Abstract
In this paper, the influence of precursors (CA, C7A3Z, C12A7, C6SrA3Z, C7A2FZ and commercial calcium aluminate cement ‘Gorkal 70’) on the structure, microstructure and thermal stability characterizations of C3AH6 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 C3AH6. The CaO/Al2O3 mass ratio of precursors before the hydration process affects the size of C3AH6 crystals: the higher the CaO/Al2O3 value, the larger the size of the crystals of C3AH6. Moreover, the presence of Sr and Fe affects the formation of stable C3AH6 crystals.
Highlights
The conversion reactions are shown schematically below: The main phases in calcium aluminate cements are CA*, CA2 and C12A7
Hydration products and their thermal stability were investigated by X-ray diffraction analysis, differential thermal analysis–thermogravimetric analysis–evolved gas analysis (DSC–TG–EGA(MS)) and scanning electron microscopy–energy-dispersive spectroscopy (SEM–EDS)
The C3AH6 was successfully synthesized from various precursors
Summary
The conversion reactions are shown schematically below: The main phases in calcium aluminate cements are CA*, CA2 and C12A7. The most predominant hydration products are CAH10, C2AH8, C3AH6 and AH3. The hydration of CAC strongly depends on the conditions of the process. The only stable hydrates are C3AH6 and AH3. At temperatures below 50 C, the metastable phases are formed [1,2,3,4]. Some authors noted that CAH10 and C4AH(11–19) are formed at low hydration temperatures (below 15 C). In the temperature range of 15–27 C, CAH10 can coexist with
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