International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
A review on the influence of metallic and polymeric fibre
addition in the mechanical property of concrete
Vikram Jothijayakumar#1,Geethu Varghese*2 & Sukanya K#3
#1
Associate Professor, Civil Engineering, METS School of Engg, MALA, KERALA, INDIA.
*2 & #3
Assistant Professor, Civil Engineering, METS School of Engg, MALA, KERALA, INDIA.
ABSTRACT
High strength concrete is used nowadays in most of
the application for its strength and durability. The
limitation in the application is due to its brittleness
which causes a sudden failure. Even if the HSC is
incorporated with fillers like silica fume, fly ash,
slags etc., because of high cement content and low
water-cement ratio, it is subjected to early age
cracking. To reduce this problem, the application of
steel fibre and polymeric fibre forming hybrid
concrete will help in reducing the crack width and
improve the load carrying capacity with large
amount of deflection before failure. The research led
to the study of various engineering properties of
different grades of concrete such as compressive
strength, splitting strength, flexural strength, relative
residual strength, Impact resistance, toughness,
durability properties such as resistance to freezing
and thawing, sulfuric acid and chloride attack,
cracked permeability and effect of elevated
temperature is studied with standard experimental
investigation. In addition, the study is made with
varying the dosage of fibre with varying volumetric
fraction between steel and polymeric fibre. To focus
on the economy in use of fibre in concrete, studies
were made by changing the volume of concrete by
reducing the thickness. Such concrete elements in
which the dimensions are altered the efficiency is
kept in consideration along with economy to avoid
loss in financial and structural aspects.
I. INTRODUCTION
High-strength concrete are concrete in which the
characteristic compressive strength at 28 days curing
will be greater than 40 N/mm2. High-strength
concrete is made by lowering the water-cement
(W/C) ratio to 0.35 or lower. Often admixtures like
silica fume are added to prevent the formation of free
calcium hydroxide crystals in the matrix of cement,
which might reduce the strength at the bond between
cement and aggregate. Low W/C ratios and the use of
admixture make concrete mixes less reduces the
workability, which is a major problem in application
of high-strength concrete where dense rebar is used.
To compensate this issue of low workability,
superplasticizers are added to the mixtures. Due to
high cement content with reduction in water-cement
ratio will cause surface cracking and also the
concrete will behave brittle. High strength concrete
should meet the properties of high performance
concrete. This issue can be addressed by the
application of hybrid concrete by using steel and
polymeric fibre in concrete. Researches has been
made on the various mechanical property of hybrid
concrete and elaborated the efficiency and economy
of the use of fibre in concrete. The addition of
metallic fibres has been reported to provide adequate
tensile strength to concrete in addition to controlling
shrinkage cracks. Moreover, the addition of non-
metallic fibres such as polypropylene, glass,
polyethylene, etc. is reported to reduce drying
shrinkage crack widths of concrete at later ages. This
paper gives a clear overview of the application of
metallic and non-metallic fibre for increasing the
properties such as compressive strength, tensile,
flexural and reducing the effects of plastic shrinkage
happening in the concrete. Other methods of NDT
investigation such as SEM analysis which helps in
micro structural investigation and IR thermography is
reviewed. To optimize the different mechanical
properties, various fiber additives can be combined
with concrete to design for specific applications.
Hybrids include the combination of metallic with
non-metallic and micro synthetic fibers with macro
synthetic fibers.
ISSN: 2231-5381
Keywords: High Strength
Concrete, volumetric fraction
Concrete,
Hybrid
II. STRENGTH CHARACTERIZATION OF
CONCRETE BY FIBRE ADDITION
Fibers addition helps to improve the ductility, crack
arresting, impact strength and eliminate temperature
and shrinkage cracks. Concrete is widely used in
structural engineering for its availability and cost
efficient. But common concrete has some defects
such as shrinkage, cracking, low mechanical
properties, poor toughness, brittleness and less shock
resistance, that restrict its applications. These
deficiencies can be overcome by additional materials
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
can be added to improve the performance of concrete.
Hence the applications of fibers come into existence.
Optimum dosage of fibers to get maximum strength
for the M30 grade concrete is evaluated. The effect of
variation in percentage of fibers on properties of
concrete, workability, compressive strength and
flexural strength is evaluated. While the mixing the
concrete, 80% of water is added first and mixed for
about 5 min then the remaining water is added and
mixed thoroughly. For each mix proportion,3 cubes
of 150 x 150 x 150 mm and 100 x 100 x 500 beams
were casted to determine the compressive and
flexural properties. The workability of each mixes is
calculated by experimentation as per Indian Standard
IS.
Compressive strength is the key factor in the analysis.
From the test result we find that maximum
compressive strength can be achieved when amount
of fiber in concrete is 0.25% in recron and amount of
fiber is 1% steel and 0.25% of recron. Flexure
strength phenomenon is also same as the compressive
strength of concrete. Normal concrete fails in flexure
without taking deflection but Fiber Reinforced
concrete fails after taking sufficient amount of
deflection. It is maximum at recron 0.25% and
Hybrid 1+0.25% but area under the load vs deflection
curve increases as the fiber content increases (Deepa
A Sinha, 2012).
Radmix Rad47s is a structural synthetic fibre made
from macro structural synthetic polypropylene fibre
with minimum tensile strength of 550MPa. These
fibres have
very good ductile behavior
characteristics. Performance level is more in ground
slab, shotcrete, precast products and highly corrosive
environment. Specifications of these fibres are width
1.28mm, thickness 0.49mm and length 47mm. It has
a very high energy absorption rate when used with
concrete mix, enabling the matrix to provide greater
flexural toughness. Higher Re3 value can be achieved
by addition of this fibre. [Re3 is calculated as the
average load carrying capacity offered after cracking
(due to the presence of fibre reinforcement) divided
by the flexural tensile strength of the uncracked
concrete matrix ] the ratio is typically expressed as a
percentage. In this study the dosage of fibre was in an
increment of 3,4,5,6,7& 8 kg/m3. The flexural tensile
strength (FTS), beam toughness index and Re3
results of fibres used in 32MPa mix. The unconfined
compressive strength decreases with increase in fibre
dosage whereas the flexural strength and the Re3
value is directly proportional. The conclusion is that
the usage of these synthetic fibres will enhance the
flexural toughness and Re3 value (Ray
Desmond,2008). The usage of polypropylene fibres is
used in a pavement of size 1.5inch with a w/c ratio
from 0.38 – 0.41. The recommended dosage of fibre
ISSN: 2231-5381
is 0.1% by volume of concrete. The addition of fibre
does not enhance the compressive and flexural
strength but the toughness after the development of
the first crack is increased. The workability decreases
with the increade in fibre level and also the W/c ratio
should be within 0.5. the impact resistance increases
with the increment of fibre dosage. Use of fibre
provides the reduction in permeability and plastic
shrinkage. Wear resistance is not studied in this
investigation. No change in the construction
procedure is required if the fibre volume is within
0.1% (James E. Shoenberger & Jeo G.Tom, 1992).
III. EFFECT OF FIBRE ADDITION IN
REDUCTION OF PLASTIC SHRINKAGE
Concrete shrinks due to dry environment which
increase the tensile stress and concrete will crack.
Reinforced concrete with short randomly distributed
fibres will reduce the plastic shrinkage. The
efficiency of fibers in reducing the cracks in
cementitious composites due to restrained plastic
shrinkage was investigated. The effects of steel, glass
and polypropylene fibers at volume fraction of
0.1%.The measurement of the maximum and average
crack width and the area of crack were measured
using the image analysis. From the test results, steel
fibers were more effective in reducing restrained
plastic shrinkage cracking compared to glass fibers
and polypropylene fibers (Tara Rahmani, Behnam
Kiani, Mehdi Bakhshi, Mohammad Shekarchizadeh,
2012). The controlling plastic shrinkage cracks in
high strength silica fume concrete by means of
adding fibre reinforcement up to 0.5% by volume of
concrete.The influence on plastic shrinkage cracking
were evaluated for individual steel fibres as well as
hybrid combinations of steel and non-metallic
(polyester, polypropylene and glass) fibres. From the
results, the hybrid fibres were most effective in
reducing shrinkage cracks, among which the steel
and polyester combination was found to reduce
plastic shrinkage cracks by more than 99% compared
to the plain concrete (A.Sivakumara and Manu
Santhanam,2011).
Rectangular slab is casted and the test procedure is
done under specific condition for calculating the
plastic shrinkage in a different set up. The mixing of
fibre with concrete itself should be done in a orderly
manner such that the time required for mixing
concrete with fibre should be 3min. VeBe
consistometer test is done for computing the
workability. With the help planimeter and hand held
microscope the reduction in crack width due to
plastic shrinkage id detected. Naturally concrete
shrinks in drying environment. If this shrinkage is
restrained, the concrete may crack due to tensile
stresses develop. The Influence of plastic shrinkage
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
cracks is harmful especially on slabs. One of the
methods to reduce the adverse effects of shrinkage
cracking of concrete is by reinforcing concrete with
short randomly distributed fibers. The study
investigated the effect of fiber volume and aspect
ratio of hooked steel fibers on plastic shrinkage
cracking behavior together with some other
properties of concrete. In this investigation two
different compressive strength namely 56 and 73
N/mm2 were studied. Concrete samples were made
by adding steel fibers of 3 different volumes and
aspect ratios. From this study, it is observed that steel
fibers can significantly reduce plastic shrinkage
cracking behavior of concretes. On the other hand,
steel fibres can adversely affect some other properties
of concrete during fresh and hardened states (Ozgur
Eren & Khaled Marar, 2010).
When fibre fractions are increased, it results in a
denser and more uniform distribution of fibres
throughout the concrete, which reduces shrinkage
cracks and improves post-crack strength of concrete.
The combination of low and high modulus fibres to
arrest the micro and macro cracks respectively. Long
and short fibres combination is also beneficial.
Different lengths of fibres can control different scales
of cracking. A number of studies indicate the overall
benefits of using combinations of fibres (Pierre et al.,
1999; Soroushianp et al., 1992; Bayasi and Zeng,
1993; Banthia and Nandakumar, 2003). The fibres
were added at low dosages, primarily from the point
of view of providing good workability, and the
overall volume fraction varied between 0.3 and 0.5%.
A factorial experimental design was carried out and
the flexural properties of various concretes were
evaluated.
IV. INVESTIGATION ON THE RESIDUAL
STRESS
DEVELOPED
IN
HYBRID
CONCRETE
The linear elastic and nonlinear fracture mechanics
principles can be used for residual strength evaluation
of concrete structural components. By employing
tension softening models, the effect of cohesive
forces due to aggregate bridging has been represented
mathematically.
Linear,
bilinear,
trilinear,
exponential and power curve are available tension
softening models and each model have been
described with appropriate expressions. Rama
Chandra Murthy, Nagesh R Iyer G S Palani, Smitha
Gopinath And B K Raghu Prasad (2012).
Hybrid fibers such as steel fiber with high elastic
modulus and synthetic macro-fiber (HPP) with low
elastic modulus as two elements used as reinforcing
materials in concrete. The flexural toughness,
flexural impact and fracture performance of the
composites were investigated systematically. Based
ISSN: 2231-5381
on ASTM and JSCE method, statistic analyses were
made to evaluate the flexural impact strength and on
observation, an improved flexural toughness
evaluating method suitable for concrete with
synthetic
macro-fiber
was
proposed.
The
experimental results showed that when the total fiber
volume fractions (Vfa) were kept as a constant (V
fa=1.5), compared with single type of steel or HPP
fibers, hybrid fibers can significantly improve the
fracture properties of concrete. Relative residual
strength , impact ductile index λ and fracture energy
GF of concrete combined with hybrid fibers were
respectively 66-80N/m, 5-12N/m and 121-137 N/m,
which indicated that the synergistic effects between
steel fiber and synthetic macro-fiber were good
(Zongcai Deng and Jianhui Li, 2006)
V. ADVANCEMENT IN EXPERIMENTAL
INVESTIGATION ON HYBRID CONCRETE
Non-Destructive testing method using Infrared
thermograph will help in detected the internal
defects. It’s a useful tool to investigate the structural
condition
and
damage
assessment.
Rapid
investigation can be made with non-contact and nondestructive method.
In adequacy in curing,
deformation of reinforcement bars due to tension and
bending can be studied. The passive method of
infrared thermograph technique for defect detection
is less time consuming and more accurate.
(D.S.Prakesh Rao 2008).
The test results elaborates that due to high
temperature the polypropylene melts and provide
voids which will in turn reduces the load carrying
capacity where as steel fibre has no significant
changes. The micro structural study is made using
SEM analysis (scanning electron microscope), which
helps in recording the effect inside the concrete due
to temperature effect. The variation in the
temperature is from 300˚C , 600˚C and 900˚C. To
prevent spalling, the dosage of polypropylene fibre
should be within 0.2% and 0.1% (Serdar Aydin, Halti
Yazici, Bulent Baradan, 2007).
VI. CONCLUSION
The effective usage of fibres in concrete will enhance
the strength and durability property is been evidently
investigated in many researches. The effect of
addition of steel fibre and polymeric fibre will
increase the strength and the minimum dosage of
fibre used is optimized. The addition of steel fibre
can be made within 0.5% by volume and
polypropylene can be within 0.2% The increase in
percentage of fibre will reduce the workability and as
a solution hence plasticizer can be added at suitable
percentage. Thereby hybrid concrete can be adopted
for dense reinforcemen. Addition of polypropylene
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International Journal of Engineering Trends and Technology (IJETT) – Volume 28 Number 1 - October 2015
fibre helps in reducing the spalling of concrete.The
effect of plastic shrinkage can also be controlled by
addition of synthetic and metallic fibre with a
minimum fraction of 1%. Along with the strength
aspect, the economy can be adopted by reduction in
the volume of concrete by varying the thickness of
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ISSN: 2231-5381
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