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 its 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
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 abrasionresistance
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 41224151
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 41224151
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 41224151 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) 42:12831294
Marco di Prisco, Giovanni Plizzari, Lucie Vandewalle, Fiber
Reinforced Concrete: New Design Prespectives, RILEM, Materials and
Structures (2009) 42:1261-1281
