The Greening of America’s Highways

Words like sustainability, carbon footprint and environmental stewardship have dominated the construction industry for the past half-decade, driving some highway engineers to protest the buzz and beg their information sources to go back to covering advances in materials and technology that make roads better.

More and more, those topics are intertwined: advances that make pavements perform better or cost less – or both – usually also bring advances in sustainability.

The other remarkable aspect of pavement sustainability is the pace of change. In the past few years, under the press of economics, science and marketing forces, the science of sustainable concrete and asphalt pavements has evolved quickly, with advances in everything from production and technology to communicating best practices.

To keep pace with the changes, Better Roads reviewed recent developments with representatives from the National Asphalt Pavement Association (NAPA) and the American Concrete Pavement Association (ACPA).

In terms of conventional methods of measuring carbon footprints, concrete pavement’s great strength is its inherent longevity. Its greatest vulnerability is the amount of carbon dioxide released in the production of Portland cement.

“The cement industry has taken dramatic steps to reduce any environmental impact of the manufacturing process, reducing the amount of energy to make a ton of product by more than 33 percent since 1972,” notes Leif Wathne, PE, ACPA vice president of highways and federal affairs. He adds that the Cement Manufacturing Sustainability Program is pledged to reduce CO2 emissions by another 10 percent per ton from 1990 levels by 2020.

In addition, he notes, research is underway at MIT’s Concrete Sustainability Hub to achieve future carbon reductions through nanotechnology. “Science is looking for a better understanding of Portland cement — at the molecular level,” says Wathne. “There are some pretty exciting prospects on that front.”

Meanwhile, the concrete paving industry is focusing on pragmatic solutions to the challenges of the day — sustainability and cost reduction.