Abstract The geochemical interactions at the interfaces of the materials used for the engineered barrier system (EBS) of spent-fuel and high-level radioactive waste repositories may impact the long-term performance of the EBS. These materials include carbon steel, compacted bentonite and concrete. The geochemical reactions are commonly studied in laboratory and in situ tests and by numerical modelling. Cuevas et al. (2016) performed double interface (2I) lab tests to study the interactions of lime-mortar, bentonite and magnetite on cylindrical cells with an internal diameter of 5 cm and an inner length of 2.5 cm, which were hydrated with a synthetic argillaceous water and heated at 60 °C during 18 months. Here, we present a reactive transport model of the 2I tests of Cuevas et al. (2016). The model confirms the proposed conceptual geochemical model and quantifies the mineralogical alterations and the changes in porosity produced by the complex geochemical interactions of lime-mortar, bentonite and magnetite at 60 °C. The model predicts the dissolution of portlandite in the mortar and the precipitation of calcite, brucite, C1.2SH and C1.6SH in the mortar and the bentonite near the mortar/bentonite interface (MBI). Anhydrite precipitates in the mortar, but it is transformed into gypsum after the cooling of the sample. The model predicts a small precipitation of ettringite. Most of the mineralogical changes are predicted to occur at or near the MBI. The high pH front (pH > 8) penetrates 11 mm into the bentonite at the end of the 2I-3 test. The porosity of the mortar near the MBI increases 1% due to portlandite and gypsum dissolution. On the other hand, the porosity of the bentonite decreases 1% in a 0.2 mm thick band near the MBI due to the precipitation of calcite, brucite, sepiolite and Mg-saponite. Model results reproduce the water content, the saturation degree and the water intake measured at the end of the test and capture the main trends of the mineralogical observations. Model results, however, fail to predict the observed ettringite precipitation in the mortar. The predicted brucite precipitation in the mortar and the bentonite is not confirmed by the experimental data.

中文翻译：

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石灰砂浆、压实膨润土和磁铁矿地球化学相互作用实验室试验的反应输运模型

摘要 乏燃料和高放废物处置库工程屏障系统 (EBS) 所用材料界面处的地球化学相互作用可能会影响 EBS 的长期性能。这些材料包括碳钢、压实膨润土和混凝土。地球化学反应通常在实验室和原位试验以及数值模拟中进行研究。奎瓦斯等人。(2016) 进行了双界面 (2I) 实验室测试，以研究石灰砂浆、膨润土和磁铁矿在内径为 5 厘米、内长为 2.5 厘米的圆柱形电池上的相互作用，这些圆柱形电池与合成泥浆水和在 60 °C 下加热 18 个月。在这里，我们提出了 Cuevas 等人的 2I 测试的反应传输模型。(2016)。该模型证实了所提出的概念地球化学模型，并量化了 60 °C 下石灰砂浆、膨润土和磁铁矿的复杂地球化学相互作用产生的矿物学蚀变和孔隙度变化。该模型预测了砂浆中硅酸盐的溶解以及砂浆中方解石、水镁石、C1.2SH 和 C1.6SH 以及砂浆/膨润土界面 (MBI) 附近膨润土的沉淀。硬石膏在砂浆中沉淀，但在样品冷却后转变为石膏。该模型预测钙矾石的少量沉淀。大多数矿物学变化预计发生在 MBI 或附近。在 2I-3 测试结束时，高 pH 前沿（pH > 8）渗入膨润土 11 毫米。由于硅酸盐和石膏溶解，MBI 附近砂浆的孔隙率增加了 1%。另一方面，由于方解石、水镁石、海泡石和镁皂石的沉淀，膨润土的孔隙率在 MBI 附近 0.2 毫米厚的带中降低了 1%。模型结果再现了测试结束时测量的含水量、饱和度和取水量，并捕捉了矿物学观察的主要趋势。然而，模型结果未能预测砂浆中观察到的钙矾石沉淀。实验数据未证实砂浆和膨润土中预测的水镁石沉淀。模型结果再现了测试结束时测量的含水量、饱和度和取水量，并捕捉了矿物学观察的主要趋势。然而，模型结果未能预测砂浆中观察到的钙矾石沉淀。实验数据未证实砂浆和膨润土中预测的水镁石沉淀。模型结果再现了测试结束时测量的含水量、饱和度和取水量，并捕捉了矿物学观察的主要趋势。然而，模型结果未能预测砂浆中观察到的钙矾石沉淀。实验数据未证实砂浆和膨润土中预测的水镁石沉淀。