clayey material from bimbo (central africa republic (c.a.r)): … · clayey material from bimbo...

European Journal of Scientific Research ISSN 1450-216X / 1450-202X Vol. 149 No 4 July, 2018, pp. 385-400 http://www. europeanjournalofscientificresearch.com

Clayey Material from BIMBO (Central Africa Republic

(C.A.R)): Physicochemical, Mineralogical Characterization and

Technological Properties of Fired Products

Gonidanga Bruno Serge Corresponding Author, Laboratory of Applied Inorganic Chemistry

University de Yaounde 1, P.O. Box 812 Yaounde (Cameroon)

UNESCO Chair on Water Management, Lavoisier Hydrosciences Laboratory

University of Bangui, Faculty of Sciences, PO Box 908, Bangui (Central African Republic)

IRCER – Université de Limoges, UMR CNRS 7315

12 Rue Atlantis – 87068 LIMOGES Cedex Atlantis (France)

E-mail: [email protected]

Njoya Dayirou Laboratory of Applied Inorganic Chemistry



Lecomte-Nana Gisèle IRCER – Université de Limoges, UMR CNRS 7315

12 Rue Atlantis – 87068 LIMOGES Cedex Atlantis (France)


Elimbi Antoine Laboratory of Applied Inorganic Chemistry



Njopwouo Daniel Laboratory of Applied Inorganic Chemistry



Abstract

The mineralogical and physicochemical analyses of two clayey materials from Bimbo, a locality of the Ombella-M'Poko division in Central African Republic are reported together with the properties of their fired bricks at 900, 1000 and 1100 °C. The mineralogical assemblage from XRD is made of kaolinite, quartz, illite, goethite and anatase. Sample, named BIM-1, is kaolinite rich (61 %) the sample named BIM-2, is quartz rich (57.26 %). The thermal analysis (TGA/DTA and dilatometry) are agreeing with the mineralogy of both samples. Upon firing, the mineralogical analysis evidence the presence of mullite, hematite, cristobalite and titanium oxide. The maximum shrinkage for BIM-1 bricks, after firing at 1100 °C is 7 % while for BIM-2 it is almost zero at all firing temperatures. The water uptake for both samples is < 25 % at all firing temperature and this

386 Gonidanga Bruno Serge, Njoya Dayirou, Lecomte-Nana Gisèle, Elimbi Antoine and Njopwouo Daniel

low water uptake make these clays usable for fired bricks making. The flexural strength of BIM-1 is > 5 MPa as from 900 °C and make this sample usable for dense bricks making. Conversely, BIM-2, is usable as degreaser due to its high quartz content. Coupled SEM-EDS observations confirms the dense nature of BIM-1 fired bricks and low cohesion for BIM-2bricks.

Keyswords: Kaolinite; physicochemical analysis; fired bricks; Flexural strength; Mineralogy

1. Introduction

Clay materials are still of constant interest in scientific research due to their applications. These applications are associated to their structural properties and their chemical composition (Caillere et al, 1982a; Murray, 2000; Nyakairu et al, 2002; Njoya et al, 2012; Touogam et al, 2014; Ndjigui et al, 2016). In several countries, clay materials are of great importance in developing their building capacities and improving people life. Many books, scientific societies and research centers are established for the study and the valorization of clays. For instance Groupe Français des Argiles, EuropeanCeramic Center, American Ceramic Society, Cameroon Clay Group, Institut de Recherche sur les Céramiques.

In central Africa regiontraditional uses of clayey materials in housing are widely spread. However, a proper characterization of clay deposits is still needed.In central Africa Sub-region, available studies indicates thatkaolinite occurrences are prevalent in Cameroon and Chad as reported by Ekosse(2010).Hence, their presence in these neighboring countries is an indication that kaolinite deposits of interest may exist in Central Africa Republic(C.A.R). However, research dealing with deposit evaluation and characterization in C.A.R. are scare.In the available literature, the potentiality of a kaolinite clay ofBangui for water filtration ceramic membrane making and pollutants removal from water was evaluated(Dehou et al, 2012a; Dehou et al, 2012b; Dehou et al, 2012c; Bangoua et al, 2016).In the sub-region, numerous works are being carried out for the valorization of local clay materials in other to identify added-value applications in building and construction materials(Nkoumbou et al, 2009; Dicko et al, 2011; Moutou et al, 2012; Nzeugang et al, 2013; Fadil et al, 2015; Boulingui et al, 2015; Mache et al, 2015; Onana et al, 2016). Thus improving quality used of clay from C.A.R is needed for quality housing and improve people living conditions.

From 1963 to 1975, state company, named BRICERAM, was producing fired clays bricks using clayey materials from BIMBO. Some study (Auriol, 1963; Boullier, 1962), on the particle size distribution of samples collected on an area of about 120000 m2 before the installation of the company have localized sandy, fine andsilty clay at several points on the deposit. These material are still harvested for bricks manufacturing by the local population. These artisanal producers used traditional furnace with woods as heating sources and the firing temperature may reached600 °C in the best cases and this firing temperature may varied a lot(Dehou et al, 2012a).In such conditions, the end products arecertainly of low quality. The valorization of this clays command a better characterization in terms of physical, chemical and mineralogical properties evaluation in order to better design their processing for improve products manufacturing. Hence, the aim of this study is to characterized these clay materials and to study their firing properties for their improve use in ceramics products making.To this end, physicochemical, mineralogical, technological and microstructuralproperties of the fired products are examined in this study.

Clayey Material from BIMBO (Central Africa Republic (C.A.R)): Physicochemical, Mineralogical Characterization and Technological Properties of Fired Products 387 2. Materials and Experimental Techniques The clayey materials used are collected from Bimbo, a locality of the Ombella-M'Poko division, situated at about 8 km in the South-west of Bangui. This deposit altitude is 340 m and the GPS coordinates are as follow: 04°19’17” North latitude and 18°31’57” East longitude. The map of the study area is given in figure 1.

Figure 1: Location of the sampling area

Two samples named BIM-1 and BIM-2 were collected at 2 m depth form two wells (P1 and P2) distant of about 300 m. After air drying at ambient, the samples were manually ground in a porcelain mortar and sieved over a 100 µm mesh.

The materials are characterized using X-ray fluorescence, powder X-ray diffraction (XRD), thermal analyses (TGA-DTG and dilatometry) and infra-red spectroscopy.

The chemical analysis is done using a PANalyticalZetium spectrometer. The samples are fused in Lithium metaborate prior to analysis; the loss on ignition is obtained from the weighing at 105 °C and 1050 °C.

X-ray diffraction is obtained using a Bruker D8 Advance diffractometeroperating with a copper radiation (CuKα = 1.5406 Å). The pattern are obtained with two theta angular scanning from 5° to 60°. Thermal analysis is done on a coupled TGA-DTA device NETZSCH STA 420 (CD), operating under air at a heating rate of 10 °C/min. The reference material is a kaolin sample fired at 1500 °C and the mass used for eachtest was about 25 mg.

Infra-red spectra are acquired on sample powder, usingBrukerSpectro Alpha equipment, from 400 cm-1 to 4000 cm-1.

For dilatometric analysis, cylindrical test samples having dimension 10x10 mm are obtained using about 2 g of sample that is pressed vertically at 30 MPa using a hydraulic press SPECAC. The dilatometric data are recorded using a Setaram TMA SetsysEvo equipment operating under air and at heating rate of 5 °C/min.

For the testing of fired samples, two types of test samples are made. Cylindrical samples 10x10 mm obtained as previously described are used for physical properties including open porosity, apparent density and water adsorption. The linear shrinkage upon firing and flexural strength are obtained using parallelepiped test samples. For this samples 60 g of the clay material are pressed under 15 MPa in a


parallelepiped mold. The samples are dried for 24 hours in an oven at 90 °C before being fired at temperature of900 °C, 1000 °C and 1100 °C using a programmable muffle furnaces CERADEL and NABERTHERM respectively for cylindrical and parallelepiped test samples. For the CERADEL operations,the heating and the cooling rates were respectively 5 °C/min and 10 °C/min. For the NABERTHERM furnace, the heating rate is 5 °C/min and the samples are left for a stay of two (02) hours at the final temperature before being furnace cooled to ambient. For each test five (05) samples are used and the means of measurements is reported. The norms used for the reported properties are NF EN ISO 10545-3, 1997-12 and NF EN ISO 10545-4, 2014-10.

The scanning electron microscopic (SEM) observations are carried out on a FEI-QUANTA FEG ESEM 450 equipment operating under at 15 kV. The micrograph are obtained on fired products after a metallization with platinum for improvesurface electrons conduction. 3. Results and Discussions 3.1. Raw Material Characterization

3.1.1. Chemical Compositions and X-Rays Diffraction The chemical compositions of the samples are reported in table 1. Table 1: Chemical composition of BIM-1 and BIM-2

SiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O TiO2 P2O5 NiO LOI 1050°C Total SiO2/Al2O3

BIM-1 50.20 25.42 09.33 <l.d 0.38 0.07 0.08 01.0 02.03 0.06 0.02 11.24 99.83 01.97 BIM-2 72.47 12.51 05.62 <l.d 0.31 0.14 0.12 0.92 01.50 0.05 <l.d 06.18 99.84 05.79

d.l : detection limit

The loss on ignition (LOI) of BIM-2 is lower than that of BIM-2.For BIM-1, the LOI is coherent with reported LOI for kaolinite clay (13 to 15%) (Abba Touré et al, 2001). For BIM-2, the low value of the LOI is associated to poor content is clay minerals and high sand content. The silicon oxide content is > 70 % for BIM-2 which lead to a high value of the molar ration SiO2/Al2O3 (5.79%). This high value is indicative of the presence of free silica (quartz and /or amorphous silica) in this sample. The content in Al2O3 is associated to clay and from this, it appear that BIM-1 is clay richer that BIM-2. The presence of clay is of interest for fired brick making (Blanchart, 2014). From the alumina oxide content, it may be assumed that better fired products may be elaborated from BIM-1. The content in iron oxide (9.33 % in BIM-1 and 5.62 % BIM-2) indicated that the fired products will probably exhibit a reddish color. Also the titanium oxide contents (< 3 %), although low will contribute to the product coloration. The contents in alkali oxide (MgO, CaO, K2O, Na2O), associated to feldspars, are very low and this could lead to poor vitrificationof the fired products.

From the XRD patterns (figure 2), it was found that Bimbo material are made of kaolinite, illite, quartz with accessory goethite and anatase.

This mineralogical assemblage is coherent with the chemical analysis.

Clayey Material from BIMBO (Central Africa Republic (C.A.R)): Physicochemical, Mineralogical Characterization and Technological Properties of Fired Products 389

Figure 2: X-ray patterns of the clayey materials BIM1 and BIM1

K : Kaolinite ; I : Illite ; Q: quartz; G : Goethite; A : Anatase 3.1.2. Infrared Spectroscopy On the infrared spectra presented in figure 3, the similarity amongst the spectra is coherent with the mineralogical assemblage which is the same for both samples.

Figure 3: FTIR spectra of the Bimbo materials: (a) global spectra and (b) zooming on the O─H stretching

35903610363036503670369037103730

36

96

36

48 3

62

1

36

67

(b)

(a)

400900140019002400290034003900

Ab

so

rba

nce

(a

.u.)

wavelength (cm-1)

BIM2

BIM1

36

96

362

1364

8

69

9

1626

78

391

1100

0

109

9

53

14

26 415

67

4


The characteristic O─H vibration band for kaolinite are clearly observed.A zooming (figure 3b) on this O─H stretching domain, revealed a poorly crystalline kaolinite because of the poor development of the bands at 3667 cm-1.The bands at 3696 cm-1 is associated to the surface in-phase stretching vibrations and at 3650 cm-1 and 3667 cm-1, the surface O─H out of phase stretching bands are observed. The inner O-H stretching is observed at 3621 cm-1. The band at 1626 cm-1 is associated to deformation vibrations of adsorbed water molecules (Famer, 1974; Fernandez-Jimenez et al, 2008; Panda et al, 2010). The stretching vibration of Si─O bonds are observed at 1099cm-1. The bandat1000 cm-1is assigned to theSi─O─Si skeleton asymmetric strectching. These bands are associated both to the aluminosilicates and the quartz within the samples. The deformations vibration of O─H associated to (Al─OH bonds) are observed at 911 cm-1(San Cristobal et al, 2010). The ─OH (Al─OH) translational vibration are observed at 783 cm-1.The stretching bands of Si─O in quartz are also observable at 699 cm−1 and 674 cm−1(Qtaitat et al, 2005).The bands at 674 cm-1is better developed in BIM-2 spectra due to its sandy nature. The bands 531 cm-1, 426 cm-1 and 415 cm-1are assigned to the deformations vibration of both Si─O─Siand Si─O─Al skeleton.The bands at 783 cm-1 associated to that at 3620 cm-

1, may account for the illite content in these samples (Petit et al, 1995). The infrared analysis was coherent with the mineralogical assemblage deduced from XRD (figure 2). 3.1.3. Differential Thermal and Thermogravimetric Analysis The TGA/DTA curves presented in figure 4 are almost similar.

Figure 4: DTA-TGA curves of BIM-1 and BIM-2

The peaks on the DTA curves are characteristic of kaolinite clay(Wilson, 1996). The first mass loss associated to the endothermic peak at 61°C (BIM-1) and 79 °C (BIM-2), on the DTA curves,was associated to the release of water moisture (physical adsorbed water). The dehydroxylation of the kaolinite wasregistered between 460 °C and 600 °C (see the TGA curves on figure 3) with a maximum dehydroxylationtemperature from DTA at 500 °C for BIM-1 and 507 °C for BIM-2. The kaolinite dehydroxylation result in the formation of metakaolinite as shown in equation (1) below:

Si2O5Al2(OH)4 Si2Al2O7 + 2H2O (1) The exothermic peaks at 969 °C (BIM-1) and 957 °C (BIM-2) is associated to the crystalline

reorganization of metakaolinite leading to the start formation of mullite through a spinel and free silica as illustrated in equation (2)

3[Si2Al2O7] 3Al2O3 .2SiO2 +4SiO2 (2) Also, itis observed on both DTA curves an endothermic peak at around 570 °C for both

samples that was attributed to the conversion of α quartz to β quartz. This peak is more intense on the BIM-2 DTA curve agreeing with the higher quartz content of this sample.

At around 300 °C for both samples, a weak endothermic peak (better observed on BIM-1) associated to the conversion of goethite into hematite (equation (3)) was registered (Gilbert et al, 2013;

Clayey Material from BIMBO (Central Africa Republic (C.A.R)): Physicochemical, Mineralogical Characterization and Technological Properties of Fired Products 391 Bonnet et al, 2001) which agree with the mineralogical identification from XRD of the presence of goethite within the samples.

2αFeO (OH) → α Fe2O3 + H2O (3) The mass loss from TGA curve during kaolinite dehydroxylation, is more important for BIM-1

in comparison to BIM-2. This observation is in line with the fact that BIM-1 is richer in clay mineral than BIM-2 (richer in quartz). 3.1.4. Mineralogical Quantification The mineralogical quantification was done using the equation (4) below. The calculation is based on the results of qualitative mineralogical identification ( obtained from XRD, FTIR and DSC-TG analyses) and the chemical composition (see table 1) of the samples(Yvon et al, 1982).

�(�) = � �� × �(�)�

� (4)

where: T(x):percentage of oxide of chemical element “x”; Mi:percentage of mineral “i” in sample containing chemical element “x”; Pi(x) :proportion of element “x” in mineral “i” (calculated from the ideal mineral formula). For the calculations, the following assumptions were done:

• The content in TiO2was attributed toanatase; • The Fe2O3 was used for goethite content determination; • K2O content was assigned to illite content based of the general formula

K(1+x)(Si3Al)O10Al(2-x)Mgx(OH)2. If tA is the percent oxide associated to cationA and MA the molar mass of this oxide, the number of mole mA the A oxide can be calculated as follow:

mA = tA / MA (5) From relation (5), the number of atomeNof cationA can be calculated knowing the number of

cationn per mole of oxide as follow: N = n*mA (6)

Associating (5) and (6) to the fact that the illiteformula in each sample, is such that : (1+x) / x = NK /NMg (7)

Using the chemical analysis of each samples (table 1), the illite molecular formula for each sample is found to be K1,8(Si3Al)O10Al1,2Mg0,8(OH)2and K1,65(Si3Al)O10Al1,35Mg0,65(OH)2 respectively for BIM-1 and BIM-2. From the amount of illite, the SiO2 and Al2O3from this mineral were deduced;

The remaining Al2O3 after illite content calculation was used to determine the Kaolinite content and from this, the amount of SiO2 associated to kaolinite was deduced;

The remaining SiO2 after subtracting the kaolinite and illite contents of SiO2, was assigned to quartz.

The undetermined species are obtained as the difference between the total chemical analysis and the total determined mineral composition.

The quantitative composition resulting from this calculation is given in table 2. Table 2: Mineralogical composition

Kaolinite Illite Quartz Goethite Anatase Total undetermined

BIM-1 61 5.05 19.67 10.38 2.03 98.13 1,70 BIM-2 28.08 5 57.26 6.26 1.5 98.1 1,74

From this table, it appears that BIM-1 is a kaolinite rich material with a content of 61.0 % while

BIM-2 kaolinite content is 28.1 %. The quartz content in (57.3 %)is higher thanin BIM-1 (19.7 %). The illite content for both samples is almost the same 5.0 % and 5.1 % respectively for BIM-1 and BIM-2.In general, these results are coherent with the previous conclusion from XRD, TGA-DTA and


Chemical composition. The Goethite content in BIM-1 (10.4 %) and in BIM-2 (6.3 %)is relatively low and make it possible to formulate white fired products as from 1000 °C. Also, this quantitative evaluation is coherent with previous works (Auriol, 1963; Boullier, 1962) in which BIM-1 and BIM-2 are respectively located in area of rich clay and sandy rich materials. 3.1.5. Thermo-Dilatometric Analysis The thermo-dilatometric analysis are illustrated on figure 5.

Figure 5: Dilatometric curves of BIM-1 and BIM-2

Both samples exhibit the behavior of phyllitic materials (Rollet et al, 1972; Caillere et al, 1989). The first bearing line is almost zerofor BIM-1and this is coherent withrich clay materials behavior (see (1) on figure 5).In the same temperature domain, on BIM-2 curve, an increase length, associated to sample dilatation, is observed. The first contraction (2) between 550 °C and 600 °C on BIM-1 and between 450 °C and 500 °C on BIM-2, correspond to an endodermic processes related the dehydroxylation of kaolinite which was converted into metakaolinite. However, on BIM-2, this contraction was enhanced due to the conversion of α-quartz into β-quartz (Figure 5). After the metakaolinite formation, on the BIM-2 curve, the conversion of α-quartz to β-quartz is clearly observable on both heating and cooling curves. The second change (3) between 900 °C and 950 °C, wasassociated to the structural reorganization of metakaolinite into a dense spinel which enhance the material densification (Caillere et al, 1963; Valette, 2015). The high densification denoted (4) at around 1050 °C (Figure 5), is attributed to the sintering of the clay phase. This phenomenon is more mark on BIM-1 sample as a result of its high clay content. After cooling the respective shrinkage for BIM-1 and BIM-2 are 11.5 % and 0.8 %. The higher shrinkage of BIM-1 was related to its high clay content (kaolinite + illite = 66 %) whereas low shrinkage of BIM-2 was related to its high quartz content (58 %) (See table 2). The dilatation of BIM-2 goes beyond 1100 °C while for BIM-1 dilatation was terminated as from 600 °C. No residual swelling is registered for both materials after cooling. 3.2. Ceramics Characterization

3.2.1. X-Ray Diffraction The XRD patterns of fired products are presented on Figures 6 and 7 respectively for BIM-1 and BIM-2.

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

-14

-12

-10

-8

-6

-4

-2

0

220 120 220 320 420 520 620 720 820 920 1020 1120 1220

∆L/L

o

∆L/L

o

Temperature (°C)

BIM1

BIM2

α−quatz β-Quartz

(1)

(2)

(3)

(4)


Figure 6: X-ray patterns of BIM1 fired product at 900 °C, 1000 °C and 1100 °C

Mu: Mullite; Q: quartz; H: Hematite; A : rutile ; C : Cristobalite

Figure 7: X-ray patterns of BIM1 fired product at 900 °C, 1000 °C and 1100 °C

Mu: Mullite; Q: quartz; H: Hematite; A : rutile ; C : Cristobalite

At 900 °C, the mineral assemblages is made of quartz, illite, anatase and hematite for both samples. The illite peaks disappeared for products fired at 1000 °C. For products fired at 1100 °C, in addition to quartz hematite and anatase, mullite peaks were observed (although with low intensity for BIM-2 base products) and cristobalite peaks were observed solely on BIM-1 based products.


3.2.2. Physical Properties The physical parameters of fired products are illustrated on figures 8. Figure 8: Physical properties of the fired bricks: (a) linear shrinkage; (b) apparent density; (c) open porosity

and (d) water absorption

This include linear shrinkage (figure 8a), apparent density (figure 8b),open porosity (figure 8c) and water absorption (figure 8d).

From 900 °C and 1100 °C, a moderate linear shrinkage was registered for BIM-1 based products. In the same temperature range, the linear shrinkage was almost zero for BIM-2 (figure 8a). At 1100 °C, the shrinkage of BIM-1 products was more significant but remain low. Given that shrinkage was associated to grain reorganization upon water release during sintering and vitreous phase formation that give rise to capillary diffusion which result in shrinkage, it is obvious that the low content of clay in BIM-2 clearly justified the almost absence of shrinkage. For BIM-1 fired products, the relative high content of clay justified the shrinkagealthough this remain low probably due to absence of vitrification which is justified by the low flux content from the chemical analysis (Table 1).

The change in apparent density (figure 8b) is associated to the mineral reorganization. Formation of more cohesive and dense mineral result in an increase of the density. Given that the main mineral changes are due to clay, one easily understand while the change of density is not much for BIM-2 and it is almost maximal(1.83 g/cm3) as from 1000 °C. The mullite formation in BIM-1 may account for the more sensitive density change from 1.67 g/cm3 at 900 °C to 2.03 g/cm3 at 1100 °C (figure 8b).

BIM-2 products exhibits a high porosity (figure 8c) which does not varied significantly upon temperature change. This poor variation is associated to quartz content of this sample for which it is evident that the grain cohesion is poor. For BIM-1 product, a significant change in porosity is observed

Clayey Material from BIMBO (Central Africa Republic (C.A.R)): Physicochemical, Mineralogical Characterization and Technological Properties of Fired Products 395 at 1100 °C, probably because of increase sintering which result in better grain cohesion that induce pores enclosure. However, absence of vitrification was also evidenced from the relatively high porosity in BIM-1 products (> 26 %) at all temperatures.

The water absorption (figure8d) is acceptable for fired product as from 1000 °C (< 20 %). However, the fact that the water absorption is relatively low for all products, although the porosity is high, can only be justified by the clay content. Clay content is the man caused of water uptake and its reorganization into mullite result in a decrease of the water uptake as observed for products fired at 1100 °C. The porosity in these products may only be made of quartz whole due to quartz grain contact which does not retained much water. 3.2.3. Mechanical Strength The flexural strength measurements of the fired bricks are presented on figure 9.

Figure 9: Flexural strength of the fired bricks

For BIM-1 and at temperature is >5MPa (Figure9). This high flexural strength is of interest for fired bricks making and it is associated to the clay content of this samples. The highest value(15.3 MPa) is registered at 1100 °C as a result of increased density upon sintering. For BIM-2 Samples, the flexural strength is almost zero up to 1000 °C (figure 9). A measurable value is reached at 1100 °C (4.2 MPa). This value remain low in comparison to BIM-1 based products as a result of the low contain in clay of sample BIM-2. An amendment in clay content of BIM-2 is a prerequisite for fired bricks making. 3.7. Microstructural Analysis SEM micrographs and EDS analyses of products fired at 1000 °C and 1100 °C are presented in figures 10 and 11.


Figure 10: SEM micrographs and EDS analyses of BIM1 and BIM2 fired samples at 1000 °C

Figure 11: SEM micrographs and EDS analyses of BIM1 and BIM2 fired samples at 1100 °C


For products fired at 1000 °C (figure 10) the surface appear denser for BIM-1 in comparison to BIM-2.The EDS analysis of grains is coherent withthe composition of kaolinite clay (A and B EDS spectra on figure 10) for BIM-1 and quartz (C and D point on figure 10) for BIM-2. The surface feature for BIM-2 exhibits grains and hole that are associated to quartz. The continuous phase due to clay sintering is more developed for BIM-1 which does not evidence much isolated grains as in BIM-2.

At 1100 °C, the densification is obviously more important in BIM-1 and as previously observed at 1000 °C.The EDS information revealed the samecomposition as previously. The surface aspect of fired product base on BIM-1 showsvitrifieddomains and it is in line with the reduce porosity at this temperature for BIM-1 (Figure8c). This vitreous formation induce pore enclosure which result in improve densification which is revealed by the high flexural strength registered (figure 9). For BIM-2 fired product, a slight flexural strength increase is registered (4.2MPa) due to the sintering of the clay in this sample (figure 9). However the low clay content limit the grain cohesion. Large free quartz grain are still observable (see H in figure 9). This low cohesion is responsible of the almost constant porosity 32 % and 31 % respectively at 1000 °C and 1100 °C for BIM-2 (figure 8c).

Mixture of BIM-1 and BIM-2 may be more appropriate for fired bricks making as the quartz content of BIM-2 may serve for dimensional controlled by inducing reduce shrinkage. The high clay content of BIM-1 is of interest for the brick densification and hence mechanical resistance (flexural and compression) due to grains sintering. For vitrified products making, amendment with fluxing agent is needed for both samples. 4. Conclusion The present study aim was to analyze the chemical, the mineralogical and the technological properties of clay from Bimbo (Central African Republic). To this end, Chemical analysis, XRD, TGA-DTA, Dilatometry, SEM-EDS, flexural strength measurement, water uptake, porosity and density measurements were done.

The mineralogical and chemical analyses revealed that the two sample study are mainly made of kaolinite, illite, quartz, goethite and illite. This composition is confirmed through the thermal analyses (TGA-DTG and Dilatometry). The sample denoted BIM-1 is kaolinite rich (61 %) and the one denoted BIM-2, is mainly made of sand (58 % quartz content). Fired product formulated from both samples were fired at 900 °C, 1000 °C and 1100 °C for technological properties evaluation. The fired products are reddish due to high iron content. BIM-1 fired product exhibit low porosity with high flexural strength indicating that this material is of interest for dense fired bricks making. The XRD analysis of the fired product revealed the formation of mullite and the conversion of free silica to cristobalite which enhance the density of the products. The Sample BIM-2, which high quartz content exhibits poor technological properties for used in fired brick making. However, due to its quartz content, the shrinkage upon firing is low and this sample may be used as an additive in BIM-1 for dimensional controlled of the fired bricks through the reduction of the shrinkage. Also, his sample, due to the thermal resistance of quartz, can be appropriate as filler for thermal isolation of wall. The SEM micrographs of the fired products confirmed the densification of BIM-1 based product as from 1000 °C with some verification as from 1100 °C. However, for vitreous products making an enrichment with fluxes is recommended. Acknowledgements The French Embassy in C.A.R is greatly acknowledged for the financial support to Mr. Bruno Serge GONIDANGA for a research stay at IRCER in Limoges-France.

The University of Bangui is acknowledge for the support during the various travels of Mr. GONIDANGA out of C.A.R.


The Local Materials Promotion Authority (MIPROMALO, Cameroon) is acknowledge for the technical assistance in bricks formulation and firing.

Dr MBEY Jean Aimé is acknowledged for fruitful discussion and assistance in the designing and the write-up of this article. References [1] Abba Touré A., Andji J. Y. Y., Sei J, Kra G., Njopwouo D, Minéralogie des argiles de

Gounioubé (Côte-d’Ivoire). Actes de la première conférence sur la valorisation des matériaux argileux au Cameroun, Yaoundé, 11 – 12 Avril 2001, pp. 57 - 69.

[2] Auriol M, Compte rendu des études granulométriques des argiles de CUGUINI (secteur de Bimbo), 1963.

[3] Bangoua B., Foto E., Allahdin O., Wartel M., Mabingui J and Boughriet A, Comparative spectroscopic and electrokinetic studies on methylene-blue adsorption on to sand and brik from Central African Republic. International Journal of Research in Engineering & Technology 4(7) (2016) 13-32.

[4] Blanchart P, Les céramiquessilicatées. Article Technique de l’Ingénieur, Université de Limoges. Ref : N4800 V1 du 10 Février 2014.

[5] Bonnet J. P., Gaillard J. M, Céramiques silicatées dans P. Boch : Matériaux et Processus céramiques, Hermès Sciences, 2001, p287.

[6] Boulingui J. E., Nkoumbou C., Njoya D., Thomas F., Yvon J, Characterisation of clays from Megafe and Mengono (Ne-Libreville, Gabon) for potential uses in fired products. Applied Clay

Science 115 (2015) 132-144. [7] Boullier R, Compte rendu des travaux de sondage à Bimbo, 1962. [8] Caillere S., Henin S., Rautereau M, Minéralogie des argiles 1, Structure et Propriétés physico-

chimiques, Ed. Masson, Paris, 1982a, 184p. [9] Caillere S., Henin S., Rautereau M, Les argiles. Ed. Septima, Paris, 1989. [10] Caillere S., Henin S., Rauterau M, Minéralogie des argiles. Ed Masson &Cie, 1963. [11] Dehou S-C., Wartel M., Recourt P., Revel B., Mabingui J., Montiel A and Boughriet A,

Physicochemical, crystalline and morphological characteristics of bricks used for ground waters purification in Bangui region (Central African Republic). Applied Clay Science 59-60 (2012)a 69-75.

[12] Dehou S-C., Wartel M., Recourt P., Revel B., Boughriet A, Acid treatment of crushed brick (from Central African Republic) and its ability (after FeOOH coating) to adsorb ferrous ions from aqueous solutions. Open Mater. Sci. J 6 (2012)b 50-59.

[13] Dehou S-C., Mabingui J., Lesven J., Wartel M., Boughriet A, Improvement of Fe(II)-adsorption capacity of FeOOH-coated brick in soulutions, and kinetics aspects. J. Water

Resour. Prot. 4 (2012)c 464-473. [14] Dicko M. L., Ekosse G. E., Ayonghe S. N and Ntasin E. E, Physical characterization of clayey

materials from tertiary volcanic cones in Limbé (Cameroon) for ceramic applications. Applied

Clay Science 51 (2011) 380-384. [15] Ekosse Georges-Evo E, Kaolin deposits and occurrences in Africa : Geology, mineralogy and

utilization. Applied Clay Science, 50 (2010) 212-236. [16] Fadil-Djenabou S., Ndjigui P. D., Mbey J. A, Mineralogical and physicochemical

characterisation of Ngaye alluvial clays (Northern Cameroun) and assessment of its suitability in ceramic product. Journal of Asian Ceramic Societies 3 (2015) 50-58.

[17] Famer V. C, The infrared spectra of minerals. Mineralogical society, London, 1974, 539p.

Clayey Material from BIMBO (Central Africa Republic (C.A.R)): Physicochemical, Mineralogical Characterization and Technological Properties of Fired Products 399 [18] Fernandez-Jimenez A., Monzo M., Vincent M., Barba A., Palomo A, Alkaline activation of

metakaolin-fly ash mixtures obtain of zeoceramics and zeocements. Microporous and

MesoporousMaterials 108 (2008) 41-49. [19] Gilbert F., Jean-Claude N., Guillaume B, Les céramiques industrielles : Propriétés, mise en

forme et applications. Dunod, Paris 2013. [20] Mache J. R., Signing P., Mbey J. A., Razafitianamaharavo A., Njopwouo D and Fagel N,

Mineralogical and Physico-chemical characteristics of Cameroonian smectitic clays treatment with weakly sulfuric acid. Clay Minerals 50 (2015) 649-661.

[21] Moutou J. M., Mbedi R., Elimbi A., Njopwouou D., Yvon J., Barres O and Ntékela H. R, Mineralogy and Thermal Behaviour of the Kaolinitic Clay of Loutété (Congo-Brazzaville). Research Journal of Environmental and Earth Sciences 4(3) (2012) 316-324.

[22] Murray H. H, Traditional and new application of kaolin, smectite and palygorskite : a general overview. Applied Clay Science 17 (2000) 207-221.

[23] Ndjigui P. D., Mbey J. A., NzeugangNzeukou A, Mineralogical, physical and mechanical features of ceramic products of the alluvial clastic clays from the Ngog-Lituba region, Southern Cameroon. Journal of Bulding Engineering 5 (2016) 151-157.

[24] NF EN ISO 10545-3, 1997-12 : Carreaux et dalles céramiques – Partie 3, Détermination de l’absorption d’eau, de la porosité ouverte, de la densité relative apparente et de la masse volumique globale.

[25] NF EN ISO 10545-4, 2014-10 : Carreaux et dalles céramiques, Détermination de la résistance à la flexion et de la force de rupture.

[26] Njoya D., Hajjaji M &Njopwouo D, Effects of some processing factors on technical properties of a clay-based ceramic material. Applied Clay Science 65-66 (2012) 106-113.

[27] Nkoumbou C., Njoya A., Grosbois C., Njopwouo D., Yvon J and Martin F, Kaolin from Mayoum (Western Cameroon) : Industrial suitability evaluation. Applied Clay Science 43 (2009) 118-124.

[28] Nyakairu G. W. A., Kurweil H., Koeberl C, Minalogical, geochemical and sedimentological characteristics of clay deposits from central Uganda and thier applications. Journal of African

Earth Sciences 35 (2002) 123-134. [29] NzeugangNzeukou A., Fagel N., Njoya A., BeyalaKamgang V., EkoMedjo R., ChinjeMelo U,

Mineralogy and Physico-chemical proporties of alluvial clays from Sanaga Valley (Center, Cameroun) : Suitability for ceramic application. Applied Clay Science 83-84 (2013) 238- 243.

[30] Onana V. L., Ntouala R. F. D., NdomeEffoudou E., Nguembou C. Y., Nguessi A., KamgangKabayene V, Mineralogical, geochemical and geomechanical characterization of lateritic and alluvial clayey mixture products from Monatele-Ebebda, as building materials. J.

Cameroon Acad. Sci. 13 (1&2) (2016) 23-38. [31] Panda A. K., Mishra B. G., Mishra D. K., Singh R. K, Effect of sulphuric acid treatment on the

physicochemical characteristic of kaolin clay. Colloids and surfaces: Physicochemical and

Engeening Aspects 363 (2010) 98-104. [32] Petit S., Robert J. L., Decarreau A., Besson G., Grausby O., Martin F, Apport des méthodes

spectrales à la caractérisation des phyllosilicates 2/1. Bull. Centre Rech. Explo. Prod. Elf.

Aquitaine, 19, [1], (1995) 119-147. [33] Qtaitat M. A & Al-Trawnesh I. N, Characterization of kaolinite of the Baten El-Ghoul

region/south Jordan by infrared spectroscopy. SpectrochimicaActa Part A:Molecular and

Bimolecular Spectroscopy 61 (2005) 1519-1523. [34] Rollet A., Bouaziz R, L’analysethermique, tome 2 – L’examen des processuschimiques, éd.

Gauthiers – Villas, Paris, 1972. [35] San Cristobal A. G., Castello R., Martin Luengo M. A., Vizcayno C, Zeolites prepared from

calcined and mechanically modified kaolin: A comparative study, Applied clay Science 49 (2010) 239-246.


[36] TouogamTouolak B and Tchangnwa Nya F, More value of Maroua Clay in the formulation of ceramic products (Terracotta, Earthenware, Stoneware, Porcelain). Advances in

MaterialsPhysics and Chemistry4 (2014) 284-299. [37] Valette S, Techniques de caractérisation des céramiques. Article Techniques de l’Ingénieur,

Université de Limoges, N4806 vol 1, 2015. [38] Wilson M. J, Clay mineralogy: spectroscopy and chemical determinative methods. Éd.

Chapman & Hall, London, 1996, 367p. [39] Yvon J., Lietard O., Cases J. M et Delon J. M, Mineralogie des argiles kaolinitiques des

Charentes. Bill. Mineral 105 (1982) 431-437.

clayey material from bimbo (central africa republic (c.a.r)): … · clayey material from bimbo...

Documents