AGGREGATES - Materials for Civil and Construction Engineers - page 180

T ABLE 5.3 Effect of Amount of Fines on the Relative Properties of Aggregate Base Material

No fines Well-Graded Large Amount of

Characteristic (Open or Clean) (Dense) Fines (Dirty or Rich)

Stability Medium Excellent Poor

Density Low High Low

Permeability Permeable Low Impervious

Frost Susceptibility No Maybe Yes

Handling Difficult Medium Easy

Cohesion Poor Medium Large

As shown in Table 5.3, the amount of fines has a major effect on the
characteristics of aggregate base materials. Aggregates with the percentage of
fines equal to the amount required for maximum density have excellent sta-
bility and density, but may have a problem with permeability, frost suscep-
tibility, handling, and cohesion.

Gradation Specifications Gradation specifications define maximum and
minimum cumulative percentages of material passing each sieve. Aggregates
are commonly described as being either coarse or fine, depending on
whether the material is predominantly retained on or passes through a 4.75-
mm (No. 4) sieve.
Portland cement concrete requires separate specifications for coarse and
fine aggregates. The ASTM C33 specifications for fine aggregates for con-
crete are given in Table 5.4. Table 5.5 shows the ASTM C33 gradation spec-
ifications for coarse concrete aggregates.

T ABLE 5.4 ASTM Gradation Specifications for
Fine Aggregates for Portland Cement Concrete
(Copyright ASTM, reprinted with permission)

Sieve Percent Passing

9.5 mm 1 3/8- 2 100

4.75 mm (No. 4) 95-100

2.36 mm (No. 8) 80-100

1.18 mm (No. 16) 50-85

0.60 mm (No. 30) 25-60

0.30 mm (No. 50) 10-30

0.15 mm (No. 100) 2-10