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STUDY ON BEHAVIOUR OF HIGH STRENGTH CONCRETE USING
COCONUT SHELL AS COARSE AGGREGATE
D.Kishore1, D. Samuel Abraham2,
1 PG Student, Structural Engineering, Tamlinadu College of Engineering, Coimbatore,
E-mail:[email protected]
2Assistant Professor, Civil Engineering Department, Tamlinadu College of Engineering, Coimbatore,
E-mail:[email protected]
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Abstract - Lightweight aggregate concrete (LWAC) is an
important and versatile material in modern construction. Many
architects, engineers, and contractors recognize the inherent
economies and advantages offered by this material, as evidenced
by the many impressive lightweight concrete (LWC) structures
found throughout the world. Use of mineral admixture in
conventional concrete and light weight concrete mix has made a
remarkable achievement in development and design of high
strength in conventional concrete (HSC) and light weight
concrete (HSLWAC). The use of high strength concrete (HSC)
has many advantages such as a reduction in beam and column
sizes, increased building height, greater span-depth ratio for
beams in pre-stressed concrete construction and improved
durability of marine concrete structures. It can be said that
HSLWACs have a significant advantage over normal weight
HSC because of the reduction of dead load and construction
cost. Among many mineral admixtures available, Silica fume
(SF) is a mineral admixture, ultrafine material with spherical
particles less than 1 μm in diameter .This makes it
approximately 100 times smaller than the average cement
particle. The bulk density of silica fume depends on the degree of
densification in the silo and varies from 130 (undensified) to 600
kg/m3. Silica fume is added to Portland cement concrete to
improve its properties, in particular its compressive strength,
bond strength, and abrasion resistance. Silica fume added 5% to
50% replacement of cement and find the Mechanical properties
such as compressive strength, flexural strength, split tensile
strength, impact resistance and modulus of elasticity can be
studied.
Key Words: Light weight aggregate concrete, high
strength concrete, silica fume, Coconut shell, GGBS.
INTRODUCTION
Concrete is the widely used number one structural material in the
world today. The demand to make this material lighter has been
the subject of study that has challenged scientists and engineers
alike. The challenge in making a light weight concrete is
decreasing the density while maintaining strength and without
adversely affecting cost. Normal concrete contains four
components are cement, crushed stone, river sand and water. The
crushed stone and sand are the components that are usually
replaced with light weight aggregate. Light weight concrete is
typically made by incorporating natural or synthetic light weight
aggregate or by entraining air into a concrete mixture. Some of
the light weight concrete used for light weight productions are
pumice, perlite, expanded clay or vermiculite, coconut shell.
Although, coarse aggregate usually take about 50% of the overall
self-weight concrete. And also, the cost of construction material
is increasing day by day because of high demand, scarcity of raw
material and high price of energy, from the stand point of energy
saving and conservation of natural resources, the use of
alternative constituents which should be light in weight to reduce
the self-weight of concrete in construction materials is now a
global concern. From the studies, the use of coconut shell as a
coarse aggregate is effective and having the double advantage of
reduction in the cost of construction material and also as a means
of disposal of wastes. Hence coconut shell is used as a
replacement for coarse aggregate.
Light weight concrete
Lightweight aggregate concrete (LWAC) is a versatile material in
modern construction. It has gained popularity due to its lower
density and superior thermal insulation properties. In recent
years, researchers have also paid more attention to some
agriculture wastes for use as building material in construction.
One such alternative is coconut shell (CS), which is one of the
most common agricultural solid wastes in many tropical
countries. Around 14,000 million coconuts are being produced
annually in India, particularly from the states of Kerala, Tamil
Nadu, Andhra Pradesh and the Union Territories. After the
coconut is scraped out, the shell is usually discarded as waste.
This has good potential to use in areas where coarse aggregate
costly. The bulk density of coconut shell is about 500 to 600
kg/m3, producing concretes of about less than 2000 kg/m3 in
density, which makes them light weight. Light weight concrete
has low density than the conventional concrete. Purpose of using
light weight concrete in building is to reduce the self-weight of
the building. As a result of growth in advance technology in
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concrete, high strength concrete (HSC) has gained world-wide
popularity in the construction industry since 1990. In practice,
high strength concrete, are generally characterized by high
cement factors and very low W/C ratios. Such concrete suffer
from two major weaknesses. It is extremely difficult to obtained
proper workability, and to retain the workability for sufficiently
long period of time with such concrete mixes. High dosage of
high range water reducing agents(HRWR) then become a
necessity, and resulting cohesive and thixotropic, sticky mixes
are equally difficult to place and compact fully and efficiently.
These problem indicate that there is probably a critical limit for
the water content below which high HRWR dosage become not
only essential but also unhelpful and undesirable, and often even
harmful from a durability point of view.
OBJECTIVE OF WORK
To develop high strength concrete mix using coconut shell as
coarse aggregate. To study the mechanical properties of coconut
shell concrete such as compressive strength, flexural strength and
impact resistance. To compare the results with conventional high
strength concrete.
SCOPE OF WORK
High strength concrete mix are developed using coconut shell as
coarse aggregate. Mechanical properties of high strength
concrete using coconut shell concrete as coarse aggregate are
studied. Results are compared with conventional high strength
concrete.
METHODOLOGY
To achieve the above objective following step by step
procedures are followed
• Literature study and material studies to determine the
objectives.
• Materials collection for casting the concrete specimens.
• Replacing the material to find the optimum
replacement percentage.
• Testing the specimen as per the standards.
• Analysis of results.
LITRETURE STUDY
Gunasekeran et al (2010) “Mechanical and bond properties
of coconut shell concrete” properties of concrete using coconut
shell as coarse aggregate were investigated in an experimental
study. Compressive, flexural, splitting tensile strengths, impact
resistance and bond strength were measured and compared with
the theoretical values as recommended by the standards. For the
selected mix, two different water–cement ratios have been
considered to study the effect on the flexural and splitting tensile
strengths and impact resistance of coconut shell concrete. The
bond properties were determined through pull-out test. Coconut
shell concrete can be classified under structural lightweight
concrete. The results showed that the experimental bond strength
of coconut shell concrete is much higher than the bond strength
as estimated by BS 8110 and IS 456:2000 for the mix selected.
Gunasekeran et al (2011) “Long term study on compressive
and bond strength of coconut shell aggregate concrete”
effects of three types of curing on coconut shell aggregate
concrete have been studied for long term performance. The pore
structure of coconut shell has been studied through scanning
electron microscope (SEM). The pore structures in coconut shell
behave like a reservoir. Intermittent curing produced the highest
coconut shell aggregate concrete strength, followed by full
water, and then by air-dry curing. Biological decay was not
evident as the concrete cubes gained strength even after 365
days. Up to an age of 90 days, the samples under all types of
curing conditions showed improved response on the pulse
velocity and subsequently an insignificant drop. The ultimate
bond strength of coconut shell aggregate concrete under all types
of curing conditions was much higher compared to the
theoretical bond strength as per BS 8110 and IS 456. Bonding
between the cement paste and the coconut shell aggregate has
been studied by measuring fissure between the coconut shell and
the cement paste through SEM analysis. It shows a tendency of
narrowing the fissure due to its age, which shows that the bond
appears to be better between the coconut shell and the cement
paste.
Gunasekeran et al (2012) “Study on reinforced lightweight
coconut shell concrete beam behavior under flexure” coconut
shell has been used as coarse aggregate in the production of
concrete. The flexural behaviour of reinforced concrete beam
made with coconut shell is analysed and compared with the
normal control concrete. Twelve beams, six with coconut shell
concrete and six with normal control concrete, were fabricated
and tested. This study includes the moment capacity, deflection,
cracking, ductility, corresponding strains in both compression
and tension, and end rotation. It was found that the flexural
behaviour of coconut shell concrete is comparable to that of
other lightweight concretes. The results of concrete compression
strain and steel tension strain showed that coconut shell concrete
is able to achieve its full strain capacity under flexural loadings.
Under serviceability condition, deflection and cracking
characteristics of coconut shell concrete are comparable with
control concrete. However, the failure zones of coconut shell
concrete were larger than for control concrete beams. The end
rotations of the coconut shell concrete beams just prior to failure
values are comparable to other lightweight concretes. Coconut
shell concrete was used to produce hollow blocks and precast
slab in 2007 and they are being subjected to some practical
loading till today without any problems such as deflection,
bending, cracks, and damages for the past five years.
MuhannadIsmeik(2009) “Effect of Mineral Admixture on
Mechanical Properties of High Strength Concrete made with
Locally Available Materials” an experimental laboratory
investigation has been carried out to evaluate the mechanical
properties of concrete made with mineral admixtures and local
Jordanian materials. Various percentages of Silica Fume (SF)
and Fly Ash (FA) were added at different water/cementious
(w/cm) ratios. Concrete specimens were tested and compared
with plain concrete specimens at different ages. Results
indicated that compressive as well as flexural strengths increased
with mineral admixture incorporation. Optimum replacement
percentage is not a constant one but depends on the w/cm ratio
of the mix. SF contributed to both short and long-term properties
of concrete, whereas, FA showed its beneficial effect in a
relatively longer time. Adding of both SF and FA did not
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increase compressive strength in the short term, but
improvements were noticed in the long-term. Compared with
compressive strength, flexural strength of SF concretes has
exhibited greater improvements. Relationships between the 28-
day flexural and compressive strengths have been developed
using statistical methods. It is concluded that local concrete
materials, in combination with mineral admixtures, can be
utilized in making High Strength Concrete in Jordan and such
concrete can be effectively used in structural applications.
PayamShafigh(2011) “A new method of producing high
strength oil palm shell lightweight concrete” this paper
presents a new method to produce high strength lightweight
aggregate concrete (HSLWAC) using an agricultural solid
waste, namely oil palm shell (OPS). This method is based on
crushing large old OPS. Crushed OPS are hard and have a strong
physical bond with hydrated cement paste. The 28 and 56 days
compressive strength achieved in this study were about 53 and
56 MPa, respectively. Furthermore, it was observed that it was
possible to produce grade 30 OPS concrete without the addition
of any cementitious materials. Compared to previous studies,
significantly lower cement content was used to produce this
grade of concrete. Unlike OPS concrete incorporating uncrushed
OPS aggregate, this study found that there is a strong correlation
between the short term and 28-day compressive strength.
Shirule et al, (2012) used an 18-storey symmetrical R.C.C
building as a test model. Lead Rubber Bearing (LRB) and
Friction Bearing (FB) is used as isolation system in this study.
Nonlinear Time History analysis is used on both of fixed base
and base isolated buildings. There are two portions; one is
comparative study of performance of fixed base condition and
base isolation (LRB and FB) condition and the comparative
study of performance by three different time histories Bhuj,
Koyna and Lacc T.H.Finally, base shear, displacement and
acceleration are compared from 3 times history analysis between
fixed base condition and base isolated condition. The base shears
in each direction are decreased with LRB by 46% and with FB
by 35% in base isolated building compared to the fixed base
building.
Shannag (2010) “Characteristics of lightweight concrete
containing mineral admixtures” this research investigates the
properties of fresh and hardened concretes containing locally
available natural lightweight aggregates, and mineral
admixtures. Test results indicated that replacing cement in the
structural lightweight concrete developed, with 5–15% silica
fume on weight basis, caused up to 57% and 14% increase in
compressive strength and modulus of elasticity, respectively,
compared to mixes without silica fume. But, adding up to 10%
fly ash, as partial cement replacement by weight, to the same
mixes, caused about 18% decrease in compressive strength, with
no change in modulus of elasticity, compared to mixes without
fly ash. Adding 10% or more of silica fume, and 5% or more fly
ash to lightweight concrete mixes perform better, in terms of
strength and stiffness, compared to individual mixes prepared
using same contents of either silica fume or fly ash.
SUMMARY OF LITERATURE
Coconut shell is one of the potential materials for the
replacement of conventional coarse aggregate in the production
of concrete. Coconut shell concrete has been established for the
production of light weight concrete. Coconut shell concrete
beams behave similar to that of conventional concrete beams
under flexure, shear and torsion as well. Coconut shell concrete
durability properties are also in acceptable limits and
comparable to conventional concrete. Silica fume improves the
physical and mechanical properties. Due to its high fines of
silica fume it provides very good compressive and flexural
strength.
MATERIALS AND METHODOLOGY
Coconut Shell Aggregates
Large quantity of coconut shell (CS) is available in coconut oil
mills, markets etc. required quantities of coconut shell were
received from the local sellers. The collected coconut shells
were stacked in the SRM University premises. The coconut
shells were well seasoned and free from vegetative matter. The
coconut shells were crushed using a crusher developed in the
coconut shell concrete research centre at SRM University. After
crushing the CS, they were sieved and the aggregate passing
12.50mm sieve size was used for CS concrete. The crushed
edges were rough and spiky and the lengths were restricted to a
maximum of 12 mm. The surface texture of the shell was fairly
smooth on concave and rough on convex faces. The CS
aggregate were pre-soaked for 24 hours in water and then taken
from water to allow dry under room temperature. The aggregate
used were in saturated surface dry (SSD) condition to prevent
absorption taking place during mixing.
Coconut shell
Cement
Ordinary Portland Cement (OPC) of grade 53 was used in this study and it confirms to IS 12269:1987. OPC 53 grade was chosen to get the maximum strength advantage out of cement and it was tested prior to use in the study.
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Cement
Coarse Aggregate
The broken stone is generally used as a coarse aggregate. For the
slabs and walls, the maximum size of coarse aggregate should be
limited to 1/3 of the concrete section. The coarse aggregates can
be classified into two types (IS 383.1970)
• Crushed aggregates
• Uncrushed aggregates.
Uncrushed aggregates are usually smoother than crushed
aggregates and in comparison with concrete made with
uncrushed coarse aggregate, concrete containing crushed coarse
aggregate will generally have superior strength and inferior
workability, although a coarse aggregate has considerably less
influence on the workability than the fine aggregate. An
angularity of 25% might be specified for angular uncrushed
aggregate. An angularity of 75% might be specified for
relatively smooth crushed aggregate. The coarse aggregate used
in concrete work generally hard, durable and of acceptable
shape, free from flaxy elongated particles. The size of coarse
aggregate used in the concrete specimen is 12.5 mm. The
physical properties of coarse aggregates used in this study.
Coarse Aggregate
Fine Aggregate
The material which is passed through IS test sieve no.4.75 mm is
termed as a fine aggregate. Usually the natural river sand is used
as a fine aggregate. Fine aggregate is of angular grains, clean
and free from dust, dirt and organic matters. Sea sand shall not
be used. Sand is an important ingredient of concrete work. The
sand particles consist of small grains of silica. It is formed by the
decomposition of sand stones due to various effects of weather.
According to natural resources from which the sand is obtained,
the three types of sand are Pit sand, River sand and Sea sand. In
that, river sand is usually available in clean conditions. It is
widely used for all purposes. The sand we are using is confined
to Zone III.
Fine Aggregate
Ground Granulated Blast Steel Slag (Ggbs)
GGBS is used to make durable concrete structures in
combination with ordinary portland cement and/or other
pozzolanic materials. GGBS has been widely used in Europe,
and increasingly in the United States and in Asia (particularly in
India, Japan and Singapore) for its superiority in concrete
durability, extending the lifespan of buildings from fifty years to
a hundred years Two major uses of GGBS are in the production
of quality-improved slag cement, namely Portland Blast furnace
cement (PBFC) and high-slag blast-furnace cement (HSBFC),
with GGBS content ranging typically from 30 to 70% and in the
production of ready-mixed or site-batched durable concrete.
Concrete made with GGBS cement sets more slowly than
concrete made with ordinary Portland cement, depending on the
amount of GGBS in the cementitious material, but also
continues to gain strength over a longer period in production
conditions. This results in lower heat of hydration and lower
temperature rises, and makes avoiding cold joints easier, but
may also affect construction schedules where quick setting is
required.
Silica Fume
The terms condensed silica fume, micro silica, silica fume and
volatilized silica are often used to describe the by-products
extracted from the exhaust gases of silicon, ferrosilicon and
other metal alloy smelting furnaces. However, the terms micro
silica and silica fume are used to describe those condensed silica
fumes that are of high quality, for use in the cement and concrete
industry. The inclusion of silica fume in concrete causes
significant changes in the structure of the matrix, through both
physical action and a pozzolanic reaction, to produce a
densified, refined pore system and greater strength. In most
cases it is the refinement of the pore system which reduces
penetrability, which has the greater effect on the performance of
the concrete than the increased strength. Use can be made of
these improved qualities in designing concretes to comply with
requirements or greater resistance to certain hostile
environments. Silica fume should be considered as an addition to
a mix rather than a replacement for cementitious content and
sensible mix design is essential. Silica fume concrete is
susceptible to poor curing and the effects are more pronounced
than in ordinary concrete. Close attention to curing methods and
times is important to ensure optimum performance.
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Silica Fume
RESULT AND DISCUSSIONS
Mix Proportion
For the production of concrete mix, the various trial mixes are
cast to find the optimum proportion for both conventional and
coconut shell.
Fresh Concrete Properties
Workability is one of the important properties of fresh concrete,
which is directly or indirectly responsible for quality of concrete
as a whole. Adequate workability on one hand improves the
desirable properties of concrete such as, finish ability, degree of
compaction and strength, etc. Whereas on the other hand it
reduces the undesirable properties like segregation and bleeding
of concrete.
Description
Fresh
concrete
density
(kg/m3
)
Slump
(mm)
Compaction
factor
Demoulded
density
(kg/m3
)
CC with
GGBS+SF
30% + 10%
2560
30
0.91
2420
CC with
GGBS+AF
30% + 10%
2550
35
0.92
2432
CSC with
GGBS+SF
30% + 10%
2028
25
0.85
1980
CSC with
GGBS+AF
30% + 10%
2030
40
0.86
1990
Compressive strength of cubes
Description
Compressive strength fck(N/mm2
)
3days 7days 28days
CC with
GGBS+SF 30%
+ 10%
42.1
61.9
69
CC with
GGBS+AF
30% + 10%
43.1
62.8
70.3
CSC with
GGBS+SF 30%
+ 10%
30.9
33.9
41.2
CSC with
GGBS+AF
30% + 10%
30.7
34.9
43.2
Compressive strength chart
Mix proportions-for Conventional Concrete : 825
kg/m3 of cement content with
binders(Cement=500 kg/m3GGBS=250 kg/m3,SF
or AF= 75 kg/m3 )
Description
Cement
content
with
binders
Sand –
FA
12.50mm–
CA
Water
Ratio by
weight
1 0.5 1.1 0.28
Mix proportions-for Coconut Shell Concrete : 825
kg/m3 of cement content with binders(Cement=500
kg/m3 GGBS=250 kg/m3,SF or AF= 75 kg/m3 )
Description
Cement
content
with
binders
Sand –
FA
Coconut
Shell –
12.50mm-
CA
Water
Ratio by
weight
1 0.5 0.55 0.28
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Flexural strength of beam
Description
Flexural strength (N/mm2
)
3days 7days 28days
Conventional
concrete
GGBS+SF
30%+10% 6.24 7.6 10.4
GGBS+AF
30%+10% 7.2 8.8 10.4
Coconut
concrete
GGBS+SF
30%+10% 4.4 6 7.6
GGBS+AF
30%+10% 4.8 6.2 8
Flexural strength chart
Split tensile strength of cylinder
Description
Split strength in
N/mm2
3days 7days 28days
Conventional
concrete
GGBS+SF
30%+10% 6.24 4.01 4.52
GGBS+AF
30%+10% 4.39 4.89 5.28
Coconut
concrete
GGBS+SF
30%+10% 2.38 3.24 3.21
GGBS+AF
30%+10% 2.04 2.96 3.43
Split tensile strength chart
CONCLUSIONS
The following conclusions have been made based on the results
obtained from the experimental investigations.
The Coconut shell has better workability due to the
smooth surface on one side and size of the coconut shell used in
this study.
The 28th day density of the high strength coconut shell
concrete is 1960 to 1990 kg/m3 and these are within the range of
structural lightweight concrete of density less than 2000 kg/m3.
Compressive strength of high strength conventional
concrete attains 70.2 N/mm2 but high strength coconut shell
concrete achieves
43.2 N/mm2.
The flexural strength of high strength coconut shell
concrete decrease at 29.5% and 33.3% at 3rd day, 21% and
29.5% at 7th day, 26.9% and 23% in 28th day compare to high
strength conventional concrete but it attains the 10-15% of
compressive strength of high strength coconut shell concrete.
The Split tensile strength of high strength coconut shell
concrete decrease at 28.5% and 53.6% at 3rd day, 27.7% and
39.4% at 7thday, 28.8% and 34.9% at 28th day compare to high
strength conventional concrete.
The impact strength of high strength coconut shell
concrete is greater than the high strength conventional concrete
at 5.5%, 8% at 7th day and 14.5%, 15.2% at 28th day due to high
impact strength.
REFERENCES
[1] Gunasekaran K, Kumar P.S, Lakshmipathy M, (2010)
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[3] Gunasekaran K, Annadurai R, Kumar P.S, (2012) “Study on
reinforced lightweight coconut shell concrete beam behavior
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Page 7
[4] Gunasekaran K,Annadurai R, Kumar P.S, (2013) “Study on
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[11] ACI committee 544, 1R-82 for impact resisitance for
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[12] Alccofine 1203 Indian Green Building Council Member.
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[13]IS383 1970 Specification for Coarse and fine aggregate
from Natural Sources for Concrete.
[14] IS 516 1959 Method of Tests for Strength of Concrete.
[15] IS 5816 1970 Method of Test Splitting Tensile Strength of
Concrete.