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This work aims to characterize local Kaolin from Djebbal Dbagh (DD1), Guelma, Algeria, in raw state and after being sintered to improve its refractoriness by mullitisation of the main phase known as kaolinite in order to exploit DD1 as a basic material to elaborate refractory bricks. The characterization of DD1was carried out by different methods of analysis such as chemical analysis, XRD, DTA/TG analysis and scanning electron microscopy (SEM). Furthermore, the measurement of some physical properties such as apparent density, porosity and microhardness of sintered material was performed. The mullitisation was tested without and with addition of potassium salts such as K 2 CO 3 , KNO 3 and K 2 SO 4 as mineralizers to find out the effect of these salts on transition phase from kaolinite to mullite and the inhibition of cristobalite existence versus sintering temperature from 1300°C to 1450°C. The influence of these mineralizers at the cited temperatures was evaluated using XRD. The results show that the additives K 2 CO 3 and KNO 3 have an effective role to accelerate the formation of mullite which is considered as the most favorite phase for high refractoriness.

The main objective of this work is to study and characterization of a refractory material made of a mixture of natural raw material and spent refractory bricks. Relative weight ratios of 25/75 and 75/25 were studied in order to obtain cordierite ceramics having an important class in the field of refractories with the stoichiometric formula (2MgO. 2Al2O3. 5SiO2), by mixing the raw material of Kaolin with spent brick powder magnesia-carbon (MgO-C). The mixtures were sintered at 1200, 1300 and 1400°C for 2 h. The phase composition of the sintered samples was analyzed by X-ray diffraction and scanning electron microscopy (SEM), porosity and density are presented and discussed. The results obtained reveal that when the level of spent brick is high ≥75%, the formation of only a spinel phase and periclase were observed, however where the kaolin level is predominant we observe the formation of the cordierite phase at 1300°C. The morphology obtained by SEM confirmed these results.

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