Structural models for C-S-H gel

4-nm tobermorite has a layer structure and the prefix relates to the layer thickness. On being heated at 55°C, it loses interlayer water and undergoes 

All data are for the pseudocells and compositions staled. The true cells have doubled values of b and can be in varying degrees disordered a and c must often be differently defined. The structure of C-S-H(I) has little more than two-dimensional order, and that of C-S H(II) has less than full three-dimensional order. 

Attempts to synthesize 1.4-nm tobermorite or jennite from aqueous suspensions at ordinary temperatures normally yield semicrystalline products. 

Pattern is for a relatively highly crystalline variety all peaks are broad, s = strong, w = weak, m = moderately, v = very, d = diffuse. Indices relate to pseudocell in Table 5.2 hkl denotes a band head given by an essentially two-dimensional lattice (T22). 

The silicate anion structures of C-S-H(I) preparations appear to be affected by how long the material remains in contact with its mother liquor and by how strongly it is subsequently dried. Experiments using the molybdate method showed that the anions in precipitates made from CaCl, and sodium silicate solutions at 0 C were mainly those present in the silicate solution, and thus monomeric if the latter is sufficiently dilute (S45). By allowing such products to stand in contact with their mother liquors at O C. and drying at — 10°C, preparations with Ca/Si ratios of 1.2-1.5 were obtained that contained only dimeric silicate anions. 

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