# Evaluation of Condition of Concrete Structures Using Ultrasonic Pulse Velocity Method
## 3 Ultrasonic Pulse Velocity Method
**} \\ \hline \hline  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & & 0.62 & \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & & 0.62 & \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & & 0.62 & \\ \cline{2-11}
16 & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & 0.62 & 0.62 \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 97 & 96 & 97 & 96 & 0.62 & \\ \cline{2-11}  & 97 & 96 & 97 & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}
20 & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 96 & 96 & 96 & 96 & 0.62 & \\ \cline{2-11}  & 1069 & 888 & 1157 & 1036 & 900 & 1069 & 896 & 1164 & 904 & 908 & \\ \cline{2-11}  & 1058 & 1005 & 1164 & 1025 & 1020 & 1069 & 888 & 1164 & 1025 & 908 & \\ \cline{2-11}  & 1047 & 995 & 1164 & 1025 & 908 & 1069 & 985 & 1164 & 1025 & 908 & \\ \cline{2-11}  & 1069 & 896 & 1164 & 1015 & 908 & 1058 & 888 & 1164 & 1036 & 908 & \\ \cline{2-11}
24 & 1069 & 888 & 1164 & 1025 & 900 & 1069 & 896 & 1164 & 904 &_Appl. Sci._**2020**, _10_, 706  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Age (h)** & \multicolumn{6}{c}{**Ultrasonic Pulse Velocity (m/s)**} & **Aver. ** & **Compressive Strength (MPa)** & **Aver. ** \\ \hline  & 2426 & 2475 & 2475 & 2414 & 2439 & 2426 & 2475 & 2475 & 2357 & 2439 & & 3.74 & \\ \cline{2-10}  & 2426 & 2475 &  
Figure 9 shows the correlation between the ultrasonic pulse velocity and the compressive strength. As shown in the Figure 9, there is a certain correlation between the ultrasonic pulse velocity and the compressive strength. For the designed concrete compressed strength of 40 MPa, the ultrasonic pulse velocity in each specimen was measured at the ages of 16, 20, 24, 48, 72, 120, 168, 360, and 672 h, and compressive strength testing was conducted. The measurement results are listed in Table 4. The measured ultrasonic pulse velocity was 96.4 m/s at 16 h of age, 96.0 m/s at 20 h, 1570.9 m/s at 24 h, 2543.5 m/s at 48 h, 2952.5 m/s at 72 h, 3157.6 m/s at 120 h, 3321.9 m/s at 168 h, 3474.6 m/s at 360 h, and 3455.7 m/s at 672 h. Figure 10 shows the ultrasonic pulse velocity according to age. As can be seen in the Figure 10, the wave velocity sharply increased from 16 to 72 h of age. It slowly increased to 120 h and then maintained a very slow increasing tendency up to 672 h.  
Figure 9: Relationship between ultrasonic pulse velocity and compressive strength (30 MPa).