The fittings are the basis of concrete walls, screeds and columns. This important element experiences all the main loads and the effects of bending moments, preventing deformation and destruction of the concrete base. As reinforcement, metal rods of different diameters, which have a circular cross section, are used. There are two main types of reinforcing metal bars: A1 and A3. To understand the difference between fittings A1 and A3, as well as the scope of their application, it is necessary to familiarize themselves with their main characteristics, consider their advantages and disadvantages.
Labeling Explanation
The marking of reinforcing bars is usually done using letter designations. The letters indicate the method by which this reinforcement was produced. So, for example, the presence of the letter A in the name indicates that the product is made by hot or cold rolling. If you compare both methods, it is worth noting that the steel obtained as a result of a cold roller, has increased strength characteristics and has a high hardness. The number is used to indicate the degree of fluidity of steel used in reinforcement; it determines the main difference between the metal grades. The yield coefficient depends on the maximum stress, which leads to the fact that the metal begins to deform. That is, the higher this indicator, the greater the strength of the rod itself. So, for example, A440 steel has a greater margin of safety compared to A240.
When constructing reinforced concrete structures, it is required to achieve the best strength of the entire structure using elements with a minimum weight. One solution is to reinforce the structure using a steel frame, for the assembly of which reinforcement of various cross-section diameters is used. It can be in the form of skeins or rods.
Additional marking of fittings
Each type of reinforcement, regardless of its profile, can be subjected to a separate temperature treatment. This can be understood by adding “At” at the end of the abbreviation. The reinforcement metal can be cleaned of excess impurities and have a uniform distribution of carbon, which increases the quality of welded joints (“C” is added to the abbreviation). Up to two percent copper may be added to the metal to improve its anticorrosion properties (at the end of the abbreviation “K”).
Difference of fittings A1 and A3
The main types used in construction are A3, as well as A1 fittings, GOST 30136-94. Sometimes you can find other names. For example, A1 fittings are often found under the name A240, and A3 - A400. The weight of reinforcement A1 and A3 is approximately the same, but the main difference between these types of reinforcement is that A1 has a smooth surface, and A3 has a corrugated surface. Corrugation provides the best contact with concrete. Due to the presence of a corrugated surface on A3, it has better reinforcing qualities compared to smooth reinforcement A1. The disadvantages of A3 include the appearance of additional stresses due to the need for an additional rolling cycle, which is necessary for the formation of a corrugated surface. Another disadvantage is the decrease in the effective cross section of the reinforcement with a constant linear meter weight, as well as a higher cost due to the complexity of its production. Strength is reduced by 6% with an asymmetric position of the corrugation pattern compared to round reinforcement.
Production material
There are differences between reinforcement A1 and A3 in terms of the type of steel used. Usually, steel with a low carbon content is used to make the materials. For the manufacture of reinforcement A3 use steel with increased ductility and low carbon content. A1 fittings are made of harder and harder steels. Also, according to GOST, the A1 variety should not have corrugation.
The diameter of the cross-section of the reinforcement rods, regardless of profile, usually varies between 8-25 millimeters. In the construction of larger structures, such as bridges and high-rise buildings, reinforcement with a diameter of 40 millimeters is used. The composition of the material of a smaller cross section includes mild steel that is more deeply purified from impurities. For large diameter fittings, any kind of low carbon steel can be used.
Fittings
Let's talk about the differences between fittings A1 and A3 in terms of application. A1 is widely used in reinforcing concrete structures in any form, whether it be a mesh or a complex frame. Smooth reinforcement is also actively used in the construction of any structures that have an auxiliary value (fences, products in the form of gratings, fences, etc.).
Reinforcement A3, which is corrugated, is mainly used for the construction of simple, light and high-strength frame structures made of concrete. This variety is not used in the construction of structures that perform an auxiliary function.