## 4 Discussion  
The structure of the analysis of the results is based on the research design illustrated in Figure 1 (see Section 2.1). First, a correlation between the Reinforcement Index and the mechanical properties of concrete (compressive strength and static elasticity modulus) was determined. Then, a correlation between the Reinforcement Index and the dynamic properties (ultrasonic pulse velocity and dynamic elasticity modulus) of concrete was identified. Finally, a correlation between the dynamic properties of concrete and its mechanical properties was established.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**UPV (m/s)**} & \multicolumn{6}{c}{**\(E_{d}\) (GPa)**} \\ \cline{2-9}
**Batch** & \multicolumn{2}{c}{**Direct**} & \multicolumn{2}{c}{**Semidirect**} & \multicolumn{2}{c}{**Indirect**} & \multicolumn{2}{c}{**Direct**} & \multicolumn{2}{c}{**Semidirect**} & \multicolumn{2}{c}{**Indirect**} \\ \cline{2-9}  & \(\overline{\mathbf{X}}\) & **CV** & \(\overline{\mathbf{X}}\) & **CV** & \(\overline{\mathbf{X}}\) & **CV** & \(\overline{\mathbf{X}}\) & \(\overline{\mathbf{X}}\) & \(\overline{\mathbf{X}}\) \\ \hline B-Pattern & 3897 & 5.0\% & 3275 & 5.0\% & 4893 & 5.8\% & 31.41 & 22.17 & 49.50 \\ B-0.4\%-40 & 4120 & 0.2\% & 3994 & 0.7\% & 4918 & 0.9\% & 36.91 & 34.67 & 52.57 \\ B-0.4\%-50 & 4146 & 0.1\% & 4136 & 2.8\% & 4681 & 1.1\% & 39.20 & 39.00 & 49.97 \\ B-0.4\%-60 & 4139 & 0.1\% & 3942 & 0.7\% & 4952 & 0.6\% & 35.81 & 32.48 & 51.27 \\ B-0.8\%-40 & 4146 & 0.1\% & 4136 & 2.8\% & 4681 & 1.1\% & 36.59 & 36.41 & 46.64 \\ B-0.8\%-50 & 4195 & 0.1\% & 4121 & 0.8\% & 5137 & 0.8\% & 27.98 & 27.00 & 41.95 \\ B-0.8\%-60 & 4040 & 0.2\% & 3859 & 1.3\% & 5073 & 3.0\% & 36.93 & 33.70 & 58.22 \\ B-1.2\%-40 & 4121 & 1.4\% & 4000 & 1.3\% & 5192 & 0.3\% & 35.28 & 33.23 & 56.00 \\ B-1.2\%-50 & 4145 & 0.2\% & 4222 & 3.7\% & 4822 & 0.9\% & 34.54 & 35.83 & 46.72 \\ B-1.2\%-60 & 4281 & 0.4\% & 4299 & 1.3\% & 6049 & 3.9\% & 39.46 & 39.80 & 78.78 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Ultrasonic pulse velocity and the dynamic modulus of elasticity of concrete.  
Figure 6: UPV results for concrete mixtures.  
The test results were processed via statistical tests. First, the Grubbs outlier test was performed for each property value group. This test identifies the smallest or the largest outlier value. A significance level of 0.100 was used. Next, the identified outliers were removed from the series, as indicated in the following sections. Then, the difference in fits (DFFITS) test was performed to identify the outliers for the regression between the two variables. Again, the data pair with the highest DFFITS value and all values exceeding 0.89 were removed from the series. Finally, the Pearson test was used to determine whether there was a correlation between the variables. If the absolute value of the Pearson correlation coefficient is 0-5%, then the correlation will be \"non-existent\"; 5-20%, the correlation will be \"very poor\"; 20-40%, the correlation will be \"poor\"; 40-60%, it will be \"medium\"; 60-80%, it will be \"considerable\"; 80-95%, it will be \"strong\"; and, finally, if the value is 95-100%, the correlation level will be \"perfect\".