While almost 99 percent of Virginia’s roadway network has an asphalt surface, not all of those roads are asphalt from top to bottom. Many of the interstate and primary roads from Northern Virginia to Richmond to the coast have a concrete layer underneath the asphalt; the original concrete pavement was eventually overlaid with asphalt to address structural failures and improve the functional condition (i.e., ride quality) of the roadway. When concrete is overlaid with asphalt, it’s known as a composite pavement. While these asphalt overlays did improve the road, much of the time the overlay projects did not address the cause of the original pavement failures – moving and deteriorated joints/cracks. As such, these failures work their way to the surface and lead to further maintenance and rehabilitation needs.

 

Since the 1990’s, Stone Matrix Asphalt (SMA) has been used to overlay most of Virginia’s concrete and composite pavements. Using polymer modified binders and higher asphalt contents, SMA delays the onset of reflective cracking, but it does not eliminate it. The delay does reduce the overall cost to VDOT and the user, but can the time between resurfacings be extended? 

 

Since 2014, VDOT and industry have been exploring the use of highly polymer modified asphalt binders in conventional asphalt and SMA. The first project performed in Virginia was in a subdivision in Northern Virginia. The goal was to explore the viability of producing and placing this material in an SM-9.5. From this initial installation, VDOT has used this material on I-95 and recently on Phase I of Interstate 64 in the Hampton Roads District. In next month’s newsletter, the experiences learned from the Phase I project will be shared. To date, Phase I is by far the largest project using highly polymer modified binder in Virginia and the United States.