steel fibres - Constructalia

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.