## 5 Discussion and Future Research
### Impact of Material Circularity Strategies at All Levels in Each Scenario  
The circularity assessment of the scenarios studied in Section 4 demonstrates how the adoption of strategies at the material level influences the circular performance of the entire structure and each of its elements.  
The evaluation of this measure through scenarios that represent the progressive application of this measure in the lifecycle of the building thereby reveals that the implementation of circularity strategies in concrete at the EOL (S2 and S3) boosts its circular performance by 8.16% compared to the linear flow in S1 (comparative analysis in Figure 19a). Moreover, the incorporation of RCA at 20% by weight of the total coarse aggregate content (S4) results in a 42.82% increase in the circularity of concrete (Figure 19a). A similar trend is observed with steel rebars (Figure 19b), where the introduction of circularity strategies at the EOL (S2) enhances circularity by 31.32% relative to a linear flow (S1). In contrast, the adoption of a circularity perspective from the design phase (S3 and S4) leads to an even more significant increase in circular performance at the material level, with an improvement of 38.27% compared to S1.  
However, the analysis of circularity at both the element and system levels reveals that since the circularity assessment scale exceeds the material level, the effectiveness of the RAC is reduced (Figure 20). This decline occurs since the disassembly potential affects the circularity of the elements, whereas the adaptability potential is decisive for changes over time at the system level.  
Figure 19: Comparative analysis of MCI: (**a**) improvements in the MCI of concrete of S2 to S4 compared to S1; (**b**) improvements in the MCI of steel rebars of S2 to S4 compared to S1 (Authors’ own).  
The findings demonstrate that replacing traditional materials with RAC enhances the circular performance of the structure by 10.81% (Figure 20b), even in residential buildings that exhibit limited potential for disassembly and adaptability. While this highlights the efficacy of RAC in promoting circularity, the circular performance score of 34.9% in S4 (Section 4.4) emphasises the need to incorporate DfD and DfA criteria to enhance circular performance at both the element and system levels. Notable measures to achieve this include using prefabricated elements with removable connections [104], off-site construction methods [105], and the arrangement of elements to facilitate the adaptability of structure over time [106,107]. Furthermore, circular performance can be further improved at the material level by integrating supplementary cementitious materials, implementing biomineralisation techniques, utilising carbon capture technologies, and employing 3D printing methods [108]. Nevertheless, successful implementation of these initiatives requires supporting standards that build confidence among stakeholders. Several existing standards, such as the Structural Code, only tangentially reference a few of these strategies. Therefore, additional research is essential to broaden their application for structural purposes.