## 1 Introduction  
Accompanied by the continuous development of material science, as well as the continuous improvement of environmental awareness [1; 2; 3; 4], recycled aggregate concrete (RAC) has been widely received by the majority of scientific and technical personnel in the field of construction for various uses. RAC is made of recycled concrete aggregate (RCA) that comes from repurposed construction waste. Preliminary exploration of recycled concrete began in the 1940s ([PERSON] [5], 1946), and currently, many scholars study the mix design method, aggregate types, and fundamental mechanical properties of RAC. [PERSON] [6] and [PERSON] [7] systematically studied the mix design method/procedure of RCA. Their results show that a suitable concrete mix design enables RAC to the achieve target strength. It also outlines the mix design parameters. The properties of concrete containing recycled fine aggregate were investigated by [PERSON] [8]. Their results show that the strength of recycled concrete is reduced when the replacement ratio of recycled fine aggregate reaches 15-30%. [PERSON] [9] and [PERSON] [10] studied the elastic modulus and strength of recycled aggregate concrete. Their results show that the strength and elastic modulus of recycled aggregate concrete are reduced by about 10% and 35%, respectively. These studies are important for studying the mechanical properties of recycled aggregate concrete, especially to understand the essential parameters for determining the deflection as well as cracking of a RAC structure. The flexural properties of recycled coarse concrete beams were previously studied by [PERSON] [11] and [PERSON] [12], who showed that the bearing capacity of recycled concrete beams is not different from that of ordinary concrete beams, although the deformation and crack width are slightly larger than those of ordinary concrete beams. The shear behavior of recycled coarse concrete beams was tested by [PERSON] [13; 14] and [PERSON] [15]. The results show that the deformation and oblique crack propagation of recycled concrete beams with the same concrete strength are essentially the same as those of made of ordinary concrete, but the shear capacity is smaller. With the increase of the replacement ratio of the recycled coarse aggregate, the shear strength of the recycled concrete beams tends to decrease. [PERSON] [16] and [PERSON] et al. [17] conducted experiments on the compressive properties of recycled coarse and fine aggregate concrete columns. The recycled reinforced concrete columns had the same failure mode as that of ordinary reinforced concrete columns. The bearing capacity of recycled reinforced concrete columns decreases with the increase of recycled aggregate replacement ratio, but the amplitude is not large. [PERSON] [18] studied the mechanical properties of recycled aggregate concrete columns filled with steel tubes, showing that the mechanical properties of recycled aggregate concrete confined with steel tubes are similar to those consisting of ordinary concrete columns and have good ductility. However, the former shows a decrease in both stiffness and bearing capacity, which decreases with the increase of the replacement ratio of recycled aggregates. This is mainly due to the lower strength of RAC compared to ordinary concrete. Seismic performance tests of low, medium, and high shear walls of recycled coarse and fine aggregate concrete were performed by [PERSON] and [PERSON] [19; 20; 21; 22; 23], showing that the bearing capacity, stiffness, ductility, and energy dissipation capacity of recycled coarse aggregate concrete shear walls are slightly worse than those of ordinary concrete shear walls. Again, with the increase of recycled aggregate replacement in the mixture, the bearing capacity and ductility of the recycled aggregate concrete shear wall decreases, although the seismic performance of the recycled concrete shear walls does meet the needs of structural design.