O'Hare Int'l Applies Cooler, Greener Taxiway Asphalt

Jennifer Bradley
Published in: 

Warm is the new "hot" at Chicago's O'Hare International Airport.

In an ongoing effort to find ways to go green and boost social responsibility during its massive modernization program, O'Hare became the first airport in the Midwest to apply warm-mix asphalt to an airport taxiway.

Before it could use warm-mix asphalt rather than


Project: Warm-mix Asphalt Installation

Location: O'Hare Int'l Airport

Taxiway: Zulu Sierra

Size: 800 x 75 ft.

Timeline: April - Oct., 2011

Material Used: 7,100 tons

Contractor: Plote Construction

Special Requirement: Modification of Standards from FAA

Benefits: Compared to traditional hot-mix, warm-mix asphalt requires less energy to heat & cools faster, which saves time at the jobsite

conventional hot-mix asphalt, the Chicago Department of Aviation (CDA) had to submit a Modification of Standards to the FAA. After about two years working closely with the federal agency, CDA received approval to use the less traditional, more environmentally friendly paving technique.

Testing to ensure the safety of the product accounted for some of the long process, explains CDA commissioner Rosemarie Andolino. "We're always looking to try things that are new and are not afraid of advanced technologies or developments," says Andolino. "We want to embrace them, but of course, with safety first."

"We've been working very closely with the FAA to push this initiative along, and we're finally here," adds Cyle Cantrell, CDA projects administrator.

All About Asphalt

The FAA, its Great Lakes Region and the University of Illinois Center for Excellence collaborated with O'Hare about its use of 7,100 tons of warm-mix asphalt mix earlier this summer. The asphalt was applied during construction of a new 800-foot-by-75-foot section of Taxiway

Zulu Sierra (ZS), which is adjacent to the southwest cargo area and runs directly south of future Runway 10C-28C on O'Hare's south airfield. Although the new taxiway segment is small in size, it's an important connector for the airfield.

An FAA-approved additive for warm-mix asphalt was included in the asphalt treated permeable base and asphalt binder during production, providing a substantial reduction in energy costs to heat the asphalt. It also decreased the time it takes the asphalt to cool, which saves time on the worksite in two ways.

While traditional hot-mix asphalt is tested at a temperature of 295° F, warm-mix is tested at 250° F, explains Michelle Beecher, CDA's quality assurance material testing project manager. Warm-mix asphalt also reaches rolling temperature (150° F) more quickly than traditional hot-mix. At O'Hare, that difference saved about four hours per day with the labor force, says Bill Trudeau, quality assurance manager for the O'Hare Modernization Program (OMP).

"It doesn't do you any good to have benefits if you don't get the same results," explains Trudeau, adding that tests in the lab and field show that the warm-mix method does not compromise strength or durability in any way. "In many ways, it is exceeding what we've done in the past," he notes.

Another benefit is the potential extension of the paving season. "We have an opportunity to pave later and gain more production on our schedule," he adds.

Leveraging the airport's onsite materials testing laboratory, technicians and engineers spent many hours analyzing samples of the warm-mix additives, including detailed density and volumetric tests. "For the Taxiway ZS project, we worked closely with the paving contractor on test strips for both the ATPB (asphalt treated permeable base) and asphalt binder," explains Trudeau, noting that samples from test strips were analyzed at both the contractor's and OMP's laboratories. "Based on the satisfactory results from those test strips, the contractor was allowed to proceed with full production. Split samples were taken twice a day on the asphalt delivered to the site, and laboratory results substantiated that the material was meeting project specifications."

Warm to the Idea

The OMP took on the warm-mix endeavor only after due consideration of pavement quality and durability, stresses Andolino. Though the product may be in use at other airports, O'Hare's Midwestern weather added unique factors to the decision. Rigorous testing was undertaken to ensure warm-mix would measure up to local conditions, explains Andolino. "Between snow, cold, warm and rain, we have contraction of pavement, and we needed to ensure the product we use is durable and provides for safe aircraft operating conditions."

Khaled Naja, CDA's chief operating officer, agrees. "What's challenging in Dallas is not challenging in Los Angeles, or at O'Hare," he says. "That's why it took the FAA to address this. Warm-mix asphalt may be a no-brainer in Florida, but when you come here to O'Hare, there are different challenges with our climate, and O'Hare is the first airport in the Midwest to use warm-mix asphalt."

Andolino says CDA hopes to expand the application of warm-mix asphalt - potentially on a full runway. During the next three to four years, O'Hare will use more than 450,000 tons on future taxiways and Runway 10R-28L.

The Bigger Picture

Warm-mix asphalt is just part of the larger OMP plan to redevelop and reorganize O'Hare.

The plan, explains Cantrell, transitions the airport away from its existing triangle configuration, a runway style that was originally established for military aircraft and 1960s jet engines. Newer planes and updated technology have led many other airports to also revamp runway operations.

When the OMP is complete, CDA will have reconfigured O'Hare's existing intersecting runway system into eight total runways, with six east-west parallel runways and two crosswind runways. The taxiways, which need to be relocated to support the realigned runway configuration, present "tremendous opportunities for the CDA to utilize the warm-mix asphalt techniques," notes Naja.

"Right now we're very excited," says Cantrell. "We have well over a billion dollars of funded work in front of us, including Runway 10R-28L, and the center section of Runway 10C-28C."

With more than $3 billion committed to date, O'Hare's reconfiguration is one of the largest airport runway renovation programs in the world, notes Naja. "The OMP is approaching 50 percent completion, and construction work has been planned and executed with minimal impacts on airfield operations," he reports. "This is amazing, given that much of the OMP work is taking place on one of the world's busiest airports."

Cantrell speaks to the juggling act of such a major project: "It's been a very detailed phasing of how to build such a substantial amount of new infrastructure while not compromising operations and the financial interest of the airport."









Greater Good

Social responsibility is something CDA takes seriously and implements in every possible project, notes Andolino. On that front, she counts the efficient relocation and use of existing soil as a major OMP accomplishment. "We've moved 18 million cubic yards of soil - enough to fill the Willis Tower eight times," she chronicles. By developing a plan to keep soil materials on site and strategically stockpiling it into categories such as topsoil and structural embankment material, CDA has prevented more than 500,000 trucks from driving through neighboring communities, she reports.

"It was just a very strategic approach to minimize movements of earth, and it saves money," Andolino explains. "The soil we kept on site saved us probably $120 million in trucking fees, disposal costs and miles traveled, not to mention the reduction in carbon. Seventy thousand tons of carbon emissions were mitigated by not hauling off site."

According to Naja, the airlines are very supportive of CDA's efforts to increase sustainability - as long as they don't impact schedule, cost or reliability of the system.

"What we're doing here will save them money," he says. "We're constantly exploring and pursuing green initiatives that meet the triple bottom line (economic viability, social responsibility and environmental consciousness)."

Andolino reflects about balancing the time needed to make large-scale improvements in a manner that's best for all involved with the pressure of showing progress as quickly as possible. "In this case, we went through a process, because we move one to two million people every week," she relates. "We want to ensure the safety of the traveling public with every action we take. We still push the envelope to bring new technologies forward by working collaboratively with our stakeholders to deliver the best product possible."


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