Asphalt Rubber Technology Information Center
Effect of Crumb Rubber Particle Size and Content on the Low Temperature Rheological Properties of
Gopal, Venu T.; Sebaaly, Peter E. and Epps, Jon
Mix Properties
Key Words:
crumb rubber, Superpave, rheological properties, creep stiffness, logarithmic creep rate, thermal cracking, low
temperature properties
This paper presents a study to evaluate low temperature rheological properties of crumb rubber modified binders and
the impact of the particle size and content on such properties.  Three sizes of the crumb rubber (0.18, 0.425 and 2.0 mm),
a control (0%) and two levels of crumb rubber content (12% and 24%) were used with four asphalt binders. The
measured rheological properties consisted of creep stiffness (St) and logarithmic creep rate (m). Results showed that:
increasing the crumb rubber content decreased the creep stiffness which improves thermal cracking resistance. The
impact of crumb rubber content on the m-value was very highly inconsistent. The crumb rubber size did not have
significant effect on the low temperature properties. The effect of the size of the crumb rubber on the resistance to
thermal cracking was dependent on the asphalt binder source. The analysis of the data generated in this experiment
showed that some combinations of crumb rubber size and content can either improve or jeopardize the PG low
temperature of the asphalt binder.
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