Elaboration et caractérisation des briques réfractaires aluminosilicates à base des matériaux argileux de Koutaba et Mayouom (Région de l’Ouest) : effet de l’ajout des résidus de production de café et des balles de riz.

Abstract

In this study, three clay materials from Koutaba and Mayouom (West Cameroon), named MY3, KK and KG were firstly collected and characterized by particle size analyasis, plasticity, chemical analysis (X-ray Fluorescence), mineralogical analysis by X-ray diffraction, infrared spectroscopy and thermal analysis. Their thermal behaviors by dilatometric analysis up to 1400 °C as well as the properties of the products of their respective firing at 1300, 1400 and 1500 °C were also carried out. All the results obtained show that the clays exhibit thermal behavior more or less different in relation with their various structurals phases. However, these materials are adapted to the manufacture of refractory products, the necessary additions of inert component or porogens agents to optimize the thermomechanical properties of the products which may vary due to the optimal sintering temperature which is 1400 °C for MY3 and KG and 1500 °C for KK richer in silica and poor in melting oxides. Thus, refractory brick formulations were made with the additions of chamottes varying from 14 to 30 % to obtain mixtures moistened with 3 to 6 % of distilled water before being shaped in cylindrical molds of 50 mm in diameter by uniaxial pressing at 120 MPa. The obtained specimens are oven-dried at 105 °C then fired from 1350 to 1450 °C for MY3 and KG and from 1400 to 1500 °C for KK with heating speed of 5 °C/min and 4h as firing time at the highest temperature. The measurement of the physical and mechanical properties shows that the products obtained have bulk density varying from 1.90 to 2.17 g/cm3, open porosity from 15 to 24 %, compressive strength from 13 to 73 MPa and refractoriness under load from 1333 to 1417°C. Therefore, they can be classified as dense refractory materials comparable to refractory bricks which are commonly sold. However, bricks from KK and KG have a lower thermal shock resistance compared to this of MY3 which no longer have a low thermal dilatation. Therefore, MY3 has been subjected of other formulations containing in addition to the chamotte, rice husks or coffee residues ground and sieved at 100 µm mesh integrally. For each type of organic additive added to the clay-chamotte mixture, the whole was moistened with 5 % distilled water, then shapped in cylindrical molds 30 mm of diameter at 42 MPa. The ceramic bodies obtained are oven-dried at 110 °C for 24 h fired at 1200 °C with a heating rate of 3°C/min and a firing time of 10 h. The characterization of products shows that firing shrinkage is less than 2 %; bulk density between 0.4 and 1.40 g/cm3; open porosity more than 45 %. These products are qualified as insulating refractory materials with a limit using temperature of 1250 °C: Therefore, they are insulating thermal refractory bricks witch can be used in intermediate walls of furnaces and which must ensure the minimum heat transfer.