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Silicone joint sealants from Dow Corning Corp. were selected for use in the reconstruction of the primary runway at Andrews Air Force Base in Prince George’s County, Md. Also referred to as Joint Base Andrews, the base operates the only military runway within the National Capital Region and supports the presidential airlift mission (Air Force One), aeromedical evacuation flights, and contingency response scenarios.
The west runway—one of just two at the base—was originally built in 1960 with an expected 25-year lifespan. Not surprisingly, by 2010 it was failing and needed to be completely replaced. The construction project, which began in late summer 2010, involved the replacement of 11,300 ft of the 200-ft-wide concrete runway and 25 ft of asphalt shoulder on each side. Dow Corning® brand silicone joint sealants were selected to provide a performance seal for the concrete and asphalt joints.
On the Fast Track
Because Joint Base Andrews only has two active runways, the replacement of the west runway needed to be done as quickly as possible to minimize the disruption of operations. The materials used for the construction of the runway also had to be easy to work with under a variety of weather conditions.
As one-component, cold-applied materials with a constant consistency over a wide temperature range, Dow Corning® 888 Silicone Joint Sealant and Dow Corning® 890-SL Silicone Joint Sealant can be used straight out of the container and can be applied by hand or with a pump—without the need to prime the concrete or asphalt. Dow Corning 888 Silicone Joint Sealant also skins over rapidly, which helps speed up the construction process.
Making a Quality Connection
The joints between the large airport runway slabs are specially designed to move within the silicone’s superior movement capabilities (+100/-50%) due to concrete and asphalt thermal expansion cycles and as opposing slabs deflect during an aircraft takeoff or landing. In fact, Dow Corning 888 Silicone Joint Sealant and Dow Corning 890-SL Silicone Joint Sealant meet the Federal Aviation Administration (FAA) P-605 silicone sealant requirements for use in airfield applications, and Dow Corning 890-SL Silicone Joint Sealant is designed for use in concrete-to-asphalt joints such as the shoulder joints of runways.
The silicone sealants must be stored properly and meet quality standards when they arrive on the job site. Kenseal Construction Products (the Dow Corning distributor for the project) knows the standards and helps run field quality checks, along with the paving contractor.
“All of the material we received on-site was in prime condition for use,” says Rob Nielsen of Pavement Contracting Services, the company that completed the installation. “There was no wastage or spoilage, which can happen if the sealant is stored improperly or kept for too long.”
The massive runway project required the use of nearly 300,000 linear ft of silicone sealant. Approximately 265,400 concrete-to-concrete contraction joints and more than 7,000 ft of concrete-to-concrete expansion joints were sealed with Dow Corning 888 Silicone Joint Sealant, while about 25,000 ft of concrete-to-asphalt joints were sealed with Dow Corning 890-SL Silicone Joint Sealant, according to Nielsen. Meeting that kind of volume demand might be challenging for some distributors, but not for Kenseal.
“The project went very smoothly from the standpoint of the sealant supply,” says Nielsen. “The people at Kenseal worked very closely with us, and as a result, we always had the amount of sealant that we needed for each phase of the project. The quality and reliability of their service was an important factor in the success of the runway construction project.”
Ensuring Reliable Performance
Sealants keep water and salts out of the joints, which helps reduce erosion of the subbase and corrosion of the metal tie bars embedded in the concrete slabs. Dow Corning sealants are designed to provide a long-term seal that gives ongoing protection.
Dow Corning silicone joint sealants have high movement capability, stretch easily without putting strain on the joint, and readily return to their original size after being stretched or compressed. They also are weather- and UV-resistant, and thus are a durable solution for runway construction projects.
“There was no doubt that we would use Dow Corning sealants on the Andrews Air Force Base runway,” says Nielsen. “We have a long, successful history of working with Dow Corning products without any performance issues, and we will continue to use Dow Corning silicone joint sealants where these types of silicone sealants are specified.”
Silicone Solutions for the Future
Silicone sealants have been specified and used successfully in many airfield applications. Dow Corning silicone pavement sealants meet the FAA Airport Construction Standard (P-605) for joint sealing of concrete runways and asphalt runway shoulders. Now, Dow Corning 888 silicone joint sealant and Dow Corning 890-SL Silicone Joint Sealant are helping to ensure that Air Force One can take off and land safely at Andrews Air Force Base.
For more information, visit www.dowcorning.com/construction.
Editor’s note: All photos courtesy of Dow Corning.
About Dow Corning
Dow Corning provides performance-enhancing solutions to serve the diverse needs of more than 25,000 customers worldwide. A global leader in silicones, silicon-based technology and innovation, Dow Corning offers more than 7,000 products and services through the Dow Corning® and XIAMETER® brands. Dow Corning is equally owned by The Dow Chemical Company and Corning, Inc. More than half of Dow Corning’s annual sales are outside the U.S.