Novel Technological Route to Overcome the Challenging Magnesia Hydration of Cement-free Alumina Castables

Mariana A. L. Braulio, Victor C. Pandolfelli, Tiago M. Souza

Federal University of São Carlos, GEMM, Materials Engineering Dept., 13565-905 São Carlos – SP/Brazil

Revision 05.06.2012, 17.09.2012

Volume 5, Issue 1, Pages 93 - 98

Abstract

Due to the expansive behavior associated with the brucite [Mg(OH)2] formation, magnesia hydration is a challenging subject in the refractory castable area. Although various anti-hydration techniques have been suggested in the literature, a technological solution for this issue has not yet been presented. Instead of inhibiting brucite formation, speeding up its formation could be a suitable microstructural engineering resulting in the Mg(OH)2 accommodation in the castable pores and increasing the green mechanical strength of the castables, without crack formation. Therefore, acetic acid was selected and added as a hydrating agent, affecting the amount of brucite generated and also its morphology. As an overall result, the reaction was accelerated and provided some structural flexibility to the Mg(OH)2. This interesting alternative route can result in technological advances on the understanding and use of higher magnesia amounts in cement-free refractory castable compositions.

Keywords

refractory castables, magnesia hydration, acetic acid

References

[1] Layden, G.K.; Brindley, G.W.: Kinetics of vaporphase hydration of magnesium oxide. J. Amer. Ceram. Soc. 46 (1963) [11] 518–522

[2] Salomão, R.; Bittencourt, L.R.; Pandolfelli, V.C.: A novel approach for magnesia hydration assessment in refractory castables. Ceram. Int. 33 (2007) 803–810

[3] Kitamura, A.; Onizuka, K.; Tanaka, K.: Hydration characteristics of magnesia. Taikabutsu Overseas 16 (1995) [3] 3–11

[4] Salomão, R.; Pandolfelli, V.C.: The role of hydraulic binders on magnesia containing refractory castables: calcium aluminate cement and hydratable alumina. Ceram. Int. 35 (2009) 3117–3124

[5] Salomão, R.; Pandolfelli, V.C.: Microsilica addition as anti-hydration technique of magnesia in refractory castables. (in Portuguese) Cerâmica 54 (2008) 43–48

[6] Souza, T.M.; et al.: Systemic analysis of MgO hydration effects on alumina-magnesia refractory castables. Ceram. Int. 38 (2012) 3969–3976

[7] Rocha, S.D.F.; Mansur, M.B.; Ciminelli, V.S.T.: Kinetics and mechanistic analysis of caustic magnesia hydration. J. Chem. Technol. Biotechnol. 79 (2004) [8] 816–821

[8] Matabola, K.P.; et al.: The influence of hydrating agents on the hydration of industrial magnesium oxide. J. Chem. Technol. Biotechnol. 85 (2010) 1569–1574

[9] Filippou, D.; et al.: On the kinetics of magnesia hydration in magnesium acetate solutions. J. Chem. Technol. Biotechnol. 74 (1999) 322–328

[10] Innocentini, M.D.M.; et al: Drying stages during the heating of high-alumina, ultra-low-cement refractory castables. J. Amer. Ceram. Soc. 86 (2003) [7] 1146–114.

[11] Vasil’eva, N.A.; Plyasova, L.M.; Odegova, G.V.: Defect magnesium oxides containing acetate and nitrate ion fragments incorporated in the oxide structure. Kinet. Catal. 47 (2006) [3] 437–444

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