A platform for research: civil engineering, architecture and urbanism
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Molecular silicate and aluminate species in anhydrous and hydrated cements
The compositions and molecular structures of anhydrous and hydrated cements are established by using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy methods to distinguish among different molecular species and changes that occur as a result of cement hydration and setting. One-dimensional and two-dimensional (2D) solid-state 29.Si and 27.Al magic-angle spinning NMR methodologies, including T1-relaxation-time- and chemical-shift-anisotropy-filtered measurements and the use of very high magnetic fields (19 T), allow resonances from different silicate and aluminate moieties to be resolved and assigned in complicated spectra. Single-pulse 29.Si and 27.Al NMR spectra are correlated with X-ray fluorescence results to quantify the different crystalline and disordered silicate and aluminate species in anhydrous and hydrated cements. 2D 29.Si{1.H} and 27.Al{1.H} heteronuclear correlation NMR spectra of hydrated cements establish interactions between water and hydroxyl moieties with distinct 27.Al and 29.Si species. The use of a 29.Si T1 filter allows anhydrous and hydrated silicate species associated with iron-containing components in the cements to be distinguished, showing that they segregate from calcium silicate and aluminate components during hydration. The different compositions of white Portland and gray oilwell cements are shown to have distinct molecular characteristics that are correlated with their hydration behaviors.
Molecular silicate and aluminate species in anhydrous and hydrated cements
The compositions and molecular structures of anhydrous and hydrated cements are established by using advanced solid-state nuclear magnetic resonance (NMR) spectroscopy methods to distinguish among different molecular species and changes that occur as a result of cement hydration and setting. One-dimensional and two-dimensional (2D) solid-state 29.Si and 27.Al magic-angle spinning NMR methodologies, including T1-relaxation-time- and chemical-shift-anisotropy-filtered measurements and the use of very high magnetic fields (19 T), allow resonances from different silicate and aluminate moieties to be resolved and assigned in complicated spectra. Single-pulse 29.Si and 27.Al NMR spectra are correlated with X-ray fluorescence results to quantify the different crystalline and disordered silicate and aluminate species in anhydrous and hydrated cements. 2D 29.Si{1.H} and 27.Al{1.H} heteronuclear correlation NMR spectra of hydrated cements establish interactions between water and hydroxyl moieties with distinct 27.Al and 29.Si species. The use of a 29.Si T1 filter allows anhydrous and hydrated silicate species associated with iron-containing components in the cements to be distinguished, showing that they segregate from calcium silicate and aluminate components during hydration. The different compositions of white Portland and gray oilwell cements are shown to have distinct molecular characteristics that are correlated with their hydration behaviors.
Molecular silicate and aluminate species in anhydrous and hydrated cements
Molekulare Silicate und Aluminate in wasserfreien und hydratisierten Zementen
Rawal, Aditya (author) / Smith, Benjamin J. (author) / Athens, George L. (author) / Edwards, Christopher L. (author) / Roberts, Lawrence (author) / Gupta, Vijay (author) / Shmelka, Bradley F. (author)
Journal of the American Chemical Society ; 132 ; 7321-7337
2010
17 Seiten, 11 Bilder, 5 Tabellen
Article (Journal)
English
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