Solid-State NMR Characterization of Organics in Cement

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Solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) has been applied to cement samples containing water-soluble organics, ethylene glycol, phenol, p­bromophenol and p-chlorophenol. Cement matrix development has been followed by 29Si and27Al NMR, which shows the organics, particularly ethylene glycol, to be promoters of silicate polymerization despite the fact that they reduce the compressive strength of the pastes. 13C NMR shows that phenol is completely ionized in cement pastes, but with substituted phenols in the presence of extra added metal salts, ionization is not always complete. 2H NMR on d5-phenol shows that even in mature cement pastes, most of the phenol is in a liquid-like environment, presumably dissolved in pore waters. When water is evaporated, the phenol begins to occupy a bound environment with a binding energy of at least 23 kJ/mol (5.5 kcal/mol). Relaxation time measurements on the ethylene glycol system can also be interpreted in terms of a major fraction of the glycol dissolved in pore water and a minor fraction bound to cement surfaces. Clearly, knowledge of the effects of additives on cement matrices and the chemical forms of wastes after cement treatment are prerequisites to u understanding and optimizing waste immobilization.

Original languageUndefined/Unknown
StatePublished - Jan 1 1992

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