## 2 Materials and Methods
### Concrete Design  
The six concrete mixes batched for the tests were divided into two groups: mixes containing 100% NA and GRC as OPC replacement at ratios of 0% (labelled NAC), 10% (labelled N10/0) or 25% GRC (labelled N25/0); and mixes with 50% MRA and GRC as an OPC replacement at ratios of 0% (labelled R0/50), 10% GRC (labelled R10/50) or 25% (labelled R25/50). The mixes with 100% NA were designed to study the effect of GRC on conventional concrete prepared with NA, and those with 50% to determine the joint effect of the two recycled materials. No plasticizers were used in any of the mixes.  
All the mixes were batched as set out in European standard EN 206-1 [19] to durability class X2 and strength class C25/30, although using 300 kg/m\({}^{3}\) of binder (OPC + GRC), slightly more than the  
\begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**Property** & **NS-F** & **NS-C** & **NC-M** & **NC-G** & **MRA** & **EHE 08** \\ \hline
**Dry density (kg/m\({}^{3}\)) [30]** & 2581 & 2583 & 2600 & 2620 & 2069 & - \\
**SSD 1 density (kg/m\({}^{3}\)) [30]** & 2601 & 2609 & 2630 & 2670 & 2256 & - \\
**24 h water absorption (wt\%) [30]** & 0.4 & 0.5 & 1.3 & 1.3 & 9.1 & 5-5 \\
**10 min water absorption (wt\%) [31]** & 0.2 & 0.3 & 0.5 & 0.6 & 8.1 & - \\
**Los Angeles coefficient (wt\%) [32]** & - & - & 28 & 26 & 46 & \(\leq\)40 \\
**Flakiness index (wt\%) [33]** & - & - & 13 & 16 & 20 & \(<\)35 \\ \hline \hline \end{tabular}  
* SSD: saturated surface dry.  
\end{table}
Table 4: Physical and mechanical properties of aggregates.  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Parameter Tested** & **Standard** & **Specimen Dimensions** \\ \hline
**Fresh properties** & \\
**Slump** & EN 12350-2 [35] & \\
**Fresh density** & EN 12350-6 [36] & - \\
**Air content** & EN 12350-7 [37] & \\
**Mechanical properties** & \\
**Compressive strength** & EN 12390-3 [38] & 150 mm \(\mathcal{O}\times 300\) mm \\
**Tensile strength** & \\
**Physical properties** & \\
**Open porosity** & \\
**Dry density** & UNE 83,980 [39] & 100 \(\times\) 100 \(\times\) 100 mm \\
**Electrical resistivity** & UNE 83988-2 [40] & 100 mm \(\mathcal{O}\times 200\) mm \\
**Thermal properties** & \\
**Thermal conductivity** & ISOMET 2114 [41] & 100 \(\times\) 100 \(\times\) 500 mm \\
**Volume heat capacity** & \\ \hline \hline \end{tabular}
\end{table}
Table 5: Properties of the concrete mixes analysed.  
standard minimum of 280 kg/m\({}^{3}\) for that exposure class. All were also prepared for a target workability of S2, as defined in EN-206-1 [19], equivalent to a 70 \(\pm\) 20 mm slump [32].  
The particle size distribution of the (fine + coarse) aggregate, irrespective of whether it was natural or recycled, fit the theoretical curve defined by [PERSON] [18] for a maximum size of 22 mm. The batching for the six materials used in the study is given in Table 6. The total amount of water used in each mix was defined as the effective water plus the water needed to offset the amount absorbed by aggregate when soaked for 10 min (approximately the mixing time) [42]. All the aggregates were used moist, subtracting the water required from the total in the mix.