Formation of magnesium silicate hydrate (M-S-H) at pH 10 and 50°C in open-flow systems

Nishiki, Yuto; Cama, Jordi; Otake, Tsubasa; Kikuchi, Ryosuke; Shimbashi, Misato; Satō, Tsutomu

doi:10.1016/j.apgeochem.2022.105544

Cited by 5 publications

(1 citation statement)

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“…The shift occurred at L/S >100 for the OPC pastes and L/S > 10 for the LAC pastes and was assumed to be caused by the dissolution of C-S-H and the formation of M-S-H as a secondary product. M-S-H structures were reported to have either a serpentine-like 1:1 type structure with tetrahedral and octahedral sheets combined 1:1 (T-O layer), or a talc-like 2:1 type structure with octahedral sheets sandwiched between tetrahedral sheets (T-O-T layer) [28,[45][46][47]. The peak positions of M-S-H identified in the immersed samples were consistent with the serpentine group (around 680 cm −1 ) for the OPC pastes and talc (around 670 cm −1 ) for the LAC pastes, indicating that the formed structure of M-S-H was different depending on the type of cement.…”

Section: Solid Characterizationmentioning

confidence: 99%

Mineralogical Evolution of High-pH/Low-pH Cement Pastes in Contact with Seawater

Kobayashi,

Sato

2024

Minerals

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In facilities for the geological disposal of radioactive waste in coastal areas, the long-term alteration of cementitious materials in engineered barriers is expected to occur due to the ingress of groundwater derived from seawater. Although the reaction between cement and seawater has been studied, the alteration behavior caused by the reaction between seawater and low-pH cement, which is expected to be used in a disposal facility, has not yet been clarified. In this study, the effects of cement type on cement–seawater interactions were investigated, and the chemical stability and mineral evolution of cement pastes caused by reactions with seawater were determined. The dissolution of cement hydrates occurred upon increased contact with seawater, and the formation of secondary minerals, including carbonate and Mg-containing minerals, was observed. The progress of dissolution depended on the mineral composition of the initially formed cement hydrates, and low-pH cement containing pozzolanic materials showed less resistance to seawater. Differences in pH and Si concentration that are due to the type of cement used had a strong influence on the evolution of minerals (especially Mg-containing minerals), implying that the formed mineral species possibly affect the migration characteristics of radionuclide.

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Section: Solid Characterizationmentioning

confidence: 99%