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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:nkr.civil@outlook.com

2Assistant Professor, Civil Engineering Department, Tamlinadu College of Engineering, Coimbatore,

E-mail:dsamuelabraham@gmail.com

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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)

“Mechanical and bond properties of coconut shell concrete”,

Construction and Building materials, Vol. 25, page 92-98.

[2] Gunasekaran K, R.Annadurai, P.S. Kumar, (2011) “Long

term study on compressive and bond strength of coconut shell

aggregate concrete”, , Construction and Building Materials, Vol.

28, page 208-215.

[3] Gunasekaran K, Annadurai R, Kumar P.S, (2012) “Study on

reinforced lightweight coconut shell concrete beam behavior

under flexure”, Materials and Design, Vol. 46, page 157-167.

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[4] Gunasekaran K,Annadurai R, Kumar P.S, (2013) “Study on

reinforced lightweight coconut shell concrete beam behavior

under shear”, Materials and Design, Vol. 50, page 293-301.

[5] Gunasekaran K, Annadurai R, Kumar P.S, (2013) “Plastic

shrinkage and deflection characteristics of coconut shell

concrete slab”, Construction and Building Materials, Vol. 43,

page 203-207.

[6] Gunasekaran K, Annadurai R, Kumar P.S, (2014) “Study on

reinforced lightweight coconut shell concrete beam behavior

under torsion”, Materials and Design, Vol.57, page 374-382.

[7] MuhannadIsmeik (2009) “Effect of Mineral Admixture on

Mechanical Properties of High Strength Concrete made with

Locally Available Materials”.Jordan Journal, Volume 3,

No.1,page 78-90.

[8]Payan Shafigh,MohdZaminJumaat,Hilmi Mahmud(2010 )“

Oil palm shell as a light weight aggregate for production of high

strength light weight concrete”.Construction and Building

Materials, page1848-1853.

[9]Payam Shafigh, MohdZaminJumaat, Hilmi Bin Mahmud,

Johnson Alengaram U (2011)“A new method of producing high

strength oil palm shell lightweight concrete” Materials and

Design 32 ,page 4839–4843.

[10]Shannag M.J,(2010) “Characteristics of lightweight

concrete containing mineral admixtures”. Issued on Construction

and Building Materials 25, page 658–662.

[11] ACI committee 544, 1R-82 for impact resisitance for

concrete.

[12] Alccofine 1203 Indian Green Building Council Member.

Issued revision 1/July 13.

[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.