# Experimental Evaluation of the Durability of Concrete Repair Materials
## 3 Results and Discussion
### Freeze-Thaw  
Table 5 and Figures 10 and 11 show the concrete relative dynamic elastic modulus and compressive strength results after repeated freeze-thaw cycles. The relative dynamic elastic modulus was measured after 100, 200, and 300 cycles. Assuming that the relative dynamic elastic modulus before the freeze-thaw cycles is 100%, the degradation in the durability performance of the concrete specimens for each repair method can be determined. The relative dynamic elastic moduli of the unrepaired 2 and 5 mm notched specimens with a target strength of 20 MPa were 78.2% and 82.5%, respectively. All the epoxy, impregnant, and epoxy/impregnant specimens exhibited higher relative dynamic elastic moduli than the unrepaired specimens. The reason for this is that moisture moves along the cracks in the non-repair specimen, which easily causes freezing and thawing and lowers the relative dynamic elastic modulus due to poor durability [33]. In particular, the epoxy/impregnant specimens exhibited relative dynamic elastic moduli of approximately 90%, indicating that the structural performance was largely maintained. The relative dynamic elastic moduli of the unrepaired 2 and 5 mm notched specimens with a target strength of 40 mm were 84.9% and 82.7%, respectively. All the repaired specimens showed an improvement in the relative dynamic elastic modulus. In addition, the epoxy/impregnant specimens exhibited better performance than the epoxy and impregnant specimens, reaching 92.2% and 95.4% for 2 and 5 mm notches, respectively. The epoxy/impregnant specimens showed higher relative dynamic elastic moduli at the higher target strength because the modulus is related to the watertightness of the concrete specimens [34]. After the freeze-thaw cycles, the epoxy and epoxy/impregnant specimens exhibited the same results when the target strength was 20 MPa and notch width was 2 mm. Under all other conditions, the epoxy/impregnant specimen exhibited the highest strength, followed by the epoxy and impregnant specimens. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Target Strength** & **Notb Width** & **Repair Method** & **Chloride Depth** & **Diffusion Coefficient** \\ \cline{3-5}
**(MPa)** & **(mm)** & **Repair Method** & **(mm)** & **(m2/s)** \\ \hline \multirow{8}{*}{20} & \multirow{8}{*}{2} & - & Intact (no notch)-NN & 30.5 \(\pm\) 0.94 & 2.83 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & \multicolumn{2}{c}{Notched (unrepaired)-N} & 21.8 \(\pm\) 7.48 & 2.02 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & \multirow{2}{*}{2} & Epoxy-E & 31.6 \(\pm\) 2.02 & 3.01 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Impregnant-I & 9.5 \(\pm\) 0.41 & 8.25 \(\times\) 10\({}^{-12}\) \\ \cline{3-5}  & & Epoxy/impregnant-E and I & 10.0 \(\pm\) 0.95 & 8.63 \(\times\) 10\({}^{-12}\) \\ \cline{3-5}  & \multirow{4}{*}{5} & Notched (unrepaired)-N & 19.3 \(\pm\) 5.92 & 1.78 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Epoxy-E & 29.4 \(\pm\) 1.72 & 2.81 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Impregnant-I & 7.7 \(\pm\) 2.07 & 6.58 \(\times\) 10\({}^{-12}\) \\ \cline{3-5}  & & Epoxy/impregnant-E and I & 9.4 \(\pm\) 0.66 & 8.05 \(\times\) 10\({}^{-12}\) \\ \hline \multirow{8}{*}{40} & \multirow{8}{*}{2} & - & Intact (no notch)-NN & 23.0 \(\pm\) 1.62 & 2.18 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Notched (unrepaired)-N & 13.4 \(\pm\) 3.07 & 1.21 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Epoxy-E & 18.5 \(\pm\) 2.71 & 1.67 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Impregnant-I & 6.5 \(\pm\) 0.66 & 5.33 \(\times\) 10\({}^{-12}\) \\ \cline{3-5}  & & Epoxy/impregnant-E and I & 8.1 \(\pm\) 1.47 & 7.00 \(\times\) 10\({}^{-12}\) \\ \cline{3-5}  & & Notched (unrepaired)-N & 13.7 \(\pm\) 2.14 & 1.24 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Epoxy-E & 15.0 \(\pm\) 1.87 & 1.34 \(\times\) 10\({}^{-11}\) \\ \cline{3-5}  & & Impregnant-I & 7.9 \(\pm\) 1.59 & 6.12 \(\times\) 10\({}^{-12}\) \\ \cline{3-5}  & & Epoxy/impregnant-E and I & 9.5 \(\pm\) 0.65 & 8.26 \(\times\) 10\({}^{-12}\) \\ \hline \hline \end{tabular}
\end{table}