The 'shrinkage' of concrete after casting is distinguished into plastic and drying shrinkage as:
Choose the correct answer
No difference — both occur after one year
Plastic: first hours while concrete is fresh (evaporation > bleeding); drying: long-term moisture loss from hardened concrete
Plastic shrinkage only in summer, drying only in winter
Both are only relevant for high-strength concrete
Correct Answer
B. Plastic: first hours while concrete is fresh (evaporation > bleeding); drying: long-term moisture loss from hardened concrete
Why is this the answer?
Concrete shrinkage types: (1) Plastic shrinkage: occurs while concrete still plastic (first few hours) → loss of bleed water + surface evaporation exceeds bleeding rate → surface tension cracks (map cracking); prevent by: fog spray, wind breaks, early covering; (2) Drying shrinkage: slow volume reduction as concrete dries (months to years) → cement paste contracts → restrained by aggregate and reinforcement; (3) Autogenous (chemical) shrinkage: internal self-desiccation, significant in low w/c (<0.4) mixes; (4) Carbonation shrinkage.
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