Use of Steel Fibre in m20 Concrete

USE OF STEEL FIBRE IN M20

CONCRETE

A MAJOR PROJECT REPORT

SUBMITTED BY

ROLL NO. NAME

CE 3450 RAHUL BHARDAWAJ

CE 3459 SANJAY KUMAR

in partial fulfilment for the award of the degreeof

BACHELOR OF TECHNOLOGY

IN

CIVIL ENGINEERING

JAWAHARLAL NEHRU GOVT. ENGG. COLLEGE, SUNDERNAGAR, MANDI -175018

JUNE 2015

TABLE OF CONTENTS

CONTENT Page No.

Cover Page i

Acknowledgement ii

Declaration iii

Certificate iv

List of Tables v

List of Figures vi

List of Abbreviation vii

List of Symbol viii

Chapter 1: INTRODUCTION 1

1.1 General 2

1.2 Aim of the project 3

1.3 Advantages of FRC 3

Chapter 2: LITERATURE REVIEW 5

2.1 Fibre properties 6

2.2 Manufactured Steel Fibres & Turn Steel Fibres 7

2.3 Casting and Testing 7

Chapter 3: PROJECT METHODOLOGY 8

3.1 General 9

3.2 Test performed 9

3.3 Material used 11

3.3.1 Cement 11

3.3.2 Fine Aggregates and coarse aggregates 11

3.3.3 Water 12

3.3.4 Fibre 12

Chapter 4: TEST AND RESULTS 14

4.1 Determination of index properties 15

4.1.1 Determination of grain size distribution 15

4.1.2 Specific gravity and fine aggregates 16

4.1.3 Specific gravity and water absorption test of coarse aggregates 17

4.2 Determination of engineering properties 18

4.2.2 Compression test 18

4.2.2 Flexural strength test 19

Chapter 5: CONCRETE MIX DESIGN RESULT 21

5.1 Concrete mix design for M20 Grade concrete 22

Chapter 6: ANALYSIS AND OBSERVATION OF RESULTS 25

6.1 Analysis and observation obtained 26

Chapter 7: CONCLUSION &RECOMMENDATIONS 31

7.1 Conclusion 32

7.2 Recommendation 32

7.3 Future scope of study 33

Chapter 8: REFERENCE 34

ACKNOWLEDGEMENT

Before submitting the project report it is pleasure to express deep regard to those who have

been associated with us in minor project work. It is include us great pleasure to express our

gratitude towards project guide Er.Babita and departmental faculty for their special

attention, guidance and helping us for completing our minor project report.

NAME ROLL NO SIGNATURE OF STUDENTS

RAHUL BHARDAWAJ CE 3450

SANJAY KUMAR CE 3459

DECLARATION

This is to certify that Project Report entitled “USE OF STEEL FIBER IN M20 CONCRETE ”which is submitted by GROUP bearing Roll no CE3450, CE3459 in partial fulfilment of the requirement for the award of degree B.Tech. in Civil Engineering in Jawaharlal Nehru Government Engineering College, Sunder Nagar, Mandi, Himachal Pradesh comprises only my original work and due acknowledgement has been made in the text to all other material used.

Date: Name of Students Roll No. Signature

RAHUL BHARDAWAJ CE 3450

SANJAY KUMAR CE 3459

JAWAHARLAL NEHRU GOVT. ENGG. COLLEGE, SUNDERNAGAR, MANDI

CERTIFICATE

This is to certify that the Project Report entitled, “USE OF STEEL FIBER IN CONCRETE”

submitted by group bearing roll no CE3450, CE3459 in partial fulfilment of the

requirements for the award of Bachelor of Technology degree in Civil Engineering is

carried out by under my supervision and guidance at the Jawaharlal Nehru Govt.

Engineering College, Sundernagar, Mandi, Himachal Pradesh.

Signature of the project guideName of the project guide Er.BabitaOfficial Designation Department of Civil Engg.J.N. Govt.Engg.College, Sundernagar

Signature of the HOD of the Department with dateName of the HOD : Dr. S.P. Guleria

This project report was evaluated by us on 20/05/2015

EXAMINER

CHAPTER 1

INTRODUCTION

1.1 GENERAL

Concrete in general has a higher brittleness with increase in strength. This is a major

drawback since brittleness can cause sudden and catastrophic failure, especially in structures

which are subjected to earthquake, blast or suddenly applied loads i.e., impact. This serious

disadvantage of concrete can at least partially be overcome by the incorporation of fibres,

especially, steel.

Fibre Reinforced Concrete (FRC) was invented by French gardener Joseph Monier in 1849

and patented in 1867. The concept of using fibres as reinforcement is not new. This can be

proved by the following: Fibres have been used as reinforcement since ancient times.

Historically, horsehair was used in mortar and straw in mud bricks. In the early 1900s,

asbestos fibres were used in concrete, and in the 1950s the concept of composite materials

came into being and fibre reinforced concrete was one of the topics of interest. There was a

need to find a replacement for the asbestos used in concrete and other building materials

once the health risks associated with the substance were discovered. By the 1960s, steel,

glass (GFRC), and synthetic fibres such as polypropylene fibres were used in concrete, and

research into new fibre reinforced concretes continues today.

In India, domestic waste plastics are causing considerable damage to the environment and

hence an attempt has been made to understand whether they can be successfully used in

concrete to improve some of the mechanical properties as in the case of the steel fibres. The

primary objective of this investigation is to study experimentally the properties of fiber

reinforced concrete containing steel fibers. The properties of concrete, namely, compressive

strength and flexural strength were studied.

Why Fibres are used in Concrete?

Fibres are usually used in concrete for the following reasons: i. To control cracking due to

both plastic shrinkage and drying shrinkage. ii. They also reduce the permeability of

concrete and thus reduce bleeding of water. iii. Some types of fibres also produce greater

impact, abrasion and shatter resistance in concrete. iv. The fineness of the fibres allows

them to reinforce the mortar fraction of the concrete, delaying crack formation and

propagation. This fineness also inhibits bleeding in the concrete, thereby reducing

permeability and improving the surface characteristics of the hardened surface.

Main Properties of Fibre in FRC:Type of fibres used, Volume percent of fibre (vf =3% and

5%), Aspect ratio (the length of a fibre divided by its diameter), Orientation and distribution

of the fibres in the matrix, It prevents spalling of concrete, Shape, dimension and length of

fibre is important, Strength of the fibre.

Steel is used as a fibre reinforcing material in concrete for the following reasons: i. It has a

high tensile strength. ii. It is also available by cutting ,grinding during lathing process. iv. It

reinforces the mortar and prevents it from spalling.

1.2 AIM OF PROJECT

Use of steel fibres in M20 concrete and also check the behaviours of these FRC on their

strength property.

1.3 ADVANTAGES OF FRC

Advantages of fibre reinforced concrete: Fibre reinforced concrete has started finding its

place in many areas of civil infrastructure applications especially where the need for

repairing, increased durability arises. FRC is used in civil structures where corrosion is to be

avoided at the maximum. Fibre reinforced concrete is better suited to minimize cavitation

/erosion damage in structures such as sluice-ways, navigational locks and bridge piers where

high velocity flows are encountered. A substantial weight saving can be realized using

relatively thin FRC sections having the equivalent strength of thicker plain concrete

sections. When used in bridges it helps to avoid catastrophic failures. In the quake prone

areas the use of fibre reinforced concrete would certainly minimize the human casualties.

Fibres reduce internal forces by blocking microscopic cracks from forming within the

concrete.

Table1.1 Mechanical properties of commonly used fibres in concrete materials

Type of Fibre Equivalent

diameter, mm

Specific gravity,

Kg/cubic m

Tensile strength,

MPa

Young’s

modulus,

GPa

Ultimate

elongation, %

Acrylic 0.02 to 0.35 1100 200 to 400 2 1.1

Asbestos 0.0015 to 0.02 3200 600 to 1000 83 to 138 1.0 to 2.0

Cotton 0.2 to 0.6 1500 400 to 700 4.8 3.0 to 10.0

Glass 0.005 to 0.15 2500 1000 to 2600 70 to 80 1.5 to 3.5

Graphite 0.008 to 0.009 1900` 1000 to 2600 230-415 0.5 to 1.0

Nylon 0.02 to 0.40 1100 760 to 820 4.1 16 to 20

Polyester 0.02 to 0.40 1400 720 to 860 8.3 11 to 13

Polypropylene (PP) 0.02 to 1.00 900 to 950 200 to 760 3.5 to 15 5.0 to 25.0

Jute 0.1 to 0.2 1030 250 to 350 26 to 32 1.5 to 1.9

Steel 0.15 to 1.00 7840 345 to 3000 200 4 to 10

CHAPTER 2

LITRATURE REVIEW

LITERATURE REVIEW

2.1 STEEL FIBRE USED IN CONCRETE Dr. B. G. Vishnuram is currently working

as Principal, EASA College of Engineering & Technology, Navakkarai, Coimbatore.

Concrete is one of the most versatile building materials. It can be cast to fit any structural

shape from ordinary rectangular beam or column to a cylindrical water storage tank in a

high-rise building. It is readily available in urban areas at relatively low cost. Concrete is

strong under compression but weak under tension. As such, a form of reinforcement is

needed. The most common type of concrete reinforcement is by steel bars. The advantages

in using concrete include high compressive strength, good fire resistance, high water

resistance, low maintenance, and long service life. The disadvantages in using concrete

include poor tensile strength, and formwork requirement. Other disadvantages include

relatively low strength per unit weight. Tensile strength of concrete is typically 8% to 15%

of its compressive strength. This weakness has been dealt with over many decades by using

a system of reinforcing bars to create reinforced concrete; so that concrete primarily resists

compressive stresses and rebars resist tensile and shear stresses. The longitudinal rebar in a

beam resists flexure (tensile stress) whereas the stirrups, which are wrapped around the

longitudinal bar not only holds the longitudinal bars in position but also resist shear stresses.

In a column, vertical bars resist compression and buckling stresses while ties resist shear

and provide confinement to vertical bars. Cracks in reinforced concrete members extend

freely until encountering a rebar and this is where the need for multidirectional and closely

spaced reinforcement for concrete arises.

Fibres are usually used in concrete to control cracking due to both plastic shrinkage and

drying shrinkage. They also reduce the permeability of concrete and thus reduce bleeding of

water. Some types of fibres produce greater impact, abrasion and shatter resistance in

concrete. Generally fibres do not increase the flexural strength of concrete, and so cannot

replace structural steel reinforcement. If the modulus of elasticity of the fiber is higher than

the matrix (concrete or mortar binder), they help to carry the load by increasing the tensile

strength of the material. However, fibres which are too long tend to "ball" in the mix and

create workability problems.

2.1 Fiber Properties

The fibre strength, stiffness, and the ability of the fibres to bond with the concrete are

important fibre reinforcement properties. Bond is dependent on the aspect ratio of the fibre.

Steel fibres have a relatively high strength andmodulus of elasticity. They are protected

from corrosion by the alkaline environment. and their bond to the matrix can be enhanced

by mechanical anchorage or surface roughness. Long term loading does not adversely

influence the mechanical properties of steel fibres. In particular environments such as high

temperature refractory applications, the use of stainless steel fibres may be required.

Various grades of stainless steel, available in fibre form, respond somewhat differently to

exposure to elevated temperature and potentially corrosive environments.

2.2 Manufactured Steel Fibres & Turn Steel Fibres

Round, straight steel fibres are produced by cutting or chopping wire, typically wire having

a diameter between 0.25 to 1.00 mm. Flat, straight steel fibres having typical cross sections

ranging from 0.15 to 0.64 mm thickness by 0.25 to 2.03 mm width are produced by shearing

sheet or flattening wire. Crimped and deformed steel fibres have been produced with both

full-length crimping, or bent or enlarged at the ends only. Some fibres have been deformed

by bending or flattening to increase mechanical bonding. Some fibres have been collated

into bundles to facilitate handling and mixing. During mixing, the bundles separate into

individual fibres.

Fibres are also produced from cold drawn wire that has been shaved down in order to make

steel wool. The remaining wires have a circular segment cross-section and may be crimped

to produce deformed fibres. Also available are steel fibres made by a machining process that

produces elongated chips. These fibres have a rough, irregular surface and a crescent-shaped

cross section.

Steel fibres are also produced by the melt-extraction process. This method uses a rotating

wheel that contacts a molten metal surface, lifts off liquid metal, and rapidly solidifies it into

fibres. These fibres have an irregular surface, and crescent shaped cross-section.

In this study the scraps from the lathe shops are used as the steel fibres.

2.3 CASTING AND TESTING

Casting and testing of concrete cubes, beams were done as per IS code recommendations.

The proportioning of concrete mixes consists of determination of the quantities of respective

ingredients necessary to produce concrete having adequate, but not excessive, workability

and strength for the particular loading and durability for the exposure to which it will be

subjected. Emphasis is laid on making the most economical use of available materials so as

to produce concrete of the required attributes at the minimum cost. The basic assumption

made in mix design is that the compressive strength of workable concrete is governed by the

water cement ratio. The concrete mix adopted was M20 concrete with varying percentage of

fibres ranging from 0, 3 & 5% by weight of concrete.

CHAPTER 3 PROJECT

METHODOLOGY

3.1 GENERAL

The methodology adopted to test the mechanical properties and strength of hair reinforced

concrete is governed by: i. Compressive Strength, ii. Flexural Strength

Various cubes and beams are tested and analysed for finding the effect of using hair as fibre

reinforcement.

The methodology adopted for the project is as follows:

Testing of various material used in major project

Design mix M20 concrete.

Concrete cube casting and beam casting

Curing of concrete cube and beam

Various test on concrete cube and beam

3.2 TEST PERFORMED

For determining the effect of steel fibre in concrete following tests were performed: i.

Compression test: It is the most common test conducted on hardened concrete as it is an

easy test to perform and also most of the desirable characteristic properties of concrete are

qualitatively related to its compressive strength. The compression test is carried out on

specimens cubical in shape as shown in figure 1 of the size 150 × 150 × 150 mm. The test is

carried out in the following steps: First of all the mould preferably of cast iron, is used to

prepare the specimen of size 150 × 150 × 150 mm. During the placing of concrete in the

moulds it is compacted with the tamping bar with not less than 35 strokes per layer. Then

these moulds are placed on the vibrating table and are compacted until thespecified

condition is attained. After 24 hours the specimens are removed from the moulds and

immediately submerged in clean fresh water. After 28 days the specimens are tested under

the load in a compression testing machine. ii. Flexural Strength test: Direct measurement of

the tensile strength of concrete is difficult. Neither specimens nor testing apparatus have

been designed which assure uniform distribution of the pull applied to the concrete. The

value of the extreme fibre stress in bending depends on the dimensions of the beam and

manner of loading. The system of loading used in finding out the flexural tension is Third-

point Loading Method as shown in fig 3. In this method the critical crack may appear at any

section, not strong enough to resist the stress within the middle third, where the bending

moment is maximum. The test is carried out in the following steps: First of all the mould

preferably of cast iron, is used to prepare the specimen of size 140 × 50 × 50 mm as shown

in figure 4. During the placing of concrete in the mould it is compacted with the tamping bar

weighing 2 kg, 400 mm long with not less than 35 strokes per layer. Then this mould is

placed on the vibrating table and is compacted until the specified condition is attained. After

24 hours the specimen is removed from the mould and immediately submerged in clean

fresh water. After 28 days (14 days) the specimen is taken out from the curing tank and

placed on the rollers of the flexural testing machine as shown in figure 5 for testing as

shown in figure 3. Then the load is applied at a constant rate of 400 kg/min. The load is

applied until the specimen fails, and the maximum load applied to the specimen during the

test is recorded.

The specimen for both the test is made in the following manner

(i.)Compression test: Three cubes are made for each M-20 with 0%, 3%, 5% steel fibre by

weight of concrete.

(ii.) Flexural Strength test: Three beam is made for each M-20 with 0%, 3%, 5% steel fibre

by weight of concrete and more three cubes and beams are cast for the 28days strength test.

Analysis of Data collected: The analysis of data collected is done in the following manner:

1. Compression test: The results from the compression test are in the form of the maximum

load the cube can carry before it ultimately fails. The compressive stress can be found by

dividing the maximum load by the area normal to it. The results of compression test and the

corresponding compressive stress is shown in table 1.

Let, P = maximum load carried by the cube before the failure A = area normal to the load =

150 × 150 mm2 = 22500 mm2 σ = maximum compressive stress (N/mm2)

2. Flexural Strength test: The results from the flexural strength test are in the form of the

maximum load due to which a beam fails under bending compression. Using the

fundamental equation of bending we can find the bending stresses as per figure 6. The

results of flexural strength test and its corresponding bending stress is shown in table 2.

We know that,

M = Moment of Resistance, I = Moment of Inertia about neutral axis, σb= Bending stress,

y = Extreme fibre distance from neutral axis, W = Maximum load at which beam fails,

b = width of the beam, d = depth of the beam.

3.3 MATERIAL USED

3.3.1 Cement

ORDINARY Portland cement (43 grade) of ACC brand is used for the experimental work.

The specific gravity of cement is assumed about 3.15 & the required water for normal

consistency is found out.

Fig. 3.1 Cement

3.3.2 Fine Aggregate & Coarse Aggregate

The sand for the above said experiment work is obtained locally. As the sand should have

maximum size of 4.75 mm, thus the sand sieved through 4.75 sieve, so that the sand

particles have size more than 4.75 mm can be eliminated. The sieve analysis of coarse

aggregate is carried out, so as to confirm the zoning grade. It is further ensured that the sand

as procured should not have any organic or inorganic impurities. The sieve analysis is

carried out separately for 10 mm and 20 mm size aggregate. The trial mix, by mixing 20

mm with 10 mm aggregate is further carried out to fix the grading zone.

Fig. 3.2 Aggregates of size 20mm

3.3.3 Water

As prescribed in IS: 456-2000, the potable water free from injurious amounts of deleterious

material should be used. It should be fit for drinking purposes as well as for curing.

3.3.4 Fibres

For this project we have used steel fibre of length 3-4cm and thickness 0.25mm to increase

the compressive strength and flexural strength of concrete structure. The various

specification and advantages of these fibre are as below.

Fig.3.3 Steel fibres

ROLE OF STEEL FIBRE USED

• Improve the crack resistance or ductility and post cracking strength

• Resistance to wear and tear

• Resistance to spalling

• Resistance to fatigue

• Safe and easy to use

Specifications of steel fibre:

A) STEEL FIBER

Diameter 0.25mm to 1.00mm

Length 12mm to 60mm

Tensile Strength 345 to 3000Ma Pa

Melting point > 1000ºC

Dispersion Excellent

Acid resistance Excellent

Alkali resistance Good

Specific gravity 7840Kg/cubic m

Young's Modulus 200 GPa

Ultimate elongation % 4 to 10

Source of fibre : Steel fibre waste in steel industry

Primary Applications:

• Manufacture of wide varieties of precast product such as bridge decks & manhole covers.

• Footings, foundations, walls and tanks.

• Used in slab elements for highways, runways and tunnel linings.

Used in machine foundation blocks, doors and window frames

Used in coal storage bins, stair cases and break waters.

Used in construction of silos and bunkers.

Used in steel fibre reinforced (shotcrete form) in tunnels lining.

Used in industrial floorings (long steel fibres are used) due to its high resistance for

wear and tear.

Less labour is required.

Less construction time is required.

CHAPTER 4

TEST AND RESULT

4.1DETERMINATION OF INDEX PROPERTIES

4.1.1 Determination of Grain Size Distribution by Sieve analysis

Sieve analysis helps to determine the particle size distribution of the coarse and fine

aggregates .This is done by sieving the aggregates as per IS: 2386 (Part I) – 1963. In this we

use different sieves as standardized by the IS code and then pass aggregates through them

and thus collect different sized particles left over different sieves. Following procedure is

followed during this test.

IS Sieve

Size

Wt. Retained

in g

% Wt.

Retained

Cumulative

% age

Wt Retained

% age Passing % Finer

4.75mm 70 7.0 7.0 93

Conforming

to grading

zone II

2.36mm 130 13.0 20.0 80

1.18mm 230 23.0 43.0 57

600mic. 140 14.0 57.0 43

300mic. 245 24.5 81.0 18.5

150mic.

75mic.

130

5

13.0

0.5

94.5

95

5.5

5.0

Pan 50 5.0 100 0

The test sample is dried to a constant weight at a temperature of 110°C and weighed. The

sample is then sieved by using a set of IS Sieves. On completion of sieving, the material on

each sieve is weighed. Cumulative weight passing through each sieve is calculated as a

percentage of the total sample weight.

Figure 4.1.1 Sieve analysis

The percentage by weight of the total sample passing through one sieve and retained on the

next smaller sieve, to the nearest 0.1 percent is calculated. The result of the sieve analysis

was recorded graphically with particle size as abscissa and the percentage passing as

ordinate.

4.1.2 Specific Gravity of Fine Aggregates

Specific gravity of fine aggregates is defined as ratio of weight of given volume of

aggregates to the weight of equal volume of distilled particles. It is based upon the principle

of displacement of water by fine aggregates in Pycnometer. The standard temperature for

reporting specific gravity is either 27o c or 4oc.

Figure 4.1.2 Pycnometer

For finding the value of specific gravity of aggregates, the Pycnometer is firstly cleaned and

weighted with its cup. After this oven dried aggregates are inserted into it and weighted.The

remaining part of Pycnometer is filled with distilled water gradually removing the entrapped

air from it. The Pycnometer is then shaked for some time and again weighted. It is then

emptied and washed thoroughly. At last the Pycnometer is filled with distilled water,

driedfrom outside and weighted.

Specific gravity(Gt) = W2 – W1

W1: Wt. of Pycnometer

W2:Wt. of Pycnometer + Wt. of fine aggregates

W3: Wt. of Pycnometer + Wt. of fine aggregates + Wt. of distilled water

W4: Wt. of Pycnometer + Wt. of distilled water

from calculation

W1= 620 g

W2= 930 g

W3= 1695 g

W4= 1500 g

Specific gravity = 310/145 = 2.60

4.1.3 Specific gravity and water absorption test of coarse aggregates

The specific gravity of aggregate is considered to be measure of strength or quality of the

material. The specific gravity test helps in identification of stone.Water absorption gives an

idea of strength of aggregate. Aggregates having more water absorption are more porous in

nature and are generally considered unsuitable unless they are found to be accepted based

on strength, impact, hardness test. About 2 kg of the aggregate was washed thoroughly to

remove fines and placed in wire basket and immersed in distilled water at a temperature

between 220 and 320 C. Then we lifted the wire basket 25mm above base of tank to remove

the entrapped air in it. Then basket and sample are weighed while suspended in water.

(W2-W1)-(W3-W4)

CALCULATIONS

Weight of saturated aggregate suspended in water with basket = W1 g (1760)

Weight of basket suspended in water = W2 g (23500)

Weight of saturated aggregate in water = W3 g (985)

Weight of saturated surface dry aggregate in air = Ws g = (W1 – W2)

1) Specific gravity = W4 /(W3 – Ws)

2) Water absorption = (W3 – W4)100/W4

The specific gravity of ranges from 2.5 to 3.0 ( From calculation 2.46)

The water absorption of aggregates ranges from 0.1 to 2.0 %

4.1.4 Free moisture content in fine aggregates.

(W1) empty wt of container = 22.5g

(W2)Empty wt. of container + moisture fine aggretes = 72.21g

(W3) Empty container +dry f. agg. = 71.32 g

% fine aggregate = (W2-W3 )/(W3-W1) *100

= 1.8 %

4.2 DETERMINATION OF ENGINEERING PROPERTIES:

4.2.1 Compression Test

Compression test is the most common test conducted on hardened concrete, partly because

it is an easy test to perform, and partly because most of the desirable properties of concrete

are qualitatively related to its compressive test.

Firstly we prepared the cube samples by proper compaction and remove them from moulds

after 24 hours. Then we put them in curing tank. Then after proper curing we placed them

under compression testing machine for checking compressive strength. Due to compression

load the cube undergoes lateral expansion owning to poissions ratio effect.

It was interesting to note that the restraining effect of plates of testing machine extends over

the entire height of the cube.

Fig. 4.2.1 Compression Testing Machine

4.2.2 Flexural Strength Test

Concrete is relatively strong in compression and weak in tension. In reinforced concrete

members, little dependence is placed on the tensile strength of concrete since steel

reinforcing bars are provided to resist all tensile forces. So knowledge of tensile strength of

concrete is of importance. The value of modulus of rupture depends upon the dimension of

beam and manner of loading. We made the beam specimens for determining flexural

strength and any loose sand or other material were removed from the surfaces of specimen.

Then the specimen was placed in machine in such a manner that the load is applied to the

uppermost surface as cast in the mould along two lines spaced 20 or 13.3 cm apart.

The axis of specimen was aligned with the axis of loading device. The load was applied

without shock and increasing continuously at a rate such that the extreme fibre stress

increases at approximately 0.7kg/sq. cm/min that is, at a rate of loading of 400kg/min for

the specimen. The load is increased until the specimen fails.

The flexural strength of specimen is expressed as the modulus of rupture f b which is given

by

fb = (P x l)

b xd2

When ‘a’ is greater than 20cm for 15 cm specimen and

fb = (3p x a)

When ‘a’ is less than 20 cm but greater than 17 cm for 15 cm specimen.

d – Measured depth in cm of specimen at point of failure

l – Length in cm of the specimen on which the specimen was supported

p – Maximum load in kg applied on the sample

Fig. 4.2.2 Flexural Test Machine

bxd2

CHAPTER 5

CONCRETE MIX DESIGN, RESULT

AND OBSERVATIONS

5.1 CONCRETE MIX DESIGN FOR M-20 GRADE CONCRETE

Procedure for design of reference concrete mix in according to IS: 10262-1982 and IS: 456-

2000, Indian standard recommended guidelines.

1. DESIGN STIPULATIONS.

Characteristic compressive strength at 28 days = 20 N/mm2

i. Maximum size of aggregate = 20 mm

ii. Degree of workability = 0.9

iii. Degree of quality control = Good

iv. Type of exposure = Moderate

v. Standard deviation as per IS: 456-2000 = 5.3

2. TEST DATA FOR MATERIALS.

i. Cement used = OPC

ii. Specific gravity of cement = 3.15

iii. Specific gravity of Coarse aggregate = 2.1

iv. Specific gravity of Fine aggregate = 2.46

v. Sieve analysis : fine aggregate conforming to zone 2

vi. Water absorption of coarse aggregates = 0.5 %

vii. Free moisture content of fine aggregate = 1.8 %

3. TARGET MEAN STRENGTH OF CONCRETE

For a tolerance factor of 1.65 and using table 1 of IS: 10262, the target mean strength for

desired characteristics cube strength (20 N/mm2) is:

20+1.65x5.3=29.25 N/mm2

4. SELECTION OF WATER CEMENT RATIO

The w/c ratio required for target mean strength of 33.745N/mm2 is 0.47. Further w/c ratio

for moderate exposure is 0.60.Thus adopting minimum of two values i.e., 0.47.As sand

confirming to zone II of table 4 of IS: 383 -1970 so here we do not need to apply adjustment

in water content and in percentage of sand in total aggregate.

5. SELECTION OF WATER AND SAND CONTENT

As sand confirming to zone II of table 4 of IS: 383 -1970 so here we do not need to apply

adjustment in water content and in percentage of sand in total aggregate.

a) Therefore required sand content as percentage of total aggregates by absolute volume= 35

%

b) Required water content = 186 lit./m^3

6. DETERMINATION OF CEMENT CONTENT

Water cement ratio = 0.42

Water = 186

Cement = 186/0.47 = 395.8 kg/m3

This cement content is adequate to for moderate exposure conditions as according to IS:

456-2000 minimum cement quantity recommended as 240 kg/m3

7. DETERMINATION OF COARSE AND FINE AGGREGATE CONTENT

From table 3 of IS:10262-1982 for the specified maximum size of aggregate of 20mm size ,

the amount of entrapped air in the wet concrete is 2%. Taking this into account and applying

equations from 3.5.1 of IS: 10262-1982.

a). Fine aggregate

0.98 = [186 + (395.8/3.15) + (Fa / (0.35 x 2.64))]/1000

Fa = 608.426 kg/m3

b). Coarse aggregate

0.98 = [186 + (395.8/3.15) + (Ca / (0.65 x 2.6))]/1000

Ca = 1129.9 kg/m3

8. THE MIX PROPORTIONS ARE:

Unit

of

batch

Water

(ltr)

Cement

(kg)

Fine

aggregate

(kg)

Coarse

aggregate

(kg)

Total

aggregate

(kg)

1) 1 cum of

concrete

186 395 608.5 1129.9 2319.4

2)Cement

unit

0.47 1 1.54 2.8 5.34

TABLE 5.1 Mix Proportions

CHAPTER 6

ANALYSIS AND OBSERVATIONS OF

THE RESULT

6.1 ANALYSIS AND OBSERVATIONS OF THE RESULTS OBTAINED

Compressive Strength Result

(A) At 14 Days

1.At the age of 14 days, the compressive strength of the control mix was 22.31MPa

Record No. 00195 Shape: Beam

Pace @ (KN/sec.) 5.2

Peak Load 430.46KN

Peak Stress 22.31MPa

Table 6.1 TESTING NOMINAL CUBE AT 14 DAYS.

2 . With the addition of steel fibres with composition 3%, 5% results are as shown as below.

Table 6.2 RESULTS USING STEEL FIBRE (3%) IN CUBE AT 14 DAYS

Table 6.3 RESULTS USING STEEL FIBRE (5%) IN CUBE AT 14 DAYS

Record No. 00195 Shape: Beam (225sq.cm)


Peak Load 765.5KN


Record No. 00195 Shape: Beam (225sq.cm)


Peak Load 914.2KN


3 530

32

34

36

38

40

42

34.6

40.63

% of FIBRE

Cop

mpr

essi

ve S

tren

gth(

MP

a)

Fig. 4.1 Compressive strength for the control mix and with 3% and 5% STEEL FIBRE at 14

days.

The compressive strength of concrete using steel fibre varies with varying the content of

steel fibre. In the case study of our project we have used steel fibre with 3% and 5% by

weight of concrete as per replacement of sand, cement and aggregates.

4.3.2 Compressive strength results

(B) At 28 Days

1.At the age of 28 days, the compressive strength of the control mix was 28.21MPa



Peak Load 633.3KN


Table 6.4 TESTING NOMINAL CUBE AT 28 DAYS

2. With the addition of steel fibres with composition 3%, 5% results are as shown as below.



Peak Load 835.41KN


6.5 RESULTS USING STEEL FIBRE (3%) IN CUBE AT 28 DAYS



Peak Load 992.31KN


6.6 RESULTS USING STEEL FIBRE (5%) IN CUBE AT 28 DAYS

3 532

34

36

38

40

42

44

46

37.27

44.29

Cop

mpr

essi

ve S

tren

gth(

MP

a)

Fig 4.2

Compressive strength for the control mix and with 3% and 5% STEEL FIBRE at 28 days.

4.3.3 FLEXURALSTRENGTH (USING STEEL FIBRE IN BEAM )

(A) AT 14 DAYS

1) At the age of 14 days, the flexural strength of the control mix was 5.02 MPa.

2) At the age of 14 days, the flexural strength of control mix with 3% steel fibre was 6.09

MPa

3) With the addition of 5% of steel fibre by weight of concrete the strength of concrete mix

was found to 6.13MPa.

(B) AT 28 DAYS:

1) At the age of 28 days, the flexural strength of the control mix was 6.82MPa.

2) With the addition of 3% & 5% dose of steel fibre by weight of concrete the strength of

concrete mix was found to be increased to 8.32MPa and 8.74MPa.

FIG 5.3 TESTING OF SPECIMEN IN FLEXURE STRENGTH TESTING MACHINE



Peak Load 17.06 KN

Peak Stress 6.82MPa

Table 6.7 RESULT OF CONTROL MIX



Peak Load 22.24 KN

Peak Stress 8.32MPa

Table 6.8 RESULT AT 3 % STEEL FIBRE ON 28 DAYS



Peak Load 23.04 KN

Peak Stress 8.74MPa

Table 6.9 RESULT AT 5% STEEL FIBRE ON 28 DAYS

FIG 5.8 BEAM FAILURE UNDER CTM

CHAPTER -7CONCLUSION AND

RECOMMENDATIONS

6.1 CONCLUSION

The present study was undertaken to investigate the influence of steel fibre in M-20 grade of

concrete on the following properties of concrete:

Compressive strength

Flexural strength

Samples of plain concrete and fibres reinforced concrete with the addition of 3% and 5%

steel fibre were prepared. The various tests like compressive strength, flexural strength were

conducted. Tests were performed at the ages of 14 days. But at the age of 28 days the

compressive strength of specimens was found to be increased. It was further observed that

with the increase in fibre dose. The increase in dose of fibres makes the fibres difficult to

mix and thus creates more voids. In M-20 grade of concrete the addition of 1% of fibres by

weight gives better values of rebound hammer test which indicates better densification and

cohesiveness in concrete as per references or literature review.

6.2 RECOMMENDATIONS

On the basis of conclusion, following recommendations are suggested. However it is also

suggested that before adopting the steel fibres for development of concrete at constructional

site, it has to be tested and verified in the laboratory, as the field results may vary due to

certain uncontrolled parameters. Specified literature may also be referred in designing and

developing concrete with the addition of steel fibres. Further, codal provision as given in IS

456-2000 are also referred to be being taken into considerations, while designing concrete

with the steel fibres.

Concrete mix with steel fibers a lot of care has to be taken up, as non homogeneous

mixing forms voids in the concrete mix and reduces the compressive strength of

concrete mix.

Steel fibre is high strength material which enhance the durability of concrete.

Due to introduction of steel fibre in concrete it increases the load wearing capacity.

Maximum quantity of steel fibre used in concrete will decrease the strength , so

limit the quantity of steel fibre to 1%-6% by weight of concrete.

6.3 FUTURE SCOPE OF STUDY

The present study was undertaken to study the effect of Steel fibres when added in the

concrete of grade M20. Further the future studies can be planned to cover the following

aspects:

Effect of hair fibres along the steel fibres on compressive strength of concrete.

Effect on the compressive strength of cement mortar when mixed with 12 mm to 15

mm size of plastic fibres.

Study of use of polyesterfibres in higher grade of concrete.

Use of polyesterfibres in high performance concrete.

Use of steel fibre with addition of coconut fibre as reinforced concrete.

Effect on abrasion strength and the resistance to external chemical attack.

Comparison of compressive strength of Recron fibres reinforced concrete for

different types of cement.

CHAPTER 7

REFRENCES

7.1 REFERENCES[1] A. Adeyanju and K. Manohar, “Effects of Steel Fibres and Iron Filings

on Thermal and Mechanical Properties of Concrete for Energy Storage

Application” 2011, Journal of Minerals & Materials Charac-terization & Engineering, Vol. 10, No.15, pp.1429-1448..

[2] D. V. Soulioti, N. M. Barkoula, A. Paipetis, T. E. Matikas. “Effects of Fibre Geometry and Volume Fraction on the Flexural Behaviour of SFRC”, June 2011, International journal of applied mechanics, Volume 47, Issue Supplement s1, pages 535–541,.

[3] Ganeshan N. Indira P V, Structural Behavior of steel fibre reinforced concrete wall panels in two way in plane actions, The Indian Concrete Journal, October 2010, Volume 84 no:10 pp 21 – 28 .

[4] Had Bayasi and Henning Kaiser (2001); “Steel fibres as crack arrestors in concrete”; Indian concrete journal, 75, 215-219.

[5] Henager, C.H. "Steel Fibrous, Ductile Concrete Joint for Seismic Resistant Structures. Reinforced Concrete Structures in Seismic Zones”, SP 53-14, American Concrete Institute, Detroit, 1977, pp.371-386.

[6] Michael Gebman, “Application of Steel Fiber Reinforced Concrete In Seismic Beam-Column Joints” A Thesis Presented to the Faculty of San Diego State University.

[7] Narayanan, R. and Kareem Palanjian. A.S. (1984); “Effect of fibre addition on concrete strength”; Indian Concrete Journal, Vol-23.

[8] P. Ramadoss and K. Nagamani Structural Engineering Division, Department of Civil Engineering, Anna University, Chennai, India. “Tensile Strength And Durability Characteristics Of High-Performance Fibre Reinforced Concrete”.

[9] S Pant Avinash,R Suresh Parekar “ Steel Fibre Reinforced concrete beams under combined torsion-bending-shear” Journal of Civil Engineering(IEB), 38(1)(2010) pp31-38.

[10] “State-of-the-Art Report on Fiber Reinforced Concrete” Reported by ACI Committee 544. ACI Committee 544.1R, (1996) Fibre reinforced concrete, American Concrete Institute, Michigan, USA.

[11] Steel Fiber Reinforced Concrete (SFRC)”. http://www.3-co.com/Pro/Contractors/ Special_Concrete/sfrc.htm.

[12] Ziad Bayasi, Fang H. Chou ,James Burns; “Application of steel fibre reinforced concrete in seismic beam-column joints”; Journal of Civil Engineering (IEB), 38(1) (2010) 31.

7.2 IS CODES [1] IS 10262:1982,2009; Mix design of concrete. [2] IS 456:2000; Plain and Reinforced concrete code of Practice. [3] IS 383:1970; Specification for coarse and fine aggregates from

natural sources for concrete [4] IS 10086:1982; Specification for moulds for use in tests of cement

and concrete [5] IS 516: 1959; Methods of tests for Strength of concrete [6] IS 5816:1999 ; Splitting tensile strength of concrete method of test

Documents

Use of Steel Fibre in m20 Concrete