2. Contents
History.
Introduction.
Why Fibers are used?
Toughening Mechanism.
Type of fibers.
Mechanical properties of FRC.
Structural behavior of FRC.
Factors affecting properties of FRC.
Advantages and Disadvantages of FRC.
Applications of FRC.
Case Study.
Conclusion.
References.
3. The use of fibers goes back at least 3500 years, when
straw was used to reinforce sun-baked bricks in
Mesopotamia.
Horsehair was used in mortar and straw in mud bricks.
Abestos fibers were used in concrete in the early 1900.
In the 1950s, the concept of composite materials came
into picture.
Steel , Glass and synthetic fibers have been used to
improve the properties of concrete for the past 30 or 40
years.
Research into new fiber-reinforced concretes continues
even today.
History
4. Introduction
Concrete containing cement, water , aggregate, and
discontinuous, uniformly dispersed or discrete fibers is
called fiber reinforced concrete.
It is a composite obtained by adding a single type or a
blend of fibers to the conventional concrete mix.
Fibers can be in form of steel fibers, glass fibers, natural
fibers , synthetic fibers, etc.
5. Why Fibres are used?
Main role of fibers is to bridge the cracks that develop in
concrete and increase the ductility of concrete elements.
There is considerable improvement in the post-cracking
behavior of concrete containing fibers due to both plastic
shrinkage and drying shrinkage.
They also reduce the permeability of concrete and thus
reduce bleeding of water.
Some types of fibers produce greater abrasion and shatter
resistance in concrete.
Imparts more resistance to Impact load.
6. Toughening mechanism
Toughness is ability of a material to absorb energy and
plastically deform without fracturing.
It can also be defined as resistance to fracture of a
material when stressed.
13. Steel fibers
Aspect ratios of 30 to 250.
Diameters vary from 0.25 mm to 0.75 mm.
High structural strength.
Reduced crack widths and control the crack widths tightly, thus
improving durability.
Improve impact and abrasion resistance.
Used in precast and structural applications, highway and airport
pavements, refractory and canal linings, industrial flooring,
bridge decks, etc.
14. Glass Fibers
High tensile strength, 1020 to 4080 N/mm2
Generally, fibers of length 25mm are used.
Improvement in impact strength.
Increased flexural strength, ductility and resistance to thermal
shock.
Used in formwork, swimming pools, ducts and roofs, sewer
lining etc.
15. Synthetic fibers
Man- made fibers from petrochemical and textile industries.
Cheap, abundantly available.
High chemical resistance.
High melting point.
Low modulus of elasticity.
It’s types are acrylic, aramid, carbon, nylon, polyester,
polyethylene, polypropylene, etc.
Applications in cladding panels and shotcrete.
16. Natural fibers
Obtained at low cost and low level of energy using local
manpower and technology.
Jute, coir and bamboo are examples.
They may undergo organic decay.
Low modulus of elasticity, high impact strength.
18. Mechanical Properties of FRC
Compressive Strength
The presence of fibers may alter the failure mode of cylinders,
but the fiber effect will be minor on the improvement of
compressive strength values (0 to 15 percent).
Modulus of Elasticity
Modulus of elasticity of FRC increases slightly with an increase in
the fibers content. It was found that for each 1 percent increase
in fiber content by volume, there is an increase of 3 percent in
the modulus of elasticity.
Flexure
The flexural strength was reported to be increased by 2.5 times
using 4 percent fibers.
19. Splitting Tensile Strength
The presence of 3 percent fiber by volume was reported to
increase the splitting tensile strength of mortar about 2.5 times
that of the unreinforced one.
Toughness
For FRC, toughness is about 10 to 40 times that of plain concrete.
Fatigue Strength
The addition of fibers increases fatigue strength of about 90
percent.
Impact Resistance
The impact strength for fibrous concrete is generally 5 to 10
times that of plain concrete depending on the volume of fiber.
20. Structural behaviour of FRC
Flexure
The use of fibers in reinforced concrete flexure members increases
ductility, tensile strength, moment capacity, and stiffness. The fibers
improve crack control and preserve post cracking structural
integrity of members.
Torsion
The use of fibers eliminate the sudden failure characteristic of plain
concrete beams. It increases stiffness, torsional strength, ductility,
rotational capacity, and the number of cracks with less crack
width.
High Strength Concrete
Fibers increases the ductility of high strength concrete. Fiber
addition will help in controlling cracks and deflections.
21. Shear
Addition of fibers increases shear capacity of reinforced concrete
beams up to 100 percent. Addition of randomly distributed fibers
increases shear-friction strength and ultimate strength.
Column
The increase of fiber content slightly increases the ductility of
axially loaded specimen. The use of fibers helps in reducing the
explosive type failure for columns.
Cracking and Deflection
Tests have shown that fiber reinforcement effectively controls
cracking and deflection, in addition to strength improvement. In
conventionally reinforced concrete beams, fiber addition
increases stiffness, and reduces deflection.
22. Factors affecting the Properties of FRC
Volume of fibers
Aspect ratio of fiber
Orientation of fiber
Relative fiber matrix stiffness
23. Volume of fiber
Low volume fraction(less than 1%)
Used in slab and pavement that have large exposed
surface leading to high shrinkage cracking.
Moderate volume fraction(between 1 and 2 percent)
Used in Construction method such as Shortcrete & in
Structures which requires improved capacity against
delamination, spalling & fatigue.
High volume fraction(greater than 2%)
Used in making high performance fiber reinforced
composites.
24. Contd.
Source: P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure,
Properties, and Materials, Third Edition, Fourth Reprint 2011
25. Aspect Ratio of fiber
It is defined as ratio of length of fiber to it’s diameter
(L/d).
Increase in the aspect ratio upto 75, there is increase in
relative strength and toughness.
Beyond 75 of aspect ratio, there is decrease in aspect
ratio and toughness.
Type of
concrete
Aspect ratio Relative
strength
Relative
toughness
Plain concrete
with
randomly
Dispersed fibers
0 1.0 1.0
25 1.50 2.0
50 1.60 8.0
75 1.70 10.50
100 1.50 8.50
26. Orientation of fibers
Aligned in the direction of load
Aligned in the direction perpendicular to load
Randomly distribution of fibers
It is observed that fibers aligned parallel to applied
load offered more tensile strength and toughness
than randomly distributed or perpendicular fibers.
28. Relative fiber matrix
Modulus of elasticity of matrix must be less than of fibers
for efficient stress transfer.
Low modulus of fibers imparts more energy absorption
while high modulus fibers imparts strength and stiffness.
Low modulus fibers e.g. Nylons and Polypropylene fibers.
High modulus fibers e.g. Steel, Glass, and Carbon fibers.
29. Advantages of FRC
High modulus of elasticity for effective long-term
reinforcement, even in the hardened concrete.
Does not rust nor corrode and requires no minimum cover.
Ideal aspect ratio (i.e. relationship between Fiber diameter
and length) which makes them excellent for early-age
performance.
Easily placed, Cast, Sprayed and less labour intensive than
placing rebar.
Greater retained toughness in conventional concrete mixes.
Higher flexural strength, depending on addition rate.
Can be made into thin sheets or irregular shapes.
FRC possesses enough plasticity to go under large
deformation once the peak load has been reached.
30. Disadvantages of FRC
Greater reduction of workability.
High cost of materials.
Generally fibers do not increase the flexural strength of
concrete, and so cannot replace moment resisting or
structural steel reinforcement.
31. Applications of FRC
Runway, Aircraft Parking, and Pavements.
For the same wheel load FRC slabs could be about one half the
thickness of plain concrete slab. FRC pavements offers good
resistance even in severe and mild environments.
It can be used in runways, taxiways, aprons, seawalls, dock areas,
parking and loading ramps.
Tunnel Lining and Slope Stabilization
Steel fiber reinforced concrete are being used to line
underground openings and rock slope stabilization. It eliminates
the need for mesh reinforcement and scaffolding.
Dams and Hydraulic Structure
FRC is being used for the construction and repair of dams and
other hydraulic structures to provide resistance to cavitation and
severe erosion caused by the impact of large debris.
32. Thin Shell, Walls, Pipes, and Manholes
Fibrous concrete permits the use of thinner flat and curved
structural elements. Steel fibrous shortcrete is used in the
construction of hemispherical domes.
Agriculture
It is used in animal storage structures, walls, silos, paving, etc.
Precast Concrete and Products
It is used in architectural panels, tilt-up construction, walls,
fencing, septic tanks, grease trap structures, vaults and
sculptures.
33. Commercial
It is used for exterior and interior floors, slabs and parking areas,
roadways, etc.
Warehouse / Industrial
It is used in light to heavy duty loaded floors.
Residential
It includes application in driveways, sidewalks, pool construction,
basements, colored concrete, foundations, drainage, etc.
34. Fiber Reinforced Concrete Normal Reinforced concrete
• High Durability • Lower Durability
• Protect steel from Corrosion • Steel potential to corrosion
• Lighter materials • Heavier material
• More expensive • Economical
• With the same volume, the
strength is greater
• With the same volume, the
strength is less
• Less workability • High workability as compared
to FRC.
35. Application of FRC in India & Abroad
More than 400 tones of Steel Fibers have been used in the
construction of a road overlay for a project at Mathura (UP).
A 3.9 km long district heating tunnel, caring heating pipelines
from a power plant on the island Amager into the center of
Copenhagen, is lined with SFC segments without any
conventional steel bar reinforcement.
Steel fibers are used without rebars to carry flexural loads at a
parking garage at Heathrow Airport. It is a structure with 10
cm thick slab.
Precast fiber reinforced concrete manhole covers and frames
are being widely used in India.
36. Case Study
Providing and laying 40 mm steel fibre reinforced cement
concrete in pavement (in panels having area not more than
1.5 sqm) consisting of steel fibre @ 40kg per cubic meter of
concrete and cement concrete mix of 1:1.95:1.95 over
existing surface.
Since in the executed item, the thickness was to be restricted,
the stone aggregates used were of 10 mm size and below
however, in case of the concrete of more than 75 mm
thickness, stone aggregates of 20 mm grading can be used.
The fibre reinforced concrete has been provided in small
panels considering the workability.
38. Experiment
Aim: To understand the effect of incorporation of polypropylene
and steel fibers together in the hardened state of concrete.
Material Specification:
Cement
Type: Ordinary Portland Cement (OPC)
Grade: 53
Fine Aggregates:
Source: Sabarmati River (Gandhinagar)
Grading: Zone-II
39. Coarse Aggregates:
Size: 10mm (maximum)
Specific Gravity: 2.79
Water Absorption: 1.19 %
Admixture:
Name: Sikament NN (SP)
Type: Super Plasticizer
40. Steel Fibres:
Type = SHAKTIMAN MSC 6050
Shape = Round Crimped Fiber
Diameter = 0.60 mm
Length = 50 mm
Aspect ratio = 83.33 (Tolerance D/L= + 10 %)
Tensile strength = 1100 N/mm2
Polypropylene Fibres:
Company = NINA Chemicals Pvt. Ltd. (Ahmedabad )
Type = FIBREMESH 150 E3
Shape = Monofilament Polypropylene Fibres
Diameter = 0.08 mm
Length = 12 mm
Aspect ratio = 150
41. Following are the tables showing mix design for
the 50 kg of Cement for different w/c ratios
W/c ratio 0.65 %
Cement 50 Kg
Water 32.5 Liters
C.A. (10 mm) 169.32 Kg
F.A. 123.95 Kg
PPF (0.5%) 0.63 Kg
PPF (1.0%) 1.28 Kg
PPF (1.5%) 1.91 Kg
SF (0.6%) 6.69 Kg
SF (1.2%) 13.4 Kg
42. W/c ratio 0.5 %
Cement 50 Kg
Water 25 Liters
C.A. (10 mm) 117.72 Kg
F.A. 97.32 Kg
PPF (0.5%) 0.52 Kg
PPF (1.0%) 1.05 Kg
PPF (1.5%) 1.57 Kg
SF (0.6%) 5.49 Kg
SF (1.2%) 10.98 Kg
43. W/c ratio 0.42 %
Cement 50 Kg
Water 23.8 Liters
C.A. (10 mm) 107.62 Kg
F.A. 94.86 Kg
PPF (0.5%) 0.46 Kg
PPF (1.0%) 0.94 Kg
PPF (1.5%) 1.4 Kg
SF (0.6%) 4.9 Kg
SF (1.2%) 9.81 Kg
44. Mixing of polypropylene and
steel fibres reinforced concrete:
The sequence for casting is as follows for FRC:
50 % quantity of coarse aggregates
PPF or SF or Both the fibres in 20% quantity
Remaining 50% coarse aggregates
Another PPF or SF or Both fibres in 20% quantity
50% quantity of sand
Another PPF or SF or Both fibres in 20% quantity
Remaining 50% quantity of sand
Another PPF or SF or Both fibres in 20% quantity
Cement
Remaining 20% of PPF or SF or Both fibres
Water
45. Compressive strength
•Increase by 5-70%
Only Steel fibers
•Reduction in strength due
to balling effect
Only PP fibers
•Reduction in strength by 1-
26% due to balling effect
Both steel and
PP fibers
46. Increase in compressive strength of concrete:
Specimens without any
fibers after compression
test
Specimens with fibers
after compression test
47. Tensile strength
•Increase by 50-140%
Only Steel fibers
•Increase by 5-50%
Only PP fibers
•Increase by 60-200%
Both steel and
PP fibers
48. Increase in tensile strength of concrete:
Specimens without any
fibers after split tensile
test.
Specimens with fibers
after slip tensile test.
49. Impact strength
• Increase by 25-150%
Only Steel fibers
• Increase by 50-100%
Only PP fibers
• Increase by 125-200%
Both steel and PP
fibers
50. Increase in impact strength of concrete:
Specimens without any
fibers after compression
test
Specimens with fibers
after compression test
51. Shear strength
• Increase by 150-200%
Only Steel fibers
• Increase by 22-125%
Only PP fibers
• Increase by 25-220%
Both steel and PP
fibers
52. Increase in shear strength of concrete:
Specimens without any
fibers after shear test.
Specimens with fibers
after shear test.
53. Type of
fiber Percentage
Weight Per
Cum of
concrete (Kg)
Cost per
kg(Rs)
Cost per
Cum of
concrete(Rs)
PPF (0.5%) 0.005 4.2 150 630
PPF (1.0%) 0.01 8.5 150 1275
PPF (1.5%) 0.015 12.73 150 1909
SF (0.6%) 0.006 44.62 50 2231
SF (1.2%) 0.012 89.37 50 4468.5
Cost analysis
57. Conclusion
The total energy absorbed in fiber as measured by the area
under the load-deflection curve is at least 10 to 40 times
higher for fiber-reinforced concrete than that of plain
concrete.
Addition of fiber to conventionally reinforced beams
increased the fatigue life and decreased the crack width
under fatigue loading.
At elevated temperature SFRC have more strength both in
compression and tension.
Cost savings of 10% - 30% over conventional concrete flooring
systems.
58. References
K.Srinivasa Rao, S.Rakesh kumar, A.Laxmi Narayana,
Comparison of Performance of Standard Concrete and Fibre
Reinforced Standard Concrete Exposed To Elevated
Temperatures, American Journal of Engineering Research
(AJER), e-ISSN: 2320-0847 p-ISSN : 2320-0936, Volume-02, Issue-
03, 2013, pp-20-26
Abid A. Shah, Y. Ribakov, Recent trends in steel fibered high-
strength concrete, Elsevier, Materials and Design 32 (2011), pp
4122–4151
ACI Committee 544. 1990. State-of-the-Art Report on Fiber
Reinforced Concrete.ACI Manual of Concrete Practice, Part
5, American Concrete Institute, Detroit,MI, 22 pp
59. Contd.
P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure,
Properties, and Materials, Third Edition, Fourth Reprint 2011, pp
502-522
ACI Committee 544, Report 544.IR-82, Concr. Int., Vol. 4, No.
5, p. 11, 1982
Hanna, A.N., PCA Report RD 049.01P, Portland Cement
Association, Skokie, IL, 1977
Ezio Cadoni ,Alberto Meda ,Giovanni A. Plizzari, Tensile
behaviour of FRC under high strain-rate,RILEM, Materials and
Structures (2009) 42:1283–1294
Marco di Prisco, Giovanni Plizzari, Lucie Vandewalle, Fiber
Reinforced Concrete: New Design Prespectives, RILEM,
Materials and Structures (2009) 42:1261-1281
