Effect of Mix Ingredients on Performance of Rubber-Modified Asphalt Mixtures Author(s): Takallou, H.B.; McQuillen, Jr., J. and Hicks, R.G. Origin: Alaska Date: May, 1985 Categories: Performance Key Words: rubber-modified asphalt, reclaimed rubber, modulus fatigue, layered analysis Summary: 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.