Transformaciones minerales durante el proceso de cocción de arcillas bauxíticas y su relación con propiedades físicas de refractarios

Herrero Cambra, Guillermo
Yuste Oliete, Alfonso (dir.)

Universidad de Zaragoza, CIEN, 2020

Graduado en Geología

Resumen: This research focuses on the mineral and textural transformations during the firing process (from 1000 to 1300ºC) of a bauxite sample from the Sant Mamet Mountain Range (Lérida). This sample, mainly made of bohemite, iron oxides and kaolinite, was mixed in a 90/10 ratio with a clay from the Escucha Fm, mainly composed by quartz and illite. Both the raw and the fired samples at different temperatures were analyzed by X-ray diffraction, optical and electronic microscopy aswell as geochemically characterized by X-ray fluorescence. Also, their physical
properties were determined, including density, linear shrinkage, colour, porosity and point load resistance. The clays were destabilized at 1000º and transformed to mullite but they kept their morphologies at this temperature. At this temperature, Fe and Al oxyhydroxides were destabilized too. At increasing firing temperatures, more mineral phases as quartz and hematite began to destabilize leading to the formation of a vitreous phase, which gave rise to the crystallization of abundant mullite, clearly the most abundant phase at 1200 and 1300ºC. With increasing temperature, mullite composition shows lower Si/Al rate and thus, it is closer to empirical mullite formula. With regard to physical properties, variations in density, linear shrinkage, weight loss, total porosity, average pores size and results in point load test are related to the destabilization of the initial mineral phases, the formation of the vitreous phase and the subsequent crystallization of mullite. Changes in colour are due to the initial crystallization of hematite and its subsequent destabilization.

Tipo de Trabajo Académico: Trabajo Fin de Grado