## 4 Circularity Assessment of Each Scenario
### Scenario 2: Implementing Circularity Strategies at the EOL  
This scenario explored the circularity of the building structure outlined in Section 3, examining a linear input flow of materials during the initial phases and a circular output flow of materials at the EOL. The analysis was based on the findings from the third and fourth EEEC reports [57; 58], which indicated that the construction sector currently prioritises the implementation of circularity strategies primarily at the EOL stage. This approach aligns with Directive 2008/98/EC [92], which established a target for the recovery of 70% of CDW by 2020. In this scenario, the output flow considered the reusable, recyclable, and biologically renewable materials in each structural element. These fractions were derived from research, reports, and databases provided by governmental and non-governmental organisations (Table 1). These sources were selected for their accuracy and up-to-date relevance to the construction sector at the national level. Table 2 organises the consulted sources according to the European List of Waste (LoW) codes [93]. In this scenario, the MCI of the most representative materials based on Table 1 are shown in Figure 13.  
At the element level, the circularity assessment considered the MCI of the materials constituting each structural element and their corresponding DP. The results of this procedure are reflected in the ECI presented in Figure 14 below. Figure 11: MCI of representative materials in S1 (Authors’ own). Figure 12: ECI of reinforced concrete structural elements in S1 (Authors’ own). The SCI was determined based on the ECI previously defined, as well as the AP. This evaluation reflects that the SCI for this scenario is 26.4%. Scenario 3: Considering Circularity Strategies for All Materials, Excluding Concrete, Throughout the Entire Life Cycle  
In this scenario, the circularity assessment of the reinforced concrete structure was grounded in the criterion that all materials within the input flow, apart from concrete, \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**LoW Code and Description**} & \multicolumn{1}{c}{**Title**} & **Author** & **Year** \\ \hline
170101 & Concrete & Spanish Guide to Recycled Aggregates from & GEAR [75] & 2012 \\ \hline  & & Guideline for recycled materials reused in & & \\  & & construction & & \\
170405 & Iron and steel & Trade in Recyclable Raw Materials (database) & Eurostat [94] & 2022 \\  & & Galvanised steel and sustainable construction & EEGA [95] & 2021 \\  & & (report) & & \\ \hline
170201 & Wood & Contribution of Recycled Materials to Raw & & \\  & & Materials Demand (database) & Eurostat [96] & 2020 \\ \hline
170203 & Plastic & The CE of plastics (report) & Plastics Europe [97] & 2022 \\  & & Packaging and environmental sustainability & Emblem et al. [91] & 2012 \\ \hline
150111 \({}^{\star}\) & Metallic packaging & Metal Recycling Factsheet & EuRIC AISBL [98] & 2022 \\ \hline
150103 & Wooden packaging & Packaging Waste by Waste Management & Eurostat [99] & 2023 \\
170604 & Insulation materials & Operations (database) & Eurostat [94] & \\
150101 & Paper and & Trade in Recyclable Raw Materials (database) & & 2022 \\  & & cardboard packaging & & \\ \hline \hline \end{tabular} \({}^{\star}\) Potentially hazardous waste.  
\end{table} 
Table 2: Sources consulted for the analysis of S2 (Authors’ own). Figure 14: ECI of reinforced concrete structural elements in S2 (Authors’ own). Figure 13: MCI of representative materials in S2 (Authors’ own). incorporate a proportion of secondary raw materials, are reused, or consist of biomaterials. Furthermore, circularity strategies are applied to the output flow of all materials. This scenario reflects the growing interest among companies, particularly in the steel industry, to include a higher percentage of secondary raw materials in their manufacturing processes while ensuring compliance with the required physical and mechanical properties [64].