On any given day, more than 87,000 flights are in the skies in the U.S., according to the National Air Traffic Controllers Association. These airplanes account for 64 million takeoffs and landings a year. The constant abuse on the runways, along with a limited time for maintenance and repairs, requires that long-lasting, durable repair materials are used.
Detroit Metropolitan Airport, which sees a high amount of airplane traffic as well as weather extremes, is one of many airports that have turned to using a durable runway patching material. Repairing a runway involves making rapid repairs that minimize downtime. These include repairing potholes, joint spalling and raveling, repairs around manhole and utility covers, lightning strike damage, corner cracking, and conduit backfilling. Making repairs that minimize future maintenance and minimize foreign-object debris that can cause airplane damage is essential. A range of repairs may be required in a short period, making a material that is easy to use and quick to cure necessary.
Klamath Falls Airport
In 2009, the Klamath Falls Airport in Oregon removed and replaced concrete pavement on one of its taxiways. Damaged sections of the taxiway and adjacent apron had previously been repaired with D.S. Brown’s Delpatch elastomeric concrete but other damage led to the decision to replace the pavement. So the pavement and patches needed to be broken into manageable pieces to allow removal.
The demolition contractor began his work by repeatedly dropping an 8-foot- wide, six-ton guillotine hammer onto the elastomeric concrete repairs and surrounding concrete. The pavement readily broke into small pieces under the blows of the 12,000-pound breaker, but the elastomeric concrete would not crack. The high-performance concrete patches never lost their structural integrity and were eventually removed intact.
“In one area, the concrete buckled next to a long application of elastomeric concrete after being struck repeatedly by the hammer,” says Bill Hancock, Klamath Falls Airport operations manager. “Not only did the patch not crack, it actually retained its adhesion to the concrete and conformed to match the pavement’s new shape. Other repairs with the product remain in use and I have confidence they will hold up as well.”
Beale Air Force Base
Performing concrete repairs on airport runways is always a time-sensitive operation but even more so for military runways. Recently, Beale Air Force Base near Marysville, Calif., began a project to repair concrete spalls on its runway. Time was a critical factor, as the airfield had to receive traffic on the same day repairs were made. California’s high springtime temperatures often caused pavement surface temperatures to reach 118 degrees during installation.
Diversified Concrete Cutting, Sparks, Nev., was contracted to perform the 485 square feet of spall repairs. Work began in March 2013 and was completed two months later. Cracking developed in the original partial-depth repairs, so another repair solution was needed.
Based on experience with similar repairs, Diversified recommended Delpatch elastomeric concrete. To begin, Diversified’s crews sawcut around the spalled areas and chipped out the damaged concrete until they reached a sound substrate. After sandblasting, the repair area was blown out with compressed air. Repairs were typically 2 to 4 inches, although in some areas as deep as 9 inches; elastomeric concrete can accommodate varying repair depths.
Because of the fast setting time, the substrate had to be completely ready to receive the patch before the Delpatch was mixed. With the concrete prepared, workers mixed the repair material with a drill in five-gallon buckets. Parts A and B were mixed and aggregate was added. When fully mixed, after about a minute, workers poured the elastomeric concrete into the repair area, brought it to grade, and troweled it flush with the surrounding concrete. Total working time from mixing to initial set was five to 10 minutes, depending on temperature. Within an hour, the runway was ready for airfield traffic.
This project demonstrates the effective use of flexible concrete repair products for partial-depth repairs. Repair materials installed in rigid pavement require that the materials have similar coefficients of expansion and similar ductility. Most do not, resulting in destroyed patches or surrounding concrete. Elastomeric concrete’s unique urethane chemistry provides a flexible patch that deflects as surrounding concrete expands and contracts.
“The repairs have made the runway much safer for aircraft,” says Gerald Pannell, civil engineer, Beale AFB. “We have established a higher standard for spall repairs.”
Ben Jacobus is the national sales manager, Pavement Products Division, D.S. Brown, North Baltimore, Ohio. For more, visit www.dsbrown.com.