# Study of Basalt Fibers and Graphene Enriched Polymers on Bond Behavior of FRP Bars in Concrete
## 2 Experimental Study
### Pull-Out Tests  
The molding and curing of the pull-out test specimens were done according to ASTM D7913 [49] in a controlled environment at 23 \(\pm\) 2 \({}^{\circ}\)C and 50 \(\pm\) 10% relative humidity. In order to avoid the crushing of the reinforcement during the test, it was necessary to place an anchoring device at the loaded end of the bars. For this purpose, a steel pipe was used and the space between the pipe and the bars was filled with an epoxy based structural adhesive, as recommended by ASTM D7205 [43]. After finishing the anchoring system on the bars, the specimens were molded for the pull-out tests. The molding procedures were performed according to the ASTM D7913 [49]. Cubic molds, with a 200 mm dimension on each edge, were used to manufacture the pull-out specimens. Figure 2 shows the dimensions of the specimens schematically. An embedment length \(l_{b}=\phi 5\) was considered. A PVC pipe was used as a bond breaker in the debonded area. Bars were positioned horizontally in the middle of the formworks, then the concrete was poured in two layers. Each layer was compacted with 25 strokes of a metal rod. The surface was smoothed with a mason trovel. After 72 hours, the concrete cubes were demolded, marked and transferred to the curing room at 23 \(\pm\) 2 \({}^{\circ}\)C and 95.0% humidity until the age of 28 days. Three specimens were molded for each combination. In the cases subjected to heating, the methodology adopted by authors such as [PERSON] et al. [35] and [PERSON] et al. [36] was followed in the present work. The specimens were molded with the insertion of K-type thermocouples at the bar-concrete interface. After the 28-day curing, the specimens were heated in an electric oven. The part of the bar inside the oven were thermally insulated with ceramic fiber blankets in order to avoid \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Concrete**} & \multicolumn{2}{c}{**Cement Consumption (kg/m\({}^{3}\))**} & \multicolumn{2}{c}{**Unit Mix**} & \\ \cline{2-6}  & & **Cement** & **Fine Aggregate** & **Coarse Aggregate** & **Water/Cement Ratio** \\ \hline C20 & 292.78 & 1.0 & 2.9 & 3.6 & 0.66 \\ C30 & 452.52 & 1.0 & 1.6 & 2.4 & 0.47 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Concrete mix proportion. \begin{table}
\begin{tabular}{l c c c c c} \hline \hline \multirow{2}{*}{**Combinations**} & \begin{tabular}{c} **Slump** \\ **(mm)** \\ \end{tabular}  & \begin{tabular}{c} **Average Compressive** \\ **Strength (MPa)** \\ \end{tabular}  & \begin{tabular}{c} **Standard** \\ **Deviation** \\ \end{tabular}  & \ \begin{tabular}{c} **Elasticity** \\ **Modulus (GPa)** \\ \end{tabular}  & \begin{tabular}{c} **Poisson’s** \\ **Ratio** \\ \end{tabular}  \\ \hline C20-8G & 140 & 23.2 & 0.91 & 34.2 & 0.2 \\ C30-8G & 145 & 33.3 & 0.77 & 38.5 & 0.2 \\ C20-12G & 140 & 23.2 & 0.91 & 34.2 & 0.2 \\ C30-12G & 145 & 33.3 & 0.77 & 38.5 & 0.2 \\ \hline C2  
thermal damage to the polymeric matrix. The heating rate was 27 \({}^{\circ}\)C/min up to the desired temperature, remaining at this temperature range for at least one hour until a uniform distribution of heat through concrete was achieved, according to measurements done. (The remaining time at the final temperature were 6 h in [PERSON] et al. [35] and 30 min in [PERSON] et al. [36]). In all cases, including the cases in the references, the specimens were then left in the oven for natural cooling. Afterwards, pull-out tests were done at room temperature. To evaluate the compressive strength of the concrete exposed to higher temperatures, cylindrical specimens were placed in the oven, which remained under heating for the same period as the specimens for the pull-out test. After cooling, the compressive strength was determined according to ABNT NBR 5739 [47] and the results are shown in Table 4.  
The pull-out tests were performed according to ASTM D7913 [49] in a Universal Testing Machine (Instron/Emic) with a 200 kN capacity. The concrete cubes were positioned at the top of the machine, remaining stationary during the test.