Transient thermal creep of concrete in service conditions at temperatures up to 300 °C.

This paper presents experimental results concerning the behaviour of ordinary, high-strength and high-performance concretes under constant mechanical loading and increasing temperatures up to near 300 °C. Heat was applied at a rate of 0.1 °C/min such that successive constant temperature levels were reached and maintained sufficiently to ensure internal temperature stabilisation. The analysis of experimental measures focuses on the so-called transient thermal creep, obtained during the transient thermal loading stages. To study the importance of changes in the internal properties, especially those related to free and bound water, some specimens were submitted to a second heating cycle. Test results confirm the existence of transient thermal strains during first heating, and its occurrence during the second cycle only when the maximum temperature of the first cycle was exceeded even if the specimen had spent a recovery period at ambient temperature. The transient thermal creep values were estimated for different temperature levels, above 105 °C, and they were inversely proportional to the water/cement ratio. [ABSTRACT FROM AUTHOR]