Bleeding is one form of segregation, where water comes out to the surface of the concrete, being lowest specific gravity among all the ingredients of concrete. Bleeding can be easily identified in the field by the appearance of a thin layer of water in the top surface of freshly mixed concrete.
Effects of Bleeding on Concrete
Due to bleeding concrete loses its homogeneity.
Bleeding is responsible for causing permeability in concrete.
In the process of bleeding (i.e. while water is in the process of coming towards top) sometimes gets accumulated below the aggregate. This accumulation of water creates a water voids and reduces bond between the aggregate and cement past. So the strength of concrete reduces (Note: This aspect is more pronounced in case of flaky aggregates)
Similarly, water that accumulates below the reinforcing bars, particularly below the cranked bars, reduces the bond between the reinforcement and concrete.
If a slip form paver is used for construction of concrete pavement, the bleeding water causes very serious problems. If too much of bleeding water accumulates on the surface of pavement slab, the bleeding water flows at over the unsupported side which causes collapsing of sides.
In pavement construction bleeding water delays surface finishing and application of curing compound.