CE marking is a mandatory requirement for fibres used for the reinforcement of concrete. EN14889 “Fibres for Concrete” covers both steel and synthetic fibres and details clearly the material properties and performance of the fibres that should be checked to ensure quality compliance is achieved and that the product is fit for use as a reinforcement material for concrete. This process is overseen by an independent notified body, ensuring compliance, and issuing certification for the fibre.
The relevant information is then presented in a “Declaration of Performance” (DoP) which allows the user to review the material properties and performance of the fibre in concrete.
The information presented differs depending on whether the fibre is intended for “structural” use, where the addition of the fibres is designed to contribute to the load bearing capacity of the concrete element, or for “non-structural” applications.
For structural applications, the fibre should comply with attestation of conformity Class 1, requiring specific characteristics to be tested and evaluated including:
- Length
- Equivalent Diameter.
- Shape
- Tensile Strength
- Elastic Modulus
- Consistence (Vebe test)
- Effect on Strength
However, which are the important characteristics to consider for structural purposes?
Individual properties from the list should not be viewed in isolation. For example, comparing tensile strength of fibres with different shape and dimensions is meaningless, just as comparing different shapes and sizes of fibres used in completely different concrete mixes is wrong.
Although Consistence will be influenced by, Length, Equivalent Diameter, and Shape (effectively anchorage), it has little bearing on structural performance.
The only specific characteristic given on the DoP that defines performance of a fibre for structural purposes is Effect on Strength. This characteristic reflects not only the influence of the other measured parameters but also the concrete mix into which the fibre is added. Hence EN14889 stipulates the reference mix for Effect on Strength testing that must be used.
EN14889
EN14889, and its sub standards, requires the fibre content in kg/m3 to be stated, corresponding to the minimum performance level of 1.5N/mm2 (Fr1) at a CMOD of 0.5mm and 1N/mm2 (Fr4) at a CMOD of 3.5mm (when tested in accordance with EN14651). This provides the user with the minimum dosage of fibres required (in accordance with EN14845) for the product to gain CE compliance for structural performance in concrete. It also gives the user an overview of the fibres overall performance, encompassing all the physical fibre characteristics, and allows a comparison to be made between other products.
By stating on the DoP the minimum dosage rate required for it to meet structural performance levels to gain CE certification, the Effect on Strength provides a relevant guide for the fibre’s use in enhancing the load carrying capability of a concrete element.
Fibre Concrete Solutions support the principle that fibres should not be promoted at less than the minimum dosage stated on a DOP for the Effect on Strength, where the fibre is being used in “structural” elements to enhance the load carrying capability. We believe this is critical in providing our customers with robust technical solutions based on the very best independent test data and guidance.
For further information on the range of fibres, solutions and engineering services that Fibre Concrete Solutions can offer, please contact us.
