Abstract The present study focuses on the interaction between cement mortar (OPC-based CEM-II) and the FEBEX-bentonite; this interaction takes place at a small spatial scale (~1 cm/~1 cm; compacted cement mortar/compacted bentonite thickness) within a timeline of 6 and 18 months. This work was designed to determine the early interaction processes and compare them with large-scale FEBEX in situ underground research laboratory experiments. The study aimed at the primary reactions that occurred at the interface in a small spatial scale (nm-μm scale). The experimental device consisted of a composite column containing the cement mortar/bentonite materials. A granitic groundwater solution was injected through the cement mortar/bentonite system and collected out of the column in sequential syringes for analysis of the chemical composition evolution. For the study of the post-mortem samples, an innovative use of grazing incidence X-ray diffraction was performed to determine the phases produced at the interface. Scanning electron microscopy coupled to energy dispersive X-rays and local specific surface area measurements were also applied. The main results showed the initial development of a Mg perturbation in FEBEX-bentonite at the interface related to the formation of 7 A precursors of Mg-clay 2:1 sheet silicates as the main neogenic phases expected in the long term. Additionally, a Ca-carbonation skin (calcite) occurred in cement mortar at the interface. The specifications of the reaction products observed at small scales of time and space (μm) are highly promising for the development of reaction concepts and support modelling in the future, which could offer a useful perspective for advancement in the upscaling of concrete/bentonite interface perturbation.

中文翻译：

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膨润土/CEM-II 水泥砂浆界面实验：代表原位深层地质处置库工程屏障系统表面反应性

摘要 本研究的重点是水泥砂浆（基于OPC 的CEM-II）与FEBEX-膨润土之间的相互作用；这种相互作用发生在一个小空间尺度（~1 cm/~1 cm；压实水泥砂浆/压实膨润土厚度），时间为 6 个月和 18 个月。这项工作旨在确定早期的相互作用过程，并将它们与大型 FEBEX 原位地下研究实验室实验进行比较。该研究针对发生在小空间尺度（nm-μm 尺度）的界面处的初级反应。实验装置由包含水泥砂浆/膨润土材料的复合柱组成。花岗岩地下水溶液通过水泥砂浆/膨润土系统注入，并用连续注射器从柱子中收集，用于分析化学成分的演变。为了研究验尸样品，创新性地使用掠入射 X 射线衍射来确定界面处产生的相。还应用了与能量色散 X 射线和局部比表面积测量耦合的扫描电子显微镜。主要结果表明，FEBEX-膨润土界面处的 Mg 扰动的初步发展与 Mg-粘土 2:1 片状硅酸盐的 7A 前驱体的形成有关，作为长期预期的主要新生相。此外，在界面处的水泥砂浆中出现了钙碳酸化表皮（方解石）。在小时间和空间（μm）尺度上观察到的反应产物的规格对于未来反应概念的发展和支持建模非常有希望，