In their pioneering work, Bowers and Kirkpatrick , showed that Ca MAS NMR spectra with reasonable signal-to-noise ratios for tobermorite and jennite (both calcium silicate hydrate minerals) with natural abundance can be obtained. In particular they observed that differences between 6-fold and 7-fold coordinated Ca are large enough to be entirely resolved by Ca NMR. Afterwards, Moudrakovski et al. carried out a combined natural abundance Ca NMR and density functional theory (DFT) study. They investigated anhydrous phases (C 3 S, β -C 2 S, C 3 A), hydrated C 3 S, Ca(OH) 2 , tobermorite 11 Å, and low Ca/Si (below 1.5) synthetic C-S-H. Their results suggest significant differences in the Ca NMR spectra of the observed phases due to differences in the local Ca environment. Further, due to the similarities between the Ca NMR spectra of tobermorite 11 Å and C-S-H they further confirmed the validity of using layered tobermorite models as model structures for C-S-H. Finally, MacDonald et al. used Ca NMR to show that poly(ethylene-vinyl acetate) (PEVAc) admixtures in white cement induce modest structural changes, while describing the formation of low-coordination Ca sites upon interaction with PEVAc.