## 3 Results and Discussion
### Hardened-State Properties of Mortars
#### 3.2.6 Eco-Efficient Material  
The values used to estimate the energy consumed to manufacture a tonne of binder are shown in Table 8. For OPC (heating of raw materials, clinkerization, and crushing), these  
Figure 7: Results of ultrasonic pulse velocity at 91 and 365 days of curing (**a,b**) on the compressive strength, \(f_{cm}\), of the mortar as a function of the ultrasonic pulse velocity, UPV.  
were extracted from the literature [30; 57]. RC does not need calcination, but was crushed, and so the energy consumed in the grinding process of the concrete specimens manufactured in lab [31] was considered to be similar to the process necessary to grind concrete debris from CDW. For FA, only the energy consumed in its collection was considered [58].  
The results of energy consumption per MPa of strength are shown in Figure 8. After 7 days of curing (Figure 8a), the binary mortars that incorporate RC show the highest energy consumption per MPa of strength as a result of a lower initial strength and low reactivity of the SCMs [15]. Additionally, the binary mortars with FA and the ternary mortars with RC and FA show a slightly lower behaviour compared to the reference mortar with OPC because the clinker dilution effect still prevails over the pozzolanic reactions [38]. At 365 days of curing (Figure 8b), the energy consumption per MPa of strength decreases (with respect to the 7 days) due to the dilution effect and low reactivity of the RC, showing a similar behaviour to the reference mortar (E\({}_{\text{con}}\)\(\sim\)12.9 kW\(\cdot\)h/t\(\cdot\)MPa). The lowest energy consumptions per MPa of strength were obtained for binary mortars with FA (E\({}_{\text{con}}\)\(\sim\)11.5 kW\(\cdot\)h/t\(\cdot\)MPa) and ternary mortars with RC and FA (E\({}_{\text{con}}\)\(\sim\)11.2 kW\(\cdot\)h/t\(\cdot\)MPa). These results coincide with previous findings obtained for mortars made with up to 20% ash from biomass-fuelled power plants compared to conventional mortar [4].  
Figure 9 shows the synergistic effects of simultaneously incorporating RC and FA _versus_ their individual incorporation. There, at 365 days of curing, the energy consumption per MPa of strength of the binary mortars with 5% of RC is similar (\(\sim\)1.2%) to that of the mortar with OPC. For the mortar with 20% FA, the energy consumption is reduced by up to 11.6% compared to the mortar with OPC. As for the ternary mortars, the reduction of consumed energy per MPa of strength can reach up to 13.2% with the simultaneous incorporation of 10% of RC and of 20% of FA, with respect to the mortar with OPC.  
Figure 8: Energy performance at (**a**) 7 days and (**b**) 365 days of mortars.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Process**} & \multicolumn{2}{c}{**Energy Consumed [Refs.]**} & \multirow{2}{*}{**FA**} \\ \cline{2-2} \cline{4-4}  & **OPC** & & **RC** \\ \hline Manufacture & \(E_{\text{OPC}}^{process}=1039\) kW\(\cdot\)h/t [45] & \(E_{\text{RC}}^{process}=0\) kW\(\cdot\)h/t [1] & \(E_{FA}^{process}=38\) kW\(\cdot\)h/t [46] \\ Grinding & \(E_{\text{OC}}^{grinding}=50\) kW\(\cdot\)h/t [21] & \(E_{\text{RC}}^{grinding}=140\) kW\(\cdot\)h/t [22] & \(E_{FA}^{grinding}=0\) kW\(\cdot\)h/t [22] \\ \hline \hline \end{tabular}  
* Notes: 1 RC requires no manufacture; 2 FA requires no grinding.  
\end{table}
Table 8: Values used to calculate the energy consumed.  
Finally, it should be noted that the use of RC and FA as supplementary cementitious materials would also imply a reduction in CO\({}_{2}\) emissions (\(\Delta\)CO\({}_{2}\) emissions) at rates close to the percentage of replacement, as observed by several authors, for 10% of RC [31] (\(\Delta\)CO\({}_{2}\) emissions = \(-\)7.5%) and for 20% of FA [58,59] (\(\Delta\)CO\({}_{2}\) emissions = \(-\)19.8%/17.8%).