While the terminology, "Perpetual Pavement," has only been around since 2000, the concept has been around for more than 50 years.
Haskell Lemon Construction Co., an Oklahoma City-based paving contractor that recently completed the first officially-let Oklahoma Department of Transportation Perpetual Pavement project (see story on page 12), is very familiar with constructing and maintaining full-depth hot mix asphalt pavements. As Larry Lemon, chairman of Haskell Lemon Construction, points out, Oklahoma began constructing full-depth HMA pavements -"Perpetual Pavements" if you will - 40 to 50 years ago, and ODOT is proud to report that those pavements continue to perform well today with only an occasional "mill and fill" surface overlay renewal. Interstate highways running through the heart of Oklahoma City are in fact full-depth asphalt pavements that were originally constructed in the '60s and have withstood the daily traffic grind for over 40 years.
There are other examples of long-lasting full-depth HMA pavements across the country that have also performed as well as the Oklahoma pavements, and the construction and materials used to build those sturdy roads is a strong testament of the benefits Perpetual Pavements offer road agencies, the driving public and taxpayers.
As Lemon put it, "If you have a good base, there's no reason why an asphalt road can't last forever." Granted, the surface will require maintenance just because the liquid asphalt binder will oxidize from the sun and weather, which will cause it to lose its elasticity, and daily traffic loads will begin to stress the brittle wearing course. But if a road agency only has to mill a couple of inches off the pavement every 15 years or so and replace it with a new HMA wearing course, it's a much more economical way to maintain the integrity of the original road and minimize traveling interruptions.
Many road agencies from across the country are well aware of these benefits, and while the initial costs to construct a Perpetual Pavement are similar to constructing a road out of Portland cement concrete, the long-term economics weigh in favor of the Perpetual Pavement. What road agencies really like about the Perpetual Pavement concept is that when it does come time for mill and fill maintenance, the process can be accomplished without a major disruption to traffic flow. The old surface can be milled off one day and the new surface placed the next. For Haskell Lemon Construction, as well as many asphalt contractors across the country, much of that work is done at night to further mitigate disruptions to commuter traffic. "We've already milled and paved in the same night and motorists often wonder when the new road was put in, because they never saw anybody working on it," Lemon notes.
So call it full-depth HMA or Perpetual Pavement - the industry, road agencies and taxpayers all know this road construction concept is an economical and good-performing design with an extendable life cycle that in all respects is perpetual as long as the base maintains its structural integrity. And whenever that occasional new surface course is required, the road will continue to deliver a smooth ride for years to come.