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Concrete bleeding

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Bleeding can be defined as a form of the local concentration of water at a specific location, usually at the bottom of coarse aggregate, the bottom of reinforcing steel and at the top surface of the placed concrete, bleeding will adversely affect the concrete by increasing the permeability and this will reduce the strength and durability, permeable concrete will allow easier passage of aggressive chemicals such as chloride, the passage of this chemical will result in reinforcing steel corrosion. 

Figure 1








The main reason behind the bleeding of concrete is the density of water, the density of water is lighter than other aggregates, heavier particles will settle down during the placing process and water will move upward, the bleeding will adversely affect the concrete
  • bleeding will increase concrete permeability.
  • bleeding will reduce the concrete mix homogeneity. the result is weak and porous concrete.
  • bleeding of concrete will reduce the ability of pumping of fresh concrete.
  • laying layers of concrete above bleeding concrete will result in low strength and durable concrete.
  • finishing of the surface by mixing bleeding water will produce weak wearing surface, bleeding water should evaporate before surface finishing which means losing time.






How to reduce bleeding in concrete?

  1. reducing W/C by adding superplasticizer admixture.
  2. design concrete mix properly.
  3. using of air-entrained admixture
  4. increasing the amount of fine particles in sand.
  5. increase the amount of cement.

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