Post-fire Study on Mechanical Properties of Damaged Ultra-high Strength Concrete

In order to study the effect of steel tube, pre-load and temperature on residual performance of heated ultra-high strength concrete (UHSC), an experimental program was carried out to investigate the physical and mechanical properties of UHSC post-fire in room temperature. With total of 54 standard cylindrical concrete specimens subjected to various temperatures ranging from 62 °C to 496 °C, their residual compressive strength, elastic modulus, peak strain was measured after natural cooling down. By comparing the test results of standard cylindrical concrete specimens with the results of the bare specimens in and after fire, it is known that the residual compressive strength of standard cylindrical concrete specimens decayed more serious after exposing to same temperature. Seen from the results, the temperature which the specimens suffered was found to be responsibility to the reduction of the compressive strength, elastic modulus, peak strain. As the temperature up to 300 °C, the strength reduction coefficient of UHSC was 0.67 ~ 0.68 and the elastic modulus reduction coefficient of UHSC was 0.41 ~ 0.51 with peak strain coefficient εcr(T)/ε0 1.57 ~ 1.67. Finally, based on the analysis of test results, simple formulae were proposed to describe the effect of temperature on residual performance of heated UHSC which infilled the steel tube.