## 3 Results  
### Tensile Strength, Stress Causing First Crack Appearance, and Ultimate Tensile Strain  
The maximal tensile load caused specimen failure, and the ratio of this load to the specimen area at the midspan is the CSFRC tensile strength. Table 2 provides the results for all specimens. Figure 2 is a graphical view of the results from Table 2.  
Analyzing the results shown in Table 2 and Figure 2, it is clear that the tensile strength at the age of 9 days is 90% of the tensile strength at the age of 28 days. In [34], the tensile strength at the age of 9 days is 70-80% of the tensile strength at the age of 28 days, depending on the concrete mixture content. This shows that carbon fibers accelerate the development of tensile strength, and autogenous shrinkage in the young concrete does not cause the formation of micro-cracks. As the tensile strength at the age of 21 days is approximately 99% of the tensile strength at the age of 28 days, it can be concluded that the CSFRC has already hardened at the age of 21 days, which enables it to be exploited at an earlier timepoint than conventional concrete. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Specimen Age** & **Specimen Name** & **Tensile Strength [MPa]** & \begin{tabular}{c} **Average Tensile** \\ **Strength [MPa]** \\ \end{tabular} & \
\begin{tabular}{c} **Elasticity** \\ **Modulus [GPa]** \\ \end{tabular} &
\begin{tabular}{c} **Average Elasticity** \\ **Modulus [GPa]** \\ \end{tabular} \\ \hline
9 & \begin{tabular}{c} S55 \\ S64 \\ S65 \\ \end{tabular} & \begin{tabular}{c} 13.57 \\ 13.33 \\ 13.41 \\ \end{tabular} & \
\begin{tabular}{c} 34.75 \\ 35.50 \\ 34.48 \\ \end{tabular} &
\begin{tabular}{c} 34.91 \\ 34.48 \\ \end{tabular} \\ \hline
14 & \begin{tabular}{c} S39 \\ S45 \\ S54 \\ \end{tabular} & \begin{tabular}{c} 13.42 \\ 13.57 \\ 14.20 \\ \end{tabular} & \
\begin{tabular}{c} 38.60 \\ 35.30 \\ 35.60 \\ \end{tabular} &
\begin{tabular}{c} 38.60 \\ 36.50 \\ \end{tabular} \\ \hline
21 & \begin{tabular}{c} S41 \\ S47 \\ S60 \\ \end{tabular} & \begin{tabular}{c} 14.66 \\ 15.05 \\ \end{tabular} & \
\begin{tabular}{c} 36.45 \\ 36.45 \\ 38.60 \\ \end{tabular} &
\begin{tabular}{c} 37.17 \\ 38.23 \\ \end{tabular} \\ \hline
28 & \begin{tabular}{c} S37 \\ S44 \\ S57 \\ \end{tabular} & \begin{tabular}{c} 14.64 \\ 15.01 \\ \end{tabular} & \
\begin{tabular}{c} 14.92 \\ 36.05 \\ \end{tabular} &
\begin{tabular}{c} 32.60 \\ 36.05 \\ \end{tabular} \\ \hline
35 & \begin{tabular}{c} S46 \\ S48 \\ S61 \\ \end{tabular} & \begin{tabular}{c} 14.47 \\ 15.03 \\ 15.67 \\ \end{tabular} & \
\begin{tabular}{c} 36.20 \\ 37.70 \\ 36.95 \\ \end{tabular} &
\begin{tabular}{c} 36.95 \\ 36.40 \\ \end{tabular} \\ \hline
49 & \begin{tabular}{c} S50 \\ S52 \\ S66 \\ \end{tabular} & \begin{tabular}{c} 14.30 \\ 15.51 \\ \end{tabular} & \begin{tabular}{c} 37.95 \\ 14.84 \\ \end{tabular} & \
\begin{tabular}{c} 37.95 \\ 35.30 \\ 35.95 \\ \end{tabular} &
\begin{tabular}{c} 36.40 \\ 35.95 \\ \end{tabular} \\ \hline
70 & \begin{tabular}{c} S53 \\ S56 \\ S59 \\ \end{tabular} & \begin{tabular}{c} 15.75 \\ 14.72 \\ 15.69 \\ \end{tabular} & \
\begin{tabular}{c} 37.20 \\ 38.20 \\ 36.15 \\ \end{tabular} &
\begin{tabular}{c} 37.20 \\ 37.18 \\ \end{tabular} \\ \hline
91 & \begin{tabular}{c} S58 \\ S62 \\ S63 \\ \end{tabular} & \begin{tabular}{c} 15.68 \\ 14.77 \\ 15.28 \\ \end{tabular} & \
\begin{tabular}{c} 35.00 \\ 37.70 \\ 37.70 \\ 35.95 \\ \end{tabular} &
\begin{tabular}{c} 35.00 \\ 36.40 \\ \end{tabular} \\ \hline \end{tabular}
\end{table} 
Table 2: Experimental results—tensile strength and elasticity modulus. The results provided in [35] for predicting the development of mechanical features (elasticity modulus, compressive strength, etc.) in conventional concrete over a specific time span show that fib Model Code 2010 [36] has lower derivation from the experimental results than other standards. Hence, expressions from [36] are modified for the temporal prediction of CSFRC tensile strength development.