibits EIP better than those developed under tropicaland sub-tropical conditions.

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2024Journal articleOpen access

Compressed earthen blocks using alluvial clays from Mbam: performance comparison using statistical analysis of cement vs heat-stabilized blocks

Christophe Enock Embom, Joël Fabrice Nyemb Bayamack, Arnaud Ngo’o Ze, Jacques Richard Mache, Jean Aimé Mbey, Vincent Laurent Onana

Clay Minerals

Abstract In the present study, a comparison of the thermal-insulation and mechanical performances of cement and heat-stabilized compressed earthen blocks (CEBs) was carried out to determine the factors which influence those properties. The raw clays used consist mainly of kaolinite, orthoclase and quartz. The mechanical strength increased with increase in both the amount of cement added and the firing temperature. However, the responses are better for cement-stabilized CEBs. The thermal insulation of fired bricks is greater than that of cement-stabilized bricks. This difference was related to the decrease in porosity and the formation of continuous-surface. The decrease in thermal insulation is mainly related to the formation of continuous-surface in cement-stabilized CEBs, whereas in the fired CEBs, it is due to the modification of pore volume. The mineralogy of the raw clays is statistically correlated to porosity and continuous-surface development that were confirmed as the main factors in the modification of both the mechanical strength and the thermal insulation. In cement-stabilization, the decrease in insulation is due to the development of continuous surface, while for heat-stabilization, mineral transformations during the sintering reduced continuous-surface formation and the insulation was controlled by both radiation and reduced surface conduction. The influence of the mineralogy of the raw material shows that clay content favours the insulation in fired bricks obtained at T ≤ 1000°C, while sand contents favour densification. In contrast, clay contents reduce the mechanical response of cement-stabilized material due to limited cement–clay interactions. In general, the mechanical response is more favourable in cement stabilization, while thermal insulation is better in fired bricks.

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2024Journal article

Influence of mineralogical and geochemical multi-parameters on the geotechnical properties of gneiss-derived lateritic gravels from an equatorial zone, center Cameroon

Aloys Thierry Ndzié Mvindi, Lise Carole Okomo Atouba, Marie Thérèse Nanga Bineli, Willy Passy Mvindi Mvindi, Ghislain Nguentchou Tchanfa, Vincent Laurent Onana and 1 more

Arabian Journal of Geosciences

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2024Journal articleOpen access

Mineralogical, geochemical, and physico-mechanical features of Bidzar (North Cameroon) termite mound materials and its suitability in producing fired bricks with marble powder additive

Roger Firmin Donald Ntouala, Brondon Ebeedom Ndjankoum, Estelle Ndome-Priso, Marie Therese Nanga Binel, Vincent Laurent Onana, Georges Emmanuel Ekodeck

Journal of the Cameroon academy of sciences

Les matériaux de termitières de Bidzar (Nord Cameroun) ont été caractérisés pour une potentielle utilisation comme matériau de construction. Pour atténuer le problème environnemental causé par l’exploitation du marbre de Bidzar, ce dernier a été utilisée comme additif (0, 5, 10, 15 et 20%) avant cuisson à 900, 1000, 1100 et 1200°C. Les matériaux de termitières sont composés de quartz, illite- smectite, vermiculite, chlorite, muscovite, calcite, hématite, et anatase avec pour principaux oxydes SiO2 , Al2O3 , et Fe2O3 . Ce sont des argiles sableuses et des argiles très sableuses dont la granulométrie est indiquée pour les produits creux, les tuiles et les briques. Certaines briques montrent des gonflements après cuisson jusqu’à 1100°C pendant que les autres présentent des retraits à la cuisson. Les autres caractéristiques des briques cuites sont : densité apparente (1,60–1,96 g/cm3 ), porosité (19,39–34,41%), absorption d’eau (10,41–21,44%), résistance à la flexion (1,25–5,64 MPa) et résistance à la compression (2,89–18,76 MPa). L’ajout de marbre couplé à la présence de matière organique (4,04–5,35%) augmente l’absorption d’eau tout en réduisant le retrait linéaire et la résistance mécanique à cause de la transformation de CaCO3 durant la cuisson qui entraîne la création d’une porosité secondaire. Ces caractéristiques physico- mécaniques répondent néanmoins aux standards des matériaux de construction. Termite mound materials (TMM) from Bidzar (North Cameroon) were characterized for their potential use as raw materials for the fired brick industry. To alleviate the environmental problem caused by the exploitation of the Bidzar marble, marble powder (0, 5, 10, 15, and 20 wt%) has been used as an additive in the formulation of bricks before firing at 900, 1000, 1100, and 1200°C. The TMM are made up of quartz, illite-smectite vermiculite, chlorite, muscovite, calcite, hematite, and anatase, with SiO2 , Al2O3 , and Fe2O3 being the main oxides. These materials are sandy clays or strongly sandy clays, which can be used for the manufacture of hollow products, roofing tiles, and masonry bricks. Some studied materials exhibit expansion up to 1100°C, while others show shrinkage at all studied temperatures. The varied characteristics of fired bricks are bulk density (1.60–1.96 g/cm3 ), apparent porosity (19.39– 34.41%), water absorption (10.41– 21.44%), flexural strength (1.25–5.64 MPa), and compressive strength (2.89–18.76 MPa). The addition of marble powder coupled with the presence of organic matter (4.04– 5.35%) increases the water absorption while decreasing the linear shrinkage, flexural strength, and compressive strength of bricks due to the transformation of CaCO3 during firing, which leads to the creation of secondary porosity. Nevertheless, these physico-mechanical characteristics meet the standards of construction materials.

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2024Journal article

Potentiality of some lateritic clayey material from Meiganga as raw material in fired bricks making

Michele Stella Ngono Mbenti, Roger Firmin Donald Ntouala, Cyriaque Rodrigue Kaze, Marie Thérèse Nanga Bineli, Arnaud Ngo’o Ze, Vincent Laurent Onana

Open Ceramics

The Meiganga lateritic clays and termite mounds were characterized for their use as construction materials. The six collected samples were subjected to mineralogical, geochemical, and physico-mechanical tests. Quartz, kaolinite, hematite, goethite, gibbsite, muscovite, and anatase are the main minerals in raw materials, while after firing at 1050 °C, mullite is formed. The SiO 2 /Al 2 O 3 ratio greater than 1 indicates a high SiO 2 content, which is consistent with the presence of quartz as an associate mineral to kaolinite. Considering linear shrinkage globally less than 5 % and flexural and compressive strengths greater than 2 and 7 MPa, respectively, four clay materials are suitable to produce bricks at all the studied temperatures, whereas two others only after firing at 1050 °C. As the studied characteristics do not depend on the nature of the material, exploring termite mound material in the Meiganga area would provide additional good-quality material to make up for any deficit that might arise.

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2022Journal article

Mineralogy, geochemistry, and physico-mechanical characterization of basalts, granites, and alluvial sands from Sanaga River (Cameroon): Potential use as construction materials

Marie Thérèse Nanga Bineli, Aloys Thierry Ndzié Mvindi, Estelle Ndome Effoudou‐Priso, Yves Robert Bikoy, Hervé Nyassa Ohandja, Vincent Laurent Onana and 1 more

Arabian Journal of Geosciences

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2021Journal articleOpen access

Chemical weathering intensity and rare earth elements release from a chlorite schist profile in a humid tropical area, Bengbis, Southern Cameroon

Vincent Laurent Onana, Estelle Ndome Effoudou, Sylvie Désirée Noa Tang, Véronique Kamgang Kabeyene, Georges Emmanuel Ekodeck

Journal of the Cameroon academy of sciences

RésuméUn profil d’altération développé sur chloritoschistes de la zone de Bengbis (Sud Cameroun) a été choisi pour quantifier l’intensité de l’altération et comprendre le comportement des terres rares. Les valeurs de l’indice d’altération mafique combinées aux diagrammes ternaires du système Al – Fe – Mg – Ca – Na – K montrent que l’hydrolyse des feldspaths est proportionnelle à celle des minéraux mafiques (pertes en Mg), bien que l’hydrolyse des plagioclases (Ca, Na) soit plus intense que celle des minéraux ferromagnésiens. Les matériaux d’altération étudiés sont localisés dans le domaine de la kaolinitisation, à l’exception des matériaux nodulaires qui sont légèrement latritiss. La modification du comportement du Mg dans le milieu d’altération s’exprime par les faibles valeurs du rapport Ca/Mg. Le potassium et Be sont lessivés dans le sol en association avec Mg. L’ordre de mobilité des éléments dans l’environnement d’altération étudié est : Ca ≈ Na > Fe2+ ≈ Sr > Mg ≈ Co > Mn > Li > Ba > Rb > P > Cd > Ni > Si > Be > K > Sn. Les enrichissements en K, Cs et Be dans les saprolites sont liés à la présence d’illite. L’accumulation en Cs dans le sol est due à la présence de kaolinite. Le système le plus stable dans le milieu d’altération étudié est : Hf – Nb – W – U. Les saprolites, les matériaux nodulaires et les matériaux argileux meubles superficiels sont appauvris en terres rares par rapport à la roche mère. Les terres rares présentent trois types de comportement le long du profil d’altération, comme l’indiquent les valeurs du rapport (La/Yb)N ((La/Yb)N < 1, (La/Yb)N ~ 1 et (La/Yb)N > 1). Les terres rares légères et les terres rares moyennes s’accumulent dans les matériaux d’altération pour des valeurs de pH comprises entre 5,5 et 5,6 et pour celles de Eh variant entre +60 et +70mV. L’ordre de mobilité de ces éléments dans ces matériaux est le suivant : terres rares moyennes > terres rares lourdes terres rares légères. Ce fait est contre-intuitif, car les terres lourdes sont plus mobiles dans les environnemenst supergènes que les terres rares légères. L’adsorption ou la co-précipitation de ces terres rares sur les oxydes de fer peut principalement contrôler la concentration de ces éléments dans le profil d’altération. Les faibles anomalies en Ce dans les matériaux d’altération de la zone de Bengbis, dues au changement de Ce3+ en Ce4+, sont probablement dues à la présence de faibles quantités de rhabdophane. Les matériaux d’altération étudiés présentent un fractionnement en Gd (Gd/Gd* ~0.70 – 0.84) dues à une intense lixiviation. Ce fait a rarement été signalé dans un environnement d’altération latéritique. Il semble qu’une partie de la distribution et de la remobilisation du gadolinium soit contrôlée par des minéraux mafiques dans les matériaux d’altération étudiés. La distribution et la mobilisation des terres rares sont donc contrôlées par (1) l’adsorption ou la coprécipitation dans les minéraux mafiques et Fe, (2) et légèrement par les minéraux contenant des terres rares tels que le rhabdophane, rencontrés dans les matériaux d’altération étudiés. Abstract An in situ weathering profile overlying chlorite schists in southern Cameroon was chosen to quantify chemical weathering intensity and to study the behaviour of rare earth elements (REE). Mafic index alteration values combined with the ternary diagrams of the Al – Fe – Mg – Ca – Na – K system show that the hydrolysis of feldspars is proportional to that of mafic minerals (losses in Mg), although the hydrolysis of the plagioclases (Ca, Na) is more intense than that of ferromagnesian minerals. The studied materials are localised in the domain of kaolinitisation, except for nodular materials which are slightly lateritised. The change in the behaviour of Mg in the weathering environment is expressed by the low values in Ca/Mg ratio. Potassium and Be are leached in the soil in association with Mg. The order of mobility of the elements in the weathering environment is: Ca ≈ Na > Fe2+ ≈ Sr > Mg ≈ Co > Mn > Li > Ba > Rb > P > Cd > Ni > Si > Be > K > Sn. The enrichments in K, Cs and Be in saprolites are linked to the presence of illite. Cesium accumulation in the soil is due to the presence of kaolinite. The most stable system is: Hf – Nb – W – U. Saprolites, nodular and loose clayey materials are depleted in REE relative to the parent rock. REE exhibit three types of behaviour along the Bengbis profile like indicated by (La/Yb)N ratio values ((La/Yb)N < 1, (La/Yb)N ~ 1 and (La/Yb)N > 1). Light REE and Middle REE accumulate in the weathering materials for pH values ranging between 5.5 and 5.6 and for those of Eh varying between +60 and +70mV. The order of mobility of REE in these horizons is: Middle REE > Heavy REE ≈ Light REE. This fact is counter-intuitive, because Heavy REE are more mobile in supergene environment than Light REE. Adsorption or co-precipitation of LREE onto Fe oxides mainly may control the concentration of these elements in the profile. Weak Ce anomalies in the weathering materials of Bengbis area, due to the change in Ce3+ to Ce4+, are probably due to the presence of low amounts in rhabdophane. The studied weathering materials show a fractionation in Gd (Gd/Gd* ~0.70 – 0.84) due to intense chemical leaching. This fact has been rarely reported in lateritic weathering environment. It appears that, a part of Gd distribution and remobilization is controlled by mafic minerals in the studied weathered materials. REE distribution and mobilization are thus controlled by (1) adsorption or co-precipitation in mafic and Fe minerals, (2) and slightly by REE-bearing minerals such as rhabdophane found in the studied weathering profile.

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2021Journal articleOpen access

DMSO Deintercalation in Kaolinite–DMSO Intercalate: Influence of Solution Polarity on Removal

Berenger ZOGO MFEGUE, Jean Aimé Mbey, Sandotin Lassina Coulıbaly, Vincent Laurent Onana, Paul‐Désiré Ndjigui

Journal of Composites Science

This study focused on the deintercalation of dimethyl sulfoxide (DMSO) from a kaolinite–DMSO complex in various solvents. The use of kaolinite as filler in polymer–clay composite generally faced the difficulty of kaolinite dispersion due to its high cohesion. For improved dispersion of kaolinite within a given matrix, previous intercalation of small polar molecules is usually done prior to its displacement during composite-making. The influence of the solvent polarity on the deintercalation in analyzed here to understand its role during the deintercalation process. The intercalation of the DMSO was done by solution-mixing and its displacement was done in distilled water, ethyl acetate, and acetone. The products of deintercalation were analyzed using Fourier transform infra-red (FTIR), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The weakening of the kaolinite cohesion after DMSO intercalation is demonstrated through the broadening of the diffraction peak associated with the kaolinite on XRD patterns. From FTIR spectra, the weakening is associated with the displacement to low wavenumbers of the Si–O or Al–O vibration bands within the kaolinite–DMSO complex. The kaolinite dehydroxylation temperatures from DSC show that the rate of DMSO displacement affects the ordering of the recovered kaolinite. The crystallite size of the kaolinite is reduced from the raw to the recovered kaolinite after DMSO displacement, indicating an exfoliation of the kaolinite. From these results, it is found that the removal of the DMSO from the kaolinite–DMSO complex is influenced by solvent polarity. The higher the polarity, the greater the removal of the DMSO from the complex. Solvent polarity affects the rate of DMSO displacement, which influences the ordering of the recovered kaolinite. It is suggested that solvent polarity can be used to control the removal rate of DMSO, which may be key to the dispersion of the kaolinite platelets.

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2018Other

Nature and Genesis of Vertisols and North Cameroon Management Experience: A Review

Primus Azinwi Tamfuh, Émile Temgoua, Vincent Laurent Onana, Pierre Wotchoko, Fritz Oben Tabi, Dieudonné Bitom

Journal of Geosciences and Geomatics

Vertisols are tropical soils that occur world-wide (335 million ha) with high agricultural and other engineering potentials. However, they are underutilized as most of their physical characteristics make management techniques difficult and highly localized. This paper aims to highlight the characteristics, genesis and management strategies of Vertisols for sustainable use. Two main types of Vertisols can be distinguished: topomorphic Vertisols with A(B)gC or difficult A(B)Cg profile and lithomorphic with A(B)C profile type. Vertisols generally show a dark colour, very high compacity, surficial desiccation cracks when dry, surface ponding when moist and large sub-surface slickensides. They contain at least 30% clay fraction, while smectite, cation exchange capacity and base saturation are very high. Lithomorphic Vertisols are developed on various parent rocks and topographic positions where weathering generates base-rich environments that promote smectite synthesis. The formation of topomorphic Vertisols is favoured by low landscape positions suitable for accumulation of basic cations. The latter cover very extensive surface areas of the globe mainly in tropical, semi-arid to (sub) humid and Mediterranean climates showing contrasting wet and dry seasons, while the former have limited geographical extensions and occur mainly in specific islands and volcanic regions. Swelling and shrinking upon wetting and drying is a major characteristic of Vertisols. Most of their properties and uses are dependent on shrink-swell behaviour. Micromorphologically, plasmic separations occur in all Vertisols especially in the middle part of the profile where shrink/swell is most pronounced. Most Vertisols fall under the A-7-5 and A-7-6 classes typical of inorganic clays of medium to very high plasticity designated as bad clays according to AASHTO. Vertisols present numerous interesting uses in the chemical industry, pharmaceutics, agronomy and environmental protection. Nevertheless, man-made structures on Vertisols are not advisable since large investments are needed to maintain and repair damaged infrastructure. In North Cameroon, vertisols cover about 1 200 000 hectares and agricultural management strategies are mainly tilted at moisture control, but also at fertility restoration.

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2016Journal article

Mineralogical, geochemical and geomechanical characterization of lateritic and alluvial clayey mixture products from Monatele - Ebebda, as building materials

Vincent Laurent Onana, Roger Firmin Donald Ntouala, Estelle Ndome Effoudou, Christelle Yollande Nguembou, Arnold Nguessi, Veronique Kamgang Kabayene

Journal of the Cameroon academy of sciences

This work focuses on the mineralogical and chemical analysis of two alluvial clays from the Sanaga River, four lateritic clays from Monatele and Ebebda regions in southern Cameroon and, on the physicomechanical characterization of these clayey mixtures. The exploitation of XRD patterns reveals that quartz, muscovite, kaolinite corundum and rutile are the main minerals in alluvial clays, associated with goethite, hematite and ilmenite in lateritic materials. The main oxides are SiO 2 , Al 2 O 3 and Fe 2 O 3 in lateritic clays. The low proportion of fluxing oxides (Na 2 O + K 2 O + CaO + MgO 2.0 MPa) in all the sites except for two mixtures at Monatele, for tiles (> 6.5 MPa) in, one site at Ebebda and for the specimens with 80 and 60 wt% lateritic clays in one site at Monatele at 950 and 1050°C. The linear shrinkage values are high, causing deformations and microcracking on the produced bricks which require an addition of degreasers in order to reduce their plasticity before being used as building materials. Keywords: Monatele-Ebebda (Centre Cameroon), lateritic and alluvial clays, mineralogy, geochemistry, geomechanical characterization

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2015Journal article

Geotechnical, mechanical and geological characterization of lateritic gravels of Boumpial (Cameroon) used in road construction

Vincent Laurent Onana, Apollinaire Nzabakurikiza, E E Ndome, B Likiby, Véronique Kabeyene Kamgang, Georges Emmanuel Ekodeck

Journal of the Cameroon academy of sciences

The present study deals with a geological, mechanical and geotechnical characterization of lateritic gravels developed on gneiss in the Boumpial region (East Cameroon). The raw materials description was done during the fieldwork. The collected samples were subjected to mechanical and geotechnical tests. The rock sample powder and lateritic gravels mineralogy were determined using optical microscopy and X-rays diffraction on the total fractions and the fine ones. The overall chemical compositions of major elements of lateritic gravels were determined by the use of X-fluorescence and titrimetry. The results obtained show that lateritic gravels of East Cameroon present: fines (18 wt.%), plasticity index (21%), CBR (72%), compressive strength (1.27 Mpa) and tensile strength of 0.08Mpa. The X-ray diffraction and the chemical analysis revealed 34 wt.% kaolinite, 24 wt.% of hematite, 13 wt.% of goethite, 11 wt.% of quartz, 10 wt.% of gibbsite and 1 wt.% of anatase. The silica/sesquioxides ratio (1.04) showed that the lateritic gravels is suitable for the sub-base course in road construction. By mixing 20 wt.% of the 5/20 rock fragment fraction (with LA< 60) and 80 wt.% of lateritic gravels (CBR = 92 %), the studied material can be employed for constructing foundations. Keywords: Lateritic gravels; Geotechnical and mechanical tests; Mineralogical and chemical analyses; Road construction; Cameroon

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Vincent Laurent ONANA

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