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

The major hydraulic phase in all the calcium aluminate cements including cimentfondue is ca (caai20 4). once hydrated, it starts to form the hexagonal crystals of cah10 andc2ahs that depending on the time and temperature of hydration convert to the cubic crystals ofc:;ah6 and ah1• the nature, sequence, crystallinity and microstructure of hydrated phases ofcommercial refractory calcium aluminate cement were analyzed using differential scanningcalorimetry (dsc), d?fferential thermal analysis (dta), x-ray diffraction (xrd) and scanningelectron microscopy (sem). the results showed that the formation ofd~fferent hydrated phases wastemperature dependent. at 28°c, the hydration products at the beginning ofhydration were a gelphase, c2ahsand gibbsite while cahlo also formed after four days ofhydration, both c2ahs andcah,o were converted to c.0h6 at latter ages. the rate ofconversion oj'c2ahs is dependent on thetemperature and time of hydration at temperatures higher than 28°c and accelerates withincreasing temperature, but still takes several week~for completion at 36°c.