During construction, it often becomes necessary to concret foundations, reinforcement or other sections in the winter season. In this case, it is necessary to prevent the water contained in the concrete from freezing. If this happens, ice crystals will significantly reduce the performance of the material and its strength.

Fundamental rules

In order for winter concreting to be successful, and the quality of concrete not to deteriorate, it is necessary to adhere to several basic rules for conducting the process in the cold season:

1. First of all, you should use special antifreeze additives that will prevent freezing and increase its strength.
2. In the absence of additives, the concrete mixture should be diluted only with heated water, and prescribed methods should be used to ensure high quality structures.
3. Machines that will transport concrete in the cold season must be insulated.
4. The base for concrete before starting work must be thoroughly cleaned of dust and dirt and heated.
5. Snow and ice should be removed from reinforcement and formwork to be used in the concreting process. If the reinforcement has a diameter of more than 25 mm or is made of a rolled profile, at an air temperature below -10 degrees it is heated until it acquires a positive temperature. The same operation must be carried out with large metal embedded parts.
6. Concreting work must be carried out at an accelerated pace, continuously, to prevent cooling of the concrete layer laid in the first place.
7. After pouring concrete, its entire surface must be insulated with wooden shields or mats.

Compliance with these simple conditions will allow you to get high-quality concreting that retains strength and reliability.

Concrete curing methods

Modern construction uses several methods of keeping concrete mortar at sub-zero temperatures, which should be considered quite effective and cost-effective.

Winter concreting methods can be divided into 3 groups:

• the thermos method, based on the conservation of heat introduced into the concrete solution during its manufacture or before pouring into structures;
• electrical heating, carried out by contact, induction or infrared heaters after laying the mortar;
• the use of special chemical antifreeze agents, with the help of which the effect of lowering the eutectic point of the water present in the mixture is achieved.

These methods, by concreting in winter period can be used individually or combined as needed. The choice of the method used when carrying out work on the construction is influenced by such factors as the massiveness and type of structure, the composition and required strength of concrete, natural conditions at certain times of the year, the equipment of the construction site with one or another type of power equipment, and some others.

So, for example, the thermos method is recommended when working with highly exothermic Portland fast-hardening cements. It is they that have the greatest heat release, providing a high heat content of the created structure. At the same time, the curing of the concrete solution on the basis of the method can be carried out in combination - "thermos with additives", where it occurs due to chemical accelerators, or according to the "hot thermos" method, where serious electrical power is required to heat concrete to high positive temperatures.

In contrast to the thermos method, artificial heating of the concrete mortar involves not only raising the temperature of the laid material to the maximum allowable, but also maintaining it for the time necessary for the concrete to gain a given strength. Usually, the artificial heating method is used when working with structures that have a high level of massiveness, where the specified strength cannot be obtained only when using the thermos method.

Antifreeze chemicals are added to concrete solutions in an amount of 3 to 16%, depending on the desired result and the mass of the mixture, and provide stable hardening of the material at low temperatures. As a rule, the choice of the type of additives depends on the type of construction, the amount of fittings used, the presence of stray currents and aggressive media, as well as the temperature at which the process takes place.

To date, the following agents are used as antifreeze additives:

• sodium nitrite;
• calcium chloride combined with sodium nitrite;
• calcium chloride combined with sodium chloride;
• calcium nitrate-nitrite in combination with urea;
• calcium nitrate in combination with urea;
• calcium nitrite-nitrate in combination with calcium chloride;
• nitrate-nitrite-calcium chloride in combination with urea;
• potash.

In addition, in modern construction in the cold season, the antifreeze additive sodium formate is often used, but its use is limited in prestressed structures with steel reinforcement intended for use in gaseous or aqueous media with an air humidity of more than 60%. It should be noted that the use of this additive is prohibited in the construction of structures with reactive silica or used in industrial plants that consume direct current.

It should be added that it is strictly forbidden to use all chemical additives when concreting reinforced concrete structures of electrified railways and industrial enterprises, where there is a stray electric current.

Warm-up methods

All of the above methods have been successfully applied on extensive and well-equipped construction sites. Some of them require the organization of a rather costly additional equipment or equipment.

In conditions of small construction works for concreting the foundation of a country house, a greenhouse or a paving slab, not all of the proposed methods look appropriate. In this case, winter concreting may be accompanied by such actions as the construction of a temporary shelter at the work site, where the required area will be heated with a heat gun, or the use of PVC film and other warming materials.

Covering the concrete mixture is recommended in cold weather at temperatures from -3 to +3 degrees. PVC film and other heaters allow heat to accumulate inside the concrete structure, which leads to faster solidification and hardening of the mortar.

If the air temperature reaches -5 to -15 degrees, experts recommend using electric or gas heat guns. They are set up as follows:

• on the wooden frame a layer of PVC film is strengthened, creating a reinforcement in the form of a tent;
• heat guns are installed in the tent.

The higher the temperature in the tent, the faster the concrete mixture will set, and, accordingly, the shorter the warm-up time.

As a rule, for concrete to acquire primary strength, which allows further work, it is enough to warm up for 1-3 days.

Guidelines

So, you need to work on laying concrete in your summer cottage. What algorithm of actions should be chosen so that concreting in winter conditions is successful?

The first step is to purchase concrete. In addition, self-production of concrete mix is ​​allowed. To prepare the M200 grade material, you will need:

• 3 parts of M500 cement (it is forbidden to use wet cement or having a solid state);
• 5 parts of sand (both quarry and washed sand are allowed; the use of sand with clay or other additives is strictly prohibited);
• 7 parts of crushed stone (it is recommended to use washed gravel crushed stone with fractions from 5 to 20 mm; the use of lime crushed stone, as well as pebbles and unwashed crushed stone is prohibited);
• water (should make up about 25% of the whole mixture).

To use concrete in the winter, chemical antifreeze elements and plasticizers can be added to it.

If the average daily temperature during the execution of work is not more than -5 degrees, the following steps must be taken:

1. Carefully check all material used for the preparation of the concrete mixture - crushed stone, sand and water - for the absence of snow and ice and in without fail warm them up.
2. Arrange a frame of lumber and cover it with insulating material, creating a tent.
3. Check the tent for cracks through which cold air can enter.
4. If the tent fits all necessary requirements, you can connect a heat gun or a heat generator.
5. should be carried out until it acquires a light white color. The mixture should be warm to the touch, indicating a setting and curing reaction. If the concrete has turned dark gray, this indicates that it has frozen and lost its characteristics. Such a solution must be gouged and the concreting work must be done again.

What to do if the re-concreting process is not possible? In this case, carefully cover the structure with PVC film. This will keep the top layer of concrete intact during frosts and thaws. Perhaps in the spring the concrete will be able to continue the hydration process. Of course, its strength will become as low as possible, but doing this is better than just leaving the structure in the rain and snow.

Concrete is a very popular building material today, for the manufacture of which components such as cement, water, aggregate and water are used. But it's one thing when you pour concrete in the summer, because the warm season favorably affects the process of curing. What happens in winter? In severe frosts, the set of strength characteristics stops, and this is highly undesirable. In this case, it is necessary to apply a number of measures that will allow the concrete to warm up. To do this, you need to know all the features of the concrete flow chart for the winter period and actual ways warming up.

Technological map and methods of heating concrete

Warm up with a welding machine

This heating method involves the use of the following materials:

• pieces of reinforcement;
• incandescent lamps and a thermometer for measuring temperature.

The process of installing pieces of fittings is carried out in parallel with the circuit, with adjacent and straight wires, between which a pouring lamp is mounted. It is thanks to her that it will be possible to make voltage measurements.

Use a thermometer to measure temperatures. In terms of time, this process takes a long time, about 2 months. At the same time, for the entire heating process, it is necessary to protect the structure from the influence of cold and water. It is advisable to use heating with a welding machine with a small volume of concrete and excellent weather conditions.

infrared method

The meaning of this method is that equipment is being installed, the operation of which is performed in the infrared range. As a result, it is possible to convert radiation into heat. Exactly thermal energy embedded in the material.

Infrared heating of the concrete mixture is an electromagnetic oscillation, in which the wave propagation speed will be 2.98 * 108 m / s and a wavelength of 0.76-1, 000 microns. Very often, tubes made of quartz and metal are used as a generator.

The main feature of the presented technology is the possibility of power supply from conventional alternating current. At infrared heating concrete power parameter may vary. It depends on the required heating temperature.

Thanks to the rays, energy can penetrate into deeper layers. To achieve the required efficiency, the heating process must be carried out smoothly and gradually. Here it is forbidden to work at high power rates, otherwise the upper layer will have a high temperature, which will eventually lead to loss of strength. It is necessary to use this method in cases where it is necessary to heat up thin layers of the structure, as well as prepare a solution to speed up the coupling time.

What are the pros and cons of a house made of aerated concrete, indicated in this

Induction method

To implement this method, it is necessary to use alternating current energy, which will be converted into thermal energy in the formwork or reinforcement made of steel.

After the converted thermal energy will be distributed to the material. It is advisable to use the induction heating method when heating reinforced concrete frame structures. It can be crossbars, beams, columns.

If you use induction heating of concrete according to external surfaces formwork, then it is necessary to install successive turns, which are isolated from inductors and wire, and the number and pitch are determined by calculation. Taking into account the results obtained, it is possible to produce templates with grooves.

When the inductor has been installed, it is possible to heat the reinforcing cage or joint. This is done in order to remove frost before concreting takes place. Now the exposed surfaces of the formwork and structure can be covered with heat-insulating material. Only after the arrangement of the wells can you start direct work.

When the mixture reaches the required temperature, the heating procedure is stopped. Make sure that the experimental indicators differ from the calculated ones by at least 5 degrees. The cooling rate can keep its limits of 5-15 C/h.

Application of transformers

To increase the temperature regime in concrete, you can use such an inexpensive and simple method as heating wire PNSV.

The design of this cable includes two elements:

• single-wire conductor of round shape, made of steel;
• insulation, for which PVC plastic or polyethylene can be used.

If you need to heat a mixture of 40-80 m3, then it will be enough to install only one transformer substation. This method is used when the outside air temperature has reached -30 degrees. It is advisable to use transformers for heating monolithic structures. For 1 m of weight, a wire of 60 m will suffice.

Which manufacturers of autoclaved aerated concrete exist are indicated in this

Such a manipulation is performed according to the following instructions:

1. A heating wire is laid inside the concrete. It is connected to the station or transformer terminals.
2. With the help of an electric current, the mass begins to gain temperature, as a result of which it manages to harden.
3. since the material has excellent thermal energy conduction properties, heat begins to move at high speed throughout the entire array.

Table 1 - Characteristics of wires of the PNSV brand

1	AC voltage, V	380
2	Cable section length for voltage 220 V:
	– PNSV1.0 mm, m	80
	– PNSV1.2 mm, m	110
	– PNSV1.4 mm, m	140
3	Specific heat dissipation power of the cable:
	– for reinforced installations, W/r.m.	30-35
	– for non-reinforced installations, W/r.m.	35-40
4	Recommended supply voltage, V	55-100
5	Average core resistance value:
	– PNSV1.2 mm, Ohm/m	0,15
	– PNSV1.4 mm, Ohm/m	0,10
6	Method parameters:
	– Specific power, kW/m3	1,5-2,5
	– Wire consumption, lm/m3	50-60
	– Cycle of thermal curing of structures, days	2-3

The heating wire, which is laid inside the concrete, should heat the structure up to 80 degrees. Electrical heating occurs with the help of transformer substations KPT TO-80. Such an installation is characterized by the presence of several stages of low voltage. Thanks to this, it becomes possible to adjust the power of the heating cables, as well as adjust it according to the changed air temperature.

Cable use

The use of this heating option does not require high costs electricity and accessories.

The whole process proceeds as follows:

1. The cable is being installed on a concrete base before pouring the solution.
2. Fix everything using fasteners.
3. Be careful during cable installation and operation to avoid damage to its surface.
4. Connect the cable to the low voltage electrical cabinet.

Antifreeze additives

With the addition of antifreeze additives, concrete is able to withstand the most aggressive atmospheric precipitation. The components included in such a mixture can be very different, but the role of the main one is assigned to antifreeze. It is a liquid that does not allow water to freeze.

If it is necessary to cock structures made of reinforced concrete, then the mixture should contain sodium nitrite and sodium format. The main feature of antifreeze mixtures is the preservation of anti-corrosion and physico-chemical properties at low temperatures.

When erecting ready-mixed concrete, the production of curbs, it is necessary to use a mixture that contains calcium chloride. This component allows you to achieve a fast hardening speed, resistance to low temperature conditions.

Potash remains the ideal antifreeze additive. It dissolves very quickly in water, and there is no corrosion. If you use potash when heating concrete in winter, you will be able to save on building materials.

If you use antifreeze additives, it is very important to adhere to all safety standards. For example, you should not use concrete with such components when the structure is under tension, monolithic chimneys are being erected.

SNiP

All installation and construction activities must be carried out in accordance with established norms. The concreting process in winter time not considered an exception. Heating of a concrete structure at low air temperatures occurs in accordance with the following documents:

• SNiP 3.03.01-87 - Bearing and enclosing structures
• SNiP 3.06.04-91 - Bridges and pipes

On the video - warming up concrete in winter, technological map:

Despite the fact that the presented documentation only indirectly touches on the topic related to the heating of concrete, it contains certain sections in which there is a technology for pouring concrete mortar in the frosty season.

Timing

When calculating the warming up of concrete, factors such as the type of structure, the total heating area, the volume of concrete and the electrical power must be taken into account.

During heating work with concrete, it is worth developing a technological map. It will contain all the values ​​of laboratory observations, as well as the warm-up time and the hardening time of the material.

The calculation of concrete heating begins with the choice of a scheme. For example, most often choose a four-stage. The first stage involves the curing of the material. After that, the temperature indicators are increased to a specific value, heating and cooling are carried out, the duration of exposure before the start of the event is approximately 1-3 hours at low temperature conditions. After this, you can proceed to the calculation of heating, which is directly dependent on the speed and final temperature.

Throughout the process, it is worth monitoring the temperature, noting all the results with an increase in 30-60 minutes, and when cooling down, control is carried out 1 time per shift. If the mode is violated, it is necessary to maintain all parameters by turning off the current and increasing the voltage. In this case, the actual indicators and those obtained during the calculation may not coincide. After that, a graph of the dependence of time on strength is built, where the required value of time and temperature of heating is indicated, and then the required value of strength is found.

The process of heating concrete is a very important event, without which the concrete structure will simply cease to gain strength during frost, as a result of which this will lead to a decrease in the grade and further destruction. It is not difficult to carry out all these activities, it is enough just to determine which of the presented ones suits you best.

5.1. Materials for heavy and fine-grained concrete

5.1.1. For the preparation of concrete mixtures, cements should be used in accordance with GOST 10178 and GOST 31108, sulfate-resistant cements in accordance with GOST 22266 and other cements according to standards and specifications in accordance with their areas of application for structures of specific types (Appendix M). The use of pozzolanic Portland cement is allowed only if specifically indicated in the project.

Requirements for sampling for cement quality control, rules for acceptance and assessment of the quality level, requirements for transportation and storage should be made in accordance with GOST 30515 and SP 130.13330.

5.1.2. For concrete road and airfield pavements, smoke and ventilation pipes, reinforced concrete sleepers, ventilation and tower cooling towers, supports of high-voltage lines, bridge structures, reinforced concrete pressure and non-pressure pipes, pillars of supports, piles for permafrost soils, Portland cement based on clinker with a normalized mineralogical composition according to GOST 10178, GOST 26633 should be used.

5.1.3. Aggregates for heavy and fine-grained concrete must meet the requirements of GOST 26633, as well as the requirements for specific types of aggregates: GOST 8267, GOST 8736, GOST 5578, GOST 26644, GOST 25592, GOST 25818.

5.1.4. As modifiers of the properties of concrete mixtures, heavy and fine-grained concrete, additives that meet the requirements of GOST 24211 and the Specifications for a specific type of additive should be used.

5.1.5. The water for mixing the concrete mixture and preparing solutions of chemical additives must comply with the requirements of GOST 23732.

5.2. Concrete mixtures

5.2.1. When erecting monolithic and prefabricated-monolithic structures and structures, concrete mixtures are delivered to the construction site in finished form or prepared at the construction site.

5.2.2. Ready-to-use and dry concrete mixtures are prepared, transported and stored in accordance with the requirements of GOST 7473.

The preparation of the concrete mixture at the construction site should be carried out on stationary or mobile concrete mixing plants in accordance with the requirements of GOST 7473 according to a specially developed technological procedure.

5.2.3. The selection of the concrete composition is carried out according to GOST 27006.

5.2.4. Transportation and supply of concrete mixtures should be carried out by specialized means that ensure the preservation of the specified properties of the concrete mixture. Concrete mixture that has lost the specified workability by the time of laying is not subject to supply to the concrete structure. It is forbidden to restore the workability of the concrete mixture by adding water at the place of laying.

5.2.5. Requirements for the composition, preparation and transportation of concrete mixes are given in Table 5.1.

Table 5.1

5.3. Substrate preparation and concrete placement

5.3.1. Before concreting, the rock base, horizontal and inclined concrete surfaces of the foundations must be cleaned of debris, dirt, oils, snow and ice. Existing cracks in the bedrock must be cleared and injected with cement mortar.

To ensure a strong and tight adhesion of the concrete base to the freshly laid concrete, the following is required:

• remove the surface cement film from the entire area of ​​concreting;
• cut down the influx of concrete and areas of the disturbed structure;
• remove formwork shtrab, plugs and other unnecessary embedded parts;
• clean the surface of concrete from litter and dust, and before starting concreting, blow the surface of old concrete with a jet of compressed air.

5.3.2. In reinforced concrete and reinforced structures of individual structures, the condition of the previously installed reinforcement must be checked for compliance with the working drawings before concreting. In this case, in all cases, attention should be paid to the outlets of reinforcement, embedded parts and sealing elements, which must be thoroughly cleaned of rust, scale and traces of concrete.

5.3.3. The formwork, the correctness of its installation, the fixing of the formwork and its supporting parts must be taken in accordance with GOST R 52085, GOST R 52752, SNiP 12-03 and SNiP 12-04. Formwork before concreting should be cleaned of snow, ice, cement film and dirt with a jet of hot air, preferably under a hood.

5.3.4. Concrete mixture should be laid according to the approved project for the production of works (PPR). At the same time, the concrete mixture is placed in a form or formwork in horizontal layers without technological gaps with the direction of laying in one direction in all layers. With significant cross-sectional areas of the concreted structure, it is allowed to lay and compact the concrete mixture in inclined layers, forming a horizontal leading section 1.5–2 m long in each layer. The angle of inclination to the horizon of the surface of the laid layer of the concrete mixture before its compaction should not exceed 30 °. After laying and distributing the concrete mixture over the entire area of ​​the laid layer, compaction begins from the leading section.

5.3.5. The concrete mixture can be supplied by concrete pumps or pneumatic blowers to all types of structures with a concreting rate of at least 6 m3 / h, as well as in cramped conditions and in places not accessible to other means of mechanization.

5.3.6. Before the start of compaction of each laid layer, the concrete mixture should be evenly distributed over the entire cross-sectional area of ​​the concreted structure. The height of individual protrusions above the general level of the surface of the concrete mixture before compaction should not exceed 10 cm. It is forbidden to use vibrators for redistribution and leveling in the laid layer of the concrete mixture fed into the formwork. The concrete mixture in the laid layer should be compacted only after the end of distribution and leveling on the area to be concreted.

5.3.7. Each subsequent layer of concrete mixture must be laid before the concrete setting in the previous laid layer begins. If the break in concreting has exceeded the time of the beginning of concrete setting in the laid layer (concrete has lost its ability to thixotropic liquefaction with the available means of vibration compaction), it is necessary to arrange a working joint. In this case, the concrete in the laid layer must be cured until it acquires a strength not less than that indicated in Table 5.2 (depending on the method of cleaning from the cement film). The term for resuming concrete laying after a break is determined by the laboratory.

Table 5.2

The position of the working seams should, as a rule, be indicated in the PPR.

In the absence of a special instruction in the project, the thickness of the concrete layer laid after the working joint must be at least 25 cm.

5.3.8. When compacting the concrete mixture, it is not allowed to rest the vibrators on the reinforcement and embedded products, strands and other elements of the formwork fastening. The depth of immersion of the deep vibrator in the concrete mixture should ensure its deepening into the previously laid layer by 5 - 10 cm.

The concrete mixture in each laid layer or at each position of the vibrator tip is compacted until the settling stops and the appearance of a cement paste shine on the surface and in places of contact with the formwork.

5.3.9. Vibrating screeds, vibrating bars or platform vibrators can only be used to compact concrete structures; The thickness of each laid and compacted layer of concrete mixture should not exceed 25 cm.

When concreting reinforced concrete structures, surface vibration can be used to compact the top layer of concrete and finish the surface.

5.3.10. The location of the working seams of concreting should be assigned in agreement with the design organization. In this case, the following rules should be followed:

• seams should be straight or stepped;
• the plane of the seam must be perpendicular to the axis of the linear elements (beams, columns, pylons, racks and walls);
• seams in the walls should not have a slope;
• seams in floor slabs (coverings) should be located at a distance from the support of at least 3 slab thicknesses, in foundation slabs - 1.5 - 2 thicknesses, mainly in the zone 1/3 - 1/4 of the span, and also parallel to one of the spans .

5.3.11. Requirements for laying and compacting concrete mixes are given in Table 5.2.

5.3.12. In the process of laying the concrete mixture, it is necessary to constantly monitor the condition of the forms, formwork and supporting scaffolds.

If deformations or displacements of individual formwork elements, scaffolds or fastenings are detected, immediate measures should be taken to eliminate them and, if necessary, work should be suspended in this area.

5.4. Curing and care of concrete

5.4.1. Exposed surfaces of freshly poured concrete immediately after the completion of concreting (including during breaks in laying) should be reliably protected from water evaporation. Freshly laid concrete must also be protected from atmospheric precipitation. Protection of exposed surfaces of concrete must be provided for a period that ensures that concrete acquires a strength of at least 70%, subsequently maintain a temperature and humidity regime with the creation of conditions that ensure an increase in its strength.

5.4.2. Measures for the care of concrete (procedure, timing and control), the procedure and timing for stripping structures should be established by the PPR.

5.4.3. The movement of people on concreted structures and the installation of formwork of overlying structures are allowed after the concrete reaches a strength of at least 2.5 MPa.

5. 5. Testing of concrete upon acceptance of structures

5.5.1. Strength, frost resistance, water resistance, deformability, as well as other concrete quality indicators established by the project, should be determined according to the methods of current regulatory documents.

5.6. Concrete on porous aggregates

5.6.1. Lightweight concrete must meet the requirements of GOST 25820.

5.6.2. Materials for lightweight concrete should be selected in accordance with the recommendations in Annexes M, H and P.

5.6.3. The selection of the composition of lightweight concrete should be carried out in accordance with GOST 27006.

5.6.4. Concrete mixtures, their preparation, supply, laying and care of concrete must meet the requirements of GOST 7473.

5.6.5. The main quality indicators of porous aggregates, lightweight concrete mix and lightweight concrete should be controlled in accordance with Table 5.3.

Table 5.3

5.7. Acid and alkali resistant concretes

5.7.1 Acid-resistant and alkali-resistant concretes must comply with the requirements of GOST 25192. The compositions of acid-resistant concretes and the requirements for materials are given in Table 5.4.

Table 5.4

5.7.2. The preparation of concrete mixtures on liquid glass should be carried out in the following order. The hardening initiator, filler and other powdered components sifted through a N 03 sieve are mixed dry in a closed mixer beforehand. Liquid glass is mixed with modifying additives. First, crushed stone of all fractions and sand are loaded into the mixer, then - a mixture of powdered materials and mixed for 1 minute, then liquid glass is added and mixed for 1 - 2 minutes. In gravity mixers, the mixing time of dry materials is increased to 2 minutes, and after loading all the components - up to 3 minutes. Adding to ready mix liquid glass or water is not allowed. The viability of the concrete mixture is no more than 50 minutes at 20 ° C, with increasing temperature it decreases. Requirements for the mobility of concrete mixtures are given in table 5.5.

Table 5.5

5.7.3. Transportation, laying and compaction of the concrete mixture should be carried out at an air temperature of at least 10 ° C within a period not exceeding its viability. Laying must be carried out continuously. When arranging a working joint, the surface of hardened acid-resistant concrete is notched, dusted and primed with liquid glass.

5.7.4. The moisture content of the surface of concrete or bricks protected by acid-resistant concrete should be no more than 5% by weight, at a depth of up to 10 mm.

5.7.5. The surface of reinforced concrete structures made of concrete on Portland cement before laying acid-resistant concrete on them must be prepared in accordance with the design instructions or treated with a hot solution of magnesium fluorosilicone (3 - 5% solution at a temperature of 60 ° C), or oxalic acid (5 - 10% solution), or primed with polyisocyanate or 50% polyisocyanate solution in acetone.

5.7.6. The concrete mixture on liquid glass should be compacted by vibrating each layer with a thickness of not more than 200 mm for 1 - 2 minutes.

5.7.7. Concrete hardening within 28 days should occur at a temperature not lower than 15 °C. Drying is allowed with the help of air heaters at a temperature of 60 - 80 ° C during the day. Temperature rise rate - no more than 20 - 30 °C/h.

5.7.8. The acid resistance of acid-resistant concrete is ensured by the introduction of polymer additives into the concrete composition: furyl alcohol, furfural, furitol, acetone-formaldehyde resin ACF-3M, tetrafurfuryl ether of orthosilicic acid TFS, a compound of furyl alcohol with phenol-formaldehyde resin FRV-1 or FRV-4 in the amount of 3 - 5% from the mass of liquid glass.

5.7.9. The water resistance of acid-resistant concrete is ensured by introducing into the composition of concrete finely ground additives containing active silica (diatomite, tripoli, aerosil, flint, chalcedony, etc.), 5 - 10% of the mass of liquid glass or polymer additives up to 10 - 12% of the mass of liquid glass: polyisocyanate, carbamide resin KFZh or KFMT, organosilicon hydrophobizing liquid GKZH-10 or GKZH-11, paraffin emulsion.

5.7.10. Protective properties acid-resistant concrete in relation to steel reinforcement is provided by the introduction of corrosion inhibitors into the concrete, 0.1 - 0.3% of the mass of liquid glass: lead oxide, a complex additive of catapine and sulfonic acid, sodium phenylanthranilate.

5.7.11. Demoulding of structures and subsequent processing of concrete is allowed when the concrete reaches 70% of the design strength.

5.7.12. An increase in the chemical resistance of structures made of acid-resistant concrete is provided by double surface treatment with a solution of sulfuric acid of 25 - 40% concentration.

5.7.13. Cements for alkali-resistant concretes in contact with alkali solutions at temperatures up to 50 ° C must meet the requirements of GOST 10178. The use of cements with active mineral additives is not allowed, with the exception of granulated slag. The content of granulated slag should not exceed 20%. The mineral content in Portland cement should not exceed 8%. The use of aluminous binder is prohibited.

5.7.14. Fine aggregate (sand) for alkali-resistant concrete, operated at temperatures up to 30 ° C, should be used in accordance with the requirements of GOST 8267, above 30 ° C - crushed sand from alkali-resistant rocks - limestone, dolomite, magnesite, etc. should be used. Coarse aggregate (crushed stone) for alkali-resistant concrete, operated at temperatures up to 30 ° C, should be used from dense igneous rocks - granite, diabase, basalt, etc.

5.7.15. Crushed stone for alkali-resistant concrete, operated at temperatures above 30 ° C, should be used from dense carbonate sedimentary or metamorphic rocks - limestone, dolomite, magnesite, etc. Water saturation of crushed stone should be no more than 5% by weight.

5.8. Prestressing concretes

5.8.1. Prestressing concretes are designed to compensate for shrinkage deformations, to create pre-stress (self-stress) in structures and structures; increase crack resistance, water resistance up to W 20 (with complete cancellation of waterproofing) and durability of structures.

5.8.3. As binders for prestressing concretes, prestressing cements according to, or Portland cement (without mineral additives) according to GOST 10178 or Portland cement type CEM I according to GOST 31108 with an expanding additive according to.

5.8.4. Prestressing concrete materials should be selected in accordance with Annexes M, H and II.

At negative outside temperatures below (-5 °C), the amount of antifreeze additives is reduced by 10 - 15%, and below a temperature (-5 °C), their use is canceled.

5.8.5. The selection of the composition of stress concrete should be carried out in accordance with GOST 27006, taking into account the requirements.

5.8.6. The manufacture of structures and products with a normalized self-stress value should be carried out with mandatory wet or water (in water, sprinkling, under wet mats, etc.) hardening at normal temperature or with heating after preliminary curing to 7 MPa when removing the formwork.

Requirements for the production of work negative temperatures should be used in accordance with Appendix M.

5.8.7. The main indicators of the quality of the concrete mix and tension concrete should be controlled in accordance with table 5.6.

Table 5.6

5.8.8. Strength, frost resistance, water resistance, deformability, as well as other indicators established by the project, should be determined in accordance with the requirements of current regulatory documents.

5.8.9. The hardening of prestressing concrete of monolithic structures before the start of moistening is carried out with covering the surface with film or roll materials to limit the evaporation of moisture and exclude the ingress of precipitation.

5.8.10. When using self-stressing concrete in structures and structures intended for operation in an aggressive environment, the following should be taken into account: Additional requirements imposed by SP 28.13330 on the protection of building structures from concrete corrosion.

5.8.11. Demoulding of structures and subsequent processing of concrete is allowed when the concrete reaches 70% of the design strength.

5.9. Heat-resistant concrete

5.9.1. Heat-resistant concretes must meet the requirements of GOST 20910 and ensure the manufacture of products, structures and the erection of structures that meet the requirements of standards or specifications, design standards and project documentation on these products, structures and structures.

5.9.2. Concrete mixtures of a dense structure are prepared according to GOST 7473, and a cellular structure - according to GOST 25485.

5.9.3. The choice of materials for the preparation of concrete mixes should be made depending on the classes according to the maximum allowable temperature of use in accordance with GOST 20910.

5.9.4. Acceptance of heat-resistant concrete in structures in terms of strength at design age and strength at an intermediate age is carried out in accordance with GOST 18105, and in terms of average density - in accordance with GOST 27005.

5.9.5. If necessary, the assessment of heat-resistant concrete in terms of the maximum allowable temperature of use, heat resistance, residual strength, water resistance, frost resistance, shrinkage and other quality indicators established by the project is carried out in accordance with the requirements of standards and specifications for heat-resistant concrete of structures of a particular type.

5.10. Concrete especially heavy and for radiation protection

5.10.1. Works with the use of especially heavy concretes and concretes for radiation protection should be carried out according to the usual technology. In cases where conventional ways concreting is not applicable due to the stratification of the mixture, the complex configuration of the structure, saturation with reinforcement, embedded parts and communication penetrations, the method of separate concreting should be used (method of ascending mortar or method of embedding large aggregates into the mortar). The choice of concreting method should be determined by the WEP.

5.10.2. The materials used for radiation protection concretes must comply with the requirements of the project.

5.10.3. Requirements for particle size distribution, physical and mechanical characteristics of mineral, ore and metal aggregates must comply with the requirements for aggregates for heavy concrete in accordance with GOST 26633. Metal aggregates must be degreased before use. Non-peeling rust is allowed on metal aggregates.

5.10.4. Passports for materials used for the manufacture of radiation protection concretes must contain data on a complete chemical analysis of these materials.

5.10.5. Works with the use of concrete on metal aggregates are allowed only at positive ambient temperatures.

5.10.6. When laying concrete mixtures, it is prohibited to use belt and vibration conveyors, vibrating bunkers, vibroshoes, dropping of a particularly heavy concrete mixture is allowed from a height of not more than 1 m.

5.11. Production of concrete works at negative temperatures

5.11.1. When the average daily outdoor temperature is below 5 °C and the minimum daily temperature is below 0 °C, it is necessary to take special measures to keep the laid concrete (mortar) in structures and structures concreted in the open air.

5.11.2. The preparation of the concrete mixture at the construction site should be carried out in heated concrete mixing plants, using heated water, thawed or heated aggregates, which ensure that the concrete mixture is obtained with a temperature not lower than that required by the calculation. It is allowed to use unheated dry aggregates that do not contain frost on grains and frozen clods. At the same time, the duration of mixing the concrete mixture should be increased by at least 25% compared to summer conditions.

5.11.3. Methods and means of transportation should ensure that the temperature of the concrete mixture does not drop below the required one by calculation.

5.11.4. The condition of the base on which the concrete mixture is laid, as well as the temperature of the base and the laying method, must exclude the possibility of freezing of the concrete mixture in the zone of contact with the base. When keeping concrete in a structure by the thermos method, when preheating the concrete mixture, as well as when using concrete with antifreeze additives it is allowed to lay the mixture on an unheated, non-porous base or old concrete, if, according to the calculation, it does not freeze in the contact zone during the estimated period of concrete curing. At air temperatures below minus 10 °C, concreting of densely reinforced structures with reinforcement with a diameter of more than 24 mm, reinforcement from rigid rolled profiles or with large metal embedded parts should be carried out with preliminary heating of the metal to a positive temperature or local vibration of the mixture in the reinforcement and formwork areas, with the exception of cases of laying preheated concrete mixtures (at a mixture temperature above 45 °C). The duration of vibrating the concrete mixture should be increased by at least 25% compared to summer conditions.

5.11.5. When concreting elements of frame and frame structures in structures with rigid coupling of nodes (supports), the need for gaps in spans, depending on the heat treatment temperature, taking into account the resulting thermal stresses, should be agreed with the design organization. Unformed surfaces of structures should be covered with vapor and heat insulating materials immediately after concreting.

Reinforcement outlets of concreted structures must be covered or insulated to a height (length) of at least 0.5 m.

5.11.6. Before laying the concrete mixture, the cavities after the installation of reinforcement and formwork must be covered with a tarpaulin or some other material from snow, rain and foreign objects. If the cavities are not closed and frost has formed on the reinforcement and formwork, it should be removed before laying the concrete mixture by blowing with hot air. It is not allowed to use steam for this purpose.

ConsultantPlus: note. In the official text of the document, apparently, a typo was made: table A.14.1 is meant, and not P.R.1.

5.11.7. Temperature and humidity curing of concrete in winter conditions is carried out (Table P.R.1)

• thermos way;
• with the use of antifreeze additives;
• with electrothermal treatment of concrete;
• with heating of concrete with hot air, in greenhouses.

The method of curing concrete is carried out according to specially developed technological maps, which should include:

• method and temperature-humidity conditions of curing concrete;
• data on the formwork material, taking into account the required thermal insulation indicators;
• data on the vapor barrier and thermal insulation cover of open surfaces;
• the layout of the points at which the temperature of the concrete should be measured and the name of the instruments for measuring them;
• expected values ​​of concrete strength;
• terms and procedure for demoulding and loading structures.

In the case of using electrothermal treatment of concrete, the technological maps additionally indicate:

• schemes for placement and connection of electrodes or electric heaters;
• the required electrical power, voltage, current strength;
• type of step-down transformer, section and length of wires.

The choice of a method for the production of concrete and reinforced concrete works in winter conditions should be made taking into account the recommendations given in Appendix R.

5.11.8. The thermos method should be used while ensuring the initial temperature of the laid concrete in the range from 5 to 10 ° C and then maintaining the average temperature of the concrete in this range for 5 to 7 days.

5.11.9. Contact heating of laid concrete in thermoactive formwork should be used when concreting structures with a surface modulus of 6 or more.

After compaction, the exposed surfaces of concrete and adjacent areas of thermoset formwork panels must be reliably protected from moisture and heat loss by concrete.

5.11.10. Electrode heating of concrete must be carried out in accordance with technological maps.

It is forbidden to use reinforcement of a concreted structure as electrodes.

Electrode heating should be carried out before the concrete acquires no more than 50% of the design strength. If the required strength of concrete exceeds this value, then further curing of concrete should be provided by the thermos method.

To protect concrete from drying during electrode heating and to increase the uniformity of the temperature field in concrete with a minimum power consumption, reliable thermal and moisture insulation of the concrete surface must be provided.

5.11.11. The use of concrete with antifreeze additives is prohibited in structures: prestressed reinforced concrete; reinforced concrete, located in the area of ​​stray currents or located closer than 100 m from high voltage direct current sources; reinforced concrete, designed for operation in an aggressive environment; in parts of structures located in the zone of variable water level.

5.11.12. The type and amount of antifreeze additive is prescribed depending on the ambient temperature. For medium-sized structures (with surface modulus from 3 to 6), the design temperature is taken as the average value of the outside air temperature according to the forecast for the first 20 days. from the time of concrete placement. For massive structures (with a surface modulus of less than 3), the calculated value is also average temperature outside air for the first 20 days. curing with a temperature increase of 5 °C.

For structures with a surface modulus of more than 6, the minimum average daily temperature of the outside air according to the forecast for the first 20 days is taken as the calculated one. concrete hardening.

5.11.13. At negative ambient temperatures, the structures should be covered with hydrothermal insulation or heated. The thickness of the thermal insulation is assigned taking into account the lowest ambient temperature. When heating concrete with an antifreeze additive, the possibility of local heating of the surface layers of concrete above 25 °C should be excluded.

To protect against moisture freezing, the exposed surfaces of freshly placed concrete, together with the adjoining formwork surfaces, must be securely covered.

5.11.14. When monolithic structures with curing concrete with antifreeze additives, the surface layers of concrete of monolithic structures may not be heated, but it is necessary to remove ice, snow and debris from the surfaces of concrete, reinforcement and embedded parts. Do not wash these surfaces with saline solutions.

5.11.15. The exposed surfaces of the laid concrete at the monolithic joints must be reliably protected from moisture freezing. Visible cracks in concrete need to be expanded only at a stable positive air temperature.

5.11.16. Requirements for the performance of work at negative air temperatures are set in Table 5.7.

Table 5.7

5.11.17. Concrete is allowed to be frozen at the critical strength given in Table 5.7. Further curing must be ensured at a positive temperature and humidity of at least 75%.

5.11.18. When the average daily outdoor temperature is below 5 °C, a concrete temperature control log should be kept. Temperature measurement is carried out in the most and least heated parts of the structure, the number of temperature measurement points is determined at the rate of one point per 3 m3 of concrete, 6 m of structure length, 4 m2 of ceiling, 10 m2 of preparation of floors or bottoms.

Frequency of temperature measurements:

a) when concreting according to the thermos method (including concretes with antifreeze additives) - twice a day until the end of curing;
b) when warming up - in the first eight hours after two hours, in the next sixteen hours after four hours, and the rest of the time at least three times a day;
c) during electrical heating - in the first three hours - every hour, and the rest of the time after two to three hours.

In the journal, the responsible persons for warming up the concrete fill in the columns for the delivery and acceptance of the shift. The concrete heating method is established in the PPR and is indicated for each structural element.

5.12. Concrete work at air temperatures above 25 °C

5.12.1. When performing concrete work at an air temperature above 25 ° C and a relative humidity of less than 50%, it is recommended to use fast-hardening cements in accordance with GOST 10178 and GOST 31108. Normally hardening cements are allowed for class B22.5 and higher.

It is not allowed to use pozzolanic Portland cement and aluminous cement for concreting above-ground structures, except as provided by the project. Cements should not have a false setting, have a temperature above 50 °C.

5.12.2. The temperature of the concrete mixture when concreting structures with a surface modulus of more than 3 should not exceed 30 - 35 °C, and for massive structures with a surface modulus of less than 3 - 20 °C.

5.12.3. Care of freshly laid concrete should be started immediately after the concrete mix has been laid and carried out until, as a rule, 70% of the design strength is reached, and with appropriate justification - 50%.

Freshly poured concrete must be protected from dehydration by film-forming coatings during the initial curing period.

When the concrete reaches a strength of 1.5 MPa, the subsequent care of it should be to ensure the wet state of the surface by installing a moisture-absorbing coating and moistening it, keeping the exposed concrete surfaces under a layer of water, and continuously spraying moisture over the surface of the structures. At the same time, periodic watering of open surfaces of hardening concrete and reinforced concrete structures with water is not allowed.

5.12.4. To intensify the hardening of concrete, solar radiation should be used by covering the structures with a rolled or sheet translucent moisture-proof material and coating them with film-forming compounds.

5.12.5. In order to avoid the possible occurrence of a thermally stressed state in monolithic structures under direct action sun rays freshly laid concrete should be protected with self-destructive polymer foams, inventory thermal and moisture-proof or film-forming coatings, polymer film with a reflection coefficient of more than 50% or any other moisture-proof material.

5.13. Special concreting methods

5.13.1. Based on the specific engineering-geological and production conditions, in accordance with the project, the following special concreting methods are allowed:

• vertically movable pipe (VPT);
• ascending solution (VR);
• injection;
• vibro-injection;
• laying the concrete mixture with bunkers;
• ramming the concrete mixture;
• pressure concreting;
• rolling of concrete mixtures;
• cementing by drilling mixing method.

5.13.2. The VPT method should be used in the construction of buried structures with a depth of 1.5 m or more; at the same time, concrete of a design class of at least B25 is used.

5.13.3. Concreting by the VR method with pouring a large stone riprap with a cement-sand mortar should be used when laying concrete under water at a depth of up to 20 m to obtain concrete strength corresponding to the strength of rubble masonry.

The VR method with pouring a crushed stone outline with a cement-sand mortar can be used at depths of up to 20 m for the construction of structures made of concrete of class up to B25.

With a concreting depth of 20 to 50 m, as well as during repair work to strengthen structures and restoration construction, pouring crushed stone aggregate with cement mortar without sand should be used.

5.13.4. Injection and vibro-injection methods should be used for concreting underground structures, predominantly thin-walled, of class B25 concrete on aggregate with a maximum size of 20 mm.

5.13.5. The method of laying the concrete mixture with bunkers can be used when concreting structures made of class B20 concrete at a depth of more than 20 m.

5.13.6. Concreting by ramming the concrete mixture should be used at a depth of less than 1.5 m for structures of large areas, concreted to a mark located above the water level, with a concrete class up to B25.

5.13.7. Pressure concreting by continuous injection of a concrete mixture at excessive pressure should be used in the construction of underground structures in flooded soils and difficult hydrogeological conditions, in the construction of underwater structures at a depth of more than 10 m and in the construction of critical heavily reinforced structures, as well as with increased requirements for the quality of concrete.

5.13.8. Concreting by rolling a low-cement rigid concrete mixture should be used for the construction of flat extended structures made of concrete of class up to B20. The thickness of the rolled layer should be taken within 20 - 50 cm.

5.13.9. For the installation of cement-soil structures of the zero cycle, it is allowed to use the drilling mixing technology of concreting by mixing the estimated amount of cement, soil and water in the well using drilling equipment.

5.13.10. When underwater (including under clay mortar) concreting, it is necessary to provide:

• isolation of the concrete mixture from water during its transportation under water and laying in a concrete structure;
• the density of the formwork (or other fence);
• continuity of concreting within the element (block, grip);
• control over the condition of the formwork (fencing) in the process of laying the concrete mixture (if necessary, by divers or with the help of underwater television installations).

5.13.11. The timing of stripping and loading of underwater concrete and reinforced concrete structures should be established based on the results of testing control samples hardened under conditions similar to the conditions for hardening concrete in the structure.

5.13.12. Concreting by the VPT method after an emergency break is allowed to be resumed only if: -

• achievement by concrete in the shell of a strength of 2.0 - 2.5 MPa;
• removal of sludge and weak concrete from the surface of underwater concrete;
• ensuring reliable connection of newly laid concrete with hardened concrete (straps, anchors, etc.).

When concreting under clay mortar, breaks lasting longer than the setting time of the concrete mixture are not allowed. If the specified limit is exceeded, the structure should be considered defective and not subject to repair using the VPT method.

5.13.13. When supplying the concrete mixture under water by hoppers, it is not allowed to freely dump the mixture through a layer of water, as well as leveling the laid concrete by horizontal movement of the hopper.

5.13.14. When concreting by ramming the concrete mixture from the island, it is necessary to ram the newly arriving portions of the concrete mixture no closer than 200 - 300 mm from the water's edge, preventing the mixture from flowing over the slope into the water.

The above-water surface of the laid concrete mixture for the time of setting and hardening must be protected from erosion and mechanical damage.

5.13.15. When constructing structures of the "wall in the ground" type, concreting of trenches should be carried out in sections no longer than 6 m using inventory intersection dividers.

If there is a clay solution in the trench, the concreting of the section is carried out no later than 6 hours after pouring the solution into the trench; otherwise, the slurry should be replaced with the simultaneous production of sludge that has settled to the bottom of the trench.

The reinforcing cage before immersion in the clay solution should be moistened with water. The duration of immersion from the moment the reinforcing cage is lowered into the clay solution until the start of concreting the section should not exceed 4 hours.

The distance from the concrete pipe to the intersection separator should be taken no more than 1.5 m with a wall thickness of up to 40 cm and no more than 3 m with a wall thickness of more than 40 cm.

5.13.16. Requirements for concrete mixtures when they are laid by special methods are given in Table 5.8.

Table 5.8

5.14. Cutting expansion joints, technological grooves, openings, holes and surface treatment of monolithic structures

5.14.1. The arrangement of openings, holes, technological furrows and the choice of the method of work must be agreed with the author of the project (design organization) and take into account the possible impact on the strength of the structure being cut, the requirements of sanitary and environmental standards.

ConsultantPlus: note. In the official text of the document, apparently, a typo was made: Appendix C is meant, not 15.

5.14.2. Tool for machining should be chosen depending on the physical mechanical properties processed concrete and reinforced concrete, taking into account the requirements for the quality of processing by the current GOST for diamond tools, and Appendix 15.

5.14.3. Cooling of the tool should be provided with water under pressure of 0.15 - 0.2 MPa, to reduce the energy intensity of processing - with solutions of surfactants with a concentration of 0.01 - 1%.

5.14.3. Requirements for the modes of mechanical processing of concrete and reinforced concrete are given in Table 5.9.

Table 5.9

5.15. Seam cementation. Shotcrete and sprayed concrete works

5.15.1. For cementation of shrinkage, temperature, expansion and structural joints, cement should be used not lower than grade (class) M 400 (CEM I 32.5). When grouting joints with an opening of less than 0.5 mm, cement slurries plasticized with additives according to GOST 24211 are used. Prior to cementation work, the joint is flushed and hydraulically tested to determine its throughput and tightness of the card (joint).

5.15.2. The surface temperature of the joint during cementation of the concrete mass must be positive. For grouting joints at negative temperatures, solutions with antifreeze additives should be used. Cementation should be carried out before the water level rises in front of the hydraulic structure after the main part of the temperature-shrinkage deformations is attenuated.

5.15.3. The quality of cementation of the joints is checked: by examining the concrete by drilling control holes and hydraulic testing them and cores taken from the intersections of the joints; measurement of water filtration through the seams; ultrasonic testing.

5.15.4. Aggregates for shotcrete and sprayed concrete devices must meet the requirements of GOST 8267.

The size of the aggregates should not exceed half the thickness of each shotcrete layer and half the mesh size of the reinforcing meshes.

5.15.5. The surface to be shotcrete must be cleaned, blown with compressed air and flushed with a high-pressure water jet. It is not allowed to sag in height more than 1/2 of the thickness of the shotcrete layer. The fittings to be installed must be cleaned and secured against displacement and vibrations.

5.16. Reinforcing works

5.16.1. The main work with reinforcement during the erection of monolithic reinforced concrete structures, the arrangement of structures of their interfaces is cutting, straightening, bending, welding, knitting, performing non-welding joints with pressed or threaded couplings and other processes, the requirements for which are given in the current regulatory and technical documentation.

5.16.2. Reinforcing steel (bar, wire) and rolled sections, reinforcing products and embedded elements must comply with the project and the requirements of the relevant standards. Fittings supplied for use must be subjected to input control, including tensile and bending tests of at least two samples from each batch. For reinforcing bars supplied with indication in the quality document of statistical indicators of mechanical properties, it is allowed not to test specimens for tension, bending or bending with straightening. The division of spatial large-sized reinforcing products, as well as the replacement of the reinforcing steel provided for by the project, must be agreed with the design organization.

5.16.3. Transportation and storage of reinforcing steel should be carried out in accordance with GOST 7566.

5.16.4. Duration of storage of high-strength wire reinforcement, reinforcing and steel ropes in enclosed spaces or special containers - no more than one year. Permissible relative air humidity is not more than 65%.

5.16.5. Control tests of high-strength reinforcing wire should be carried out after straightening.

5.16.6. Procurement of bars to measure length from bar and wire reinforcement and the manufacture of non-stressed reinforcing products should be carried out in accordance with the requirements of SP 130.13330, and the manufacture of load-bearing reinforcing cages from bars with a diameter of more than 32 mm - in accordance with Section 10.

5.16.7. The manufacture of spatial large-sized reinforcing products should be carried out in assembly jigs.

5.16.8. Reinforcing and embedded products are manufactured and controlled in accordance with GOST 10922.

5.16.9. Preparation (cutting, formation of anchor devices), installation, tension of prestressing reinforcement in construction conditions must be carried out according to the project and in accordance with the requirements of SP 130.13330. Tensioned reinforcement must be injected, concreted or covered with anti-corrosion compounds provided for by the project, within a timeframe that excludes its corrosion.

5.16.10. During the installation of prestressed reinforcement, it is forbidden to weld (tack) distribution reinforcement, clamps and embedded parts to it, as well as to hang the formwork, equipment, etc. Directly before installing the prestressing reinforcing elements, the channels must be cleaned of water and dirt by blowing with compressed air. Reinforcement tensioned on concrete should be installed immediately before tensioning within a period that excludes the possibility of its corrosion. When pulling reinforcement through channels, care must be taken to prevent damage to it.

5.16.11. Electric arc cutting of high-strength reinforcing wire, ropes and prestressed rod reinforcement, gas cutting of ropes on a drum, as well as welding in the immediate vicinity of prestressed reinforcement without protecting it from exposure to high temperatures and sparks, including prestressing reinforcement in the circuit of electric welding machines or grounding of electrical installations is prohibited. .

5.16.12. Installation of reinforcing structures should be carried out mainly from large-sized blocks or unified prefabricated meshes, ensuring that the protective layer is fixed in accordance with Table 5.10.

Table 5.10

5.16.13. Installation of pedestrian, transport or mounting devices on reinforcing structures should be carried out in accordance with the PPR, in agreement with the design organization.

5.16.14. Non-welding connections of rods should be made:

• butt - overlap or crimp sleeves and screw couplings to ensure equal strength of the joint;
• cruciform - viscous annealed wire. It is allowed to use special connecting elements (plastic and wire clamps).

5.16.15. Welded joints shall be made in accordance with the requirements of section 10.3 of these standards.

5.16.16. Reinforcement of structures should be carried out in accordance with the design documentation, taking into account the allowable deviations in Table 5.10.

5.16.17. During the operational control, each reinforcing element is checked, during the acceptance control, a random check is performed. If unacceptable deviations are detected during selective acceptance control, continuous control is assigned. When deviations from the project are identified, measures are taken to eliminate or coordinate with the design organization their admissibility.

5.16.18. When monitoring the condition of reinforcing products, embedded products, as well as welded joints, each product is visually checked for the absence of rust, frost, ice, concrete contamination, scale, traces of oil, flaking rust and continuous surface corrosion.

5.16.19. During acceptance control of deviations in the distances between reinforcing bars, rows of reinforcement, as well as the reinforcement spacing, measurements are taken at least in five sections with a step of 0.5 to 2.0 m for every 10 m3 of the concreted structure.

5.16.20. During the acceptance control of the compliance of the joints of the reinforcement bars with the design and technological documentation, at least five joints are checked in increments of 0.5 to 2.0 m for every 10 m3 of the structure.

5.16.21. During acceptance control, the deviations of the thickness of the protective layer of concrete from the design one are checked in each structure, performing measurements at least in five sections for every 50 m2 of the construction area or in a section of a smaller area in increments of 0.5 to 3.0 m.

5.16.22. Acceptance control of welded reinforcement joints must be carried out by an accredited testing laboratory in accordance with the requirements of the project, GOST 10922, GOST 14098 and section 10.4 of these standards.

5.16.23. Mechanical connections of fittings (couplings, threaded connections) are controlled according to specially developed regulations.

5.16.24. According to the results of acceptance control, certificates of examination of hidden works are drawn up. Reinforcement acceptance prior to receiving the results of the quality assessment of welded or mechanical joints is not allowed.

5.17. Formwork

5.17.1. The formwork must comply with the requirements of GOST R 52085 and ensure the design shape, geometric dimensions and surface quality of the erected structures within the established tolerances.

5.17.2. When choosing the type of formwork used in the construction of concrete and reinforced concrete structures, the following should be considered: -

• accuracy of manufacturing and installation of formwork;
• the quality of the concrete surface and monolithic structure after stripping;
• formwork turnover.

5.17.3. Loads and data for formwork calculation are given in Appendix T.

5.17.4. Installation and acceptance of formwork, stripping of monolithic structures, cleaning and lubrication is carried out in accordance with SP 48.13330 and PPR.

5.17.5. The formwork prepared for concreting should be taken in accordance with GOST R 52752 and the act.

5.17.6. The surface of the formwork in contact with the concrete must be coated with a lubricant before placing the concrete mixture. The lubricant should be applied in a thin layer to a thoroughly cleaned surface.

The surface of the formwork after applying the lubricant must be protected from dirt, rain and sunlight. It is not allowed to get grease on fittings and embedded parts. It is allowed to use emulsol in its pure form or with the addition of lime water to lubricate wooden formwork.

For metal and plywood formwork, it is allowed to use emulsols with the addition of white spirit or surfactants, as well as other lubricant compositions that do not adversely affect the properties of concrete and the appearance of structures and reduce the adhesion of the formwork to concrete.

Lubrication from used machine oils of random composition is not allowed.

5.17.7. Formwork and reinforcement of massive structures before concreting must be cleaned with compressed (including hot) air from snow and ice. Cleaning and heating of fittings with steam or hot water is not allowed.

All exposed surfaces of freshly laid concrete after concreting and during breaks in concreting must be carefully covered and insulated.

5.17.8. The technical requirements that should be met when concreting monolithic structures and checked during operational control, including the allowable strength of concrete during stripping, are given in Table 5.11.

Table 5.11

5.17.9. When installing intermediate supports in the span of the ceiling with partial or sequential removal of formwork, the minimum strength of concrete during stripping can be reduced. In this case, the strength of the concrete, the free span of the ceiling, the number, place and method of installing the supports are determined by the PPR and agreed with the design organization. Removal of all types of formwork should be carried out after preliminary detachment from concrete.

5.18. Acceptance of concrete and reinforced concrete structures or parts of structures

5.18.1. When accepting finished concrete and reinforced concrete structures or parts of structures, the following should be checked:

• compliance of structures with working drawings;
• the quality of concrete in terms of strength, and, if necessary, frost resistance, water resistance and other indicators specified in the project;
• the quality of materials, semi-finished products and products used in the construction;
• quality of working seams of concreting.

5.18.2. Acceptance of finished concrete and reinforced concrete structures or parts of structures should be formalized in the prescribed manner by an act of inspection of hidden works or an act of acceptance of critical structures.

5.18.3. The requirements for finished concrete and reinforced concrete structures or parts of structures are given in Table 5.12.

Table 5.12

5.18.4. During the acceptance control of the appearance and quality of the surfaces of structures (presence of cracks, concrete chips, shells, exposure of reinforcing bars and other defects), each structure is visually checked. Requirements for the quality of the surface of monolithic structures are given in Appendix C. Special requirements for the quality of the surface of monolithic structures should be presented in the design documentation. Requirements for the surface quality of prefabricated structures are established in accordance with GOST 13015.

6. Installation of prefabricated reinforced concrete and concrete structures

6.1. General instructions

6.1.1. Preliminary storage of structures in on-site warehouses is allowed only with appropriate justification. The on-site warehouse should be located in the area of ​​the assembly crane.

6.1.2. Installation of the structures of each overlying floor (tier) of a multi-storey building should be carried out after the design fixing of all installation elements and the concrete (mortar) reaching the strength of monolithic joints load-bearing structures specified in the PPR.

6.1.3. In cases where the strength and stability of structures during the assembly process are provided by welding field connections, it is allowed, with the appropriate indication in the project, to mount structures of several floors (tiers) of buildings without monolithic joints. At the same time, the project should provide the necessary instructions on the order of installation of structures, welding of joints and monolithic joints.

6.1.4. In cases where permanent connections do not ensure the stability of structures during their assembly, it is necessary to use temporary mounting connections. The design and number of connections, as well as the procedure for their installation and removal, should be indicated in the PPR.

6.1.5. The mark of the mortar mixture according to mobility at the place of use for making a bed when installing walls made of large concrete and reinforced concrete blocks and panels, jointing horizontal and vertical joints in walls made of panels and blocks should be Pk2 (4 - 8 cm) according to GOST 28013.

6.1.6. It is not allowed to use a mortar whose setting process has already begun, as well as to restore its plasticity by adding water.

6.1.7. Limit deviations from the alignment of landmarks during the installation of prefabricated elements, as well as deviations of the finished mounting structures from the design position, should not exceed the values ​​\u200b\u200bgiven in Table 6.1.

Table 6.1

6.2. Construction of bases and foundations

Works on the arrangement of bases and foundations should be carried out in accordance with the requirements of SP 22.13330, SP 24.13330, SP 25.13330, the instructions of this section and the project.

6.2.1. Pile and shell pile driving

6.2.1.1. The piles should be driven with a hammer to the design embedment depth until the calculated failure is obtained, but less than 0.2 cm from the impact, and the shell piles should be deepened with a vibratory driver with an immersion rate of at least 5 cm/min at the last stage. If these requirements cannot be met, it is necessary to use flushing or installation of piles in leader wells with finishing up to design failure, and for shells, use advance excavation below the knife or a more powerful loader.

Advanced development of sandy soils should be carried out 1–2 m below the shell knife, provided that there is excess water pressure in its cavity, which exceeds the level of surface or groundwater by 4–5 m.

6.2.1.2. The depth of the leader wells should be taken equal to 0.9 of the pile penetration into the ground, and the diameter - 0.9 of the diameter of a cylindrical or 0.8 of the diagonal of a prismatic pile, and be specified based on the results of test driving.

6.2.1.3. Pile elements should be immersed in the thickness of frozen soils in leader holes.

Direct pile driving is allowed in plastic-frozen clay or loamy soils that do not have solid inclusions.

The practical possibility of driving piles with an existing hammer and the depth of their immersion in permafrost soil must be established based on the results of test driving in specific local conditions.

Pile immersion in pre-thawed soil is allowed if it is necessary to deepen their bottom into non-frozen soil through a layer of seasonal freezing, as well as into the thickness of hard-frozen sand.

6.2.1.4. Shell piles in the zone of positive soil and water temperatures (along their entire height or only in the lower part) should be filled with concrete after acceptance of work on their immersion, extraction from the soil cavity, stripping, acceptance of foundations (including a widened cavity) and installation , if necessary, a reinforcing cage.

After a forced break, the laying of the concrete mixture can be resumed if the duration of the break did not lead to a loss of mobility of the laid mixture. Otherwise, the work may be continued after the implementation of measures to ensure a high-quality connection of the laid mixture with the previously laid one.

6.2.1.5. Works on filling the cavity of reinforced concrete pile elements with a concrete mixture within the zone of influence of alternating ambient temperatures (water, air, soil) with a margin down to the diameter of the element, but not less than 1 m, should be carried out in compliance with the special requirements specified in the project and PPR ( regarding the selection of the composition of the mixture, its laying, cleaning the inner side surface, etc.), aimed at preventing the appearance of cracks in the concrete of the elements.

6.2.1.6. Operational and acceptance control of the quality of driving piles and shell piles into different soils should be carried out in accordance with the technical requirements given in Table 6.2.

Table 6.2

6.2.2. The device of bored piles

6.2.2.1. Excessive water pressure or clay solution may be used to fix the surface of wells developed no closer than 40 m from existing buildings and structures.

6.2.2.2. In wells that are not cased with inventory pipes or casings and are developed with a grab (especially if there is water in the wells), it is necessary to clean them side surfaces up to the design diameter with a cylindrical device (calibrator).

6.2.2.3. In order to prevent lifting and displacement of the reinforcing cage in the borehole by the laid concrete mixture or in the process of extracting the concrete casting inventory casing pipe, as well as in all cases of reinforcement not to the full depth of the bored pile, it is necessary to provide clamps in the frame structure to fix it in the design position.

6.2.2.4. Dry wells in sands, cased steel pipes or reinforced concrete shells, as well as open wells drilled in layers of loams and clays located above the groundwater level and not having interlayers and lenses of sands and sandy loams, it is allowed to concrete without the use of concrete pipes by free dropping of the concrete mix from a height of up to 6 m. concrete mixture by the method of free dropping from a height of up to 20 m, provided that positive results are obtained during the experimental verification of this method using a mixture with a specially selected composition and mobility.

In wells filled with water, the concrete mixture should be laid using the vertically displaced pipe (VPT) method.

6.2.2.5. Operational and acceptance quality control of the installation of bored piles should be carried out in accordance with the technical requirements specified in Table 6.3.

Table 6.3

6.2.3. Construction and lowering of wells

6.2.3.1. For an informed choice in specific local conditions, the best solution should be examined technical capability and the economic feasibility of implementing (by available means) different methods of manufacturing wells: at the site of foundation construction (on a previously prepared site, on the surface of a backfilled island, on stationary scaffolds) and away from the site of foundation construction (on a special site, on floating or stationary scaffolds) , as well as methods of immersing wells into the ground: under the influence of their own weight (with additional surcharge using ballast, jacks and without them; using washing; using a thixotropic jacket, etc.) and using vibratory pile drivers.

6.2.3.2. For the period of lowering the wells to the design level, it is necessary to take measures to prevent the possibility of distortions of the wells (use guide devices, uniform excavation of soil over the area of ​​the face, uniform surcharge of the well in case of using ballast or hydraulic jacks etc.) or rubbing them with soil (use a thixotropic jacket, hydraulic or hydropneumatic washing, surcharges, etc.).

6.2.3.3. To prevent the possibility of an influx of sandy or gravel-sandy soils into the cavity of a lowered well, it is necessary that its knife be constantly buried in the ground by 0.5 - 1 m, and the water level in the well should not fall below the water level outside it. If, when the wells hang or if it is necessary to remove boulders from under their knife, it is necessary to select the soil below the knife, then this can only be done if there is a constant overpressure of water in the cavity of the well by topping it up to a level that rises 4-5 m above the water surface around the well.

6.2.3.4. Acceptance quality control of the manufacture and lowering of wells should be carried out in accordance with the technical requirements given in table 6.4.

Table 6.4

6.2.4. Construction of shallow foundations

6.2.4.1. A break between the end of the excavation and the construction of the foundation, as a rule, is not allowed. In case of forced breaks, measures must be taken to preserve the natural properties of the base soil. The bottom of the pit to the design marks (by 5 - 10 cm) must be cleaned immediately before the foundation is laid.

6.2.4.2. Prior to the installation of foundations, work must be carried out to drain surface and groundwater from the pit. The method of removing water from the pit (open drainage or drainage, dewatering, etc.) must be selected taking into account local conditions and agreed with the design organization. At the same time, measures should be taken to prevent the removal of soil from under the erected and existing structures, as well as to prevent the violation of the natural properties of soil foundations.

6.2.4.3. Prior to the commencement of work on the installation of foundations, the prepared foundation must be accepted by an act by a commission with the participation of the customer and a representative of the construction organization, and, if necessary, a representative of the design organization and a geologist.

The commission must establish the compliance of the foundation with the project: the location, dimensions, elevation of the bottom of the pit, the actual stratification and properties of the soil, as well as the possibility of laying the foundation at the design or modified elevation.

Checks to establish the absence of violations of the natural properties of the base soils should, if necessary, be accompanied by sampling for laboratory tests, sounding or stamping tests of the base.

If the commission establishes significant discrepancies between the actual and design characteristics of the foundation soils and, as a result, the need to revise the project arises, the decision to carry out further work should be made with the mandatory participation of representatives of the design organization and the customer.

6.2.4.4. Blocks of prefabricated foundations should be laid on a carefully leveled sandy base or a sand-cement pad with a thickness of at least 5 cm (on clay base soils).

Random selections of soil in certain places must be filled with the same soil, brought to natural density.

6.2.4.5. Acceptance quality control of work should be carried out in accordance with the technical requirements specified in Table 6.5.

Table 6.5

During the construction of foundations, it is necessary to control:

• ensuring the necessary shortfalls of soil in the pit, preventing overshoots and violations of the structure of the base soil;
• prevention of violations of the soil structure during cutting shortfalls, preparation of foundations and laying foundation blocks;
• protection of soils in the pit from underflooding by underground or surface waters with softening and erosion of the upper layers of the base;
• compliance with the characteristics of the exposed soils of the base provided for in the project;
• the sufficiency of the measures taken to protect the foundation soil from freezing in the period from the opening of the pit and until the end of the construction of the foundation;
• compliance with the actual depth and dimensions of the foundation, as well as its design and the quality of the materials used, provided for in the project.

6.2.5. Installation of foundation blocks and walls of the underground part of buildings

6.2.5.1. The installation of glass-type foundation blocks and their elements in the plan should be carried out relative to the alignment axes in two mutually perpendicular directions, combining the axial risks of the foundations with the landmarks fixed on the base, or controlling the correct installation with geodetic instruments.

6.2.5.2. The installation of blocks of strip foundations and basement walls should be carried out, starting with the installation of lighthouse blocks in the corners of the building and at the intersection of the axes. Beacon blocks are installed, combining their axial risks with the risks of the center axes, in two mutually perpendicular directions. The installation of ordinary blocks should be started after reconciling the position of the lighthouse blocks in terms of and in height.

6.2.5.3. Foundation blocks should be installed on a layer of sand leveled to the design mark. The maximum deviation of the leveling layer of sand from the design level should not exceed minus 15 mm.

Installation of foundation blocks on bases covered with water or snow is not allowed.

Foundation glasses and supporting surfaces must be protected from contamination.

6.2.5.4. The installation of basement wall blocks should be carried out in compliance with the dressing. Ordinary blocks should be installed, orienting the bottom along the edge of the blocks of the lower row, the top - along the center axis. Blocks of external walls installed below the ground level must be aligned on the inside of the wall, and above - on the outside. Vertical and horizontal seams between blocks must be filled with mortar and embroidered on both sides.

6.3. Installation of columns and frames

6.3.1. The design position of columns and frames should be verified in two mutually perpendicular directions.

6.3.2. The bottom of the columns should be aligned, combining the risks that indicate their geometric axes in the lower section, with the risks of the center axes or geometric axes of the columns below.

The method of supporting the columns on the bottom of the glass should ensure that the bottom of the column is secured from horizontal movement for a period until the node is monolithic.

6.3.3. The top of the columns of multi-storey buildings should be aligned by combining the geometric axes of the columns in the upper section with the risks of the center axes, and the columns of one-story buildings - by combining the geometric axes of the columns in the upper section with the geometric axes in the lower section.

6.3.4. The alignment of the bottom of the frames in the longitudinal and transverse directions should be carried out by combining the marks of the geometric axes with the marks of the center axes or the axes of the racks in the upper section of the underlying frame.

Alignment of the top of the frames should be carried out: from the plane of the frames - by combining the notches of the axes of the frame racks in the upper section relative to the center axes, in the plane of the frames - by observing the marks of the supporting surfaces of the racks of the frames.

6.3.5. The use of gaskets not provided for by the project at the joints of columns and frame racks for leveling elevations and bringing them to a vertical position without agreement with the design organization is not allowed.

6.3.6. Landmarks for aligning the top and bottom of columns and frames should be indicated in the PPR.

6.4. Installation of crossbars, beams, trusses, floor slabs and coatings

6.4.1. The laying of the elements in the direction of the overlapped span must be carried out in compliance with the dimensions of the depth of their support on the supporting structures established by the project or the gaps between the mating elements.

6.4.2. Installation of elements in the transverse direction of the overlapped span should be carried out:

• crossbars and inter-column (tie) plates - combining the risks of the longitudinal axes of the installed elements with the risks of the axes of the columns on the supports;
• crane beams - combining the risks that fix the geometric axes of the upper chords of the beams with the center axis;
• rafter and roof trusses(beams) when supported on columns, as well as roof trusses when supported on truss trusses - combining the risks that fix the geometric axes of the lower chords of the trusses (beams) with the risks of the axes of the columns in the upper section or with the reference risks in the supporting node of the truss truss;
• truss trusses (beams) resting on the walls - combining the risks that fix the geometric axes of the lower chords of the trusses (beams) with the risks of the center axes on the supports.

In all cases, roof trusses (beams) should be installed in compliance with the one-sided direction of deviations from the straightness of their upper chords:

• floor slabs - according to the markup that determines their design position on the supports and is carried out after the structures on which they rest (beams, crossbars, trusses, etc.) are installed in the design position;
• roofing slabs along trusses (rafter beams) - symmetrically with respect to the centers of truss nodes (embedded products) along their upper chords.

6.4.3. Crossbars, intercolumn (bonded) slabs, trusses (truss beams), roofing slabs along trusses (beams) are laid dry on the supporting surfaces of load-bearing structures.

6.4.4. Floor slabs must be laid on a layer of mortar with a thickness of not more than 20 mm, combining the surfaces of adjacent slabs along the seam from the side of the ceiling.

6.4.5. Alignment of crane beams in height should be carried out according to the highest mark in the span or on the support using gaskets made of steel sheet. In the case of using a package of gaskets, they must be welded together, the package is welded to the base plate.

6.4.6. The installation of trusses and rafter beams in a vertical plane should be carried out by aligning their geometric axes on the supports relative to the vertical.

6.4.7. The use of pads not provided for by the project to align the position of the stacked elements according to the marks without agreement with the design organization is not allowed.

6.5. Installing wall panels

6.5.1. Installation of exterior panels internal walls should be made, relying on beacons verified relative to the mounting horizon. The strength of the material from which the beacons are made should not be higher than the compressive strength of the solution used for the bedding, established by the project.

Deviations of marks of beacons relative to the mounting horizon should not exceed +/- 5 mm. In the absence of special instructions in the project, the thickness of the beacons should be 10 - 30 mm. There should be no gaps between the end of the panel after it has been aligned and the mortar bed.

6.5.2. Alignment of panels of external walls of single-row cutting should be carried out:

• in the plane of the wall - combining the axial risk of the panel at the bottom level with the orientation risk on the floor, taken out from the center axis. If there are zones of compensation of accumulated errors in the joints of the panels (when panels are overlapped in the places where loggias, bay windows and other protruding or sinking parts of the building are installed), alignment can be performed using templates that fix the design size of the seam between the panels;
• from the plane of the wall - combining the lower edge of the panel with the installation risks on the floor, taken out from the center axes;
• in the vertical plane - aligning the inner edge of the panel with respect to the vertical.

6.5.3. Installation of belt panels of external walls frame buildings should be made:

• in the plane of the wall - symmetrically with respect to the axis of the span between the columns by aligning the distances between the ends of the panel and the risks of the axes of the columns at the installation level of the panel;
• from the plane of the wall: at the level of the bottom of the panel - by aligning the lower inner edge of the installed panel with the edge of the underlying panel; at the level of the top of the panel - by combining (using a template) the edge of the panel with the notch of the axis or the edge of the column.

6.5.4. The alignment of the wall panels of the outer walls of frame buildings should be carried out: -

• in the plane of the wall - combining the risk of the axis of the bottom of the panel being installed with the reference risk marked on the waist panel;
• from the plane of the wall - aligning the inner edge of the installed panel with the edge of the underlying panel;
• in the vertical plane - by aligning the inner and end faces of the panel relative to the vertical.

6.6. Installation of ventilation units, volumetric units of elevator shafts and sanitary cabins

6.6.1. When installing ventilation units, it is necessary to monitor the alignment of the channels and the thoroughness of filling the horizontal joints with mortar. Alignment of ventilation units should be carried out by aligning the axes of two mutually perpendicular faces of the units to be installed at the level of the lower section with the marks of the axes of the lower unit. Relative to the vertical plane, the blocks should be installed by aligning the planes of two mutually perpendicular faces. The joints of the ventilation ducts of the blocks should be thoroughly cleaned of the solution and prevent it and other foreign objects from entering the ducts.

6.6.2. Volume blocks elevator shafts should be mounted, as a rule, with brackets installed in them for fixing guide cabins and counterweights. The bottom of the volumetric blocks must be installed according to the reference risks placed on the ceiling from the center lines and corresponding to the design position of two mutually perpendicular walls of the block (the front and one of the side walls). Relative to the vertical plane, the blocks should be installed by aligning the faces of two mutually perpendicular walls of the block.

6.6.3. Sanitary cabins should be installed on gaskets. The alignment of the bottom and verticality of the cabins should be carried out according to 6.6.2. When installing the cabins, the sewer and water risers must be carefully aligned with the corresponding risers of the cabins below. Holes in the floor panels for passing the risers of the cabins after installing the cabins, mounting the risers and carrying out hydraulic tests must be carefully sealed with mortar.

6.7. Construction of buildings by lifting floors

6.7.1. Before lifting the floor slabs, it is necessary to check the presence of design gaps between the columns and collars of the slabs, between the slabs and the walls of the stiffening cores, as well as the cleanliness of the holes provided for by the project for lifting rods.

6.7.2. Floor slabs should be lifted after the concrete reaches the strength specified in the project.

6.7.3. The equipment used must ensure uniform lifting of floor slabs relative to all columns and stiffeners. The deviation of the marks of individual reference points on the columns during the lifting process should not exceed 0.003 span and should not exceed 20 mm, unless other values ​​are provided for in the project.

6.7.4. Temporary fastening of slabs to columns and stiffeners should be checked at each stage of lifting.

6.7.5. Structures raised to the design mark should be fixed with permanent fasteners; at the same time, acts of intermediate acceptance of structures completed by installation should be drawn up.

6.8. Welding and anti-corrosion coating of embedded and connecting products

6.8.1. Welding of embedded and connecting products must be carried out in accordance with Section 10.

6.8.2. Anti-corrosion coating of welded joints, as well as areas of embedded parts and connections, must be carried out in all places where the factory coating is violated during installation and welding. The method of anti-corrosion protection and the thickness of the applied layer must be specified in the project.

6.8.3. Immediately before applying anticorrosion coatings, the protected surfaces of embedded products, ties and welded joints must be cleaned of welding slag residues, metal spatter, grease and other contaminants.

6.8.4. In the process of applying anti-corrosion coatings, it is necessary to ensure that the corners and sharp edges of the products are covered with a protective layer.

6.8.5. The quality of anti-corrosion coatings should be checked in accordance with the requirements of SP 28.13330.

6.8.6. Data on the performed anti-corrosion protection of joints must be documented in certificates of examination of hidden works.

6.9. Sealing joints and seams

6.9.1. Sealing of joints should be performed after checking the correct installation of structures, accepting the connections of elements in the junctions and performing an anti-corrosion coating of welded joints and damaged areas of coating of embedded products.

6.9.2. The class of concrete and the brand of mortar for embedding joints and seams must be indicated in the project.

6.9.3. Concrete mixtures used for sealing joints must meet the requirements of GOST 7473.

6.9.4. For the preparation of concrete mixes, fast-hardening Portland cements or Portland cements M400 and higher should be used. In order to intensify the hardening of the concrete mixture at the joints, it is necessary to use chemical additives - hardening accelerators. largest size coarse aggregate grains in the concrete mixture should not exceed 1/3 of the smallest size of the joint section and 3/4 of the smallest clear distance between the reinforcement bars. To improve the workability in the mixture, plasticizing additives should be introduced that meet the requirements of GOST 24211.

6.9.5. Formwork for embedding joints and seams, as a rule, must be inventory and meet the requirements of GOST R 52085.

6.9.6. Immediately before embedding joints and seams, it is necessary to: check the correctness and reliability of the installation of the formwork used for embedding; clean the mating surfaces from debris and dirt, snow and ice.

Installation of prefabricated reinforced concrete panels on a layer of frozen mortar is not allowed. The strength of the solution in the horizontal and vertical joints of prefabricated panels for various stages of building readiness, depending on the floor to be installed, should be indicated in the project or WEP.

6.9.7. When embedding joints, concrete (mortar) compaction, maintenance, curing mode control, and quality control should be carried out in accordance with the requirements of Section 5.

6.9.8. The strength of concrete or mortar at the joints by the time of stripping must correspond to that specified in the project, and in the absence of such an indication, it must be at least 50% of the design compressive strength.

6.9.9. The actual strength of the laid concrete (mortar) should be controlled by testing a series of samples made at the place of pouring. To check the strength, at least three samples should be made per group of joints concreted during a given shift.

Samples must be tested in accordance with GOST 10180 and GOST 5802.

6.9.10. Methods of preliminary heating of joined surfaces and heating of monolithic joints and seams, duration and temperature and humidity conditions of curing concrete (mortar), insulation methods, timing and procedure for stripping and loading structures, taking into account the peculiarities of performing work in winter conditions, as well as in hot and dry weather must be specified in the PPR.

6.10. Water, air and vapor permeability, heat and sound insulation of joints of external walls and assembly units adjoining window and door blocks to wall openings

6.10.1. Indicators of the main performance characteristics of heat transfer resistance, air, water and vapor permeability, sound insulation, deformation resistance of the joints of external walls and junctions, window and door blocks to wall panels are set in the working documentation.

The construction of the mounting seams of the junctions of window and door blocks to wall openings must meet the requirements of GOST 30971 and these building codes.

6.10.2. Joints and seams of mounting units must be resistant to various operational influences: atmospheric factors, temperature and humidity influences from the premises, force (temperature, mechanical, shrinkage, etc.) influences.

6.10.3. The choice of materials for the arrangement of joints and mounting joints, as well as the determination of the dimensions of mounting gaps, should be made taking into account possible operational (temperature, sedimentary) changes in the linear dimensions of structures and products in terms of deformation resistance. At the same time, elastic insulating materials, intended for operation in a compressed state, must be selected taking into account their design (working) compression ratio.

6.10.4. The value of the heat transfer resistance of the joint and the mounting seam of the junction must ensure that the temperature of the inner surface of the structure, window and door slope is not lower than required by building codes and regulations.

The value of indicators of air and water resistance, sound insulation of joints and assembly seams should not be lower than the values ​​of these indicators for the structures and products used.

6.10.5. Materials for joints and assembly joints must comply with the requirements of standards, the terms of supply contracts and technical documentation approved in the prescribed manner.

6.10.6. Transportation, storage and use of insulating materials should be carried out in accordance with the requirements of standards or specifications.

Insulating materials after the expiration of the storage period established by the standards or technical conditions before use are subject to control check in the laboratory.

6.10.7. Panels must be delivered to objects with primed surfaces forming joints. The primer should form a continuous film.

6.10.8. The surfaces of the panels of the outer walls, forming joints, before performing work on the installation of water and air insulation, must be cleaned of dust, dirt, concrete sagging and dried.

Surface damage to concrete panels at the joints (cracks, shells, chips) must be repaired using polymer-cement compositions. The disturbed primer layer must be restored in construction conditions.

The application of sealing mastics to wet, frosty or icy joint surfaces is not allowed.

6.10.9. For air insulation of joints, air-protective tapes are used, fixed on adhesives or self-adhesive. It is necessary to overlap the air-protective tapes along the length with the length of the overlapping section of 100 - 120 mm. The joints of the tapes in the wells of vertical joints should be located at a distance of at least 0.3 m from the intersection of vertical and horizontal joints. In this case, the end of the underlying tape should be glued over the tape installed at the junction of the floor to be installed.

It is not allowed to connect the tapes in height until the wells of the joints of the lower floor are monolithic.

6.10.10. The glued air barrier tape must adhere tightly to the insulated joint surface without bubbles, swellings and folds.

6.10.11. Thermal insulation inserts should be installed in the wells of the vertical joints of the panels of the outer walls after the installation of air insulation.

Lining materials must have a moisture content established by the standards or specifications for these materials.

6.10.12. The installed liners must fit snugly against the surface of the well along the entire height of the joint and be fixed in accordance with the project.

There should be no gaps at the joints of the heat-insulating inserts. When eliminating gaps between the liners, they must be filled with material of the same density.

6.10.13. Sealing gaskets in the mouths of joints of closed and drained types should be installed dry (without coating with glue). At the intersections of closed joints, sealing gaskets should first be installed in horizontal joints.

6.10.14. In closed-type joints when overlapping external wall panels, in drained-type horizontal joints (in the area of ​​the drainage apron), in open-type horizontal joints, as well as in joints of tongue-and-groove panels, it is allowed to install sealing gaskets before mounting the panels. In this case, the gaskets must be fixed in the design position. In other cases, the installation of sealing gaskets must be carried out after the installation of the panels.

It is not allowed to nail sealing gaskets to the surfaces forming the butt joints of the outer wall panels.

6.10.15. Sealing gaskets should be installed in joints without breaks.

It is necessary to connect the sealing gaskets along the length "by the mustache", placing the junction at a distance of at least 0.3 m from the intersection of the vertical and horizontal joints.

Sealing joints with two gaskets twisted together is not allowed.

6.10.16. Compression of gaskets installed at the joints should be at least 20% of the diameter (width) of their cross section.

6.10.17. Isolation of joints with mastics should be carried out after the installation of sealing gaskets by injecting mastics at the mouth of the joint with electric seals, pneumatic, manual syringes and other means.

It is allowed to apply hardening mastics with spatulas when performing repair work. Liquefaction of mastics and their application with brushes is not allowed.

6.10.18. When preparing two-component hardening mastics, it is not allowed to violate the passport dosage and disassemble their components, mix the components manually and add solvents to them.

6.10.19. The temperature of the mastics at the time of application at positive outside temperatures should be 15 - 20 °C. In winter periods, the temperature at which the mastic is applied, as well as the temperature of the mastic at the time of application, must comply with those specified in the technical specifications of the mastic manufacturer. In the absence of relevant instructions in the technical specifications, the temperature of the mastics at the time of application should be: for non-hardening - 35 - 40 ° C, for hardening - 15 - 20 ° C.

6.10.20. The applied layer of mastic should fill without voids the entire mouth of the joint to the elastic gasket, not have gaps, sagging.

The thickness of the applied layer of mastic must correspond to that established by the project. The maximum deviation of the thickness of the mastic layer from the design should not exceed plus 2 mm.

The resistance of the applied mastics to separation from the surface of the panel must comply with the indicators given in the relevant standards or specifications for the mastics.

6.10.21. Protection of the applied layer of non-hardening mastic must be made with the materials specified in the project. In the absence of special instructions in the project, polymer-cement mortars, PVC, styrene-butadiene or coumarone-rubber paints can be used for protection.

6.10.22. In open type joints, rigid water barriers should be inserted into the vertical channels of open joints from top to bottom until they stop against the drainage apron.

When using rigid water barrier screens in the form of corrugated metal strips, they should be installed in vertical joints so that the opening of the extreme corrugations faces the facade. The shield must fit freely into the groove. When opening the vertical joint of panels more than 20 mm, two tapes riveted along the edges should be installed.

Flexible water barriers (tapes) are installed in vertical joints both outside and inside the building.

6.10.23. Non-metallic drainage aprons made of elastic materials should be glued to the upper edges of the joined panels for a length of at least 100 mm on both sides of the axis of the vertical joint.

6.10.24. Acceptance of mounting units adjoining to wall openings is carried out in accordance with GOST 30971 by carrying out:

• input quality control of the materials used;
• quality control of the preparation of window openings and window blocks;
• production operational control;
• acceptance tests in the course of work;
• classification and periodic laboratory testing of materials and assembly seams.

The incoming quality control of materials and products, the quality control of the preparation of window openings and the installation of window blocks, as well as periodic tests during the performance of work on the installation of assembly joints, are carried out by a construction laboratory or a quality control service of a construction (installation) organization that has the appropriate permit.

The results of all types of control are recorded in the appropriate quality logs.

Completion of work on the installation of assembly joints is drawn up by an act of hidden work and an act of acceptance.

7. Installation of light enclosing structures

7.1. General requirements when installing light enclosing structures

7.1.1. Before starting the installation of light enclosing structures, the construction site is cleared of foreign building structures, materials, mechanisms and construction waste and is fenced in accordance with the requirements of SNiP 12-03. Fencing must meet the requirements of GOST 23407; warning signs are installed in accordance with GOST R 12.4.026.

7.1.2. Temporary storage of metal lightweight enclosing structures is carried out in the original packaging, which ensures the waterproofness of the package, in a warehouse (under a canopy), protecting from direct sunlight, precipitation and dust. The warehouse must be closed, dry, with hard flooring.

7.1.3. Temporary storage of metal lightweight building envelopes in their original packaging can be organized in an open area, subject to the following conditions:

• the site is equipped with a slope towards water drainage and removal of melt water;
• Panel packs are stacked in a stack with a height of not more than 2500 mm per wooden blocks not less than 100 cm thick, with a step of 1 - 1.5 m. Packs of corrugated sheets can be stacked in no more than two tiers;
• packages and packs are covered with a waterproof material, such as a tarpaulin, so that the bottom of the packages remains open and air circulation occurs under the packages.

7.1.4. Temporary storage of thermal insulation, fasteners, flashings, slopes, sealants, glue, paint, etc. at the construction site is carried out in the original packaging in a closed ventilated warehouse.

Temporary storage and laying of sandwich panels is carried out taking into account the sequence of their installation.

7.1.5. Cutting of galvanized steel thin-walled profiles, shaped, fasteners and facing of sandwich panels should be done with jigsaws, circular saws, hand hacksaws with a fine tooth, insulation - with special knives. Steel shavings must be removed immediately so that they do not damage the facing surface of the panel.

7.1.6. Abrasive wheels should not be used to cut panels, shaped and fasteners.

7.1.7. Welding and mechanical work related to cutting and grinding with abrasive wheels is carried out at such a distance from profiled sheets, profiles exterior finish and panels so as not to damage their facing surfaces.

7.1.8. Works on the installation of light enclosing structures are carried out at ambient temperatures from minus 15 °C to plus 30 °C in several grips in one or two shifts. Several teams (links) of installers can work simultaneously in a shift, each on its own vertical grip, four or five people in each team (link).

7.2. Enclosing structures made of chrysotile cement sheets, extrusion panels and slabs

7.2.1. The walls of horizontal and vertical cuts should be mounted, as a rule, with preliminary pre-assembly into "cards". With an appropriate feasibility study, element-by-element installation is allowed.

7.2.2. Enlargement assembly of wall panels into "cards" must be performed on stands in the area of ​​operation of the main assembly crane.

7.2.3. Partition panels in multi-storey buildings should be mounted after mounting the load-bearing elements on the floor using special devices (tilters, towers with winches, etc.) without using mounting cranes; in one-story buildings - using assembly cranes or special devices.

7.2.4. The installation of panels and slabs in plan and in height must be carried out by combining the installation marks applied on the mounted and supporting structures. The top of the panels must be aligned with respect to the center axes.7.2.5. Sealing gaskets in the horizontal and vertical joints of the panels must be laid before the installation of the panels.

7.2.6. Wall structures made of chrysotile cement sheets of extrusion panels finished with installation should be taken floor by floor, section by section or by spans.

7.2.7. Upon acceptance, it is necessary to check the reliability of fixing the panels, the absence of cracks, fluctuations, damaged areas. Intermediate control is subject to insulation of joints between wall panels.

7.2.8. If there are no special requirements in the project, the deviations of the mounted panels in the structures of walls and partitions should not exceed the values ​​\u200b\u200bgiven in Table 7.1.

Table 7.1

7.3. Installation of metal enclosing roof structures of sheet assembly and sandwich panels

7.3.1. Before starting the installation of roofing sheets and roof panels it is necessary to complete the installation of rafters and girders, check the horizontal, vertical, parallelism and flatness of the installation sites of roof panels for compliance with the project.

7.3.2. Before installation roofing it is necessary to build an auxiliary working platform on the supporting structures - flooring, prepare scaffolding for the installation of roofing sheets and panels. When preparing places for mounting panels on steel rafters, crossbars, purlins, it is necessary to apply an anti-corrosion paint and varnish coating to the junction and contact points. The final leveling and marking of the location of the bottom of the first panels is being carried out.

A sealant is glued onto the roof girders - a thermal separating strip (UPTP) to reduce air permeability through the joints of the enclosing structure and reduce the sound vibration of sandwich panels.

7.3.3. The panels must be prepared for installation in the factory or on the construction site as follows:

• on the side of the overhang, the lower lining and the inner part (insulation) are previously removed from the panels by the amount specified in the project (usually 100 mm);
• adhesive residues from the inside of the metal cladding are removed using a solvent for polyurethane foam and mechanically, the damaged anti-corrosion coating during this operation must be restored by tinting;
• at the first panel, as well as at the panels adjacent to the end of the building, must be cut off along longitudinal edge loose corrugation of the upper skin flush with mineral insulation for installation of the end framing flashing.

7.3.4. A sealing compound made of silicone or a sealing butyl rubber cord is applied to the bottom row panel at the overlap. A layer of sealing compound is applied to the "groove" type lock of the bottom sheet of the mounted panel, as well as to the groove of the lock corrugation of the panel prepared for continued mounting. It is allowed to apply the sealing compound directly to the top of the outer corrugation of the mounted panel. Instead of sealant, you can use a TSP tool joint seal (8 mm x 30 m) or sealing tape (10 mm x 100 m).

7.3.5. The panels are fastened first to the supporting structures of the roof, and then at the joint. In this case, self-tapping screws are used, the diameter and length of which depend on the supporting structure of the roof and the thickness of the panels, and which are specified in the roof design (see table 4.5). The panels are fastened from the top along the slope of the roof slope down, from the ridge to the overhang.

The panel may be preliminarily fastened with two hardware, but at the end of the shift it is necessary to fasten the panel with a full number of screws according to the project.

7.3.6. The installation of steel sheet bent profiles with trapezoidal corrugations (hereinafter referred to as corrugated sheets) during sheet-by-sheet assembly of roofs and walls should be carried out according to markings that ensure fixation of the calculated width of the profiled sheet (distance between the axes of the extreme corrugations), in accordance with the values ​​\u200b\u200bestablished by GOST 24045 and the corresponding regulatory documents, with an accuracy of +/- 10 mm per profiled sheet width. 7.3.7. When the end overhangs of the supporting corrugated roofing sheet come out onto the facade of the building, in the case of installation of front end combs, deviations from the accuracy of mounting the sheet along its width should not exceed +/- 4 mm.

7.3.8. Fastening of corrugated sheets of load-bearing sheathing of the roof and walls to the load-bearing elements of the frame is carried out using self-tapping or self-drilling screws, or by adjusting with dowels in accordance with the requirements of the working documentation. In cases where the fastening step is not specified in the documentation, corrugated sheets must be fastened to the supporting elements of the roof in the transverse direction through the wave on the intermediate supports and in each wave along the perimeter of the building. It is allowed to fasten the sheet in advance with two hardware, but at the end of the shift, it is necessary to fasten the sheets with a full number of screws according to the working documentation.

7.3.9. Fastening corrugated roofing sheets with electric rivets is allowed only in cases where the sheets are not painted and when the width of the shelves of the supporting elements (for roof trusses, the width of the belt or shelf of one of the two corners of the belt), on which the corrugated sheet rests, should be more than 100 mm.

7.3.10. In the longitudinal direction, corrugated sheets are fastened together using combined rivets or self-tapping screws, the fastening pitch is 500 mm, unless this is specified in the project documentation.

7.3.11. The vapor barrier of the roof must be laid on the lower corrugated sheet with an overlap of individual sheets of film of at least 300 mm or glued with adhesive tape. In case of breaks in the vapor barrier film, the damage must be sealed with patches from the same film, extending to the sides beyond the damage by at least 250 mm.

7.3.12. Before laying the vapor barrier, the lower decking of the roof must be thoroughly brushed to remove dirt, dust, chips, ice, snow and water.

Thermal insulation is laid in dry weather in a continuous layer. Mineral wool or rigid mineral wool boards must have a natural moisture content. thermal insulation high humidity must be dried beforehand.

7.3.13. The upper waterproof layer of the roof made of corrugated sheets, if it is not a load-bearing one, is attached to the roof bowstrings laid along the load-bearing flooring of the roof made of corrugated sheets, or on rigid mineral wool insulation boards using self-tapping or self-drilling screws installed with a step of at least 400 mm on intermediate strings and with a step of 200 mm for cornice strings, if there are no other requirements in the working documentation.

7.3.14. The upper sheets in the longitudinal direction are fastened together with blind combined rivets or self-tapping and self-drilling screws with a pitch of 500 mm, if this is not specified in the working documentation.

7.3.15. All longitudinal and transverse joints of the top layer of the roof must be sealed with sealant, except in cases where the longitudinal seam of adjacent sheets is rolled into a double seam seam.

7.3.16. In case of poor-quality installation of fasteners (screw shaft shear, head breakage, loose fit, etc.), a new fastener element is installed nearby, at a distance of at least five diameters of the fastener shaft and not more than 60 mm. In cases where it is possible to drill an old hole, a screw is placed large diameter. The old hole in the top layer of the roof is sealed with sealant, puttied and painted to match. paintwork roof sheets.

7.3.17. To avoid damage to the paintwork of the upper roof deck, when drilling holes, remove chips with brushes from the surface of the deck.

All work on the movement of goods, storage of materials and installation of structural layers of the roof should be carried out from inventory wooden ladders and bridges, excluding damage to the stacked layers of the roofing and plastic deformation of the waterproofing roofing sheet.

The order and volumes of storage of materials and structural elements on the roof surface must be agreed with the authors of the project.

7.3.18. Loading and unloading operations on the installation of the roof should be carried out using soft halyards, traverses with vertical slings, or in other ways that exclude damage to sheets and paintwork.

7.3.19. The storage of corrugated roofing sheets at the construction site must be carried out on wooden spacers with a cross section of at least 50 x 100 mm, installed at a distance of no more than 2500 mm. Packs of corrugated sheets can be stacked in no more than two tiers.

7.3.20. If galvanized unpainted corrugated sheets are stored at a construction site or in a warehouse for more than two weeks, they should be placed under a canopy or covered with a film from atmospheric precipitation.

7.3.21. Sheets of profiled flooring should be laid and upset (in places of overlap) without damaging the paintwork and zinc coating and distorting the shape. Metal tools should only be placed on wooden pads to avoid damage to the protective coating.

7.3.22. The quality of the facade installation is ensured by the current control of the technological processes of the preparatory and main works, as well as during the acceptance of works. According to the results of the current control of technological processes, certificates of examination of hidden works are drawn up (for the installation of supporting structures and insulation).

7.3.23. In the absence of special requirements in the working documentation, the deviations of the mounted panels and profiled sheets in the roof structures should not exceed the values ​​\u200b\u200bgiven in Table 7.2.

Table 7.2

7.4. Hinged ventilated facades

7.4.1. When organizing installation work, the area of ​​​​the facade of the building is divided into sections, within which work is carried out by different parts of the installers.

The dimensions of the catch when using scaffolding are determined, in the general case, by the total length of the working platform and the height of the scaffolding.

7.4.2. For installation, scaffolding is installed on a grip corresponding to the factory set of scaffolding. When installing cladding panels on high-rise buildings, special scaffolding with a double rack is installed. If necessary, scaffolding can be installed not at the zero mark, but at a height, on the floor of the building, on a support device mounted in the opening of the building. The installation of the scaffolding and the facade lift is carried out in accordance with the instructions of the manufacturers of the scaffolding and the lift. A protective polymer mesh is hung on the scaffolding.

7.4.3. On the open area for work and storage of building materials and structures, the following work is carried out:

• cutting guide profiles with electric saws;
• cutting and cutting of thermal insulation plates is carried out with special knives;
• cut the windproof film.

Do not use abrasive wheels for cutting guide profiles, fittings and fasteners.

Upon completion of the installation of scaffolding, sites or platforms, an act is drawn up on their readiness for use. When transferring structures (changing grips), a new act should be drawn up.

7.4.4. Preparatory work ends with marking the attachment points of the brackets on the facade. The marking from scaffolding is carried out along the front of the scaffolding. When using a facade lift, the marking is performed on each grip according to pre-set control points.

Mounting works are carried out in both serial and parallel technological streams.

7.4.5. When performing work, installation work is performed in the following sequence:

• installation of brackets;
• installation of thermal insulation boards;
• installation of guide profiles;
• installation of shaped elements (sills and slopes);
• installation of facing tiles.

7.4.6. Installation of thermal insulation boards is carried out on a dry wall. Before installation, the plate is pre-cut, holes are drilled in the wall. Diameter and depth drilled hole must match the size of the dowel. The thermal insulation plate is pre-fixed with two dowels. A wind-moisture protective film is laid, connecting it at the seams with a stapler. And only after covering with a film, they are fixed with the rest of the dowels provided for by the project. Film panels are installed with an overlap of 100 mm.

7.4.7. Installation of thermal insulation boards is carried out from the bottom up. Insulation plates are installed tightly to each other so that there are no voids in the seams. The inevitable voids are sealed with the same material.

7.4.8. Shaped elements: drains and junctions (to window and door openings, roofing, to parapets, plinth, etc.) are mounted before installation of facing tiles made of porcelain stoneware, chrysotile cement and fiber cement. Fire boxes are installed in window and door openings.

7.4.9. In the process of installation work, they check for compliance with the project:

• facade marking accuracy;
• diameter, depth and cleanliness of holes for anchors (dowels);
• accuracy and strength of mounting brackets;
• correctness and strength of fastening to the wall of insulation boards;
• the accuracy of the installation of horizontal and vertical profiles and, in particular, the gaps at their joints;
• flatness of facing tiles and air gaps between them and insulation boards;
• correct arrangement of frames for corners and openings of a ventilated facade, plinth and parapet.

7.4.10. When accepting work, the facade is inspected as a whole and especially carefully the junctions, framing of corners and window openings, the basement and parapet of the building. Defects found during the inspection are eliminated before the facility is put into operation.

7.4.11. Finished installation of the frame structure, windshield film and insulation should be taken in grips or sections.

7.4.12. Upon final acceptance of the assembled structures, the documentation specified in 3.23 shall be presented.

7.4.13. The maximum deviations of the actual position of the structures of the facade systems from those provided for by the project should not exceed the values ​​given in Table 7.3.

Table 7.3

Continuation of tab.7.3

7.5. Sheathed frame partitions

7.5.1. Transportation and storage of sheathing sheets must be carried out in conditions that exclude the possibility of their moisture, contamination and mechanical damage.

7.5.2. The temperature in the premises where the partitions are installed must be at least 10 °C, the humidity of the air must not exceed 70%.

7.5.3. Docking of sheathing sheets must be performed only on the frame elements.

7.5.4. With a two-layer sheathing of the frame, the joints between the sheets should be spaced apart.

7.5.5. Screws and screws in the places of attachment of two adjacent sheets should be spaced apart.

7.5.6. Limit deviations of partition elements from the design position should not exceed the values ​​given in Table 7.4.

Table 7.4

7.5.7. Partition structures completed by installation should be taken floor by floor or by sections.

7.5.8. Upon acceptance, it is necessary to check the stability of the frame, the reliability of fastening of the sheathing sheets, the absence of tears, damage, knocked-down corners along the length of the edge, oil stains and dirt on the sheets.

7.5.9. Partitions finished with installation and prepared for finishing should have no more than two irregularities with a depth or height of 3 mm when applying a rule or template 2 m long; deviation of the partition from the vertical - no more than 2 mm per 1 m of height and 10 mm for the entire height of the room.

7.6. Walls made of sandwich panels and sheet assembly

7.6.1. Before installing wall profiles and panels, check the accuracy of the metal frame: verticality, horizontality, flatness of the installation sites, column spacing. On existing metal structures at the points of contact, it is necessary to restore the anti-corrosion paintwork.

7.6.2. Installation of walls and partitions of buildings from light metal panels of the "sandwich" type and monopanels of vertical and horizontal cutting, cassettes should be carried out mainly in panels.

7.6.3. Installation of scaffolding for mounting walls is carried out in accordance with the instructions of the enterprises - manufacturers of scaffolding. For the possibility of mounting sandwich panels, the distance from the scaffolding to the plane of fixing the sandwich panels on columns, girders, crossbars should be increased from 150 to 300 mm.

7.6.4. Scaffolding is allowed for operation after acceptance by a commission appointed by the head of the construction organization, and is registered in the register in accordance with GOST 26887. Scaffolding should be operated in accordance with the manufacturer's instructions and SNiP 12-03. The technical condition of scaffolding is controlled before each shift and periodic inspections every 10 days. The results of periodic inspections are noted in the mentioned journal.

7.6.5. Slinging of panel packages is allowed only for strapping with vertically located slings.

7.6.6. When mounting panels with vertical cutting, it is prohibited to sling from the side of the upper edge of the panel and lift it by turning it relative to the opposite edge.

7.6.7. Sealing gaskets in vertical and horizontal joints of sandwich panels should be laid before the panels are installed.

7.6.8. Enlargement assembly of walls from light panels "in cards" must be carried out on stands in the area of ​​​​the main assembly crane. Limit deviations of "maps" must be specified in the project. In the absence of such instructions, the maximum deviations in length and width are +/- 6 mm, in the difference in diagonal sizes - 15 mm.

7.6.9. All overlays of horizontal and vertical joints, as well as corner elements panels must be placed on a sealant to prevent moisture from entering the joint.

7.6.10. For thermal insulation of the supporting profiles and the frame of the panels from facing materials, a thermal separation strip made of foamed polyethylene foam or hard mineral wool 30 mm thick is used. Self-adhesive aluminum tape is used to seal the joints between the profiles.

7.6.11. When mounting wall structures on the frame or wall of the building, the location of the lighthouse attachment points of sheet profiles is noted. Marking of points is carried out in accordance with the working draft for the installation of the facade.

First, the beacon lines for marking the facade are determined - the lower horizontal line of the installation points and the two vertical lines extreme along the facade of the building. The extreme points of the horizontal line are determined using a level and marked with indelible paint. At two extreme points, using a laser level and a tape measure, determine and mark intermediate points for installing sandwich profiles. Then, vertical lines are determined at the extreme points of the horizontal line. Indelible paint marks the installation points of the profiles on the extreme vertical lines.

7.6.12. Installation of walls with horizontal cutting is carried out from the bottom up, in tiers. In places where wall structures adjoin, a sealant is glued to the columns of the building. Installation of walls with a vertical gas cutter is carried out from left to right.

7.6.13. Before installing the next panel, an outdoor sealant or 8 mm diameter butyl rubber sealant or 8 x 3 mm RTD sealant is applied to the installed panel's groove lock. The lock is sealed from the inside of the wall.

7.6.14. Shaped elements - socle, corner, frames of openings, flashings and others are installed with an overlap with sealing of the joint in accordance with the design solutions of the mounting angles. The overlap must be for horizontal elements not less than 50 mm, and for vertical - from 80 to 100 mm. The sequence of installation should be such as to ensure the tightness of the components being made out. The installation of shaped elements is usually carried out from the bottom (basement) of the building to the roof ridge. Fitting of shaped elements, their trimming and trimming is carried out, if necessary, in place. The shaped elements are sealed with a sealant for outdoor work along the planes of adjunction to the panels. Gaps and gaps are not allowed.

7.6.15. The shaped elements are fastened to the panels from the outside of the building using self-tapping screws 4.8 x 28 mm with an EPDM gasket or combined rivets 3.2 x 8 mm. If it is necessary to fasten shaped elements directly to metal structures, use self-tapping screws 5.5 x 32 mm or 5.5 x 19 mm with an EPDM gasket (for fastening to metal structures with a shelf thickness of up to 12 mm or up to 5 mm, respectively) without pre-drilling.

7.6.16. Wall structures are attached to steel columns and half-timbered racks with walls up to 12 mm thick. self-tapping screws without pre-drilling holes. If the column is reinforced concrete, then the structures are fixed with anchors (dowels) with pre-drilled holes. To install and fasten the anchor through the panel, a hole with a diameter of 4.8 or 6.3 mm is drilled in the concrete of the column. In this case, the anchor's penetration into concrete should be at least 32 mm for a diameter of 4.8 and 38 mm for a diameter of 6.3 mm, and the hole depth should be 20 mm more. For drilling holes, drills with a working length of 100, 250 and 300 mm with a diamond cutting edge are used.

7.6.17. Shaped elements: drains and junctions (to window and door openings, to the roof, to parapets, to the basement, etc.) are mounted before the installation of wall facing materials from profiled sheets, siding, linear panels, facade cassettes and tiles made of porcelain stoneware, chrysotile cement facade slabs and flat sheets.

7.6.18. Acceptance of the facade of sandwich panels is carried out by an acceptance committee consisting of representatives of the customer and the contractor and is formalized by signing an acceptance certificate. The documents specified in 3.23 are attached to the act.

7.6.19. The maximum deviations of the actual position of the structures of the facade systems from those provided for by the project should not exceed the values ​​given in Table 7.5.

Table 7.5

8. Installation of wooden structures

8.1. General provisions for the acceptance and installation of wooden structures

8.1.1. Acceptance of wooden structures (DC) must be carried out in accordance with the requirements of sections 3 and 8. When accepting glued wooden structures (LWC), the requirements of GOST 20850 should also be taken into account.

Structures that have or received defects and damage during transportation and storage, the elimination of which is not allowed under the conditions of the construction site (for example, delamination of adhesive joints, through cracks, etc.), must not be mounted until the conclusion of the design organization-developer. In conclusion, a decision is made on the possibility of application, the need to strengthen damaged structures or replace them with new ones.

8.1.2. Prefabricated load-bearing elements of wooden structures should be supplied by the manufacturer to the construction site in a complete set. After the control assembly, together with all the details necessary for making design connections - linings, fastening bolts, ties, hangers, turnbuckles, bracing elements, etc.

Cladding slabs and wall panels must be supplied complete with standard fasteners, suspension parts (for suspended ceiling slabs), materials for sealing joints.

8.1.3. When performing work on warehousing, transportation, storage and installation of wooden structures, their specific features should be taken into account:

• the need for protection from long-term atmospheric influences, in connection with which, in the course of work, it should be provided, as a rule, for the installation of the building along the grips, including the consistent erection of load-bearing structures, enclosing structures and roofs in a short time;
• ensuring the minimum possible number of operations for tilting and shifting the DC in the process of loading, unloading and installation.

Wooden structures or their elements should be stored protected from atmospheric influences (rain, snow, UV rays). Structures should be placed in the design position on pads or temporary supports at a height of at least 0.5 meters from the level of the storage area.

If the work (character of loading) of wooden structures during transportation or installation differs from the expected nature of work in the design position, it is necessary to calculate the structure for mounting and transport loads, taking into account, if necessary, their dynamic components.

8.1.4. Bearing wooden structures of buildings should be mounted in the most enlarged form: in the form of trusses, semi-frames and semi-arches, arches, sections or blocks, taking into account their features and types.

Larger assembly of wooden structures with metal puffs must be carried out only in a vertical (design) position, without puffs and with wooden puffs - both in a vertical and horizontal position. This condition must be specified and taken into account in the project documentation.

The installation of linings in the ridge nodes of structures, braces of trusses or braces of frames should be carried out after reaching a tight abutment of the joined surfaces over a given area. When shipped from the factory or marked for installation, holes for bolts or studs can only be in one overlay. Through them, through holes are drilled in place.

8.1.5. The installation of structures in prefabricated elements should be started only after tightening all metal joints and eliminating defects that occur during transportation and storage, marking the installation sites for girders, struts, etc.

8.1.6. Before the installation of wooden structures that are in contact with more heat-conducting materials (brick, concrete, etc.), it is necessary to perform work on the installation of waterproofing and, if necessary, heat-insulating gaskets between them.

8.1.7. Tolerances and deviations that characterize the accuracy of construction and installation works are regulated in the project for the production of works, depending on the specified accuracy class (determined by functional, structural, technological and economic requirements, the type of enclosing structures) and are determined in accordance with GOST 21779. The remaining limit deviations should not exceed the specified in table 8.1.

Table 8.1

8.1.8. The installation of load-bearing wooden structures should be carried out in accordance with the PPR developed by a specialized organization with the participation of the design organization-developer. Installation of prefabricated wooden load-bearing structures should be carried out only by a specialized installation organization.

8.1.9. In the process of assembling the joints of belts and nodes of trusses, arches, frames and other recreation centers, before the installation of decorative and protective overlays, it is necessary to ensure the acceptance of work for compliance with the project for welding the releases of glued rods, for fire and bioprotection, for monolithic gaps with polymer concrete, draw up acts for hidden work, perform control of welded joints, conduct laboratory tests of the strength of polymer concrete.

8.1.10. Fire-retardant coatings are applied to the KDK after their installation in the design position and the mandatory installation of the roof, unless otherwise justified by the fire protection project.

8.2. Installation of wooden columns and racks

8.2.1. Prior to installation on a column or rack, marks should be made at the installation sites of crossbars, girders, spacers, ties, panels, etc., and embedded parts should be installed.

8.2.2. In case of rigid pinching of racks equipped with steel shoes on glued rods, it is allowed to weld them with embedded parts of foundations or fasten anchor bolts with mandatory decoupling from the frame plane. 8.2.3. When the struts are hinged without support shoes, it is necessary to achieve a tight abutment of the ends of the struts to the support through waterproofing gaskets or using a layer of polymer concrete. At the time of installation, such racks must be fixed in supports and untied in two planes with temporary connections.

8.3. Installation of glued wooden beams

8.3.1. When installing beams with a constant section along the span, gable or with a different shape of the upper face (wavy, segmented, etc.), i.e. for which the center of gravity is higher than the line connecting the supports, the unfastening of the upper edges from the plane is mandatory, as well as the fastening of the supports and the unfastening of the support sections.

8.3.2. Installation of glued beams and curved beams with an edge curved downwards, including lenticular ones, is allowed to be carried out without bracing or spacers in the span for the duration of installation, but always with fixing in supports and unfastening along the upper edges in support nests or between adjacent braces.

8.4. Installation of wooden prefabricated trusses

8.4.1. Trusses for installation must be fully assembled and installed on special temporary supports in a vertical position in the area of ​​​​the crane. On the truss belts, a brand, risks of the axes of the runs, struts, slinging points should be applied, movable and fixed supports are indicated, for asymmetric trusses - the numbers of the axes of the supports.

8.4.2. Enlargement assembly of wooden large-span trusses should be carried out with a construction lift of the upper belt in a horizontal or vertical position on the slipway, which ensures fixing the dimensions and the possibility, if necessary, of welding rigid joints of the belts and in knots, sealing the gaps in the joints with polymer concrete, setting dowels and studs for fastening elements lattices and belts.

8.4.3. To mount the trusses on the assembly stand, it is necessary to make the necessary mounting reinforcement of the joints of the truss chords and the attachment points of the braces to increase their rigidity from the plane when the trusses are brought to a vertical position.

8.4.4. When tilting large-span trusses, special self-release devices should be used that fix two turning points, as well as traverses that exclude the possibility of the truss elements leaving the plane between the fixing points and cantilever sections. It is allowed to perform this operation using additional light cranes in order to reduce the free length of the truss sections while simultaneously bringing it to a vertical position.

8.4.5. Prior to lifting the trusses at the joints of the chords and in other places along the upper chords, means of unfastening from the plane must be provided. For lenticular-shaped trusses and trusses with a straight upper chord, fastening should also be provided along the lower chords.

8.4.6. Pre-assembly of metal-wood trusses, trussed trusses with a metal lower chord, including those with an elevated lower chord (above the support line), must be carried out in a vertical position in special stocks with devices for installing and leveling truss elements.

8.4.7. Truss slinging points with metal lower chords and split upper chords during lifting should ensure that the metal chords work in tension. It is allowed to use temporary mounting struts and compressive clamps for lifting metal-wood trusses up to 18 m with split upper chords when slinging in the middle part of the span.

8.4.8. For trusses with a span of more than 24 m and for all trusses with an elevated lower chord, when installing hinged movable supports, it is necessary to ensure the possibility of unhindered horizontal movement of the support by the calculated value in accordance with the project.

8.4.9. Installation of trusses with a slide should be carried out in rigid spatial blocks of 2 - 3 pcs. in a vertical design position at a given level using collapsible spatial stocks on steel rails. The movement of blocks should be carried out synchronously by winches with fastening of cables at two points of support of the block and in accordance with the PPR.

8 .5. Installation of glued wooden arches and ram

8.5.1. Three-hinged arches and frames with a hinge in the key and with the transfer of thrust to the foundations should be mounted either with the help of two cranes working simultaneously, or using a mobile mounting tower in the ridge area, equipped with jacks or wedges, allowing straightening of the elements vertically and ease of moving the tower. The slinging of the structure is possible only after design fixing in the supports and unfastening from the plane in the zone of rigid joints, in the key and in other places.

Three-hinged arches and frames with spans up to 18 m can be assembled in a horizontal position and mounted by turning with preliminary mounting reinforcement with clamps in the key to ensure rigidity from the plane, while it is necessary to calculate the mounting loads.

8.5.2. The assembly of large-sized semi-arches or semi-frames with one or two rigid joints before installation must be carried out in a horizontal or vertical slipway equipped with overall clamps, work platforms in the joint area, welding stations (if necessary) and allowing the possibility of monolithic gaps in the joints with polymer concrete, if this is provided for by the project . Prior to installation, the axes of purlins, spacers, embedded parts, crossbars, holes, etc. should be applied to the structures.

8.5.3. When pre-assembling in a horizontal slipway, the tilting of the assembled semi-arches or semi-frames should be carried out after strengthening the pre-assembly joints from the plane.

8.5.4. Installation of large-span prefabricated double-hinged arches and frames supported by foundations, as well as hingeless frames with reinforced concrete or steel posts with rigid joints in the span, must be carried out in the design position using mobile mounting supports located in the joint area and equipped with appropriate clamps, jacks, etc. devices that allow for preliminary bending of structures in accordance with the PPR.

8.5.5. Large-scale assembly and installation of three- and two-hinged arches with metal puffs should be carried out similarly to metal-wood trusses.

8.5.6. When assembling ridge knot arches and frames wooden slips holes for studs and dowels must be made in advance on only one lining. These holes are used as guides when drilling through holes.

8.5.7. In arches with puffs consisting of more than two branches, adjustment and control of tension forces are necessary.

8.6. Installation of ribbed domes made of laminated wood

8.6.1. The assembly of meridional prefabricated ribs of a solid or through section with rigid joints on obliquely glued rods should be carried out on a special slipway, similar to arches or trusses with rigid joints. AT special occasions, with a large length of the meridional ribs or the absence of cranes of the required carrying capacity or boom outreach, it is allowed to perform rigid joints in the design position using intermediate mounting towers.

8.6.2. The canting of the assembled meridional ribs should be carried out with mounting reinforcement of the joints from the plane, as in arches and trusses.

8.6.3. The storage of the assembled meridional ribs should be carried out in a vertical plane on special supports (trestle) with protection from precipitation so that they occupy a stable position and are located in the area of ​​​​the crane and are not lower than 0.5 meters from the surface of the storage site.

8.6.4. Mounting of meridional ribs of domes should be carried out using self-balancing traverses and a mounting tower installed in the center and equipped with a system of jacks, screws, wedges, etc., on which the upper support ring must first be installed.

8.6.5. To ensure a stable shape of the dome, the mounting central tower must be unfastened by three braces (with lanyards) or struts located in plan at an angle of 120 ° to each other, which must remain until the tower is uncircled and dismantled. Under this condition, the order in which the ribs are installed does not matter.

8.6.6. The installation of the frame should begin with the connection block of the sector. The first meridional rib must be unfastened from the plane at the joints. Subsequent ribs should be mounted after permanent connections are made in the connection sector with the ribs fixed in support rings according to the project.

8.6.7. Ring elements and girders should be installed as the meridional ribs are installed in each sector, as stiffeners, and first of all, in the areas of rigid joints.

8.7. Installation of wall panels and floor slabs

8.7.1. When installing wall panels, the top panel should not sink in relation to the bottom one.

8.7.2. Covering slabs should be laid in the direction from the eaves to the ridge with platforms for their support on the supporting structures of at least 5 cm. Gaps must be maintained between the slabs to ensure tight sealing of the joints.

It is forbidden to carry out general construction and special work: registration of adjunctions of slabs to walls, sealing of joints between slabs, roofing and minor repairs. To perform these works on the pavement, as well as to store materials and parts, install various devices and mechanisms on certain areas of the pavement, in accordance with the work execution project, it is necessary to arrange a temporary boardwalk, as well as use portable ladders.

After laying the roofing slabs and sealing the joints on them, the roof should be laid immediately.

When laying corrugated board in the places of support, it is necessary to arrange an overlap, in which the bottom sheet protrudes beyond the edge of the wooden element by at least 20 mm, which excludes moisture of the wooden structures by rainfall and roof leaks.

With a radial arrangement of the supporting structures, before laying the corrugated board in sectors under the joints along the upper faces of the structures, local roofs in the form of drains from sheet materials on sealant in the form of a self-adhesive tape. The surfaces of wooden structures under a local roof must be protected from moisture (self-adhesive waterproofing tape, rolled waterproofing melted material, sealant, etc.).

Go to SP 70.13330.2012 Sections 9-10 Download joint venture 70.13330.2012. Bearing and enclosing structures (Updated version of SNiP 3.03.01-87 ) in PDF format

The most common method of heating concrete during pouring in winter is electrical heating, which is used in cases where conventional insulation of the object is not enough. It is about him that we will talk today.

There are several ways to warm up concrete in winter:

1. Heating of concrete with electrodes.
2. Electric heating of concrete with wire PNSV
3. Electrical heating of the formwork
4. Heating by induction method
5. Infrared

It should be noted that regardless of the method, electric heating of concrete must be accompanied by its insulation or at least the creation of a thermos around the object. Otherwise, uniform heating may not work, and this will not have a very good effect on its final strength.

Warming up concrete with electrodes - connection diagram

Concrete heating with electrodes is the most common method of electric heating in winter. This is due, first of all, to simplicity and cheapness, because, in some cases, there is no need to spend money on heating wires, expensive transformers, etc.

The principle of operation of this method of electrical heating is based on the physical properties of an electric current, which, when passing through a material, releases a certain amount of heat.

In this case, the conductive material is the concrete itself, in other words, when the current passes through the water-containing concrete, it heats it up at the same time.

Attention! If the concrete structure contains a reinforcing cage, it is not recommended to apply a voltage of more than 127 V to the electrodes. In the absence of a metal frame, both 220 V and 380 V can be used. Higher voltage is not recommended.

There are several types of electrodes for heating concrete in winter:

Rod electrodes. To create them, metal fittings d 8 - 12 mm are used. Such rods are inserted into concrete at a short distance and connected to different phases, as in the diagram. In cases of complex structures, such electrodes for heating concrete will be indispensable. Fiberglass reinforcement is not suitable for such purposes, because it is a dielectric.

Plate electrodes. Sometimes they are called plate electrodes. The connection scheme for such heating is very simple - the plates are located on both opposite inner sides of the formwork and are connected to different phases, and the passing current will heat the concrete. Instead of wide plates, narrow strips are sometimes used, the principle of operation of these strips is the same.

String electrodes. Used when pouring columns, beams, pillars and similar structures. The principle of operation is still the same, the strings are connected to different phases, thereby heating the concrete in the winter.

Heating of concrete with electrodes must be carried out only with alternating current, since D.C., passing through the water, contributes to its electrolysis. In other words, water will chemically decompose without fulfilling its main function in the hardening process.

Electric heating of concrete with PNSV wire: technology and scheme

If heating concrete with electrodes is one of the cheapest options for electric heating in winter, then, in turn, heating with a PNSV wire is one of the most effective.

This is due to the fact that not the concrete itself is used as a heater, but the PNSV heating wire, which releases heat when current passes through it. Using such a wire, it is much easier to achieve a smooth increase in the temperature of the concrete, and in general such a wire will lead predictably, which will facilitate the necessary gradual increase in temperature in winter.

It is worth mentioning the PNSV wire itself (P - wire, H - heating, C - steel core, B - PVC insulation). There are various sections 1.2, 2, 3. Depending on the section used, its quantity is selected per 1 meter of cubic concrete mix.

The technology of electric heating of concrete with the PNSV wire, as well as the connection diagram, is very simple. The wire without tension is passed along the reinforcing cage, and it is attached to it. It is necessary to fix it so that when concrete is fed into the trench or formwork, it is not damaged.

When electrically heating concrete with the PNSV wire in winter, it is laid so that it does not touch the ground, the formwork, and also does not go beyond the concrete itself. The length of the wire used depends entirely on its thickness, resistance, expected sub-zero temperature, and the applied voltage, using a special transformer, is usually about 50 V.

There are also cables that do not require the use of a transformer. Using them will save you some money. It is very convenient to use, but still the conventional PNSV wire has wider applications.

Electrical heating of formwork in winter

This method of electrical heating involves the manufacture of formwork with pre-laid heating elements in it, which, when heated, will give so necessary for concrete warmly. It resembles the heating of concrete with plate electrodes, only the heating is carried out not on the inside of the formwork, but inside it or outside.

Electrical heating of the formwork in winter is not often used, given the complexity of the structure, especially since when pouring the foundation, for example, the formwork does not come into contact with the entire concrete structure. Thus, only part of the concrete will heat up.

Induction and infrared methods of concrete heating

The induction method of heating concrete is used extremely rarely, and even then, mainly in beams, crossbars, girders, due to the complexity of its device.

It is based on the fact that wrapped insulated wire around the steel bar of the armature, will create induction and heat the armature itself.

Electrical heating of concrete in winter using infrared rays is based on the ability of such rays to heat the surface of opaque objects, followed by heat transfer throughout the volume. When using this method, it is necessary to provide for wrapping the concrete structure with a transparent film, which will pass the rays through itself, preventing the heat from leaving so quickly.

The advantage of this method is that it is not necessary to use special transformers. The disadvantage is that infrared radiation is not able to provide uniform heating. large structures. This method is only suitable for thin structures.

Do not forget that regardless of the method of electric heating of concrete in winter, it is necessary to constantly monitor its temperature, because too high (more than 50 0 С) is just as dangerous for it as too low. The rate of heating of concrete, as well as the rate of cooling, should not exceed 10 0 C per hour.

If you need to fill the foundation or carry out other similar work at low temperatures, then you cannot do without heating procedures. Moreover, they must be carried out according to building codes. You will now learn how concrete is heated in winter according to SNIP No. 3_03_01-87.

Why Preheat Concrete?

As already noted, concrete is poured not only in summer, but also in winter. The difference lies in the fact that in winter the cement composition requires heating, the price of which can be quite high.

This process is necessary for the following reasons:

• at negative temperatures;
• there is a destruction of the structure of the material, due to which deformed areas form on it, and it eventually becomes less durable.

Advice! Cutting of reinforced concrete with diamond wheels will help you remove protruding irregularities. In this case, it is imperative to use protective equipment in the form of a respirator and special glasses. As for small depressions, they will require diamond drilling of holes in concrete and subsequent filling of depressions with cement mortar to clean them up.

These processes can be avoided, but this will require equipment for heating concrete in winter. You can do without it only if, before the appearance of low temperatures, the composition managed to gain a certain strength. For convenience, the data is included in the table:

Brand composition	Percentage of design value
M-150	Not less than 50%
M-200	Not less than 40%
M-300	Not less than 40%
M-400	Not less than 30%
M-500	Not less than 30%

Types of concrete heating

SNiP number 3_03_01-87 establishes which methods of heating concrete in winter should be used for certain structures.

These methods include:

• thermos;
• preheating of the composition;
• heating in the formwork;
• induction method;
• electrode heating;

• use of heating wires;
• thermos with antifreeze components;
• infrared heating.

We will look at the most common of them.

Heating of concrete with a heating wire

To minimize the heating time of concrete in winter, a special heating wire is used - PNSV.

Its constituent parts are:

1. steel core, consisting of one wire;
2. insulating layer made of polyethylene or PVC.

This method of heating is based on the use of transformer substations, which strongly heat the wires. From them, heat is transferred to the concrete composition. It should be noted that this method is very convenient, since it allows you to adjust the heating level depending on weather conditions.

To mount such a system, you will need a technological map for warming up concrete in winter. It is usually compiled by an energy specialist who is an employee of a construction organization. There are also standard samples of such a document.

This map determines the number and location of heating stations, as well as the placement order and number of heating wires. As the calculation of warming up concrete in winter shows, heating 1m³ of mortar requires an average of 50-60 meters of cable.

This technology is implemented as follows:

1. the heating wire is placed inside the structure being erected - this is done so that the conductors are placed evenly, do not touch the formwork, do not go beyond the edges of the concrete and do not come into contact with each other;

In the photo - laying the wire

1. cold ends are soldered to the heating wire - after that they are removed from the heating zone;

Advice! In order to maintain a thermal field in the soldering area, wrap this area with foil.

1. the wire leads are connected to the transformer equipment in accordance with the instructions contained in the technological maps:
2. the assembled electrical circuit is checked with a megohmmeter;
3. voltage is applied to the created system and the heating process begins, for the correct implementation of which it will be necessary temperature graph warming up concrete in winter, contained in the technological map.

Thermos method

As the name implies, this method is not intended to transfer, but to store heat. It consists in protecting concrete with thermal insulation materials placed outside of it. Thanks to them, the applied mixture loses heat more slowly and gains strength faster ().

The advantage of this method lies in its affordable cost, because even ordinary sawdust can be used as a heater. However, it should be noted that passive heat storage alone may not be enough. In this case, in addition to it, additional methods of heating concrete in winter will have to be applied.

Infrared heating of concrete structures

This method is based on the use of infrared heaters. They are installed in such a way that the radiation emanating from them is directed to an open concrete surface or formwork. The energy transferred by them causes heating of the cement slurry and its accelerated hardening.

Advice! Do not use this method to warm up a structure with a large volume. Infrared rays will not be able to heat it evenly, which will lead to a decrease in the strength of the material. Therefore, for massive products it is better to use other types of concrete heating in winter.

induction heating

This method uses the phenomenon of electromagnetic induction to generate heat. With her energy electromagnetic field is modified and becomes thermal radiation, which is transmitted to the processed material. This transformation takes place in the steel formwork or on the reinforcement.

The instruction for the implementation of this method states that it can only be used in those structures that have a closed loop. In addition, they must have dense reinforcement, in which the reinforcement coefficient is more than 0.5. Another necessary condition is the presence of a metal formwork or the ability to wrap the structure with a cable in order to create an inductor.

Conclusion

When carrying out reinforced concrete work in frosty weather, it is necessary to use heating. Without it, the resulting structure will be less strong and durable ().

The most common heating methods include the use of heating wires, infrared emitters, the use of electromagnetic induction, and thermal insulation. The video in this article will tell you more about how concrete is heated in winter.