https://hdl.handle.net/10481/62111 2026-04-11T16:07:44Z https://hdl.handle.net/10481/110463 Cold Mix Asphalt for sustainable bituminous sub-ballast for railway: mechanical, vibratory and environmental assessment Guerrero Bustamante, Oswaldo; Guillén, Amparo; Moreno Navarro, Fernando Manuel; Rubio Gámez, María Del Carmen; Del Sol Sánchez, Miguel This study focuses on developing cleaner and functional bituminous sub-ballast for sustainable railway infrastructure using rubberized Cold Mix Asphalt (CMA) technologies. The proposed approach integrates high contents of Reclaimed Asphalt Pavement (RAP), and rubber from end-of-life tires, aiming to enhance vibration damping capacity while maintaining high load-bearing capacity and sub-layer protection. The research identifies optimal design parameters to improve stiffness, stress dissipation, vibration damping, and sustainability. A total of 17 sustainable mixtures were analyzed, assessing the influence of cement content, mineral skeleton, rubber content and size, and emulsion type and content, in comparison to two reference materials: granular sub-ballast from natural aggregates, as the most common solution and Hot Mix Asphalt (HMA) as conventional bituminous sub-ballast. A comprehensive multivariable analysis was conducted through mechanical characterization, vibrational assessment, and Life Cycle Assessment (LCA) techniques, allowing for an integrated evaluation of structural, functional, environmental, and economic performance. The results demonstrated that all sustainable mixtures significantly outperform conventional granular sub-ballast in mechanical performance, with improvements of up to 500 % in stiffness and 59 % in stress dissipation. Rubberized mixtures achieved damping improvements of up to 195 %, while the best-performing CMA alternatives reduced Global Warming Potential (GWP) by approximately 20–40 % compared to HMA. Cement content, optimized mineral skeleton, and rubber content emerged as the most influential variables. The findings highlight the need for balanced designs integrating moderate cement content (2–3 %) and optimized mineral skeleton to improve the mechanical performance while incorporating high rubber dosages (around 3.0 %) to achieve multifunctional performance. CMA demonstrates the potential to serve as a competitive alternative for railway infrastructure compared to granular sub-ballast, offering higher structural and functional properties, aligning with goals of durability, vibration mitigation, and sustainability while advancing circular economy practices. https://hdl.handle.net/10481/110363 Recycling Tire-Derived Aggregate as elastic particles under railway sleepers: Impact on track lateral resistance and durability Del Sol Sánchez, Miguel; Moreno Navarro, Fernando Manuel; Tauste Martínez, Raúl; Saiz, Leticia; Rubio-Gámez, M.C. The use of recycled Tire-Derived Aggregate (TDA) under railway sleepers has been demonstrated to be a sustainable and effective way to improve the durability and mechanical behaviour of ballasted train tracks. This solution enables the optimization of a track’s vertical performance, as different rubber quantities can be employed depending on track vertical requirements, while recycling a waste material abundantly available. However, before the widespread adoption of TDA, joined to previous studies focused on track vertical behaviour, it is still necessary to assess its influence on the lateral resistance of the track, given the importance of this parameter on the infrastructure’s quality and safety. Thus, the present paper focused on determining the effects on the lateral resistance of the section when employing varying quantities of rubber particles under the sleeper, along with its impact depending on the level of track degradation. For this study, laboratory tests were carried out to simulate realistic traffic conditions on full-scale sections. Results showed that TDA under sleepers could lead to higher lateral oscillations of the track due to the flexibility of the rubber particles, but resulting in similar, or even lower, permanent displacements to those in conventional ballasted tracks, as long as not excessive rubber volumes are applied. Particularly, for the study cases assessed in this article, it was seen that quantities up to around 1500–2000 cm3 (applied under half sleeper) could reduce permanent lateral movements due to dynamic efforts up to 45% in reference to traditional ballasted tracks, while increasing close to 130% the number of loads required to reach a lateral displacement of 10 mm (selected as example of failure criteria). https://hdl.handle.net/10481/110340 Toward sustainable railway track foundation: Recycling RAP from road asphalt pavements Guerrero Bustamante, Oswaldo; Guillén, Amparo; Moreno Navarro, Fernando Manuel; Del Sol Sánchez, Miguel; Rubio Gámez, María Del Carmen 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 load-bearing 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 ºC) and considering its particle size distribution, it is possible to cre https://hdl.handle.net/10481/110336 Benchmarking the embodied environmental impacts of the design parameters for asphalt mixtures Mattinzioli, Tom; Del Sol Sánchez, Miguel; Moreno Navarro, Fernando Manuel; Rubio Gámez, María Del Carmen; Martínez Montes, Germán For the full abatement of road construction emissions and the enhancement of green public procurement, the embodied environmental and social impacts of asphalt mixture typologies must be better understood. Therefore, the aim of this paper was to explore the environmental impact of five key asphalt mixtures classes (dense-graded, gap-graded, open-graded, porous and stone mastic) and the influence of their design parameters. This was achieved through carrying out 160 life-cycle assessment case study simulations to explore the upper and lower bounds for key design parameters, such as granulometric curve, filler and bitumen content, and filler and bitumen type. Results identified dense-graded (AC) and stone mastic (SMA) mixtures were the most impacting, per tonne, and gap-graded (BBTM A) and stone mastic to be the most impacting per unit depth. Porous mixtures had the largest impact range. Higher traffic classes also would experience an increase in emission levels, due to the need for better, or modified, binders. Future work would require the application of these results to case study projects, to better understand current mixture and construction impacts and the influence of durability. https://hdl.handle.net/10481/110331 MASAI: sustainable, automated and intelligent asphalt materials. The way to the next generation of asphalt pavements Moreno Navarro, Fernando Manuel; Sierra Carrillo de Albornoz, Francisco Javier; Del Sol Sánchez, Miguel; Rubio Gámez, María Del Carmen Despite the efforts made during decades, pavement construction still uses essentially the same traditional model as that employed one hundred years ago. This makes road construction actions less efficient, thereby affecting the productivity and the possibilities of economic growth of the sector. To help establish a model based on the circular economy, but also to promote the implantation of the new technologies, the Laboratory of Construction Engineering of the University of Granada has created the conception of sustainable and smart asphalt materials named MASAI, which enable the combination of the most important sustainable techniques developed in last decades in a single material. This paper describes the main characteristics of MASAI and presents several of the experiences carried out in Spain that demonstrate their viability and great potential regarding the minimisation of the environmental impact of asphalt pavements and their adaptation to the future needs of users and administrators.