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In-Situ Interaction between Cement and Clay: Implications for Geological Disposal

Published online by Cambridge University Press:  21 March 2011

A. Sneyers ,
M. Paul ,
M. Tyrer ,
F.P. Glasser ,
J. Fays  and
P. Van Iseghem
A. Sneyers
Affiliation:
Belgian Nuclear Research Center SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
M. Paul
Affiliation:
University of Aberdeen, Department of Chemistry, Meston Walk, Aberdeen AB9 2UE, United Kingdom
M. Tyrer
Affiliation:
Imperial College, London, United Kingdom
F.P. Glasser
Affiliation:
University of Aberdeen, Department of Chemistry, Meston Walk, Aberdeen AB9 2UE, United Kingdom
J. Fays
Affiliation:
Belgian Nuclear Research Center SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
P. Van Iseghem
Affiliation:
Belgian Nuclear Research Center SCK•CEN, Boeretang 200, B-2400 Mol, Belgium
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Abstract

The extent and the consequences of interactions between cementitious materials used in radioactive waste management and clay host rock are described. In-situ tests were performed on seven cement formulations representing materials applied in repository construction, for backfilling or for solidification of radioactive waste. Samples were exposed to realistic repository conditions of the Boom Clay Formation in the HADES underground laboratory. Chemical, physical and mineralogical changes across the cement-clay interface were identified by combined observations from Electron Probe Microanalysis, Infrared microscopy and X-Ray powder diffraction. Significant interactions in both the cement and the clay part were found in a zone extending up to several hundreds of microns. The most prominent features are (1) leaching of cement with loss of calcium and/or silicon; (2) development of a calcium-rich zone in Boom Clay close to or at contact; (3) the formation of a contact zone marked by the precipitation of a (hydrated) magnesium aluminate phase; (4) reduction in apparent porosity of initially porous/permeable materials and (5) precipitation of calcite within the cement. This elemental exchange tends to diminish pH and reduce the buffering capacity of the cement. Although hydroxide will diffuse into the clay, the development of an extensive alkaline halo in the surrounding clay is unlikely owing to the buffering capacity of the Boom Clay pore water.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 663: Symposium – Scientific Basis for Nuclear Waste management XXIV , 2000 , 123
Copyright
Copyright © Materials Research Society 2001

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References

REFERENCES

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