Fernando Moreno-Navarro

Exploring the recovery of fatigue damage in bituminous mixtures: the role of healing

In recent years, many studies have assessed how the healing phenomenon could recover the stiffness or the strength of bituminous materials. Nevertheless, some factors that appear during these studies have opened up a debate about whether a recovery of the damage actually occurs, and whether this recovery is lasting. This study attempts to provide an approach to these questions. For this purpose, an analysis at both micro- and macro-damage levels has been carried out, taking into account different variables. The main conclusions drawn from this study are that during rest periods without heating induction, the recovery produced in the material is mainly due to reversible phenomena. Furthermore, it has been demonstrated that although healing can recover part of the damage caused by fatigue processes it cannot restore the initial properties of the material. The restored material is still relatively brittle and due to this, the stresses generated in the zone in closer proximity to the healed cracks are higher, and the restored properties fail prematurely.

Use of Reclaimed Geomembranes for Modification of Mechanical Performance of Bituminous Binders

AbstractThe use of modified binders plays a very important role in the construction of more durable pavements. However, the addition of modifiers to the binders could considerably increase their cost, making these materials less competitive. Thus, in recent years, various research studies have been carried out to obtain new modified binders that could lead to an improvement in the mechanical performance of asphalt pavements without a notable increase in their construction costs. To this end, the reuse of wastes and by-products from other industries has been posited as an interesting and sustainable alternative. This study investigates the reuse of scraps from reclaimed geomembranes composed of low-density polyethylene and polyester fibers as modifiers for asphalt binders. For this purpose, different blends of this waste and neat bitumen were manufactured and tested [penetration, softening point, storage stability, frequency sweep, multiple stress creep-recovery (MSCR), and time sweep tests). In addition, ...

The influence of temperature on the fatigue behaviour of bituminous materials for pavement rehabilitation

The rehabilitation of deteriorated pavements has become one of the main concerns in road engineering. Thus, the development of more resistant bituminous mixtures to be used as surface layers is a priority for the sector. Gap graded bituminous mixtures manufactured with modified binders at high dosages have been used with satisfactory results. Nevertheless, these materials are susceptible to temperature, and their performance is dependent on the climatic conditions. In order to improve the design of these mixtures, this research has focused on a better understanding of their fatigue behaviour as a function of temperature. This study has been conducted at both binder and mixture levels using the EBADE (Ensayo de BArrido de DEformacioes) and University of Granada - Fatigue Asphalt Cracking Test (UGR-FACT) tests, and it involves the analysis of various types of bituminous materials. The results showed that the temperature could play an important role in the success of this type of solution for the rehabilitation of deteriorated roads. It is therefore of interest to take this parameter into account for the effective design of bituminous mixtures.

The Use of Deconstructed Tires as Elastic Elements in Railway Tracks

Elastic elements such as rail pads, under sleeper pads and under ballast mats are railway components that allow for a reduction in track deterioration and vibrations. And they are furthermore commonly used to obtain an optimal vertical stiffness of the infrastructure. However, the use of elastomeric materials can increase construction costs and the consumption of raw materials. Thus, the utilization of used tire layers offers an alternative to reuse an abundant waste reducing the cost of elastic elements. In addition, an innovator technique allows deconstructing tire layers without grinding up the material, reducing production costs at the same time that tire properties are remained. This research is focused on the study of the viability of developing elastic components from used tire layers by evaluating the influence of thickness, the resistance capacity of the elements and their behavior in a ballast box. Results indicate the ability of tire pads to manufacture elastic elements (rail pads, under sleeper pads and under ballast mats) to be used in railway tracks.

Exploring the recovery of fatigue damage in bituminous mixtures at macro-crack level: the influence of temperature, time, and external loads

Recently, the analysis of the healing capacity of bituminous materials has become an important research topic in pavement engineering. Although many studies have demonstrated the potential of some techniques (e.g. self-healing agents or induced healing) to recover the properties of these materials, there still remain some questions that need to be addressed. One of the most important issues is how to define the optimal moment for inducing healing (at micro or macro-crack levels), along with determining the optimal conditions for using the technique. Accordingly, this paper aims to provide an approach to answer these questions. In this research, several mixtures were tested under various conditions until their fracture, and then healed using a range of healing techniques. Following the healing process, the materials were re-tested and the efficiency of the healing at macro-crack level was assessed. The results indicate that the healing capacity at macro-crack level appears to be sensitive to the service conditions; in general, as the temperature of the healing treatment increases, the rate of recovery increases. Furthermore, it was observed that the recovery potential of conventional binder is higher than modified binders at macro-damage level. Additionally, the presence of external loads during application of the healing treatment could increase the rate of recovery. Nonetheless, it is important to note that the application of heating and/or external force as healing techniques produced low levels of recovery in macro-damaged asphalt materials.

Fatigue cracking in asphalt mixtures: the effects of ageing and temperature

Bituminous mixtures are viscoelastic materials whose mechanical performance is highly influenced by temperature. In addition, during their service life, these types of materials suffer an ageing process that induces an increase in bitumen viscosity and therefore, a variation in the response of the mixture. The changes produced by these phenomena are mainly manifested in terms of stiffness, which could exert a considerable influence on the fatigue cracking resistance of asphalt materials. In this respect, this article attempts to provide a better understanding of the effect of temperature and ageing on the bituminous mixtures’ resistance to cracking. For this purpose, the rheological response of the binder has been correlated with the mechanical performance of the bituminous mixture. Results obtained showed that binder ageing has a negative impact on fatigue cracking resistance of asphalt mixtures, which would be more notable as the temperature increases.

Understanding the effects of ageing and temperature on the fatigue cracking resistance of bituminous mixtures

Bituminous mixtures are visco-elastic materials whose mechanical performance is highly influenced by temperature. In addition, during their service life, these type of materials suffer an ageing process which induce an increase in bitumen viscosity and therefore, a variation in the response of the mixture. The changes produced by these phenomena are mainly manifested in terms of stiffness, which could exert a considerable influence on the fatigue cracking resistance of asphalt materials. In this respect, this paper attempts to provide a better understanding of the effects caused by temperature and ageing on the resistance of bituminous mixtures to the propagation of cracking phenomena. For this purpose, the rheological response of the binder has been correlated with the mechanical performance offered by the bituminous mixture.

An analysis of the performance of deconstructed tires for use as pads in railroad tracks

The use of end-of-life (EOL) tires is now widespread in civil engineering work. In most cases, the tires are shredded and recycled as crumb rubber. However, this research focuses on an alternate method in which EOL tires were deconstructed to manufacture rail pads. In other words, their outer layer was removed, which made it possible to benefit from the mechanical properties of the tires without having to grind them up. The performance of the recycled tire rubber was analyzed by means of static and dynamic stiffness tests as well as by fatigue tests. The results reflected the long-term performance of the material. Also analyzed was the deterioration of its properties after various thermal and anti-ageing treatments. The results obtained were compared with those of commercial crumb rubber rail pads. The excellent performance of the rail pads made from deconstructed EOL tires shows the high potential of this material for use in railroad tracks.

Tire crumb rubber effect on hot bituminous mixtures fatigue-cracking behaviour

AbstractThe use of tire crumb rubber in road engineering as a modifier of bituminous mixes constitutes one of the revalorization techniques for this waste. The main objective of this research consists of analysing the possible fatigue cracking improvements in the performance of bituminous mixtures containing crumb rubber in comparison to bituminous mixtures manufactured with conventional bitumen and bitumen modified with SBS polymers. For this purpose, four different types of mixes with the same mineral skeleton but different bitumens were studied. The test used to evaluate their behaviour was the UGR-FACT with an additional system for taking pictures, which allows controlling the propagation of the cracks at every moment. The results show that the addition of crumb rubber retards the appearance of cracks; however, once it begins, the damage propagation is faster. Therefore, the fatigue cracking life of mixes with crumb rubber seems considerably longer than the fatigue cracking life of those with conventi...

The Effect of the Nature of Rejuvenators on the Rheological Properties of Aged Asphalt Binders

Pavement rehabilitation will become the main activity in the road engineering sector in the majority of developed countries. Thus, large quantities of reclaimed asphalt pavements (RAP) will be generated and their reuse in asphalt mixtures would provide considerable economic and environmental benefits. To overcome the problems caused by using an excessive amount of RAP in asphalt mixtures, the use of rejuvenators will play a key role. Recent years have seen the emergence of many types of asphalt rejuvenators. The main objective of this study is to characterize the effect of different rejuvenators (varying in nature) on the rheological properties of aged asphalts binders. For this purpose, an aged binder extracted from RAP was blended with four rejuvenators at different dosages. Their rheological properties were then evaluated using frequency sweep tests and several rheological parameters that assess the brittleness of aged binders (“G*·sin δ”; R-value and crossover frequency; G-R parameter). The results indicate that the rejuvenator based on oleyldiamine ethoxylate showed the best performance. However, similar results can also be achieved using bio-rejuvenators from plant-based ester resins.