Evaluation of Highly Polymer-Modified Asphalt Mixtures: Phase I

About the report:

Reflective cracking in asphalt overlays placed over jointed concrete pavement has been a concern of the Virginia Department of Transportation (VDOT) for years. Although there are many techniques to delay crack propagation through an asphalt overlay, they may require specialized equipment, unique mix designs, or other specific mixture additives. The introduction of highly polymer-modified (HP) binders to the market brings forward a new potential crack mitigation method requiring only the use of the HP binder in an asphalt mixture to provide mitigation.

Before asphalt mixtures with HP binder were used on a jointed concrete overlay project, a trial project to evaluate the constructability and laboratory performance of a mixture using this type of binder was conducted. The trial project compared an asphalt surface mixture with an HP binder and a standard surface mixture (control) in a mill and resurfacing pavement project in a subdivision in Northern Virginia. The asphalt surface mixture with the HP binder was found to be constructible without major changes in paving operations; in addition, the laboratory performance was equivalent or superior to that of the control mixture.

The results were promising enough to support investigating the use of HP binders in asphalt mixtures over jointed concrete as a reflective crack mitigation technique or when deemed appropriate as a tool for increased crack resistance. The study recommends that VDOT consider the use of asphalt mixtures with HP binders as a tool for increased crack resistance when deemed appropriate by the appropriate VDOT decision maker (e.g., the district materials engineer). The study also recommends that the Virginia Transportation Research Council and the VDOT districts with concerns about reflective cracking potential in asphalt overlays investigate the use of HP mixtures as a reflective crack mitigation layer.

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