## 3 Analysis and Discussion of Results
### Compressive Strength
\begin{table}
\begin{tabular}{c c c} \hline \hline  & \(\mathbf{f_{cm,28}}\) (MPa) & \(\mathbf{\Delta}\) (\%) \\ \hline
**NAC** & 47.8 \(\pm\) 0.4 & - \\
**C10C-Valnor** & 47.7 \(\pm\) 1.1 & \(-\)0.2 \\
**C25C-Valnor** & 44.1 \(\pm\) 4.0 & \(-\)7.7 \\
**C50C-Valnor** & 43.2 \(\pm\) 0.1 & \(-\)9.6 \\
**C100C-Valnor** & 39.3 \(\pm\) 1.9 & \(-\)17.9 \\
**C10F-Vimajas** & 47.5 \(\pm\) 1.5 & \(-\)0.6 \\
**C25F-Vimajas** & 43.2 \(\pm\) 1.2 & \(-\)9.7 \\
**C50F-Vimajas** & 37.6 \(\pm\) 0.6 & \(-\)21.4 \\
**C100F-Vimajas** & 27.1 \(\pm\) 0.3 & \(-\)43.4 \\
**C10F-Ambilei** & 48.4 \(\pm\) 1.2 & 1.2 \\
**C25F-Ambilei** & 43.3 \(\pm\) 1.4 & \(-\)9.5 \\
**C50F-Ambilei** & 41.8 \(\pm\) 0.7 & \(-\)12.5 \\
**C100F-Ambilei** & 36.4 \(\pm\) 0.4 & \(-\)23.9 \\
**C10C-Retria** & 47.1 \(\pm\) 1.2 & \(-\)1.6 \\
**C25C-Retria** & 43.1 \(\pm\) 0.3 & \(-\)9.9 \\
**C50C-Retria** & 42.3 \(\pm\) 1.3 & \(-\)11.6 \\
**C100C-Retria** & 37.7 \(\pm\) 0.8 & \(-\)21.2 \\ \hline \hline \end{tabular} Abbreviations: C10C-Valnor, concrete with 10% of coarse RA from Vlanor; \(\ell_{\text{cm,28}}\), average compressive strength values of the concrete mixes at 28 days; \(\Delta\), variation of strength values.  
\end{table} 
Table 10: Compressive strength at 28 days. Figure 4: Comparison of the macro-porosity of concrete mixes with 50% FRA: detail of the interfacial transition zone of a FRA of a concrete mix made with 50% [PERSON]’s FRA (L—limestone, Qz—quartz). [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON]; [PERSON] [PERSON] Microstructure of Concrete with Aggregates from Construction and Demolition Waste Recycling Plants, _Microsc. Microanal._ 22, 149–167, reproduced with permission [10]. Figure 5: Comparison of the macro-porosity of concrete mixes with 100% FRA: detail of the interfacial transition zone of a FRA of a concrete mix made with 100% [PERSON]’s FRA (L—limestone, V—voids). [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON]; [PERSON] [PERSON] Microstructure of Concrete with Aggregates from Construction and Demolition Waste Recycling Plants, _Microsc. Microanal._ 22, 149–167, reproduced with permission [10]. Figure 3: Comparison of the macro-porosity of concrete mixes with 50% FRA: detail of the interfacial transition zone of a FRA of a concrete mix made with 50% [PERSON]’s FRA. [PERSON]; [PERSON]; [PERSON] [PERSON] and [PERSON] [PERSON] Microstructure of Concrete with Aggregates from Construction and Demolition Waste Recycling Plants, _Microsc. Microanal._ 22, 149–167, reproduced with permission [10]. The size of the RA used was another factor that influenced the results obtained. The decrease in compressive strength of the concrete mixes with FRA was higher than that of their counterparts with CRA. Table 3 shows that CRA have a lower amount of \"concrete, mortar and natural stone\" and a higher amount of \" masonry-clayey materials\" in their composition, when compared to FRA. Therefore, CRA were expected to result in a higher decrease in compressive strength than FRA. However, the apparently contradicting results obtained are justified by the amount of clay that FRA tend to possess. As mentioned earlier, the presence of clay resulted in a need to increase the effective w/c ratio used in the composition of the mixes with these FRA, in order to obtain a similar workability in all mixes. This increase in the effective w/c ratio resulted in a decrease in compressive strength. [PERSON] et al. [49] gathered the results available in 65 publications on the compressive strength of concrete mixes made with RA from CDW. Compressive strength test results of 787 concrete mixes with FRA and CRA from different types and origins were analysed. Figure 7 shows that, as found in this investigation, concrete mixes with CRA present, on average, a compressive strength higher than those with FRA. The straight lines in Figure 7 define the upper and lower limits of the results analysed for a 95% confidence interval. Hence, it is interesting to compare the slopes (m) of the straight lines of the study made by [PERSON] et al. [49] with those obtained in our investigation.