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The testing requirements for rebar in China are mainly in accordance with the standard GB/T 1499.2 – 2018 “Steel for the reinforcement of concrete – Part 2: Hot rolled ribbed bars”. The details are as follows:
- Chemical composition detection:
- Testing methods: Commonly used standard testing methods include GB/T 223 and others.
- Composition indicators: The indicators for assessing the content of rebar composition mainly include elements such as carbon (C), silicon (Si), manganese (Mn), phosphorus (P), and sulfur (S). Different grades of rebar have different chemical composition contents. For example, generally, the carbon content is between 0.10% – 0.40%, the manganese content is less than 1.80%, the phosphorus and sulfur contents are both less than 0.050%, and the silicon content is between 0.60% – 1.00%.
- Dimension and shape detection:
- Diameter deviation: The nominal diameter range is usually 6mm – 50mm. Different nominal diameters of rebar have corresponding allowable deviation ranges. For example, for common rebar with a nominal diameter of 12mm – 25mm, the diameter allowable deviation is ±0.4mm.
- Rib height and rib spacing: The rib height and rib spacing of transverse ribs also have corresponding requirements and allowable deviations. The height of transverse ribs should be within the numerical range specified by the standard, and the rib spacing should be evenly distributed.
- Bending degree: The bending degree of the steel bar should be within a certain range. Generally, the bending degree per meter should not be greater than 4mm, and the total bending degree should not exceed 0.4% of the length of the steel bar.
- Mechanical property detection:
- Tensile test: Measure indicators such as the tensile strength, yield strength, and elongation of rebar. For example, for HRB400 grade rebar, the tensile strength should not be less than 400MPa, the yield strength should not be less than 335MPa, and the elongation should not be less than 16%.
- Bending test: Bend the steel bar according to the specified bending diameter. It is required that there shall be no cracks on the surface of the bent part of the steel bar. For example, for rebar with a diameter of not more than 25mm, the bending diameter for the bending test is 3d (d is the nominal diameter of the steel bar).
- Reverse bending test: First bend forward at a certain angle (such as 90 degrees), and then bend backward at a certain angle (such as 20 degrees). After the reverse bending test, there shall be no cracks on the surface of the bent part of the steel bar.
- Surface quality detection:
- Appearance requirements: The surface of rebar shall be free of cracks, scabs, folds and other defects. The surface of the steel bar may have bumps, but they shall not exceed the height of the transverse ribs. The depth and height of other surface defects shall not be greater than the allowable deviation of the size at the corresponding location.
- Weight deviation detection:
- Allowable range: Different specifications of rebar have corresponding allowable values of weight deviation. For example, for rebar with a nominal diameter of 6mm – 12mm, the weight deviation shall not exceed ±7%; for rebar with a nominal diameter of 14mm – 20mm, the weight deviation shall not exceed ±5%, etc.
The above testing requirements are important bases to ensure that the quality of rebar meets the usage requirements of construction projects. In the actual production and use process, testing must be carried out in strict accordance with the standards.
