Hydration kinetics of CA2 and CA—Investigations performed on a synthetic calcium aluminate cement

Much is already known about the hydration of monocalcium aluminate (CA) in calcium aluminate cements (CACs). CA2 is known to be weakly hydraulic. Therefore, the hydration kinetics of CA2 were not of as great interest as those of the hydration of CAC. We were able to show that the hydration of CA2 begins as soon as the hydration rate of CA has reached its maximum and the first precipitation of C2AH8 has started. The hydration of different CA/CA2 ratios was analyzed by the G-factor quantification. The individual contributions of the phases CA and CA2 to the heat flow were calculated based on the amounts dissolved by applying thermodynamic data. The heat flow as calculated from XRD data was then compared with the measured heat flow. It obtained a good consistency between the two. The very pronounced influence of CA2 during hydration of CAC can be clearly demonstrated.