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Steel Fibers and Steel Fiber Reinforced Concrete in Civil Engineering
Jacek Katzer, Ph.D.
Department of Civil and Environmental Engineering, Laboratory of Building Engineering,
Technical University of Koszalin, Poland
http://www.wbiis.tu.koszalin.pl/ltb/
E-mail: katzer@tu.koszalin.pl
ABSTRACT
Since the beginning of applications of civil
engineering materials based on clay, lime, and
cement, there has been a need to find a way to
decrease their brittleness. In ancient times, the
problem was solved by modifying brittle clay
bricks with the addition of fibers of an organic
origin. These approaches can be examined
through a reading of the descriptions of Roman
baths construction (Vitruvius 1999). Today it is
steel fiber which is mainly used to reinforce
concrete and overcome the problem of
brittleness. This paper describes the most
interesting applications of steel fiber reinforced
concretes (SFRC) all over the world. Firstly, the
author presents the evolution of steel fibers and
SFRC. Secondly, the paper covers the
contemporary importance of SFRC in civil
engineering.
(Key words: tensile strength, construction material,
engineering technology).
INTRODUCTION
The long process of inventing modern steel fiber
reinforced concrete started in 1874, when A.
Bernard, in California, patented the idea of
strengthening concrete with the help of the
addition of steel splinters (Maidl 1995). Another
36 years passed before Porter in 1910
mentioned the possibility of applying short wire
to concrete. This was supposed to improve
homogeneity of concrete reinforced by thick wire.
In 1918, in France, H. Alfsen patented a method
of modifying concrete by long steel fibers, long
wooden fibers, and fibers made of other
materials. According to him, the addition of such
fibers was to increase tensile strength of
concrete (Maidl 1995). Alfsen was the first to
mention the influence of coarseness of the
surface of fibers onto their adhesiveness to
matrix, and it was also he who paid special
attention to the problem of anchorage of fibers.
After these first patents, there were numerous
others, but generally they concerned different
shapes and probable applications of ready made
SFRC. For instance, the patent from 1927
worked out in California by G.C. Martin, regarded
the production of SFRC pipes. In 1938, N.
Zitkewic patented a way to increase the strength
and impact resistance of concrete by adding cut
pieces of steel wire (Jamrozy 1985). Steel fibers,
patented in 1943 by G. Constancinesco, were
already very similar to the ones used at present.
The patent, apart from different shapes of fibers,
contained information about the kind and
dispersion of cracks during loading of SFRC
elements and it made mentioned of the great
amount of energy which is absorbed by SFRC
under impact. The largest number of patents
concerning the use of steel fibers to modify
concrete have been submitted in the USA,
France, and Germany in the years following.
Wide applications of fiber reinforced composites
in civil engineering were limited for a long time
by lack of reliable methods of examination and
mainly by the sudden progress of traditional rod
reinforcement.
FIBERS
Currently in the world, there are about 30 major
producers of steel fibers used for modifying
concrete, and they offer over 100 types of fiber
(Katzer 2003 and Odelberg 1985). Steel fibers
for modifying concrete are produced not only in
Europe and in the USA but also in such
countries as the Republic of South Africa,
Australia, and South Korea.
The oldest, and at the same time, the most basic
type of steel fibers are straight fibers cut out of
smooth wire. Unfortunately, such fibers do not
ensure the full utilization of the strength of steel
because of a lack of appropriate anchorage in
the concrete matrix. Over 90% of currently
produced fibers are shaped fibers. The shape of
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fibers is adjusted in such a way that it increases
the anchorage of fibers in concrete. Throughout
the last 40 years there have been produced
twisted, crimped, flattened, spaded, coned,
hooked, surface-textured, and melt-cast steel
fibers. These steel fibers had circular, square,
rectangular, or irregular cross-sections. Each of
the types was additionally varied by diameters
and length (Jamrozy 1985 and Maidl 1995).
Sometimes, in order to modify concrete, waste
steel shavings and chips of different shapes
were used instead of produced fibers (Keyvani
1995).
Decades of the experience had led to the
production of the five most efficient steel fiber
types. The efficiency of the currently produced
fiber is based on both its effectiveness in
concrete matrix and the simplicity of its
production, which in turn has a significant
influence on its price. These five most popular
types of steel fiber are: traditional straight,
hooked, crimped, coned, and mechanically
deformed. The geometries of the non-straight
fibers mentioned above are shown in Figure 1.
Other types of fiber are rarely encountered and
they are almost always produced for specific
client orders.
Figure 1: Fiber Profiles: Hooked, Crimped,
Coned, and Mechanically Deformed.
A statistical analysis of the assortment produced
in the world indicates that 67.1% of fiber consists
of the hooked type. The other most popular
fibers are: straight fiber (9.1%), mechanically
deformed fiber (9.1%), crimped fiber (7.9%), and
other fiber of different endings (6.6%).
The efficiency of dispersed reinforcement
depends on numerous factors. However, the
most important of them is the aspect ratio of the
fibers, which influences the workability and
spacing of fibers in fresh concrete mix. Because
of workability, the concrete mix aspect ratio of
steel fiber should not be higher than 150. A
statistical analysis of the aspect ratio of
produced steel fibers is shown in Figure 2 with
the help of a frame chart.
Figure 2: Aspect Ratio of Steel Fibers.
The aspect ratio of fibers available on the world
market ranges from 20.4 to 152, which is
indicated in Figure 2. In order to describe the
frequency of a specific fiber aspect ratio, Figure
2 presents a frame showing a distance between
the lower and upper quartile which is very narrow
and encompasses the aspect ratio from 45 to
63.5. In other words, fiber of the aspect ratio
from 45 to 63.5 constitutes 50% of the population
of all types offered by producers of steel fiber
used for modifying concrete.
APPPLICATIONS
The first serious civil engineering constructions
with the application of SFRC were carried out in
the 1960s. Nevertheless, the advantages of the
material were not fully appreciated until a decade
later. Since that time, SFRC has found
numerous applications on a wider scale.
Moreover, the application of SFRC is continually
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increasing. Firstly, SFRC was used to build
runways of airports. In the USA, 28 runways built
of SFRC modified by 0.3-2.0% of steel fiber of
different kinds were finished between 1972 and
1980 (Lankard 1975). During these 14 years of
observation of the construction projects, only
scarce cracks and local damage were noticed. In
the USA, fiber reinforced concrete is used to
repair surfaces of motorways and airports as well
as to build dams and canals (Lankard 1975).
Recently it has been shotcrete with the addition
of steel fiber which is gaining more and more
popularity among constructors. Unstable slopes,
landslides, and road embankments have been
secured with shotcrete put on a previously
stretched steel mesh.
Thanks to the application of steel fiber reinforced
shotcrete (SFRS), the mesh, whose attachment
and laying are time-consuming, may be
abandoned. With traditional spraying of shotcrete
onto mesh, it often happens that shotcrete is
stopped by the mesh and spraying shadows
appear. Apart from that, the mesh can vibrate as
spraying causes grains of sand hit it. This in turn,
hinders a good bond between the mesh and
shotcrete. With the application of SFRS the loss
of material during the laying phase is reduced by
half in comparison with shotcrete without fibers
(Jamrozy 2002). The application of SFRS allows
one to avoid these technological problems and
additionally creates a possibility of making
thinner sprayed layers, which simultaneously are
more resistant to cracks as is schematically
shown in Figure 3.
Figure 3: A Scheme of Securing a Rock Slide by
putting Traditional Reinforced Concrete and
SFRS.
SFRS also has greater early strength (after a
three or seven day curing period) than traditional
shotcrete on mesh. SFRS is more and more
willingly applied to buildings, all kinds of new
tunnels, and repaired older ones. Due to the
employment of SFRS, it is possible to shorten
the work time by half in comparison to the time
needed to make the same application with the
help of shotcrete sprayed on wire mesh.
SFRS enables a quick and effective regeneration
of existing reinforced concrete elements. Such a
regeneration of the coat of one out of four
hyperboloid cooling towers was carried out at the
Siersza Electricity Plant in Poland. The example
of strengthening a concrete T-beam by spraying
a layer of SFRS is shown in Figure 4. SFRS is
also applied to build whole thin-walled
constructions. Figure 5 shows a way in which a
cylinder water tank is built by using fiber
reinforced shotcrete. In this way the possibilities
of achieving the most sophisticated and complex
shapes of concrete elements are unlimited,
which is displayed in an example of a fiber
reinforced concrete shell shown in Figure 6.
Figure 4: A Scheme of Strengthening a
Concrete Beam by adding SFRS (Maidl 1995).
SFRC is more and more often employed to
produce pre-cast elements (Shah 1985). The
addition of steel fibers significantly decreases the
risk of cracks of pre-cast elements or of their
damage when transporting or assembling them.
One of the first SFRC pre-cast elements
produced in series were railway tunnel tubings.
Beside the traditional solid pre-cast elements
there are also produced thin-walled pre-cast
elements made of SFRC.
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Figure 5: Building of a Cylinder Water Tank
Employing Shotcrete Techniques (Shah 1985).
Figure 6: A Storage Room made by Employing
Shotcrete Techniques (Shah 1985).
In Poland, there currently is production of curtain
wall pre-cast elements made of SFRC (Shah
1985). Such an element consists of two SFRC
outer layers which are 12-18mm across and the
thermo-insulation layer which is 160-230mm
across. The described elements (presented in
Figure 7) are very light, durable and cheap to
produce. In Kenia, SFRC thin-walled pre-cast
concrete elements are produced with foamed
polystyrene core. These elements (presented in
Figure 8) are used to build living shelters (Boer
2004). Such pre-cast elements (whose sizes are
147.5cm ·20cm·40cm and mass equals 100kg)
are very simple in production and later
assembling.
An interesting example of thin-walled SFRC pre-
cast elements are Swedish ones of a trapeze
section (Shah 1985). A single prefabricate is 7m
long (of a diameter from 1.2 to 1.8m) and weighs
6 tones. These elements are used to build a
seaport harbor or breakwaters. Six elements in
an upright position shaped in a semicircle forms
the head of a single breakwater, which is shown
in Figure 9. The interior of the positioned
elements is filled with ordinary concrete.
Figure 7: A Vertical joint of Precast Wall
Elements (1- Sealing Compound; 2-gasket; 3-
Cement Mortar; 4- Sealing Compound; 5- Air
Canal; 6- Rock Wool).
Figure 8: A Thin-Walled Element Made of SFRC
with Foamed Polystyrene Insulating Core (Boer
2004).
A rare example of a SFRC application is the
reconstruction of foundations under a hammer
200kN of a percussive action described by
Jamrozy (1983). The foundation in question used
to crack every few years. After a subsequent
removal of the cracked part of the foundation as
deeply as four meters, the part was
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reconstructed with SFRC. The basis of the
foundation was 12·14m. A layer of ordinary
concrete was covered with a one meter thick
layer of SFRC situated directly under the anvil.
The described SFRC was based on the addition
of 65kg/m3 of steel fibers. The length of the
mentioned fibers was 25mm with the diameter of
0.25mm.
Figure 9: A View of a Thin-Walled SFRC
Element used to build a Seaport Harbor (Shah
1985).
While working, the hammer causes stress inside
the foundation from +0.2 MPa to -0.7MPa. The
foundation was examined two years after the
hammer started working. The hammer was taken
off in order to uncover the whole surface of the
foundation. During the inspection, no damage
was found and the rebound hammer test showed
a considerable growth of compressive strength
of the examined concrete. Figure 10 shows a
scheme of the foundation of the described
hammer with marked areas in which ordinary
concrete and SFRC were used in its renovation.
In Russia and Ukraine, SFRC is used to build
and renovate industrial concrete chimneys. A
chimney, apart from being exposed to severe
weather conditions, is also exposed to
considerable temperature difference between its
outer surface (e.g. frost -30oC) and inner side,
which can be heated up to +250C by the fumes.
The application of steel fibers allowed increased
flexural strength of the chimney elements by
250%. The increased strength stopped the
appearance of micro-cracks and fast degradation
of chimneys previously caused by water
penetration into the chimney barrel.
The addition of steel fiber to fireproof concretes
turned out to be extremely effective. Moreover,
the usually brittle fireproof concrete became
resistant to cracks caused by sudden
temperature changes up to 1,500C and
mechanical blows (Jamrozy 1983).
Figure 10: A Scheme of a Foundation Under a
Hammer Reconstructed with SFRC (1- Anvil, 2-
Shock Absorption Pad, 3- SFRC, 4- Ordinary
Concrete, 5- Old Concrete Block)
(Jamrozy 1983).
Besides for the civil engineering applications of
SFRC presented above, there are also examples
of fiber reinforced pipe production. The first
patent for SFRC pipes was filed in 1927, in
California, by G.C. Martin (Maidl 1995). In 1978,
a successful production of pre-cast SFRC pipes
and masts was established in Sweden (Sallstrom
1985).
These elements, of a length up to 13 meters, are
produced with the help of spinning and axial
moving forms. The advantages of this rotating
manufacturing process lie in the significantly
higher strength and lower permeability of the
SFRC as compared to conventionally produced
SFRC pipes and masts.
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CONCLUSIONS
Romualdi, J.P. & Baston, G.B. 1963. “Mechanics of
Crack Arrest in Concrete”. Proc. ASCE. 89 EM3.
Over 40 years ago, Romualdi, Baston, and
Mandel published the papers (Romualdi &
Baston 1963, Romualdi & Mandel 1964) that
brought SFRC to the attention of academic and
industrial research scientists around the world. In
the ensuing four decades, SFRC has been
constantly examined and its technology was
continually developed. Today, SFRC is a
commercially available and viable construction
material.
REFERENCES
Boer, S. and Groeneweg, T. and Leegwater, G., and
Pieterse, I. 2004. Low-cost Housing in Kenia. Delft
University of Technology.
Odelberg, G. 1985. “Producing and Promoting of
Swedish Steel Fibers to the Market”. Steel Fiber
Concrete US-Sweden Joint Seminar, Stockholm 3-5
June, 1985.
Jamrozy, Z. 1983. Mechanika Kompozytów
Betonopodobnych. Zakład Narodowy Imienia
Ossolińskich, Wydawnictwo Polskiej Akademii Nauk.
Jamrozy, Z. 1985. Drutobeton. Wydawnictwo
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Jamrozy, Z. 2002. “Betony ze Zbrojeniem
Rozproszonym”. XVII Ogolnopolska Konferencja
Warsztat Pracy Projektanta Konstrukcji. Ustron.
Johnston, C. D. 2001. Fibre Reinforced Cements and
Concretes. Gordon and Breach Science Publishers.
Katzer, J. 2003. “Wlokna Stalowe Stosowane do
Modyfikacji Betonu”. Polski Cement. (3/2003).
Kayvani, A. and Saeki, N. and Shimura, K. 1995.
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PA,USA.
Lankard, D.R. 1975. Fiber Concrete Applications.
Rilem Symposium. The Construction Press, LTD.
Lankard, D. R. 1985. “Preparation, Properties and
Applications of Cement-based Composites Containing
5 to 20 Percent Steel Fiber”. Steel Fiber Concrete US-
Sweden Joint Seminar. Stockholm.
Maidl, B.R. 1995. Steel Fibre Reinforced Concrete.
Ernst & Sohn.
Romualdi. J.P. & Mandel. J.A. 1964. “Tensile Strength
of Concrete Affected by Uniformly Distributed Closely
Spaced Short Lengths of Wire Reinforcement”. ACI J.
Proc. 61(6)
Sallstrom, I. 1985. “Products Made of Steel Fiber
Reinforced Concrete on the Scandinavian Market”.
Steel Fiber Concrete US-Sweden Joint Seminar,
Stockholm 3-5 June, 1985.
Shah, S. P. and Skarendahl, A. 1985. Steel Fiber
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Vitruvius. 1999. De Architektura Libra Decem.
Prószyński i Spółka. Warszawa.
ABOUT THE AUTHOR
Jacek Katzer, Ph.D., M.Sc., B.Sc. is a
headmaster of the Laboratory of Building
Engineering at Technical University of Koszalin.
He earned his B.Sc., M.Sc., and Ph.D. from the
Technical University of Koszalin in 1994, 1994,
and 2000, respectively. He is a member of
Concrete Society of Southern Africa and
International Society for Concrete Pavements.
He is a former headmaster of Division of Civil
Engineering and Building Materials at the
Technical University of Koszalin. His research
interest focuses on concrete technology and
especially on steel fiber reinforced concrete.
SUGGESTED CITATION
Katzer, J. 2006. “Steel Fibers and Steel Fiber
Reinforced Concrete in Civil Engineering”.
Pacific Journal of Science and Technology.
7(1):53-58.
Pacific Journal of Science and Technology
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