What is a vibrator? Types? | Q & A

A concrete vibrator is a mechanical device used to compact fresh concrete by removing entrapped air, ensuring the concrete becomes dense, uniform, and strong.

Proper vibration improves strength, durability, and bond with reinforcement.

Why Vibration Is Necessary

• Removes air voids

• Prevents honeycombing

• Improves bond between concrete and steel

• Increases strength and durability

Types of Concrete Vibrators 1. Needle Vibrator (Internal Vibrator)

Most commonly used on site

How it works:

• A vibrating needle is inserted directly into fresh concrete

Used for:

• Beams

• Columns

• Slabs

• Footings

Advantages:

• Effective compaction

• Easy to handle

2. Surface Vibrator

How it works:

• Placed on the surface of concrete

Used for:

• Slabs

• Pavements

• Thin concrete sections

Limitation:

• Not effective for deep sections

3. Shutter (Formwork) Vibrator

How it works:

• Fixed to shuttering/formwork

Used for:

• Thin walls

• Congested reinforcement areas

• Precast elements

4. Table Vibrator

How it works:

• Vibration provided through a vibrating table

Used for:

• Precast concrete units

• Paver blocks

• Tiles

5. External Vibrator

How it works:

• Mounted outside the formwork

Used for:

• Heavily reinforced or thin sections

Quick Interview Table TypeLocation of Use

Needle	Inside concrete
Surface	On top of concrete
Shutter	On formwork
Table	Precast items
External	Outside formwork

One-Line Interview Answer (Perfect)

A concrete vibrator is a device used to compact fresh concrete by removing air voids; common types include needle, surface, shutter, table, and external vibrators.

Common Interview Follow-Up

Q: What happens if vibration is improper?
A: Honeycombing, low strength, and poor durability.

Q: What happens if over-vibration is done?
A: Segregation of aggregates.

Site Tip for Fresh Engineers

• Insert needle vertically

• Avoid touching reinforcement repeatedly