Suggested Citation:
Liang, Yanlong, Mohammad Zia Alavi, David Jones, John T. Harvey (2018) Development of Performance Grading Testing Procedures for Asphalt Rubber Binders Containing Large Rubber Particles. Transportation Research Board 97th Annual Meeting

Asphalt rubber binder is a durable pavement material incorporating rubber from waste tires, but its use is limited because the current Superpave Performance Grading (PG) testing methods are not appropriate for measuring the properties of binders that contain particulates, in this case large rubber particles. In California, rubber particles up to 2.36 mm in size are permitted in asphalt rubber binders. These particles are considerably larger than the accepted limits of standard parallel plate geometry (<250 micron particle sizes for 25 mm plates with 1 mm gap). The large rubber particles can contact the plates and dominate the measured rheology results. An alternative method using a concentric cylinder geometry with 6 mm and 9.5 mm gaps was investigated and compared with the parallel plate geometry in previous studies. The research discussed in this paper covers further additional testing to refine the method. ANOVA results confirm that the new geometry is potentially appropriate for asphalt rubber binder tests at high and intermediate temperatures, and provide realistic rheological values. As part of the test development, the Rolling Thin Film Oven test was modified, based on actual plant production temperatures, to better simulate the short-term aging of the binder. The Bending Beam Rheometer beam preparation mold was also modified to facilitate pouring the stiffer binder to produce more consistent beams for testing. The final phase of testing will compare binder properties with mix performance test results to validate that PG gradings determined using the proposed procedure are representative of field performance.

Key words: Asphalt rubber, bituminous binders, crumb rubber, particles, performance tests