Morphology Evolution of the Hydration Products of Hydratable Aluminas at 40 °C

Wenjing Gu1, Dafei Ding1, Xuekun Tian1, Guotian Ye1, Guihua Liao2, Liugang Chen3

1 Henan Key Laboratory of High Temperature, Functional Ceramics, School of Materials, Science and Engineering, Zhengzhou University, Zhengzhou/China
2 Department of Materials Science and Engineering, Luoyang Institute of Science and Technology, Luoyang/China
3 Henan Key Laboratory of High Temperature, Functional Ceramics, School of Materials, Science and Engineering, Zhengzhou University, Zhengzhou/China

Revision

Volume 11, Issue 2, Pages 66 - 70

Abstract

Hydratable Alumina (HA) is an important CaO-free hydration binder for no-cement castables. Different sources of hydratable alumina have varied phase compositions and physical properties (such as specifc surface area and particle size), which could generate hydration products with different phases and structures during hydration. In this work, two sources of HA with different phases and specifc surface areas (named HA1 and HA2) were used to investigate the morphology development of the hydration products during hydration. The hydration process of the pastes of HA with water cured at 40 °C was halted by a freeze vacuum drying method to examine the evolution of phase composition and microstructure of hydrates with XRD and SEM, respectively. The results showed that the initial hydration products of HA1 with a higher amount of crystalline phases and a lower specifc surface area were bayerite with a dense structure, which became denser with increasing curing time. In comparison, the initial hydration products of HA2 with a higher amount of amorphous phase and a higher specifc surface area were composed of amorphous substances with a honeycomb structure, and the pore size of the honeycomb structure increased with extended curing time. The above results indicate that HA2-bonded castables could have a better explosion resistance than HA1-bonded castables.

Keywords

hydratable alumina, freeze vacuum drying

References

[1] Azizian, F.: Improving the performances of cement-free castables. Ceram. Industry 147 (1997) [2] 42–48 [2] Poddar, D.D.; et al.: Spinel-bonded basic castables in relation to spinel formation agents. Interceram Int. Ceram. Rev. 51 (2002) [4] 282–288 [3] Studart, A.R.; et al.: Rheological design of zero-cement self-fow castables. Amer. Ceram. Soc. Bull. 78 (1999) [5] 65–72 [4] Cardoso, F.A.; et al.: Drying behavior of hydratable alumina-bonded refractory castables. J. Europ. Ceram. Soc. 24 (2004) [5] 797–802 [5] Innocentini, M.D.M.; et al.: Permeability of high‐alumina refractory castables based on various hydraulic binders. J. Amer. Ceram. Soc. 85 (2002) [6] 1517–1521 [6] Salomão, R.; et al.: The role of hydraulic binders on magnesia containing refractory castables: Calcium aluminate cement and hydratable alumina. Ceram. Int. 35 (2009) [8] 3117–3124 [7] Wefers, K.; et al.: Oxides and hydroxides of aluminum. Alcoa Technical Paper No. 19. Aluminum Company of America, Pittsburgh, PA, 1987 [8] Ma, W.; et al.: Mechanisms of reaction of hydratable aluminas. J. Amer. Ceram. Soc. 82 (1999) [2] 453–456 [9] Vaidya, S.D.; et al.: Effect of temperature, pH and ageing time on hydration of rho alumina by studying phase composition and surface properties of transition alumina obtained after thermal dehydration. Mater. Lett. 51 (2001) [4] 295–300 [10] Vaidya, S.D.; et al.: Study of phase transformations during hydration of rho alumina by combined loss on ignition and X-ray diffraction technique. J. of Phys. & Chem. of Solids 62 (2001) [5] 977–986 [11] Violante, A.; et al.: Influence of inorganic and organic ligands on precipitation products of aluminum. Clays & Clay Minerals 33 (1985) 181–192 [12] Yamaguchi, G.; et al.: The Hydration and crystallization of r-Alumina and alumina-gel in aqueous solutions of various basic reagents. Bull. Chem. Soc. Jap. 41 (1968) [2] 348–353 [13] Mista, W.; et al.: Rehydration of transition aluminas obtained by fash calcination of gibbsite. Thermochimica Acta. 331 (1999) [1] 67–72

Copyright

Göller Verlag GmbH