How to determine the class of reinforcement

Classification and types of building reinforcement, properties

The development of the modern housing market and other facilities requires the creation of new building materials that meet modern conditions. An increase in the number of floors in buildings leads to an increase in the requirements placed on construction reinforcement used to strengthen the building frame and foundation. Based on the type of material from which this building product is made, a distinction is made between steel and non-metallic reinforcement.

Steel construction reinforcement

According to the manufacturing method, metal fittings are divided into:

• core;
• wire;
• cable car

Bar reinforcement

One of the most common types is hot-rolled bar construction reinforcement. According to mechanical characteristics, this type of fittings is divided into classes with designations - A400, A500, and so on.

When using rebar to strengthen a foundation, it is tied rather than welded to avoid creating extreme stress centers at the welding points.

Rod reinforcement is made of carbon or low-alloy steels. The introduction of alloying additives into reinforcing steel makes it possible to increase:

• resistance of metal products to corrosion cracking in contact with concrete solutions;
• strength;
• plastic.

Alloy steel reinforcement is used for the construction of buildings in areas with high seismic activity, in regions with cold climates, for the construction of critical facilities and in structures operating with variable loads.

Thermal or thermomechanical hardening operations make it possible to bring the mechanical properties of carbon steel reinforcement closer to the similar characteristics of low-alloy steel. Thermally strengthened reinforcement is marked At.

According to performance characteristics, the reinforcement is divided into weldable - marking C and resistant to corrosion cracking - marking K.

Wire and rope reinforcement

Wire reinforcement is made from cold-drawn wire of ordinary quality or high-strength. For the production of prestressed reinforcement, only high-strength metal products are used.

Rope reinforcement is usually used in a prestressed form. Located in the body of the foundation slab, the rope reinforcement, due to its high strength, successfully absorbs the bending moment from the soil resistance to the load.

To extend their service life, reinforcing ropes are protected with lubricant or a special sheath made of polymer materials.

Non-metallic construction reinforcement

An alternative to metal reinforcement is the result of the introduction of new technologies - composite reinforcement. Otherwise it is called fiberglass or polymer. The basis of this building product is fiberglass, to which polymers based on epoxy resins are added.

Fiberglass reinforcement in appearance consists of rods with a continuous spiral relief with a diameter of up to 12 mm. This is a modern, promising material that has found application in many areas of industry.

In road construction, non-metallic composite reinforcement is used:

• in the production of concrete slabs used for the construction of in-building and temporary bypass roads;
• for reinforcing asphalt concrete pavement of highways, eliminates rutting, prevents the formation of cracks, ensures the integrity of the pavement during its guaranteed service life;
• for the construction of embankments on weak foundations - soils with high humidity, swamps, strengthening the banks of reservoirs;
• in the construction of highway driveways and temporary roads.

In industrial and civil engineering, composite reinforcement is used for:

• reinforcement of structures for various purposes made of heavy, light - cellular and porous, fine-grained concrete; temperature operating conditions of such buildings can range from -70°C to +100°C;
• production of flexible connections in layered brickwork;
• repair of damaged surfaces of brick and concrete buildings.

This group of fittings is also used for:

• strengthening bridge structures;
• installation of enclosing structures;
• runway structures;
• construction of berths, dry docks, to strengthen the coastal zone;
• creating structures that are constantly exposed to aggressive, corrosive environments.

Advantages of composite reinforcement compared to metal:

• the specific gravity of these products is four times less than the density of steel reinforcement;
• higher resistance to corrosion, rotting, warping;
• material savings due to the possibility of using smaller profiles compared to steel ones;
• higher resistance to chemical effects of acids, alkalis, sea water;
• increasing the reliability and durability of constructed structures;
• the ability to carry out installation work without the involvement of heavy construction equipment.

Other types of classification of reinforcement according to various criteria

There are many types of classification of building reinforcement; we list the main defining features.

Classification by profile:

• reinforcement of a periodic profile - the rods have transverse protrusions evenly distributed over the surface at an angle to the longitudinal axis, which are called corrugations, designed to increase the level of adhesion to concrete;
• reinforcement with a smooth profile - rods with a round cross-section and a smooth surface.

According to the nature of the loads perceived, the reinforcement is divided into the following types:

• transverse - these building products prevent the appearance of inclined cracks that arise from oblique shear stresses near the supports;
• longitudinal, which absorbs tensile stresses and prevents the formation of vertical cracks in stretched zones. In structures operating in compression, longitudinal reinforcement together with concrete takes on part of the load.

According to the principle of operation, reinforcement is divided into non-tensioned and stressed. Prestressed reinforcement is subjected to pre-tensioning, which during operation of the structure allows to reduce deflections, prevent the appearance of cracks, reduce metal consumption, and, consequently, the weight of the entire structure.

According to their purpose, fittings are divided into:

• working - serves to accept external loads and stresses from the structure’s own weight;
• distribution - corrugated reinforcement, designed to accurately distribute the load, which allows you to maintain the position of the working rods in their original form;
• mounting - used for assembling a frame, this type of reinforcement helps maintain the desired position of the rods during the concreting process; it can take the form of a mesh or frame;
• anchor - embedded parts;
• structural - a type of reinforcement that is installed without preliminary calculations, solely based on practical considerations, in places where random force impacts may occur.

When constructing grids and frames, distribution and mounting fittings are used in combination with working fittings.

According to the method of distribution, the reinforcement is:

• piece, which are round rods or another profile, assembly of such reinforcement is carried out directly at the construction site by welding;
• reinforcing mesh - ready-made welded or bonded reinforcing products;
• reinforcement frames.

Pipeline fittings have their own classification, and the following main types are distinguished:

• shut-off valves, which are designed to shut off the flow of the working medium in the pipeline. Types of shut-off valves: gates, valves, gate valves, etc.
• control valves - based on the name, this type of pipeline valves regulates the parameters of the working environment.
• safety fittings, for example, safety valves, prevent accidents by establishing a critical value for the state of the medium.

New technologies for reinforcing concrete structures

A new type of reinforcement of concrete structures, such as the use of fiber fiber, is rapidly gaining popularity. Although the use of fiber is not a new idea. The distant ancestors of fiber-reinforced concrete can be considered building mixtures, to which straw, reeds, and sheep's wool were added to give them increased strength.

Modern types of fiber fibers include:

• Steel fiber is a piece of low-carbon wire with ends of a special configuration, which ensures strong adhesion of steel fibers to concrete. Steel fiber-reinforced concrete is used for the production of slabs for airfield runways, for high-speed highways, in shotcrete, anti-landslide structures, in the construction of earthquake-resistant objects, bank vaults, and is used for the construction of self-leveling floors.
• Polypropylene fiber is small fibers of certain sizes, evenly distributed throughout the entire volume of the concrete structure. This group of reinforcing materials significantly increases the operational properties of the structure, preventing the formation of shrinkage cracks, increases the compactability of concrete during vibration and the resistance of materials to temperature fluctuations. This fiber is used to produce leveling solutions. It increases the bending and tensile strength of the material and reduces delamination.
• Alkali-resistant glass fiber is used to prevent the opening of tensile cracks, reduce shrinkage deformation and creep rates, increase moisture resistance, frost resistance, and impact strength.
• Polyamide fiber is a synthetic fiber of the latest generation. Used for additional (secondary) strengthening of concrete structures. It is highly resistant to alkaline environments, solvents, and has high abrasion resistance. The fiber is introduced into the concrete mixture along with sand.

Due to its high melting point, polyamide fiber can be used to construct structures with the required high fire resistance.

• Basalt fiber - pieces of complex basalt fiber of a certain length. They look like friable monofilaments - monofilaments. The introduction of this reinforcing material, due to its high strength, can significantly increase the important properties of concrete: resistance to abrasion, impact, spalling, and temperature fluctuations. Basalt fiber is perfectly distributed throughout the entire volume of concrete, providing high sound insulation, heat insulation and dielectric properties of mortars.

The presence of basalt fiber in concrete makes it possible to reduce stress concentration in places weakened by the presence of structural defects in concrete - shells and microcracks.

The variety of reinforcement products offered by manufacturers indicates the expanding use of new, advanced materials that can bring the construction industry to a completely new qualitative level.

Source: https://www.navigator-beton.ru/articles/klassifikatsiya-i-vidy-stroitelnoj-armatury.html

Reinforcement classes: marking, table of classification of reinforcing steel grades, characteristics and their application

Today, not a single large construction project that uses concrete can do without reinforcement. After all, the latter, despite its high strength, is easily damaged when working in bending and tension.

Thanks to metal rods, this drawback is eliminated, and the material that has gained sufficient strength is able to withstand significant loads of all types without harm to itself. But for each construction project, different materials and, accordingly, different classes of reinforcement will be the appropriate choice.

In one case, it is worth giving preference to thin reinforcement of one grade of steel, capable of working in an aggressive environment for years without harm. And in another you will need thick reinforcement from a different grade of steel. Let's talk about it.

Why are reinforcement classes used?

Today, metal rods are manufactured that differ in a number of factors. To display the characteristics of the material that are most important when choosing for a specific construction project, a special classification of reinforcement was developed. An experienced builder or designer only needs to look at the grade of material to accurately find out all the necessary information:

• manufacturing method;
• Class;
• diameter;
• special properties.

In the same way, when performing design or construction work, a professional can easily imagine all the loads that the material will have to withstand and accurately name the class of reinforcement that will be needed for a particular object. Let's start decoding from the very beginning.

How are fittings made?

First of all, the marking of fittings mentions the manufacturing method. For example, in the A240 brand, the letter “A” indicates that the material is hot-rolled or cold-rolled.

Another letter is “At”. It means that you are dealing with heat-strengthened reinforcement. Its cost is higher, since it is more difficult to produce.

First, the rod heats up to a temperature of 1000 degrees Celsius, after which it cools to +500 degrees in a matter of seconds. Thanks to this, the rod has much greater strength.

Therefore, it finds application in various fields, from construction, when reinforced concrete bears a large load, to mechanical engineering and furniture manufacturing.

Also in some cases the letter “B” is found. It indicates that the reinforcement is cold-formed. In addition, there is the letter “K” - ropes. This is a different specialization, but in order to be able to easily and quickly decipher the class, it will also be useful to remember this letter.

Main types of fittings

The class of reinforcing steel itself is mentioned next. There are six classes in total:

• A240;
• A300;
• A400;
• A600;
• A800;
• A1000.

In addition, in some cases there is a different designation - A1, A2 A6. But this designation is considered obsolete - it was used in the Soviet Union and it was the one that was used by the GOST in force at that time. Today, most manufacturers and buyers use a different classification of the range of fittings.

A240 is the only brand that is produced with a smooth section. Its diameter can range from 6 to 40 millimeters. Simplicity of manufacture reduces the cost of the material, but it cannot be used as a main worker - only as an auxiliary one, for example, in the manufacture of a frame. A smooth surface impairs adhesion to concrete, resulting in deterioration of the properties of reinforced concrete. Temporarily can resist stretching up to 380 megapascals.

All other classes have a periodic cross-section, that is, there are ribs on the surface that improve the quality of adhesion to concrete. For greater clarity, let’s bring all their characteristics together - the table will make it easy to select the appropriate material, as well as understand the meaning of the marking:

Class Diameter, mm Tensile strength, MPa Yield strength, not less than, MPa

A-2	10—80	500	300
A-3	6—40	600	400
A-4	10—22	900	600
A-5	10—22	1050	800
AT-4	10—40	900	600
AT-5	10—40	1000	800
AT-6	10—22	1200	1000
AT-7	10—32	1400	1200

As you can see, the diameter may vary, which allows you to select the appropriate material for each specific construction project.

How to determine the diameter?

The most important parameter is the diameter. It determines what load it can withstand, its ductility limit and a number of others. Therefore, when designating the brand of reinforcement, its diameter must be indicated. The entire classification is as follows: A200 D30. It is the last number coming after the letter D or the symbol Ø that shows the thickness of the rod.

Some meticulous buyers, when choosing a suitable material, check its actual thickness with that indicated in the passport using a caliper. They are often surprised by a serious discrepancy - the difference can be several millimeters.

However, it is worth considering that with a periodic section (that is, the presence of ribs on the rod), it is impossible to measure the nominal diameter. In narrow places it will be less than the specified value, and on the edges it will be more. Therefore, experts use the average value.

Its characteristics are indicated in the tables.

Special properties

Also, fittings are distinguished by purpose. In relatively rare cases, a metal rod must have a number of properties that make it suitable for the application. This is achieved in different ways - by adding special impurities to the alloy or by special processing. In any case, the fittings acquire unique characteristics. The presence of special properties is indicated by the letter at the end of the encoding. The following designations are usually found:

• C – weldable. Usually, when assembling a frame from reinforcement, the use of welding is extremely undesirable - overheating reduces strength and, in addition, reduces resistance to corrosion. But there is a special metal that contains additives that increase its ability to withstand negative consequences;
• K – resistant to corrosion. Thanks to special additives (chrome, tungsten and others), the fittings are able to work for many years not only in conditions of high humidity, but also in contact with an aggressive environment - alkaline, acidic, with a high oxygen content;
• SK is a reinforcement that has both of the above properties. It has a high cost, so it is used relatively rarely, only when the usual one cannot cope with difficult operating conditions.

Of course, there is a special GOST for this product that imposes special requirements on it.

What fittings are the most popular?

Experienced specialists will agree that A3 (A400) fittings have a number of qualities that make it the most popular.

To begin with, class A3 reinforcement is always produced with a corrugated surface, which allows it to be used as the main load-bearing rod in the frame.

Fitting class A-III (A400)

Different production technologies make it possible to produce any type of material: hot-rolled, cold-rolled and thermally strengthened. Therefore, choosing exactly the steel grade that is needed to perform a specific job is as easy as possible.

It is important that the range of diameters is very wide - metal rods with a thickness of 6 to 40 millimeters are produced. So, they can be used both when reinforcing small products (strip foundation for a garage or bathhouse) and when working with huge volumes of concrete (bridges, tunnels, multi-story monolithic buildings).

In addition, important advantages of the material include its resistance to high humidity and significant loads. It is durable and strong.

The ability to bend rods at an angle of up to 90 degrees without heating simplifies the process of assembling corner frames. This is extremely important - corner joints often cause serious problems for builders. Reinforcement bent at the right angle guarantees the reliability and durability of the frame even under heavy loads.

Currently, in civil and industrial construction of monolithic structures, more and more preference is given to A500C class reinforcement, due to its high strength, welding properties and ability to withstand any type of load.

Now you can easily navigate the classification developed for fittings, you know about the main properties of this valuable building material, which means that without any problems you will select exactly the products that will be the best option for a particular object. You won’t have to overpay when purchasing material or sacrifice the reliability of the structure being built.

Source: https://VseoArmature.ru/vidy/klass-armatury

Types of fittings

   Reinforcement is a set of interconnected elements that, when working together with concrete in reinforced concrete structures, perceive tensile stresses (beams), and can also be used to strengthen concrete in a compressed zone (columns).

   Reinforcement elements are divided into rigid (rolled I-beams, channels, angles) and flexible (individual bars of smooth and periodic profile, as well as welded or knitted meshes and frames). Due to personal interests, in this article I will consider flexible rod reinforcement. Reinforcing bars can be steel, composite and even wood origin (for example, bamboo), etc.

Classification

    Reinforcement is classified according to a number of criteria: by purpose, orientation in the structure, conditions of use, and by the type of material from which the reinforcement is made.

The fittings are designed according to their purpose:

• working reinforcement (the cross-section is assigned by calculation, it absorbs forces in the elements from the main load)
• structural (distribution) (the cross-section is assigned according to the minimum percentage of reinforcement, absorbs shrinkage/expansion, exposure temperature)
• mounting (installed to combine working and structural into grids and frames)
• anchor (embedded parts)

By orientation in the design:

• transverse - reinforcement that prevents the formation of inclined cracks from emerging shear stresses near the supports and connects the concrete of the compressed zone with reinforcement in the tensile zone;
• longitudinal - reinforcement that absorbs tensile stresses and prevents the formation of vertical cracks in the tensile zone of the structure.

According to the conditions of use:

• prestressed reinforcement;
• non-stressed reinforcement.

Prestressed reinforcement in prestressed reinforced concrete structures can only be working.

By production:

— hot-rolled rod reinforcement;

- cold-drawn wire reinforcement.

In appearance it happens:

— smooth fittings (smooth matte surface along the entire length);

- periodic profile (protrusions, rib notches). This shape allows for increased adhesion to concrete and accordingly strengthens the structure. Today, 3 types of periodic profiles are produced - crescent-shaped, ring-shaped and mixed.) The profile of the reinforcement affects the degree of its adhesion to concrete.

The ring-shaped (a) profile complies with GOST 57-81, the crescent-shaped profile (b) is typical of European manufacturers, but domestic factories also produce reinforcement of this profile. The mixed profile (c) is a relatively new profile with increased adhesion, introduced for reinforcement of class A500, i.e. Lower class fittings with this profile are not produced.

This profile not only allows you to easily and unambiguously determine the class of reinforcement, but also significantly improves its adhesion to concrete (by an average of 20%) and rigidity (by 30%). Information for those particularly interested is presented in more detail here.

    Depending on the chemical composition, strength, rolling technology, post-rolling treatment, weldability, corrosion resistance, etc. — reinforcing steel has a certain marking. Reinforcing steel classes are designated as the letter A with an alphanumeric index.

Strength classes of reinforcement (yield strength)

• A-I, A-II, A-III, A-IV, A-V, A-VI. Outdated marking according to GOST 5781-82
• A240, A300, A400, A500, A600, A800, A1000 - Modern designation.
• At400, At500, At600, At800, At1000, At1200 Thermally strengthened construction reinforcement for the manufacture of reinforced concrete products and reinforced concrete products. There is thermomechanically strengthened reinforcing steel, which is used in reinforced concrete factories in the manufacture of prestressed structures and products. For example: prestressed floor slabs.

Additional designations, depending on operational characteristics.

• The letter A at the beginning of the marking means that this is a rod reinforcement;
• The letter B at the beginning of the marking is wire;
• The letter K at the beginning of the marking is ropes;
• The letter C indicated after the numbers indicates that this reinforcement can be welded by electric welding. Basically, in private construction, reinforcement cages are knitted with wire. But if electric welding is used, you need to be sure that your reinforcing bars can be welded. For example: A500C fittings;
• The letter T indicates that this reinforcement is thermally strengthened;
• Letter B - reinforcement reinforced by hood;
• The letter K indicated in the class indicates resistance to stress corrosion cracking.

Marking

To conveniently and quickly determine the class of reinforcement, some metallurgical plants apply rolling markings to rods in the form of convex marks on the protrusions; the number of protrusions between the marks means the class of the reinforcement (see figure below). Markings are applied every meter.  

    If there is no such marking, then identification is provided by the applied paint on the ends or tail parts of the reinforcing bars. Marking colors:

A400С - white;

A500C - white and blue;

A600 - yellow;

A600C - yellow and white;

A600K - yellow and red;

A800 - green;

A800K - green and red;

A1000 - blue;

A1000K - blue and red;

A1200 - black.

     And sometimes you come across reinforcement with direct alphanumeric rolling markings on the rod, and even indicating the diameter. In the photo above, for example, A500 C fittings with a diameter of 12 and 16 mm.

   The weight of one linear meter of reinforcing bar directly depends on the diameter (profile number). On the left is a table of the ratio of lengths and weights of reinforcing bars of different diameters in accordance with GOST 5781-82, as well as the cross-section of the reinforcement.

It is worth noting that GOST provides for amendments and possible maximum deviations from the data indicated in the table. Depending on the manufacturer’s plant, the GOST ratio of the weight of the reinforcement to its length can range from -7 to + 9%.

So, when ordering A500C reinforcement for the foundation from Steel Materials LLC, the manager considered the weight of the reinforcement to be 5% greater than I expected from the reference books, which, however, he immediately warned me about.

What to choose? Practice  

   For the reinforcement of monolithic strip foundations, periodic profile reinforcement of class A-III (A400) made of steel grades 35GS, 25G2S is mainly used. Such steel reinforcement is a round profile with two longitudinal ribs and transverse projections running along a three-way helical line.

The periodic profile of the reinforcement provides better adhesion of the reinforcement to the concrete, in contrast to smooth profile reinforcement, which is recommended for use as strapping (clamps) of longitudinal reinforcement bars. Marking A400 corresponds to the yield strength of this class of steel reinforcement (390 N/mm2). This class of fittings is already obsolete.

Since the 1990s, European countries have switched to a single class of welded reinforcement with a yield strength of 500 N/mm2. The use of such reinforcement of class A500C instead of reinforcement of class A400 (A-III) provides more than 10% savings in steel in construction.

 Rebar A-400 and A500C of periodic profile are produced in a domestic version with annular projections (option “a” in the figure above) and in a version with crescent-shaped projections (option “b” in the figure above).

The ring profile (a) provides better adhesion strength of the reinforcement to the concrete, and the crescent profile (b) increases the endurance of the reinforcement to periodically repeated loads. For reinforcing foundations, the domestic ring reinforcement profile is better suited. Less common is a four-sided crescent-shaped reinforcement profile, which combines the advantages of both types of periodic reinforcement profile (c).  

   Reinforcement of class A-III (A400) is not allowed to be connected by welding. When exposed to local temperature, a significant weakening of the steel structure occurs. Structural changes in steel occur in the welding area and in adjacent areas over a length equal to four reinforcement diameters in each direction. Only special weldable classes of reinforcement are intended for welding - A400C, A500C.

The American Concrete Institute code emphasizes that welding of cross bars is prohibited, as this may cause the rebar to break. If the class of reinforcement is not known and it is necessary to make a welded connection of longitudinal bars, then the welded reinforcement (45-55% along the length of the bar) must be preheated to 200 °C to minimize loss of steel strength.

The minimum length of the weld must correspond to 10 diameters of the rod of the reinforcement being welded. 

   The most popular diameters of longitudinal working reinforcement in domestic construction are 10, 12, 14 and 16 mm. Transverse mounting - 6.8mm.

     When I bought reinforcement for my foundation, I didn’t know anything about what I’m writing now - I just came to the office and ordered reinforcement with a diameter of 12 mm.

It’s good that the invoices have been preserved, thanks to which I know that I have A500C reinforcement poured into my concrete, which I’m very happy about! Now we still have to buy fittings and I have already formed some statistical observations in this regard.

At metal depots in Brest, fittings with a periodic profile with a diameter of 12 mm are mainly made in Ukraine and mainly of the A500C brand. I personally haven’t come across another one yet. I would recommend it for use in foundations.

Source: https://www.project-house.by/types-reinforcement

Valve class: modern and outdated markings

Buyers of machines for bending reinforcement have a serious problem: the lack of a clear idea of ​​what kind of material they will be working with.

As a result of communicating with customers, we came to a very disappointing conclusion - most people, at best, have an idea of ​​​​the diameter of the fittings. They sincerely believe that differences in types of material are determined solely by this parameter. But that's not true! Like all other building materials, reinforcement is classified according to the tasks it is intended to perform.

Reinforcing steel is classified according to several parameters:

• chemical composition;
• manufacturing technologies;
• conditions of use;
• character of the profile and others.

International designations of reinforcement classes

They were introduced relatively recently, at the request of metallurgical plants. This step was taken with the aim of introducing their products abroad.

Today in our country there are two parallel classifications for the designation of the same fittings.

For convenience, the fittings are marked with two markings at once

For example, it might look like this: “A-I (A240).”

The above notation is a combination of two systems:

• outdated (still Soviet) - A-I, A-II, A-III, A-IV4, A-V, A-VI;
• modern - A240, A300, A400, A500, A600, A800, A1000.

The fittings can also be indicated by additional symbols:

• “At” - heat-treated (for example, At400).
• “C” - weldable (for example, A500C).
• “K” - corrosion-resistant (for example A600K).

As you can see, the letter “A” is always preserved. The numerical designations change: the higher the number (yield strength), the higher the class of reinforcement. Accordingly, the strength and reliability of a structure built using reinforcement increases in proportion to the increase in numerical values ​​(yield strength).

For example:

• A240 (A-I) are smooth cold-rolled rods;
• A400 (A-III) are corrugated hot-rolled rods that provide better adhesion to concrete and can withstand significant loads.

Today, the most popular reinforcement in domestic construction is class A400 (A – III).

Subtype of fittings, marked VR and VR – I

This is reinforcing wire with a diameter of 3-5 mm of a smooth and periodic profile.

Table of modern and outdated valve class designations

A240	A.I.
A300	A-II
A400	A-III
A600	A-IV
A800	A-V
A1000	A-VI

A500 is a new class, introduced in 1993. It did not receive the outdated marking, but almost completely repeats the performance of A400 (A-III).

How to determine the class of reinforcement

This is not difficult to do - just carefully study the inscriptions on the label. Each coil of reinforcement must have a label with information about the manufacturer, reinforcement class, batch number, rod length, etc.

The coils or ends of the reinforcement bundles are painted with paint (in case the label is lost during transportation).

Correspondence of color to reinforcement class:

• white - At 400 C;
• white and blue – At 500 C;
• yellow – At 600;
• yellow and white – At 600 C;
• yellow and red – At 600 K;
• green – At 800;
• green and red – At 800 K;
• blue – At 1000;
• blue and red - At 1000 K;
• black – At 1200.

The non-heat-treated ends are painted red.

You don't have to memorize the classification of fittings by heart. However, before you buy a machine for fittings, decide what type of material it will work with. Be sure to inform your manager about this, who will help you make the right choice.

Source: http://s-awangard.ru/articles/klass_armatury_sovremennye_i_ustarevshie_markirovki/

Classes and grades of reinforcement steel

06.06.2019

Reinforcement is used to improve the performance of concrete. It gives an increase in strength and allows you to withstand heavy loads without cracking or crumbling. Without the use of a frame made of metal rods or wire mesh, it would be impossible to construct concrete supports, bridges, underground structures and other structures.

According to purpose, reinforcement is divided into four types:

• Anchor . Used to create embedded elements in concreting.
• Constructive . Eliminates deformation of the structure and distributes loads. Thanks to this, the concrete does not settle and thermal expansion is compensated.
• Working . It is necessary to take the main load and increase strength.
• Assembly . It is used when you need to connect disparate parts into a single frame.

Product characteristics indicate where it can be used. We sell prestressed and non-prestressed reinforcement, adapted for installation in supporting and unloaded structures.

According to the installation method, longitudinal and transverse varieties are selected. The first type resists vertical cracks well, the second - inclined ones.

Classes of fittings and areas of their use

On sale you will find rods that vary in diameter, length and surface type. There are smooth and grooved varieties. For ease of designation, they were divided into classes, for each the area of ​​use and a set of characteristics, as well as the steel grade of the reinforcement, were specified.

There are the following types:

• A1 (A240, AI). One of the most common types of materials for the manufacture of reinforced concrete products is trays, floor slabs, and support elements. The diameter ranges from 6 to 40 mm. Depending on this parameter, the product is supplied in skeins or rods.
• A2 (A300, AII). The diameter reaches 80 mm. Can be used as a frame for piles. Installation in concrete increases its resistance to vertical loads.
• A3 (A 400, A III ). There are ribs on the surface of the rod. Corrugation improves adhesion to concrete. Diameter up to 40 mm. Products up to 10 mm are supplied in skeins, larger quantities in rods.
• A4 (A600, AIV). Metal elements are used as the basis for reinforced concrete products for various purposes. They are suitable for the production of parts subject to dynamic loads. It is also widely used in construction – not only civil, but also industrial.
• A5 (A800, AV). The material is created from structural low-alloy steel. The recommended area of ​​application is the creation of prestressed concrete products. Suitable for the construction of bridges and hydraulic structures.
• A6 (A1000, AVI). The characteristics allow the use of steel rods in the most critical areas - from nuclear industry facilities to dams. Since the product is expensive, it is produced upon pre-order. Provides good adhesion to concrete due to the special structure of the ribs - they are ring-shaped or crescent-shaped. Can also be used with reinforced concrete products. Reinforcement significantly extends their service life.
• A400C . Manufactured using the hot-rolled method. The diameter reaches 40 mm. It is distinguished by the presence of two ribs located longitudinally. Used in private construction, in the construction of low structures.
• A500C . Additionally strengthened by mechanical and thermal methods. Not adapted to strong dynamic loads, used with basic types of reinforced concrete products.
• A600C . It is characterized by increased resistance to corrosion due to the addition of molybdenum and vanadium to the alloy. Suitable for monolithic houses, construction in areas with high seismic activity.

Below is a table of classes and brands of fittings with the main characteristics listed.

Reinforcement class	Rolled diameter	steel grade	Mechanical properties, no less
σ T , N/mm2 yield strength	σ B , N/mm2 tensile strength	σ S , % relative. elongation	Cold bending test, C – mandrel diameter, B – rod diameter
A-I (A 240)	6-40	St3kp, St3ps, St3sp	235	373	25	180 deg C=d
A-II (A 300)	10-40	St5sp, St5ps	295	490	19	180 deg C=3d
40-80	18G2S
AC-II (AC 300)	10-32	10GT	295	441	25	180 deg C=d
A-III (A 400)	6-40	35GS, 25G2S	390	590	14	90 deg C=3d
6-22	32G2Rps
A-IV (A 600)	10-18	80C	590	883	6	45 degrees C=5d
10-32	20ХГ2Ц, 20ХГ2Т
А-V (А 800)	10-32	23Х2Г2Т, 23Х2Г2Ц	785	1030	7	45 degrees C=5d
A-VI (A1000)	10-22	22Kh2G2AYu, 22Kh2G2R, 20Kh2G2SR	980	1230	6	45 degrees C=5d

Steel grades for the production of fittings

The grade classification and classes of reinforcing steel indicate the performance characteristics. Among the most common varieties:

• 20GS . Structural low alloy steel. It lends itself well to welding, therefore it is suitable for the manufacture of reinforcing frames.
• 35GS . Another structural low-alloy variety. Well protected from aggressive environments and pressure.
• St3kp . Structural carbon of ordinary quality. Shows good adhesion to concrete and does not deteriorate due to pressure, vibration, or exposure to aggressive environments.
• 22Х2Г2АУ . The characteristics of this low-alloy structural steel make it suitable for use in both conventional and prestressed concrete structures.
• 80C . Durable material that can withstand high stress and aggressive environmental influences.

The table below shows the correspondence of the class of reinforcing steel, the grade of raw materials used in the manufacture and the profile diameter of the created rod.

Table of reinforcement classes and steel grades - steel for reinforcement according to GOST 5781-82

Profile type	Class	Diameter, mm	steel grade
Smooth profile	A1 (A240)	6-40	St3kp, St3ps, St3sp
Periodic profile	A2 (A300)	10-40, 40-80	St5sp, St5ps, 18G2S
Periodic profile	A3 (A400)	6-40, 6-22	35GS, 25G2S, 32G2Rps
Periodic profile	A4 (A600)	10-18 (6-8), 10-32 (36-40)	80С, 20ХГ2Ц
Periodic profile	A5 (A800)	10-32 (6-8), (36-40)	23Х2Г2Т
Periodic profile	A6 (A1000)	10-22	22Х2Г2АУ, 22Х2Г2Р

What determines the scope of application of fittings?

Several factors influence where a particular type of rod will be used:

• Degree of workload.
• Potential threats.
• Scope of application of reinforced concrete products or location of the reinforced building.

Before you buy a batch of steel rods, you need to understand what the loads acting on them will be - static or dynamic. The mechanical parameters of the future frame are also taken into account. If you need to connect several parts by welding, the steel must have a good level of weldability.

Source: https://spbrmk.ru/klassy-i-marki-stali-armatury/

Classification of fittings

Construction fittings are a universal product used in various industries from the construction of buildings to the assembly of parts in mechanical engineering, the manufacture of machine tools and other mechanisms. Due to the wide range of applications and expected design loads, reinforcement is divided into classes according to strength, diameter and type of section.

Classification of fittings as a way of arranging products

The group of reinforcing products includes many types of profiles, which differ in:

• Section shape;
• Diameter from 6 mm to 80 mm;
• According to strength, which is determined by the raw materials used (grade of steel).

One class includes a group of rolled products with a certain range of characteristics. This greatly simplifies the orientation of specialists in the material group when calculating and selecting products with the required characteristics.

Thus, we can formulate a definition: a reinforcement class is an indicator that characterizes the properties of products in a certain range of values ​​according to regulatory documents.

To simplify the work, tables have been compiled indicating the main characteristics of the products.

Profile type	Old designation	New is indicated.	Diameter, mm	Tensile strength, MPa	Relative elongation after rupture, %	steel grade
Smooth	AI	A240	640	373	25	St3kp, St3ps, St3sp
Periodic	AII	A300	1040	490	19	St5sp, St5ps
4080	18G2S
Periodic	AII	AC300	1032	441	25	10GT
Periodic	АIII	A400	640	590	14	35GS, 25G2S
Periodic	622	32G2Rps
Periodic	АIV	A600	1018	883	6	80C
Periodic	1032	20ХГ2Ц, 20ХГ2Т
Periodic	А.V.	A800	1032	1030	7	23Х2Г2Т(Ц)
Periodic	AVI	A1000	1022	22Kh2G2AYU (R, SR)

The old and new classes of reinforcement are determined by different regulatory documents, but their values ​​do not change significantly. Outdated markings (AI, AII-AVI) are given in 5781-75, and modern ones in GOST 5781-82. Currently, calculations are carried out on the basis of the new standard, but the designations are still often written in pairs as AII (A300).

There is a way to determine the class of reinforcement: manufacturers paint the ends of low-alloy steel rods in different colors:

• A4 – red;
• A5 – red and green;
• A6 – Red and blue.

What does the reinforcement class mean: explanation

The range of rolled steel is regulated by GOST 5781-82. According to the document, products are divided into main groups according to their main characteristics:

1. According to manufacturing technology
   • Hot rolled rod;
   • Cold drawn (wire).
2. By the nature of the profile:
   • Smooth;
   • Periodic, which, in turn, can be ring-shaped, crescent-shaped, mixed.
3. According to the method of work in structures and products:
   • Strained;
   • Unstressed.

Diameter of reinforcement, mm Sectional area, cm2 Weight of reinforcement, kg/m Steel class

3	0,071	0,055 (0,051)	Ordinary and high-tensile wire
4	0,126	0,098 (0,090)	Ordinary and high-tensile wire
5	0,196	0,154 (0,139)	Ordinary and high-tensile wire
6	0,283	0,222	A-III, ordinary and high-tensile wire
7	0,385	0,302	A-III, ordinary and high-tensile wire
8	0,503	0,395	A-III, ordinary and high-tensile wire
9	0,636

Source: https://stroikadialog.ru/articles/fundament/klassifikaciya-armatury

Classes and types of building reinforcement

Concrete itself has high compressive strength, but tensile strength is 10-15 times less, and this can be compensated for by placing reinforcement in it. The combination of these two materials makes it possible to obtain products that have excellent characteristics for both the first type of load and the second.

Construction fittings

First of all, construction reinforcement is divided into classes, set depending on the steel used. Here are some examples of such markings - A240, A400C, A600, A600K, A800, A800SK and A1000 . Additional letters in the designation have their own meaning.

So C stands for welded by electric welding , and K indicates resistance to corrosion under voltage .

The absence of these letter indices in the marking indicates that the reinforcement is non-weldable and not resistant to corrosion cracking.

Knitting reinforcement without markings

Most of these products are now produced without the C marking, which means they should be mounted together with wire. When welded, such reinforcement will become brittle at the joint. Among other things, during production, reinforcement can be subjected to additional heat treatment, which increases the strength characteristics of the steel. Such improved fittings are A.

Reinforcement is usually supplied in three types - coils, rods and in the form of welded mesh . It is usually produced as a coil with a diameter of less than 10 mm; with a larger diameter it is produced in rods. At the moment, products of 10-12 mm are most in demand. And the last type is used for reinforcing slabs, floors, walls and foundations, etc., and is a welded structure.

Steel reinforcement by type, profile and application

In addition to classes, reinforcement can be divided depending on the method of its production - rod, wire and rope . The rod is made from rolled steel, and it is the most common in both private and industrial construction. The range of diameters of such fittings is from 6 mm to 0.8 meters.

Rope fittings

A much rarer type, mostly used for reinforcing masonry and having a small cross-section, from 3 to 5 mm, is wire reinforcement. It is made from cold drawn wire. For this purpose, ordinary quality wire is used, but high-strength wire is also in demand and even mandatory in the production of prestressed reinforcement.

Rope reinforcement is used in a stressed, that is, tensioned, form and copes well with bending loads. Thanks to this, concrete structures are significantly strengthened. Also, the service life of such fittings can be extended using special lubricants or polymer coatings.

Classification by profile divides reinforcement into only two groups - periodic and smooth . A periodic profile requires the presence of special stiffening ribs, which, among other things, increase the adhesion of the reinforcement to concrete. Moreover, here we can note three subspecies depending on the type of corrugation - ring, crescent and mixed . Well, the smooth profile, in accordance with its name, has no ribs, the rods are smooth and have a round cross-section.

The purpose of the reinforcement according to the loads it accepts is also important - transverse and longitudinal . The transverse one will prevent cracks from appearing in reinforced concrete products from oblique, shearing stresses on the structure, and the longitudinal one will be useful in structures with a large compressive load, taking on part of the load.

Innovation

Composite reinforcement

Relatively recently, a new type of reinforcement has appeared - non-metallic , also known as composite, polymer and fiberglass . It is produced on the basis of glass fiber with special polymer additives based on epoxy resins. Visually, it consists of rods with a spiral cross-section and a rather small diameter of up to 12 mm.

Now such fittings have already partially found their application in industry, but it is too early to talk about mass application. In private construction, they are not yet used at all. Considering the above circumstances, talking about the prospects for the practical operation of such products can be very vague. No voluminous statistics have yet been accumulated on this issue, and how it will behave under different conditions is not known for certain.

Source: https://nerudnye-spb.ru/blog/klassy-i-vidy-stroitelnoj-armatury

Steel (Metal) reinforcement

Steel rod reinforcement is widely used in construction. This is an integral element of reinforced concrete structures, increasing the flexural and compressive strength of cement stone. We will tell you what metal fittings are, what they are made from, what classes they are divided into and the features of their use.

Rebar manufacturing technologies

According to the production method, the fittings are:

• Hot rolled rod;
• Cold drawn wire.

In both cases, low-alloy or carbon steel of different grades is used, depending on this, it is divided into 6 classes A-IA-VI.

The hot production method involves forming a softened steel rod blank using rollers. As the temperature increases, the bonds of the metal structure are strengthened; accordingly, reinforcement made from it is able to withstand greater loads compared to cold-drawn products, and the tensile strength increases.

Cold drawn reinforcement is obtained from an unheated workpiece passing through crimping rollers.

To increase the strength of the reinforcement, it is subjected to heat treatment or galvanizing - the procedure ensures the resistance of the metal to moisture and aggressive environments.

Rod reinforcement with a cross-section of 8 mm or more is produced in individual rods, thin wire reinforcement is produced in coils.

Classification and marking of fittings

The classification of reinforcement involves dividing products according to the class of steel used for the production of rods. The division is regulated by GOST 5781-82 “Hot-rolled steel for reinforcement of reinforced concrete structures”:

Class, old designationClass, new designationProfile typeColor designation of rod

A.I.	A240	Smooth	—
A-II	A300	Periodic*
A-III	A400
A-IV	A600	Red
AV	A800	Red and green
A-VI	A1000	Red and blue

*by agreement with the customer, A-IIA-V steel can be manufactured with a smooth profile.

Classes, in turn, are divided into subclasses, which are designated by additional indices:

• “C” is a rod steel that is suitable for welding;
• “T” - heat-treated product;
• “K” - corrosion-resistant steel, i.e. treated with zinc;
• "SK" is a corrosion-resistant steel that can be welded.

Metal fittings of different classes are made from various steel alloys, which determine its technical properties. In this case, the diameter of the rods is taken into account:

Reinforcing steel class Steel grade Profile diameter, mm

A-I (A240)	StZkp, StZps, StZsp	640
A-II (A300)	St5sp, St5ps18G2S	10404080
Ac-II (Ac300)	10GT	1032(3640)
A-III (A400)	35GS, 25G2S32G2Rps	640622
A-IV (A600)	80C	1018(68)
20ХГ2Ц	1032(3640)
AV (A800)	23Х2Г2Т	(6-8)1032(3640)
A-VI (A1000)	22Kh2G2AYu, 22Kh2G2R, 20Kh2G2SR	1022

The table is compiled according to GOST 5781-82.

Mechanical properties of reinforcing steel

Bar reinforcement of different brands has individual mechanical properties, which are taken into account when choosing a product for reinforcing concrete structures. The main ones are given in table No. 8 GOST 5781-82:

Reinforcing steel class Yield strength st Tensile strength sv Relative. elongation d5,% Uniform elongation dr, % Impact strength at a temperature of -60 ° Bending and cold testing, where c is the thickness of the sender, d is the diameter of the rod

N/mm2	kgf/mm2	N/mm2	kgf/mm2	MJ/m2	kgf×m/cm2
AI (A240)	235	24	373	38	25	—	—	—	180°; c = d
A-II (A300)	295	30	490	50	19	—	—	—	180°; c = 3d
Ac-II(Ac300)	295	30	441	45	25	—	0,5	5	180°; c = d
A-III(A400)	390	40	590	60	14	—	—	—	90°; c = 3d
A-IV(A600)	590	60	883	90	6	2	—	—	45°; c = 5d
AV (A800)	785	80	1030	105	7	2	—	—	45°; c = 5d
A-VI (A1000)	980	100	1230	125	6	2	—	—	45°; c = 5d

The properties of the reinforcement bars are determined by laboratory tests, based on the results of which a protocol is drawn up. Deviation from GOST rules is allowed in agreement with the customer.

Reinforcement cross-sectional area table

When calculating reinforcing rods, in addition to the diameter, the mass of the products is also taken into account. It is given in the assortment GOST 5781-82:

Nominal diameter of the rod, mmCross-sectional area, cm2Average* weight of 1 m profile

6	0,283	0,222
8	0,503	0,395
10	0,785	0,617
12	1,131	0,888
14	1,54	1,21
16	2,01	1,58
18	2,54	2
20	3,14	2,47
22	3,8	2,98
25	4,91	3,85
28	6,16	4,83
32	8,01	6,31
36	10,18	7,99
40	12,57	9,87
45	15,00	12,48
50	19,63	15,41
55	23,76	18,65
60	28,27	22,19
70	38,48	30,21
80	50,27	39,46

*weight is given as an average value - a more accurate parameter depends on the specific grade used for the production of rolled steel bars.

Areas of application of steel reinforcement

The characteristics of steel reinforcement determine the scope of its application. Smooth profile rods are used:

• For dressing the working rods of the frame;
• Knitting of decorative items for design;
• Installation of individual elements of complex mechanisms.

Periodic profile bars are more in demand:

• Strengthening concrete structures in areas of greatest tension and compression;
• Installation of supporting elements and structures;
• Reinforcement of plaster layers, floor screeds;
• Construction of road surfaces and sidewalk areas;
• Installation of reinforcing belts for laying blocks and bricks.

The main purpose of bar reinforcement with a periodic profile is to strengthen concrete structures. Their rods are knitted into flat or spatial frames. The fittings in them perform different functions:

• Compensation for concrete fracture by creating tensile stress on the rod. Maximum loads are concentrated in the lower part of beam-type structures on two supports or with rigid pinching;
• Compensation for compression that is concentrated in the upper part of the same beam.

Flaws

Bar reinforcement has several disadvantages that need to be taken into account:

• In the absence of an anti-corrosion coating, the rods are subject to oxidation upon contact with water. Processes can even begin from exposure to water in the cement during its hardening.
• Inability to perform functions with rod products if the rod class and its diameter are incorrectly selected.
• Excessively stressed reinforcement can have the opposite effect and form cracks in the concrete structure.
• A protective layer of concrete is required - at least 2 diameters of the section size to prevent water from entering the rods.

Packaging, transportation and storage

For convenience, steel rods are painted in different colors:

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

It is allowed to apply paint to the ends of 0.5 meters.

The rod reinforcement is assembled in batches of 15 tons and tied with wire and cordage. Thin wire is also packaged in coils. If necessary, dressings of a different weight are made for the customer - 3 or 5 tons, as well as individual tonnage. Complete bundles must be marked with a class of rods.

Transportation of metal products is allowed only in a horizontal position to avoid kinks and deformations.

It is recommended to store rod reinforcement in closed, dry rooms, excluding contact with water.

Source: https://betonopedia.ru/armatura/stalnaya.html

How to determine the class of reinforcement

Construction fittings are a universal product used in various industries from the construction of buildings to the assembly of parts in mechanical engineering, the manufacture of machine tools and other mechanisms. Due to the wide range of applications and expected design loads, reinforcement is divided into classes according to strength, diameter and type of section.

Reinforcement class: table and technological characteristics of metal rods – Machine

Today, the construction of any building or technical structure cannot be completed without the use of concrete mortar.

The reinforced frame of the structure greatly increases the strength of the structure, preventing cracking and destruction of concrete buildings.

Modern rolled metal products offer various types of steel construction reinforcement for the formation of reinforced concrete structures for various purposes.

Main characteristics of steel reinforcement

To absorb tension and strengthen compressed zones of concrete structures is the main purpose of construction reinforcement. To implement this function, reinforcing bars are manufactured with the highest possible strength and ductility. To obtain a high-quality product, metal rolling enterprises increase the strength properties of raw materials:

• regulate the chemical composition of steel, increasing the content of carbon and chemical additives;
• in a cold state, steel is strengthened by twisting, drawing, stretching, flattening and other methods;
• heat treatment is applied;
• several methods are combined.

Durable and ductile, not susceptible to corrosion under a layer of concrete, withstanding temperature changes, time-tested steel building reinforcement is used both in the construction of low-rise residential buildings and in the construction of complex industrial and technical structures.

Types of reinforcement products

According to their purpose, fittings are divided into 4 types:

• Working. It absorbs tensile forces that arise in reinforced concrete structures under the pressure of external loads and its own weight.
• Distribution. It is a reinforcement mesh or frame connected by wire or welding. By tying the rods together, it prevents the working base from shifting during concreting and is intended to distribute a uniform load between the elements of the working reinforcement.
• Clamps. They are used when assembling the frame, protecting against the appearance of cracks near the supports in the beams.
• Assembly room. Used when concreting or assembling a frame to ensure the correct position of clamps and working reinforcement. It does not take any loads and is usually removed upon completion of work.

Types of building reinforcement

According to the orientation in the structure, it is divided into transverse and longitudinal. Transverse reinforcement binds concrete in the compressed and tensile zones of the structure to prevent the formation of inclined cracks near the supports. Longitudinal reinforcement, perceiving compressive and tensile stress, prevents vertical cracking in the tensile zone of the structure.

According to the conditions of use, it is divided into prestressed and non-prestressed reinforcement. Only working reinforcement that has been pre-tensioned to increase the strength of a reinforced concrete structure can be prestressed. Tensioning the reinforcing bars, reducing deflections and reducing the weight of the structure, prevents the formation of cracks and reduces the amount of steel reinforcement.

Reinforcement manufacturing methods

According to production technology, reinforcement for reinforced concrete buildings is of two types:

• Hot rolled rod. Reinforcement with any diameter, supplied in steel rods up to 13 meters long or in coils weighing up to 1.3 tons.
• Cold drawn wire. In the process of pulling (drawing) steel through the holes of drawing mills, the wire or rods change their cross-sectional shape and dimensions. A longer and more expensive production process, which results in high-quality reinforcement with a thickness of no more than 5 mm.

Hot-rolled steel reinforcement is significantly less expensive than cold-drawn steel reinforcement and has a higher level of corrosion resistance. Hot-rolled reinforcement bars are used more often and to increase strength they undergo subsequent thermal and mechanical treatment. This type of reinforcement is divided into 2 types according to the shape of the surface:

1. Smooth – metal rods with a smooth surface. Used for mounting the frame.
2. Periodic profile (corrugated) - rods with transverse protrusions and longitudinal ribs on the surface, twisted along a helix.

When casting reinforced concrete products or buildings, recesses and surface protrusions provide better adhesion of concrete to the reinforcement frame.

Classification of fittings

The strength of reinforcing bars depends on the steel alloy from which they are made. Reinforcement is classified according to its mechanical properties. Today there are several types of marking of steel construction reinforcement by class:

• A240 A-I.
• A300 A-II.
• A400 A-III.
• A600 A-IV.
• A800 AV.
• A1000 A-VI.

Class A240 (A-I) produces smooth fittings, other classes are produced with periodic corrugated profiles. Special properties, production method or purpose of fittings are indicated in the marking of finished products with additional indices.

Thermo-mechanical treatment is designated “At”, hardening by drawing is designated “Ab”. For regions of the Far North, frost-resistant reinforcement is marked “c”. Increased resistance to corrosion is designated “K”, and rods for welding are marked “C”.

Requirements for the strength of steel reinforcement are determined by GOSTs, which set yield limits for each class. For hot-rolled rod reinforcement GOST 5781, rod reinforcement strengthened by thermomechanical method is produced in accordance with GOST 10884. In accordance with the requirements of GOST, steel reinforcement cannot have holes, membranes, cracks or sunsets on its surface. Steel reinforcement bars are produced with a diameter from 6 mm to 80 mm.

Marking of finished products in production includes a class, an additional index and painting of the ends of the rods with a color corresponding to the brand. The class designation looks like this: At400S or At800KS.

Steel for the production of reinforcing bars

Low-alloy and carbon steel grades are used in the production of reinforcing bars. By changing the amount of chemicals, the alloy is given certain properties. Aluminum, silicon, manganese, nitrogen, chromium, boron, titanium, and zirconium are used as alloying additives.

Adding, for example, manganese to the alloy increases the rigidity of the material without reducing its elasticity. By changing the crystal lattice, silicon increases the density of steel rods, which improves the performance properties of the reinforcement, but makes it difficult to weld the elements. The strength of steel increases significantly when carbon is added to the alloy.

But an overdose of this substance impairs the ductility of building reinforcement.

The steel grade of the reinforcement is specified by the customer. If there are no brand requirements in the order, the manufacturer agrees it with the recipient, or the plant determines it at its own discretion.

Frequency of use

12 mm reinforcement made of steel class A3500C is in wide demand. Welding can be used to fasten plastic ribbed rods of this type. 12 mm reinforcement bars give the frame higher strength.

Application of construction reinforcement

Flat or three-dimensional structures made of steel rods are connected to each other by electric welding, knitting wire or special reinforcement clamps.

The high-quality adhesion of flat reinforcing meshes (grids) and volumetric frames to concrete depends on its strength and shrinkage amount, as well as on the type of surface and cross-sectional shape of the reinforcing bars.

Reliable adhesion of concrete and reinforcement is ensured by three factors:

1. Mechanical engagement of protrusions and surface irregularities of reinforcement with concrete.
2. Frictional forces arising on the surface of reinforcing bars when they are compressed by concrete during the shrinkage process.
3. Adhesion (gluing) of a reinforcing surface to concrete due to the viscosity of the cement mortar.

Currently, any concrete structure has a strong, reliable steel reinforced “skeleton”. Modern office or commercial buildings, residential or technical buildings, power plant dams or bridges are constructed using cast-in-place concreting technology.

Source: https://regionvtormet.ru/instrumenty/klass-armatury-tablitsa-i-tehnologicheskie-harakteristiki-metallicheskih-prutev.html