Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite-The Initial State and the State following Thermal Treatment at 200 degrees C

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00025798%3A_____%2F21%3A00000069" target="_blank" >RIV/00025798:_____/21:00000069 - isvavai.cz</a>

Alternative codes found

RIV/00216208:11310/21:10433366

Result on the web

<a href="https://www.mdpi.com/2075-163X/11/8/871" target="_blank" >https://www.mdpi.com/2075-163X/11/8/871</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.3390/min11080871" target="_blank" >10.3390/min11080871</a>

Result language

angličtina

Original language name

Mineralogical, Geochemical and Geotechnical Study of BCV 2017 Bentonite-The Initial State and the State following Thermal Treatment at 200 degrees C

Original language description

Bentonites are considered to be the most suitable materials for the multibarrier system ofhigh-level radioactive waste repositories. Since BCV bentonite has been proved to be an ideal representativeof Czech Ca-Mg bentonites in this respect, it has been included in the Czech RadioactiveWaste Repository Authority (SÚRAO) buffer and backfill R&D programme. Detailed knowledgeof processes in the material induced by thermal loading provides invaluable assistance regardingthe evolution of the material under repository conditions. Samples of both original BCV 2017 bentoniteand the same material thermally treated at 200 C were characterised by means of chemicalanalysis, powder X-ray diffraction, infrared spectroscopy, thermal analysis, cation exchange capacity,specific surface area (BET) measurements, the determination of the swell index, the liquid limit, theswelling pressure and water retention curves. The smectite in BCV 2017 bentonite comprises Ca-Mgmontmorillonite with a significant degree of Fe3+ substitution in the octahedral sheet. Two maintransformation processes were observed following heating at 200 C over 27 months, the first ofwhich comprised the dehydration of the montmorillonite and the subsequent reduction of the 001basal distance from 14.5 angstroem (the original BCV 2017) to 9.8 angstroem, thus indicating the absence of watermolecules in the interlayer space. The second concerned the dehydration and partial dehydroxylationof goethite. With the exception of the dehydration of the interlayer space, the PXRD andFTIR study revealed the crystallochemical stability of the montmorillonite in BCV 2017 bentoniteunder the selected experimental conditions. The geotechnical tests indicated no major changes in themechanical properties of the thermally treated BCV 2017 bentonite, as demonstrated by the similarswelling pressure values. However, the variation in the swell index and the gradual increase in theliquid limit with the wetting time indicated a lower hydration rate. The retention curves consistentlyshowed the lower retention capacity of the thermally treated samples, thus indicating the incompletere-hydration of the thermally treated BCV 2017 exposed to air humidity and the difference in itsbehaviour compared to the material exposed to liquid water.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10504 - Mineralogy

Project

Result was created during the realization of more than one project. More information in the Projects tab.

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2021

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Minerals

ISSN

2075-163X

e-ISSN

—

Volume of the periodical

11

Issue of the periodical within the volume

8 : 871

Country of publishing house

CH - SWITZERLAND

Number of pages

20

Pages from-to

nestránkováno

UT code for WoS article

000690554900001

EID of the result in the Scopus database

2-s2.0-85112196548