Toward sustainable railway track foundation: Recycling RAP from road asphalt pavements

The granular sub-ballast layer commonly used in the construction of modern railway tracks, but its use involves a significant consumption of natural aggregates, which, moreover, must meet certain requirements that are sometimes unavailable. Therefore, the possibility of using recycled aggregates arises to promote sustainable development. In this context, this research focuses on assessing the feasibility of using RAP (Reclaimed Asphalt Pavement) as a sub-ballast layer in railway tracks, these recycled materials can contribute to increased loadbearing capacity and waterproofing of the lower layers due to the presence of adhered bitumen, studying the optimal application process to achieve a layer with high mechanical performance. It presents a laboratory investigation on the influence of different design factors on the mechanical performance of the layer, evaluating the effects of RAP characteristics, and the impact of the compaction procedure. Although these recycled materials primarily presented challenges in terms of size, particle distribution, and strength, which differ from the aggregates commonly used in similar high-demand layers, laboratory tests simulating expected service conditions for these materials in railway tracks have shown the viability and suitability of using recycled asphalt materials to achieve more sustainable railway tracks. Under compaction conditions at temperatures commonly achieved in construction (above 40 degrees C) and considering its particle size distribution, it is possible to create a layer with high performance in terms of strength and durability.