Environmental Advantages / LEED

Sustainability

Asphalt is the sustainable material for constructing pavements. From the production of the paving material, to the placement of the pavement on the road, to rehabilitation, through recycling, asphalt pavements minimize impact on the environment. Low consumption of energy for production and construction, low emission of greenhouse gases, and conservation of natural resources help to make asphalt the environmental pavement of choice.
 

Asphalt for Recycling and Energy Reduction

Asphalt pavements are America’s most recycled product. According to the U.S. Environmental Protection Agency and the Federal Highway Administration, about 90 million tons of asphalt pavement is reclaimed each year, and over 80 percent of that total is recycled.

Reclaimed asphalt pavement (RAP) can be recycled into pavement that is as high, or even higher, in quality as pavements made of all-virgin materials. And, the same material can be recycled again and again; it never loses its value. The asphalt cement—the glue that holds the pavement together—retains its ability to function as glue or cement, so that it is reused for its original purpose. The aggregates (rocks, sand, and gravel) in the original pavement are also conserved. Many pavements that are more than 20 years old are actually worth more than they were when originally constructed.

It is estimated that recycling of asphalt pavements saves the American taxpayer $1.8 billion per year. It also saves hundreds of acres of landfill space each year.

Materials from other industries are routinely recycled into asphalt pavements instead of going into landfills. Some of the most common are rubber from used tires, glass, asphalt roofing shingles, and blast furnace slag.

Asphalt plants also recycle the fine mineral particles that are generated in the process of producing asphalt pavement material. This routine recycling of co-generated material helps to conserve natural resources.

Asphalt for Better Water Quality

Porous asphalt can help improve water quality. These pavements . . .

• Conserve water
• Allow for better use of land
• Reduce runoff
• Promote infiltration
• Clean stormwater
• Replenish aquifers
• Protect streams

Porous asphalt offers a powerful tool in the toolbox for stormwater management.

In the natural environment, rainfall sinks into soil, filters through it, and eventually finds its way to streams, ponds, lakes, and underground aquifers. The built environment, by way of contrast, seals the surface. Rainwater and snowmelt become runoff which may contribute to flooding. Contaminants are washed from surfaces directly into waterways without undergoing the filtration that nature intended.

For these reasons, managing storm water is a significant issue in land use planning and development. Storm water management tools can serve to mitigate the impact of the built environment on natural hydrology. Unfortunately, however, they also can lead to unsound solutions such as cutting down stands of trees in order to build detention ponds.

Porous asphalt pavements allow for land development plans that are more thoughtful, harmonious with natural processes, and sustainable. They conserve water, reduce runoff, promote infiltration which cleanses stormwater, replenish aquifers, and protect streams.

A typical porous pavement has an open-graded surface over an underlying stone recharge bed. The water drains through the porous asphalt and into the stone bed, then, slowly, infiltrates into the soil. If contaminants were on the surface at the time of the storm, they are swept along with the rainfall through the stone bed. From there they infiltrate into the sub-base so that they are subjected to the natural processes that cleanse water.

Asphalt for Clean Air and Cool Cities

Asphalt plants are environmentally sound
Emissions from asphalt plants, including greenhouse gases, are very low and well-controlled. Since 1970, the asphalt industry has decreased total emissions from plants by 97 percent while increasing production by 250 percent. Emissions from asphalt plants are so low, the EPA considers them as only minor sources of industrial pollution.

Cool Cities
The urban heat island effect is not a black and white issue. Porous asphalt pavements have been shown to lower nighttime surface temperatures as compared to impervious pavements. In at least one city, the hottest heat signature is at the airport, with its thick, dense, impervious runways.

Traffic relief
When cars and trucks are mired in congestion, they consume fuel and produce greenhouse gases. Asphalt's speed of construction allows planners and managers a way to fix congestion hot spots and bottlenecks, quickly and cost-effectively.

Asphalt for Performance

One of the keys to sustainability is long life. With Perpetual Pavements, asphalt pavements have an extremely long lifespan.

A Perpetual Pavement is constructed so that distress occurs in the the top layer only. The only rehabilitation required is removal of the surface and resurfacing with an asphalt overlay. Using current pavement technologies, this can be done on an infrequent basis - every 15 to 20 years. The reclaimed material is then recycled. Perpetual Pavement is the ultimate in sustainable design and construction.

While the Perpetual Pavement name is relatively new, the concept is not. In fact, more than 50 pavements have received the Perpetual Pavement Award since 2001. These award-winning roads, streets, highways and airport runways have been in place for at least 35 years, with a minimum of maintenance and no full-depth reconstruction.

Material produced by the National Asphalt Pavement Association, Lanham, MD