To reach a high Ca/Si C-S-H, as in real cementitious systems, C-S-H needs to be precipitated in a high pH, Ca-rich solution . In such systems, a difference between the Ca concentration in solution after synthesis as predicted by thermodynamic modeling, and experimentally measured is observed , which suggests high adsorption rates of Ca at the surface . It is expected that Ca sites near the particle surfaces (Figure ) will have local symmetries, bond angles, and bond distances that differ from those in the bulk C-S-H and therefore a different chemical shift .