Synthesis of Magnesium Silicate Hydrate Based on Bischofite and Its Application in Magnesia Castables

Abstract

Abstract: Bischofite is a very promising magnesium salt resource with abundant reserves and low cost. Magnesium silicate hydrate (M-S-H) gels with different MgO/SiO₂ molar ratios (0.5:1, 1:1, 1.5:1) were synthesized using bischofite from Qinghai Salt Lake and sodium silicate. The synthesis mechanism and structural characteristics of M-S-H were studied by XRD, SEM, infrared, and nuclear magnetic resonance tests. Then, the synthesized M-S-H was compounded with microsilica to prepare magnesia castable, and the influence of M-S-H structure on the bonding characteristics of castable was explored. The results show that M-S-H obtained from different MgO/SiO₂ molar ratios exhibits a layered stacking structure. When the MgO/SiO₂ molar ratio is 1:1, the interlaminar free water is the least and the crystallinity is the highest. The synthesized M-S-H is used to replace part of microsilica to prepare magnesia castable, which significantly improves the mechanical properties of the castable after heat treatment at 1 550 ℃. The magnesia castable prepared with M-S-H (MgO/SiO₂ molar ratio of 1:1) and microsilica obtains the best comprehensive properties. Compared with the magnesia castable prepared by adding 6% (mass fraction) microsilica, the flexural strength at room temperature and high temperature increases by 75% and 8%, respectively.

Key words: bischofite, magnesium silicate hydrate, magnesia castable, flexural strength, microstructure

CLC Number:

TQ175

SONG Shaohui, LI Yawei, LIAO Ning, ZHANG Sisi, LIU Wenjing, LI Yueying, TIE Shengnian. Synthesis of Magnesium Silicate Hydrate Based on Bischofite and Its Application in Magnesia Castables[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2023, 42(2): 751-760.

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