## 3 Experimental Results
### Electrical Resistance Testing  
An experiment on the electrical resistance property was conducted with the type of cement-based material, mixing concentration, number of curing days, and the presence of damage as parameters. The electrical resistances of the composites according to these parameters are listed in Table 4. Figure 11 shows an electrical resistance property graph of the composites after 7 d of curing. The graph of the electrical resistance of the composites with 0.125 wt% MWCNT according to the parameters is shown in Figure 11a. The electrical resistance of the cement paste was 3.4 k\(\Omega\) for CP-0.125-7D-X and 10.2 k\(\Omega\) for CP-0.125-7D-O. Thus, the difference in the electrical resistance caused by damage was 6.8 k\(\Omega\). The electrical resistance of the mortar was 62.0 k\(\Omega\) for M-0.125-7D-X, which is 18.2-times higher than that of cement paste, and 90.2 k\(\Omega\) for M-0.125-7D-O. The difference in resistance of the mortar owing to the occurrence of damage was 28.2 k\(\Omega\), which is 4.1-times higher than that of the cement paste. The electrical resistance of the concrete was 81.0 k\(\Omega\) for Co-0.125-7D-X and 118.0 k\(\Omega\) for Co-0.125-7D-O. Thus, the difference in the electrical resistance owing to the presence of damage was 37.0 k\(\Omega\). The electrical resistance of concrete with 0.125 wt% MWCNT was up to 23.8-times higher than that of the cement and up to 1.3-times higher than that of the mortar. This result indicates that cement paste and mortar have higher electrical conductivities than concrete. Figure 11b shows a graph of the electrical resistance of the composites with 0.25 wt% MWCNT. The electrical resistances of the composites without damage were 1.6 k\(\Omega\) for cement paste, 21.4 k\(\Omega\) for mortar, and 46.0 k\(\Omega\) for concrete, respectively. The resistance of the cement paste was 19.8 k\(\Omega\) lower than that of mortar and 44.4 k\(\Omega\) lower than that of concrete. The resistance of the composites with damage was 2.5 k\(\Omega\) for cement paste, 39.2 k\(\Omega\) for mortar, and 71.1 k\(\Omega\) for concrete. The electrical resistance after the occurrence of damage increased by 0.9 k\(\Omega\) for cement paste, 17.8 k\(\Omega\) for mortar, and 25.1 k\(\Omega\) for concrete. Concrete had an increased resistance owing to the large size of the aggregates in the concrete. Figure 11c shows the graphs of the electrical resistance of the cement paste, mortar, and concrete with 0.5 wt% MWCNT. The electrical resistance of the cement paste was 0.4 k\(\Omega\) for CP-0.5-7D-X and 1.1 k\(\Omega\) for CP-0.5-7D-O. Thus, the 0.5 wt% MWCNT-cement-paste composites exhibited up to 9.3-times higher electrical resistance than 0.125 wt% MWCNT composites and up to 4.0-times higher electrical resistances than those of 0.25 wt% MWCNT composites. The electrical resistance of mortar was 7.6 k\(\Omega\) for M-0.5-7D-X and 20.5 k\(\Omega\) for M-0.5-7D-O. Thus, the electrical resistance of 0.5 wt% MWCNT-paste composites was up to 8.2-times lower than that of the 0.125 wt% composite and up to 2.8-times lower than that of the 0.25 wt% composite. The electrical resistance of the concrete was 35.8 k\(\Omega\) for Co-0.5-7D-X and 50.5 k\(\Omega\) Co-0.5-7D-O. Thus, the electrical resistance was up to 2.3-times lower than that of the 0.125 wt% composites and up to 1.4-times lower than that of the 0.25 wt% composites. The difference in electrical resistance owing to the occurrence of damage was 0.7 k\(\Omega\) for cement paste, 12.9 k\(\Omega\) for mortar, and 14.7 k\(\Omega\) for concrete. The electrical resistance of the composites cured for 7 d decreased  
Figure 10: Crack by voltage supply. because of the damage that occurred as the MWCNT concentration increased. This is because the change in the resistance owing to such damage decreased as the MWCNTs with high electrical conductivities became detached, thus lowering the resistance of the composite itself.