Molecular Silicate and Aluminate Species in Anhydrous and Hydrated Cements

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• 作者：Aditya Rawal ; Benjamin J. Smith ; George L. Athens ; Christopher L. Edwards ; Lawrence Roberts ; Vijay Gupta ; Bradley F. Chmelka
• 刊名：Journal of the American Chemical Society
• 出版年：2010
• 出版时间：June 2, 2010
• 年：2010
• 卷：132
• 期：21
• 页码：7321-7337
• 全文大小：462K
• 年卷期：v.132,no.21(June 2, 2010)
• ISSN：1520-5126

文摘

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- and two-dimensional (2D) solid-state ²⁹Si and ²⁷Al 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 ²⁹Si and ²⁷Al 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 ²⁹Si{¹H} and ²⁷Al{¹H} heteronuclear correlation NMR spectra of hydrated cements establish interactions between water and hydroxyl moieties with distinct ²⁷Al and ²⁹Si species. The use of a ²⁹Si 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.