Rubber concentrations on rheology of aged asphalt binders

Three different concentrations of crumb rubber were mixed with two different asphalts by means of a wet process to investigate the effect of rubber particles on the fundamental internal structure of asphalt binders with respect to their long-term aging performance. The theological properties of unaged and aged unmodified and rubber-modified asphalt binders were studied as a function of long-term oxidative aging. Master curves were constructed by shifting the aging time-frequency data to assist in the interpretation. A generalized power-law model used in neat asphalt based on the time-temperature superposition principle was applied to construct the master curves of the theological parameters. Based on a limited study, the results indicate that the amount of rubber particles added into the asphalt binder is asphalt dependent. The results also show that the stiffness effect of crumb rubber to one less-compatible asphalt is higher than the other highly compatible asphalt. Addition of crumb rubber to both asphalts reduced viscosity buildup with aging. In addition, rubber modification dramatically increased the elasticity of both asphalts. It is possible that rubber modification will improve rutting resistance because of the increased viscosity and elasticity at high temperatures and will improve fatigue resistance by either decreasing viscosity or lowering viscosity buildup with aging at low temperatures.