## 5 Conclusions  
Waste plastic food packaging, used for the preparation of plastic sheets to be used as fibre reinforcement in concrete, showed low release levels of the elements determined by the Council Decision 2003/33/EC and they were under the inert limits, except for antimony. Hence, they are classified as non-hazardous material. The environmental feasibility of RPF was proven when added to the manufacturing of reinforced concrete with macro recycled plastic fibres at different amounts (2, 4 and 6 kg per m\({}^{3}\)). The low release levels in concrete  
Figure 5: Graphical representation of diffusion-controlled leaching (mg/m\({}^{2}\)) vs. time (days) in samples: (**a**) control C-REF; (**b**) control FRC-REF; (**c**) FRC2 specimen; (**d**) FRC4 specimen; and (**e**) FRC6 specimen. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Parameters** & **C-REF** & **FRC2-REF** & **FRC2** & **FRC4** & **FRC6** \\ \hline Cr & SQD limit for shaped materials emission limits \(\varepsilon_{64}\) (mg/m\({}^{2}\)) & & & 120.0 & & \\  & _Slope_ of the linear regression & 0.522 & 0.566 & 0.299 & 0.197 & 0.299 \\  & Correlation coefficient, \(R^{2}\) & 0.907 & 0.739 & 0.992 & 0.951 & 0.989 \\  & Standard deviation & 0.146 & 0.294 & 0.023 & 0.039 & 0.027 \\ \hline Zn & SQD limit for shaped materials emission limits \(\varepsilon_{64}\) (mg/m\({}^{2}\)) & & & 800.0 & & \\  & _Slope_ of the linear regression & 0.369 & 0.343 & 0.326 & 0.293 & 0.327 \\  & Correlation coefficient, \(R^{2}\) & 0.944 & 0.946 & 0.936 & 0.960 & 0.963 \\  & Standard deviation & 0.078 & 0.072 & 0.075 & 0.052 & 0.056 \\ \hline Sb & SQD limit for shaped materials emission limits \(\varepsilon_{64}\) (mg/m\({}^{2}\)) & & & 8.7 & & \\  & _Slope_ of the linear regression & 0.317 & 0.255 & 0.287 & 0.378 & 0.272 \\  & Correlation coefficient, \(R^{2}\) & 0.951 & 0.911 & 0.936 & 0.997 & 0.977 \\  & Standard deviation & 0.063 & 0.070 & 0.075 & 0.017 & 0.036 \\ \hline Ba & SQD limit for shaped materials emission limits \(\varepsilon_{64}\) (mg/m\({}^{2}\)) & & & 1500.0 & & \\  & _Slope_ of the linear regression & 0.716 & 0.530 & 0.763 & 0.777 & 0.764 \\  & Correlation coefficient, \(R^{2}\) & 0.989 & 0.962 & 0.986 & 0.983 & 0.984 \\  & Standard deviation & 0.065 & 0.091 & 0.079 & 0.090 & 0.086 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Limits for diffusion release levels from shaped construction materials (in mg/m\({}^{2}\)). Slope of linear regression and correlation coefficient. with RPF confirms that the process of stabilisation/solidification (S/S) of the waste in the cement matrix of the concrete, reduces the concentrations in leachatedso a minimum. The concentrations of the elements with higher mobility, in the long-term, were much lower than the limits imposed by regulations for \"shaped\" construction materials, such as SQD. The study carried out to identify the transport and chemical mechanisms, indicated that the release patterns were: wash-off for Sb, Zn (although Zn also presented depletion in the final steps) and Cr in concrete samples with RPF; dissolution for Ba, except for FRC-REF samples; and diffusion for Cr in FRC-REF and C-REF samples. These were identified in the curves of the cumulative leaching vs. time graphs, obtained by conducting the dynamic tank leaching test. Therefore, the present study contributes to the recycling of wastes, such as plastic packaging with a thickness of 0.125 mm and layers of different polymers, as reinforcement in concrete. This type of material does not present any possible environmental impact and could be a viable alternative that would help increase the valorisation of such types of plastic residue, which is considered as being one of the biggest concerns worldwide. Conceptualization, J.A. and A.P.G. ; methodology, A.P.G. ; Software, A.L.-U. ; Validation, J.A. and A.P.G. formal analysis, P.A.V. and A.L.-L.; investigation, P.A.V. and A.L.-U. ; resources, J.A. ; data curation, P.A.V. and A.L.-U. ; writing--original draft preparation, P.A.V., A.L.-U. and A.P.G.