Civil Engineering Reference
In-Depth Information
The value of the exponent
n
recommended by Fuller is 0.5. In the
1960s, the Federal Highway Administration recommended a value of 0.45
for
n
and introduced the “0.45 power” gradation chart, Figures 5.12 and
A.22, designed to produce a straight line for maximum density grada-
tions (Federal Highway Administration 1988). Table 5.2 presents a sample
Sieve size
100
90
80
70
60
50
40
30
20
10
0
Sieve size, mm
FIGURE 5.12
Federal Highway Administration 0.45 power gradation chart show-
ing the maximum density gradation for a maximum size of 25 mm. See Table 5.2.
T ABLE 5.2
Sample Calculations of Aggregate Distribution
Required to Achieve Maximum Density
0.45
Sieve
P
i
=
100
1
d
i
/
D
2
25 mm (1 in.)
100
19 mm (3/4 in.)
88
12.5 mm (1/2 in.)
73
9.5 mm (3/8 in.)
64
4.75 mm (No. 4)
47
2.36 mm (No. 8)
34
0.60 mm (No. 30)
19
0.30 mm (No. 50)
14
0.075 mm (No. 200)
7.3
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