# Mechanical, Electrical and Fractural Characteristics of Carbon Nanomaterial-Added Cement Composites
## 3 Results
### Electrical Conductivity  
Figure 8 shows the electrical conductivity test results for CNM/cement composites as the CNM content ratio increased from 0 to 1.0%; the results are stated as follows. In the CNT/cement composite samples, the electrical conductivity increased exponentially with an increase in the CNT content ratio, which is a trend similar to that reported in a previous study [71]. A previous investigation concluded that an exponential increase in electrical conductivity indicated an even distribution of MWCNTs in the cement matrix. In this study, a maximum electrical conductivity of 4.79 \(\times\) 10\({}^{3}\) S/cm was obtained after adding a 1.0% dosage of CNT. The electrical conductivity of the CNF/cement composites increased with an increasing CNF content. The maximum electrical conductivity was 0.0002 S/cm at a 1.0% CNF content ratio. The conductivity of cement composites increased when CNF content was increased from 0.3% to 1.0%. Similar to the CNT/cement composite, it can be concluded that there is an even distribution of CNF in the cement matrix.  
Regarding CNT/cement composites, it was found that the electrical conductivity increased dramatically in the range of 0.1-0.3% CNT content ratios; a similar trend was also observed in the range of 0.1-0.3% CNT content ratios.  
Figure 8: Electrical conductivity diagram of CNT/cement composite samples, GNP/cement composite samples, graphene/cement composite samples, and CNF/cement composite samples with increasing CNM content ratios.  
Figure 7: Correlation graphs between load and displacement of cement composites containing (**a**) CNF, (**b**) CNT, (**c**) GNP, (**d**) graphene with various CNM content ratios, and (**e**) the cement-only sample.  
reported in previous studies [27; 71]. Moreover, regarding CNF/cement composites, the electrical conductivity rose dramatically in the range of 0.3-1.0% CNF content ratio. When the conductivity drastically increases with an increase in carbon nanomaterial content, the composite sample behavior changes from an insulator to a conductor; this phenomenon is believed to occur when the CNM content is at or above the percolation threshold [83]. The percolation threshold is defined as the average of the CNM content range where electrical conductivity drastically increases [12]. Therefore, it can be concluded that between 0.1% and 0.3% CNT content ratio, the percolation threshold for CNT/cement composites is approximately 0.2%. Moreover, the CNF/cement percolation threshold ranges between 0.3% and 1.0%. Because CNT and CNF exhibit percolation phenomena, it can be concluded that they are well dispersed in the cement composite.  
Both the graphene and GNP-incorporated samples showed significantly less improvement in electrical conductivity than that observed with the CNT- and CNF-added cement composites. GNP/cement composite samples exhibited a maximum electrical conductivity of 1.14 \(\times\) 10\({}^{8}\) S/cm at a 0.3% GNP content ratio. Similarly, graphene/cement composite samples attained a maximum electrical conductivity of 1.44 \(\times\) 10\({}^{8}\) S/cm at a 0.1% graphene content ratio. However, neither the GNP- nor graphene-added cement composites showed the percolation phenomenon in this study. Studies conducted by [PERSON], [PERSON], and [PERSON], 2014 [61], and [PERSON], [PERSON], and [PERSON], 2013 [84], showed that the percolation threshold of GNP/cement composites was between 2.4 to 3.6% of cement volume. Meanwhile, [PERSON] et al., 2023 [85], showed the percolation threshold of graphene/cement composites was between 0.9 to 1.8% of cement weight. Referring to these studies, GNP or graphene content ratio should be increased further to values higher than 1%.