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Five mixtures (M1 to M5) of silica-alumina geomaterials and two varieties of alumina (A P and A R ) were used for the elaboration of mullite refractory materials between 1500˚C and 1600˚C. An X-ray diffraction (XRD) analysis showed that the refractory samples are composed of mullite, corundum and silica. The length of the mullite crystals was measured by a method of image analysis of scanning electron microscopy (SEM). Chemical and mechanical properties of these materials were investigated and correlated with their microstructure. Resistance towards Acid Attack test showed that the refractory samples present good resistance, as well as, the alumina powder A R obtained from waste of silica-alumina bricks proves to be efficient for an eventual use.

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One of the most important elements of furnaces, boilers and other heating units is the structure (lining), usually made of silica-alumina, basic or special refractories. The basic refractories are materials that are increasingly in demand and whose manufacturing involves necessarily the use of MgO and CaO. In this article, the description and characterization of magnesite (MgCO 3) and dolomite (Mg,Ca(CO 3) 2) and their contribution in industrial ceramics-refractories have been reviewed.