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Phase Relations and Solubility Modelling in the Cao- SiO2- Al2O3- MgO- SO3-H2O System: For Application To Blended Cementss.

Published online by Cambridge University Press:  28 February 2011

M. Atkins ,
F. P. Glasser  and
A. Kindness
M. Atkins
Affiliation:
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB9 2UE, U.K.
F. P. Glasser
Affiliation:
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB9 2UE, U.K.
A. Kindness
Affiliation:
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB9 2UE, U.K.
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Abstract

Cement blends are likely to form a large fraction of the materials in the near field of radioactive repositories. Being chemically reactive and slightly soluble, their effect on near field chemistry will be very marked. Predictions of nuclide migration in this zone will therefore depend in part on accurate modelling of cement chemistry.

The models being developed require the establishment of correct phase relations in the Cao- SiO2- Al2O3- MgO- SO3-H2O system (the major cement components). More than 40 compatibility experiments were carried out to determine these relationships. Purified cement hydrates were shaken continuously in CO2- free water, for 10 weeks. The results from these experiments together with data from the literature, enabled us to construct a better validated phase relations scheme than has hitherto been possible.

Interpretational problems were encountered. Thus, mixtures containing Ca(OH)2, gave rise to the precipitation of metastable phases. This is due to special dissolution/ precipitation equilibria obtaining at early age, allowing ‘AFm type’ (4CaO.Al2O3.SO3.12H2O) phases to form, where C3AH6 (3CaO.Al2O3.6H2O) and AFt (6CaO.Al2O3.3SO3.32H2O) are thermodynamically favoured.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 212: Symposium P – Scientific Basis for Nuclear Waste Management XIV , 1990 , 387
Copyright
Copyright © Materials Research Society 1991

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References

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