Effects of Disodium Hydrogen Phosphate Addition and Heat Treatment on the Formation of Magnesium Silicate Hydrate Gel
Main Article Content
Abstract
The formation of magnesium silicate hydrate gel is crucial in preventing magnesia aggregates from over hydrated during the construction of refractory castables since the presence of magnesium hydroxide diminish the mechanical properties of the material. This work aimed to investigate the accelerating effects of sodium hydrogen phosphate and heat treatment on the formation of magnesium silicate hydrate gel. Time-dependent pH of magnesia - silica fume slurries with and without sodium hydrogen phosphate addition and heat treatment was measured to verify the dissolution of MgO and magnesium silicate hydrate formation. The effects of sodium hydrogen phosphate were differentiable only at small added amounts, whereas heat treatment at 50 degrees Celsius performed noticeable acceleration. This observation could be applicable in molding to maintain the stability of basic refractory castables.
Keywords
Magnesium silicate hydrate, gel, pH
Article Details
References
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https://doi.org/10.1149/1.2412273
[3] R. Salomão and V. C. Pandolfelli, Microsilica addition as an antihydration technique for magnesia-containing refractory castables, American Ceramic Society Bulletin, vol. 86, no. 6, (2007) 9301-9306.
[4] L. Amaral, I. Oliveira, P. Bonadia, R. Salomão, and V. Pandolfelli, Chelants to inhibit magnesia (MgO) hydration, Ceramics International, vol. 37, no. 5, (2011) 1537-1542.
https://doi.org/10.1016/j.ceramint.2011.01.030
[5] T. Souza et al., Phosphate chemical binder as an antihydration additive for Al2O3.3MgO refractory castables, Ceramics International, vol. 40, no. 1, (2014) 1503-1512.
https://doi.org/10.1016/j.ceramint.2013.07.035
[6] I.-H. Jung, S. A. Decterov, and A. D. Pelton, Critical thermodynamic evaluation and optimization of the CaO–MgO–SiO2 system, Journal of the European Ceramic Society, vol. 25, no. 4, (2005) 313-333.
https://doi.org/10.1016/j.jeurceramsoc.2004.02.012
[7] V. Chernyakhovskii, Technology of unfired periclase-spinel parts with a phosphate binder, Refractories, vol. 26, no. 1-2, (1985) 41-44.
https://doi.org/10.1007/BF01398613
[8] H. Seidel, L. Csepregi, A. Heuberger, and H. Baumgärtel, Anisotropic etching of crystalline silicon in alkaline solutions: I. Orientation dependence and behavior of passivation layers, Journal of the Electrochemical Society, vol. 137, no. 11, (1990) 3612-3626.
https://doi.org/10.1149/1.2086277
[9] E. Prud’homme et al., Silica fume as porogent agent in geo-materials at low temperature, Journal of the European Ceramic Society, vol. 30, no. 7, (2010) 1641-1648.
https://doi.org/10.1016/j.jeurceramsoc.2010.01.014
[10] S. A. Walling, H. Kinoshita, S. A. Bernal, N. C. Collier, and J. L. Provis, Structure and properties of binder gels formed in the system Mg (OH)2–SiO2–H2O for immobilisation of Magnox sludge, Dalton Transactions, vol. 44, no. 17, (2015) 8126-8137.
https://doi.org/10.1039/C5DT00877H