Dec. 18, 2012
Public Affairs Office
TYNDALL AIR FORCE BASE, Fla.—The U.S. Air Force (USAF) is seeking technologies to repair 120 airfield craters in 6.5 hours using eight repair teams. Researchers with ERDC’s Geotechnical and Structures Laboratory (GSL) are currently working with the Air Force Research Laboratory and the U.S. Air Force Civil Engineer Center to develop the materials and techniques, tactics and procedures (TTP) to reach that goal.
Armed with cameras, stop watches and clip boards, ERDC’s Jeb Tingle, Haley Bell, Lulu Edwards, Will Carruth, and Jonathon Griffin are determined to develop TTPs that use the cementitious fill and rapid setting cap material being identified by ERDC as the best material.
They have identified the 11 steps that take a crater-pocked runway to usable landing strip in two hours after the last repair truck rumbles off the airfield. The TTPs have been tested in wet weather conditions simulating rainfall of 3/8-inch per hour and in cold weather air temperatures that hover in the 30- to 35-degree range.
After training, the airmen from the USAF’s 823rd and 819th Rapid Engineer Deployable, Heavy Operational Repair Squadrons, Engineer (RED HORSE) head to the crater-pocked runway to test the steps:
- Remove all the foreign object damage (FOD). This could be chunks of runway material from the craters to bits of metal from surrounding buildings or aircraft.
- Then, four compact track loaders with wheel saw attachments start working; two per crater. For testing purposes, the saws cut along the lines marked by the battle damage team to a depth of 34 inches and define the repair area including upheavals. Bell said, “In real life, you are only going to remove what is disturbed.”
- A wheeled excavator with a heavy hammer attachment is then used to break up the concrete into chunks so it can be removed. Then we break out the damaged runway in the repair area.
- The clean up team comes in next with a wheeled excavator and bucket attachment to excavate the old material and debris so the new repair material can be placed in the hole.
- Four 3,000-pound bags of rapid setting flowable fill material are placed in each 34-inch deep 8 ½ foot by 8 ½ foot hole.
- The bags are opened and the Air Force Engineer team evenly spreads out the dry powder. The nearby water truck sprays the right amount of water to get the wet fill material to the right consistency.
- The simplified volumetric mixer, which replaces the cement mixer truck, arrives about 30 minutes after the flowable fill material is placed in the crater. The ADR team has developed a technique to continuously load the mixer with rapid setting cap material to continuously place the repair material. “It is like in-flight refueling,” Bell said.
- The rapid setting cap material is placed over the cementitious rapid setting flowable fill material.
- The rapid setting cap material is placed over the cementitious repair and the runway repair team spread and screed the rapid set cap to smooth out the repair.
- A final FOD removal sweep is done to remove any remaining debris and dust on the runway. Hand tools are picked up and stored.
- After two hours, trafficking tests begin, simulating a fully loaded F-15E.
At the end of the wet weather crater repair test at Tyndall Air Force Base, Fla., in June, the ERDC team reported that the six-crater repair sequence using the rapid-setting concrete caps took less time than the same repair sequence using the pelletized asphalt concrete caps. They also learned that the moisture did not affect the equipment and that the flowable fill backfill, rapid setting concrete cap and pelletized asphalt caps met the time and strength requirements when they withstood 3,500 passes of test cart traffic.
The cold weather crater repair test revealed similar results. The equipment was not affected by the cold. The flowable fill backfill met the time and strength requirements. While the rapid setting concrete cap met the time and strength requirements, noticeable shrinkage cracks appeared. The cracks were attributed to mixture not having a water reducing admixture due to miscommunication by the manufacturer.
The next test of evolving TTPs, equipment as well as the backfill and pelletized asphalt caps, is set for February 2013 at Malmstrom Air Force Base, Mont.
Read more: Joint project develops airfield damage repair materials, techniques