The use of polymer-modified binders in asphalt mixtures has become more widespread due to their reduced thermal susceptibility and improved rutting and fatigue resistance. Nevertheless, their high cost limits their application, thus making the use of reclaimed polymers (RP) an interesting alternative for both reducing price and extending the service life of pavements. This paper; therefore, presents a comparative review of the recycled polymers most commonly studied as bitumen modifiers: polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), ethyl vinyl acetate (EVA), and ground tire rubber (GTR), in order to facilitate their selection and extend the use of the bitumen. The differences in terms of melting point, mixing conditions, and maximum quantity of added polymer are analyzed. Moreover, their effect on the mechanical behavior of the asphalt binders and their stability with and without the use of additives is presented. According to the literature revision, the performance of the new binder is more influenced by the kind of polymer that was incorporated and the mixing conditions than by the base bitumen that was chosen, although rheological evaluation is needed to fully understand the modification mechanisms of the modified binder. In general terms, plastomers have a stronger effect in terms of increasing the stiffness of the bitumen in comparison with crumb rubber (elastomers), thus providing an improved rutting resistance. The joint use of polyethylene (plastomer) and crumb rubber (elastomer) can be an interesting option for its recycling potential and mechanical performance, although further study is needed to achieve stable bitumen across the entire range of temperatures; additives, such as maleic anhydride (MA), are commonly employed to improve the stability of the binder and enhance its characteristics, but their use could limit the economic benefits of using recycled materials.

The 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 results obtained were compared with those obtained by using neat bitumen and traditional polymer modified bitumen. This study indicates that reclaimed geomembranes could be an interesting modifier for asphalt binders because they can increase their resistance to permanent deformation, stiffness and elasticity, reduce their temperature susceptibility, and extend their fatigue life.

The Multiple Stress Creep and Recovery (MSCR) test is widely used to analyse the mechanical performance of asphalt binders. It has commonly been used to analyse resistance to permanent deformations and identify and quantify how the polymer is working in the binder. However, this test also offers other useful information that can be studied to provide a better understanding of the mechanical performance of asphalt binders. This paper presents a new approach that analyses binder performance in terms of mechanical loads, thermal gradients, ageing and low temperatures, based on the results obtained from the MSCR test. For this purpose, several parameters and indexes are defined to characterise the response of asphalt binders. To evaluate the potential of this new approach, a research study was carried out with ten different binders (neat and modified) and three types of bituminous mixtures. The indexes obtained from binder performance show a strong correlation with the performance of bituminous binders against the main distresses that appear in road pavements, thus providing an efficient tool for selecting the most appropriate asphalt binder to use under certain traffic and climatic conditions.

The main characteristics of bituminous mixtures manufactured with a considerable amount of reclaimed asphalt pavement (RAP), compared to conventional mixtures, are a reduction in workability, an increase in stiffness, and a loss of ductility, due to the presence of the aged bitumen contained in the RAP particles. To minimize these impacts, softer binders or rejuvenators are commonly used in the design of these mixtures in order to restore part of the ductility lost and to reduce the stiffness. In spite of previous investigations demonstrating that the mortar plays an essential role in the workability, long-term performance, and durability of bituminous mixtures (where cracking, cohesion, and adhesion problems all start at this scale), not many studies have assessed the impacts caused by the presence of RAP. In response to this, the present paper analyzes the workability, fatigue performance, and water sensitivity of bituminous mortars containing different amounts of RAP (from 0% to 100%) and rejuvenators. Mortar specimens were compacted using a gyratory compactor and studied via dynamic mechanical analysis under three point bending configuration. The results demonstrated that the presence of RAP reduces the workability and ductility of asphalt mortars. However, it also causes an increase in their stiffness, which induces a more elastic response and causes an increase in their resistance to fatigue, which could compensate for the loss of ductility. This aspect, together with the low water sensitivity shown, when using Portland cement as an active filler, would make it possible to produce asphalt materials with high RAP contents with a similar long-term mechanical performance as traditional ones. In addition, the use of rejuvenators was demonstrated to effectively correct the negative workability and ductility impacts caused by using RAP, without affecting the fatigue resistance and material adhesion/cohesion.