Compressive stress-strain curve of recycled concrete under repeated loading

In order to study the compressive mechanical properties and stress-strain relationships of recycled aggregate concrete(RAC) under repeated loading with equal stress, the stress-strain curve tests of 45 RAC specimens under constant repeated loading and varying repeated loading were completed using recycled coarse aggregate(RCA) substitution rate and repeated load amplitude (LA) as parameters. The effects of RCA substitution rate and LA on the peak stress, peak strain and elastic modulus of concrete were analyzed to establish the relationship between the above mechanical parameters and the repetitive LA. Meanwhile, the calculation equations of the loading and unloading strain and the equation of the stress-strain curve under the repetitive load were established. The results show that: the peak stress of RAC decreases and the peak strain increases gradually with the increase of LA, showing a quadratic function; The elastic modulus decreases linearly with the increase of LA; Also, the strain ratio at the beginning of loading point and at the end of unloading point increases as a power function with the increase of strain ratio at the beginning of unloading point. Based on WEIBULL distribution, it is found that an equation of loading and unloading curves in repeated phase is similar to the monotonic equation. And the equations and measured curves of the damage constitutive model in the loading phase can be well predicted.