## 3 Tests Results and Discussion
### Results of the Pull-Out Test
#### 3.2.1 Local Bond-Slip Relationship and Bond Strength of LWAC at Room Temperature
2.3 Local Bond-Slip Relationship and Bond Strength in Healed LWAC after Exposure to High Temperatures  
The results of the pull-out tests indicated rebar pull-out failures in all the samples after exposure to a temperature of 300 \({}^{\circ}\)C and being subjected to healing, as shown in Figure 5:2 The corresponding \(\tau\)-s curve is shown in Figure 5:3 The \(\tau\)-s curve of the first pull-out test of the healed specimen after 300 \({}^{\circ}\)C was the same as that of the unhealed specimen and could be divided into three stages. As shown in Figure 13a, after 28 days of healing, the peak bond stresses of the experimental group and the control group were similar. In addition, the corresponding slip to the peak bond stress was very small, approximately 0.5-1 mm. In contrast, as shown in Figure 13b, after 90 days of healing, the peak bond stress of Group C was higher than that of Group A. Furthermore, the corresponding slip to the peak bond stress was approximately 1-1.5 mm. From this point of view, the improvement in the peak bond stress in Group C was better after 90 days of healing. Moreover, after the 28-day healing period of the first pull-out specimen, the \(\tau\)-s curve of the secondary \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Group**} & **BS at RT** & \multicolumn{2}{c}{**Residual BS (MPa)**} & \multicolumn{2}{c}{**Relative BS Ratio**} \\ \cline{3-6}  & **(MPa)** & **300 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** & **300 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** \\ \hline Group A & 27.99 (1.56) & 27.35 (0.68) & 30.53 (1.75) & 0.98 & 1.09 \\ Group B & 28.38 (1.34) & 27.07 (1.14) & 30.02 (1.97) & 0.95 & 1.06 \\ Group C & 28.02 (0.40) & 27.41 (0.69) & 30.34 (1.20) & 0.98 & 1.08 \\ \hline \end{tabular} Note: BS: bond strength; RT: room temperature. The data in brackets are standard deviations.  
\end{table} 
Table 4: Bond strength of unhealed LWAC after exposure to high temperatures. \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Group**} & **BS at RT** & \multicolumn{2}{c}{**Residual BS (MPa)**} & \multicolumn{2}{c}{**Relative BS Ratio**} \\ \cline{3-6}  & **(MPa)** & **300 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** & **300 \({}^{\circ}\)C** & **500 \({}^{\circ}\)C** \\ \hline Group A & 27.99 (1.56) & 18.89 (0.89) & 18.17 (1.20) & 0.68 & 0.65 \\ Group B & 28.38 (1.34) & 20.48 (1.57) & 18.35 (1.24) & 0.72 & 0.65 \\ Group C & 28.02 (0.40) & 20.70 (1.46) & 19.00 (0.58) & 0.74 & 0.68 \\ \hline \end{tabular} Note: BS: bond strength; RT: room temperature.  
\end{table} 
Table 5: Results of the secondary pull-out test of the unhealed LWAC after exposure to high temperatures. pull-out test still went through the four stages described previously. On the other hand, after 28 days of healing, the peak bond stress of Group C was slightly higher than that of Group A in the secondary pull-out test. However, after 90 days of healing, the peak bond stress of Group C was significantly higher than that of Group A in the secondary pull-out test. After being subjected to 300 \({}^{\circ}\)C, the \(\tau\)-\(s\) curves of the Group A specimens under different healing age conditions are shown in Figure 14. As shown in Figure 14, with the increase in healing age, the peak bond stress of the Group A specimens increased significantly. In addition, with the increase in the healing age, the peak bond stress of the secondary pull-out test in Group A also increased. Moreover, the \(\tau\)-\(s\) relationship curves of the experimental group specimens at different healing ages after being subjected to a temperature of 300 \({}^{\circ}\)C are shown in Figure 15. As shown in Figure 15a, with the increase in the healing age, the peak bond stress of the Group B specimens increased significantly. As the healing age increased, the peak bond stress in the secondary pull-out test of Group B also increased. As shown in Figure 15b, with the increase in the healing age, the peak bond stress of the Group C specimens increased significantly.