Resiliency and sustainability—some of asphalt’s greatest (but lesser-known) benefits
There are plenty of reasons agencies and contractors choose to pave with asphalt—from lower lifecycle costs, to greater opportunity for minimally-invasive rehabilitation, to faster opening to the driving public. Resiliency and sustainability are two more reasons asphalt should be your pavement of choice.
When we use the word resiliency, we’re referring to a community’s ability to recover from natural disasters such as hurricanes, floods, landslides, fires or earthquakes. Roads that are damaged by such disasters severely limit response and recovery efforts.
In considering road construction options that promote resiliency, asphalt pavement is the clear winner. It is the fastest application for road construction and repair, allowing miles of surface to be constructed in a single shift, and roadways to be opened to traffic immediately in most cases. In addition, many asphalt plants are portable so they can be situated near the construction site and be fully operational within a 24-hour period. Asphalt is also less rigid than other construction options like concrete, resulting in greater flexibility and more resistance to cracking when disasters do occur.
Asphalt proved its benefits in response to severe damage caused by catastrophic flooding in Colorado in 2013. Seventeen inches of rain in just a few days wiped out entire sections of roadway and cut off communities like the Town of Estes Park from critical resources. The Colorado Department of Transportation quickly partnered with paving contractors who immediately hauled in rock crushing equipment and set up asphalt plants. The pavers worked non-stop to get the roads to the mountain communities open before winter.
“Obviously, asphalt is the fastest response method,” Tom Clayton of the Colorado Asphalt Pavement Association said. “It lets you get in there and get the roads built, as people were cut off in their homes. People live up and down the canyons, and after the roads were cut off, they were either stranded in their house if they were lucky to be high enough, or they couldn’t get back to their houses after they evacuated. The governments wanted to provide access as soon as possible, and trying to do that with any other pavement but asphalt would not have worked.”
Closer to home, Oregon coastal communities deal with road failures caused by shifting earth on a regular basis. Just last summer a culvert failure under Highway 101 south of Wheeler caused a large sinkhole right before the Fourth of July. ODOT was forced to close the highway. Within 2-1/2 days and in time for the holiday weekend, Bayview Transit Mix of Astoria was able to repair the culvert (which was 20 feet below grade), place base rock, pave the surface, and open the Highway.
Even if a disaster prevents making asphalt locally, research conducted at Mississippi State University for the Department of Homeland Security has shown that warm-mix asphalt mixtures can be made several hours away and trucked to the disaster zone to successfully rebuild pavements.
When we think about sustainability as it relates to asphalt, it’s usually about asphalt’s ability to be constructed using recycled materials, and for the asphalt pavement itself to be rehabilitated or recycled. There are sustainability features related to warm mix asphalt pavement and porous asphalt pavement structures as well. But these are not the only ways asphalt contributes to sustainability.
The condition of a road significantly impacts vehicle maintenance and fuel costs. Rolling resistance, which considers stiffness, surface texture and smoothness of the road, influences these costs. Of these traits, smoothness–measured by the number of irregularities like cracks, potholes and bumps in the pavement–has the greatest cost impact.
A 2012 report from the National Cooperative Highway Research Program (NCHRP Report 720) estimates that fuel efficiency can drop as much as 2 to 6 percent for rough pavements. Similarly, rough pavements can increase tire wear by 5 percent, and repair and maintenance costs by 70 percent, for a total net vehicle operating cost increase of 22 percent with all factors considered.
Smoother pavements provide cost benefits for the agency responsible for the structure as well. Studies show that improving pavement smoothness (and thereby reducing wheel bounce on the pavement structure) by 25 percent can increase a pavement’s longevity by almost 10 percent.
Asphalt pavement is the smoothest option because it is placed continuously without the need for expansion joints, and surface overlays or inlays quickly restore smoothness in older pavements and provide like-new conditions, which are benefits that most other preservation treatments can’t provide.
Asphalt provides many advantages over other materials. Resiliency and sustainability are just two more examples of how asphalt provides greater benefit for the agency, taxpayer and driving public.