PERFORMANCE OF POLYMER-MODIFIED ASPHALT-AGGREGATE MIXTURES IN ALASKA

Polymer-modified asphalts are used in Alaska to address problems with rutting, cracking, and premature aging. This usage raises two important issues—the improvement of the pavement performance with polymer modification while maintaining the ability to properly place and compact polymer-modified mixes. This study addresses both issues. Base asphalts and polymer-modified binders were analyzed for storage stability, compatibility, and consistency using traditional and Superpave tests. Thermal stress restrained specimen tests and Georgia wheel rutting tests were conducted for asphalt-aggregate mixtures. The test results indicate that polymer-modified asphalts should always be an end result of an extensive product development program. The premanufactured binders had the best performance and workability. The polymer modification improved the performance of all base asphalts in several polymer-asphalt combinations. Some binders smoked excessively during mixing, which warrants further research. A storage stability test should be added to specifications or the contractor should address the storage stability with techniques such as tank circulation. On the basis of the test results, the Superpave PG grading needs to be adjusted for polymer-modified asphalts.