## 2 Experimental Programme
### Recycled Aggregate Properties
As seen in this table, the maximum allowable value of these contaminants is 0.5%, according to EN 12620 [19]. Furthermore, if there is special concern with the final finish of the concrete, this value should not exceed 0.25%. Most of the RA analysed in this investigation have values higher than the limits mentioned (of up to 1.7%). [PERSON] et al. [24] performed a chemical analysis of eight types of RA from CDW and also obtained high amounts of light contaminants (between 0.3% and 17.1%). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Chemical Characterization** & **CRA Valnor** & **CRA Retria** & **FRA Ambilei** & **FRA Vimajas** & **Maximum limit** \\ \hline Water-soluble chloride salts & \textless{}0.010 & \textless{}0.010 & \textless{}0.010 & 0.016 & 0.010  \\ Water-soluble sulphates & 0.04 & 0.04 & 0.11 & 0.18 & 0.20  \\ Acid soluble sulphates & 0.2 & 0.3 & 0.2 & 0.8 & 0.8  \\ Sulphur content & 0.1 & 0.1 & 0.1 & 0.3 & 1.0  \\ Lightweight contaminators & 1.5 & \textless{}0.1 & 1.8 & 1.7 & 0.5  \\ Potential presence of humus & Neg. & Neg. & Neg. & Neg. & Neg. \\ Water solubility & 1.0 & 1.2 & 0.5 & 2.1 & 10.0  \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Results of the chemical characterization of the recycled aggregates. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Physical Characterization** & **Limestone 2** & **Limestone 1** & **CRA Valnor** & **CRA Retria** \\ \hline Particle dry density (kg/m\({}^{3}\)) & 2599 & 2609 & 2091 & 2137 \\ Water absorption (\%) & 1.5 & 1.3 & 8.6 & 8.4 \\ Loose bulk density (kg/m\({}^{3}\)) & 1360 & 1350 & 1095 & 1236 \\ Shape index (\%) & 15 & 17 & 24 & 24 \\ Los Angeles wear (\%) & 26 & 28 & 52 & 46 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Results of the physical characterization of coarse aggregates. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Physical Characterization** & **Fine Sand** & **Coarse Sand** & **FRA Ambilei** & **FRA Vimajas** \\ \hline Particle dry density (kg/m\({}^{3}\)) & 2583 & 2581 & 2112 & 2070 \\ Water absorption (\%) & 0.3 & 0.7 & 12.9 & 10.1 \\ Loose bulk density (kg/m\({}^{3}\)) & 1530 & 1540 & 1435 & 1332 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of the physical characterization of fine aggregates. The chemical tests carried out also indicate that RA from Vimajas have a percentage of water-soluble chloride salts higher than the limit imposed. The alkaline salts, namely sodium chloride and potassium chloride, are the ones that mostly contribute to the chlorides present in the aggregates and that most affect concrete [35]. Limiting the amount of chlorides is necessary to minimize the risk of corrosion of the steel rebars in reinforced concrete elements. In addition to that present in the aggregates, it is also important to consider the chloride content of the other materials used in the composition of concrete. According to APEB [36], the chloride content of a concrete is expressed as a percentage of chloride ions per mass of cement, which means that a high chloride content present in the aggregates may not be decisive if a high mass of cement is also used. It should be noted that the results obtained in the remaining chemical tests performed on the RA are within the upper boundaries imposed, except for the sulphur content of the fine RA from Vimajas, which is equal to the maximum limit. Internal sulphates are a potential risk source for the chemical attack of concrete [37]. Some of the other chemical tests have also shown that RA from Vimajas have a number of harmful elements which lie above those found in the remaining RA, even though they are within the maximum limits. Hence, one of the possible solutions for the use of these RA in concrete is to previously wash them.