EVALUATION OF PERMEABILITY OF SUPERPAVE MIXES IN MAINE

This study was carried out to evaluate the permeability of Superpave mixes used by the Maine Department of Transportation, and determine the effect of voids, gradation and lift thickness on permeability. A field permeameter was developed on the basis of the National Center for Asphalt Technology field permeameter, and was used for testing projects with 9.5 mm, fine and coarse, 12.5 mm coarse, 19 mm coarse, and 25 mm coarse graded mixes. Testing of cores taken from location of field testing were also conducted in the laboratory according to Florida Department of Transportation method. Samples of loose mix obtained during construction were also compacted to different thickness in the laboratory, prior to permeability testing. Results from permeability tests indicated that mixes with different gradations and nominal maximum aggregate size have significant increase in permeability at different voids in total mix content. All of the mixes tested in this project showed permeability below critical permeability at or below 5% in place construction voids. Hence, the average specified 5% construction voids in total mix or 95% of theoretical maximum density seems to be justified for Superpave coarse graded mixes used by the Maine Department of Transportation.