FTIR study on the polymorphic structure of tricalcium silicate

The infrared (IR) spectra of various tricalcium silicate (C3S) polymorphs were studied. The effects of variation in the polymorph and substituent ions on the IR spectra of C3S were discerned by synthesizing samples with differing types and amounts of foreign ions but the same polymorphic form. The IR spectrum of C3S mainly depends on the polymorphic form. Substituent ions have a weak influence. The IR spectra of T1 and T2 are very similar. Both show forbidden bands corresponding to symmetric vibration, indicating that [SiO4]4 − tetrahedra are strongly distorted from an ideal tetrahedron. With an increase in the crystal symmetry of C3S, the number of bands for the polymorphs T1 → T2 → T3 → M1 → M3 → R decrease, and the peaks become broader. The absence of symmetric stretching bands with a sharp peak at approximately 812 cm− 1 indicates that the [SiO4]4 − tetrahedra retain an approximately regular tetrahedron symmetry in T3, M1, M3 and R C3S.