Zeolite formation in Class F fly ash blended cement pastes is under investigation. A Na-P type zeolite and Zeolite Y were synthesized from Class F fly ash and NaOH solution after 2 days of aging at room temperature and 6 days of curing at 80°C. However, no zeolites formed when KOH was used. In additional experiments, a Na-P type zeolite, Zeolite Y, and chabazite developed in cement pastes blended with Class F fly ash and NaOH solution which had been aged 2 days at room temperature and then cured 6 days at temperatures ranging from room temperature to 90°C. Seeding the pastes with natural zeolites was also investigated. [

The structures of aluminum‐substituted calcium silicate hydrate (C‐S‐H) forming in a series of aqueous suspensions formulated with colloidal silica, reactive alumina, and lime and aged for 1 year have been studied using 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy (with and without cross polarization (CP)), solution pH, electron microscopy, and X–ray diffraction. As in earlier work dealing with the nature of C‐S‐H in the system CaO‐SiO2H2O2 two aluminum‐substituted C‐S‐H phases, having distinctly different anionic structures on the atomic level (Q2 versus Q1Q2), were found to extend into the system CaO‐Al2O3‐SiO2‐H2O2 X‐ray diffraction patterns of the two aluminum‐containing C‐S‐H phases are nearly identical, suggesting that their intermediate‐range order is very similar, but MASNMR spectra show that these two phases have markedly different silicate structures on the atomic‐level scale. Both C‐S‐H structures can accommodate approximately 5 mol% of Al2O3 in tetrahedral and possibly octahedral coordination as well.

Stratlingite (2Ca0.AI,03.Si0,.8HzO) is a complex calcium aluminosilicate hydrate commonly associated with the hydration of slag-containing cements or other cements enriched in alumina. Stratlingite can coexist with the hydrogarnet solid solution [hydrogarnet (3Ca0.AI,03. 6HzO)-katoite (3CaO-A1,O,~SiOZ~4HzO)] and calcium silicate hydrate (C-S-H). Since stratlingite is present in many blended cements, the knowledge of stratlingite's characteristic silicate anion structure and how aluminum is accommodated by the structure is important. Phase pure stratlingite 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 29Si, with and without cross-polarization (CP), and %I solid-state magic angle nuclear magnetic resonance spectroscopy (MASNMR). For the most part, NMR data for these stratlingites corroborate structural information available in the literature. The aluminum atoms are both tetrahedrally and octahedrally coordinated, and the silicon atoms exist predominantly as QZ, Qz(lAl), and Qz(2AI) species. The presence of alkali affects the structure of stratlingite in subtle ways, significantly reducing the A1'"/AIV' ratio.