Fracture Properties of Aged Asphalt Mixtures Incorporating Recycled Tire Rubber and Styrene-Butadiene Rubber at Low Temperatures

ABSTRACT A laboratory investigation was conducted to evaluate the fracture properties of aged asphalt mixtures containing recycled ground tire rubber (GTR) and styrene-butadiene rubber(SBR) modifiers at low temperatures. Asphalt mixtures were compacted by the gyratory testing machine and aged according to the SHRP short term oven aging (STOA) and long term oven aging (LTOA) procedure. An experimental program was to evaluate the effects of different modifiers and aging conditions on the indirect tensile strength, creep compliance, resilient modulus, and fracture energy of compacted asphalt mixtures.The results indicate that the fracture energy of asphalt mixtures at -10°C decreases slightly after the STOA or LTOA process in general, but the SBR-modified asphalt mixtures tend to increase at ultimate compaction condition.The GTR-modified asphalt mixtures have lower elastic stiffness (higher creep compliance intercepts) as compared with the unmodified mixtures before and after the LTOA process.The SBR-modified asphalt mixtures have higher fracture energy at -10°C than that of mixtures containing the unmodified AC-30 and the GTR-modified asphalt. Based on indirect tensile creep compliance, tensile strength, failure strain and fracture energy, the GTR and SBR-modified mixtures show a greater potential to resist low temperature cracking as compared with the unmodified mixtures.