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Crumb rubber modification (CRM) is an effective means of improving neat asphalt performance. Numerous studies have investigated the effects of CRM using the current Superpave® laboratory tests. Recent studies have shown that the assumption of linear viscoelastic behavior or employing insufficient stress or strain levels makes current tests inadequate for properly assessing the performance of binders, especially when modified. This problem has resulted in the development of improved test methods such as the time sweep binder fatigue test and the multiple stress creep and recovery (MSCR) test for permanent deformation. The present study assesses the performance of binders modified with a wide range of crumb rubber content using these newly developed test methods. Additional binder and mixture performance tests were used to compare and validate the results. The results showed that the new tests performed well in predicting performance. Current Superpave criteria also showed good conformance with mixture test results for CRM binders. Tests results suggest that the MSCR can complement current rutting prediction testing. Also, the time sweep test produces results similar in accuracy to current Superpave tests, but it requires longer testing time and is thus not recommended for performance grading.

No 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.