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The ageing phenomenon in asphalt mixtures is one of the most important factors affecting its service life. The current paper provides an overview of a number of studies related to the ageing process in bitumen, to determine the main component affecting this phenomenon. Moreover, a review is presented of the in-laboratory tests used to simulate the different ageing processes (short-term ageing, long-term ageing, UV ageing) that occur in the field, along with a description of the techniques currently employed to analyse, from different perspectives, what happens to the binder after ageing. Finally, a summary is presented of the various types of anti-ageing additives (antioxidants, UV blockers, UV absorbers) that are currently most commonly studied, along with their effects. This document reveals the importance of assessing the influence of UV radiation in any ageing study that is related to field data, and the need for a standard to simulate bitumen ageing. In addition, it highlights the importance of considering the influence of other components of the mixture on the ageing of the bitumen and the need to conjointly consider different types of techniques in order to fully understand the phenomenon.

Graphene is considered to be a promising material for the development of the next generation of asphalt binders to be used in road engineering. Nonetheless, in spite of the potential advantages that graphene could add to bitumen, there are currently very few studies able to quantify its real contribution to the performance of existing binders. This research therefore aims to evaluate the mechanical and thermal properties of graphene modified binders. For this purpose, rheological and thermal tests were conducted on binders manufactured with different dosages of graphene flakes. The results indicate that the presence of graphene produces a more elastic response in asphalt binders. However, the resulting recovery capacity is not as effective as that provided by other asphalt modifiers such as elastomers. In addition, it has been shown that graphene can reduce the thermal susceptibility of these binders, increasing their capacity to be heated and to produce heat transfer.

The present paper focuses on an initial assessment into the applicability of sensored sustainable pads, made from recycled polymers and embedded with commonly-accessible piezoelectrics. These sensing devices were used as smart rail pads and inside bituminous sub-ballast to monitor traffic and track state by measuring the stress variations in the components. A series of full-scale laboratory tests were carried out simulating train passage under diverse traffic scenarios and varying track section conditions in a testing box. Results indicated that the smart sustainable pads in both components showed the capacity to detect traffic load variations by measuring relative changes in signal amplitude of the sensor. Nonetheless, the smart rail pads presented higher accuracy to monitor axle loads, while the signals from the sub-ballast were influenced by the position of the sensor and so a higher potential to monitor track performance, rail-sleeper load distribution and detecting phenomena like hanging sleepers.

The long-term advantages of using of polymer-modified binders are not commonly observable in traditional tests or pavement design methods. Because of this fact and for economic reasons, their application is limited to high traffic volume roads. This paper examined the structural behaviour of bituminous mixtures used in road surface layers (considering costs and performance), and analysed the viability of using these materials for the rehabilitation of light-medium traffic volume roads. The results demonstrate that polymer-modified materials could be more structurally and economically efficient than unmodified materials, offering a solution to designers for the rehabilitating of light-medium traffic volume roads.

Ballasted railway tracks, despite their benefits, present some limitations and drawbacks, mainly associated with geometry degradation due to ballast settlement and particle breakage. Periodic maintenance interventions are thus required as well as renewal processes, which lead to the significant consumption of natural materials and energy whilst causing frequent interruptions to traffic. This is made more problematic when aggregates with appropriate characteristics for ballast are not available in the proximity of the construction/maintenance site, which is becoming increasingly common due to restrictive environmental guidelines. In this context, this paper presents a review of the effectiveness of the major conventional techniques/materials for track design and maintenance as well as innovative solutions that are being developed to reduce track degradation, whilst also analysing their main parameters to optimize track behaviour and durability, depending on its design and the required changes in its mechanical performance. The aim is to then provide a set of recommendations and guidelines for the use of such technologies to improve track response and durability as well as highlighting possible further research associated with both the development of innovative solutions and the improvement of conventional techniques.

The construction and maintenance of road pavements need to be undertaken to ensure proper economic and social growth. Considering the high environmental impact that the production of asphalt mixtures for road pavements entails, in terms of energy consumption and greenhouse gas (GHG) emissions, these operations must follow the global transition towards more sustainable development practices. In response to this, previous research has been focused on the development of manufacturing low temperature asphalt mixtures and the use of recycled modifiers such as tire crumb rubber to improve their durability. However, the use of high dosages of the latter reduces mixture workability, thus requiring high manufacturing temperatures to reduce the viscosity of the binder, and therefore limiting the advancement towards more sustainable mixtures. In this regard, further knowledge is needed on this topic to promote the combination of such techniques to maximise their advantages. This study aims to check the viability of producing asphalt mixtures with high crumb rubber contents at reduced temperatures, testing their workability, stiffness, cohesion, resistance to permanent deformations and resistance to moisture damage. Results show that it is possible to manufacture viable, warm, rubberised asphalt mixtures at 150 °C using a high penetration bitumen and reduce this temperature to 130 °C (45 °C less than conventional rubberised asphalt mixtures) by including warm additives, without compromising their mechanical performance.

The aim of this paper was to analyze the mechanical behavior of various asphalt mixtures for application in pavements for ports, particularly with a view to developing and designing asphalt materials that could be used as an alternative to traditional concrete pavements in ports. The advantages of using such materials include a reduction in the time and costs associated with the construction and periodic maintenance operations required for port pavements, particularly in areas designated for container operations. For this purpose, five High Modulus Asphalt Mixtures (HMAM), with different types of aggregates and bitumen were analyzed through laboratory tests specifically developed to assess the main failure modes of these materials when used in port pavements. The tests focused on static punching due to container storage; impacts of loads generated during the unloading of containers; and the combined effect of heavy vehicles with fuel action due to spills from vehicles and containers. Additionally, these properties were measured in a full-scale section reproduced in laboratory to evaluate the performance of the bituminous under real conditions. The results demonstrate that the type of bitumen – as opposed to the type of aggregate – has a stronger impact on the mechanical performance of HMAM when used in port pavements. Thus, the use of modified bitumens generally allows for improving the resistance of the HMAM in comparison with conventional bitumen, particularly under adverse service conditions, where the mixture with rubberized bitumen was found to be the most appropriate solution.

Climatic actions such as rain, sun or ice are one of the major contributors in asphalt pavement degradation. The effect of these climatic agents can be a long-term process of asphalt mixture deterioration when long rainy or sunny periods are expected as well as a series of freeze–thaw cycles due to wide range of temperature. However, laboratory studies are mainly focused on short-term effect from climatic actions. Thus, the present paper aims to analyze the evolution of the strength and bearing capacity of asphalt mixtures exposed to long-term moisture, several freeze–thaw cycles and diverse days of thermal aging. In addition, the recovery of the material mechanical properties was evaluated when a rest period was applied after climate processes. This study was developed for two different asphalt mixtures (dense and open), finding that air void content has significant influence on the trend of the long-term evolution of mixture properties under moisture action, which is a reversible process unlike the other two climate agents studied. On the other hand, freeze–thaw cycles whose effect is higher on dense mixtures was found to be a short-term process regardless the air void content while thermal aging presented the lowest variations in the properties measured for both types of asphalt mixtures.

Railway is envisaged as the transportation mode of the future, but in spite of its advantages, its development is not exempt from technical difficulties that lead to track deterioration. To overcome these drawbacks, research in this field needs to be developed. Geometry degradation, as well as noise and vibration, have been identified as problems that need to be reduced, which could be possible by modifying track vertical stiffness and obtaining a more homogeneous value along the track. One measure to minimize these problems involves the installation of elastic elements (e.g. rail pads, under-sleeper pads, and under-ballast mats) in the railway track. In fact, this has now become the most effective means to vary track vertical stiffness as well as to abate noise emission and vibrations caused by the passage of trains. This paper discusses the problems associated with track stiffness, geometry degradation, and vibrations, and at the same time, studies the characteristics of elastic elements as well as the research carried out to test and evaluate their effectiveness. After reviewing and analyzing a wide range of research initiatives, this paper proposes a set of recommendations and guidelines for the use of elastic elements in railway infrastructure as well as highlighting a series of possible further investigations.

Ballasted track is the most common form of construction used in railway transportation due to a number of benefits in comparison with other solutions such as slab track. However, the degradation of the ballast particles and the layer settlement lead to important maintenance costs. Thus, diverse research has been carried out to develop new materials with the aim of increasing the service life of the track. To this end, the present paper focuses on the use of crumb rubber (from end-of-life tires) as elastic aggregates mixed with ballast particles, which could reduce ballast degradation and consumption of natural aggregates. At the same time, an abundant waste source is reused and the use of raw binders (proposed technique employed to bond elastic particles to ballast particles) is not necessary, which potentially reduces costs and consumption of raw materials. For this reason, the influence of different percentages of crumb rubber was studied in the laboratory using a ballast box. In addition, once the optimal quantity of rubber had been determined, its effect on ballast behaviour under high stress level was analysed. Results show that the use of 10% of crumb rubber (by volume) could reduce ballast degradation and at the same time as the capacity of the ballast layer to dissipate energy is increased and its stiffness is reduced. Additionally, based on the present laboratory study, the track settlement could be reduced with 10% rubber particles used as elastic aggregates.

The high stiffness provided by high modulus asphalt mixes significantly decreases the loads transmitted by the traffic to the road foundation whilst at the same time increases their resistance against plastic deformations. Thus, the use of these types of mixtures can be an effective solution in road construction, due to the fact that they can reduce the thickness of the pavement, saving economic and material resources. Nevertheless, in some cases this high stiffness constitutes a drawback because it could reduce the fatigue resistance offered by these materials, leading to a premature appearance of cracks in the pavement, which decreases its service life. Due to this fact, the use of high modulus asphalt mixes is limited, especially in cold climates. In order to solve this problem, this research has been focused on the improvement of the mechanical performance of high modulus asphalt mixtures through the use of additives (crumb rubber and acrylic fibers), which could increase their fatigue resistance by maintaining the stiffness required. Different tests have been carried out under different temperatures for the mixtures assessment. The results obtained have shown that the incorporation of these additives could lead to a better mechanical behavior of high modulus asphalt mixes, and thus it could improve their performance.

This research study focused on the design of under sleeper pads made from deconstructed end-of-life tires. The rubber was obtained without grinding up the tires. This cost-effective process has a lower environmental impact and at the same time preserves the mechanical characteristics of the material. The analysis was focused on how certain design parameters of the under sleeper pads affected their static performance (at different stress levels) and their dynamic performance (at different load frequencies). Their long-term performance and durability were also evaluated with a mechanical fatigue test. In addition, a ballast box was used to assess the impact of the pads on lateral resistance and stress distribution in a ballasted railway track system. The results of this study showed that under sleeper tire pads with different static and dynamic stiffness moduli can be obtained by varying pad thickness and by applying different physical treatments to the material. Moreover, the fatigue results revealed that these tire pads are suitable for use in railway systems. In addition, it was found that the pads distributed loads to a higher ballast area and at the same time increased the lateral resistance of the track.

Fatigue cracking is one of the most common distresses that affect roads all over the world. The development of new techniques that allow minimizing the effect caused by this pathology is crucial to reduce road rehabilitation costs. For this purpose, a new product obtained from deconstructed tires has been designed and tested “anti-reflective cracking mats”. Manufactured from the resistant layers of the tyre (metallic and textile layers), it is used as a system placed between the courses of the pavement in order to reduce the effect caused by fatigue cracking processes. This article presents the characteristics of these products and resumes their mechanical performance in a pavement section tested in laboratory. The results obtained showed that the application of these anti-reflective cracking systems could be an interesting solution in order to reduce the impact caused by this pathology.