## 3 Results and Discussion
### Physical-Chemical Characterization of the Waste Vitreous Enamels
#### 3.2.3 Effects of Waste Enamels on Concrete Properties  
Related to testing the pozzolanic activity of used materials it was concluded that WEP has a higher pozzolanic activity (Class of pozzolanic materials is 15) compared to WETM waste material (Class of pozzolanic materials is 5). Therefore, it was decided that the replacement of cement with waste material WEP should be up to 40%, and the replacement of cement WETM should be up to 30%. The different steps of replacing cement with WEP and WETM (10% for WEP, i.e., 7.5% for WETM, etc.) do not affect the final result of the research. In addition, for all tests performed on composites, there are results of both, WEP and WETM, samples with 30% added waste. Test results of physical, mechanical and durability properties of concrete mixtures with addition of waste enamels are given in Tables 12-15 and Figures 11-13. \begin{table}
\begin{tabular}{l c c c c c c} \hline
**Property** & **Unit** & **WETM-C-E** & **WEP-C-10** & **WEP-C-20** & **WEP-C-30** & **WEP-C-40** \\ \hline \hline \multirow{2}{*}{Flexural strength} & 28 days & \multirow{2}{*}{mPa} & 7.0 \(\pm\) 0.2 & 5.1 \(\pm\) 0.3 & 4.9 \(\pm\) 0.2 & 4.7 \(\pm\) 0.2 & 4.6 \(\pm\) 0.2 \\  & 90 days & mPa & 7.4 \(\pm\) 0.3 & 5.5 \(\pm\) 0.3 & 5.4 \(\pm\) 0.1 & 5.1 \(\pm\) 0.3 & 5.0 \(\pm\) 0.2 \\ Compressive strength & \multirow{2}{*}{28 days} & mPa & \multicolumn{4}{c}{See Figure 11} \\ Tensile splitting strength & \multirow{2}{*}{28 days} & mPa & 3.9 \(\pm\) 0.2 & 3.8 \(\pm\) 0.3 & 3.7 \(\pm\) 0.2 & 3.5 \(\pm\) 0.3 & 3.2 \(\pm\) 0.2 \\  & & & & & & \\ \hline \multirow{2}{*}{Secant modulus of elasticity} & 28 days & gPa & 33.0 \(\pm\) 0.3 & 34.2 \(\pm\) 0.3 & 34.9 \(\pm\) 0.2 & 33.5 \(\pm\) 0.2 & 32.7 \(\pm\) 0.3 \\  & & & & & & \\ \hline \multirow{2}{*}{Dept of penetration of water under pressure} & \multirow{2}{*}{mm} & 12 \(\pm\) 2 & 10 \(\pm\) 2 & 14 \(\pm\) 3 & 12 \(\pm\) 2 & 13 \(\pm\) 3 \\ \multicolumn{2}{l}{Freeze–thaw resistance with de-icing salts—Scaling} & \multirow{2}{*}{kg/m\({}^{2}\)} & 0.14 \(\pm\) 0.02 & 0.16 \(\pm\) 0.03 & 0.12 \(\pm\) 0.03 & 0.15 \(\pm\) 0.02 & 0.18 \(\pm\) 0.03 \\ \hline \end{tabular}
\end{table} 
Table 14: Mechanical and durability properties of concrete mixtures with WEP. \begin{table}
\begin{tabular}{l c c c c c c} \hline
**Property** & **Unit** & **C-E** & **WEP-C-10** & **WEP-C-20** & **WEP-C-30** & **WEP-C-40** \\ \hline \hline \multirow{2}{*}{Flexural strength} & 28 days & \multirow{2}{*}{mPa} & 7.0 \(\pm\) 0.2 & 6.3 \(\pm\) 0.1 & 5.9 \(\pm\) 0.3 & 5.7 \(\pm\) 0.2 \\  & 90 days & & 7.4 \(\pm\) 0.3 & 6.7 \(\pm\) 0.2 & 6.5 \(\pm\) 0.223 & 6.2 \(\pm\) 0.3 \\ Compressive strength & \multirow{2}{*}{28 days} & mPa & \multicolumn{4}{c}{See Figure 12} \\ Tensile splitting strength & \multirow{2}{*}{28 days} & mPa & 3.9 \(\pm\) 0.2 & 3.8 \(\pm\) 0.3 & 3.6 \(\pm\)0.2 & 3.5 \(\pm\) 0.2 \\  & & & & & \\ \hline \multirow{2}{*}{Secant modulus of elasticity} & \multirow{2}{*}{28 days} & gPa & 33.0 \(\pm\) 0.3 & 32.6 \(\pm\) 0.3 & 32.3 \(\pm\) 0.3 & 31.8 \(\pm\) 0.2 \\  & & & & & & \\ \hline \multirow{2}{*}{Dept of penetration of water under pressure} & \multirow{2}{*}{mm} & 12 \(\pm\) 2 & 14 \(\pm\) 2 & 15 \(\pm\) 3 & 17 \(\pm\) 3 \\ \multicolumn{2}{l}{Freeze–thaw resistance with de-icing salts—Scaling} & \multirow{2}{*}{kg/m\({}^{2}\)} & 0.14 \(\pm\) 0.02 & 0.14 \(\pm\) 0.03 & 0.16 \(\pm\) 0.02 & 0.19 \(\pm\) 0.03 \\ \hline \end{tabular}
\end{table} 
Table 15: Mechanical and durability properties of concrete mixtures with WETM. \begin{table}
\begin{tabular}{l c c c c c c} \hline
**Property** & **Unit** & **C-E** & **WEP-C-10** & **WEP-C-20** & **WEP-C-30** & **WEP-C-40** \\ \hline \hline \multirow{2}{*}{Consistency—slump test Density of fresh concrete Air content in fresh concrete Air content in fresh concrete Air content in fresh concrete Air content in fresh concreteAs can be seen from the results of the concrete consistency test, the replacement of cement with WEP up to 20% caused an increase in the slump, while a further increase in WEP amount decreased the slump.