Modeling experimental results of diffusion of alkaline solutions through a compacted bentonite barrier
- Instituto Eduardo Torroja de Ciencias de la Construccion (CSIC), C/Serrano Galvache, 4, 28033 Madrid (Spain)
- Dpto. Geologia y Geoquimica, Facultad de Ciencias, Universidad Autonoma de Madrid, Campus Cantoblanco, 28049 Madrid (Spain)
- Institut fuer Geologie, Universitaet Bern, Baltzerstrasse 3, CH-3012 Bern (Switzerland)
The interaction between concrete/cement and swelling clay (bentonite) has been modeled in the context of engineered barrier systems for deep geological disposal of high-level radioactive waste. The geochemical transformations observed in laboratory diffusion experiments at 60 and 90 {sup o}C between bentonite and different high-pH solutions (K-Na-OH and Ca(OH){sub 2}-saturated) were reconciled with the reactive transport code CrunchFlow. For K-Na-OH solutions (pH = 13.5 at 25 {sup o}C) partial dissolution of montmorillonite and precipitation of Mg-silicates (talc-like), hydrotalcite and brucite at the interface are predicted at 60 {sup o}C, while at 90 {sup o}C the alteration is wider. Alkaline cations diffused beyond the mineralogical alteration zone by means of exchange with Mg{sup 2+} in the interlayer region of montmorillonite. Very slow reactivity and minor alteration of the clay are predicted in the Ca(OH){sub 2}-bentonite system. The model is a reasonable description of the experiments but also demonstrates the difficulties in modeling processes operating at a small scale under a diffusive regime.
- OSTI ID:
- 21483647
- Journal Information:
- Cement and Concrete Research, Vol. 40, Issue 8; Other Information: DOI: 10.1016/j.cemconres.2009.09.011; PII: S0008-8846(09)00253-1; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0008-8846
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BENTONITE
CALCIUM HYDROXIDES
CATIONS
CEMENTS
CONCRETES
DIFFUSION
DISSOLUTION
ENVIRONMENTAL TRANSPORT
GEOCHEMISTRY
HIGH-LEVEL RADIOACTIVE WASTES
INTERACTIONS
INTERFACES
KINETICS
MAGNESIUM IONS
MAGNESIUM SILICATES
MONTMORILLONITE
PH VALUE
PRECIPITATION
RADIOACTIVE WASTE DISPOSAL
REACTIVITY
SIMULATION
SOLUTIONS
SWELLING
TEMPERATURE RANGE 0273-0400 K
ALKALINE EARTH METAL COMPOUNDS
BUILDING MATERIALS
CALCIUM COMPOUNDS
CHARGED PARTICLES
CHEMISTRY
CLAYS
DEFORMATION
DISPERSIONS
HOMOGENEOUS MIXTURES
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
IONS
MAGNESIUM COMPOUNDS
MANAGEMENT
MASS TRANSFER
MATERIALS
MINERALS
MIXTURES
OXYGEN COMPOUNDS
RADIOACTIVE MATERIALS
RADIOACTIVE WASTE MANAGEMENT
RADIOACTIVE WASTES
SEPARATION PROCESSES
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TEMPERATURE RANGE
WASTE DISPOSAL
WASTE MANAGEMENT
WASTES