In this paper, the influence of precursors (CA, C 7 A 3 Z, C 12 A 7 , C 6 SrA 3 Z, C 7 A 2 FZ and commercial calcium aluminate cement 'Gorkal 70') on the structure, microstructure and thermal stability characterizations of C 3 AH 6 through hydration was investigated. The materials were characterized by X-ray diffraction, differential thermal analysis-thermogravimetric analysis-evolved gas analysis and scanning electron microscopy combined with energy-dispersive spectroscopy 24 h and 72 h after starting the hydration process. Results of investigation confirmed the influence of precursor on shape and grain size of C 3 AH 6 . The CaO/Al 2 O 3 mass ratio of precursors before the hydration process affects the size of C 3 AH 6 crystals: the higher the CaO/Al 2 O 3 value, the larger the size of the crystals of C 3 AH 6 . Moreover, the presence of Sr and Fe affects the formation of stable C 3 AH 6 crystals.