The here generated DFT database of chemical shieldings for C-S-H model structures was analyzed for mainlayer Ca sites with an 7-fold coordination whereby only those sites were considered that are coordinated to 6 oxygens of in-chain silicates (Q 1 or Q 2p ). The seventh oxygen is either from a Q 2b silicate, a water molecule, or a hydroxide ion. For this Ca site a mean Ca chemical shift of 33.38 ppm is predicted (Table ).