Aggregates are defined as inert, granular materials consisting of stone or stone-like solids. Coarse aggregates are predominantly retained on a No. 4 sieve (4.75 mm) and are generally broken stones. Fine aggregates pass through a No. 4 sieve but are retained on a No. 200 sieve (75μm) and are generally natural river sand. Aggregates can be classified according to size, source, and unit weight.

2. Aggregates are defined as the inert,
granular and inorganic materials that
normally consists of stone or stone like
solids.

3. IN ACCORDANCE WITH THE SIZE :

4. Aggregate predominantly retained on Sieve
no.4 (4.75 mm) is termed as Coarse aggregates.
For mass concrete the ,maximum size can be
as large as 150 mm.
Generally broken stones are used as the coarse
aggregates.

6. Aggregate passing on sieve No.4(4.75mm) and
predominantly retained on Sieve no.200
(75µm) is termed as Fine aggregates.
In general natural river sand is used as the
fine aggregates.

7. IN ACCORDANCE WITH THE SOURCES:

8. This kind of aggregates are taken from natural
deposits without changing their nature during
production such as crushing and grinding.
Sand, crushed limestone & gravel are some
examples.

9. This is a kind of man made materials
produced as a main product or an industrial
by product.
Blast furnace slag, lightweight aggregates
(expanded perlite),heavy weight aggregates
(iron ore or crushed steel) are some examples .

10. IN ACCORDANCE WITH THE UNIT
WEIGHT:

11. The unit weight of aggregates is less than 1120
Kg/m3
Cinder, Blast-furnace Slag, Volcanic Pumice
are some examples.

12. The unit weight of aggregates is between 1520
to 1680 Kg/m3

13. The unit weight of aggregates is greater than
2400 Kg/m3
A typical heavy weight aggregates is used in
special structures .

14. • As per IS:383-1970 shape of the
particles of the aggregates may be
round, angular and flaky..
• Rounded particles do not have good
interlocking, where as irregular and
angular particles show very good inter-
locking properties.

15. • Rounded particles show good
workability.
• They should have a rough surface
to get better bond between
particles and cement paste.
• Porosity and water absorption
should be less.

16. • Harmful ingredients such as iron pyrites,
coal, mica, shale, clay, alkali and organic
impurities should be avoided.
• These materials should not be present in
such quantities that they may effect
strength and durability of the concrete.
• Total amount of deleterious materials in
aggregates should not exceed 5%.