2024
ACL
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S.Grangeon , M.Debure , V.Montouillout , E.Elkaim , C.Lerouge , N.Maubec , N.Michau , X.Bourbon , C.Martin , B.Cochepin, N.Marty, 'Mineralogical and geochemical composition of a cementitious grout and its evolution during interaction with water', npj Mat. Degrad. 8 75 (2024) doi:10.1038/s41529-024-00488-0
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 CO3
2− (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 CA-S-H dissolution. The evolution of solution chemistry and of the solid phase composition are
reproduced successfully using a thermokinetic model
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