Aggregate. Test results for the natural and crushed prod-
Table 1. Sieve size frac-
ucts (material retained on the No. 4 sieve) and the fine
tions.
fraction are presented in Table 2. The 136-kg samples
having the proportions of crushed and natural material
Passing
Retained
presented in Table 3 were placed in 189-L containers
2 in.
1 in.
and delivered to CRREL.
1 in.
3/4 in.
3/4 in.
2/3 in.
2/3 in.
3/8 in.
MOISTURE DENSITY
3/8 in.
No. 4
No. 4
No. 8
Moisture density relationships were conducted by
No. 8
No. 16
CRREL and VAOT. VAOT conducted the tests using
No. 16
No. 30
AASHTO T-99 test method Moisture-Density Relations
No. 30
No. 50
No. 50
No. 100
of Soils Using a 2.5-kg Rammer and a 305-mm Drop--
No. 100
No. 200
Method D. Aggregates larger than 19 mm were removed
No. 200
pan
and replaced with an equal amount of material retained
on the No. 4 sieve. A typical gradation curve for the
aggregates used in the T-99 test is shown in Figure 5.
material as well. Material placed in the "natural" cat-
For comparison, the actual gradation of the test aggre-
egory was generally rounded, although some
gate is shown in the same figure. The T-99 test used a
subrounded particles were included. This part of the
152-mm-diameter mold; the sample was compacted in
procedure was done manually and was independently
spot-verified by a second party.
After both the crushed and natural materials were
Table 2. Aggregate specific gravity and
separated into each size fraction, the materials were
absorption.
combined to meet the test gradation shown in Figure 4.
Absorption Bulk specific
The test aggregate gradation was selected to fit near
Material
(%)
gravity
the center of the specification as shown. The test ag-
Crushed gravel
0.59
2.71
gregate gradation had 100% passing 75 mm and 85%
Natural gravel
0.68
2.71
passing the 50-mm sieve and classified as an A-1-a us-
Minus No. 4
1.2
2.66
ing the AASHTO classification or as GP or GP-GM
using the Unified Soil Classification System. Aggre-
gate samples were tested for specific gravity and ab-
Table 3. Test sample proportions.
sorption in accordance with AASHTO test methods T
Crushed particles, %
100
75
50
25
0
84, Specific Gravity and Absorption of Fine Aggregate,
Natural particles, %
0
25
50
75
100
and T 85, Specific Gravity and Absorption of Coarse
100
80
60
40
Test Gradation
20
0
0.01
100
10
1
0.1
Grain Size (mm)
Figure 4. Gradation limits meeting VAOT subbase specification.
4
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