Effect of heating–cooling cycles on transient creep strain of high performance, high strength and ordinary concrete under service and accidental conditions

In this paper, the variations of transient creep strain of high performance concrete, high strength concrete and ordinary concrete during a heating–cooling cycle are presented. Two heating rates are applied: 1.5 and 0.1 °C/min corresponding, respectively, to accidental and service conditions. The temperatures of 400 and 220 °C are the heating’s final temperature phase of the accidental and service conditions, respectively. Further, during the heating phase, the corresponding heating rates are applied until successive constant temperature levels are achieved: 150, 200, 300 and 400 °C under accidental conditions and 140, 190 and 220 °C under service conditions. Those applied temperatures are maintained for several hours to ensure the stabilisation of internal temperature and physico-chemical thermo-dependent processes. To study the importance of internal properties changes, especially those related to free and bound water, some specimens are submitted to a second heating cycle. Moreover, the influence of the difference in mix concretes and the influence of the heating rate are also presented.