evaluation of properties of coconut coir fiber reinforced concrete

1

EVALUATION OF PROPERTIES OF

COCONUT COIR FIBER REINFORCED

CONCRETE

A Project Report

Submitted by

JAWALE NIRAJ PRAVIN (110701025) NIKALJE ROHIT SARJERAO (110701034)

BABJE ROHIT PRADEEP (110801007) GAVHANE NILESH BABAN (110801055)

KOTWAL PRAKASH RAJARAM (110901089)

Under the Guidance of

Dr. I.P.SONAR

In partial fulfillment for the award of the degree

of

BACHELOR OF TECHNOLOGY IN

DEPARTMENT OF CIVIL ENGINEERING

AT

COLLEGE OF ENGINEERING,

SHIVAJI NAGAR, PUNE-411005

2011-2012

2

CONTENTS

Content page No.

Acknowledgements ......................................................................................................3

Abstract ………………………………………………………………………………4

1. Introduction…………………………………………………………..6

2. Literature Review………………………………………………….....7

3. The proposed work…………………………………………………..12

4. Properties of materials used………………………………………...14

5. Concrete Mix design…………………………………………………19

6. Test program………………………………………………………...25

6.1 Workability…………………..………………………………….25

6.2 compressive strength…………………………..………………..28

6.3 split tensile strength…………………………………..……….....66

6.4 flexural strength………………………………………………….70

7. Discussion…………….……………………………………………….76

8. Conclusions…………………………………………………………...77

9. Future scope…………………………………………………………..78

10.Reference……………………………………………………………...79

Appendix…………………………………………………………………80

Number of Tables – 39

Number of Figures - 53

3

ACKNOWLEDGEMENT

It is indeed a great pleasure and moment of immense satisfaction for us to express our sense

of profound gratitude towards “Dr. Prof. I. P. Sonar” for his constant encouragement and

valuable guidance.

We also thank our Head of Department “Dr. Prof. S.R. Pathak” for her help in various

aspects.

A special thanks to Mr. U.M. Paranjape and his NGO for demonstration of role of

coconut coir mat in their actual project of under ground water tanks for rainwater harvesting

in the field.

At last our sincere thanks to professors and staff of the Civil Engineering Department, the

Applied Mechanics Lab who helped us directly or indirectly during the course of our work.

Jawale Niraj P. (110701025)

Nikalje Rohit Sarjerao (110701034)

Babje Rohit Pradeep (110801007)

Gavhane Nilesh Baban (110801055)

Kotwal Prakash Rajaram (110901089)

4

ABSTRACT

EVALUATION OF PROPERTIES OF COCONUT COIR FIBER REINFORCED CONCRETE.

Concrete is a heart of construction industry. Investigations to overcome the brittle response

and limiting post-yield energy absorption of concrete led to the development of fiber reinforced

concrete using discrete fibers within the concrete mass. A wide variety of fibers have been

proposed by the researchers, such as steel, glass, polypropylene, carbon, polyester, acrylic

,aramid and natural fibers.

Out of these, coconut coir is found to be impressive being natural and available everywhere.

Coir provides a natural, non-toxic replacement for asbestos in the production of cement

fiberboard. The Coir-reinforced concrete is strong, flexible and may be less expensive to produce

than other reinforcement methods such as wire mesh or rebar, according to a paper by Ben

Davis of Georgia Tech University. Some studies related to durability aspects of natural fiber such

as coconut coir and sisal are carried out by researchers.

Over half of the population around the world is living in slums and villages. The

earthquake damages in rural areas get multiplied mainly due to the widely adopted non–

engineered constructions. On the other hand, in many smaller towns and villages in southern

part of India, materials such as nylon, plastic, tyre, coir, sugarcane bagasse and rice husk are

available as a waste. So, here an attempt has been made to investigate the possibility of using

these locally available rural waste fibrous materials as concrete composites.

A concrete mix of grade M20 has been designed to achieve the minimum grade of M20

as specified in IS 456-2000. The project work is carried out in three phases.

In the first phase, we studied the mechanical properties of constituents of concrete mix

and coconut coir fibers. The effect of various percentages of coconut coir fibers (0.5% to 2.0%)

on workability and strength properties of concrete are studied. Standard specimens for

compressive strength, Modulus of elasticity, split tensile strength, modulus of rupture, are cast

as per relevant IS codes. The results are compared with plain cement concrete.

In Second phase, total 30 cubes,15 cylinders, 15 beam specimens were cast and tested.

Based on the experimental results of workability and mechanical strength properties obtained

from phase one, effect of coconut coir fibers of specified length and selected percentage

fractions on concrete are studied.

5

In third phase, study of ground water tank constructed in field by using coconut coir mat

reinforced cement mortar is done. To observe the strength properties of such coir mat

reinforced cement mortar panels, an effort was taken to test panels prepared as per actual site

conditions practised by ‘Jalvardhini’ an active NGO working in the field of rainwater harvesting in

Thane district.

6

1 INTRODUCTION

Selection of this topic:

Applications of natural fibers in composite materials is an attractive options. Literature

survey indicates some research work carried out on various natural fiber and their applications in

low cost products.

Considering availability of sugarcane bagasse as waste, it was initially decided to work on

sugarcane bagasse.

First of all various properties of sugarcane bagasse fiber were studied. But it was

rejected to use as fiber reinforcement in concrete because of following reasons.

It has very high water absorption (about 800%) and water content (about 50%).

High cost as compared to coconut coir fiber.

It is currently used as a fuel in cogeneration power plants.

It is highly biodegradable as compared to coconut coir fiber.

Therefore we have decided to use another natural fiber i.e. coconut coir fiber having

enhanced properties.

Coconut coir fiber as reinforcement in concrete:

Coconut coir fiber is found to have good tensile strength and abrasion resistance. It can

easily withstand heat and saltwater. Coconut coir is Eco-friendly and available

everywhere. Coconut coir is strong and light. It does not contain any harmful materials. It

is therefore a good option as fiber reinforcement in concrete.

Objective of the work:

To evaluate different properties of coconut coir fiber reinforced concrete in different

aspects; such as compressive strength, split tensile strength, flexural strength, etc. These

properties will be compared with respective properties of plain concrete. The concrete

using coir fiber of different aspect ratios and with different percentages of coconut coir

fiber is to be prepared and tested.

After conducting the tests and comparing the results, we have found that the

strength properties of concrete are improved by the use of coconut coir fiber.

7

2 LITERATURE REVIEW

Fiber Reinforced concrete(FRC)

Fiber Reinforced Concrete can be defined as a composite material consisting of mixtures

of cement, mortar or concrete and discontinuous, discrete, uniformly dispersed suitable

fibers. Fiber reinforced concrete (FRC) is concrete containing fibrous material which

increases its structural integrity. It contains short discrete fibers that are uniformly

distributed and randomly oriented. Continuous meshes, woven fabrics and long wires or

rods are not considered to be discrete fibers. Fiber is a small piece of reinforcing material

possessing certain characteristics properties. They can be circular or flat. The fiber is

often described by a convenient parameter called aspect ratio. The aspect ratio of the fiber

is the ratio of its length to its diameter. Typical aspect ratio ranges from 30 to 150. Fibers

include steel fibers, glass fibers, synthetic fibers and natural fibers. Within these different

fibers that character of fiber reinforced concrete changes with varying concretes, fiber

materials, geometries, distribution, orientation and densities.

Fiber-reinforcement is mainly used in shotcrete, but can also be used in normal

concrete. Fiber-reinforced normal concrete are mostly used for on-ground floors and

pavements, but can be considered for a wide range of construction parts (beams, pliers,

foundations etc) either alone or with hand-tied rebars. Concrete reinforced with fibers

(which are usually steel, glass or plastic fibers) is less expensive than hand-tied rebar,

while still increasing the tensile strength many times. Shape, dimension and length of

fiber is important. A thin and short fiber, for example short hair-shaped glass fiber, will

only be effective the first hours after pouring the concrete (reduces cracking while the

concrete is stiffening) but will not increase the concrete tensile strength

Why FRC is needed?

Plain, unreinforced concrete is a brittle material, with a low tensile strength and a low

strain capacity. The role of randomly distributes discontinuous fibers is to bridge across the cracks

that develop provides some post- cracking “ductility”. If the fibers are sufficiently strong,

sufficiently bonded to material, and permit the FRC to carry significant stresses over a relatively

large strain capacity in the post-cracking stage.

Table 1 describes different types of fibers and their properties

8

Table 1:Types of fibers and their properties

FIBER TYPE DIAMETER(0.001

in.)

SPECIFIC

GRAVITY

E, ksi x1000 TENSILE

STRENGTH

(ksi)

STRAIN AT

FAILURE, %

STEEL

HIGH TENSILE

STAINLESS

0.1-1.016 7.8 29 50-250 3.5

0.01-0.33 7.8 23.2 300 3

GLASS 2.5-2.7 10.44-11.6 360-500 3.6-4.8

POLYMERIC 0.01-0.013

POLYPROPYLENE 0.5-4.01 .9 0.5 80-110 8

POLYEHYLENE 0.025-1.016 .96 0.725-25 29-435 3-80

POLYESTER 0.01-0.076 1.38 1.45-2.5 80-170 10-50

AMARID 0.01-0.011 1.44 9-17 525 2.5-3.6

ASBESTOS 0.00002-0.03 2.6-3.4 23.8-28.4 29-500 2-3

CARBON 0.0076-0.0089 1.9 33.4-55.1 260-380 0.5-1.5

NATURAL

WOOD

CELLULOSE

0.02-0.119 1.5 1.45-5.88 44-131 3-5

SISAL <0.203 - 1.89-3.77 41-82 10-25

COCONUT COIR 0.1-0.41 1.12-1.15 2.76-3.77 17-29 -

BAMBOO 0.05-0.41 1.5 4.79-5.8 51-73 1.5-1.9

JUTE 0.1-0.2 1.02-1.04 3.7-4.64 36-51

AKWATA 1.02-4.06 0.96 0.076-0.464 -

Why coconut coir?

• Coconut coir is strong and light.

• Coconut coir can easily withstand heat.

• Coconut coir can easily withstand salt water.

• Coconut coir is an abundant, versatile, renewable, cheap .

9

• Coconut coir is Eco-friendly and available everywhere.

• Coconut coir has the lowest thermal conductivity and bulk density.

• Therefore, it is an interesting alternative which would solve environment and energy

concern.

Coconut Coir

• Coir is the fibrous material found between the hard, internal shell and the outer coat of a coconut.

• The individual fiber cells are narrow and hollow, with thick walls made of cellulose. • Fibers are typically 10 to 30 centimetres (4 to12 in) long and are consistent and uniform

in texture. • It is a completely homogenous material composed of millions of capillary micro-

sponges. • Water absorption is less as compared to other natural fibers.

Types of Coconut Coir Fibers

White fibers -White fibers are extracted from immature coconuts.

They are smooth and fine in texture but are weaker.

Brown fibers-brown fibers are extracted from matured coconuts.

They are thick, strong and have high abrasion resistance

10

Table 2: Physical Properties of Coconut Coir Fibers D

iam

eter

(mm

)

Len

gth

(mm

)

Ten

sile

stre

ng

th

(MP

a)

Elo

ng

atio

n

(mm

)

Yo

un

g‟s

mo

du

lus

Sp

ecif

ic

yo

ung

‟s

mo

du

lus

To

ug

hn

ess

Per

mea

ble

vo

id (

%)

Mo

istu

re

con

ten

t(%

)

Wat

er

abso

rpti

on

satu

rati

on

(

%)

Ela

stic

mo

du

lus(

MP

a)

Den

sity

(kg

/m³)

Ref

eren

ces

0.4-

0.10

60-

250

15-323 75 - - - - - - - - Ramakris

hna et

al.(2005a)

.21 - 107 37.7 - - - 56.6-

73.1

- 93.8-

161

2.8 110

4-

137

0

Agopyan

et al.

2005

.3 - 69.3 - - - - - - - 2 114

0

Paramasi

vam et

al.1984

- - 50.9 17.6 - - - - 10 181 - 100

0

Ramakris

hna et

al.(2005b

)

.27±

0.00

73

50±

10

142±3

6

24±1

0

- - - - - 24 2±3 - Li et al

2007

0.11-

0.53

- 108-

252

13.7-

41

- - - - - 85-135 2.5-

4.5

670

-

100

0

Toledo et

al (2005)

0.12

±0.0

05

- 137±1

1

- 3.7

±.6

4.2 21.

5±

2.4

- - - - 870 Munawar

et al.(

2007)

Table 3: Chemical Properties of Coconut Coir Fiber Fiber Hemicelluloses(%) Cellulose (%) Lignin (%) Reference

Coconut coir 31.1 32.2 20.5 Ramkrishna et

al.(2005a)

15.28 35-60 20-48 Agopyan et

al.(2005)

16.8 68.9 32.1 Asasutjarit et al

(2007)

- 43 45 Satyanarayana et

al (1990)

0.15-0.25 36-43 41-45 Corradini et al

(2006)

pH value of coconut coir is in between 6.5 and 7.0

11

Baruah and Talukdar (2007) investigated the static properties of plain concrete (PC) and coconut

fiber reinforced concrete (FRC) with different fiber volume fractions ranging from 0.5% to 2%.

Results are summarised below.

Table 4: Test results Fiber volume

fraction (% )

Compressive

strength (MPa)

Split tensile

strength (MPa)

Modulus of

rupture (MPa)

Shear

strength(MPa)

- 21.42 2.88 3.25 6.18

0.5 21.70 3.02 3.38 6.47

1 22.74 3.18 3.68 6.81

1.5 25.10 3.37 4.07 8.18

2 24.35 3.54 4.6 8.21

The scientist Ben Davis (Georgia Tech University)had a research on “Natural Fiber Reinforced Concrete” and he concluded that the addition of fibers has negligible effect on cement hydration and durability of fibers can be increased by chemical coating. And also Cellulose fibers reduce plastic shrinkage.

The scientist Reis (2006) investigated the mechanical characterization (flexural strength, fracture toughness ) of concrete reinforced with natural fibers (coconut, sugarcane bagasse and banana fibers) and gave conclusion as fracture toughness of coconut fiber reinforced concrete were higher than that of other fibers reinforced polymer concrete.And flexural strength was increased up to 25 % with coconut fiber only.

The scientists Matsuoka Shigeru (TEKKEN Corp., JPN) and Horii Hideyuki (Univ. of Tokyo, Grad. Sch.) had a research paper on fiber reinforced concrete and they concluded that in short fiber reinforced concrete, tensile stresses are transmitted in crack faces because of the bridging effect of fibers, thereby offering a higher ductility of concrete. The tensile failure characteristic, discussed in this paper, is therefore a key parameter when evaluating the properties of short fiber reinforced concrete. In addition, new application techniques of short fibers are presented here for enhancing the shear strength and seismic performance of concrete structures. These techniques resort to satisfactory crack dispersing and increased energy absorbing capabilities provided by the bridging effect of fibers.

12

3.THE PROPOSED WORK

Following types and no. of specimens were casted and tested to determine

following properties.

1. Compressive strength test

2. Split tensile strength

3. Flexural test

Table 5: Sizes of Specimen

Type of specimen Size of specimen

Length (mm) Breadth(mm) Height(mm)

Cube 150 150 150

Beam 500 100 100

Cylinder 300 Diameter=150mm

13

Table 6: No. of Concrete Specimens Casted and Tested

Description % of fiber Type of test conducted

Compression test Split tensile

strength test

Flexure test

No. of cubes No. of cylinders No. of beams

7days 28days 28days 28days

Without fiber 0 3 3 3 3

Coir fiber as

available in raw

form

0.5 3 3 3 3

1 3 3 3 3

1.5 3 3 3 3

2 3 3 3 3

3cm long fiber 0.5 3 3 3 3

1 3 3 3 3

1.5 3 3 3 3

5cm long fiber 0.5 3 3 3 3

1 3 3 3 3

1.5 3 3 3 3

Total 33 33 33 33

66 33 33

14

4 PROPERTIES OF MATERIAL USED

Material Used:-

1. Coconut coir:-

The properties of coconut coir are discussed in table 4 and table 5

2. Cement :-

Birla super 43 grade Ordinary Portland Cement.

3. Sand :-

Natural Sand

Crushed Sand

4. Aggregates:-

10 mm aggregates

20 mm aggregates

4.1 Coconut Coir Fiber:

Determination of Mechanical properties:-

Table 7: Tensile Strength of Coconut Coir Fiber

Type of fiber No of fiber Average

diameter of

fiber

Total load

taken

Tensile

strength

Stress/strain

Coconut wire

26 0.42 mm 245.2 N 68.07 MPa 3.72Pa

4.2 Cement:

4.2.1 Fineness of Cement

Fineness of cement was tested by sieving 100 gms of cement through I.S.Sieve No. 9

Cement to Sand ratio is 1:3

Table 8: Properties of BIRLA SUPER 43 Grade OPC

Test performed

Results obtained IS:12269-1999

FINENESS 7% NOT MORE THAN

10%

Results:-

The properties of Birla Super 43 OPC cement satisfy the IS:12269-1999 specifications.

15

4.2.2 Consistency of Cement

Table 9: Results for Consistency of Cement

Wt. of cement

(gm)

% of water Quantity of water

(ml)

Reading on Vicat‟s

Apparats

(penetration)measured

from top (mm)

400

40 160 38

400

38 152 36

400

36 144 35

Results:

The results obtained are within permissible limits specified by IS12269-1999

4.2.3 Initial and Final Setting Time:

Table 10: Initial & Final Setting Time Test performed Result obtained Requirement as per IS:12269-

1999

Initial setting time

1 Hr. 10 min. Not less than 30 min.

Final setting time

5 Hr. 20 min. Not more than 10 Hrs.

Results: The results obtained are within permissible limits specified by IS12269-1999

16

4.2.4 Compressive Strength of Cement

Table 11: Compressive Strength of Cement Compressive strength of cement in MPa Average

strength(MPa)

Remarks

3 days

22.35 26.01 Not less than

22 N/ mm²

3 days

29.2

3 days

26.5

7 days


30 N/mm²

7 days

34.93

7 days

32.05

28 days


43 N/ mm²

28 days

45.56

28 days

47.89

Results:

The results obtained are within permissible limits specified by IS12269-1999

4.3 Sand:

Fineness Modulus

For determination of fineness modulus, 1kg of sample was sieved through the IS

sieves given in following tables.

Fineness Modulus is then calculated as cumulative % retained divided by 100.

17

4.3.1 Natural Sand

Table 12: Sieve Analysis Results IS sieve Weight

retained

(kg)

Cumulative

Weight

retained

(kg)

Cumulative

% retained

Cumulative

% passing

Zone 2

Grading

Limits

IS383-2002

4.75mm

0 0 0 100 100

2.36mm

0.063 0.063 6.30 90.90 90-100

1.18mm

0.118 0.181 18.10 51.60 75-100

600µ

0.121 0.302 30.20 36.80 55-90

300 µ

0.189 0.491 49.10 23.80 35-59

150 µ

0.449 0.940 94.00 18.90 8-30

75 µ

0.085 1.025 100 0 0-10

pan

1.025 297.70

Results:

Fineness Modulus of natural sand is

297.7/100 = 2.97

18

4.3.2 Crushed Sand

Table 13: Sieve Analysis Results

IS sieve Weight

retained

(kg)

Cumulative

Weight

retained

(kg)

Cumulative

% retained

Cumulative

% passing

Zone 2

Grading

Limits

IS383-

2002

4.75mm

0 0 0 100 100

2.36mm

0.081 0.081 8.10 91.90 90-100

1.18mm

0.138 0.219 21.90 78.10 75-100

600 µ

0.121 0.340 34.00 66.00 55-90

300 µ

0.179 0.520 52.00 48.00 35-59

150 µ

0.409 0.930 93.00 7.00 8-30

75 µ

0.077 1.005 100 0.00 0-10

1.005 309

Result:

Fineness Modulus of crushed sand is

309/100 = 3.09

4.4 Aggregates:

Similarly, Fineness Modulus of aggregates has been obtained as shown in following

table.

Table 14: Properties of Aggregates Material

Fineness modulus Specific gravity

10 mm aggregates

9.35 2.92

20 mm aggregates

9.07 2.88

19

5 CONCRETE MIX DESIGN

Mix design methodology:

Normal concrete was designed using IS Code method.

Mix designing of coconut fiber reinforced concrete was carried out using

same IS Code method with certain modifications.

1] Target Mean Strength:

For M 20 grade of concrete S = 4.00

Target mean strength = fck + (1.65× S)

= 20 + (1.65 × 4.00)

= 26.6 MPa.

2] Determination of W/C Ratio:

Refer Fig., as grade of cement (28days strength) is 43 N/mm2

considering curve C, for target

mean strength of 26.6 N/mm2

corresponding W/C ratio is 0.49. This is lower than maximum value

of 0.55 prescribed for 'Mild' exposure.

Fig.1 Relation between Free Water-Cement Ratio and Concrete Strength at 28 Days for

different Cement Strengths.

Adopt W/C ratio 0.49.

20

Table 15: Minimum cement content, maximum W/C ratio and minimum grade

of concrete for different exposures with normal weight aggregates of 20 mm

nominal maximum size, IS 456-2000.

Exposure Plain

Concrete

Reinforced

Concrete

Min.

Cement

content

Max.

Water

cement

ratio

Min. grade

of

concrete

Min.

cement

content

Max.

Water

cement

ratio

Min. grade

of

concrete

Mild 220 0.6 - 300 0.55 M 20

Moderate 240 0.6 M15 300 0.50 M 25

Severe 250 0.50 M 20 320 0.45 M 30

Very

Severe

260 0.45 M20 340 0.45 M35

Extreme 280 0.40 M 25 360 0.40 M 40

3] Determination of water and Sand content:

For 20mm maximum size aggregate and sand conforming to zone II, from Table (1). Water

content per cubic meter of concrete = 186 kg.

Sand content as percent of total aggregate by absolute volume = 35percent.

These two values are for water cement ratio of 0.6 and for compacting factor of 0.80.For water

cement ratio of 0.49 and compacting factor of 0.85 adjustments are carried out using Table (2).

21

Table 16: Approximate Sand and Water Contents per cubic meter of Concrete

A) W/C = 0.60 Workability=0.80 C.F Concrete up to grade M35

B) W/C = 0.35 Workability=0.80 C.F Concrete above grade M35

Maximum size of

Aggregate

Water content

including surface

water per cubic meter

of concrete

(kg)

Sand as percent of

total aggregate by

absolute volume.

10 208 40

20 186 35

40 165 30

22

Table 17: Adjustment of Values in Water Content and Sand Percentage for

Other Conditions

Change in conditions

Stipulated for table no.

17

Adjustments required in

Water Content percent Sand in total

aggregate

For sand conforming

grading zone I, Zone III or

Zone IV of table 4, IS 383-

1970

0

+1.5percent for Zone I

-1.5percent for Zone III

-3percent for Zone IV

Increase or decrease in the

value of compacting factor

by 0.1

±3.0percent 0

Each 0.05 increase or

decrease in water cement

ratio

0 ±1.0percent

For rounded aggregate

-15 Kg/m3 -7.0percent

Table 18

Sr.

No.

Change in

Condition

Percent adjustment required

Water

content

Sand in Total

aggregate

1 For decrease in water cement ratio by (0.6-0.49) =

0.11

0 -0.11/0.05×1

= - 2.2percent

2 Increase in

compacting factor

By (0.85-0.8) = 0.05

0.05/0.1×3

=+1.5percent

0

Overall adjustment +1.5percent - 2.2 percent

23

Finial values after adjustments

Sand = 35.00 - 2.2=32.8

Water content = 186 + 186 × (1.5/100)=188.80 liters

4] Cement Content:s

Water content/ water cement ratio = 188.8 / 0.49 = 385.30 kg.

This is greater than minimum cement content required for mild exposure condition that is 300

kg/m3 and less than maximum limit i.e. 450 kg/m

3

Hence adopt cement content=385.30 kg/m

3

5] Quantities of Coarse Aggregate and Fine Aggregate:

Entrapped air percent for 20mm size aggregate = 2.0percent

Volume of concrete = 1 - 0.02 = 0.98 cu.m.

Volume of fine aggregate:

V=[W+(C/Sc)+(1/P) (fa/ Sfa)] 1/1000

0.98 = {188.8 + (385.3/3.15) + (FA/(0.328×2.94))} × 1/1000

FA = 693.63 kg / m3

Volume of Coarse Aggregate:

Ca=(1 – P)/P fa (Sca / Sfa)

0.98= {188.8 + (385.3/3.15) + (CA/((1-0.328) × 2.92))} × 1/1000

CA = 1311.01 kg / m3

6] Combining the aggregate to obtain specified grading:

First trial = Assuming 60percent Coarse aggregate 20mm

40percent Coarse aggregate 10mm

Fraction of Sand = 1

In our case Coarse Aggregate 20mm = 755.14 kg/m3

Coarse Aggregate 10mm = 503.42 kg/m3

24

Fraction of Coarse aggregate 20mm = 755.14/598.94 = 1.260

Fraction of Coarse aggregate 10mm = 503.42/598.94 = 0.840

Table 19

Sieve size

(mm)

Sand

* 1

20mm

*1.260

10mm

*0.840

Combined grading

1+2+3/(1+1.260+0.840)

Specified combined grading

40.00 100 126.00 84.0 100.00 100

20.00 100 106.75 84.0 93.79 95-100

4.75 93.8 0 0 30.55 30-50

0.60 47.8 0 0 15.55 10-35

0.15 1 0 0 0.328 0-6

As seen from Table, Combined grading of given coarse and fine aggregate satisfies the specified

combined grading given by IS.

Table 20: Final Proportions for M20: BY IS METHOD

Cement Sand 10mm 20mm Water

385.30 kg/m^3 693.63 kg/m3 755.14 kg/m3

503.42 kg/m3 188.80 liters/ m3

1 1.533 1.96. 1.306 0.49

Natural crushed

0.6 0.933

Number of specimen were cast as per table 4 and table 5 for testing of concrete.

25

6 Test program

Following teats were conducted on plain cement concrete and coconut coir

reinforced concrete

Tests on concrete:-

1. Workability of concrete

2. Compressive strength of concrete

3. Split tensile strength of concrete

4. Flexural strength of concrete

6.1 Workability of concrete

References: 1) IS:7320-1974 Specifications for concrete slump test

2) IS: 6461-Part 10- Compaction factor test apparatus.

3) IS: 1199-1959 Methods of sampling and analysis of concrete.

Introduction:

Workability of concrete is the ease with which concrete can be mixed, transported, placed,

compacted and finished to get dense and homogeneous mass of concrete. It is the amount of

useful internal work necessary to produce full compaction. The work done is to overcome the

internal friction between the individual particles in the concrete and between concrete and the

mould or surface of reinforcement.

Concrete must have workability, such that it can be compacted to maximum density with

reasonable amount of work. The strength of concrete is significantly and adversely affected by the

presence of voids in the compacted mass therefore it is vital to achieve maximum possible

density. This requires a significant amount of workability for virtually full compaction to be

possible using a reasonable amount of work under the given conditions. The presence of voids in

the concrete greatly reduces the density and the strength; five percent of voids can lower the

strength by as much as thirty percent.

Workability of concrete is governed by water content, chemical composition of cement and its

fineness, aggregate/cement ratio in concrete, size and shape of aggregate, porosity, water

absorption of aggregates, use of admixtures etc. More use of water facilitates easy placing and

compaction of concrete.however,it may cause bleeding. The designed degree of workability (low,

very low, medium, high, very high) depends upon the several factors such as methods of mixing,

methods of compaction, size and shape of structure amount of reinforcement, hence a concrete

mix suitable for one work may prove to be too stiff or too wet for another work on the same site.

The workability of concrete is measured by various methods, which are as follows:

1) Slump Cone test.

26

A) Slump cone test:

This test is extensively used on site. The test is very useful in detecting variations in uniformity of

a mix for a given nominal proportion. This test shows behavior of compacted concrete under the

action of gravitational field. Slump occurs due to self-weight of concrete. There is no external

energy supplied for the subsidence of concrete.

Fig 2 slump cone apparatus

Apparatus:

Slump cone (bottom diameter 200 mm, top diameter 100 mm and height 300 mm), standard

tamping rod l6 mm in diameter and 600 mm in length along with bullet end.

27

Table 21:Workability test results

Fig 3 Comparison of workability for different types and percentages of fibers

0

10

20

30

40

50

60

70

1 2 3 4

PLAIN

3 cm

5 cm

LONG FIBERS

Length of fiber %of fiber Workability

long 0.5 50

1.0 38

1.5 16

2.0 05

3cm 0.5 55

1.0 48

1.5 30

5cm 0.5 53

1.0 42

1.5 24

Without fiber 0 60

28

6.2 Compressive Strength

Object: To determine the compressive strength of concrete.

References: IS : 516 – 1959 Methods of tests for strength of concrete.

Introduction:

Concrete is very widely used in variety of structures. Among the many properties of concrete, the

compressive strength of concrete is considered to be most important and useful property. It has

been held as an index of its overall properties. Although in some cases, the durability and

impermeability of concrete may be more important, yet, compressive strength is directly or

indirectly related to other properties viz. tensile strength, shear strength, resistance to shrinkage,

young‟s modulus, etc. Thus, compressive strength reflects overall quality of concrete and hence, it

is graded according to its compressive strength. Compressive strength of concrete can be found by

destructive and non-destructive tests. Following procedure is for destructive testing. Concrete

attains its maximum strength at the end of 28 days. Therefore, on the basis 28 days strength, the

grade of concrete is defined such as M20, M25, etc. The letter „M‟ stands for 'mix' and number

denotes the compressive strength of concrete at the end of 28 days. The lean grade of concrete

like M5, M10, M15, etc are used for plain concrete construction works, whereas the grades M20,

M25, M30 and M35 are used for reinforced concrete construction. Further, for prestressed concrete

construction grades higher than M35 are recommended.

Materials and Equipments:

Six cube moulds, tamping rods, scoop trowels, spades, weighing balance (accuracy of 0. 1percent

of total weight of batch), vibrating platform, compression testing machine of capacity of 3000 kN.

Test specimen cubical in shape should be of size 150 mm x 150 mm x 150 mm. If the largest size

of aggregate does not exceed 20 mm, 100 mm size cubes may be used as an alternative.

`Diagram:

Figure 4 : Concrete Cube under Compression

P

Concrete Cube

29

Procedure:

1) Select a suitable proportion of ingredients of concrete. The quantity of cement, coarse and

fine aggregates and water for each batch shall be determined by weight to an accuracy of

0.1percent of total weight of the batch.

2) The concrete shall be mixed in a concrete mixer. Hand mixing is not recommended by IS

specification. However, under unavoidable condition, hand mixing may be done and it

shall be done on a watertight non-absorbent platform as follows:

a) The cement and fine aggregates shall be mixed dry until they uniformly blend into

a uniform colour.

b) The coarse aggregates shall be added to the above dry mix and mixed until they are

uniformly distributed in the batch.

c) Water shall then be added and the entire batch is mixed until concrete appears to be

homogeneous and has the desired workability.

3) While assembling the moulds, the joints of mould shall be tightened sufficiently, in order

to ensure that no slurry escapes during filling. The inner surfaces of assembled mould

should be given a thin coat of oil to prevent the adhesion of concrete.

5) After mixing is complete, the concrete shall be filled in the cubes. If the concrete

segregates, such batch should be discarded and the test be repeated. The concrete shall be

filled in the mould using a trowel in three layers of approximately 5 cm thickness. By

using a trowel, the layer of filled concrete inside the mould should be spread uniformly.

The tamping should be done by a standard tamping rod of length 600 mm, and 16 mm in

diameter with a bullet head at one end. Each layer shall be given 35 strokes in case of the

150 mm size cube moulds. The strokes shall penetrate in the lower layer.

6) After the top layer has been compacted, the surface of concrete shall be finished leveled

with the trowel. The identification mark is labeled on the top surface of the specimen.

7) The filled moulds are placed on the vibrating table and vibrated till a thin film of water

appears on the top. The test specimen shall be stored in moist air with 90percent relative

humidity and at a temperature of 27˚ C ± 2˚C for 24 hours from the time of addition of

water to dry ingredients.

8) After 24 hours, the specimens are removed from the moulds and then immersed into water

in a water tank. The cubes are then tested after 7 and 28 days. Before testing the cube

specimens, the dimensions and weight of cubes are noted. Three specimens are tested for

compression and the average strength of these is the compressive strength of concrete.

Each specimen is placed in between the loading platen such that the top face of cube while

casting becomes the vertical while loading. The load is applied at the rate of 14 N/sq mm

until the specimen fails.

9) The average maximum load shown on the appropriate dial of the compression-testing

machine is noted.

Compressive strength = Crushing load of specimen / cross sectional area

Average of three values shall be taken as a representative of batch.

30

Table 22: 7 days compressive strength of plain concrete cubes

Load(kN) Stress(N/mm²) Deformation (mm)

Cube1 Strain Cube2 Strain

50 2.22 1.1 0.0073 1.12 0.0075

100 4.44 1.3 0.0086 1.4 0.0093

150 6.66 1.4 0.0093 1.66 0.011

200 8.88 1.55 0.01 1.84 0.012

250 11.1 1.66 0.011 2.08 0.0138

300 13.32 1.9 0.013 2.27 0.015

350 15.54 2.2 0.015 2.45 0.016

400 17.76 2.3 0.0153 2.63 0.0175

450 19.98 2.66 0.018 3 0.02

500 22.2 3 0.02 3.17 0.0.21

550 24.42 3.15 0.021 3.45 0.023

600 26.64 3.35 0.022 1.12 0.0074

Failure 580kN 600kN

Fig.5 stress vs strain for 7 days compressive strength of plain concrete

0

5

10

15

20

25

30

0 0.005 0.01 0.015 0.02 0.025

stress vs strain for 7 days compressive strength

stress vs strain for 7 days compressive strength

31


0

5

10

15

20

25

30

0 2 4 6 8 10 12 14

stress vs strain

stress vs strain

32

Table 23: 28 days compressive strength of plain concrete cubes

Load(kN) Deformation (mm)

Cube1 Cube2 Cube3

50 0.2

0.81 0.9

100 0.6

1.05 1.05

150 1

1.23 1.11

200 1.3

1.4 1.12

250 1.32

1.49 1.12

300 1.42

1.65 1.12

350 1.52

1.8 1.12

400 1.64

1.91 1.12

450 1.82

2.2 1.23

500 2

2.32 1.5

550 2.32

2.55 2.14

600 2.65

2.7 2.14

650 3

2.85 3

700 0 3.1 3.52

750 0 3.42 3.78

800 0 4.1 3.9

Failure 650kN 780kN 790kN

33



0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02 0.025

stress vs strain(28 days plain concrete)


0

5

10

15

20

25

30

35

40

0 0.01 0.02 0.03



34


Table 24: Comparison of 28 days strength using 5cm long fibers (aspect

ratio=50/0.4)

% of coconut fiber Compressive

strength (MPa)

Split tensile

strength(MPa)

Flexural

strength(MPa)

Stress/strain

(GPa)

0 32.88 2.95 4.8 1.63

0.5 34.22 3.16 5.6 1.64

1 34.66 3.11 5.86 1.62

1.5 35.40 3.16 6.13 1.68

0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02 0.025 0.03


35

Fig 10 compressive strength vs % of fiber

Table 25:Comparison of 28 days strength using 3cm long fibers


strength

(MPa)

Stress/strain

(GPa)

0 32.88 1.63

0.5 32.75 1.61

1 33.03 1.65

1.5 33.77 1.67

32.5

33

33.5

34

34.5

35

35.5

36

0 0.5 1 1.5 2

compressive strength vs % of fiber


32.8

32.9

33

33.1

33.2

33.3

33.4

33.5

33.6

33.7

33.8

33.9

0 0.5 1 1.5 2



36

Fig.11 compressive strength vs % of fiber

37

Table 26: 7 days compressive strength of 1% coconut coir fiber (long fiber) reinforced concrete cubes


Cube1 Cube2 Cube3

50 1 0.1

0.15

100 1.2 0.12

0.27

150 1.4 0.15

0.33

200 1.55 0.18

0.34

250 1.6 0.2

0.34

300 1.65 0.26

0.34

350 1.71 0.28

0.34

400 1.79 0.35

0.34

450 1.82 0.42

0.34

500 1.87 0.52

0.34

550 1.9 0.65

0.34

600 1.92 0.78

0.34

650 1.97 1.03

0.34


38

Fig.12 stress vs strain

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015

stress vs strain

stress vs strain

39

Table 27: 28 Days Compressive Strength of 1% Long Coconut Coir Fiber

Reinforced Concrete Cubes


Cube1 Cube2 Cube3

50 0.4 0.3 0.2

100 0.45 0.35 0.3

150 0.49 0.45 0.35

200 0.54 0.56 0.4

250 0.6 0.6 0.45

300 0.7 0.68 0.5

350 0.95 0.95 0.55

400 1.09 1.1 0.59

450 1.6 1.5 0.64

500 1.75 1.5 0.7

550 2 1.8 0.85

600 2.28 2.1 0.98

650 2.5 2.3 1.2

700 2.85 2.5 1.24

750 2.85 2.9

Failure 760 750 680

40

Fig.13 stress vs strain

Fig 14 stress vs strain

0

5

10

15

20

25

30

35

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02 0.025

stress vs strain

stress vs strain

41



0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02 0.025

stress vs strain

stress vs strain

0

5

10

15

20

25

30

35

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

42

Table 28:7 days compressive strength of 0.5% long coconut coir fiber reinforced

concrete cubes


Cube1 Cube2 Cube3

50 0 0.45

100 0.5 0.52

150 0.56 0.54

200 0.67 0.57

250 0.92 0.6

300 1.1 0.65

350 1.3 0.7

400 1.62 0.75

450 1.78 0.82

500 2 0.87

550 2.38 1


43



0

5

10

15

20

25

30

0 0.5 1 1.5 2 2.5

stress vs strain

stress vs strain

0

5

10

15

20

25

30

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

44

Table 29: 28 days compressive strength of 0.5% long coconut coir fiber reinforced

concrete cubes


Cube1 Cube2 Cube3

50 0.1 0 ---

100 0.34 --- ---

150 0.42 --- ---

200 0.5 --- ---

250 0.6 --- ---

300 0.65 --- ---

350 0.67 --- ---

400 0.68 --- ---

450 0.69 --- ---

500 0.7 --- ---

550 0.71 --- ---

600 0.71 --- ---

650 0.71 --- ---

700 0.71 --- ---

750 0.71 --- ---


45


Table30:7 days compressive strength of 2% long coconut coir fiber reinforced

concrete cubes


Cube1 Cube2 Cube3

50 0.07 0 0.15

100 0.15 0 0.25

150 0.35 0 0.5

200 1 0 0.7

250 1.45 0.05 0.9

300 2 0.15 1.05

350 2.9 0.2 3.5

400 5 0.25 ---

450 --- 0.4 ---

500 --- 0.7 ---

550 --- 1.05 ---

Failure 500 505 350

0

5

10

15

20

25

30

35

0 0.001 0.002 0.003 0.004 0.005

stress vs strain

stress vs strain

46



0

2

4

6

8

10

12

14

16

18

20

0 0.01 0.02 0.03 0.04

stress vs strain

stress vs strain

0

5

10

15

20

25

30

-0.002 0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

47


0

2

4

6

8

10

12

14

16

18

0 0.005 0.01 0.015 0.02 0.025

stress vs strain

stress vs strain

48

Table31:28 days compressive strength of 2% long coconut coir fiber reinforced

concrete cubes


Cube1 Cube2 Cube3

50 0.05 0.07 0.5

100 0.09 0.05 1.72

150 0.12 0 2.5

200 0.12 0.05 2.97

250 0.12 0.1 3.25

300 0.12 0.19 3.45

350 0.12 0.25 3.64

400 0.12 0.36 3.84

450 0.12 0.5 4

500 0.41 0.68 4.35

550 1.1 1.12 5


49



0

5

10

15

20

25

30

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

0

5

10

15

20

25

30

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

50


0

5

10

15

20

25

30

0 0.01 0.02 0.03 0.04

stress vs strain

stress vs strain

51

Table 32: 5 cm 7 days 1%

LOAD

DEFORMATION(mm)

CUBE1 CUBE2 CUBE3

50 0.26 0.21 0.25

100 0.28 0.25 0.27

150 0.35 0.29 0.31

200 0.42 0.31 0.39

250 0.52 0.41 0.45

300 0.65 0.53 0.6

350 0.78 0.72 0.75

400 1.03 0.97 1

450 1.06 1.01 1.05


0

5

10

15

20

25

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

52



0

5

10

15

20

25

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

0

5

10

15

20

25

0 0.002 0.004 0.006 0.008

stress vs strain

stress vs strain

53

Table 33: 5CM 1% 28 DAYS

LOAD

DEFORMATION(mm)

CUBE1 CUBE2 CUBE3

50 0.3 0.35 0.25

100 0.35 0.45 0.39

150 0.45 0.57 0.49

200 0.56 0.65 0.68

250 0.6 0.8 0.79

300 0.68 0.9 0.9

350 0.95 0.91 0.93

400 1.1 0.95 0.97

450 1.5 0.97 0.97

500 1.5 1.1 1.2

550 1.8 1.3 1.25

600 2.1 1.35 1.35

650 2.3 1.4 1.39

700 2.5 1.7 1.9

750 2.9 1.9 2.1

800 3.1 --- 2.5

54

Fig 30 Stress vs Strain


0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02 0.025

stress vs strain

stress vs strain

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015

stress vs strain

stress vs strain

55


0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

56

Table34: 3cm 1% 7 days

LOAD

DEFORMATION(mm)

CUBE1 CUBE2 CUBE3

50 0.28 0.25 0.28

100 0.4 0.3 0.35

150 0.45 0.44 0.49

200 0.53 0.52 0.55

250 0.67 0.65 0.67

300 0.72 0.73 0.75

350 0.82 0.85 0.83

400 1.15 1.1 1.15

450 1.25 1.15 1.2

500 1.3 1.35 1.32


0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

57



0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

58

Table 35: 3cm 1% 28 days

LOAD

DEFORMATION(mm)

CUBE1 CUBE2 CUBE3

50 0.35 0.43 0.3

100 0.47 0.45 0.45

150 0.52 0.55 0.58

200 0.65 0.68 0.66

250 0.75 0.73 0.79

300 0.85 0.87 0.89

350 0.97 0.98 0.95

400 1.07 1.05 1.06

450 1.2 1.3 1.25

500 1.6 1.7 1.3

550 1.9 1.8 1.6

600 2.2 1.85 1.9

650 2.3 1.95 2.1

700 2.35 2.15 2.2

750 2.5 2.3 2.4

800 2.6 2.55

59



0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

60



0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

61

Table 36: 5CM 0.5% 7 DAYS

LOAD

DEFORMATION(mm)

CUBE1 CUBE2 CUBE3

50 0.21 0.25 0.3

100 0.25 0.3 0.4

150 0.29 0.44 0.5

200 0.31 0.52 0.63

250 0.41 0.65 0.73

300 0.53 0.73 0.8

350 0.72 0.85 0.93

400 0.97 1.1 1.01

450 1.01 1.15 1.15

500 1.3 1.35 1.3


0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

62



0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

63


0

5

10

15

20

25

0 0.002 0.004 0.006 0.008 0.01

stress vs strain

stress vs strain

64

Table 37: 5CM 0.5% 28 DAYS

LOAD

DEFORMATION(mm)

CUBE1 CUBE2 CUBE3

50 0.37 0.5 0.6

100 0.45 0.6 0.65

150 0.55 0.65 0.72

200 0.66 0.7 0.75

250 0.76 0.8 0.82

300 0.87 0.92 0.97

350 0.97 1.05 1.07

400 1.06 1.1 1.12

450 1.25 1.35 1.25

500 1.5 1.6 1.38

550 1.8 1.85 1.51

600 1.98 2.1 1.64

650 2.12 2.35 1.77

700 2.23 2.6 1.9

750 2.4 2.85 2.03

800 2.57

0

5

10

15

20

25

30

35

40

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

65




Conclusion:

Compressive strength of fiber reinforced concrete has increased with increase in % of fiber up to

certain % of fiber. In our case this optimum % is 1.5%. Beyond this if we increase % fiber

compressive strength decreases.

For small aspect ratio compressive strength is higher than high aspect ratio fiber reinforced

concrete. In our case for aspect ratio 75, compressive strength is high.

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02

stress vs strain

stress vs strain

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015

stress vs strain

stress vs strain

66

Comparison of Young’s Modulus

% of fiber 5 cm Long Fiber 3 cm Long Fiber Long Fiber

0 1.63 1.63 1.63

0.5 1.64 1.61 1.65

1 1.62 1.65 1.68

1.5 1.68 1.67 1.71

1.56

1.58

1.6

1.62

1.64

1.66

1.68

1.7

1.72

0 0.5 1 1.5

5 cm long fiber

3 cm long fiber

long fiber

67

6.3 Split tensile strength

Objective: To determine the Split tensile strength of concrete.

Reference: IS 5861-1970 Method of test for split tensile strength of concrete.

Introduction: The tensile strength of concrete can be obtained indirectly by compressing the

concrete cylinder ( kept in horizontal position ) between the platens of the compressive testing

machine. The knowledge of tensile strength of concrete is required for the design of structural

concrete elements subjected to transverse shear, torsion, shrinkage etc. The tensile strength is also

useful in design of prestressed concrete structures, concrete roads, etc. As the direct tensile strength

is difficult to find, the split tensile strength is normally used, and it can be determined as,

ft = 2P/πDL

Where, ft ─ Split tensile strength of concrete in N/mm 2

P─ Load at failure in N.

D─ Diameter of cylinder = 150 mm.

L─ Length of cylinder = 300 mm.

Since the test cylinder splits vertically into two halves, this test is known as splitting test.

Materials and Equipments: Compression testing machine, standard cylinder moulds, and

plywood strips of size, 8 mm x 12 mm x 300 mm. Cement, sand, aggregates and water, etc.

Test specimen: The specimen shall be cylindrical with the diameter not more than four times the

maximum size of coarse aggregate and not less than 150 mm. The length of specimen shall be

300mm.

68

Diagram: P

(a) Concrete Cylinder before testing (b) Concrete Cylinder after testing

Figure 40: Split Tensile Test Setup

Procedur

1) Concrete cylinders are cast by adopting suitable proportions of cement, sand and aggregates with

suitable water cement ratio.

2) The cylinders are cured in water for 28 days. Prior to testing they are taken out of water and the

excess water is removed from the surfaces of cylinder.

3) Concrete cylinder in horizontal position is placed in between the platens of the compressive

testing machine, along with the plywood packing at top and bottom.

4) Load is applied gradually, till the concrete cylinder fails.

5) Repeat the procedure for remaining cylinders and finally calculate the indirect tensile strength of

concrete.

Table38 Observation table:

% of coconut fiber Split tensile strength(MPa)

Using long fibers Using 5cm fibers Using 3 cm fibers

0 2.95 2.95 2.95

0.5 3.07 3.11 3.06

1 3.14 3.15 3.16

1.5 3.25 3.20 5.86

2 3.27

69

Fig.47 split tensile strength vs % of fiber using long fibers

Fig.48 split tensile strength vs % of fiber using 5cm long fibers

2.9

2.95

3

3.05

3.1

3.15

3.2

3.25

3.3

0 0.5 1 1.5 2 2.5

split tensile strength vs % of fiber(long fiber)

split tensile strength vs % of fiber

X -axis: % of fiber Y-axis: split tensile strength

2.9

2.95

3

3.05

3.1

3.15

3.2

3.25

0 0.5 1 1.5 2

split tensile strength vs % of fiber (5cm)

split tensile strength vs % of fiber

70

Fig.49 split tensile strength vs % of fiber using 3cm long fibers

Conclusion:

Addition of coconut coir fiber in concrete causes increase in split tensile strength of member, as

volume fraction of fiber increases there is increase in split tensile strength and vice versa.

0

1

2

3

4

5

6

7

0 0.5 1 1.5 2

split tensile strength vs % of fiber(3cm)

split tensile strength vs % of fiber(3cm)

71

6.4 Flexural strength

Object: To determine the flexure Strength (Modulus of Rupture) of Concrete.

References:

1) IS:516 - 1959; Method of test for strength of concrete.

2) IS:9399 - 1979; Specification for apparatus for flexure testing of concrete.

Introduction:

Concrete is quite strong in compression and, comparatively weak in tension. Hence in most of the

design of concrete structures, its tensile strength is completely ignored. However, at certain situations

like, water retaining and pre-stressed concrete structures, the tensile strength of concrete is an essential

requirement and the study of tensile strength carries the importance. Tensile cracking may occur due to

shrinkage, corrosion of steel in concrete, temperature gradient etc. Tensile strength of concrete is closely

related to its compressive strength but there is no simple proportional relation between the two. A direct

application of pure tensile stress is difficult. An indirect way is adopted by measuring the flexure

strength of a beam. The theoretical maximum stress reached at bottom fiber is known as modulus of

rupture.

The flexural tensile strength of concrete is related to its compressive strength in IS:456 – 2000, by a

formula, fcr = 0.7√fck .

This property is useful in evaluating cracking moment in water retaining structures and pre-stressed

concrete beam, etc.

Equipments:

6 metal mould (inner dimensions 100x100x500 mm-cube or 150x150x700 mm), tamping rod

(weight 2 kg, 40 cm. long and shall have a running face 25 mm-sq.), Universal Testing Machine,

with attachment of two point-loading, c-clamp, spade, trowels.

Materials:Cement, fine aggregates, coarse aggregates, water, etc.

Size of specimen:

The standard size shall be, 100 mm x 100 mm x 500 mm used.

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Diagram : P Rigid plate

Roller

Concrete Beam

Span L

L/3 L/3 L/3

Figure 50: Flexural Test Setup

Procedure:

1. Measure the materials by weigh balance. Prepare concrete (e.g. M20 ) by taking water cement ratio

0.5. Apply oil to the inner faces of the beam mould.

2. Fill the moulds with fresh concrete in layers of 5-cm depth. The strokes of tamping rod shall be

well distributed.

3. Place the filled mould on vibrating table. Give the vibrations for a maximum period of 2

minutes. If a thin film of water is observed at the top, the vibrations should be stopped

before 2 minutes.

4. Cover the freshly filled mould by wet gunny bag, remold the specimen after 24 hours, and

place them in a water tank for curing.

5. Test specimens which are stored in water at a temperature of 24 3 shall be tested

immediately on removal from water. Three specimens shall be tested each at the end of three

and seven days. The dimension of each specimen should be noted before the testing.

6. The specimen shall then be placed in the machine in such a manner that the load shall be

applied to the uppermost surface as cast in the mould. The specimen shall be supported on 38

mm dia. roller with 600 mm span for 150 mm size specimen and 400 mm span for 100 mm

size specimen.

7. The load shall be applied through two similar rollers mounted at the third points of the

supporting span, that is spaced at 200 mm or 133 mm c/c. The spacing of the two load

application points at top of specimen is 200mm for a specimen size of 150 mm x 150 mm x

700 mm and or 133 mm for 100 mm x 100 mm x 500 mm. The loading arrangement

employed for the test as shown in figure 10.1. The axis of the specimen shall be carefully

aligned with the axis of loading device.

8. The load is applied without shock at a rate of 4 kN/minute for 150 mm specimen and 1.8

kN/minute for 100 mm specimen. The load shall be increased until the specimen fails and the

maximum load applied to the specimen during the test shall be recorded.

9. If the line of rupture occurs in the middle third, the modulus of rupture is given by fcr=

PL/(bd2)

10. In case line of rupture lies outside the middle third at a distance „a‟ from the

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support , then modulus of rupture is given by,

fcr = 3P*a/bd2

If „a‟ is less than 170 mm for 150 mm specimen, or less than 110 mm for 100 mm specimen,

the results of the test shall be discarded.

The flexural stress of specimen shall be expressed as the modulus of rupture, fcr.

fcr = ( M/l)*y

= PL/bd2

Where;

P = Applied load in N

b, d, are the width and depth of the beam respectively in mm.

L = Span of beam in mm.

Table39: observation table of coconut fiber Flexural strength(MPa)

Using long fibers Using 5cm fibers Using 3 cm fibers

0 4.8 4.8 4.8

0.5 5.07 5.6 5.07

1 5.33 5.86 5.6

1.5 5.86 6.13 5.86

2 4.53

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Fig.51 flexural strength vs % of fiber using long fiber

Fig.52 flexural strength vs % of fiber using 5cm long fiber

0

1

2

3

4

5

6

7

0 0.5 1 1.5 2

flexural strength vs % of fiber


0

1

2

3

4

5

6

7

0 0.5 1 1.5 2 2.5



75

Fig.53 flexural strength vs % of fiber using 3cm long fiber

Conclusion:

Addition of coconut coir fiber in concrete causes increase in flexural strength of member. As

volume fraction of fiber increases there is increase in flexural strength and vice versa.

0

1

2

3

4

5

6

7

0 0.5 1 1.5 2



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7 DISCUSSION

Following problems were observed while performing the tests

1. Separation of Fibers: for good mixing of coconut coir fibers in concrete, the fibers

need to separate from each other. Though this work was on minor scale the fibers were

very difficult to separate.

2. Balling of Fibers: when we used long fibers (i.e. fibers with high aspect ratio), the

problem of balling was observed during mixing of concrete. Due to more length of fibers,

they were tangled with each other and did not mix with concrete.

3. Difficulties in Mixing: when we used fibers with high aspect ratio, machine mixing of

concrete was very difficult due to balling. Hand mixing of concrete was also difficult

because of bunch of the fibers

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8 CONCLUSION

Following conclusions are made after performance of the tests and analysis of the results.

1. Compressive strength of concrete is decreased while using long fibers.

2. Compressive strength of concrete is increased while using short fibers (i.e. fibers with

low aspect ratio) up to 0.5%

3. Flexural strength of concrete is increased using any type of coconut coir fiber

4. Split tensile strength of concrete is also increased

Compressive strength of concrete is more than plane concrete for 0.5 % of coconut coir

fiber. As increase in volume fraction there is considerable decrease in compressive

strength,

Addition of coconut coir fiber in concrete causes increase in split tensile strength of

member. As volume fraction of fiber increases there is increase in split tensile strength and

vice versa

Addition of coconut coir fiber in concrete causes increase in flexural strength of member.

As volume fraction of fiber increases there is increase in flexural strength and vice versa.

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9 FUTURE SCOPE

As coconut coir is available almost in every part of the world and is having less cost, it can be

used in rural construction works. It can also be used in water retaining structures. It is economical,

easily available. There is lot of scope for research in applications of coconut coir fiber.

The coconut coir fiber has a good tensile strength, therefore it is best suitable in water

retaining structures. Because, water retaining structures are subjected to alternate compression and

tension.

The coconut coir fibers can also be used as a low cost construction product in rural

development projects.

79

10 REFERENCES

Castro, J. & Naaman, N. E. (1981). Cement mortar reinforced with natural fibers. ACI

Balaguru, P. (1985). Alternative reinforcing materials for less developed countries.

Balaguru, P. (1994). Contribution of fibers to crack reduction of cement composites during

the initial and final setting period. ACI Materials Journal. V. 91, No. 3, May-June,280-288

AC 217 C, Acceptance Criteria for Concrete with Virgin Cellulose Fibers, ICC

EVALUATION SERVICE Inc, Whitter, CA, 2003.

ASTM C 995, Standard Test Method for Time of Flow of Fiber-Reinforced Concrete

Through Inverted Slump Cone, American Society for Testing and Materials, West

Conshohocken, PA, 2001.

International Journal for Development Technology. V. 3, 87-107

Banthia, N. & Bhargava, A. (2007). Permeability of stressed concrete and role of fiber

reinforcement. ACI Materials Journal. V. 104, No. 1, January-February, page. 70-76.

Buckeye Technologies Inc. UltraFiber500. Retrieved March 27, 2007, from

http://www.bkitech.com/

Materials Journal. V. 78, January-February, page 69-78.

80

APPENDIX

A Brief report on Coconut Coir Reinforced Under Ground Water

Tank

Introduction

Jalvardhini Pratishthan is a registered Voluntary organization based at Mumbai, started its

operation in early 2003. With a clear intention of supporting rural and Tribal population in Rain

water harvesting and management.

After exploring avenues in rural and tribal Maharashtra, we found that the areas where there is

immense waterfall, but still during off season farmer has to strive for irrigation due to shortage of

water availability.

Understanding all these scenarios, we found that the rain water which falls was not canalized,

resulting the whole rain water is drained and wasted.

Jalvardhini found that even if the running gutters in monsoon are blocked by a simple check dams

which can even be made by gunny bags or loose stones, helps the water percolation and increases

the level of under ground water table, resulting enhancing capacity of open wells and bore wells

in the vicinity.

Hence Jalvardhini focuses on, Agricultural Development by enhancing the water Resources. &

developed various low cost rain water storage tanks and methodologies for rain water

management.

Jalvardhini provides Technical assistance and Resources to needy people who understand the

importance of Rain water harvesting and are willing to implement.

Trustees :

1. Mr.Ulhas Paranjpe 2. Mr.Avinash Paranjpe 3. Mrs.Uttara Paranjpe

Jalvardhini Pratishthan

Reg. No. E21435 (Mumbai)

Address :

1, Janki Niwas, Gokhale Road (North), Dadar,

Mumbai - 400 028.

81

Present status :

The technique for construction of under ground water tank for rainwater harvesting in

rural field areas is developed by Jalvardhini, (NGO in Mumbai). It involves storing the rainwater

in underground water tanks of trapezoidal shape with side slopes normally 1:1. To prevent

leakage and strengthen the side slopes of tanks, coconut coir mat is placed on the surfaces of

pit. Coir mattress having 3 to 4 mm thickness and 350 gm/sq. m.are used.

A mixture of cement and water (slurry) is applied by brush on the coir mat. Then cement

sand plaster with proportion 1: 2 is applied on the coir mat. After curing for 7 days tanks are

filled with water. Then tank is covered with “Saldi” or other covering material to reduce

evaporation losses ( “Saldi” is prepared with the help of Bamboo & Grass or Bhatacha pendha )

.Normally small sized tanks(upto 10 cu.m.) are constructed so that water can be removed easily

with hand and can be easily covered so as to reduce evaporation losses. Two tanks are

constructed in year 2004 and 2006

A tank at Sommaya Trust Naresh wadi Taluka Talasari Dist. Thane

A photo of tank at Kahele Resource Centre Taluka Karjat Dist. Raigad

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Few consultants have suggested that instead of laying coconut coir over excavated portion,

there should be brick work ( kodi brick work ) & then coconut coir mat should be fixed on it.

Then next procedure is as usual as explained earlier.

Photos at tank at M.L.Dhawale Trust Taluka Vikaramgad Dist. Thane

As per this revised procedure NGO has developed four tanks during last two years at four

different locations. Capacity of such tanks vary from 5000 litres to 20,000 litres.

Identification of Problems

For better understanding of some problems related to tanks constructed using the

techniques available, site visits, observations of local conditions and testing of core samples of

such tanks is necessary. From the information furnished, following problems can be identified

related to techniques adopted for construction of small and large sized under ground water

tanks.

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1. It is stated that the performance of small tanks constructed 2 to 4 years back, is found

satisfactory. This is due to fact that lower depth of tank (say approximately less than 1.5 m)

smaller lateral forces due to soil or water pressure are resisted by composite action of

coconut coir reinforced cement mortar. Moreover surface area of tank being less, shrinkage

cracks that might be developed due to alternate dry and wet conditions and other

environmental factors are fine and less in numbers. Hence, life of such tanks may be more as

compared to large tanks.

2. In case of large tanks, brick work provided on sloping surface resists lateral earth pressure of

soil to some extent due to self weight of bricks. Since brickwork provides more or less stable

and plain surface for the coconut coir mat and plaster helps in maintaining the workmanship and

quality of the work. The cement slurry applied to coir mat and from the cement sand plaster,

percolates through the joints in bricks. This further adds some strength to the tank.

The technique for construction of underground water tank using coconut coir mat and

cement plaster is innovative. It is eco-friendly, economical and it saves valuable steel

reinforcement. The storage and utilization of rainwater in fields can be achieved on large scale.

Therefore, this technology need to be propagated through NGO, people participation along-with

government scheme. Present tanks constructed in Thane, Raigad and Konkan by Jalvardhini (

NGO), have proved successfully in local region due to proper adoption of techniques and

favorable soil conditions ( stiff and laterite soil with stable slopes ).

There is serious lack of knowledge in the development of theory based on scientific and

engineering calculations since no scientific literature is available on this type of technique. There

is doubt related to durability of coconut coir fibers being natural. Due to non-availability of

effective protection to coconut coir mat, it may remain as a weak plane in the structure. To

develop and strengthen this innovative technology further it is necessary carry out research

work in this area. Involvement of NGO, Research institute and Govt. Agencies in the

development of knowledge circle of field to lab , lab to field with experience will lead to fruitful

solution in the area of rain water harvesting on large scale in large region of the country.

The development of appropriate technology for construction of underground water

storage tanks by using coconut coir or similar natural fiber material with judicious use

conventional construction materials will have following objectives.

1. To identify the problems related to water tanks constructed using available technique.

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2. To investigate the performance of the material used through necessary tests.

3. To conduct experimental works on coconut coir mat reinforced cement mortar panel

with varying density of coir mat.

4. To carry out analysis of stability of slopes for underground water tanks of various sizes

and in different soil conditions.

5. To develop suitable eco-friendly and economical composite construction technology

using coconut coir and similar natural fiber materials, for underground water tanks.

6. To transfer the technology in field application through NGO.

An effort is taken to cast cement mortar tiles specimens similar to material and procedure

adopted at field for underground water tanks . Some test results are given below.

86

Comparison of 28 Days Strength Using Long Fibers


strength(MPa)

Split tensile

strength(MPa)

Flexural

strength(MPa)

0 32.88 2.95 4.8

0.5 33.18 3.07 5.07

1 32.44 3.14 5.33

1.5 33.40 3.25 5.86

2 23.92 3.27 4.53

evaluation of properties of coconut coir fiber reinforced concrete

Documents

coirreinforced concrete

coconut coir mat

concrete mass

natural fibers

concrete mix design19

babje rohit pradeep

nikalje rohit sarjerao

civil engineering department