DIN 488: Reinforcing steel tensile test + quality requirements
DIN 488 is the relevant standard for Reinforcing steel, which are used as reinforcement in reinforced concrete construction. It defines the mechanical properties, dimensional requirements and testing methods for reinforcing bars, reinforcing steel in rings, mats and lattice girders.
The Tensile test This is the central testing procedure for determining the yield strength, tensile strength and uniform elongation – characteristic values that are crucial for the load-bearing capacity and ductility of reinforced concrete structures.
Key facts at a glance
DIN 488 ensures that Reinforcing steels that meet the minimum mechanical requirements for use in structural engineeringThe focus is on the tensile test, which is used to check the load-bearing capacity and deformability of the reinforcing steel under defined conditions.
Essential points:
- Applies to weldable reinforcing steel in bars, rings and mats.
- Determination of ReH or Rp0,2, Rm, Ag/Agt and Rm/Re
- Typical nominal diameters: 6 to 40 mm (and beyond, depending on the product shape)
- Test force ranges depending on diameter up to the range of 1200 kN
- Calibration requirements according to ISO 7500-1 (force) and ISO 9513 (elongation)
- Relevance for production monitoring and conformity assessment
- Difference from ISO 6892-1: The cross-section is difficult to determine = use of the nominal diameter
- However, a lower limit for the cross-sectional deviation (QAW) according to DIN 488 applies: ΔAs = −4,5 % / +0 %
- The cross-section is determined using the weight method (scales): weight g / length mm / density 7,85 g/cm³
What does DIN 488 regulate?
DIN 488 specifies the technical requirements for reinforcing steel used to absorb tensile forces in reinforced concrete. Since concrete has high compressive strength but low tensile strength, the embedded reinforcing steel absorbs the tensile stress.
The standard defines:
- approved steel grades
- Minimum mechanical properties
- Dimensional and surface requirements
- Labeling requirements
- Requirements for production and quality control
It is closely linked to the requirements of Eurocode 2 and forms the basis for the safe use of reinforcing steel in construction.
Overview of standard parts: DIN 488-1 to DIN 488-6
The DIN 488 series of standards is divided into several parts in order to systematically depict the different product forms of reinforcing steel as well as their technical requirements and monitoring mechanisms.
- DIN-488 1 lays down the approved Steel grades, whose mechanical properties as well as the requirements for marking and delivery condition are defined. In particular, the relevant characteristic values such as yield strength, tensile strength and yield strength ratio are defined here.
- DIN-488 2 specifies the requirements for ribbed concrete barsIt contains specifications regarding dimensional tolerances, surface characteristics, and minimum mechanical values for reinforcing steel bars with typical nominal diameters of 6 to 40 mm.
- DIN-488 3 describes the requirements for Reinforcing steel in coils and takes into account in particular the special features of the manufacture, processing and testing of this product form.
- DIN-488 4 regulates Reinforcing steel mesh, including their mechanical properties, geometry and marking.
- DIN-488 5 treated lattice girder, which are used in construction for the reinforcement of prefabricated elements or ceilings, and defines the corresponding mechanical and structural requirements.
- DIN-488 6 It defines the requirements for conformity assessment and factory production control and is therefore central to continuous quality assurance. Quality monitoring.
For the execution of the tensile test, DIN 488-1 in conjunction with DIN 488-2 are particularly relevant, as they define the mechanical properties and the product-related requirements for reinforcing steel bars.
Tensile test according to DIN 488: Test conditions and characteristic values
The tensile test is used to determine the mechanical properties of the reinforcing steel.
Key performance indicators:
- Upper yield strength ReH or 0,2% proof strength Rp0,2
- Tensile strength Rm
- Uniform elongation Ag or Agt
- Yield strength ratio Rm/Re
Typical minimum requirements:
- ReH > 500 MPa
- Rm > 550 MPa
- Ag or Agt > 8%
- Rm/Re > 1,05
Samples and cross-sectional determination
The samples are taken from ribbed round bars. Due to the irregular surface, a direct geometric measurement of the cross-section is often inaccurate.
The standard therefore allows the cross-sectional area to be determined using the weight method, in which the sample weight is calculated back to the effective cross-sectional area.
Strain measurement in ribbed reinforcing steel
Extensometers with a large initial gauge length (e.g. 100 or 200 mm) are required to determine Ag/Agt and the modulus of elasticity.
Key requirements:
- Secure grip on ribbed surfaces
- sufficient measuring distance
- robust cutting edge geometry
Test speed and execution
The testing speed must be selected so that the yield strength and plastic deformation are recorded according to standards. A uniform and controlled increase in load is crucial for this.
Furthermore, attention must be paid to a central clamping system and clean and maintained clamping devices in order to avoid bending effects.
Additional testing requirements – bending test
In addition to the tensile test, DIN 488 contains requirements for bending tests to assess the formability of reinforcing steel. These complement the tensile test and are particularly relevant for processing on construction sites or in precast concrete applications.
Testing machines for reinforcing steel according to DIN 488
For testing in accordance with standards, universal testing machines with sufficient testing force and high rigidity are required.
Depending on the diameter, machines with capacities of approximately 50 kN to 1200 kN are used.
Requirements for testing technology:
- Force measurement at least class 1, better 0,5 according to ISO 7500-1
- Strain measurement class 1 according to ISO 9513
- Suitable wedge clamping devices for ribbed round bars
- stable frame construction
Wedge clamping devices are particularly suitable for reinforcing steel, as they enable a secure grip and exhibit only minimal wear.
FAQ about DIN 488
How does DIN 488 differ from international standards such as ISO 15630 or ASTM A370?
In addition to DIN 488, other standards exist for reinforcing steel, including ISO 15630 and ASTM A370. These differ in details such as testing speed, definition of individual characteristic values, and evaluation methods.
While DIN 488 is specifically tailored to the requirements of the German and European construction industry, ISO and ASTM standards are primarily used in international trade and global construction projects. Therefore, in international supply relationships, it should be clearly defined which standard applies.
What strain gauge length is typical for reinforcing steel?
Typically, initial gauge lengths of 100 or 200 mm are used to determine Ag and Agt according to standards.
How is the cross-section determined for ribbed reinforcing steel?
Usually via the weight method, as the ribbed surface makes direct geometric measurement difficult.
What calibration requirements apply to testing machines?
The force measurement must meet at least class 1 according to ISO 7500-1, the strain measurement class 1 according to ISO 9513.
