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. ©, 2015, Science Press. All right reserved.