## 2 Materials and Methods
### Mix Design  
The design of the mix has been made using the Faury method, to obtain maximum compactness. The maximum aggregate size has been set at 20 mm, in accordance with EHE-08. The coarse aggregates (>4 mm, EN 13139) of the reference concrete (NAC) have been replaced at several ratios (20%, 50%, and 100% vol.) with CRA. The content of cement has been set at 350 kg/m\({}^{3}\) and the effective w/c ratio of the reference concrete (NAC) at 0.5. The total w/c ratio has been determined by adding compensation water equal to that estimated for the mixing time (10 min) from the water absorption over time test, according to the method proposed by [PERSON] et al. [58]. The strength class of concrete has been defined as C30/37 in accordance with EN 1992-1-1. The slump has been defined as 70 \(\pm\) 10 mm (S2) according to EN 12350-2 and without plasticizers (in order not to introduce more variables) for all replacement ratios. To maintain the same slump in all the mixes, the effective w/c has been slightly modified. RAC has been manufactured from the theoretical curve of NAC (Figure 1), maintaining between mixes the same volume of aggregates of each sieve fraction, so the mix grading for NAC and for RAC is the same. The mix proportions used are shown in Table 3.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Bulk Density** & **Apparent Bulk** & **Water Absorption** & **Shape Index** & **Los Angeles** \\  & **[g/cm\({}^{3}\)]** & **Density [g/cm\({}^{3}\)]** & **[\%wt.]** & **[\%]** & **Wear [\%]** \\ \hline
12/20 & 2.66 & 1.36 & 1.3 & 14.5 & 26 \\
6/12 & 2.66 & 1.38 & 1.5 & 19.7 & 28 \\
2/6 & 2.66 & 1.41 & 1.0 & 16.4 & - \\
0/4 & 2.67 & 1.54 & 0.3 & - & - \\
0/2 & 2.67 & 1.57 & 0.2 & - & - \\ CRA 4/20 & 2.96 & 1.52 & 3.5 & 13.4 & 26.9 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Characterization of the aggregates.  
The aggregates were dried at 100 \(\pm\) 2 \({}^{\circ}\)C until constant weight before mixing and the mixing process consisted of a sequence of 4 min with the coarse aggregates and 2/3 of the water, 2 more minutes after adding the fine aggregates and a further 4 min after adding the cement and 1/3 of the water. The concrete was demoulded after 24 h of manufacture and it has been cured in a humidity chamber at 20 \(\pm\) 2 \({}^{\circ}\)C and 95 \(\pm\) 2% humidity (except for drying shrinkage testing specimens).  
A scheme illustrating the successive steps of RAC's manufacturing process is shown in Figure 2. The process describes the possible multi-recycling of RAC.  
Figure 1: Theoretical curve and grading of the different aggregates according to EN 933-1.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material/Property** & \multicolumn{4}{c}{**Mix Proportions [kg/m\({}^{3}\)]**} \\ \hline CRA replacement & 0\% & 20\% & 50\% & 100\% \\ CEM I 42.5 R & 350 & 350 & 350 & 350 \\ Effective water & 175 & 174.3 & 173.3 & 171.5 \\ Compensation water & 18.0 & 29.1 & 34.6 & 43.9 \\ NA gravel (12/20) & 434.4 & 347.5 & 217.19 & - \\ NA gravel (6/12) & 566.6 & 453.26 & 283.29 & - \\ NA gravel (2/6) & 207.8 & 173.67 & 122.1 & 36.2 \\ NA sand (0/4) & 417.1 & 417.1 & 417.1 & 417.1 \\ NA sand (0/2) & 265.4 & 265.4 & 265.4 & 265.4 \\ CRA \(>\) 22.4 mm & - & 1.5 & 3.9 & 7.7 \\ CRA 16–22.4 mm & - & 35.6 & 88.9 & 177.9 \\ CRA 11.2–16 mm & - & 76.7 & 191.8 & 383.6 \\ CRA 8–11.2 mm & - & 56.8 & 142,0 & 283.9 \\ CRA 5.6–8 mm & - & 49.8 & 124.6 & 249.2 \\ CRA 4–5.6 mm & - & 39.5 & 98.7 & 197.4 \\ \hline Effective w/c ratio & 0.500 & 0.498 & 0.495 & 0.490 \\ Slump [mm] & 70 & 65 & 68 & 72 \\ Fresh state density [kg/m\({}^{3}\)] & 2424 & 2470 & 2563 & 2603 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Concrete mix proportions.