Tmo for concrete heating: purpose, characteristics,

18-03-2018

Building

Heating of concrete TMO is a technology that allows laying and casting ready-mixed concrete in monolithic construction at negative temperatures without disrupting the technological process, providing the material with normal conditions of ripening and hardening. We want to tell about the purpose and characteristics of equipment for transformer heating of concrete.

The photo shows a transformer for heating concrete in operation.

Concrete heating

Purpose

Instructions for laying requires compliance with the temperature regime.

Concrete is an artificial stone, obtained after hardening of a specially selected solution of binders and aggregates, closed with water. The hardening process is provided by the cement hydration reaction, for which the Portland cement and water in the liquid state are necessary.

Despite proper planning and serious organization of construction activities, it is not possible to avoid work in the winter. As a result, there is a need for laying concrete or casting monolithic structures at negative temperatures, and this requires a certain approach to work and a special technology of laying.

Winter concreting requires a special approach.

As you might have guessed, when the air temperature drops below zero degrees Celsius, the water in the concrete solution begins to freeze and crystallize, which causes the hydration reaction to stop due to lack of free fluid. As a result, concrete does not gain design strength and cannot perform its tasks.

Note! There is an opinion that after defrosting the concrete continues to gain strength and ripen, as if nothing had happened. However, this is not so: the material will not be able to gain the calculated strength and will still be worse in all respects.

The ability to work in the winter can significantly speed up construction.

The only way to prevent water from freezing in the solution is to heat it. It allows the material to gain the main strength for the period when almost all the water will react to the hydration of cement and there is practically no free liquid in the concrete.

Note! Heating of concrete allows you to speed up the construction time, optimally organize its stages, reduce the cost of simple equipment and seasonal shortage of materials and labor.

Ways

For heating, you can use infrared radiation.

There are various ways to heat concrete for winter laying and casting.

Such technologies are used with different frequency:

Construction of shelters, teplushk, superstructures and other structures that prevent direct contact of the working area with cold air. Often used in conjunction with heaters for electric, solid fuel, diesel or gas power. Refers to costly and inefficient methods, unsuitable for large-scale objects;
Use heated formwork. It assumes the presence of special equipment for the construction of formwork with heating elements, as well as a complex of connecting and supply wires, transformers and automation systems for control and protection of the system. Suitable for small structures, walls and other standard elements;
Electrode heating concrete. Based on the thermal effect characteristic of the passage of electric current through a conductor with resistance, only the solution here is the solution itself. It features low efficiency and high energy costs, suitable for pouring vertical walls, diaphragms and columns;
Concrete heating с помощью провода ПНСВ (1, 2). Inside the formwork is placed a special wire that heats up when electric current passes through it. The heating of concrete with TMO and wires is distinguished by a rather high efficiency and low energy consumption, suitable for various, including massive and non-standard structures, it is characterized by complex preparation;
Infrared heating. Here the solution is heated with special radiating mats, however, there is the problem of water evaporation. The method is suitable for plates and small horizontal and thin-walled structures;
Induction heating. Based on the phenomenon of electromagnetic induction: a coil with a conductor creates an alternating electromagnetic field that induces a current in the reinforcement cage of the structure, as a result of which it heats up. Differs in expensive equipment and complex calculation of the number of turns and thermal effect.

The construction of shelters - a popular way to combat frost.

Note! Analysis of all methods for increasing the temperature of the solution allows you to select heating with wires as the most versatile and effective, relevant to structures of various sizes and shapes and suitable for working with large volumes of concrete.

Next, we consider the main power source for electric heating systems for concrete - transformers and stations that convert the mains voltage to acceptable values, as well as supply and adjust the operating current at the facility.

Equipment

The most common transformer station KTPTO-80.

For the implementation of electric heating requires special equipment. In addition to heating wires or electrodes, you will need a power source with the specified parameters of current and voltage at the output.

The most common type of such equipment is a KTPTO-80 station on a TMTO-80 / 0.38 U-3 power transformer. This is a power-cooled step-down transformer with oil cooling and a three-threaded three-phase winding with a power of 80 kW.

Control panel of the concrete heating station.

The output voltage (LV) is 42 V, the input voltage (HV) is 380 V. The frequency of the supply current is 50 Hz, a three-phase power supply with a rated power of 2.5 kVA is required. On the side of the CH are available such voltage stages of idling - 55 V, 65 V, 75 V, 85 V and 95 V.

The power of the winding of a power transformer from the side of NN is 2.5 kVA, the current on the side of the SN at a voltage of 55 - 65 V - 520 A, at a voltage of 75 - 85 - 95 V - 471 A.

In automatic mode, it is possible to adjust the temperature of electrical heating in the range of 20 - 100 degrees Celsius. Power 80 kW allows to warm up to 90 m3 of concrete.

The wire is laid and fixed on the reinforcement cage.

The station is equipped with a power transformer in the enclosure, a protective case with doors that facilitate inspection and repair of the units, the control and protection module for emergency operation, brackets, skids or frame for the transportation of equipment. The weight of the transformer is 665 kg, dimensions - 147x140x101 mm.

The price of equipment varies from 90 to 120 thousand rubles, rent is about 10% of the cost per day. Connecting the station and putting it into work with the load is made by a professional power engineer, it is undesirable to do it yourself, moreover, it is prohibited by building regulations and safety engineering. Power engineering should have a standard tolerance of 1000 V.

Modern version of lightweight equipment.

Note! The station can be used as a power source for power tools with a voltage of 42 V and for lighting the object. Cutting of reinforced concrete with diamond circles and diamond drilling of holes in concrete at such a voltage is not performed.

Conclusion

Equipment for transformer heating of the concrete solution during the winter laying allows to significantly speed up construction and optimize organizational processes regarding seasons and seasons.

The video in this article will show the device in operation and help to understand its use.