How "green" is your airport runway? Can runway designs really make a difference for the environment? Yes, argues George Vittas, senior vice president of AECOM's global aviation group. And what's more, he adds, the answer to greener, more sustainable runways has been around for decades, but only a few airports have seized the opportunity.

A majority of scientists agree that the global climate is heating up...and that goes for concern about the weather as well as the weather itself. Carbon footprints, global warming, sustainability — we can't go a day anymore without hearing these terms, and that's probably just as well.

The McGraw-Hill China Airports Construction Summit, held in Xi-An May 14, was no exception. Held at the Hyatt Regency Xian, it featured some 100 participants who listened as the on-scene interpreters struggled valiantly to translate real-time between English and Mandarin. Wang Jian, secretary general for the China Civil Airport Association, avowed that China civil airport officials "have paid little attention" to the issue of green construction. "We know environmental problems are increasing, yet we have still paid little attention. But once the issue explodes, we will be baffled. This conference can help our industry pay equal attention to the issue."

Vittas then gave his presentation, pointing to the success of the Port Authority of New York and New Jersey—which operates Kennedy, LaGuardia and Newark airports—and the Houston Airport System. Back in 1965, he said, Newark embarked on a $10-million research and developmeng program to test use of lime cement fly ash in the paving. Chinese engineer Nai Yang led the effort, and received a newsmaker award (then known as "marksman) by our very own ENR a few years later. The effort saved "millions" and the runway has needed minimal maintenance, said Vittas.

Houston picked up on the concept and used it successfully for a new runway in 1986. I poked around the web and found a summary of a talk given by Adil Godiwalla, Assistant Director of Civil Projects for HAS.

"The additives (based on weight) were 4.0% Lime, 0.5% Cement and 9.5% Flyash, added to 12.5% bank sand and 73.5% of aggregate. The mixture tested out with an ultimate bearing strength of 1200 psi after 6 months. However, when tested again in 2000, its strength had increased three-fold, meaning that after 14 years of curing, they had the equivalent of 3000 psi concrete in the base."

Godiwalla recalls Yang as a mentor and friend who asked him to carry on his legacy of pioneering lime cement fly ash for runways. It can save 35% off paving costs, and may have a life cycle range of more than 100 years, he says.

The U.S. Environmental Protection Agency, with the aid of the American Coal Ash Association, put out in 2005 a publication encouraging the use of coal byproducts, like fly ash, in pavements. The test cases cited all were highway projects. Why not more runways?

Finally, our own ENR ran a prescient article on Dec. 21, 1998, long before global warming was THE hot topic of the day. Former California bureau chief David Rosenbaum quoted several paving experts who touted fly ash as an excellent source of strength and durability, while combatting the carbon dioxide emissions of Portland cement, which they blamed for up to 7% of all total emissions in the world. Adding more substitutes like fly ash (in part by changing regulations that limit the percentage of substitution) is one way "we can do something about global warming," stated Berkley professor emeritus Kumar Mehta.
Why hasn't lime cement fly ash been used more frequently in American runways, then? Abdiwalla says that when he presents papers at
conferences, the audience members "are fascinated, they ask questions—but they don't use it. It's fear of the unknown."

Vittas believes the time has finally come. The practice "will spread around the world, and thus we will be able to contribute much more as civil engineers to sustainability," he said.

May 31, 2007

This is a very biased report. Did Mr. Vittas ghost-write it for you? The use of lime, cement and flyash to stabilize soils is well known. However to add a total of 14% by weight to soil for base course is prohibitively expensive and only justifiable in rare cases, none of which is mentioned in your article. At 14% by weight, it's equivalent to about 500 pounds per cubic yard. At $100 per ton (what we pay here for lime and cement; flyash is a little cheaper), that's an additional $25/cubic yard. We get good natural base course material for 60% of that. Not only is this NOT rocket science, it's dishonest reporting. It reads like every runway should be built this way and will save billions. It's baloney.

Dave O'Day