The construction of any building, except for small architectural forms, cannot do without the use of reinforcement.

Reinforcing steel performs a lot of tasks, the main of which is to help in the formation reinforced concrete structures... It is produced in a large number of variations. The classification of fittings implies dividing it into different types, intended for different, sometimes directly opposite requirements.

In this article, we will look at what reinforcement classes are, what they are, how to determine the correct reinforcement class, etc.

1 Features and purpose

It should be understood that the use of reinforcement, classes and its varieties is a fairly wide sphere. It is used for various tasks, including not only construction ones.

The main direction is the assembly of load-bearing frames of reinforced concrete structures. The very essence of reinforced concrete structures lies in the combination of reinforcing cages and monolithic concrete.

Without an internal metal rod, concrete will crack and collapse quickly. If it contains construction fittings, then everything changes.

1.1 Classification

The construction industry is huge, it is easy to get confused in it even for a professional. A large number of tasks require a large number of materials that are different in their structure and purpose, and building fittings are no exception.

The rebar classification was invented just for all kinds of simplification and unification processes.

A class of reinforcement or a class of reinforcing steel is a special designation, the so-called marking, indicating the ultimate strength of the bar, its permissible dimensions, definition of tasks, etc.

The table of reinforcement classes allows us to navigate in all the variety that construction reinforcement offers us.

This table is very simple and contains several columns. In the first marking, and then its parameters are indicated:

• limiting diameters;
• withstand loads and resistance;
• the possibility or impossibility of embedding its composition of stressed reinforced concrete structures, etc .;
• relative extension;
• rod length.

The table can be short and extended. A large sample table can contain a lot of parameters, for ordinary people who are completely unfamiliar, the abbreviated table contains only a brief minimum of the necessary information.

2 Classes and their differences

Reinforcing steel and rods are divided into specific classes, each with its own marking. There are old and new designations.

In civil and industrial construction fittings are used:

• A2 (A300);
• A4 (A600);
• A5 (A800);
• A6 (A1000).

The first is the so-called old marking. It is based on the old GOST, which was used in Soviet times. Now builders are gradually moving away from it, taking new brands as a basis.

See also: What is a Christmas tree and what is it for?

Moreover, there are practically no differences between them, except of course the name. Let's take a look at the specific differences between the classes.

The first two samples are - mounting hardware... As you probably already know, rods come in a variety of shapes, from smooth to grooved or crescent.

A smooth profile is made only for unstressed fittings intended for installation works... It is prohibited to install them in the frame of supporting structures. They do not have enough strength, and the lack of edges worsens adhesion to concrete.

Products of the first class have a diameter of 6 to 40 mm and a smooth profile. Products of the second class are produced with a corrugated profile, diameters from 10 to 80 mm, and in some cases even more.

Fittings A3 and higher are produced with a corrugated profile. It is the A3 class that is considered the most popular.

Rods of class A3 have a unique combination of strength, stress resistance, and also have a grooved profile. Reinforcing steel of class A3 is durable and very strong, it is more than enough to cover most construction tasks.

The cost of A3 fittings is not too high, unlike high-class models, which also distinguishes it well from the rest. The range of working diameters is 8-40 mm.

Unlike A3 reinforcement, A4 class can withstand more loads, and better cope with the role of a frame for highly stressed structures, for example, the foundation of a house.

Classes A5 and A6 c civil engineering have not found their application. For him, they are too expensive, if one can say so, of course. Their performance limits exceed any possible requirements and norms in civil engineering.

They are bought for the industry, where it is necessary to build the strongest bearing structures for large-scale projects, such as huge workshops, factories that can withstand a lot of heavy equipment, etc.

For the production of rods of all classes in our time, reinforcing steel 3-5SP is used, if standard carbon samples are meant, and 25G2S or 35GS, if alloy steel is needed

2.1 Additional markings

We have already considered the main types of reinforcement, as well as a table of classes. However, the differences between them do not end there. There are additional markings that indicate certain features of a particular rod.

For example, a record of type A3K is the definition of a reinforcement bar of class A3 with additional corrosion protection. The addition of grade "K" means that the steel has been treated with special compounds, it will be more durable, will not corrode, at least at first, but it will also cost you more.

The addition of the letter "C" means that the fittings are easy to weld. It is very easy to distinguish the entry, just look at the last letter in the abbreviation. For example, reinforcement of class A500C, a typical example of welded construction rods.

Here you need to understand that not every class of such reinforcement products is easily connected to other metals by means of welding. In some situations, steel does not hold welding well, and even such tasks are not always faced by it.

Most knitting reinforcement cages reduced to connecting rods with wire or couplings. Welding plays a secondary role in it.

However, this does not mean that one can do without welded products at all, for which they came up with an additional subclass, intended, among other things, for convenient welding with other metal structures.

There are other, less popular elements of the abbreviation, but we will not consider them. For those interested, the complete class table will help.

2.2 Classification of fittings (video)

2.3 Other species

There is also a concept, shut-off or pipeline fittings. This is a separate type of equipment used in plumbing. It has its own classes, including the most important class of tightness.

The tightness class affects how well the unit performs in the pipeline. Without tightness, it is impossible to assemble a normal pipeline, therefore, serious attention is paid to the tightness indicator.

You only need to know that the level of tightness of the assembly is indicated in its characteristics, which can be viewed upon purchase.

2.4 Determination by eye

Any reinforced building construction, one way or another, consists of fittings. In order not to get confused in the types of structures and their frames, it is advisable to be able to distinguish rods by eye, at least their main characteristics.

This skill will help you in the future. Plus, it's not that hard to develop. Construction reinforcement is very different from industrial one, and the rods of the first classes, with their difference in the profile, are completely recognized without any difficulty.

All you have to do is memorize a few rules, and then follow them every time you need to recognize what kind of product lies under your feet.

First of all, we look at the profile of the rod. A smooth profile is always the first, less often the second class. Products of the third and higher class with a smooth profile are not produced at all. Accordingly, a corrugated profile is evidence that you have fittings of class A3 or higher in front of you.

Industrial grade A5 and A6 products are easier to spot when you've seen them. But in general terms, it can be described as enlarged steel products, with a large length and enlarged crescent or annular profile.

By learning these simple rules, you will learn to distinguish one class from another, without the need for documentation. Everything else will come with experience.

Reinforcing bars are in demand in many areas, therefore they are produced in an extensive range. Each manufacturer is obliged to apply a certain marking to the product, which reflects the physical and mechanical properties and performance of the products.

What are fittings for?

Concrete is not in vain considered one of the strongest and most durable building materials... It withstands compressive loads very well, but has little resistance to tensile or shear loads. Because of this, the structure can quickly crack or break.

To improve the quality characteristics, reinforced concrete has been used for many years. This is a kind of alloy of metal and artificial stone... First, a frame of steel rods is formed in the formwork -. And then concrete is poured. The resulting structure possesses all the necessary set of properties: it is strong, yet quite plastic, withstands almost all types of deformation loads, including vibration, bending, and the like.

Description construction fittings will be incomplete if we do not list the areas of use of steel products. It:

1. Construction of residential small and multi-storey buildings(foundation, monolithic walls, overlap), industrial buildings, complex structures for special purposes (berths, hydroelectric power plants, subway).

2. Construction of various supporting and protective structures (greenhouses, pipeline supports, columns).

3. Screed device, plaster reinforcement.

4. Production reinforced concrete products shaped type (rings, pipes, floor slabs, beams, foundation blocks).

5. Formation of the roadbed, sidewalks, airfield runways, etc.

For each of the above areas, reinforcement of a certain grade, type and diameter is produced. These parameters are indicated as an alphanumeric character set on each bar.

We read the marking symbols

The symbolic code of reinforcing bars begins with the letter:

• A - hot-rolled or cold-rolled (heat-strengthened) products;
• B - cold-deformed;
• K - ropes.

The following series of reinforcing bars are distinguished:

1. А240 or А1 - made of steel grades St3SP, St3PS, St3KP, classified as mounting rods with a smooth profile with a diameter of 4 to 40 mm.

2. A300 or A2 - made of metal of the ST5SP (ps) or ST18G2S series, refers to work items with a corrugated surface with a section of 10-80 mm. Depending on the diameter, it is produced in the form of wire, coiled coils or rods 6-12 m long.

3. A400 / A500 or A3 - produced from steel grades 35GS, 25G2S, 32G2R. This is a working reinforcement of a periodic profile with a cross section of 6-40 mm. It is also produced in the "B" series from metal by cold drawing. This is the most demanded reinforcement for slab, strip or pile foundations.

4. А600 or Аt4 - made of low-alloy heat-strengthened (cold-rolled) steel of class 80С, 20ХГ2Ц, intended for welded structures. The length of the rods is classified as measured (rods of 6, 9 and 11.7 m) or off-gauge (rods and coils up to 12 m). The diameter varies from 10 to 32 mm. The surface is periodic, crescent-shaped.

5. А800 or Аt5 - is made from low-alloyed metal raw materials of 23Х2Г2Т grade. The products are manufactured in a diameter of 6-40 mm and are intended for the formation of welded frames in conventional and prestressed concrete products.

6. А1000 or А6 - from low-alloy steel of 22Х2Г2АЮ, 22Х2Г2Р and 20Х2Г2СР classes. Distinctive feature- the use of any type of welding work without restrictions. The diameter of the rods varies from 6 to 32 mm.

The marking also includes an indication of the special properties of the product:

• K - corrosion resistance. Products undergo galvanizing, galvanizing and other processes, as a result of which a protective film is formed on the surface that prevents oxidation.
• C - connection by welding.
• T - thermomechanically hardened steel.

After the main parameters, the diameter is indicated. For example, the marking А500С Ø12 stands for hot-rolled rebar with a yield index of 500 MPa and a periodic profile, intended for welding, the product diameter is 12 mm.

For certain types of products, GOSTs require the ends of the rods to be painted. The following colors are used for different classes:

1. For low alloy steel fittings:

• A4 - red;
• A5 - red and green;
• A6 - red and blue.

2. For rolled products from heat-strengthened metal:

• AT3 - white and blue;
• AT4 - white and yellow;
• At4K - green;
• AT5 - blue;
• At5SK - white and green;
• At5K - yellow and green;
• AT6 - yellow;
• AT6K - green and black.

Color coding complements alphanumeric coding, provides additional information about the product.

Any concrete structure, especially a foundation monolith, needs reinforcement. It will prevent its deformation and premature destruction. For these purposes, fittings are used. Its rods increase the foundation's ability to withstand heavy construction loads and ground pressure. The most important parameter when choosing a reinforcing material is the diameter of the reinforcement. It is he who ensures the strength of the reinforcing frame and its joint work with the concrete monolith.

Types of reinforcement used in construction

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Metal rods

Manufactured from scrap metal by hot rolling. The process is simple: the scrap is sorted, crushed and melted to the desired temperature, then the molten steel is distributed over the molds. After solidification, the ingots are reheated, crimped and rolled. The final stage is cooling in refrigerators and quality control. Depending on the thickness of the reinforcement, it is produced in the form of rods or coils and is of the following types:

• ductile steel rods (most commonly used to reinforce the foundation);
• channel;
• metal corner;
• I-beam

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Characteristics and marking of metal rods

Rod reinforcement (GOST 5781-822) is corrugated and smooth. The latter is marked A-1. In relation to the first, it is more difficult: depending on the type of corrugation (uniform protrusions, in the form of a screw, at a certain angle, etc.), the marking is A-2, A-3, A-4, A-5 and A-6. But the difference between these products is not limited to the type of corrugation, they differ in strength and steel grade. Depending on these factors, an additional classification of the fittings is made.

The letter “T” in the marking indicates that heat-hardened steel was used for the production of rods. “K” - that the metal has increased resistance to corrosion. “C” - that products of this brand can be welded. “B” - about imparting strength by drawing the rods. The diameter of any type of reinforcement is different, but each marking has its own limitations on this parameter.

For example, products of GOST 10884-81 (thermomechanical and thermally hardened corrugated rods) have a standard diameter of 6 to 40 mm. They are used to reinforce the foundation. For floor slabs and other purposes, more flexible rods STO ASSCHM 7-93 or A500S are used. According to their functional purpose, the fittings are subdivided into working and assembly. The first is designed to compensate for weight loads, the second - for the construction of frames and fixing the working rods.

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Fiberglass (composite) reinforcement

It is made of basalt fiber with an admixture of special strengthening additives in the form of rods of different thicknesses and fibrous additives. The peculiarity of these products is that concrete, into which fiberglass is introduced, breaks at any axial displacement. If the metal rods, after the destruction of the monolith, continue to somehow connect its parts together, then the concrete with the basalt component immediately breaks into separate pieces.

Fiberglass reinforcement can be not only internal, but also external. For this, a layer of the required thickness is applied to the surface of the structures, which will perform a waterproofing and anti-corrosion function. The best way to use basalt reinforcement is road surfaces, walls, partitions.

To strengthen the foundation, it can only be used along with metal rods.

This requirement is due to the fact that the tensile strength of composite rods is 3 times higher than that of steel rods, but the flexural strength is much lower.

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The choice of the diameter of the reinforcement for strengthening the foundation

In order not to be mistaken about the required thickness and number of rods, you need to make a preliminary calculation of the reinforcing frame. Most private developers save on and choose rods by eye, compensating for the possible lack of diameter with a significantly larger number of rods than required.

The choice of reinforcement depends not only on its thickness and quantity, but also on the grade of concrete, the structure of the foundation, its height, the expected weight load, and the type of soil. But there is a single rule for the design of the reinforcing frame: horizontal bars are always made of corrugated reinforcement of suitable thickness. The required parameters of the rods can be found in the table, the data of which are regulated by a complex of construction documentation.

• CIS countries:
  • GOST 5781. Hot-rolled steel for reinforcing reinforced concrete structures,
  • STO ASChM 7–93. Rolled bars made of reinforcing steel,
  • GOST 10884–94. Reinforcing steel thermomechanically hardened for reinforced concrete structures,
  • GOST R 52544. Rolled reinforcing bar welded periodic profile of classes A500C and B500C for reinforcement of reinforced concrete structures;
• Ukraine:
  • DSTU 3760–98. Reinforcing bars for reinforced concrete structures,
  • GOST 10884–94. Reinforcing steel thermomechanically hardened for reinforced concrete structures;
• Eurozone:
  • EN 10080. Steel products for concrete reinforcement. Weldable steel fittings,

as well as technical conditions developed for certain types of reinforcing bars.

Standards STO ASChM 7-93 and GOST 10884-94 are focused on the manufacture of hot-rolled and thermomechanically hardened reinforcement class A500C of the European type. GOST R 52544-2006 differs from the above standards in that it is unified in terms of the main components with the European standard EN 10080. The DSTU 3780 standard was introduced in Ukraine with the abolition of GOST 5781 and GOST 10884 and regulates the properties of smooth and periodic profile reinforcing bars with a diameter of 5, 5 to 40 mm.

European standards (EN 10080), in contrast to GOSTs, for reinforcing bars assume the presence of plasticity categories: A, B, C. Classification of reinforcement by strength class does not imply.

Calculation formulas

Reinforcement for reinforced concrete structures according to DSTU 3760-98

General technical conditions for reinforcing bars are regulated by DSTU 3760–98, introduced in Ukraine with the abolition of GOST 5781–82 and GOST 10884–94. This standard applies to rolled reinforcing bars with a smooth and periodic profile with a diameter of 5.5 to 40 mm, intended for the reinforcement of conventional and prestressed reinforced concrete structures. DSTU 3760–98 permits, by agreement between the manufacturer and the consumer, the manufacture of rolled products with other periodic profiles.

In accordance with DSTU 3760–98, reinforcing bars (indicated by the index A) are subdivided into classes. Classes are determined depending on the normalized value of the conventional yield strength in MPa.

Rental is subdivided into:

• weldable (indicated by the index C);
• resistant to stress corrosion cracking (indicated by the index K);
• non-weldable (no C index);
• not resistant to stress corrosion cracking (no K index).

Reinforcing bars are manufactured in the following classes:

• А240С with a smooth profile;
• А300С, А400С, А500С, А600, А600С, А600К, А800, А800К and А1000 with a periodic profile.

Table 1. Nominal diameter of reinforcing bars, number of meters per ton, weight of one running meter of rolled steel and permissible deviations in weight

Note. The mass of 1 m of reinforcement is calculated at a steel density of 7850 kg / m 3 and is a reference value.

The standard provides for the production of flat bar rebar with a diameter of 5.5 to 40 mm and a periodic profile with a nominal diameter of 6.0 to 40 mm. Reinforcing bars are supplied in rods and coils. Reinforcing bars of a smooth profile of class A240 are manufactured in accordance with GOST 2590 of normal accuracy.

Rice. 2. Reinforcing bars of a smooth profile of class A240

Reinforcing bars of a periodic profile should have crescent-shaped transverse protrusions, which should not be connected to longitudinal protrusions. Longitudinal ridges are optional.

Table 2. Requirements for the main geometric dimensions of the profile

The standard allows the manufacture of rolled products of intermediate sizes and with a different type of periodic profile. The ovality of smooth reinforcing bars is in accordance with GOST 2590. The out-of-roundness of rolled sections (the difference d 1 and d 2) should be no more than 1.2 mm for rolled products with a diameter of 6 to 14 mm, no more than 1.6 mm for rolled products with a diameter of 16 to 25 mm and no more than 2.4 mm for rolled products with a diameter over 25 mm.

Rice. 3. Reinforcing bars of a periodic profile without longitudinal protrusions

Rice. 4. Reinforcing bars of periodic profile with longitudinal protrusions

Reinforcing bars in bars are manufactured in measured and unmeasured lengths. The length of the bars should be between 6 and 12 m.

The standard regulates the maximum deviations along the length of the measured bars. They can be from 0 to +100 mm. By agreement between the manufacturer and the consumer, it is allowed to establish other limit deviations. The curvature of reinforcing bars should not exceed 0.6% of the measured length.

Reinforcing bars with a diameter of 25 mm, class A800:

25 А800 DSTU 3760-98.

Reinforcing bars with a diameter of 10 mm, class A300C welded:

Reinforcement for reinforced concrete structures in accordance with GOST 5781-82

Range and weight of 1 m of rolled metal

Currently, a number of domestic producers of rolled metal products produce reinforcing bars in accordance with GOST 5781–82. GOST 5781–82 was canceled on the territory of Ukraine with the introduction of DSTU 3760–98. This standard applies to round hot rolled steel of smooth and periodic profile intended for the reinforcement of conventional and prestressed reinforced concrete structures.

Depending on the mechanical properties, reinforcing steel according to this standard is divided into classes AI (A240), A-II (A300), A-III (A400), A-IV (A600), AV (A800), A-VI (A1000) ...

Reinforcing steel is produced in rods or coils. Reinforcing steel class A-I(A240) are made smooth, classes A-II (A300), A-III (A400), A-IV (A600), A-V (A800) and A-VI (A1000) - periodic profile. At the request of the consumer, steel of classes A-II (A300), A-III (A400), A-IV (A300) and A-V (A800) are made smooth.

Basic parameters and dimensions. The nominal diameters of periodic profiles should correspond to the nominal diameters of smooth profiles of equal cross-sectional area. Limit deviations of the diameter of smooth sections must comply with GOST 2590–88 for normal rolling accuracy.

Table 1. Profile numbers,
weight of 1 m length of smooth and periodic reinforcing steel
profile, maximum deviations in mass for periodic profiles

Note. The mass of 1 m of the profile is calculated according to the nominal dimensions with a steel density equal to 7850 kg / m 3.

Rice. 1. Reinforcing steel of class A-II (A300) in the usual version

Rice. 2. Reinforcing steel of class Ac-II (Ac300) for special purposes

Reinforcing steel of classes A-II (A300) and Ac-II (Ac300) should have protrusions running along helical lines with the same lead on both sides of the profile.

Steel grades A-III (A400), A-IV (A600), AV (A800), A-VI (A 1000) of both conventional and special design must have protrusions along helical lines that have a right-hand profile on one side of the profile, and on the other - left approaches.

Rice. 3. Reinforcing steel of class A-III (A400) and classes A-IV (A600), A-V (A800), A-VI (A 1000)

Rice. 4. Reinforcing steel of classes A-IV (A600), A-V (A800), A-VI (A 1000) for special purposes

The relative displacements of the helical protrusions on the sides of the profile, separated by longitudinal ribs, are not standardized.

Rice. 5. Fittings in accordance with GOST 5781–82 of conventional design

Rice. 6. Armature in accordance with GOST 5781–82 of special design

Limit deviations of dimensions and weight

Table 2. Dimensions and limits
deviations in dimensions of standard fittings

Table 3. Dimensions and limits
deviations in the dimensions of special fittings

Dimensions for which maximum deviations are not set are not monitored on the finished profile.

Table 4. Mechanical properties of reinforcement

Marking, packaging, transportation

Packing, marking, transportation and storage - according to DSTU 3058–95 (GOST 7566–94) with additions:

• the ends of rods made of low-alloy steels of class A-IV (A600) must be painted with red paint, class A-V- red and green, class A-VI (A1000) - red and blue. Coloring of ligaments is allowed at a distance of 0.5 m from the ends;
• rods are packed in bundles weighing up to 15 tons, tied with wire or wire rod. At the request of the consumer, rods are packed in bundles weighing up to 3 and 5 tons;
• on the bundles, paint is applied in strips of at least 20 mm wide on the side surface along the circumference (at least 1/2 of the circumference) at a distance of not more than 500 mm from the end;
• paint is applied to the skeins in stripes at least 20 mm wide across the turns from the outside of the skein;
• on unpackaged products, paint is applied to the end or to the side surface at a distance of no more than 500 mm from the end;
• on the label attached to each bundle of rods, the accepted designation of the class of reinforcing steel (for example, A-III) or the designation of the class according to the yield strength (A400) is applied.

Symbols

Reinforcing steel with a diameter of 20 mm, class A – II (A300):

20 - A-II GOST 5781-82.

Reinforcing steel with a diameter of 18 mm, class A-I (A240):

18 - A-I GOST 5781-82.

In the designation of rods of class A-II (A300) for special purposes, the index "c" is added:

Thermomechanically hardened fittings for reinforced concrete structures in accordance with GOST 10884-94

Reinforcing steel according to this standard is divided into classes depending on:

• from mechanical properties - strength class (established by the standard of the normalized value of the conditional or physical yield strength);
• from operational characteristics - to welded (index C), resistant to corrosion cracking (index K).

Reinforcing steel is made of classes At400C, At500C, At600, At600C, At600K, At800, At800K, At1000, At1000K and At1200 with a periodic profile according to Figures 1 and 2 or GOST 5781. By agreement between the manufacturer and the consumer, reinforcing steel of strength class At800 and higher is allowed to be made smooth ...

Rice. 1. Periodic profile of reinforcement in accordance with GOST 10884-94 with a longitudinal protrusion

Rice. 2. Periodic profile of reinforcement according to GOST 10884-94 without longitudinal protrusion

Basic parameters and dimensions. Linear density (mass of a rod with a length of 1 m), maximum deviations in size and mass must comply with the established GOST 5781.

Rice. 3. Geometric parameters of reinforcement in accordance with GOST 10884-94

The angle between the transverse protrusions and the longitudinal axis of the bar β is recommended to be taken equal to 45 °. The specified angle is allowed to be taken equal from 35 ° to 70 °.

The values ​​and permissible deviations of size d 2 correspond to those given in this table for size d 1.

The ovality of the rods (the difference between d 1 and d 2 in one section) should not exceed the sum of plus and minus limit deviations in size d 1.

The dimensions for which the maximum deviations are not set are given for building the caliber and are not controlled on the finished rental.

Reinforcing steel with a diameter of 10 mm or more is made in the form of rods, specified in the order in length.

Reinforcing steel with diameters of 6 and 8 mm is produced in coils. The manufacture of reinforcing steel of classes At400C, At500C and At600C with a diameter of 10 mm is allowed in coils.

The rods are made with a measured length from 5.3 to 13.5 m. It is allowed to manufacture rods with a measured length of up to 26 m.

The length of the rods is at the request of the consumer.

The welded reinforcing steel is allowed to be supplied in the form of rods:

• measured length with off-gauge lengths of at least 2 m in an amount of not more than 15% of the batch weight;
• off-gauge length from 6 to 12 m. In a batch of such reinforcing steel, the presence of rods with a length of 3 to 6 m in an amount of not more than 7% of the batch weight is allowed.

Limit deviations of dimensions and weight

Table 1. Geometric parameters of heat-strengthened reinforcement and their maximum deviations, mm

* Limit deviations are ± 15%.

Limit deviations in length

Maximum deviations along the length of rods of measured length must comply with the requirements of GOST 5781.

Mechanical properties and chemical composition

Table 2. Standards for the mechanical properties of reinforcing bars

Marking, packaging, transportation

Rice. 4. Parameters of markings for reinforcement in accordance with GOST 10884-94

Reinforcing steel of a periodic profile is marked with strength class and manufacturer, applied during its rolling in the form of marking short transverse ribs or points on transverse protrusions.

Table 3. Dimensions of marks

Marking short transverse ribs with a height of 0.5 mm, not exceeding the overall size along a circle with a diameter of d 1, are placed on surfaces adjacent to the longitudinal ribs.

Marking points with a height equal to the height of the transverse protrusion are cone-shaped bulges on the transverse protrusions.

The strength class of reinforcing steel is indicated by the number of transverse protrusions according to table 4 in the interval t 1 (see Figures 5 (Scheme of rolling marking) and 4).

Table 4. Marking of the strength class of thermomechanically hardened

* For reinforcing steel of class At800K with a diameter of 18–32 mm.

In the absence of rolling markings, the ends of the bars or bundles of reinforcing steel of the corresponding class must be painted with an indelible paint of the following colors:

• At400C - white; At800 - green;
• At500C - white and blue; At800K - green and red;
• At600 - yellow; AT1000 - blue;
• At600S - yellow and white; AT1000K - blue and red;
• At600K - yellow and red; AT1200 - black.

Coloring of ligaments is allowed at a distance of 0.5 m from the ends. The rods are packed in bundles weighing up to 10 tons, tied with wire. At the request of consumers, rods are packed in bundles weighing up to 3 tons. When delivered in coils, each coil must consist of one piece of reinforcing steel. Coil weight - up to 3 tons. The coil must be evenly tied around the circumference in at least four places. Each of these knits should have an intermediate tie (knit), which is located at the level of the average thickness of the skein. Each skein or bundle of rods must be firmly attached to a label indicating:

• trademark or trademark and name of the manufacturer;
• conventional designation of reinforcing steel;
• batch number;
• stamp of technical control.

If the mechanical properties of reinforcing steel do not correspond to the marking applied during its rolling, the actual strength class must be indicated on the label and in the quality document, and the ends of the bars must be painted with paint in accordance with the given marking rules.

Transportation and storage - according to DSTU 3058–95 (GOST 7566–94).

Symbols

Reinforcing steel designation should contain (according to GOST 10884-94):

• nominal diameter (profile number), mm;
• strength class designation;
• designation of its performance characteristics - weldability (index C), resistance to corrosion cracking (index K).

Reinforcing steel with a diameter of 20 mm, strength class AT800:

20 At800 GOST 10884-94.

The same, with a diameter of 10 mm, strength class At400, weldable (C):

10 At400S GOST 10884-94.

The same, with a diameter of 16 mm, strength class At600, resistant to corrosion cracking (K):

Reinforcing bar welded periodic profile of classes А500С and В500С for reinforcement of reinforced concrete structures in accordance with GOST R 52544

Terms and Definitions. In this standard, the following terms are used with the corresponding definitions:

• rebars of periodic profile- rods with transverse ribs evenly spaced on their surface at an angle to their longitudinal axis to improve adhesion to concrete;
• reinforcing bars of nominal diameter dн, mm - reinforcing bars, the actual diameter of which d, taking into account the permissible deviations, corresponds to the diameter from the assortment according to table 1;
• d, mm - the diameter of a round smooth rod of the same size with a length of 1 m with the same mass as the rolling of a periodic profile, determined by the formula:

,

where m is the mass of rolled section, l is the length of rolled section, mm;

Classification and assortment. Reinforcing bars are subdivided:

• by production method into classes:
  • А500С - hot rolled without further processing or thermomechanically hardened in the rolling flow;
  • В500С - mechanically hardened in a cold state (cold-deformed);
• by product type:
  • rods;
  • skeins.

In the designation of the class: A - hot-rolled or thermomechanically hardened reinforcing bars; B - cold-deformed reinforcing bars; C - welded; 500 - yield point not less than 500 MPa.

Nominal diameter, cross-sectional area and mass of 1 m of rolled length must correspond to the values ​​given in table 1.

Table 1. Nominal diameters,
cross-sectional area and weight of 1 m of rolled length

Note. At the request of the consumer, reinforcing bars are manufactured with a nominal diameter: 4.5; 5.5; 6.5; 7; 7.5; 8.5; nine; 9.5; 45; 50 mm.

The nominal mass of 1 m of the length of the rolled product is determined based on the nominal diameter at a steel density equal to 7850 kg / m 3.

The periodic profile of reinforcing bars should consist of at least two rows of transverse ribs that have a crescent shape and are not connected to the longitudinal ribs. Delivery of reinforcing bars without longitudinal ribs is allowed.

The values ​​of the parameters of the periodic profile and its relative area of ​​crushing f k should correspond to table 2.

Table 2. Values ​​of the parameters of the periodic profile

For hot-rolled and thermomechanically hardened reinforcing bars, the configuration of the periodic profile should correspond to Figure 1 and Table 1, and for cold-worked steel - Figure 2 and general requirements to the profile (see Table 2).

By agreement with the consumer, it is allowed to supply reinforcing bars with a different configuration of the periodic profile, provided that the properties of the rolled products meet the requirements of this standard.

Reinforcing bars are manufactured with a nominal diameter:

• up to 6 mm - in skeins;
• from 6 to 12 mm inclusive - in coils or bars;
• 14 mm and over - in rods.

Bars are made:

• measured length (MD) within the range from 6 to 12 m, specified by the consumer in the order;
• off-gauge length (OD) in the range from 6 to 12 m, determined by the manufacturer. In a batch of bars of unmeasured length, bars with a length of 3 to 6 m are allowed in an amount of not more than 7% of the batch weight.

Limit deviations along the length of bars of measured length - plus 100 mm.

The curvature of the bars should not exceed 0.6% of the measured length.

Construction fittings, specifications and the types of which we will consider further, is used for the reinforcement of prestressed and the manufacture of conventional reinforced concrete structures.

1

The products we describe are used for the production of critical structures and building parts, which, as a rule, operate under high loads. For this reason, they are made from special grades of steel called reinforcing steel. All modern is subdivided into several types, depending on various indicators and characteristics. It happens:

• according to the source material - non-metallic or steel;
• by designation - distribution, working, assembly;
• by the type of profile - smooth, round, periodic profile;
• according to the principle of application - tensioned and non-tensioned;
• by production technology - rope, rod, wire;
• according to the installation method - knitted and welded in the form of nets, individual rods and frames.

In practice, the division of reinforcement into three main types is used:

• on corrugated, which is intended for the production of especially high-quality and high-quality reinforced concrete structures;
• smooth, used as building blocks of standard strength levels;
• for products with a periodic profile that have round shape with protrusions (transverse) and ribs (longitudinal).

Standardization of finished reinforcing products different types perform according to the following indicators:

• angle of inclination, height and pitch of transverse protrusions;
• the value of the actual or conditional yield stress;
• the distance between the centers of the protrusions running sequentially one after the other;
• cross-sectional area (equivalent);
• the angle between the axis of the product rod and its transverse protrusions;
• for corrugated reinforcement - a section of a round profile of equal area.

More details on the classification of reinforcement products will be discussed in the next section.

2

All the required information about the products of interest to us, used in the construction industry, is set out in the 1982 State Standard 5781. It covers all hot rolled steel (round), characterized by periodic and smooth profile. It is this steel that is used to reinforce prestressed and conventional reinforced concrete structures. As a rule, such steel is called reinforcing steel.

According to the voiced GOST, the specified steel is divided into six classes:

• A240 (A-I);
• A300 (A-II);
• A400 (A-III);
• A600 (A-IV);
• A800 (A-V);
• A1000 (A-VI).

The nominal cross-section indicators of periodic profiles vary from 6 to 80 mm (the diameter value denotes the generally accepted profile number), their cross-sectional areas can be 0.283-50.27 square centimeters, and the weight (theoretical) meter of finished products is 0.222-39.46 kilograms.

They produce fittings from low-alloy and carbon steels. The following brands are traditionally used:

• steel 3 (kp, ps, cn) for products with a profile diameter from 6 to 40 mm of class A-I;
• 1NG2S (diameter - from 10 to 80 mm), steel 5 cn / ps (diameter - from 10 to 40 mm), class A-II;
• 10GT: section from 36 to 40 and from 10 to 32 mm, class A-II (special frame);
• 25G2S and 35GS: 6-40 mm, A-III;
• 20ХГ2Ц and 80С: diameter, respectively, 10–32 and 10–18 mm, А-IV;
• 23X2G2T: diameters - 10–32, 6–8 and 36–40 mm, A-V;
• 22Х2Г2Р, 22Х2Г2АЮ, 20Х2Г2СР: 10-22 mm, А-VI.

The chemical composition for the production of reinforcing products is stipulated in the standard 380–88. Check chemical composition finished steel rods are carried out according to State standards 18895–81, 12355–78, 12352–81, 12348–78, 12355–78, 12350–78, 12344–88.

Products of classes A-I-A-V are produced using hot-rolled technology. Steel A-VI is subjected to thermomechanical treatment or tempering at low temperatures, and A-V is only tempered at low temperatures. In some situations, vacation may not be carried out, but only when, twelve hours after rolling, the elongation (uniform) of the finished product is at least two percent, and the elongation is at least nine percent.

The quality of products is determined by various test methods, during which valves are checked for:

• geometric dimensional accuracy;
• ovality and cross-section of profiles;
• toughness (impact) and bending (measurements and analysis according to GOST 1973 7564);
• stretching (standard 12004–81);
• surface quality.

If necessary, non-destructive and dynamic methods are used to control the weight of the rods and their mechanical characteristics. The finished fittings are marked, as you understand, by class. In addition to this, other letters may be present in the product brand, which indicate any specific properties of the products:

• thermally durable - "t";
• for welding - "s";
• hardened by exhaust technology - "v";
• rust resistant - "k".

Thus, if you see the designation AT-V, you can understand that we have in front of us thermally hardened reinforcement, which, by the way, is most often used to create highly loaded structures from reinforced concrete material.

3

All fittings А-VI-А-VI, on which there is no indication of its class, must be marked with paints of different colors:

• blue and red - rods A-VI;
• green and red - A-V;
• red - A-IV.

These products are delivered in bundles (packed) weighing no more than 15 tons. The packaging is tied with wire rod or wire. At the same time, on each individual bundle there must be a label containing information about the class of rods. This information can be indicated in the classical form - А-I, А-II, and so on, or according to the yield strength of the reinforcement (А240, А300, etc.). The paint is applied to the ligaments along the circumference on the side surface, the thickness of the marking line should be from 2 centimeters or more.

Delivery of steel rods is carried out by rail or road (it all depends on the availability of access roads to the construction and on the geometric dimensions of the reinforcement). Naturally, the carrying capacity of the transport should also be taken into account. Transportation of products is allowed in wagons and cars equipped with special spacers, spacers, guy wires, ensuring the safety of the dimensions of the reinforcing bars. The methods for unloading the rods and the types of rigging equipment used for this purpose are established in the technical project.

Warehousing of products is allowed in dry, closed equipped rooms. In open areas, it is possible to store and store fittings with a cross section of 38 millimeters and more. Products with a smaller diameter are stored under a shed. For storage of steel rods, stacks with lining and wooden spacers are used between packages or in cassettes. It is necessary to leave passages between the stacks with a width of one meter or more. The height of the stacks should be up to two meters.