Early Strength Development and Hydration of Ordinary Portland Cement/Calcium Aluminate Cement Pastes

The early strength development of ordinary Portland cement (OPC)/calcium aluminate cement (CAC) pastes (92.5/7.5, 80/20, and 20/80) was studied. Conduction calorimetry, X-ray diffraction, and scanning electron microscopy methods were used to monitor the heat evolution and microstructural changes of these pastes. It is apparent that ettringite formation contributes to the early “set strength” in the 80/20 paste. The OPC hydration seems to be delayed by the presence of CAC.