Electroheating of concrete in winter: methods, technologies, equipment

In modern conditions, there are many technologies that make it possible not to stop the construction process even in winter. If the temperature decreases, it is required to maintain a certain level of heating of the concrete mixture. In this case, the erection of houses, various objects does not cease for a minute.

The main condition for carrying out such work is to maintain a technological minimum, at which the solution will not freeze. Electroheating of concrete is a factor that ensures the fulfillment of technological norms even in winter. This process is rather complicated. But nevertheless, it is actively used everywhere at various construction sites.

Electroheating

Electric heating of concrete is a rather complex and expensive process. However, to prevent the effect of low temperatures on the solidifying cement mixture, it is required to provide a number of conditions. In winter, cement freezes unevenly. To prevent such a deviation from the norm, the technology of electrical heating should be applied. It promotes a constant throughout the area process of solidification of the mixture.

Concrete is able to freeze evenly at a temperature that will be close to +20 ºС. Forced electric heating becomes an effective tool in the preparation of mortars.

Most often, electric heating technology is used for such purposes. If simple insulation of the object becomes insufficient, such an alternative can solve the problem of unevenly solidifying concrete.

Construction companies can choose one of several approaches. For example, the electric heating can be carried out with the aid of a conductor, such as the PNSV cable, or with the help of electrodes. Also, some companies resort to the principle of heating the formwork itself. At the present time, induction approaches or infrared rays can also be used for similar purposes.

Regardless of which way the management chooses, the heated object must necessarily be insulated. Otherwise, uniform heating will be achieved unrealistically.

Warming up with electrodes

The most popular method of heating concrete is the use of electrodes. This method is relatively inexpensive, because there is no need to purchase expensive equipment and devices (for example, wire type PNSV 1,2, 2, 3, etc.). The technology of its implementation is also not very difficult.

For the fundamental principle of the presented technology, physical properties and features of electric current are taken. When passing through concrete, it releases a certain amount of thermal energy.

When using this technology, it is not necessary to apply voltage to the electrode system above 127 V if there is a metal structure inside the product (frame). The instruction for electric heating of concrete in monolithic constructions allows using a current of 220 V or 380 V. However, a higher voltage is not recommended.

The heating process is performed using alternating current. If a direct current participates in this process, it passes through the water in the solution and forms electrolysis. This process of chemical decomposition of water will interfere with the performance of its functions, which has a substance in the process of solidification.

Types of electrolytes

Electric heating of concrete in winter can be carried out using one of the main types of electrodes. They can be string, rod and made in the form of a plate.

Rod electrolytes are installed in concrete at a short distance from each other. To create the presented product, scientists use metal reinforcement. Its diameter can be from 8 to 12 mm. Connect the rods to different phases. Especially indispensable for the presented devices in the presence of complex structures.

Electrolits, which have the form of plates, are characterized by a fairly simple connection scheme. Their devices must be located on opposite sides of the formwork. These plates are connected to different phases. The current passing between them will heat the concrete. Plates can be wide or narrow.

String electrodes are necessary in the manufacture of columns, pillars and other products of elongated shape. After installation, both ends of the material are connected to different phases. So there is heating.

Heating with cable ПНСВ

Electric heating of concrete with wire PNSV, the technological map of which will be considered a little further, is considered one of the most effective technologies. As a heater in this case, there is a wire, and not a concrete mass.

When laying concrete in the presented wire, it is possible to warm the concrete evenly, ensuring its quality during drying. The advantage of this system is the predictability of the work period. For high-quality heating of concrete in conditions of temperature reduction, it is very important that it rises smoothly and evenly over the entire area of the cement slurry.

The abbreviation PNVS means that the conductor has a steel core, which is packed in PVC insulation. The cross-section of the wire during the presented procedure is selected in a certain way (PNSV 1.2, 2, 3). This characteristic is taken into account when calculating the amount of wire per 1 cubic meter of cement mixture.

The technology of heating concrete with a wire is relatively simple. Along the framework of the armature, electrocommunications are allowed. Mount the wire in accordance with the manufacturer's recommendations. In this case, when the mixture is fed into a trench, formwork or a conductor mixture, it does not damage the pouring and operation of the solidified substance.

The wire in the layout should not touch the ground. After pouring, it is completely immersed in the concrete environment. The indicator of the length of the wire will have an effect on its thickness, negative temperatures in this climatic zone, resistance. The applied voltage will be 50 V.

Method of using the cable

Electric heating of concrete with wire PNSV, the technological map of which consists in placing the product in a container immediately before pouring, is considered a reliable system. The wire must have a certain length (depending on the conditions of its operation). Due to the good thermal conductivity of the concrete, the heating is smoothly distributed throughout the thickness of the material. Due to this feature it is possible to raise the temperature of the concrete mix to 40 ºС, and sometimes even higher.

The PNSV cable is allowed to be supplied to the network, which is supplied by KTP-63 / OB or 80/86 substations. They have several degrees of voltage of reduced type. One substation of the presented type is capable of heating up to 30 m3 of material.

To increase the temperature of the solution, it is necessary to spend about 60 m of the wire of PNSV 1,2 for 1 m³. The ambient temperature can be up to -30 ° C. Heating methods can be combined. This depends on the solidity of the structure, the weather conditions, the specified strength. Also an important factor for creating a combination of methods is the availability of resources on the construction site.

If the concrete manages to gain the required strength, it can withstand destruction due to low temperatures.

Other options for wire heating

The technology of warming concrete with PNSV cable is effective provided all the instructions and requirements of the manufacturer are observed. If the wire goes beyond the limits of concrete, it is likely to overheat and out of order. Also, the wire should not touch the formwork or the ground.

The length of the wire represented will depend on the conditions in which the wire is applied. For their work requires the work of a transformer. If, using the PNSV wire, the use of such a system is not very convenient, there are other types of conductor products.

There are cables for the operation of which you do not need to apply the washing to special transformers. This makes it possible to save a little money for servicing the presented system. A conventional wire has a wide range of applications. However, the PNSV wire, which was discussed above, has more possibilities and scope.

The scheme of application of the heat gun

Warming concrete with wire is considered one of the newest and most effective technologies. However, more recently, no one knew about it. Therefore, a fairly costly but simple method was used. Above the cement surface a shelter was built. For this method, the concrete base should have a small area.

Thermal guns were brought to the built tent. They pumped in the required temperature. This method was not devoid of certain drawbacks. It is considered one of the most time consuming. Workers need to erect a tent, and then monitor the operation of the equipment.

If we compare the warming of concrete with wire and the method of using heat aggregates, it becomes clear that the old approach will require more. Most often, certain equipment of an autonomous type of work is purchased. They work on diesel fuel. If there is no access to the usual fixed network on the site, this option will be the most advantageous.

Thermometers

A heating wire or an infrared film can serve as a basis for creating special thermo-mats. They are quite effective. The only condition is the flat surface of the concrete base. Some versions of the presented heaters can work as winding on columns, elongated blocks, pillars, etc.

In the same solution, when using matte technology, a plasticizer is added, which makes it possible to accelerate the drying process. However, they can also prevent the formation of crystallization of water.

When using the presented technologies, it should be remembered that there are special documents regulating the electrical heating of concrete in the winter. SNiP draws the attention of construction organizations to the need to constantly monitor the temperature characteristics of this substance.

Cement mixture should not overheat above +50 ºС. This is just as unacceptable for the technology of its production, as well as great frosts. At the same time, the cooling and heating rate should not be faster than 10 ° C per hour. To avoid mistakes, the calculation of electric heating of concrete is carried out in accordance with the current regulations and sanitary requirements.

Infrared mats can replace cable analogs. They can be used to wrap curly columns, other elongated objects. This approach is characterized by low energy costs. Concrete structures under the influence of infrared rays begin to rapidly lose moisture. To prevent this from happening, you need to cover the surface with a conventional polyethylene film.

Decking with heating

Electric heating of concrete in winter can be carried out immediately in the formwork. This is one of the new ways that is very effective. Heating elements are installed in the formwork panels . In the event of failure of one or more of them, dismantling of the defective equipment is carried out. It is replaced by a new one.

To equip the infrared heaters directly with the mold in which the concrete solidifies, has become one of the successful decisions taken by the managers of construction companies. This system is able to provide the required conditions with a concrete product located in the formwork, even at a temperature of -25 ° C.

In addition to high efficiency, these systems have a high efficiency. It takes very little time to prepare for heating. This is extremely important in conditions of severe frosts. The profitability of the heating formwork is determined higher than that of conventional wire systems. They can be used repeatedly.

However, the cost of the presented type of electric heating is quite high. It is considered unprofitable if it is necessary to heat the construction of non-standard dimensions.

Principle of induction and infrared heating

In the above systems of thermoforms and formwork with heating, the principle of infrared heating can be used. In order to better understand the operation of these systems, it is necessary to understand the question of what infrared waves are.

Electric heating of concrete with the help of the presented technology takes as a basis the ability of solar rays to heat opaque, dark objects. After heating the surface of the substance, the heat is evenly distributed throughout its volume. If the concrete structure is wrapped in a transparent film in this case, when heated, it will let the beams pass into the concrete. The heat will stay inside the material.

The advantage of infrared systems is the lack of requirements for the use of transformers. The disadvantage of the experts is the impossibility of the presented heating to evenly distribute heat throughout the structure. Therefore, it is used only for relatively thin products.

Induction approach in modern construction is used quite rarely. It is more suitable for structures such as girders, beams. This affects the complexity of the device presented equipment.

The principle of induction heating is based on the fact that a wire is wound around the steel rod. It has a layer of insulation. When the electric current is connected, the system produces an induction disturbance. This is how the concrete mixture heats up.

Having considered the electric heating of concrete, as well as its basic methods and technologies, it can be concluded that it is expedient to use this or that method in production conditions. Depending on the type of manufactured structures and production conditions, technologists choose the appropriate option. A scrupulous approach to the technology of solidification of concrete mix allows you to produce high-quality products, screed, foundations, etc. The rules for working with cement in winter should be known to every builder.