Long before “sustainability” became an eagerly pursued part of the American business plan, the asphalt industry initiated research and field practices that have constantly enhanced the viability of asphalt as an environmentally sound building material.
To date, the monumental accomplishment of this initiative lies in recycling. Asphalt is the most recycled material in America. About 100 million tons of old pavement are reclaimed every year, with about 60 million tons reused in new asphalt mixes, and some 40 million used in other pavement-related applications, such as aggregate road base. Reclaimed asphalt pavement is commonly referred to as RAP.
Asphalt pavement is unique not only in the volume recycled, but also its renewability. It is comprised of approximately 95 percent aggregates (stone, sand and gravel) and about 5 percent asphalt cement. When asphalt pavement is reused in a new asphalt mix, the old asphalt cement is rejuvenated so that it becomes an active part of the glue that holds the new pavement together, just like the old aggregate becomes part of the aggregate content of the new mix. These singular properties make asphalt a uniquely renewable pavement.
Powering the trend to recycling/reusing asphalt is economics. Decades of research and engineering have improved the cost efficiency of converting old asphalt into a reusable resource that has tangible value. Today, pavement engineers, government agencies and contractors regard old asphalt as an asset, not waste, and the trend to recycling and reuse continues to gain momentum as a result.
The industry has worked on other technologies that reduce air emissions including greenhouse gases and other contributors to climate change. These technologies include warm-mix asphalt, with lower emissions due to reduced temperatures, and long life pavements which reduce greenhouse gas emissions by reducing the frequency of repair and replacement.
And modern asphalt technology has delivered asphalt pavement designs that actually enhance the quality of stormwater runoff even as they improve driving safety by reducing the amount of spray produced by vehicle tires.
Past, current and future advancements in asphalt as an environmentally sustainable paving material are especially important because asphalt is such a primary component of America’s transportation system and because the quantities of material used annually are so large.
Of the 2.6 million miles of paved roads in the United States, over 94 percent are surfaced with asphalt. Approximately 85 percent of the nation’s airfield pavements and 85 percent of the parking lots are also surfaced with asphalt. There are about 4000 asphalt mixing plants located in the United States and the industry employs, directly or indirectly, 300,000 U.S. workers. Because of the vast extent of use of this material, even small changes in asphalt pavement technology can make a big difference in terms of greenhouse gas emissions.
Black and Green, Sustainable Asphalt, Now and Tomorrow, National Asphalt Pavement Association, Special Report 200, September 2009
 Hansen, K., and D. Newcomb, RAP Usage Survey, National Asphalt Pavement Association, Lanham, Maryland, August 2007.