UFC 3-250-03
15 May 2001
pavement imperfections that may result from laying unsatisfactory mixes or using faulty construction
procedures.
5.
POROUS FRICTION COURSE.
a. General. A porous friction course (PFC) is an open-graded, free-draining asphalt paving mixture
that can be placed on an existing pavement to minimize hydroplaning and to improve skid resistance in
wet weather. This surface should not be used for low speed applications or in areas subjected to tank
traffic (especially tank turning areas). The thickness of the finished course can vary from approximately
19 millimeters (3/4 inch) to 25 millimeters (1 inch). A PFC has a coarse surface texture and is
sufficiently porous to permit drainage of water internally as well as along the surface. A combination of
water pressure relief through the internal and surface voids and the rough surface texture promote tire-
to-aggregate contact. PFC paving mixtures are produced in hot-mix asphalt plants and placed with
conventional asphalt paving machines. They should be placed on pavements which are in good
condition. A leveling course may be required to achieve the desired conditions before construction of
the PFC.
b. Materials.
(1) Aggregates. High quality aggregates are required for PFC's with a maximum LA abrasion
loss (ASTM C 131) of 25 percent and 40 percent for high and low tire pressure loadings, respectively. A
crushed aggregate is required and shall have a minimum of 90 percent by total weight of aggregate with
one crushed face and 70 percent with two crushed faces. Antistrip agents shall be specified when
required. The Air Force currently requires an antistripping agent in all PFC and the underlying hot-mix
asphalt layer regardless of the results of the immersion compression test. Table 2-11 presents the
Table 2-11
Percent Passing by Weight of Total Aggregates
Gradation "A"
Gradation "B"
19 mm (3/4-inch) Maximum
12.5 mm (1/2-inch) Maximum
Sieve Designation
(Compacted Nominal Thickness,
(Compacted Nominal Thickness,
(Square Openings)
25 mm, 1 inch)
19 mm, 3/4 inch)
19 mm (3/4 inch)
100
100
12.7 mm (1/2 inch)
70-100
100
9.5 mm (3/8 inch)
35-75
80-100
4.75 mm (No. 4)
25-40
25-40
2.36 mm (No. 8)
10-20
10-20
600 Fm (No. 30)
3-10
3-10
75 Fm (No. 200)
0-5
0-5
(2) Asphalt cement. Test requirements for asphalt cements are outlined in the appropriate
specification (ASTM D 946, D 3381, or AASHTO MP-1). The asphalt type should be selected as
indicated in paragraph asphalt cement selection by temperature region of this chapter. Several PFC's
with latex rubber added to the asphalt have been constructed. The addition of a latex rubber additive
2-30