# Resonance Fatigue Behaviour of Concretes with Recycled Cement and Aggregate
## 2 Materials and Methods
### Materials
#### 2.1.2 Aggregates  
The crushed greywacke natural aggregate used comprised three particle sizes: 0 mm to 6 mm (NA-S), 6 mm to 12 mm (NA-M) and 12 mm to 22 (NA-C). The recycled aggregate used, which was supplied by a CDW processing plant located in the Spanish region of Extremadura, had two particle size fractions: 6 mm to 12 mm (MRA-M) and 12 mm to 22 mm (MRA-C). The composition analysis of recycled aggregates (Table 2), conducted as specified in standard EN 933-11 [43], revealed that the main components were concrete and mortar (47.0-44.0 wt%), ceramic (7.2-10.9 wt%) and natural stone (44.8-43.8 wt%), with others (glass and metals) (\(<\)0.5 wt%) as minor constituents. On the grounds of these data and the criteria set out in Spain's structural concrete code [44] with its \(<\)95 wt% Rcu (Rcu = Rc + Ru) content and \(>\)5 wt% Rb content, MRA-M and MRA-G qualified for classification as a mixed recycled aggregate.  
The particle size distribution and the physical and mechanical properties of all the aggregates used to prepare the concrete mixed are listed in Figure 1 and Table 3, respectively. Due primarily to their higher porosity, the recycled aggregates had a lower density than the natural materials in all particle sizes. The saturated surface dry density was found to lie in the 2.42 Mg/m\({}^{3}\) to 2.45 Mg/m\({}^{3}\) range. These aggregates also absorbed more water than the NA, a consequence of the adhered mortar and masonry particles present in the new materials, which exhibited absorption percentages within the range of 4.0 to 10% observed by other authors [7; 17; 32] for this type of recycled aggregates. As the adhered mortar tended to smooth its sharpest angles, RA had a lower flakiness index than NA. The recycled materials had a higher Los Angeles coefficient than the NA, likewise due to the adhered mortar and the presence of masonry. Here also, the values ranged within the 20 to 40% reported in the literature for recycled aggregate [16; 33; 45]. Finally, these recycled aggregates complied with the requirements set out in the European standard EN 12620 [46] for use as recycled aggregate in concrete.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multicolumn{8}{c}{**Chemical Composition (\%wt.)**} \\ \cline{2-13}  & **SiO\({}_{2}\)** & **Al\({}_{2}\)O\({}_{3}\)** & **Fe\({}_{2}\)O\({}_{3}\)** & **CaO** & **MgO** & **SO\({}_{3}\)** & **Na\({}_{2}\)O** & **K\({}_{2}\)O** & **TiO\({}_{2}\)** & **P\({}_{2}\)O\({}_{5}\)** & **Cl-** & **SiO\({}_{2}\)(\({}^{3}\))** & **LOI** \\ \hline OPC & 20.00 & 6.03 & 2.57 & 60.00 & 1.75 & 3.90 & 0.56 & 1.49 & 0.15 & 0.15 & 0.02 & - & 3.26 \\ RWP-CDW & 59.63 & 18.51 & 5.92 & 4.78 & 3.08 & 0.42 & 0.70 & 3.58 & - & - & - & 35.10 & 2.15 \\ OPC-25 CDW & 31.30 & 8.26 & 3.24 & 48.99 & 2.86 & 2.43 & 0.51 & 1.58 & 0.35 & 0.19 & 0.04 & - & 2.66 \\ \hline \hline \end{tabular} Note: \({}^{(1)}\) Reactive.  
\end{table}
Table 1: Chemical composition of RWP-CDW and OPC-25 CDW XRF analysis.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Composition (wt%)** & **MRA-M** & **MRA-G** \\ \hline Ceramic & 7.2 & 10.9 \\ Concrete and mortar & 47.0 & 44.0 \\ Natural stone & 44.8 & 43.8 \\ Bituminous & 0.6 & 0.9 \\ Others & 0.4 & 0.4 \\ \hline \hline \end{tabular} Note: MRA-M: mixed medium recycled aggregate (6/12 mm); MRA-G: mixed gravel recycled aggregate (4/22 mm).  
\end{table}
Table 2: Composition of recycled aggregates.