Viscosity mixing rules for asphalt recycling
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abstract
Forty-seven aged asphalt-softening agent pairs were blended at multiple levels of aged material content. The relationship between 60C low-frequency limiting viscosity and aged material mass fraction for 45 of the asphalt-agent pairs can be described using the Grunberg model. The value of the viscous interaction parameter is a strong function of the viscosity difference between the aged asphalt and the softening agent. A normalized Grunberg model was developed to eliminate this dependency. An average normalized interaction parameter can be used to generate a 'universal' mixing rule for commercial-type recycling agents. This new mixing rule was compared to the Epps mixing rule and the mixing rule specified in ASTM D4887. Comparison was based on the ability of each mixing rule to predict the quantity of softening agent required to produce blends with a specific target viscosity. It was concluded that for low-viscosity asphalt softening agents, the method specified in ASTM D4887 should be used. However, for supercritical fractions and commercial recycling agents, the universal normalized Grunberg mixing rule developed in this study is superior to the other two mixing rules.
