TM 5-822-5/AFM 88-7, Chap. 1
CHAPTER 6
FLEXIBLE PAVEMENT BASE COURSES
6-1. Materials. High-quality materials must be
mold, the laboratory CBR test will not be used in
used in base courses of flexible pavements. These
determining CBR values of base courses. In-stead,
high-quality materials provide resistance to the high
selected CBR ratings will be assigned as shown in
stresses that occur near the pavement surface.
the following tabulation. These ratings have been
Guide specifications for graded crushed aggregate,
based on service behavior records and, where
limerock, and stabilized aggregate may be used
pertinent, on in-place tests made on materials that
without qualification for design of roads, streets,
had been subjected to traffic. It is imperative that
and parking areas. Guide specifications for dry- and
the materials conform to the quality requirements
water-bound macadam base courses may be used
given in the guide specifications so that they will
for design of pavements only when the cost of the
develop the needed strengths.
dry- or water-bound macadam base does not
exceed the cost of stabilized-aggregate base course,
and the ability of probable bidders to construct
pavements with dry- or water-bound macadam base
to the required surface smoothness and grade
tolerances has been proved by experience in the
area.
6-2. Compaction. Base courses placed in flexible
pavements should be compacted to the maximum
density practicable, generally in excess of 100
percent of ASTM D 1557 maximum density but
never less than 100 percent of ASTM D 1557
maximum density.
6-5. Minimum Thickness. The minimum allow-
able thickness of base course will be 4 inches as
shown in table 6-1, except that in no case will the
should be accomplished in accordance with TM 5-
total thickness of pavement plus base for class A
820-2/AFM 88-5, Chap. 2.
through D roads and streets be less than 6 inches
nor less than frost design minimum specified in
6-4. Selection of Design CBR. Because of the
chapter 18 when frost conditions are controlling.
effects of processing samples for the laboratory
TM 5-822-5/AFM 88-7, Chap. 1
CBR tests and because of the effects of the test
6-1
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