# Cyclic Behaviors of Geopolymeric Recycled Brick Aggregate Concrete-Filled Steel Tubular Column
## 1 Introduction  
Over the past decades, the shortage of natural construction material and social concerns about the environmental issues have been pushing the whole construction industry to seek sustainable and environmentally friendly materials as an alternative to the common concrete material. It has been reported that about 2.4 billion tons of construction waste was produced per year, approximately accounting for 40% of the total urban waste [1]. Most of construction waste was used for landfill, greatly reducing the utilization efficiency of land resources and damaging the natural environment [2]. However, with the industrialization and development of constructional industry, the need for construction material, i.e., concrete, greatly increases, of which the preparation consumes a large proportion of natural aggregates, and it results in great environmental pressure. Therefore, how to reasonably deal with the problem of construction waste accumulation and the depletion of natural stone resource becomes a looming issue. Moreover, another critical issue attributed by the production of construction material relates to the greenhouse effect. It has also been reported that the production of Ordinary Portland Cement (OPC), which usually serves as the common cementitious material for concrete, consumes a large number of naturalresources and produces a large amount of CO\({}_{2}\) emission [3; 4]. As a result, it is essential to find an alternative material to the OPC as the cementitious material for concrete. Nowadays, the development of green buildings with low emission of harmful gases and the reuse of construction waste with high efficiency have become hot research issues. The utilization of recycled crushed wasted concrete rubble from construction waste is achieved by recycled aggregate concrete (RAC) technology, which has been relatively mature in the preparation of RAC as well as its derivatives [5; 6]. Considerable research has been carried out on the mechanical properties of recycled aggregate concrete, in terms of the static behavior, dynamic behavior, impact and temperature performance [7; 8; 9; 10; 11], durability [12], creep and shrinkage [13; 14]. However, micro-cracks produced during the crushing process and weak bond behavior of interfacial transition zone between recycled aggregate (RA) and new cement mortar lead to the relatively poor quality of RAC. It has been demonstrated that the strength of RAC is reduced by about 10-25% [15; 16; 17]. Numerous studies on the RAC verified that the application of RAC was an effective solution to the problem of shortage of natural aggregates. The wasted clay bricks from demolished buildings takes up a large proportion of the construction waste, and the reuse of wasted clay bricks could, furthermore, relieve the environmental issues of shortage of natural aggregates. The application of recycled clayed bricks (RBA) is gaining more and more research attention. However, there still exists problems that hinder the promotion of recycled clay bricks, such as lower apparent density, higher water absorption and higher crushing index [18; 19]. Several treatment methods were used to reduce the drawbacks of RBA, such as addition of admixtures [20; 21; 22; 23; 24; 25]. It was validated that the quality and mechanical strength of crushed brick aggregate were strengthened by pozzolan slurries, and the loss of compressive strength, flexural strength and modulus of elasticity was about 12-25%, 9-22% and 16-30%, respectively, compared with natural aggregate concrete [22]. In recent decades, a new type of cementitious material, geopolymers, has been used to replace the traditional OPC for the preparation of concrete [26; 27]. Geopolymer is synthesized by the combination of aluminosilicate materials and high-concentration NaOH solution.