Valorization of Fine Recycled Concrete Aggregate By-Products from Construction Waste as a Sustainable Material for Granular Subbases: Mechanical and Environmental Assessments

The valorization of by-products from construction waste offers significant potential for developing sustainable materials in road infrastructure. Accordingly, this study investigates the incorporation of Fine Recycled Concrete Aggregate (FRCA) as a partial replacement of virgin aggregates in Granular Subbases (GSB), considering both mechanical performance and environmental impacts. Replacement levels of 10% and 15% FRCA are examined and benchmarked against standard specifications for GSB within the Colombian context. The experimental campaign is composed of grain size distribution, Atterberg limits, Proctor compaction, Los Angeles abrasion, and California bearing ratio tests. Furthermore, a cradle-to-gate life-cycle assessment was conducted to evaluate the potential environmental benefits of diverting FRCA by-products from disposal and valorizing them as construction materials. Overall, the mechanical and environmental assessments reveal that if the Los Angeles abrasion criterion is set aside (because any FRCA content surpasses the allowable limits), the optimal mixture is the one formed by 85% GSB38 and 15% FRCA. This combination satisfies the standards for high-traffic roads while providing approximately 22.5–25% relative environmental savings.