Hot-rolled rebar, depending on the mechanical properties, is divided into the following classes:
A-I (A240), A-II (A300), A-III (A400), A-IV (A600), A-V (A800), A-VI (A1000) (according to GOST 5781-82).

According to the nature of the profile, the reinforcement is divided into smooth and periodic profile. Reinforcing steel class A-I(A240) are made smooth, classes from A-II (A300) to A-VI (A1000) - a periodic profile, but at the request of the consumer steel classes A-I I (A300), A-III (A400), A-IV (A600), A-V (A800) can be made smooth.

Weight of a running meter of a profile and cross-sectional area(according to GOST 5781-82)

Profile number	Cross-sectional area, cm2 1.2	Weight 1 m profile
		Theoretical, kg	Limit deviations, %

Note. The mass of 1 m of the profile is calculated according to the nominal dimensions. When calculating the mass of 1 m, the density of steel is assumed to be 7.85 g/cm3. The probability of providing a mass of 1 m must be at least 0.9.

Steel grades for the manufacture of reinforcement (according to GOST 5781-82)

Reinforcing steel is made from carbon and low-alloy steel grades listed below. The steel grade is indicated by the consumer in the order. In the absence of an indication, the steel grade is set by the manufacturer. For class A-IV (A600) rods, steel grades are set by agreement between the manufacturer and the consumer.

Reinforcing steel class	Profile diameter, mm	steel grade
		StZkp, StZps, StZsp
		St5sp, St5ps
		22H2G2AYU, 22H2G2R, 20H2G2SR

It is allowed to manufacture reinforcing steel of class A-V (A800) from steel grades 22Kh2G2AYU, 22Kh2G2R and 20Kh2G2SR.

1. Hot-rolled steel for reinforced concrete structures

Reinforcing steel of a periodic profile rods with transverse protrusions (grooving) evenly spaced on their surface at an angle to the longitudinal axis of the rod to improve adhesion to concrete.

Reinforcing steel smooth
round rods with a smooth, non-grooved surface to improve adhesion to concrete.

Strength class
the normalized value of the physical or conditional yield strength of steel established by the standard.

The angle of inclination of the transverse ledges
the angle between the transverse protrusions (grooving) and the longitudinal axis of the rod.

Step of transverse ledges
the distance between the centers of two successive transverse projections, measured parallel to the longitudinal axis of the bar.

Height of transverse projections
the distance from the highest point of the transverse protrusion to the surface of the core of the rod of a periodic profile, measured at right angles to the longitudinal axis of the rod.

Nominal diameter of reinforcing steel of a periodic profile (profile number)
the diameter of a round smooth rod of equal cross-sectional area.

Nominal cross-sectional area
cross-sectional area equivalent to the cross-sectional area of ​​a round smooth bar of the same nominal diameter.

Depending on the mechanical properties, reinforcing steel is divided into classes A-I (A240), A-II (A300), A-III (A400), A-IV (A600), A-V (A800), A-VI (A1000).

Reinforcing steel is made in rods or coils. Reinforcing steel of class A-I (A240) is made smooth, classes A-II (A300), A-III (A400), A-IV (A600), A-V (A800), A-VI (A1000) - periodic profile. At the request of the consumer, steel of classes A-II (A300), A-III (A400), A-IV (A600), A-V (A800) is made smooth.

Reinforcing steel of a periodic profile is a round profile with two longitudinal ribs and transverse ledges running along a three-start helix. For profiles with a diameter of 6 mm, protrusions running along a single-start helix are allowed, with a diameter of 8 mm - along a two-start helix.

Reinforcing steel of class A-II (A300), made in the usual version, and special purpose Ac-II (Ac300), must have protrusions running along helical lines with the same approach on both sides of the profile.

Steel of class A-III (A400) and classes A-IV (A600), A-V (A800), A-VI (A1000) must have protrusions along helical lines that have right-handed on one side of the profile and left-handed entries on the other.

The relative displacements of the helical protrusions along the sides of the profile, separated by longitudinal ribs, are not standardized.

Reinforcing steel of classes A-I (A240) and A-II (A300) with a diameter of up to 12 mm and class A-III (A400) with a diameter of up to 10 mm incl. are made in coils or rods, large diameters - in rods. Reinforcing steel of classes A-IV (A600), A-V (A800) and A-VI (A1000) of all sizes is made in rods, with a diameter of 6 and 8 mm - by agreement between the manufacturer and the consumer in coils.

Reinforcing steel is made from carbon and low-alloy steel of the grades indicated in the table. For class A-IV (A600) rods, steel grades are set by agreement between the manufacturer and the consumer.

Reinforcing steel class	Profile diameter, mm	steel grade
		St3kp, St3ps, St3sp
		St5sp, St5ps
Ac-II (Ac300)
		22X2G2AYU, 22X2G2R, 20H2G2SR

Notes: It is allowed to manufacture reinforcing steel of class A-V (A800) from steel grades 22Kh2G2AYU, 22Kh2G2R and 20Kh2G2SR. Dimensions in parentheses are made according to
agreement between the manufacturer and the consumer.

Profile number (nominal di rod diameter), mm	Weight of 1 m profile, kg	Number of meters in 1 ton

Reinforcing steel is divided into classes depending on:

• from mechanical properties - strength class (established by the standard of the normalized value of the conditional or physical yield strength in newtons per square millimeter);
• from performance characteristics- for weldable (index C), resistant to corrosion cracking (index K).

Reinforcing steel is produced in classes At400S, At500S, At600, At600S, At600K, At800, At800K, At1000, At1000K and At1200. By agreement between the manufacturer and the consumer, reinforcing steel of strength class At800 and above is allowed to be made smooth.

Marking:

• o At400C - white;
• o At500C - white and blue;
• o At600 - yellow;
• o At600C - yellow and white;
• o At600K - yellow and red;
• o At800 - green;
• o At800K - green and red;
• o At1000 - blue;
• o At1000K - blue and red;
• o At1200 - black.

Reinforcing steel class	steel grade
	St3sp, St3ps
	St5sp, St5ps
	25G2S, 35GS, 28S, 27GS
	10GS2, 08G2S, 25S2R
	20GS, 20GS2, 08G2S, 10GS2, 28S, 25G2S, 22S, 35GS, 25S2R, 20GS2
	20GS, 20GS2, 25S2R

GOST 10884-94: Reinforcing steel thermomechanically hardened for iron concrete structures

Technicalconditions

Thermomechanically hardened steel bars for reinforcedconcrete constructions. Specifications

Introduction date 1996-01-01

Foreword

• 1. DEVELOPED TC 120 "Iron, steel, rolled products" INTRODUCED by the State Standard of Russia
• 2. ADOPTED by the Interstate Council for Standardization, Metrology and Certification (Minutes No. 6-94 dated 10/17/94). Voted for the adoption of the standard:

State name	Name of the national standardization body
Republic of Azerbaijan	Azgosstandart
Republic of Armenia	Armstate standard
Republic of Belarus	Belstandard
Republic of Georgia	Gruzstandard
The Republic of Kazakhstan	State Standard of the Republic of Kazakhstan
Republic of Kyrgyzstan	Kyrgyzstandart
The Republic of Moldova	Moldovastandard
Russian Federation	Gosstandart of Russia
The Republic of Uzbekistan	Uzgosstandart
	State Standard of Ukraine

• 4. Resolution of the Committee Russian Federation on standardization, metrology and certification No. 214 dated April 13, 1995 Interstate standard GOST 10884-94 was put into effect directly as the state standard of the Russian Federation on January 1, 1996.
• 5. Instead of GOST 10884-81.

1 AREA OF USE.

This standard applies to thermomechanically hardened smooth and periodic reinforcing steel with diameters of 6-40 mm, intended for reinforcing reinforced concrete structures. The standard contains certification requirements for thermomechanically hardened reinforcing steel for reinforced concrete structures.

• GOST 380-88 Carbon steel of ordinary quality. Stamps
• GOST 2999-75 Metals and alloys. Vickers hardness method
• GOST 5781-82 Hot-rolled steel for reinforcing reinforced concrete structures. Specifications
• GOST 7564-73 Steel. General rules sampling, blanks and samples for mechanical and technological tests
• GOST 7565-81 Cast iron, steel and alloys. Sampling method for chemical composition
• GOST 7566-81 Rolled products and further processing products. Rules for acceptance, labeling, packaging, transportation to storage
• GOST 10243-75 Steel. Method of testing and evaluation of macrostructure
• GOST 12004-81 Reinforcing steel. Tensile test methods
• GOST 12344-88 Alloyed and high-alloyed steels. Methods for determining carbon
• GOST 12345-88 Alloyed and high-alloyed steels. Methods for the determination of sulfur
• GOST 12346-78 Alloy and high alloy steels. Methods for the determination of silicon
• GOST 12347-77 Alloyed and high-alloyed steels. Phosphorus determination methods
• GOST 12348-78 Alloyed and high-alloyed steels. Methods for determination of manganese
• GOST 12350-78. Alloy and high alloy steels. Chromium determination methods
• GOST 12352-81 Alloy and high alloy steels. Nickel determination methods
• GOST 12355-78 Alloy and high alloy steels. Methods for determining copper
• GOST 12356-81 Alloy and high alloy steels. Titanium determination methods
• GOST 12357-84 Alloyed and high-alloyed steels. Methods for the determination of aluminum
• GOST 12358-82 Alloy and high alloy steels. Arsenic determination methods
• GOST 12359-81 Carbon steels, alloyed and high-alloyed. Nitrogen determination methods
• GOST 12360-82 Alloyed and high-alloyed steels. Boron determination methods
• GOST 14019-80 Methods and alloys. Bend Test Methods
• GOST 14098-91 Welded fittings and embedded products of reinforced concrete structures. Types, design and dimensions
• GOST 18895-81 Steel. Photoelectric spectral analysis method

3. DEFINITIONS

The following terms apply in this standard:

• Reinforcing steel of a periodic profile - rods with transverse protrusions (corrugated) evenly spaced on their surface at an angle to the longitudinal axis of the rod to improve adhesion to concrete.
• Reinforcing steel smooth - round rods with a smooth surface that does not have a corrugation to improve adhesion to concrete.
• Strength class - the normalized value of the physical or conditional yield strength of steel established by the standard.
• The angle of inclination of the transverse protrusions is the angle between the transverse protrusions (corrugation) and the longitudinal axis of the rod.
• Step of transverse protrusions - the distance between the centers of two successive transverse protrusions, measured parallel to the longitudinal axis of the rod.
• The height of the transverse protrusions is the distance from the highest point of the transverse protrusion to the surface of the core of the rod of a periodic profile, measured at right angles to the longitudinal axis of the rod.
• The nominal diameter of the reinforcing steel of a periodic profile (profile number) is the diameter of a round smooth rod of equal cross-sectional area (table 1).
• Nominal cross-sectional area - the cross-sectional area equivalent to the cross-sectional area of ​​a round smooth bar of the same nominal diameter.

4. MAIN PARAMETERS AND DIMENSIONS

• Reinforcing steel is divided into classes depending on: - on mechanical properties - strength class (established by the standard of the normalized value of the conditional or physical yield strength in newtons per square millimeter); - on operational characteristics - on weldable (index C), resistant to corrosion cracking (index TO).
• Reinforcing steel is produced in classes At400S, At500S, At600, At600S, At600K, At800, At800K, At1000, At1000K and At1200.
• Reinforcing steel is made with a periodic profile according to Figure 1 or GOST 5781. The dimensions of the periodic profile corresponding to Figure 1 are shown in Table 1. By agreement between the manufacturer and the consumer, reinforcing steel of strength class At800 and higher can be made smooth.

Table 1. In millimeters.

Nominal diameter of reinforcing steel (profile number)	Periodic profile parameters
		h, not less than							s, no more
			nominal	accuracy deviations
				ordinary	elevated

* Limit deviations are ±15%.

• Reinforcing steel with a profile corresponding to Figure 1 is a round rod with or without two longitudinal ribs and with transverse sickle-shaped protrusions located at an angle to the longitudinal axis of the rod, with a height in the middle, not intersecting with the longitudinal ribs and running along a multi-start helical line having on sides of the profile in different directions.
• The nominal diameters of reinforcing steel, cross-sectional areas, linear density (mass of a rod 1 m long), maximum deviations in size and weight, ovality and curvature of the rods must comply with those established by Table 1 and GOST 5781. Note - The nominal diameter of reinforcing steel of a periodic profile (profile number ) corresponds to the nominal diameter of a smooth reinforcing steel of equal cross-sectional area.
• Reinforcing steel with a diameter of 10 mm or more is made in the form of rods with a length specified in the order. Reinforcing steel with a diameter of 6 and 8 mm is produced in coils. The manufacture of reinforcing steel of the At400S, At500S and At600S classes with a diameter of 10 mm is allowed in coils.
• Limit deviations along the length of bars of measured length must comply with the requirements of GOST 5781.
• The designation of reinforcing steel should contain: - nominal diameter (profile number), mm; - designation of strength class (4.1); - designation of its operational characteristics - weldability (index C), resistance to corrosion cracking (index K). Examples of symbol Reinforcing steel with a diameter 20 mm, strength class At800:20At800 GOST 10884-94. The same, with a diameter of 10 mm, strength class At400, weldable (C): 10At400C GOST 10884-94. The same, with a diameter of 16 mm, strength class At600, resistant to corrosion cracking (K): 16At600K GOST 10884-94

5. TECHNICAL REQUIREMENTS

Reinforcing steel is manufactured in accordance with the requirements of this standard according to the technological regulations approved in the prescribed manner. 5.2 Reinforcing steel is made from carbon and low-alloy steel with a mass fraction of chemical elements according to the ladle sample given in table 2.

Table 2.

Notes:

• For reinforcing steel of At400S and At500S classes, while ensuring mechanical properties and weldability, a mass fraction of silicon up to 1.2% is allowed.
• For reinforcing steel of the At500C class, a mass fraction of carbon of not more than 0.37% is allowed.
• Recommended steel grades and their chemical composition are given in Appendix A.5.3. For weldable reinforcing steel of the At400C class, the carbon equivalent, determined by the formula, must be at least 0.32%, the At500C class - at least 0.40%, the At600C class - at least 0.44%. In this formula - the mass fraction of the corresponding chemical elements.5.4. Maximum deviations in chemical composition in finished rolled products from the standards established by Table 2 must correspond to those given in Table 3.

Table 3

• Weldability and resistance to stress corrosion cracking of reinforcing steel are ensured chemical composition and manufacturing technology in accordance with Appendix B.5.6 The mechanical properties of reinforcing steel before and after electric heating, as well as the results of its bending tests, must comply with the requirements established by Table 4. Statistical indicators of the mechanical properties of reinforcing steel must comply with those established by Table 5 and Appendix C.

Table 4

Strength class of reinforcing steel	Nominal diameters, mm	Mechanical properties				Cold bending test, degree	Mandrel diameter (d - nominal rod diameter)
		tensile strength, N/mm2	Conditional or physical yield strength, N/mm2	Relative extension, %

* For reinforcing steel of class At800K with diameters of 18-32 mm.
Notes:

• For reinforcing steel of the At600C class, it is allowed to reduce the tensile strength by 50 N/mm2 below the norms established by the table, with an increase in relative elongation by 2% (abs.) and uniform elongation by 1% (abs.).
• For reinforcing steel of At400S, At500S and At600 classes in bars, the tensile strength should not exceed the values ​​given in the table by more than 200 N/mm2.
• For reinforcing steel of strength class At1200 in the state of delivery, it is allowed to reduce the conditional yield strength to 1150 N/mm2.
• When testing reinforcing steel of strength classes At800, At1000 and At1200 immediately after rolling, a decrease in ductility by 1% (abs) is allowed.

Table 5

Nominal diameter of reinforcing steel (profile number), mm	Statistical indicators of mechanical properties
	Standard deviation, N/mm 2				Attitude
	S		S

Notes:

• At the request of the consumer, the requirements for stress relaxation, fatigue strength and bending test with extension are regulated.
• For reinforcing steel of strength classes At800, At1000 and At1200, the conditional elastic limit must be at least 0.85.
• The surface quality of reinforcing steel must comply with the requirements of GOST 5781.
• Marking applied during rolling

• In the absence of a rolling marking, the ends of the rods or bundles of reinforcing steel of the corresponding class must be painted with indelible paint of the following colors:
• The rods are packed in bundles weighing up to 10 tons, tied with wire. At the request of consumers, the rods are packed in bundles weighing up to 3 tons.
• When supplied in coils, each coil must consist of one piece of reinforcing steel. The mass of the skein is up to 3 tons. The skein must be evenly tied around the circumference in at least four places. Each of these knittings should have an intermediate screed (knitting), which is located at the level of the average thickness of the skein.
• A label must be firmly attached to each coil or bundle of rods, indicating: - trademark or trademark and the name of the manufacturer; - symbol of reinforcing steel (4.8); - batch number; - technical control stamp.
• If the mechanical properties of the reinforcing steel do not correspond to the marking applied during its rolling, the actual strength class must be indicated on the label and in the quality document, and the ends of the rods must be painted in accordance with 5.11.

6. ACCEPTANCE RULES.

• Reinforcing steel is accepted in batches. The batch must consist of reinforcing steel of the same class and the same diameter, made from one melting ladle. The mass of the batch is in accordance with GOST 5781.
• To control the geometric parameters of reinforcing steel and its linear density (mass of a rod 1 m long), the following are selected from the batch: - when delivered in rods - at least 5% of the lot; - when delivered in coils - two coils.
• To check the chemical composition of steel, one sample is taken from the melting ladle. Sampling is according to GOST 7565.
• To control the mechanical properties of reinforcing steel, two samples are taken from the batch for tensile testing before and after electric heating.
• Two specimens are taken from the lot for the bending test.
• The control of tensile strength and conditional yield strength after electric heating is carried out in the absence of special tempering in the technological process or in the presence of tempering with heating below the temperatures indicated in Table 4.6.6
• To control stress relaxation, fatigue strength and bending with extension (when these parameters are regulated at the request of the consumer), a batch is selected for testing: - for stress relaxation and bending with extension - four samples each; - for fatigue strength - six samples.
• Sampling for control of mechanical properties and bending tests, as well as for stress relaxation, fatigue strength and bending with extension is carried out in accordance with GOST 7564. The sampling interval should be at least half the time spent on rolling reinforcing steel of this batch.
• Definition of statistical indicators strength characteristics reinforcing steel - in accordance with Appendix B.
• The control of mechanical properties is allowed to be carried out by non-destructive methods in accordance with the regulatory and technological documentation.
• Upon receipt of unsatisfactory test results for at least one of the indicators, repeated tests should be carried out in accordance with GOST 7566.
• A batch of reinforcing steel must be accompanied by a quality document in accordance with GOST 7566 with additional data: - nominal diameter (profile number), mm; - class of reinforcing steel; - mechanical properties before and after electric heating; - minimum average value and standard deviation of tensile strength values rupture and batch yield strength; - cold bending test results; - uniform elongation values.
• When regulating, at the request of the consumer, stress relaxation, fatigue strength and bending with extension (5.7), the test results of these characteristics are given in the quality document. At the request of the consumer, the chemical composition of the steel must be indicated.

7. CONTROL METHODS.

• The geometric parameters of reinforcing steel are checked with a measuring tool of the required accuracy.
• The linear density of reinforcing steel is determined as the arithmetic mean of the mass of two samples 1 m long, weighed to the nearest 0.01 kg. The length of the sample is measured with an accuracy of 0.001 m.
• The chemical composition of steel is determined according to GOST 12344 - GOST 12348, GOST 12350, GOST 12352, GOST 12355, GOST 12356 - GOST 12360, GOST 18895 or other methods that are not inferior in measurement accuracy to the requirements of these standards. In case of disagreement in evaluating the results, the chemical composition of steel should be determined by the methods established by these standards.
• Tensile test - according to GOST 12004. To determine the mechanical properties, the nominal cross-sectional area of ​​\u200b\u200breinforcing steel should be used.
• The method of heating samples to control the tensile strength and conditional yield strength after heating is established by agreement between the manufacturer and the consumer. It is allowed to use furnace heating at temperatures 50 ° C lower than those indicated in Table 4, and holding the samples after heating for 15 minutes.
• Bending test in a cold state - according to GOST 14019 on samples with a cross section equal to the cross section of the tested profile.
• The test for stress relaxation, fatigue strength and bending with extensions is carried out according to the normative and technical documentation.

8. TRANSPORT AND STORAGE.

Transportation and storage - according to GOST 7566.

Table A.1.

Reinforcing steel class	Designation according to the previous NTD	Nominal size	steel grade
			St3sp, St3ps
			St5sp, St5ps
			25G2S, 35GS, 28S, 27GS
			10GS2, 08G2S, 25S2R
			20GS, 20GS2, 08G2S, 10GS2, 28S, 25G2S, 22S
			35GS, 25X2R, 20GS2
			20GS, 20GS2, 25S2R

• The chemical composition of carbon steel - according to GOST 380, low-alloyed - according to the standards given in table A.2, grades 35GS and 25G2S - according to GOST 5781 s additional requirements under paragraph 3 of this annex.
• In steel grade 35GS, intended for the manufacture of reinforcing steel of the At600S, At800 and At800K classes, the mass fraction of carbon should be 0.28-0.33%, and the mass fraction of manganese 0.9-1.2%.

Table A.2

steel grade	Mass fraction of chemical elements
	carbon	manganese

Notes:

• 1. In steel grade 08G2S, intended for the manufacture of reinforcing steel of the At600K class, the mass fraction of silicon should be 0.6-1.2%.
• 2. For steel, from which reinforcing steel of the At600, At600S, At600K, At800 and At800K classes is made, it is allowed to increase the mass fraction of sulfur and phosphorus to 0.045% each.
• 3. For steel grade 25S2R, the mass fraction of boron should be 0.001-0.005%, titanium - 0.01-0.03%.
• 4. For reinforcing steel of all classes, the mass fraction of arsenic should be no more than 0.08%.
• 5. For steel grade 22C, the mass fraction of titanium should be no more than 0.05%, aluminum - no more than 0.10%
• Limit deviations in chemical composition in finished rolled products from carbon steel - according to GOST 380, from low-alloy steel - according to table A.3. Table A.3

Note- For reinforcing steel of strength classes At600, At800 and At1000 (except for steel grade 35GS), subject to the standards of mechanical properties and resistance to corrosion cracking, minus deviations in chemical composition (excluding silicon) are not a rejection sign.

• Reinforcing steel of At800K classes, prepared from steel grade 35GS, must have a tempered layer on the surface with a thickness of at least 0.3 mm and a hardness of not more than 280 HV.

APPENDIX B (mandatory)

REQUIREMENTS FOR RESISTANCE AGAINST CORROSION CRACKING AND WELDABILITY OF REINFORCING STEEL

• Resistance to corrosion cracking and weldability of reinforcing steel are provided by its chemical composition in accordance with the requirements of 5.2-5.4 of this standard, the level of its mechanical properties in accordance with Table 4 and the manufacturing technology established by the technological regulations.
• For reinforcing steel resistant to stress corrosion cracking when testing samples in a nitrate solution consisting of 600 parts by weight of calcium nitric acid, 50 parts by weight of ammonium nitrate and 350 parts by weight of water at a temperature of 98-100 ° C and at a stress equal to (taken according to table 4 of this standard), the time to failure from stress corrosion cracking shall be at least 100 hours.
• For welded thermomechanically hardened reinforcing steel, welded joints by type, design and dimensions that meet the requirements of GOST 14098 must have a tensile strength of at least that specified in Table 4.

APPENDIX B (mandatory)

REQUIREMENTS FOR STATISTICAL INDICATORS OF STRENGTH CHARACTERISTICS

• The manufacturer guarantees the consumer the average values ​​of the strength characteristics of reinforcing steel (tensile strength and conditional or physical yield strength before and after electric heating) in the general population and the minimum average values ​​of these characteristics in each batch-melting based on the following conditions: , where:
  - rejection values ​​of strength characteristics, established by table 4;
  S - standard deviation of parameters in the general population of tests;
  S 0 - standard deviation of the parameter in the party.
• The required quality indicators of reinforcing steel are ensured by compliance with the technology for the production of reinforcing steel during its mass production and are controlled in accordance with the requirements of Section 3 of this standard.
• The values ​​are determined on the basis of test results in accordance with the provisions of Annex E.
• If it is necessary to check the strength characteristics of reinforcing steel by the consumer before and after its electric heating to the temperatures indicated in Table 4, as well as in cases of disagreement in assessing the quality of reinforcing steel from each batch, six samples are tested taken from different bundles (coils) and rods, and according to The results of these tests verify the fulfillment of the conditions for the relevant characteristics:

Where:
Xmin- the minimum value of the tested parameter from the test results of six samples;
- the minimum average value of the tested parameter for a given batch;
S0- standard deviation of the tested parameter in the heat batch;
- the average value of the tested parameter based on the results of testing six samples;
- the rejection value of the checked parameter, set in table 4. Values ​​and - according to the document on the quality of this batch of reinforcing steel.

APPENDIX D (informative)

REQUIREMENTS FOR THE BENDING TEST

The bending test with subsequent extension consists in the plastic deformation of a sample of bar reinforcing steel by bending to a predetermined angle in heating and cooling the bent sample under specified conditions and subsequent extension (reverse bending) under the action of a force in the direction opposite to the original one. The axes of the two supports during bending and subsequent unbending must remain in a plane perpendicular to the direction of the force. The test shall be carried out on universal testing machines or presses equipped with bending and unbending devices. Device diagrams are shown in Figures D.1 and D.2. The test should be carried out at a speed of not more than 20 deg / s so that the transverse ribs of the sample made of bar reinforcing steel are in the tension zone. The distance between the supports shall not change during the test and shall be equal to:
where: D - mandrel diameter (table D.1).

The bending angle before heating (aging) should be 90°. The bent sample is subjected to aging by heating to 100°C, holding at this temperature for at least 30 minutes and then cooling in air to a temperature of 10 to 36°C. After the specimen has cooled down, a bend test is carried out to a bend angle of 20° (Figure D.3). Both angles are measured before unloading. The tested sample of reinforcing steel of classes At400C and At500C is bent around a mandrel, the diameter of which is given in the table. Table D.1 in millimeters.

The diameter of the mandrel for reinforcing steel with diameters of 14, 18 and 28 mm, as well as for reinforcing steel of strength classes At600, At800, At1000 and At1200, must be agreed between the manufacturer and the consumer. The sample is considered to have passed the test in the absence of cracks visible without the use of magnifying agents.

APPENDIX D (mandatory)

MARKING STRUCTURE OF REINFORCING STEEL OF PERIODIC PROFILE, APPLIED DURING MARKING

• The marking of reinforcing steel of a periodic profile, applied during its rolling in the form of marking short transverse ribs or dots on the transverse protrusions of the profile, has the following structure: - sign of the beginning of marking; - designation of the manufacturer; - designation of the strength class of reinforcing steel.
• Examples of marking of reinforcing steel are shown in Figure E.1.

Marking:

• in the form of marking points on the transverse ledges of the profile manufacturer - Cherepovets Metallurgical Plant (n 1 = 3), reinforcing steel of strength class At600 (n 2 = 4)
• in the form of marking short transverse ribs manufacturer - Sulinsky Metallurgical Plant (n 1 = 3), reinforcing steel of strength class At800 (n 2 = 5) Figure E.1

APPENDIX E (mandatory)

METHOD FOR DETERMINING STATISTICAL INDICATORS OF STRENGTH CHARACTERISTICS OF REINFORCING STEEL

• This methodology establishes the procedure for applying statistical control methods for analyzing and regulating the quality level of reinforcing steel, manufactured in the form of individual rods or in coils, in its mass production and is used to assess the reliability of its strength characteristics and reinforcing steel in general, as well as to control the stability of technological process in the production of reinforcing steel.
• To determine the statistical indicators of the strength characteristics of reinforcing steel established by the standard (tensile strength and conditional or physical yield strength before and after electric heating), the results of control tests, called the general population, are used. , forming a sample from the general population of control tests of a specific parameter of the strength characteristics of reinforcing steel. The conclusions drawn on the basis of the sample refer to the entire population.
• The sample on the basis of which statistical indicators are determined should be representative and cover a sufficiently long period of time (at least three months) during which technological process the production of this reinforcing steel did not change. The number of heat batches in each sample should be at least 50.
• The sample should include the results of control tests of reinforcing steel of the same class, rolled to one or groups of similar size profiles from the same steel grade with one method of its smelting.
• When forming a sample, it is necessary to comply with the condition of random sampling from each batch. The assessment of the anomaly of the test results and the verification of the homogeneity of the sample is carried out according to the regulatory and technical documentation.
• During statistical processing of the results of control tests, the average value of a specific parameter of the strength characteristics of reinforcing steel in the sample (general population) is determined - , the standard deviation of this parameter in this sample is S and its standard deviation in the heat batch - S 0 , as well as the root mean square deviation of melting averages - S 1. The values ​​and S are determined according to the normative and technical documentation. The value of S 0 is determined experimentally for at least two heats for each steel grade of the same class and reinforcing steel diameter by random sampling of at least 100 samples from each heat. The value of S 1 is determined by the formula
• The stability of the characteristics and S is checked in accordance with OST 14-34.
• The minimum average value of a specific parameter of the strength characteristics of reinforcing steel in each batch-melt is determined by the formula. The minimum value of the test results of two samples (n = 2) in each batch subjected to control should be at least X min determined by the formula, where is the average value of a specific parameter of the strength characteristics of reinforcing steel in the sample (general population); S 0 or S - characteristics determined in paragraph 6 of this Appendix.

To provide a guarantee to the consumer of the strength characteristics of reinforcing steel established by the standard, the following conditions must be satisfied with a probability of 0.95:

where: - the average value of the tested parameter of the strength characteristics of reinforcing steel in the sample (general population);
- the rejection value of this parameter, established by Table 4 of this standard;

• CIS countries:
  • GOST 5781. Hot-rolled steel for reinforcing reinforced concrete structures,
  • STO ASCHM 7–93. Rolled periodic profile from reinforcing steel,
  • GOST 10884–94. Reinforcing steel thermomechanically hardened for reinforced concrete structures,
  • GOST R 52544. Weldable rolled bars of A500C and B500C classes for reinforcing reinforced concrete structures;
• Ukraine:
  • DSTU 3760–98. Reinforcing bars for reinforced concrete structures,
  • GOST 10884–94. Reinforcing steel thermomechanically hardened for reinforced concrete structures;
• Eurozone:
  • EN 10080 Steel products for concrete reinforcement. Weldable steel fittings,

as well as specifications developed for certain types of rebar.

Standards STO ASChM 7-93 and GOST 10884-94 are focused on the manufacture of hot-rolled and thermomechanically hardened rebar of class A500C of the European standard. GOST R 52544-2006 differs from the above standards in that it is unified in terms of its main components with the European standard EN 10080. The DSTU 3780 standard was introduced in Ukraine with the abolition of GOST 5781 and GOST 10884 and regulates the properties of smooth and periodic reinforcing bars with a diameter of 5, 5 to 40 mm.

European standards (EN 10080), in contrast to GOSTs, for reinforcing bars assume the presence of ductility categories: A, B, C. They do not imply classifications of reinforcement by strength class.

Calculation formulas

Rebar for reinforced concrete structures according to DSTU 3760–98

Are common specifications for rebar are regulated by DSTU 3760-98, introduced in Ukraine with the abolition of GOST 5781-82 and GOST 10884-94. This standard applies to rolled reinforcing smooth and periodic profile with a diameter of 5.5 to 40 mm, intended for reinforcing conventional and prestressed concrete structures. DSTU 3760-98 allows, by agreement between the manufacturer and the consumer, the manufacture of rolled products with other periodic profiles.

In accordance with DSTU 3760–98, rebar (indicated by index A) is divided into classes. Classes are determined depending on the normalized value of the conditional yield strength in MPa.

Rental is divided into:

• weldable (indicated by index C);
• resistant to stress corrosion cracking (indicated by index K);
• non-weldable (without index C);
• unstable against corrosion cracking (without index K).

Reinforcing bars are produced in the following classes:

• A240C with a smooth profile;
• A300C, A400C, A500C, A600, A600C, A600K, A800, A800K and A1000 with a periodic profile.

Table 1. Nominal diameter of rebar, number of meters per ton, mass of one linear meter of rolled products and permissible deviations in mass

Nominal diameter rolled products, d n, mm	Number of meters in ton, m	Weight of 1 linear meter of fittings, kg
		Estimated value, kg	Permissible deviations, %
5,5	5362	0,1865	±8.0
6	4505	0,222
8	2534	0,3946
10	1622	0,6165	±5.0
12	1126	0,8878
14	827,5	1,208
16	633,6	1,578	±4.5
18	500,6	1,998
20	405,5	2,466
22	335,1	2,984
25	259,5	3,853
28	206,9	4,834
32	158,4	6,313
36	125,2	7,99
40	101,4	9,865

Note. The mass of 1 m of reinforcement is calculated at a steel density of 7850 kg / m 3 and is a reference value.

The standard provides for the production of reinforcing bar of a round smooth profile with a diameter of 5.5 to 40 mm and a periodic profile with a nominal diameter of 6.0 to 40 mm. Reinforcing bars are supplied in bars and coils. Reinforcing steel of a smooth profile of class A240 is made in accordance with GOST 2590 of normal accuracy.

Rice. 2. Reinforcing steel of a smooth profile of class A240

Reinforcing steel of a periodic profile must have crescent-shaped transverse protrusions, which should not be connected with longitudinal protrusions. Longitudinal projections are not required.

Table 2. Requirements for the main geometric dimensions of the profile

Geometric profile parameters	Nominal rolled diameter, dn, mm	Profile dimensions
Minimum height of transverse ledges, h, mm	6–18	0.070 d n
	20–40	0.065 d n
Step of transverse ledges, t, mm	6–8	(0.64–0.86) d n
	8–14	(0.55–0.75) d n
	14–40	(0.51–0.69) d n
Tilt angle, β°	6–40	40–60
Distance between the ends of the transverse ledges C, no more than, mm	6–40	0.25 d n
Dimensions of protrusions, b, h1, b1, mm	6–40	(0.10–0.15) d n

The standard allows the manufacture of rolled products of intermediate sizes and with a different type of periodic profile. The ovality of smooth reinforcing bars is in accordance with GOST 2590. The ovality of rolled products of a periodic profile (difference d 1 and d 2) should be no more than 1.2 mm for rolled products with a diameter of 6 to 14 mm, no more than 1.6 mm for rolled products with a diameter of 16 to 25 mm and not more than 2.4 mm for rolled products with a diameter of more than 25 mm.

Rice. 3. Reinforcing steel of a periodic profile without longitudinal protrusions

Rice. 4. Reinforcing steel of a periodic profile with longitudinal ledges

Reinforcing bars in bars are made in measured and unmeasured lengths. The length of the bars should be in the range from 6 to 12 m.

The standard regulates the maximum deviations along the length of the measuring rods. They can be from 0 to +100 mm. By agreement between the manufacturer and the consumer, it is allowed to establish other limit deviations. The curvature of reinforcing bars should not exceed 0.6% of the measured length.

Reinforcing steel with a diameter of 25 mm class A800:

25 A800 DSTU 3760-98.

Reinforcing steel with a diameter of 10 mm class A300C weldable:

Rebar for reinforced concrete structures according to GOST 5781–82

Range and weight of 1 m of rolled products

Currently, a number of domestic manufacturers of rolled metal produce rebar in accordance with GOST 5781–82. GOST 5781–82 was canceled on the territory of Ukraine with the introduction of DSTU 3760–98. This standard applies to round hot-rolled steel of smooth and periodic profile, intended for the reinforcement of conventional and prestressed concrete structures.

Depending on the mechanical properties, reinforcing steel according to this standard is divided into classes A-I (A240), A-II (A300), A-III (A400), A-IV (A600), A-V (A800), A-VI (A1000) .

Reinforcing steel is made in rods or coils. Reinforcing steel of class A-I (A240) is made smooth, classes A-II (A300), A-III (A400), A-IV (A600), A-V (A800) and A-VI (A1000) - a periodic profile. At the request of the consumer, steel of classes A-II (A300), A-III (A400), A-IV (A300) and A-V (A800) is made smooth.

Basic parameters and dimensions. The nominal diameters of periodic profiles must correspond to the nominal diameters of smooth profiles of equal cross-sectional area. Limit deviations of the diameter of smooth profiles must comply with GOST 2590–88 for normal rolling accuracy.

Table 1. Profile numbers,
weight of 1 m length of smooth and periodic reinforcing steel
profile, mass deviations for periodic profiles

Profile number	Weight 1 m profile
	Theoretical, kg	Limit deviations, %
6	0,222	+9,0/–7,0
8	0,395
10	0,617	+5,0/–6,0
12	0,888
14	1,21
16	1,58	+3,0/–5,0
18	2
20	2,47
22	2,98
25	3,85
28	4,83	+3,0/–5,0
32	6,31	+3,0/–4,0
36	7,99	+3,0/–4,0
40	9,87
45	12,48
50	15,41	+2,0/–4,0
55	18,65
60	22,19
70	30,21
80	39,46

Note. The mass of 1 m of the profile is calculated from nominal dimensions with a steel density of 7850 kg/m 3 .

Rice. 1. Reinforcing steel of class A-II (A300) in the usual version

Rice. 2. Reinforcing steel of class Ac-II (Ac300) for special purposes

Reinforcing steel of classes A-II (A300) and Ac-II (Ac300) must have protrusions running along helical lines with the same lead on both sides of the profile.

Steel of classes A-III (A400), A-IV (A600), A-V (A800), A-VI (A 1000), both ordinary and special execution, must have protrusions along helical lines, having on one side of the profile right, and on the other - left entries.

Rice. 3. Reinforcing steel of class A-III (A400) and classes A-IV (A600), A-V (A800), A-VI (A 1000)

Rice. 4. Reinforcing steel of classes A-IV (A600), A-V (A800), A-VI (A 1000) for special purposes

Relative displacements of helical protrusions along the sides of the profile, separated by longitudinal ribs, are not standardized.

Rice. 5. Fittings in accordance with GOST 5781–82 of the usual design

Rice. 6. Fittings according to GOST 5781–82 of special execution

Limit deviations of dimensions and mass

Table 2. Dimensions and limits
dimensional deviations of conventional reinforcement

Profile number (nominal diameter, d n)	d		h		d1	h1	t	b	b 1	r
	Rated	Previous off	Rated	Previous off
Dimensions, mm
6	5,75	+0,3/–0,5	0,5	±0.25	6,75	0,5	5	0,5	1	0,75
8	7,5		0,75	±0.25	9	0,75	5	0,75	1,25	1,1
10	9,3		1	±0.5	11,3	1	7	1	1,5	1,5
12	11		1,25	±0.5	13,5	1,25	7	1	2	1,9
14	13		1,25	±0.5	15,5	1,25	7	1	2	1,9
16	15		1,5	±0.5	18	1,5	8	1,5	2	2,2
18	17		1,5	±0.5	20	1,5	8	1,5	2	2,2
20	19		1,5	±0.5	22	1,5	8	1,5	2	2,2
22	21	+0,4/–0,5	1,5	±0.5	24	1,5	8	1,5	2	2,2
25	24		1,5	±0.5	27	1,5	8	1,5	2	2,2
28	26,5	+0,4/–0,7	2	±0.7	30,5	2	9	1,5	2,5	3
32	30,5		2	±0.7	34,5	2	10	2	3	3
36	34,5		2,5	±0.7	39,5	2,5	12	2	3	3,5
40	38,5		2,5	±0.7	43,5	2,5	12	2	3	3,5
45	43		3	±0.7	49	3	15	2,5	3,5	4,5
50	48		3	±0.7	54	3	15	2,5	3,5	4,5
55	53	+0,4/–1,0	3	±1.0	59	3	15	2,5	4	4,5
60	58		3	±1.0	64	3	15	2,5	4	5
70	68	+0,3/–0,5	3	±1.0	74	3	15	2,5	4,5	5,5
80	77,5		3	±1.0	83,5	3	15	2,5	4,5	5,5

Table 3. Dimensions and limits
dimensional deviations of special fittings

Nominal diameter, d n, mm	d		h		d1	h1	hr	hb	t	b	b 1	r1	α, °
	Rated	Previous off	Rated	Previous off
Dimensions, mm
10	8,7	+0,3/–0,5	1,6	±0.5	11,9	1,6	0,6	1	10	0,7	1,5	11	50
12	10,6		1,6		13,8	1,6	0,6	1	10	0,7	2	11
14	12,5		2	+0,65/–0,85	16,5	2	0,8	1,2	12	1	2	12
16	14,2		2,5		19,2	2,5	1	1,5	12	1	2	12
18	16,2		2,5		21,2	2,5	1	1,5	12	1	2	12
20	18,2		2,5		23,2	2,5	1	1,5	12	1	2	12
22	20,3	+0,4/–0,5	2,5		25,3	2,5	1	1,5	12	1	2	12
25	23,3		2,5		28,3	2,5	1	1,5	14	1,2	2	14
28	25,9	+0,4/–0,7	3	+1,0/–1,2	31,9	3	1,2	1,8	14	1,2	2,5	14
32	29,8		3,2		36,2	3,2	1,2	2	16	1,5	3	14
36	33,7		3,5		40,7	3,5	1,5	2	18	1,5	3	19
40	37,6		3,5		44,6	3,5	1,5	2	18	1,5	3	19

Dimensions for which limit deviations are not set are not controlled on the finished profile.

Table 4. Mechanical properties of reinforcement

Reinforcing class become	Yield strength, σ t, MPa, not less than	Temporary resistance, σ in, MPa, not less than
A-I (A240)	235	373
A-II (A300)	295	490
Ac-II (A300)	295	441
A-III (A400)	390	590
A-IV (A600)	590	883
A-V (A800)	785	1030
A-VI (A1000)	980	1230

Marking, packaging, transportation

Packaging, marking, transportation and storage - according to DSTU 3058–95 (GOST 7566–94) with additions:

• the ends of rods made of low-alloy steels of class A-IV (A600) must be painted with red paint, class A-V - red and green, class A-VI (A1000) - red and blue. It is allowed to color the bundles at a distance of 0.5 m from the ends;
• the rods are packed in bundles weighing up to 15 tons, tied with wire or rolled wire. At the request of the consumer, the rods are packed in bundles weighing up to 3 and 5 tons;
• on ligaments, paint is applied in stripes with a width of at least 20 mm on the side surface around the circumference (at least 1/2 of the circumference) at a distance of not more than 500 mm from the end;
• on coils, paint is applied in stripes with a width of at least 20 mm across the coils from the outside of the coil;
• for unpacked products, paint is applied to the end or to the side surface at a distance of not more than 500 mm from the end;
• on the label attached to each bunch of rods, the accepted designation of the class of reinforcing steel (for example, A-III) or the symbol of the class for the yield strength (A400) is applied.

Conventions

Reinforcing steel with a diameter of 20 mm, class A–II (A300):

20 - A-II GOST 5781-82.

Reinforcing steel with a diameter of 18 mm, class A-I (A240):

18 - A-I GOST 5781-82.

In the designation of rods of class A-II (A300) for special purposes, the index "c" is added:

Armature thermomechanically hardened for reinforced concrete structures in accordance with GOST 10884–94

Reinforcing steel according to this standard is divided into classes depending on:

• from mechanical properties - strength class (established by the standard of the normalized value of the conditional or physical yield strength);
• from operational characteristics - to weldable (index C), resistant to corrosion cracking (index K).

Reinforcing steel is made of classes At400S, At500S, At600, At600S, At600K, At800, At800K, At1000, At1000K and At1200 with a periodic profile according to figures 1 and 2 or GOST 5781. By agreement between the manufacturer and the consumer, reinforcing steel of strength class At800 and higher is allowed to be manufactured smooth .

Rice. 1. Periodic reinforcement profile according to GOST 10884–94 with a longitudinal ledge

Rice. 2. Periodic reinforcement profile according to GOST 10884–94 without longitudinal protrusion

Basic parameters and dimensions. Linear density (weight of a rod 1 m long), limit deviations in size and weight must comply with the established GOST 5781.

Rice. 3. Geometrical parameters of reinforcement according to GOST 10884–94

The angle between the transverse projections and the longitudinal axis of the rod β is recommended to be taken equal to 45°. It is allowed to take the specified angle equal to from 35° to 70°.

The values ​​and tolerances for the size d 2 correspond to those given in this table for the size d 1 .

The ovality of the rods (the difference between d 1 and d 2 in one section) should not exceed the sum of plus and minus limit deviations in size d 1.

Dimensions for which limit deviations are not set are given for the construction of a caliber and are not controlled on the finished product.

Reinforcing steel with a diameter of 10 mm or more is made in the form of rods, the length specified in the order.

Reinforcing steel with diameters of 6 and 8 mm is produced in coils. The manufacture of reinforcing steel of the At400S, At500S and At600S classes with a diameter of 10 mm is allowed in coils.

The rods are made in measured lengths from 5.3 to 13.5 m. It is allowed to manufacture rods with a measured length of up to 26 m.

The length of the rods - at the request of the consumer.

Weldable reinforcing steel is allowed to be supplied in the form of rods:

• measured length with unmeasured segments with a length of at least 2 m in an amount not exceeding 15% of the batch weight;
• random length from 6 to 12 m. In a batch of such reinforcing steel, rods with a length of 3 to 6 m are allowed in an amount of not more than 7% of the batch weight.

Limit deviations of dimensions and mass

Table 1. Geometric parameters of heat-strengthened reinforcement and their limiting deviations, mm

Nominal diameter of reinforcing steel (profile number), dn	d	h	d1			t*	b	b1	with, no more
		at least	nominal	accuracy deviations
				ordinary	elevated
6	5,8	0,4	7	+0,8/–1,0	±0.6	5	0,6	1,0	1,9
8	7,7	0,6	9,3			6	0,8	1,25	2,5
10	9,5	0,8	11,5	+0,9/–1,6		7	1	1,5	3,1
12	11,3	1	13,7			8	1,2	2,0	3,8
14	13,3	1,1	15,9			9	1,4		4,4
16	15,2	1,2	18	+1,2/–1,8	±0.8	10	1,6		5
18	17,1	1,3	20,1			11	1,8		5,6
20	19,1	1,4	22,3			12	2		6,3
22	21,1	1,5	24,5			14	2,2		6,9
25	24,1	1,6	27,7			15	2,5		7,9
28	27	1,8	31	+1,7/–2,5	±1.2	17	2,8	2,5	8,8
32	30,7	2	35,1			18	3,2	3,0	10
36	34,5	2,3	39,5			19	3,6		11,3
40	38,4	2,5	43,8			20	4		12,5

* Limit deviations are ±15%.

Limit deviations in length

Limit deviations along the length of bars of measured length must comply with the requirements of GOST 5781.

Mechanical properties and chemical composition

Table 2. Norms for the mechanical properties of reinforcing bars

Strength class of reinforcing steel	Nominal diameters, mm	Electric heating temperature, °С	Tensile strength, σ in, MPa	Conditional or physical yield strength, σ 0.2 (σ t), MPa
			at least
At400	6–40	-	550	440
At500	6–40	-	600	500
At600	10–40	400	800	600
At800	10–32*	400	1000	800
At1000	10–32	450	1250	1000
At1200	10–32	450	1450	1200

Marking, packaging, transportation

Rice. 4. Parameters of reinforcement marks according to GOST 10884–94

Reinforcing steel of a periodic profile is marked with a strength class and a manufacturer, applied during its rolling in the form of marking short transverse ribs or dots on transverse ledges.

Table 3. Sizes of markings

Nominal diameter of reinforcing steel (profile number), mm	Dimensions of markings, mm
	h1	lm	b2	d3
6	0,4	2	3	–
8	0,6			4
10	0,8	3
12	1
14	1,1
16	1,2			5
18	1,3	4
20	1,4
22	1,5
25	1,6
28	1,8
32	2			6
36	2,3
40	2,5

Marking short transverse ribs with a height of 0.5 mm, not exceeding the overall size along a circle with a diameter of d 1, are placed on surfaces adjacent to the longitudinal ribs.

Marking points with a height equal to the height of the transverse ledge are cone-shaped thickenings on the transverse ledges.

The strength class of reinforcing steel is indicated by the number of transverse projections according to table 4 in the interval t 1 (see figures 5 (Rolled marking scheme) and 4).

Table 4. Marking of the strength class of thermomechanically hardened

* For reinforcing steel of the At800K class with a diameter of 18–32 mm.

In the absence of a rolling marking, the ends of the rods or bundles of reinforcing steel of the corresponding class must be painted with indelible paint of the following colors:

• At400C - white; At800 - green;
• At500C - white and blue; At800K - green and red;
• At600 - yellow; At1000 - blue;
• At600C - yellow and white; At1000K - blue and red;
• At600K - yellow and red; At1200 - black.

It is allowed to color the bundles at a distance of 0.5 m from the ends. The rods are packed in bundles weighing up to 10 tons, tied with wire. At the request of consumers, the rods are packed in bundles weighing up to 3 tons. When supplied in coils, each coil must consist of one piece of reinforcing steel. The mass of the skein is up to 3 tons. The skein must be evenly tied around the circumference in at least four places. Each of these knittings should have an intermediate screed (knitting), which is located at the level of the average thickness of the skein. Each coil or bundle of rods must be permanently affixed with a label stating:

• trademark or trademark and name of the manufacturer;
• symbol of reinforcing steel;
• lot number;
• technical control mark.

If the mechanical properties of the reinforcing steel do not correspond to the marking applied during its rolling, the actual strength class must be indicated on the label and in the quality document, and the ends of the rods must be painted in accordance with the given marking rules.

Transportation and storage - according to DSTU 3058–95 (GOST 7566–94).

Conventions

The designation of reinforcing steel must contain (according to GOST 10884–94):

• nominal diameter (profile number), mm;
• strength class designation;
• designation of its operational characteristics - weldability (index C), resistance to corrosion cracking (index K).

Reinforcing steel with a diameter of 20 mm, strength class At800:

20 At800 GOST 10884-94.

The same, with a diameter of 10 mm, strength class At400, weldable (C):

10 At400S GOST 10884-94.

The same, with a diameter of 16 mm, strength class At600, resistant to corrosion cracking (K):

Rolled reinforcing welded periodic profile of classes A500C and B500C for reinforcing reinforced concrete structures in accordance with GOST R 52544

Terms and Definitions. In this standard, the following terms are used with their respective definitions:

• rebar- rods with transverse ribs evenly spaced on their surface at an angle to their longitudinal axis to improve adhesion to concrete;
• rebar of nominal diameter dn, mm - rebar, the actual diameter of which d, taking into account the allowable deviations, corresponds to the diameter from the assortment according to table 1;
• d, mm - the diameter of a round smooth rod of equal area, 1 m long, with the same mass as the rolling of a periodic profile, determined by the formula:

,

where m is the mass of rolled products of a periodic profile, l is the length of rolled products of a periodic profile, mm;

Classification and assortment. Reinforcing steel is subdivided:

• by production method into classes:
  • А500С - hot-rolled without further processing or thermomechanically hardened in the rolling stream;
  • В500С - mechanically hardened in a cold state (cold-worked);
• by product type:
  • bars;
  • skeins.

In the designation of the class: A - hot-rolled or thermomechanically hardened rebar; B - cold-formed rebar; C - weldable; 500 - yield strength not less than 500 MPa.

The nominal diameter, cross-sectional area and weight of 1 m of the length of the rolled products must correspond to the values ​​\u200b\u200bgiven in table 1.

Table 1. Nominal diameter,
cross-sectional area and mass of 1 m of rolled length

Nominal diameter d n, mm	Nominal area cross section F n, mm 2	Rated weight 1 m of rolled length, kg
4	12,6	0,099
5	19,6	0,154
6	28,3	0,222
8	50,3	0,395
10	78,5	0,616
12	113,1	0,888
14	153,9	1,208
16	201,1	1,578
18	254,5	1,998
20	314,2	2,466
22	380,1	2,984
25	490,9	3,853
28	615,8	4,834
32	804,2	6,313
36	1017,9	7,990
40	1256,6	9,865

Note. At the request of the consumer, rebar is produced with a nominal diameter of: 4.5; 5.5; 6.5; 7; 7.5; 8.5; 9; 9.5; 45; 50 mm.

The nominal mass of 1 m of the rolled length is determined based on the nominal diameter at a steel density of 7850 kg/m 3 .

The periodic profile of reinforcing bars must consist of at least two rows of transverse ribs, crescent-shaped and not connected to longitudinal ribs. Delivery of rebar without longitudinal ribs is allowed.

The values ​​of the parameters of the periodic profile and its relative crushing area f k must comply with Table 2.

Table 2. Values ​​of the parameters of the periodic profile

Name of the periodic profile parameter	Value for rental class
	A500S	B500C
Nominal diameter, mm	6–40	4–12
Permissible deviation from the nominal cross-sectional area and weight of 1 m of the profile length,%, for rolled products with a diameter, mm:
up to 5.5	-	±45
from 5.5 to 8 incl.	± 8	±4.5
from 8.5 to 14 incl.	±5	±4.5
from 16 to 40 incl.	±4	-
Relative crushing area fk of transverse profile ribs, not less than, for diameter, mm:
up to 4 incl.	0,036
from 4.5 to 6 incl.	0,039
from 6.5 to 8 incl.	0,045
from 8.5 to 10 incl.	0,052
from 10.5 to 40 incl.	0,056
Height of transverse ribs h, mm	(0.065–0.1) d n	(0.05 - 0.1) d n
Step of transverse ribs t, mm	(0.4–1.0) d n
Relative step of transverse ribs t/b, not less than	-	3
The angle of inclination of the transverse ribs β	35–60°
The angle of inclination of the side surface of the rib α, not more than	45°
The total distance between the ends of the transverse ribs Σe i , mm, no more	0.2 π d n	0.25 π d n
Rebar ovality, mm, max, for diameter, mm:
up to 5.5 incl.	-	0,5
from 6 to 14 incl.	1,2	1
from 16 to 25 incl.	1,6	-
from 28 to 40 incl.	2,4	-

For hot-rolled and thermomechanically hardened reinforcing bars, the configuration of the periodic profile should correspond to Figure 1 and Table 1, and for cold-worked bars - to Figure 2 and general requirements to the profile (see Table 2).

By agreement with the consumer, it is allowed to supply reinforcing bars with a different configuration of a periodic profile, provided that the properties of the bars comply with the requirements of this standard.

Reinforcing steel is produced with a nominal diameter:

• up to 6 mm - in coils;
• from 6 to 12 mm inclusive - in coils or bars;
• 14 mm and more - in bars.

Rods are made:

• measured length (MD) ranging from 6 to 12 m, specified by the consumer in the order;
• random length (ND) ranging from 6 to 12 m, determined by the manufacturer. In a batch of bars of random length, bars with a length of 3 to 6 m are allowed in an amount not exceeding 7% of the batch weight.

Limit deviations along the length of bars of measured length - plus 100 mm.

The curvature of the bars should not exceed 0.6% of the measured length.

The construction of any building, except for small architectural forms, can not do without the use of reinforcement.

Reinforcing steel performs a lot of tasks, the main of which is to help in the formation of reinforced concrete structures. It is produced in a large number of variations. The classification of fittings implies dividing it into different types, intended for different, sometimes directly opposite requirements.

In this article, we will look at what rebar classes are, what they are, how to determine the correct rebar class, etc.

1 Features and purpose

It should be understood that the use of reinforcement, classes and its varieties is a rather wide sphere. It is used for various tasks, including not only construction.

The main direction is the assembly of load-bearing frames of reinforced concrete structures. The very essence of reinforced concrete structures lies in the combination of monolithic concrete.

Without an internal metal core, concrete quickly cracks and breaks down. If there is building reinforcement in it, then everything changes.

1.1 Classification

The construction industry is huge, it is easy to get confused even for a professional. A large number of tasks require a large number of materials of different structure and purpose, and building reinforcement is no exception.

The reinforcement classification was invented just for all kinds of simplification and unification processes.

Reinforcement class or reinforcing steel class is a special designation, the so-called marking, indicating the ultimate strength of the rod, its allowable dimensions, task definition, etc.

To navigate in all the variety that construction reinforcement offers us, the table of reinforcement classes allows.

This table is very simple, and contains several columns. In the first marking, and then its parameters are indicated:

• limiting diameters;
• withstand loads and resistance;
• the possibility or impossibility of embedding its composition in stressed reinforced concrete structures, etc.;
• relative extension;
• rod length.

The table is short and extended. A large sample table can contain a lot of parameters that are completely unfamiliar to ordinary people, an abbreviated table contains only a brief minimum of the necessary information.

2 Classes and their differences

Reinforcing steel and rods are divided into specific classes, each has its own marking. There are old and new designations.

Rebar is used in civil and industrial construction:

• A2 (A300);
• A4 (A600);
• A5 (A800);
• A6 (A1000).

The first is the so-called old marking. It is based on the old GOST, which was used back in Soviet times. Now builders are gradually moving away from it, taking new brands as a basis.

See also: what is referred to, and why is it needed?

Moreover, there are practically no differences between them, except of course the name. Consider the specific differences between the classes.

The first two samples mounting fittings. As you probably already know, the rods have a different profile, from smooth to grooved or sickle-shaped.

A smooth profile is made only for non-stressed reinforcement intended for installation work. It is forbidden to install them in the frame of load-bearing structures. They do not have enough strength, and the lack of edges worsens adhesion to concrete.

Products of the first class have a diameter of 6 to 40 mm and a smooth profile. Products of the second class are produced with a corrugated profile, diameters from 10 to 80 mm, and in some cases even more.

Fittings A3 and above are produced with a corrugated profile. It is class A3 that is considered the most popular.

Class A3 rods have a unique combination of strength, stress resistance, and also have a corrugated profile. Reinforcing steel of class A3 is durable and very strong, it is more than enough to cover most construction tasks.

The cost of A3 fittings is not too high, unlike high-class models, which also distinguishes it well from the rest. The range of working diameters is 8-40 mm.

Unlike A3 reinforcement, class A4 withstands more loads, and better copes with the role of a frame for highly stressed structures, for example,.

Classes A5 and A6 have not found their application in civil engineering. For him, they are too expensive, if you can put it that way. The limit of their performance exceeds any possible requirements and norms in civil engineering.

They are purchased for industry, where it is necessary to build the strongest supporting structures for large-scale projects, such as huge workshops, factories that can withstand a lot of heavy equipment, etc.

For the production of rods of all classes in our time, reinforcing steel 3-5SP is used, if standard carbon samples are meant, and 25G2S or 35GS, if alloyed steel is needed

2.1 Additional markings

We have already considered the main types of reinforcement, as well as the class table. However, the differences between them do not end there. There are additional markings that indicate certain features of a particular rod.

For example, an entry of type A3K is the definition of a rebar of class A3 with additional corrosion protection. The addition of the “K” grade means that the steel has been treated with special compounds, it will be more durable, it will not succumb to corrosion, at least at first, but it will also cost you more.

The addition of the letter "C" means that the reinforcement is easily welded. It is very easy to distinguish the entry, just look at the last letter in the abbreviation. For example, a typical example of welded building bars.

Here you need to understand that not every class of such reinforcing products is easily connected to other metals by welding. In some situations, steel does not hold welding well, and it does not always face such tasks.

The knitting of most reinforcing cages comes down to connecting rods or. Welding plays a secondary role in it.

However, this does not mean that you can do without welded products at all, for which they came up with the idea of ​​​​producing an additional subclass, designed, among other things, for convenient welding with other metal structures.

There are other, less popular elements of the abbreviation, but we will not consider them. For those interested, the full table of classes will help.

2.2 Reinforcement classification (video)

2.3 Other species

There is also a concept, shut-off or. This is a separate type of equipment used in plumbing. It has its own classes, including the most important - the tightness class.

The tightness class affects how well the assembly performs in the pipeline. Without tightness, it is impossible to assemble a normal pipeline, therefore, serious attention is paid to the tightness indicator.

You only need to know that the level of tightness of the assembly is indicated in its characteristics, which can be viewed upon purchase.

2.4 Eye detection

Any reinforced building construction, one way or another, consists of reinforcement. In order not to get confused in the types of structures and their frames, it is desirable to be able to distinguish the rods by eye, at least their main characteristics.

This skill will help you in the future. In addition, it is not so difficult to develop it. Building reinforcement is very different from industrial, and the rods of the first classes, with their difference in profile, are completely recognized without any difficulty.

All that is required of you is to remember a few rules, and then follow them every time you are required to recognize what kind of product is under your feet.

First of all, we look at the profile of the rod. A smooth profile is always the first, less often the second class. Products of the third and higher class with a smooth profile are not produced at all. Accordingly, a corrugated profile is evidence that you have reinforcement of class A3 or higher.

Classes A5 and A6 industrial products are easier to identify when you have already seen them. But in general terms, it can be described as an enlarged steel-rolling product, with a large length and an enlarged sickle-shaped or annular profile.

By learning these simple rules, you will learn to distinguish one class from another, without involving documentation. Everything else will come with experience.

Among the types of rolled metal, building reinforcement occupies a special position - it is always in high demand, and the need for it does not decrease. This is due to the growth of the housing market and the active construction of industrial and public facilities. The extensive field of application imposes a number of requirements on reinforcing products and implies a wide range of them. The features and types of building reinforcement will be discussed in this article.

Main purpose

Construction mounting fittings are intended for the manufacture of frame products for reinforcing concrete used for the construction of objects for various purposes. As a rule, these are rods of a periodic profile with different diameters.

Volumetric and flat frames are calculated constructively. They are made from individual bars by welding or wire binding.

The need to use fittings in reinforced concrete structures due to the weakness of concrete to bending and compression. Such loads are experienced by floor slabs, wall and foundation blocks, jumpers and other structural elements. Without reinforcement, the products crack and collapse. The frame solves the problem - rigid reinforcement works in tension and compensates for the destructive stress in concrete. Moreover, the frames are necessarily located in the lower stretched part, where the maximum deformation force occurs, as well as throughout the volume to stabilize and redistribute the load.

Kinds

The widespread use of building reinforcing bars dictates the need for a wide range of rods, so that for each design, according to calculations, it is possible to take the most suitable blanks for the manufacture of the frame. According to the characteristics of the reinforcement, the products can be divided into several types.

According to the material of manufacture:

1. Mounting of different quality is the most common and well-known. For manufacturing, high-carbon and low-alloy steel is used.
2. Construction - a relatively new reinforcing product for concrete structures. These are bars made of basalt, fiberglass and hydrocarbon with polymers. They are close in characteristics to metal products, in many cases they serve as a worthy replacement for a steel frame.

The cross section of the reinforcement in the base is round, the surface of the bar can be of two types:

• Ribbed. This redistributes the load in the concrete structure.
• serves as a dressing product for the manufacture of the frame. Bars without relief can also be used as a redistributing frame, then their ends are bent to prevent slipping.

According to the conditions of use:

• Non-stressed - this is the usual rigid reinforcement, from which the frame is knitted and installed in the formwork before pouring the mortar. Used to reinforce products intended for use under normal conditions.
• Prestressing reinforcement is pre-stretched at the factory settings, where the molding of the structures takes place. These are used in conditions of increased bending loads: floors in industrial premises, public buildings with wide spans between load-bearing walls, etc.

By functional purpose building reinforcement can be:

• Longitudinal prevents the formation of cracks in tension zones - usually in the lower part of reinforced concrete products;
• Transverse rigid reinforcement is located in the compression zone.

Classes and marking of building reinforcement

The use of reinforcement in construction is carried out in accordance with the requirements that are determined constructively. Specialists calculate structures and accept rods with markings containing the necessary information about the reinforcing product.

Classes are a designation of the parameters not of the rod itself, but of the steel from which it is made. On this basis, building reinforcement is conditionally divided into 3 classes:

• A - brand of ordinary hot-rolled or cold-drawn bar steel;
• At - heat-treated (reinforced) steel;
• Ac - steel can be assembled into a frame by welding;
• Ak - corrosion-resistant with a protective coating (galvanized or galvanized).

Rod hot rolled rebar in the designation contains a numeric index. General marking contains some properties of metal products:

* designation/marking of old and new samples.

Technical characteristics of building reinforcement

GOST 5781-82 defines the main technical requirements to fittings of each class (table 8):

Steel class	Yield strength s t		Tensile strength s in		Relative elongation d5,%	uniform elongation d r, %	Impact strength at -60 °C		Bending and cold test
	N/mm 2	kgf/mm 2	N/mm 2	kgf/mm 2			MJ / m 2	kgf m / cm 2
	Not less than
A-I (A240)*	235	24	373	38	25	—	—	—	180°; c=d**
A-II (A300)	295	30	490	50	19	—	—	—	180°; c = 3d
Ac-II (Ac300)	295	30	441	45	25	—	0,5	5	180°; c = d
A-III(A400)	390	40	590	60	14	—	—	—	90°; c = 3d
A-IV(A600)	590	60	883	90	6	2	—	—	45°; c = 5d
A-V (A800)	785	80	1030	105	7	2	—	—	45°; c = 5d
A-VI (A1000)	980	100	1230	125	6	2	—	—	45°; c = 5d

**с – sending thickness, d – rod diameter.

The construction length of the rods according to GOST is from 6 to 12 meters. The document also regulates the composition of steels for the manufacture of building rods and their other properties.

For convenience of distinguishing rods, their ends are painted in different colors:

• A-IV - red;
• A-V - red and green;
• A-VI - red and blue.

Rebar range

GOST 5781-82 contains a conditional assortment of frame reinforcement (table 1):

Profile number (nominal bar diameter d n)	Cross-sectional area of ​​the rod, cm 2	Weight 1 m profile
		Theoretical; kg	Limit deviation, %
6	0,283	0,222	+9,0
8	0,503	0,395	-7,0
10	0785	0,617	+5,0
12	1,131	0,888	-6,0
14	1,540	1,210
16	2,010	1,580
18	2,540	2,000
20	3,140	2,470	+3,0
22	3,800	2,980	-5,0
25	4,910	3,850
28	6,160	4,830
32	8,010	6,310
36	10,180	7,990	+3,0
40	12,570	9,870	-4,0
45	15,000	12,480
50	19,630	15,410
55	23,760	18,650	+2,0
60	28,270	22,190	-4,0
70	38,480	30,210
80	50,270	39,460

The theoretical mass of products may vary - it depends on the grade of the alloy used and has an error, usually in the specified range.

Calculator

Summary

Reinforcement in reinforced concrete structures is an important element, the choice of which is always approached thoroughly, because as a result, the service life of structures and buildings is determined, which means the safety of people. Understanding the range of products for a beginner is not easy, this is the lot of professionals. If you want to independently master this issue, pay attention to the regulating GOST - it contains all the necessary information about the selection, storage and installation of building reinforcement.

To make it convenient to classify, store and sell valves, they are marked and marked in a certain way. At the same time, the marking of stop valves, on the one hand, should not take up much space on the product, on the other hand, be as informative as possible for the consumer and the manufacturer. To date, all existing species domestic shut-off valves are marked in accordance with Russian legislation (GOSTs).

The marking of stop valves must necessarily include:

Trademark or manufacturer's name;
conditional passage, mm. This refers to the conditional (nominal) diameter. It is designated as Du (DN), and then without a space comes the diameter value;
conditional pressure, MPa. Rated pressure. Designated as Ru or PN. In addition to pressure, an indication of the operating temperature range is allowed;
medium flow direction. Indicated as an arrow on the body. It is applied at the stage of casting, stamping;
case material grade. The body and valve materials are marked as follows: nzh - stainless steel, ls - alloy steel, h - gray cast iron. Sealing surfaces: br - bronze, brass, p - plastic, p - rubber.

How are valves marked?

In accordance with domestic state standards, the marking of valves is applied directly to the body of the product. All information about a particular model is applied on the front side, and the mark of the manufacturer on the back. The marking of stop valves on the metal surface of the body is applied in three main ways:
stamping. It is the process of material deformation. Such embossing on the surface of the valve body creates letters and numbers. The durability of this embossing is the same as that of the reinforcement itself;
engraving. It is one of the oldest methods of applying inscriptions to metals. Engraving can be found on pre-revolutionary valves and taps. Drawing letters and numbers is carried out with the help of a cutter, which can be a chisel, cutter, punch (outwardly similar to a nail);
branding. It is a rather complicated process that will require a certain skill and professionalism from the performer. For application, special equipment is used - an electric spark pencil. This method is rarely used.

It should be noted that depending on the material of the body parts, the outer surfaces of the valves can be painted in the appropriate color:
blue color means alloy steel;
blue - corrosion steel;
black color corresponds to gray ductile iron;
gray - carbon steel.

Let's describe the marking of valves on the example of the products of the Admiral plant:

19s63nzh. The number 19 means the check valve, the valve is sealed. The small letter "c" means the case is made of carbon steel. The letters "nzh" indicate that the sealing surfaces in the product are made of stainless steel;
30nzh541nzh. "30" means that the shut-off valve belongs to the valve type. "nzh" - the body is made of stainless steel. "5" indicates that the mechanical control method with bevel gear is used for control. "41" is the model number. "nzh" - sealing surfaces in the product are made of stainless steel;
32s908r. "32" - the product is a butterfly valve. "c" - made of carbon steel. "9" - controlled by an electric drive. Model number 08. "p" - sealing surfaces are made of rubber.

Plant "Admiral" pays due attention to the marking of valves. Moreover, this is done not only to make life easier for the consumer and the exploiter of the products, but also to make it easier to store products in the warehouses of the enterprise and distribute them to representative offices and sales outlets. Marking makes it easy to classify rebar.

The clear, clearly visible marking of the valves makes their handling easier and more convenient. This applies to both purchase and delivery, as well as further maintenance, repair, and the purchase of spare parts for it. Badly visible markings can eventually lead to incorrect part replacement and complete failure of the product.

Stop valves are marked at the final stage of production, but before testing procedures. If a marriage was detected, the model will not be lost and will be quickly finalized (corrected). Marking is applied by qualified specialists using modern equipment. The quality of the marking is a sign of a good reputation and responsibility of the manufacturer.