Early hydration properties of composite binder containing limestone powder with different finenesses

The early hydration properties of composite binder containing limestone powder with different finenesses were studied by determining the hydration heat of binder within 3 days using an isothermal calorimeter, the pore structure of hardened paste using a mercury intrusion porosimeter and the compressive strength of mortar cured for 3 days. Results show that for the samples containing fine limestone powder, the hydration heat of binder is large, the pore structure of hardened paste is fine, and the compressive strength of mortar is high compared with the samples containing coarse limestone powder at the same cement replacement ratio. The promoting effect of limestone powder on the early hydration of cement is more evident in the case of lower water to binder ratio, especially for the coarse limestone powder. The decreasing percentage of strength of mortar is far below the replacement ratio of limestone powder in the case of high water to binder ratio, especially for the fine limestone powder.