FT-IR spectra of original and activated samples are shown in Figs. 8,
9. The as synthesised, non-hydrated sample, gave a main broad band at
800 – 1100 cm−1, assigned mostly to asymmetric and symmetric
vibrations of Si–O bonds [50]. The peaks at 511 – 535 cm−1, 864cm−1
and 936 cm−1 could be assigned to γ-C2S, whereas the peaks at 883
cm−1, 903 cm−1and 996 cm−1 could be related to the presence of β-
C2S [51]. Small differences are visible between the obtained spectra
and those published by Ghosh [52] on pure C2S polymorphs. This is
due to the presence of β polymorph and if Ghosh's FT-IR data from β
and γ are combined, a good agreement between the published data
and our data can be found.