jp302218j_si_002.pdf (130.04 kB)
29Si NMR in Cement: A Theoretical Study on Calcium Silicate Hydrates
journal contribution
posted on 2012-05-03, 00:00 authored by Pawel Rejmak, Jorge S. Dolado, Malcolm
J. Stott, Andrés AyuelaThe NMR spectra of 29Si in cement-based materials
are
studied through calculations of the isotropic shielding of silicon
atoms within the density functional theory. We focus on the main component
of cement, the calcium-silicate-hydrate gel, using widely accepted
models based on the observed structures of jennite and tobermorite
minerals. The results show that the 29Si chemical shifts
are dependent not only on the degree of condensation of the (SiO4) units, as commonly assumed, but also on the local arrangement
of the charge compensating H and Ca cations. We find that the NMR
spectra for models of the calcium-silicate-hydrate gel based on tobermorite
are in better agreement with experiment than those for jennite-based
models.