IJSRD - International Journal for Scientific Research & Development| Vol.

4, Issue 02, 2016 | ISSN (online): 2321-0613

To Study the Behavior of High Strength Concrete Beam Reinforced with
Hybrid Fiber Subjected to Cyclic Loading
K.P.Suganraj1 T.Sakthi Subramanian2
M.E. Student 2Assistant Professor
Department of Structural Engineering
Valliammai Engineering College, Kancheepuram, India
Abstract— The use of two or more types of fibers in a
suitable combination may potentially improve the overall
properties of concrete and also result in performance
concrete. The combining of fibres, often called
hybridization, is investigated in this paper for a M50 grade
concrete. Control and two-fiber hybrid composites were cast
using different fibre proportions of steel and polypropylene.
Reinforced HSC beams containing fibres of two different
types in hybrid forms were constructed and tested under
cyclic loading to investigate the possibility of obtaining
ductile and energy dissipating Reinforced HSC beams to be
used in seismically active area. compressive test, Split
tensile strength and Flexural strength using cyclic loading
were performed and results were extensively analyzed to
associated with above fibre combinations. Based on
experimental studies, the paper identifies fiber combinations
that demonstrate maximum Compressive strength, split
tensile strength and flexural strength of concrete.
Key words: Compressive strength, Hybrid fibre, Split tensile
strength, Flexural strength, Cyclic loading, Workability
Concrete is characterized by quasi-brittle failure the nearly
complete loss of loading capacity, oncefailure is initiated.
This characteristic, which limits the application of the
material, can be overcome bythe inclusion of a small
amount of short randomly distributed fibers (steel, glass,
synthetic andnatural) and can be practiced among others
that remedy weaknesses of concrete, such as lowgrowth
resistance, high shrinkage cracking, low durability, etc.
Fiber reinforced concrete (FRC) is a fibre einforcing
cementitious concrete composite, and by adding discrete
short fibers randomly in concrete it exhibits many
improved engineering
compressive strength,tensile strength, flexural strength etc.
The fibers are able to prevent surface cracking through
bridging action leading to an increased impact resistance of
the concrete. The combination of two or moredifferent
types of fibres (different fibre types and/orgeometries) is
becoming more common, with theaim of optimizing
overall system behaviour. Theintent is that the
performance of these hybridsystems would exceed that
induced by each fibretype alone. That is, there would be
a synergy.Banthia and Gupta [2004] classified these
themechanisms involved:
1) Hybrids based on the fibre constitutive response,in
which one fibre is stronger and stiffer and provides
strength, while the other is more ductileand provides
toughness at high strains [Banthia and Gupta 2004].
2) Hybrids based on fibre dimensions, where one fibre
is very small and provides microcrack controlat early

stages of loading; the other fibre is larger, to provide a
bridging mechanism across macrocracks.
3) 3.Hybrids based on fibre function, where one type of
fibre provides strength or toughness in the hardened
composite, while the second type provides fresh mix
properties suitable for processing.
The usefulness of fiber reinforced concrete in
various Civil Engineering applications is thus
indisputable. Hence this study explores the feasibility of
hybrid fiber reinforcement; aim is to do parametric study
on compressive strength, flexural strength using cyclic
loading, tensile strength study etc. withg iven grade of
concrete, proportions and percentage of steel.
1) 1.To find the optimum percentage of hybrid fibre can be
added to the high strength concrete to increase the
ductility of the element.
2) 2. To find the behaviour of the element made of
high strength concrete reinforced with hybrid fibre
subjected to the cyclic loading.
3) 3. To investigate the mechanical properties like split
tensile strength and compressive strength of hybrid
fibre reinforced concrete beam
A. Material Used
In this experimental study, Cement, sand, coarse aggregate,
water, steel fibers and polypropylene fibres were used.
Cement: Ordinary Portland cement of 53 grade
wasused in this experimentation conforming to I.S-1226
:1987 Coarse aggregates: Locally available, maximum size
20 mm, specific gravity 2.65.
Sand: Locally available sand zone I with
specific gravity 2.61, water absorption 1% and fineness
modulus 2.72, conforming to I.S. – 383-1970.
Potable water was used for the
Chemical Admixture Type: Super Plasticizer
Steel Fibers: - In this experimentation, Hook end Steel
fibers (L=60 mm, dia=0.5 mm) were used.
Polypropylene Fibers: Fibrillated 20 mm cut length
fibers were used.
Different proportions of steel and polypropylene
fibers are shown below table:
HFRC SO.75PP0.25
HFRC SO.25PP0.75







Table 1: Different Proportions of Fibres

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To Study the Behavior of High Strength Concrete Beam Reinforced with Hybrid Fiber Subjected to Cyclic Loading
(IJSRD/Vol. 4/Issue 02/2016/363)

B. Concrete Mix Proportion
Coarse aggregate

422 kg/m3
621 kg/m3
1284 kg/m3

Table 2: Mix Proportion
C. Specimen Details
Cube moulds of 150x150 x150 mm and cylindrical
moulds of 150 mm diameter and 300 mm long are used for
casting the specimen for compressive strength and split
tensile strength test respectively. For flexure test using
cyclic loading, specimen size of 200x150x1200 mm is cast.
Specimens were cured for 28 days. 3 specimens of
compressive strength test are cured for 7 days and 14 days
to obtain the compressive strength after 7 days and 14
days respectively.
D. Testing
Flexural test were carried out on 8 beams,out of that each
of 2 beams are tested for hybridization ratio HFRC
S0.75PP0.25, HFRC S0.5PP0.5, HFRC S0.25PP0.75. For
all hybridization ratio fiber volume 1% by volume of
concrete is kept constant.

(HFRC) with 50-50% (Steel-polypropylene) hybridization
ratio is maximum. Fiber addition with equal percentage
assures maximum availability of fiber in thefibrous matrix
of concrete as regard to volume. Maximum availability of
fibers are advantageous as under the axial load cracks occur
in microstructure of concrete, fiber reduces the crack
formation and development. Because of high strength and
stiffness, Metallic fibers (steel) are responsible to arrest
the macro cracks also modulus ofelasticity of steel fibers
is more hence provide ductility to the concrete. Concrete is
very alkaline and as such it will corrode steel fiber very
quickly so that non-metallic fibers(polypropylene) are used
for effective reinforcement. Use of non-metallic fiber is to
arrest only a micro cracks developed due to shrinkage.
Modulus of elasticity of PP fiber is less than steel fiber
hence PPFRC undergoes brittle failure after loading. Due to
hybridization of steel and polypropylene (50-50%) mix
provide better response to arrest micro and macro cracks
hence improve thecompressive strength of concrete as
compare to plain concrete and all other combination of
hybridization ratio.

Fig. 2: Compressive strength test
Fig: 1: Test setup
The beams were kept on UTM as shown in fig.1
the end of the beams where tied using steel frames to avoid
moving of beam during reverse cyclic loading and the
beams were tested under gradually applied loading in the
increasing manner in cyclic and reverse cyclic loadings
UTM machine for flexural strength. Ultimate load and
modes of failure of beams were noted. Compressive
strength and split tensile strength are carried out on cubes
and cylinders respectively, tested under compression testing

B. Split Tensile Test

In present study cube compression test, split tensile test,
flexural test on beams, and on plain and varying
hybridization ratio of steel and polypropylene fibers
reinforced concrete at 1%fiber volume fraction by
volume of concrete are carried out. The experimental
results and discussion for various tests are described below.
A. Compressive Strength
The results of compressive strength test at 28days are
given in table No.1. It is seen that at 1%volume
fraction of fibers by volume of concrete the
compressive strength of Hybrid fiber reinforced concrete

Fig. 3: Split Tensile Tes
The results of split tensile strength test at 28 days
are given in graph. The increase in split tensile strength due
to incorporation of steel fiber is greater than polypropylene
fiber. High modulus of elasticity of steel fiber makes the
concrete more ductile. Tensile strength of ductile material is
higher than brittle materials. Therefore gradual increase in
% of steel fibers for different hybridization ratio split tensile
strength of concrete also increases. Once thesplit occurs
and continues the steel fibers provide bridging effect

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To Study the Behavior of High Strength Concrete Beam Reinforced with Hybrid Fiber Subjected to Cyclic Loading
(IJSRD/Vol. 4/Issue 02/2016/363)

across the split portion. The split portion of the matrix
transfer the stresses from matrix to the fibers and thus steel
fibers are gradually supports the entire load. Stress transfer
also improves the tensile strain capacity of the fiber
reinforcedoncrete and increase the split tensile strength.
C. Cyclic Loading
Cyclic loading is the application of repeated or fluctuating
stresses, strains, or stress intensities to locations on
structural components. The degradation that may occur at
the location is referred to as fatigue degradation.by applying
the repeated loading on the beam as the cyclic and reverse
cyclic loads by increasing the loads per cycle. Thereby, the
loads applied on the cycles will be 20KN, 40KN, 60KN and
till failure occurs respective. It is also seen that the addition
of polypropylene fibers increase the flexural strength.
Flexural strength primary increase due tofiber
intersecting the cracks in the tension half portion of the
specimen. This fibers accommodate the crack
separation by process of stretching thefibers, thus
providing additional energy absorbing capacity. It also
provides stress relaxing mechanismat the tip of the cracks
during micro cracks formation.The modulus of rupture of
steel fibers is more as compare to polypropylene fibers.
Therefore steel fibers are effective to arrest the macro
cracks and undergoes ductile failure while Polypropylene
fibers are only effective to arrest the micro cracks and
undergoes brittle failure. Therefore steel and polypropylene
combination also shows better performance during flexural
strength by cyclic loadingtest.

Compressive strength of HFRC S0.75 PP0.25 after 28days
for (steel-polypropylene) hybridizationratio is maximum. It
is increased by 9.4% with respect to normal conventional
concrete (i.e. Hybridizationratio 0-0 %). At 28 days
Compressive strength of HFRC S0.5 PP0.5 (i.e.
Hybridization ratio 50-50 % ) isincreased by 2.37%
with respect to normal concrete & compressive strength
of HFRC S0.25 PP0.75 (i.e. Hybridization ratio 25-75% )
decreased by 1.2% with respect to normal concrete.The
maximum compressive strength reaches in the HFRC
S0.75P0.25, i.e., 75% steel fibres and 25%
polypropylene fibres because of the high elastic modulus
of steel fibre and the low elastic modulus of polypropylene
fibre work in perfect combination.
Split tensile strength of HFRC S0.75 PP0.25
for 28days
contribution of steel fiber in hybridization ratio. Split
tensile strength of HFRC S0.75 PP0.25 (i.e. Hybridization
ratio75-25%) is maximum. Split tensile strength of HFRC
S0.75 PP0.25 increases19.7% & Split tensile strength of
HFRC S0.5 PP0.5
(i.e. Hybridization ratio 50-50%)
8.16% with respect to normal concrete
Flexural strengthusing cyclic loading of HFRC
S0.75 PP0.25 increases 24.8% than conventional concrete
flexural strength of HFRC S0.5 PP0.5 is increases 15.4%
than conventional concrete beam.It can be observed that,
under cyclic loading,cracks occur in microstructure of
concrete and fibres limit the formation and growth of cracks.

Fig. 4: comparison of Deflection of Beams using Cyclic

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Fig. 5: Ultimate loads of beams (KN)

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To Study the Behavior of High Strength Concrete Beam Reinforced with Hybrid Fiber Subjected to Cyclic Loading
(IJSRD/Vol. 4/Issue 02/2016/363)

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