Microstructural, physical and mechanical behavior of pastes containing clays and alumina waste

The purpose of this study is to analyze the influence of an aluminum oxide-rich precursor added to clays (smectite/kaolinite) during heat treatment on their mineralogical and microstructural changes, emphasizing the presence of mullite phase. Three clays were used. The samples were subjected to physical, chemical, thermal and mineralogical characterizations. Clay compositions containing alumina waste were then formulated and heat-treated at temperatures ranging from 900 to 1400 °C, applying a heating rate of 5 °C/min and 60 min dwell time, after which mineralogical and morphological analyses were performed. The results indicated that mullite can be obtained from clay formulations containing alumina waste, and that the amount of the mullite phase formed is determined by the composition, particle size and applied temperature.