Formation of ettringite in Portland cement/calcium aluminate cement/calcium sulfate ternary system hydrates at lower temperatures

To explore the formation of ettringite at lower temperatures in the Portland cement/calcium aluminate cement/calcium sulfate ternary system hydrates, the effect of calcium sulfate variety on the setting time of the ternary system and the strength development of its mortars at 0, 5, 10 and 20 degrees C were investigated. The formation of ettringite was further analyzed using XRD and ESEM. The results show that, as temperature increases, both initial and final setting time are shortened and that compressive and flexural strength are enhanced. In particular, mortars with anhydrite develop higher strength between 0 and 10 degrees C but lower strength at 20 degrees C than those with hemihydrate. Further, pastes with anhydrite set faster than those with hemihydrate. It is also found that both the formation rate and amount of ettringite are sensitive to temperature and calcium sulfate variety. (C) 2011 Elsevier Ltd. All rights reserved.