Asphalt Rubber Technology Information Center
Effect of Mix Ingredients on Performance of Rubber-Modified Asphalt Mixtures
Takallou, H.B.; McQuillen, Jr., J. and Hicks, R.G.  
May, 1985  
Key Words:
rubber-modified asphalt, reclaimed rubber, modulus fatigue, layered analysis  
This research project consisted mainly of a laboratory study of mix properties as a function of variables, such as rubber
gradation and content, void content, aggregate gradation, mix process, temperature, and asphalt content.  Twenty
different mix combinations were evaluated for diametrical modulus and fatigue at two different temperatures (-6°C,
+10°C).  Layered theory was used to evaluate the effects of mixture variations on pavement life.  The information
resulting from the study was used to develop guidelines for use of rubber asphalt mixes in Alaska.
The findings of this study indicate that the rubber gradation and content, aggregate gradation, and use of surcharge
during sample preparation have considerable effect on modulus and fatigue life of the mix.  Also, due to greater
allowable tensile strain in rubber-modified mixtures, the thickness of the modified mixture can be reduced, using a layer
equivalency of approximately 1.4 to 1.0.  An economic comparison between rubber asphalt and conventional mixtures
constructed in Alaska indicated that rubber mixes are slightly less cost effective.  Other reported benefits of
rubber-modified mixes, such as noise and ice control, were not included in the analysis.
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