This work investigated the changes in the permeability of high-alumina self-flowing refractory castables based on calcium aluminate cement (CAC) and hydratable alumina binder (HAB) pretreated between 110°and 1650°C. Permeability constants k 1 and k 2 were fitted from Forchheimer's equation based on airflow tests conducted at room temperature. The results indicated that dehydration was the main contributing factor for increased permeability in bodies pretreated up to 600°C and that sintering effects prevailed between 900°and 1650°C. Castables based on HAB were less permeable than those based on CAC, a behavior ascribed to the type of hydrates formed and to the particle-packing features of the matrix and the matrix-aggregate interfaces. † Cement notation: C is CaO; A is Al 2 O 3 ; and H is H 2 O.
This work describes the use of a new permeametry technique to evaluate microstructural changes that take place in castables with high alumina‐fiber content during the dewatering process. It is shown that the mass loss due to cement dehydration and the permeability increase caused by fiber burnout can be independently assessed, based on the fluid dynamic conditions established for the experiment. Control of the pressure drop through the sample was the key procedure used to analyze the phenomenon of interest.
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