冷却方式对高温后不同类型混凝土残余力学性能的影响研究

Influence of cooling methods on residual mechanical properties of concrete after exposed to high temperatures

为了揭示高温后不同冷却方式对高强、普通及再生混凝土力学性能的影响,以历经温度和冷却方式为变化参数,对灾后的三类混凝土进行单轴抗压试验研究,获取了试件的质量变化率以及轴心受压应力-应变曲线,对比分析了高温后不同冷却方式下3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能量耗散规律。结果表明:喷水冷却下的再生混凝土受骨料影响,其质量变化率及峰值应变在400℃以下时相对常温为递减趋势;在温度超过400℃后,自然冷却下的峰值应变均比喷水冷却的大,曲线下降段相比喷水冷却的更缓;冷却方式对高强及普通混凝土的抗压强度和弹性模量影响不显著,而对再生混凝土影响较大;温度较低时,普通混凝土的抗压强度和弹性模量退化最快,而温度较高时,再生混凝土退化最快。基于试验结果,提出高温后不同冷却方式下3种混凝土的抗压强度计算式,计算式的决定系数R平方值均大于0.75,表明模型拟合效果较好。

The standard prism specimens of high-strength concrete,plain concrete and recycled concrete are designed to reveal the influence of natural and water cooling on the compressive performance after elevated temperature.The mass change of the specimen,the stress-strain curve,energy absorption and mechanical properties like peak stress,peak strain,elastic modulus are compared and analyzed.The results show that when the temperature is below 400℃,because of the influence of the aggregate,the mass change and peak strain of recycled concrete with water cooling show a decreasing trend;after the temperature exceeds 400℃,the peak strain of natural cooling is larger than that of water cooling,and the curve descending section is slower;the cooling method has no significant effect on the compressive strength and elastic modulus of high-strength concrete and plain concrete,but has a greater impact on recycled concrete;when at a lower temperature,the compressive strength and elastic modulus of plain concrete degrade fastest,and when the temperature is higher,recycled concrete degrades fastest.Based on the test results,the calculation formulas for the compressive strength of three types of concrete with natural and water cooling are put forward.The coefficient of determination of the calculation formula are all greater than 0.75,indicating that the model fitting effect is well.