Rebar

Rebars are profiles with a circular cross section that can be considered as one of the most important types of construction metal materials. Rebar is used to increase the tensile strength of concert to prevent it from collapsing under pressure. Today, there is no building in which rebar is not used, but the rebars used are different.  To choose the right rebar for a building, one should consider various factors and have a proper understanding of the categories of rebar types. Rebars are generally made of carbon steel, but they can be divided into different categories based on production method, raw materials, size, standard, and manufacturer brand. Iran, as one of the largest steel producers in the world, has reached self-sufficiency in terms of rebar production, and various factories on our country produce this product.

In the following article, we intend to provide you with information about the types of rebar and their production. That information will help you choose the right rebar for your construction or industrial project.

 

Types of rebar shapes

The rebars are divided into two categories simple and ribbed, in terms of shape:

• Simple rebar: It is a rebar that has a smooth and polished surface and it doesn’t have treads. Less carbon is used in making simple rebar, and for this rebar has less tensile strength but is more malleable. This type of rebar is rarely used in construction and it is mostly used in industry. The possibility of easier cutting and bending in simple rebar makes it a good option for making all kind of bolt and nuts and zigzag rebar, use in welding and forging and use as screw in amateur banding or thermal rebar in block beam ceilings. But at the same time, its use in heavy structures is not suitable.
• Ribbed rebar: as its named suggest, ribbed rebar is a type of rebar that has tread on its outer surface. The tread, or the ridges that are created on the surface of the rebar when rolling, helps the rebar to be well attached to the concrete and not be separated from it easily, and in this way, it can better perform its task, which is to increase the tensile strength of the concrete. Ribbed rebars are divided into types of crossbar , spindle, and spiral based on the shape of the tread. While plain rebars are mostly used in industry, ribbed rebars are mostly used in construction. This type of rebars is used to increase the strength of concrete, the shear force, metal frame construction, etc.

 

Type of rebar

While there are only two types of rebars in terms of appearance, in terms of the material used in production, rebars can be divided in to six categories:

• European rebar: the most important material used in the production of European rebar is manganese. Although this type of rebar is very resistance and has bending properties it is not suitable for use in earthquake-prone areas or in projects that require a unified structure.
• Black rebar: the most widely used rebar in construction projects is the black rebar, which is made of high carbon steel. This type of rebar has high strength and tensile strength, but it is very erosive. For this reason, it is not recommended to use it in projects that are implemented in wet areas or in the vicinity of water.
• Epoxy rebar: this type of rebar is actually a black rebar coated with epoxy. In other words, epoxy coating is used to compensate for the erodibility characteristic of black rebar. However, due to the delicacy of the epoxy coating, this type of rebar is only slightly more resistant to corrosion than black rebar.
• Galvanizeh rebar: galvanizeh rebar is much more to corrosion than black rebar. As such, this type of rebar is naturally more expensive than black or epoxy rebar. The use of galvanizeh rebar is recommended in projects that require high corrosion resistance.
• Polymer rebar (GFRP): this type of rebar is made of GFRP polymer reinforced with fibers GFRP rebar is very similar to more traditional form of rebar, but weights less and is much more resistant to corrosion. I construction projects that are not located near electric or magnetic fields, GFRP rebar is the best choice. The very high resistance of this type of rebar against chlorides and sulfates and the low probability of corrosion and rust in them have made them become widely used products.
• Stainless steel rebar: this type of rebar is made of stainless steel instead of carbon steel and is much more expensive than black rebar due to its strength and corrosion resistance. For this reason, they are used in large-scale projects such as road construction, high way construction, bridge construction, where long life cycles are more important than initial cost.

 

Type of rebar production methods

The method of making rebar determines many of its feature. Some types of rebar have more strength and hardness, and others are more flexible. Different methods of rebar production have a lot in common, especially in the initial process, but the difference is usually in the type of material used and the final processes.

• Hot rolling method: in this method, the casting ingot is heated to a temperature of 1000to 1100 degrees Celsius and then rolled.
• Cold rolling method: in this method, the rolling operation is performed at a low temperature and almost close to room temperature. Actually, in this method, more pressure and a greater number of reduce the steel diameter. Rebars produced by cold rolling have higher strength than rebars produced by hot rolling.
• Termax method: this method is used to make rebar with less carbon steel. In this method; the rebar produced by the hot rolling method is immediately cooled using water or oil. In this way, while the outer surface of the product is cooled, the inner surfaces still have heat and send this heat to the outer surface. As a result, the hardness and fragility of the product is reduced.
• Micro alloy method: the process used in this method is similar to the hot rolling method, but in this method, materials such as titanium, vanadium, and niobium are added to the steel alloy at the beginning of the strength of the work, which greatly increases the rebar. Rebars produced by micro alloying method have more flexibility and elasticity. At the same time, the rebars produced in this way have high quality and therefore high price.

 

All kind of rebar sizes

Rebar is produced in different sizes, the most used of which are 8,10,12 and 14 diameter bars. The diameter bars. The diameter of the rebar is important because it determines the distance limit and the minimum protective concrete over required in the building. The suitable rebar diameter for the project is determined by the accounting engineer according to the national building regulations.

Standard types of rebar: since the steels used in the production of rebars in the Iran are mainly produced by the Isfahan iron smelting factory operates according to the Russian standard, the same standard is used throughout Iran. According to the Russian standard, rebars are divided into four types A1, A2, A3 and A4in terms of mechanical properties of steel:

• A1: it is simple rebar, which is also known as ductile rebar. Almost 24% of carbon and 60% of silicon are used in the production of this rebar, which it is soft and has low tensile strength. This rebar is more suitable for use in forging and welding and generally industrial uses such as nail making. However, due to not having a tread, this rebar should not use as resistance rebar.
• A2: this group refers to ribbed rebar whose tread continues spirally from the beginning to the end of the rebar without being interrupted. For this reason, this rebar is also called “simple spiral tread” this type of rebar is semi-dry or semi- soft and it is known as tread 340 in Iran’s national standard 3132. Type A2 rebar can be used in light construction and in situation where high ductility is required. It is recommended to use this type of rebar in areas with extreme temperature changes.
• A3: this standard is related to a group of ribbed rebars, whose treads are created in the form of two half-spirals opposite direction in the two longitudinal halves of the rebar. This rebar is considered a dry rebar due to the characteristics of the steel itself. It is forbidden to perform welding operations on this type of rebar and it cannot be used for forging or in places where there is a need to change the shape with a sharp angle.
• A4: the strongest type of rebar that has the greatest strength in load bearing is A4 rebar. The tread s of this rebars are compound treads that continue with 7-8 pattern throughout the body of the rebar. This type of rebar is used in projects that require very high resistance, especially earthquake- resistance structures, although it should not be used in rotating frames or shear walls. In projects that are implemented in desert areas with extreme temperature changes, A4 rebar is the best option. Currently, in Iran, the demand for rebar is mostly related to A2 and A3 types, and the other two types are less used. For this reason, most factories produce one of these two types of rebar.

 

Types of rebar manufactures

As mentioned in the introduction, Iran is self-sufficient in rebar production. There are many factories in Iran that produce rebar, among them are Isfahan iron smelter; Rad Hamedan, Zafar Bonab, Amir Kabir Khazar, Siyaden Abhar, Hashtroud, Yazd steel, Hirband, Zarandieh, Tabriz Arg, Kavir Kashan, Rohina Jonob, Zagros steel, Steel Amin, Arian Steel, Darpad Tabriz, Persian Steel, Steel Gharb, Hasan roud, pardis Azerbaijan, Anahita Gillan, and Shahin Bonab.                                        each of these factories produce specific types of rebar in term of production method, shape size and material, and you can see the product specifications of some of the best rebar brands in Iran in the table below

 Rebar pricing

Various factors, including the type of raw materials and the production method, are involved in determining the price of rebar. The characteristics of the final product, such as ductility or high strength, also play a role in determining the price of rebar the Termax method is a fast method and as a result, the final product obtained from it has a lower price. Also, micro alloy bar is of higher quality and they are used in more limited projects and therefore more expensive.

The production of rebars with a larger diameter requires, which result in a higher price. Of course, this factor loses its importance in the case where the sales is made by weight, because the rebar wight and its cost are calculated based on the price of the iron unit used. There is no doubt that the production of ribbed rebar requires more time, labor, and cost than plain rebar and therefore, it has a higher price. At the same time, the shape and type of ribbed rebar tread is also effective in determining its price.

Also, pay attention that the brand of these manufacturers has an effect on the price of the rebar they produce. There is no doubt that the quality of rebars produced by iron smelting factories is higher and, as a result, their prices are higher. Therefore, to choose the right rebar for your project, you should also consider the cost of the brand.  Currently, Isfahan iron smelting rebar is the best rebar produced in Iran.

In the next ranks, we can mention Kavir Kashan steel rebar, Khorasan steel, Miyaneh steel, Anahita Gillan steel, Rohina steel complex, Kousar Ahvaz steel, Bafq Yazd steel, Abarkoh Yazd steel, and Shahin Bonab steel complex.

 

Conclusion

Due to fluctuations in the price of row materials and works shop costs, usually the price of rebar also faces many changes. For this reason, many factories determine the price of their products on a daily basis. Therefore, if you need to use rebar, you should consider its price on the day of purchase. Various sources publish the price of rebar brands based on the date of the day, and you can choose the right product according to the needs of the project and the considered cost.