## 3 Experimental Results  
### Heat Test and Thermal Imaging Analysis Results  
The experiment on the heating properties was conducted using the cement-based material type, mixing concentration, curing days, and presence of damage as the parameters. Figure 5 shows the temperature variation at the center of the composites after curing for 7 d according to the type of cement-based material, mixing concentration, and presence of damage. The voltage applied to the composites was 60 V. The temperatures of the composites without damage were measured as 31.5 \({}^{\circ}\)C for CP-0.125-7D-X, 3.8 \({}^{\circ}\)C for M-0.125-7D-X, and 2.9 \({}^{\circ}\)C for Co-0.125-7D-X. However, the temperatures for composites with damage were 25.7 \({}^{\circ}\)C for CP-0.125-7D-O, 1.4 \({}^{\circ}\)C for M-0.125-7D-O, and 0.8 \({}^{\circ}\)C for Co-0.125-7D-O. Thus, the temperature gradients of the composites with damage were lower than those of the composites without damage (Figure 5a). The heat properties of the cement paste were 8.3-times better than those of mortar and 10.9-times better than those of concrete. The temperature decrease owing to the presence of damage was 5.8 \({}^{\circ}\)C for cement paste, 2.4 \({}^{\circ}\)C for mortar, and 2.1 \({}^{\circ}\)C for concrete. The temperature differences owing to the occurrence of damage to the mortar and concrete with 0.125 wt% MWCNT were less than 3 \({}^{\circ}\)C and, therefore, insignificant. Thus, damage detection based on the heat property is difficult for mortar and concrete with 0.125 wt% MWCNT. This result suggests that the cement paste with a MWCNT concentration of 0.125 wt% has excellent heating properties. Because this cement paste has no aggregates, the current increases and the heat generation is excellent. Figure 5b shows a heating value plot according to the parameters of the composites with 0.25 wt% MWCNT. The temperatures of the cement paste generated by the applied voltage were 47.4 \({}^{\circ}\)C for CP-0.25-7D-X and 40.6 \({}^{\circ}\)C for CP-0.25-7D-O. Thus, the temperature gradients decreased by 6.8 \({}^{\circ}\)C owing to the occurrence of damage. The temperatures of the mortar were 12.9 \({}^{\circ}\)C for M-0.25-7D-X and 7.4 \({}^{\circ}\)C for M-0.25-7D-O. Thus, the temperature decreased by 5.5 \({}^{\circ}\)C owing to the damage that occurred. The maximum temperature differences of the concrete were 8.9 \({}^{\circ}\)C for Co-0.25-7D-X and 6.1 \({}^{\circ}\)C for Co-0.25-7D-O. Thus, although the temperature gradients decreased by 2.8 \({}^{\circ}\)C, the temperature difference of concrete was lower than that of the cement paste and mortar. It can be inferred that the mixed aggregates of cement paste and mortar are relatively smaller in size than those of concrete at 0.25 wt% MWCNT, thus increasing the number of CNT networks formed. Therefore, it was more challenging to detect damage in concrete with 0.25 wt% MWCNT than in that of cement paste and mortar. Figure 5c shows the temperature variation of composites with 0.5 wt% MWCNT according to the parameters. The temperatures of the cement paste were 67.8 \({}^{\circ}\)C for CP-0.5-7D-X and 51.2 \({}^{\circ}\)C for CP-0.5-7D-O, and thus are up to 2.2-times higher than that of 0.125 wt% and 1.4-times higher than that of the 0.25 wt% cement paste. The temperatures of the mortar were 23.5 \({}^{\circ}\)C for M-0.5-7D-X and 10.1 \({}^{\circ}\)C for M-0.5-7D-O, and thus 1.8-times higher than that of 0.25 wt%. The temperatures of the concrete were 10.4 \({}^{\circ}\)C for Co-0.5-7D-X and 8.0 \({}^{\circ}\)C for Co-0.5-7D-O and were thus up to 2.1 \({}^{\circ}\)C higher than that of  
Figure 5: Temperature variations by voltage supply for 7 curing days: (**a**) 0.125 wt%, (**b**) 0.25 wt%, and (**c**) 0.5 wt%. 0.25 wt%. The temperature differences of the composites owing to damage were 16.6 \({}^{\circ}\)C for cement paste, 13.4 \({}^{\circ}\)C for mortar, and 2.4 \({}^{\circ}\)C for concrete. The heating properties of each composite improved with increasing MWCNT concentration.