火灾高温后混凝土的轴心抗压强度及评估方法

Axial compressive strength and assessment of concrete after fire temperature

为了更深入地揭示高温后骨料类型对混凝土轴压性能的影响,设计了普通混凝土、高强混凝土、再生碎石混凝土和再生卵石混凝土标准棱柱体试件进行了不同受火温度后混凝土单轴抗压强度试验,获取了试件的高温烧失率以及轴心受压全过程应力-应变曲线,对比分析了高温对4种混凝土试件的峰值应力、峰值应变、弹性模量等力学性能指标的影响规律和损伤过程。结果表明:随着温度升高,再生碎石和再生卵石混凝土质量烧失率上升较为显著;温度高时,再生卵石混凝土应力—应变曲线峰值点降低最明显;随着温度的升高,高强混凝土峰值应力下降最少;温度较低时,不同混凝土峰值应变相差不大,温度较高时,再生卵石混凝土峰值应变上升最明显;温度高时,再生碎石和再生卵石混凝土弹性模量下降最快且最多。再生碎石和再生卵石混凝土损伤发展最慢且有明显的温度分界点。基于试验结果,分别通过历经最高温度和质量烧失率提出了高温后不同类型混凝土强度评估公式,其计算值与实际值吻合较好。

In order to further reveal the influence of aggregate type on the behavior of concrete axial compression after high temperature,uniaxial compressive strength tests of concrete under different fire temperatures were carried out on standard prismatic specimen of ordinary concrete,high strength concrete,recycled gravel aggregate concrete and recycled pebble aggregate concrete.The mass loss ratio and the stress-strain curve during the whole axial compression process were obtained.The effects on peak stress,peak strain,elastic modulus of four kinds of concrete specimens after high temperature were compared and analyzed.The test results show that with the increase of temperature,the mass loss rate of recycled gravel and recycled pebble aggregate concrete increased significantly.The peak point of the stress-strain curve of recycled pebble aggregate concrete decreases most obviously at higher temperature.The peak stress of high strength concrete decreases least with the increase of temperature.The peak strain of different concrete has little difference at lower temperature,while the peak strain of recycled pebble aggregate concrete increases most obviously at higher temperature.When the temperature is higher,the elastic modulus of recycled gravel and recycled pebble aggregate concrete decreases fastest and most.The damage development of recycled gravel aggregate concrete and recycled pebble aggregate concrete is the slowest,and their damage process has an obvious dividing point on temperature.Based on the test results,the strength evaluation formulas of different concrete after high temperature were put forward respectively through the maximum temperature and mass loss rate,and the calculated values are in good agreement with the actual values.