Abstract
Unmodified and crumb rubber modified mixes conforming to the Arkansas State Highway and Transportation Department Type II surface course specifications were designed for heavy traffic conditions and environmental conditions typical to Arkansas by using the Marshall and Superpave Level I methods. Specimens prepared at appropriate design asphalt contents were evaluated for both volumetric and performance considerations. Three mix types, an unmodified hot-mix asphalt concrete, a dry process rubber modified asphalt, and a wet process asphalt rubber, were included in the investigation. For the asphalt cement, crumb rubber, aggregate type, and aggregate gradation used, the design asphalt content and the VMA were reduced for the SHRP Level I method relative to the Marshall method. Incorporation of crumb rubber into hot-mix asphalt concrete provided increased rutting resistance; however, the rubber modified mixes did not show enhanced resilient and tensile properties when tested at 25°C. Also, the performance-related properties of the SHRP Level I asphalt-rubber mixes (5, 10, and 15 percent A-R blends) evaluated did not differ significantly at 5 percent level of significance.
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