# Mechanical, Electrical and Fractural Characteristics of Carbon Nanomaterial-Added Cement Composites
## 3 Results
### Mechanical Properties
The flexural strength of cement composites increased up to 4.01% for 0.1% GNP content compared to that of the cement-only sample, which proved that even a minimum amount of GNP could improve the flexural strength of cement composites. GNP/cement samples showed a different trend from that of CNT- and CNF-added cement samples, and maximum compressive strength was observed when 0.1% GNP ratio of cement weight was added to the cement composite. Above that, the compressive strength decreased with an increase in the ratio. The compressive strength of cement composites increased by 69.90% for 0.1% GNP content compared to that of the cement-only sample. The GNP/cement composite showed significant improvements in both mechanical properties, which were attributed to the refinement of the pore structure and its filler effect in the cement matrix [57]. The flexural strength of CNF/cement exhibited the maximum value at a 1.0% CNF content ratio, which was 9.06 MPa. This corresponded to a 52.38% increase compared to the flexural strength of the cement-only sample. CNF ratios of 0.1%, 0.3%, and 0.6% exhibited an increase of 22.25%, 29.05%, and 20.33%, respectively, in the flexural strength of the cement composite compared to that of the cement-only sample. For the CNF/cement samples, the compressive strength gradually increased with increasing CNF content ratios, as shown in Figure 5. The compressive strength at a 1.0% CNF ratio was 118.94 MPa, an 111.9% increase compared with that of the cement-only sample. CNF ratios of 0.1%, 0.3%, and 0.6% showed an increase of 77.28%, 88.04%, and 68.35%, respectively, in compressive strength compared to that of the cement-only sample. Multiple studies have concluded that the improvement in mechanical properties can be attributed to the CNF nanostructure. The outer surface of the CNF consists of a conical graphite plane that is angled in relation to the fiber's longitudinal axis, which improves the mechanical properties by anchoring and creating an interfacial bond between the cement and CNF [18; 79; 80]. The proper dispersion of CNF also improves the mechanical properties by restricting the propagation of nanocracks in the cement composites, due to pore filling [39; 81]. The flexural strength of the graphene-incorporated sample was similar to that of the GNP- and CNF-incorporated samples. The maximum flexural strength value for graphene/cement samples was 8.951 MPa at the 1% content ratio, which is an increase of 50.42% compared to that of the cement-only sample. The flexural strength of the composite increased by 40.29%, 24.16%, and 24.72% for 0.1%, 0.3%, and 0.6% graphene content, which indicated that graphene at all dosages could improve the flexural strength of cement composites. The compressive strength test results indicated that the graphene/cement samples exhibited similar characteristics to those of the GNP/cement samples. At a 0.1% graphene content ratio, the compressive strength of the sample was 115.75 MPa, which was the maximum compressive strength compared to other content ratios. When the graphene content was maintained at 0.1%, 0.3%, 0.6%, and 1% of cement weight, the compressive strengths of the graphene/cement samples increased by 106.22%, 75.82%, 86.52%, and 100.74%, respectively, compared to that of the cement-only sample. The overall improvement in the graphene/cement composite can be attributed to graphene providing a nanofiller effect that limits microcrack formation owing to crack bridging and graphene's ability to promote the production of calcium-silicate-hydrate (C-S-H) gel, which enhances the mechanical properties of cement composites [45].