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Swelling characteristics of bentonite after long-term dissolution in alkaline solution

Published online by Cambridge University Press:  16 December 2019

Guo-sheng Xiang*
Affiliation:
Anhui University of Technology, Maanshan, Anhui, 243000, China Geological Resources and Geological Engineering Post-Doctoral Mobile Station, Tongji University, Shanghai, 200092, China
Wei-min Ye
Affiliation:
Geological Resources and Geological Engineering Post-Doctoral Mobile Station, Tongji University, Shanghai, 200092, China
Li-yong Lv
Affiliation:
Anhui University of Technology, Maanshan, Anhui, 243000, China

Abstract

In a high-level radioactive waste repository, bentonite may react with the alkaline solution produced by cement degradation. In this study, bentonite was mixed with alkaline solution in a closed system and reacted for 3–24 months. Furthermore, swelling tests were conducted on the alkaline-dissolved bentonite immersed in distilled water. The swelling deformation decreased significantly with increases in the concentration of NaOH solution and reaction time, and this was mainly due to montmorillonite dissolution. The fractal ep relationship (e is the void ratio and p is the vertical pressure) with two calculation coefficients (the swelling coefficient and the fractal dimension) was employed to determine the swelling of alkaline-dissolved bentonite. The fractal dimension increased slightly with increasing reaction time or concentration of NaOH solution, as the dissolution traces caused by the alkaline solution favoured an increase in the irregularity and fractality of the bentonite surface. The swelling coefficient decreased linearly with decreasing montmorillonite content. In addition, the swelling coefficient and the fractal dimension were related exponentially to the reaction time in alkaline solution. A relationship between the swelling of alkaline-dissolved samples and the reaction time was proposed, which might be used to assess the swelling properties of bentonite barriers that would be affected by long-term dissolution of the alkaline solution in a closed repository.

Type
Article
Copyright
Copyright © Mineralogical Society of Great Britain and Ireland 2020

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Footnotes

Associate Editor: Stephan Kaufhold

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