Why Choose Asphalt?
Asphalt has been and will be the predominant choice for paving Georgia's roads. An overwhelming 95% of Georgia's state maintained roads are surfaced with asphalt pavement, and these roads have served the taxpayers well and are still in overall great condition. In fact, two recent 3rd party studies (by the Research Foundation and the U.S. Public Interest Research Group) ranked Georgia's roads first in the nation in terms of pavement smoothness. The fact that most of the roads in the state are surfaced with asphalt is a great testimony to the understood benefits of this material. But what makes asphalt so great?
First of all, even in today’s environment, asphalt pavements are the most cost-effective option for pavement type when designs are equivalent, both in the actual material costs and the cost of traffic delays. This is true for new construction, rehabilitation, and pavement preservation. Asphalt pavements are called flexible pavements because of their ability to “flex” under traffic loads, but this term has a dual meaning. Asphalt is flexible in that it can be specifically designed for the traffic level, environmental conditions, and subgrade materials for each project. Individual lifts can be engineered to withstand rutting, fatigue cracking, and other distresses as needed. During construction, traffic control and staging are much easier; furthermore, asphalt does not need time to cure so it can be opened to traffic sooner, causing fewer delays to the traveling public.
Georgia uses a special type of open-graded asphalt mixture as the surface layer for interstates – either open-graded friction course (OGFC) or porous European mix (PEM) – to improve safety. These mixtures are designed with high air void contents to shed water off the roadway, which reduces splash and spray from vehicles traveling on wet pavements, and eliminates the hazard of hydroplaning. These benefits have been measured and quantified in other states, and the results are impressive. In 2004, the Texas Department of Transportation decided to pave a road known for wet weather crashes and fatalities with OGFC. In the year after the mixture was placed, the average number of crashes decreased by 58%, and there were no injuries or fatalities (down from 21 injuries and 5 fatalities in the previous year). What makes these statistics even more impressive is that this area had a 55% increase in annual rainfall during the year the benefits were measured. As added bonuses, these open-graded asphalt mixtures also reduce glare and improve the visibility of traffic markings on the roadway, and have been proven to reduce tire-pavement noise by 3 to 5 decibels compared to other pavement alternatives.
Asphalt pavements are excellent examples of green construction and sustainable design. In fact, the asphalt industry is America’s top recycler, reclaiming 100 million tons of asphalt pavements annually, and reusing or recycling 95% of that material. Georgia’s mixes typically have approximately 25% reclaimed asphalt included, which provides a substantial savings on material costs. Aside from reusing reclaimed asphalt pavement back into the mix, tire rubber and roofing shingles are also used in Georgia’s mixes, keeping those materials out of landfills.
Research has shown that asphalt pavements can be designed to withstand distresses only in the surface lift, and maintain an overall structure that will last indefinitely. These structures, termed perpetual pavements, can be infrequently milled and inlaid every 12 to 20 years without ever needing major reconstruction. The reclaimed material from the top lift is recycled, making perpetual asphalt pavements the ultimate in sustainable design and construction. For instance, in 2007 over 15 miles of existing asphalt pavement on I-75 near Perry were micro-milled 1¼” and overlaid with PEM after 15 years of service and no distresses in the underlying pavement structure. Now, almost four years later, this segment is still performing well. Because the underlying “E” mix was still in such good condition, the rehabilitation strategy cost only one-tenth of the original proposed project cost, which saved millions of Georgia’s taxpayer dollars. This section of I-75 is one of a multitude of asphalt pavement sections throughout the state that have been in place for many years and the pavement structure is still in great condition.
Warm Mix Asphalt
Warm mix asphalt (WMA) is a new trend in asphalt paving that is rapidly spreading across the nation. WMA, in essence, is the same as hot mix asphalt except the production and compaction temperatures are decreased by 30°F to 50°F. Additives are used to achieve adequate coating at lower temperatures, and the additive can be a chemical, wax, zeolite, or water. The initial interest in WMA technology was the lower energy and greenhouse gas emissions associated with its production, but the as the technology spread, the asphalt paving industry realized other benefits as well. WMA technology can be used to incorporate higher RAP percentages, improve compaction, increase haul distances, extend the paving season, improve conditions for paving crews, and decrease the amount of binder aging that occurs during production. In 2010 GDOT drafted a specification that allows for contractors to pave with WMA on any project under certain conditions, and let one project as WMA that was constructed on US Highway 27 in Coweta County. Contractors in Georgia placed several thousand tons of WMA, and GDOT set a minimum goal of 40,000 tons to be placed during the 2011 paving season.
Researchers have found that pavement smoothness directly affects fuel economy. Asphalt roads are held to high smoothness standards in Georgia, which can be felt when riding on a newly paved asphalt road. Not only are smoother roads better for the traveling public, but they are also better for the roadways. In fact, studies have shown that improving pavement smoothness by just 25% results in an almost 10% increase in pavement life. In 2008, 41 miles of Georgia’s I-185 were milled and inlaid with asphalt, and the smoothness of the roadway was improved by 35%. This will increase the longevity of the road, saving taxpayer money and conserving natural resources. It is also important to note that this project was completed seven months ahead of schedule (another benefit of paving with asphalt), so the traveling public was able to enjoy the smooth new roadway even sooner.
In short, asphalt pavements are economical, safe, quiet, sustainable, and smooth. With such a combination, it is easy to see why Georgia’s roads are predominantly surfaced with asphalt. For more reasons on why asphalt should be your choice, please browse our website or contact us!