Dewalt Concrete Vibrator

We continue with the posts on concrete care, this time I want to talk about something as important as vibrating concrete . Well, more than vibrating, I should talk about the importance of compaction, which is really what we achieved with vibrating, but let me focus on the most common compaction method that in the end is the most neglected in my opinion. has in the works.

As in the previous ones in which I talked about curing concrete and about the terrible habit of adding water to concrete, I do not try in the post so much to show the how, but rather the reason for these much-needed care but on too many occasions so sloppy.

You already know that what the main objective of this post series on concrete care is to show those who execute it , yes, yes, what they are on the job site staining with the concrete, how tremendously important it is to do their job well. work and make it clear that the demands of the technician on duty are not just whims, but that it is essential to follow his instructions so that the concrete fulfills its function for a long, long time .

Importance of making a good vibration of the concrete
As I have already mentioned on several occasions, concrete, contrary to what it may seem at first, is a very delicate material that needs to be executed with certain care in order to really fulfill its function , not only shortly after construction, that is easy, but so that it continues to fulfill its function after a long time.

At first glance it will always seem to us that the concrete is hard after pouring it and many think that it is the only property that it must fulfill, even some who call themselves professionals, but they are very, very wrong.

Obviously, at first glance the concrete will be hard, surely you will not break it with your hand, but is the hardness achieved enough? It may not break, but will the armor be well integrated to prevent it from flying? For how long will you be able to maintain your properties?

These are some of the issues that vibrate concrete influences . Let's see how.

When the concrete arrives in the trucks and is poured into the formwork, either with buckets, direct from the truck, pumped or as you want to pour it, along with the concrete a large amount of air enters, which is trapped inside the mass.

As you can imagine, that air does not resist the same as the concrete itself, so it does not seem a good idea to keep the air inside the mass, because wherever there is air, there will be no resistance.

The mission of vibrating (actually compacted, but I focus on vibrating as I have said before) is to make that air that is trapped in the concrete mass go up to the surface and be eliminated, making the mass not air, but only concrete.

The vibrating mission is to compact the concrete mass, eliminating the air that has been trapped in the mass during the pour.

Comparison of vibrated and non-vibrated concrete

What do we achieve with vibrating concrete?

With the vibrating of the concrete we achieve several things, each one more important. Yes, I know that I have said that what we do with the compacted is to eliminate the air inside the mass, but that is not the final objective, but the objective is to avoid the consequences of the air remaining, that is, improve concrete performance in several ways. Let's see some:

Improvement of resistance. It is most evident, since as I have explained, the air is not resistant, so the areas of the mass that instead of concrete have air, because they will not resist ANYTHING. Important especially in the meetings between different elements.

Badly vibrated in the meeting of beam with column

Improves the durability of concrete. As I already mentioned in the post on curing concrete and adding water , the air remaining in the concrete mass will end up favoring oxidation in the reinforcing reinforcement, since it creates a network of pores that will facilitate the entry of aggressive external agents towards the interior of the mass, such as CO2, water, pollution, etc.
Improves the anchorage of the reinforcements. The air that, in addition to being trapped in the concrete mass, is in contact with the reinforcing bars, represents a metal surface that is not in contact with the concrete. The smaller the surface in contact with the concrete, the less its anchorage capacity will be and therefore it loses the ability to help the concrete resist traction, so with vibrating we can eliminate that air, increase the concrete / steel contact surface and Thus improving the anchoring of reinforcements.

If there is no concrete, anchoring capacity with the steel is lost

Rearrange concrete components. Sands, gravels, cement ... different materials with different grain sizes. When applying the vibrate, the smallest particles are repositioned between the gaps that leave the thickest particles, favoring the homogeneity of the mixture, helping to fill small gaps (such as space between bars very close together), correctly filling corners and complicated shapes formwork and ultimately improve the quality of the concrete.
Avoid holes and the consequent touch-ups on the finished concrete. If holes appear on the surface of the concrete when stripping, it is due to the fact that it has not been vibrated correctly, the air has not been removed and therefore, when the mass hardened, the one that was in contact with the formwork has been left there leaving the typical coquettes , which in the end ends up being an additional cost because it is necessary to repair, wouldn't it be better cheaper to avoid it during the spill?

Vibration failure on wall base

Improves the aesthetics of the finish. Directly related to the previous one, in exposed concretes it is the worst that can happen, since the repairs in the seen concretes are going to be difficult to hide, they are going to be noticed, so the vibrating, in addition to the importance of the previous points is essential to achieve a perfect finish. In the case of exposed concrete, the truth is that I consider it more interesting to use self-compacting concretes , since this way we guarantee a perfect finish.

10 points to take into account for a correct vibrating of the concrete

I know that I said that the post did not try to talk about the how, but about the why, but since I am here, I cannot stop giving some points that must be considered to execute the vibrating of the concrete , without going into depth, simply mentioned in case you did not take any into account.

If you are interested in the subject, you can comment on it and I will prepare a post delving into the execution of vibrating.

Let's see some of the points to keep in mind:

Introduce the vibrator vertically and with speed up to the vibrating depth. If we introduce it slowly, the upper layers will compact and it will make it difficult for the air from the lower layers to rise to the outside.
Take it out slowly and inclined , this way we will make sure that the entire depth is well compacted and when removing it inclined we will avoid marking the exit point.
Keep it in the dough for 10-15 seconds maximum.
Better to enter many times for a short time than few for a long time
In the vibrators the manufacturers indicate the radius of action of their equipment. The distance between two vibrating points should be approximately one and a half times that radius of action , so that they overlap and no areas remain without vibrating.
It is necessary to introduce the needle to a sufficient depth so that it penetrates into the previous layer poured, so that with the vibrated we "sew" both layers to obtain a homogeneous mass.
Especially in the first layers, it is recommended to approach the vibrator to corners and recesses to guarantee that the fines are repositioned, achieving these shapes, but with caution not to hit the formwork.
Avoid using the vibrator to "move" the concrete.
To lower concrete clusters, you should not enter the top of the cluster, but click around until it is distributed by its weight.
You have to have a reserve vibrator on site , it would be disastrous, as well as very expensive, if the vibrator were to break down just with a recently dumped truck, because all that mass would have to be chopped.

I could grow the list indefinitely, but as I have commented it is not the object of the post, so I think that with the ones I have commented it is enough for the moment.

Conclusions

As you can see, another one of those operations that requires concrete, simple but very important that does not depend so much on projects or technicians, but rather on the professional on-site, the operators in charge of the pouring, so as a religious would say, (in your hands I entrust my… structure).

If you are one of those professionals in charge of placing concrete on site and did not know the importance of vibrating, now you have no excuse to do it correctly. You are part of the process, so projects, calculations or technicians are useless if you do not take responsibility for something so simple and important.