The influence of initial curing temperature on the stability of calcium silicate hydrates (C-S-H) produced by alite hydration in the temperature range of 110 °C–240 °C was investigated. Test results showed that, alite pastes directly cured under high temperatures yielded dramatically faster crystallization of C-S-H compared to those precured at a low temperature of 80 °C before the high temperature curing. The direct high-temperature curing also resulted in simplified crystalline phase evolution with only α-CSH produced below 200 °C. Detailed analyses employing XRD, TGA and MAS-NMR techniques revealed that the crystallization of C-S-H is accompanied by the increases of its Ca/Si and HO/Si ratios as well as the reduction in the number of bridging tetrahedra in silicate chains. The decreased stability of C-S-H formed at direct high-temperature curing was probably induced by the generation of α-CSH nuclei during the initial stages of alite hydration, enabling selective control of C-S-H crystallization.

中文翻译：

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阿利特水合生成的硅酸钙水合物在高温和超高温下的稳定性

研究了110℃~240℃温度范围内初始固化温度对阿利特水合生成的水合硅酸钙(CSH)稳定性的影响。测试结果表明，与高温固化前在 80 °C 低温下预固化的糊剂相比，在高温下直接固化的阿利特糊剂产生的 CSH 结晶速度显着加快。直接高温固化还导致简化的结晶相演化，在 200 °C 以下仅产生 α-CSH。采用 XRD、TGA 和 MAS-NMR 技术的详细分析表明，CSH 的结晶伴随着其 Ca/Si 和 H2O/Si 比率的增加以及硅酸盐链中桥联四面体数量的减少。直接高温固化时形成的CSH稳定性下降可能是由于阿利特水合初始阶段α-CSH核的生成引起的，从而能够选择性控制CSH结晶。