## 3 Results
### Digital Image Correlation (DIC)  
DIC data for two different levels of stress in the specimens are presented below. In Figure 8a-h, the presented results correspond with a stress level of 5 MPa (linear behavior), and the red color is the highest presented strain of 0.3%, while blue color is the state without any strain (0.00%). The strain state immediately before failure of specimens is provided in Figure 9a-h, in which the red color is the highest presented strain of 2.0%, while the blue color, like in Figure 8, is the state without any strain (0.00%). Figure 8: \(Cont.\)  
Figure 8: View of the strain state at the stress level of 5 MPa at the following ages: 9 (**a**), 14 (**b**), 21 (**c**), 28 (**d**), 35 (**e**), 49 (**f**), 70 (**g**), and 91 days (**h**). Figure 9: _Cont._  
By observing specimens from \"life periods\" 2 and 3, Figure 8c-h show that the older the specimen, the higher the strain. Thus, the later the specimen is loaded, the more significant the state of observed strain. This is caused by the influence of concrete shrinkage on CSFRC behavior as explained in Section 3.4. Namely, the later the specimen is tested, the higher the prevented concrete shrinkage strain, \(\epsilon_{sh,p}\). \(\epsilon_{sh,p}\) represents the beginning, or zero strain state, of the specimen immediately before it is loaded during testing. Since \(\epsilon_{sh,p}\) is higher in the specimens tested at the later age (\"life period\" 3--Figure 8g,h) than in those tested at the earlier age (\"life period\" 2--Figure 8c-f) they will experience faster strain development for the same magnitude of external load. Figure 8a,b show the strain development of the specimens from \"life period\" 1. However, these results cannot be compared with those from \"life periods\" 2 and 3 (Figure 8c-h), because in \"life period\" 1 there are two different processes taking place, namely hardening and shrinkage. Since the concrete is still \"soft\" in this \"life period\", the state of strain is more pronounced than it would be in \"life periods\" 2 for the same load level (Figure 8a-c). The specimen is slightly \"softer\" at 9 days old (Figure 8a) than at 14 days of age (Figure 8b). This fact causes the strain state to be slightly more pronounced in Figure 8a than in Figure 8b. By looking at Figure 9a-h, we can see, similarly to the previous analysis, the existence of the three \"life periods\". The CSFRC specimens in \"life period\" 1 (Figure 9a,b) are the most damaged, because they have not yet reached full tensile strength, and the concrete tensile strength in this area is also relatively low. This is especially visible in Figure 9a, where due to the low concrete tensile strength, the CSFRC damage is so significant that the carbon fiber bearing capacity is fully utilized. Due to such significant CSFRC damage, the energy dissipation capacity is huge, and this significantly contributes to the high-ductile behavior observed in Figure 6a. At the age of 14 days (Figure 9b), the CSFRC and concrete tensile strength are slightly higher such that the concrete contributes more to the bearing  
Figure 9: View of the strain immediately before failure at the following ages: 9 **(a)**, 14 **(b)**, 21 **(c)**, 28 **(d)**, 35 **(e)**, 49 **(f)**, 70 **(g)**, and 91 days **(h)**. capacity of the specimen, resulting in slightly lower utilization of the carbon fiber bearing capacity. The lower degree of damage degree also means lower ductility (Figure 6b). In \"life period\" 1, the CSFRC hardening process is completed, so in \"life periods\" 2 and 3, it is possible to estimate the influence of concrete shrinkage, and the actual prevented concrete shrinkage strain, on the nonlinear ductile behavior of the specimens as well as on their failure. It can be observed that the specimens at 21, 28, 35, and 49 days of age (Figure 9c-f) are more damaged than specimens at the age of 70 and 91 days (Figure 9g,h).