Asphalt Rubber Technology Information Center
Characterization of Asphalt Cements Modified with Crumb Rubber from Discarded Tires
Daly, William H. and Negulesce, Ioan I.  
January, 1997  
Key Words:

Blends with up to 20% ground vulcanized rubber (both crumb and 200 mesh powder particles) from recycled tires were
prepared with asphalt cements of various grades (AC-5 to AC-30) and evaluated using dynamic mechanical analysis
(DMA).  Blends produced from powdered rubber particles exhibited Newtonian behavior at high temperatures.  Similar
behavior was not observed with crumb rubber blends.  The mechanical properties of asphalt-rubber blends depend upon
the concentration of rubber additives, the particle sizes, and the chemical composition of the asphalt.  The dynamic
mechanical characteristics of all blends are discussed in terms of G*sin and G”; comparative data is presented according
to the SHRP binder specifications.  Pressure aging vessel (PAV) tests of the asphalt rubber blends revealed a significant
difference between crumb rubber and powdered rubber additives.  Simple blends of crumb rubber with asphalts ranging
in grade from AC-5 to AC-30 exhibited phase separation during the thin film oven aging test.  In contrast, blends with
powdered rubber appeared to remain compatible or at least partially compatible through the PAV aging process and the
blends retained the physical properties associated with the additive.  The DMA data suggest that the low temperature
cracking resistance of asphalt/powdered rubber blends is enhanced.
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