Why will need vibrate concrete mixture?

From the quality of the concrete placement largely depends on his strength, and hence the durability facilities. The quality of installation, in turn, depends on the workability of the concrete mix. A workability controlled by the amount of water in the concrete mix and internal friction.Not to introduce a mixture of excess water, it was necessary to dilute the mixture at the time of installation. Of the many methods offered the most effective was vibrating, destroying the internal friction of the concrete mix.

How is vibration destroys the internal friction of concrete? To understand this, we perform the following experiment. Put on the table a cube made of concrete. To make the cube to slide on the table, you need to make him a force to its relation to the mass of the cube exceeded the coefficient of friction of the cube on the table surface. If this table together with a concrete cube to put on vibroplatform and tell him impulses - impulses, the cube will slide across the table. After adhesion to the surface of the cube table with shaking weakens, then decreases the coefficient of friction. Thus, the vibration allowed to pass through a heavy cube. "Mechanism" of the vibration is quite simple: under the influence of vibration cube receives impulses - impulses to throw it up. Separated from the surface of the table for a short period of time, the cube jumps. Consequently, its movement will be composed of a sequence of small jumps, each of which he will move a certain distance.

How then is the process of vibration? On concrete cube, placed on a concrete board the force of friction, impeding the independent movement of the cube. To make the cube to slide on the surface of the board, you have to put some force or significantly increase the angle of the board. Well, if you bring the board into a state of vibration, the cube will bounce, and then slip even at very small inclination board. We return to the concrete mix. What happens to it when the vibration? Internal friction in it is because the surface of the aggregates in contact with each other. With stirring, they rub against each other and the more friction surfaces, the greater the overall coefficient of internal friction. Vibration is a concrete mix to reduce or eliminate these contacts and reduce internal friction. In other words, the vibration of "thins" concrete mix. And, therefore, the mixture acquires the ability to easily fill in forms and squeeze out the air contained therein. I must say, more important is the frequency of vibration. It can vary within wide limits, depending on the type of vibrator.

Vibration frequency differentially affects the grain filling of various sizes. In concrete aggregates of various sizes surrounded by mortar and swing like a pendulum with a certain natural frequency. The frequency of vibration of concrete should be chosen depending on the size of the aggregates. The size is determined by the aggregate nature of vibration aggregates of different sizes at low and high frequencies.

The most appropriate action to expose the concrete mix several vibrators with different frequencies of vibration. In this case, aggregates of different sizes move with varying intensity, and the concrete will be compacted uniformly.