Aggregate are the major ingredient of concrete which occupy 70 to 80 % of the volume of concrete and therefore it increases the density of the concrete mix. Therefore aggregates improve the volume stability and durability of concrete. They are chemically inert materials and are broadly divided into two categories i.e. fine agg. and coarse agg.
Functions of aggregate:
- Firstly they act as a structural filler material in concrete.
- It is provide strength to the concrete.
- They help in increasing the durability of concrete.
- They decrease the amount of shrinkage that could occur in concrete
- Therefore it helps to produce the workability and uniformity in the mixture.
- Lastly to reduce the amount of cement paste required in creates to make it economical
Classification of aggregates:
A. Based on grain size
- Fine
- Coarse
B. Based on its unit weight
- Light weight
- Normal weight
- Heavy weight
C. Based on geological origin
- Natural
- Artificial
D. Based on shape
- Rounded
- Irregular
- Angular
- Flaky and elongated
1. Classification based on grain size
- Fine : The agg. with grain size below 4.75 mm is termed as fine aggregate.
- Coarse : The aggregate with grain size above 4.75 mm is termed as coarse aggregate.
2. Classification based on unit weight
- Light weight: An it has unit weight upto 12 kN/m^2 is termed as light weight.
- Normal weight: An it has unit weight ranging from 23 to 26 kn/m^2 is termed as normal weight
- Heavy weight: An it which has unit weight ranging from 28 to 30 kn/m^2 is termed as heavy weight.
3. Classification based on shape
- Rounded : It is in round in shape
- Irregular : The aggregate which are partly rounded and partly angular in shape.
- Angular : The aggregate which are sharp angular and rough particles are termed as angular aggregate.
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