## 4 Conclusions and Future Research  
This article describes the principal work on the mechanical and environmental characterization of bituminous concrete incorporating a high rate of recycled concrete aggregate, suitable for use in surface layers of road pavements. This application, whose industrial viability was confirmed during the \"_CirMat_\" project, increases environmental sustainability and significantly reduces the consumption of natural aggregates. This project has confirmed that asphalt mixtures with RCAs have such interesting properties that practical applications on an industrial scale should be encouraged. For example, whenever the work to be carried out involves the demolition of concrete structures, the resulting materials (RCD) must be processed with a view to incorporate the resulting RCAs, at significant rates, into the surface layers of pavements. A comparison of the results obtained with those of a reference mix (produced only with natural aggregates) allows several conclusions to be drawn, the most important of which are the following:  
* Except for water absorption, methylene blue value, flakiness index, and shape index, these recycled aggregates can have properties very similar to those exhibited by natural aggregates;
* The composition of asphalt mixtures can also be similar, including the optimum binder content;  
Figure 12: Comparison between the normalized results of the RCA and NA mixture. * In the Marshall test and in the characteristics of the voids, only tiny variations were obtained, with reductions of around 3% (in S, \(\rho_{\text{mh}}\), \(\rho_{\text{b}}\) and VMA) and 6% (in F), while V\({}_{\text{a}}\) increased slightly from 3.1% to 3.3%;
* When using natural aggregates of a granitoid nature, the water sensitivity assessed using the ITSR is similar, but, when using the IRS, the result is better in the mixture with RCAs (99% against 93%);
* The results in the assessment of resistance to permanent deformation were much better in the case of the mixture with RCAs (33% lower in PRD\({}_{\text{AIR}}\), 35% lower in RD\({}_{\text{AIR}}\), and 50% lower in WTS\({}_{\text{AIR}}\));
* The data on environmental impacts suggest that incorporating RCAs into AC can lead to overall reductions in several impact categories, including GWP, AP, EP, and WDP. On the one hand, nine indicators were improved (from 1% to 93%, with an average of \(\approx\)43%). On the other hand, only four indicators worsened slightly (the variation ranged from 5% to 9%, with an average of \(\approx\)8%). Although some processes, such as aggregate extraction and bitumen production, contribute to strong environmental impacts, the benefits of using RCAs outweigh these impacts, thus resulting in the more sustainable and environmentally friendly production of asphalt mixtures. However, it is essential to consider each production facility's specific context and practices to accurately assess the total environmental impact. In conclusion, the \"_CirMat_\" project has undoubtedly contributed to greater efficiency in using resources in the construction sector. As the bituminous mixture with RCAs was produced and applied on a pavement, it was also possible to demonstrate the industrial viability of using this more sustainable material. These contributions will make it possible to achieve higher targets for the recovery of CDW and the promotion of secondary raw materials (SRMs) in more noble applications than those currently found in some construction projects. These results align with the circular economy concepts that should rule any production process. They can also contribute to harmonization, a crucial factor in accelerating circularity. Finally, disseminating knowledge from the activities carried out under this project will encourage more practical applications and boost future research.