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- Title
Mineralogical and geochemical composition of a cementitious grout and its evolution during interaction with water.
- Authors
Grangeon, Sylvain; Debure, Mathieu; Montouillout, Valerie; Elkaim, Erik; Lerouge, Catherine; Maubec, Nicolas; Michau, Nicolas; Bourbon, Xavier; Martin, Christelle; Cochepin, Benoit; Marty, Nicolas
- Abstract
In the present study, the chemical composition, mineralogy, and mechanisms of alteration of a cementitious grout based on a CEM III/C with addition of smectite, hydrotalcite, and silica fume, are studied using a combination of chemical and physical methods. This material was designed in the context of geological repository of radioactive wastes, with a twofold aim: first, to fill the technical voids left by drilling operations at the interface between the geological formation and the disposal galleries. Second, to neutralize a potential acidic transient due to pyrite oxidation, and to create an environment that favors low corrosion rates of carbon steels. The grout is mainly composed of calcium silicate hydrates having a Ca/Si ratio of ~0.8, incorporating Al in the bridging site of the Si chains (C-A-S-H), and accounting for 29–36 wt.% of the sample. It also contains silica fume (38–48 wt.%), smectite with interlayer Na (11–17 wt.%), hydrotalcite with interlayer CO32− (3–4 wt.%), and lower amounts of portlandite, calcite, and possibly gibbsite and gypsum. Upon alteration by water in a flow-through reactor, the main modifications affecting the sample are calcite and gypsum dissolution, hence releasing aqueous Ca2+ that is adsorbed in smectite interlayer by replacing Na+, and stoichiometric C-A-S-H dissolution. The evolution of solution chemistry and of the solid phase composition are reproduced successfully using a thermokinetic model.
- Subjects
GYPSUM; GEOLOGICAL repositories; RADIOACTIVE waste repositories; CALCIUM silicate hydrate; GROUTING; GIBBSITE; CARBON steel corrosion; RADIOACTIVE waste disposal
- Publication
NPJ Materials Degradation, 2024, Vol 8, Issue 1, p1
- ISSN
2397-2106
- Publication type
Article
- DOI
10.1038/s41529-024-00488-0