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

Kód výsledku v 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>

Nalezeny alternativní kódy

RIV/00216208:11310/21:10433366

Výsledek na webu

<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>

Jazyk výsledku

angličtina

Název v původním jazyce

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

Popis výsledku v původním jazyce

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.

Název v anglickém jazyce

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

Popis výsledku anglicky

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.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10504 - Mineralogy

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

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

Rok uplatnění

2021

Kód důvěrnosti údajů

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

Název periodika

Minerals

ISSN

2075-163X

e-ISSN

—

Svazek periodika

11

Číslo periodika v rámci svazku

8 : 871

Stát vydavatele periodika

CH - Švýcarská konfederace

Počet stran výsledku

20

Strana od-do

nestránkováno

Kód UT WoS článku

000690554900001

EID výsledku v databázi Scopus

2-s2.0-85112196548