2013©vv, CTU in Prague
Fibre Reinforced Concrete
This presentation was created thanks to the support of FRVŠ
project 915/2013 B1d „Tools for teaching design of concrete
and masonry structures in English“
Ing. Vladimíra Vytlačilová, PhD.
2013©vv, CTU in Prague
Terminology
• NSC = Normal Strength Concrete
• FRC = Fibre Reinforced Concrete
• FC = Fibre Reinforced Concrete
• SFRC = Steel Fibre Reinforced Concrete
• SFRC = Synthetic Fibre Reinforced Concrete
• GFRC or GRC = Glass Fibre Reinforced Concrete
• PPFRC = Polypropylene Fibre Reinforced Concrete
2013©vv, CTU in Prague
Concrete X Fibre Reinforced Concrete (FRC)
• Concrete is relatively brittle, and its tensile strength is
typically only about one tenths of its compressive strength.
• Regular concrete is therefore normally reinforced with steel
reinforcing bars.
• FRC is the concrete with small, randomly distributed fibers.
• Compared to plain concrete is FRC much tougher and more
resistant to impact.
• Their main purpose is to increase the energy absorption
capacity and toughness of the material, but also increase
tensile and flexural strength of concrete.
2013©vv, CTU in Prague
FRC – Historical Perpective
• BC: horse Hair, straw, feathers
• 1900: asbestos fibers, Hatscheck process
• 1950: Composite materials
• 1960: FRC
• 1970: New initiative for asbestos cement replacement
• 1970: SFRC, GFRC, PPFRC, Shotcrete
• 1990 micromechanics, hybrid systems, wood based fiber
[Source: www.bydleni.lidovky.cz ]
2013©vv, CTU in Prague
Advantage
• Better durability
• Limitations contraction cracks
• Improvement of ductility
• Improvement tensile strength
• Better fire resistance
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Disadvantage
• Exacting of production technology
• Higher price (per cubic meter concrete)
• Higher specific gravity
• Corrosion of steel fibres
2013©vv, CTU in Prague
Fibre Reinforced Concrete (FRC)
• FRC is a structural material having nearly the same
cementitious – matrix composites as a plain concrete (PC)
except fibres of different types and forms.
• Concrete containing a hydraulic cement, water, fine or fine
and coarse aggregate, and discontinuous discrete fibers is
called fiber-reinforced concrete (FRC).
• It may also contain pozzolans and other admixtures
commonly used in conventional concrete.
• The addition of any type of fibers to plain concrete reduces
the workability.
STEEL FIBRE REINFORCED CONCRETE
Plain concrete Steel fibre reinforced
concrete
Aggregate
Steel
fibres
Cement
8/35
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Fibres of various materials, shapes and sizes
• Fibres: 1. Steel fibres
2. Micro synthetic fibres
3. Macro synthetic fibres
• Produced from steel, plastic, glass, and natural materials
• For most structural and nonstructural purposes, steel fiber is
the most commonly used of all the fibers.
• Steel – and Synthetic Fibre Reinforced Concrete
2013©vv, CTU in Prague
Fibres of various materials, shapes and sizes
• Steel Fibers
• Polyvinyl Alcohol (PVA) Fibers
• Polypropylene or Nylon Fibers
• Alkali Resistant Glass Fibers
• Cellulose Fibers
• Carbon Fibers
2013©vv, CTU in Prague
Fibres of various materials, shapes and sizes
• Aspect Ratio = Length / Diameter
• Aspect ratio= l/d 50 - 100
• Typical aspect ratios range from about 30 to 150.
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Steel Fibres
• Steel Fibres increase:
• Ductility
• Energy absorption
• Shear resistance
• Stiffness
Observations - Steel fibres
Dℓ
F
Tension
Compression
Dℓ/ℓ
s
Dℓ
F
Dℓ
ℓ
F F
Increasing fibre content
Increasing fibre content
14/3
5
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Steel Fibres
Steel fibre reinforced concrete model for tensile behaviour
based on local strain
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Steel Fibres
Steel fibre reinforced concrete model for tensile behaviour based
on fracture energy
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Mix Design -Aggregate
• Optimization grading curve (length and quantity of fibres)
a) Short fibres
b) Low dose of fiber
c) Optimal design
d) Segregation fibres
e) Segregation
aggregate
f) Homogenous mixture
2013©vv, CTU in Prague
Steel Fibres
Tritreg Dramix Strax Fibrex
Material Steel Steel Steel Steel
Type
Specific
gravity 7850 kg/m3 7850 kg/m3
7850
kg/m3
7300
kg/m3
Tensile
strength 1000 N/mm2 800 N/mm2
800
N/mm2
400
N/mm2
Length 50 mm 60 mm 60 mm 35 mm
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Effect of fibres type
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0
Průhyb [mm]
Síl
a [
kN
]
Fmax = 35,2 kN
200200 200
S
F/2 F/2
600
100 100
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0
Průhyb [mm]
Síl
a [
kN
]Fmax = 36,6 kN
200200 200
S
F/2 F/2
600
100 100
Deflection [mm]
Deflection [mm]
Lo
ad
[kN
]
Load [k
N]
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Synthetic Fibres
Forta Fero BeneSteel Strax PET
Material Poly-propylene
mixture of
Polypropylene and
Polyethylene
Synthetic Poly-ethylene-
terephthalate
Type Monofilament and
polyfilament fibres
Mono-filament
fibres
Mono-filament
fibres
Mono-filament
fibres
Specific
gravity 910 kg/m3 920 kg/m3 920 kg/m3 1050 kg/m3
Tensile
strength 700 N/mm2 660 N/mm2 620 N/mm2 not known
Length 54 mm 55 mm 40 mm 80 mm
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Glass Fibres
• Alkali Resistant (AR) glass fibers
It can replicate virtually any surface detail and reproduce the
appearance of materials such as stone, slate, terracotta and
marble.
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Classification according to volume fraction
• Low volume fraction < 1% (reduce shrinkage cracking)
• Moderate volume fraction between 1-2% (increase the
modulus of rupture, fracture toughness, impact resistance)
• High volume fraction > 2% (strain-hardening of the
concrete)
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Areas of Application of FRC materials
• thin sheets
• shingles
• roof tiles
• pipes
• prefabricated shapes
• panels
• shotcrete
• curtain walls
• slabs on grade
• precast elements
• composite decks
• vaults, safes.
• impact resisting structures
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Areas of Application
Precast
• Wall panels
• Storage Tanks
[Source: Bosfa.com]
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Areas of Application
Ground Supported Slabs
• � Heavy parking areas
• � Drive through areas
• � Roadways
• Pavements & Roadways
[Source: Bosfa.com]
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Areas of Application
Ground Supported Slabs
• Warehouse Slabs
• Bottling Hall
• Storage Bins
[Source: Bosfa.com]
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Areas of Application of FRC materials
Slope Stabilisation
• Shotcrete
[Source: Bosfa.com]
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Areas of Application of FRC materials
Other Application
• Skate Park Reinforced with Fibres
[Source: Bosfa.com]
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Areas of Application of FRC materials
Mining
• Shocrete Application
• Tunel lined with Shocrete
• Civil Tunnelling
41
Testing of FRC
• Standard tests
• cube 150/150/150 mm
• cylinder Φ150/300 mm
• prism 150/150/700 mm
42
Calculation and design procedures
• Cross-section design in bending – FC without
reinforcement bars
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Example of Typical Slide
• Thus unlike plain concrete, a fiber-reinforced concrete specimen does not break immediately after initiation of the first crack.
• This has the effect of increasing the work of fracture, which is referred to as toughness and is represented by the area under the load-deflection curve.
• In FRC crack density is increased, but the crack size is decreased.
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FRC
• The most important contribution of fibres in concrete is the
flexural toughness of the material.
• When flexural strength is the main consideration, fiber
reinforcement of concrete is not a substitute for
conventional reinforcement.
• The greatest advantage of fiber reinforcement of concrete is
the improvement in flexural toughness (total energy
absorbed in breaking a specimen in flexure).
2013©vv, CTU in Prague
Example of Typical Slide
• The beam test results in a resistant force – deflection
diagram FR - d characterize the behaviour of FRC
specimen .
• The diagram FR - d shows two different manners of beam
specimens behaviour
• Typical load-deflection curves for plain
• concrete and fiber-reinforced concrete