Interfaces between cement and clay are common in engineered barrier systems for the underground disposal of radioactive waste. The geochemical contrast between clay and cement leads to alterations of both materials following dissolution and precipitation reactions. Porosity is a key parameter for, and a key outcome of, such reactive transport. Here we report on the evolution of porosity within small samples made from ordinary portland cement and Na montmorillonite. Water contents, a proxy for porosity in saturated samples, were derived from neutron imaging. Specific calibration procedures were developed to account for multiple scattering effects. An increase in cement porosity was observed propagating similar to 2 mm away from the interface within 600 days, and a considerable decrease in clay porosity within similar to 2 mm. Our experiments provide unique information on the dynamics of the processes up to nearly two years. The data set provides valuable input to better constrain reactive transport models.

中文翻译：

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来自中子成像的水泥-粘土界面的时间分辨孔隙度变化

水泥和粘土之间的界面在用于放射性废物地下处置的工程屏障系统中很常见。粘土和水泥之间的地球化学对比导致两种材料在溶解和沉淀反应后发生变化。孔隙度是这种反应输运的关键参数和关键结果。在这里，我们报告了由普通硅酸盐水泥和 Na 蒙脱石制成的小样品中孔隙率的演变。水含量是饱和样品孔隙度的代表，来自中子成像。开发了特定的校准程序以解决多重散射效应。在 600 天内观察到水泥孔隙度增加，距离界面大约 2 毫米，而粘土孔隙度在大约 2 毫米范围内显着下降。我们的实验提供了长达近两年的过程动态的独特信息。该数据集提供了有价值的输入，以更好地约束反应传输模型。