The Cement–Opalinus Clay Interaction (CI) Experiment at the Mont Terri rock laboratory is a long-term passive diffusion–reaction experiment between contrasting materials of relevance to engineered barrier systems/near-field for deep disposal of radioactive waste in claystone (Opalinus Clay). Reaction zones at interfaces of Opalinus Clay with two different types of concrete (OPC and “low-pH”/ESDRED) were examined by sampling after 2.2 and 4.9 years. Analytical methods included element mapping (SEM, EPMA), select spot analysis (EDAX), 14C-MMA impregnation for radiography, and powder methods (IR, XRD, clay-exchanger characterisation) on carefully extracted miniature samples (mm). The presence of aggregate grains in concrete made the application of all methods difficult. Common features are a very limited extent of reaction within claystone, and a distinct and regularly zoned reaction zone within the cement matrix that is more extensive in the low-alkali cement (ESDRED). Both interfaces feature a de-calcification zone and overprinted a carbonate alteration zone thought to be mainly responsible for the observed porosity reduction. While OPC shows a distinct sulphate enrichment zone (indicative of ingress from Opalinus Clay), ESDRED displays a wide Mg-enriched zone, also with claystone pore-water as a source. A conclusion is that substitution of OPC by low-alkali cementitious products is not advantageous or necessary solely for the purpose of minimizing the extent of reaction between claystone and cementitious materials. Implications for reactive transport modelling are discussed.

中文翻译：

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蒙特利岩石实验室（瑞士），混凝土-粘土岩界面的5年化学-物理演化

Mont Terri岩石实验室的水泥-Opalinus粘土相互作用（CI）实验是一项长期的被动扩散-反应实验，用于对比深层处理粘土石中放射性废物的工程屏障系统/近场的对比材料（Opalinus粘土）。在2.2年和4.9年后，通过取样检查了Opalinus粘土与两种不同类型混凝土（OPC和“低pH” / ESDRED）的界面处的反应区。分析方法包括元素图谱（SEM，EPMA），选择点分析（EDAX），用于放射线照相的14C-MMA浸渍以及对精心提取的微型样品（mm）的粉末方法（IR，XRD，粘土交换剂表征）。混凝土中骨料颗粒的存在使所有方法的应用变得困难。共同的特征是粘土中的反应程度非常有限，以及水泥基质内明显且规则划分的反应区，在低碱水泥（ESDRED）中更为广泛。两个界面都具有脱钙区和覆盖碳酸盐蚀变区的套印区，据认为这主要是所观察到的孔隙度降低的原因。OPC显示了一个明显的硫酸盐富集区（表明是从蛋白石粘土进入的区域），而ESDRED显示了一个宽广的Mg富集区，也有粘土岩孔隙水作为来源。结论是，仅出于最小化粘土石与胶凝材料之间反应程度的目的，用低碱性胶凝产品替代OPC既无优势也不是必需的。讨论了反应性运输模型的含义。