How to use a concrete preheating transformer during winter
Such a device as a transformer for heating concrete may be needed when we carry out work at low temperatures. The need for additional heating in this situation is due to the fact that in the cold the properties of the material vary greatly. That is why additional measures should be taken to ensure the desired strength of concrete.
How such devices work, and how to use them as efficiently as possible, we will describe below.
Work in the winter
Why warm up the concrete
Concrete heating with a transformer or other methods is necessarily applied when the temperature drops below zero during foundation work (and to be completely accurate, even below 40WITH).
The reason is quite simple:
- In the cold, the water in the cement slurry freezes. Of course, with a liquid in the thickness of the material, this will not happen so quickly, but in any case, in a few hours it will turn into microscopic ice crystals.
- Being in an inert state, water does not react with cement, therefore, it does not hydrate, and hence the concrete does not harden.
- In addition, when water freezes, its volume increases by about 10-12%. This leads to the fact that the foundation begins to collapse from the inside due to the "spreading" of microscopic pores with ice. Cutting reinforced concrete with diamond circles can clearly demonstrate an example of such destruction: on a cut, the material will look heterogeneous.
Note! Worst of all, if this process occurs repeatedly, which often happens in temperate climates with frequent thaws. Then the structural strength may not reach 50% of the nominal.
To avoid such a situation, and apply a transformer for heating concrete, as well as other methods of maintaining temperature.
Methodы обогрева
To date, three methods are actively used to prevent the freezing of cement mortar. You can analyze their features by studying the table below:
| Method | Features of use |
| Chemical | Special additives that prevent water freezing are added to the mixture. The technique is usually used on a small scale, since the price of the solution increases very significantly. |
| Thermal insulation | Foundation is poured into a special formwork, insulated to 15-200C. To increase the efficiency of this method, accelerators of solidification, such as calcium chloride, potassium carbonate, etc., are introduced into concrete. A variation of the method is the so-called "hot thermos", in which the mixture is heated to 60-70 before pouring into insulating formwork0C, and then - carefully closed. |
| Active heating | The technique is to increase the temperature of the filled solution using various devices. As heaters used: · Infrared emitter - saves energy, but is effective only on the surface. · Submersible electrodes that transmit high-amp current through the concrete mass - the method is simple to implement, but its effectiveness in drying the solution decreases. · The transformer for heating concrete - transfers the electric power to special heating cables.
|
In principle, all the above-mentioned methods can be used in the work, all the more so since some of them are quite accessible for realization by hand. But lately, the heating of concrete without a transformer or special heating devices is becoming increasingly rare. That is why we will focus on the description of this technology.
Transformer application
The method of heating concrete using transformer stations provides for the following actions:
- Special heating wires are laid in the formwork before pouring the concrete mix.. The best result is demonstrated by the use of steel conductors with a core diameter of 3 mm.
- Also, to prevent freezing, special heating wires in PVC insulation (PNSV with a 1.2 mm core) or double conductors (PNHG 2x1.2 mm) can be used.
- Wires are laid in such a way that they do not come into contact with the formwork or metal reinforcement.. You also need to ensure that the heating element along the entire length was covered with a solution, otherwise the conductor will burn due to insufficient heat dissipation.
- For better control of the heating of concrete with a transformer connected to the foundation, wells are usually provided to take temperature readings.. Diamond drilling holes in the concrete is not required, since mortgages in the form of thin tubes are installed during the casting stage.
After pouring the solution, a step-down transformer station of DC is connected to the heating elements:
- For the heating of concrete with a transformer, devices such as KTP, TMOB, KTPTO and their analogues are used. They effectively convert alternating current into a constant high power, which actively gives energy to heat-carrying wires.
Note! Some stations, such as KTPTO 80, can be connected directly to the reinforcement cage. This technique is more energy-intensive, but it can be used without first laying the conductors in the formwork.
- These devices allow you to adjust the thermal power of the entire system by increasing or decreasing the voltage applied to the conductors. In this case, the operation of the system is regulated depending on the outdoor temperature.
- The transformer can be controlled only with the appropriate tolerance (qualification group is not lower than the third). In this case, electrical safety instructions should be strictly followed.
As a result of the work of the system in the first days after pouring, the material has time to gain more than 50% of the normative strength, which positively affects its performance in the future.
Conclusion
Конечно, информация о том, как прогревать бетон с помощью трансформатора, будет полезна в первую очередь профессиональным строителям. Но, в принципе, эта технология может быть реализована и самостоятельно, тем более, если вы обладаете достаточными навыками работы с таким сложным оборудованием (см.также статью «Бетонные панели для забора – преимущества и установка»).
So, before planning construction in the winter, carefully review the above recommendations and the video in this article.