Concrete is an amalgam of different ingredients. It is formed with cement, sand, aggregate, and water. One always aims for compressive strength in concrete; to attain that, all elements must form a homogeneous matrix.
Segregation of concrete is the process in which the particles present in concrete segregate from each other. The segregation process occurs related to the size, shape, and other factors involved in the composition of a concrete application. The solid particles segregate depending on the size.
Concrete segregation can occur from internal factors such as the mixture is not mixed proportionately. There are external factors as well which can lead to the segregation of concrete. It can occur due to vibration, bad transport conditions, and mismanagement.
See also: Significance of mix design of concrete in construction industry
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Known: about workability of concrete
Segregation of concrete: Types
In simple words, concrete segregation means separating concrete ingredients from each other. Workable concrete is a type of concrete that does not segregate easily. Segregation reduces the strength of the concrete due to the creation of pores in it. Not only that, segregation of concrete leads to leakage in the house. Concrete segregation is generally of mainly two types.
1) Segregation occurring due to the separation of aggregates
It occurs when the concrete mixture is a dry mix. Dry mix means the addition of water in the mixture of concrete is lower than the usual amount of water that must be added to get that perfect consistency in that concrete mix. As the mixture is dry, the coarser elements are present in the mix separate because they settle down more easily and quickly than the finer elements which are present in that mix.
2) Segregation due to the separation of cement slurry
Sometimes the mixture of the concrete may be too wet than usual. This happens when the concentration of water in the cement is more than the usual amount of water that must be present in the mixture. Cement slurry is a mixture of cement and water. When the concrete mixture is too wet, the cement slurry separates from the rest of the material.
A perfect proportion of the concrete mixture is very much necessary to increase the workability of the concrete. The workability of the concrete is its most important variable. When the concrete is workable, it results in the formation of durable concrete. Durable concrete leads to a higher life expectancy for a house. When the concrete is durable, it will automatically lead to the formation of a house with strong pillars, whereas if the concrete is weak, it might lead to demolishing of the house.
Segregation of concrete: What are the causes of the segregation of concrete?
The main reason for the segregation of concrete is the improper mixture of concrete; adding an excessive amount of water to the concrete mix is the one mistake that a person should avoid while making the mix. Sometimes it also happens that a sufficient amount of matrix is not added to the concrete mix, thus resulting in bad binding of aggregates.
Excessive vibration also leads to the segregation of concrete. Many times it is seen that concrete is transported over a long distance, and these long journeys over a long time weaken the binding of the concrete. There is a detailed explanation of the causes of segregation below.
1) Improper constituents in the mixture
The segregation of concrete is interdependent with the constituents of the elements present in the mixture. When you go for the correct quantity of every element that is required to make a perfect concrete mixture, you are eradicating the chances of segregation, which is mainly dependent on the water-cement ratio added to the mixture. The mixture must not be too dry or too wet.
So, it is important that the constituents in the mixture are always added by someone who has good knowledge about it. Unskilled workers might damage the entire consistency of the mixture and end up with an inferior one.
2) Long transportation times
In each industrial element, transportation plays a very important role. Long-distance transportation always invites more and more challenges in the flow of work. Big projects such as the making of roads, metro, etc., require a huge amount of concrete mixes. Sometimes the material might be delivered rather than being prepared on the spot. And that could be a problem.
It can happen because excess transportation time can make the concrete mix dryer, or the thickness of the mixture could get affected. A poor environment can also affect the mixture, and hence there can be a lack of consistency in the mixture which can end up affecting the concrete and leading to segregation.
3) Vibration of concrete
Sometimes mechanical needle vibrators are used for mixing concrete. If the use of it is done excessively, it will lead to the settling of heavier particles at the bottom, and the particles which are light in weight will come on the top. So, the use of mechanical needle vibrators must be restricted or limited in use.
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Segregation of concrete: Effects
Concrete segregation occurs when there is a default in the ratio of the concrete mixture, and its effects can be adverse. A slight mistake can lead to a huge disaster. So one must be very cautious while preparing the mixture of concrete. Here are some of the major problems of concrete segregation:
1) Problems regarding leakage and corrosion
Segregation causes the formation of pores in the concrete. When pores occur automatically, there are huge chances of leakage of water. Water leakage is very problematic because there will be corrosion when there is continuous leakage of water. Corrosion will have a direct impact on the structure of the building. The leakage makes a structure weak from the inside.
2) Formation of cracks
Due to the occurrence of segregation, the strength of the concrete becomes weak. As the strength decreases, there can be visible cracks on the households’ slabs and columns or whichever area the segregation is taking place. Whenever there are visible cracks, it is a sign that the concrete is segregating. Cracks are mostly seen on the beams of the structure as well as on the columns of the structure. The formation of cracks in these specific areas is a clear red signal that the building is in danger.
3) Lowers the strength of the concrete
The strength of the concrete is a critical factor. Its strength and consistency influence everything. Whenever the combination is improper, the concrete tends to lose its strength, and the formation of cracks and leakages can be seen. Columns and beams hold the entire structure. So, whenever there is segregation of concrete, the very first visible effects can be seen on them.
Segregation of concrete: How to prevent the segregation of concrete?
Segregation of concrete mainly occurs due to improper mixing of the contents that are in the mixture. It can also occur due to poor usage of materials. Sometimes it happens due to discharging of the concrete mix from a high-speed mixing machine and sometimes because of the damaged blades of the machine.
However, there are always some ways with the help of which we can prevent the segregation of concrete. By following some of the simple ways, we can increase the workability of the concrete and make the structure of a home secure for a larger amount of time.
- Height is critical in getting a perfect composition of concrete mix. When the concrete is poured, it must be ensured that the height from which the pouring of concrete happens must not be more than the specified height, i.e. 1.5 meters. The angle of inclination must also be maintained, preferably between a 1:3 and 1:2 ratio, so that it travels smoothly from top to bottom. Using a small amount of water is very much helpful as its bits help in lubricating, making the flow of concrete smooth.
- Grading the aggregates properly is very much required to prevent the segregation of concrete.
- One should always have a core test to ensure that the concrete has attained the desired strength that one has been aiming for. If it fails to prosper in the core test, the concrete mix needs to be made again, considering every tiny detail to attain the core strength that the person has been aiming for.
- To clear any doubt, one can also go through random ultrasonic tests. It is always better to take the opinion of the designer if there is any scope for doubt.
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- Sometimes there is the usage of mechanical vibrators. This generally occurs during mass concreting. Special care should be taken in this type of case. One must not use it for a long time.
- Air entraining agents must be used in the concrete mix. This increases the viscosity of the mixture, which helps to avoid the occurrence of segregation in the mixture.
Segregation of concrete: How is segregation different from the bleeding of concrete?
Segregation and bleeding are the two most common things that affect the nature of concrete. Most people confuse these two terms as the same, but in reality, they are very much different. While segregation occurs due to the separation of the aggregates from the cement slurry, bleeding occurs due to water separation.
- In the case of segregation, it occurs due to excessive fall of the concrete pouring, whereas bleeding occurs due to the addition of excessive water.
- The most common cause of segregation is improper mixing of the elements and placing them at an improper height, whereas bleeding is caused due to excessive vibration.
- When the segregation of concrete happens, it makes the concrete porous and also makes the concrete weak, but in the case of bleeding, it leads to a honeycomb.
- When it is about segregation, there is the slightest chance of repairing after formation. When talking about bleeding, there is no chance of repairing after the formation.
FAQs:
Does maintaining a specific w/c ratio help to overcome the segregation of cement?
Yes, maintaining a proper water and cement ratio helps one to achieve the desired consistency in concrete mixture as well as reduces the chances of segregation.
Are segregation and bleeding similar to each other?
No, segregation and bleeding are not similar to each other. They are interrelated to each other but not similar.
Do height and time play an important role in the segregation of concrete?
Yes, height and time do play a very important role in getting a perfect mixture and thus eliminating the scope of segregation of concrete.