## 4 Post-Sustained Loading Bond Behaviour of NSM CFRP-Concrete Specimens
### Effect on the Ultimate Load and Failure Mode  
Overall, no significant differences were obtained in the PSL ultimate load compared to the instantaneous characterization values (the mean ratio of all specimens being equal to 0.99). Likewise, ratios close to the unity were observed when analysing the global results of groups of specimens under either 15% or 30% \(P_{u}\). Some aspects should be highlighted when analysing the different series. For instance, series S1 does not present any significant effects from the sustained loading conditions, despite presenting a mean global reduction of \(P_{u,PSL}\) lower than 1%, and no relevant differences being observed either for load values or bonded length and groove thickness. Some differences, however, can be identified in series S2 and S3-B. For example, series S2 presents a mean global increment of 6.3% (probably due to the post-curing effect on the adhesive) with similar values for the two load levels, and a slightly more pronounced increment for the 10 mm groove thickness (9%) than for the 7.5 mm thickness (3%). Meanwhile, for S3-B in terms of temperature cycles, an 8% global reduction can be seen. This influence is greater in the specimens loaded at 30% \(P_{u}\) (12% reduction) than in those loaded at 15% \(P_{u}\) (4% reduction), which might indicate that there the temperature cycles exert some influence, albeit mainly for the higher sustained load value. On the other hand, with a \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Series** & **Specimen** & \(\frac{P_{u,PSL}}{P_{u}}\) & \(\frac{K_{u,PSL}}{K_{u}}\) \\ \hline \multirow{8}{*}{S1} & S1-PSL-150-10-15 & 1.05 & 0.95 \\  & S1-PSL-150-7.5-15 & 0.95 & 0.94 \\  & S1-PSL-150-10-30 & 1.03 & 0.84 \\  & S1-PSL-150-7.5-30 & 0.99 & 0.90 \\  & S1-PSL-225-10-15 & * & 1,11 \\  & S1-PSL-225-7.5-15 & 0.95 & 0.78 \\  & S1-PSL-225-10-30 & * & 0.93 \\  & S1-PSL-225-7.5-30 & * & 0,81 \\ \hline \multirow{8}{*}{S2} & S2-PSL-150-10-15 & 1.08 & 1.02 \\  & S2-PSL-150-7.5-15 & * & 1.02 \\  & S2-PSL-150-10-30 & 1.10 & 0.85 \\  & S2-PSL-150-7.5-30 & 1.03 & 0.65 \\  & S2-PSL-225-10-15 & 1.06 & 0.79 \\  & S2-PSL-225-7.5-15 & 1.07 & 0.92 \\  & S2-PSL-225-10-30 & 1.12 & 0.67 \\  & S2-PSL-225-7.5-30 & 0.98 & 0.57 \\ \hline \multirow{8}{*}{S3-B} & S3-B-PSL-150-10-15 & 1.07 & 1.05 \\  & S3-B-PSL-150-7.5-15 & 0.93 & 0.95 \\  & S3-B-PSL-150-10-30 & 0.89 & 0.90 \\  & S3-B-PSL-150-7.5-30 & 0.86 & 0.77 \\  & S3-B-PSL-225-10-15 & 0.88 & 0.89 \\  & S3-B-PSL-225-7.5-15 & 0.97 & 0.96 \\  & S3-B-PSL-225-10-30 & 0.96 & 0.61 \\  & S3-B-PSL-225-7.5-30 & 0.80 & 0.71 \\ \hline \multirow{8}{*}{S4} & S4-PSL-150-10-15 & 0.91 & 0.94 \\  & S4-PSL-150-7.5-15 & 0.97 & 1.10 \\  & S4-PSL-150-10-30 & 0.99 & 0.82 \\ \cline{1-1}  & S4-PSL-150-7.5-30 & 0.99 & 0.88 \\ \cline{1-1}  & S4-PSL-225-10-15 & 1.01 & 0.99 \\ \cline{1-1}  & S4-PSL-225-7.5-15 & 1.04 & 0.89 \\ \cline{1-1}  & S4-PSL-225-10-30 & 0.92 & 0.73 \\ \cline{1-1}  & S4-PSL-225-7.5-30 & 1.06 & 0.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Post-sustained loading results. final global mean value of the ratio close to the unity, no clear tendencies are observed in series S4 with temperature cycles but without preconditioning. The results presented are in accordance with the observations made in [PERSON] et al. [7], where small decreases of the ultimate load were observed in specimens subjected to outdoor environmental conditions (around 12%). As for the failure mode of the NSM CFRP-concrete joint, no differences were generally obtained in comparison with the instantaneous characterization, with the main failure mode being the cohesive failure in the concrete for specimens with a 7.5 mm groove thickness and failure in the FRP-adhesive interface for specimens with a 10 mm groove thickness. However, specimens S3B-PSL-150-10-30 and S3B-PSL-225-10-30 experienced a failure in the adhesive-concrete (A-C) interface, which indicates a decrease in the bond at the interface.