Trackless Tack Coat Materials: A Laboratory Evaluation for Performance Acceptance

About the report:

The purpose of this study was to develop, demonstrate, and document laboratory procedures that could be used by the Virginia Department of Transportation (VDOT) to evaluate non-tracking tack coat materials.  The procedures would be used to qualify candidate material formulations for field validation. 

The procedures were developed and were demonstrated through an evaluation of five “trackless” tacking materials and two conventional tacking materials.  The evaluation demonstrated that the trackless materials outperformed the conventional materials in the laboratory tracking test and in the bond performance tests for tensile and shear strength.

The study recommends that VDOT formalize the described laboratory procedures to produce a Virginia Test Method to qualify candidate non-tracking tack coat materials for field verification.  It further recommends that VDOT formalize the field verification system and includes general direction on the elements to include in that process. 

This work is part of a program of research designed to support a move to performance-oriented specifications for the interlayer bond for pavement construction.  The non-tracking tack coat materials investigated in this study are expected to facilitate the improved performance of this bond and, as a consequence, the pavement system as a whole.  This work supports an anticipated incremental improvement to an annual asphalt concrete program that is worth between $200 million and $400 million per year (not including new construction).  When applied to investments on this scale, even nominal improvements easily translate into considerable savings.

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