1, Dr.Sunil Rangari.2 1 [email protected] 2 ...gmail.com 2Dr. Sunil Rangari, college of engineering, Kharghar, Maharashtra, India. [email protected] International Journal

ABSTRAC:

Concrete is the most commonly used construction material

worldwide. Concrete is a brittle, composite material that is

strong in compression and weak in tension. Cracking occurs

when the tensile stress produced from the externally applied

loads, temperature changes, or shrinkage in a member reaches

the tensile strength of the material. The fiber reinforced

concrete (FRC) contains randomly distributed short discrete

fibers which act as internal reinforcement so as to enhance the

properties of the concrete. In this paper compare and analyses

of steer & polypropylene fibers reinforced concrete with plain

concrete. Finally conclusion from result is presented.

Key words: Fiber, FRC, toughness, steel, compression,

tensile strength.

INTRODUCTION

Fiber reinforced concrete can be defined as composite

material consisting of cement mortar or concrete and

discontinuous, discrete, uniformly dispersed fibers. The

continuous meshes, woven fabrics and long wires or rods are

considered to be discrete fibers.

The inclusion of fibers in concrete and shotcrete generally

improves material properties including ductility, toughness,

flexural strength, impact resistance, fatigue resistance, and to

a small degree, compressive strength. The type and amount of

improvement is dependent upon the fiber type, size, strength

and configuration and of fiber

.

REINFORCEMENT MECHANISAM IN FRC

In the hardened state, when fibers are properly bonded,

they interact with the matrix at the level of micro-cracks and

effectively bridge these cracks thereby providing stress

transfer media that delays their coalescence and unstable

growth. If the fiber volume fraction is sufficiently high, this

may result in an increase in the tensile strength of the matrix.

Indeed, for some high volume fraction fiber composite, a

notable increase in the tensile/flexural strength over and

above the plain matrix has been reported. Once the tensile

capacity of the composite is reached, and coalescence and

conversion of micro-cracks to macro-cracks has occurred,

fibers, depending on their length and bonding characteristics

continue to restrain crack opening and crack growth by

effectively bridging across macro-cracks. This post peak

macro-crack bridging is the primary reinforcement

mechanisms in majority of commercial fiber reinforced

concrete composites.

Figure 1

THE CONCEPT OF THE TOUGHNES:

Toughness is defined as the area under a load-deflection (or

stress-strain) curve. As can be seen from Figure, adding fibres to

concrete greatly increases the toughness of the material.

That is, fiber-reinforced concrete is able to sustain load at

deflections or strains much greater than those at which cracking first

appears in the matrix.

Figure 2

METHODOLOGY:

1. Mix Design of concrete as per IRC 44: 2008.

2. Mix Design of SFRC as per IRC SP: 46-1997.

3. Check out compressive strength of mixes with

compression test carried out on cubes.

4. Check out Flexural Strength of beams with flexural

testing machine.

5. Check out Modulus of Elasticity of Cubes with

modulus of elasticity testing machine

SCOPE AND OBJECTIVE:

Conduct experimental and analytical investigation to

characterize principal mechanical properties of FRC and to

study the effect of volume fraction and length of fibers on the

mechanical properties.

For the measurement of workability of the FRC, following

tests are used.

1. Slump test- subsidence in mm

2. Inverted slump test-time in seconds

3. Compacting factor test-degree of compaction

Effect of addition of fiber in concrete Ajay Vitthal Shinde

1, Dr.Sunil Rangari.

2

1P.G.Student. Saraswati College of engineering, Kharghar, Maharashtra, India.

[email protected] 2Dr. Sunil Rangari, college of engineering, Kharghar, Maharashtra, India.

[email protected]

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4. VB test-time in seconds

For the mechanical properties, the following tests are

conducted to study the effect of amount of fibers and the

length of fibers on the compressive, tensile and flexure

strength and the associated straining capacity.

1) Compressive Strength of concrete Cubes (IS 516-1959).

2) Split Tensile Strength of concrete Cubes (IS 5816-1999)

3) Flexure Strength of concrete beams under two point

loading (IS 516-1959)

MATERIAL:

Cement:

Ordinary Portland cement of grade 53 by the manufacturer

ultratech was used.

Aggregate:

Course aggregate of maximum size 10 mm is used I.e. only

M1 is used as per IRC: SP: 46-1997. Fine aggregate

comprised of crushed sand only.

Admixture:

Super plasticizer was use to increase the workability of

fresh prepared concrete.

Water:

Water is an important ingredient of concrete and it initiates

chemical reaction with cement. Ordinary potable water is

used.

CLASSIFICATION OF FIBERS:

FIBER DIA

MM

DENSITY

KG/M3

YOUNGS

MODULUS

OF

ELASTICIT

Y

MPA

TENSILE

STRENGTH

MPA

Asbestos 0.02 – 20 2.55–3.37 164 – 196 3100 – 3500

Carbon 3 1.9 230 – 380 1800– 2800

Polypropyle

ne

20 – 200 0.9 5000 500

Nylon Over 4 1.14 4000 900

Kevlar 10-12 1.44 69-133 2900

Glass 9 – 15 2.6 80,000 2000-4000

Steel 5 – 500 7.8 200,000 1000-3000

STRENGTH:

The strength of the fiber reinforced concrete can be

measured in terms of its maximum resistance when subjected

to compressive, tensile, and flexural and shear loads. In field

conditions, usually some combination of these loads is

imposed; however for evaluation purposes, the behavior is

characterized under one type of loading without the

interaction of other loads. The strength under each individual

type of loading is a useful indicator of the FRC material's

performance characteristic for design consideration.

COMPRESSION:

The compressive properties of fiber-reinforced concrete

(FRC) are relatively less affected by the presence of fibers as

compared to the properties under tension and bending.

Figure 3

FLEXURAL:

There are a number of factors that influence the behavior

and strength of FRC in flexure. These include: type of fiber,

fiber length (L), aspect ratio (L/df) where df is the diameter of

the fiber, the volume fraction of the fiber (Vf), fiber

orientation and fiber shape, fiber bond characteristics (fiber

deformation). Also, factors that influence the workability of

FRC such as W/C ratio, density, air content and the like could

also influence its strength. The ultimate strength in flexure

could vary considerably depending upon the volume fraction

of fibers, length and bond characteristics of the fibers and the

ultimate strength of the fibers.

Figure 3

TENSILE & SPLIT TENSILE STRENGTH:

Most investigations in the field of FRC derive tensile

properties of the composite indirectly on the basis of

observations from flexural tests or split cylinder tests. This is

because there are difficulties associated with the

interpretation of results obtained from direct tension tests.

The difficulties are due to differences in specimen sizes,

specimen shapes, instrumentation and methods of

measurement. The stress-strain or load-elongation response

of fiber composites in tension depends mainly on the volume

fraction of fibers. In general, the response can be divided into

two or three stages, respectively, depending on whether the

composite is FRC (fiber volume less than about 3%) or Slurry

Infiltrated (SIFCON) where the volume of fibers normally

varies between 5% and 25%.

International Journal of Scientific & Engineering Research, Volume 6, Issue 12, December-2015 ISSN 2229-5518 254

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Figure 4

TEST APPARATUS:

Test apparatus are shown in Figure 1, Figure 2, Figure 3 are

compression testing machine & flexural strength testing machine.

MIXING PROCEDURE:

Following procedure was followed while preparation of FRC

1. Dry mix of coarse aggregate, fine aggregate and cement in

mixture for 2 min.

2. Fiber is added after it and mixing continued for 2 min.

3. Calculated water is added to the mixer to achieve uniform

mixing and mix for 2 min.

4. Total mixing time shall be around 5 - 7 min.

RESULT:

Compression test:

No Mix Compressive

strength

(7 days)

N/mm2

Compressive

strength

(28 days)

N/mm2

1 Steel fiber

(80/60)

43.13 53.5

2 Steel fiber

(50/35 & 30)

36.8 53.3

3 Polypropelene 35.7 52.8

4 Plain concrete 35 49.1

Flexural strength of beam:

No Mix Flexural

strength

(7 days)

N/mm2

Flexural

strength

(28 days)

N/mm2

1 Steel fiber

(80/60)

8.6 10.2

2 Steel fiber

(50/35 & 30)

6.4 7.6

3 Polypropelene 5.2 6.6

4 Plain concrete 6.2 6

Split tensile strength of concrete cube:

No Mix Split tensile strength

(28 days) N/mm2

1 Steel fiber

(80/60)

6.77

2 Steel fiber

(50/35 & 30)

6.01

3 Polypropelene 5.1

4 Plain concrete 3.15

Load deflection curve for beam:

Figure 5

Load deflection curve for plain concrete:

Figure 6

CONCLUSION:

1. Fiber reinforced concrete give more tensile strength

than plain concrete.

2. FRC controls cracking and deformation under impact

load much better than plain concrete and increased

the impact strength 25 times.

3. Fiber addition improves ductility of concrete and its

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post-cracking load-carrying capacity.

4. Use of fiber produces more closely spaced cracks and

reduces crack width. Fibers bridge cracks to resist

deformation.

REFERENCES

[1] Nataraja M. C., Dhang N and Gupta, “Fiber Reinforced

Concrete”, Indian Concrete Journal , Vol. 75, No. 4,

April 2,001, A. P (1998), ‘Steel Fiber Reinforced

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[3] Nataraja, M. C., Dhang, N and Gupta, A. P (1999).

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6,No. 2, May 1, 2002. ©ASCE, ISSN

1090-0268/2002/2-73–87

[5] Properties and Applications of Fiber Reinforced

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CONCRETE PAVEMENT: A REVIEW National

Conference on Recent Trends in Engineering &

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[7] Sravana1 P., Srinivasa Rao P., Chandramouli K.,

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FLEXURAL BEHAVIOUR OF GLASS FIBRE

REINFORCED CONCRETE MEMBERS 36th

Conference on Our World in Concrete & Structures

Singapore, August 14-16, 2011

[8] Some Studies on Steel Fiber Reinforced Concrete

International Journal of Emerging Technology and

Advanced Engineering (ISSN 2250-2459, ISO

9001:2008 Certified Journal, Volume 3, Issue 1, January

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[9] Flexural Design of Fiber-Reinforced Concrete by Chote

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JOURNAL TECHNICAL PAPER September-October

2009

[10] Colin D. Johnston, “Fiber reinforced cements and

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[11] IS 10262-2009: Mix Design of concrete.

[12] .IRC SP: 46-1997: Steel Fiber Reinforced Concrete for

Pavements.

[13] Testing of SFRC - ACI 544.

[14] ACI Committee 544. 1988. Design Considerations for

Steel Fiber Reinforced.

[15] ACI Committee 544. 1990. State-of-the-Art Report on

Fiber Reinforced Concrete.

[16] ACI Committee 544. 1993. Guide for Specifying,

Proportioning, Mixing, Placing, and Finishing Steel

Fiber Reinforced Concrete .

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