Morphology Evolution of the Hydration Products of Hydratable Aluminas at 40 °C
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
Volume 11, Issue 2, Pages 66 - 70
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.
hydratable alumina, freeze vacuum drying
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