Why do we need to vibrate the concrete mix
From the quality of concrete placement depends largely on its strength, durability and hence the construction.The quality of packing, in turn, depends on the workability of concrete mix.A controlled workability of water in the concrete mix and internal friction.In order not to enter into a mixture of excess water, it was necessary to thin out the mixture at the time of installation.Of the many proposed methods of the most effective was the vibration that removes the internal friction of the concrete mix.
How does vibration destroys the internal friction:/ / Beton2006.ru / list / Rastvor-i-beton / "> solution? To understand this, we perform an experiment.We put on the table, cube, made of concrete.To get the cube to slide on the table, you must attach to it a power to weight ratio to its cube exceeded the coefficient of friction on the surface of the cube table.If this table together with a concrete cube, put on vibroplatform and inform him of pulses & ndash;shocks, the cube begins to slide on the table.After adhesion to the surface of the cube table by shaking weakened, so decrease the coefficient of friction.Thus, vibrations allowed to pass through a heavy cube.";Mechanism ";Vibration is quite simple:under the influence of vibration cube receives impulses & ndash;shocks, which tossed it up.Separated from the surface of the table for a short period of time, the cube jumps.Consequently, its movement will consist of a series of small jumps, each of which he moves a certain distance.
How is the process of the same vibration? On a concrete cube, put on a slab the force of friction, impeding the independent movement of the cube.To get the cube to slide along 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 start to jump and then glide, even at very small angle the board.Let us return to the concrete mix.What happens to it when the vibration? Internal friction in it 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 total coefficient of internal friction.Vibration as the concrete mix to reduce or eliminate these contacts and reduce internal friction.In other words, the vibration ";dilutes ";concrete mix.And, then, the mixture acquires the ability to easily fill out the form and squeeze the air contained in it.I must say, greater importance is the frequency of vibration.It can vary within wide limits and depends on the type of vibrator.
The frequency of vibration of different influences on 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 of the filler is determined by the nature of vibration aggregates of various sizes at low and high frequencies.
The most appropriate action to expose the concrete mix multiple oscillators with different frequency of vibration.In this case, the aggregates of various sizes will move with varying intensity, and concrete will be compacted uniformly.