Armature A1 - rolled metal, without which almost no construction site can do today. It is widely used for the manufacture of reinforced concrete products, as well as various metal structures and parts. This rolled metal is produced in accordance with GOST 5781-82.

1

According to GOST 5781, reinforcement A1 is designated differently - reinforcement (reinforcing steel - hereinafter AC) A-I (A240). This is a more correct name for this rolled metal product, used by all its manufacturers and professional consumers. In the technical language of GOST 5781, which classifies all types of reinforcing steel produced on it for reinforcing conventional as well as prestressed various reinforced concrete structures, this designation stands for "A1 class reinforcement".

The division into classes in this GOST is made according to one of the mechanical characteristics of the AU - according to the yield strength. Its conditional value for product A1 is indicated in parentheses after the index A - the number 240. This is the value of the yield point in kgf / mm 2, but multiplied by 10. Thus, the reinforcement A1 has a yield point of 24 kgf / mm 2 (corresponds to 235 N / mm 2).

According to GOST 5781, AS A-I is manufactured only with a smooth profile - without corrugation of the surface of a regular circular cross-section. Outwardly, depending on the nominal thickness, it looks like a steel wire or a bar.

Rebar without corrugation

Produce AUA240 hot rolled and carbon steel only. In this case, according to standard 5781, only St3sp, St3kp and St3ps brands are used. It is because of this that the A1 reinforcement, in contrast to GOST 5781, is most in demand and is used both for reinforcement and as ordinary rolled metal - for the manufacture of various steel parts and structures. After all, St3 is the most flexible, ductile of all carbon and even more low-alloy grades, and the best weldability of all alloys. Its chemical composition for finished fittings A-I must meet the requirements listed in GOST 380.

The range of production of smooth AS A-I includes 14 standard sizes in diameter in the range of 6–40 mm. Products with a thickness of 6–12 mm are produced with rods or in the form of coils, and reinforcement A1 of larger diameter is supplied only with rods. АС A240 rods are made in lengths of 6–12 m. Moreover, they can be of measured or unmeasured length. Unmeasured rods with a length of not less than 2 m and in a quantity constituting a maximum of 15% of the mass of the released batch can be supplied together with the measured ones. The consumer can order the option he needs himself, and upon agreement with the manufacturer, it is also possible to manufacture rods of 5–25 m.

2

In the table of GOST 5781 for the assortment of smooth AS A-I, the cross-sectional area, the weight of 1 m of the profile and the permissible maximum deviations in% of the last parameter for the finished products are indicated. The weight is theoretical (calculated), in the calculation of which it was assumed that the reinforcement A1 has a nominal diameter without deviations, and the density of steel is 7850 kg / m 3. Weight values ​​from the GOST table for all standard sizes АС A240 in kg:

• with a diameter of 6 mm - weight 0.222 kg;
• 8 – 0,395;
• 10 – 0,617;
• 12 – 0,888;
• 14 – 1,21;
• 16 – 1,58;
• 18 – 2;
• 20 – 2,47;
• 22 – 2,98;
• 25 – 3,85;
• 28 – 4,83;
• 32 – 6,31;
• 36 – 7,99;
• 40 – 9,87.

Maximum permissible deviations according to standard 5781:

• from the nominal diameter - must comply with the standards of GOST 2590;
• from weight for standard sizes:
  • from +9 to –7% of the theoretical weight of 1 m - with a diameter of 6, 8 mm;
  • from +5 to –6% - 10–14 mm;
  • from +3 to –5% - 16–28 mm;
  • from +3 to –4% - 32–40 mm.

The ovality of smooth reinforcement (the difference in one cross-section of the profile between the largest and smallest actual diameters) should not exceed the sum of the permissible minus and plus deviations in diameter.

For measuring rods АС A-I, requirements are imposed on maximum permissible deviations of length values, depending on the accuracy of cutting the rolled metal:

• for rods up to 6 m long inclusive: in case of increased cutting accuracy +25 mm, normal - +50 mm;
• more than 6 m: +35 and +70 mm, respectively.

The curvature of a speaker made in the form of rods should not exceed 0.6% of its measured length.

Smooth rods AC A-I

In addition to the yield strength, which was indicated above, for smooth AS A-I in the standard 5781, other mechanical properties are given. Flexural elongation (tests) - 25%. The ultimate tensile strength of the reinforcement is 373 N / mm 2 (corresponds to 38 kgf / mm 2).

After manufacturing, the A1 armature is subjected to bending tests in a cold state (must withstand them). It is bent around the mandrel at an angle of 180 °. For profiles with a thickness of 6–20 mm, a mandrel of the same diameter as that of the reinforcement itself is used. For speakers thicker than 20 mm, take with a diameter equal to 4 product sizes.

GOST 5781 obliges manufacturers to provide mechanical properties specified in it for A-I valves with a probability of at least 0.95.

There are also requirements for the surface quality of the finished speaker in GOST. Flaws, stress cracks and rolling, rolling sunsets and captivity on it should not be. The standard allows for individual rolling prints, sagging, dirt, traces of rolled bubbles, slight rust, as well as scaly and ripple.

3 Briefly about the areas of application of the A1 profiles

For reinforcement, they are used in almost all cases. In high-strength reinforced concrete, reinforced with a strong (usually corrugated) AS of a higher class, for mutual fixation of the latter and hardening of the surface layer of a product or a monolithic structure of objects such as dams, mines, bridges, airfields, tunnels, high-rise buildings, and so on.

When the design load on reinforced concrete allows, reinforcement A1 is used independently. Beams and panels are reinforced with products with a diameter of 12–32 mm, columns - 14–36 mm, foundation - 10–40 mm. In individual construction, AC 10-16 mm is usually used. Thin reinforcement - 6 and 8 mm - is used as wire for strapping, fastening a thick wire to each other, making construction and masonry nets, reinforcing frames, reinforcing concrete screeds of walls and floors, as well as plaster.

Armature A1 is widely used for the manufacture of decorative, load-bearing, frame and other metal structures, as well as parts for them and various equipment and technical equipment. It is used wherever ordinary rolled metal products from steel grade St3 are used.