WHAT IS BLEEDING IN CONCRETE? CAUSES, EFFECTS AND REMEDIES OF BLEEDING.

BLEEDING


Bleeding is the form of segregation in which some of water from the concrete comes out to the surface of the concrete, Being of the lowest specific gravity among all the ingredients of concrete. It is sometimes referred as water gain.

Causes of bleeding :
  1. It is due to inability of the solid particles in the mix to hold all the mixing water during the setting of particles under compaction.
  2. It is due to higher water cement ratio. If the water cement ratio is higher than 0.7 then the water escalated due to capillary movements.
  3. When the surface is excessive work by the towel and floats, the aggregate goes down and water comes up and cause bleeding.
  4. If the mix proportion is inappropriate then concrete does not bind the particles homogeneously and water get escaped from concrete.

Effects of bleeding in concrete :
  1. It reduces bond between cement paste and aggregates.
  2. Bleeding creates extra mortar on the surface which cause plastic shrinkage.
  3. It increases permeability of concrete.
  4. It reduces bond between steel and concrete.
  5. If concrete placed in different layers the bond between layers will be weak.

Remedies to prevent bleeding :
  1. Use rich mix.
  2. Use finer cement with low alkali content.
  3. Proper proportioning the mix.
  4. Uniform and sufficient mixing of concrete.
  5. Use of air entraining agents also reduces the bleeding.
  6. Maintain proper water cement ratio.

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