中文摘要：

通过四种水灰比混凝土的高温后强度试验,分析了混凝土的残余强度衰减规律和其高温衰退机理,并与高温时作对比.结果表明,两者都经历了低温衰退、强度恢复、高温衰退三个阶段,但它们的强度衰减程度有所不同.温度低于300℃时的混凝土残余强度要小于高温时强度,而温度高于300℃时则相反.这些结果可为混凝土结构的抗火及灾后加固提供参考.

英文摘要：

Based on testing data for concrete with 4 water cement ratios after elevated temperature, the decaying regulations of concrete residual strength and its decaying mechanism are analyzed, and are compared with that at high temperature. These results show that the development of both concrete residual strengths includes three phases： strength decline at low temperature, recovery and decaying at higher temperature. But their strength decaying degree is different. When temperature is lower than 300℃, the concrete residual strength is lower than its strength at high temperature, but after temperature reaches 300℃ ,the former is greater than the latter. These test results given in this paper can offer a reference for RC structural fire-resistant design and its strengthening after fire.