水灰比对高温下混凝土力学性能影响试验研究

Effect of water-cement ratio on mechanical behavior of concrete at elevated temperatures

采用高温抗压试验炉进行水灰比对高温下混凝土轴压力学性能影响试验,用FEIQUANTA 2000环境扫描电镜观测高温后混凝土结构的典型微观结构,主要研究水灰比对不同温度下混凝土的抗压强度、弹性模量和峰值应变等力学性能指标的影响规律。结果表明,水灰比对高温下混凝土的力学性能有着显著影响,不同水灰比的混凝土经历了低温区（20~200℃）的强度衰减和随后的强度明显恢复（200~400℃）,随着温度升高（〉400℃）,强度又出现大幅下降。

A specially-built electrical furnace was used to experimentally study the effect of water-cement ratio of concrete on the mechanical behaviors of concrete at elevated temperatures.The FEI QUANTA 2000 Environmental Scanning Electron Microscope was used to observe the typical microstructures of concretes with different water-cement ratio at elevated temperatures in order to study the change mechanism of mechanical behaviors.The experimental study mainly focused on the effect of water-cement ratio on compressive strength,modulus of elasticity,stress-strain relations and mechanical strain corresponding to peak stress of concrete at elevated temperatures.The tested results show that water-cement ratio has a significant influence on the mechanical behaviors of concrete at elevated temperature.The compressive strength and modulus of elasticity of concrete with different water-cement ratio experience almost the same damage development due to exposure to elevated temperatures.There are remarkable effect of water-cement ratio on mechanical behaviors of hot concrete and unobvious effect of high temperature on mechanical behaviors of hot concrete with different water-cement ratios.All the specimens with different water-cement ratio suffer different compressive strength damage development at different elevated temperatures.The compressive strength of concrete with different water-cement ratios experiences an initial stage of strength loss（20-200 ℃）,a stage of strength recovery（200-400 ℃） and a stage of remarkable strength decrease（above 400 ℃） with increase in temperature.The modulus of elasticity of concrete at elevated temperatures experiences an approximate damage development with different compressive strengths of concrete.The mechanical strain corresponding to peak stress of concrete with different water-cement ratio has an approximate changing rule,and it increases as the temperature increase.The tested results can provide a reference for assessing the fire resistance of concrete structures and a reasonable fire-resistant design method.