55
50
45
40
35
30
0
2
4
6
8
10
12
14
16
18
Particle Index
Figure 27. Void volume vs. particle index at a compactive effort of 10 blows per layer.
10
8
6
4
2
0
0
40
60
80
20
100
120
% Crushed Aggregate
Figure 28. Relationship between particle index and percent crushed aggregate in mixture.
cent crushed aggregates may lead to erroneous results.
ence of the percent of crushed fine aggregates on PI
The corrected percentage of crushed materials for the
was minor.
40/60 and 60/40 crushed/natural aggregates and PI are
The next step in the process was to determine whether
shown in Figure 31. PI as a function of percentage of
we could relate PI to the aggregate mixture's mechani-
crushed aggregate can also be estimated from the fol-
cal properties. Resilient modulus from the 300-mm-
lowing equation:
diameter tests at two bulk stress values was plotted as a
function of PI (Fig. 32). The bulk stresses chosen were
PI = 0.601(% crushed) + 3.124.
(14)
400 kPa and 200 kPa. These values were based on a
Average PI values for the coarse aggregates are pre-
theoretical analysis of a 100-mm asphalt concrete pave-
sented in Table 15. PI for the aggregate mixture ranges
ment over 600-mm base course over a weak subgrade.
between 2.9 and 8.6; the crushed aggregate content
The modulus values used in the analysis were 2750
increases from 0 to 100%. As seen in Table 15, the influ-
MPa, 345 MPa, and 35 MPa, respectively. Based on
21
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