Rebar

Rebar is a type of long and thick profile that is used to improve the tensile strength of concrete, because concrete is a very strong and resistant material against compressive stresses, but it performs very poorly against tensile stress. For this reason and with the aim of compensating for the weak tensile strength of concrete, they use various types of ribbed rebar in concrete.

Rebars are one of the most basic and best-selling steel sections in the construction industry and have different types. Rebar steel type is usually used in the construction industry, because the increase in steel length due to high temperatures (thermal expansion coefficient) is almost equal to concrete. In general, the use of rebar in concrete structures leads to the construction of a structure with higher load capacity, more ductility and longer life.

The definition of rebar in the national standard of Iran:

The hot-rolled steel product is plain or ribbed with a round cross-section, which is packed as a branch (straight in a certain length) or coil (in a continuous ring).

What is the difference between rebar and reinforcement?

Usually, rebar and reinforcement are confused with each other. To know the difference between reinforcement and rebar, we must first familiarize ourselves with the definition of reinforcement. Reinforcements are deformed rebars that are ready to be placed in concrete. In other words, when the rebar is deformed and ready to be concreted, it is called reinforcement.

As a result, it can be said that reinforcement is the same as rebar, with the difference that operations such as bending, cutting or welding to other rebars are performed on it before being placed in concrete.

The history of using rebar in structures

Concrete has been used for thousands of years for a wide variety of construction projects. For example, in ancient Rome, concrete was used a lot. However, the construction of reinforced concrete or concrete reinforced with rebar is relatively new, less than 200 years old.

Historians disagree on the name of the first person who used reinforced concrete in a construction project. Some assign this issue to the craftsman named François Coignet, who built the first house with reinforced concrete.

After that, the use of reinforced concrete quickly became a method for building construction in Europe, and then it was developed in America. In 1878, a person named Thaddeus Haight was the first to receive a patent for this system in the United States. After that, a refinery owned by The Pacific Coast Borax Company implemented America's first reinforced concrete construction project. Finally, in the first quarter of the 20th century, construction with reinforced concrete system had become the main choice for new projects.

Among the advantages of using reinforced concrete is the possibility of building a building with a high number of floors. Buildings built using wood were limited in the number of floors. Even though stone construction made it possible to build more floors, it was not a cost-effective method. For more than a century now, the construction of bridges, highways, sports fields, schools, dams, airports and many other projects rely on the strength and durability of reinforced concrete.

Standards International Rebar

The specifications of rebars are different based on the national standards of different countries. In the table below, you can see international standards and national standards for the production of steel bars.

Among the above standards, American standards (ASTM), Russian (GOST), German standard (DIN), British standard (BS), JIS (Japanese standard) and Indian standard (IS) are more famous and used more. In Iran, the GOST 5781 standard of Russia is the most widely used standard for this steel section, according to which the products are classified in 4 grades A1, A2, A3 and A4.

Table of international standards and national standards of different countries

Rebar standards in Iran

The national standard of Iran for the production of steel rebars is the INSO3132 standard, which was prepared under the title "Hot-rolled steel rebars for concrete reinforcement - characteristics and test methods" in 1369, and a new version was revised and presented in 1381. The purpose of developing this standard is to determine the characteristics and test methods of simple and ribbed hot-rolled steel rebars for concrete reinforcement. Zob Ahan factory, as one of the largest rebar producers in Iran, uses this standard to produce its products.

The sources that have been used to prepare Iran's National Standard No. 3132 are a summary of the international standards DIN, ISO, GOST, JIS, BS and ASTM, which will be introduced and given a brief explanation about each of them. We pay:

• DIN standard: The letters DIN stand for "Deutsches Institut für Normung" meaning "German Institute for Standardization". The DIN standard is a standard developed at the German Institute for Standardization (DIN) in Berlin, which sets unified standards such as quality, minimum performance, characteristics, dimensions, etc. for products and processes. The German standards used in the Iranian National Standard No. 3132 include DIN 488-1:2009, DIN 488-2:2009 and DIN 488-3:2009.
• ISO standard: The term ISO stands for the International Organization for Standardization and means the ISO International Standard Organization. The work of preparing international standards is usually done through ISO technical committees. However, the influence of the ISO standard on rebar is low, and national standards are more applicable in this field. The standards ISO 6935-1:2007 and ISO 6935-2:2007 are among the references used in the Iranian national standard 3132.
• GOST standardGOST stands for Government Standard Russia and represents a group of standards developed in the Soviet Union. Standard No. GOST 5781-82: 1993 is used in the national standard of Iran.
• JIS standard: Japanese Industrial Standards (JIS) are the standards used for industrial activities in Japan. The standardization process is coordinated by the Japan Industrial Standards Committee and published through the Japan Standards Association. Japan standard JIS G 3112:2010 is another reference of Iranian national standard No. 3132 in the field of rebar specifications.
• BS standard: The British Standards Institution is the standardization authority in England. This institute sets standards for a wide range of goods and services. In the national standard of Iran, BS 4449:2005+A2:2009 is used as one of the rebar specification references.
• ASTM standard: ASTM is one of the largest international standards development organizations. The extensive standards of this organization are approved based on consensus. This organization has 30,000 members from 120 countries.  ASTM A 615/A 615M is used in the national standard of Iran No. 3132.

Types of rebar based on appearance

according to Iranian National Standard No. 1797-4 Steel rods are divided in terms of appearance as follows:

• rebars (bar with circular cross-section)
• Square bars square shape (four-sided rebar)
• Hexagonal bars (six-point rebar)
• Octagonal rods
• Steel belts (smooth rebar)

All these rebars are produced and supplied as branches.

Round bars or rebars are the main subject of this article, which we will examine further in terms of types and other specifications. Among other square, hexagonal, octagonal and belt bars, square or four-sided bars are more popular and used.

square shape (four-sided rebar)

In the four-sided rebar, the cross-section of the rebar is made in the form of a square instead of a circle. The advantages of square rebar are high stability against sliding and the ability to be used in complex designs. Four-sided rebar can be produced in diameters of 8 to 120 mm and lengths of 3 to 12 meters.

Four sides are used almost in most industries and as an intermediate product for the production of supports, axles, connections, bases, rails, handle bars, etc. Read the types of four sides, production standards, manufacturing factories and other specifications and features of this rebar in the following article.

The appearance of various types of rebar with a circular cross-section

according to Iranian National Standard No. 3132, hot-rolled round bars for reinforcing concrete are divided into two groups, simple bars and ribbed bars, in terms of appearance. The classification of simple and ribbed rebars is done in 4 grades as follows:

1. Simple rebar or A1 rebar
2. Spiral ribbed rebar or A2 rebar
3. Ribbed rebar or A3 rebar
4. Ribbed rebar or A4 rebar

1- Rebar type A1

A1 rebar or simple rebar is a rebar that does not have any treads or ridges on its entire surface. Simple rebars are usually produced and supplied in sizes from 6 to 20 mm and are shown in the national standard of Iran No. 3132 with the characteristic symbol S240. This type of rebar has the lowest amount of carbon in its chemical composition, which leads to high flexibility and suitable formability and weldability. To learn more about this type of rebar, we recommend reading the following dedicated article.

The price of simple rebar

In general, the price of plain rebar is a little lower than the price of ribbed rebar of the same size due to the lack of tread and the different production method. To know the daily price of simple rebar and its price fluctuation, you should check the price list of this type of rebar on a daily basis. For this purpose, it is enough to refer to the following page and see the price of simple rebar of all factories in the market on a daily basis.

2- Rebar type A2

A2 rebars are ribbed rebars. The tread of this type of rebar is of a spiral type (uniform or spindle) which continues from the beginning to the end of the rebar and does not stop anywhere.  A2 rebar has a higher resistance than plain rebars, but at the same time it is less hard than other ribbed rebars, and for this reason it is also known as semi-hard rebar. A2 rebar is mostly used in shear walls and in the construction of Khamut.

This type of rebar is known in standard No. 3132 with two characteristics "Aaj 340" and "Aaj 350".

3- Rebar type A3

A3 rebar is also a type of ribbed rebar, but its tread is cross-shaped. The difference between A2 and A3 rebar is in the mechanical characteristics, such as the strength of the rebar and their malleability and weldability. In this way, the A3 rebar has a higher resistance than the A2 rebar due to the higher percentage of carbon in its chemical composition, but its malleability and weldability are also lower.

A3 rebar is marked with "Aaj 400" and "Aaj 420" in the national standard of Iran.

4- Rebar type A4

A4 rebar, which is known in standard 3132 with the characteristic mark of 500 tread and 520 tread, is in the last hardness category and is made of high carbon grade steel. The shape of the treads of this rebar is completely different from the ribbed rebars A2 and A3 and has spindle-shaped transverse treads. Due to the advancement in its manufacturing technology, the A4 rebar has good flexibility and weldability in addition to its high strength, and the main difference between the A3 and A4 rebar is related to this.

Now that we are familiar with the types of all 4 grades of rebar, we recommend that you read the following article to learn more and check the differences between these 4 types of rebar.

Types of rebar in terms of shape and material

Rebar is one of the main and best-selling steel sections in the construction industry, so that without this metal section, it is almost impossible to proceed with the construction today. The standard of rebar is undoubtedly one of the influencing factors in the mechanical properties of rebar, and this causes its application to be different in different parts of the structure. In addition to the production standard, rebars can be classified in other aspects as well, such as the appearance and material of the rebar, which we will examine in the following categories.

Types of rebar in terms of condition

Types of rebars are divided into the following two categories in terms of condition and appearance:

• branch rebar: Simple and ribbed rebars that are produced in the form of 12-meter branches are called branch rebars.
• Coiled rebar: Coiled rebars are a type of simple and ribbed rebars. Depending on the customer's order, simple coils are made from size 5.5 to 10, and ribbed coils are also made with A2 and A3 rods. Coiled rebars are used to increase the strength of concrete structures, the strength of brick walls and columns, the strength of blocks, and the strength of gas connections. Read the full introduction of coiled rebar in the relevant article.

The price of coiled rebar

Determining the price of coiled rebar depends on factors such as the price of raw materials for coil production, whether it is plain or ribbed, the weight of coiled rebar and its thickness, as well as the price of steel, currency fluctuations, etc., which causes the price of this product to fluctuate. For this reason, before buying coiled steel, be sure to inquire about the current price of simple and ribbed coils through reliable sources and compare them before making a purchase. You can see the daily price of coiled steel through the link below.

 Which rebars are classified as branches and which as coils depends on the mechanical and structural characteristics of the rebars. For example, rebars made of hard steel are packaged and supplied in bundles. According to their diameter, soft and semi-hard steel rebars can be packed in both branches and coils. To learn more about rebar packing method, read the following article.

Types of rebar in terms of gender

According to the type of material used in the production of rebar, there are different types of rebar. In the construction industry and in reinforced concrete structures, carbon steel rebar is usually used, but this type of rebar may not have the desired performance in environments with high humidity. In this situation, epoxy-coated rebar may work better in wet environments and maintain the strength and durability of concrete without corrosion. For this reason, the type of rebar should be selected according to the project environment and volume.

1. European rebar

European rebar is made of manganese and therefore bends easily.

Although this rebar is used in many countries, due to its high flexibility, it is not recommended to use it in earthquake-prone areas or with special weather conditions such as storms and tornadoes, as well as for projects that require an integrated structure. However, its price is affordable.

2. Carbon steel rebar

The most common type of rebar in the project scale is carbon steel rebar or black rebar. Due to the fact that this type of rebar does not have a high resistance to moisture, the rate of rusting will be high and it is not suitable for use in areas with high humidity.

However, the strength and high tensile strength of black rebar make it one of the best choices.

3. Rebar with epoxy coating

This rebar is actually the same black rebar that has been coated with epoxy. With this method, the rebar becomes more resistant to rust. Although the epoxy coating used in this rebar is extremely delicate, this product is about 70 to 1700 times more resistant to rust than carbon steel.

Despite the difference in corrosion, the tensile strength of epoxy rebar and black rebar are similar. Also, the price of black rebar is lower than epoxy rebar.

4. Galvanized rebar

Galvanized rebar is ordinary steel rebar whose surface is covered with a protective layer of zinc metal (Zn). The zinc coating is usually created by the hot-dip galvanizing process. Galvanized rebar is much more resistant to corrosion than black rebar. Also, it is more difficult to damage the coating of galvanized rebar than epoxy rebar. For this reason, the price of galvanized rebar is higher than epoxy rebar.

5. Composite rebar (glass fiber reinforced polymer (GFRP))

Composite rebar is also called FRP rebar (fiber-reinforced polymer composite bars). Since this type of rebar is made of fiber, bending is not allowed. The most important feature of this type of rebar is high resistance and strength, as well as Their lightness. Also, this type of rebar is very resistant to corrosion and is more expensive compared to other rebars. FRPs are usually used in the aerospace, automotive, and construction industries.

6. Stainless steel rebar

Stainless steel is an iron alloy with at least 10.5% chromium, which makes the metal resistant to corrosion and rust. One of the types of stainless steel rebar can be referred to as stainless steel rebar or steel rebar. This type of rebar is 1500 times more resistant to corrosion than black rebar. Another important advantage of this type of rebar is its extraordinary resistance to heat treatment. Hence, stainless rebar is much more expensive than other rebars.

This rebar is used to strengthen concrete in structures such as bridges, highways, buildings, etc. You can read other uses of this type of rebar and get to know its specifications in the following article.

All types of rebar available in the market

As we said, rebars have a high variety and can be classified in different aspects. In addition to the classification that we mentioned so far, rebars can also be classified according to the amount of use in the market and the amount of use in the project scale. Next, we examine the rebars used in the construction industry.

Types of rebar in terms of application in the structure

In all construction projects, it is necessary to use different types of rebar according to the shape of the bend, the state of the rebar, the type of alloy used in it, etc. be used In general, the types of rebar used in the structure can be classified as follows.

1- Reinforcing bar

Reinforcing bars are used for parts of the building that do not have enough durability or are expected to be damaged under tensile and compressive forces. They are most commonly used in block beam ceilings, foundations and shear walls. This type of rebar is produced with hot-rolled steel ingots and has the ability to bend up to 180 degrees. Read other features of reinforcing bars, usage tips and how to calculate its length and weight in the following article.

2- Normal rebar

Normal rebar is usually produced in sizes from 3 to 11 meters. Normal rebars are produced using A2 and A3 type rebars and are used in both branch and coil forms for special purposes. Normal rebar will be the most suitable option for making joists, trusses, Luke beams, because in these industries, rebars shorter than the standard size are needed. Read more information about normal rebar, such as mechanical specifications, uses, price, etc., in the article introducing normal rebar.

3- Bed rebar

The bed rebars consist of two parallel rebars of 3 meters length, and the width distance between them will vary between 5.5, 11 and 15 cm. Also, a wire is welded vertically or zigzag to two parallel bars. Bed rebars are used to increase resistance to bending and shear stresses. In addition, bed reinforcement has a good effect on the vertical and inclined load of building columns. Among its other advantages, there is no need for grouting and earthquake strength.

The price of bed rebar

Buying bed rebar due to its reasonable price, along with the advantages of this type of rebar, has a significant impact on the strength of the structure and the cost-effectiveness of the project. In general, the price of bed rebar is calculated according to its weight and length. You can follow the daily price of bed rebar through the link below.

4- HSD rebar

HSD rebars are a type of ribbed rebar with high strength and resistance. The use of this type of rebar due to its high resistance to tensile and compressive stresses reduces the need for reinforcing bars, and as a result, the need for reinforcements in the structure is reduced. Another advantage of HSD rebar is its high weldability and malleability. The production process of HSD rebar and its specifications and benefits can be read in full in the full introduction article of HSD rebar.

5- Zigzag rebar

Zigzag rebars, which are also called trusses, consist of two models of simple and ribbed rebars that are connected to each other through welding or hooks. In fact, this steel section consists of three upper, lower and transverse sections. In this way, 3 ribbed bars are placed in the upper and lower parts, and simple bars (A1) are placed in the transverse part of the truss. It is better to use hot rolling method to produce zigzag rebars. This type of rebar is used in the construction of various types of roofs.

6- trans rod

Transke bars, also known as tension bars, have a smoother and more polished appearance than other bars. The smooth and uniform appearance of this rebar is due to the polishing process, and according to the polishing method, its quality and degree of polishing will also be different. In general, the polishing process in this rebar is divided into two categories: single polishing and double polishing. To learn more about the types of trans rebar, its use and price, read the review article on trans rebar.

7- Thermal rebar

Thermal rebar has much higher tensile strength than other types of rebar; For this reason, this type of rebar is a more suitable option to prevent concrete cracking. to Thermal rebars They are also called heat sink bars. The most common use of this rebar is to increase the strength of the roof of structures and prevent the roof diaphragm from breaking. In general, this rebar increases the resistance of the structure by reducing the width of the cracks. Read more applications of thermal rebar and how to implement it, as well as different views on the use of this rebar and alternative methods in the introduction article of thermal rebar.

8- Milgerd Sardar (milgerd with a cap)

Capped rebar or Sardar rebar is the branch rebar that is attached to one or both ends of the cap. These steel caps are in different shapes of square, rectangle, circle and rhombus that are connected to the head of the rebar. Sardar rebar types are mostly used as Sardar ribbed rebar, Sardar stud and Sardar screw. The use of sardar or capped rebars reduces the crowding of rebars in different parts of the structure.

To read more about this type of rebar, from its history to its types, applications, advantages and methods of construction and implementation, read the introduction article of this article.

9- Connecting rebar

Connecting rebar is a simple or ribbed rebar in the sizes of 8 to 10 mm, which is used as an electrical conductor and to equipotentialize the contact points in the building to prevent danger. Of course, other objects besides rebar can also be used for this purpose. For example, the most suitable electrical conductors are in the form of circular conductors, belts, etc.; But in our country, due to the lower cost of steel rebar, it is mainly used as a conductor, which is called a rebar.

10- Torsional rebar

Torsional rebar is a type of ribbed rebar that is responsible for providing the torsional anchor of the piece. Rebars such as closed vertical bars, screws, and some longitudinal reinforcements are considered a type of torsional reinforcement if they provide torsional anchorage. We have brought torsion armature step by step from introduction and applications to how to design and implement in the link below.

The importance of using rebar in the construction industry

The use of concrete for construction increases the strength and resistance of the structure against compressive stresses, but the weakness of concrete is that its resistance against shear and tensile stresses is low, and because of this, it cracks. This is where you can understand the importance of using rebar in concrete. In order to strengthen the tensile strength of concrete, a combination of concrete and rebar is used, which is called reinforced concrete or reinforced concrete.

The same coefficient of thermal expansion of concrete and steel also prevents the occurrence of additional stresses in the concrete structure in different temperature conditions and as a result premature destruction of concrete.

Rebar test

Different types of rebar tests are used in order to know the characteristics of the rebar and its compliance with the standard specifications. With the rebar test, which includes a variety of chemical and mechanical tests, the quality of the rebars is measured and matched with the relevant standards. According to the relevant national standards, 6 types of tests can be performed on rebars, some of which are mandatory.

Rebar diameter measurement

In general, all kinds of rebars are produced and supplied with diameters from 8 to 50 mm, but the most widely used ones are 6 to 32 mm in diameter. Also, each size of rebar is used for a specific use. If the rebar plate or its technical certificate is available, the diameter of the rebar can be easily found, but if there is a need to measure the diameter of the rebar, different methods can be used for this purpose. Some of these methods do not require any tools.

The most widely used rebar sizes for bending are size 8 and 10 rebars. We will examine the rebar bends below.

Types of rebar bends

In all construction projects, it is necessary to use different types of rebar bends according to their application. Bending of rebar is done by two methods, manual and machine, and the most used of them are placed in the following 6 categories.

1- Khamut rebar: In general, transverse reinforcements that are used to resist shear and torsional forces in the member are called Khamut. In fact, the bending of Khamut prevents failure and cracks in concrete members. Khamoots have different types and are made of ribbed bars in the shape of U or L. In the introduction article of Khamut, which you can see below, we have examined the types of Khamut and its application in structures.

Khamut rebar price

The price of rebar depends on the type of rebar and the diameter and quality of the rebar and is announced daily. You can see the price table for quiet days in the link below.

2- Vault rebar: Rebar or vault reinforcement has a role similar to Khamut. In fact, because it is not possible to use Khamut in the foundation, they use the vault to take advantage of the bend of the foundation reinforcement. However, the vault has no structural use and is used only to stabilize the upper mesh of the foundation and to place two consecutive horizontal grids with a certain distance.

3- Pin bar: Pin bar or pin bar is a type of transverse reinforcement that is used to resist the longitudinal bar of the column against the shear force. Also, this type of rebar plays an important role in the stability and resistance of the structure against forces such as wind and earthquake. You can see the types of rebar, its applications and the field of use in the article about rebar.

4- Adaka rebar: This type of rebar bend helps a lot to bear the forces on the structure and is usually installed at the joint of the roof beam to the beam. Among the advantages of using this rebar, we can mention the reduction of vibrations and the rise of the roof, the reduction of loads and pressures from the upper floor and the prevention of roof cracking. Of course, negative moment reinforcement, like Edca reinforcement, helps to increase the strength of the roof and prevent it from cracking, which is why these two reinforcements may be confused with each other.

5- Straight rebar: Straight rebar, which is also called Sitka rebar, is another type of rebar bend and is used to increase the tensile strength of concrete and in some cases to increase the compressive strength of concrete.

6- Stabilized rebar: This type of rebar bend is similar to the letter U, whose two edges are bent inward, and its most important role is to create and adjust the distance between two rebar networks.

The extent of application of rebar bending in the construction industry is such that it can be said that almost no structure can be implemented without the use of rebar bending. Learn more about types of rebar bends, bending methods and the reason for rebar bends, important points of execution and bend length in the introduction article on rebar bends.

After the construction of the structure and the placement of the rebars in the concrete, in many cases it is necessary to repair, reconstruct the drilling, etc., in this case, before any action, the condition of the existing concrete must be evaluated and the amount of reinforcement of the concrete, the number, diameter and location of the rebars must be identified. . For this purpose, different methods of identifying rebar in concrete are used.

Rebar connection methods

In order to increase the length of the rebar and also to create a continuous tensile or compressive function in two rebars along each other, a variety of rebar connection methods are used. Connecting rebars is one of the operations that should be paid special attention to in construction.  All types of rebar connection or patching methods should be used in one of the following four standard methods or a combination of them.

• Overlap: Two rebars are connected by overlapping the length of the rebars. The cover patch is made in two types, contact and non-contact.
• Mechanical patch (coupler): Using a piece called a coupler, they connect two rebars to each other. There are different types of couplers and they can be classified according to the direction of the coupler thread, the type of connection of the rebars to each other, the size of the rebars that can be connected, etc.
• Welding patch (forging): Connection is made by welding two rebars together. If we want to use rebar welding connection, we must put the rebars under weldability test.
• Reliability patch: This type of connection is made by placing two ends of compression bars together. This type of patch is allowed for pressure bars with a diameter of 25 mm and more.

We recommend that you read the article on types of rebar connection (patch) to learn about each of the rebar connection methods and their related tips.

Rebar fracture factors

 Rebars may fail for various reasons and damage the structure. In general, the breaking of rebar can be done for various reasons, such as the use of low-quality rebar, excessive bending, improper maintenance of rebar, etc. Also, some rebars are more fragile than other rebars, the reason is the amount of carbon used in their chemical compounds. In general, it can be said that rebars with more carbon are more likely to fail.

To know all the reasons for rebar failure as well as ways to prevent this problem, we recommend reading the following article.

The importance of identifying rebar in concrete

Using special equipment and devices to identify rebar in concrete is one of the non-destructive methods of determining the state of concrete.  This work is an initial step in the evaluation of reinforced concrete structures or pavements. The importance of using rebar identification methods in concrete is that if operations are needed on concrete such as drilling, cutting, grinding, etc., no damage is caused to the reinforcements inside the concrete or the equipment used. In general, it can be said that knowing the location of reinforcements and rebars prevents damage to the integrity of the structure.

Nailing soil with rebar

The nailing of rebars in the soil is done to strengthen the structure and to fix the supporting structure, and it has the role of strengthening and arming the soil. In the process of nailing, holes are created on the soil surface so that the rebars can be placed inside them. After grout injection and installation of drainage strips, concrete spraying is done. This procedure continues until reaching the level of the bottom of the pit.

If you want to learn more about soil nailing with rebar as well as other guarding structure methods, read the following article.

Correct maintenance conditions for rebar

The rebars must be kept in certain conditions, because not paying attention to the proper maintenance of the rebar will lead to damage, corrosion or breakage of the rebar. In the following, we state some of the most important points of rebar maintenance:

• Before using the rebar, tests such as measuring the tensile strength, breaking strength, elongation at break and gaining confidence about the standard of the rebar should be done.
• Rebars should be stored in a place so that they do not come into contact with corrosive and harmful substances. It should also be prevented from increasing the temperature of the rebars inside the molds due to direct sunlight before concreting. In fact, the temperature of the rebars should be reduced by spraying water before concreting.
• Usually, rebars with a diameter of 8 mm and less can be produced as coils. Therefore, it is not allowed to use rebars with a diameter higher than 10 mm in the form of coils. Uncoiling is done in the workshop with the appropriate device and with the approval of the monitoring device.
• Rebars should be stored in a place where they are not exposed to direct moisture. It is also necessary to protect the rebars from the wind.
• It is strongly recommended not to place the rebars on the soil, because the rebars are contaminated in contact with the soil and materials that contain corrosive salts.  The use of contaminated rebars will absorb moisture through solvents and as a result corrosion in concrete.
• Rebars should be stored so that they are at least 15 cm away from the ground.
• Rebars should be separated and stored according to their type and diameter. If there are rebars with similar diameters but with different strength and mechanical characteristics, they should be stored in separate places and marked.
• Rebars contaminated with soil, salts and harmful substances that have been contaminated by contact with the ground or for other reasons must be completely cleaned and their rust removed before use. These rebars can be used only if their physical, mechanical and chemical properties have not changed and they have standard characteristics.

We recommend that you read all the tips and conditions of rebar storage in the article below.

Rebar production process

The production process of most steel sections such as bars, beams, corners, studs, etc. requires the production of steel ingots. The steel ingot used for this purpose is billet. Therefore, the first stage of rebar production also begins with billet production.

In order to get familiar with the process of rebar production, it is necessary to briefly explain the process of ingot production.

Production of steel ingots

Steel ingot is the first and main material for rebar production. In the production of steel ingots, first the iron obtained from the blast furnace of iron smelting factories enters the steelmaking process and after going through the necessary steps, it enters the ingot production stage.  In general, ingots are produced in the following two ways:

1. Production of ingots in molds
2. Ingot production by continuous casting

Preparation of ingots using a mold: In this method, molten steel is poured into special molds using a crucible. After cooling, the ingots are discharged from the molds.

Preparation of ingots using continuous casting method: In the continuous casting method, molten materials are first poured into a chamber called a divider. Then these materials leave the divider and enter the freezing chamber to cool down to the initial temperature of the steel. After this step, the ingots are placed in the rolling line to equalize the length and width. Finally, the obtained ingots are cut into the required dimensions and enter the cooling stage. Unlike the molding method, this method is more common in large factories.

After ingot production, it is time to produce rebar. To produce rebars, first the ingots that were produced using the two mentioned methods are prepared by going through steps such as cutting, removing the ingot surface shells and rust removal. In general, rebars are produced by 4 methods. In the following, we will explain each of them:

Types of rebar production methods

In general, rebar production methods in Iran are divided into the following 4 categories.

1. Hot rolling method
2. Cold rolling method
3. Microalloy method
4. Termex method

In the following, we briefly describe each of these methods, but we recommend that you read the following article to learn more about rebar production methods.

1- Rebar production by hot rolling method

In this method, the ingots are heated in special furnaces to a temperature of 1000-1100 degrees and then they enter the rolling stage. In the rolling stage, during a process called roughing, the ingots pass through rollers in 3 stages and reach a circular cross-section with a suitable diameter. Next, after the ingots pass through the rolling racks, which have different outputs to produce different diameters of rebar, rebar with different diameters is produced. After that, it's time for treading

2- Rebar production by cold rolling method

Rebar production is done by cold method up to the roughing stage, similar to the hot method process; with the difference that after roughing, the ingot first enters the cooling stage and becomes cold. Then the cooled billet enters the rolling stage and more rolling is done on it to produce the desired rebar. This operation makes the rebars have more resistance and hardness; For this reason, the rebars produced in cold rolling are very suitable for areas that require high strength rebars.

3- Production of rebar by microalloying method (alloying)

The production of rebar by the micro-ejection method is similar to the hot rolling method. The only difference between this method and the hot rolling method is the addition of elements such as titanium, niobium and vanadium to the rebar molten material. Alloy bars are cooled in the air after the production process is completed. For this reason, in this method, rebars have higher strength, elasticity and flexibility than other methods and are very suitable and ideal for earthquake-prone areas. Also, the price of microalloyed rebars is higher than other rebar production methods.

4- Production of rebar by Termax method

 Termax rebar is made by QST (Quenching and Self-tempering) technology. QST technology means quenched and self-watering process. That is, after the hot rolling stage, the rebars are watered with an in-line operation, their surface is cooled. Then the internal temperature of the rebar naturally drops and the rebar cools down. The heat that is transferred from the inside of the bars to the outside will create a hard and brittle surface.

One of the other advantages of Termax rebars compared to other rebars is the possibility of butt welding, which is essential in many construction projects.

Rebar cutting methods

There are two methods for cutting rebar, each of which has different devices:

• Cold cutting
• Hot cutting

Cold cutting

If we use the cold cutting method to cut the rebar, it will have a greater effect on maintaining the quality of the product and significantly stabilizes its properties. The cold cutting method itself is performed by different devices, which include:

1. Waterjet cutting machine
2. Band saw cutting machine
3. Disc saw cutting machine
4. Hand saw cutting machine
5. Claw saw cutting machine

To use the cold cutting method, one should pay attention to the weight of the rebar and choose the best method for cutting the rebar according to its weight, size and dimensions. The cold cutting method is such that the heat is not in direct contact with the rebars and the rebars are cut to desired sizes. The advantages of using the cold cutting method are as follows:

• No change in the molecular structure of metals
• Ability to cut in different sizes and shapes
• Reduce waste
• More flexibility
• Good surface quality
• The sameness of the cut pieces
• No production of any toxic gas during cutting

In addition to the mentioned advantages, the cold method also has disadvantages. For example, economically, it will result in high costs; For example, the cold method requires special devices that are very expensive. Also, periodic maintenance and services of cutting tools require spending money. Another thing is that to perform this method, the presence of specialist and technician will be necessary.

1- Water jet cutting machine

In this method, hard materials are cut by high-pressure water motors. Of course, in addition to cutting stone, this method is also used for cutting rebar and metals. The waterjet device has gained many fans due to the following advantages within a limited period of time. Among the best features of this method are:

• High accuracy and speed of the waterjet machine
• Its automatic operation

2- Band saw cutting machine

This machine cuts thick parts with high precision. The working process of the band saw is that first, the saw band rotates with the help of an electric motor; Next, the piece is moved using a hydraulic jack to cut. The advantages of this device include the following:

• The cutting operation is done automatically.
• This device is programmable.
• The pieces are cut at an angle.
• When working and using this device, waste is reduced.

3- Disc saw cutting machine

The disc saw machine is actually an alternative to the dangerous fire saw machine. This device has more quality and security. The disc saw machine can easily cut metals due to the variety of blades it has.

4- Manual saw cutting machine

The simplest and oldest tool for cutting rebar is using a hand saw cutting machine. Saws have different teeth with the same sizes. If the rebar is thick, it is cut with coarse toothed saws, and if the rebar is thin, it is cut with fine toothed saws. When using this device, the amount of human hand strength will be very important.  In this method, the parts are exactly divided into two equal parts.

The important thing about hand saws is that you must use safety equipment because there are many risks such as the possibility of warping or breaking the blade during work.

5- Crank saw cutting machine

The chainsaw cutting machine produces a lot of waste and is less accurate. The operation of this device during cutting is done by moving the piece back and up;  That is why they use it less than other devices.

Hot cutting

The hot cutting method is performed by the following devices:

1. Plasma cutting machine
2. Disc saw blade machine (fire)
3. Laser cutting machine

Among the advantages of using the hot cutting method, the following can be listed:

• The cutting operation using this method is very fast.
• Cutting time in this method is short.
• No chips are created when cutting in the hot method.

In addition to the mentioned advantages, hot cutting has the following disadvantages:

• A change in the molecular structure of the steel as well as a change in appearance at the edges of the cutting site
• Improper performance
• Low accuracy when working
• A lot of bounce

1- Plasma cutting machine

Using its internal burner, this device releases gas at a high speed and in a compressed form. Blowing this gas causes an electric arc between the nozzle and the workpiece. This process will make the gas plasma. The heat of about 25,000 degrees Celsius is focused on the metal to melt the desired point on the product. The use of this device is not recommended due to disadvantages such as error occurrence, possibility of electric shock and high radio radiation.

2- Fire disk saw blade device

When using this device, a lot of heat is generated in the cutting area, which will cause parts to separate. Due to its high accuracy and speed, this device produces fewer changes on the molecular structure of iron. The blade on this device rotates at approximately 45,000 rpm. It should be added that an operator is necessary to move and cut the product.  This device poses many risks for the operator, such as breaking the saw blade; For this reason, they do not use it for cutting.

Laser cutting machine

 They use a laser cutting machine for burning and melting. It should be noted that the least damage to metals is done in the laser cutting method. There are different types of lasers such as fiber, gas, solid and chemical. In the industry, only solid and gas lasers are used.

The best manufacturers of rebar

The production of rebar in Iran is more than half a century old and many factories are engaged in the production of rebar.

From Top rebar manufacturers Top rebar manufacturers

• Isfahan Iron Smelting Factory
• Khorasan Steel Complex (Nishabour)
• Azarbaijan Steel Factory (middle)
• Bardsir Kerman Steel Industries
• Anahita Gilan Steel Complex
• South Rohina Steel Complex
• Bafaq steel complex
• Zafar Bonab factory
• Kaveh Tikeme Dash Steel Industries
• Sirjan Jahan Steel Factory
• Sarmad Abarkoh factory, Yazd
• Iran alloy steel factory
• Khorramdasht Takestan Steel
• Kashan desert steel factory

Also, in the following article, we have introduced rebar production factories that have the highest demand in the market compared to other factories.

The best time to buy rebar

Maybe this question has arisen for you, when is the best time to buy rebar? In fact, it is not possible to give a definite answer to this question, because the purchase of iron requires consideration of several factors, including economic and political factors, inflation rate, currency fluctuations, global price of rebar, etc.

Even though due to the extreme fluctuations of the market and its direct impact on the iron market, it is not possible to specifically determine the best and worst time to buy rebar, but in general, it can be said that the best time to buy is during the market recession. Postponing the purchase of hardware is a mistake if you detect a recession in the market where prices have reached relative stability and the market has a steady downward trend.

rebar price

As you know, a fixed price cannot be set for this product. The price of rebars varies depending on whether they are ribbed or not, the shape of the tread, their tensile strength and flexibility. Also, the manufacturer's brand and product quality have a great impact on their price. In addition, the daily price of all types of rebar changes depending on various factors such as the internal conditions of the country, exchange rate and even according to the seasons. Therefore, it is necessary to inquire about the price from the most reliable sites and companies before buying rebar.

Bendil rebar

One of the important things in rebar transportation is their packaging.  Among the packing methods of this steel section, we can mention the use of bandil. In general, some products, including rebar and thin pipes, are packed with this method. In fact, it can be said that packing rebars with tape is an economical and safe method. Another noteworthy point is that the packing capacity of each rebar bundle will be different in different factories.

Golden tips for transporting rebar

In rebar transportation, many factors, including the volume of rebar purchased and the capacity of the vehicle, will be effective. The low cost of rebar transportation is one of the most important factors for buyers, and for this reason, in most cases, road transportation, which will be economically more affordable, is the first choice of buyers. Other factors affecting the cost of transporting rebar can be mentioned the distance from the origin to the destination.

Summary

Rebars are divided into two general categories, ribbed and simple. A rebar without a tread is called a simple rebar, and a rebar with ridges on its surface is called a ribbed rebar. Rebars are usually used to increase the strength of concrete and strengthen the foundation, and for this reason, the main use of rebar, especially ribbed rebar, is in the construction industry.

In order to maintain and prevent rusting, it is necessary to store the rebars in a place that is not exposed to direct sunlight and moisture. Regarding the price of rebar, it should be said that it will undergo changes depending on various factors such as the exchange rate and the internal conditions of the country; Therefore, it is not possible to predict and determine a fixed price for this metal section.