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Interstate 70 is one of the most heavily traveled East-West interstate highways in the county. Increased traffic due to population growth of the eastern metro Indianapolis area had taken its toll on a stretch of the interstate that runs through Greenfield, Ind.
The existing composite pavement had an underlying portland cement concrete (PCC) pavement with five inches of asphalt concrete over it. The asphalt had deteriorated due to surface water infiltration that weakened the pavement foundation layers and enabled fines pumping, erosion, and freeze/thaw damage. To rehabilitate the roadway, all asphalt was milled to the old PCC surface, so that it could be replaced.
To ensure that the rehabilitation provided long-term benefits, the Indiana Department of Transportation (INDOT) wanted a solution that would mitigate cracking from the PCC pavement that could reflect up into the new overlay. The worst PCC joints were patched. Moderately stable joints were covered with strips of Petrotac® to extend the life of the replacement overlay. Petrotac is a self-adhering paving membrane interlayer designed to retard reflective cracking through stress absorption/attenuation.
Along a 7.5 mile stretch of the interstate, existing joints and other cracks were filled, a primer was applied directly to the milled surface, and Petrotac strips were applied over select joints and cracks on the PCC pavement. The contactor then pneumatically rolled the installed Petrotac strips to maximize adhesion to the pavement.
A number of less active and spalled joints and cracks remained. Petromat® Enviro was also included in the design to provide a full pavement moisture barrier and stress absorption interlayer. INDOT had previously used Petromat Enviro on a section of Interstate 65, and was pleased with the performance and ability to extend the life of the pavement. INDOT also liked that the paving fabric can be milled and recycled.
A tack coat of 0.26 gallon/square yard of PG64-22 was sprayed onto the milled pavement and over the Petrotac strips. Next, Petromat Enviro was applied, and then the intermediate HMA course was placed. Finally, the wearing surface course of asphalt cement was placed to complete the rehabilitation.
The strategy of using Petrotac over the worst joints and cracks, followed by a full width installation of Petromat Enviro provides the pavement with a one-two punch that will greatly extend the life of the replacement overlay.