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Gilsonite and Crumb Rubber Modified-Asphalt

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Gilsonite has been found to work well with crumb rubber-modified asphalts (CRMAs). The Crumb Rubber (CR) generally imparts excellent medium and low temperature flexibility into the asphalt binder. Hence, CRMA’s have been found to exhibit superior durability and cracking resistance even in extreme climatic conditions. These improved properties can be traced back to the enhanced elastic properties of the rubber-modified binders. The excellent low temperature properties come from the aromatic process oils in the CR, which leach out during CRMA production. In addition, the high viscosity of the CRMA allows incorporation of 6 to 12w% binder into the HMA. However, while CR modification and the enhanced binder thickness’ dramatically improve pavement durability under heavy loading and/or extreme climatic conditions the binders often exhibit a tendency to fail due to premature rutting and/or bleeding. As previously mentioned Gilsonite significantly improves the high temperature properties without sacrificing the low temperature properties to the same degree that a stiffer base asphalt would result in. Thus, Gilsonite can be very effectively utilized in mitigating bleeding and rutting versus the non-modified CRMA. Equivalent performance can be achieved at lower CR levels and asphalt contents.