Type of Aggregates and Requirements of good aggregates

 AGGREGATES

 Aggregates is the broad category of basis materials used in costruction, including and, gravel, crushed stone, slag saw dust, broken bricks etc. It constitutes about 85% of the volume of concrete. They are chemically insert and forms morter and concrete when mixed with cement. Aggregate do not take part  in the various chemical reactions take place in concrete during setting and harding of concrete, thus they are called inert materials. The agregates are generally used to increase the volume of concrete. They are econimial and cheaper then cement. Aggregates also contribute toward greater volume stability and durability to concrete.

Aggregate

Requirement of good aggregates: 

A good aggregate should meetcetain requirements which are as follows:

(1) It should be chemically inactive.

(2) It should be sufficiently strong.

(3) It should be hard enough.

(4) It should be durable.

(5) There should be limited pores (porosity).

(6) It should have rough surface.

(7) Its surface should be clean and free from clay and other materials.

(8) It should be well graded.

(9) It should be resistant to wear and tear.

Type of Aggregates:-

Aggregates are classified into two category 

(1) Course aggregates

(2) Fine aggregates

(1) Course Aggregates : 

The size of aggregates having size varing 75mm to 4.75mm size that is pass through 75mm IS sieve and retain from 4.75mm IS sieve is known as course aggregates.

(2) Fine Aggregates :  

The size of partical size pass through 4.75 mm sieve and retain from 0.15 mm mesh is known as fine aggregates.