Abstract The stability of C-S-H nanostructures with varying bulk CaO/SiO2 (C/S) ratios under cryogenic attack (−170 °C) was experimentally studied by means of XRD, TG, SEM-EDS, 29Si MAS NMR, and FTIR. An efficient hydrothermal method was adopted to synthesize C-S-H by accelerating the thermodynamic equilibrium. The results show that the C-S-H atomic structure with a lower bulk C/S ratio is more stable under cryogenic attack. Ca2+ is more likely to leach out from C-S-H with a high C/S ratio. An increase in the bound water fraction was also observed in C/S1.5. At the atomic level, the number of interlayer Ca2+ per tetrahedral site in C/S1.5 significantly decreased from 0.201 to 0.083. The number of vacant bridging sites in C/S2.0 declined from 0.208 to 0.178, probably indicating a slight polymerization. Based on the deconvolution results of 29Si MAS NMR spectra, three reaction equations were proposed to characterize these observed variations.

中文翻译：

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低温侵蚀下不同体积CaO/SiO2比的CSH纳米结构稳定性的实验研究

摘要 通过 XRD、TG、SEM-EDS、29Si MAS NMR 和 FTIR，实验研究了不同体积 CaO/SiO2 (C/S) 比的 CSH 纳米结构在低温攻击 (-170 °C) 下的稳定性。采用高效的水热法通过加速热力学平衡来合成CSH。结果表明，体积 C/S 比较低的 CSH 原子结构在低温攻击下更稳定。Ca2+ 更有可能从高 C/S 比的 CSH 中浸出。在 C/S1.5 中也观察到结合水分数的增加。在原子水平上，C/S1.5 中每个四面体位点的夹层 Ca2+ 数量从 0.201 显着减少到 0.083。C/S2.0 中空桥位点的数量从 0.208 下降到 0.178，可能表明存在轻微聚合。