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Cracking in a cementitious backfill and its implications for flow and chemistry

Published online by Cambridge University Press:  05 July 2018

B. T. Swift ,
P. B. Bamforth  and
G. M. N. Baston
B. T. Swift*
Affiliation:
AMEC, Building 150, Thomson Avenue, Harwell Oxford, Didcot, Oxfordshire OX11 0QB, UK
P. B. Bamforth
Affiliation:
8 Hamilton Court, Hamilton Road, Ealing, London W5 2EJ, UK
G. M. N. Baston
Affiliation:
AMEC, Building 150, Thomson Avenue, Harwell Oxford, Didcot, Oxfordshire OX11 0QB, UK
*
*E-mail: [email protected]
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Abstract

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In the UK, disposal of packaged intermediate-level radioactive waste may involve waste packages being placed in a geological disposal facility (GDF) and surrounded by a cementitious backfill. Cracking of the backfill could occur due to a number of mechanisms, and this could affect the post-closure performance of the GDF.

This work has assessed potential cracking in the backfill during the backfilling and early post-closure period of GDF vaults with an open crown space in a higher strength rock. From the comprehensive range of processes considered, three were identified as potentially causing cracking: (1) during backfilling, plastic settlement under solid horizontal surfaces could result in horizontal gaps beneath waste packages; (2) within days of backfilling, early-age thermal contraction of the backfill could result in primarily vertical cracks; (3) over a number of years, expansion of waste packages could result in large horizontal cracks.

A groundwater flow model incorporating a representation of the cracks was used to calculate flows through a backfilled GDF vault, and through the cracks themselves. Including cracks increased the flow rate significantly. A reactive transport model was used to estimate the evolution of the pore water chemistry as groundwater flows through the cracked backfill. Calcite and brucite were predicted to precipitate, with brucite subsequently dissolving. Calcite build-up could seal some cracks.

Keywords

wastegeological disposalcementitious backfillcrackinggroundwater flowpHbrucitecalcitearmouring
Type
Research Article
Information
Mineralogical Magazine , Volume 76 , Issue 8 , December 2012 , pp. 3071 - 3082
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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