+-----------------------------------+-----------------------------------+
| ![](media/image1.wmf)             | **Advisory**                      |
|                                   |                                   |
| U.S. Department                   | **Circular**                      |
|                                   |                                   |
| of Transportation                 |                                   |
|                                   |                                   |
| ### Federal Aviation              |                                   |
|                                   |                                   |
| **Administration**                |                                   |
+-----------------------------------+-----------------------------------+

+-----------------------------------+---------------+-----------------+
| **Subject:** MEASUREMENT,         | **Date:**     | **AC No:**      |
| CONSTRUCTION, AND MAINTENANCE OF  | 9/2/04        | 150/5320-12C    |
| SKID-RESISTANT AIRPORT PAVEMENT   |               |                 |
| SURFACES                          | **Initiated   | **Change:** 2   |
|                                   | by:** AAS-100 |                 |
+-----------------------------------+---------------+-----------------+

1.  **PURPOSE.** This change updates references to polymer-based runway
    surface chip seals to account for current materials technology.

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![](media/image2.png){width="2.5375in" height="0.5888888888888889in"}

DAVID L. BENNETT

Director, Office of Airport Safety and Standard

9/2/04 AC 150/5320-12C Chg. 2

recommends that PFC overlays not be constructed on airport runways that
have high aircraft traffic operations (over 91 turbojet arrivals per day
per runway end).

**2-7. CHIP SEAL.** Recent advances in polymer technology have
demonstrated the ability for durable, long term improvement of runway
surface friction through the use of polymer-based chip seals. Sound
engineering judgment should be exercised in the selection of a product
when considering the use of polymer-based chip seals for longer term
improvements. This technology has not been demonstrated to be compatible
with grooved surfaces. A fog seal must be applied on top of the chip
seal to minimize loose chips and tire damage. Chips should have a
maximum size of 4.75mm (No. 4 sieve) to further minimize aircraft and
tire damage.

**2-8. AGGREGATE SLURRY SEAL.** Temporary improvement of skid-resistance
for pavement surfaces can be gained by constructing an aggregate slurry
seal, either gradation type II or type III, as given in the
specification in AC 150/5370-10. Aggregate slurry seals are recommended
only as an interim measure until an overlay is constructed. This type of
construction is usually adequate for 2 to 5 years. Figure 2-2 shows a
typical type II aggregate slurry seal. Experience has shown that slurry
seals do not hold up well in cold climates where snow removal occurs. A
life cycle cost analysis should be conducted to determine the long term
benefits.

# Section 3. Portland Cement Concrete (PCC) Pavement

**2-9. CONSTRUCTION TECHNIQUES FOR PCC PAVEMENT.** Several methods are
available to the paving contractor for constructing skid-resistant PCC
pavement surfaces. When PCC pavement is still in the plastic condition,
it is strongly recommended that some type of textural finish be
constructed in the pavement surface prior to grooving. Such texturing
can be accomplished by using either a brush or broom finish or a heavy
burlap drag finish. Wire combed or wire tined construction provides an
excellent textural finish to the surface. Also, plastic grooves can be
constructed in the pavement before it has hardened. For PCC pavements
that have hardened, grooves can be saw cut in the pavement. The textural
and grooving construction techniques are briefly described in the
following paragraphs. The basic construction specifications for PCC
pavement are given in AC 150/5370-10. Quality concrete is a prerequisite
to the retention of pavement skid-resistance. The physical properties of
the fine aggregates and effectiveness of curing are important factors in
improving wear resistance.

**2-10. TIMING AND CURING.** Timing in applying the curing compound is
as important as timing the final finishing operations to assure long
lasting, nonskid pavement surface texture. The timing of the texturing
operation is critical because PCC pavements rarely lose surface moisture
evenly or set at a uniform rate, especially during warm weather paving
operations. The best time to texture a PCC pavement during construction
is when the water spots have dried enough to reasonably hold the texture
but before the drier spots have dried too much to texture at all. This
is one of the toughest decisions for the paving contractor. After
texturing of the pavement surface has been completed, immediate
application of the curing compound assures that the pavement surface
will not lose water and cure too rapidly. If the pavement cures too
quickly, the ridges of mortar left by the finishing technique will not
set properly and their durability will be greatly reduced, resulting in
a faster rate of diminishing skid-resistance. Therefore, extreme care
must be taken in this process to assure an effective cure.

**2-11. BRUSH OR BROOM FINISH.** If the pavement surface texture is to
be a type of brush or broom finish, it should be applied when the water
sheen has practically disappeared. The equipment should operate
transversely across the pavement surface, providing corrugations that
are uniform in appearance and approximately 1/16 inch (1-1/2 mm) deep.
It is important that the texturing equipment not tear or unduly roughen
the pavement surface during the operation. Any imperfections resulting
from the texturing operation should be corrected immediately after
application before the concrete becomes too stiff to work. Figure 2-3
shows the texture formed by the broom finish.

**2-12. BURLAP DRAG FINISH.** Burlap used to texture the pavement
surface should be at least 15 ounces/square yard (355 gm/square m). To
produce a rough textured surface, the transverse threads of the burlap
should be removed from approximately 1 foot (0.3 m) of the trailing edge
and grout should be allowed to accumulate and harden on the trailing
burlap threads. A heavy buildup of grout on the burlap threads produces
the desired wide sweeping longitudinal striations on the pavement
surface. The aggregate particles form the corrugations which should be
uniform in appearance and approximately 1/16 inch (1-1/2 mm) deep. A
runway pavement constructed with a burlap drag finish is shown in Figure
2-4.

5

AC 150/5320-12C 3/18/97

**2-13. WIRE COMBING.** The wire comb technique uses rigid steel wires
to form a deep texture in the plastic concrete pavement. An excellent
example of this method is the runway constructed at Patrick Henry
Airport in Virginia, where the spacing of the ridges is approximately ½
inch (13 mm) center to center (see Figure 2-5). The spring steel wires
which were used had an exposed length of 4 inches (100 mm), thickness of
0.03 inch (0.7 mm), and width of 0.08 inch (2 mm). The wire comb
equipment should provide grooves that are approximately 1/8 inch x 1/8
inch (3 mm x 3 mm) spaced ½ inch (13 mm) center to center. It is not
necessary to provide preliminary texturing before constructing the wire
comb texture. Because of the closeness of the spaced grooves, the
preliminary texturing of the remaining land areas would not be
effective. The wire comb technique should be constructed over the full
pavement width. **The technique is not to be confused with saw cut or
plastic grooved runway pavements.** Wire combing is a texturing
technique and cannot be substituted for saw cut or plastic grooves
because it does not prevent aircraft from hydroplaning.

**2-14. WIRE TINING.** Flexible steel wires are used to form deep
texture in the plastic concrete pavement. The flexible steel bands are 5
inches (125 mm) long, approximately ¼ inch (6 mm) wide, and spaced ½
inch (13 mm) apart. The appearance of this technique is quite similar to
the wire comb method. **This technique is not to be confused with saw
cut or plastic grooved runway pavements.** Wire tining is a texturing
technique and cannot be substituted for saw cut or plastic grooved
because it does not prevent aircraft from hydroplaning.

## Section 4. Runway Grooving

**2-15. GENERAL GROOVING TECHNIQUES.** Cutting or forming grooves in
existing or new pavement is a proven and effective technique for
providing skid-resistance and prevention of hydroplaning during wet
weather. In existing pavement (both HMA and PCC), grooves must be saw
cut; in new PCC pavement, grooves may be formed while the concrete is
still plastic. Grooves in HMA pavement must be saw cut whether new or
existing pavement is to be treated.

**2-16. DETERMINING NEED FOR GROOVING.** Grooving of all runways,
serving or expected to serve turbojet aircraft, is considered high
priority safety work and should be accomplished during initial
construction. Such existing runways without grooving should be
programmed as soon as practicable. For other runways, the following
factors should be considered:

**a.** Historical review of aircraft accidents and incidents related to
hydroplaning at the airport.

**b.** Wetness frequency (review of annual rainfall rates and
intensity).

**c.** Transverse and longitudinal grades, flat areas, depressions,
mounds, or any other surface abnormalities that may impede water runoff.

**d.** Surface texture quality as to slipperiness under dry or wet
conditions. Polishing of aggregate, improper seat coating, inadequate
micro-macrotexture, and contaminant buildup are some examples of
conditions that may cause the loss of surface friction.

**e.** Terrain limitations such as dropoffs at the ends of the runway
safety areas.

**f.** Adequacy of number and length of available runways.

**g.** Crosswind effects, particularly when low friction factors prevail
at the airport.

**h.** The strength and condition of the runway pavements at the
facility.

**2-17. SUITABILITY OF EXISTING PAVEMENTS FOR GROOVING.** Existing
pavements may have surfaces that are not suitable for sawing grooves. A
survey should be conducted to determine if an overlay or rehabilitation
of the pavement surface is required before grooving.

**a. Reconnaissance.** A thorough survey should be made of the entire
width and length of the runway. Bumps, depressed areas, bad or faulted
joints, and badly cracked and/or spalled areas in the pavement should
not be grooved until such areas are adequately repaired or replaced. To
verify the structural condition of the pavement, tests should be taken
in support of the visual observations.

6