Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube's side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.