Vibrators are commonly used as a way of compacting concrete on site. In the case of vibration, compaction is affected by the reduction in internal friction between different particles of concrete due to oscillation of the particles resulting in a dense and compact mass of concrete.
vibrations can be either
- produced in the interior of concrete internal vibrator, or
- Concrete is produced by vibrating formwork shutter form vibrator, or
- Produced on the surface of concrete. use Surface Vibrator, or
- Produced using the whole solid mass Vibration table.
So there are usually 4 different types of vibrators, namely:
- internal or immersion or poker or needle type vibrator
- Shutter Form Or External Type Vibrator
- Surface or Screed or Pan Type Vibrator
- Hill Tables
1. internal vibrator
These are also called immersion, poker or needle vibrators. They essentially consist of a power unit and a long flexible tube with a vibrating head attached to the end. Electricity is provided by electric motor, compressed air or petrol engine. The long tube consists of a flexible shaft that rotates an eccentric load inside the vibrating head. The frequency of the vibrator is about 700 cycles per minute.
The vibrating head is inserted into the concrete. They are most effective because the vibrating head comes into close contact with the concrete.
2. form vibrator
They are also called external vibrators. They are fastened in the formwork horizontally and vertically at a suitable distance not exceeding 90 cm in any direction. They are shifted as the work progresses. They vibrate the concrete by the vibrations of the forms and thus a lot of energy is wasted.
These are used only when the use of internal vibrators is not practical as in the case of thin and congested sections, arches and tunnel linings, etc.
3. Surface Vibrator
They are also called screed or pan vibrators. They are tied with screws. They vibrate the concrete off the surface when screeding (striking off) the concrete. They are effective only if the depth of the concrete is up to 20 cm. They can be used in conjunction with internal vibrators if the depth is greater. They are used for long horizontal surfaces such as pavements and slabs.
4. Hill Tables
These are rigidly constructed steel platforms mounted on steel springs and driven by electric motors. Concrete is placed into platform-mounted molds and securely affixed to a vibrating table, so that the mold and concrete vibrate in union.
Vibration tables are used in factories and laboratory samples to compress hard and rigid mixtures used in precast structural members.
Read also: How to use a poker vibrator to compact concrete?
Also read: 10 Points To Consider When Compressing Concrete Using Vibrators