Thermal behavior and physical-mechanical properties of red mud

The present work studied the thermal behavior, the evolution of the crystalline phases with temperature and the ceramic properties of the red mud (bauxite tailing) from an aluminium industry of the Maranhao state. The research was carried out by Simultaneous Thermal Analysis (TG-DTA), Optical Dilatometry up to 1350 ºC, while the evolution of the crystalline phases was performed by X-ray diffraction analysis upon heating between 750 to 1150 ºC. Physical-mechanical properties, like Specific Surface Area, Particle Size Distribution, Plastic Limit (PL), Liquid Limit (LL), Plasticity Index (PI), Flexural Strength, Water Absorption (WA), Linear Shrinkage After Firing (LS) and the Apparent Porosity (AP) were also determined at the same range of temperature. The following major crystalline phases were detected: hematite, sodalite, and anatase at 750 < T < 850 ºC; and hematite, nepheline and sodalite at 950 < T < 1150 ºC. The technological experiments indicated that red mud can be used for the processing of structural ceramic materials, since it is an inert material between 870-950 ºC and presents highest water absorption and lowest shrinkage and flexural strength. At 950 < T < 1350 ºC, red mud presented a high shrinking of almost 5 to 50 % with total fusion at 1350 ºC, due to the presence of feldspathoids phases in its mineral composition.

Bauxite tailing; ceramic materials; characterization; red mud


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