This work offers in-depth understanding about the behavior of different M-S-H phases under carbonation. Here, we carbonated 8-year-old M-S-H samples under i) wet carbonation and ii) dried or steamed pressurized CO. Both solid and liquids samples were analyzed using various techniques while thermodynamic modelling was coupled to shed light on the response of M-S-H phases under carbonation. We found that M-S-H with Mg/Si = 0.8 showed excellent carbonation resistance in which the phase remained stable in all investigated conditions. M-S-Hs with higher Mg/Si ratios (1.1 and 1.5) released Mg to obtain the stable M-S-H (Mg/Si = 0.8) while the released Mg dissolved in water or formed Mg‑carbonates under wet carbonation or pressurized carbonation, respectively. Hence, high temperature and/or pressure are needed to carbonate M-S-H with high Mg/Si ratios to form Mg‑carbonates. The remarkable stability of the strength-forming M-S-H phase under carbonation holds promising potential for future applications of such cements.

中文翻译：

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碳酸镁水合物 (MSH) 在碳酸化作用下的稳定性

这项工作提供了对碳酸化下不同 MSH 相行为的深入了解。在这里，我们在 i) 湿碳酸化和 ii) 干燥或蒸汽加压 CO 条件下对 8 年历史的 MSH 样品进行碳酸化。使用各种技术对固体和液体样品进行分析，同时耦合热力学模型以揭示 MSH 相在碳酸化。我们发现 Mg/Si = 0.8 的 MSH 表现出优异的抗碳化性，其中该相在所有研究条件下都保持稳定。具有较高Mg/Si比（1.1和1.5）的MS-Hs释放Mg以获得稳定的MSH（Mg/Si = 0.8），而释放的Mg分别在湿碳酸化或加压碳酸化下溶解在水中或形成碳酸镁。因此，需要高温和/或高压来碳化具有高 Mg/Si 比的 MSH，形成碳酸镁。在碳化作用下形成强度的 MSH 相具有显着的稳定性，为此类水泥的未来应用带来了广阔的前景。