## 2 Materials and Methodology
### Methodology  
The first step consisted of the selection and collection of RAs, which were then dried at 60 \({}^{\circ}\)C until constant mass was reached. Next, the RAs were ground and sieved according to the European Standard EN 1015-1 [25], and only particles under 2 mm were subjected to forced carbonation. The RAs will be used in mortars in future applications. The samples were prepared with the same particle size distribution in order to obtain different aggregates with the same granulometric distribution, eliminating the granulometry factor [14]. Then, the samples went through an automatic separator for better homogenization, obtaining a representative sample for each period of carbonation selected. Forced carbonation was carried out in an ARALAB Fitoclima 300 EP climatic chamber with different exposure times to a 99.7% pure CO\({}_{2}\) flow, varying the temperature, RH, and CO\({}_{2}\) concentration between 23 and 60 \({}^{\circ}\)C, 40 and 60%, and 10 and 25%, respectively. Figure 1 presents the workflow used in this study, adapted from [PERSON] et al. [14]. The temperature range studied extended from room temperature (23 \({}^{\circ}\)C) to 60 \({}^{\circ}\)C, as 60 \({}^{\circ}\)C is the highest temperature that can be used without degrading RA [26]. The RH range was selected as it is a well-defined parameter for carbonation reactions (around 60%). The RH levels of 40% and 50% were chosen to evaluate the effect of reduced water availability on carbonation efficiency. The CO\({}_{2}\) concentration was initially studied at 25%, representing high-purity CO\({}_{2}\) streams typically used in controlled carbonation experiments. Subsequently, it was reduced to 10% to reflect the variability in CO\({}_{2}\) concentrations in industrial flue gases, which often range between 10% and 25%. All these conditions are guaranteed by sensors placed inside the carbonation chamber. The XRD analysis of the RA prior to the carbonation was performed with an AERIS Malvern Panalytical X-ray diffractometer, Almelo, the Netherlands, with 40 kV and 15 \begin{table}
\begin{tabular}{l l l l} \hline \hline
**RA Type** & **Designation** & **Portlandite Content (\%)** & **Cement Paste Content (\%)** & **Origin (Collected at)** \\ \hline \multirow{3}{*}{\begin{tabular}{l} Mixed recycled aggregate \\ (MRA) \\ \end{tabular} } & MRA-RP1 & 0 & 5.7 & Recycling plant \\ \cline{2-4}  & MRA-RP2 & 0 & 8.3 & Recycling plant \\ \cline{2-4}  & MRA-RP3 & 0 & 5.0 & Recycling plant \\ \hline \multirow{3}{*}{\
\begin{tabular}{l} Recycled concrete \\ aggregate (RCA) \\ \end{tabular} } & RCA-IW1 & 2.1 & 12.2 & Concrete producer \\ \cline{2-4}  & RCA-RP1 & 0.1 & 7.8 & Recycling plant \\ \cline{2-4}  & RCA-RP2 & 0.4 & 12.0 & Recycling plant \\ \hline \multirow{3}{*}{
\begin{tabular}{l} Control concrete \\ aggregate (CA) \\ \end{tabular} } & CA-L & 0.6 & 12.2 & Concrete produced in laboratory \\ \hline \end{tabular}
\end{table} 
Table 4: RA portlandite quantification from TG analysis. \begin{table}
\begin{tabular}{l l l l l l l} \hline \hline
**Identified Minerals** & **MRA-RP1** & **MRA-RP2** & **MRA-RP3** & **RCA-RP1** & **RCA-RP2** & **RCA-IW** & **CA-L** \\ \hline Muscovite & + & + & + & + & + & n.d. \\ \hline Ettringite & n.d. & n.d. & + & + & + & n.d. \\ \hline Gypsum & + & n.d. & + & + & + & + & + \\ \hline Kaolinite & + & + & + & + & + & n.d. \\ \hline Microcline & ++ & ++ & ++ & ++ & ++ & ++ & + \\ \hline Albite & ++ & ++ & ++ & ++ & ++ & n.d. \\ \hline Quartz & ++ & ++ & +++ & ++ & ++ & ++ & ++++ \\ \hline Calcite & ++ & +++ & ++ & ++ & ++ & +++ & ++ \\ \hline Hydrocalumite & n.d. & n.d. & n.d. & + & n.d. & + & n.d. \\ \hline Portlandite & n.d. & n.d. & n.d. & ++ & + & ++ & + \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Semi-quantitative XRD analysis of RA (adapted from [14]). mA, using Copper K\(\alpha\) radiation (\(\lambda\) = 1.5406 A). Diffractograms were recorded in the range of 5-85 \({}^{\circ}\)20 at a step size of 0.20\({}^{\circ}\)/s.