Grooving & Grinding
By John Roberts, International Grooving & Grinding Association
January/ February 2001
Options for maintaining pavement smoothness at reduced costs
Air Base in the Republic of Korea is home of the U.S.
Air Force's 7th Air Force command and 51st Fighter Wing.
The main runway was constructed in the 1950s and went
through several modifications, including a concrete
overlay, extension, replacement of a portion of the
keel section, and several major patching contracts.
There was probably some roughness built in initially, but significant complaints from pilots began after a major patching contract in the mid-1980s. Two-thirds of the runway surface on the east end is 40 years old and has considerable patching. The bumps were generally less than a half-inch high, but there were so many that it transmitted considerable vibration to the aircraft.
One option considered was total replacement of the runway, or at least the center 75 feet for the entire runway length. However, the downtime and cost were prohibitive, so the Air Force patched the center portion, then diamond-ground a 100-ft. wide section along the entire runway length.
The diamond grinding process gently abrades saw cuts through the top surface of the pavement close enough together so the fins between the cuts break away, leaving longitudinal lines in a pattern resembling corduroy.
Following the grinding, the surface was re-grooved and the joints and cracks were resealed. The contract allowed 40 calendar days for total closure, plus 10 nights at the beginning and 30 nights at the end of the contract.
The diamond grinding was completed in 20-hour shifts by Mass Grinding & Grooving, McHenry, IL, using one modified Cushion Cut PC 5000-A grinding machine during the 40-day total closure.
A California profilograph was used to measure the roughness both before and after the grinding. The initial profile had test sections ranging in roughness from 14 inches per mile to as high as 92 inches per mile. Every test section produced either a 70 percent improvement or a profile index of less than seven inches per mile.
Air Force pilots reported they were very pleased with the end result, noting how much more control they felt during takeoffs and landings on the improved runway surface.
History of Diamond Grinding
Diamond grinding was first used to correct roughness on airfield concrete pavements in 1956 at Davis Monthan Air Base in Tucson, AZ. A constructed, 16-in. thick taxiway failed to meet the straight-edge requirements. Rather than remove and replace the pavement, the high spots were ground with a Concut bumpcutter, which was invented by Cecil Hatcher for the project. The project was brought into tolerance at considerable savings to the paving contractor.
In the more than 44 years since the advent of grinding and grooving, the process has been used on numerous airfield surfaces to improve ride quality and skid resistance. A sampling of other projects include:
• Davis Monthan Air Base, Tucson, AZ. (1956). A new portland cement (PCC) concrete taxiway was ground to meet a straight-edge test. The project spared the cost of removal and replacement of major pavement sections.
• Cigli Air Base, Izmir, Turkey (1962). A 100-ft. wide runway keel section was ground for a length of 5,000 feet to reduce vibration damage to surveillance instruments.
• King Khalid Military City, Saudi Arabia (1982). Blisters were removed from a new PCC runway and ramp to create a durable, uniform, damage-free surface.
• Rochester International Airport, MN. (1992). To restore a 25-year old PCC pavement on the airport's main runway, grooving and grinding were used as the final step in this CPR project to extend pavement life and enhance the high level of service.
• Pittsburgh International Air-port. (1993). Two runways were relieved of shallow grooves and minor roughness, thereby improving ride quality and safety.
• Lahore International Airport, Pakistan (1994). The keel of the five-year old main runway was smoothed along a 100x7,000-ft. section. The process corrected built-in roughness from a PI of 70 to a PI of 10.
• Varna Airport, Bulgaria (1996). The main runway was smoothed and sealed to correct roughness from use and initial construction.
• LaGuardia International Air-port, N.Y. (1997). Shallow grooves and minor roughness were removed from one runway end to increase safety and improve ride quality.
In addition to these projects, hundreds of grinding projects have been completed on airfield pavements around the world.
Construction began Aug. 18 on the $17.5 million project to reconstruct the 3,800-foot center section of pavement, which dated back to 1967.
A series of public and private celebrations are planned for the days leading up to the May 27 opening.