A growing concern in the development community is for construction that exhibits good environmental stewardship. That is, practices that conserve resources in a manner that allow growth and development to be sustained for the long-term without degrading the environment. Asphalt pavements are economical, efficient and contribute to sustainability in many different ways.
Leadership in Energy and Environmental Design (LEED®)
Developed by the U.S. Green Building Council, the Leadership in Energy and Environmental Design (LEED) Green Building Rating System™ is the nationally accepted benchmark for the design, construction, and operation of high performance green buildings. LEEDpromotes a whole-building approach to sustainability by recognizing performance in five key areas of human and environmental health: sustainable site development, water savings, energy efficiency, materials selection, and indoor environmental quality. Visit www.usgbc.org
for more information on the LEED certification process.
Earning LEED® Certification
To earn certification a building project must meet certain prerequisites and performance benchmarks ("credits") within each category. Projects are awarded Certified, Silver, Gold, or Platinum certification depending on the number of credits they achieve.
How Asphalt Pavements Contribute to Attaining LEED®Credit
Asphalt pavements contribute to LEED credits in a variety of ways. Asphalt pavements are 100% recyclable. They are used and reused with each cycle of road paving. As such, credits associated with recycling and waste management are attainable. Pervious asphalt mixtures have been used in Ohio for over a generation. Research in the 1970s by the Franklin Institute launched porous (pervious) asphalt pavements, a strategy that both reduces quantity and improves quality of stormwater runoff. Credits can be attained for porous pavement use under categories for stormwater management (both quantity and quality), and heat island reduction. In recent times, coating materials have been introduced to the industry. These allow designers to express their creativity and ingenuity while at the same time improving pavement reflectance and capturing credit for heat island reduction. From conventional, to porous, to pattern-stamped, asphalt pavements provide flexibility and options to architects and engineers designing sustainable pavements.
Tables have been developed to show for the different LEED programs the potential credits attainable by using asphalt pavements. Each table provides the rating category, credit description, available points, and a discussion of the applicability/contribution that asphalt pavements have in attaining credits. This information has been provided for the following LEED programs:
It’s reclaimed asphalt pavement (RAP). In Ohio the asphalt industry recycles millions of tons of RAP into new asphalt pavement every year, the largest tonnage of any industry. And, asphalt's 80% recycling rate is higher than for any other material. Because this recycling is beneficial and economical, it happens without government mandates or subsidies. For more information on recycling, see the Flexible Pavements of Ohio Statement on Recycling, view the NCAT brochure, Reclaimed Asphalt Pavement FAQs, view the NAPA brochure "Take the RAP"
and view the article from the Fall Issue of Ohio Asphalt on "The Case for Using Reclaimed Asphalt Pavement"
For more suggestions on ways to save money in your paving program, read the NAPA Special Report 191.
What are the advantages, other than cost, of using asphalt pavement?
There really are many reasons to prefer an asphalt pavement including: smoothness, quiet, stage construction, ease of maintenance, speed of construction, least user delay cost, ease of repair of utility cuts, no cure time, recyclability and now, that technology exists to design HMA mixtures to reliably perform under any conditions of load and environment, there is no longer any reason to consider anything else.
What impact does the production and use of asphalt have on the environment?
In many respects asphalt is the environmentally friendly paving material. First, asphalt materials are 100% recyclable. Virtually all of the reclaimed Asphalt Pavement (RAP) that is removed from existing streets and highways is recycled into new asphalt. Because this recycling of asphalt is economical, it occurs without the need for government mandates or subsidies.
The use of asphalt pavement can result in environmentally friendly, sustainable development as well. For more information on this subject visit the Asphalt Education Partnership website www.beyondroads.com
and www.asphaltroads.org/Environment
HMA also has been shown to consume less energy than other materials and systems. A study done by the Asphalt Institute indicated that a comparably designed asphalt pavement required only about half the total energy to construct as a comparable portland cement concrete pavement.
Improvements in technology have been steadily reducing the airborne emissions from the production and placement of asphalt. Dust from the drying of aggregates is the major emission and is now almost totally captured and recycled. Other emissions are primarily combustion products from the burning of fuel to heat the aggregates and fumes from hot asphalt itself. Fuel burners are now much more efficient, resulting in very complete combustion. Studies to date by the government and industry have shown emissions levels to be very low. Nevertheless, the industry continues to develop improved technology for reducing emissions and minimizing exposure.
Articles relating to the environmental effects of HMA production:
SR-166, Evaluation of Stack Emissions from HMA Facility Operations;
IS-123, PS-23, Special Report #134, Study of Paving Asphalt Fumes; and,
press release ; "Asphalt Pavement is the surprise leader in recycling---"
How can asphalt help reduce noise pollution?
Highway noise is becoming a social issue with which transportation departments have to deal. Most state DOT's will build noise walls under certain circumstances in accord with federal regulations. However, in recent cases in Michigan, Pennsylvania and Arizona affected residents have demanded a change in pavement surface from concrete to quieter asphalt. The United Kingdom purposely surfaces its freeways with asphalt to reduce noise.
Many studies over the years have shown that sound produced at the tire-pavement interface with asphalt pavements lacks the level of annoying frequencies commonly generated from concrete pavement surfaces. Special asphalt surfaces, such as open-graded friction course (OGFC) and stone matrix asphalt (SMA) reduce highway noise at the source even further.
Warm Mix Asphalt (WMA) is a term being used to describe several different technologies that are being used to produce hot-mix asphalt (HMA) paving mixtures at significantly lower mixture and placement temperatures. Potential advantages of these technologies include: lower energy consumption; lower fumes, odors and emissions; easier placement and less aging of the binder from exposure to heat. For a complete description of this developing technology visit www.warmmixasphalt.org
or the FHWA site http://www.fhwa.dot.gov/pavement/asphalt/wma.cfm