Separation of coarse aggregates from mortar during transportation of concrete is known as:
Correct Answer: C. Segregation
📚 Detailed Explanation: Segregation — Coarse Aggregate Separating from Mortar
Why C (Segregation) is correct: Segregation is defined as the separation of the constituent materials of a concrete mix. When coarse aggregate (being heavier) separates from the cement-sand mortar during transportation, jolting over rough terrain, or dropping from height, the concrete loses its homogeneity and its quality is severely compromised.
Types of Segregation in Concrete
| Type | What Separates | Primary Cause |
|---|---|---|
| Type 1 (most common) | Coarse aggregate separates and rolls away from mortar | Dropping from height >1.5 m; rough transport; over-vibration |
| Type 2 | Cement paste separates from aggregate matrix | Highly wet mixes (high slump); excess water |
Distinguishing Key Concrete Defect Terms
| Term | Definition | What Moves/Separates |
|---|---|---|
| Segregation | Separation of concrete constituents | Coarse aggregate from mortar |
| Bleeding | Water rising to concrete surface | Free mix water (upward migration) |
| Creeping | Slow lateral soil movement under load | Not a concrete term |
| Shrinkage | Volume reduction on drying | Dimensional change, not separation |
Effects and Prevention of Segregation
| Effect | Prevention |
|---|---|
| Voids increase in concrete | Do not drop concrete >1.5 m (IS 456:2000) |
| Homogeneity destroyed | Correct w/c ratio; use transit mixer for long hauls |
| 2% voids → 10% strength loss | Proper gradation of aggregates; avoid wet mixes |
| 5% voids → 30%+ strength loss | No over-vibration; max slump 50 mm when vibrating |
- Segregation = coarse aggregate separating from mortar during transportation or handling.
- IS 456:2000: concrete must not be dropped from a height exceeding 1.5 m (150 cm).
- Adding excess water to concrete increases segregation risk significantly.