Temperature-dependent rehydration of magnesium silicate hydrate (M-S-H): Development of no-cement binder through MD/DFT validation

作者：Zhang, Yu; Nath, Mithun; Wang, Junkai; Li, Yawei^*; Zhang, SiSi; Zhu, Tianbin; Xue, Zhengliang; Chen, Junfeng^*

来源：Ceramics International, 2022, 48(5): 7063-7070.

DOI：10.1016/j.ceramint.2021.11.265

• Magnesia refractory castables
• Magnesium silicate hydrate
• Dehydration-rehydration
• Density functional theory
• No -cement binder
• Binding strength

The MgO-SiO2-H2O binding system was vital for the strength properties of magnesia castables. However, the low yield of magnesium silicate hydrate (M-S-H) during the curing process limited the further improvement in the service performance of magnesia castables. The introduce of synthesized M-S-H into magnesia castables was a potential approach to address the above issue, and it was explored in this work. The effect of dehydration temperature (from 200 to 800 degrees C) on the rehydration behavior of M-S-H and the strength of magnesia castables was investigated. The results indicated that the magnesia castables with pre-dehydrated M-S-H below 600 degrees C processed an enhanced binding property. The highest strength occurred in the sample with pre-dehydrated M-SH at 200 degrees C, and the strength dramatically decreased in the presence of M-S-H calcinated at 800 degrees C. According to Molecular Dynamics (MD) simulations, structural distortion was generated from the dehydration process of M-SH and was worsened by temperature increase. The minimum distortion occurred in the dehydration of M-S-H at 200 degrees C, which was confirmed as merely 8% physical water removal based on the Density Functional Theory (DFT) calculations. Ultimately, the appropriate structural distortion could increase the hydration reactivity and improve the strength of magnesia castables.