Study on groundnut shell ash as partial replacement of cement in concrete

JIMMA UNIVERSITY
School of Graduate Studies
Jimma Institute of Technology
Faculty of Civil and Environmental Engineering
Department of Civil Engineering
Construction Engineering and Management
Stream
Study on Groundnut Shell Ash as Partial
Replacement of Cement for C-25 Concrete
By: Eliyas Dessalegn
A Thesis submitted to the School of Graduate Studies of Jimma University in
Partial Fulfillment of the Requirements for the Degree of Master of Science in
December/ 2018
Jimma, Ethiopia

Study on Groundnut Shell Ash as Partial Replacement of Cement for C-25 Concrete
Jimma University
Jimma Institute of Technology
School of Graduate Studies
Faculty of Civil and Environmental Engineering
Department of Civil Engineering
Stream
Study on Groundnut Shell Ash as Partial
Replacement of Cement for C-25 Concrete
By:
Eliyas Dessalegn
A Thesis submitted to the School of Graduate Studies of Jimma University in
Partial fulfillment of the requirements for the Degree of Master of Science in
Civil Engineering (Construction Engineering and Management)
Advisor: Dr. Ing. Tamene Adugna(PhD)
Co-Advisor: Eng. Lucy Feleke (MSc)
December/ 2018
Jimma, Ethiopia

By: Eliyas Desssalegn I
Declaration
This thesis is my original work and has not been presented for the award of any degree
in this university or elsewhere, except where due acknowledgement has been made in
the text.
Eliyas Dessalegn _____________________ _____________________
Name Signature Date
This thesis has been submitted for examination with my approval as university
supervisor.
Dr. Ing. Tamene Adugna(PhD) ___________________ ___________________
Advisor Signature Date
Eng. Lucy Feleke (Msc) ___________________ _________________
Co-Advisor Signature Date

By: Eliyas Desssalegn II
JIMMA UNIVERSITY
JIMMA INSTITUTE OF TECHNOLOGY
FACULTY OF CIVIL AND
ENVIRONMENTAL ENGINEERING
CONSTRUCTION ENGINEERING AND
MANAGEMENT
Study on Groundnut Shell Ash as Partial Replacement of Cement in
C-25 Concrete
By
Eliyas Dessalegn Maru
APPROVED BY BOARD OF EXAMINERS:
Name Signature Date
1. External Examiner _____________________ / ____________/_______________
2. Internal Examiner ______________________ /____________/________________
3. Chair Person Eng. Bien Maunahan /____________/________________
4. Dr. Ing. Tamene Adugna /________________/_________________
Main Advisor
5. Ms. Lucy Feleke (Msc) /_________________/________________
Co-advisor

By: Eliyas Desssalegn III
Abstract
Among the ingredients of concrete making materials, cement is the expensive and the
most energy-intensive during its production. Its mining, transportation, and production
needs a substantial investment and cost. The quarry of raw materials needs a
substantial volume to balance the large demand of cement in the market. The
production process releases high amount of heat from hydration and carbon dioxide to
the atmosphere. The production of groundnut in Ethiopia is low relative to other
African countries. Nowdays, the groundnut is produced in Oromiya region East
Hararghe and Western Wolega, Benishangul-Gumuz region Metekel, and Amhara
region Western Gojam. Ethiopia has potential to produce about 500,000 tons per year
on estimated land of 40,000 hectares.
The general objective of this study was to assess the effects of cement replacement with
Groundnut Shell Ash in C-25 concrete by examining physical properties of concrete
with and without Groundnut Shell Ash (GSA) and chemical composition of GSA,
assessment of direct cost of concrete replaced with GSA, and amount of GSA to be
replaced based on the concrete properties. The compressive strength of concrete was
measured in terms of strength at 7, 14, and 28 days of age. For the compressive
laboratory test, quartering and weighting was the system for sampling technique. In
this study compressive strength of concrete with and without GSA at ages 7, 14, and 28
days with percentage cement replacement of 0%, 5%, 10%, 15 %, and 20 % of GSA by
weight with a total of 45 samples were used for mixes.
As per the results of this study, there is extra amount of silica in the groundnut retarded
the initial setting time, the direct cost was decreased with increased amount of GSA in
concrete, and the optimum amount of GSA as cement replacement in concrete was 10%
based on the slump, setting time, density, and compressive tests carried out.
Keywords: Compressive Strength, Cost, Groundnut shell ash, Setting time, Workability

By: Eliyas Desssalegn IV
Acknowledgements
First, I would like gratefully acknowledge the Almighty God for his divine help. My
deepest gratitude goes to my advisor Dr. Ing. Tamene Adugna and Eng. Lucy Feleke
for their limitless efforts in guiding and correcting my work. Next, I would like to give
thanks to my father, Dessalegn Maru and all other family members for their heart full
advice.
Finally, my deepest appreciation goes to Jimma University School of Graduate Studies,
Jimma Institute of Technology, Faculty of Civil and Environmental Engineering,
Construction Engineering and Management Chair and my classmate friends for their
valuable assistances.

By: Eliyas Desssalegn V
Table of Contents
Title page
Declaration..................................................................................................................... I
Abstract........................................................................................................................III
Acknowledgements......................................................................................................IV
Table of Contents..........................................................................................................V
List of Tables ............................................................................................................VIII
List of Figures..............................................................................................................XI
Acronyms................................................................................................................... XII
1. Introduction ............................................................................................................1
1.1. Background .....................................................................................................1
1.2. The Statement of the Problem.........................................................................3
1.3. Significance of the Study ................................................................................4
1.4. Research Questions .........................................................................................5
1.5. Objectives........................................................................................................5
1.5.1. General Objective ....................................................................................5
1.5.2. Specific Objectives ..................................................................................5
1.6. Scope and Limitations.....................................................................................6
2. Literature Review ...................................................................................................7
2.1. Physical Properties of Concrete ......................................................................7
2.2.1. Compressive Strength of concrete ...........................................................8
2.2.2. Workability of concrete ...........................................................................8
2.3. Cement for Concrete .......................................................................................9
2.3.1. Types of cement.......................................................................................9
2.3.2. Chemical Composition of Cement.........................................................10
2.4. Pozzolanic Materials .....................................................................................11
2.4.1. Types of Pozzolanic Materials...............................................................13
2.5. Groundnut Shell Ash (GSA) .........................................................................15
2.5.1. Production of GSA in Ethiopia..............................................................17

By: Eliyas Desssalegn VI
2.6. Direct Cost of Concrete.................................................................................18
3. Research Materials and Methodology..................................................................19
3.1. Introduction...................................................................................................19
3.2. Materials for Research ..................................................................................19
3.2.1. Materials for concrete without GSA......................................................19
3.2.2. Materials for concrete with GSA...........................................................19
3.2.3. Groundnut Shell.....................................................................................20
3.2.4. Cement...................................................................................................21
3.2.6. Water......................................................................................................21
3.3. Determining Properties of Materials.............................................................22
3.3.1. Laboratory tests of material property of concrete produced..................22
3.4. Production of concrete ................................................................................23
3.4.1. Proportioning concrete materials ...........................................................23
3.4.2. Compressive strength test ......................................................................24
3.5. Study Area.....................................................................................................25
3.6. Study Design .................................................................................................27
3.7. Sample Size and Sampling Procedure...........................................................27
3.8. Study Variables .............................................................................................28
3.8.1. Dependent Variable ...............................................................................28
3.8.2. Independent Variables ...........................................................................28
3.9. Data Collection Process ................................................................................28
3.10. Data Processing and Analysis....................................................................28
4. Results and Discussion.........................................................................................29
4.1. Introduction...................................................................................................29
4.2. Physical Properties of Concrete Materials ....................................................29
4.2.1. Coarse Aggregate...................................................................................29
4.2.2. Fine Aggregate.......................................................................................31

By: Eliyas Desssalegn VII
4.2.3. Cement...................................................................................................33
4.2.4. Groundnut Shell Ash..............................................................................35
4.2.5. Setting time............................................................................................35
4.3. Proportioning of Ingredients .........................................................................40
4.4. Physical Properties of Concrete with and without GSA ...............................41
4.5. Chemical Composition of GSA.....................................................................46
4.6. Direct Cost of Concrete with GSA................................................................50
4.7. Optimum Amount of GSA Replacement in Concrete...................................56
4.7.1. Slump.....................................................................................................56
4.7.2. Initial Setting Time ................................................................................56
4.7.3. Unit Weight............................................................................................57
4.7.4. Compressive Strength ............................................................................57
4.7.5. Chemical Composition...........................................................................57
4.7.6. Direct Cost .............................................................................................57
5. Conclusions and Recommendations.....................................................................58
5.1. Conclusions...................................................................................................58
5.2. Recommendations.........................................................................................59
References....................................................................................................................60
APPENDICES .............................................................................................................62
APPENDIX A:.............................................................................................................62
Properties of Concrete Ingredients...............................................................................62
APPENDIX B:.............................................................................................................67
Fresh Concrete Properties............................................................................................67
APPENDIX C:.............................................................................................................70
Hardened Concrete Properties .....................................................................................70
3.11. Photo Galleries ..........................................................................................77

By: Eliyas Desssalegn VIII
List of Tables
Table 2-1: Chemical Composition of Portland Cement...............................................10
Table 2-2:- Common chemical compositions of pozzolanic materials........................12
Table 3-1: Property tests and test methods of material................................................23
Table 3-2: Amount of GSA and cement with their ratio .............................................24
Table 4-1: Sieve Analysis format and Standard for coarse aggregate according to ES
C.D3.201......................................................................................................................29
Table 4-2: Summary of Test Results for Coarse Aggregate........................................30
Table 4-3: Sieve Analysis Standard for fine aggregate according to ES C.D3.201 ....31
Table 4-4: Summary of Fine Aggregate Properties .....................................................33
Table 4-5: Sieve analysis of OPC Cement...................................................................34
Table 4-6: Test result of Consistency of OPC Cement................................................34
Table 4-7: Sieve analysis of GSA................................................................................35
Table 4-8: Initial Setting time test result of Cement paste with and without GSA .....39
Table 4-9: Proportion of Blending of Groundnut shell ash and Cement .....................40
Table 4-10: Final mix proportion of control concrete ingredients...............................41
Table 4-11: Slump Test Results...................................................................................41
Table 4-12: Unit Weights of Control and Blended concretes at age of 7 days............43
Table 4-13: Unit Weights of Control and Blended concretes at age of 14 days..........43
Table 4-14:Unit Weights of Control and Blended concretes at age of 28 days...........43
Table 4-15: Average Compressive Strengths of OPC-GSA Concretes for 7 day age of
samples.........................................................................................................................44
samples.........................................................................................................................45
samples.........................................................................................................................45
Table 4-18: Summary of Compressive Strength Tests ................................................46
Table 4-19: Chemical composition test result of GSA ................................................47
Table 4-20: Chemical composition limits of OPC.......................................................47
Table 4-21:Comparison of Oxides of OPC and GSA..................................................48
Table 4-22: Na2O analysis based on 28 day unit weight of concrete ..........................49
Table 4-23: reduction of cost with respect to GSA percentage replacements in concrete
......................................................................................................................................56

By: Eliyas Desssalegn IX
Table A-1: Grain Size Distribution for OPC Cement..................................................62
Table A-2: Grain Size Distribution for Groundnut shell ash.......................................62
Table A-3:- Sieve Analysis format and Standard for fine aggregate according to ES
C.D3.201......................................................................................................................63
Table A-4: Specific gravity and Absorption of fine aggregate ASTM C127..............63
Table A-5: Unit weight of fine aggregate ASTM C29 ................................................63
Table A-6: Moisture Content of Fine Aggregate.........................................................64
Table A-7: Silt Content of Fine Aggregate ASTM C117............................................64
Table A-8: Sieve Analysis format and Standard for coarse aggregate according to ES
C.D3.201......................................................................................................................64
Table A-9: Unit Weight of Coarse Aggregate ASTM C29 ........................................65
Table A-10: Specific gravity and Absorption of coarse aggregate ASTM C127........65
Table A-11: Moisture Content of coarse Aggregate ASTM C566..............................65
Table A-12:- Proportion of Blending of Groundnut shell ash and Cement.................66
Table B-1:- Slump Test Results...................................................................................67
Table B-2:- Initial Setting Time of Paste GSA0..........................................................67
Table B-3: Initial Setting Time of Paste GSA5 ...........................................................67
Table B-4: Initial Setting Time of Paste GSA10 .........................................................68
Table C-1: Unit Weights of Control and Blended concretes at age of 7 days.............70
Table C-2: Unit Weights of Control and Blended concretes at age of 14 days...........70
Table C-3:Unit Weights of Control and Blended concretes at age of 28 days............71
Table C-4: Compressive Strength of OPC-GSA Concretes for 7 day age of samples for
GSA0............................................................................................................................71
Table C-5:Compressive Strength of OPC-GSA Concretes for 14 day age of samples for
GSA0............................................................................................................................71
Table C-6: Compressive Strength of OPC-GSA Concretes for 28 day age of samples
for GSA0......................................................................................................................72
Table C-7: Compressive Strength of OPC-GSA Concretes for 7 day age of samples for
GSA5............................................................................................................................72
for GSA5......................................................................................................................73

By: Eliyas Desssalegn X
for GSA5......................................................................................................................73
for GSA10....................................................................................................................74
for GSA10....................................................................................................................74
for GSA10....................................................................................................................74
for GSA15....................................................................................................................75
for GSA15....................................................................................................................75
for GSA15....................................................................................................................75
for GSA20....................................................................................................................76
for GSA20....................................................................................................................76
for GSA20....................................................................................................................76

By: Eliyas Desssalegn XI
List of Figures
Figure 3-1: Groundnut Shell from drying to burning ..................................................21
Figure 3-2: Curing and Compressive test Methods .....................................................25
Figure 3-3: Study area Map (GIS) ...............................................................................26
Figure 4-1: Sieve Analysis of Coarse Aggregate.........................................................30
Figure 4-2: Sieve Analysis of Fine Aggregate.............................................................32
Figure 4-3: Sieve Analysis of Fine Aggregate.............................................................32
Figure 4-4: Sieve Analysis of Cement.........................................................................33
Figure 4-5: Consistency Test .......................................................................................35
Figure 4-6: Initial Setting time graph of 0% GSA.......................................................36
Figure 4-7: Initial Setting time graph of 5% GSA.......................................................37
Figure 4-8: Initial Setting time graph of 10% GSA.....................................................37
Figure 4-9:Initial Setting time graph of 15% GSA......................................................38
Figure 4-10: Initial Setting time graph of 20% GSA...................................................38
Figure 4-11: Setting time of Cement with and without GSA ......................................39
Figure 4-12: Slump test for Concretes with and without GSA....................................42
Figure 4-13: Compressive Test results for all percentages and ages...........................46

By: Eliyas Desssalegn XII
Acronyms
ACI American Concrete Institute
ASTM American Society for Testing and Materials
C-25 25 Pascal compressive strength
C2S Dicalcium silicate
C3A Tricalcium aluminate
C3S Tricalcium silicate
C4AF Tetracalciumaluminoferrite
CaCO3 Calcium carbonate
CO2 Carbondioxide
CSH Calcium silicate hydrate
CSH2 Calcium sulfate dihydrate (gypsum)
EBCS Ethiopian Building Code of Standard
GGBFS Ground Granulated Blast Furnace Slag
GHA Groundnut Husk Ash
Gs Specific Gravity,
GSA Groundnut Shell Ash
H2SO4 Hydrochloric Acid
MgSO4 Magnesium-sulfate
MPa Mega Pascal
NaCl Sodium-chloride
OPC Ordinary Portland cement
POC Ordinary Portland cement
PPC Portland pozzolanic cement
RPRD Research publication and research design office
W/C water to cement ratio
SiO2 silicon oxide
Al2O3 alumina
Na2O sodium oxide
K2O potassium oxide
Cl chlorine

By: Eliyas Desssalegn 1
1. Introduction
1.1. Background
The construction industry is one of the basic sectors of our country’s economic
development. The Growth and Transformation plan of our country incorporates and
focused on the construction of infrastructure expansion throughout the country. That is
why the construction industry is crucial to realize the plan. In recent time, the
commonly used material of construction industry is cement concrete (Edward G. Nawy,
2008).
Cement concrete is a mixture of cementitious materials, inert, and water to form rock
like hard and strong structure. It is a composite material mainly made up of binding
materials, hydraulic cement with water, and fragments of aggregates (Kumar & J. M.,
2006). In some cases of need of improvements in concrete properties, admixtures may
be used. As revealed by researchers, it is made by composing portland cement and other
cementing materials like fly ash slag cements, coarse, and fine aggregates or minerals,
water and admixtures (Edward G. Nawy, 2008), (Mujedu & Adebara, 2016).
Among the other ingredients of the cement concrete, Portland cement is the most
important material which can react with water and set by binding the other concrete
making materials. It is environmentally unfriendly and most expensive material
compared with the other ingredients. The expensiveness and environmental impact of
cement forced the user to look for other replacing material. The replacement materials
which are found recently were fly ash, granulated blast furnace slag, silica fume, rice
husk ash and other pozzolanic materials which are classified as supplementary
cementitious materials (SCM) (Edward G. Nawy, 2008).
Supplementary Cementitious Materials (SCM) are preferred for the replacing cement
because they have high amount of silica and cause the reduction of heat of hydration
caused by reaction of C3S (Tricalcium silicate) compound in Portland cement, hence
reduce thermal stress resulted from the heat of hydration which may cause a crack
(Christopher C. Ferraro, 2017).

It also facilitates excess silica for continuous reaction with free calcium to produce the
C-S-H, known as pozzolanic reaction, which is main desirable product in concrete
microstructure, gives strength and other qualities. Actually C-S-H is produced from
reaction of C3S and C2S with water (Christopher, et al., 2017).
Groundnut Shell Ash (GSA) or Groundnut Husk Ash (GHA) is one of artificial
pozzolanic or SCM material that can be incorporated in concrete as partial replacement
as concluded by empirical report of Adole, et al. (2011) in their experimental tests. They
have also tested in three chemical solutions, MgSO4, NaCl and H2SO4 and declared that
concrete with GSA/GHA can resist magnesium sulfate (MgSO4) and sodium chloride
(NaCl) which may found in soil.
Groundnut shell is the agro-industry waste product which is disposed as simply land-
fill or burned after its disposal. The engineering application of this material is not
practical in our country and almost no one of our farmers know about it. Like most
other farm land wastes, it has no contribution to any of local use or soil fertilizing in
our country. This waste product could take over two years to decay in soil.

1.2. The Statement of the Problem
Among the ingredients of concrete making materials, cement is expensive and its
production is the most energy-intensive process. Its mining, transportation, and
production needs a substantial investment to produce it. To produce 1 ton of cement, it
needs 1.5 ton of raw materials and emits about 1 ton of CO2 to the atmosphere (Edward
G. Nawy, 2008). This implies that this industry is contributing to the environmental
pollution and the greenhouse effect at high level. It is also not sustainable material as
described by different researchers as it releases high amount of heat from hydration and
carbon dioxide from production plus hydration to the atmosphere (Christopher C.
Ferraro, 2017).
The raw materials of cement production are lime, aluminia, and clay. These materials
are extracted from the earth crust and directly transported to burnning process. It is
obvious that there is a depletion in natural resource and disturbance of the ecosystem if
the extraction of such raw materials continue. The quarry of raw materials need
substantial volume to balance the large demand of cement in todays and tomorrows
market. This is the big deal to be optimized by finding out any mechanism to come up
with the solution.
Incase of our country, the cost of cement is high and our natural resource for raw
material of cement is declining for cement production purpose. The ecological nature
is also in crises if this extraction of the raw materials continues. Therefore we have look
for other alternative materials such as agricultural by-products as it could replace the
cement in concrete and it will contribute sustainability as it minimize the problems
described.
Considering these problems, this study investigated the use of locally available, 20,000
hectar production capacity (Getahun* & Tefera, 2017), agricultural waste which is
Groundnut Shell Ash, in the cement concrete as cement replacement and to improve
the sustainability of coccrete and direct cost of concrete by using this cheap material to
make economical concrete production without affecting the quality of concrete.

1.3. Significance of the Study
Ethiopia is one of the developing countries in the world. It is clear that one of bases for
economic evaluation or measurement of a country’s economy is the natural resource
that the country has for the future generation and this natural resource is to be used
wisely. Among the natural resources, the raw materials of cement are included.
Replacing cement can potentially contribute to the reduction of using these natural
resources.
The other main contribution of the study is the cost minimization following partial
replacement of the cement in the concrete. Cement is costly material among concrete
ingredients. Its mining, transportation, and production needs substantial investment to
produce it. It needs a high energy for burning and processing. Those are functions of
cost that have direct proportion. Therefore, it contributes for minimizing the cost by
replacing part of cement used in concrete.
It is also not a sustainable material as described by different researchers in sections
above. Because it releases high amount of heat from hydration and carbon dioxide from
production plus hydration to the atmosphere. Using of waste materials as cementing
material in concrete when properly used that it reduces coal usage in cement production
as a result it will make sustainable and fair cost material (Christopher C. Ferraro, 2017).
Therefore, we need to replace cement even up to full replacement if possible.
“The benefits of SCM additions are not limited to the physical and chemical effects on
the concrete; one of the larger benefits that are realized is the reduction in cost. This
provides a financial gain to the producers and lowered cost to the consumers...”
(Christopher C. Ferraro, 2017). From this perspective, replacing cement by pozzolanic
material is preferable directly or indirectly.
This research work also contributes to the sustainability of construction industry by
studying the suitability of GSA as cement replacement. Since cement is not
environmentally sustainable material, replacing it with other similar sustainable
material is the crucial treatment of the environment. Replacing cement with some
amount is very beneficiary for the environment by minimizing high release of CO2.

1.4. Research Questions
The questions that were addressed during this research work were:
 Does Groundnut Shell Ash replacement affect the physical properties of
concrete?
 What is the chemical composition of Groundnut Shell Ash?
 Does replacement of cement with Groundnut Shell Ash affect cost of concrete?
 What is the amount of Groundnut Shell Ash to be replaced in concrete based on
concrete properties?
1.5. Objectives
1.5.1. General Objective
The general objective of the Study is;
 To assess the effects of Groundnut Shell Ash on properties of concrete as partial
cement replacement.
1.5.2. Specific Objectives
The specific objectives are;
 To examine the physical properties of concrete with and without groundnut
shell ash (GSA).
 To examine the chemical composition of GSA.
 To assess the direct cost of concrete by replacing cement with groundnut shell
ash(GSA).
 To determine the amount of GSA to be replaced based on the concrete
properties.

1.6. Scope and Limitations
This study is limited to tests of the concrete materials and concrete properties, initial
setting time, slump, gradations, chemical composition of GSA, compressive strength,
and density of harden concrete.
The direct cost calculated was limited to the study area, Metekel, Ethiopia. This
concentrated cost may vary in other areas. The input data for calculating the cost were
obtained by oral communication and site investigation as there is no fixed standard
price rate of materials, equipment and labor. Therefore, the data used were the market
value in use during this study in the area.
The burning machine used was char-machine available in Jimma University College of
Agriculture and Veterinary. This machine uses temperature below the desired to get
ash.

2. Literature Review
2.1. Physical Properties of Concrete
Concrete is versatile and cheap material compared with other materials like steel and
hence it is the most abundant material for civil engineering structures all over the world.
It is a mixture of water, cement, aggregate or inert and other additives, where necessary,
in which water and cement are combined to form bond between aggregates to form
monolithic whole structure (Domone, 2002).
In the current condition of requirements of materials, green construction is the essential
criteria which any proposed material should fulfill. The sustainability required is to
maintain the environmental suitability to the next generations and living things.
Because this environment is the borrowed asset from the coming generation, but the
environmental impact from CO2 emission is becoming high level threat to our world.
Therefore, preventing or minimizing levels greenhouse effect of toxic gases is essential
and great deal for continuity of life. This issue is leading researchers to find out other
alternative materials which may replace cement in concrete with low CO2 emission and
low energy of production, by using blast-furnace slag, and fly ash which does not emit
the greenhouse gases, as described by (Edward G. Nawy 2008).
There are also main qualities of concrete that should be maintained during
proportioning and construction of any structure to resist and receive the load coming to
it. Those qualities are controlled during and after construction at fresh and hardened
stage. Fresh concrete quality requirements are workability, consistency, ability to be
compacted and finished and curing. The hardened concrete should have good
compressive strength, durability, abrasion resistance, resistance to weathering and
termite attack and the like. Thus, at both stage of conditions the qualities are mainly
dependent on the cement paste quality. The cement paste is the binding medium (Kumar
& J. M., 2006) to bond the aggregate particles and fines. Its quality is dependent on the
qualities of water, cement and water to cement (W/C) ratio (Domone, 2002). Hence in
this chapter, cement and its production, pozzolanas and groundnut shell ash is
discussed.

2.2.1. Compressive Strength of concrete
Strength of concrete is commonly considering as its most valuable property, although
in many practical cases other characteristics, such as durability and permeability, may
in fact be more important. Nevertheless, strength usually gives an overall picture of the
quality of concrete because it is directly related to the structure of the hardened cement
paste. Hydration reaction, water to cement ratio, aggregate type, amount and size, water
content, cement content, curing condition, cement type, compaction method used etc.
properties of concrete have an effect on the strength of concrete. Different pozzolanic
materials have different effect on concrete strength (Neville, 2000).
2.2.2. Workability of concrete
Workability is the measure of how easy or difficult it is to place, consolidate and finish
concrete. It contains in it different aspects like consistency, flow ability, mobility,
compact ability, finish ability, and harshness. In addition, it also defined in terms of the
amount of mechanical work, or energy required producing full compaction of the
concrete without segregation. This property of concrete is affect by a number of factors
like water content of the mix, mix proportions, aggregate properties, time, temperature,
characteristics of the cement and admixtures (Kumar & Monterio, 2006) The effect of
cement replacing materials depends on their nature. Finer materials result in reduction
of workability while spherical materials increase it (Biruk, 2011).

2.3. Cement for Concrete
Cementitious materials of concrete materials are the binding concrete ingredients which
is used to bind the aggregate particles or fragments together. This binding properties
are insured by different chemical reaction of the cementitious materials with other
reacting material to facilitate the bond and workability of the concrete (Domone, 2002).
There are two types of cementitious materials for concrete construction depending on
the way it gains strength. These are hydraulic and non-hydraulic cements. The non-
hydraulic cement reaction undergoes without water. There is no need of water to attain
the desired strength. Hydraulic cements should react with water by hydration process
to get workable and to attain the desired strength (Domone, 2002).
The hydraulic cement is the widely used material for huge structure, different
infrastructures and residential building constructions. This study focus on this hydraulic
cement.
Cement is a finely ground inorganic material which has cohesive (the tendency of a
material to maintain its integrity without separating or rupturing within itself when
subject to external forces) & adhesive (the tendency of a material to bond to another
material) properties; able to bind two or more materials together into a solid mass.
When it mixes with water form a paste which sets and harden by means of hydration
reactions, and which after hardening retain its strength and stability even under water
(Domone, 2002).
2.3.1. Types of cement
There are different types of hydraulic cement depending on their composition, method
of manufacturing (grinding, burning, etc.) and the relative proportion of the different
compounds. The most commonly used cements are OPC, PPC and special cement for
special construction activities.
Ordinary Portland cement is one of the most widely used and the most important
hydraulic cement. It uses in all types of structural concrete (walls, floors, bridges,
tunnels, etc.), masonry works (foundations, footings, dams, retaining walls) and
pavements. It is usually satisfactory and advisable to use general-purpose cement that
is readily reachable locally when such cement is manufacture and use in large quantity,

it is likely to be uniform and its performance under local conditions will know (ACI,
1999).
2.3.2. Chemical Composition of Cement
The three main constituents of hydraulic cements are lime (CaO), silica (SiO2) and
alumina (Al2O3). In addition, most cements contain small proportions of iron oxide,
magnesia, Sulphur trioxide and alkalis. There has been a change in the composition of
Portland cement over the years, mainly reflected in the increase in lime content and in
a slight decrease in silica content. An increase in lime content beyond a certain value
makes it difficult to combine completely with other compounds. Consequently, free
lime will exist in the clinker and will result in an unsound cement. An increase in silica
content at the expense of alumina and ferric oxide makes the cement difficult to fuse
and form clinker (Duggal, 2008)
Table 2-1: Chemical Composition of Portland Cement (Duggal, 2008).
Oxide Function Composition (%)
CaO Controls strength and soundness. Its efficiency
reduces strength and setting time.
60-65
SiO2 Gives strength. Excess if it cause slow setting. 17-25
Al2O3 Responsible for quick setting, if in excess, it lowers
the strength.
3-8
Fe2O3 Gives color and helps in fusion of different
ingredients.
0.5-6
MgO Imparts color and hardness. If in excess, it causes
cracks in mortar and concrete and unsoundness.
0.5-4
Na2O+K2O
TiO2
P2O5
These are residues, and if in excess cause
efflorescence and cracking.
0.5-1.3
0.1-0.4
0.1-0.2
SO3 Makes cement sound. 1-2

2.4. Pozzolanic Materials
The modern concrete technology uses different types of additional materials in order to
enhance the properties of the fresh and hardened concrete. Mineral admixtures are one
of these materials used in concrete for a variety of purposes. They may found naturally
or artificially. These materials can be dividing into three main categories, which are
pozzolanic, cementitious and non-reactive materials (Christopher, et al., 2017).
Nowdays great efforts are being made aimed to find out the alternative cement replacing
materials to minimize environmental impact, cost of concrete and to improve concrete
quality. Those replaciment materials are reffered to as supplimentary cementitious
materials (SCM) from waste, such as coal fly ash, byproducts of steel indusries like
blast furnace slag, sugarcane bagasse ash, rice husk ash, biomass combustion ash and
ground glass. By using such SCM, there are possitive impacts of environment that can
be obtained and there are reduction of volume of wastes, reduction of depletion of raw
materials and minimization of environmental impacts of construction industry
(Christopher, et al., 2017).
SCM are preferred in replacing cement because they have high amount of silica and
cause reduction of heat of hydration caused by reaction of C3S compound in Portland
cement hence reduce thermal stress resulted from heat of hydration which may cause
crack. It also facilitates excess silica for continuous reaction with free calcium to
produce C-S-H, known as pozzolanic reaction, which is main desirable product in
concrete microstructure gives strength and other qualities. Actually C-S-H is produced
from reaction of C3s and C2S with water. The chemical composition of pozzolanic
materials analyzed by (Christopher, et al., 2017) see Table 2-2.

Table 2-2:- Common chemical compositions of pozzolanic materials (Christopher, et
al., 2017).
Chemical
Composition
Fly
Ash-F
Silica-
Fume
Grounded
Glass
Rice
Husk
Ash
Sugarcane
Bagasse
Ash
Biomass
Combustion
Ash
SiO2 45 –
64.4
85 -
97
50 – 80 87.0 –
87.3
78.0 – 78.4 1.9 – 68.2
Al2O3 19.6 –
30.1
0.2 –
0.9
1.0 – 10 0.1 – 0.8 8.6 – 8.9 0.12 – 15.1
Fe2O3 3.8 –
23.9
0.4 –
2.0
<1.0 0.1 – 0.8 3.5 – 3.6 0.37 – 9.6
CaO 0.7 –
7.5
0.3 –
0.5
5 – 15 0.5 – 1.4 2.1 – 2.2 5.8 – 83.5
MgO 0.7 –
2.8
0.0 –
1.0
0.6 – 4.0 0.3 – 0.6 0 – 1.7 1.1 – 14.6
K2O 0.7 –
4.1
0.5 –
1.3
<1.0 2.4 – 3.7 3.4 – 3.5 2.2 – 32.0
SO3 0 – 0.5 0.0 –
0.4
<1.0 0.0 – 0.3 – 0.36 – 11.7
TiO2 0.9 –
1.2
– <1.0 – – 0.06 – 1.2
Na2O 0.2 –
0.5
0.1 –
0.4
1 – 15 0.1 – 1.1 0.0 – 0.1 0.22 – 29.8
Other 0.1 –
5.5
0.0 –
1.4
<5.0 1.8 – 5.2 1.2 – 3.0 0.66 – 13.0
LOI 0.2 –
7.2
0.0 –
2.8
<1.0 2.1 – 8.6 0.4 –
SCM are classified as self-cementing and pozzolans. Self-cementing materials are like
Portland cement and they have cementitious property. Pozzolans are siliceous rich
materials which have no cementitious property by themselves. Pozzolans can be further

classified as natural, (volcanic ash, diatomaceous earth, chert, and shale) and artificial
pozzolans (ground granulated blast furnace slag, rice husk ash, sugar cane bagasse ash,
silica fume, recycled glass, biomass combustion ash, and coal fly ash). (Christopher, et
al., 2017)
Artificial pozzolans can be produced by burning wastes in an oven or open air. The
burning temperature can be used as source of heat as fuel that can be used in different
purpose. This is one of advantages of using it. The other uses of artificial pozzolans is
cost minimization from cement. Since cost of cement in concrete is higher than other
components, it is crucial to minimize it replacements (Christopher, et al., 2017).
A pozzolan is a siliceous or alumino-siliceous material that, in finely divided form and
in the presence of moisture, chemically reacts with the calcium hydroxide released by
the hydration of Portland cement to form calcium silicate hydrate (CSH) and other
cementitious compounds. Most of the pozzolans in use today are mainly byproduct
materials which widely available (Biruk, 2011).
The reason behind using pozzolans is the improvement found on both the fresh and
hard concrete. Lowering of the heat of hydration and thermal shrinkage, increase in
water tightness, reduction in the alkali aggregate reaction, resistance to sulfate attack,
better workability, and cost efficiency are some of the improvements achieved by using
pozzolans blended with Portland cement (Biruk, 2011).
2.4.1. Types of Pozzolanic Materials
In the current time there are many different materials that could replace cement partially
at different content with differing benefit and effects. Those are Fly Ash F, Blast
furnace, Grounded Glass, Rice Husk Ash, Silica Fume, Groundnut Shell Ash, Bone
Powder, Coffee Husk Ash and Groundnut Shell Ash are some of pozzolanic materials.
The chemical composition of some of these are shown in Table 2-2 above (Christopher,
et al., 2017).
As discussed above in detail, the desired properties from are permeability, reduction of
heat of reaction, strength, workability and density are the main microstructure
properties. The fine grains of pozzolanic materials contributes for water resistance by
filling micro pore spaces in between cement particles. This mechanism of densification

makes the concrete non permeable material and the pozzolanas, in this case, called filler
(Kumar & Monterio, 2006).
Reduction of heat of hydration is by pozzolanic reaction which is between oxides and
C3A to form ettringite gel. Ettringite is a temporary gel like compound which will react
with C3S to form calcium-silica-hydrate paste at latter after setting. This is to slow down
fast reaction of C3A with water. The other physical properties of fresh and harden
concrete like workability, consistency, strength and durability are also the requirements
which limits maximum use of the replacements. Those qualities may be disturbed if
high amount of pozzolans were used (Christopher, et al., 2017).
Fly ash
Fly ash is, a supplementary cementitious material in concrete, a byproduct of the
combustion of pulverized coal in electric power generating plants. It is a fine-grained
material consisting primarily silicate glass containing silica, alumina, iron, and calcium.
Minor constituents are magnesium, sulfur, sodium, potassium, and carbon. Deferent
scholars recommended 10-15 % of fly ash cement replacements are recommend (Steven
H. Kosmatka, 2003).
Ground granulated blast furnace slag
Blast-furnace slag is a byproduct of iron manufacturing. It is non-metallic hydraulic
cement consisting essentially of silicates and alumino-silicates of calcium developed in
a molten condition simultaneously with iron in a blast furnace. The molten slag at a
temperature of about 1500°C is rapidly chilled by quenching in water to form a glassy
sand like granulated material which is one of the recommended cement replacing
materials. Due to this GGBFS in the presence of water and an activator NaOH or CaOH
supplied by Portland cement, hydrates and sets in a manner similar to Portland cement
(Steven H. Kosmatka, 2003).
Silica Fume
Silica fume is a byproduct material that is use as a pozzolan. This byproduct is a result
of the reduction of high-purity quartz with coal in an electric arc furnace in the
manufacture of silicon or ferrosilicon alloy. Silica fume is use in amounts between 5%
and 10% by mass of the total cementitious material. It is use in applications where a

high degree of impermeability is need and in high strength concrete (Steven H.
Kosmatka, 2003).
Bagasse ash
Bagasse is a cellulose fiber remaining after the extraction of the sugar-bearing juice
from sugarcane. The bagasse ash is about 8-10% of the bagasse and contains unburned
matter, silica and alumina. Sugarcane bagasse ash as described before contains silica,
which is the most important component of cement replacing materials. It is also finding
in large amount as a byproduct in sugar factories. Some studies show that replacement
of OPC by bagasse ash from 5% to 10% results in a better compressive strength than
that of the control mortar (Biruk, 2011).
Rice husk ash (RHA)
RHA, which is an agricultural by-product, has been report to be a good pozzolan by
numerous researchers. They investigated the use of RHA to reduce temperature in high
strength mass concrete and got result showing that RHA is very effective in reducing
the temperature of mass concrete compared to OPC concrete (Obilade, 2014).
2.5. Groundnut Shell Ash (GSA)
Groundnut shell is the agro industry waste product which is disposed as simply land fill
or by collecting and burning. The engineering application of this material is not
practical and almost no one of our farmers know about it. Like most other farm land
wastes, it has no contribution to any of local use or soil fertilizing. This waste product
could take over two years to decay in soil as my experience locally.
Groundnut Shell Ash (GSA) or Groundnut Husk Ash (GHA) is one of artificial
pozzolanic material that can be incorporated in concrete as partial replacement as
concluded empirical report of (Adole, et al., 2011), in their experimental test. They have
also tested in three chemical solutions, MgSO4, NaCl and H2SO4 and declared that
concrete with GSA/GHA can resist magnesium sulfate (MgSO4) and sodium chloride
(NaCl) which may found in soil.
Mahmoud, (2012) also tested GSA as partial replacement of portland cement in
sandcrete block and revealed that it can be replaced up to 20% with desired strength,
but there is decrease in strength with increasing amount of GSA above optimum level

which is 20%. The author also pointed out that using GSA have an advantage in its low
cost and economy base for the farmers.
Buari, et al. (2013) have tested the GSA as partial replacement of Portland cement in
concrete and carried out its chemical analysis. They tested by varying amount of GSA
in concrete from 0% to 20% and find out that the compressive strength of the concrete
is good at optimum level of 10% and decreases with increasing the GSA above 10%.
The other recommendation forwarded from those authors is that GSA is better if it is
used in mass concrete production as it is low heat pozzolanic material.
As the experimental investigation evaluation of compressive strength with replacement
of GSA conducted by (Navaneetha & Mohamed, 2016) indicated, the optimum amount
of replacement is 10%. As most of other researchers investigated, the optimum amount
is almost similar, and approaches 10%. This amount may result good properties of
concrete and GSA replacing material can satisfy 70% of major materials in concrete.
(Padmavathi.S, 2016).
Experimental research investigation conducted on GSA as partial cement replacement
by Mujedu & Adebara, (2016) varying the replacing amount in 15% interval concluded
that GSA is not good pozzolanic material and it is not recommended to use above 15%.
They also indicated that it would decease density of concrete and decrease concrete
strength if the amount of GSA exceeds 15%. There are various advantages of GSA in
its low energy to produce it compared to that of cement and it contributes to waste
management at little cost as well as economic base for farmers. (Mujedu & Adebara,
2016).
Samidurai, et al., (2017) also researched on replacing cement by GSA and sea shell
together and concluded that both are good pozzolans which fulfill the basic requrements
and the compressive strength gain increases only up to 10% of GSA and other
supplimentary benefits. They declared that the workability of concrete is decreasing
with increasing of GSA and increase in consistency.
Using sisal fiber as natural fiber with GSA as cement replacemet, aimed to test its
compressive strength and flexural strength, is also posible as the research carried out
by. The optimum amount indecated by these aothors is 5% of GSA and 2% of sisal

fiber. They recomennded that those materilas better for light weight structures and
simple foundations (HADIL & DINESH, 2017).
D & Thiravida, (2017) also find out that the compressive strength of concrete increases
with increase GSA to 10% and decreases when it exceedes 10%. The also conducted
chemical analysis and declared that GSA has better acceptable pozzolanic properties.
The main reason behind decreasing of comprensive strenght above 10% is presence of
potassiom oxide (K2O) at higher amount that could disturb the concrete by its alkalinity.
On the other hand, It is better in resistance to acid, chloride and water absorption. (D &
Thiravida, 2017).
From the characteristic test conducted, 10% of GSA replacement is acceptable with its
all other pozzolanic contribution benefits. They concluded that the concrete is less
workable with use of GSA and it contributes to surface hardness of concrete by forming
gel and drying, as a result they concluded that using GSA would preserve the
environment from agro waste (Vignesh & Lemessa, 2017).
2.5.1. Production of GSA in Ethiopia
The engineering properties of groundnut shell is suitable for use and it is essential to
know about the production of groundnut in our country. Because, we have to balance
the demand and supply of the material to reveal the economical distribution over the
country. If the production quantity and location is not identified, we are only dealing
with the amount and quality of GSA by ignoring its economy. Therefore, we have to
assess about the production parallel to its engineering property.
According to research conducted by Getahun* & Tefera, (2017), the production of
groundnut in Ethiopia is relatively low. Nowdays, the groundnut is produced in
Oromiya region East Hararghe and Western Wolega, Benishangul-Gumuz region
Metekel, and Amhara region Western Gojam. They referred from central statistics
agency that Ethiopia has potential to produce about 500,000 tons per year on estimated
land of 40,000 hectares per year is harvested for production. As this research indicates,
an average of 12.5 ton per hectare can produced. On the other hand, Babile Agricultural
and Rural Development Bureau have reported that 40% of agricultural land were
covered by groundnut harvesting in 2009/2010 fiscal year. Other districts near Western

wolega, Babile like Gursum in Wolega reported that the farmland covered by ground
nut is about 35% (Getahun* & Tefera, 2017). The other main and major area of
potential producer of groundnut is Metekel Zone in Benishangul Gumuz region and
Awi zone in Amhara region as bureau of agriculture reports. (Getahun* & Tefera,
2017). According to the research, about 50% of production is from those areas. In 2013
fiscal year report, about 46,000 tons is produced in Metekel and 24.300 tons is from
Awi zone. As (Getahun* & Tefera, 2017) the production places or regions, the
production is concentrated to some specific areas which is not suitable for transporting
the ground nut for overall country, but it is advantageous for farmers to supply the shell
at fair cost to the users of the country rather than just disposing it in landfilling or
burning. That is why it may be promising good source of economy for farmers
(Getahun* & Tefera, 2017).
2.6. Direct Cost of Concrete
Costing is the basic element of construction management which governs the overall
function of construction project management. There are two types of cost in
construction projects, those are direct cost and indirect cost. Direct cost includes
material, labor and equipment costs, and these costs affects the overall cost directly.
Indirect costs are costs which are expressed as function of direct cost, and these are
general overhead cost and site overhead cost which have further classifications. The
indirect costs affect the overall cost indirectly depending on the size and quality of the
project quantified as direct cost (Hendrickson, 2003).
Let Qi be the quantity of work for task i, Mi be the unit material cost of task i, Ei be the
unit equipment rate for task i, Li be the units of labor required per unit of Qi, and Wi
be the wage rate associated with Li. In this case, the total cost y is (Hendrickson, 2003):
𝑦 = ∑ 𝑄𝑖(𝑀𝑖 + 𝐸𝑖 + 𝑊𝑖𝐿𝑖)𝑛
𝑖=1 …………… Eq (2.1)
According to Calin M, (2003):
𝑃𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑣𝑖𝑡𝑦 =
𝑞𝑢𝑎𝑛𝑡𝑖𝑡𝑦 𝑜𝑓 𝑤𝑜𝑟𝑘 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑
𝑡𝑖𝑚𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛
…………… Eq (2.2)
𝑢𝑡𝑖𝑙𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 =
1
𝑐𝑟𝑒𝑤 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛(𝑜𝑢𝑡𝑝𝑢𝑡)
……….. Eq (2.3)
𝑙𝑎𝑏𝑜𝑟 𝑐𝑜𝑠𝑡 = 𝑢𝑡𝑖𝑙𝑖𝑧𝑎𝑡𝑖𝑜𝑛 𝑓𝑎𝑐𝑡𝑜𝑟 ∗ 𝑤𝑎𝑔𝑒 𝑟𝑎𝑡𝑒𝑠(𝑑𝑎𝑖𝑙𝑦 𝑜𝑟 ℎ𝑜𝑢𝑟𝑙𝑦)…. Eq (2.4)

3. Research Materials and Methodology
3.1. Introduction
This research work was focused on the physical properties of fresh and hardened
concrete, chemical composition of GSA and direct cost of concrete in order to
determine the suitability and optimum amount of proposed cement replacing material,
GSA.
The physical properties of fresh concrete tested were slump and setting time. The
testing methods of necessary standards were followed. The harden physical properties
tested were density and compressive strength. The chemical composition of GSA and
the direct cost of concrete were also investigated to determine the optimum amount of
replacement.
3.2. Materials for Research
3.2.1. Materials for concrete without GSA
Materials used to produce concrete without GSA were:
Cement: - Type of Cement used to produce concrete was Dangote- Ordinary
Portland cement (OPC) Cement Grade 42.5N CEM which is available in
market.
Coarse aggregate 02 (20mm aggregate size)
River Sand
Water: - potable water
Sources of materials:
Cement- local market
Coarse aggregate 02 - From market in Jimma town, Ethiopia
Sand - local market which is from Worabe Silte, Ethiopia.
3.2.2. Materials for concrete with GSA
Materials used to produce Concrete with GSA were:
Dangote Ordinary Portland cement(OPC)

Coarse aggregate (02)
Sand and
GSA
Sources of materials:
Cement- local market
Coarse aggregate- From market in Jimma town, Ethiopia.
Sand - local market which is from Worabe Silte Zone, Ethiopia.
GSA - collected from Metekel, Ethiopia and processed in Jimma University
College of Agriculture and Veterinary.
The researcher conducted chemical analysis of GSA sample in Geological survey of
Ethiopia at Addis Ababa to determine silica analysis. The test method determined was
according to ASTM 04-01 C114 C141.
3.2.3. Groundnut Shell
The groundnut shell for this research was collected from agricultural farmlands around
Metekel zone. Then it was exposed to sun to avoid surface moisture for about 30 hours.
After drying, it was filled in sacks and transport to Jimma Institute of Technology
laboratory research center. Figure3-1 show that the groundnut shell drying the surface
moisture, first burning in the Bio-char machine and finally burned to give the needed
ash. The first round burning give black and hard char material which is not suitable for
the cementing purpose, because the particle size is larger and the black color indicates
that there is extra carbon dioxide in the material. Therefore, the char should be burned
to get the final ash that to be used as concrete material. The two round burning was
carried out because of the hardness of groundnut shell and the burning machine could
not give the final desired ash material by first round.
After transporting of it to the research center, the groundnut shell was burned, in Bio-
char machine in Jimma University Agriculture college campus, cooled down and
collected carefully. Finally, it was grinded to the required size of fineness and sieve
through 150-μm in order to get the standard fineness and to remove coarse particles.

Figure 3-1: Groundnut Shell from drying to burning
3.2.4. Cement
Among all types of OPC cement available on the market for the study, Dangote cement
is one of the product of Dangote cement factory and was Purchased from available
shops. This cement complies with the requirements of Ethiopian Standards, EBCS 2,
ACI, ASTM 33 and Abebe Dinku laboratory manual, June (2002).
3.2.5. Aggregates
The tests were conducted to identify the properties of the aggregates according to the
relevant standards. After that, corrective measures were taken in advance before
proceeding to the mix proportioning, like blending in order to meet the grading
requirement. In general, aggregates were hard and strong, free of undesirable
impurities, and chemically stable. Soft and porous rock can limit strength and wear
resistance; it may also break down during mixing and adversely affect workability by
increasing the amount of fines. Aggregates were also free from impurities: silt, clay,
dirt or organic matter.
3.2.6. Water
Water available in Jimma institute of technology material laboratory was used for the
study. Natural water that is drinkable and has no pronounced taste or odor is used as
mixing water for concrete. Excessive impurities in mixing water not only may affect
setting time and concrete strength, but can also cause efflorescence, discoloration,
corrosion of reinforcement, volume instability, and reduced durability.

3.3. Determining Properties of Materials
3.3.1. Laboratory tests of material property of concrete produced
Tests on coarse aggregate and sand according to ASTM Standard Procedures were: -
Sieve analysis or gradation –ASTM C136
Water absorption –ASTM C127
Unit weight of aggregates –ASTM C33
Specific gravity –ASTM C127
Moisture content –ASTM C566
Silt content for sand –ASTM C117
Compressive strength of concrete – ES596 C. D4.2001
Tests on cement according to ES and ASTM: -
Consistency test/ ASTM C187
Initial and final setting time test with and without GSA
Fineness of cement test with and without GSA
Test on workability according to standard
Slump test with and without GSA /ASTM C143
The property of all materials necessary for describing the type of materials used and
also properties that can affect the production of concrete were determined prior to
production. The test methods used for the aggregates are listed in Table 3-1 below.

Table 3-1: Property tests and test methods of material
Property Tests Test Method
Sieve analysis( sand and coarse aggregate or gravel 02) ES C.D3.201
Unit weight (sand and coarse aggregate or gravel 02) ASTM C29
Silt content( sand) ASTM C117
specific gravity and absorption (sand and coarse aggregate or
gravel 02)
ASTM C127, BS 812: part
2:1995
Moisture content (sand and coarse aggregate or gravel 02)
ASTM C 566
Test Methods used to determine properties of Cement
Setting Time ASTM C 191
3.4. Production of concrete
Producing the concrete was conducted by following mixing procedures and steps by
mixing machine.
3.4.1. Proportioning concrete materials
The mixing ratio used for the concrete production was 1:2.1:3.2; cement, sand and
coarse aggregate respectively. The proportion of material used to produce concrete with
GSA was varying in cement content from concrete produced without GSA. The amount
of cement was decrease by (5%, 10%, 15% and 20%) in the concrete mixing for 1bag/
50kg of cement. Table 3-2 below shows the detail.

Table 3-2: Amount of GSA and cement with their ratio
%age of GSA
of
50kg cement
Cement(kg) GSA(kg) Ratio (GSA in kg/50kg in cement, sand,
coarse aggregate respectively.)
0% 50 0 1:2.1:3.2 (for conventional concrete)
5% 47.5 2.5 2.5/50:2.1:3.2
10% 45 5 5/50 :2.1:3.2
15% 42.5 7.5 7.5/50:2.1:3.2
20% 40 10 10/50 :2.1:3.2
Table 3-2 indicated the amount of sand and coarse aggregate were constant for all
percentage (%) but the amount of cement and GSA varies depend on percentage. So
the ratio of cement described with GSA as fractional form; that means for example
10/50, in Table 3-2, 10kg of GSA out of 50kg cement indirectly 10kg GSA and 40kg
cement was used for 20% replacement of GSA.
3.4.2. Compressive strength test
The minimum compressive strength at 28 days being the average strength of three
cubes, and the minimum compressive strength at 28 days of individual units were
tested. Compressive strength test was carried out on the cubes prepared to compare
the compressive strength of the conventional or control concrete and concrete with GSA
in varied percentage. Compressive strength test of 7th
, 14th
and 28th
days were conducted
and the 28 days’ age of concrete cubes average for the three units were recorded and
also compare the result according to ES 596 C. D4.2001 after regularly cured in water
for 7, 14 and 28 days. The ES 596 C. D4.2001 standard of test method and procedures
are the same with ASTM C-684.

Figure 3-2: Curing and Compressive test Methods
3.5. Study Area
This study area is Benishangul-Gumuz region Metekel Zone, where there is high
amount of production of groundnut and supplied to the domestic and export up to 50%
of total country’s production capacity. The groundnut shell and other concrete
ingredients were collected and processed in the Jimma University Institute of
technology material testing research center.

Figure 3-3: Study area Map (GIS)

3.6. Study Design
The purpose of this research was to determine the effects of groundnut shell ash on the
concrete strength as cement replacement material and it was experimental study. The
groundnut shell ash was partially replaced cement with different ratios and apply in C-
25 concrete production to explore the influential relation with each character of
concrete.
In the conducted experiment and assessment, workability(slump), density, consistency,
setting time and direct cost of concrete were conceived as the independent variables
and compressive strength was the dependent variable. Compressive strength of normal
concrete was measured in terms of strength at 7, 14 and 28 days of age. The research
flow design was look like the chart given in Figure 3-4 below.
The amount and kind of aggregates and mixing water were constant but the
quantity of groundnut shell ash was varied with cement.
The cost of concrete was analyzed by using unit rate pricing system of costing. The
total replacement material costs of each percentage was inserted in the cement cost by
considering cement reduction in ratio that it replaced.
3.7. Sample Size and Sampling Procedure
This study followed a non-probabilistic purposive sample selection process. To conduct
a laboratory test, the test samples were depending on the types of test requirement and
standards. For each tests quartering and weighting was the system for sampling
technique.
The output of the study was to compare the compressive strength of conventional or
control concrete with the blended concrete with GSA through laboratory tests.
According to EBCS 2, ACI, ASTM 33 and Abebe Dinku laboratory manual, June
(2002), it requires a minimum of three sample of cubic size of 150*150*150mm for
each test of the concrete characteristic strength determination. In this study, the concrete
cube of age at 7, 14 and 28 days with a ratio of 0%, 5%, 10%, 15%, and 20% of
groundnut shell ash with a total of 45 samples were used.

3.8. Study Variables
3.8.1. Dependent Variable
The dependent variable is amount of Groundnut Shell Ash (GSA) replacement in C-25
concrete.
3.8.2. Independent Variables
The independent variables are, those which was helped to assess the effect of
replacement of GSA on strength of concrete; these are compressive strength,
workability(slump), density, setting time and direct cost of concrete.
3.9. Data Collection Process
First, the ingredients were collected from their respective location to the research
center. After that, laboratory data were collected and coded according to the relevant
formats and standards. The analysis was made based on the collected and organized
data in order to draw conclusion and recommendations.
3.10. Data Processing and Analysis
Fresh and hardened properties of C-25 concrete with different ratio of groundnut shell
ash was examined through laboratory tests. Analysis of the gathered data was conducted
in the format attached in the appendix section. After analysis were made, the obtained
result was presented using different graphs, tables and charts as required. Parallel to
presenting of this analysis result, discussion on the obtained result was made by
comparing it with the available national and international standards and specifications
in order to answer the objectives of the study.

4. Results and Discussion
4.1. Introduction
This chapter elaborates the general properties of the materials used in the production
of concrete for the research, cost and chemical property of GSA and also finally
compressive strength test of concrete was done. The test results were summarized in
tables and figures for further clarification. The results were also discussed and
summarized under each sub-titles last paragraphs.
4.2. Physical Properties of Concrete Materials
To specify the type of materials used in this research and to check whether the
materials used are recommended by available standards and documents regarding
concrete production, physical properties tests of materials were conducted and the
detailed data sheets with results are attached on appendix of this paper.
4.2.1. Coarse Aggregate
The normal weight aggregates for making concrete conform with the standards of
concrete aggregates. The test method used was (ASTM C 136) and the detailed result
obtained is attached on appendix A.
Sieve analysis of coarse aggregate
Table 4-1: Sieve Analysis format and Standard for coarse aggregate according to ES
C.D3.201
Sieve size(mm) Cum. %pas ES limits Remark
Min Max
37.5 100.00 100 100 Ok
19 92.10 95 100 Need adjustment
12.5 73.00 40 85 Ok
9.5 29.80 25 55 Ok
4.75 7.20 0 10 Ok
Pan 0.00

According to ES C. D3.201 Standard Specification for Aggregates of Concrete, Table
4-1 above, the passing percentage requirements full fill the standard except that of
19mm size aggregates. But it can be acceptable because it is approximately close to
the range. And if we take the maximum size aggregate as 20mm, we could get the
cumulative passing in the range recommended. The maximum size of coarse
aggregates used for the concrete was 20 mm which was found between sieve 37.5 and
sieve 19. Therefore, the used coarse aggregate fulfilled the standard requirement and
it is acceptable.
Figure 4-1: Sieve Analysis of Coarse Aggregate
Table 4-2: Summary of Test Results for Coarse Aggregate
No. Test Description Test Result
1 Maximum size 20mm
2 Moisture Content 1.2%
3 Unit weight in kg/m3 1662.67
4 Absorption capacity 1.5%
5 Silt content -
6 Bulk Specific Gravity (SSD) 2.52
0
20
40
60
80
100
120
pan 4.75 9.5 12.5 19 37.7
Cum.Passingin%
Sieve Sieve
Cumulative % passing Min. Cumulative % passing
Max. Cumulative % passing

According to ASTM C33 limits the bulk unit weight from 1200-1760 kg/m3. The unit
weight described in Table 4-2 is within the limits. Therefore, the aggregates fulfill
specification of ASTM C33.
According to ASTM C33, the limitation for bulk specific gravity (SSD) is from 2.4 to
3.0. Accordingly, the aggregates were within ASTM limitations. Absorption for
coarse aggregate from 0.2% to 4% and for fine aggregates 0.2 to 2%. So the test result
of Table 4-2 satisfies the requirement of ASTM C33.
4.2.2. Fine Aggregate
The fine aggregate was natural or river sand. In order to investigate its properties for
the required application, gradation and fineness modulus, specific gravity and
absorption capacity, moisture content, silt content and unit weight were determined.
Table 4-3: Sieve Analysis Standard for fine aggregate according to ES C.D3.201
Sieve size(mm) Cum.
%pas
ES limits Remark
Min Max
9.5 100 100 100 Ok
4.75 97.75 95 100 Ok
2.36 84.1 80 100 Ok
1.18 64.85 50 85 Ok
0.6 41.8 25 60 Ok
0.3 21.55 10 30 Ok
0.15 4 0 10 Ok
pan 0
Fineness Modulus (F.M) = 3.14

Figure 4-2: Sieve Analysis of Fine Aggregate
According to ASTM C33 fine aggregates should have fineness modules between 2.3
and 3.1; the sand used has fineness modules of 3.14, this means it is almost near the
maximum limit of the ASTM limits and the cumulative percentage passes was with
the interval as shown on Figure4-3 below.
Figure 4-3: Sieve Analysis of Fine Aggregate
0
50
100
150
pan 150µm 300µm 600µm 1.18mm 2.36mm 4.75mm 9.5mm
Cum.passing(%)
Sieve Size
Cumulative % passing Min. Cumulative % passing
Max. Cumulative % passing

Table 4-4: Summary of Fine Aggregate Properties
No. Test Description Test Result
1 Maximum size 4.75
2 Moisture Content 2.0%
3 Unit weight in kg/m3 1734.67
4 Absorption capacity 0.7%
5 Silt content 2.47%
6 Bulk Specific Gravity (SSD) 2.11
According to ES silt content of sand should not be greater than 6%. Therefore, the
sand fulfilled ES requirement. And the moisture contents should be within 0.5% to
2%. As shown in Table 4-4, moisture content of the sand lays within the limits as
ASTM C33.
4.2.3. Cement
Among all types of OPC (cement available at market in Jimma university research
center for the study), Dangote OPC cement is one of the product of Dangote cement
factory and was Purchased from available shops. Cement properties were tested as
follows.
Grain Sisze distribution of cement
Figure 4-4: Sieve Analysis of Cement

Table 4-5: Sieve analysis of OPC Cement
Sieve size
Mass
retained[g]
Percent
retained
Cumulative
percent
retained
Cumulative
percent
passing
150µm 0 0 0 100
125µm 8 0.4 0.4 99.6
75µm 54 2.7 3.1 96.9
63µm 163 8.15 11.25 88.75
32µm 261 13.05 24.3 75.7
Pan 14 0.7 25 75
Total 500 460.95
Consistency of OPC cement
Consistency is the property which help to determine the optimum amount of mixing
water. The test was conducted with three trials until the penetration of plunger become
between 9mm-11mm. As shown in Table 4-6 below, the mixing water used for
determination of setting time was 32.5% or water to cement ratio was 0.325. This result
was used in the setting time test.
Table 4-6: Test result of Consistency of OPC Cement
Sample
weight of
cement(g)
weight of
water
added(g)
penetration W/C ratio
1 400 110.00 6mm 0.275
2 400 120.00 7mm 0.300
3 400 130.00 9mm 0.325
W/C 32.50%

Figure 4-5: Consistency Test
4.2.4. Groundnut Shell Ash
Table 4-7: Sieve analysis of GSA
Sieve
size
Mass
retained[g]
Percent
retained
Cumulative
percent
retained
Cumulative
percent
passing
150µm 0 0 0 100
125µm 108 5.4 5.4 94.6
75µm 135 6.75 12.15 87.85
63µm 199 9.95 22.1 77.9
32µm 52 2.6 24.7 75.3
Pan 6 0.3 25 75
Total 500 435.65
4.2.5. Setting time
Setting time is the duration that the cement need to get harden. It is the most important
property of cement as it affects the mixing, transporting and placing times. Those
times are the function of productivity of cement production. Therefore, it has indirect
effect on the cost of concrete production. So that it is very essential to determine the
initial and final setting times of the cement containing other replacement materials to
assess its effect.

The test conducted was given in Table 4-8. As the test shows, the setting times were
increasing compared with conventional or control cement paste from 0% through
20%.
Figure 4-6: Initial Setting time graph of 0% GSA
As we can see from figure 4-6 above and 4-7 below, the penetration value increase after
30 minutes and 40 minutes for 0% and 5% of GSA replaced pastes respectively. The
graphs also show that the penetration values of 0% and 5% were increasing smoothly
compared to other pastes. It indicates that the hardening of the pastes was going
uniformly.
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
0 10 20 30 40 50 60 70 80
Penetration(mm)
Time (min)

The initial setting time of 10% GSA replaced paste was altered by GSA, see Figure 4-
8 above. It is almost steady from 10min to 60min; means the paste was workable for
about 60 minutes.
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
0 10 20 30 40 50 60 70 80 90 100
Penetration(mm)
Time (min)
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Penetration(mm)
Time (min)

Figure 4-9:Initial Setting time graph of 15% GSA
Like 10% GSA replaced paste, 15% initial setting time was also altered or retarded by
the replacement.
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
0 10 20 30 40 50 60 70 80 90 100 110 120 130
Penetration(mm)
Time (min)
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
Penetration(mm)
Time (min)

Table 4-8: Initial Setting time test result of Cement paste with and without GSA
% of GSA replacement
Weight of
Cement(g)
Weight of
GSA(g)
Weight of
water(g)
Setting
time(min)
0 300 0 99 75.91
5 285 15 99 93.08
10 270 30 99 121.20
15 255 45 99 126.52
20 240 60 99 156.88
Generally, the initial setting time were increased when the amount of GSA increased,
see Table 4-8 and Figure 4-11. The penetration values at the first 10 minutes, as shown
in appendix section, were also decreased from 0% to 20%. The reason is the water to
cement ratio or percentage of water used was constant, which is 0.325 or 32.5%, to find
out effect of the GSA replacements on the properties of pastes.
Figure 4-11: Setting time of Cement with and without GSA
75.91
93.08
121.20
126.52
156.88
0.00 50.00 100.00 150.00 200.00
0
5
10
15
20
Initial setting time(min)
%ofGSAreplacement

4.3. Proportioning of Ingredients
Table 4-9: Proportion of Blending of Groundnut shell ash and Cement
S. No Code
Proportion by Weight
Cement (%) Groundnut shell ash (%)
1 GSAP0 100 0
2 GSAP5 95 5
3 GSAP10 90 10
4 GSAP15 85 15
5 GSAP20 80 20
4.3.1. Mix Design of concrete
The mix design method used for the study was American Concrete Institute (ACI)
method of ASTM C-685:98a mix design. All procedures were followed to get the first
trial mix proportion of ingredients.
The water to cement ratio used for concrete was determined by considering the
absorption capacity and moisture content of coarse and fine aggregates. The moisture
content and absorption capacity of coarse aggregate was 1.2% and 1.5% respectively.
Therefor the adjusted water added to the water to cement ratio was 0.3% of coarse
aggregate by weight. Similarly, the net water amount contributed from fine aggregate
was;
Moisturenet = 2%(moisture content) - 0.7%(absorption capacity) = 1.3% of fine
aggregate by weight.

Table 4-10: Final mix proportion of control concrete ingredients
Item Amount in
Free water
(kg)
Adjusted
water (kg)
Ratios
Target mean strength
(Mpa)
31.25
Cement kg/m3
333.53 1.0
Water kg/m3 190.11 184.28 0.57
Fine agg. kg/m3 694 -9.02 2.1
Coarse agg. kg/m3
1064.46 3.19 3.2
Total 2282.1kg/m3
-5.83kg
Slump = 57mm
The final mix ratio used for the study was 1:2.1:3.2 cement, fine aggregate and coarse
aggregate respectively as shown in table 4-11. The water to cement ratio was 0.57 or
57% of cement by weight.
4.4. Physical Properties of Concrete with and without GSA
4.4.1. Fresh Concrete Properties
Table 4-11: Slump Test Results
S. No
Mix
Code
Replaced
OPC (%)
W/C
Observed
Slump (mm)
Reduction
(%)
1 GSA0 0 0.57 57
2 GSA5 5 0.57 45 21.05
3 GSA10 10 0.57 34 40.35
4 GSA15 15 0.57 28 50.88
5 GSA20 20 0.57 17 70.18
The slump of concrete tested with replacement of GSA by varying percent was
decreased from 0% to 20% of GSA replaced, see Figure 4-12. According to ACI 211.

1-81, the slumps were lay in the desired slump range, which was 25mm-100mm labeled
as medium slump, except 20% GSA replaced concrete.
Figure 4-12: Slump test for Concretes with and without GSA
The slump test result of fresh concrete indicates that GSA absorbed the mix water and
caused stiffer concrete. The reduction percent of each mix from conventional was as
shown in Table 4-11. That was because of pozzolanic material, GSA.
4.4.2. Harden Concrete Properties
Unit weight of concrete
Unit weight is one of the parameters which determines the design criteria of concrete
structures as it gives the dead load of concrete section. Therefore, this property of
harden concrete was tested in this study. The unit weights were determined for each
percent replaced for ages of 7, 14 and 28 days. The reduction percent relative to control
or 0% concrete was also calculated as given in Tables 4-12, 4-13 and 4-14.
57
45
34
28
17
0
10
20
30
40
50
60
GSA0 GSA5 GSA10 GSA15 GSA20
Slump(mm)

Table 4-12: Unit Weights of Control and Blended concretes at age of 7 days
S. No Mix Code
Replaced OPC
(%)
Unit wt. (kg/m3)
Reduction or
incremental
(%)
1 GSA0 0 2542.8
2 GSA5 5 2425.8 -4.60%
3 GSA10 10 2449.5 -3.67%
4 GSA15 15 2408.8 -5.27%
5 GSA20 20 2408.9 -5.27%
Table 4-13: Unit Weights of Control and Blended concretes at age of 14 days
S. No Mix Code
Replaced OPC
(%)
Unit wt. (kg/m3)
Reduction or
incremental
(%)
1 GSA0 0 2477.5
2 GSA5 5 2469.6 -0.32%
3 GSA10 10 2477.0 -0.02%
4 GSA15 15 2443.7 -1.36%
5 GSA20 20 2450.4 -1.09%
Table 4-14:Unit Weights of Control and Blended concretes at age of 28 days
S. No Mix Code
Replaced OPC
(%)
Unit wt. (kg/m3)
Reduction or
incremental
(%)
1 GSA0 0 2485.8
2 GSA5 5 2438.4 -1.91%
3 GSA10 10 2449.3 -1.47%
4 GSA15 15 2421.9 -2.57%
5 GSA20 20 2440.6 -1.82%

As we could see from unit weight test results, there is no major effect of replacement
of GSA on the density of concrete. Obviously there is slight variation on the densities
but this would be happened by compaction method during casting.
4.4.3. Compressive strength of Concrete
Compressive strength of concrete is the basic and targeted parameter on which all of
tests, started from material properties test to fresh concrete properties test, depend. That
means the final output that determine the quality of concrete is compressive strength.
The researcher also conducted this essential test to determine the quantified decrement
of compressive strength of concrete with increased amount of GSA in concrete.
samples
Code Dimensions (mm) weight (g) Failure
load
(KN)
Compressive
strength
(MPa)
L W H
GSA0 150 150 150 8582.0 559.4 24.9
GSA5 150 150 150 8187.0 556.2 24.7
GSA10 150 150 150 8267.0 542.2 24.1
GSA15 150 150 150 8129.7 490.5 21.8
GSA20 150 150 150 8130.0 423.8 18.8
The target mean strength requirement of concrete of 7-day age should attain 65% of 31
Mpa, equals to 20.2Mpa. As shown in Table 4-15 above, all concrete strengths were
above the limit except 20% GSA replaced. Depending on this result GSA 5%, GSA
10% and GSA 15% were met the minimum requirement, but GSA 20% didn’t. (Buari,
et al., 2013) also recommended that the optimum amount of GSA replacement in
concrete should be 10%. The experimental investigation conducted by (C.Navaneetha
Krishnan, 2016) result indicated that the recommended amount is 10%.

samples
Code Dimensions (mm) weight (g) Failure
load
(KN)
Compressive
strength
(MPa)
L W H
GSA0 150 150 150 8268.7 656.2 29.2
GSA5 150 150 150 8242.3 640.3 28.5
GSA10 150 150 150 8416.0 594.6 26.4
GSA15 150 150 150 8156.0 516.9 23.0
GSA20 150 150 150 8178.3 436.9 19.4
For 14-day compressive strength the set limit is 90% of 31Mpa, which is 27.9Mpa. In
case of this test result, only 5% GSA replaced concrete fulfilled the minimum
requirement. Others are below the minimum requirement as shown in table 18. This is
because of retarding property of pozzolanic materials. Since GSA is also pozzolanic
material, the almost early age strength of the concretes were altered and reduced to
below the minimum limit.
samples
Code
Dimensions (mm)
weight (g)
Failure
load
(KN)
Compressive
strength
(MPa)
L W H
GSA0 150 150 150 8389.7 774.3 34.4
GSA5 150 150 150 8229.7 753.4 33.5
GSA10 150 150 150 8266.3 691.8 30.7
GSA15 150 150 150 8174.0 616.6 27.4
GSA20 150 150 150 8237.0 529.2 23.5
The 28-day age compressive strength of this study experiment result was as given in
the Table 4-17 above. The lower limit strength that should be attained by 28-day age
concrete is 99% of 31Mpa, that means 30.7Mpa. Therefore, compared to the result

concretes with GSA up to 10% fulfilled the minimum requirement. The others GSA
15% and 20% were out of the limit. Since 28-day compressive strength of concrete
governs the other age strengths, almost the recommended amount of GSA replacement
was maximum of 10%. This is based on the compressive strength parameter. Other
recommendations were discussed under recommendation section of this paper.
Table 4-18: Summary of Compressive Strength Tests
Code
Compressive strength
(MPa) 7days
Compressive
strength (MPa)
14days
Compressive
strength (MPa)
28days
GSA0 24.9 29.2 34.4
GSA5 24.7 28.5 33.5
GSA10 24.1 26.5 30.7
GSA15 21.8 23.0 27.4
GSA20 18.8 19.4 23.5
Figure 4-13: Compressive Test results for all percentages and ages
4.5. Chemical Composition of GSA
Chemical composition of cementitious materials majorly affects the binding property,
strength, workability and durability of the concrete. The chemical composition of basic
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
GSA0 GSA5 GSA10 GSA15 GSA20
CompressiveStrength(Mpa)
7days 14days 28days

oxides was tested and given in Table 4-19. The main compounds, SiO2, A2O3, Fe2O3,
CaO and MgO, in the cement found in GSA and constitutes 66.01%. According to ES
1177-1 sum of SiO2 and CaO should not be less than 50% by mass. And also SiO2
content should not be less than 25%. The GSA also had those compounds amounts to
exactly 53% and the SiO2 is 38.12%. Therefore, it fulfilled the minimum requirement
of the Ethiopian standard.
Table 4-19: Chemical composition test result of GSA
Compounds SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O H2O SO3 Cl Others
Percent 38.12 5.72 4.83 14.88 2.46 0.44 9.14 1.21 0.79 4.15 18.3
According to ASTM C-618, GSA is classified under Class C pozzolanic material
because it has more than 10% CaO.
Table 4-20: Chemical composition limits of OPC (Duggal, 2008)
Oxide Function Composition (%)
CaO Controls strength and soundness. Its inefficiency
reduces strength and setting time.
60-65
SiO2 Gives strength. Excess if it cause slow setting. 17-25
Al2O3 Responsible for quick setting, if in excess, it lowers
the strength.
3-8
Fe2O3 Gives color and helps in fusion of different
ingredients.
0.5-6
MgO Imparts color and hardness. If in excess, it causes
cracks in mortar and concrete and unsoundness.
0.5-4
Na2O+K2O
TiO2
P2O5
These are residues, and if in excess cause
efflorescence and cracking.
0.5-1.3
0.1-0.4
0.1-0.2
SO3 Makes cement sound. 1-2

Table 4-21:Comparison of Oxides of OPC and GSA
Legend
Above Max. limit ---
Within the limit ---
Below min. limit ---
The last row of table 4-20 was calculated as;
Less amount = ((Amount in GSA% - Min. limit%)/100) *1000g
Excess amount = ((Max. limit% - Amount in GSA%)/100) *1000g
The minus sign indicates that the oxide was less than the minimum limit and the positive
number indicates that the oxide was contributed as excess from GSA.
The clear comparison of oxide components and their limit was assessed as given in
tables 4-19 and 4-20. The CaO is under lower limit by 451g per kg. For example, if we
replace 10% of OPC by GSA in total weight of 1kg, the mix needs 0.1*451=45g less
to get in the limit. Thus it has no effect on strength and setting time as Table 4-8. SiO2
was in excess by 131.2g per 1kg and it slowed the setting times. Al2O3, Fe2O3, MgO
and TiO2 were within the limits and they contributed their respective advantages.
Oxide CaO SiO2 Al2O3 Fe2O3 MgO
Na2O+
K2O
TiO2 P2O5 SO3
Min. limit of
OPC 60 17 3 0.5 0.5 0.5 0.1 0.1 1
Max. limit of
OPC 65 25 8 6 4 1.3 0.4 0.2 2
GSA 14.88 38.12 5.72 4.83 2.46 9.58 0.34 1.34 0.79
Excess or
Less per 1kg
(g)
-451 131.2 82.8 11.4 -2.1

Na2O+K2O and P2O5 were above their limits by 82.8g and 11.4g per 1kg and
contribution of Na2O of GSA to the cement per 1kg is 0.046*82.8g = 3.726g since it is
4.6%. To prevent alkali-aggregate reaction, there is Equivalent mass set by (Haavic and
mielenth, 1991) and ASTM C-618. They said that the Equivalent mass of Na2O should
not be greater than 3kg/m3
. To determine this optimality, the researcher calculated the
amount of contribution of each percent replacement based on the density of concrete
and found out as given Table 4-22 below. As we can see from the analysis below, the
Na2O content of GSA at all percentages were less than 3kg/m3
. Therefore, there is no
alkali-aggregate reaction resulted from replacement of GSA at all percentages of
replacements.
Table 4-22: Na2O analysis based on 28 day unit weight of concrete
Mix Code
Replaced OPC
(%)
Unit wt. (kg/m3
)
Na2O (kg/m3
)
GSA0 0% 2485.8 0.0
GSA5 5% 2438.4 0.4
GSA10 10% 2449.3 0.8
GSA15 15% 2421.9 1.2
GSA20 20% 2440.6 1.6
P2O5 in excess percentage above the maximum limit. This oxide could result
efflorescence and crack at later age. Loss of ignition or LOI was about 16%, because
the groundnut shell was very hard material and needs high temperature to fuse inorganic
cellulose matter.
As investigation of groundnut chemical composition conducted by Perea-Moreno, et
al., (2018), Cl-
content is 0.071%. According to Chowdhury, et al., (2015), there is Cl-
in wood ash in trace amount. Since groundnut shell is similar with wooden materials
by its grains and hardness with high amount of cellulose (79.3%), it have similar
chemical composition (Bharthare, et al., 2014). In this study, the Cl-
content of GSA
was 4%.

4.6. Direct Cost of Concrete with GSA
The direct cost of concrete was computed based on the material that the researcher was
used. The calculation of each component cost, material cost, labor cost and equipment
cost, were computed based on the current cost of materials, labor and equipment around
the study area, Metekel, Benishangul-Gumuz, Ethiopia. The cost data were collected
from local contractors.
Three quintals of, loosely compacted, groundnut shell were used to analyze the unit
cost of GSA per kilogram. One quintal of groundnut before burning weighs 15kg
to18kg. the Final ash weighs 2.7kg to 3.8kg. Each of loose groundnut shell was assumed
to have cost of 5birr per quintal not including transportation cost. Because,
transportation cost varies as we go far.
Depending on the data collected, as described above, the average output per quintal of
GSA was 3.25kg and the average cost become 5/3.25 = 1.54birr/kg. This value was
used to calculate the direct unit cost of each percentage as follows.

Study on groundnut shell ash as partial replacement of cement in concrete

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