The difference between fittings A1 and A3.

The most common types of fittings are A1 and A3. What is the specificity of these materials?

What is the A1 armature?

This type of reinforcement has a smooth surface. It is usually supplied from the factory in the form of riots or rods. The diameter of the A1 reinforcement can be 6-40 mm. The fact that A1 is a material with a smooth surface predetermines the relatively low stability of its adhesion to concrete, and therefore it is not always possible to use it as the main one for reinforcement in reinforced concrete structures.

Armature A1

The considered type of reinforcement is most often produced from carbon steels of the type:

  1. St3kp (or boiling);
  2. St3ps (or semi-calm);
  3. St3sp (or calm).

Reinforcement from the first type of steel is used in structures that do not involve a large external load. The most durable material is the one that is made using St3sp steel.

The main regulatory document that defines the characteristics of type A1 fittings is GOST 5781-82.

The material in question is most often used in monolithic buildings, as well as in the production of various products from reinforced concrete. A1 fittings are also widely used in industry.

It can be noted that the corresponding material is characterized by high resistance to aggressive media, and what is especially important - to low, high air temperatures, as well as their abrupt change.

Among other important advantages of the considered reinforcement is a relatively low price. Therefore, its application where possible from the point of view of production technologies can significantly reduce the project budget.

Another important characteristic of A1 reinforcement is good weldability. This increases the versatility of the respective material.

What is the A3 armature?

This type of reinforcement is made from hot rolled steel. Most often, A3 material is used in the construction of various structures - residential, industrial. Unlike smooth A1, the considered reinforcement is corrugated. On its surface there is a special pattern - in the form of 2 longitudinally located ribs, as well as many transverse ones, which are located at a small distance from each other.

Reinforcement A3

The noted feature, which characterizes the surface of the reinforcement, makes it possible to increase its adhesion to concrete in the corresponding building structures. Therefore, the material of type A3 can be used as the main one when reinforcing reinforced concrete structures.

In addition, A3 reinforcement in many cases is produced from high-alloy steels - with impurities of chromium, manganese, titanium, and silicon. This predetermines the very high strength of the respective material.

Armature A3 can have a diameter of 6-80 mm. It is customary to classify it into 3 main varieties:

  • hot-rolled;
  • hardened by quenching;
  • Strengthened by drawing.

The main advantage of A3 reinforcement is the ability to significantly improve the operational properties of building structures, in the structure of which it may be present. Reinforced concrete structures with A3 reinforcement acquire extremely high resistance to various mechanical and, in many respects, atmospheric influences.

Like the material of type A1, the reinforcement in question is well welded. It is also characterized by its resistance to many aggressive environments - in particular, it resists oxidation very well. But from the point of view of resistance to high and low air temperatures, as well as their differences, A3 fittings, according to many experts, are inferior to A1 type material.


The main difference between A1 and A3 reinforcement is that the first material is smooth and is produced from carbon steels. The second is corrugated, produced in many cases from high-alloy steels. This property predetermines a significant difference between the considered reinforcement from the point of view of:

  • adhesion to concrete;
  • strength;
  • ​​
  • universality.

According to the first criterion, the A3 reinforcement wins - due to the corrugated surface. In terms of strength, A3 material also surpasses A1.

But from the point of view of versatility, according to many experts, the A1 armature has advantages. This is due to its higher resistance to aggressive environments, and above all - to high and low temperatures, their drop. So, in the conditions of the Far North, A1 reinforcement can be indispensable, since A3 material is not always resistant to low temperatures.

Having determined what is the difference between the reinforcement A1 and A3, we fix the conclusions in the table.


Armature A1 Armature A3
Has a smooth surfaceHas a corrugated surface
Made from carbon steelsMade from high alloy steels
Provides a weaker bond to concreteProvides a stronger bond to concrete
More resistant to low temperatures, their abrupt change to higherLess resistant to low temperatures, their frequent change to higher