## 3 Result and Discussion
### Corrosion-Induced Cracks Analysis  
Each surface of the stirrup-corroded column is expanded in Figure 7. The distribution of corrosion-induced cracks and physical diagrams of the three stirrup-corroded columns under the coupling of axial load and chloride are given in Figure 8.  
As can be seen from Figure 8, the number of corrosion-induced cracks, the width of the cracks, and the degree of spillage of corrosion produced on different surfaces of the same column varied, with some surfaces having more corrosion products and corrosion-induced cracks but some surfaces even having none. Overall, with the increasing stirrup corrosion rate, the corrosion-induced cracks on the column surface gradually increased and the corrosion-induced cracks mainly developed along the direction of the longitudinal reinforcing steel bars (cracks along longitudinal reinforcing steel bars caused by corrosion). In addition, there were almost no transverse corrosion-induced cracks along the direction of the severely corroded stirrup, which differed from the conclusion that stirrup corrosion under no load conditions mainly produced transverse corrosion-induced cracks [27]. This was because under the coupled action of load and chloride, the corrosion-induced expansion force caused by corroded stirrups was in the opposite direction to the axial compression, and the compression counteracted the corrosion-induced expansion force caused by the corroded stirrups. Thus, no transverse corrosion-induced cracks appeared along the direction of the stirrups. The corrosion-induced cracks formed along the direction of the main reinforcing steel bars, which may have been due to the following reasons: firstly, the long-term axial compressive load caused the column to produce transverse expansion, and the transverse expansion stress was in the same direction as the corrosion-induced expansion force caused by the main reinforcing steel bars corrosion. Secondly, the main reinforcing steel bars produced slight corrosion and there was a certain corrosion-induced expansion stress. Thirdly, the corrosion products of the stirrups partially penetrated into the concrete around the main reinforcing steel bars through the internal void of the concrete and the corrosion products increased as a result of the superposition of several influencing  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Specimen Number** & \(\rho_{\textbf{mr,th}}/\%\) & \(\rho_{\textbf{mr,ex}}/\%\) & \(\rho_{\textbf{vc,th}}/\%\) & \(\rho_{\textbf{vc,ex}}/\%\) \\ \hline GZ0 & 0 & 0.00 & 0 & 0.00 \\ GZ5 & 0 & 2.28 & 5 & 4.95 \\ GZ10 & 0 & 1.69 & 10 & 9.26 \\ GZ15 & 0 & 2.81 & 15 & 12.57 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Corrosion rates of reinforcing steel bars in columns.  
Figure 7: Diagram of the unfolded corroded column.  
factors, which led to the development of corrosion-induced cracks that extended along the direction of the main reinforcing steel bars. From the above analysis, it can be seen that the load effect was the main factor affecting the distribution of corrosion-induced cracks.  
In addition, the process and development of corrosion-induced cracks were mainly manifested in two cracking forms: the cracking of the concrete cover on one side and the  
Figure 8: Corrosion-induced crack maps.  
cracking of the concrete cover on both sides. Corrosion-induced cracks mainly manifested as single-sided cracking along the main reinforcing steel bars when the stirrup corrosion rate was low. As the corrosion rate of the stirrups increased, more corrosion products penetrated into the main reinforcing steel bars and double-sided cracking gradually occurred. Thus, corrosion-induced cracks appeared on both adjacent surfaces of the same longitudinal reinforcing steel bars.