CONCRETE FIBRE

1. SUBMITTED BY:
MOHD AAQUIB(029)
ABHISHEK MITTAL(032)
MOHIT MAHAJAN(033)

2. Contents
Introduction
History
Introduction to FRC
Types of Fiber
Why Fiber
Workability
Application of FRC
Benefits of FRC
Toughening Mechanism
Factor affecting the properties of FRC
Comparison of Mix Proportion of FRC and Plain Concrete
Type of fibers
Steel Fiber Reinforced Concrete (SFRC)
Structural behavior & Durability of SFRC
Problems with SFRC
Application Of FRC
Conclusion

3.  Concrete is one of the most versatile building material.
 Concrete is strong under compression yet weak under tension, brittle and
limited ductility material.
 Therefore, a form of reinforcement is needed, steel bars reinforce concrete
against tension only locally.
 Cracks in reinforced concrete members extend freely until encountering a
rebar.
 The need for Multidirectional and closely spaced reinforcement for concrete
arises.
 FRC is a concrete mix that contains short discrete fibers that are uniformly
distributed and randomly oriented.
INTRODUCTION

4. Workability
 We know that it is usually wrong to add water to concrete for workability.
 The main problem with workability of steel fiber reinforced concrete is in getting proper distribution of
the fibers so that they don't ball up.
 This difficulty is usually overcome by slow, continuous and uniform feeding of the fibers into the wet
or dry mix by means of vibratory feeders.
 Sometimes the fibers are passed through screens as they are introduced. Proper feeding can virtually
eliminate the problem of balling.
 Addition of water to improve workability can reduce the flexural strength significantly, a critical matter
when one considers that one of the main reasons for using steel fibers is to improve the flexural
strength.
 In such cases use of suitable admixture probably would improve the workability to certain extent and
may not to the extent that you require

5. History
 1900s, asbestos fibers were used in concrete. In the 1950s, the concept
of composite materials came into being and fiber-reinforced concrete was one
of the topics of interest. Once the health risks associated with asbestos were
discovered, there was a need to find a replacement for the substance in concrete
and other building materials. By the 1960s, steel, glass (GFRC), and synthetic
fibers such as polypropylene fibers were used in concrete. Research into new
fiber-reinforced concretes continues today.

6. Introduction to Fiber Reinforced Concrete
 Concrete containing a hydraulic cement, water , aggregate, and
discontinuous discrete fibers is called fiber reinforced concrete.
 Fibers can be in form of steel fiber, glass fiber, natural fiber , synthetic
fiber.

7. Types of fibers
 Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers – each
of which lend varying properties to the concrete. In addition, the character of
fiber-reinforced concrete changes with varying concretes, fiber materials,
geometries, distribution, orientation, and densities.
 the composite (concrete and fibers) termed Vf. Vf typically ranges from 0.1 to
3%. Aspect ratio (l/d) is calculated by dividing fiber length (l) by its diameter
(d). Fibers with a non-circular cross section use an equivalent diameter for the
calculation of aspect ratio.

8. Why fiber ?
 Fibers are usually used in concrete to control cracking due
to plastic shrinkage and to drying shrinkage. They also reduce
the permeability of concrete and thus reduce bleeding of water.
 Cracks in reinforced concrete members extended freely until
encountering a rebar.
 Fiber reinforced concrete is used when there is requirement for
elimination small cracks.

9. Applications 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

10. Benefits of FRC
 Main role of fibers is to bridge the cracks that develop in concrete
and increase the ductility of concrete elements.
 Improvement on Post-Cracking behavior of concrete
 Imparts more resistance to Impact load
 controls plastic shrinkage cracking and drying shrinkage cracking
 Lowers the permeability of concrete matrix and thus reduce the
bleeding of water

11. 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.

12. Contd.

13. Contd.
Source: P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure, Properties, and
Materials, Third Edition, Fourth Reprint 2011

14. Factors affecting the Properties of FRC
 Volume of fibers
 Aspect ratio of fiber
 Orientation of fiber
 Relative fiber matrix stiffness

15. 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 (HPFRC)

16. Contd.
Source: P.K. Mehta and P.J.M. Monteiro, Concrete: Microstructure, Properties, and
Materials, Third Edition, Fourth Reprint 2011

17. 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.

18. 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.

19. 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

20. Comparison of Mix Proportion
between Plain Concrete and Fiber
Reinforced Concrete
Material Plain concrete Fiber reinforced concrete
Cement 446 519
Water (W/C=0.45) 201 234
Fine aggregate 854 761
Coarse aggregate 682 608
Fibers (2% by volume) -- 157
The 14-days flexural strength, 8 Mpa, of the fiber reinforced was about 20% higher than that of plain
concrete.
Source: Adapted from Hanna, A.N., PCA Report RD 049.01P, Portland cement Association, Skokie, IL, 1977

21. Types of fiber used in FRC
 Steel Fiber Reinforced Concrete
 Polypropylene Fiber Reinforced (PFR) concrete
 Glass-Fiber Reinforced Concrete
 Asbestos fibers
 Carbon fibers and Other Natural fibers

22. Contd.
Type of fiber Tensile
strength
(Mpa)
Young’s
modulus
(x103Mpa)
Ultimate
elongation
(%)
Steel 275-2757 200 0.5-35
Polypropylene 551-690 3.45 ~25
Glass 1034-3792 ~69 1.5-3.5
Nylon 758-827 4.14 16-20
Source: ACI Committee 544, Report 544.IR-82, Concr. Int., Vol. 4, No. 5, p. 11, 1982

23. Steel Fiber Reinforced Concrete
 Diameter Varying from 0.3-0.5 mm (IS:280-1976)
 Length varying from 35-60 mm
 Various shapes of steel fibers

24. Advantage of Steel fiber
 High structural strength
 Reduced crack widths and control the crack widths tightly, thus improving
durability
 less steel reinforcement required
 Improve ductility
 Reduced crack widths and control the crack widths tightly, thus improving
durability
 Improve impact– and abrasion–resistance

25. Structural Behavior of Steel Fiber Reinforced
Concrete
 Effect on modulus of rupture
 Effect of compressive strength
 Effect on Compressive strength & tensile Strength at fire condition i.e. at
elevated temperature

26. Effect on Modulus of Rupture
Ref: Abid A. Shah, Y. Ribakov, Recent trends in steel fibered high-strength concrete, Elsevier,
Materials and Design 32 (2011), pp 4122–4151

27. Effect on Compressive Strength
Ref: Abid A. Shah, Y. Ribakov, Recent trends in steel fibered high-strength concrete, Elsevier, Materials
and Design 32 (2011), pp 4122–4151

28. Structural behavior at Elevated
Temperature
Ref: 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

29. Contd.
Ref: 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

30. Durability
 Resistance against Sea water (In 3% NaCl by weight of water)
 Maximum loss in compressive strength obtained was about 3.84%
for non-fibered concrete and 2.53% for fibered concrete
 Resistance against acids (containing 1% of sulfuric acid by
weight of water)
 Maximum loss in compressive strength obtained was found to be
about 4.51% for non-fibered concrete and 4.42% for fiber concrete

31. Problems with Steel Fibers
 Reduces the workability;
 loss of workability is proportional to volume concentration of fibers in concrete
 Higher Aspect Ratio also reduced workability

32. Application of FRC in India & Abroad More than 400 tones of Steel Fibers have been used recently 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 is 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.

33. 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.

34. 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

35. 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