We studied the relationship between the strength development and hydration reaction in concrete containing silica fume and having an actual strength of 150N/mm2 or more. By the age of 91 days, concrete that had been exposed to a high-temperature history at an early age by a simple adiabatic curing method was some 20 to 30N/mm2 stronger than concrete that had been cured by the standard method. This outcome was the opposite to that exhibited by concrete without silica fume and having a compressive strength in the range of 60 to 80N/mm2. In concrete with such a low water-binder ratio, the water content required for hydration was so small that it took one year or more by the standard curing method to develop the strength according to decrease in water-binder ratio. On the other hand, we considered that when structural concrete is exposed to a high-temperature history at an early age, the reaction of the silica fume increases remarkably, to form an extremely dense, hardened composite at an early age, thereby even at the age of 91 days, further significant difference in strength between this concrete and concrete cured by the standard method still remained. The reaction ratio of the silica fume in concrete cured by the simple adiabatic method for 7 days was higher than in that cured by the standard method for 1 year, which corresponds to the trend in strength development.
