# Study of Basalt Fibers and Graphene Enriched Polymers on Bond Behavior of FRP Bars in Concrete
## 4 Results and Discussions
### Thermal Effects
For the present results the following parameters were obtained by optimization analysis (see Equation (4)): \(P_{r}=0.62\), \(B=-1238.95\) and \(C=-0.1214\). Results of average bond stress versus slip in the cases of GRFPg bars are shown in Figure 13a. Average values per temperature are shown in Figure 13b, including also room temperature results. From Figure 13b is possible to observe that bond strength after heating process at 60 and 120 \({}^{\circ}\)C decays by 15.48% and 35.64% respectively. As pointed out earlier, the existence of other GRFPg studies are unknown. However, as a matter of comparison, the Figure 13b shows again results presented by [PERSON] et al. [33]. As discussed in the room temperature results, polymer used is also polyester and other conditions of the experiments in this case are similar to present GRFPg experiments, except for the addition of GNP. Temperature tested in [PERSON] et al. [33] were not the same used in the present work, but through interpolation it was possible to estimate a decay in bond strength of 32.93% for  
Figure 11: (**a**) All experimental tests and corresponding numerical simulations for GFRP at 60 and 120 \({}^{\circ}\)C (corresponding cases at room temperature included for comparison). (**b**) Average values compared to [PERSON] et al. [33] and [PERSON] et al. [34]. Figure 12: Temperature degradation for GFRP cases compared to [PERSON] et al. [33] and [PERSON] et al. [34]. [PERSON] et al. [55] model used. 60 \({}^{\circ}\)C and a decay of 63.19% for 120 \({}^{\circ}\)C. [PERSON] et al. [36] also considered thermal effects in bars made with polyester but the bond strength at room temperature presented was far below 120 \({}^{\circ}\)C bond strength of the present experiments and for this reason they were not considered here. Visually the degradation with temperature can be seen in Figure 14 for the analysis done in the present work, as well as the interpolated results obtained by [PERSON] et al. [33], considering the model by [PERSON] et al. [55]. For the present results parameter obtained by optimization analysis are \(P_{r}=0.64\), \(B=-1124.95\) and \(C=-0.1201\). It is observed that [PERSON] et al. [33] results presented a degradation with temperature around 44% greater when compared to present results, which may indicate a positive effect of the GNP addition. Finally, in Figure 15a thermal effects on average bond vs slip relations are shown for BRFP bars. The average per temperature obtained is shown in Figure 15b. Bond strength in this case deteriorated by 10.18% and 28.99% after 60 and 120 \({}^{\circ}\)C heating, respectively. Thermal effects for BRFP bars are also shown in Figure 15b for a case analyzed in the  
Figure 14: Temperature degradation for GFRPg cases compared to [PERSON] et al. [33]. [PERSON] et al. [55] model used. Figure 13: (**a**) All experimental tests and corresponding numerical simulations for GFRPg at 60 and 120 \({}^{\circ}\)C (corresponding cases at room temperature included for comparison). (**b**) Average values compared to [PERSON] et al. [33]. [PERSON] et al. [35] ([PERSON] et al. [36] also tested BRFP bar at high temperature. Results are not shown here because room temperature bond strength was already far below present results at 120 \({}^{\circ}\)C). Bond strength degradation for this case are 7.92% and 20.77% for 60 and 120 \({}^{\circ}\)C, respectively. Figure 16 shows the thermal degradation for both cases using the model by [PERSON] et al. [55]. In the present simulations the parameters obtained by optimization are \(P_{r}=0.71\), \(B=-858.81\) and \(C=-0.1119\). It is observed a greater degradation in the present results when compared to [PERSON] et al. [35], but room temperature bond strength of the latter is already relatively low when compared to present results. Discussion  
In Figure 17a all thermal results are grouped for the three types of bars considered.