Classification of Aggregates

Hi,

Aggregates are used for the manufacturing of the concrete. Aggregates are classified into two categories according to their size:

1. Coarse Aggregates These are the aggregates which have sizes more than 4.75 mm. In laboratories they are separated as the aggregates which are retained on the BIS test sieve no. 480. Generally, broken stones are used as the coarse aggregates.
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3. Fine Aggregates These are the aggregates which have a size less than 4.75 mm. In the laboratory, they are classified as the aggregates which pass through the BIS sieve no. 480. In general, Natural river sand is used as a fine aggregate.

Now we will discuss the characteristics of the coarse aggregates:

• As per IS:383-1963, the shape of the particles of the aggregates may be round, angular and flaky. Rounded particles do not have good interlocking, whereas irregular and angular particles show very good inter-locking properties. Rounded particles show good workability.
• They should have a rough surface to get the better bond between particles and cement paste.
• Porosity and water absorption should be less.
• 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 affect the strength and durability of the concrete. The total amount of deleterious materials in aggregates should not exceed 5%.

Thanks for visit!