Concept of Segregation of Concrete

Segregation of concrete means separation of ingredients from design fresh concrete resulting in the non-uniform mix. More specifically this implies the separation of coarse aggregates from the mortar because of differences in size, density, shape and other properties of ingredients in which they are composed.

Because of segregation honeycomb is created in the concrete and it basically affects the strength of the concrete and its porosity. During construction work, segregation and concrete can occur on site and it affects the durability of your structures.

If you are constructing your own house or working on a site you have to understand about segregation and concrete. In good concrete all the ingredients are properly distributed and make a homogeneous mixture. If a concrete sample exhibits a tendency for separation of coarse aggregates from the rest of the ingredients, it indicates segregation and concrete depending upon the dryness or wetness of the concrete mix.

Types of Segregation of Concrete

There are mainly 2 types :

1. The coarser and the heavier particles tend to separate out or setting down from the rest of the mix because they tend to travel faster along a slope or settle more than finer materials. This type of segregation may occur if the concrete mix is too dry

2. Grout (water + cement) separating out from the rest of the material because of lowest specific gravity. This type of segregation may occur if the concrete mix is too wet. A well-designed concrete does not segregate if rightly mixed and batched.

Causes of Segregation in Concrete ?

Following are the major causes :

• The difference in the specific gravity of the mix constituents i.e fine aggregates and coarse aggregates.
• The difference in the size of aggregate.
• Improper grading of aggregates.
• Improper handling of aggregates.
• Bad practices and handling and transporting of concrete.
• Too much vibration of concrete.
• Concrete that is not proportioned properly and not mixed adequately for 2 workable mix.
• Placing of concrete from a greater height.
• Concrete is discharged from a badly designed mixer or from a mixture with worn-out blades.

Also Read : What is Bleeding of Concrete ?

How to Prevent Segregation of Concrete ?

• At the time of construction, especially while using transit mixers care should be taken that the concrete is not poured from a height greater that 1.5 meter.
• Aggregates should be properly graded as it will prevent the segregation.
• To improve the viscosity of concrete which prevents the segregation, air entraining agents can be used.
• In case of mass concreting where mechanical vibrators are used care should be taken that they are not used for longer period.

Also Read : What is Lightweight Concrete ? Types & Uses