It is described by American Society for Testing and Materials as follows: Segregation in concrete is commonly thought as separation of some size groups of aggregates from cement mortar in isolated locations with corresponding deficiencies of these materials in other locations. Segregation results in proportions of the laid concrete being in variation to those as designed .A good picture of cohesion of the concrete mix is obtained by flow test.
If the concrete is not cohesive the larger particles of aggregate will separate out and will move towards the edge. Segregation cannot be measured in qualitative terms but can be detected by an expert eye, and hence it is very important.
Effect of Segregation in Concrete
Nowadays houses are made of concrete to get the long service life of house. But, generally segregation in concrete reduces the strength of structural members of houses. This may result into the failure of building during the earthquake or other natural disasters or will reduce its overall life.
Following are the awful effects of segregation
1- Segregation results into the lower strength of concrete.
2- Segregation causes the porous or honeycombed concrete which develops the problem of leakages in your house. It ultimately results into the defects like corrosion in concrete, carbonation, etc.
3- Segregation develops the cracks in concrete which ultimately leads to the early repair of house. A segregated concrete is a concrete of a variable strength and is relatively prone to cracking and leakages. Therefore, it is very important to avoid segregation in concrete to make your structure long lasting.
Prevention of Segregation in Concrete
Following are useful tips to avoid segregation in concrete1- The concrete mix should be properly designed with optimum quantity of water i.e. not too wet nor too dry.
2- Make sure the concrete is properly mixed at the correct speed in a transit mixture for at least two minutes. Regularly check the performance of mixer with respect to adequate uniformity of distribution of constituents in each batch.
3- Transport the concrete mix correctly. Choose the shortest route for transportation of concrete mix.
4- Place the concrete in its final position as soon as possible. Never place a concrete from large heights.
5- Formwork should be water tight so that paste should leakage from the forms. Do not vibrate formwork.
6- Do not allow concrete to flow.
7- Use the vibrator correctly and never use the vibrator to spread a heap of concrete over a large area.
8- Vibrate the concrete for just the right time-not too long, not too less.
9- Use chemical admixtures such as air entraining agent in the mix. Entrained air reduces the danger of segregation.
10- If any segregation is observed in concrete, remixing should be done so to make it homogeneous again.