Recycled Concrete Aggregate (RCA)-based Asphalt Trackbeds: Structural Design and Environmental Impact Assessment

The recycling of construction and demolition residues is essential to reduce virgin aggregate consumption, landfill disposal, and environmental burdens in transport infrastructure. In this context, Recycled Concrete Aggregate (RCA) represents a promising alternative for improving the sustainability of railway structures. Specifically, the implementation of RCA-based asphalt trackbeds can enhance resource efficiency and promote more sustainable railway systems by partially replacing natural aggregates with these recycled materials. Accordingly, this research evaluates three asphalt trackbed configurations for the Caribbean Regional Railway corridor in Colombia, namely (i) asphalt overlayment trackbed, (ii) asphalt underlayment trackbed, and (iii) asphalt combined trackbed. For each of these trackbed types, Hot Mix Asphalts (HMAs) incorporating coarse RCA at dosages of 0%, 15%, 30%, and 45% were evaluated. The structural design was developed using a KENTRACK-based methodology, with tensile strain at the bottom of the asphalt layer and compressive stress at the top of the subgrade soil as the primary mechanical response criteria. Subsequently, an attributional life-cycle assessment was performed to quantify the environmental impacts associated with the designed alternatives. The designs obtained show that asphalt trackbeds can provide structurally feasible solutions for railway substructures, while RCA inclusion can yield substantial environmental savings. The comparison among configurations indicates that each asphalt arrangement modifies the mechanical response and environmental profile of the trackbed system. Overall, the proposed framework demonstrates that RCA-based asphalt trackbeds can support more sustainable railway infrastructure planning, especially when structural performance and environmental impacts are jointly considered during early design stages.