# Multifunctional Graphene-Concrete Composites: Performance and Mechanisms
## 3 Results and Discussion
### Mechanical Property  
As illustrated in Figure 9a, the test block doped with graphene exhibited fewer cracks and maintained better structural integrity after failure, suggesting that graphene enhances the strength and toughness of concrete, thereby inhibiting the propagation of macroscopic cracks and preventing the transition of microscopic cracks to the macroscopic level. Figure 9b presents the measurements of the height of the damaged test blocks, which were recorded as 8.3 cm, 9.0 cm, 9.5 cm, 10.0 cm, and 8.2 cm, respectively. From Figure 5c, it is evident that, in terms of compressive failure, the test block numbered 2-1 displayed a larger size, improved compactness, and superior integrity compared to the other test blocks after failure, indicating its excellent compressive performance. In Figure 9c, the failure mode of the test block without graphene predominantly initiated at the edges and corners, with cracks progressively extending toward the opposite end, resulting in the detachment of large fragments during failure. In contrast, the damage observed in the graphene-doped test block began with only a few small cracks; the extent of crack propagation was limited, and the overall integrity of the block remained good upon failure, with only a minor number of small fragments detaching. In summary, the incorporation of an appropriate amount of graphene significantly enhanced the strength and structural density of concrete. In future research, computer vision techniques will be employed to automatically quantify the crack propagation, pore structure, and surface defects in graphene-concrete composites, ensuring more objective and reproducible results. For instance, binary image segmentation will be performed using a convolutional neural network (CNN) based on the DeepLab architecture, enabling pixel-level crack detection with high precision [38]. Additionally, EfficientNet can be integrated  
Figure 9: (**a**) Compression failure of 3D test block (these images were captured under identical loading conditions to ensure consistency in the experimental observations and facilitate a comparative analysis of the material’s response). (**b**) Three-dimensional test block compression failure specimen diagram. (**c**) Comparison of damage over time between undoped and doped specimens. as a feature extractor within the target detection framework, significantly improving the efficiency and accuracy of crack recognition [39]. The stress-strain curve provides a comprehensive representation of the mechanical properties and deformation characteristics of materials under stress. As illustrated in Figure 10a, the stress-strain curve of the undoped graphene test block exhibits a relatively low slope in the initial rising section, whereas the curve for the graphene-doped test block demonstrates a steeper slope in the same region. This indicates that the incorporation of a certain amount of graphene enhances the elastic modulus of concrete, allowing it to effectively bear and transfer stress, thereby improving the compressive strength of the material. Three replicate specimens were prepared for each graphene content level, and the mean compressive strength derived from these replicates was adopted as the representative compressive strength for the corresponding graphene content. According to Figure 10b, after 28 days of curing, the compressive strength of the graphene-modified concrete increased by as much as 44% compared to the control group (66.82 MPa was 20.48 MPa higher than 46.34 MPa in the control group). However, it is crucial to maintain an appropriate concentration of graphene dispersion; excessively high concentrations can lead to a reduction in the strength of the test block. This reduction occurs because, while graphene effectively transfers stress and enhances the toughness of concrete, it can also promote crack bridging and improve hydration, thereby increasing the compressive strength. Nonetheless, the relationship between the graphene content and compressive strength is complex, influenced by multiple mechanisms.