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Abstract—Polypropylene Fiber Reinforced Concrete is an
embryonic construction material which can be described as a
concrete having high mechanical strength, Stiffness and
durability. By utilization of Polypropylene fibers in concrete
not only optimum utilization of materials is achieved but also
the cost reduction is achieved. This paper presents a
comprehensive review on various aspects Polypropylene Fiber
Reinforced Concrete concerning the behaviour, applications
and performance of Polypropylene Fiber Reinforced
Concrete. Various issues related to the manufacture and
strength of Polypropylene Fiber Reinforced are also
discussed.
INTRODUCTION
Concrete has better resistance in compression while
steel has more resistance in tension. Conventional concrete
has limited ductility, low impact and abrasion resistance
and little resistance to cracking. A good concrete must
possess high strength and low permeability. Hence,
alternative Composite materials are gaining popularity
because of ductility and strain hardening. To improve the
post cracking behaviour, short discontinuous and discrete
fibers are added to the plain concrete. Addition of fibers
improves the post peak ductility performance, pre-crack
tensile strength, fracture strength, toughness, impact
resistance, flexural Strength resistance, fatigue performance
etc. The ductility of fiber reinforced concrete depends on
the ability of the fibers to bridge cracks at high levels of
strain. Addition of polypropylene fibers decreases the unit
weight of concrete and increases its strength.
II POLYPROPYLENE FIBERS
Polypropylene fibers are new generation chemical
fibers. They are manufactured in large scale and have
fourth largest volume in production after polyesters,
polyamides and acrylics. About 4 million tonnes of
polypropylene fibers are produced in the world in a year
Polypropylene fibers were first suggested for use in
1965 as an admixture in concrete for construction of blast
resistant buildings meant for the US Corps of Engineers.
Subsequently, the polypropylene fiber has been
improved further and is now used as short discontinuous
fibrillated material for production of fiber reinforced
concrete or as a continuous mat for production of thin sheet
components. Further, the application of these fibers in
construction increased largely because addition of fibers in
concrete improves the tensile strength, flexural strength,
toughness, impact strength and also failure mode of
concrete
These fibers are manufactured using conventional melt
spinning. Polypropylene fibers are thermo plastics
produced from Propylene gas. Propylene gas is obtained
from the petroleum by products or cracking of natural gas
feed stocks. Propylene polymerizes to form long polymer
chain under high temperature and pressure. However,
polypropylene fibers with controlled configurations of
molecules can be made only using special catalysts.
Polypropylene fibers were formerly known as Stealthe,.
These are micro reinforcement fibers and are 100% virgin
homopolymer polypropylene graded monofilament fibers.
They contain no reprocessed Olifin materials. The raw
material of polypropylene is derived from monomeric C3H6
which is purely a hydrocarbon.
For effective performance, the recommended dosage
rate of polypropylene fibers is 0.9 kg/m3
, approximately
0.1% by volume.
Monofilament polypropylene fibers can be used in
much lower content than steel fibers. The tensile strength
and other mechanical properties are enhanced by
subsequent multi stage drawing. These fibers have low
density of 0.9 g/cc. They are highly crystalline, with high
stiffness and excellent resistance to chemical and bacterial
attack. The crystallinity of these fibers is about 70% while
the molecular weight is 80,000 to 300,000 gm/mole.
Polypropylene fibers should not be used for structural
reinforcement. These fibers should not be used to produce
thinner sections and also to increase joint spacing than
those suggested for unreinforced masonry.
Polyrpopylene when copolymerized with ethylene is
generally tough and flexible, which allows polypropylene
to be used as engineering plastic. Polypropylene is
reasonably economical and when uncoloured appears
translucent. It is generally not readily available transparent
as acrylic, polystyrene or other plastics. It is often opaque
or made coloured using colouring pigments. It has good
resistance to fatigue. Perfectly isotactic Polypropylene has
a melting point of 171 °C while Commercial isotactic
Polypropylene has a melting point ranging from 160 to
166 °C. Polypropylene is used in hinges of flip flop bottles,
piping, loud speaker units etc. Thin sheets of polypropylene
are used as dielectric in capacitors
Advantages
Polypropylene fibers are Non-Magnetic, rust free, Alkali
resistant, safe and easy to use. Polypropylene twine is
cheap, abundantly available and is of consistent quality.
Polypropylene fibers are also compatible with all concrete
chemical admixtures and can be handled with ease. The
high molecular weight of polypropylene, gives it many
useful properties.
Polypropylene fibers are chemically inert and hence, any
chemical that will not attack the concrete constituents will
not have any effect on the fiber also. When more aggressive
chemicals come in contact, the concrete will always
deteriorate first before fibers.
The hydrophobic surface of fibers not being wet by cement
paste, helps to prevent balling effect by chopped fibers and
The water demand is nil for polypropylene fibers when
used in concrete and there is no need for minimum amount
of concrete cover. Presence of fibers reduces the settlement
and bleeding in concrete. The resistance to abrasion, freeze
and thaw, Impact is improved.
III NEED FOR POLYPROLYLENE FIBERS IN CONCRETE
Concrete develops micro cracks with curing and these
cracks propagate rapidly under applied stress resulting in
low tensile strength of concrete. Hence addition of fibers
improves the strength of concrete and these problems can
be overcome by use of Polypropylene fibers in concrete.
Application of polypropylene fibers provides strength to
the concrete while the matrix protects the fibers.
The primary role of fibres in a cementitious composite
is to control cracks, increase the tensile strength, toughness
and to improve the deformation characteristics of the
composite. The performance of FRC depends on the type
of the fibers used. Inclusion of polypropylene fibers
reduces the water permeability, increases the flexural
strength due to its high modulus of elasticity. In the post
cracking stage, as the fibers are pulled out, energy is
absorbed and cracking is reduced.
IV. LITERATURE REVIEW
The term fibre reinforced concrete (FRC) is defined by
ACI Committee 544 as a concrete made of hydraulic
cements containing fine and coarse aggregates and
discontinuous discrete fibres [1].
Many researchers have investigated the effect of various
types fibers on the mechanical properties of concrete.
However, the research on polypropylene fiber reinforced
concrete is limited and it is presented blew.
A. Workability
With addition of fibers, the entrapped air voids increase
and hence the increased air content reduces the workability
causing difficulty in compaction of mixes. The fibers may
also interfere and cause finishing problems.
Workability of concrete decreased with increase in
polypropylene fiber volume fraction
Thirumurgan and Siva Kumar [3], reported that the
workability of concrete decreased with the addition of
polypropylene fibers but it can be overcome by addition of
High Range Water Reducing Admixtures.
Gencel et al [4] used monofilament polypropylene
fibers in self compacting concrete with fly ash and studied
the workability and Mechanical properties. The materials
used in this study showed no workability or segregation
problems.
Preti A Patel et al [5] reported that the workability of
concrete reduced with higher polypropylene fiber content.
Vee Bee time indicated that at 0.5% of fiber content
workability is high while at 1% it is medium.
B. Compression Strength
Compressive strength of concrete is one of the most
important properties of concrete. It is a qualitative measure
of concrete. Failure of concrete under compression is a
mixture of crushing and shear failure. The compressive
strength varies as a function of both cement paste and
fibers. Higher binder ratio gives higher compressive
strength.
Priti A. patel et al [5] found that the compressive, split
tensile and flexural strength improved on addition of 1.5 %
of polypropylene fibre in the concrete.
Vinod Kumar and Dr. M. Muthukannan [6] carried out
experimental Investigations on Hybrid fibers using steel,
glass and polypropylene fibres in different combinations to
examine the mechanical properties of Hybrid Fiber
Reinforced Concrete as compared to the conventional
concrete.
Kumar et al carried out experimental investigations on
M15, M20 and M25 grade fly ash concrete reinforced with
0%, 0.5% and 1% polypropylene fibers. The compressive
strength also increased with increase in fiber content up to
1% for all the three grades of concrete.
Mehul and Kulkarni [2] used fibrillated polypropylene
fiber of length 12mm and diameter 34 micron and low
density of 0.9 kN/m3
, in percentages of 0.5%, 1% and 1.5%
in high strength concrete. Super plasticizer Conplast-Sp430
was used. They observed that the compressive strength of
concrete increased with addition of fibers.
APPLICATIONS
Polypropylene fibers are versatile and widely used in
many industrial applications such as ropes, furnishing
products, packaging materials etc. They are also used in
packaging, labeling, carpets, textile, apparel markets,
stationery, plastic parts, reusable containers, laboratory
equipment, automotive components, loud speakers, etc
Polypropylene Fiber reinforced Concrete is used in
roads and pavements, drive ways, Overlays and toppings,
ground supported slabs, Machine foundations, Off shore
structures, tanks and pools etc.
V CONCLUSIONS
1. Polypropylene fibers reduce the water
permeability, plastic, shrinkage and settlement and
carbonation depth.
2. Workability of concrete decreases with increase in
polypropylene fiber volume fraction. However,
higher workability can be achieved with the
addition of HRWR admixtures even with w/c ratio
of 0.3.
3. Polypropylene fibers enhance the strength of
concrete, without causing the well known
problems, normally associated with steel fibers.
4. The problem of low tensile strength of concrete
can be overcome by addition of polypropylene
fibers to concrete.
5. Notable increase in compressive strength is
reported with addition of polypropylene fibers.
6. The failure is gradual and ductile in polypropylene
fiber reinforced concrete.