Effect of Micro-Sized Alumina Powder on the Hydration Process of Calcium Aluminate Cement

Micro-sized alumina powder is widely used in low cement high-alumina refractory castables. The hydration of calcium aluminate cement can be affected by adding micro-sized alumina powder. This work addresses the hydration of a commercial cement at 25°C with 50 wt% micro-sized alumina powder added. The hydration heat was measured by isothermal micro-calorimetry. The phase composition and microstructure of the hydration products at the designated times were studied by XRD and SEM, respectively. The results showed that micro-sized alumina powder accelerated the dissolution of CAC. The induction period of the cement hydration reduced from 13h to 4.5h, and the hydration heat within 50hs was increased from 469J/g to 587J/g with the addition of micro-sized alumina powder. The morphology of the hydrates was flocculent amorphous at the beginning, and then transformed to short rods or cubic shape with micro-sized alumina powder added.