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
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.
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
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.