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25. Evaluation of long-term durability of concrete in contact with bentonite mixed with NaHCO3 by electrical migration technique



Title: 25. Evaluation of long-term durability of concrete in contact with bentonite mixed with NaHCO3 by electrical migration technique
Author(s): K. Nakarai, M. Watanabe, K. Koibuchi
Paper category : conference
Book title: NUCPERF 2009 - Long Term Performance of Cementitious Barriers and Reinforced Concrete in Nuclear Power Plants and Waste Management
Editor(s): V. L'Hostis, R. Gens, C. Gallé
Print-ISBN: 978-2-35158-072-1
e-ISBN: 978-2-35158-087-5
Publisher: RILEM Publications SARL
Publication year: 2009
Pages: 229 - 235
Total Pages: 7
Nb references: 8
Language: English


Abstract: In Japan, an engineered barrier system consisting of a bentonite-sand mixture and cementitious materials is presently being studied for a low level radioactive waste repository.
Calcium leaching from the cementitious materials into bentonite materials is one of the main issues for discussing the degradation of the engineered barrier system over a long service life.
In this study, the mixing of sodium hydrogen carbonate into a bentonite-sand mixture was proposed so that the precipitation of calcium carbonate at the cement/bentonite interface can improve the performance of the multiple engineered barrier system. For evaluating the extremely long-term durability of the barrier system, an electrical migration technique was applied as an accelerated method. In the experiment, the influence of mixing a concentration of sodium carbonate into the bentonite sand mixture was investigated. As a result, in the specimen without sodium hydrogen carbonate, a large decrease in calcium hydroxide in the cement paste and a decrease in the swelling capacity with the increase in the calcium ion concentration in the bentonite were observed. On the other hand, in the specimens mixed with sodium hydrogen carbonate, degradation was reduced with the increase in calcium carbonate.


Online publication: 2009-11-16
Publication type : full_text
Public price (Euros): 0.00