In recent years, cold recycling techniques have been widely used all over the world thanks to their huge environmental advantages. However, their performances are lower than the traditional hot-mix asphalt, both for the longer time to develop the final mechanical properties, which leads to delays in the reopening to road traffic, and for the lower fatigue resistance. The present paper deals with the characterization of cold recycled asphalt mixtures (CRAM), made with 100% reclaimed asphalt pavement, where synthetic fibers were included to improve the fatigue performance. The investigation involved the analysis of the curing time, volumetric properties, stiffness, strength, rheological behavior and resistance to cyclic loading. The results showed that the use of synthetic fiber, with the optimum dosage, determined a higher CRAM performance, especially in terms of fatigue resistance.

In recent years, the increased use of heavy commercial vehicles with higher axle weights has required the development of innovative technologies to improve the mechanical properties of asphalt concrete conglomerates, such as fatigue resistance and rutting. This study offers a comprehensive comparative analysis of different types of asphalt concrete tested in four trial sections (S1, S2, S3, S4) of the SP3 Ardeatina rural road in Rome, under actual traffic and operational conditions. More precisely, the pavement technologies applied include modified asphalt concrete with graphene and recycled hard plastics for S1, asphalt concrete modified with styrene–butadiene–styrene (SBS) for S2, asphalt concrete with a standard polymeric compound for S3, and traditional asphalt concrete for S4. The evaluation approach involved visual inspections in order to calculate the pavement condition index (PCI) and falling weight deflectometer (FWD) tests. In addition, back-calculation analyses were performed using ELMOD software to assess the mechanical properties. The laboratory tests revealed superior properties of M1 in terms of its resistance to permanent deformations (+13%, +15%, and +19.5% compared to M2, M3, and M4, respectively) and stiffness (10,758 MPa for M1 vs. 9259 MPa, 7643 MPa, and 7289 MPa for M2, M3, and M4, respectively). These findings were further corroborated by the PCI values (PCI_S1 = 65; PCI_S2 = 17; PCI_S3 = 28; PCI_S4 = 29) as well as the FWD test results after 5 years of investigation, which suggests greater durability and resistance than the other sections.

Nowadays, the most widespread solutions to increase the sustainability of bituminous mixes deal with the recycling of reclaimed asphalt pavement (RAP) and the use of warm mix asphalt (WMA). However, the possibility of combining RAP recycling and WMA technologies needs to be further investigated and validated. This comprehensive laboratory study aimed at assessing the feasibility of recycling RAP in WMA mixes without compromising performance. For this purpose, WMA containing 40% RAP was produced by using softer virgin bitumen (160/220), to compensate for the high stiffness and viscosity of the RAP binder, and a WMA chemical additive. The mix was designed and characterized in terms of indirect tensile strength, water sensitivity, complex modulus, resistance to low-temperature cracking, resistance to rutting at high temperatures, and fatigue resistance. Its mechanical properties were compared with those of ordinary HMA made with virgin bitumen (50/70) and aggregates. The experimental results showed that the WMA+RAP mix had comparable volumetric properties with respect to the reference HMA despite its reduced production temperatures. Moreover, WMA+RAP exhibited similar or improved mechanical performance, with enhanced resistance to water damage, rutting, and fatigue cracking, without penalizing low-temperature behavior.