30 June 2001
a. Sawcut grooving is a proven way of reducing the hydroplaning potential of runways.
Grooves drain water laterally, permit water to escape under tires, prevent buildup of surface water,
and increase the texture of the pavement.
(1) Pavement condition. Grooves should only be applied to structurally adequate
pavement free from defects. Pavements requiring corrective action should be overlaid or
rehabilitated prior to grooving. Porous Friction Surfaces should not be grooved.
(2) Grooving flexible pavements. Studies indicate that grooving of flexible pavements
does not cause any appreciable deterioration of the pavement nor has maintenance effort been
increased. No problems have occurred from ice and snow removal. Minor distortion and creeping
of grooves have been observed, but these conditions have not required maintenance or adversely
affected pavement performance.
(3) Groove pattern. Grooves will be continuous for the entire length of the usable runway
and perpendicular to the centerline. Grooves should terminate within 1.5 to 3 meters (5 to 10 feet)
of pavement edge to allow for operation of grooving equipment. The standard groove configuration
is 6 millimeters (3 inch) + 2 millimeters (+ 1/16 inch) in depth by 6 millimeters (3 inch) + 2
millimeters 0 millimeters (+1/16 inch, -0 inch) in width by 38 millimeters (1 1/2 inch) 3
millimeters + 0 millimeters (-1/8 inch, + 0 inch) center-to-center spacing. The recommended
groove detail for airfield pavements is shown in Figure 21-1.
(4) Limitations. Do not groove within 6 inches (+ 3 inches) of the runway centerline.
Do not groove within 152 millimeters (6 inches) of transverse joints or working cracks, through
compression seals, in-runway lighting fixtures or similar items, or the first 3 meters (10 feet) either
side of an arresting barrier cable which requires hook engagement for operation. There is no need
for grooving on either side of barrier cables that are placed on overruns.
b. Porous Friction Surfaces. A porous friction course is an open-graded, free draining asphalt
mixture that can be placed on an existing pavement to minimize hydroplaning and to improve skid
resistance. A PFS is placed in a layer varying from 19 to 25 millimeters (3/4 to 1 inch) thick. It
has a coarse surface texture and is sufficiently porous to permit internal drainage as well as along
the surface. Existing pavements should be in good condition before placing the mix. Concerns
with PFS include rubber buildup that might prevent internal drainage, possible freezing of water
trapped in voids, and loss of expertise in designing and constructing these surfaces. PFS should
not be placed within 3 meters (10 feet) of an arresting gear cable.
c. Retexturing. Retexturing of runways has been successfully accomplished using several
types of equipment. Contact the MAJCOM Pavements Engineers for guidance on Air Force
projects and the TSMCX on Army projects.