Introduction Benefits of FRC Toughening Mechanism Factor affecting the properties of FRC Comparison of Mix Proportion of FRC and Plain Concrete Type of fibres Steel Fiber Reinforced Concrete (SFRC) Structural behaviour & Durability of SFRC Problems with SFRC Application Of FRC Conclusion

1. Fiber Reinforced Concrete
(FRC)
AHSAN RABBANI

2. Contents
 Introduction
 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. 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.

4. 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

5. 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.

6. Contd.
Reference: Cement & Concrete Institute
http://www.cnci.org.za

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

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

9. 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)

10. Aspect Ratio of fiber
 It is defined as ratio of length of fiber to it’s diameter (L/d).
 Increase in the aspect ratio up-to 75,there is increase in
relative strength and toughness.
 Beyond 75 of aspect ratio there is decrease in aspect ratio
and toughness.

11. 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.

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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.

22. 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.