Durability of Concrete MCQ with answer and solution

Concept

Bleeding is when mixing water rises and collects on the surface of fresh concrete as the heavy solids settle down.

Step-by-step solution

1. During placing and compaction, heavy particles (cement and aggregate) settle down. 2. Water, being lighter, moves up and collects on the top surface. 3. This upward movement of water to the surface is called bleeding.

Explanation

Bleeding is a form of segregation in which water comes out of the concrete mix and collects on the top surface. It makes a weak, porous top layer called laitance. Too much bleeding reduces strength and durability.

Why the other options are wrong

B: Permeability is the ease with which water passes through hardened concrete. C: Seepage is the flow of water through soil or porous media, not water rising in fresh concrete. D: Efflorescence is a white salt deposit on the surface of masonry or concrete.

Shortcut

Water rising to the top of fresh concrete = bleeding.

Common mistake

Confusing bleeding with efflorescence or with segregation of coarse aggregate.