# Electrical Characteristics of Ultra-High-Performance Concrete Containing Carbon-Based Materials
## 3 Results and Discussions
### Alternating Current Measurements  
As shown in Table 4, and Figures 9 and 10, the AC measurements exhibited a similar overall trend to the DC measurements. The conductivity of the CNT specimens increased on increasing the mixing content; however, it was difficult to increase the conductivity of concrete significantly. The CF specimen with a mixing content of 1.5% showed the highest conductivity, while the MF and CNT specimens exhibited similar conductivity. Furthermore, as the mixing content increased, the conductivities of the GP specimens decreased.  
DC resistances are lower than AC resistances. Here, the AC conductivities were higher than the DC conductivities; the AC and DC results exhibited conductivity differences of up to 4.6 times. AC measurements are more reliable than DC measurements; the measured electrical resistance increases gradually in DC measurement methods due to polarization  
Figure 8: Direct current measurements at the age of 28 days.  
that occurs when the electrode moves to both ends of the apparatus [50; 51]. Therefore, the measurement value changes over time, making it difficult to define a single resistance value. Contrarily, in the AC measurement method, the resistance of the specimen is defined from the impedance measured at a specific frequency, making it more reliable than the DC measurement method. Here, the DC and AC measurement methods showed a similar tendency, while the latter exhibited higher reliability; thus, the AC method is more suitable for measuring the electrical conductivity of concrete.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{\begin{tabular}{c} **Carbon** \\ **Materials** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Concentration** \\ **(\%)** \\ \end{tabular} } & \multicolumn{2}{c}{**At the Age of 3 Days**} & \multicolumn{2}{c}{**At the Age of 28 Days**} & \multicolumn{2}{c}{**Reduction Rate (\%)**} \\ \cline{3-6}  & & **Impedance, Z** & \
\begin{tabular}{c} **Conductivity** \\ **(S/m \(\times\) 10\({}^{-3}\))-3** \\ \end{tabular} & **Impedance, Z** &
\begin{tabular}{c} **Conductivity** \\ **(S/m \(\times\) 10\({}^{-3}\))-1** \\ \end{tabular} & **(S)** & **(S)** & **(S)** & **(S)** \\ \hline \multirow{4}{*}{[CNT]} & 0.5 & 10,818 & 7.4 & 260,823 & 0.3 & 95.9\% \\  & 1.0 & 6884 & 11.6 & 129,849 & 0.6 & 94.7\% \\  & 1.5 & 4577 & 17.5 & 81,727 & 1.0 & 94.4\% \\  & 2.0 & 6278 & 12.7 & 80,992 & 1.0 & 92.2\% \\ \hline \multirow{4}{*}{[CF]} & 0.5 & 4668 & 17.1 & 74,373 & 1.1 & 93.7\% \\  & 1.0 & 5535 & 14.5 & 97,736 & 0.8 & 94.3\% \\  & 1.5 & 387 & 206.9 & 4005 & 20.0 & 90.3\% \\  & 2.0 & 453 & 176.7 & 3376 & 23.7 & 86.6\% \\ \hline \multirow{4}{*}{[MF]} & 0.5 & 11,066 & 7.2 & 196,317 & 0.4 & 94.4\% \\  & 1.0 & 10,967 & 7.3 & 170,319 & 0.5 & 93.6\% \\  & 1.5 & 3224 & 24.8 & 38,819 & 2.1 & 91.7\% \\  & 2.0 & 2038 & 39.3 & 36,788 & 2.2 & 94.5\% \\ \hline \multirow{4}{*}{[GP]} & 0.5 & 4438 & 18.0 & 49,640 & 1.6 & 91.1\% \\  & 1.0 & 1673 & 47.8 & 27,999 & 2.9 & 94.0\% \\ \cline{1-1}  & 1.5 & 3504 & 22.8 & 34,432 & 2.3 & 89.8\% \\ \hline \end{tabular}
\end{table}
Table 4: Alternating current measurements with reduction rates according to the age of concrete.  
Figure 9: Alternating current measurements at the age of 3 days.