Separation of coarse aggregates from mortar during transportation of concrete is known as:
Correct Answer: C. Segregation
📚 Detailed Explanation: Segregation — Separation of Coarse Aggregate from Mortar
Why C (Segregation) is correct: Segregation in concrete refers to the tendency of the constituent materials to separate from one another. Most commonly this means the heavier coarse aggregates settle or roll away from the lighter cement-sand mortar, especially during transportation or improper handling. IS 456 defines segregation as one of the major defects to be avoided in concrete work.
Types of Segregation
| Type | What Separates | Common Cause |
|---|---|---|
| Type 1 — Aggregate separation | Coarse aggregate separates from mortar | Dropping from height (>1.5 m), transportation on rough roads, excessive vibration |
| Type 2 — Paste separation | Cement paste separates from aggregate | Very wet mixes; high w/c ratio; over-vibration |
Distinguishing Segregation from Similar Terms
| Term | Definition | What Separates |
|---|---|---|
| Segregation | Separation of concrete constituents during handling/transport | Coarse aggregate from mortar |
| Bleeding | Water rising to the concrete surface | Free water migrates upward |
| Creeping | Movement of soil under load; not a concrete defect term | — |
| Shrinkage | Volume reduction on drying or cooling | Not a separation — dimensional change |
Prevention of Segregation
- Do not drop concrete from more than 1.5 m height.
- Use correctly designed mix (proper w/c ratio, good aggregate gradation).
- Avoid over-vibration; use vibrators only within the recommended slump range.
- Use transit mixers with agitation rather than dump trucks for long hauls.