## 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
After the high-temperature test and without self-healing, the results of the first pull-out test for each group are shown in Table 4. In the case of 300 \({}^{\circ}\)C, the maximum temperature of the concrete inside the pull-out specimen was approximately 98.2 \({}^{\circ}\)C. In this case, there was no degradation of the concrete substrate. Therefore, the residual BS of the specimen did not decrease significantly. Table 4 shows that, after exposure to 300 \({}^{\circ}\)C, the average bond strength of the unhealed specimens in each group was close to 27 MPa. These bond strength values were only slightly lower than their bond strength values at room temperature. After being subjected to 500 \({}^{\circ}\)C, the average first bond strength of the unhealed specimens in each group was close to 30 MPa. These bond strength values were higher than those of each group of specimens at room temperature. In the case of 500 \({}^{\circ}\)C, the maximum temperature of the concrete inside the pull-out specimen was approximately 235.7 \({}^{\circ}\)C. Under this temperature condition, water vapor evaporated inside the specimen, causing a drying effect [57]. As a result, the bond strength of the specimen increased slightly. Furthermore, the residual BS after exposure to high temperatures was divided by that at room temperature. The calculated relative bond strength (BS) ratios are shown in Table 4. As shown in Table 4, the relative BS ratios of Groups A, B, and C after exposure to 500 \({}^{\circ}\)C were 1.09, 1.06, and 1.08, respectively. Figure 5:0 The \(\tau\)–\(s\) curves of unhealed experimental group specimens after exposure to different temperatures: (**a**) Group B; (**b**) Group C.  
In addition, the specimens damaged by high temperatures and the first pull-out test were subjected to self-healing. The results of the secondary pull-out test after 28 days of self-healing are shown in Figure 5:1 It can be seen that, in the case of 300 \({}^{\circ}\)C, the residual bond strengths of the secondary pull-out test results of Groups A, B, and C were 18.89, 20.48, and 20.70 MPa, respectively. Compared with Group A, the relative BS ratios in Groups B and C after 28 days of self-healing increased by 5.9% and 8.8%, respectively. However, in the case of 500 \({}^{\circ}\)C, the residual bond strengths of the secondary pull-out test results of Groups A, B, and C were 18.17, 18.35, and 19.00 MPa, respectively. As shown in Table 5, the relative BS ratios of Groups A, B, and C in the secondary pull-out test after exposure to 300 \({}^{\circ}\)C were 0.68, 0.72, and 0.74, respectively. Compared with Group A, the relative BS ratios in Group C after 28 days of self-healing increased by 8.4%. Overall, the relative BS ratio of the secondary pull-out test results of Group C was higher than that of Groups A and B. This result once again means that the healing method with an ambient temperature of 40 \({}^{\circ}\)C and a two-day cycle had a better effect. In summary, for the specimens that did not heal themselves after being exposed to high temperatures, the residual BS of each group in the first pull-out test was not significantly reduced. 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 during the first pull-out test was more severe. The experimental group healed itself in a better environment, resulting in a significant improvement in the residual BS in the secondary pull-out test.