高温后再生混凝土单轴受压应力-应变关系试验研究

利用废弃混凝土经机械破碎后制成的再生粗、细骨料，制作168个不同再生粗、细骨料取代率尺寸为100mm×100mm×300mm的再生混凝土试件，经历20～800℃作用后进行单轴受压应力-应变全曲线试验，分析了不同再生粗、细骨料取代情况和经历温度对再生混凝土峰值应力、峰值应变、弹性模量、泊松比和单轴受压应力-应变全曲线的影响。结果表明：相同温度作用后，随着不同再生骨料取代率的增加，峰值应变增大，弹性模量减小，单轴受压应力-应变曲线峰值应力减小，峰值应变增大，脆性增大；随着经历温度的升高，峰值应变与泊松比先降后增，并在温度400℃后增幅最大，而峰值应力与弹性模量均持续减小，应力-应变曲线渐趋扁平，与横轴包围面积显著减小；再生粗、细骨料单独掺入对混凝土受力性能的影响比较一致，同时掺入时性能退化较快。通过回归分析，建立各组再生混凝土试件单轴受压分段式应力-应变本构方程。

Experimental research on uniaxial compressive stress-strain relationship of recycled concrete after high temperature

The uniaxial compressive stress-strain curve experiments were conducted on 168 recycled concrete specimens made of different replacement rate recycled coarse and fine aggregates with the size of 100 mm×100 mm×300 mm after being exposed to 20-800 ℃. The effects of recycled aggregates content and exposure temperature on peak stress, peak strain, elastic modulus, Possion’s ratio and stress-strain curve of recycled concrete were investigated. The test results show that: after the same temperature, the peak strain and brittleness increase with the increase of recycled aggregate replacement rate, the elastic modulus decreases, the peak point moves down and right, and the ductility deteriorates gradually. As the temperature increases, the peak strain and the Poisson’s ratio increase after the first drop, while the peak stress and elastic modulus continue decreasing. Besides, the stress-strain curve turns to be flat and the area which is surrounded by the X axis also reduces significantly. The performance of RCC and RFC are consistent, while the RC deteriorates faster. Through regression analysis, the segmented constitutive equation of recycled concrete under uniaxial compression is proposed to fit the test results, and the fitting curve is in good agreement with the test results.