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.