Sustainability

Introduction

Asphalt is the pavement of choice for sustainability. It’s 100 percent reusable and recycled at a higher rate than any other material in America — including soda cans and newspaper. In fact, more than 99 percent of asphalt reclaimed from old roads and parking lots goes back into new pavements.1

In addition, asphalt pavements are able to use waste and byproducts from other industries — reducing environmental impacts. Instead of going to landfills, materials such as rubber from used tires, glass, asphalt roofing shingles and blast furnace slag can all be put to use in asphalt pavements.2 Over nearly 2.8 million tons of these materials were used in asphalt mixtures in 2013.1

Asphalt pavements require less energy3 to produce and their production generates less material waste19 than other paving materials, and its production emits fewer greenhouse gases than concrete pavement.4 In fact, the asphalt binder used to make asphalt pavements is a result of fossil fuels that were never burned and put to energy uses, such as diesel fuel or gasoline. Thus, the inherent CO2 is never released into the atmosphere. According to the U.S. Environmental Protection Agency (EPA), 99.6 percent of the carbon in asphalt binder is stored instead of contributing to greenhouse gases.5 Not only are asphalt pavements a very effective means of sequestering carbon, the production of liquid asphalt from the heaviest fraction of a barrel of oil is much less energy intensive than trying to convert it to a fuel for energy use.6

Beyond these benefits, full-depth porous asphalt pavements can be an important tool for stormwater management and have even shown to help filter water to keep pollutants out of the environment.7,8 The use of an open-graded friction course atop a dense-graded asphalt pavement has helped to filter water running off a roadway,9 reducing water pollution.

Key Pavement Technologies

To further reduce our environmental footprint, the asphalt industry continues to make great strides in the use of warm-mix asphalt (WMA) production. WMA technologies reduce the production and placement temperature of asphalt pavement mixtures by 30°F to 120°F.10 This lowers fuel consumption further and cuts greenhouse gas emissions.

On average, contractors report energy savings of almost 25 percent during warm-mix production. When WMA is fully implemented across the industry, the U.S. will save an estimated 150 million gallons of No. 2 fuel oil per year, while also cutting carbon dioxide emissions by an equivalent of 210,000 cars annually.11 The use of warm-mix asphalt grows each year. As of 2013, nearly a third of all asphalt tonnage in the U.S. was produced using warm-mix technologies1 and 49 state departments of transportation, along with the Federal Highway Administration (FHWA), support the use of warm-mix asphalt.10 In fact, the U.S. Department of Transportation (DOT) has estimated that by 2020 the use of warm mix will save more than $3.5 billion by reducing the amount of fuel needed to produce asphalt mixes.12

The Construction Innovation Forum recognized warm-mix asphalt with a 2013 NOVA Award for the innovations the technology has brought to the road construction sector.

Emerging Research

The asphalt industry is continually looking for new ways to make its products more sustainable and environmentally friendly.

Currently, the industry is working with pavement engineers at the National Center for Asphalt Technology (NCAT) to further develop pavement preservation techniques that utilize high binder replacement in thin asphalt overlay surface mixes that have the equivalent or better performance of a standard mix and reduces the virgin materials used in construction. After undergoing fatigue and low temperature cracking tests, initial results show an improved performance over standard mixes.13

Annually, the asphalt pavement industry works in partnership with FHWA to quantify the use of recycled materials and warm-mix asphalt production in the U.S.1 This serves as a way to track the uptake of innovations in technological and environmental conservation.

Drivability

As the most recycled product in America, asphalt is the pavement of choice for sustainability. In 2013, 67.8 million tons of asphalt pavement material and nearly 1.7 million tons of roofing shingles were put to use in new asphalt pavement mixes. The asphalt pavement industry saved American taxpayers some $2 billion by replacing the virgin liquid asphalt binder with binder reactivated from old pavements and shingles.1 And that’s before the value of reclaimed aggregate and landfill diversion are calculated.

Beyond the economic and environmental benefits, smooth asphalt pavements have been shown to lead to better fuel economy for drivers14 and reduced wear and tear on their vehicles.15 But asphalt isn’t just for cars and trucks. Smooth asphalt pavements are recommended for use with rapid transit busways16 and they have been demonstrated to be more comfortable for cyclists17 and joggers,18 too.

Sources

  1. Hansen, K.R., and A. Copeland (2014). Information Series 128: Annual Asphalt Pavement Industry Survey on Recycled Materials and Warm-Mix Asphalt Usage: 2009–2013. National Asphalt Pavement Association. Lanham, Maryland.

  2. Chesner, W.H., R.J. Collins, and M.H. MacKay (1998). User Guidelines for Waste and Byproduct Materials in Pavement Construction. Report FHWA-RD-97-148. Federal Highway Administration. McLean, Virginia. 

  3. Chappat, M. and J. Bilal (2003). The Environmental Road of the Future: Life-Cycle Analysis (French report: La Route Écologique du Futur: Analyse du Cycle de Vie). Colas Group. Boulogne-Billancourt, France.

  4. Mahasenan, N., S. Smith, K. Humphreys (2003). The Cement Industry and Global Climate Change: Current and Potential Future Cement Industry CO2 Emissions. In Proceedings of the 6th International Conference on Greenhouse Gas Control Technologies (J. Gale and Y. Kaya eds.), Vol. 2, pp. 995–1,000.

  5. EPA (2014). Draft Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2012. U.S. Environmental Protection Agency. Washington, D.C.

  6. Pellegrino, J., S. Brueske, T. Carole, and H. Andres (2007). Energy and Environmental Profile of the U.S. Petroleum Refining Industry. Energetics Inc. Columbia, Maryland.

  7. Roseen, R.M., T.P. Ballestero, J.J. Houle, J.F. Briggs, and K.M. Houle (2012). Water Quality and Hydrologic Performance of a Porous Asphalt Pavement as a Storm-Water Treatment Strategy in a Cold Climate. Journal of Environmental Engineering, Vol. 138, No. 1, pp. 81–89.

  8. Zhao, Y. and C. Zhao (2014). Lead and Zinc Removal With Storage Period in Porous Asphalt Pavement. WaterSA, Vol. 40, No. 1, pp. 65–72.

  9. AASHTO (2011). The Use of Permeable Friction Course (PFC) Pavement for Water Quality Improvement. AASHTO Technology Implementation Group, American Association of State Highway and Transportation Officials. Washington, D.C. 

  10. FHWA (2013). Every Day Counts: Warm Mix Asphalt. Federal Highway Administration. Washington, D.C.

  11. NAPA (2008). Warm-Mix Asphalt (PS-30). National Asphalt Pavement Association. Lanham, Maryland.

  12. Foxx, A.R. (2013). Working to Improve Transportation Efficiency, Performance. Fast Lane: The Official Blog of the U.S. Department of Transportation. U.S. Department of Transportation. Washington, D.C.

  13. Currently underway PEC project “Development of Thin Asphalt Overlay Mixes with High Recycle Content.” Research being conducted at NCAT expected to be completed in the third quarter of 2014.

  14. Sime, M., S.C. Ashmore, and S. Alavi (2000). Tech Brief: WesTrack Track Roughness, Fuel Consumption, and Maintenance Costs. Report FHWA-RD-00-052. Federal Highway Administration. McLean, Virginia.

  15. TRIP (2012). Bumpy Roads Ahead: America’s Roughest Rides and Strategies to Make our Roads Smoother. TRIP: A National Transportation Research Group. Washington, D.C.

  16. Monismith, C.L., S.L. Weissman, L. Popescu, and N.J. Santero (2008). Establishing Infrastructure Requirements for Bus Rapid Transportation Operations in Dedicated Bus Lanes. Report UCB-ITS-PRR-2008-32. University of California, Berkeley. Berkeley, California.

  17. Hölzela, C., F. Höchtla, and V. Sennera (2012). Cycling Comfort on Different Road Surfaces.Procedia Engineering: Engineering of Sport Conference 2012, Vol. 34, pp. 479–484.

  18. Knobloch, K., U. Yoon, and P.M. Vogt (2008). Acute and Overuse Injuries Correlated to Hours of Training in Master Running Athletes.Foot & Ankle International, Vol. 29, No. 7, pp. 671–676.

  19. Gambatese, J., and S. Rajendran (2005). Sustainable Roadway Construction: Energy Consumption and Material Waste Generation of Roadways. Construction Research Congress 2005: pp. 1–13.