STEEL FIBRES FOR CONCRETE REINFORCEMENT

TREFILARBED, one of the worlds leading suppliers for steel fibres TREFILARBED is part of the Long Carbon division of the ARCELOR group, specialising in low carbon wire products. The major product lines of TREFILARBED are industrial wires (bright, galvanized, annealed, coppered,…), agricultural products (fencing, barbed wire,…), nails and fibres. TREFILARBED have been producing steel fibres for over 25 years now and have become one of the leading suppliers for steel fibres worldwide. The main production plant for fibres is located in Bissen (L), but since 2002, two new sites, in Cheb (CZ) and Sheffield (GB), have been launched. Other production sites are under preparation. The aim of this decentralisation is to be closer to our customers in order to further improve our service.

TREFILARBED BISSEN plant

All the fibres produced by TREFILARBED are made of cold drawn, high-strength wire produced on the most modern equipment available in their field. Our policy of continuous investment is the warranty for the durable performance of our products. The fact that TREFILARBED is one of the few fibre producers worldwide with an integrated production (wire drawing + fibre production + galvanization if required) is another guarantee of the consistent high quality of our steel fibres, which benefit from the ISO 9001 and ISO 14001 labels.

TREFILARBED CHEB plant

ESTATE WIRE plant, Sheffield

Who is ARCELOR ? ARCELOR is by far the largest steel producer in the world with a total production of 46 million tons of crude steel and employing more then 110,000 people all over the globe. The new company was created in spring 2002 by the merger of three European steel producers ARBED (L), ACERALIA (E) and USINOR (F). The headquarters of the company are in Luxembourg. Today ARCELOR is the market leader in Flat Carbon with sales of 15 billion Euros, in Long Carbon (including wire products) with sales of 4 billion Euros, in Stainless with sales of 5 billion Euros and in distribution, trading and processing with sales of 6 billion Euros. In Europe, 20% of all the steel employed in construction is ARCELOR steel.

ARCELOR headquarters Luxembourg-City

What is Steel Fibre Reinforced Concrete ? Steel Fibre Reinforced Concrete (SFRC) is a composite material with specific properties and advantages. By adding steel fibre reinforcement to the concrete prior to discharge at site, SFRC obtains a material resistance similar to that of traditional reinforced concrete. This load bearing resistance can be used to substitute, partially or completely, more traditional forms of reinforcement (bars and/or mesh) for a lot of applications, allowing major cost and time savings. Depending on the type of application and on the customer needs, different fibre types and sizes will be used in order to meet the technical, economical and handling requirements in an optimal way.

Applications for SFRC

- precast concrete elements, like tunnel lining segments, sewer pipes, railway sleepers, … - composite concrete decks - foundations and rafts

Today, SFRC is used mainly in flooring / flatwork, housing and shotcrete applications. However the range of applications for SFRC is much larger. In fact, SFRC can be used without any other additional reinforcement in almost all applications where the flexural stresses are not overwhelming (like in beams for instance). But even in these applications, a combination between SFRC and pre-stressed or traditional reinforced concrete can be of interest - for example, using the good shear resistance of SFRC, allows a sensible reduction of the stirrups. Major and potential applications for steel fibres today are: - industrial floors, including joint-free design or floors on piles

- wall elements, insitu or precast - roller compacted concrete - bank safes

Benefits of SFRC

- all kind of shotcrete applications (wet and dry process)

Steel fibres improve the physical properties of concrete, making the concrete perform better under certain stress conditions like dynamic loads, uniform distributed loads, vibration...etc. Unlike traditionally reinforced concrete (rebars or mesh), SFRC provides a 3D reinforcement throughout the concrete and acts as a uniform composite material. The fibres enable the concrete to continue to carry the load after cracking has occurred. The failure mode is no longer brittle; once the first crack has appeared, the concrete behaves in a ductile manner, freeing additional bearing capacities. Depending on the application,the benefits of SFRC are numerous: - Excellent impact strength - Enhanced edge protection - Improved shrinkage and crack control - Enhanced resistance to abrasion - Improved fatigue endurance

- No reinforcement placement mistakes

The undulated fibre type TABIX is one of oldest shapes known in SFRC. By optimising the amplitude to wave length ratio, TREFILARBED has succeeded in combining a fair workability with a good static performance and an outstanding shrinkage control behaviour. This fibre type is to be recommended each time, when concrete shrinkage, even at young age, is a concern. The TABIX+ 1/60 fibre, with a 50% higher tensile strength than standard fibres, allows the construction of structural applications like slabs on piles and rafts, using fibres as the sole means of reinforcement.

- Reduced element thicknesses - Excellent resistance to corrosion - Time savings up to 50% - Increased tensile-,compression-, shear- and flexural strength, equal in all directions (isotropic material)

- Improved ductile behavior after matrix failure - Additional bearing capacities due to plastic moment redistribution

The hooked-end fibre HE is probably the best known shape in SFRC around the world. HE fibres are general purpose fibres with a good workability and a good performance level as well. Thanks to the hooked ends, the fibre is well anchored in the concrete matrix and demonstrates good load transfer in the crack.

The FE fibre is a straight fibre with flattened ends, which assume the anchorage in the matrix. The straight shape guarantees an optimal workability even at increased aspect ratios. Especially used in shotcrete applications, the FE fibre is excellent because of its low rebound ratio.

Our product range TREFILARBED offers probably the largest variety of steel fibre types available today from one single supplier, which allows us to provide our customers with the level of performance needed for their specific application. All of the fibres produced by TREFILARBED are made of high strength steel wire, with a low carbon content. The various shapes provide a strong bond between the fibre and the concrete matrix. Our fibres are produced and delivered in accordance with the requirements of ISO 9002 quality standard. All of our fibres comply with ASTM A820, Type I, cold drawn high tensile deformed steel wire.

The HFE (Hooked Flat End) fibre is a combination of the HE and the FE fibre. The initial objective for creating this fibre was to increase the anchorage capabilities of the fibre in order to improve its performance within the concrete matrix. Additionally, the workability of the fibre was greatly improved, thus allowing even higher fibre aspect ratios and to be used without risk of balling. This fibre also has outstanding properties regarding the shrinkage control of fresh concrete.

How is SFRC batched?

The TABIX FE is an undulated TABIX fibre with flattened ends. This shape was developed because of the discovery made with the HFE fibre, that the flattening of the ends improves the workability of the fibre. The TABIX FE is a high-end performance fibre, combining excellent anchorage properties, with high ductility and good workability, even at increased aspect ratios (other fibres need glueing to avoid balling). With the correct choice of length and diameter, this fibre type is suited for almost any known application in SFRC.

The Twincone® fibre is a straight fibre with conical heads at each end. Unlike the flattened ends, these cones assure a unique and total anchorage capacity within the concrete matrix. This means that the fibre can be stressed up to the limit of the wire's resistance without being pulled out of the concrete matrix. Furthermore, shear failure in the anchorage zone can be excluded. The Twincone® fibre, which is exclusively produced by TREFILARBED, is specially suited for all kind of structural applications. (Twincone® is a registred trademark of RINOL Germany)

Which fibre for which application ?

SFRC comprises concrete and steel fibres. The basic concrete mix is defined in the same way as it is for ordinary reinforced concrete. SFRC requires a high quality concrete with a low water/cement ratio, low shrinkage properties and a good blend of quality aggregates. The particular type of steel fibres is chosen in order to achieve specific technical and load-carrying requirements of the SFRC-element. Concrete mix, fibre type and fibre dosage rate have to be harmonized in order to obtain the best possible solution. It should be noted that the addition of steel fibres will reduce the slump of the concrete. Therefore, in order to ensure the workability of the final mix, the slump has to be increased by adding plasticizers accordingly. It is important to understand that increasing the slump by adding more water is strictly prohibited. best suited suitable

The steel fibres can be added either at the concrete batching plant or at a later stage on the job site. Fibre integration can be done manually or mechanically. At the batching plant, fibres are usually added directly into the stationary mixer or together with the coarse aggregates on the conveyor belt. On the job-site, the FE and HE fibres can be integrated most economically into the concrete mixer truck, by using conveyor belts or elevators. For major or long lasting projects and for those utilising the TABIX fibre, more sophisticated equipment like blast machines or dosage feeders can be used. Additional mixing time after adding fibres is around one minute per m3 of concrete at high rotation speed. The concrete must contain enough fines, including cement, to assure an adequate binding of the fibres in the concrete matrix and avoid fibres on the surface.

Frequently asked questions

What is the difference between steel fibres and synthetic fibres? Steel fibres and synthethic fibres show a completely different stress-strain behaviour. Synthetic fibres only have a positive influence on the properties of wet concrete, they do not increase the post-cracking behaviour. However, steel fibres show a significant improvement in the load bearing resistance after cracking and, depending on the fibre type and the dosage rate, this can even be up to full ductility. Does it make sense to use a combination of synthetic and steel fibres? The so-called cocktails are becoming rather trendy today. In a case where the customer does not control the W/C-ratio and the curing process, it can be useful to add synthetic fibres to improve the plastic shrinkage of the concrete. However the customer should be aware, that using a good quality concrete with a correct mix and water/cement ratio makes it superfluous to spend money for synthetic fibres. Can SFRC be pumped? Steel fibre reinforced concrete can normally be pumped with the standard equipment up to a fibre dosage rate of 60 kg/m3. In order to avoid problems, especially for high dosage rates, the concrete mix and the pumping set-up should be checked. What are the typical dosage rates for steel fibres? Typical dosage rates for steel fibres range from 15 kg/m3 (crack control) to 50 and sometimes up to 80 kg/m3 (structural elements). Are there any compatibility problems with fibers? Steel fibres are compatible with all mid & high range water reducers, hardeners, superplasticizers, air entrainers, curing compounds and coatings.