GB/T 28900-2012 in English

《GB/T 28900-2012钢筋混凝土用钢材试验方法》由TC183（全国钢标准化技术委员会）归口，TC183SC7（全国钢标准化技术委员会钢筋混凝土用钢分会）执行，主管部门为中国钢铁工业协会。

Test methods of steel for reinforcement of concrete

1 Scope

This standard specifies the test methods of steel for reinforced concrete, covering tensile test, bending test, rebending test, axial fatigue test, chemical analysis, geometric dimension measurement, determination of specific projected rib area, determination of mass deviation and metallographic examination of steel bar.

This standard is applicable to steel bar products for reinforced concrete.

This standard is not applicable to prestressed steel.

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 documents (including any amendments) applies.

GB/T 228.1-2010 Metallic materials - Tensile testing - Part 1: Method of test at room temperature (ISO 6892-1:2009, MOD)
GB/T 232-2010 Metallic materials - Bend test (ISO 7438:2005, MOD)
GB/T 4336 Standard test method for spark discharge atomic emission spectrometric analysis of carbon and low-alloy steel (routine method)
GB/T 12160 Calibration of extensometers used in uniaxial testing (GB/T 12160-2002, ISO 9513:1999, IDT)
GB/T 13298 Inspection methods of microstructure for metals
GB/T 16825.1 Verification of static uniaxial testing machines - Part 1: Tension/ compression testing machines - Verification and calibration of the force measuring system (GB/T 16825.1-2008, ISO 7500-1:2004, IDT)

3 Symbols

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

Table 1 Symbol description

4 General provisions concerning specimens

4.1 Preparation

Unless otherwise agreed, the specimen shall be taken from the steel bar in the as-delivered condition.

4.2 Straightening

In the case of a specimen taken from coil, the specimen shall be straightened prior to any tests by a bend operation with a minimum amount of plastic deformation.

Note: The straightness of the specimen is critical for the tensile test and the fatigue test. To obtain a satisfactory straightness, it is recommended to straighten the specimen manually or mechanically.

The means of straightening the specimen (manual, machine) shall be indicated in the test report.1）

4.3 Artificial aging

For the determination of the performance indexes in the tensile test and the fatigue test, the specimen can be artificially aged according to the need (specimens that need to be straightened shall be artificially aged after straightening).

When there is no artificial aging process specified in the product standard, the following process conditions may be adopted: heating the specimen to 100 °C, maintaining the temperature at 100 °C ± 10 °C for 60 min to 75 min, and then naturally cooling it to room temperature in still air.

If an artificial aging treatment is applied to the specimen, the conditions of the artificial aging treatment shall be stated in the test report.

5 Tensile test

5.1 Specimen

In addition to the general requirements specified in Clause 4, the parallel length of the specimen shall be sufficient for the determination of the percentage elongations in accordance with 5.3.

 
If the percentage elongation after fracture (A) is determined, the specimen shall be marked with the original gauge distance L0 according to GB/T 228.1.

If the percentage total elongation (Agt) at maximum force Fm is determined by the manual method, equidistant marks shall be made on the parallel length of the specimen. The distance between the marks shall be 10 mm (or 5 mm or 20 mm as needed) according to the diameter of the steel products for reinforcement.

5.2 Apparatus

The testing machine shall be verified and calibrated in accordance with GB/T 16825.1 and shall be at least of Grade 1.

If an extensometer is used, it shall be of Grade 1 (see GB/T 12160) for the determination of ReL or Rp0.2; for the determination of Agt, a Grade 2 extensometer (see GB/T 12160) can be used.

Any extensometer used for the determination of the percentage total elongation (Agt) at maximum force Fm shall have a gauge length of at least 100 mm. The gauge length shall be indicated in the test report.

Foreword i
1 Scope
2 Normative references
3 Symbols
4 General provisions concerning specimens
4.1 Preparation
4.2 Straightening
4.3 Artificial aging
5 Tensile test
5.1 Specimen
5.2 Apparatus
5.3 Test procedure
6 Bend test
6.1 Specimen
6.2 Test apparatus
6.3 Test procedure
6.4 Judgment of test results
7 Rebend test
7.1 Specimen
7.2 Test apparatus
7.3 Test procedure
7.4 Judgment of test results
8 Axial force fatigue test
8.1 Principle of test
8.2 Specimen
8.3 Test apparatus
8.4 Test procedure
9 Chemical analysis
10 Measurement of the geometrical characteristics
10.1 Specimen
10.2 Test apparatus
10.3 Test procedure
11 Determination of the specific projected rib area (fR)
11.1 Introduction
11.2 Measurements
11.3 Calculation of fR
12 Determination of mass deviation
12.1 Specimen
12.2 Accuracy of measurement
12.3 Test procedure
13 Metallographic examination of steel bar
13.1 Specimen
13.2 Test procedure
Annex A (Informative) Technical differences between this standard and ISO 15630-1: 2010 and their causes