# Experimental Study on the Seismic Performance of Recycled Concrete Hollow Block Masonry Walls
## 1 Introduction  
Since the beginning of human civilization, construction and demolition wastes (CDW) had been becoming a global problem that affects the sustainable development of the resources and the environment [1]. To date, more than a hundred billion tons of CDW were generated in the world, while approximately 30% to 50% of them were waste concrete [2]. However, this considerable amount of waste concrete is mainly disposed of in landfills, resulting in a severe environmental problem [3; 4; 5; 6]. In order to protect the ecological environment and achieve sustainable development, reducing, reusing, and recycling construction waste is a desirable approach to preserve the ecological environment [7; 8; 9; 10; 11]. Therefore, many countries have passed legislation to encourage the recycling of waste concrete for the resource utilization of recycled concrete. Recycled concrete aggregates (RCA) can be obtained from waste concrete by crushing, screening, cleaning, and separating [12; 13]. Previous studies have been conducted to characterize the potential advantages and drawbacks of RCA. Being different from natural aggregates (NA), RCA has a layer of old mortar attached to the surface, which has more loose pores at the interface [14]. The attached old mortar brings with it worse properties: a lower apparent density and higher water absorption [15; 16]. Consequently, these properties cause the mechanical properties of RCA to be inferior to that of NA, which limits the application of recycled concrete in civil engineering. Although the mechanicalproperties of recycled aggregates are poor, different scholars, institutions, and countries have been applying recycled aggregates into structures through rational design and experiment in recent years, and in some cases, good results have been achieved [17; 18; 19; 20; 21; 22; 23]. To further promote the recycling of construction waste, growing studies on the production of recycled concrete blocks prepared by RCA have been conducted in years. Researchers proposed that the mechanical properties of recycled concrete blocks mainly depend on the substitution rate and qualities of RCA. [PERSON] et al. [24] pointed out that the increase of recycled fine aggregates content has a more significant impact on the reduction of recycled concrete block strength. Therefore, the maximum replacement rate of recycled fine aggregates is recommended to be 20%. [PERSON] et al. [25] also confirmed the findings through a similar experiment. A study conducted by [PERSON] et al. [26] aimed to investigate the mechanical properties of recycled concrete blocks. They found that the substitution rate of RCA below 50% had little effect on the compressive strength of recycled concrete blocks. However, the compressive strength of recycled concrete hollow block (RCHB) decreases with the increase of the content of low-grade RCA (The content of soil or broken brick in aggregates being \(>\)10%) [27]. [PERSON] et al. [28] investigated the influence of different substitution rates of recycled concrete aggregates on the mechanical properties of recycled concrete blocks. The test results illustrated that with the substitution rate up to 75%, the strength of recycled concrete blocks slightly decreases but still complies with the standards. An experiment by [PERSON] et al. [29] showed that the compressive strength of recycled concrete blocks with 100% RCA can achieve the target of 7 MPa, and even the minimum strength requirement of construction. Despite the fact that the compressive strength of the concrete block is the critical performance index about whether the block can be used in a masonry structure, the mechanical performance of a masonry prism is more reflective of the actual stress state of the masonry structure. [PERSON] et al. [30] studied the compressive, shear, and bond strength of recycled mortar prisms, and found that the shear and compressive strength of recycled mortar prisms were close to or even better than that of ordinary mortar prisms. [PERSON] et al.