Quick access to the content of this article
What is thermal rebar?
What are the reasons for using thermal rebars?
Application of thermal rebar in different parts of the structure
Calculation method of thermal rebar for use in the roof
How to close the thermal armature?
Alternative methods of thermal rebar
Price per kilo of heat
The best producers of thermal rebar in Iran
One of the challenges of building a concrete building is the temperature changes and the resulting expansion and contraction. This can cause the concrete to crack and fail. If this happens, the strength and stability of the entire building will be jeopardized. To prevent such incidents, various solutions are used. One of them is to use thermal rebar.
The presence of these steel sections in the structure controls the thermal stresses of concrete (expansion and contraction). In engineering books, this type of product is also called “heat drop rebar”. In the rest of this article, we will talk about thermal rebar, how to calculate and its price. Please stay with us.
What is thermal rebar?
Thermal rebar is a group of steel sections that are used in concrete structures to prevent the effect of temperature changes. This product is placed vertically in the structure; so that its final shape will be similar to the letter T.
Normally, temperature changes can cause expansion and contraction of concrete and rebars. But by using thermal rebar, this is prevented. The result is that the concrete does not crack and the stability and strength of the building is maintained.
The use of these products, like any other new member in construction, has many pros and cons.
Some consider its use as necessary and its presence improves the performance of concrete in certain conditions. If many others consider the use of thermal rebar a waste of time and money. Like other rebars, size is also effective in the price per kilo of heat. For this reason, we suggest you to check the site or the current price channel of Isfahan Ahan for detailed information on the prices.
During the construction of the roofs, a certain number of thermal bars of the block beam roof are placed at a certain distance, in the upper third of the concrete slab, left and right and perpendicular to the beams (the concrete slab is a part of the structure whose task is to bear vertical loads).
The production process of this product is that during the cement hydration reaction, which is basically the reaction resulting from the combination of water and cement, the thermal rebar engages with the concrete and prevents excessive expansion and contraction of the concrete. This issue prevents the occurrence of deep cracks in the roof.
The important thing in this field is the pressure on these bars. Since the diameter of the rebar used is usually small, the thermal rebar has little resistance to pressure. Therefore, after installation, care should be taken that the movement of building contractors does not cause bending in it. Because in case of bending, the rebars do not show proper performance when the concrete hardens.
What are the reasons for using thermal rebars?
As mentioned, the most important reason for using thermal reinforcement is to reduce the stress resulting from the hardening of concrete and prevent cracking. But regarding the use of thermal reinforcements, we can also mention three other cases.
Many structural engineers are of the opinion that if thermal reinforcements are not used in the roof and deep and transverse cracks occur, the integrity of the roof diaphragm will be broken, and in case of an earthquake, this break will cause the roof to collapse.
The use of this product, in addition to its main use, also helps a lot to improve the load.
Using thermal rebar in the roof increases its resistance to fire.
Application of thermal rebar in different parts of the structure
One of the most important uses of thermal rebar is its application in the block beam roof. In addition, this product can be used in chromite roof, retaining wall, slabs, etc. In general, it is possible to use this section of steel in parts of the building that need more resistance and according to the opinion of the project managers.
Calculation method of thermal rebar for use in the roof
In general, the calculation of the required product for use on the roof is done by the structural engineer of the project and based on the regulation of the use of thermal rebar in the building. But in order to get a little familiar with the calculation method and rules of this work, pay attention to the four points mentioned below.
1. Rebar type
Usually, due to the reduction of costs and due to the lack of tension between reinforcement and concrete, there is no need to use ribbed rebar. Therefore, it is better to use simple type as thermal rebar.
2. Rebar size
Normally, the cross-section size used as heat loss rebar is 5 to 6 mm, depending on the type of rebar. But you should keep in mind that the diameter of the steel product may change based on engineering calculations and a larger diameter rebar is needed.
3. Amount of rebar
By determining the distance of rebars from each other, its amount in the roof can be calculated. In general, the distance of thermal bars should not be more than 50 cm or more than 5 times the thickness of the slab. For this reason, the distance of 25 cm is a suitable number for placing this product in small buildings.
4. Rebar weight
After considering the type of rebar and calculating its diameter, measuring the thickness of the slab and calculating the distances of use, the structural engineer calculates the required number of rebars. After that, considering the maximum standard weight for the roof and calculating the available concrete, beams and blocks, it calculates the allowed weight for the thermal bars.
Of course, in engineering calculations, this step is done first so that, if needed, the type and diameter of the rebar used to reach the standard weight can be reduced.
How to close the thermal armature?
First of all, pay attention to the fact that the installation of thermal rebar, as well as its welding in columns, roofs and foundations, is prohibited by the engineering system organization due to the possibility of welding failure. For this reason, like other components of the structure, these products must be closed with wire. The thermal armature is usually restrained by a cross method and by means of a wire.
In the cross method, the thermal reinforcement is placed vertically next to other rebars. Then, the wire is crossed under it and comes to the armature. By repeating this movement from the opposite side, they are closed in the center using pliers. The noteworthy point is that, like other methods and for greater strength, the wire can be doubled and a double cross knot can be used.
As we mentioned in the calculation section, generally, due to the reduction of costs and lack of obligation to use ribbed rebars, the simple type is used as thermal rebars. Simple reinforcement, which is also called A1 rebar in the country’s market, has a different price according to the chemical composition and the manufacturing plant. But the price of this product in Azar 1402 is about 25 thousand tomans.
Azar Gostar Sodid factory, Ayan Sanat, Zob Ahan of Isfahan, and Sooreh Science and Industry of Kashan Desert are among the factories that produce various types of rebar in the country.
Alternative methods of thermal rebar
For those who do not agree with the use of heat rebar, they can use alternative methods. The use of fiber concrete, the use of super-lubricants, and increasing the ratio of water to cement are among the things that can be used instead of thermal rebar.
Price per kilo of heat
The price of thermal zigzag has been fluctuating in recent years and even months. These price changes can be seen in other steel sections as well. But in the last six months, the price of this product has decreased. To buy thermal rebar, you have the possibility to choose from the products of different factories. This can be done based on the distance between the manufacturer and the project site.
The best producers of thermal rebar in Iran
Among the best producers of this product, we can mention Isfahan Iron Smelter, Yazd Steel, Kashan Desert Steel, Natanz Steel, Aligoders Steel and Iran’s National Steel Industrial Group. Most of these factories are located in the center of the country. Therefore, to buy the product, buyers’ hands are open to choose. Because the cost of transporting the product from each factory does not change much.
In general, the use of thermal rebar for strengthening concrete is one of the common methods. Of course, this work has its opponents. These people can use alternative methods. To buy a thermal armature, you can choose from different manufacturers. Finally, to place an order, it is possible to buy the product by phone and online.
