The DFT predicted Ca chemical shifts for tobermorite 11 Å and 14 Å, which are expected to have the same mainlayer Ca structure as C-S-H , are at 23 and 25 ppm . However, the Ca shift shifts to more positive values as the Ca/Si increases due to Ca being deshielded . The deshielding is due to the seventh coordination stemming from the water molecule or the hydroxide ions instead of the Q 2b silicate oxygen. Since the number of Q 2b sites decreases with an increase in Ca/Si 30 , a shift of the mainlayer Ca shift to more positive values was expected.