Bleeding can be defined as the tendency of water to
rise to the surface of freshly placed concrete. It is another form of
segregation where some amount of water comes to the concrete surface after
placing and compacting, before setting.
The water content carries some particles of sand and
cementing materials. Sometimes bleeding helps to reduce the plastic shrinkage
cracks in concrete.
Effects of Bleeding in concrete:
1. Concrete loses its homogeneity which results in weak and
porous concrete.
2. It makes the concrete permeable.
3. It delays the surface finishing in pavement construction.
4. Bleeding of concrete causes high water-cement ratio at
the top surface.
5. The bond between two concrete layers become weaker.
6. Pumping ability of concrete is significantly reduced.
Bleeding in concrete can be reduced by taking following
precautions:
1. Design the concrete mix properly.
2. Add minimum water content in the concrete mix.
3. Add more cement in the mix.
4. Increase the number of fine particles in the sand.
5. Use a little amount of air entraining admixture.
6. Use more finely ground cement.
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