Recommendation of RILEM TC 264 RAP on the evaluation of asphalt recycling agents for hot mix asphalt

Abstract

This recommendation is based on the results of an inter-laboratory study organised by the RILEM technical committee TC 264-RAP "Asphalt Pavement Recycling"—Task Group 3 (TG3) focusing on Asphalt Binder for Recycled Asphalt Mixture. The TG3 aimed to evaluate the effect of a specific family of materials known as asphalt recycling agent (ARA) on the aged binder under different configurations. Even though ageing is an irreversible phenomenon, effective ARA must have the capability to improve the flexibility of the bituminous materials and their resistance against cracking susceptibility with no adverse effect on the rutting resistance of pavements containing reclaimed asphalt. A total of 17 participating laboratories analysed the properties of binder blends composed of aged binder from reclaimed asphalt in three different contents (60, 80, 100%), ARA and virgin binder. The physical properties of the blends were thoroughly evaluated through traditional and rheological binder testing. This recommendation proposes to restore the original material properties at low and intermediate temperatures (i.e. cracking resistance) while balancing the high-temperature characteristics (i.e. rutting susceptibility) with durable impact throughout the progression of ageing phenomena. Therefore, useing of the Dynamic Shear Rheometer is foreseen as a more suitable and sustainable means to evaluate binder blends containing an asphalt recycling agent. Compared with conventional testing, the proposed approach requires fewer materials while resulting in a faster experimental procedure with one single test.

Effect of Fractionation Process and Addition of Composite Crumb Rubber-Modified Asphalt on Road Performance Variability of Recycled Asphalt Mixtures with High Reclaimed Asphalt Pavement (RAP) Content

“…The cylindrical specimens with a diameter of 100 mm and a height of 63.5 mm were prepared for the indirect tensile (IDT) test. Considering that the actual load acting on the pavement is constant and the deformation of the pavement grows with the growth of the constant load, the stress-controlled mode was used to perform the IDT test at 25 • C. To obtain the fatigue life of RAM, the average indirect tensile strengths of the different types of mixtures under dry conditions were first obtained from the IDT test, and then the stress ratio (0.25) for the fatigue test was determined [32,33]. Finally, the fatigue life was obtained based on the vertical permanent strain curve of the asphalt mixture, which was used to evaluate the medium-temperature fatigue performance of RAM.…”

Low temperature performances of fiber-reinforced asphalt mixtures for surface, binder, and base layers

“…It was found that different types of fiber can ultimately lead to an increment in moisture, fatigue, and rutting resistance performance in asphalt mixtures containing high content of RAP (Fakhri and Hosseini, 2017;Wu et al, 2020;Ziari et al, 2020Ziari et al, , 2021. In Europe, up to 50% RAP can be recognized as high RAP content (EAPA, 2022;Hugener et al, 2022). Hence, it was validated that the use of fiber could reinforce the performance properties of AC and PA mixtures, with and without RAP, at intermediate and high temperatures.…”

Effect of Blending Behavior on the Performance of Hot Recycled Asphalt Mixtures

“…The findings revealed that the fine particles within the RAP aggregates were not adequately separated from the original aggregates, resulting in decreased mixture density and increased void content [40][41][42]. Other relevant studies have demonstrated that the role of mineral particles and asphalt in RAP differs from that in conventional mixtures, leading to deviations in the expected gradation and compromising pavement compaction quality [43,44]. The RAP in the mixture can result in poorer performance if conventional design methods are applied.…”