A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange
Shaft seals are geotechnical barriers in nuclear waste deposits and underground mines. The Sandwich sealing system consists of alternating sealing segments (DS) of bentonite and equipotential segments (ES). MiniSandwich experiments were performed with blended Ca-bentonite (90 mm diameter and 125 mm...
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| Format: | Article |
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MDPI AG
2021-09-01
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| Series: | Minerals |
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| Online Access: | https://www.mdpi.com/2075-163X/11/10/1061 |
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| author | Katja Emmerich Eleanor Bakker Franz Königer Christopher Rölke Till Popp Sarah Häußer Ralf Diedel Rainer Schuhmann |
| author_facet | Katja Emmerich Eleanor Bakker Franz Königer Christopher Rölke Till Popp Sarah Häußer Ralf Diedel Rainer Schuhmann |
| author_sort | Katja Emmerich |
| collection | DOAJ |
| description | Shaft seals are geotechnical barriers in nuclear waste deposits and underground mines. The Sandwich sealing system consists of alternating sealing segments (DS) of bentonite and equipotential segments (ES). MiniSandwich experiments were performed with blended Ca-bentonite (90 mm diameter and 125 mm height) to study hydration, swelling, solute transport and cation exchange during hydration with A3 Pearson water, which resembles pore water of Opalinus Clay Formation at sandy facies. Two experiments were run in parallel with DS installed either in one-layer hydrate state (1W) or in air-dry two-layer hydrate (2W) state. Breakthrough at 0.3 MPa injection pressure occurred after 20 days and the fluid inlet was closed after 543 days, where 4289 mL and 2984 mL, respectively, passed both cells. Final hydraulic permeability was 2.0–2.7 × 10<sup>−17</sup> m<sup>2</sup>. Cells were kept for another 142 days before dismantling. Swelling of DS resulted in slight compaction of ES. No changes in the mineralogy of the DS and ES material despite precipitated halite and sulfates occurred. Overall cation exchange capacity of the DS does not change, maintaining an overall value of 72 ± 2 cmol(+)/kg. Exchangeable Na<sup>+</sup> strongly increased while exchangeable Ca<sup>2+</sup> decreased. Exchangeable Mg<sup>2+</sup> and K<sup>+</sup> remained nearly constant. Sodium concentration in the outflow indicated two different exchange processes while the concentration of calcium and magnesium decreased potentially. Concentration of sulfate increased in the outflow, until it reached a constant value and chloride concentration decreased to a minimum before it slightly increased to a constant value. The available data set will be used to adapt numerical models for a mechanism-based description of the observed physical and geochemical processes. |
| first_indexed | 2024-03-10T06:20:49Z |
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| institution | Directory Open Access Journal |
| issn | 2075-163X |
| language | English |
| last_indexed | 2024-03-10T06:20:49Z |
| publishDate | 2021-09-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Minerals |
| spelling | doaj.art-1be4f03aa961421bb53d2dfd31b3d50d2023-11-22T19:16:12ZengMDPI AGMinerals2075-163X2021-09-011110106110.3390/min11101061A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation ExchangeKatja Emmerich0Eleanor Bakker1Franz Königer2Christopher Rölke3Till Popp4Sarah Häußer5Ralf Diedel6Rainer Schuhmann7Karlsruher Institut für Technologie (KIT), Kompetenzzentrum für Materialfeuchte (IMB-CMM), 76344 Eggenstein-Leopoldshafen, GermanyKarlsruher Institut für Technologie (KIT), Kompetenzzentrum für Materialfeuchte (IMB-CMM), 76344 Eggenstein-Leopoldshafen, GermanyIngenieur-Gesellschaft für Sensorik in der Umwelttechnik mbH (ISU), 76185 Karlsruhe, GermanyInstitut für Gebirgsmechanik (IfG), 04279 Leipzig, GermanyInstitut für Gebirgsmechanik (IfG), 04279 Leipzig, GermanyStephan Schmidt KG, 65599 Dornburg-Langendernbach, GermanyStephan Schmidt KG, 65599 Dornburg-Langendernbach, GermanyKarlsruher Institut für Technologie (KIT), Kompetenzzentrum für Materialfeuchte (IMB-CMM), 76344 Eggenstein-Leopoldshafen, GermanyShaft seals are geotechnical barriers in nuclear waste deposits and underground mines. The Sandwich sealing system consists of alternating sealing segments (DS) of bentonite and equipotential segments (ES). MiniSandwich experiments were performed with blended Ca-bentonite (90 mm diameter and 125 mm height) to study hydration, swelling, solute transport and cation exchange during hydration with A3 Pearson water, which resembles pore water of Opalinus Clay Formation at sandy facies. Two experiments were run in parallel with DS installed either in one-layer hydrate state (1W) or in air-dry two-layer hydrate (2W) state. Breakthrough at 0.3 MPa injection pressure occurred after 20 days and the fluid inlet was closed after 543 days, where 4289 mL and 2984 mL, respectively, passed both cells. Final hydraulic permeability was 2.0–2.7 × 10<sup>−17</sup> m<sup>2</sup>. Cells were kept for another 142 days before dismantling. Swelling of DS resulted in slight compaction of ES. No changes in the mineralogy of the DS and ES material despite precipitated halite and sulfates occurred. Overall cation exchange capacity of the DS does not change, maintaining an overall value of 72 ± 2 cmol(+)/kg. Exchangeable Na<sup>+</sup> strongly increased while exchangeable Ca<sup>2+</sup> decreased. Exchangeable Mg<sup>2+</sup> and K<sup>+</sup> remained nearly constant. Sodium concentration in the outflow indicated two different exchange processes while the concentration of calcium and magnesium decreased potentially. Concentration of sulfate increased in the outflow, until it reached a constant value and chloride concentration decreased to a minimum before it slightly increased to a constant value. The available data set will be used to adapt numerical models for a mechanism-based description of the observed physical and geochemical processes.https://www.mdpi.com/2075-163X/11/10/1061anion distributionCECexchangeable cationshydrationMiniSandwichsandwich sealing system |
| spellingShingle | Katja Emmerich Eleanor Bakker Franz Königer Christopher Rölke Till Popp Sarah Häußer Ralf Diedel Rainer Schuhmann A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange Minerals anion distribution CEC exchangeable cations hydration MiniSandwich sandwich sealing system |
| title | A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange |
| title_full | A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange |
| title_fullStr | A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange |
| title_full_unstemmed | A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange |
| title_short | A MiniSandwich Experiment with Blended Ca-Bentonite and Pearson Water—Hydration, Swelling, Solute Transport and Cation Exchange |
| title_sort | minisandwich experiment with blended ca bentonite and pearson water hydration swelling solute transport and cation exchange |
| topic | anion distribution CEC exchangeable cations hydration MiniSandwich sandwich sealing system |
| url | https://www.mdpi.com/2075-163X/11/10/1061 |
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