A concrete vibrator is used to ensure that the concrete becomes compact while putting concrete i.e. the concrete is placed without the inclusion of air bubbles which can affect its strength and it is necessary in most cases because the fluidity of concrete is limited by the amount of water used in the mixture.

What Is Vibrator?

Vibrators are used on construction sites to compact concrete. Concrete vibrators come in a variety of sizes and shapes and are primarily used in construction applications. They are primarily used for concrete compaction in the construction of roads, railways, and buildings. Concrete vibrators remove trapped air and excess water from freshly poured concrete. They are used to secure the concrete in place of the formwork in order to ensure proper concrete consolidation and avoid product defects.

Furthermore, vibrators are available in a variety of frequencies, ranging from 2800 to 15000 rpm. The various types of concrete vibrators are listed below:

Types of Vibrators Used In Construction

Vibration works best for concrete compaction. The best and most efficient method for compacting concrete is vibration; other methods include rodding, tamping, and spading. On vibration, the concrete mix fluidizes and the internal friction between the aggregate particles decreases, resulting in entrapped air rising to the surface. The highest amount of entrapped air is forced out by continuing vibration, and this is when the majority of the consolidation occurs.

The coarser particles settle when an overly wet concrete mixture vibrates. Concrete’s density, strength, bonding with reinforcement steel, and surface imperfections are all enhanced by compaction, which also significantly contributes to the structure’s durability.

Broadly Vibrator Can be Classified In two

  • Internal Vibrators
  • Externa Vibrators

Generally, mechanical compaction is done using internal i.e. using immersion or poker vibrators. This compaction method is preferred because the poker works directly on the concrete and can be moved from position to position very easily and quickly.

Internal Vibrator

The most common types of vibrators used on construction sites are internal vibrators, also known as immersion or concrete needle vibrators.

It is made up of a steel tube with an eccentric vibrating element inside (one end closed and rounded). The poker vibrator machine is made up of a steel tube that is connected to an electric engine, a diesel engine, or a gasoline engine through a flexible tube.

A poker has a diameter that varies from 40 to 100 mm. The formwork’s distance between reinforcing bars is taken into consideration when determining the poker’s diameter.

Internal vibrator machines have needle sizes ranging from 25 mm to 90 mm, with a minimum of 25 mm and a maximum of 35 mm being used for casting roof slabs.

A vibrator machine with needles of 40 mm and 60 mm should be used to compact concrete mass in beam and columns structures.

The concrete mass should be compacted by capturing air gaps and preventing honeycomb using a vibrator machine with a 75 mm and 90 mm needle when proposing a sturdy footing and various bridge structures. 

Vibrations from vibrator machines can reach 15000 rpm. However, a range of 3000 to 6000 rpm is suggested as a preferable minimum when using an accel.

External Vibrator

The external vibrator is also called a shutter-shaped vibrator. It comes with a base plate. Both freshly poured concrete and precast concrete’s surface can be compacted using it. It has a three-phase induction motor.

Its construction is complete and shut off. With a power cord comprised of four cables with a rubber coating, it is also reliable and simple to maintain. Typically, an aluminum alloy casting is used to create the case. Its motor structure is lightweight and extremely efficient.

The machine is fastened to the formwork in accordance with the building design, either horizontally or vertically, at a suitable distance that doesn’t exceed 90 cm in each direction.

Surface Vibrators

These are positioned directly on the mass of concrete. These are best suited for compacting small areas and shouldn’t be utilized if the vibrating depth of the concrete to be compacted is greater than 250 mm. Surface vibrators work best for compacting, especially dry mixtures. Pan vibrators and vibrating screeds are the most commonly utilized surface vibrators. This kind of vibrator is mostly used for patching and repairing pavement slabs as well as compacting small slabs that are no thicker than 150 mm. At accelerations between 4 and 9 g, the operating frequency is roughly 4000 rpm.

Vibrating Table

Although the formwork is secured to the vibrator, the vibrating principle of the concrete and formwork stays the same. The flavor of the vibration is similarly comparable.

In general, an eccentric weight that spins quickly causes the table to vibrate in a circular manner. Two shafts that rotate in opposing directions make up the mechanism.

The table can be subjected to a horizontal vibration component that can be neutralized. A simple harmonic motion exists only in the vertical direction.

There are a few minor advantages as well. Vibrating tables of high quality are powered by an alternating current electromagnet. The frequency range of 1,500–7000 rpm is reached.

For vibrating concrete pieces of varying diameters or for laboratory uses, a table with adjustable amplitude should be used. It’s advantageous to have vibrations with different frequencies. Precast concrete can be compacted safely and efficiently using a vibrating table.

For precasting work, constant treatment by electrically or pneumatically controlled vibrating tables is highly helpful.

Advantages of concrete vibrator:

  • The honeycomb structure is avoidable.
  • Structures with heavy reinforcement can be compacted easily.
  • The vibrators created a dense and watertight structure.
  • It can be used with a low water-to-cement ratio.
  • Work progresses more quickly.
  • A high aggregate-to-cement ratio can be utilized.

Disadvantages of concrete Vibrator:

  • Over vibration causes additional power consumption and energy dissipation if the concrete mixture is designed with low workability.
  • Precautions to be taken when using a concrete vibrator to compact concrete:
  • Layers of concrete with a thickness of 20 to 50 cm should be compacted.
  • In order to completely compact all of the concrete, the vibrator should be inserted vertically in a sufficient number of steps.
  • The formwork should be tight and strong to prevent motor leakage.
  • When the cement slurry appears on the surface, the vibration should be stopped.
  • It is never advisable to use excessive vibration.
  • To avoid concrete segregation, the vibrator should never be used to move the concrete mix laterally.
  • To avoid damage, vibrators should not be allowed to touch the formwork.
  • To avoid weeping holes in the concrete, the vibrator should be withdrawn slowly and kept operating while being withdrawn.
  • Concrete re-vibration is not harmful unless the concrete is so well established that vibration does not cause it to become plastic again.

Leave a Reply

Your email address will not be published. Required fields are marked *