APPLICATION, MAINTENANCE and PRECAUTIONS

COMPRESSING FRESH CONCRETE

During shuffling of the concrete material at the ready mixed concrete facilities and also during placing process of fresh concrete into its place an amount of air spontaneously (involuntarily) is caught in the concrete mixture.  

Fresh concrete with an air bubble does not fill the formwork completely and is in a state of being concrete of low density. Right after concrete is dumped in place the air bubbles locked up within the contexture needs to be thrown out as much as possible. This process, throwing out the locked up air within the contexture of concrete, is called, "concrete consolidation".  

With the development of concrete technology, the ready mixed concrete consolidations are done with mechanical methods. In determination of the applicable consolidation methods, some factors like the workability of the fresh concrete, formwork shape and dimensions, the density and amount of the components of concrete should be taken into consideration.    

In the ready mixed concrete sector, the vibration process that is carried out to get rid of the air bubble that has been locked up in the fresh concrete and turn the concrete in a state with fewer bubbles is performed by a mechanical tool called vibrator.

The consolidation process by the vibration method is carried out in two stages: In the first stage the mortar in concrete liquefies with the effect of vibration and move downwards and in the second stage the air locked up in concrete is released out. The two stages almost happen at the same time.   


BENEFITS OF THE VIBRATION APPLICATION TO FRESH CONCRETE :  

• As consolidation is easy it provides economy.  
• A more dense and homogeneous concrete is attained.  
• When the formworks are moved a smooth edged concrete is attained.  
• A higher resistant concrete is attained.
• In reinforced construction concretes, a better adherence is maintained between the iron material and concrete.  
• A higher resistance is maintained.

Types of Concrete Vibrators:

To perform consolidations according to the density of concrete, the place it is used in the construction (girder, flooring etc.) and the type of the element used in production the vibrators are manufactured in four groups:

• Internal vibrators,
• External vibrators,
• Vibration tables,
• Surface vibrators.

Internal vibrator is the most wide used vibrator type in ready mixed concrete sector. It is made up of a steel tube with a rotation element heavily eccentric and an elastic handle like a hose attached to the top of the tube. The upper end of the elastic handle is connected to electricity or a diesel engine. The bottom end of the steel tube is rounded and called plunger.  

The plunging ends of internal vibrators vary in diameter from 2 - 18 cm and are produced at frequencies that vary between 4000- 15000 revolution / minute.  

For construction concretes at plastic density: 8500 - 15000 revolution / minute,
For concretes elements like walls, columns, girders: 8000 - 12000 revolution / minute,
For mass concretes: 7000 - 10500 revolution / minute frequency vibrators are recommended.

The effective area of the internal vibrator changes according to the diameter of the plunger end.