The bauxite residue (BR) is the solid waste of largest generation by the aluminum industry, with a generation estimated in 10 million ton/year in Brazil. Its high alkalinity demands elevated costs to store it safely. Due to the high content of Al2O3 and Fe2O3 in BR, the present study evaluated its application for the synthesis of iron rich sulfobelite clinkers. Because of its composition, the cement made with this clinker presents environmental (30% to 62% reduction of CO2-equivalent emission), economic and even technical advantages over Portland cements. Formulations containing: limestone, gypsum, BR and clay, were fired at 1230°C to synthesize the clinkers. Variations in BR and clay content were studied to obtain three formulations, F-15, F-18 and F-21, of different Al2O3/Fe2O3 ratio values. Cements containing more than 10.5 wt-% of BR achieved mechanical resistance comparable to Portland cements (CP-II-Z32 and CP-V-ARI) for 7 and 28 days of curing age.

Este estudo ilustra o impacto da calcinação de resíduo de bauxita (RB) nas propriedades de suspensões formuladas com cimento Portland, tanto no estado fresco como no endurecido. As suspensões foram avaliadas contendo uma razão constante de água-cimento e teor de resíduo variando de 5% a 20% em peso e em substituição ao cimento. As propriedades reológicas e a resistência mecânica foram alteradas em função do aumento do teor de RB, mas a calcinação não teve influência no resultado final obtido, seja no estado fresco ou no endurecido. Assim, pode-se afirmar que a utilização de resíduo de bauxita, natural ou calcinada, em formulações com cimento Portland pode reduzir o consumo de cimento, sendo uma alternativa para a utilização de uma grande quantidade deste tipo de resíduo.

This research work shows the impact of bauxite residue (BR) calcination on the rheological and hardened properties of Portland cement suspensions. These suspensions were evaluated with water-to-cement ratio of 0.5 and variations of residue content from 5% to 20% in partial substitution of cement. Both properties had influence of BR content, but had a negligible influence of calcination. Therefore, it can be inferred that the utilization of BR, in nature or calcinated, in formulations with Portland cement, may reduce the consumption of cement, being an alternative to use large amounts of this type of residue.