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Desiccation Cracking Behavior of Carbon Microfiber Reinforced Bentonite Clay for Deep Geological Repositories.

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Title: Desiccation Cracking Behavior of Carbon Microfiber Reinforced Bentonite Clay for Deep Geological Repositories.
Authors: Azzam, Abdullah1 (AUTHOR), Kim, Yong-Rak1 (AUTHOR) yong-rak.kim@tamu.edu, Rahmani, Mohammad1 (AUTHOR), Eun, Jongwan2 (AUTHOR), Kim, Seunghee3 (AUTHOR)
Source: Geotechnical & Geological Engineering. Mar2026, Vol. 44 Issue 2, p1-19. 19p.
Abstract: Soil desiccation is a widely observed phenomenon that significantly affects soil integrity and hydromechanical behavior. Bentonite clay is considered the most promising material to be used as an engineered barrier material (EBM) for nuclear waste storage in deep geological repositories. However, bentonite desiccation raises a concern as it can create pathways for water to reach the canister and corrode it, causing potential leakage of nuclear waste and contamination of groundwater. Usage of inorganic fiber reinforcement can be effective in mitigating desiccation phenomena and minimizing desiccation cracking. This study investigates the effect of carbon microfiber reinforcement on bentonite clay desiccation behavior and internal microstructure change due to desiccation. We designed and conducted restrained ring and unrestrained disc free shrinkage tests coupled with digital image correlation and X-ray computed tomography (CT). Bentonite samples with carbon microfiber by varying length (12.5 and 25 mm) and content (0, 0.5, 1.0, and 1.5% wt) mixed at 40% moisture content were prepared and tested at an ambient condition. Results showed that the shrinkage and desiccation behavior between plain bentonite and carbon microfiber-reinforced bentonite was significantly changed, while a marginal effect was observed on moisture loss. Microfiber reduced the extent of macrocracks observed in the plain bentonite case and induced microcracks, as demonstrated by X-ray CT images that are aligned with digital image correlation surface images over the period of desiccation. Among the dosages attempted in this study, 1.0% reinforcement was better than 0.5%, and greater than 1.0% does not help much due to fiber entanglement during the mixing process. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Soil desiccation is a widely observed phenomenon that significantly affects soil integrity and hydromechanical behavior. Bentonite clay is considered the most promising material to be used as an engineered barrier material (EBM) for nuclear waste storage in deep geological repositories. However, bentonite desiccation raises a concern as it can create pathways for water to reach the canister and corrode it, causing potential leakage of nuclear waste and contamination of groundwater. Usage of inorganic fiber reinforcement can be effective in mitigating desiccation phenomena and minimizing desiccation cracking. This study investigates the effect of carbon microfiber reinforcement on bentonite clay desiccation behavior and internal microstructure change due to desiccation. We designed and conducted restrained ring and unrestrained disc free shrinkage tests coupled with digital image correlation and X-ray computed tomography (CT). Bentonite samples with carbon microfiber by varying length (12.5 and 25 mm) and content (0, 0.5, 1.0, and 1.5% wt) mixed at 40% moisture content were prepared and tested at an ambient condition. Results showed that the shrinkage and desiccation behavior between plain bentonite and carbon microfiber-reinforced bentonite was significantly changed, while a marginal effect was observed on moisture loss. Microfiber reduced the extent of macrocracks observed in the plain bentonite case and induced microcracks, as demonstrated by X-ray CT images that are aligned with digital image correlation surface images over the period of desiccation. Among the dosages attempted in this study, 1.0% reinforcement was better than 0.5%, and greater than 1.0% does not help much due to fiber entanglement during the mixing process. [ABSTRACT FROM AUTHOR]
ISSN:09603182
DOI:10.1007/s10706-026-03621-9