Concrete warming up with the PNSV wire, the laying scheme of which will be described below, is used when working outdoors in winter. Such manipulations are necessary for the reason that when exposed to lower temperatures, the solution slowly begins to gain strength, in it the water simply begins to turn into ice. A longer hardening of concrete becomes the reason that the work drags on for weeks and months, in addition, there is a chance that the structure will not gain the proper strength, will crumble during operation.
The principle of the wire
The technology for heating concrete with the PNSV wire is that before starting the pouring, a cable of the desired cross-section and voltage is taken, laid, and then poured. Then the cable is plugged into the network. Do not be afraid that the quality of concrete will change under the influence of high temperatures, bubbles will not appear, as well as cracks after solidification, but the hardening process will not be stopped by low temperatures, which will provide a strong and reliable design.
Technical Features of Concrete Wire
The wire for heating concrete PNSV, as a rule, has some features. This is usually a conductive core that has an insulating coating. Protection can be made of polyester or polyvinyl chloride. The diameter is 1.2 mm, but the average resistance is equivalent to 0.15 Ohm / m. It can be used in the temperature range of -60- + 50 ° . During operation, the current can be equal to 14-16 amperes.
Laying can be done at -25- + 50 ° . Before purchasing, you need to determine how much wire you will need to use, so for 1 m 3 of the solution you need about 55 m.
Winter heating of concrete with the PNSV wire is completely safe, since the product receives high-quality insulation during production, which prevents fire. There is almost no danger that the core will be broken, since it is strong enough. Do not operate the wire until it is immersed in the solution. Otherwise, burnout will occur due to increased current. However, such phenomena are not afraid of conclusions, since they have wires of a more impressive cross-section in the composition, representing the so-called cold ends. They are made from APV – 4, the maximum length of which is 1 m.
Area of use
The method of heating concrete with the PNSV wire suggests the possibility of using it not only on a domestic but also on an industrial scale. Sometimes installation is carried out in
foundations and fences.
Cable installation
Work with the cable involves conducting responsible manipulations. Before starting the installation process, it is necessary to free the surface from debris and foreign objects, as for those elements that can damage the wire. During this, it is important to ensure that the cable does not bend. To do this, it is recommended to lay in a semicircle, but there should be no empty zones. The snake is the simplest laying method.
After switching on, be careful. So, voltage drops should not occur, to achieve this goal it is required to use a stabilizer, otherwise the wire will simply burn out, and it will not be possible to remove it.
The scheme for heating concrete with the PNSV wire is in the article. After you actually implement it, you can fill and connect, which involves connecting the cable to a power source. It is recommended to use a transformer when connecting. As a rule, experts recommend using stations for heating grades SPB-40, SPB-80.
Connection can be made according to two electrical circuits, the first of which is called a “star”, while the second is a “triangle”. In the latter case, the wires in the wire are divided into 3 equal parts and the wires of each are paired in parallel. The formed sets must be connected in 3 nodes and connected to the 3 clamps of the station.
Features of warming up
Before you begin, you need to know the time of heating up the concrete with the PNSV wire.
During the first period, the solution will warm up, while it is unacceptable to increase the temperature by more than 10 0 C in two hours. The second period should be accompanied by a temperature increase of not more than 80 0 C. At the final stage, cooling is performed. At the same time, one should not rush, and the decrease should not be more than 5 0 within an hour.
Concrete heating with the PNSV wire, the laying scheme of which is described here, does not differ much from the installation technology of the “warm floor” system. In addition, this cable can be used to achieve such goals. However, at the same time, the system will have to be slightly modified by constructing a heater from the wire strands, while the system must be protected by insulation from above.
The cost of a heating cable
Before purchasing, you must familiarize yourself with the prices of the cable. In different areas it may cost differently, but the average price remains unchanged, it is 2 rubles / m. You should not buy goods without checking whether it complies with the established GOSTs, so the cable is manufactured according to the standards 12.1.013-78.
Concrete processing after warming up
Many builders are wondering if it is possible to manipulate the cutting or drilling of concrete after it gains strength. This question is due to the fact that at the time of stopping the heating, the design does not yet gain brand strength. This question can be answered positively, but with some caveat. Although it is possible to cut, it is unacceptable to produce shock loads. In this case, the use of a diamond tool is the most suitable solution. So, if you use diamond drilling in this stage, the holes in the concrete will get smooth edges, and cracks will not occur. Moreover, if you drill a concrete body using a diamond crown, you will not have to change the tool at the moment of overcoming the reinforcement, which is true for reinforced concrete.
Specialist recommendations
Concrete warming up with the PNSV wire, the laying scheme of which is in the article, can be produced by the method of its initial winding onto a steel frame, and it is necessary to ensure the absence of tension. You can simply lay it between the elements of the metal frame. It should be remembered that the wire should not touch the surface of the formwork, it should not protrude from the body of concrete after pouring.
The heating wire can be mounted only after the reinforcing cage has been laid, it is not worthwhile to begin carrying out these works until the embedded elements are in the space of the building envelope. Welding work must also be completed by this time. Warming up of concrete with the PNSV wire, the laying scheme of which is shown in the figure, should not continue after the mortar has set strength by 50%.
The heat that comes from the core should be able to heat the solution to 40-800 0 C. The period until the mixture has fully gained strength will depend on the characteristics of the object and, as a rule, takes up to three days. The heating station must operate according to the intermittent or continuous principle. The pitch between the wires should not be more than 15 mm.
The calculation of concrete heating with the PNSV wire is presented in the article, but its observance does not yet give complete success. After all, it is still important to take into account the installation technology, which involves the exclusion of contact between the wire or its intersection. In order to be able to control the temperature regime in the structures poured with mortar, it is necessary to make special wells. Do not start the heating process until the solution is completely laid, as this is contrary to safety considerations, and in addition, it may damage the wire. It is preferable to entrust this kind of work to specialists, since the installation of the cable is accompanied by certain difficulties and requires the master to have skills in conducting such manipulations.
Calculation of a wire for heating concrete
In view of the above, the following conclusion can be made: for 1 m 3 of concrete it will be necessary to spend about 55 m of cable. In order to calculate the wire, you must first find out how much solution will be poured into the formwork. So, for 20 m 3 of the mixture you need to purchase 1100 m.
In general, it is preferable to carry out construction work in the warm season, which is especially true for private developers. As a rule, the conduct of concrete pouring in the cold period is associated with the need to hand over the object by a certain time. Such work in the framework of home construction involves additional costs for the purchase of antifreeze additives, heating cables and other things. Yes, and the labor costs in winter when pouring concrete are much greater, because mixing is more difficult, as well as the subsequent distribution of the mixture over the formwork.