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Define shrinkage, creep, segregation, bleeding

Short answer

Shrinkage is time-dependent volume reduction without load due to moisture loss and hydration/carbonation. Creep is gradual strain increase under sustained stress beyond elastic strain, mainly from gel water seepage. Segregation is separation of fresh concrete constituents (coarse aggregate from mortar), while bleeding is the rise of mixing water to the surface as solids settle.

What do you mean by shrinkage, creep, segregation and bleeding in concrete?

Shrinkage

Shrinkage is the time-dependent reduction in volume of concrete, without any applied load, caused by loss of moisture and by chemical reaction (hydration and carbonation). Typical long-term values are 0.0003 to 0.0008 (300 to 800 microstrain).

Creep

Creep is the gradual increase in strain of concrete with time under a constant sustained stress, over and above the instantaneous elastic strain. It is caused mainly by seepage of gel water out of the C-S-H layers and by slip of gel particles. Creep continues for years, with about 50% occurring in the first 3 months and 75 to 80% in the first year.

Segregation

Separation of the ingredients of fresh concrete (coarse aggregate from mortar, or paste from aggregate) so that the mass is non-uniform. Causes: wet or harsh mix, poor grading, free fall over 1.5 m, over-vibration and rough handling. It produces honeycombing and weak spots.

Bleeding

Rise of mixing water to the surface of freshly placed concrete as solids settle. It happens with high W/C, lack of fines and coarse cement. It leaves a weak, porous layer (laitance), reduces bond with steel and aggregate, and lowers durability. Control by lowering W/C, adding fines and using air-entraining agents.

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