Characteristics of the hydration heat evolution of composite binder at different hydrating temperature

• Composite binder hydrates slower than pure cement at room temperature.
• The hydration of composite binder is accelerated by the elevated temperature.
• Raising temperature promotes the hydration of composite binder greater than OPC.
• The hydration of composite binder containing slag is very sensitive to temperature.

Hydration heat evolution rate and quantity of cement–slag binder and cement–fly ash binder were measured at 25 °C, 45 °C and 60 °C by isothermal calorimetry. Composite binder hydrates slower than pure cement at 25 °C. The hydration of composite binder is accelerated by the elevated temperature. The hydration heat of composite binder containing no more than 50% of slag and that of pure cement have little difference in the later period at 45 °C. It becomes the same or even higher at 60 °C. The hydration heat between composite binder containing fly ash and pure cement still has certain gap at 45 °C, but the gap is narrowed obviously at 60 °C. Raising temperature promotes the hydration of composite binder greater than that of pure cement. The hydration of composite binder containing slag is very sensitive to temperature.