Wednesday, 10 April 2019

What is aggregate and there properties ?

·       Aggregates are the inert or chemically inactive materials which are considered to be as important constituents' in concrete.
·       The aggregates may be classified as natural and artificial aggregates based on sources of the aggregates.
Examples for natural aggregates include sand, gravel, crushed -rock such as granite quartz, basalt , sand stone etc. Similarly, examples for artificial aggregates include broken-brick , slag , bloated clay ,sintered fly ash, etc.

Properties of Aggregates:

1. Size : On the basis of size , these are classified into two categories .
These are:
a) Fine Aggregates
b) Course Aggregates
·       The size of aggregates bigger than 4.75 mm is considered as coarse aggregates. The size of aggregates whose size is 4.75 mm and less is considered as fine aggregate. The maximum size of aggregates should be as possible within the specified limits. but in any case not greater than 1/a of the minimum  thickness of the member.

2. Shape: Since shape of aggregates affects, the workability of concrete , it is considered to be an important characteristics of aggregate.
·       Rounded aggregates are preferable to angular aggregates for a given water cement ratio.
·       In contrast , angular aggregates exhibits better interlocking effect, higher bond strength than rounded aggregates which makes this suitable for roads and pavements construction.

3. Texture: Rough textured aggregate develops higher bond strength in tension than smooth textured aggregate. 

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