Hydration heat evolution rate and quantity of cement-slag binder and cement-fly ash binder were measured at 25 degrees C, 45 degrees C and 60 degrees C by isothermal calorimetry. Composite binder hydrates slower than pure cement at 25 degrees 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 degrees C. It becomes the same or even higher at 60 degrees C. The hydration heat between composite binder containing fly ash and pure cement still has certain gap at 45 degrees C, but the gap is narrowed obviously at 60 degrees 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. (C) 2014 Elsevier B.V. All rights reserved.