## 3 Repair Materials
### Discussion  
Cyclic behavior and pressure were applied with respect to the artificial cracks into which the repair materials were injected, and Table 8 shows a summary of the responsiveness and water tightness performance of the water leakage repair materials. (1) In the case of the synthetic-rubber-based (RG) materials, the slip-down phenomenon occurred in the crack behavior test, but all the nine specimens showed responsiveness to the crack behavior. This suggests that such materials respond flexibly to the behavior of the cracks that occur in concrete structures due to the elastic properties of non-curable polymer resin using asphalt with a rubber component and a viscous nature. With respect to the permeability resistance after the completion of the crack behavior test, seven synthetic-rubber-based (RC) specimens did not exhibit permeability while the other two specimens did, as shown in Table 8. Therefore, the existence of water leakage was determined according to the differences in rubber viscosity of the materials in the case of the synthetic-rubber-based (RG) repair materials. (2) In the cement-based (CG) and epoxy-based (EG) repair materials, all the 18 specimens did not show responsiveness to the crack behavior. In the case of the cement-based (CG) material, the rigid material properties with little flexibility made it impossible to proceed with the test due to the adhesive surface's detachment from the main body, which was caused by even a microscopic crack behavior. As for the epoxy-based (EG) material, the main body of the specimen (attached equipment) was damaged due to the solid properties after the curing, and as such, the test could not be conducted. In particular, although the epoxy-based (EG) repair material has very strong material strength, it does not have sufficient responsiveness to the crack behavior after the repair, and the repaired area can be damaged under the continuous crack behavior effects, posing the risk of re-leakage. In this regard, the crack behavior responsiveness should be reviewed when the cement-based (CG) and epoxy-based (EG) water leakage repair materials are applied to the water leakage or crack areas in concrete structures. (3) As for the acrylic-based (AG) and urethane-based (UG) repair materials, all the 12 AG-2, AG-3, UG-1, and UG-2 specimens did not pass the 100-cyclerack behavior test, and only six AG-1 and UG-3 specimens were found to have crack behavior responsiveness. The observation results revealed, however, that the excitation phenomenon occurred at certain places. This excitation resulted in the loss of the repair materials in the permeability test, and as such, permeability was shown by all the specimens. This shows that as the soft-body acrylic-based material of the jelly type and the urethane-based (RG) material that takes the form of silicon are harder than the synthetic-rubber-based (RG) materials and are softer than the cement-based (CG) or epoxy-based (EC) materials, they have a large material deviation in crack behavior responsiveness and permeability resistance. (4) The summary of the artificial-crack-behavior test results shows that of the 45 types of repair materials, 24.4% were found to have crack behavior responsiveness, and about 75.6%were lacking in responsiveness. In addition, the permeability test confirmed that about 15.6% did not show water leakage whereas about 84.4% did. (5) With regard to the crack behavior responsiveness performance deviation, shows that the material deviation of the synthetic polymer (RG) was 0% as its average crack behavior was 100 times; that of acryl (AG)was 31%, with 80.3 times average crack behavior; and that of urethane (UG)was 100 times.