Fibre reinforced concrete

1. PRESENTED BY : RAVIKIRAN KATTOLI

2.  In all countries, the construction industry is rapidly
developing based on the invention of different materials
and products in engineering fields.
 Engineers have attempted various types of materials in
order to make the task more efficient reducing time,
cost, improving durability, quality and performance of
structures during their lifetime.
 Concrete is weak in tension and strong in compression.
 Even though reinforcement is provided in tension zone
microcracks are developed in the tension and
compression zone.

3.  The propogation of these cracks can be
arrested by using fibre reinforcement in
concrete.
 The fibres are very small which are
distributed over the whole area of concrete.
 Because of this we can not only arrest crack
formation but also we can increase flexural,
shear ,torsion, strength, freezing and thawing
resistance.

4.  It is a Small piece of reinforcing material
possessing certain characteristic properties.
 It Can be circular or flat.
 Parameter used to describe fiber – “Aspect
ratio”.
 Aspect ratio is ratio of its length to its
diameter.
 Typical aspect ratio for fibers ranges from 30
to 150

5.  Fiber reinforced concrete (FRC) is concrete
containing fibrous material which increases
its structural integrity.
 It contains short discrete fibers that are
uniformly distributed and randomly
oriented.
 Fibers include steel fibers, glass fibers,
synthetic fibers and natural fibers

6.  Fibers have been used for concrete reinforcement
since prehistoric times.
 In the early age, straw and mortar were used for
producing mud bricks, and horsehair was used for
their reinforcement.
 As the fiber technology developed, cement was
reinforced by asbestos fibers in the early twentieth
century.
 Later, the use of asbestos for concrete reinforcement
was discouraged due to the detection of health risks.
 New materials like steel, glass, and synthetic fibers
replaced asbestos for reinforcement.
 Active research is still in progress on this important
technology.

7. 2.1 STEEL FIBER REINFORCED CONCRETE
Steel fiber-reinforced concrete is basically cheaper and easier
to use.
Steel fiber-reinforced concrete uses thin steel wires
mixed in with the cement.

8.  This imparts the concrete with greater structural strength and
reduces cracking
 Steel fiber is often used in conjunction with rebar or one of
the other fiber types.

9.  Glass fiber-reinforced concrete uses fiberglass
 The glass fiber helps insulate the concrete in addition to
making it stronger.
 Glass fiber also helps prevent the concrete from
cracking over time due to mechanical or thermal stress.
 In addition, the glass fiber does not interfere with radio
signals like the steel fiber reinforcement does.

10.  Synthetic fiber-reinforced concrete uses plastic, nylon
and polyproplene fibers to improve the concrete's
strength.
 They help to improve the cement pumpability.
 The synthetic fibers do not expand in heat or contract
in the cold which helps prevent cracking.
 Finally synthetic fibers help keep the concrete from
spalling during impacts or fires.
Polyproplene
fiber

11.  Historically, fiber-reinforced concrete have used natural
fibers, such as hay or coir.
 While these fibers help the concrete's strength they can also
make it weaker if too much is used.
 In addition if the natural fibers are rotting when they are
mixed in then the rot can continue while in the concrete.
 This eventually leads to the concrete crumbling from the
inside, which is why natural fibers are no longer used in
construction.
COIR HAY

12. 3.1. Volume of fibres:
 low volume fraction (less then 1%):
 Used in slabs and pavement that have large exposed surface
leading to shrinkage cracking
 Moderate volume fraction(between 1 and 2%):
 Used in construction method such as shotcrete
 High volume fraction (greater then 2%):
 Used in making high performance FRC

13.  Aspect Ratio is the ratio of length of the Fibre
to the diameter of its cross - section.
 Aspect Ratio = Length(L) / Diameter(D)

14.  Aligned in the direction of load
 Aligned in the direction perpendicular to load
 Randomly distribution of fibers

15.  Fibre should be significantly stiffer than matrix.
 Low modulus of fibres imparts more energy
absorption while high modulus of fibres imparts
strength and stiffness.
 Low modulus fibres e.g. nylon, polypropylene
 High modulus of elasticity e.g. steel, glass and carbon
fibres.

16.  Usage of steel fibres , higher aspect ratio and
non-uniform distribution of fibres will reduce
workability
 Prolonged external vibration fails to compact
the concrete
 These properties can be improved by
increasing water/cement ratio or by using
water reducing admixtures

17.  Restricted to 10mm
 Friction between fibres and between fibres
and aggregates controls orientation and
distribution.
3.7. Mixing:
 Mixing of FRC needs careful precautions to
avoid segregation
 Increase in aspect ratio, volume percentage
and size of coarse aggregate will increase the
difficulties.

18.  Addition of 4% of fibres report 2.5 times
more increase in flexural strength.
 Presence of 3% of fibres develop 2.5 times
more splitting tensile strength.
 Compressive strength- Improves(0-15 %).
 Toughness is about 20-40 times that of plain
concrete.
 Impact strength is 5 to 10 times of plain
concrete and improves wear and tear.

19.  Main role of fibres is to bridge the cracks that
develop in concrete and increase the ductility
of concrete elements.
 Improvement on Post-Cracking behaviour of
concrete
 Imparts more resistance to Impact load
 Lowers the permeability of concrete matrix
and thus reduce the bleeding of water

20.  Increase in specific gravity of the concrete.
This means that the concrete will be heavier
than normal concrete in case of some fibres
 Higher cost because of its control issues
(production issues) as well as the cost of raw
material is high.
 Corrosion of steel fibres

22. Highway pavements

23. Hydraulic structures

24. Precast applications

25.  More than 400 tones of Shakti man Steel Fibers have been
used recently in the construction of a road overlay for a project
at Mathura (UP).

26.  The efficient utilisation of fibrous concrete involves
improved static and dynamic properties like tensile
strength, energy absorbing characteristics, Impact
strength and fatigue strength.
 The efficient utilisation of fibrous concrete involves
improved static and dynamic properties like tensile
strength, energy absorbing characteristics, Impact
strength and fatigue strength.
 At elevated temperature, SFRC have more strength
both in compression and tension.

27.  Properties of Concrete- Nevilla.
 Concrete Technology- MsShetty.
 ‘Fibre Reinforced Concrete’-N. Banthia
 ‘Synthetic Fibre Reinforcement for Concrete’- D.
Ludirdja, J.F. Young, 1993.
 ‘Synthetic Fibres- Anne Laning, 1992.
 ‘Glass Fibre reinforced Concrete (GFRC)’ - By
Wallace Neal, 1978.
 ‘Tensile behavior of Glass Fibre reinforced
Concrete’- J.A.O.Barros, J.A.Figueiras, C.V.D.Veen