## 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
With the increase in the healing age, the peak bond stress of the secondary pull-out test in Group C also increased significantly. As shown in Figures 9 and 13, the slip  
Figure 12: Pull-out failure of healed LWAC specimens after exposure to a temperature of 300 \({}^{\circ}\)C: (**a**) a healing age of 28 days; (**b**) a healing age of 90 days. Figure 13: The \(\tau\)–\(s\) curves of healed LWAC specimens after exposure to 300 \({}^{\circ}\)C: (**a**) a healing age of 28 days; (**b**) a healing age of 90 days. in the experimental group was slightly smaller than that of the control group when the maximum load occurred, and this phenomenon showed the same trend in each healing age and target temperature. In addition, as shown in Figure 14, the trends of Group A at the healing ages of 28 days and 90 days were similar. This result shows that the hydration reaction of the cement itself had been roughly developed in 28 days, and there was no obvious increase in the late age. In contrast, as shown in Figure 15, as the age increased, the bond strength of Group C showed a more obvious improvement. This was especially true in the secondary pull-out test, where the repair rate was higher when the healing age was 90 days. From this perspective, the curing method of Group C was more effective. The pull-out test results of the healed specimens after exposure to 300 \({}^{\circ}\)C are shown in Table 6. As shown in Table 6, taking the specimen that underwent 28 days of self-healing as an example, the residual bond strengths of Groups A, B, and C were 28.82, 28.36, and 28.64 MPa, respectively. In addition, taking the specimen that underwent 90 days of self-healing as an example, the residual bond strengths of Groups A, B, and C were 29.99, 30.37, and 31.08 MPa, respectively. Moreover, for the specimens of different self-healing ages after 300 \({}^{\circ}\)C, the relative BS ratio was calculated based on the bond strength without self-healing after 300 \({}^{\circ}\)C, and the results are shown in Table 6. As shown in Table 6, taking the specimen that underwent 90 days of self-healing as an example, the relative BS ratios of Groups A, B, and C were 1.10, 1.12, and 1.13, respectively. Compared with Group A, the relative BS ratios in Groups B and C after 90 days of self-healing increased by 2.3% and 3.4%, respectively. In terms of self-healing for 90 days, the relative BS ratio of Group C was the highest, which again proved that the curing method with a curing temperature of 40 \({}^{\circ}\)C and a two-day cycle was better. Figure 14: The \(\tau\)–s curves of healed Group A specimens after different healing ages. Figure 15: The \(\tau\)–s curves of the healed experimental group after different healing ages: (**a**) Group B; (**b**) Group C.  
On the other hand, each group of specimens exposed to a temperature of 300 \({}^{\circ}\)C that underwent different self-healing ages and were damaged in the first pull-out test were allowed to self-heal for another 28 days. The results of the secondary pull-out test after self-healing for 28 days were analyzed. As shown in Figure 16, taking the case after exposure to 300 \({}^{\circ}\)C and a healing period of 90 days as an example, the relative BS ratios of the secondary pull-out test results of Groups A, B, and C were 0.69, 0.73, and 0.83, respectively. Compared with Group A, the relative BS ratios in Groups B and C after 90 days of self-healing increased by 5.8% and 20.3%, respectively. In summary, for the specimens that healed themselves after being exposed to 300 \({}^{\circ}\)C, the residual BS of the first pull-out test in each group did not significantly attenuate. This is attributed to the fact that the high-temperature test did not cause serious degradation of the internal composition of the concrete in each group of specimens. However, the damage caused by the first pull-out test was relatively severe. Group C healed itself in a better environment. As a result, its residual BS in the secondary pull-out test was significantly better than that of Group A.