27Al MAS NMR Study on Cement Paste Degradation by Water

Faucon, P.; Jacquinot, J. F.; Adenot, F.; Gautier, N.; Massiot, Dominique; Virlet, J.

doi:10.1007/978-3-642-80432-8_34

Cited by 2 publications

(1 citation statement)

References 6 publications

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“…The C-S-H phases were, however, neither pure nor well-separated from other mineralogical species. Thus, small amounts of aluminum incorporated in C-S-H were frequently observed, in line with the findings of Faucon et al (27) who demonstrated, using 27 Al MAS NMR, that Al substituted for the tetrahedrically coordinated Si in C-S-H. In addition, precipitated CaCO3 was superimposed during the weathering process on already present C-S-H and gibbsite phases, especially near the borders of the samples.…”

Section: Discussionsupporting

confidence: 87%

Retention of Trace Metals by Solidified/Stabilized Wastes: Assessment of Long-Term Metal Release

Badreddine

Mingelgrin

et al. 2004

Environ. Sci. Technol.

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Toxic elements found in wastes may have a negative impact on the environment, especially through the contamination of groundwater and plants. To reduce their mobility and availability, French regulations mandate the solidification and stabilization of toxic wastes. Many methods to stabilize and solidify wastes exist, among them the Ecofix process which employs low cost materials and consists of mixing wastes with lime, aluminum hydroxide, and silica. To evaluate the long-term behavior of solidified/stabilized (S/S) samples, their alteration under saturated conditions was studied in a water extractor, a Soxhlet-like device, used to follow the weathering of rocks. Kinetic measurements have shown that the release of Fe, Pb, Cd, Cr, and Cu was very slow, indicating a strong retention of these elements by the S/S materials prepared by the Ecofix process. To elucidate the mechanisms of retention of the trace metals, the mineral phases that existed in the S/S samples throughout and at the end of the extraction runs were studied by X-ray diffraction and by infrared and nuclear magnetic resonance spectroscopies. Scanning electron microscopic (SEM) examinations and electron microprobe analyses of the S/S samples were also performed at different stages of weathering. These observations revealed that assorted calcium silicate hydrates (C-S-H) were the predominant phases in the S/S preparations and that gradual alterations occurred in the structure of the investigated materials. The overall Ca/Si ratio of the C-S-H phases decreased as the enhanced alteration progressed. Although trace metals in oxide, hydroxide, and carbonate forms were found in the S/S materials, the bulk of the trace metals was incorporated in the matrix of the C-S-H phases.

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Section: Discussionsupporting

confidence: 87%

Retention of Trace Metals by Solidified/Stabilized Wastes: Assessment of Long-Term Metal Release

Badreddine

Mingelgrin

et al. 2004

Environ. Sci. Technol.

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Study of oilwell cements by solid-state NMR

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Rivereau

et al. 2004

Comptes Rendus. Chimie

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The prime objective of the plug-and-abandon operations is to provide zonal isolation for infinite time. Cement-based materials are generally used as plugging materials. Therefore, it is important to understand physical and chemical processes causing cement degradation in downhole environment. In this study, we have characterised two cement formulations at different ageing conditions using NMR and XRD techniques. In particular, we evidence that an increase in pressure and temperature leads to more polymerised calcium silicate hydrates (C-S-H). In the low permeability cement samples, it was shown that the pozzolanic activity of silica fumes increases with temperature and pressure and leads to the consummation of all the portlandite released during cement hydration. RésuméL'objectif d'une opération d'abandon de puits est d'établir une zone d'isolation pour une durée infinie. Les bouchons mis en place pour fermer les puits sont majoritairement des bouchons de ciment. Il est donc important de comprendre les différents processus physiques et chimiques de la dégradation du ciment dans les conditions de puits. Dans cette étude, nous avons caractérisé la structure de deux formulations dans différentes conditions de vieillissement, en utilisant les techniques de RMN et de DRX. Nous avons pu montrer que l'augmentation de pression et de température conduisait à une polymérisation plus importante des silicates de calcium hydratés (C-S-H). Dans le cas des ciments de faible perméabilité, nous avons mis en évidence une accélération de l'activité pouzzolanique de la fumée de silice lorsque la température et la pression augmentent.

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27Al MAS NMR Study on Cement Paste Degradation by Water

Cited by 2 publications

References 6 publications

Retention of Trace Metals by Solidified/Stabilized Wastes: Assessment of Long-Term Metal Release

Retention of Trace Metals by Solidified/Stabilized Wastes: Assessment of Long-Term Metal Release

Study of oilwell cements by solid-state NMR

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