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Pore forming behavior of water in high alumina castable structure

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Document pages: 10 pages

Abstract: Direct casting is a processing method that can produce large and complex geometric parts. It uses dispersion of ceramic particles in water and hydraulic adhesive for consolidation. The study of castable structure shows that a large number of pores will be produced due to the presence of water. This effect occurs because drying retains part of the interparticle pores initially occupied by water. In these cases, the pore fraction obtained can reach a level higher than 50 , which affects the performance of the structure. However, the pore forming behavior of water in these materials has not been deeply studied. In this work, aqueous suspensions of calcined alumina and hydrated alumina (hydraulic binder) with different water content (40 – 60 vol. ) were prepared in a paddle mixer. aboutcompositions of lower (5–35 vol. ) or higher (66–80 vol. ) water amounts, casting and curing steps were assisted by external pressure and a rotating device, respectively, to produce homogeneous microstructures. The total porosity after drying was similar to the initial volumetric content of water in the compositions when side effects, such as sedimentation and air entrapment, were prevented. Below water content of 25 vol. , particles packing flaws became the main pore generator and the hydroxylation reaction of the binder no longer occurred effectively.

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