10.1021/jp302218j.s002 Pawel Rejmak Pawel Rejmak Jorge S. Dolado Jorge S. Dolado Malcolm J. Stott Malcolm J. Stott Andrés Ayuela Andrés Ayuela <sup>29</sup>Si NMR in Cement: A Theoretical Study on Calcium Silicate Hydrates American Chemical Society 2012 29 Si results show 29 Si chemical shifts tobermorite minerals Theoretical Study 29 Si NMR silicon atoms gel Calcium Silicate HydratesThe NMR spectra NMR spectra model 2012-05-03 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/_sup_29_sup_Si_NMR_in_Cement_A_Theoretical_Study_on_Calcium_Silicate_Hydrates/2526259 The NMR spectra of <sup>29</sup>Si 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 <sup>29</sup>Si chemical shifts are dependent not only on the degree of condensation of the (SiO<sub>4</sub>) 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.