# Cyclic Behaviors of Geopolymeric Recycled Brick Aggregate Concrete-Filled Steel Tubular Column
## 2 Test Program
### Material Properties  
Table 2 demonstrates the primary properties of steel, which were obtained by a coupon test according to Chinese Standard GB/T 228.1-2010 [44]. GRBAC is prepared with river \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**No.** & **D/mm** & **\(t\)/mm** & **\(r\)/\%** & **\(n\)** & **N/RN** \\ \hline STG4-0-0.25 & 130 & 4 & 0\% & 0.25 & 320.43 \\ STG4-0.3-0.25 & 130 & 4 & 30\% & 0.25 & 298.85 \\ STG4-0.5-0.25 & 130 & 4 & 50\% & 0.25 & 292.6 \\ STG4-0.7-0.25 & 130 & 4 & 70\% & 0.25 & 294.2 \\ STG4-1-0.25 & 130 & 4 & 100\% & 0.25 & 280.73 \\ STG4-0.5-0.05 & 130 & 4 & 50\% & 0.05 & 585.52 \\ STG4-0.5-0.25 & 130 & 4 & 50\% & 0.5 & 585.21 \\ STG6-0.5-0.25 & 130 & 6 & 50\% & 0.25 & 325.44 \\ STM4-0.0-25 & 130 & 4 & 0\% & 0.25 & 328.55 \\ STM4-0.5-0.25 & 130 & 4 & 50\% & 0.25 & 294.87 \\ STM4-1-0.25 & 130 & 4 & 100\% & 0.25 & 275.15 \\ \hline \hline \end{tabular} Note: \(D\) and \(I\) are the width and thickness of square steel tube, respectively; \(r\) means the replacement ratio of RBA; \(n\) is the axial compression ratio, defined as \(n=N/(\text{A}_{\text{c}}f_{\text{y}}+\text{A}_{\text{c}}\text{I}_{\text{c}})\), where \(N\) is the applied d axial load under test, \(\text{A}_{\text{s}}\) and \(\text{A}_{\text{c}}\) are the cross-section area of steel tube and inner concrete, respectively, and \(f_{\text{y}}\) and \(\text{I}_{\text{c}}\) are the yield strength of steel and compressive strength of inner concrete, respectively.  
\end{table} 
Table 1: Design parameters of specimens. Figure 1: Geometric details of the proposed composite column. sand, crushed brick aggregates, fly ash, slag and alkali activator, where the fly ash, slag and alkali activators were used to prepare geopolymers. The alkali activator was made of Na\({}_{2}\)SiO\({}_{3}\) and NaOH solution, where the NaOH solution was prepared by dissolving solid NaOH flakes (98% purity, density 2.13 g/cm\({}^{3}\)) in pure water with a constant modulus of 1.4 M. The particle size and gradation of river sand was same with that for recycled brick aggregates, with particle size of 4.75 mm-26.5 mm. The measured water absorption of recycled brick aggregate was 14.97%, higher than river sand of 3.1%; therefore, saturated wetting treatment on brick aggregate was necessary before the preparation of GRBAC. Moreover, 1.5% borax and sucrose were added as retarders to ensure the workability during the preparation of the concrete. Benchmark strength of C50 was selected for ordinary geopolymeric concrete without RBA, and then natural coarse aggregates were replaced with different RBA replacement ratio to prepare GRBAC. It should be noted that the natural coarse aggregates were replaced with RBA by weight. Besides, to explore the influence of different cementitious material, recycled brick aggregate concrete with OPC (RBAC) was also prepared, and replacement ratios of RBA of 0%, 50% and 100% was considered. The mix design for GRBAC and RBAC is outlined in Tables 3 and 4, respectively. The material property test for GRBAC and RBAC was also conducted according to Chinese Standard GB/T50081-2019 [45]. Three cubic specimens in 150 mm for concrete \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Specimens**} & \multirow{2}{*}{\(r_{\text{BA}}\)/\%} & \multicolumn{6}{c}{**Materials**} & \multirow{2}{*}{\(f_{\text{cu}}\)} \\ \cline{3-3} \cline{5-8}  & & **Sand** & & **Stone** & & **RBA** & **Water** & **OPC** \\ \hline RBAC-0 & 0 & 698 & 1080 & 0 & 180 & 460 & 58.73 \\ RBAC-50 & 50 & 698 & 540 & 540 & 180 & 460 & 43.38 \\ RBAC-100 & 100 & 698 & 0 & 1080 & 180 & 460 & 34.97 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The mix design for RBAC (kg:m\({}^{-3}\)) and measured strength (MPa).