Civil Engineering Reference
In-Depth Information
100
90
80
70
60
50
40
30
20
10
0
0.075 0.15 0.3
0.6
1.18
2.00
2.36
4.75
Sieve size, mm
Other Types of Gradation
In addition to maximum density (i.e.,
well-graded
),
aggregates can have other characteristic distributions, as shown in Figure 5.13.
A
one-sized
distribution has the majority of aggregates passing one sieve
and being retained on the next smaller sieve. Hence, the majority of the ag-
gregates have essentially the same diameter; their gradation curve is nearly
vertical. One-sized graded aggregates will have good permeability, but poor
stability, and are used in such applications as chip seals of pavements.
Gap-
graded
aggregates are missing one or more sizes of material. Their gradation
curve has a near horizontal section indicating that nearly the same portions
of the aggregates pass two different sieve sizes.
Open-graded
aggregates are
missing small aggregate sizes that would block the voids between the larg-
er aggregate. Since there are a lot of voids, the material will be highly per-
meable, but may not have good stability.
100
Dense
Open
Gap
One-sized
FIGURE 5.13
Types of aggregate grain
size distributions plotted on a 0.45 gra-
dation chart.
0
Size
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