Creep behavior of high-strength concrete with polypropylene fibers at elevated temperatures

Experimental studies have been conducted to examine the creep behavior of high-strength concrete (HSC) with polypropylene (PP) fibers of 2 kg/m3(0.125 lbr/ft3) when exposed to elevated temperature. Various types of heating and loading schemes are considered, including transient temperature and stepwise loading paths. Tests are carried out at temperatures up to 700°C (1292°F) and a stress ratio up to 0.6. HSC with PP fibers performs better than normalstrength concrete (NSC) at temperatures below 500°C (932°F) and shows an obvious increase in creep behavior at 700°C (1292°F). At the same stress ratio and duration of 120 minutes, the creep strain developed at 700°C (1292°F) was approximately 10 times more than that developed at 500°C (932°F). There was no abrupt change in creep behavior at or approximately 2200°C (428°F) when the PP fibers evaporated. It is likely that the markedly different response at 7000°C (1292°F) was related to the change in the microstructure of HSC at high temperatures. Increasing the stress ratio at constant temperature will lead to an abrupt increase in creep strain rate. HSC with PP fibers showed a large transient creep strain, and this phenomenon becomes obvious at higher temperatures. Finally, fitting equations are proposed to represent the creep behavior of HSC with PP fibers.