Page 8 - zana-training e book

Fine Sand

Coarse Sand

Silt

Medium Sand
Clay

Figure 1.3: Size variation of fine aggregate

Coarse Aggregate

i. When the aggregate is sieved through 4.75mm sieve, the aggregate retained is
called coarse aggregate.
ii. Gravel, cobble and boulders come under this category.
iii. The maximum size aggregate used may be dependent upon some conditions. In
general, 40mm size aggregate used for normal strengths and 20mm size is used
for high strength concrete. The size range of various coarse aggregates given
below.

Table 1.2 : Size coarse aggregate
Coarse Aggregate Size (mm)

Fine Gravel 4 - 8
Medium Gravel 8 - 16
Coarse Gravel 16 - 64

Cobble 64 - 256
Boulders >256