Per §5.6, 'laitance' formed at the surface of concrete by bleeding is:

Question

Accepted Answer

C. {'text': 'A weak surface layer of paste that reduces bond with the next pour', 'label': 'C'}

1. §5.6 lists laitance under Harmful Effects: 'When the surface of concrete is worked up with trowel and floats, the aggregates go down and cement and water moves up. This forms a layer of paste at the surface which is called Laitance.' It produces dust and shrinkage cracks and weakens the bond with the next concrete lift.
2. Remedy: brush away the laitance completely before the next lift is poured.
_Source: IGNOU ET-522 Block-2 Unit-5 Workability & Fresh Concrete-I, §5.6 (Laitance), p. 15_

Answer

{'text': 'A waterproof crystalline coating that improves durability', 'label': 'A'}

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{'text': 'A protective alkaline layer that passivates the steel reinforcement', 'label': 'B'}

Answer

{'text': 'A pozzolanic skin that boosts long-term strength of concrete', 'label': 'D'}