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Reaction of bentonite in low-alkali cement leachates: an overview of the Cyprus Natural Analogue Project (CNAP)

Published online by Cambridge University Press:  05 July 2018

W. R. Alexander ,
A. E. Milodowski ,
A. F. Pitty ,
S. M. L. Hardie ,
S. J. Kemp ,
P. Korkeakoski ,
M. Rigas ,
J. C. Rushton ,
P. Sellin  and
C. J. Tweed
W. R. Alexander*
Affiliation:
Bedrock Geosciences, Veltheimerstrasse 18, 5105 Auenstein, Switzerland
A. E. Milodowski
Affiliation:
British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK
A. F. Pitty
Affiliation:
Pitty (EIA) Consulting, 17 Black Horse Opening, Norwich, Norfolk NR3 4EP, UK
S. M. L. Hardie
Affiliation:
SUERC, Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride G75 0QF, UK
S. J. Kemp
Affiliation:
British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK
P. Korkeakoski
Affiliation:
Posiva, Olkiluoto, FI-27160 Eurajoki, Finland
M. Rigas
Affiliation:
Geological Survey Department, Lefkosia, Cyprus
J. C. Rushton
Affiliation:
British Geological Survey, Environmental Science Centre, Keyworth, Nottingham NG12 5GG, UK
P. Sellin
Affiliation:
SKB, Blekholmstorget 30, Box 250, SE-101 24 Stockholm
C. J. Tweed
Affiliation:
Radioactive Waste Management Directorate, Nuclear Decommissioning Authority, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0RH, UK
*
*E-mail: [email protected]
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Abstract

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The Cyprus Natural Analogue Project was carried out due to the requirement to support ongoing laboratory and modelling efforts on the potential reaction of the bentonite buffer with cementitious leachates in the repository engineered barrier system. Although it is known that the higher pH (12.5–13) leachates from ordinary Portland cement will degrade bentonite, it is unclear if this will also be the case for the lower pH (10–11) leachates typical of low alkali cements. Ongoing laboratory and underground rock laboratory programmes, which are currently investigating this, face the obstacle of slow kinetics and the production of short-lived metastable phases, meaning obtaining unambiguous results may take decades. It was therefore decided to implement a focussed natural analogue study on bentonite/low alkali cement leachate reactions to provide indications of the probable long-term reaction products and reaction pathways to provide feedback on the existing short-term investigations noted above and to ascertain if any critical path research and development needs to be instigated now. The results of the analyses presented here, in this short overview of the project, suggest that there has been very limited alkaline groundwater reaction with the bentonite. This is generally supported by both the geomorphological evidence and the natural decay series data which imply groundwater/rock interaction in the last 105 a.

Keywords

low alkali cementengineered barrier systems
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 8 , December 2012 , pp. 3019 - 3022
Creative Commons
Creative Common License - CCCreative Common License - BY
© [2012] The Mineralogical Society of Great Britain and Ireland. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2012

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