STUDY ON STRENGTH PROPERTIES OF COCONUT SHELL CONCRETE

International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),

ISSN 0976 – 6316(Online), Volume 6, Issue 3, March (2015), pp. 42-61 © IAEME

42

STUDY ON STRENGTH PROPERTIES OF COCONUT

SHELL CONCRETE

Kalyanapu Venkateswara Rao

Associate Professor, Gudlavalleru Engineering College

A.H.L.Swaroop

Assistant Professor, Gudlavalleru Engineering College

Dr.P.Kodanda Rama Rao

Professor, Gudlavalleru Engineering College

Ch.Naga Bharath

Assistant Professor, Gudlavalleru Engineering College

ABSTRACT

Concrete is the premier construction material around the world and is most widely used in all

types of construction works, including infrastructure, low and high-rise buildings, and domestic

developments. It is a man-made product, essentially consisting of a mixture of cement, aggregates,

water and admixture(s). Inert granular materials such as sand, crushed stone or gravel form the major

part of the aggregates. Traditionally aggregates have been readily available at economic prices and of

qualities to suit all purposes. But, the continued extensive extraction use of aggregates from natural

resources has been questioned because of the depletion of quality primary aggregates and greater

awareness of environmental protection.

In light of this, the non-availability of natural resources to future generations has also been

realized. Different alternative waste materials and industrial by products such as fly ash, bottom ash,

recycled aggregates, foundry sand, china clay sand, crumb rubber, glass were replaced with natural

aggregate and investigated properties of the concretes. Apart from above mentioned waste materials

and industrial by products, few studies identified that coconut shells, the agricultural by product can

also be used as aggregate in concrete.

INTERNATIONAL JOURNAL OF CIVIL ENGINEERING AND

TECHNOLOGY (IJCIET)

ISSN 0976 – 6308 (Print)

ISSN 0976 – 6316(Online)

Volume 6, Issue 3, March (2015), pp. 42-61

© IAEME: www.iaeme.com/Ijciet.asp

Journal Impact Factor (2015): 9.1215 (Calculated by GISI)

www.jifactor.com

IJCIET

©IAEME



43

According to a report, coconut is grown in more than 86 countries worldwide, with a total

production of 54 billion nuts per annum. India occupies the premier position in the world with an

annual production of 13 billion nuts, followed by Indonesia and the Philippines. Limited research has

been conducted on mechanical properties of concrete with coconut shells as aggregate replacement.

However, further research is needed for better understanding of the behavior of coconut shells as

aggregate in concrete.

Thus, the aim of this work is to provide more data on the strengths of coconut shell concretes

at different coconut shells (CS) replacements and study the transport properties of concrete with

coconut shells as coarse aggregate replacement. Furthermore, in this study, the effect of fly ash as

cement replacement and aggregate replacement on properties of the coconut shells replaced concrete

was also investigated.

The concrete obtained using coconut shell aggregates satisfies the minimum requirements of

concrete. Concrete using coconut shell aggregates resulted in acceptable strength required for

structural concrete. coconut shell may offer itself as a coarse aggregate as well as a potential

construction material in the field of construction industries and this would solve the environmental

problem of reducing the generation of solid wastes simultaneously. The coconut shell cement

composite is compatible and no pre-treatment is required. coconut shell concrete has better

workability because of the smooth surface on one side of the shells. The impact resistance of coconut

shell concrete is high when compared with conventional concrete. Moisture retaining and water

absorbing capacity of coconut shell are more compared to conventional aggregate. The amount of

cement content may be more when coconut shell are used as an aggregate in the production of

concrete compared to conventional aggregate concrete. The presence of sugar in the coconut shells

as long as it is not in a free sugar form, will not affect the setting and strength of concrete.

Keywords: Natural Resources, Alternative Waste Materials, Coconut Shells, Coconut Shell

Concrete, Strength Properties.

1. INTRODUCTION

1.1 Scope of the Work

The aim of this study is to assess the utility and efficacy of coconut shells as a coarse

aggregate as an alternative to natural aggregate in concrete. Coconut shells have not been tried as

aggregate in structural concrete.

1.2 Waste Materials In India

Almost all over the world various measures aimed at reducing the use of primary aggregates

and increasing reuse and recycling have been introduced, where it is technically, economically, or

environmentally acceptable. As a result, in developing countries like India, the informal sector and

secondary industries recycle 15–20% of solid wastes in various building materials and components.

As a part of integrated solid waste management plan that includes recycle, reuse and recovery, the

disposed solid waste, representing unused resources, may be used as low cost materials. Presently in

India, about 960 MT of solid wastes are being generated annually as by-products from industrial,

mining, municipal, agricultural and other processes. Of this, 350 MT are organic wastes from

agricultural sources; 290 MT are inorganic wastes of industrial and mining sectors. However, it is

reported that about 600 MT of wastes have been generated in India from agricultural sources alone.

1.2.1 Present status of coconut shell

The coconut palm is one of the most useful plants in the world. Coconut is grown in 92

countries in the world. Global production of coconut is 51 billion nuts from an area of 12 million



44

hectares. South East Asia is regarded as the origin of coconut. The four major players India,

Indonesia, Philippines and Sri Lanka contribute 78% of the world production.

According to FAO statistics (Food and Agriculture Organization) 2007, global production of

coconuts was 61.5 MT with Indonesia, Philippines, India, Brazil and Sri Lanka as the major

contributors to coconut production. The total world coconut area was estimated as approximately 12

million hectares and around 93 percent is found in the Asian and Pacific region. The average annual

production of coconut was estimated to be 10 million metric tons of copra equivalents. Of the world

production of coconut, more than 50 percent is processed into copra. While a small portion is

converted into desiccated coconut 5 and other edible kernel products, the rest is consumed as fresh

nuts.

According to a study done by the Central Plantation Crop Research Institute (CPCRI) at

Kasargod, the country’s coconut production was headed for an all-time high of 5 14,370 million nuts

in 2006-07. Higher productivity in Tamil Nadu was the main reason for the escalation in the

production. In India, the southern states account for 90 per cent of the total production. Kerala tops

with 5400 million nuts while Tamil Nadu with 4190 million nuts is the second highest producer.

Currently, the crop is grown in 1.91 million hectares with an annual production of nearly

14,000,15700&17500million nuts. As per the recent Government of India statistics 2008-09, 2009-

10&2011-12 India has emerged as the largest producer of coconut in the world with a production of

15,840 million nuts. India accounts for 26.9 per cent of the world’s production. In India, the four

south Indian states namely Kerala, Tamil nadu, Karnataka and Andhra Pradesh account for around

90% of the coconut production in the country.

1.2.2 Present use of coconut shell

Coconut shells have good durability characteristics, high toughness and abrasion resistant

properties; it is suitable for long standing use. Coconut shells are mostly used as an ornament,

making fancy items, house hold utensils, and as a source of activated carbon from its charcoal. The

powdered shell is also used in the industries of plastics, glues, and abrasive materials and it is widely

used for the manufacture of insect repellent in the form of mosquito coils and in agarbathis. The

purpose of this research work is to develop a concrete with coconut shells as coarse aggregate. The

whole entity could be called coconut shell aggregate concrete (CSAC). After the coconut is scraped

out, the shell is usually discarded as waste as shown in Figure 1.1. The vast amount of this discarded

coconut shells resource is as yet unutilized commercially; its use as a building material, especially in

concrete, on the lines of other LWA is an interesting topic for study. The study of coconut shells will

not only provide a new material for construction but will also help in the preservation of the

environment in addition to improving the economy by providing new use for the coconut shells.

Therefore attempts have been taken to utilize the coconut shells as coarse aggregate and develop the

new structural LWC.

1.3 Objectives of the Research

If structural LWC can be developed from coconut shells, which is locally available in

abundance, it would be a milestone achievement for the local construction industries. Therefore, the

main objective of this research is to 8 determine the feasibility of using solid waste coconut shells as

coarse aggregate for structural LWC. The research objectives are briefly summarized below.

• To study the properties of coconut shells, compatibility of coconut shells with cement and to

produce coconut shell aggregate concrete with 28 day compressive strength more than 20

N/mm2.

• To study the strength properties of concrete in replacement of coarse aggregate .

• To study the strength properties of concrete in replacement of coarse aggregate and

replacement of flyash with cement.

• To study the behavior of compressive and split tensile strengths.



45

1.4 Methodology

The basic properties of coconut shells such as physical, chemical, mechanical properties, and

the compatibility of coconut shells with cement were studied. Based on the standard procedures and

methods followed for the production of conventional LWC, the coconut shell aggregate concrete

were produced. Numerous trial mixes were conducted by varying cement content, sand, coconut

shells and water-cement (w/c) ratio. The acceptable trial mixes were then identified and finally, the

workability, strength, density and durability requirements for different applications of LWC were

taken into consideration during the selection of the optimum coconut shell aggregate concrete mix.

Also, the concrete mix was optimized for coconut shells cement ratio and w/c ratio. This optimum

mix was then used throughout the entire investigation for the production of coconut shell aggregate

concrete specimens. Control concrete (CC) using crushed granite stone aggregate concrete (normal

weight concrete – NWC) was also produced for comparison purposes. Comparison studies between

CC and coconut shell aggregate concrete were conducted only on the fresh concrete properties,

compressive strength, basic and mechanical properties. The behavior of NWC, namely the structural

bond, durability and temperature properties are well established. Therefore these properties were not

investigated for CC in this study. Structural properties such as flexural and shear behavior of

reinforced coconut shell aggregate concrete beams were studied by making prototype elements and

the results are compared with the other LWA used in concrete. Comparisons of some properties for

coconut shell aggregate concrete were made using some codes of practice and other LWC. Also,

tests conducted on temperature characteristics of coconut shell aggregate concrete are studied.

2. EXPERIMENTAL INVESTIGATION

2.1 Materials

The constituent materials used in this investigation were procured from local sources. These

materials are required by conducting various tests. Due to these results we were define what type of

materials are used. We are using cement, fly ash, coarse aggregate, fine aggregate, coconut shells

and water.

2.1.1 Cement

Ordinary Portland cement of C53 grade conforming to both the requirements of IS: 12269 and

ASTM C 642-82 type-I was used. We are conducting different types of tests on cement, those are

Normal Consistency, Initial and Final setting times, Compressive strength of cement, Specific

Gravity and Fineness of cement. From the test results obtained the conventional concrete can be

designed according to IS10262-82(MIX DESIGN CODE). Finally M30 Grade concrete is designed.

2.1.2 Coarse Aggregate

Normal aggregate that is crushed blue granite of maximum size 20 mm was used as coarse

aggregate. We are conducting tests on coarse aggregate are Water Absorption Capacity, Specific

Gravity and Fineness Modulus of coarse aggregate.

2.1.3 Fine Aggregate

Well graded river sand passing through 4.75 mm was used as fine aggregate. The sand was air-dried

and sieved to remove any foreign particles prior to mixing. We are conducting tests on fine aggregate

are Water Absorption Capacity, Specific Gravity and Fineness Modulus of fine aggregate.

2.1.4 Fly Ash

Fly ash closely resembles volcanic ashes used in production of the earliest known hydraulic cements

about 2,300 years ago. Those cements were made near the small Italian town of Pozzuoli – which

later gave its name to the term pozzolan. A pozzolan is siliceous/aluminous material that, when

mixed with lime and water, forms a cementitious compound. Fly ash is the best known, and one of

the most commonly used, pozzolans in the world. Instead of volcanoes, today’s fly ash comes



46

primarily from coal-fired, electricity-generating power plants. These power plants grind coal to

powder fineness before it is burned. Fly ash – the mineral residue produced by burning coal – is

captured from the power plant’s exhaust gases and collected for use.The difference between fly ash

and portland cement becomes apparent under a microscope. Fly ash particles are almost totally

spherical in shape, allowing them to flow and blend freely in mixtures. That capability is one of the

properties making fly ash a desirable admixture for concrete.

First of all, the spherical shape of fly ash creates a ball bearing effect in the mix, improving

workability without increasing water requirements. Fly ash also improves the pump-ability of

concrete by making it more cohesive and less prone to segregation. The spherical shape improves the

pump-ability by decreasing the friction between the concrete and the pump line. In addition, some fly

ashes have been shown to significantly decrease heat generation as the concrete hardens and

strengthens. Fly ash, as do all pozzolanic materials, generally provide increased concrete strength

gain for much longer periods than mixes with portland cement only. The biggest reason to use fly

ash in concrete is the increased life cycle expectancy and increase in durability associated with its

use. During the hydration process, fly ash chemically reacts with the calcium hydroxide forming

calcium silicate hydrate and calcium aluminate, which reduces the risk of leaching calcium

hydroxide and concrete’s permeability. Fly ash also improves the permeability of concrete by

lowering the water-to-cement ratio, which reduces the volume of capillary pores remaining in the

mass. The spherical shape of fly ash improves the consolidation of concrete, which also reduces

permeability. Other benefits of fly ash in concrete include resistance to corrosion of concrete

reinforcement, attack from Alkali-silica reaction, sulfate attack and acids and salt attack.

2.1.4.1 Types of Fly ash

1) Class F fly ash

The burning of harder, older anthracite and bituminous coal typically produces Class F fly ash. This

fly ash is in nature, and contains less than 20% (CaO). Possessing pozzolanic properties, the glassy

silica and alumina of Class F fly ash requires a cementing agent, such as Portland cement, quicklime,

or hydrated lime, with the presence of water in order to react and produce cementitious compounds.

Alternatively, the addition of a chemical activator such as (water glass) to a Class F ash can lead to

the formation of a.

2) Class C fly ash

Fly ash produced from the burning of younger lignite or sub bituminous coal, in addition to having

pozzolanic properties, also has some self-cementing properties. In the presence of water, Class C fly

ash will harden and gain strength over time. Class C fly ash generally contains more than 20% lime

(CaO). Unlike Class F, self-cementing Class C fly ash does not require an activator. Alkali and

(SO4) contents are generally higher in Class C fly ashes. Fly ash is used as a replacement of cement

or aggregate. It contains solid spherical particles. It increases workability of concrete.

2.1.4.2 Physical Properties Fly ash consists of fine, powdery particles that are predominantly spherical in shape, either solid or

hollow, and mostly glassy (amorphous) in nature. The carbonaceous material in fly ash is composed

of angular particles. The particle size distribution of most bituminous coal fly ashes is generally

similar to that of a silt (less than a 0.075 mm or No. 200 sieve).

The specific gravity of fly ash usually ranges from 2.1 to 3.0, while its specific surface area may

range from 170 to 1000 m2/kg. The colour of fly ash can vary from tan to gray to black, depending

on the amount of unburned carbon in the ash. The lighter the color, the lower the carbon content.

Lignite or sub bituminous fly ashes are usually light tan to buff in color, indicating relatively low

amounts of carbon as well as the presence of some lime or calcium. Bituminous fly ashes are usually

some shade of gray, with the lighter shades of gray generally indicating a higher quality of ash.



47

Property / Source A B C D E

Specific Gravity 1.91 2.12 2.10 2.25 2.14 to 2.429

Wet Sieve Analysis

(% Retained on

No:325BS Sieve)

16.07 54.65 15.60 5.00 51.00 (dry)

Specific Surface

(cm2/g Blaines)

2759 1325 2175 4016 2800 to 3250

Lime Reactivity

(kg/cm2)

86.8 56.0 40.3 79.3 56.25 to 70.31

2.1.4.3 Chemical Properties The chemical properties of fly ash are influenced to a great extent by those of the coal burned

and the techniques used for handling and storage. There are basically four types, or ranks, of coal,

each of which varies in terms of its heating value, its chemical composition, ash content, and

geological origin. The four types, or ranks, of coal are anthracite, bituminous, sub bituminous, and

lignite. In addition to being handled in a dry, conditioned, or wet form, fly ash is also sometimes

classified according to the type of coal from which the ash was derived.

The principal components of bituminous coal fly ash are silica, alumina, iron oxide, and

calcium, with varying amounts of carbon, as measured by the loss on ignition (LOI). Lignite and sub

bituminous coal fly ashes are characterized by higher concentrations of calcium and magnesium

oxide and reduced percentages of silica and iron oxide, as well as a lower carbon content, compared

with bituminous coal fly ash. Very little anthracite coal is burned in utility boilers, so there are only

small amounts of anthracite coal fly ash.

The chief difference between Class F and Class C fly ash is in the amount of calcium and the

silica, alumina, and iron content in the ash. In Class F fly ash, total calcium typically ranges from 1

to 12 percent, mostly in the form of calcium hydroxide, calcium sulfate, and glassy components in

combination with silica and alumina. In contrast, Class C fly ash may have reported calcium oxide

contents as high as 30 to 40 percent. Another difference between Class F and Class C is that the

amount of alkalis (combined sodium and potassium) and sulfates (SO4) are generally higher in the

Class C fly ashes than in the Class F fly ashes.

Loss on ignition %

SiO2

SO3

P2O5

Fe2O3

Al2O3

Mn2O3

CaO

MgO

Na2O

5.02

50.41

1.71

0.31

3.34

30.66

0.31

3.04

0.93

3.07

11.33

50.03

-

-

10.20

18.20

-

6.43

3.20

-

1.54

63.75

-

-

30.92

-

-

2.35

0.95

-

4.90

60.10

-

-

6.40

18.60

-

6.3

3.60

-

1-2

45-59

Traces to 2.5

-

0.6-0.4

23.33

-

5-16

1.5-5

-

2.1.5 Coconut Shell

The coconut palm is one of the most useful plants in the world. Coconut is grown in 92

countries in the world. Global production of coconut is 51 billion nuts from an area of 12 million

hectares.

Coconut shells which were already broken into two pieces were collected from local temple;

air dried for five days approximately at the temperature of 25 to 30 C; removed fiber and husk on



48

dried shells; further broken the shells into small chips manually using hammer and sieved through

12.5mm sieve. The material passed through 12.5mm sieve was used to replace coarse aggregate with

coconut shells. The material retained on 12.5mm sieve was discarded. Water absorption of the

coconut shells was 8% and specific gravity at saturated surface dry condition of the material was

found as 1.33.

The sugar present in wood may cause incompatibility between wood and cement. Since the

coconut shells aggregates are wood based, to estimate the sugar present in coconut shells, 15

Generally, the parameters that determine the compatibility requirements for the coconut

shells cement composite are maximum hydration temperature, time taken to attain maximum

temperature, ratio of the setting times of coconut shells fines-cement mixture, neat cement and

inhibitory index. Inhibitory effect is the measure of the decrease in heat release during the

exothermic chemical process of cement hydration. The coconut shells cement compatibility was

analyzed with the properties such as normal consistency, initial and final setting times, compressive

strength and hydration using the samples of coconut shells fines with cement and neat cement.

Fig Coconut Shells

2.1.6 Water

The quality of water is important because contaminants can adversely affect the strength of

concrete and cause corrosion of the steel reinforcement. Water used for producing and curing

concrete should be reasonably clean and free from deleterious substances such as oil, acid, alkali,

salt, sugar, silt, organic matter and other elements which are detrimental to the concrete or steel. If

the water is drinkable, it is considered to be suitable for concrete making. Hence, potable tap water

was used in this study for mixing and curing. fine particles passing through IS sieve 9, IS sieve 15,

IS sieve 30 were taken and analyzed without any treatment. Also coconut shells fines passing

through IS sieve 15 was taken and analyzed with treatment. The treatment consisted of soaking the

coconut shells fine particles in water for durations of 30 min, 1 h, 2 h, and 1 day, 2 days and also

soaked with hot water for 2 h.

Generally, the parameters that determine the compatibility requirements for the coconut

shells cement composite are maximum hydration temperature, time taken to attain maximum

temperature, ratio of the setting times of coconut shells fines-cement mixture, neat cement and

inhibitory index. Inhibitory effect is the measure of the decrease in heat release during the

exothermic chemical process of cement hydration. The coconut shells cement compatibility was

analyzed with the properties such as normal consistency, initial and final setting times, compressive

strength and hydration using the samples of coconut shells fines with cement and neat cement.



49

2.2 Tests on Materials

2.2.1 Cement

2.2.1.1 Normal Consistency of Cement

2.2.1.2 Initial and Final Setting Times of Cement

2.2.1.3 Compressive Strength of Cement

2.2.1.4 Specific Gravity of Cement

2.2.1.5 Fineness of Cement

2.2.2 Coarse Aggregate

2.2.2.1 Specific Gravity of Aggregates

2.2.2.2 Water Absorption Capacity of Aggregates

2.2.2.3 Fineness Modulus of Aggregates

2.2.3 Fine Aggregate 2.2.3.1 Bulking of Sand

PHYSICAL PROPERTIES OF

MATERIALS

RESULTS

Normal consistency of cement 31%

Setting Times of cement

Initial

Final

28 min

9 hr 57 min

Specific Gravity of cement 3.15

Fineness of cement 2%

Specific Gravity of aggregates

Coarse aggregates

Fine aggregates

2.65

2.63

Water absorption capacity

Coarse aggregates

Fine aggregates

0.495

0.96

Specific gravity of coconut shells 1.33

Specific gravity of fly ash 2.06

Water absorption capacity of coconut shells 4.5%

3. DISCUSSION

3.1 Mix Proportion

Mix design is the process of selecting an optimum proportion of cement, fine and coarse

aggregates and water to produce a concrete with specified properties of workability, strength, and

durability. The best mix involves a balance between economy and the required properties of

concrete.

Based on the properties of the available materials, the mix proportions of the coconut shells

concrete were first approximated using absolute volume method. This approximation gave a starting

point from which modifications of trial mixes were made to achieve a practical end result and to

produce coconut shells aggregate concrete of the desired properties. Hence, the mix design for the

coconut shell aggregate concrete in this study was based on performances of trial mixes and the

measure of the selected mix was so adjusted to get the most favorable mix proportion. Finally, an

optimum mix was selected.

In order to investigate properties of coconut shells concretes, five mixes were employed.

Control mix (M1) that is, without coconut shells was made. Coarse aggregate was then replaced with

coconut shells in 10 (M2), 20 (M3), percentages to study effect of CS replacement. Furthermore, a



50

mix with both coconut shells and fly ash (M4) was also employed, in which, 10% of coconut shells

was replaced with coarse aggregate and 10% of fly ash was replaced with coarse aggregate. M5 mix

contained 10% of coconut shells and 20% of fly ash both replaced with aggregate.

3.2 Water Cement Ratio (w/c)

It is difficult to specify the optimal w/c ratio for all kinds of wood cement composite. Hence,

it is necessary to optimize the coconut shells aggregate - cement ratio and w/c ratio. It is seen that

with the increase of w/c ratio, the strength of coconut shell aggregate concrete reduced. Therefore

w/c ratio was considered as 0.38, 0.42, and 0.45.

Sufficient water amount is the prerequisite for high quality cement based products. However,

because water can increase the distance between cement particles before and during hydration, and

increase the volume of capillary pores, i.e. the porosity of the hydrated products, excess water may

adversely affect the physical-mechanical properties of the hydrated products. Few studies have been

done on the effect of w/c ratio on wood/cement concrete composites. It seems that it is not easy to

specify an optimal w/c ratio for all kinds of wood/cement concrete composites, because of the wide

varieties of raw materials and the dependence of water requirement on wood/cement ratio all found

that with the increase of w/c ratio, the strength of the wood/cement concrete composites was

reduced. With an increase of wood/cement ratio, more water was needed to obtain maximum

bending strength. Hence, it is very much necessary to optimize the wood/cement ratio and w/c ratio

for coconut shell aggregate concrete and therefore trial mixes were made and analyzed.

3.3 Coconut Shell Aggregate Concrete (CSAC):

Literature shows that when wood based materials are used as aggregate in concrete, the

biological decomposition is not apparent. Coconut shells aggregate has comparatively high water

absorption characteristics. As a result, to avoid water absorption during the mixing process, it is

essential to mix coconut shells aggregate at SSD condition based on 24 h immersion in potable

water. It is targeted to produce coconut shell aggregate concrete of compressive strength more than

17 N/mm2 to meet the minimum strength of structural concrete as per ASTM C 330. But as per IS

456:2000, the minimum strength of structural concrete is more than 20 N/mm2 and this was also

considered to produce coconut shell aggregate concrete. Mix design is the process of selecting an

optimum proportion of cement, fine and coarse aggregates and water to produce a concrete with

specified properties of workability, strength, and durability. The best mix involves a balance between

economy and the required properties of concrete.

3.4 Mix Design for M30 Grade Concrete

Grade of concrete: M30

Method used : IS code method

Fck = fck + t s = 38.25 ( t =1.65, s =5)

Water cement ratio: 0.45

Compaction factor: 0.9

Maximum size of aggregate: 20 mm

Specific gravity of cement Sc : 3.15

Specific gravity of fine aggregate Sfa : 2.63

Specific gravity of coarse aggregate Sca : 2.65

Cement content : 186 kg / m3

Sand percentage of total aggregate: 35 %

Sand percentage of total aggregate after adjustments = 35 – 4.5 = 31.5 %

Water content after adjustments = 186 + (186 x 0.03) = 191.61

From water cement ratio



51

Cement content = 191.61 / 0.45 = 425.8

Fine aggregate content = 517.99

Coarse aggregate content = 1180.36

Mix proportion is 191.61: 425.8: 517.99: 1180.36

Mix proportion is 0.45: 1: 1.21: 2.77

M.S.A (mm) Air Content (%)

10 3

20 2

40 1

Mix Name Cement (kg) Fine

Aggregate

Coarse

Aggregate

Coconut

Shells (kg) Fly ash (kg)

M1 41.38 45.2 112 0 0

M2 41.38 45.2 100.8 5.6 0

M3 41.38 45.2 89.6 11.2 0

M4 37.24 40.68 90.72 5.04 2.75

M5 33.10 36.16 80.64 4.48 4.5

3.5 Casting of Sample

The size of from work adopted for concrete cub was 150x150x150mm. The concrete was

mixed with various constituent in their respective percentage, placed and compacted in three layers

after proper mixing by hand. The samples were remoulded after 24 hours and kept in a curing tank

for 3, 7 and 28 days as required.

Sl

No

Type of Concrete Mix No. of

Cubes

1 M30 Grade 24

2 100% Coarse Aggregate 24

3 10% Coconut Shells + 90% Coarse Aggregate 24

4 20% Coconut Shells + 80% Coarse Aggregate 24

5 10% Coconut Shells + 10% Fly ash 24

6 10% Coconut Shells + 20% Fly ash 24

Total 144

3.6 Curing

The objective of curing is to keep concrete saturated or as nearly saturated to get the products

of hydration of cement in water-filled space. The temperature of curing and the duration of moist

curing are the key factors for proper curing. The method of curing is one of the main factors

affecting the strength development of concrete. The loss of moisture in the capillary pores due to



52

evaporation or dissipated hydration may cause reduction in hydration resulting lower strength. The

moist cured samples give higher compressive strength than dry cured samples of concrete with

certain admixtures. In all types of curing the strength of concrete is dependent to some extent upon

the strength of aggregate. The increment rate in strength is more in crushed stone concrete than in

OPS concrete.

3.7 Test Program

The main objective of the present investigation was to study the performance of coconut

shells concretes in terms of strength and transport properties with normal water curing and with no

chemical admixtures in the mixes. Performance of the concretes was assessed through: compressive

strength, split tensile strength, water absorption and sorption. The specimens were tested for

compression and split tensile strengths at 3, 7 and 28 days. The strengths were obtained by

considering the average of two replicate specimens. However, if the variation of any individual value

from the average was greater than + 10 %, a third specimen was tested. Absorption and sorption tests

were conducted at 28 days of curing. These tests were also conducted on two replicate specimens

and the average values were reported.

3.7.1 Compressive Strength

The compression test is simply the opposite of the tension test with respect to the direction of

loading. In some materials such as brittle and fibrous ones, the tensile strength is considerably

different from compressive strength. Therefore, it is necessary to test them under tension and

compression separately. Compression tests results in mechanical properties that include the

compressive yield strength, compressive ultimate strength, and compressive modulus of elasticity in

compression, % reduction in length etc.

The compressive loading tests on concretes were conducted on a compression testing

machine of capacity 2000 kN. For the compressive strength test, a loading rate of 2.5 kN/s was

applied as per IS: 516–1959. The test was conducted on 150mm cube specimens at 3, 7 and 28 days.

Each sample was weighed before putting into the crushing machine to ascertain it density. The

compression strength of each sample was determined as follows

Compressive strength = Crushing Load (kN) /Effective Area (mm2)



53

3.7.2 Split Tensile Strength

Split tensile strength test was conducted in accordance with ASTM C496. Cylinders of 100 x

200 mm size were used for this test, the test specimens were placed between two platens with two

pieces of 3 mm thick and approximately 25 mm wide plywood strips on the top and bottom of the

specimens. The split tensile strength was conducted on the same machine on which the compressive

strength test was performed. The specimens were tested for 3, 7 and 28 days.

3.7.3 Permeable Voids and Water Absorption

Volume of Permeable Voids is an essential property of concrete as it affects the transfer

mechanisms through the concrete such as outpouring of liquids and gases. Absorption and permeable

void of concrete tests were performed according to American Standards ASTM C 642-97 (oven-

drying method). The test was conducted to evaluate the structure of concrete by determining the

absorption capacity and void space available. For this test, cylinders were cast. After 24 h the

specimens were demoulded and kept immersed in water for 28 days. At the end of 28 days, the

specimens were taken out and air-dried to remove the surface moisture.

An absorption study was conducted to understand the relative porosity permeable void space

of the concretes, in according to ASTM C 642-82. The absorption and permeable voids tests were

conducted on two 150 mm cubes. Saturated surface dry specimens were kept in a hot air oven at

1050C until a constant weight was attained. The ratio of the difference between the mass of saturated

surface dry specimen and the mass of the oven dried specimen at 1050C to the volume of the

specimen gives the permeable voids in percentage as: Permeable voids = (A-B)/V*100 where A is

the weight of surface dried saturated sample after 28 days immersion period. B is the weight of oven



54

dried sample in air. V is the volume of sample. The specimens removed from the oven were allowed

to cool to room temperature. These specimens were then completely immersed in water and weight

gain was measured until a constant weight was reached. The absorption at 30 min (initial surface

absorption) and final absorption (at a point when the difference between two consecutive weights

was almost negligible) were reported to assess the concrete quality. The final absorption for all the

concretes was observed to be at 72 h

3.7.4 Sorption Test

The sorption test was conducted on the concretes in order to characterize the rate of moisture

migration of water into the concrete pores. One hundred fifty millimeter cube specimens were

marked on all four sides at 10 mm interval to measure the moisture migration. As explained in the

water absorption test, the specimens were oven-dried. They were then allowed to cool down to the

room temperature. After cooling, the cubes were placed in water on the wedge supports to make sure

that only the bottom surface of the specimens was in contact with the water. A cotton cloth was

covered on top of the wedge supports to ensure the specimens are in contact with water throughout

the test period. Moisture rise in the cubes was measured through the weight gain of the specimen ate

the regular intervals. The sorption of the concretes was thus calculated using linear regression

between the weight gain of specimen per unit area of concrete surface in contact with water and

square root of time for the suction periods.



55

4. RESULTS

4.1 Compressive Strength

The strength of all the concretes increased with curing age. Control concrete gained 31

percent and 50 percent over its 28 day compressive strength at 3 days and 7 days of curing

respectively. Strength of the coconut shells concretes increased 24-42 percent at 3 days and 38-84

percent after 7 days of curing than its corresponding 28 day strengths respectively. This observation

suggests that as coconut shells percentage increased the 7 day strength gain also increased with

corresponding 28 day curing strength. The coconut shells concretes, especially 20% (M3)

replacement level the concretes failed to maintain same strength gain, which had first 7 days of

curing. This may be due to lack of sufficient bond between the particles. As the first 7 days of

curing, majority of the compressive strength of the concretes depends on paste strength. However, at

later age, the strength of concrete depends on strength of the paste, strength of the aggregate and

bond strength between the aggregate particles and cement paste. Evidently, in the present

investigation, the visual observations on specimens failed in compressive strength test suggested that

the coconut shells particles were separated from the paste phase. Fly ash as cement replacement

reduces strength of the paste at early age, thus, strength gain was reduced. The 28 day compressive

strength of M2 concrete was 61 percent when compared to control concrete. Furthermore, the

strength decreased with coconut shells replacement. The trend of the results was in line with the

earlier studies. The strength of M3 was 32% respectively when compared to control concrete. This

observation suggests fly ash as a cement replacement had reduced compressive strength of coconut

shells concrete. Furthermore, compressive strength of M4 concrete was nearly equal to M2 concrete.

From this observation it can be understood that addition of fly ash as an aggregate replacement had

no influence on compressive strength when compared to corresponding coconut shells replaced

concrete.

4.2 Split Tensile Strength

Concretes could not achieve even 0.5MPa at one day. The split tensile strengths of the

concretes were between 0.8 - 1.4 MPa at 7 days of curing. The control concrete (M1) attained 32

percent of its 28 day split tensile strength. The coconut shells concretes had higher strength

enhancement than control concrete at 7 days of curing when compared to corresponding demoulded

strength. Maximum strength gain was for M3 concrete with 70 percent of its 28 day split tensile

strength. Similar to compressive strength, the split tensile strength also decreased with increase in

coconut shells replacement. The M2 concrete with 10% coconut shells replacement had 63 percent of

control concrete at 28 days of curing. M3 concrete had only 48 percent of control concrete strength

at 28 days. The split tensile strengths at 28 days were between 1.15-2.39MPa, control concrete had

highest strength. This observation suggests that, similar to compressive strength, for 28 days of

curing addition of fly ash as cement replacement reduces overall strength of coconut shells concrete

and fly ash addition as an aggregate replacement shows no major difference with corresponding

coconut shells replaced concrete (M3). It appears there is a good relationship between compressive

strength and split tensile strength.

4.3 Permeable Voids and Water Absorption

As can be seen the permeable voids increased with increase in coconut shells replacement.

For control concrete the permeable voids were 7.7%. However, 10% coconut shells replacement

increased permeable voids to 10.07 % which was 30 percent higher than control concrete. Similarly,

the permeable voids were 88% higher than control concrete for 20% coconut shells replacement.

Addition of fly ash as an aggregate replacement reduced permeable voids. There was good

relationship between the parameters, permeable voids increased with increase in coconut shells



56

replacement. Although there was little difference of initial water absorption between coconut shells

concretes, the final absorptions of the concretes were nearly same for all the coconut shells

concretes. Addition of fly ash an aggregate replacement did not show any marked difference when

compared to corresponding coconut shells replaced concrete (M3). With the increase in permeable

voids water absorption also increases. Strength and water absorption are dependent on pore structure

of the concrete and are inversely proportional to one another, that is, if porosity increases, strength

decreases and absorption increases.

4.4 Sorptivity – Capillary Water Absorption

Sorptivity of the concretes was between 0.12-0.18 mm/s0.5. The lowest sorptivity was for

control concrete and the highest sorptivity was for M5 concrete. Similar to water absorption,

sorptivity also increased with coconut shells replacement. Furthermore, fly ash as cement

replacement further increased sorption when compared to corresponding coconut shells replaced

concrete, but, fly ash as an aggregate replacement showed little lower sorption. As water absorption

increased sorption also increased. As in water absorption, sorptivity also increased with increase in

permeable voids. Overall, the main factors that control the transport properties of concrete materials

are relative volume of paste matrix, the pore structure of the bulk matrix and the interfacial zone

around the aggregate particles. As explained earlier, it is thought that the coconut shells with

elongated and curved shape and lack of bond between the paste and aggregate particles resulted more

porous structure and thus had higher values of absorption and sorption for coconut shells replaced

concretes than control concrete.

CONVENTIONAL CONCRETE TEST RESULTS

S No Compressive

Strength, MPa

Split Tensile

Strength, MPa

Water

Absorption

(%)

Permeable

Voids (%)

Sorptivity

(mm/sec1/2

)

Days 3 7 28 3 7 28

1 15.1 23.4 37.3 1.7 2.5 3.7 0.431 9.67 0.124

2 14.7 24.2 38.1 1.74 2.52 3.6 0.51 8.45 0.126

3 14.9 23.9 37.1 1.79 2.9 3.7 0.45 8.92 0.123

10% REPLACEMENT OF CS AS COARSE AGGREGATE

S No Compressive Strength,

MPa

Split Tensile

Strength, MPa

Water

Absorption

(%)

Permeable

Voids (%)

Sorptivity

(mm/sec1/2

)

Days 3 7 28 3 7 28

1 16.6 26.67 36.7 1.45 2.31 3.6 2.43 10.7 0.134

2 16.83 27.43 37.0 1.40 2.2 3.5 2.43 13.42 0.135

3 17.10 27.14 36.8 1.43 2.27 3.4 2.429 11.29 0.133



57

20% REPLACEMENT OF CS AS COARSE AGGREGATE


MPa

Split Tensile

Strength, MPa

Water

Absorption

(%)

Permeable

Voids (%)

Sorptivity

(mm/sec1/2

)

Days 3 7 28 3 7 28

1 17.34 25.01 34.7 1.32 1.96 3.5 4.22 13.71 0.156

2 18.02 25.42 34.9 1.28 1.98 3.2 4.45 13.72 0.163

3 18.47 24.78 32.8 1.33 2.34 3.3 4.6 13.25 0.159

10% COCONUT SHELL AGGREGATE + 10% FLY ASH REPLACEMENT


MPa

Split Tensile

Strength, MPa Water

Absorptio

n (%)

Permeable

Voids (%)

Sorptivity

(mm/sec1/2

) Days 3 7 28 3 7 28

1 17.34 24.7 37.3 1.8 2.6 3.7 4.31 8.67 0.16

2 17.89 24.98 37.9 1.82 2.8 3.8 4.35 8.9 0.162

3 18.53 24.6 37.5 1.89 2.67 3.85 4.33 8.6 0.161

10% COCONUT SHELL AGGREGATE + 20% FLY ASH REPLACEMENT


MPa

Split Tensile

Strength, MPa Water

Absorptio

n (%)

Permeable

Voids (%)

Sorptivity

(mm/sec1/2

) Days 3 7 28 3 7 28

1 17.92 24.2 37.7 1.78 2.5 3.76 6.4 8.43 0.188

2 17.84 24.6 38.0 1.76 2.4 3.5 6.38 8.28 0.192

3 17.81 24.33 37.6 1.76 2.6 3.72 6.29 8.33 0.190

M 30 Grade Concrete

COMPARISON OF RESULTS: (COMPRESSIVE STERNGTH)

DAYS CONVENTIONAL

CONCRETE 10% CS 20% CS

10% CS +

10% FLY

ASH

10% CS +

20% FLY

ASH

3 days 19.9 16.83 18.02 17.89 17.81

7 days 23.9 2443 25.01 24.7 24.33

28 days 37.3 36.8 34.2 37.5 37.7



58

COMPARISON OF RESULTS: (SPLIT TENSILE STERNGTH)

DAYS CONVENTIONAL

CONCRETE 10% CS 20% CS

10% CS +

10% FLY

ASH

10% CS +

20% FLY

ASH

3 days 1.74 1.43 1.32 1.8 1.77

7 days 2.52 2.27 1.98 2.67 2.5

28 days 3.7 3.4 3.3 3.8 3.72

COMPARISON OF DETAILS

S No MIX DENSITY (kg/m3) WEIGHT

1. Conventional Concrete 2365 7.981

2. 10% CS + 0% FA 2186 7.377

3. 20% CS + 0% FA 2061 6.955

4. 10% CS + 10% FA 2027 6.841

5. 10% CS + 20% FA 2023 6.827



59



60



61

CONCLUSION

Results of experiments on compressive strength, split tensile strength, water absorption and

sorption for different coconut shells replaced concretes have been presented with those of control

concrete. However, performance of coconut shells aggregate concrete having a marginal variation

than normal aggregate concrete. The main points of this study are:

1. Addition of coconut shells decreases workability and addition of fly ash as cement

replacement increases workability of coconut shells concrete. Increase in coconut shells

percentage decreased densities of the concretes.

2. By replacement of coconut shells in place of aggregates, 10% &20% replacement will have

been decreased marginally the strength properties of concrete compared to the normal

concrete.

3. But the replacement of coconut shells in place of aggregates and replacement of fly ash in

place of cement will increase the strength properties of concrete compared to the normal

concrete.

4. The replacement of the 10%coconut shells as coarse aggregate will decreases the marginal

value of 2.88% in compression and 2.7% in split tensile strength.

5. The replacement of the 20%coconut shells as coarse aggregate will decreases the marginal

value of 8.39% in compression and 10.25% in split tensile strength.

6. The replacement of the 10%coconut shells as coarse aggregate and 10%fly ash as cement will

decreases the marginal value of 0.525% in compression and increase of 4.05% in split tensile

strength.

7. The replacement of the 10%coconut shells as coarse aggregate and 10%fly ash as cement will

decreases the marginal value of 0.205% in compression and increase of 2.7% in split tensile

strength.

8. From the graph no: 2 the compressive strength of concrete will decrease with increase of

coconut shell percentage.

9. From the graph no:3 Replacement of coconut shell as coarse aggregate and Fly ash as cement

will increase the compressive strength of concrete.

REFERENCES

1. Dewanshu Ahlawat and L.G.Kalurkar, “Strength Properties of Coconut Shell Concrete”

International Journal of Civil Engineering & Technology (IJCIET), Volume 4, Issue 7, 2012,

pp. 20 - 24, ISSN Print: 0976 – 6308, ISSN Online: 0976 – 6316.

2. M.R. Kolhe and Dr. P.G. Khot, “Utilization Of Natural Resources With Due Regards To

Conservation/Efficiency or Both” International Journal of Management (IJM), Volume 5,

Issue 12, 2014, pp. 1 - 11, ISSN Print: 0976-6502, ISSN Online: 0976-6510.

3. Dewanshu Ahlawat and L.G.Kalurkar, “Strength Properties of Coconut Shell Concrete”

International Journal of Advanced Research in Engineering & Technology (IJARET),

Volume 4, Issue 7, 2013, pp. 20 - 24, ISSN Print: 0976-6480, ISSN Online: 0976-6499.

4. Mohsin M Jujara, “Comparative Performance and Emission Charactristics of 4-Cylinder 4-

Stroke Ci Engine Fueled with Coconut Oil-Diesel Fuel Blend” International Journal of

Mechanical Engineering & Technology (IJMET), Volume 4, Issue 3, 2013, pp. 367 - 372,

ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359