Electric heating concrete. the main types. warming up using

Concrete refers to those materials, the strength of which is directly dependent on external conditions. That is why the electric heating of concrete in the winter time according to SNiP 3.03.01-87 "Bearing and enclosing structures" is provided. According to this regulatory act, all work in the winter time should be carried out in accordance with the technological maps for each type of heating, this guarantees quick durability and eliminates the freezing of the monolith.

The main types of process

The technology of electric heating of concrete may differ in the method of implementation, but the main goal of all such activities remains unchanged - to accelerate the ripening of concrete in winter. As you know, in the first 4 days after pouring, the construction should in no way freeze, since all drying processes stop, and in the future, the strength characteristics will be several times lower than those laid down in the project.

Most often used two options for heating, it is them we consider in this review.

Warming up using a PNSV wire

This method is suitable for temperatures not lower than -17 degrees, if the frosts are more, then additional warming of the concrete surface with the help of heat-insulating mats will be needed.

The process of laying is quite simple, so this option is popular when working with your own hands, but do not forget about a number of requirements:

• For work, a PNSV wire with a cross section of 1.2-1.4 mm is used, it can be purchased at any electrical goods store. The section is selected on the basis of specific conditions, it should be remembered that standard projects do not exist, and you will have to do the development yourself or with the help of specialists.

• Another very important part of the system is a step-down transformer, whose power is selected from the volume of concrete.. As practice shows, an 80 kW transformer is enough for about 90 m³ monolithic construction. If there is no such equipment, then a welding transformer can be used, but you should consult with a specialist about this issue.

• This method is the most economical, the energy costs of this option are quite low, as is the cost of the project.. The option is used in most cases, both in private and industrial construction.
• It is worth remembering that concreting with electric heating is a rather complicated and laborious process.. Whichever option you choose, be prepared for the fact that the work ahead is difficult and long enough. It is important to do everything right, because the price of the wire is not so low that it can be spoiled.
• Instructions for laying wires similar to the work on the installation of underfloor heating. Of course, it is more difficult to do, because you need to work in adverse weather conditions. At the same time, the depth of the bookmark should be sufficient, if you suddenly need to cut reinforced concrete with diamond circles, then the wires should not be damaged.

Note! Pay special attention to the fact that each heating loop must be of the same length; in the process, make sure that the insulation is not damaged.

Warming up with electrodes

This option is not suitable for plates, but is ideal for walls, columns and diaphragms.

The main properties are as follows:

• Armature or a circle of metal with a diameter of about 10 millimeters is most often used as electrodes. It should be remembered that the bars should be clean enough without a rust layer, as this reduces the efficiency of heating.
• Naturally, the elements are laid before pouring, since even diamond drilling of holes in concrete will not be able to provide a cavity of the required depth, and the cost of such work is very high. You can do otherwise: enter the pins immediately after pouring concrete, as practice shows, this is the easiest way to install, which is why it is used by all professional installers.

• The distance between the elements should be from 0.6 to 1 meter. It all depends on the ambient temperature: the lower it is, the closer the electrodes should be to each other, but if the frosts are small, then you can position the pins and a meter.

Note! Remember that the elements with the help of which the heating is carried out are non-removable and remain in the material forever. This significantly increases the material consumption of work, because with large volumes of metal it will take quite a lot.

• If it is necessary to warm up the column, then one pin is inserted into it, heating is done by means of the transformer phase and the earth from the reinforcement belt of the filled column.
• Of course, this method is quite simple in terms of implementation, but its energy intensity is very high, so be prepared for high electricity consumption. This factor determines the use of this method only by large construction organizations.
• It is very important to correctly calculate the power of transformers, and it should be done by qualified specialists, because errors are fraught with low system efficiency, or even equipment failure.
• Both single phase and three phase wiring can be used. If everything is clear with a single-phase system, then the connection diagram of the three phases is shown in the diagram.

What gives electric heating

To decide whether to use this method, it is worth knowing that it gives:

• The structure does not freeze, which is very important for the maturation of concrete and the selection of optimum strength and durability characteristics by it.
• Thanks to preheating, Portland cement-based concrete gains 80 to 90 percent strength in 4 weeks. This can significantly reduce the time of work, since such a schedule of concrete strength development during the electric heating of concrete will not provide any other event.
• Do not apply too much stress, it causes over-drying of the concrete and a decrease in its strength.
• In order to ensure optimal conditions for the drying and ripening of the material, it is desirable to cover the surface with plastic wrap, this has a very positive effect on the reliability of the material.

Conclusion

In fact, if there is a possibility of working in the summer season, then it is worth it. But if you still need to pour concrete structures in the winter, the electric heating will be the only solution for the quality of the solidification of the monolith. The video in this article will help to understand some features of the work in more detail.