The masters say that it is possible to thermally affect concrete after pouring into the formwork only when carrying out repair work in a room with a low temperature. Heating the solution is carried out for its rapid solidification - this ensures the homogeneity of the mixture. For active methods of thermal action, a heating cable for concrete is used.
Content
- Varieties of wires
- Heating technique
- Laying conditions
Varieties of wires
Visually, the cable for heating concrete does not differ from other wires. It contains one vein. When concreting, temperatures of 55 degrees are achieved. The wire passes the maximum maximum current strength - up to 16 A. The flexibility of the product is achieved due to the conductor cross-section - from 0.5 to 3 mm. One cubic meter of concrete can be heated with a 55 meter wire.
Among the variety of types of heating cables, there are:
- PNSV;
- PTPZH.
PNSV wire has a low cost, therefore it is very popular. The abbreviation stands for "Vinyl steel heating wire". The first two letters determine the purpose of the product, the third is the material from which the core is made, the fourth is the type of insulation.
There may be some problems after loading the concrete, but they can be fixed with a 3mm cable. The insulation of the wire is quite strong, so it will not be damaged when the solution is compacted. Intensive development often causes phase imbalance, which leads to poor quality power supply.
PNSV has a low probability of overheating, but if the outer sheath is broken, the cable will be short-circuited. However, usually the wire does not deform during the setting of the concrete.
The PTPZh wire was originally used to connect acoustic equipment. This is a two-core element that differs little from PNSV. Its cross-section ranges from 0.5 to 1.2 mm, the braid is galvanized. You can work with it at a temperature of at least 30 degrees. A radius of 10 mm must be observed when bending the wire. Thin PTPZh is intended for the construction of a warm floor, a thicker cable is required when heating monolithic structures.
Heating technique
The main advantage of heating concrete with a cable is the complete avoidance of heat loss. The solution absorbs all energy, while the material costs are negligible. The cost of wires practically does not affect the size of the estimate. You can independently lay the heating element if you choose the right material.
First, the frame is installed in the formwork and the cable is laid. Then the concrete solution is loaded and compacted manually or using a vibrating press. After that, you can apply voltage to the system. Electrical energy turns into heat and heats the concrete from the inside. For installation, it is better to use cables rather than wires, although they have a higher price.
The solution is reinforced with a metal rod, so the wire cannot be connected to the network. The voltage can be reduced by installing a stabilizing transformer.
The use of a cable makes it possible not to lower the voltage. It is easy to install as it does not require cutting. At the ends there are special couplings that serve as connecting elements when laying. The cable cannot be dismantled and reused.
Laying conditions
The laying pattern is chosen by the master individually and closely related to the specifics of the work. The quality of the entire structure, as well as the uniformity of the structure of the concrete solution, depends on the installation. The wires are connected to a voltage source using cold ends, because their cores have a lower resistivity.
When working, they follow some recommendations:
-
the wires in the circuit are located at a distance of 1.5 centimeters from each other; - all cables are laid in the formwork in parallel, no overlaps or contact should be allowed - this can lead to melting of the insulating sheath of the wires or a short circuit;
- during installation, the temperature regime must be observed.
It is impossible to carry out work when the frost is below 15 degrees. In the cold, the sheath of the wires will crack and break, the veins will be exposed and may touch, which will lead to overheating, flashes and short circuits. And although the instructions for the elements indicate that you can mount the cable at temperatures up to minus 55 degrees, you should not take it literally.
You can further improve the quality of heating. To do this, each wire is wrapped in foil. It will increase heat transfer, spreading it over the entire surface of the concrete, and accelerate the process of its hardening. This method of insulation is used for small rooms, where the number and length of cables are insignificant.
The cost of a wire for heating concrete depends on the length and material from which it is made. It is necessary to purchase not the cheapest options, since they are not of high quality. This kind of work is not worth saving.
