## 8 Conclusions  
The construction sector is progressing toward greater sustainability by harnessing secondary resources, such as cellulose waste, mining tailings, and metallurgy slags. Traditionally viewed as waste, these materials are now being repurposed into valuable components for construction, significantly reducing the need for virgin raw materials and minimizing environmental impacts. By integrating these secondary resources, the industry can achieve notable reductions in greenhouse gas emissions, enhance the performance of construction materials, and align with global sustainability goals. The reuse of cellulose waste, for example, contributes to the development of eco-friendly insulation and composite materials, enhancing thermal efficiency in buildings. Mining tailings, when used as aggregates in concrete and road construction, improve durability and reduce the demand for natural aggregates, while metallurgy slags offer robust properties for cement and concrete production, lowering the sector's carbon footprint. These practices underscore the potential of secondary resources to transform the construction industry, promoting a circular economy that emphasizes resource efficiency and waste reduction. However, the widespread adoption of these sustainable practices faces significant challenges, including the economic costs of processing and refining secondary materials, technological limitations related to material quality and performance, and restrictive regulatory frameworks that often classify these by-products as waste. To overcome these barriers, it is crucial to invest in research and development to improve material processing technologies, develop innovative treatments, and optimize the performance of these resources. Regulatory frameworks also need to be updated to facilitate the safe and effective use of secondary materials, encouraging their integration into mainstream construction practices. Innovative business models, such as industrial symbiosis, where companies collaborate to utilize each other's by-products, can play a pivotal role in overcoming logistical and economic challenges. These models, along with public-private partnerships, can help scale up the use of secondary resources, demonstrating their viability and driving market confidence. The future of construction hinges on the ability to scale these sustainable practices and integrate them into standard industry operations. By embracing circular economy principles, the construction sector can achieve significant environmental and economic benefits, reducing waste, conserving natural resources, and enhancing the resilience of the built environment. This approach not only addresses current environmental challenges but sets the foundation for a more efficient, sustainable, and forward-looking construction industry aligned with global environmental objectives.  
Among the three material streams reviewed, metallurgical slags currently exhibit the most mature and standardized integration in construction due to their chemical consistency and availability. Mining tailings offer a versatile but highly site-specific potential, whereas cellulose-based materials provide unique advantages in lightweight and insulating applications, though their durability requires careful design considerations. These distinctions underline the need for tailored valorization strategies aligned with the specific demands and constraints of each construction context. These findings reinforce the notion that secondary raw materials are not interchangeable but complementary. Their incorporation should be guided by performance-based criteria rather than merely availability or environmental appeal. Future efforts should therefore prioritize the development of adaptive standards, targeted material conditioning techniques, and application-specific performance benchmarks. This will ensure that circular construction strategies move beyond material substitution toward truly optimized, resilient, and scalable solutions.