Particle size analysis, Atterberg limits, X-ray diffraction, X-ray fluorescence and firing tests were used to determine physico-chemical, mineralogical and technological characteristics of residual lateritic (K1M, Ma2) and alluvial (KB3, KG3) clays from Foumban (West-Cameroon). For technological properties, the samples were pressed and fired over a temperature range of 900 °C - 1200 °C to determine the open porosity, linear shrinkage, bulk density and compressive strength. Kaolinite (31% - 65%) and quartz (35% - 50%) are dominant in Foumban clays with accessory K-feldspar, plagioclase, illite, smectite, rutile, and goethite. But their proportion changes from one sample to another, having a significant effect on the behaviour of the clay materials: highest proportion of quartz (50%) in sample K1M; relative high feldspars (20%) and illite contents (10%) in KB3 and MA2; high smectite content in KG3 (up to 20%). Chemical analyses indicate high SiO2 (49% - 77%) and low Al2O3 (14% - 23%) contents in the four samples, with comparatively low contents of iron oxides (4% - 7% in samples KB3 and KG3, 2.5% in MA2 and ~1.5% in sample K1M). The particle size distribution of the alluvial clays (KG3 and KB3) differs considerably: 7% to 37% of clay fraction, 20% to 78% of silt, and 15% to 58% of sand, while residual clays (K1M and MA2) present on average 12% of clay, 51% of silt and 37% of sand. Two raw clays (KB3 and MA2) can be used for bricks/tiles production without beneficiation or addition. K1M requires some flux addition to decrease the sintering temperature while KG3 presents poor properties due to the combined occurrence of smectite and a high clayey fraction (37%). Such mineralogical composition is responsible for very high plasticity (PI: 50), high shrinkage (LS: 5% - 16%), low porosity (OP: up to 21%) and high flexural strength (FS: 16 - 23 N/mm2) above 1050 °C. This last clay is therefore less appropriate for bricks and roofing tiles production since degreasers must be added to the raw material.
Clays have been used in a wide range of ceramic products as a major component in most ceramic bodies [
In Foumban (West Cameroon), clay raw materials display a widespread distribution and they have been exploited for the traditional production of small-scale ceramic products (pottery, bricks). In particular, clay materials from the localities of Marom and Koutaba, located eastern and southern Foumban respectively, are both residual and alluvial [
Foumban raw clays can be divided into two groups based on field observations: homogeneous clayey laterite in the upper part of a laterite cover on interfluves (e.g. at Marom and Koutaba) and heterogeneous hydromorphic clayey material in the valley (e.g., at Koutaba) [
The raw clay samples were dried in an oven at 40˚C for 24 hours. They were characterized by XRD, chemical analyses (XRF), particles size distribution (PSD) and plasticity. Firing test including linear shrinkage, open porosity, dry bulk density and compressive strength were evaluated for fired press.
The X-ray diffraction (XRD) patterns were obtained with a Bruker D8-Avance Eco 1Kw diffractometer (Copper Kα radiance, α = 1.548 Å, V = 40 Kv, I = 25 mA)
Sample | Depth | Clays | Quartz | K-F | Plag. | Rut. | Goe. | Kao. | Illite | Smec. |
---|---|---|---|---|---|---|---|---|---|---|
K1M | 3 | 44 | 50 | - | - | - | 6 | 32 | 12 | - |
K1b1 | 0.1 | 44 | 56 | - | - | - | - | 44 | 28 | - |
K1b2 | 0.5 | 92 | 1 | 4 | - | - | 3 | 82 | 10 | - |
K1b3 | 1.2 | 42 | 54 | 4 | - | - | - | 32 | 13 | - |
K1b4 | 1.5 | 44 | 52 | - | - | - | 4 | 31 | 13 | - |
K1b5 | 1.6 | 44 | 55 | - | - | - | 1 | 32 | 12 | - |
K1b6 | 1.95 | 46 | 150 | - | - | - | 4 | 36 | 10 | - |
K1b7 | 2 | 41 | 57 | - | 2 | - | - | 30 | 10 | - |
K1b8 | 2.1 | 40 | 54 | - | 4 | - | 2 | 27 | 5 | - |
K1b9 | 2.4 | 20 | 75 | - | - | - | 5 | 14 | 16 | - |
K1b10 | 2.5 | 53 | 47 | - | - | - | - | 37 | 15 | - |
K1b11 | 2.8 | 46 | 54 | - | - | - | - | 31 | 28 | - |
MA2 | 5.2 | 48 | 32 | 15 | 5 | - | - | 31 | 14 | 3 |
MA21 | 0.4 | 60 | 15 | 11 | 13 | - | - | 45 | 12 | 3 |
MA22 | 0.6 | 45 | 33 | 20 | 3 | - | - | 24 | 17 | 4 |
MA23 | 2.5 | 28 | 50 | 19 | 3 | - | - | 16 | 11 | 1 |
MA24 | 0.6 | 26 | 44 | 26 | 4 | - | - | 16 | 8 | 2 |
MA25 | 0.4 | 63 | 26 | 7 | 4 | - | - | 39 | 21 | 3 |
KB3 | 5 | 50 | 32 | 13 | 3 | 2 | - | 40 | 6 | 4 |
KB31 | 0.9 | 47 | 42 | 7 | 4 | - | - | 33 | 10 | 3 |
KB32 | 1 | 56 | 39 | 5 | - | 2 | - | 45 | 10 | |
KB33 | 1 | 35 | 37 | 5 | 23 | 3 | - | 27 | 5 | 3 |
KB34 | 0.8 | 0 | 48 | 47 | 4 | - | - | 40 | 7 | 1 |
KB35 | 0.5 | 50 | 24 | 26 | - | 4 | - | 50 | - | - |
KB36 | 0.5 | 79 | 21 | - | - | 5 | - | 40 | 13 | 25 |
KG3 | 5.2 | 75 | 20 | 2 | - | 1 | 2 | 50 | 5 | 20 |
KG31 | 0.3 | 59 | 34 | 6 | - | - | - | 43 | 10 | 4 |
KG32 | 1.1 | 61 | 19 | - | - | 3 | 17 | 49 | 2 | 11 |
KG33 | 0.3 | 88 | 10 | - | - | - | 2 | 62 | 3 | 23 |
KG34 | 0.6 | 78 | 22 | - | - | - | - | |||
KG35 | 1.3 | 86 | 11 | 3 | - | - | - | |||
KG36 | 0.9 | 59 | 40 | 1 | - | - | - | 30 | 5 | 24 |
KG37 | 0.3 | 81 | 15 | 3 | - | 2 | - | 32 | 18 | 31 |
K-F = alkali feldspars; Plag = plagioclase; Rut = rutile; Goe = goethite; Kao = kaolinite; Sm = smectite.
with LynxeyeXe energy dispersive (one dimensional coupled 2θ/θ detector with 3.28) in the laboratory of “Argiles, Géochimie et Environnements sédimentaires (AGEs)” at the University of Liège, Belgium. The analyses were carried out on the non-oriented powder with grinded particles <250 μm (bulk material) and the oriented powder <2 μm (clay fraction) according to [
For firing test, homogeneous mixture pieces (24 × 23 × 25 mm) were obtained by uniaxial pressing of a clay powder (20 g) at (45,73 Mpa) with a Graseby-Specac apparatus at the Belgian Ceramic Research Center (BCRC), Mons-Belgium. The firing stage took place at the temperature 900˚C - 1200˚C, at the intervals of 50˚C. The high pressing loads in dry process tends to increase the bending strength and reduce the shrinkage of fired bodies [
XRD patterns of the investigated clays are characterized by the peaks of quartz and kaolinite (
Chemical analyses allowed a rapid classification of the studied clays. The high SiO2 (49% - 77%) and low Al2O3 (14% - 23%) contents, are in agreement with the proportion of kaolinite [
The grain-size distribution of raw materials for building clay products influences in particular the behavior of the material during the shaping and drying processes. Grain-size distribution also affects the microstructure and the mechanical properties of fired materials [
Sample name | ||||
---|---|---|---|---|
K1M | MA2 | KB3 | KG3 | |
Physical properties (%) | ||||
Clay | 12 | 22 | 78 | 37 |
Silt | 51 | 20 | 7 | 45 |
Sand | 37 | 58 | 15 | 18 |
Wl | 42 | 43.6 | 59 | 103.7 |
Wp | 34 | 26.5 | 32 | 53. 2 |
Ip | 8 | 17.1 | 27 | 50.5 |
Chemical composition (wt%) | ||||
SiO2 | 77.25 | 60.89 | 58.21 | 49.04 |
TiO2 | 0.16 | 1.3 | 3.04 | 1.72 |
Al2O3 | 14.67 | 20.16 | 22.28 | 22.75 |
Fe2O3 | 1.4 | 2.59 | 3.97 | 6.92 |
MnO | 0.01 | 0.01 | 0.02 | 0.02 |
MgO | 0.08 | 0.39 | 0.13 | 0.53 |
CaO | 0.06 | 0.63 | 0.18 | 0.46 |
Na2O | nd | 0.88 | 0 | 0 |
K2O | 1.08 | 4.64 | 1.29 | 0.74 |
P2O5 | 0.02 | 0.08 | 0.11 | 0.11 |
LOI | 5.2 | 8.42 | 10.78 | 17.71 |
(A + AT + Fe2O3) | 1.22 | 6.54 | 5.57 | 8.65 |
A = K2O + Na2O; AT = CaO + MgO.
78% of silt, and 15% to 58% of sand. The residual clays (K1M and MA2) present a less variable particle size distribution with on average 12% of clay, 51 of silt and 37% of sand. The raw clayey samples were plotted in the diagram of ideal particle size for bricks and tiles (
The plasticity of clay materials depends to its particle size distribution and mineralogy composition [
The results of open porosity, linear shrinkage, density and compressive strength as a function the firing temperature are presented in
Sample name | ||||
---|---|---|---|---|
K1M | MA2 | KB3 | KG3 | |
Temperature (˚C) | Linear shrinkage (%) | |||
900 | 1.6 | 1 | 2.8 | 12.1 |
950 | 2.3 | 1.1 | 4.3 | 8.2 |
1000 | 0.9 | 1.8 | 3.7 | 15.3 |
1050 | 0.7 | 4.2 | 3.6 | 17.1 |
1100 | 0.6 | 5.5 | 8.7 | 25 |
1150 | 0.6 | 10 | 12.6 | 37 |
1200 | 8 | 15.2 | 13.2 | 38.7 |
Open porosity (%) | ||||
900 | 41.4 | 40.2 | 40.1 | 40.8 |
950 | 41.3 | 40.95 | 40.1 | 42.8 |
1000 | 41.3 | 40.05 | 40.1 | 40.2 |
1050 | 41.6 | 38.4 | 40.4 | 41.2 |
1100 | 41.7 | 36.6 | 37.4 | 34.8 |
1150 | 41.7 | 33.9 | 33.4 | 21.9 |
1200 | 40.7 | 38.9 | 33.2 | 21 |
ρ (g/cm3) | ||||
900 | 1.523 | 1.562 | 1.593 | 1.496 |
950 | 1.531 | 1.543 | 1.602 | 1.421 |
1000 | 1.544 | 1.565 | 1.599 | 1.551 |
1050 | 1.543 | 1.568 | 1.585 | 1.576 |
1100 | 1.537 | 1.634 | 1.669 | 1.743 |
1150 | 1.563 | 1.714 | 1.76 | 2.076 |
1200 | 1.583 | 1.794 | 1.753 | 2.126 |
σ (Mpa) | ||||
900 | 2.7 | 3.7 | 6.2 | 9.3 |
950 | 3.8 | 2.7 | 9.2 | 9.8 |
1000 | 3.6 | 3.2 | 4.6 | 11.7 |
1050 | 4 | 1.5 | 5.3 | 11.5 |
1100 | 4.4 | 2.9 | 4.5 | 15.7 |
1150 | 6.1 | 5.4 | 4.5 | 22.7 |
1200 | 5.6 | 7.4 | 3.8 | 22.2 |
with the other samples. This different densification behavior is probably induced by their mineralogy due to the relative abundance of impurities [
An open porosity is closely related to the densification of the clay matrix. The decrease of open porosity is associated with a considerable liquid phase formation, which penetrated and isolated the adjacent pores [
This study focuses on the composition and ceramic properties of four kaolinitic clays sampled from three deposits in Foumban (West Cameroon). The combination of mineralogical, physico-chemical and technological properties allow us to classify the raw clays according to their optimal application.
Technological properties of fired samples from both alluvial (KB3, KG3) and lateritic clays (K1M, MA2) are sufficient for bricks production. However, the addition of flux agent is recommended for sample K1M to decrease its sintering temperature. The low amount of fluxes, gives sample K1M a refractory firing behavior, which results in small variations in the properties above 1150˚C. Samples K1M and KG3 display an extrusion behavior (low plastic and high plastic clay respectively) not acceptable for building ceramics. Those samples require a proper adjustment of their sand-silt-clay ratio to improve their workability (i.e., addition of a plastic material for K1M and non-plastic material for KG3). The mineralogical composition of sample KG3 renders it inappropriate due to the high smectite content; this can be solved by some treatment or addition of quartz.
Further study of mineralogical transformations during firing can be carried out on Foumban raw clays (K1M, MA2 and KB3) to determine the influence of neoformation on the technological properties like porosity. They would provide valuable data regarding the choice of temperature, and the firing duration.
Mefire Nkalih, A., Pilate, P., Yongue, R.F., Njoya, A. and Fagel, N. (2018) Suitability of Foumban Clays (West Cameroon) for Production of Bricks and Tiles. Journal of Minerals and Materials Characterization and Engineering, 6, 244-256. https://doi.org/10.4236/jmmce.2018.62018