Abstract
Castable porous ceramics combine the high refractoriness of ceramics, the useful characteristics of porous materials and the straightforward installation of castable systems. In this study, particles of aluminium hydroxide (Al(OH)3) and magnesium hydroxide (Mg(OH)2) of similar average size were added separately to an alumina castable (up to 67 vol.-%). During thermal treatment (1100–1500°C), variations occurred in their porosity levels, mechanical properties, phase composition and microstructure. These were related to physical-chemical changes and Al2O3-MgO solid-state reactions. Both systems have potential to be technologically useful. AH-based structures showed intermediate levels of porosity (around 60%) and higher compression strength (above 10 MPa), which enable them to be employed as sintered lightweight aggregates for refractory insulating mortars. The MH-based castables, on the other hand, exhibited higher porosity levels (above 60%) and excellent dimensional stability. They can therefore be used as primary thermal insulators for long-life services at steelmaking, cement production and petrochemical plants.
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