## 2 Test Survey
### Column Specimens  
There were six specimens in this test. The parameters of the column specimens are shown in Table 5. The concrete strength grade of existing columns was C30. Section size was 150 mm \(\times\) 150 mm. The reinforcement ratio of existing columns was designed according to code for the design of concrete structures (GB50010-2010) [36]. Longitudinal bars were 4 C 12. The distribution of the stirrups at the top and bottom of the column were 4 A 6 @ 40 and 3 A 6 @ 100 in the middle of the column, as shown in Figure 1a. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Concrete** & **Used Part** & **Measured Cubic** \\
**Number** & & **Compressive Strength (MPa)** \\ \hline C30 & Column C1 and concrete columns to be strengthened & 30.8 \\ \hline C50 & Concrete for column strengthening & 46.6 \\  & for Column C2 & \\ \hline  & Concrete for column strengthening & 45.7 \\  & for Column C3 & \\ \cline{2-3}  & Concrete for column strengthening & 46.5 \\ LC50 & & 45.5 \\  & for Column C5 & 46.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Measured concrete cubic compressive strength during the compression test of column specimens. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Strength** & **Cement** & **Ceramsite** & **Pottery** & **Water** & **Water** \\
**Grade** & & **Sand** & **Reducer** & **Water** \\ \hline LC50 & 550 & 620 & 600 & 5.1 & 154 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: LC50 all-light ceramsite concrete mix proportion (kg/m\({}^{3}\)). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Strength** & **Cement** & **Coal Ash** & **Sand** & **Gravel** & **Water** & **Water** \\
**Grade** & & **Sand** & **Reducer** & **Reducer** \\ \hline C50 & 400 & 120 & 700 & 1050 & 170 & 4.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: C50 ordinary concrete mix proportion for reinforcement (kg/m\({}^{3}\)). Figure 1: Column specimen construction and strain gauge arrangement (unit: mm). (**a**) Column specimen C1; (**b**) Column specimens C2–C6. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Column Summer**} & **Concrete Strength** & **Column Cross-Section Size/** & **Length of Main Steel** & **Strengthened** & **Slenderness Ratio** \\  & **Grade (Existing** & **(mm) (Existing Columns)** & **Columns/Strengthened** & **Software Treatment** & **Strengthened** \\  & **Columns/Strengthened Columns)** & **Strengthened Columns)** & **Columns/Strengthened** & **Software Treatment** & **Strengthened** \\ \hline C1 & C30/- & 150 \(\times\) 150 & 4 C 12 & - & 4.93 \\  & & /- & /- & - \\ \hline C2 & C30/C50 & 150 \(\times\) 150 & 4 C 12 & \multirow{2}{*}{Chiseling} & 2.96 \\  & & /250 \(\times\) 250 & /4 C 14 & & \\ \hline C3 & C30/LC50 & 150 \(\times\) 150 & 4 C 12 & \multirow{2}{*}{Chiseling} & 2.96 \\  & & /250 \(\times\) 250 & /4 C 14 & & \\ \hline C4 & C30/LC50 & 150 \(\times\) 150 & 4 C 12 & \multirow{2}{*}{Interfacial} & 2.96 \\  & & /250 \(\times\) 250 & /4 C 14 & & \\ \hline C5 & C30/LC50 & 150 \(\times\) 150 & 4 C 12 & \multirow{2}{*}{Post-installed rebar} & 2.96 \\  & & /250 \(\times\) 250 & /4 C 14 & & \\ \hline C6 & C30/LC50 & 150 \(\times\) 150 & 4 C 12 & \multirow{2}{*}{Post-installed rebar+} & 2.96 \\  & & /250 \(\times\) 250 & /4 C 14 & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Main parameters of the column specimens. The dimensions of the strengthened column were 250 mm \(\times\) 250 mm. The reinforcement part was designed according to the Code for Design of Strengthening Concrete Structures (GB50367-2013) [37]. The distribution of the stirrups at the top and bottom of the column were 4 A 8 @ 40 and 3 A 8 @ 100 in the middle of the column, as shown in Figure 1b. The concrete protection-cover depth was 25 mm in all cases. Column specimen C1 was an existing column without strengthening. Column specimen C2 was strengthened with ordinary C50 concrete. Column specimens C3-C6 were strengthened with LC50 all-light ceramsite concrete. Column specimens C2-C6 reinforcement size and distributed steel were consistent.