National Standard TCVN 1651-1:2018 for Steel for the reinforcement of concrete - Part 1: Plain bars

NATIONAL STANDARD

TCVN 1651-1:2018

STEEL FOR THE REINFORCEMENT OF CONCRETE - PART 1: PLAIN BARS

Foreword

TCVN 1651-1:2018 supersedes TCVN 1651-1:2008.

TCVN 1651-1:2008 is developed by the National Technical Committee TCVN/TC 17 Steel, requested by the Directorate for Standards, Metrology and Quality and issued by the Ministry of Science and Technology.

TCVN 1651 consists of the following parts, under the general title Steel for the reinforcement of concrete:

- TCVN 1651-1:2018, Part 1: Plain bars;

- TCVN 1651-2:2018, Part 2: Ribbed bars;

- TCVN 1651-3:2008 (ISO 6935-3:1992), Part 3: Welded fabric.

STEEL FOR THE REINFORCEMENT OF CONCRETE - PART 1: PLAIN BARS

1 Scope

This standard specifies technical requirements for plain bars to be used as reinforcement in concrete.

This standard covers CB240-T, CB300-T and CB400-T. The production process is at the discretion of the manufacturer.

NOTE: The first “CB” indicates reinforcing concrete. The next three digits represent the specified characteristic value of upper yield strength. The last “T” indicates plain bar.

This standard covers products delivered in straight lengths. It also applies to plain bars supplied in coil form and straightened products.

Plain bars produced from finished products, such as plates and railway rails, are excluded.

2 Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

TCVN 1811 (ISO 14284), Steel and iron - Sampling and preparation of samples for the determination of chemical composition.

TCVN 4399 (ISO 404), Steel and steel products - General technical delivery requirements.

TCVN 7937-1 (ISO 15630-1), Steel for the reinforcement and prestressing of concrete - Test methods - Part 1: Reinforcing bars, wire rod and wire.

TCVN 7938 (ISO 10144), Certification scheme for steel bars and wires for the reinforcement of concrete structure,

TCVN 8998 (ASTM E 415), Standard Test Method for Analysis of Carbon and Low-Alloy Steel by Spark Atomic Emission Spectrometry.

ISO/TS 4949, Steel names based on letter symbols.

ISO/TR 9769, Steel and iron - Review of available methods of analysis.

3 Symbols

The symbols used in this standard are listed in Table 1.

Table 1 - Symbols

4 Terms and definitions

For the purposes of this document, the following terms and definitions apply.

4.1

cast analysis

chemical analysis representative of the cast determined by the steelmaker in accordance with his own procedures.

4.2

conformity assessment scheme

certification system as related to specified objects of conformity assessment to which the same particular standards and rules, and the same procedure, apply

NOTE 1: A conformity assessment scheme may be operated at an international, national or sub-national level.

NOTE 2: Third-party certification as related to specified products, processes, services or persons is applicable to all objects of conformity assessment, except for conformity assessment bodies themselves.

4.3

characteristic value

value having a prescribed probability of not being attained in a hypothetical unlimited test series.

NOTE 1: Equivalent to fractile, which is defined in ISO 3534-1.

NOTE 2: A nominal value is used as the characteristic value in some circumstances.

4.4

product analysis

chemical analysis carried out on the product.

5 Dimensions, masses per unit length and permissible deviations

Dimensions, mass per unit length and permissible deviations are given in Table 2. By agreement between the manufacturer and purchaser, plain bars whose nominal diameters are other than those shown in Table 2 may be used. By agreement between the manufacturer and purchaser, the permissible deviation on mass per length may be replaced by tolerances on diameters.

Delivery length should be agreed between the manufacturer and purchaser. Permissible deviation on delivery length from rolling mill shall be mm.

NOTE: The preferred delivery length of straight bars is 11,7 m.

Table 2 - Dimensions, mass per unit length and permissible deviations

6 Chemical composition

The chemical composition of the steel, as determined by cast analysis, shall conform to Table 3.

The permissible deviation of the product analysis relative to the cast analysis as specified in Table 3 are given in Table 4.

Table 3 - Chemical composition based on cast analysis - Maximum values of mass fractions, in percentage

Table 4 - Chemical composition based on product analysis - Permissible deviation of the product analysis in percentage by mass

7 Mechanical properties

7.1 Tensile properties

The tensile test shall be performed in accordance with 8.1.

The material shall conform to the requirements for tensile properties specified in Table 5.

In the context of this standard, the characteristic value is (unless otherwise indicated) the lower or upper limit of the statistical tolerance interval at which there is a 90 % probability (1 − α = 0,90) that 95 % (p = 0,95) of the values are at or above this lower limit, or are at or below this upper limit, respectively. This definition refers to the long-term quality level of production.

If a yield phenomenon is not present, the 0,2 % proof strength (R_p0,2) shall be determined.

Table 5 - Tensile properties

7.2 Bending properties

After testing in accordance with 8.2, the bar shall show neither rupture nor cracks visible to a person of normal or corrected vision.

8 Testing

8.1 Tensile test

The tensile test shall be carried out in accordance with TCVN 7937-1 (ISO 15630-1).

For the determination of percentage elongation after fracture, A₅, the original gauge length shall be 5 times the nominal diameter.

For the determination of percentage total elongation at maximum force, A_gt, equidistant marks shall be made on the free length of the test piece. The distance between the marks shall be 20 mm, 10 mm or 5 mm, depending on the bar diameter.

For determination of tensile properties, the nominal cross-sectional area of the bar shall be used.

8.2 Bend test

The tensile test shall be carried out in accordance with TCVN 7937-1 (ISO 15630-1).

The test piece shall be bent to an angle between 160° and 180° over a mandrel of the diameter specified in Table 6.

Table 6 - Mandrel diameter to be used for the bend test

Dimensions in millimeters

8.3 Chemical analysis

The chemical composition is determined in accordance with TCVN 8998 (ASTM E 415).

In case of dispute about the analytical method, the chemical composition shall be determined by an appropriate referee method specified in ISO/TR 9769.

9 Designation

Plain bars according to this standard shall be designated in the following order:

a) reinforcing steel;

b) a reference to this standard;

c) nominal diameter, in millimeters, according to Table 2;

d) steel grade.

EXAMPLE: Reinforcing steel TCVN 1651-1 - 12 CB240-T.

10 Marking

Each bundle of bars shall have a label stating the name of the manufacturer, a reference to this standard, the steel grade, the nominal diameter, the batch number, the date of manufacturing, the cast number or reference related to test record and country of origin.

11 Evaluation of conformity

11.1 General

Certification and inspection of reinforcement shall be performed;

a) in accordance with a certification scheme monitored by an external body; or

b) according to acceptance testing of a specific delivery.

11.2 Certification scheme

In the case of a certification scheme, certification and inspection shall be performed in accordance with TCVN 7938 (ISO 10144).

11.3 Acceptance testing of a specific delivery

11.3.1 General

Provisions regarding the nature, extent and evaluation of acceptance testing on deliveries of reinforcing steel not subject to a certification scheme are given in 11.3.2 and 11.3.3.

Acceptance testing of a specific delivery shall be performed according to 11.3.2.

By agreement between the manufacturer and purchaser, 11.3.3 may be used.

11.3.2 Verification of characteristic values

11.3.2.1 Organization

The tests shall be organized and carried out according to an agreement between the purchaser and manufacturer, taking into consideration the national rules of the receiving country.

11.3.2.2 Extent of sampling and testing

For the purpose of testing, the delivery shall be subdivided into test units with a maximum mass of 50 t or a fraction thereof. Each test unit shall consist of products of the same steel grade and the same nominal diameter from the same cast. The manufacturer shall confirm in the test report that all samples in the test unit originate from the same cast. The chemical composition (cast analysis) shall be stated in this test report.

Test pieces shall be taken from each test unit as follows:

a) two test pieces from various bars, for testing the chemical composition (product analysis);

b) a minimum of 15 test pieces (if appropriate, 60 test pieces, see 11.3.2.3.1) from various bars for testing all other properties specified in this standard.

11.3.2.3 Evaluation of the results

11.3.2.3.1 Inspection by variables

For properties which are specified as characteristic values, the following shall be determined:

a) all individual values xi of the 15 test pieces (n = 15);

b) the mean value m₁₅ (for n = 15);

c) the standard deviation s₁₅ (for n = 15).

The test unit corresponds to the requirements, if the condition stated below is fulfilled for all properties:

m₁₅ – 2,33 x s₁₅ ≥ ¦_k             (1)

where

¦_k is the specified characteristic value;

2,33 is the value for the acceptability index k for n = 15 for a failure rate of 5 % (p = 0,95) at a probability of 90 % (1 − α = 0,90).

 (2)

If the condition stated above is not fulfilled, the index

 (3)

is determined from the test results available. Where k' ≥ 2, testing can be continued. In this case, 45 further test pieces shall be taken and tested from different bars in the test unit, so that a total of 60 test results are available (n = 60).

The test unit shall be considered to comply with the requirements, if the condition stated below is fulfilled for all properties:

m₆₀ – 1,93 x s₆₀ > ¦_k      (4)

where 1,93 is the value for the acceptability index k for n = 60 for a failure rate of 5 % (p = 0,95) at a probability of 90 % (1 − α = 0,90).

11.3.2.3.2 Inspection by attributes

When testing properties are specified as maximum or minimum values, all results determined on the 15 test pieces shall comply with the requirements of the product standard. In this case, the test unit shall be considered to comply with the requirements.

The tests may be continued when at most 2 results not conforming to the conditions occur In this case, 45 further test pieces from various bars in the test unit shall be tested, so that a total of 60 test results are available. The test unit complies with the requirements, if not more than 2 of the 60 results do not conform to the conditions.

11.3.2.3.3 Chemical composition

Both test pieces shall comply with the requirements in this standard.

11.3.3 Verification of specified minimum/maximum values

Tests shall be carried out according to the following.

a) Bars of the same cast shall constitute one group. For every 50 t or fraction thereof, one tensile test and one bend test shall be carried out for each bar diameter.

b) Each individual test result shall meet the required values in Table 6, and the required bending properties in 7.2;

c) One cast analysis shall be carried out for every cast to verify chemical composition (Clause 6). Samples shall be taken in accordance with TCVN 1811 (ISO 14284);

d) If any test result does not meet the requirements, retests may be carried out, according to TCVN 4399 (ISO 404);

e) The manufacturer shall submit a test report stating that the products of the delivery satisfy the chemical and mechanical properties defined in Clauses 6 and 7, and a confirmation that the other requirements of this standard are fulfilled.

11.3.4 Test report

The test report shall contain the following information:

a) designation of the reinforcing steel in accordance with this standard;

b) marking details (on the tag, painting, etc.);

c) date of testing;

d) mass of the test unit;

e) test results.

Bibliography

[1] TCVN 8244-1 (ISO 3534-1), Statistics - Vocabulary and symbols - Part 1: General statistical terms and terms used in probability.

 [2] ISO 16020, Steel for the reinforcement and prestressing of concrete - Vocabulary.

[3] TCVN 6450 (ISO/IEC Guide 2), Standardization and related activities - General vocabulary.

[4] ISO 6935-1, Steel for reinforcement of concrete - Part 1: Plain bars.

[5] JIS G 3112:2010, Steel bars for concrete reinforcement.

[6] GB 1499.1-2008, Steel for reinforcement of concrete - Part 1: Hot rolled plain bars.