UFC 3-260-02
30 June 2001
CHAPTER 8
AGGREGATE BASE COURSES
1. USE OF AGGREGATE BASE COURSES. Aggregate base courses may be required for one or
more of the following reasons: distribution of load, provide drainage, protect from frost, provide uniform
bearing surface for the pavement surfacing, replace unsuitable soils, provide working platform, increase
strength of pavement system or prevent pumping.
2. MATERIALS FOR AGGREGATE BASE COURSES IN FLEXIBLE PAVEMENTS. Aggregate base-
course materials for flexible pavement must be of high quality and conform to agency guide
specifications. Since natural cementation of the materials listed in subparagraphs c, d, e, f, and g occurs
progressively in place, there is a potential that the strength of these materials will increase with time,
resulting in higher CBR values than laboratory tests indicate. Special requirements for aggregate base
courses in frost areas are discussed in Chapter 20. Aggregate base courses used as drainage layers
must meet the requirements of EI 02C202/AFJMAN 32-1016. Those materials generally used as
aggregate base-course materials are listed below:
a. Graded Crushed Aggregate Base Course--100 CBR. Stone is quarried from formations of
granite, traprock, and limestone. Gravel is quarried from deposits of river or glacial origin. The stone
and gravel are crushed and screened to produce a dense-graded crushed aggregate material meeting
requirements of guide specifications. The percentage of loss shall not exceed 40 when tested in
accordance with ASTM C-131. The material shall also meet the requirements listed in CEGS 02722 for
flat and elongated particles, liquid limit and plasticity index, and magnesium sulfate soundness when
tested in accordance with ASTM C 88. Gradation requirements for graded crushed aggregates are as
follows:
Table 8-1
Gradation Requirements for Graded Crushed Aggregates, Base Courses, and Aggregate Base
Courses
Percentage by Weight Passing Square-Mesh Sieve
Sieve Designation
No. 1
No. 2
No. 3
50-mm (2-in.)
100
--
--
37.5-mm (1-1/2-in.)
70-100
100
--
25-mm (1-in.)
45-80
60-100
100
12.5-mm (1/2-in.)
30-60
30-65
40-70
4.75-mm (No. 4)
20-50
20-50
20-50
2.0-mm (No. 10)
15-40
15-40
15-40
0.425-mm (No. 40)
5-25
5-25
5-25
0.075-mm (No. 200)
0-8
0-8
0-8
b. Aggregate Base Course--80 CBR. This material is a blend of crushed and natural materials
processed to provide a dense graded mix (often referred to as mechanically stabilized base course).
8-1
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