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 Al 2 O 3 and Fe 2 O 3 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 CO 2 -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 Al 2 O 3 /Fe 2 O 3 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.

Resistance to thermal shock damage is an important characteristic in refractory materials, since it determines their performance and service life in many applications. Therefore, the use of more sensitive techniques is desirable to improve the evaluation of thermal shock damage and monitoring of nucleation and propagation cracks and microcracks.The aim of this work was to evaluate the potential of damping change characterization to quantify thermal shock damage and to estimate the retained mechanical strength in complement to the dynamic Young's modulus test. Variations in damping and retained Young's modulus and their correlation with the mechanical strength of a high alumina refractory castable were evaluated at different thermal shock temperatures and number of cycles. The changes in damping were proportional to the retained mechanical strength, similarly to the retained Young's modulus. Changes in damping were also detected which were not indicated by the Young's modulus measurements.

Primeiramente, gostaria de agradecer a minha família, pelos exemplos e ensinamentos, proporcionando o suporte essencial para eu concluir esta tese. Em especial agradeço a minha mãe pelo seu exemplo de força, dedicação e conquista, ao meu falecido pai que me ensinou a amar a vida e os seus valores, aos meus irmãos, Laura e Francisco, pelo apoio. Também à minha namorada Joseleine pela compreensão e incentivo. E agradeço a Deus pela minha vida. Agradeço a orientação do Prof. Dr. Douglas Gouvêa, pelos ensinamentos de nano-óxidos e pela possibilidade do estágio do doutorado sanduíche. Agradeço ao Dr. Fábio Coral Fonseca pelas medidas de impedância no IPEN e pelos ensinamentos com o tratamento dos resultados destas medidas. Agradeço ao Prof. Dr. Ricardo H. R. Castro pela possibilidade do doutorado sanduíche e toda a atenção e suporte durante a estadia na UCD, em Davis, Califórnia (EUA). Agradeço ao Prof. Dr. Roland Faller pelos ensinamentos em Molecular Dynamics, e a paciência com o meu aprendizado desde o início. E também aos colegas de trabalho pelo convívio no laboratório e aprendizado em conjunto: