{sup 29}Si and {sup 27}Al MASNMR study of straetlingite
- Pennsylvania State Univ., University Park, PA (United States). Intercollege Materials Research Lab.
Straetlingite (2CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}SiO{sub 2}{center_dot}8H{sub 2}O) is a complex calcium aluminosilicate hydrate commonly associated with the hydration of slag-containing cements or other cements enriched in alumina. Straetlingite can coexist with the hydrogarnet solid solution [hydrogarnet (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}6H{sub 2}O)-katoite (3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}SiO{sub 2}{center_dot}4H{sub 2}O)] and calcium silicate hydrate (C-S-H). Since straetlingite is present in many blended cements, the knowledge of straetlingite`s characteristic silicate anion structure and how aluminum is accommodated by the structure is important. Phase pure straetlingite samples have been synthesized from oxides in the presence of excess water and from metakaolinite, calcium aluminate cement, CaO, NaOH, and water. the samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) and then further examined using {sup 29}Si, with and without cross-polarization (CP), and {sup 27}Al solid-state magic angle nuclear magnetic resonance spectroscopy (MASNMR). For the most part, NMR data for these straetlingites corroborate structural information available in the literature. The aluminum atoms are both tetrahedrally and octahedrally coordinated, and the silicon atoms exist predominantly as Q{sub 2}, Q{sub 2}(1Al), and Q{sub 2}(2Al) species. The presence of alkali affects the structure of straetlingite in subtle ways, significantly reducing the Al{sup IV}/Al{sup VI} ratio.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-91ER45456
- OSTI ID:
- 103623
- Journal Information:
- Journal of the American Ceramic Society, Vol. 78, Issue 7; Other Information: PBD: Jul 1995
- Country of Publication:
- United States
- Language:
- English
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