## 4 Circularity Assessment of Each Scenario  
This section outlines the circularity performance of the building structure discussed in Section 3 across four different scenarios: (i) S1, maintaining material linearity throughout its lifespan; (ii) S2, implementing circularity strategies at the EOL; (iii) S3, considering circularity strategies for all materials, excluding concrete, throughout the entire life cycle; (iv) S4, incorporating circularity strategies for all materials, including concrete, throughout the entire life cycle.  
Figure 8: Structural characteristics of multi-family residential buildings in Spain. (**a**) Materials used to construct vertical structural elements; (**b**) characteristics of floor systems (Authors’ own).  
Figure 9: Structural system modelled by [72] on the BIM software Autodesk Revit 2023: (**a**) 3D Model view; (**b**) cross-section.  
The evaluation of circular performance was conducted using the CARES-F [62], a circularity assessment tool focused on the circularity of residential building structures. This evaluation consists of three consecutive levels: material, element, and system, each comprising several sub-indices, as illustrated in Figure 10.  
A special feature of this framework is that, for the assessment of circularity, in addition to considering the materials that end up as a product, it also includes other materials such as formwork, packaging, and material losses. Another particular aspect at the material level is the transportation impact assessed through the Distance Index (DI). In this study, only distribution centres and waste management facilities within a 20 km radius of the project were considered for all scenarios. This assumption was based on a fuel optimisation criterion, which aimed to reduce GHG emissions and transportation costs. The analysis used the logistics software CargosApps 2.0 [88] (IMPARGO, Berlin, Germany) to identify the optimal routes, and focused on roads that permit heavy-good vehicles. It also considered truck capacity based on the type of material and adhered to specifications from the General Vehicle Regulations [89]. In the specific instance of concrete, the capacity of the truck mixer and the discharge rate were determined based on the Spanish Structural Code [45]. Moreover, speed regulations from the General Traffic Regulations [90] were considered in the estimation of the transportation time for concrete, thereby ensuring that the material did not set during transit.  
At the element level, the CARES-F [62] normalises the MCI with the mass representativeness of each material and modifies this sub-index with the disassembly potential (DP) factor. The DP considers disassembled connections, the geometry of the edges of elements, prefabricated elements, and materials that do not require periodical secondary finishes to ensure acceptable structural performance over time. This last aspect primarily influences the circularity of the reinforced concrete elements.  
Lastly, the system level was analysed by modifying the normalised sub-index derived from the element level with the adaptability potential (AP) factor. The AP consid  
Figure 10: CARES-F conceptual and assessment model overview developed by [62].  
ers the geometric characteristics of the structure, as well as the arrangement and load-bearing capacity of the structural elements. In this study, these data were obtained from the building structure presented in Section 3. The building data set is provided in the Supplementary Data File.