Residual Mechanical Properties of High-Strength Concretes after Exposure to Elevated Temperatures

This paper presents the results of a study on the effect of high temperatures on the mechanical properties of high-strength concretes. Mixtures were prepared with water to cementitious material ratios of 0.40, 0.35, and 0.30 containing silica fume at 0, 6, and 10% cement replacement. After heating to 100, 200, 300, and 600 degrees C, the compressive strength, the splitting tensile strength, and the corresponding ultrasonic pulse velocity were measured. A substantial loss of strength was observed for all compositions at 600 degrees C, particularly the silica fume concretes in spite of the superior mechanical properties provided by silica fume at room temperature. The average residual compressive and splitting tensile strengths of the concretes at 600 degrees C were 30 and 25% of the room-temperature strengths, respectively. It was found that the rate of the splitting tensile strength loss is higher than the rate of the compressive strength loss at elevated temperatures and that the ultrasonic pulse velocity measurements slightly underestimates the residual strength of the high-strength concretes after exposure to temperature over 200 degrees C.