Poulsen, Søren Lundsted6; Kocaba, Vanessa4; Le Saoût, Gwenn4; Jakobsen, Hans Jørgen7; Scrivener, Karen L.4; Skibsted, Jørgen7
1 Interdisciplinary Nanoscience Center, Faculty of Science, Aarhus University, Aarhus University2 Department of Chemistry, Faculty of Science, Aarhus University, Aarhus University3 Interdisciplinary Nanoscience Center, Science and Technology, Aarhus University4 EPFL5 Department of Chemistry, Science and Technology, Aarhus University6 Interdisciplinary Nanoscience Center, Science and Technology, Aarhus University7 Department of Chemistry, Science and Technology, Aarhus University
The applicability, reliability, and repeatability of 29Si MAS NMR for determination of the quantities of alite (Ca3SiO5) and belite (Ca2SiO4) in anhydrous Portland cement was investigated in detail for 11 commercial Portland cements and the results compared with phase quantifications based on powder X-ray diffraction combined with Rietveld analysis and with Taylor-Bogue calculations. The effects from paramagnetic ions (Fe3+) on the spinning sideband intensities, originating from dipolar couplings between 29Si and the spins of the paramagnetic electrons, were considered and analyzed in spectra recorded at four magnetic fields (4.7 - 14.1 T) and this has led to an improved quantification of alite and belite from 29Si MAS NMR spectra recorded at "high" spinning speeds of νR = 12.0 - 13.0 kHz using 4 or 5 mm rotors. Furthermore, the impact of Fe3+ ions on the spin-lattice relaxation was studied by inversion-recovery experiments and it was found that the relaxation is overwhelmingly dominated by the Fe3+ ions incorporated as guest-ions in alite and belite rather than the Fe3+ sites present in the intimately mixed ferrite phase (Ca2AlxFe2-xO5).
Solid State Nuclear Magnetic Resonance, 2009, Vol 36