Ultra-High-Strength Concrete and paste over 200 MPa made using low-heat portland cement and silica fume was subjected to thermal histories with different maximum temperatures (Tmax) in early age. As a result, the compressive strength and autogenous shrinkage properties were found to undergo a drastic change when Tmax exceeds 45 to 60°C. It was also found that the amount of bound water, Ca(OH)2 and ettringite in paste, measured under the same condition as above experiment changed significantly when Tmax exceeded 45 to 60°C. Comparing these test results with past studies, the mechanism of drastic change around Tmax of 45 to 60°C was considered.