THE ROLE OF FUME SILICA AS A SOLID DISPERSANT FOR MULTI-WALLED CARBON NANOTUBES IN CALCIUM ALUMINATE CEMENT BASED REFRACTORY CASTABLE

Reference	Presenter	Authors (Institution)	Abstract
14-096	Norval Rodrigues de Oliveira Jr	Oliveira Jr, N.R.(rhimagnesita); Fernandes, M.R.(Universidade Católica de Minas Gerais); Furtado, C.A.(Centro de desenvolvimento de Tecnologia Nuclear); Ribeiro, F.A.(Centro de Desenvolvimento de Tecnologia Nuclear); Brito, M.A.(rhimagnesita); Dutra, P.(Centro de desenvolvimento de tecnologia nuclear); Santos, A.P.(Centro de Desenvolvimento da Tecnologia Nuclear);	In order to evaluate the effects of multi-walled carbon nanotubes (MWCNT) on the properties of refractory castable, the addition of two commercial MWCNT (CheapTubes IGMWNT-OH and Nanocyl NC7000) were tested. Also, part of the castable cement content was replaced by fume silica to evaluate its effect on the nanocarbons dispersibility in the castable matrix. The castable compositions were 60% of two fine aluminas, plus (1) 40% of high calcium aluminate cement (Secar Plenium 1.6) and (2) 30% of Secar Plenium and 10% of microsilica 971D. The MWCNT amount was fixed at 0.15 wt% of the dry castable mass, with direct introduction, before water addition. The composites were evaluated regarding fresh workability, appearance and mechanical and physical properties. The incorporation of both kinds of MWCNT reduced the castable workability, being worse for NC7000 which required more water. After firing, the introduction of IGMWNT-OH had negative effect on apparent density and porosity, but kept the cold strength. The castable containing fume silica showed better mechanical properties at high temperatures, mainly when IGMWNT-OH was introduced. The comparative analysis of digital images revealed a much better homogeneity and distribution of nanocarbons in the concrete pieces when was introduced fume silica. The fume silica contributes to the improvement of the MWCNT dispersion through the refractory matrix and, as a consequence, to the improvement of the castable properties.
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