Segregation causes of segregation and preventing

 Segregation :  

Segregation can be defined as the seperation of the constitute materials of concrete. A good concrete is one in which all  the ingredients are properly distributed to make homogeneous mixture. If a sample of concrete exhibits a tendency for separation of say, course aggregates from the rest of the ingredients, then, that sample is said to be showing the tendency for segregation. A concrete which has a tendency to segregation will lack homogenerity as well as will be weak.

    There are considerable differences in the sizes and specific gravities of the constituent ingredients of concrete. Therefore, it is natural that the materials show a tendency to fall apart. Segregation may be of three types -

    1. The course aggregate separating out or settling down from the rest of matrix.

    2. The paste or matrix separating away from course aggregates.

    3. Water separating out from the rest of the material being a material of lowest specific gravity.

Segregation of concrete

Causes of segregation  : The Causes of segregation are :-

1. The presence of too much water in mix.

2. When there is improper mixing of ingredients of concrete.

3. Due to the presence of badly graded aggregates.

4. The presence of heavy weight aggregates which do not compact with cement paste cause segregation.

5. When concreting is done under water.

6. When too much shocks during transportation of concrete from mixing site to placing side or when concrete is thrown from a considerable height.

Prevention of segregation 

1. Reducing the height of drop of concrete.

2. The mix should be designed properly and with adequate quantity of water as designated by water cement ratio.

3. Air entraining agent should be used for reducing segregation as the reduce there water content.

4. Reducing the continuous vibration over a longer time as this leads to setting of course aggregates.