Electronic thermometers for measuring concrete temperature

Let's get acquainted with the concrete work log and learn how to fill it out

Author: Author · Published 03/10/2016 · Updated 08/18/2017

Greetings, friends. In the last article, I explained to you how to fill out a general work log, but besides it there is a whole bunch of special journals that a responsible work producer should know like the back of his hand. One of these magazines will be discussed in this article.

So, today we’ll talk about the concrete work magazine. The sample is given in Appendix “F” of SP 70.13330.2012 “Load-bearing and enclosing structures. Updated edition to SNiP 3.03.01 - 87.” You can download the electronic version of the magazine for free at the end of the article.

What it is

This log is not large, registration also does not take much time, but it must be filled out if concrete work is being carried out at the site; this is established in clause 3.5 of SP 70.13330.2012. It is filled out by the responsible foreman on the days when concrete work is being carried out.

This joint venture provides a new form of the journal; the old form must be written off. Keep this in mind.

I used to read somewhere that if the volume of concrete work does not exceed 50 m3, then it is not necessary to keep a log of concrete work and you can make entries directly in the general work log. But I just can’t remember where I read this. If anyone knows, please write in the comments.

Below is a sample of filling out a concrete work log. Click on the pictures to enlarge the image.

How to fill it out?

Many people ask this question, but I think everything here is intuitive and after reading the example of a completed journal, many of your questions have disappeared, but I will still try to explain some points to you.

The magazine consists of a title page and a table of 14 columns. The first 8 columns are filled out by the responsible contractor, and from 9 to 13 are completed by the one who tests concrete structures for strength. Strength is tested at intermediate and design (28 days) age.

When you fill out column 4, try to indicate all the symbols of concrete. For example, if the project specifies the use of concrete B20F100W6, then indicate all this data in the journal. If you indicate only class B20 concrete in the concrete work log, then during the inspection the inspector of the state construction supervision may doubt the concrete used and demand proof of its compliance with the requirements of frost resistance and water resistance.

And you will have to prove this by presenting a quality document for the concrete mixture, but they may also miss and not write down the data on frost resistance and water resistance. And you will have to do additional technical inspection of concrete structures. Do you need it?

The concrete work journal, like all other journals, must be numbered, laced and secured with the organization’s seal. Also, corrections and blots are not allowed. It is included in the list of as-built documentation and, upon completion of construction, is transferred to the developer, and then to the operating organization.

If concrete work is carried out at an outside temperature of less than +5°C, especially in winter, it will be necessary to keep a concrete maintenance log. We will talk about it in the following articles.

Ps If you have any questions, feel free to ask them in the comments, and I will try to answer them. Subscribe to the blog and be the first to receive new articles.

What kind of documentation is kept (concrete care log, sample filling)

When performing construction work, the quality of which determines the reliability of the structure, each stage must be documented. In our case, this is a magazine on concrete care; you can download it freely online. It is stitched and sealed, and each entry in it is confirmed by signatures. Let's look at an example of filling by columns.

1. this is the name of the design;
2. volume of laid mixture;
3. surface modulus - the ratio of the surface area of ​​a structure to its volume;
4. aging methods - regular heating, thermos method, etc.;
5. Date and time when installation began;
6. date and time of start of aging;
7. holding period (not in days, but in hours);
8. outside air temperature;
9. average holding temperature;
10. date and time of temperature measurements at several points (wells) in the volume;
11. penultimate column: signature of the person who carried out the measurements;
12. At the end there is a column for notes.

A correctly filled out concrete care log allows, in most cases, to determine the cause of defects in finished structures - whether they are caused by poor-quality materials, improper concreting, or formed during the hardening process. Therefore, its maintenance is no less important than the execution of hidden work reports and the availability of quality certificates for the components of the mixture.

Concrete heating temperature sheet

Concreting in the winter season is associated with great difficulties. After all, in order to make strong concrete, it is necessary to provide it with comfortable hardening conditions, and first of all this is high temperature. There are two ways to solve this problem: use antifreeze additives in concrete and heating. The use of additives allows concrete to independently generate heat, which is so essential for proper and gradual hardening. Additives bind water, lowering its freezing point, and accelerate the process of formation of cement stone.

Warming up concrete in winter can be done in different ways, but the most popular method is heating the concrete using a transformer and PNSV wire. During such work, we recommend using a concrete heating sheet in order to accurately know all hardening coefficients and correctly regulate power.

Purpose of devices

A thermometer for measuring the temperature of concrete is used in production to obtain a certain quality with the necessary parameters. After all, the temperature of the mixture is the main factor that can affect the brand of manufactured products. The device has high accuracy and is quite easy to use.

In addition, electronic thermometers for concrete are often used when pouring mortar into molds, because the installation instructions state that the temperature of the mixture when hardening should be a certain degree. In this regard, professionals recommend mixing concrete with a special anti-freeze solution in the winter season.

It should be noted that when cutting concrete with a diamond wheel is easy, this indicates a violation of the mixture preparation technology. As a rule, such material crumbles and cracks appear in it over time.

Why do you need a concrete heating sheet?

The temperature sheet is needed to control heating and predict the quality of concrete after complete hardening. Using this data, you can correctly determine the time and order of concrete hardening. In addition, if you do everything correctly, the chances of getting a low-quality concrete structure are minimized.

Temperature control should be carried out using technical thermometers, which are lowered into the concrete in special tubes. The concrete temperature must be recorded every 2 hours, at least. While the structure is cooling, if it is less than 10 cm thick, then its temperature must be measured once every 4-5 hours. If the structure is thicker than 15 cm, then its temperature is measured only once per shift.

All measurements must be made in the hottest and coldest areas of the structure. Twice a shift it is necessary to measure the ambient air temperature, which is also reflected in the concrete heating temperature sheet.

The strength of concrete is predicted based on the temperature in the coldest areas of the entire structure.

Results

Depending on the temperature, the strength gain of concrete can be fast or slow. If the solution is poured in the cold season, you need to take care of external and internal methods of heating the site. When concreting in summer, it is important to prevent drying out. To do this, special quick-hardening Portland cements are used and the composition is constantly moistened with water.

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You can also familiarize yourself with prices and our products

Basic requirements for the solution

Pouring and curing of concrete can occur within a narrow temperature range. Today, special brands and varieties of Portland cement have been developed that can be worked with at subzero temperatures. However, standard varieties of this material still harden poorly at extreme temperatures, and at elevated temperatures the solution may rapidly lose moisture, which leads to cracking and other strength problems.

Ensuring the correct temperature conditions, including additional heating of poured structures in the winter, will ensure excellent quality of completed building elements. That is why it is necessary to fill out a temperature sheet, and also take into account the permissible humidity levels in the room where construction work is being carried out.

Types of thermometers and main characteristics

During the production of concrete, it is necessary to monitor its temperature at each stage of creation in order to obtain the required brand quality. For this purpose, special devices are used - technical thermometers:

• Wireless. It is controlled via the Internet, which makes it very convenient to use. It determines, in addition to temperature, density, after which it transmits the data to the computer. When using the device, it is possible to be absent from the area being tested, which saves time on the regulatory process.
• Infrared thermometer. A distinctive feature is remote metering. The device registers these radiations using a photographic or photoelectric method.
• Thermometer for heating concrete. To preserve the properties of concrete, the device is used in the winter, when the mixture needs to be heated.
• Complete. The device has a set of devices that allows you to measure temperature in two containers simultaneously. The thermometer also has a wire ten meters long and two sensors, one of which is lowered into the concrete mixture, and the other is mounted on the formwork. The advantage of the device is its durability and a very bright indicator.
• Bimetallic. It has meter-long probes in the form of needles and is used both in construction and for other economic purposes.

As a rule, a concrete temperature meter is used in a factory or when it is necessary to make a certain grade. In this case, a heating device must be used; it is connected to a stove or to another device that increases the temperature.

Additional heating of concrete

When performing construction work in the winter season, there is a need for additional heating of poured concrete structures. This warming up can be done in various ways:

• Additional insulation and heating with a blowtorch.
• Electric heating mats.
• Ultraviolet installations.
• Use of heated formwork.
• Supplying voltage to the fittings.

The most primitive and at the same time effective way to warm up concrete is to arrange a warm area over which a tent made of cellophane film is erected. If necessary, you can install a heat gun or light a blowtorch inside such a tent.

This heating method is simple, but it can only be used for small volumes of concreting.

Electric mats are popular because they are easy to use. They are effective and allow for concreting both indoors and outdoors. All you need to do is pour the solution, wait for its initial hardening, then lay out the electric mats over the structure to be poured and set the regulator to the desired temperature. The disadvantage of electric mats is the difficulty of using them for large volumes of concreting. It is problematic to cover walls, columns and various vertical supports with mats.

Professional builders use ultraviolet installations to heat concrete, which do not involve contact with the heated solution. Thanks to the presence of radiation intensity adjustment, it is possible to reduce and increase the heating power. With equal success, such ultraviolet installations cope with thick formwork, allowing for high-quality heating of the building structures being built.

Advantages of infrared installations:

• Ease of use.
• Warm-up efficiency.
• Can be used with formwork.

When constructing vertical reinforced concrete structures, various supports, partitions and walls, heated formwork can be used. This technology is easy to use, so it can be used both in the construction of high-rise buildings and in private low-rise construction.

Thermometer for concrete: thermometer (device) for measuring temperature

A concrete thermometer is a device that is increasingly used during repair and construction work both in the industrial and private sectors. Every year the range of concrete additives is expanding, thanks to which pouring can be carried out at any temperature, and the technologies for creating structures and buildings are becoming more and more advanced and demanding in terms of precision of implementation.

A thermometer for measuring the temperature of concrete allows you to measure this parameter and monitor the passage of all stages of preparation, pouring, and hardening of the solution. During the process of setting and gaining strength, various chemical reactions occur in the mixture that can generate heat (or, conversely, require heating). Therefore, strict adherence to technology and guaranteed high results of work require careful control of temperature, among other things.

Most often, measurements are carried out in factories, during the production of certain grades of concrete and products made from them with the required characteristics. Such thermometers for heating the concrete mixture are usually connected to furnaces, other heating elements and structures. In private construction and industrial facilities, compact temperature meters are used, made in the form of small and easy-to-use devices.

Temperature sheet calculation

All concrete used today fully complies with GOST; accordingly, the hardening time of the solution at certain temperatures has already been calculated . On the Internet you can easily find a completed sample temperature sheet for heating concrete, on the basis of which you can obtain all the necessary information about the curing time of the material at a specific temperature. It is not difficult to download such a form and standard filling out samples.

Based on typical examples of filling out a concrete heating temperature sheet, you can independently calculate the necessary data and, taking into account the current air temperature, select the optimal option for additional heating of the reinforced concrete structures being built. The use of such sheets will be relevant not only for professional builders, but also for ordinary homeowners who independently pour the foundation and various reinforced concrete structures. The sheets themselves can be downloaded on the Internet.

Professional builders use temperature forms with calculations, which contain data on the maturity of concrete, calculation of the average temperature in all shafts at a certain point in time after pouring the product. The use of such sheets with calculations allows you to obtain up-to-date information about the current state of poured reinforced concrete products.

The quality of poured reinforced concrete structures will largely depend on compliance with the temperature regime. To simplify the work with reinforced concrete products, temperature sheets for heating concrete were calculated. Using already completed standard samples, you can obtain all the necessary information about concrete hardening , which will be the key to performing high-quality work on the manufacture of reinforced concrete products.

Recommendations for use

To avoid problems in the future with low quality concrete, the appearance of deformations and cracks due to non-compliance with the technology for preparing the material and ignoring the rules of temperature conditions, you cannot help but use thermometers and do this correctly. In Moscow and the regions you can find a variety of instrument models, although the key measurement requirements are standard.

The main world views on the use of a thermometer for concrete:

When making measurements with your own hands, it would be a good idea to take several readings in a row, and over the years find the arithmetic average among them by summing all the results and dividing the number to get the number of measurements. It’s worth looking at the price when choosing a device - it’s better to look at the functions and options, suitability for the conditions of use and ease of carrying out research (something like, in everyday conditions there may be little opportunity and not to buy up the knowledge to perform measurements with a naturally complex industrial device). When choosing, pay attention to the measurement scale used: information can be displayed in Celsius or Fahrenheit, the second option is not very convenient due to the need to convert the values ​​into the usual system. When performing measurements, bring up the data and enter it into a table, without relying on memory and without writing down incomprehensible numbers on scraps of paper. This way, you will be able to better control the temperature of the mixture and guarantee compliance with the technology. It is necessary that the received data can be noted in the device (presence of memory). (until, if necessary (and there are no records in the table), it will be possible to resurrect the necessary values ​​and use them in work.

A concrete thermometer is a device that, when it is necessary to measure the temperature of a concrete solution, allows you to carry out work correctly and accurately, inspect the implementation of each stage and guarantee the best result in the end.

How to fill out the temperature sheet?

• thermometer readings
• blue ballpoint pen
• black ballpoint pen
• simple pencil

In medical practice, the general characteristics of the patient (physiological constants) are important for correct diagnosis. These include: blood pressure, pulse, respiratory rate, temperature, etc. These readings are recorded on a temperature sheet twice a day. The temperature sheet graphically records blood pressure, pulse and temperature.

Filling out the temperature sheet begins with recording your last name, first name and patronymic. patient, writing the date and room number of the patient. At the very top of the sheet there are three scales “Date”, “Day of illness” and “Day of hospital stay”. They are filled accordingly. Below them, on the left, there are also three columns, in which there are the letters P, AD and T, which mean pulse, blood pressure and temperature, respectively. At the bottom of the temperature sheet, the figures for breathing, daily diuresis (urine), measurement of body weight, as well as the amount of urine drunk and excreted per day - water balance - are recorded in numbers.

Please note that the column “Day of stay in hospital” is divided into two parts “y” - morning and “in” - evening.” Therefore, indicators are recorded on the temperature sheet in the morning and evening. This is done by paramedics after measuring the temperature of patients. The vertical line “T” indicates temperature readings from 35 to 45°. The price of one division corresponding to the temperature column is 0.2, you should pay attention to this in order not to make mistakes.

It is important to know that temperature indicators are indicated by a dot, and then connecting all the points a broken curve is built, which is called a temperature curve. Temperature readings are usually written in black ink, while blood pressure and pulse readings are written in red ink. It is important to remember some nuances and correctly calculate the temperature scale; you also need to remember that in some medical institutions the temperature sheet looks slightly different. In addition to all the above indicators, it may reflect additional ones. Knowing all this, constructing a temperature curve will not be difficult.

So, as you can see, filling out the temperature sheet is a simple matter that anyone can do. But simplicity does not mean insignificance - it is the temperature sheet that clearly shows the dynamics of the disease.

How to correctly fill out a temperature sheet for heating concrete

Temperature sheet sample completed example. Sample journal for selecting the composition of an asphalt concrete mixture Rosavtodor example Position, surname, initials and signature of the person responsible for welding work and maintaining the journal.

1. A temperature sheet is a medical document that graphically reflects fluctuations in the patient’s body temperature during the day.
2. Filling out the temperature sheet in MS Excel (Open Office. Cals). (slide number 2 on the screen) The goal of our lesson is to learn how to correctly fill out a temperature sheet in a medical history using a PC. Temperature sheet sample..
3. Samples of filling temperature sheets for heating concrete. temperature sheet for winter concreting. On this page you can find a temperature sheet for heating concrete..

At your request, a sample for filling out a sheet for recording pressure, pulse, and temperature has been added to the nurse's journal. As experience shows.

As soon as the thermometer crosses the mark at 3. Upper - - the lower edge of the third rib along l. Objectively: vesicular breathing over the entire surface of the lungs. Myocardial infarction is an acute disease caused by the occurrence of foci of ischemic necrosis in the heart muscle due to insufficient blood flow to it. Here is an example of a completed concrete heating temperature sheet in accordance with all standards and rules.

Harsh everyday life temperature control sheet, print out temperature sheet, how to fill out sample temperature sheet. Sample temperature sheet completed. A certificate of incapacity for work is issued to care for a sick family member 3. Lists of persons subject to examination are compiled by the administration. Rules and features of filling out a new sick leave form (for a personnel officer).

Temperature sheet for the patient, filled out by the nurse. Thanks to the use of a temperature sheet, the attending physician can monitor the patient’s condition and promptly determine the tendency for the patient’s health to deteriorate. Temperature sheet. 004/у. Form. 25 years. Transfusion media transfusion registration sheet. 005/у. Form. 1 month after filling out the “Summary Statement”. Daily record sheet for the work of an orthopedic dentist. 037–1/у.

Q expansion is more than 0.3. Other abdominal organs—the liver, spleen, and small intestine—are not palpable. Sometimes a pericardial friction noise and gallop rhythm are heard for 2-3 days. Sample temperature sheet completed.

Sample temperature sheet completed. The kidneys are not detected by palpation, there is no pain on palpation. Objectively: the condition upon admission is unsatisfactory, the skin is pale, the apical impulse is determined in the 5th intercostal space on the left along the L. Body temperature is an important indicator of our health. Wanders for self-moderation of classes - comments from license plates with a negative reputation. This sheet is a little more complicated than the first, but more informative.

How to correctly fill out a temperature sheet for heating concrete

By standard number By date of introduction. Download Guide to Electrical Heat Treatment of Concrete. Concrete temperature control log Appendix 15. Concrete heating control log in winter. How to fill out a concrete heating log. In this case, any technology can be used: electric heating, steam, heat guns, and so on. This is not a concrete temperature control log, but a kind of temperature sheet. I will give you the opportunity to download not only a temperature sample.

The concrete work log is filled out by the foreman or foreman. During the laying of concrete, at least 2 samples of concrete from the replacement supply must be taken, each sample. Journal of quality control of concrete in winter conditions. JOURNAL of quality control of concrete in winter conditions. Logbook for monitoring the strength of concrete laid in a heated state. Gosstroyizdat 1964).

Warming up concrete - prices, reviews, calculations. Electric heating of concrete with wire. The technology of heating concrete with PNSV wires using heating stations (transformers) The method is quite simple to understand, but still requires qualified specialists. The power engineer must draw up documentation for warming up (diagram, log) and calculate the required amount of materials and equipment. Electricians will have to monitor the warm-up process around the clock, in shifts, recording readings in a log.

The essence of heating with a PNSV type wire is that the heating cable placed inside the structure, when current is supplied to it, heats up and heats the concrete solution itself. It is very important to lay the wire correctly so that there are no areas that the wire cannot heat, and also to connect correctly so that there is no phase imbalance (which warm-up transformers really don’t like). A complete list of equipment and materials for electrical heating of concrete. The table below roughly shows the sequence of necessary wires and equipment. Power cable - required for connecting heating transformers from the power supply. The station is also a transformer for heating concrete, produced with a power of 2. W, power supply is only three-phase 3.

B. 3. Route - aluminum wire with large cross-section insulation is used, connected to the low side and laid along the fill, as close as possible to the terminals of the PNSV. This wire is laid along a wooden flooring, this can be seen in the photographs below. The length of the route is usually used 1. Cold ends are also aluminum wires in insulation, but of a thin cross-section, conventionally selected with a cross-section three times higher than the heating wires being laid. They are used to connect the terminals of the three ends of the PNSV wire with the route; the length of these ends should be no more than 1.5 m. PNSV wires - the heating cable itself, have an annealed steel core of various sections, covered with heat-resistant insulation.

Heating cable connection diagram star diagram (five triples) triangle diagram (three threads) laying the route installation of the heating cable connection of the route and the PNSV cable When insulating cable connections, use either a heat-shrinkable tube (TV-4 cambric. Variant of the heating wire layout diagram. Warm-up technological map. Compilation of this The document should be handled by the construction organization's power engineer. From this map, it becomes clear the location of the heating stations, their number and how many and what kind of heating and connecting wires are required. It is important when drawing up the map to take into account the number of transformers involved at the same time, the limit on this is usually given by the maximum possible power at the site. Option TTK (standard technological map) for heating concrete.

Calculation of the heating wire - Approximate consumption 5. When heating the concrete, it is necessary to record data on temperature measurements at control points at intervals of about 3-4 hours. Data is taken using special mechanical or digital thermometers, placed in special sleeves, which are first placed inside the concrete and filled with oil. Sheet - 1. Sheet - 2.

Control log form. Concreting with electric heating is possible up to - 4. C. When is it necessary to start heating concrete?

According to standards, this process should be used when establishing an average daily temperature of +5. C, because The time for complete heating of concrete is 3 - 4 days. Electric heating of concrete - a short video (Flash player must be installed to view).

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Rules for heating concrete. Use at home

For civil, industrial, as well as handicraft (home) construction at subzero temperatures, there are various ways to warm up concrete, allowing you not to stop work during the winter.
Such auxiliary procedures allow you not only to continue installation work in cold weather, but also increase the rate of hardening of the solution, especially with the addition of special chemical hardening accelerators. Below we will talk about such methods in general, and we will consider one of them (the most popular) in particular, and also show you a video in this article on the topic of electrical heating of concrete.

Pouring concrete at sub-zero temperatures

What methods are used for warming up?

Elektromat

• The most primitive way of pouring mortar in the winter is to build a very ordinary tent made of cellophane film over the site with your own hands, where you can install a burning blowtorch or heat gun in the middle . The method is extremely simple, but it can only be used on objects with a small area, and it is difficult to build such a dome over vertical structures.
• It is somewhat easier in such a situation to use electric mats, which simply cover the pouring area, setting the regulator in the desired mode, depending on the air temperature outside . But here, too, there is a serious drawback - electromats are inconvenient to use when pouring large areas, moreover, only horizontally located reinforced concrete structures can be covered with mats, but not walls, supports or columns.

Ultraviolet emitter

• An ultraviolet concrete heating installation is perhaps the most convenient of all existing ones, since it does not involve contact with the solution itself, and the thermal intensity of the device is simply regulated by the distance between the UV emitter and the object . Another advantage of this method is the ability to heat structures of any configuration and in any position (both horizontal and vertical), while the formwork is not an obstacle. However, this method is used quite rarely - it requires a large number of heaters.

Heated formwork

• Another method of creating monolithic reinforced concrete structures in winter is the use of heated formwork, only it is applicable exclusively for vertical reinforced concrete structures (walls, partitions, supports) . This is very convenient, since the shields here are reusable, and the heating elements on them must be replaced, and this is quite simple to do. The main disadvantage of such formwork is its very high price, which, however, pays off with its frequent use.

Warming up with electrodes

• For electrode heating of reinforced concrete structures, reinforcement or wire rod with a cross-section of 8 to 10 mm and a step-down transformer are used, but this method is more suitable for vertically standing reinforced concrete structures . Here it is not the electrodes themselves that are heated, but the moisture between them (a boiler made of two blades works on the same principle), only here the distance between the pins is from 60 to 100 cm - it all depends on the air temperature. The main disadvantage, despite its simplicity, is the very high electricity consumption (one electrode consumes about 45-50A), therefore, the cost of construction increases.

Warm-up table

• In this case, in order to maintain the required temperature, it is checked every two hours and special wells are made in advance for this . During the heating of the solution, such testing is performed every hour. During the entire process, it is necessary to constantly monitor the condition of the solders and contacts.

PNSV wire and step-down transformer

Note. PNSV (Heating Wire Steel Vinyl Insulation) can have different cross-sections and is used one-time. After the mass hardens, it remains there forever.

Using a Step-Down Transformer

The above-mentioned methods of heating concrete are not as popular as the one we will discuss now - this is the use of PNSV wire as a heater and a step-down transformer for converting electricity.

The essence of this method is as follows: the cable is laid in loops at the place where the solution is poured, and its cross-section will depend on the power of the transformer and the air temperature outside (in the building) where the work is being carried out.

Depending on the air temperature, a load is applied to the loops from the step-down transformer and heating begins, but the structure of the concrete does not change, but the rate of hardening of the solution increases significantly.

The resistance of the PNSV depends on the wire cross-section

Important! Before laying the PNSV, it is imperative to ensure the integrity of the wire and its sheath.

The fact is that the control of concrete heating is carried out only in relation to the temperature regime, and the wire itself, if it burns out, cannot be replaced, since it is completely immersed in the solution (in addition, its short circuit can lead to a fire). Therefore, for such purposes it is better to use new material.

Table of optimal loop lengths for different wire sections and types of concrete

Schematic diagram of concrete heating

When laying PNSV, the instructions require that there be no debris in this place that could damage the sheath, which in turn will lead to a short circuit and burnout of the cable (as we have already said, it is impossible to replace it). In addition, when creating a loop, it is unacceptable to make sharp bends and leave “wings”, which leads to a break in the wire - all turns should be made smoothly.

The installation itself is usually done either with a “snake”, as shown in the diagram, or with a single loop - everything will depend on the length of the PNSV and the area of ​​the structure being poured.

In no case should heating wires be allowed to intersect with each other - the optimal distance between the cores is about 100 mm, although it can be changed depending on the length and cross-section of the PNSV, as well as on the size of the working site.

In any case, the heating wire must be completely filled with concrete (including twists), since it will overheat in air, and as a result, both the insulation and the steel core will burn.

In addition, you should take care to protect the transformer and, as a result, the entire heating structure, from voltage surges, since a surge can cause sudden overheating and burnout.

Step-down transformer KTPTO-80

To visualize the connection diagram, let's look at how this is done in accordance with SNiP 111-4-80/chap.11 and GOST 12.1.013-7 - in this case, a step-down transformer KTPTO-80 is used, as in the photo above.

This unit, before assembling the electrical circuit, must be grounded, and this is done using the fourth core of the power cable to terminal N from the XT6 block, bypassing it with the metal body of the control cabinet. Grounding is carried out from the skid legs of the unit, where there is a special bolt with a nut for this purpose, and the circuit is made of steel wire with a cross-section of at least 4 mm.

Schematic diagram of KTPTO-80

For safety reasons, the insulation resistance must be at least 0.5 MOhm, which must be verified before connection, and all twists and contact connections must also be checked.

Then install the position switches SQ1 and SQ2 so that it is possible to reliably close the contacts of the same name when opening the casing cover and the control panel.

In addition, be sure to check the integrity of the fuses in case of short circuit.

Set the power transformer switch to position 1 (correspondingly - 55V), and set the auto switch and SA3 to the “OFF” position. After all these procedures, the chain installed in a concrete or reinforced concrete structure is connected to the block using XT6 clamps.

380V power is supplied to the input, we check the voltage of HL1 and HL3, after which QF1 closes and, using SB1 (emergency “OFF” button), we try an emergency shutdown. After such a test, the switch is turned on again - we supply power to KL1 using the SB3 button, after which the KM1 magnetic starter is triggered.

Concrete heating map (home page)

In accordance with SNiP 3.03.01-87 (on heating load-bearing and enclosing reinforced concrete structures at temperatures down to -40⁰C), a technological map for electric heating with PNSV type wires is used.

This document contains technical, organizational and technological solutions to issues related to the wire heating method with all technical and technological parameters used, that is, the entire concrete heating schedule.

Temperature warm-up sheet

To control the heating, as well as to be able to predict the quality of reinforced concrete concrete after final hardening, a concrete heating sheet is used - a form for which can always be downloaded via the Internet. Such data allows you to accurately verify the time and order of hardening of the poured mortar, that is, it is like a step-by-step guide to achieving the greatest strength.

Control or calculation of concrete heating is carried out using a technical thermometer - special funnels are made in the poured mass, where a tube is placed, and a thermometer is lowered into it. The temperature is recorded every two hours, and if the thickness of the structure does not exceed 10-115 cm, then this is done every 4-5 hours.

We should not forget that with normal heating of the PNSV - up to 80⁰C - the temperature of the concrete during heating reaches 40⁰C-50⁰C, and this happens in the cold!

Using a welding machine as a step-down transformer

At home, you can use a welding machine with a power of at least 250A as a step-down transformer, as in the photo above, and therefore the resistance. The number of PNSV wires in such cases can be calculated using the formula R=U/I.

As a rule, our U indicator will be 220-230V, and if we use a unit of the above-mentioned power, then I=250A. in this case, R=U/I=220/250=0.88 ohm and, based on this, you can use tables to determine the required cross-section and length of the wire.

It should be said that when immersing the PNSV in the mass of concrete, it should be connected to the transformer with an aluminum wire of the APV type with a cross-section of at least 4 mm, but the twist must be in the solution.

We mentioned this point for a reason - you will have to connect two non-uniform metals - steel and aluminum, therefore, the connection may not be tight, which will lead to sparking, overheating and burnout of the wire. But it will no longer be possible to redo the twist filled with solution, therefore, pay special attention to this moment - the possibility of completing the process at all will depend on it.

Conclusion

In conclusion, we can say that the lowest cost of concrete heating is in the case of using a PNSV cable and a step-down transformer, and although this method is quite inconvenient to use for vertical reinforced concrete structures, it is still sometimes used to save money. Despite the complexity of laying the wire (it takes a lot of time), wire heating of reinforced concrete structures is used most often.

Source: https://masterabetona.ru/progrev/575-pravila-progreva-betona