Second, C-S-H in Figure assumes the same MCL structure and has no Ca 2+ surface adsorption, which is the same as the C-S-H model in Figure . However, the additional assumption is a 0.7 Ca/dimer packing in the interlayer , which results in 0.35 Ca pairing sites per silicate dimer in the C-S-H interlayer. In such a C-S-H structure roughly one-third of interlayer silicate dimers coordinate with pairing Ca, while approximately three-fourths of bridging sites are occupied by bridging Ca. This additional occupancy of the pairing site is seen as a slight right broadening of the mainlayer Ca peak in Figure , due to the pairing site exhibiting a 27.50 ppm chemical shift, which overlaps with the right side of the mainlayer peak. Due to this broadening the mainlayer peak shifts from 33.5 to 33 ppm. Figure represents the same C-S-H structure as Figure , except Ca adsorption at the surface is assumed that increases the Ca/Si ratio to 1.75 . A C-S-H structure with these properties was synthesized by Kumar et al. who used the drop-wise precipitation method. It is seen that due to the surface site (19.72 ppm), a right shoulder of the main peak forms. The position of the main peak remains at 32.5 ppm.