What is concrete vibration?

Vibrating concrete is one of the most important stages of construction projects that should not be neglected. As an essential part of the concrete placement process, most of the concrete vibration steps have been developed as standard instructions so that project managers can perform the concrete curing process in a principled manner. For this reason, in this article, we point out the importance of vibrating concrete and present some important points at this time.

Vibration and compaction are described as a process that expels trapped air from fresh concrete and binds aggregate particles together to increase the density of the concrete. The process is done with a device called a vibrator, which is available in several different shapes and sizes in the market.

Some of them are small and run on gasoline or batteries, while others are wired and work with electricity. Choosing the right vibrator can help your concrete last longer.

Vibrating concrete

Vibrator device

The importance of vibrating concrete

Vibration of concrete is vital because it increases the density and strength of concrete by removing air and placing aggregates together. Vibration regulates cement and aggregate particles in concrete.

Vibrating the concrete helps to achieve the ideal configuration. Proper configuration means reducing empty spaces as much as possible. This results in a compacted concrete mix that makes the concrete structure stronger and more durable. Non-vibrated concrete is full of air pores, which results in a weak concrete structure.

Benefits of concrete vibration

Coarse aggregates are irregular in size and have cavities. Fine aggregates and cement paste are used to fill the cavities. Even the smallest particles of cement have air cavities that fill with water.

Even after filling the mixture with water, there is still the possibility of air. Empty spaces in fresh concrete have been shown to make up about 5 to 8% of its total volume. The presence of voids in concrete leads to segregation and bleeding. Also, lack of vibration leads to increased cracks and honey combing of concrete.

By vibrating the concrete, there is no need to reduce the water to cement ratio. Adding less water than required reduces the risk of empty volume of water, which compromises the efficiency of the concrete. Vibration is the only way to have an ideal mixing plan, without compromising the workability of concrete!

Vibrating concrete

Concrete vibration methods

Concrete vibrators are available in various forms in the market that determine the method of concrete vibration. These methods are as follows:

  • Mold vibration: Mold vibration is commonly used in the manufacture of precast concrete and involves the installation of vibrators outside concrete molds. For large concrete placements, formwork vibrators should be 2 meters away from the formwork.
  • Surface Vibration: Surface vibrators are large vibrators that are manually guided to the placed concrete surface. This method is limited to a depth of 15 cm or less but provides a smooth surface that is especially suitable if the appearance of concrete is important.
  • Internal vibration: Internal vibrators are the most common method of concrete vibration. They are relatively simple to use, the worker quickly inserts the vibrator hose into the wet concrete and then gently removes it.


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The correct method of vibrating concrete:

The step-by-step guide to concrete vibration is as follows

Step 1: Select the appropriate series size

First you need to check if the concrete vibrator is equipped with a suitable series (head or nozzle) or not! Although difficult to detect at a glance, differences in vibrating heads can have a major impact on density.

For example, to achieve the lowest level of concrete density, a head with a diameter of 20 to 30 mm should be used. Such a head will be suitable for concrete in thin sections. The 35 to 40 mm series may be suitable for vibrating columns. Finally, a series of 50 to 75 mm is used for maximum compaction level in concrete placement of roofs.

Step 2: Learn how to vibrate manually

After selecting the appropriate series, start vibrating the concrete. For this purpose, you must provide the appropriate safety equipment in advance. In most cases, those who work inside the concrete should always wear special boots. Also, everyone should protect their mouth, eyes and hands. Turn on the vibrator and go to the first point.

When the concrete starts to fill the space, insert the vibrator into the concrete and hold it in place for 5 to 15 seconds. After that, the vibrator can be gently removed and moved to the next point. The next point should be about 50 cm away from the starting point. This process should continue until the entire concrete surface is properly vibrated.

Never force your concrete vibrator into the concrete mix! Instead, let the vibrator go into the concrete with its own weight. If the vibrator does not sink into the concrete on its own, this may indicate the low efficiency of the concrete mix (Stiffness of the concrete).

Step 3: Watch out for air bubbles

During the concrete vibration process, be aware that air bubbles appear on the concrete surface. These show that the vibration process is successful. To do this, use a vibrator for 5 to 15 seconds until bubbles appear.

If no bubbles appear at first, this problem may be a sign of manual vibrator operation. Make sure you follow the steps correctly. Stop vibrating when no more air comes out of the concrete. Should be mentioned, the vibration speed should be 9000 rpm.

Important points in vibrating concrete

  • Do not vibrate too much, as this will cause heavy aggregates to move down the mix and water and cement to rise. Air may also become trapped in the underlying layers of cement, resulting in a weak structure in the concrete that breaks easily with minimal pressure.

  • To prevent cold connections between the concrete layers, make sure that the vibrator penetrates completely into each part and mixes the previous layer with the new layer.
  • For maximum efficiency, use only vertical movements to have a mixture of aggregate and concrete. Horizontal movement can lead to uneven distribution of aggregates and increase the likelihood of vibrator entanglement in the rebar.
  • Do not use a vibrator to move or push the concrete in the mold! This leads to the separation of the concrete constituents.
  • Use the right type of vibrator. Consider lightweight and compact vibrators for smaller projects.
  • Always try to consider two vibrators in the construction site as one may break down and finding the other vibrator wastes time and stiffens the concrete mix.

How concrete vibrates work

We have two types of vibrators, one is gasoline and the other is electric. The gasoline type has a large engine that is connected to a hose. The electric type has a small motor and, like the gasoline model, is connected to a hose. Gasoline does not require a power supply and is easier to use, but the electric model is lighter and more powerful.

How to use a concrete vibrator is very simple. After turning on the device, the vibration nozzle of the vibrator hose can be adjusted. The nozzle goes into the concrete with a vibrator series to separate the air from the mixture.

Last word

Hundreds or perhaps thousands of air bubbles may form during concrete placement, which can severely weaken the concrete structure. These air bubbles, which are a recurring problem, are a serious problem for most contractors. But following the principles of concrete vibration and high readiness of workers to do so, can mean the removal of air bubbles and having high-strength and dense concrete.