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SOME LITERATURE STUDIES ON ENGINEERING PROPERTIES
OF FIBRE-REINFORCED CONCRETE 1Ankit sharma,
1Nikesh Kalani,
1Monil Mehta,
2Gaurav gohil
1Student Civil Department, Sardar Patel College of Engineering, Anand, India
2Asst.Professor Civil Department, Sardar Patel College of Engineering, Anand, India
Corresponding Author Address:
Ankit sharma
Student Department of Civil Engineering,
Sardar Patel College of Engineering,
Anand, India.
ABSTRACT
In conventional concrete, micro-cracks develop before structure is loaded because of drying
shrinkage and other causes of volume change. When the structure is loaded, the micro
cracks open up and propagate because of development of such microcracks, results in
inelastic deformation in concrete. Fibre reinforced concrete (FRC) is cementing concrete
reinforced mixture with more or less randomly distributed small fibres. In the FRC, a
numbers of small fibres are dispersed and distributed randomly in the concrete at the time
of mixing, and thus improve concrete properties in all directions. The fibers help to transfer
load to the internal micro cracks. FRC is cement based composite material that has been
developed in recent years. It has been successfully used in construction with its excellent
flexural-tensile strength, resistance to spitting, impact resistance and excellent permeability
and frost resistance. It is an effective way to increase toughness, shock resistance and
resistance to plastic shrinkage cracking of the mortar. These fibers have many benefits.
Steel fibers can improve the structural strength to reduce in the heavy steel reinforcement
requirement. Freeze thaw resistance of the concrete is improved. Durability of the concrete
is improved to reduce in the crack widths. Polypropylene and Nylon fibers are used to
improve the impact resistance. Many developments have been made in the fiber reinforced
concrete.
KEYWORDS: Fiber Reinforced Concrete; Types of fibre; Mechanical and Structural
Properties.
INTRODUCTION
Concrete is weak in tension and has a brittle character. The concept of using fibers to
improve the characteristics of construction materials is very old. Early applications include
addition of straw to mud bricks, horse hair to reinforce plaster and asbestos to reinforce
pottery. Use of continuous reinforcement in concrete (reinforced concrete) increases
strength and ductility, but requires careful placement and labour skill. Alternatively,
introduction of fibers in discrete form in plain or reinforced concrete may provide a better
solution. The modern development of FRC started in the early sixties [1]
. Addition of fibers
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to concrete makes it a homogeneous and isotropic material. When concrete cracks, the
randomly oriented fibers start functioning, arrest crack formation and propagation, and thus
improve strength and ductility. The failure modes of FRC are either bond failure between
fiber and matrix or material failure. In this paper, the state-of-the-art of fiber reinforced
concrete is discussed and results of intensive tests made by the author on the properties of
fiber reinforced concrete using local materials are reported. The advantage of reinforcing
and prestressing technology utilizing steel reinforcement as high tensile steel wires have
helped in overcoming the incapacity of concrete in tension but the durability and resistance
to cracking is not improved. These properties can be improved by the use of fibres in the
concrete. It has been revealed that concrete reinforced with a permissible amount of fibre
acquires better performance in compression, flexure, toughness and energy absorption, in
which the degree of improvement relies on the types of fibres used. Experiments have been
carried out by several investigators using fibres of glass, carbon, asbestos, polypropylene
etc[2]
.Moreover fibres also helps in restricting the growth of micro-cracks at the mortar-
aggregate interface thus transforming an inherently brittle matrix i.e. cement concrete with
its low tensile and impact resistances, into a strong composite with superior crack
resistance, improved ductility and distinctive post cracking behavior prior to failure[3]
. It
must be well noted however that the benefits of adding fibres to concrete in construction,
which is principally to improve on the residual load-bearing capacity, is influenced by the
content, orientation and type of fibres in use [4].
The world has a witnessed rapid increase in
the use of fibre reinforced polymer FRP materials as a substitute for conventional steel bars
in some concrete structures, due to the numerous benefits: high strength, improved
toughness, resistance to post-crack propagation and light weight amongst others [5]
. There
have been extra efforts by researchers with respect to the various fibre concrete types.
Different experimental and theoretical studies have reported on varied mechanical
properties of steel, synthetic, natural and glass fibre reinforced concrete, in view of
structural applications [6]
. Therefore, the use of FRC, derived by the combination of steel or
synthetic fibres and plain-concrete, is gradually gaining ground in civil engineering and
structural applications due to its beneficial mechanical properties [7]
. There is considerable
improvement in the post-cracking behavior of concretes containing fibers. Although in the
FRC the ultimate tensile strengths do not increase appreciably, the tensile strains at rupture
do. Compared to plain concrete, FRC is much tougher and more resistant to impact. Plain
concrete fails suddenly once the deflection corresponding to the ultimate flexural strength is
exceeded; on the other hand, FRC continue to sustain considerable loads even at deflections
considerably in excess of the fracture deflection of the plain concrete. Examination of
fractured specimens of FRC shows that failure takes place primarily due to fiber pull-out or
de-bonding. Thus unlike plain concrete, a fiber-reinforced concrete specimen does not
break immediately after initiation of the first crack. This has the effect of increasing the
work of fracture, which is referred to as toughness and is represented by the area under the
load deflection curve [9]
. In FRC crack density is increased, but the crack size is decreased.
The failure mechanism is by pullout. You never exceed the tensile strength of the fiber.
Bond is much weaker. Steel fiber in terms of durability is the best. The addition of any type
of fibers to plain concrete reduces the workability [10]
. Concrete mixtures containing fibers
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possess very low consistencies; however, the place ability and compatibility of concrete is
much better than reflected by the low consistency.[11]
Fibre used in FRC
STEEL FIBER-The presence of fibers may alter the failure mode of concrete, but the
fibers effect will be minor on the improvement of compressive strength values (0 to 15
percent). The strain of SFRC corresponding to peak compressive strength increases as the
volume fraction of fibers increases. As aspect ratio increases, the compressive strength of
SFRC also increases marginally.
GLASS FIBER – Glass fibers mixed thoroughly mixed in the composition and filled in the
Steel mould of size 150 x 150 x 150 mm is well tighten and oiled thoroughly. They were
allowed for curing in a curing tank for 28 days and they were tested in 200tonnes electro
hydraulic closed loop machine.
POLYMER FIBER - Compressive strength is essentially matrix dependent.In-plane
(“edgewise”) compressive strength will be somewhat lower than cross-plane strength due to
the layers of glass fibers affecting the continuity of the matrix. Crossplane compressive
strength (“flatwise”) is not influenced by the presence of glass fibers and will be about the
same as the compressive strength measured on bulk matrix materials in cube or cylinder
tests
NATURAL FIBERS - The cubes tests prepared with different fibers, different fibers
volumetric ratios and different reductions in coarse aggregate, showed large variations in
the test results as compared to the control specimens with no fibers. The variation in the
results could be attributed to the relatively small size of the cube which may result in
erroneous data compared with 15x30 cm standard cylinders.
SYNTHETIC FIBERS - The compressive strength of concrete is one of the most
important and useful properties of concrete. In most structural applications concrete is used
primarily to resist compressive stress. The compression test was conducted on cube
specimens cured for 7, 14 & 28 days. The test cubes were removed from the moist storage
24 hours before testing. The top and bottom bearing plates of the compression testing
machine were wiped and cleaned before the placement of the specimen.
GLASS FIBER - Flexural stress-strain curves are used to determine values of modulus of
elasticity for design purposes. Values of flexural modulus of elasticity are normally in the 1.5
to 2.9 X 106 Psi range, and will vary in accordance with water-cement ratio, sand content,
cure, density, and degree of micro cracking. There is a lack of a continuous network of micro
cracks at low stress level versus well develop network of micro cracks at or near flexural
strength, thus giving lower E-value than normally associated with precast concrete panels.
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NATURAL FIBER - The elastic modulus of composites was determined using tensile
tests. Tensile tests were performed according to ASTM D 638 specification. Tensile tests
were carried out using an MTS testing machine with load cell capacity of 10kN at a cross-
head speed of 5 mm/min. Tensile elastic moduli were determined from the slopes of the
stress strain curves.
STEEL FIBERS - For flexural strength test beam specimens of dimension 100x100x500
mm were cast. The specimens were demoulded after 24 hours of casting and were
transferred to curing tank wherein they were allowed to cure for 28 days. These flexural
strength specimens were tested fewer than two point and four point loading as per I.S. 516-
1959
From Various Literature Studies the following are the mechanical properties showing
below :
Toughness:
For FRC, toughness is about 10 to 40 times that of plain concrete.
Fatigue Strength: The addition of fibers increases fatigue strength of about 90 percent and
70 percent of the static strength at 2 x 106 cycles for non-reverse and full reversal of loading,
respectively.
Flexure: The flexural strength was reported [8]
to be increased by 2.5 times using 4 percent
fibers.
Modulus of Elasticity: Modulus of elasticity of FRC increases slightly with an increase in
the fibers content. It was found that for each 1 percent increase in fiber content by volume
there is an increase of 3 percent in the modulus of elasticity.
Impact Resistance: The impact strength for fibrous concrete is generally 5 to 10 times that
of plain concrete depending on the volume of fiber use [8]
.
The following Literature studies carried by authors shows the engineering properties of
FRC:
Rajarajeshwari B Vibhuti studied the effect of addition of mono fibers and hybrid fibers on
the mechanical properties of concrete for pavements. Steel fibers of 1% and polypropylene
fibers 0.036% were added individually to the concrete mixture as mono fibers and then they
were added together to form a hybrid fiber reinforced concrete. Mechanical properties such
as compressive, split tensile and flexural strength were determined. The results show that
hybrid fibers improve the compressive strength marginally as compared to mono fibers.
Whereas, hybridization improves split tensile strength and flexural noticeably. She suggested
that the improved mechanical properties of HFRC would result in reduction of warping
stresses, short and long term cracking and reduction of slab thickness.
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Kukreja et al conducted some experiments and reported that, based on the results of three
methods such as split tensile test, direct tensile test and flexural test, split tensile strength
test was recommended for fibrous concrete. Also increase in tensile strength and post
cracking strength, toughness were reported.
Goash et al studied tensile strength of SFRC and reported as inclusion of suitable short
steel fibres increases the tensile strength of concrete even in low volume fractions.
Optimum aspect ratio was found as 80 and the maximum increase in tensile strength was
obtained as 33.14% at a fibre content of 0.7% by volume. Also it was reported that cylinder
split tensile strength gave more uniform and consistent results than the modulus of rupture
test and direct tension test.
Kumar et al made a study on statistical prediction of compressive strength of steel fibre
reinforced concrete and they reported that the compressive strength of SFRC increased
steeply with the increase of fibre content upto 1% (by volume) and beyond which the rate of
increase in strength reduced. It was also reported that the compressive strength of SFRC
increases with the increase in the aspect ratio upto 60 and beyond this the rate of increase in
strength reduces. It was further concluded that Fibre Reinforcing Index (FRI) significantly
influences the compressive strength and the strength increased upto FRI = 90 for stright
fibres and FRI = 60 for crimpled fibres. Beyond these values, the rate of increase in strength
started to decrease. They also proposed some statistical emprical relationships between
compressive strength and FRI.
Nataraja et al conducted a study on steel fibre reinforced concrete under compression.
Here the behavior of steel fibre reinforced concrete under compression for cylinder
compressive strength ranged from 30 to 50 N/mm2. Round crimpled fibres with three
volume fracions of 0.5 percent, 0.75 percent and 1.0 percent and for two aspect ratios of 55
and 82 are considered. The effect of fibre addition to concrete on compressive strength was
studied. It was concluded that the addition of fibres increased the compressive strength and
toughness. Some empirical equations were also proposed for compressive strength of
concrete in terms of fibre reinforcing index.
G. Jyothi Kumari, et al studied behavior of concrete beams reinforced with glass fiber
reinforced polymer flats and observed that beams with silica coated GFRP flats shear
reinforcement have shown failure at higher loads. Further they observed that GFRP flats as
shear reinforcement exhibit fairly good ductility. The strength of the composites, flats or
bars depends upon the fiber orientation and fiber to matrix ratio while higher the fiber
content higher the higher the tensile strength.
Avinash Gornale, et al studied the strength aspect of glass fiber reinforced concrete. The
study had revealed that the increase in compressive strength, flexural strength, split tensile
strength for M20, M30 and M40 grade of concrete at 3, 7 and 28 days were observed to be
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20% to 30%, 25% to 30% and 25% to 30% respectively after the addition of glass fibers as
compared to the plain concrete.
Yaghoub Mohammadi and Kaushik (2003) about the effect of mixed aspect ratio of fibres
on mechanical strength properties of concrete. 25 mm – 50 mm long crimped type flat steel
fibres were mixed in different proportions with concrete and tested for split tensile,
compressive and static flexural strength. Compressive toughness and flexural toughness
were obtained from the test results. It is found that 65% of long fibres and 35% of short
fibres gave the optimum composite properties when compared with other mixes. An
important note also was given in that literature that use of mixed aspect ratio of fibres does
not have a significant effect on the static modulus of elasticity.
Piti Sukontasukkul conducted an experimental investigation on toughness of steel and
polypropylene fibre reinforced concrete beams under bending using two different methods
such as ASTM C1018 and JSCE SF-4. The behaviour of steel fibre reinforced concrete
indicated single peak response whereas polypropylene fibre reinforced concrete should
double peak response. The deformations under two methods were compared.
Faisal F Wafa and Samir A. Ashour . They tested 504 test specimens for different
mechanical properties such as compressive strength, split tensile strength, flexural
toughness and modulus of rupture. The mix was designed to achieve compressive strength
of 94 N/mm2. Three volume fractions of steel fibres such as 0.5%, 1.0% and 1.5% were
selected. It was concluded that no real workability problem was encountered upto the
addition of 1.5% volume fraction of fibres in concrete. Steel fibres enhanced the ductility
and post cracking load carrying capacity of high strength concrete. Some emprical relations
were proposed in terms of volume fraction of fibres and compressive strength of
conventional concrete
CONCLUSION
Conclusions drawn from reviewing the published literature are:
• Workability of the fresh mix is adversely affected by the addition of fibers and further
decreases by increasing the fiber volume fraction. .
• Flexural and tensile strength, ductility, drying shrinkage and toughness of the material is
usually benefited by the addition of fibers.
• Use of fibers in the cement-based material improves its durability. It has been well
established by observing improvement in various tests such as freeze-thaw resistance,
permeability, carbonation depth and fire resistance.
REFRENCES
1. Ramualdi, J.P. and Batson, G.B., The Mechanics of Crack Arrest in Concrete, Journal
ofthe Engineering Mechanics Division, ASCE, 89:147-168 (June, 1983)
International Journal of Scientific Research in Engineering (IJSRE) Vol. 1 (4), April, 2017
IJSRE Vol. 1 (4), April, 2017 www.ijsre.in Page 89
2. R.Gowri, M.AngelineMary (2013). “Effect of glass wool fibres on mechanical
properties of concrete.” International Journal of Engineering Trends and Technology,
Volume-4 Issue-7 July 2013.
3. Shah, Surendraand Rangan (1994), “Effect of Fiber addition on concrete strength”,
Indian Concrete Journal. [5] Nataraja M.C., Dhang, N. and Gupta, A. P (1999),
“Stress strain curve for steel fiber reinforced concrete in compression”, “Cement and
Concrete Composites”,
4. Zerbin, R., Tobes, J.M., Bossio, M.E. and Giaccio, G., 2012. On the orientation of fibres
in structural members fabricated with selfcompacting fibre reinforced concrete, Cement
and Concrete Composites
5. Yan, J.M. 2012. Effect of steel and synthetic fibres on flexural behaviour of high-
strength concrete beams reinforced with FRP bars. Composites: Part B. [e-journal,
Accessed through: Science Direct.] Vol. 43, pp. 1077- 1086. [6] ]
6. Kazemi, S. And Lubell, A.S., 2012, “Influence of Specimen Size and Fibre Content on
Mechanical Properties of UltraHigh-Performance Fiber-Reinforced Concrete”, ACI
materials Journal, Vol. 109, No. 6, pp. 675-684
7. Burati,N., Mazzotti,C. and Savoia, M., 2011. Post-crack behaviour of steel and Macro-
Synthetic fibre-reinforced concretes. Construction and Building Materials, Vol. 25, pp.
2713-2722
8. ACE Committee 544, State-of-the-Art Report on Fiber Reinforced Concrete, ACI
Concrete International, 4(5): 9-30 (May, 1982) [9] Silva, D. A. D., Betioli, A. M.,
Gleize, P. J. P., Roman, H. R., Gomez, L. A., & Ribeiro, J. L. D. (2005). Degradation of
recycled PET fibers in Portland cement-based materials. Cement and Concrete
Research, 35(9), 1741-1746.
9. Nia, A. Alavi, M. Hedayatian, M. Nili, and V. AfroughSabet. "An experimental and
numerical study on how steel and polypropylene fibers affect the impact resistance in
fiber-reinforced concrete." International Journal of Impact Engineering 46 (2012): 62-73
10. Mohammadi, Y., Singh, S. P., & Kaushik, S. K. (2008). Properties of steel fibrous
concrete containing mixed fibres in fresh and hardened state.Construction and Building
Materials, 22(5), 956-965.
11. Wang, H. T., & Wang, L. C. (2013). Experimental study on static and dynamic
mechanical properties of steel fiber reinforced lightweight aggregate concrete.
Construction and Building Materials, 38, 1146-1151
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