---
title: "Segregation and bleeding with causes"
subject: "Concrete Technology and Masonry Structure"
chapter: 3
key: "semester_5/concrete_technology_and_masonry_structure:segregation-bleeding-causes"
source: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/segregation-bleeding-causes
site: BCT Engineering
---

# Segregation and bleeding with causes

Concrete Technology and Masonry Structure · Chapter 3: Mix design of concrete and property of green concrete

- Asked in: 2076 Chaitra, 4 marks
- Video: [What is Segregation and Bleeding of Concrete?](https://www.youtube.com/watch?v=LUkZFD6auKc) — Engineering Motive
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/concrete_technology_and_masonry_structure/segregation-bleeding-causes
- Whole chapter: https://www.bctengineer.com/md/semester_5/concrete_technology_and_masonry_structure/chapter-3

## Question

Explain segregation and bleeding along with their causes.

## Short answer

Segregation is separation of coarse aggregate from mortar caused by too wet/harsh mix, poor grading, excessive free fall, over-vibration, or density differences. Bleeding is water gain on the surface resulting from high w/c, lack of fines, low cement content, prolonged vibration, or low temperature. Both harm homogeneity, strength, and durability.

## Answer

**Segregation** is the separation of the constituents of fresh concrete so that the mix is no longer uniform: coarse aggregate separates from the mortar (or, in a wet mix, cement paste separates from aggregate). It gives honeycombing, weak and porous patches and a loss of strength and durability.

**Causes of segregation**
- Too wet or too dry (harsh) mix, high slump with poor cohesion.
- Poorly graded aggregate: excess of coarse or very large size, lack of fines.
- Dropping concrete from more than about 1.0 to 1.5 m, or letting it slide down a chute.
- Over-vibration, or vibrating a very wet mix; striking against reinforcement or form.
- Long transport on rough ground, or discharging a heap that rolls to the edges.
- Large difference between density of aggregate and mortar (e.g. light-weight aggregate).

**Control:** well-graded aggregate, adequate cement paste, correct W/C, short free fall, trunk or tremie pipes, proper vibration.

**Bleeding** (water gain) is the upward movement of mixing water to the top surface of freshly placed concrete as the heavier solids settle. The water collects as a layer on the surface or under coarse aggregate and reinforcement bars.

**Causes of bleeding**
- High water content / high W/C ratio and high slump.
- Lack of fines in the aggregate, or coarse and poorly graded sand.
- Low fineness of cement or low cement content (less surface area to hold water).
- Prolonged vibration, or deep placing in one lift.
- Low temperature (slower setting gives more time for settlement).

**Effects:** a weak, porous, dusty surface (laitance) with poor wear resistance; weak bond with the next lift; water pockets under bars and aggregate, which lower bond and make the concrete more permeable. **Control:** lower W/C, more fines, finer cement, air entrainment, correct vibration, and removal of laitance before the next lift.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which promotes bleeding?
   A. High w/c and lack of fines
   B. Low w/c
   C. Fine cement
   D. Air entrainment
   Answer: A. High water and few fines let water rise. (Key point: Bleeding causes)

2. Which causes segregation?
   A. Well-graded aggregate
   B. Dropping concrete from a great height
   C. Short free fall
   D. Cohesive mix
   Answer: B. Free fall over about 1.5 m and over-vibration cause segregation. (Key point: Segregation causes)

3. An effect of bleeding is
   A. denser surface
   B. stronger bond
   C. weak, porous laitance layer and water pockets under bars
   D. less permeability
   Answer: C. Laitance and water pockets weaken bond. (Key point: Bleeding effect)

4. Bleeding is controlled by
   A. adding water
   B. using coarse cement
   C. prolonged vibration
   D. lowering w/c and adding fines
   Answer: D. Lower w/c, fines, finer cement, air entrainment. (Key point: Bleeding control)

## Related in Concrete Technology and Masonry Structure

- [Segregation and bleeding; control during placing](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Asegregation-bleeding-control) — Concrete Technology and Masonry Structure, chapter 3
- [Define shrinkage, creep, segregation, bleeding](https://www.bctengineer.com/question.md?key=semester_5%2Fconcrete_technology_and_masonry_structure%3Ashrinkage-creep-segregation-bleeding-define) — Concrete Technology and Masonry Structure, chapter 3