Question

Define the terms segregation and bleeding. What are the contributing factors.

Answer 1

Segregation is the separation of concrete ingredients as a result of the differences in the sizes and specific gravities of the mixture constituents. Typically, the coarse aggregates tend to settle out from the bulk of the concrete. Segregation can be controlled by choice of suitable grading and by care in handling during placement and consolidation.

Bleeding is a process in which free water rises to the surface of the concrete, as the heavier particles settle. Finishing operations should be conducted after most of the bleed water has evaporated. Otherwise, concrete near the surface can have problems such as laitance. Laitance is wet cement paste scum that forms on the surface of segregated concrete. A weak and dusty surface is created upon hardening and the surface is susceptible to crazing.Bleeding helps in finishing operations.