Why do You Need a Deep Vibrator for Concrete

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Contents:

Why and how to seal the concrete mix;
Reasonable exceptions;

This article is intended to help summer residents-developers to avoid mistakes in the construction of a concrete (ribbon, columnar, slab) foundation.

We regularly receive letters about deplorable situations of” self-destruction ” of foundations, their constant sagging or cracking. The reasons for the latest technological failure may be several, but the most likely is the insufficient quality of compaction of the concrete mixture. Although fake cement is also not excluded.

Therefore, in today’s article, we will consider not the most frequent representatives of construction equipment in the country – deep vibrators for compacting concrete mixes.

Why and how to seal the concrete mix

This is a concrete mix, not concrete. Since the latter is understood as an already solidified, solid mass of silicate components. And while the mass is liquid, like sour cream of dubious quality, it is called a concrete mixture.

To feel the need to use a vibrator in the construction of the foundation, it is necessary, in my opinion, to get acquainted with the simplified scheme of interaction between the components of the concrete mixture.

The concrete mixer mixes the components of the future concrete – cement, sand, small and large aggregates and, of course, water.
After high-quality mixing, the smallest particles of these materials begin to contact each other, forming stable bonds between them. In the first approximation, we call them intermolecular. Serious physicists-specialists in the field of fine intermolecular interactions-please do not scold the author: he clearly understands the approximate name of such connections.
So, the particles of water, cement, sand, and filler were qualitatively mixed and formed a spatial network of connections, invisible to the human eye. Have you imagined this picture? And now it’s time for me to repent and admit that when I listed the components that got into the concrete mass, I deliberately did not finish the main thing. The fact is that mixing the mass with the mixer blades is inevitable and a lot of air bubbles are forcibly introduced into it. Yes, air, and where from it when mixing?

Thus, in addition to the above components, there are numerous air bubbles in the concrete mass. And they are in the spatial network of intermolecular interactions of other components.

So what? Who are they actually interfering with, and why should we know about it? The fact is that:

The concrete mass after its closure will capture and block many bubbles in its array.
On cool and humid days, of which there are quite a few, these microscopic air bubbles are deposited by condensation, that is, moisture.
And when winter comes, this moisture can turn into ice, the volume of which, as you remember from the high school physics textbook, is 20% more than the initial humidity. And because the volume of the bubbles does not change, because the concrete is already gripped.
What will the ice do? Gradually affect the surrounding concrete and try to break it. This would not be a problem if winter turned into a warm spring for one working day per season. Concrete with bubbles would survive such a cycle. But in the spring, the ambient temperature drops to zero every now and then, about twenty times a month. This means that the same number of times the ice will appear in the bubbles and try to break the concrete. And in the end, he will succeed.

The conclusion from the above is only one: it is necessary to remove air bubbles from the plastic concrete mixture, so to speak, in the bud.

How do I do this? The answer here is quite clear-use deep vibrators for concrete. The vibration of the concrete mass destroys the above-mentioned connections between the particles of cement, sand, etc., completely expelling air bubbles. In this case, the mass acquires the properties of a liquid, in which the Archimedes ‘ law completely prevails. It is thanks to him that the light air bubbles are released from the bonds, rise to the upper level of filling with the mixture and safely return to their native atmosphere. After the end of the vibration, the space freed from bubbles is filled with useful components of the concrete mixture. Thus, the latter is compacted.

Reasonable exceptions

Is it possible to do without the use of a cement vibrator and concrete compaction? Yes, you can, and here I will give real examples. One of them I saw in the desert of Israel, where workers” monolithic ” poured the supporting column of a low-rise building. To my initial surprise, they didn’t even have a vibrator in a very wide range of equipment. And the reason is very simple. This geographical area is not familiar with sub-zero temperatures, and the land there is really deserted. That is, there are simply no conditions for the formation of dangerous condensate under the influence of frost, which passes into another aggregate state.

If these lines catch the eye of a competent builder observing the latest innovations in the industry, he can reproach me for the lack of information about self-compacting concrete. The main advantage of this brainchild of Japanese nanotechnology is its amazing ability to deform without mechanical intervention. High deformability and tear resistance allows the self-compacting concrete to penetrate 100% through the tightly reinforced frame and fill the molds exclusively under the action of its own mass, without vibration. However, the price of these building mixes, which corresponds to the progress, will not allow them to be used for the construction of a concrete base, even at the average price level, let alone at the budget level.

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