Coconut shell as coarse aggregate in the concrete

Seminar report 2019-20 Coconut shell as coarse aggregate in the concrete
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1. INTRODUCTION
Concrete is widely used as structural material in the world today. The high demand for
concrete in construction drastically reduces the natural stone deposits such as gravel and granite
and this has damaged the environment thereby causing ecological imbalance. Normal concrete
contains four components, cement, crushed stone, river sand and water. The crushed stone and
sand are the components that are usually replaced with lightweight aggregates. The use of
alternative aggregate has become necessity for the construction industry because of the
economic, environmental and technological benefits derived from their use.
Further, with increased population and modern living habits, production of waste material
is increasing at fast pace and its disposal has become a genuine problem. To resolve the problem,
solution is either to minimize the waste at production level or to utilize the waste materials for
some positive activity. In view of these issues, reuse of various types of waste materials for
concrete production has been investigated and reported such as ﬂy ash ,industrial slag ,waste
plastic ,over burnt bricks ,coconut shell ,oil palm shell , waste rubber tyres ,Waste glass ,
recycled coarse aggregate,papercrete etc.
Lightweight aggregate concrete can be used produced using a variety of lightweight
aggregate. Lightweight aggregate can be originated from natural materials like pumice, the
thermal treatment of natural raw materials like clay slate or shale. The other byproduct may
include fly ash. The required properties will have bearing on the best type of lightweight
aggregate used. the benefits of using lightweight aggregate concrete includes reduction in dead
load, improved thermal properties, improved fire resistance and reduction in formwork.

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2. COCONUT SHELL
Coconut is grown in more than 93 countries. India is the third largest, having cultivation
on an area of about 1.78 million hectares for coconut production. Annual production is about
7562 million nuts with an average of 4248 nuts per hectare .coconut industry in India accounts
for over a quarter of the world's total coconut oil output and is set to grow further with the global
increase in demand. However, it is also the main contributor to the nation's pollution problem as
a solid waste in the form of shells, which involves an annual production of approximately 3.18
million tones. It also presents serious disposal problems for local environment, is an abundantly
available agricultural waste from local coconut industries. In developing countries, where
abundant coconut shell waste is discharged, these wastes can be used as potential material or
replacement material in the construction industry. This will have the double advantage of
reduction in the cost of construction material and also as a means of disposal of wastes.
Fig. 1 Coconut Shell
(Source: http://upload.wikimedia.org)
Fig. 2 Crushed Coconut Shell
(Source: http://upload.wikimedia.org)

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2.1 Coconut shell Processing
The coconut shell was sun dried for two months before being crushed in the quarry. This
is to ensure that the moisture content is reduced to the barest minimum. The crushed Coconut
shell material was later transported to the laboratory where they were thoroughly cleaned and
washed, then allowed to dry under ambient temperature. The coconut shells were available in
various shapes, such as curved, flaky, elongated, roughly parabolic and other irregular shapes as
shown in Plate v. Plate VI is the sizes obtained after crushing. In order to ascertain the properties
of coconut shell aggregate the following tests was carried out which includes the specific gravity,
bulk density, particle size distribution, aggregate impact value, aggregate crushing value,
aggregate abrasion value, porosity/water absorption capacity, elongation index and flakiness
index.
Table 1. Chemical composition of Coconut Shell
(Source: Asian Journal of Science and Technology)
2.2 Mechanical properties of Coconut shell
2.2.1 Specific gravity
The specific gravity of an aggregate is of importance in the calculation of the quantity of
aggregate required for a given volume of concrete. The specific gravity adopted in this research
is the apparent specific gravity. The apparent specific gravity is the ratio of the mass of the
aggregate dried in an oven at 100 to 110°c for 24 hours to the mass of water occupying a volume
equal to that of the solid including the impermeable pores. Apparent specific gravity of an
aggregate depends on the specific gravity of the minerals of which the aggregate is composed
and also on the amount of voids. The British standard BS 1330: part 2: 1995 stipulates the
procedure for determining the specific gravity of an aggregate. It also gave the specific gravity of
majority of natural aggregate to be between 2.6 and 2.7.

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The results showed that coconut shell has an average specific gravity of 1.31. The
average specific gravity value of 1.31 for coconut shell aggregate is about 50 percent lower than
the specific gravity of naturally occurring aggregate as stated above. This implies that more
aggregate is needed for concrete mix.
Table 2. Coconut shell specific gravity values
2.2.2 Bulk density
The bulk density gives information in respect of shape and grading of the aggregate. This
is test was performed in accordance to BS 812: Part 2: 1990. The coconut shell bulk density
ranges from 622kg/m3 to 639.48kg/m3.This value is within the limit specified for light weight
aggregate. The result shows that coconut shell aggregate have about 50% less weight compare
with that of both fine and normal stone aggregate making it light weight aggregate.
Table3. Coconut shell aggregate bulk density results
2.2.3 Particle size distribution analysis

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The sieve analysis is conducted to determine the particle size distribution in a sample of
aggregate, often referred to as gradation. A good aggregate particle size distribution implies that
a sample of aggregates contains all standard fractions. That is aggregate in required proportion,
such that the sample contains minimum voids. The essence of particle size distribution analysis
is to have well graded aggregate which have direct influence on producing workable concrete.
The particle size distribution analysis was carried to ensure that the resulting concrete is
workable, since good grading of aggregates is one of the factors in producing good concrete. The
single aggregate size used in the analysis is reflected, as the highest percentage of the aggregate
passing fell between sizes 14-20mm.
Table 4. Particle size distribution- coconut shell aggregate (16mm)
2.2.4 Impact value
The aggregate impact value test was done in accordance with BS 812: Part 112: 1990.
The aggregate Impact value can be described as a standard hammer falling 15 times under its
own weight upon the aggregate in a cylindrical container. This results in fragmentation in
manner similar to that produced by the pressure of the plunger in aggregate crushing value. The
British standard (BS 812: Part 112:1990 and BS 882: 1992) specified maximum value of 25
percent when the aggregate is to be used in heavy duty floors; 30 percent when the aggregate is
to be used in concrete for wearing surfaces and 45 percent when it is to be used in the other
concrete. Resistance to wear is an important property of concrete used in pavements, and in floor
surfaces subjected to heavy traffic. The impact values for coconut shell aggregate ranges from
1.29 to 1.32 percent. This means that coconut shell aggregate is resistance to wear. Hence it can
be used for all types of light weight concrete. The average impact value for Coconut shell
aggregate is 1.32 percent which is far less than 25 percent allowed in BS 812: Part 112:1990 and

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BS 882: 1992. The Coconut shell aggregate impact value indicates that it can also be used as
construction material.
Table 5. Coconut shell aggregate impact value results
2.2.5 Crushing value
This test was carried out in accordance with BS 812: Part 110: 1990.The test of aggregate
crushing value is a measure of aggregate resistance to pulverization. The British standard code of
practice BS 812: part 110: 1990 specified that aggregate crushing value should not be more than
45% for aggregate used for concrete other than for wearing surfaces and 30% for concrete used
for wearing surface such as runways, roads and air field pavement.
The crushing value of coconut shell aggregate ranges from 1.153% to 1.169%. Hence the
coconut shell aggregate can be used for other concrete work other than the ones mentioned
above. The average of coconut shell aggregate crushing value is 1.16% which is lower than 30%
maximum specified in the code. Therefore, the coconut shell aggregate crushing value shows
that the material can be used as alternative coarse aggregate in construction.
Table 6. Coconut shell aggregate crushing value results

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2.2.6 Abrasion value
The abrasion value test on aggregate particles was done as prescribed by BS 812: part
113:1990. The aggregate abrasion value is defined in terms of the percentage loss in mass on
abrasion. The aggregate sample is subjected to abrasion in a standard machine, the grinding lap
being turned 500 revolutions. High aggregate abrasion value denotes a low resistance to
abrasion. The aggregate abrasion test is of great importance if the aggregate is to be used for road
construction, warehouse floors and pavement constructions. The code specified that for
aggregates to be used for above type of construction should have max abrasion value between
30% - 50%.
The coconut shell abrasion value ranges between 2.19 to 2.26 percent. While the average
abrasion value is 2.23% this is far less than 30%. Hence the coconut shell aggregate is a suitable
material for construction as it satisfied the abrasion provision in the code. The implication of this
result is that coconut shell aggregate have high resistance to wear.
Table 7. Coconut shell aggregate abrasion value results
2.2.7 Porosity /water absorption capacity
The standard procedures for assessing the porosity and water absorption of aggregate is
prescribed in BS 812: Part 2: 1975 and BS 812: part 109: 1990. The presence of internal pores in
the aggregate particles and the characteristics of these pores are of paramount importance in the
study of its properties.

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The porosity of aggregate, the permeability and the absorption influences such properties
of aggregate as the bond between it, the hydrated cement paste, the resistance of concrete to
freezing and thawing as well as its chemical stability and resistance to abrasion. Since aggregate
represents three quarters of the volume of concrete, it is clear that the porosity of aggregate
materially contributes to the overall porosity of concrete. The water absorption of aggregate is
determined by measuring the increase in mass of an oven dried sample when immersed in water
for 24 hours. The ratio of the increase in mass to the mass of the dried sample expressed as a
percentage is termed absorption. The value of coconut shell absorption capacity ranges from
23.65% to 23.80%. While the average coconut shells absorption capacity is approximately 24%.
This value is within the range for absorption capacity of light weight aggregates as stipulated by
Portland cement association, which is between 5% and 30%. Hence the coconut shell aggregate
can also be used or classified as light weight aggregate.
Table 8: Coconut shell aggregate water absorption capacity results
2.2.8 Elongation index
The test was carried out in accordance with BS 812 section 105.2: 1990.Although BS 812
section 105.2: 1990 has no recognized limits but this result is acceptable for a light weight
aggregate. The result shows that coconut shell aggregate have approximately 27%. Although,
there are no recognized limits laid down, the presence of elongated particles in excess of 10 to
15% of the mass of coarse aggregate is generally considered undesirable.

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Table 9. Coconut shell aggregate Elongation index result
2.2.9 Flakiness index
The flakiness index of an aggregate is the percentage by weight of particles whose least
dimension (thickness) is less than three fifths of their mean dimension. The coconut shell
flakiness index test ranges from 86.09% to 86.16% .The result shows that coconut shell
aggregate is a flaky material, based on BS 882:1992 which limits the flakiness index of the
coarse aggregate to 50% for natural gravel and 40% for crushed coarse aggregate.
Table 10. Coconut shell aggregate flakiness index results

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3. EXPERIMENTAL INVESTIGATIONS
The test was carried out for M20 grade concrete, the mix which has characteristic
strength of 20MPa. Mix design was done as prescribed by Indian standards. Tests, as prescribed
by Indian Standards, were performed to determine the properties of the ingredients. The study
was carried out in two phases. In the ﬁrst part, mix design of M20 grade of control concrete (i.e.
concrete with no coconut shell) was carried out for maximum permissible w/c ratio of 0.55.
Then, CA was replaced by CS in the proportions (i) 10%, (ii) 20%, (iii) 30% and (iv) 40% by
volume respectively, keeping w/c ratio and quantity of other ingredients constant. 7 days and 28
days compressive strength and density of concrete was obtained for these concrete mixes.
3.1. Material used
In this study, the materials used were Ordinary Portland Cement, Potable Water, Natural
Sand, and Crushed Coarse Aggregates. Waste coconut shell was used as a partial replacement of
conventional crushed coarse aggregate. Details of materials used are provided in following
section.
3.1.1. Ordinary Portland cement
Ordinary Portland cement of 53 grades was used in this study. Tests for cement were
carried out according to standards.
3.1.2. Fine aggregate - Natural sand
Various tests were conducted on natural sand as per standards to ﬁnd the properties of
natural sand.
3.1.3. Crushed coarse aggregates
Crushed coarse aggregate (CA) of two types with respect to particle sizes were used for
the experimental work. Two were mixed in proportion of (2:3) to satisfy the grading requirement
of 20mm size nominal aggregate. The aggregates were tested in accordance with standards to
know their properties.

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3.2. Mix design of M20 grade concrete
M20 mix design was carried out for control mix (i.e. without coconut shell) according to
Indian standards. Detailed procedure of mix design is provided in Annexure A. The concrete mix
was designed for slump of 60 mm. Using same mix design, coconut shell concrete was prepared
by replacement of conventional crushed coarse aggregate (CA) with waste coconut shell (CS).
Coconut shell replaced conventional aggregate by 10%, 20%, 30% and 40% respectively (by
volume) and the effect on compressive strength and density of concrete was observed.
Table 11 Quantities of ingredients per m3 of concrete.
(Source: Performance of coconut shell as coarse aggregate in concrete, Construction
and Building Materials)
3.3. Testing of concrete
7 days and 28 days compressive strength of concrete was obtained by compression
testing machine. Compressive load was increased till the specimens were broken. Cubes were
used for ﬁnding out the compressive strength of various concrete mixes. The compression test
was carried on concrete mixes according to standards. Weight of the specimens was taken before
compression testing to ﬁnd the density.

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4. RESULTS AND DISCUSSION
Mix design was carried out for M20 grade control concrete (i.e. without coconut shell).
Cubes of control concrete were prepared according to this mix design. In order to investigate the
effect of replacing partially the conventional aggregate (CA) by coconut shell (CS), cubes of
coconut shell concrete were also casted. Same proportion of ingredients was maintained for
coconut shell concrete also except replacing partially (by volume) the CA with CS.
Table 12 Compressive strength of concrete with different quantity of coconut shell.
4.1 Effect of Coconut Shell On Compressive Strength Of Concrete
Compressive strength of cube for different ratios of CA and CS; taking quantity of
ingredients (except coarse aggregate) corresponding to M20 grade of control concrete
.Compressive strength of coconut shell concrete is decreasing gradually with increase in quantity
of coconut shell. Gain in strength after 7 days is signiﬁcantly higher for coconut shell concrete
than that for control concrete. Table 9 shows the decrement in compressive strength due to
increasing percentage of coconut shell. It can be observed that the decrement in the 28 days
compressive strength of coconut shell concrete is lesser than the decrement in compressive
strength at 7 days. Results also indicate that coconut shell concrete gain less strength initially (7
days) but shows rapid strength gain at later stage.

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Table 13 Effect of coconut shell quantity on compressive strength.
4.2. Effect Of Coconut Shell On Concrete Density
Cubes of concrete prepared for control concrete and with different percentages of CA
replacement by CS were weighed just before testing them for compressive strength. The density
of concrete was evaluated to investigate the effect of the replacement. The results show that
density decreases with increase in percentage of coconut shell. Decrease is about 7.5% for
replacement of 40%. The reason for decrease in density owes to relatively low speciﬁc gravity of
coconut shell.
Table 14: Effect of coconut shell quantity on density of concrete
(Source: Performance of coconut shell as coarse aggregate,Construction and
Building Materials)

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4.3. Effect Of Coconut Shell On Cement Content
Water/cement ratio variation for different coconut shell concretes, as estimated from trial
mixes. As shown in the Table, increase in percentage of coconut shell contents requires gradual
reduction in water/cement ratio so as to maintain the desired target mean compressive strength.
For M20 grade concrete, no additional cement was required for 5% replacement of CA by CS. In
case of 10% replacement, additional quantity of cement required was only 3.6%. However, for
25% replacement, additional cement content of 81.6kg per m3 of concrete was required to save
271.9 kg of conventionalcoarseaggregateperm3 of concrete and at the same time getting added
advantage of disposing 115.4 kg of waste coconut shell.
Table 15: Change in quantities of coarse aggregate, cement and CS per m3 concrete
(Source: Performance of coconut shell as coarse aggregate in concrete,
Construction and Building Materials)

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Fig. 3. Variation of cement; CA and CS content per m3 of M20 grade concrete.
(Source: Performance of coconut shell as coarse aggregate in concrete, Construction and
Building Materials)
5. FUTURE SCOPE OF THE PROJECT
Our study had many limitations, of which the time was a major concern. The durability
properties of coconut shell concrete are to be rested before practically applying our project.
Durability tests on CSC which may take around a year to complete can be conducted as a future
work. The strength properties of CSC depend on the aggregate properties of coconut shells and
its individual strength characteristics. Experiments on impact value, crushing value etc can be
done in order to analyze the strength properties of coconut shells. When CSC is used along with
reinforcement, the surface bonding between coconut shell aggregates and steel comes into play.
Therefore study about bond properties of these can be useful. Furthermore the action of coconut
shell aggregates in cement matrix is also an area requiring future research. We can also study
about the use of coconut shell aggregates along with other non-conventional aggregates like
palm kernel shells, coir pith, volcanic debris, etc

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6. CONCLUSION
Use of coconut shell in cement concrete can help in waste reduction and reduction in
pollution. The need of the hour is to encourage such a use of the wastes as construction material
in low cost housing. The construction industries have identified many artificial and natural
lightweight aggregate that have replaced conventional aggregates thereby reducing the size of the
members in the structure. Replacement of conventional aggregate by waste coconut shell
(keeping quantity of other ingredients unchanged) results into decrease in compressive strength.
40% replacement resulted in about 22% reduction in the 28 days strength. Addition of coconut
shell shows low strength development at early age but later it shows rapid strength development.
The ratio of 7 days to 28 days strength ranges from 0.87 (for concrete without CS) to 0.42 (for
concrete with 40% CS). 3. Replacement of conventional aggregate by waste coconut shell makes
the concrete lighter. Reduction in concrete density is about 7.5% for 40% replacement. 4.
Strength obtained for conventional concrete can be maintained for waste coconut shell concrete
also by reducing the W/C ratio. The required reduction in W/C ratio for achieving same strength
is more for increased waste coconut shell contents thereby increasing the cement consumption.
Workability of concrete is increases as the replacement increases. Specific gravity of the
concrete reduces as the replacement of coarse aggregate increases. The density of concrete is
decreases as the replacement increases. Density of concrete should not be less than 2000 kg/cum

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REFERENCES
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Coconut shell as coarse aggregate in the concrete

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