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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
30.31 32.43 Not less than
30 N/mm²
7 days
34.93
7 days
32.05
28 days
42.21 45.22 Not less than
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
Fig.6 stress vs strain for 7 days compressive strength of plain concrete
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
Fig.7 stress vs strain for 28 days compressive strength of plain concrete
Fig.8 stress vs strain for 28 days compressive strength of plain concrete
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)
stress vs strain(28 days plain concrete)
0
5
10
15
20
25
30
35
40
0 0.01 0.02 0.03
stress vs strain(28 days plain concrete)
stress vs strain(28 days plain concrete)
34
Fig.9 stress vs strain for 28 days compressive strength of plain concrete
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
stress vs strain(28 days plain concrete)
35
Fig 10 compressive strength vs % of fiber
Table 25:Comparison of 28 days strength using 3cm long fibers
% of coconut fiber Compressive
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
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
compressive strength vs % of fiber
compressive strength vs % of fiber
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
Load(kN) Deformation (mm)
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
Failure 645kN 650kN 610kN
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
Load(kN) Deformation (mm)
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
Fig 15 stress vs strain
Fig 16 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
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
Load(kN) Deformation (mm)
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
Failure 520kN 330kN 535kN
43
Fig 17 stress vs strain
Fig 18 stress vs strain
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
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
45
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
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
Fig 20 stress vs strain
Fig 22 stress vs strain
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
Fig 23 stress vs strain
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
Load(kN) Deformation (mm)
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
Failure 560kN 525kN 530kN
49
Fig 24 stress vs strain
Fig 25 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
0
5
10
15
20
25
30
0 0.002 0.004 0.006 0.008
stress vs strain
stress vs strain
50
Fig 26 stress vs strain
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
Fig 27 stress vs strain
0
5
10
15
20
25
0 0.002 0.004 0.006 0.008
stress vs strain
stress vs strain
52
Fig 28 stress vs strain
Fig 29 stress vs strain
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
Fig 31 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
Fig 32 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
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
Fig 33 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
57
Fig 34 stress vs strain
Fig 35 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
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
Fig 36 stress vs strain
Fig 37 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
0
5
10
15
20
25
30
35
0 0.005 0.01 0.015 0.02
stress vs strain
stress vs strain
60
Fig 38 stress vs strain
Fig 39 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
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
Fig 40 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
62
Fig 41 stress vs strain
Fig 42 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
0
5
10
15
20
25
0 0.002 0.004 0.006 0.008 0.01
stress vs strain
stress vs strain
63
Fig 43 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
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
Fig 44 stress vs strain
Fig 45 stress vs strain
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.
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
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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.
72
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
74
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
flexural strength vs % of fiber
0
1
2
3
4
5
6
7
0 0.5 1 1.5 2 2.5
flexural strength vs % of fiber
flexural strength vs % of fiber
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
flexural strength vs % of fiber
flexural strength vs % of fiber
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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.
78
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.
83
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.
84
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.
85
86
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