Strength and Constitutive Model of Recycled Concrete under Biaxial Compression

The mechanical properties of recycled concrete under biaxial compression were tested in this study. Five grades of replacement ratio of recycled coarse aggregate (0%, 30%, 50%, 70%, 100%) and four groups of stress ratio (−0.25:−1, −0.5:−1, −0.75:−1, −1:−1) were designed to evaluate their influence on mechanical properties.The strength and deformation values of concrete specimens were tested by servo-controlled static-dynamic triaxial machine (TAWZ-5000/3000). The result shows that the stress and strain of recycled concrete under biaxial compression were both higher than the corresponding values that under uniaxial compression. The stress ratio and recycled aggregate ratio have different effects on mechanical properties of concrete. The initial elastic modulus was also affected by the two factors. Based on the analysis of the test data and combined with the stress-strain curve, a constitutive model for recycled concrete under biaxial compressive state was proposed. The comparison between the test results and the fitted curves shows that the proposed model can suitably describe the stress-strain relationship for recycled concrete.