Evaluation of Properties of Coconut Coir Fiber Reinforced Concrete

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

1

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

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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)

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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.

4

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.

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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 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.

was

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.

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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

7

Table 1:Types of fibers and their properties DIAMETER(0.001 SPECIFIC in.) GRAVITY

E, ksi x1000

TENSILE STRENGTH (ksi)

STRAIN AT FAILURE, %

HIGH TENSILE

0.1-1.016

7.8

29

50-250

3.5

STAINLESS

0.01-0.33

7.8

23.2

300

3

2.5-2.7

10.44-11.6

360-500

3.6-4.8

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

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

0.96

0.076-0.464

-

FIBER TYPE

STEEL

GLASS POLYMERIC

0.01-0.013

NATURAL

AKWATA

1.02-4.06

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 . 8

•

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 concern.

environment and energy

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 microsponges.

•

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

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Water absorption saturation( %) Elastic modulus( MPa) Density (kg/m³)

References

-

-

-

-

56.6- 73.1

93.8161

2.8

-

-

-

-

2

110 4137 0 114 0

Ramakris hna et al.(2005a) Agopyan et al. 2005

-

-

-

10

181

-

100 0

24±1 0

-

-

-

-

24

2±3

-

108252

13.7- 41

-

-

-

-

85-135 2.54.5

137±1 1

-

4.2

21. 5± 2.4

-

-

-

Diameter (mm)

Length (mm)

Tensile strength (MPa)

Young‟s modulus

Specific young‟s modulus

Toughness

Permeable void (%)

Elongation (mm)

Moisture content(%)

Table 2: Physical Properties of Coconut Coir Fibers

0.40.10

60250

15-323 75

-

-

-

-

.21

-

107

37.7

-

-

-

.3

-

69.3

-

-

-

-

-

50.9

17.6

-

.27± 50± 0.00 10 73 0.11- 0.53

142±3 6

0.12 ±0.0 05

-

3.7 ±.6

Table 3: Chemical Fiber Coconut coir

-

670 100 0 870

Paramasi vam et al.1984 Ramakris hna et al.(2005b ) Li et al 2007 Toledo et al (2005)

Munawar et al.( 2007)

Properties of Coconut Coir Fiber

Hemicelluloses(%) Cellulose (%) 31.1 32.2

Lignin (%) 20.5

15.28

35-60

20-48

16.8

68.9

32.1

-

43

45

0.15-0.25

36-43

41-45

Reference Ramkrishna et al.(2005a) Agopyan et al.(2005) Asasutjarit et al (2007) Satyanarayana et al (1990) Corradini et al (2006)

pH value of coconut coir is in between 6.5 and 7.0

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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 (% ) 0.5 1 1.5 2

Compressive strength (MPa) 21.42 21.70 22.74 25.10 24.35

Split tensile strength (MPa) 2.88 3.02 3.18 3.37 3.54

Modulus of rupture (MPa) 3.25 3.38 3.68 4.07 4.6

Shear strength(MPa) 6.18 6.47 6.81 8.18 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.

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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

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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

0.5

3

3

3

3

1

3

3

3

3

1.5

3

3

3

3

0.5

3

3

3

3

1

3

3

3

3

1.5

3

3

3

3

Total

33

33

33

33

33

33

3cm long fiber

5cm long fiber

66

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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

Coconut wire

26

Average diameter of fiber 0.42 mm

Total load taken

Tensile strength

Stress/strain

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.

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4.2.2 Consistency of Cement Table 9: Results for Consistency of Cement Wt. of cement (gm)

% of water

Quantity of water (ml)

400

40

160

Reading on Vicat‟s Apparats (penetration)measured from top (mm) 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

Initial setting time

1 Hr. 10 min.

Requirement as per IS:122691999 Not less than 30 min.

Final setting time

5 Hr. 20 min.

Not more than 10 Hrs.


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4.2.4 Compressive Strength of Cement Table 11: Compressive Strength of Cement Compressive strength of cement in MPa 3 days

22.35

3 days

29.2

3 days

26.5

7 days

30.31

7 days

34.93

7 days

32.05

28 days

42.21

28 days

45.56

28 days

47.89

Average strength(MPa) 26.01

Remarks Not less than 22 N/ mm²

32.43

Not less than 30 N/mm²

45.22

Not less than 43 N/ mm²


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.

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4.3.1 Natural Sand Table 12: Sieve Analysis Results IS sieve

Weight retained (kg)

Cumulative % retained

Cumulative % passing

0

Cumulative Weight retained (kg) 0

0

100

Zone 2 Grading Limits IS383-2002 100

4.75mm 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

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4.3.2 Crushed Sand IS sieve

Table 13: Sieve Analysis Results Weight Cumulative Cumulative Cumulative retained Weight % retained % passing (kg) retained (kg)

4.75mm

0

0

0

100

Zone 2 Grading Limits IS3832002 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

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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.

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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

Mild

220

0.6

Moderate

240

Severe Very

Min. grade of concrete

Min. cement content

Max. Water cement ratio

Min. grade of concrete

-

300

0.55

0.6

M15

300

0.50

M 25

250

0.50

M 20

320

0.45

M 30

260

0.45

M20

340

0.45

M35

280

0.40

M 25

360

0.40

M 40

M 20

Severe Extreme

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).

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Table 16: Approximate Sand and Water Contents per cubic meter of Concrete Water content including surface Maximum size of

Sand as percent of

water per cubic meter

Aggregate

total aggregate by

of concrete

absolute volume.

(kg) 10

208

40

20

186

35

40

165

30

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

21

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 percent Sand in total aggregate

Water Content

For sand conforming

+1.5percent for Zone I

grading zone I, Zone III or

0

Zone IV of table 4, IS 383-

-1.5percent for Zone III -3percent for Zone IV

1970 Increase or decrease in the value of compacting factor

±3.0percent

0

0

±1.0percent

-15 Kg/m3

-7.0percent

by 0.1 Each 0.05 increase or decrease in water cement ratio

For rounded aggregate

Table 18 Sr.

Change in

No.

Condition

1

2

For decrease in water cement ratio by (0.6-0.49) = 0.11 Increase in compacting factor

Percent adjustment required Water

Sand in Total

content

aggregate

0

-0.11/0.05×1 = - 2.2percent

0.05/0.1×3

0

=+1.5percent

By (0.85-0.8) = 0.05 Overall adjustment

+1.5percent

- 2.2 percent 22

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/m3 Hence adopt cement content=385.30 kg/m3 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

23

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

Specified combined grading

Sand

20mm

10mm

Combined grading

*1

*1.260

*0.840

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

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

(mm)

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 385.30 kg/m^3

Sand 693.63 kg/m3

10mm 755.14 kg/m3

1

1.533 1.96. Natural crushed 0.6 0.933

20mm 503.42

kg/m3

1.306

Water 188.80 liters/ m3 0.49

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

24

6 Test program Following teats were conducted on plain cement concrete and coconut coir reinforced concrete Tests on concrete:1. 2. 3. 4.

Workability of concrete Compressive strength of concrete Split tensile strength of concrete 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. 25

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.

26

Table 21:Workability test results Length of fiber long

%of fiber 0.5 1.0 1.5 2.0 0.5 1.0 1.5 0.5 1.0 1.5 0

3cm

5cm

Without fiber

Workability 50 38 16 05 55 48 30 53 42 24 60

Fig 3 Comparison of workability for different types and percentages of fibers 70

60

50

PLAIN

40

3 cm 5 cm

30

LONG FIBERS 20

10

0 1

2

3

4

27

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:

Concrete Cube

Figure 4 : Concrete Cube under Compression

P 28

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. 29

Table 22: 7 days compressive strength of plain concrete cubes Load(kN)

Stress(N/mm²)

Deformation (mm) Strain Cube2 0.0073 1.12

2.22

Cube1 1.1

Strain 0.0075

4.44

1.3

0.0086

1.4

0.0093

6.66

1.4

0.0093

1.66

0.011

8.88

1.55

0.01

1.84

0.012

11.1

1.66

0.011

2.08

0.0138

13.32

1.9

0.013

2.27

0.015

15.54

2.2

0.015

2.45

0.016

17.76

2.3

0.0153

2.63

0.0175

19.98

2.66

0.018

3

0.02

22.2

3

0.02

3.17

0.0.21

24.42

3.15

0.021

3.45

0.023

26.64

3.35

0.022

1.12

0.0074

50 100 150 200 250 300 350 400 450 500 550 600 Failure

580kN

600kN

stress vs strain for 7 days compressive strength 30 25 20 stress vs strain for 7 days compressive strength

15 10 5 0 0

0.005

0.01

0.015

0.02

0.025

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

30

stress vs strain 30 25 20 15

stress vs strain

10 5 0 0

2

4

6

8

10

12

14


31

Table 23: 28 days compressive strength of plain concrete cubes Load(kN) Cube1 0.2 50

Deformation (mm) Cube2

Cube3

0.81

0.9

1.05

1.05

1.23

1.11

1.4

1.12

1.49

1.12

1.65

1.12

1.8

1.12

1.91

1.12

2.2

1.23

2.32

1.5

2.55

2.14

2.7

2.14

2.85

3

0.6 100 1 150 1.3 200 1.32 250 1.42 300 1.52 350 1.64 400 1.82 450 2 500 2.32 550 2.65 600 3 650 700

0

3.1

3.52

750

0

3.42

3.78

800

0

4.1

3.9

Failure

650kN

780kN

790kN

32

stress vs strain(28 days plain concrete) 35 30 25 20 stress vs strain(28 days plain concrete)

15 10 5 0 0

0.005

0.01

0.015

0.02

0.025


stress vs strain(28 days plain concrete) 40 35 30 25 20

stress vs strain(28 days plain concrete)

15 10 5 0 0

0.01

0.02

0.03


33

stress vs strain(28 days plain concrete) 40 35 30 25 20 15 10 5 0 0

0.005

0.01

0.015

0.02

0.025

0.03


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

34

compressive strength vs % of fiber 36 35.5 35 34.5 compressive strength vs % of fiber

34 33.5 33 32.5 0

0.5

1

1.5

2

Fig 10 compressive strength vs % of fiber

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

% of coconut fiber

Stress/strain (GPa)

(MPa) 0

32.88

1.63

0.5

32.75

1.61

1

33.03

1.65

1.5

33.77

1.67

compressive strength vs % of fiber 33.9 33.8 33.7 33.6 33.5 33.4 33.3 33.2 33.1 33 32.9 32.8

compressive strength vs % of fiber

0

0.5

1

1.5

2

35

Fig.11 compressive strength vs % of fiber

36

Table 26: 7 days compressive strength of 1% coconut coir fiber (long fiber) reinforced concrete cubes Load(kN) Cube1


1

0.1

50

0.15 1.2

0.12

100

0.27 1.4

0.15

150

0.33 1.55

0.18

200

0.34 1.6

0.2

250

0.34 1.65

0.26

300

0.34 1.71

0.28

350

0.34 1.79

0.35

400

0.34 1.82

0.42

450

0.34 1.87

0.52

500

0.34 1.9

0.65

550

0.34 1.92

0.78

600

0.34 1.97

1.03

650 Failure

Cube3

645kN

650kN

0.34 610kN

37

stress vs strain 35 30 25 20 stress vs strain

15 10 5 0 0

0.005

0.01

0.015

Fig.12 stress vs strain

38

Table 27: 28 Days Compressive Strength of 1% Long Coconut Coir Fiber Reinforced Concrete Cubes Load(kN)


Cube2

50

0.4

0.3

100

0.45

0.35

150

0.49

0.45

200

0.54

0.56

250

0.6

0.6

300

0.7

0.68

350

0.95

0.95

400

1.09

1.1

450

1.6

1.5

500

1.75

1.5

550

2

1.8

600

2.28

2.1

650

2.5

2.3

700

2.85

2.5

750

2.85

2.9

Failure

760

750

Cube3 0.2 0.3 0.35 0.4 0.45 0.5 0.55 0.59 0.64 0.7 0.85 0.98 1.2 1.24

680

39


15 10 5 0 0

0.002

0.004

0.006

0.008

Fig.13 stress vs strain


15 10 5 0 0

0.005

0.01

0.015

0.02

0.025

Fig 14 stress vs strain

40


15 10 5 0 0

0.005

0.01

0.015

0.02

0.025



15 10 5 0 0

0.002

0.004

0.006

0.008

0.01


41

Table 28:7 days compressive strength of 0.5% long coconut coir fiber reinforced concrete cubes Load(kN)


Cube2

Cube3 0.45

50

0

100

0.5

150

0.56

200

0.67

250

0.92

300

1.1

350

1.3

400

1.62

450

1.78

500

2

550

2.38

Failure

520kN

0.52 0.54 0.57 0.6 0.65 0.7 0.75 0.82 0.87 1

330kN

535kN

42


stress vs strain

10 5 0 0

0.5

1

1.5

2

2.5



stress vs strain

10 5 0 0

0.002

0.004

0.006

0.008


43

Table 29: 28 days compressive strength of 0.5% long coconut coir fiber reinforced concrete cubes Load(kN)

Deformation (mm) 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

---

---

Failure

740kN

740kN

760kN

44


15 10 5 0 0

0.001

0.002

0.003

0.004

0.005

Fig 19 stress vs strain Table30:7 days compressive strength of 2% long coconut coir fiber reinforced concrete cubes Load(kN)

Deformation (mm) 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

45

stress vs strain 20 18 16 14 12 10 8 6 4 2 0

stress vs strain

0

0.01

0.02

0.03

0.04



stress vs strain

10 5 0 -0.002

0

0.002

0.004

0.006

0.008


46

stress vs strain 18 16 14 12 10 stress vs strain

8 6 4 2 0 0

0.005

0.01

0.015

0.02

0.025


47

Table31:28 days compressive strength of 2% long coconut coir fiber reinforced concrete cubes Load(kN)


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

Failure

560kN

525kN

530kN

48


stress vs strain

10 5 0 0

0.002

0.004

0.006

0.008



stress vs strain

10 5 0 0

0.002

0.004

0.006

0.008


49


stress vs strain

10 5 0 0

0.01

0.02

0.03

0.04


50

Table 32: 5 cm 7 days 1% DEFORMATION(mm) LOAD

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

stress vs strain 25 20 15 stress vs strain

10 5 0 0

0.002

0.004

0.006

0.008


51


10 5 0 0

0.002

0.004

0.006

0.008



10 5 0 0

0.002

0.004

0.006

0.008


52

Table 33: 5CM 1% 28 DAYS DEFORMATION(mm) LOAD

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

53

stress vs strain 40 35 30 25 20

stress vs strain

15 10 5 0 0

0.005

0.01

0.015

0.02

0.025

Fig 30 Stress vs Strain


15 10 5 0 0

0.005

0.01

0.015


54


stress vs strain

15 10 5 0 0

0.005

0.01

0.015

0.02


55

Table34: 3cm 1% 7 days DEFORMATION(mm) LOAD

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


10 5 0 0

0.002

0.004

0.006

0.008

0.01


56


10 5 0 0

0.002

0.004

0.006

0.008

0.01



10 5 0 0

0.002

0.004

0.006

0.008

0.01


57

Table 35: 3cm 1% 28 days DEFORMATION(mm) LOAD

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

58


stress vs strain

15 10 5 0 0

0.005

0.01

0.015

0.02



15 10 5 0 0

0.005

0.01

0.015

0.02


59


stress vs strain

15 10 5 0 0

0.005

0.01

0.015

0.02



stress vs strain

15 10 5 0 0

0.005

0.01

0.015

0.02


60

Table 36: 5CM 0.5% 7 DAYS DEFORMATION(mm) LOAD

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


10 5 0 0

0.002

0.004

0.006

0.008

0.01


61


10 5 0 0

0.002

0.004

0.006

0.008

0.01



10 5 0 0

0.002

0.004

0.006

0.008

0.01


62


10 5 0 0

0.002

0.004

0.006

0.008

0.01


63

Table 37: 5CM 0.5% 28 DAYS DEFORMATION(mm) LOAD

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


stress vs strain

15 10 5 0 0

0.005

0.01

0.015

0.02 64



15 10 5 0 0

0.005

0.01

0.015

0.02



15 10 5 0 0

0.005

0.01

0.015

Fig 46 stress vs strain 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.

65

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

1.72 1.7 1.68 1.66 5 cm long fiber 1.64

3 cm long fiber

1.62

long fiber

1.6 1.58 1.56 0

0.5

1

1.5

66

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.

67

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

68

split tensile strength vs % of fiber(long fiber) 3.3 3.25 3.2 3.15 3.1

split tensile strength vs % of fiber

3.05 3

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

2.95 2.9 0

0.5

1

1.5

2

2.5

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

split tensile strength vs % of fiber (5cm) 3.25 3.2 3.15 3.1 split tensile strength vs % of fiber

3.05 3 2.95 2.9 0

0.5

1

1.5

2

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

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split tensile strength vs % of fiber(3cm) 7 6 5 4 split tensile strength vs % of fiber(3cm)

3 2 1 0 0

0.5

1

1.5

2

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.

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

References: 1) 2)

IS:516 - 1959; Method of test for strength of concrete. 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/3

L

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 72

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

73

flexural strength vs % of fiber 7 6 5 4 flexural strength vs % of fiber

3 2 1 0 0

0.5

1

1.5

2

2.5

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


3 2 1 0 0

0.5

1

1.5

2

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

74


3 2 1 0 0

0.5

1

1.5

2

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.

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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.

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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.

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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.

80

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. 82

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. 83

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.

84

85

Comparison of 28 Days Strength Using Long Fibers % of coconut fiber

Compressive 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

86

Evaluation of Properties of Coconut Coir Fiber Reinforced Concrete

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