Bleeding of concrete – its causes, reasons, effects & prevention | Bleeding of concrete | Bleeding in concrete | what is bleeding of concrete | causes of bleeding in concrete |Reasons for bleeding of concrete | ways to reduce bleeding of concrete.
Bleeding of concrete
Today in construction project you will require fresh concrete with its gredient cement, sand, aggregate and water for concreting work, these construction materials you will need to be deliver pre casting or post casting concrete at your constraction site which is need to be fresh concrete but some problems can occur in concrete due to improper mixing, curing and placing, one such problem is bleeding in concrete.
I will discussed about the bleeding of concrete that is play a important harmful role in loss of homogeneity in concrete, weaker the top surface of concrete and reduces it’s interconnected bonding with cement and water particles, types of bleeding, causes of bleeding in concrete and control ability of bleeding.
Bleeding of concrete is defined as the phenomenon of tendency of the water to rise to the surface of new laid concrete being the lowest specific gravity among the constituents of concrete is a form of segregation due to results solid materials of concrete to hold the water in mixed preparation of concrete and during this process of material downward settling. The bleeding in concrete is occured after placing and compaction in the state of plastic state of concrete which is freshly mixed fresh concrete gains a transient state that is harmfully affects the behavioural properties of concrete.
Bleeding in concrete is consist also different types such as normal bleeding associated with a uniform seepage of water over the top surface of the freshly mixed concrete structures that is good and it enhances the Workability of concrete and another type channel bleeding associated with to water rising through particular paths that is very harmful to construction of structures.
What is bleeding of concrete?
Regarding this, “what is bleeding of concrete?”, bleeding is generally defined as the free water in the mix rises up to the surface of freshly concrete due to the settlement of heavier particles like as cement and water and forms of paste of cement on the surface that is known as laitance, due to the formation of laitance freshly concrete structures loss it’s resistance capacity, strength and decreases its life of structure.
Bleeding in concrete occures when course aggregate tends to settle down and free water rises up in the condition of plastic state as a form of segregation, the early bleeding in concrete is associated with fully plastic which is not much harm due to fact that in case of fully plastic will get subsided and compacted, in other type of bleeding occured when the concrete has lost its plasticity form that is known as delayed bleeding which is much harmful to the bleeding in concrete.
Some important fact about bleeding in concrete
1. Bleeding of concrete occured in a form of segregation.
2. Top surface of freshly mixed concrete is weaker due to identified by appearance of thin layer of water, this surface is finally formation of laitance on the surface due to reason bleeding water in concrete.
3. Bleeding of concrete is observed in case of highly wet and improper proportioned mixing of concrete gradient sand,cement , aggregate and water.
4. Bleeding occurred in concrete is not harmful,when rate of evaporation is equal to rate of beeding.
5. It occurs after placing and Compaction in freshly mixed concrete as a form of known as plastic state of concrete.
Causes of bleeding in concrete
Bleeding in concrete is the occured due to the segregation ( separation of the constituent materials of concrete in the firm of coarse aggregate separation, the paste separation and water separating out) in the concrete mix as a form of plastic state in which heavy aggregate particles settle down due to settling of particles, water rises up to the top of freshly concrete surface and formation of laitance in surface , it is the play a important role to causes of bleeding in concrete
Bleeding in concrete occures more frequent on the top surfaces of freshly concrete construction and highly effect the strength of concrete and its life deacreases ,when water to cement ratio is higher and improper slump value according to construction of structure, other factor like as type of cement used, quantity of fine aggregates, improper proportione of concrete constituents also play a effective role in causes of bleeding in concrete construction.
Effects of bleeding in concrete
Bleeding of concrete is a greatly harmful on construction of civil engineering structure concrete, it is highly effect the strength of concrete structures, the biggest factor in bleed water rates is the water to cement ratio can lead to excessive bleeding and the cement type and fine aggregates can play a role to find bleed rate,we can discussed the some effect of bleeding on concrete as follows-:
1. Bleeding in concrete finally formed laitance in top surface.
2. Internal bleeding is also observed.
3. Makes the concrete porous
4. Concrete loses its homogeneity.
5. Constituents of concrete and reinforcement between layers is occurring poor bond formation.
6. Strength and resistance of concrete is decreses.
7. Delays in work finishing in surface and curing due to forming of water at the top surface.
8. Excessive bleeding break the bond between the concrete and reinforcement and also the accumulation of water occured a water voids and reduces bond between the cement paste and aggregate.
9. It is responsible for causing permeability in concrete.
10. Pumping ability of concrete is also effect
11. Increase in the water cement ratio at the top surface is highly effect due to bleeding will be more frequent on the surface of concrete .
12. Sand deficient in fine also tend to increase the bleeding characteristics of concrete
How to reduce bleeding in concrete
There are some factors or ways used in properly help to reduce bleeding in concrete as follows-:
1. Concrete bleeding is reduced by add minimum water content in the concrete mix and used chemical admixtures to reduce demand to water for required Workability. Use slump mix,
2. Concrete constituents cement, Coarse aggregate,fine aggregate mix propertional in properly to design of concrete structures.
3. Adding more cement in the mix
4. Used the air entraining admixtures is play a highly effective in reducing the bleeding.
5. Use fly ash or other supplementary cementitous materials such ad slag cement or silica fume.
6. Increase the amount of fines in sand
7. The allowing free water to migrate to a surface and evaporate the water cement ratio of the structures decreases thus decreasing capaliary porosity and increasing its density and durability.
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How to prevent bleeding in concrete
Regarding this, “how to prevent bleeding in concrete?”, is effective some fectors that is associated with proper used in concrete construction which is to prevent bleeding in concrete as follows-:
1. Controlling the water cement ratio, use slump value mix according to structure design of concrete due to reduced the bleeding in concrete.
2. Providing the finer grading of fine aggregates,used according to require in design mix structure associated with properly mixed propertion
3. Using more finely ground cement .
4. The add air entraining agents should be controlled the bleeding.
5. Controlling compaction.
6. Vibrating concrete for a sufficient time .
7. Removing the laitance fully before pouring the next lift
8. Uniform, complete mixing and proper propertioning.
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