Effect of micro-sized alumina powder on the hydration products of calcium aluminate cement at 40 °C.

In this work, the effect of different micro-sized alumina powders on the hydration products of calcium aluminate cement (CAC) during hydration at 40 °C is studied. The cement hydration at the designated times is terminated by the freeze-vacuum method. The phase development and microstructure evolution during the cement hydration are investigated by XRD and DSC, and SEM, respectively. It is found that 3CaO·Al 2 O 3 ·6H 2 O (C 3 AH 6 ) is the dominant product of the pure CAC after hydration at 40 °C for 3.5 h. But 2CaO·Al 2 O 3 ·8H 2 O (C 2 AH 8 ) is the dominant hydrate and C 3 AH 6 is not found in the mixtures of CAC and micro-sized alumina powder under the same condition. The results indicate that the addition of alumina powders promotes the formation of C 2 AH 8 and retards the conversion of C 2 AH 8 to the C 3 AH 6 phase. Moreover, such phase development with alumina addition is discussed. [ABSTRACT FROM AUTHOR]