The Hydration Products of a Refractory Calcium Aluminate Cement at Intermediate Temperatures

The major hydraulic phase in all the calcium aluminate cements including ciment fondue is CA (CaAl۲O۴). Once hydrated, it starts to form the hexagonal crystals of CAH۱۰ and C۲AH۸ that depending on the time and temperature of hydration convert to the cubic crystals of C۳AH۶ and AH۳. The nature, sequence, crystallinity and microstructure of hydrated phases of commercial refractory calcium aluminate cement were analyzed using differential scanning calorimetry (DSC), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the formation of different hydrated phases was temperature dependent. At ۲۸ oC, the hydration products at the beginning of hydration were a gel phase, C۲AH۸ and gibbsite, while CAH۱۰ also formed after four days of hydration, both C۲AH۸  and CAH۱۰ were converted to  C۳AH۶ at latter ages. The rate of conversion of C۲AH۸ is dependent on the temperature  and  time  of  hydration  at  temperatures  higher  than  ۲۸ ºC  and  accelerates  with increasing temperature, but still takes several weeks for completion at ۳۶ ºC.

کلیدواژه ها:

Calcium aluminate cement (CAC) ، Hydration reactions ، CA (CaAl۲O۴) ، CA۲ (CaO.۲Al۲O۳) ، CAH۱۰ (CaO.Al۲O۳.۱۰H۲O) ، C۲AH۸ (۲CaO.Al۲O۳.۸H۲O) ، C۳AH۶ (۳CaO. Al۲O۳. ۶H۲O) ، AH۳ (Al۲O۳.۳H۲O)