Hydration mechanism and sintering characteristics of hydratable alumina with microsilica addition |
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| Affiliation: | 1. The State Key Laboratory of Refractories and Metallurgy, Department of Materials Science and Engineering, Wuhan University of Science and Technology (WUST), Wuhan, 430081, PR China;2. National-provincial Joint Engineering Research Center of High Temperature Materials and Lining Technology, Wuhan University of Science and Technology (WUST), Wuhan, 430081, PR China;1. Henan Key Laboratory of High Temperature Functional Ceramics, School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, 450001, China;2. Puyang Refractories Group Co., Ltd, Middle West Circle Road, Puyang, 457100, China;3. Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, Leuven, 3001, Belgium;1. Federal University of São Carlos, Materials Engineering Department, Rod. Washington Luiz, km 235, São Carlos, SP 13565-905, Brazil;2. Petrobras, Research and Development Center, Rio de Janeiro, RJ 21941-915, Brazil;1. Henan Key Laboratory of High Temperature Functional Ceramics, School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, Henan, 450001, China;2. State Key Laboratory of Advanced Refractories of China, Sinosteel Luoyang Institute of Refractories Research Co., Luoyang, Henan, 471039, China |
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| Abstract: | Hydratable alumina is potential for the application in refractory industry as one of Ca-free binders, but it is greatly limited because of the excess hydration of rho-alumina (ρ-Al2O3). In this study, hydration mechanism and sintering characteristics of hydratable alumina with different microsilica addition are researched, via the rheological, hydration, and morphological characteristics of ρ-Al2O3–SiO2–H2O system during aging are analyzed using various techniques. Boehmite (AlOOH) initially appears and increases in content after 1 h aging at the setting temperature of 30 °C and relative humidity of 80%. As the addition of microsilica increases from 0 wt% to 8 wt%, the SiO2 coating combines with the boehmite gel and efficiently suppresses the hydration reaction, resulting in decrease of relative hydrated densities from 5.42% to 4.27% and increase of zeta potential from −10.1 mV to −21.3 mV. Further, the thus-formed SiO2-AlOOH gels cover the surface of hydratable alumina particles, connect with each other, and get distributed homogeneously around hydratable alumina particles to harden, thus inhibiting the further hydration. This is reflected by the high-temperature X-ray diffraction and the final sintering microstructures. Overall, these results indicate that the 6 wt% addition of microsilica makes hydratable alumina promising for application as a kind of controlled binders. |
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| Keywords: | Hydratable alumina Microsilica Hydration control Phase evolutions Microstructures |
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