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Segregation in concrete means separation of concrete ingredients as concrete mix is not homogeneous. 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. Another form of segregation happens, if concrete mix carried out on a sloppy surface. Cement particles tend to run away from the center of the concrete mix and leave the coarser material behind. Segregation cannot be measured in qualitative terms but can be detected by an expert eye, and hence it is very important.
Know about concrete mix design.
Why Segregation Occurs?
Normally segregation occurs due to the following aspects:
01. Uneven proportion of concrete ingredients. I.e. Concrete ingredients are not as specified in concrete mix design (generally, use of poorly graded aggregates or bad water cement ratio).
02. Concrete ingredients are not properly mixed. i.e. Insufficient mixing time
03. Concrete is transported from the long distance.
04. Pouring concrete from the height more than 1.5 meter.
05. Vibrating the concrete for a longer duration at same place (poor compaction).
06. Poor workmanship i.e. proper engineering practices are not followed while concreting.
07. Use of poor shuttering materials. I.e. shuttering which leaks.
08. Concrete is discharged from a mixer with high speed, or the inside blades of mixture are damaged.
To know more about this topic, refer Segregation of Concrete and Its Types and Causes.
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.
Also Read: Factors Affecting Strength of Concrete
Following are the awful effects of segregation:
01. Segregation results into the lower strength of concrete.
02. 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.
Also read: How to Repair Corrosion Damaged Concrete
03. 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 concrete:
01. Always use concrete which is predesigned with optimum quantity of water i.e. not too wet nor too dry.
02. Weight the ingredients of concrete properly before you mix them. They should be in proportion according to the concrete mix design. The proportioned of concrete ingredients can be decided by carrying out weigh or volumetric batching of concrete . The weigh batching of concrete ingredients is an essential task to get the durable concrete. Weigh batching is always recommended than volumetric batching of volumetric batching of concrete.
03. Make sure the concrete is properly mixed at the correct speed in a mixture for at least two minutes. Regularly check the performance of mixer with respect to adequate uniformity of distribution of constituents in each batch.
04. If you buy ready mix buy ready mix concrete, choose the supplier in such a way that the transportation of concrete should be done via shortest route. Before you order ready mix concrete, read the tips to order a ready-mix tips to order a ready-mix concrete.
05. Place the concrete in its final position as soon as possible. Never pourconcrete fromhigher heights. Remember that the distance between the mixing and pouring place is minimum.
06. Use proper shuttering materials and make the formwork water tight.This will prevent the leakages of cement paste from the formwork and will give smooth finished concrete.
07. Do the compaction of concrete properly while placing of concrete. There are different methods of compaction and types of vibrators to be used to vibrate a concrete. To overcome the effect of segregation, vibrate concrete at the particular location for the particular time of interval. i.e. Vibrate the fresh concrete for just the right time-not too long, not too less.
08. Use the vibrator correctly and never use the vibrator to spread a heap of concrete over a large area. i.e. Do not allow concrete to flow.
09. Useadmixtures in concrete 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 to make it homogeneous again.
Segregation in concrete is difficult to measure, but it is easily detected when concrete is handled on a site. If the aggregates separate from the concrete mix in larger amount, you can’t get homogeneous or cohesive mix of concrete. To avoid segregation in concrete follow afore mentioned tips which will helps to get durable concrete while you construct a house.