Two samples clayed materials, LO and NG from central region in Cameroon were characterized for their valorization in the manufacture of refractory bricks and ceramics. In order to assess the technological properties of these clays, cooking tests were carried out on the test specimens at different temperatures. From particle size analysis, clayed materials studied have a spreading particle size and their plasticity index is between 18 and 47. The mineralogical study reveals the presence of Quartz, illite, kaolin, hematite and feldspars. High level of silica content explains the sandy nature of these clays. Linear shrinkage and density increase with temperature while compressive strength decreases with temperature. Analyses performed on the ceramic specimens after firing show that clay materials studied are suitable for the manufacture of refractory bricks.
Clays have been used by man since the beginning of time. The characteristics and chemical composition of clay deposit usually determine its industrial application [
The main objective of this work is to study the technological ability of this material for the manufacture of ceramic products for wide dissemination and sustainable local development. This study is a scientific contribution in the knowledge and characterization of industrial minerals which contributes to the promotion of local materials in Cameroon.
Clay samples were collected from a well located at latitude 9.285126˚ North and longitude 13.455767˚ East. Sample from Lobo was denoted LO and sample from Ngoya was denoted NG. About 2.0 kg of each sample was collected and placed in small polyethylene bags. 1.0 kg of each sample was dried, pulverized and sieved before analysis. Documentary studies [
Sieve series, a densimeter, a pycnometer, X-ray diffraction and infrared spectrometry were used to study the particle size as well as the physical and chemical properties of the material.
Sample clay material LO consists of 1.5% gravel, 55.92% sand, 6.08% silt and 36.49% clay while sample clay material NG consists of 0.6% gravel, 57.63% sand, 17.56% silt and 24.14% clay. The high percentage of sand in these samples allows us to deduce that it is clayey sand having homogeneous and spread particle size. [
The results of the ATTERBERG limit test are shown in
These clay materials have a plasticity index in the range of 18 to 47. The sample LO has a plasticity index of 26.22% while the NG sample has a plasticity index of 17.52%. These values from
Samples | Gravel (%) | Sand (%) | Silt (%) | Clay (%) |
---|---|---|---|---|
LO | 15 | 55.92 | 6.08 | 36.49 |
NG | 0.6 | 57.63 | 17.56 | 24.14 |
Gravel: (f > 2 mm), Sand: (0.02 mm < f > 2 mm), Silt: (0.002 mm < f > 0.02 mm) Clay: (f < 0.002 mm)
Samples | Limit of liquidity | Limit of plasticity | Plasticity index |
---|---|---|---|
LO | 44.87 | 18.65 | 26.22 |
NG | 44.87 | 27.35 | 17.52 |
material consists of quartz (in the form of sand) associated with clay minerals (illite, kaolinite) while in NG clay material, in addition to quartz (in the form of sand) and kaolinite, other minerals such as k-feldspars and hematite are also present [
These spectra reveal two zones of absorbance; the first zone is between 4000 and 3500 cm−1 and the second zone of absorbance is between 2000 and 500 cm−1. These bands are characteristic of the elongation vibrations of the external hydroxyl (OH) bonds of kaolinite network (Al-OH-Al) [
[
The results of the thermogravimetric analysis are shown in
These thermograms show five zones of anomalies: The first zone is between 100˚C and 150˚C and has endothermic peaks centered at 97˚C for LO and at 98˚C for NG. These peaks correspond to the mass loss of water contained in the studied materials; the second anomaly zone is between 150˚C and 450˚C with endothermic peaks centered at 199˚C and 290˚C for LO clay material, then at 220˚C and 360˚C for NG clay material; these peaks correspond to the dehydroxylation of phyllosilicates; the third anomaly zone is between 450˚C and 600˚C with endothermic peaks centered at 540˚C for LO clay and at 520˚C for NG clay material. These peaks are due to the dehydroxylation of kaolinite; the fourth anomaly zone is between 650˚C and 800˚C with endothermic peaks centered at 790˚C for LO clay and 760˚C for NG clay; these peaks come from the dehydroxylation of 2/1 clay minerals such as illite. Losses of mass below 180˚C are related
to the disappearance of adsorbed or capillary water. Between 150˚C and 450˚C, losses of mass are due to dehydroxylation of phyllosilicates. Mass losses observed between 450˚C and 650˚C are due to dehydroxylation of kaolinite to give metakaolinite which has a very poorly organized structure [
Organic matter content of LO clay material is 6.03% with a pH of 7.73 while NG sample has an organic matter content of 2.40% with a pH of 5.56. The chemical composition of the clay materials studied is summarized in
It can be seen from
Samples | SiO2 | Al2O3 | Fe2O3 | K2O | MgO | TiO2 | P2O5 | CaO | MnO | Na2O | L.O.I |
---|---|---|---|---|---|---|---|---|---|---|---|
LO | 64.09 | 20.24 | 1.82 | 1.19 | 0.28 | 1.87 | 0.09 | 0.06 | 0.02 | 0 | 9.39 |
NG | 59.12 | 22.06 | 2.34 | 1.07 | 0.19 | 1.81 | 0.17 | 0.11 | 0.03 | 0 | 12.02 |
magnesium oxide (0.28%), manganese oxide (0.02%), calcium oxide (0.06%), phosphorus oxide (0.09%). NG clay is also mainly composed of silica (59.12%), aluminum oxide (22.06%), iron oxide (2.34%), titanium oxide (1.81%), potassium oxide (1.19%). Other oxides are also present in trace such as magnesium oxide (0.19%), potassium oxide (0.17%), manganese oxide (0.03%), calcium oxide (0.11%). The SiO2:Al2O3 ratio is greater than 2%; 3.16% for LO clay and 2.67% for NG clay, reflecting the abundance of sand in the studied clay materials [
The quality control tests carried out are designed to evaluate certain ceramic properties such as linear shrinkage during cooking, bulk density, compressive strength, and water absorption rate.
Linear shrinkage is a parameter that reflects the reactivity of material during firing [
The resulting curves of apparent density are shown in
From
Water absorption rates are shown in
Generally, the water absorption of ceramic products should decrease with the increase in firing temperature caused by the gradual disappearance of porosity during sintering [
rate is 12.5% at 1000˚C, 11.33% at 1100˚C and 11.17% at 1200˚C. The NG sample absorbs less water than the LO sample.
LO and NG clay materials samples were subjected to various analyzes; particle size analysis reveals a continuous and spread granulometry. Atterberg limits of these clay materials reveal the low plasticity due to the high percentage of sand. Chemical analysis shows SiO2:Al2O3 ratio greater than 2 and other minerals such as quartz, illite, kaolinite, hematite and feldspars are also present. The thermal analysis shows characteristic mass losses of adsorbed water and kaolinite dehydroxylation to yield peak metakaolinite at 450˚C - 650˚C. The pH of these clay materials is weakly basic for LO sample while it is weakly acidic for NG sample. These clay materials have a low linear shrinkage due to their sandy nature, decreasing with temperature. The density and compressive strength increase with temperature while the rate of water absorption is low. These clay materials can then be used in the field of ceramic and the manufacture of bricks at a higher temperature (1200˚C).
The authors declare no conflicts of interest regarding the publication of this paper.
Mominou, N., Richard, M.J. and Aicha, S.I. (2019) Physicochemical Characterization and Valorization of Clay from Lobo and Ngoya in Cameroon Central Region. Open Journal of Inorganic Chemistry, 9, 23-33. https://doi.org/10.4236/ojic.2019.93003