study on strength properties of coconut shell

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study on strength properties of coconut shell
International
Journal of Civil Engineering
and OF
Technology
ISSN 0976 – 6308
INTERNATIONAL
JOURNAL
CIVIL(IJCIET),
ENGINEERING
AND(Print),
ISSN 0976 – 6316(Online), Volume 6, Issue 3, March (2015), pp. 42-61 © IAEME
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)
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IJCIET
©IAEME
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.
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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
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
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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
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, 200910&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.
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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
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
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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
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.
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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
Property / Source
Specific Gravity
Wet Sieve Analysis
(% Retained on
No:325BS Sieve)
Specific Surface
(cm2/g Blaines)
Lime Reactivity
(kg/cm2)
A
B
C
D
E
1.91
2.12
2.10
2.25
2.14 to 2.429
16.07
54.65
15.60
5.00
51.00 (dry)
2759
1325
2175
4016
2800 to 3250
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
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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
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.
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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
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
Normal consistency of cement
Setting Times of cement
Initial
Final
Specific Gravity of cement
Fineness of cement
Specific Gravity of aggregates
Coarse aggregates
Fine aggregates
Water absorption capacity
Coarse aggregates
Fine aggregates
Specific gravity of coconut shells
Specific gravity of fly ash
Water absorption capacity of coconut shells
3.
RESULTS
31%
28 min
9 hr 57 min
3.15
2%
2.65
2.63
0.495
0.96
1.33
2.06
4.5%
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
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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
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
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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
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)
10
20
40
Mix Name
M1
M2
M3
M4
M5
Cement (kg)
41.38
41.38
41.38
37.24
33.10
Fine
Aggregate
45.2
45.2
45.2
40.68
36.16
Air Content (%)
3
2
1
Coarse
Aggregate
112
100.8
89.6
90.72
80.64
Coconut
Shells (kg)
0
5.6
11.2
5.04
4.48
Fly ash (kg)
0
0
0
2.75
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
1
2
3
4
5
6
Type of Concrete Mix
M30 Grade
100% Coarse Aggregate
10% Coconut Shells + 90% Coarse Aggregate
20% Coconut Shells + 80% Coarse Aggregate
10% Coconut Shells + 10% Fly ash
10% Coconut Shells + 20% Fly ash
Total
No. of
Cubes
24
24
24
24
24
24
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
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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
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)
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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
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 (ovendrying 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
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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
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.
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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
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
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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
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.
S No
Days
CONVENTIONAL CONCRETE TEST RESULTS
Compressive
Split Tensile
Water
Permeable
Strength, MPa
Strength, MPa
Absorption Voids (%)
3
7
28
3
7
28 (%)
Sorptivity
(mm/sec1/2)
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
S No
Days
10% REPLACEMENT OF CS AS COARSE AGGREGATE
Compressive Strength,
Split Tensile
Water
Permeable
MPa
Strength, MPa
Absorption
Voids (%)
3
7
28
3
7
28 (%)
Sorptivity
(mm/sec1/2)
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
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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
S No
Days
20% REPLACEMENT OF CS AS COARSE AGGREGATE
Compressive Strength,
Split Tensile
Water
Permeable
MPa
Strength, MPa
Absorption Voids (%)
3
7
28
3
7
28 (%)
Sorptivity
(mm/sec1/2)
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
Compressive Strength,
Split Tensile
Water
S No
Permeable
Sorptivity
MPa
Strength, MPa
Absorptio
Voids (%) (mm/sec1/2)
n (%)
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
Compressive Strength,
Split Tensile
Water
S No
Permeable
Sorptivity
MPa
Strength, MPa
Absorptio
Voids (%)
(mm/sec1/2)
n (%)
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
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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
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
7 days
28 days
1.74
2.52
3.7
1.43
2.27
3.4
1.32
1.98
3.3
1.8
2.67
3.8
1.77
2.5
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
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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
59
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
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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
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.
2.
3.
4.
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.
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.
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.
Mohsin M Jujara, “Comparative Performance and Emission Charactristics of 4-Cylinder 4Stroke 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
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