Stratlingite is a constituent hydrate of a bonding matrix of low cement castables（LCC）which consists of high alumina cement（HAC）with silica fume（SF）. In this study, crystallization processes of stratlingite with or without deflocculant were monitored at curing temperature of 50℃ and 30℃ . In the sample with deflocculant at 50℃, stratlingite began to crystalize one day after, then X-ray intensity of stratlingite reached the maximum value after 3 days and has been held for over a year. At 30℃, stratlingite began to crystalize 6 days after, X-rays intensity gradually increased and peaked after two weeks and has been held for over a year. On the other hand, in the sample without deflocculant, X-ray intensity of stratlingite was rather lower. BSE images revealed that the bonding matrixes of the cured samples were heterogenous mixture of hydrates. Stratlingites with platy or radial shapes were crystallized inside or rim or surrounding part of SF aggregates, and also crystallized at matrixes or voids. The relatively higher molar ratio of SiO2 observed in almost all of stratlingites could be considered that the crystals grew up rapidly taking surrounding SF as impurities under relatively high curing temperatures.

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