Pure clinker phases

Cement powders contain four major hydraulic constituents, ie clinker phases (Figure 1), which hydrate at different rates and thus influence important factors such as setting time, workability and mechanical strength. The two major clinker phases are tricalcium silicate (C3S) and dicalcium silicate (C2S) which hydrate after an initial induction period and provide the long-term mechanical strength. The two other major components are tricalcium aluminate (C3A) and tetracalcium aluminoferrite (C4AF) which hydrate rapidly with no induction period. Note that standard cement chemistry nomenclature uses C = CaO, S = SiO2, A = Al2O3, F = Fe2O3, H = H2O, S = SO2 and C = CO2

The silicate spectra are dominated by bands at 800-1000 cm-1, characteristic of orthosilicates (ie isolated silicate tetrahedra). The spectra of both C3A and C4AF also show characteristic Raman bands.