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Comparison of the dry densities of highly compacted bentonites

S. Kaufhold, M. Klinkenberg and R. Dohrmann
Comparison of the dry densities of highly compacted bentonites
Clay Minerals (March 2013) 48 (1): 105-115


Bentonites are in worldwide use as candidate materials for the encapsulation of high-level radioactive waste (HLRW). To effectively seal waste canisters, bentonite is compacted to bentonite blocks which can be used to build a wall around the canisters. Compaction significantly improves the swelling pressure, which is currently considered as one of the most important parameters for assessing barrier performance. Most of the studies on compressibility of bentonites consider a few different materials only, which does not lead to a general understanding of bentonite performance. In order to identify the actual compressibility differences of different bentonites, a sizeable set of well characterized materials was investigated with respect to the dry densities after compaction. Different results were obtained for bentonites that had been dried and bentonites that were equilibrated at 70% r.h. (relative humidity) prior to compaction. The dry density of dried bentonites depends on total porosity and particle density. However, the dry density of microporous bentonites depends on the microporosity rather than total porosity because microporosity is not reduced upon compaction. On the other hand, for the samples previously equilibrated at 70% r.h., the water content is most important. However, the water content, i.e. the water uptake capacity at 70% r.h., in turn largely depends on the CEC but also on microporosity. Therefore, under a given load, the 36 bentonites studied showed a significant range of resulting dry densities, depending on water content, CEC and porosity. In conclusion, for a given bentonite, the dry density after compaction explains some geotechnical parameters such as the swelling pressure. However, for reasons explained in the present study, the dry density cannot be generally used to predict these parameters.

ISSN: 0009-8558
EISSN: 1471-8030
Serial Title: Clay Minerals
Serial Volume: 48
Serial Issue: 1
Title: Comparison of the dry densities of highly compacted bentonites
Affiliation: Bundesanstalt fuer Geowissenschaften und Rohstoffe, Hanover, Germany
Pages: 105-115
Published: 201303
Text Language: English
Publisher: Mineralogical Society, London, United Kingdom
References: 21
Accession Number: 2013-032298
Categories: Sedimentary petrologyEnvironmental geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 plate
Secondary Affiliation: Institut fuer Energieforschung-Sicherheitsforschung und Reaktortechnik (IEF-6), DEU, GermanyLandesamt fur Bergbau, Energie und Geologie, DEU, Germany
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Mineralogical Society of Great Britain and Ireland. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201320
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