asmamaw tadege

STUDY OF COMPRESSED CEMENT

STABILISED SOIL BLOCK AS AN

ALTERNATIVE WALL MAKING MATERIAL

BY

ASMAMAW TADEGE

ADVISOR: PROFESSOR ABEBE DINKU

A thesis submitted to

The Schools of Graduate Studies of Addis Ababa University

in partial fulfillment of the requirements for the Degree of

Master of Science in Construction Technology and Management

October 2007

STUDY OF COMPRESSED CEMENT STABILISED SOIL

BLOCK AS AN ALTERNATIVE WALL MAKING

MATERIAL

BY

ASMAMAW TADEGE

ADVISOR: PROFESSOR ABEBE DINKU

A thesis submitted to

The Schools of Graduate Studies of Addis Ababa University

in partial fulfillment of the requirements for the Degree of

Master of Science in Construction Technology and Management

October 2007

i

ACKNOWLEDGEMENTS

First of all, I praise the Lord God Almighty for providing me with the power and grace to

carry out this thesis work.

I am very pleased to thank my advisor Professor Abebe Dinku for his kind cooperation,

constant encouragement and valuable comments at the various stages of this research work.

I am also very pleased to thank Dr.-Ing. Surafel Ketema for his constructive suggestions.

I take this opportunity to express my gratitude to the Addis Ababa University for financing

my thesis work. In addition, I am extremely thankful to Selam Technical and Vocational

Center for providing me the research center facilities.

My profound gratitude also goes to the following people for their invaluable material as

well as technical support, which was extremely essential to my work.

Ato Tadesse Mekuria from the Ministry of Works and Urban Development.

Ato Solomon Negash and Ato Mekonen Biru from Selam Technical and Vocational Center.

AtoYonas Mekonen and Ato Daniel kifle from the Addis Ababa University Faculty of

Technology, Department of Civil engineering.

I also like to acknowledge Ato Dawit Taye and W/t Haimanot Etsubdink who were of help

for me during the thesis work.

Special thank goes to all my family members in general and my mother in particular for her

lovely support and encouragement.

Asmamaw Tadege

Addis Ababa, October 2007

ii

TABLE OF CONTENTS

ACKNOWLEGEMENTS ----------------------------------------------------------------------------i

ABSTRACT------------------------------------------------------------------------------------------- ii

TABLE OF CONTENTS--------------------------------------------------------------------------- iv

LIST OF TABLES ---------------------------------------------------------------------------------- ix

LIST OF FIGURES ---------------------------------------------------------------------------------- x

CHAPTER ONE

INTRODUCTION

1.1 General ---------------------------------------------------------------------------------------- 1

1.2 Justification for this work ------------------------------------------------------------------ 2

1.3 Objectives of the thesis --------------------------------------------------------------------- 3

1.4 Scope of the study --------------------------------------------------------------------------- 4

1.5 Methodology --------------------------------------------------------------------------------- 4

1.6 Structure of the research-------------------------------------------------------------------- 5

CHAPTER TWO

CONTEXTUAL FRAME WORK OF EARTH AS A BUILDING MATERIAL

2.1 Building materials improvement needs -------------------------------------------------- 6

2.2 Building materials and economic development ----------------------------------------- 9

2.3 Traditional housing construction in Ethiopia------------------------------------------ 10

2.4 Salient features of earth as a building material---------------------------------------- 11

2.5 Main techniques using earth as a building material ---------------------------------- 15

2.6 Compressed Earth Block ----------------------------------------------------------------- 17

2.6.1 Historical background of compressed earth block--------------------------- 17

2.6.2 Compressed earth block role in development -------------------------------- 21

2.6.3 The future of Compressed Earth Block --------------------------------------- 22

2.7 Social acceptance -------------------------------------------------------------------------- 22

2.8 Comparison of Compressed Earth Block with other building materials----------- 23

2.8.1 Compressive strength ------------------------------------------------------------ 24

2.8.2 Density and Thermal properties ------------------------------------------------ 24

2.8.3 Moisture movement -------------------------------------------------------------- 25

iii

2.8.4 Durability, Maintenance and Appearance ------------------------------------ 25

CHAPTER THREE

CONCEPTUAL REVIEW

3.1 General -------------------------------------------------------------------------------------- 27

3.2 Properties and analysis of soil for soil cement block--------------------------------- 28

3.2.1 General properties ---------------------------------------------------------------- 28

3.2.2 Classification of soil ------------------------------------------------------------- 30

3.2.2.1 Classification by grain size ------------------------------------------------- 31

3.2.2.2 Classification by plasticity (Fine content)-------------------------------- 33

3.3 Suitable soil-------------------------------------------------------------------------------- 35

3.4 Available criteria for soil suitability ---------------------------------------------------- 35

3.4.1 Criteria based on African Regional Standards ------------------------------- 36

3.4.2 Criteria based on Spence, R.J.S & Cook, D.J.1983 Building

materials in developing countries --------------------------------------------- 38

3.5 Test for soils-------------------------------------------------------------------------------- 39

3.5.1 Types of tests---------------------------------------------------------------------- 39

3.5.1.1 Field tests---------------------------------------------------------------------- 40

3.5.1.2 Laboratory tests -------------------------------------------------------------- 41

3.6 Soil as a building material---------------------------------------------------------------- 43

3.7 Soil Stabilization--------------------------------------------------------------------------- 44

3.7.1 Mechanical stabilisation --------------------------------------------------------- 44

3.7.2 Cement stabilisation-------------------------------------------------------------- 47

3.7.3 Lime stabilisation----------------------------------------------------------------- 51

3.7.4 Bitumen stabilisation------------------------------------------------------------- 52

3.7.5 Gypsum stabilisation------------------------------------------------------------- 52

3.7.6 Pozzolanas stabilisation --------------------------------------------------------- 53

3.7.7 Other stabilisers------------------------------------------------------------------- 53

3.8 Rationale of soil cement ----------------------------------------------------------------- 53

iv

CHAPTER FOUR

PROPERTIES OF MATERIALS, MIX PROPORTIONS AND TESTS ON BLOCKS

4.1 Introduction-------------------------------------------------------------------------------- 56

4.2 Soil ------------------------------------------------------------------------------------------ 56

4.3 Cements ------------------------------------------------------------------------------------ 57

4.4 Water --------------------------------------------------------------------------------------- 58

4.5 Mix proportions --------------------------------------------------------------------------- 58

4.6 Specimen preparation -------------------------------------------------------------------- 60

4.7 Tests on blocks ---------------------------------------------------------------------------- 62

4.7.1 Compressive strength test ------------------------------------------------------ 62

4.7.2 Water absorption test------------------------------------------------------------- 63

CHAPTER FIVE

TEST RESULTS AND DISCUSSIONS ON THE SUITABILITY OF SOIL SAMPLE

FOR THE PRODUCTION OF COMPRESSED STABILISED SOIL BLOCK

5.1 Introduction--------------------------------------------------------------------------------- 65

5.2 Laboratory tests and results on soil sample-------------------------------------------- 66

5.2.1 General classification -------------------------------------------------------------- 66

5.2.2 Soil compaction test ---------------------------------------------------------------- 72

5.3 Chemical analysis--------------------------------------------------------------------------73

5.4 Summery------------------------------------------------------------------------------------74

CHAPTER SIX

TEST RESULTS AND DISCUSSIONS ON THE PRODUCED COMPRESSED

CEMENT STABILISED SOIL BLOCK

6.1 Introduction--------------------------------------------------------------------------------- 75

6.2 Compressive strength --------------------------------------------------------------------- 75

6.2.1 Effects of cement and cement content on the compressive

strength of soil block-------------------------------------------------------------- 76

6.2.2 Comparison of compressive strength of soil cement block made

using Mugher and Messobo Portland pozzolana cements ------------------ 79

6.3 Effects of Compaction pressure on compressive strength of

soil cement block -------------------------------------------------------------------------- 80

v

6.4 Water absorption--------------------------------------------------------------------------- 82

6.5 Summery ------------------------------------------------------------------------------------83

CHAPTER SEVEN

ECONOMIC ANALYSIS OF CEMENT STABILISED COMPRESSED EARTH

BLOCK VERSUS OTHER CONVENTIONAL BUILDING MATERIALS

7.1 Production cost of Cement Stabilised Compressed Earth block --------------------- 85

7.2 Parameters that influence the production cost of CSEB------------------------------- 85

7.3 Details for cost calculation ---------------------------------------------------------------- 86

7.3.1 Variable costs ----------------------------------------------------------------------- 86

7.3.2 Fixed costs --------------------------------------------------------------------------- 87

7.3.3 Profit Margin ------------------------------------------------------------------------ 87

7.4 Unit cost -------------------------------------------------------------------------------------- 87

7.5 Sensitivity analysis ------------------------------------------------------------------------- 90

7.5.1 Comments on how the parameters influence the cost of CSEB-------------- 90

7.6 Comparison of CSEB with Hollow Concrete Blocks per m2 area of wall --------- 94

CHAPTER EIGHT

CONCLUSIONS AND RECOMMENDATIONS

8.1 Conclusions--------------------------------------------------------------------------------- 96

8.2 Recommendations--------------------------------------------------------------------------98

REFERENCES------------------------------------------------------------------------------------- 100

APPENDIX ONE

SOIL INDEX PROPERTIES TEST RESULTS ---------------------------------------------- 102

APPENDIX TWO

CHEMICAL ANALYSIS OF THE SOIL------------------------------------------------------107

APPENDIX THREE

COMPRESSIVE STRENGTH TEST RESULTS USING MUGHER PPC -------------- 108

vi

APPENDIX FOUR

COMPRESSIVE STRENGTH TEST RESULTS USING MESSOBO PPC ------------- 113

APPENDIX FIVE

EFFECTS OF COMPACTION PRESSURE ON THE COMPRESSIVE

STRENGTH OF SOIL BLOCK BY USING 6% CEMENT-------------------------------- 118

APPENDIX SIX


STRENGTH OF SOIL BLOCK BY USING 8% CEMENT-------------------------------- 119

APPENDIX SEVEN


STRENGTH OF SOIL BLOCK BY USING 10% CEMENT ------------------------------ 120

APPENDIX EIGHT


STRENGTH OF SOIL BLOCK BY USING 12% CEMENT ------------------------------ 121

APPENDIX NINE

WATER ABSORPTION TEST RESULT----------------------------------------------------- 122

APPENDIX TEN

COST OF M7 E 380 MACHINERY AND ACCESSORIES ------------------------------- 123

APPENDIX ELEVEN

PICTURES---------------------------------------------------------------------------------------- 124

vii

LIST OF TABLES

Table 2.1 Average cost break-up of Building Construction

Table 2.2 Properties of compressed stabilised earth blocks versus other walling

materials

Table 3.1 Soil classifications according to particle size in mm

Table 3.2 The grain size classification based on the ASTM-AFNOR Standards

Table 3.3 Cement to soil ratio

Table 4.1 Physical properties of the soil

Table 4.2 Chemical composition of the soil

Table 4.3 Composition and properties of cements produced in Ethiopia

Table 4.4 Mix proportions for the first series

Table 4.5 Mix proportions for the second series

Table 4.6 Mix proportions for the third series

Table 5.1 Atterburg limit test results of soil sample from Kara area

Table 6.1 Mean compressive strength of soil cement blocks using Mugher PPC

Table 6.2 Mean compressive strength of soil cement blocks using Messobo PPC

Table 6.3 Rate of increase in compressive strength for Mugher cement content

increments

Table 6.4 Rate of increase in compressive strength for Messobo cement content

increments

Table 6.5 Comparison of the 56th

day compressive strength of CSEB by using Mugher

and Messobo PPC as stabilisers

Table 6.6 Effects of compaction pressure on the 28th

day compressive strength of CSEB

Table 7.1 On-site /Cost calculation table for (220x220x110 mm) block using 7% cement

Table 7.2 Block yard /Cost calculation table for (220x220x115 mm-) block using 7%

cement

Table 7.3 Effects of cement content on the cost of soil cement block

Table 7.4 Cost calculation for (200x200x400) mm HCB “Class C”

Table 7.5 Cost calculation for (200x200x400) mm HCB “Class B”

Table 7.6 Comparison of CSEB with other wall making building materials

viii

LIST OF FIGURES

Figure 2.1 Soil block building in India

Figure 2.2 Use of Earth as building material

Figure 2.3 The first manual press Cinvaram

Figure 2.4 Typical Compressed Earth Block

Figure 3.1 Diagram of texture

Figure 3.2 Diagram of Plasticity

Figure 3.3 Triangular chart for particle size classification

Figure 3.4 Plasticity chart

Figure 3.5 Unconfined, semi-confined and confined compaction

Figure 3.6 Diagram of particle intimacy around the O.M.C.

Figure 3.7 O.M.C. for soil at different compaction energies

Figure 3.8 Crystal line cement growth in sandcrete

Figure 4.1 M7 E380 machine

Figure 4.2 Compressive strength testing of blocks samples.

Figure 5.1 Particle size distribution of soil from Kara area

Figure 5.2 Particle size distribution of the sample soil on the diagram of texture

Figure 5.3 Triangular chart for particle size classification of soil sample from Kara area

Figure 5.4 Diagram of Plasticity

Figure 5.5 Plasticity chart

Figure 5.6 Proctor compaction curve

Figure 6.1 Effects of cement content on the compressive strength of soil block using

Mugher PPC

Figure 6.2 Effects of cement content on the compressive strength of Soil Block using

Messobo PPC

Figure 6.3 Comparison of the Compressive Strength of CSEB using Messobo and Mugher

cement

Figure 6.4 Effects of compaction pressure on compressive strength of CSSB

Figure 6.5 Effects of cement content on the absorption capacity of soil cement block

Figure 7.1 Sensitivity test chart

ix

ABSTRACT

This research is intended to provide detailed technical and economic information on the

production of compressed cement stabilised earth blocks. These include information on

suitable soil types, local stabilisers, stabilisation techniques, production of compressed

stabilised earth blocks and their economical value and potential.

Critical review of related literatures show that soil types, proportions between soil and

stabiliser and compaction pressure applied to the moist soil mix affects the quality of the

compressed earth block. Since soil in the Kara area of Addis Ababa is mainly used to

compressed stabilised earth block production, this area was the prime target for the

investigation and testing. Laboratory tests conducted on Kara area soil provided more

precise and detailed information on the soils grading, plasticity, chemical composition and

the result proved the soil’s suitability for block production.

Using two types of cements manufactured in Ethiopia as stabiliser and soil sample from

Kara area of Addis Ababa, three different series of tests were prepared based on literature

recommendations. Tests were conducted on soil blocks performance like compressive

strength and water absorption on which the durability of the blocks depend. The effects of

compaction pressure on the quality of the soil blocks, the optimum cement content for

stabilisation and cost comparison with hollow concrete blocks are prepared. The

performance characteristics of local stabilisers are evaluated and comparisons are made.

The investigation has revealed that from the blocks produced at the varying cement

contents from 4% in increments of 2% up to 12% at constant compressive pressure of

10MPa, all the blocks except blocks produced by 4% cement have 56th

day wet

compressive strength values well above most of the recommended minimum values for use

in structural work. Thus 6% cement is taken as optimum cement content for stabilisation of

Kara area soil for block production. Further increasing cement content results in an increase

in the compressive strength value and a decrease in the absorption capacity of the soil

block. Increment of the compaction pressure also improves the compressive strength of soil

cement block. Comparisons of the effects of local cement stabilisers, Mugher PPC and

x

Messobo PPC showed that Mugher PPC has shown better stabilisation effect based on the

56th

day compressive strength of blocks. The cost comparison with the conventional

walling making material, hollow concrete blocks, has revealed that compressed cement

stabilised soil block is preferred because it is more economical walling material in itself

and permits the use of economical building techniques.

1

CHAPTER ONE

INTRODUCTION

1.1 General

It has been generally agreed that slums and squatter settlements are steadily growing at

alarming rates in cities of developing countries. In most cases, this growing phenomenon is

an outcome of failed polices, poor governance, inappropriate planning regulations,

unresponsive financial systems, strong pressure of rural-urban migration and lack of

political will to reverse the situation amicably. The dominance of slums in urban areas adds

to the toll on the people already burdened deeply by abject poverty and constrains the

enormous potential for human development that urban life offers [1].

According to the Ethiopian Urban Sector Study, Ethiopian urban population is currently

estimated to be 11 Million; 80% of these live in substandard housing units and

environmentally unfit living conditions in slum neighborhoods. This fact coupled with high

urbanization rate and other urban development challenges left urban areas with complex

and rooted physical, environmental, economic and social problems where the urban poor,

who reside in slums, are most vulnerable [1].

The scarcity of houses, the very low standard of the existing houses and the ever-increasing

cost of construction also demands the need for producing low cost construction materials of

acceptable quality. This initiated professionals to seek low cost materials and low cost

methods of construction to solve the problems. In this research compressed stabilised earth

blocks are considered as an alternative walling material.

In this chapter, attempts have been made to outline the motivation and objectives for the

research work, and explain the need of the research.

The limitations and delimitations and the methods to achieve the research objectives are

also presented. The final section of the chapter outlines the structure of the thesis and

informs the reader certain conventions used throughout the thesis.

1. Introduction

Department of Civil Engineering 2

1.2 Justification for the thesis

There is a self- evident need for adequate and durable housing, especially in the urban and

peri-urban areas of Ethiopia. The poorest sector of the community is most affected by this

housing shortage, as it is least able to afford construction materials classified as permanent

under prevailing building regulations. Assuming land availability and planning permission

for further development, the need is to deliver more durable housing of lower cost.

Building materials accounts large portion of the housing construction cost. Production of

building components using techniques imported from the developed World is highly capital

and energy intensive. By using improved locally available traditional building materials,

the construction cost of housing can be reduced significantly [2].

Earth construction is very successful in arid areas, but significant stabilisation is required

for adequate performance in humid areas. With good production control compressed

stabilised soil block can perform quite adequately, but further improvement in material

performance will help in meeting the same requirements as other present day building

materials.

Compressed and cement stabilised soil blocks are building components of growing

importance in tropical countries. Their performance has sometimes been lacking, so that its

improvement is critical to their obtaining a larger market share. Compressed stabilised

block durability is influenced by the interplay of three main factors:

i). the process by which the compressed stabilised block was produced,

ii). the choice of the constituent materials and

iii).the nature of the exposure conditions in service.

This thesis addresses a critical aspect of these factors, by examining proportions between

soil and stabiliser, the compaction pressure and the amount of water to be applied taking

into consideration the specific characteristics of the soil so as to produce blocks that are

dense and strong with regular surfaces and edges. In this way, higher strength blocks,

1. Introduction


which are therefore dimensionally stable and durable, can be produced at tolerable cement

cost.

A further motivation of this research is its extensive use of raw earth as main building

material, thereby using a local resource to help develop technologies that are energy saving,

eco friendly and sustainable. Currently popular alternatives such as fired brick and concrete

blocks do not have these advantages.

1.3 Objectives of the thesis

As the population of the world continues to grow, so does the need for housing, thus cheap,

easy to build accommodation for the thriving masses is a big problem in the developing

World. Soil has been used as a building material for thousands of years, but unprotected

structures seldom withstand wet climates for long periods of time. Relatively new materials

such as cement have meant that blocks can be made which will last for centuries, but they

are too expensive for most people in developing countries.

A possible solution to this would be to make blocks using soil that is then stabilised, as this

adds strength and durability to the raw material, even in less arid conditions. Stabilisation

fulfills a number of objectives that are necessary to achieve a lasting structure from locally

available soil. Some of these are: better mechanical characteristics (leading to better wet

and dry compressive strength), better cohesion between particles (reducing porosity which

reduces changes in volume due to moisture fluctuations), and improved resistance to wind

and rain erosion. Using one or more of the stabilisation techniques listed latter, many of

these objectives may be fulfilled. Optimum methods depend greatly on the type of soil, and

a careful study of the local soil is necessary to suggest an effective method of stabilisation.

The objective of this thesis is thus to provide detailed technical and economic information

on the production of compressed stabilised earth blocks with a view to making available

existing experiences in this field to those who produce or plan to manufacture blocks so as

to improve production techniques and quality of output. This includes information on

suitable soil types, local stabilisers, production of compressed stabilised earth blocks,

1. Introduction


quality of the blocks, and their economical value. It also comes up with optimum cement

content of stabilised soil blocks for low cost housing.

1.4 Scope of the study

The research will cover only the technical and economic analysis of cement stabilised soil

block. It focuses on the soil from Addis Ababa Kara area. The research is delimited to the

general study in Addis Ababa Kara area soil. Relevant data are acquired for cements from

the two manufactures, and index properties of the raw materials and compressive strength

tests are conducted at Addis Ababa University, Civil Engineering Department Soil

Mechanics and Construction Materials laboratory. Mix design, blocks production and

curing are conducted at Selam Technical and vocational center.

During the investigation, the research is limited to get soil sample from a single site,

because of time and budget constraints. Therefore this research investigation is relied on

the soil from Kara area of Addis Ababa.

1.5 Methodology

The research work begins with literature review followed by assessment of the case in

Ethiopia. For the development of concepts, which are fundamental for the formulation of

the whole research work, both conceptual and contextual frameworks of the problem are

reviewed.

The method of approach to the solution of the problem determines the required data, which

intern is a ground to decide on type and method of data collection and their analysis.

Different alternative data collection methods such as experiments, observations, and

archival records are examined and used where proved suitable.

Both primary data (collected personally) from the source itself and secondary data from

different countries is collected and used for the analysis. Primary data is collected at

controlled environments by testing in laboratories by using electro mechanical equipments.

The analysis of the collected data is both qualitative and quantitative.

1. Introduction


1.5 Structure of the research

This thesis is designed to report the academic findings from the research carried out during

this M.Sc. research work. Its function is also to present information to examining body for

assessment for awarding masters degree to the author. The thesis has been written to

reflect the chronological order of events with a minimum of forward and backward

referencing of the different chapters.

The thesis is divided in to 8 chapters and each chapter contains a number of sections and

further subsections. These three hierarchical levels are identified by numbers and break

down the majority of the text in to manageable portions.

The contextual framework of earth as a building material is described in chapter two. The

conceptual review comes in chapter three. The properties of materials, mix proportions and

tests are reported in chapter 4. Chapters 5 and 6 detail the results of tests on soil and cement

stabilised compressed soil blocks. Economic analysis and comparisons with other

alternative walling material is described in chapter 7. Finally chapter 8 summaries the

conclusions made throughout the thesis and makes recommendation for further research to

work.

Data is presented in three different formats in this thesis. Graphs are used to show trends

and to highlight possible relationships. Tables are used to present statistical analysis of the

data collected. These two formats appear in the body of the text close to their point of

reference as possible, but not necessarily on the same page. Other important data are

recorded in the appendices for cross- referencing.

6

CHAPTER TWO

CONTEXTUAL FRAMEWORK OF EARTH

AS A BUILDING MATERIAL

2.1 Building materials improvement needs

The choice of building materials is one of the important criteria, which determines the

strength, quality, and economy of any construction. Originally, stone, sand, earth, grass,

logs, skin, etc were used as construction/building materials in their crude form. As

technique advanced, the crude as well as the partly refined materials were replaced by

others, especially made for different purposes. The history of development of house

facilities reveals that man has been modeling his environment throughout the ages for more

comfortable living [3].

Provision of housing for developing countries is one of the most important basic needs of

low-income groups. It is a very difficult requirement to meet, since land and construction

costs are mostly beyond the means of both the rural and urban poor. In order to address this

issue various governments have undertaken housing schemes that aim to facilitate some

form of housing ownership by low-income groups. These ideas include self-help housing

schemes that provide housing subsidies, provision of credit, and/or low interest rates etc

[4].

Due to limited means within developing countries, it is necessary to seek ways to reduce

construction costs, especially for low-income housing, as well as adopting easy and

effective solutions for their repair and maintenance. Such objectives can be achieved

partially through the production and use of cheap yet durable locally available building

materials [4].

Two-third of the expenditure in housing construction goes for building materials.

Production of building components using techniques imported from the western world is

highly capital and energy intensive. A significant cost cut down can be achieved in building

construction using improved locally available traditional building materials with

appropriate technology [2].

2. Contextual Framework of Earth

as a Building Material


In the case of low cost housing, building materials account for 70-75 % of the total cost of

construction as shown Table 2.1 below [5].

Table 2.1. Average cost break-up for low cost building construction [5].

Due to large-scale construction programs in Ethiopia, the demand for conventional building

materials like cement, steel, bricks and timber has outstripped their supply. The major cost

of construction is incurred on building materials and most of these building materials are

cement products. The ever increasing price of cement coupled with the rise in the price of

other construction materials make the construction cost far from the reach of the low and

the middle income group of urban dwellers. Alternative solutions have to be thought to

rectify such problems and minimize the burden of the community.

Since the early 1950s, much attention has been focused on the importance of access to

housing for low-income populations, notably by undertaking research into building

materials and techniques which aim to make the best possible use of local resources, both

material and cultural [6].

In Ethiopia there are various traditional construction materials which have proved to be

suitable for a wide range of buildings and which have a great potential for increased use in

the future. One such material is the compressed stabilised earth block, an improved form of

one of the oldest materials used in building construction (Adobe).

Soil is one of the primary materials used for construction of traditional low-cost dwellings

and is well suited to local weather conditions and occupancy patterns. Different soil

construction methods are used in the majority of urban and rural areas of Ethiopia.

Materials Labor Component wise

Cement 18% Masons Wage 10% Foundation 10%

Iron &steel 10% Carpenters wage 15% Wall 30%

Bricks 17% Unskilled labor 12% Roofs 25%

Timber 13% Doors & Windows 15%

Sand 7% Flooring 10%

Aggregate 8% Finishing 10%

Sum 73% 27 % 100%




Buildings are constructed entirely, or partially of soil, depending on location, climate,

available skills, cost, building use and local tradition. Traditional earth construction

techniques such as wattle and daub, cob and adobe need continuous maintenance in order

to keep them in good condition. Research works to increase the durability of earth as a

construction material is very important.

Unfortunately the quality of compressed stabilised earth blocks in some construction

schemes is far from adequate and often materials are wasted in the production process. To

extend the use of compressed stabilised earth building blocks to all types of housing e.g.

low-cost housing in rural and urban areas and middle income housing in urban areas,

production techniques need to be further improved so as to achieve better quality and

reduce production costs [7].

In order to do this the following points need to be considered carefully:

i) Proportions between soil and stabiliser need to be optimized, taking into

consideration the specific characteristics of the soil,

ii) Compaction pressure applied to the moist soil mix needs to be sufficient so as to

produce blocks that are dense and strong with regular surfaces and edges.

iii) Block surfaces need to be smooth so that they have the potential to be used

without an additional surface coating or render.

Long term planning for building materials development based on an assessment of future

needs, is generally lacking in many developing countries. Poor co-ordination of the

research institutions and government offices concerning aspects of building materials

industry does not promote an effective planning effort. The absence of clearly defined

polices and failure to accord explicit recognition to the industry in national development

plans must also be seen as constraints to be overcome.

The successful exploitation of indigenous resources for increasing the supply of building

materials will depend on the fulfillment of some conditions, namely: renewed political

commitment, strengthening of building research and information infrastructure, manpower




development and training, development of tools and spare parts industry, and sustained

promotion of the local building materials industry and its products [7].

2.2 Building materials and economic development

The building materials and construction industry is one of the most important sectors of

economic activity and represents an essential instrument of socio economic development. It

provides a wide range of services and capabilities for designing and constructing facilities

necessary for economic development.

The links between consumption, production and construction show that economic growth

and social equality are dependent on construction. The activities of construction industry

are not confined to the construction of dwelling houses, but extend to infrastructure,

equipment and services as well as their repair and maintenance. Thus, construction is

powerful stimulator of social growth and well being. It is therefore not surprising that in the

developed countries investment in the construction sector, including building materials is

higher than in any other sector, (over half the total investment) [7].

At present, the Ethiopian construction industry accounts for only 5.5% of GDP, compared

to a sub-Saharan Africa average of 6%. However with sustained economic growth over the

past four years, the sector has registered 8.2% growth; and public construction projects

account for nearly 60% of the Government’s capital budget [8].

The building materials and the construction industry is one of the most important sectors of

economic activity and represent an essential instrument of socio-economic development. It

provides a wide range of services and capabilities for designing and constructing facilities

necessary for economic development [7].

Considering the other factors needed for the smooth operation of the construction industry

such as the goods produced by other industries, manpower and other inputs, it is easy to see

why this sector is so sensitive to socio-economic conditions and why political leaders

attach so much importance to controlling its development by formulating and adopting

clearly defined policies and strategies.




Reciprocally, it can be said that, because they have in the past misjudged or still misjudging

the importance of the building materials and construction industries sector and its primary

links with other socioeconomic sectors, some countries, despite their material resources,

have repeatedly made unsuccessful experiments in the field of construction which, instead

of serving as an instrument of development, represents, in the last analysis a bottomless pit

swallowing up their wealth and efforts and constitutes no more than a socio-economic dead

weight [7].

Strategic planning for building materials development should be based on an assessment of

future needs. Firm polices on the use of non conventional materials, backed by a

demonstration of the government’s commitment to use them in government sponsored

projects would contribute greatly in enhancing their increased application in both public

and private housing and building projects. There is also an urgent need for governments to

ensure that are expected to make significant contributions to an improvement of the supply

of essential building material receive priority in the allocation of funds.

2.3 Traditional housing construction in Ethiopia

In Ethiopia like many countries in the third world, there is a big gap between the income of

the majority of the population and the cost of the buildings. Based on Climatic conditions

and altitude, Traditional house construction in Ethiopia are divided in to houses of low

lands-Kolla (<1400m); houses of highlands- Woina Dega (1400-2700m) and houses of

highlands Dega (2700 above sea level) [3].

In Ethiopia soil is used extensively in the traditional construction of mud walls (Chika)

both in the Kolla, Woina Dega and Dega area, especially in the central, northeast,

northwest and in the southern eastern rift valley area of the country. “Chika” is a mixture of

Clay, fine and short straw of the Ethiopian common cereal,”teff” (Eragroetis Abyssinica)

and water [7]. The mixture, after it has thoroughly been mixed by treading with the human

feet is either immediately used, or is left to ferment for some time before it is used as a

filling material of the opening between wood poles and finally as plaster. Unfortunately the

traditional building techniques adopted for mud walls in Ethiopia have serious defects. The

mud walls suffer from extended shrinkage cracks, which weaken the walls. Mud walls can




easily be eroded by rain. The practice was to cover mud walls with protective coating

consisting of animal dung. This was intended to serve as a wearing surface. The protective

surface needed continued maintenance and some times renewal almost every year. These

entire drawbacks lead most of the people to the misconception that buildings with soil are

of inferior quality and should be avoided.

2.4 Salient features of earth as a building material

Earth as a building material has the following salient features:

A) Strength

Earth block buildings are structurally sound. New Mexico adobe code requires a minimum

of 2MPa for traditional adobe blocks. The strength, durability and longevity of Earth

Blocks stand in stark contrast to other building materials. A typical wood frame building

has an average life span of 75 years while earthen structures will stand for centuries [9].

The technology of the hydraulic press machine has enhanced the fundamentals of earthen

construction, durability, simplicity and sustainability. These characteristics have remained

constant throughout the ages. For thousands of years people around the world have relied

on earthen construction for their shelter with minimal impact on the environment.

Approximately about half of the world’s population currently resides in earthen dwellings.

Earth block construction combines the purity and timelessness of a natural material with

the opportunities and innovations of today, a timeless technology.

B) Cost and Energy efficient

Probably the most impressive and important selling point of earth block building is the

incredible energy savings the owner will be awarded throughout the life of the building.

The thermal mass quality alone defines the strongest attribute of earth block and can be

spelled out in energy savings to the owner, which means the community, saves as well.

Energy efficiency can also be realized in the construction process itself. Earth blocks are

made on-site saving in transportation costs and fuel consumption and require little energy

in the block making process.




C) Virtually Sound proof

Earth Block is so dense a building material that occupants are relatively protected from the

outside World [9]. Sound recording studios have been built with pressed block for that very

quality. Earth block buildings create their own world on the inside, which most people find

is an added bonus.

D) Non-Toxic

Block making itself is a non-toxic process; therefore, buildings themselves are clean. Often,

man-made ingredients of modern construction set up an environment that is filled with

toxic chemicals and gases. Earth block is a frequently chosen material for home

construction for those people suffering from chemical sensitivity [9]. It’s a win-win for

both occupant and the community when new buildings are constructed with earth-friendly

materials.

E) Environmentally friendly

When you consider the attributes listed above, the underlying theme is that building with

Earth block is environmentally friendly. From the construction of the block itself to the

finished product, this is a way to build that benefit everyone.

F) Durable

Durability is the measure of the ability of the block to endure or sustain its distinctive

characteristics of strength, dimensional stability and resistance to weathering under

conditions of use for the duration of the services lifetime of the structure [10].Earth blocks

have to be durable and water proof to exclude any undesirable influences of the

environment such as rain, winds, rising damp or other severe weather conditions of

exposure. When you consider that the oldest structures standing throughout the world today

are made of earth, the statement that earth block is durable speaks for itself. Earth block has

a good resistance for fire and pest.




For the purpose of this thesis, cement stabilised soil block is defined as a durable material

which is produced from a natural or modified soil containing sufficient fines to provide

cohesion on densification, sufficient to allow unsupported handling or stack curing.

G) Uses available and abundant raw materials

Three ingredients make up the right combination used for earth block: sand, clay and silt

materials, which are combined with a small percentage of Portland cement. The only other

ingredient needed for wall construction is water, to make the mud slurry that binds the

blocks together.

H) Aesthetically pleasing

Earth block buildings can be made to look like any kind of finished structure; however,

most people who adopt for this type of construction find they love the look of the block

itself and the adobe look of a finish plaster. Exteriors typically are given a weather-resistant

skin that can be colored or left natural and interiors plastered with a variety of mixtures or

left exposed. Arches and rounded corners are an option that allow for flexibility in design

as shown in Fig 2.1 below. They have a look and a feel that envelops their occupants and

blends beautifully with the natural world.




Fig 2.1 Soil block building in India

I) Thermal Properties

Building materials are rated for thermal performance based on measurements known as R-

and U -values. The R-value indicates the ability of a wall to insulate efficiently. Insulation

is nothing more than the resistance of a material to the transference of heat. It makes sense

that the higher the R-value, or resistance, the better insulator the material is.

The R-value is calculated by dividing the thickness of the wall by the wall’s thermal

conductivity, a value established by the amount of heat (per sq. ft. per hour) flowing from

the hotter to the cooler side of the wall [9].

The U-value, or value of conductance, is represented by the reciprocal of the R-value and

reflects the rate at which heat is conducted through material. Total R- and U- values may be

calculated for a given wall by adding the sum of the values of each of the individual

components of the wall structure (all insulation, interior sheathing, framing, or masonry

must be taken into consideration) [9].




[ Both of these values reflect the rate at which heat passes through a wall only after it has

achieved the steady-state condition or the state when heat energy is passing uninterrupted

from one side of the wall to the other at a constant rate. What is not taken into

consideration and is of critical importance in the case of masonry-mass walls like adobe, is

the heat capacity of the wall, which determines the length of time which passes before a

steady state of heat flow is achieved.

The higher the heat capacity of the wall, the longer period of time it will take for heat flow

to reach a steady state. In reality, external and internal temperatures are changing

constantly so that a true steady state condition is rarely achieved. What does occur, in the

high-capacity wall such as adobe, is the constant comfort zone found in adobe buildings.

For example, in the morning, when the sun rises, heat from the warmer, exterior side of the

wall begins to move through the adobe mass. Depending not only on the resistance (R-

value) of adobe, but also on the heat capacity of the wall (a factor both of the specific heat

capacity and the thickness of the wall), the heat takes a certain length of time to reach the

cooler, interior side of the wall and be released into the surrounding air. In adobe walls of

sufficient thickness and of sufficient R-values, the normal daily fluctuations of

temperatures never really allow much heat to pass through the wall at a steady state.

At night, when the warmer side of the wall drops in temperature, heat already absorbed into

the masonry-mass wall continues to flow, not just in one direction, but to both sides of the

wall until a temperature equilibrium has been reached.

This cycle is repeated in what is known as the flywheel effect [9]. It is responsible for the

comfort well known to those who live in properly designed compressed earth block homes.

2.5 Main techniques using earth as a building material

For 10,000 Years, earth has been used as a building material. Today, one third of the world

population is living in earth buildings [11]. There are eighteen principal well-known

methods using earth as a building material as shown in the Fig. 2.2 below. Amongst these,

eight are widely employed and constitute the following major techniques:




1. Adobe: The earth, in a malleable state, often improved by addition of straw or other

fibers, is moulded in to a brick form and dried in the sun (11, 12, 13).

2. Rammed earth: The earth is massively dumped into formworks, compacted by

means of a rammer, layer by layer, and formwork (5).

3. Straw clay: The earth is spread out in water until a homogenous thick liquid state is

attained. This muddy liquid is mixed with straw in order to form a film on every

wisp. The building material obtained conserves its straw like aspect. It is put in to

place by means of a formwork in order to erect a monolithic wall, which necessitates a

primary support structure (16).

4. Wattle and Daub: Clayey material, mixed with straw or other fibers, is layered on

top of wattles that fill in a timber structure (14, 15).

5. Shaped earth: The earth, often improved by the addition of straw or other fibers is

shaped in to a wall using the same technique as that used for pottery, without tools.

This ancient technique is still widely used. (4).

6. Extruded earth: The earth is extruded by a powerful machine similar to, or derived

from, the machines used for the manufacture of fired brick (10).

7. Cob: The earth, often improved by the addition of straw or other fibers, is shaped in to

big balls, which are piled on top of one another and lightly packed, by hand or foot, in

order to erect shaped monolithic walls. In order cases, the cob is incorporated into a

timber framework or structure (3).

8. Compressed Earth: The earth is compressed, in block form, in a mould in the past; the

earth was compressed in the mould by means of a small pestle, or by tamping a very

heavy lid forcefully on the mould. Nowadays, a wide variety of presses is used (6, 7).




Fig.2.2 Use of Earth as Building material [11]

2.6 Compressed Earth Block

2.6.1 Historical background of compressed earth block

From the roof of the World in Tibet or in the Andes Mountains in Peru, to the shores of the

Nile in Egypt or in the fertile valleys of China, many are examples of earth used as a

building material. The oldest one can still be seen in Egypt, near Luxor, which was built

around 1300 BC: the vaults of Ramasseum, in the "rest" of the Thebes. It has been built

with adobes, the sun dried mud bricks [12].




India also shows very old earthen buildings, like the Shey Palace in Ladakh, which was

built with adobe in the 17th

century. The oldest one has withstood 1006 Himalayan winters:

the Tabo monastery in Spiti Vally, Himachal Pradesh, which was built with rammed earth

in 996 AD [4].

Raw earth for building has been used world wide for millennia but during the 20th

century,

most of the skills of earth builders were lost and building with earth became marginal.

Thanks a lot to the Egyptian architect Hassen Fathy for the renaissance of earthen

architecture in the middle of the 20th

century [12].

The new development with earth construction really started in the nineteen fifties, with the

technology of compressed stabilised earth blocks (CSEB): a Colombian research program

for affordable houses proposed the first Manual press, the CINVARAM (Fig 2.3). This has

led to a renaissance of the tradition of earthen architecture and construction-a revival,

which is benefiting from the results of scientific research [12].

The compressed earth block is the modern descendent of the moulded earth block, more

commonly known as the adobe block. The idea of compacting earth to improve the quality

and performance of moulded earth blocks is, however, far from new, and it was with

wooden tamps that the first compressed earth blocks were produced.

Fig 2.3 The first Manual press, Cinvaram [13].




The first machines for compressing earth probably date from the 18th

century. In France,

Francois Cointeraux, inventor and fervent advocate of "new pise" (rammed earth) designed

the "crecise", a device derived from a wine-press. But it was not until the beginning of the

20th

century that the first mechanical presses, using heavy lids forced down into moulds,

were designed. Some examples of this kind of press were even motor-driven. The fired

brick industry went on to use static compression presses in which the earth is compressed

between two converging plates. But the turning point in the use of presses and in the way in

which compressed earth blocks were used for building and architectural purposes came

only with effect from 1952, following the invention of the famous little ClNVA-RAM

press, designed by engineer Raul Ramirez at the CINVA centre in Bogotá, Columbia. With

the 70's and 80's there appeared a new generation of manual, mechanical and motor-driven

presses, leading to the emergence today of a genuine market for the production and

application of the compressed earth block [6].

In view of the history of earth construction, the compressed block technique is a new

technique. It has been developed in the fifties in the frame of a research program

concerning rural housing in Columbia. It is an improvement of the adobe technique.

Instead of being molded by hand in a wooden frame, the blocks are formed by compressing

earth, slightly moistened, in a steel press. Compared to the hand-moulded block, the

compressed earth Block is very regular in size and shape, and much denser as shown in the

Fig. 2.4 below. It has better resistance to compressive stresses and to water.

Earth blocks are blocks of compressed soil that are aesthetically pleasing as well as cost

and energy efficient, fire and pest resistant, virtually soundproof, durable and structurally

sound. They provide complete architectural freedom and are made from non-toxic readily

available natural raw material dirt [9].




Fig.2.4 Typical compressed earth blocks [9].

Since the very earliest of times, earth has been used as a major building material and today

we can find evidence of this fact over vast areas of our planet. The developments of

industrial building materials such as concrete and steel have to a large extent suppressed the

use of unfired earth.

Today, however, there is a re-awaking of the use of this traditional building material, not

only in developing countries, but also in the developed Western world. Earth, the oldest of

building materials on our planet, is still today the most commonly used [9]. There is now a

worldwide tendency towards using soil as a building material to achieve economy in the

final cost of a building [7].

It is also the most popular material amongst Europe’s bio-ecological constructors on

account of its physical attributes and ability to regulate moisture and temperature.

This in turn allows for heating/energy reductions of up to 30 % and in some cases even up

to 80% [9]. The technology behind the production of compressed earth blocks is based on a

mechanical process. This ensures a high quality product regular in dimension and of

durability consistent with high quality traditional brick building. Earth, as opposed to pure

clay, is the raw material used in the production of earth blocks.




2.6.2 Compressed earth block role in development

Since its emergence in the 50's, Compressed Earth Block (CEB) production technology and

its application in building have continued to progress and to prove its scientific as well as

its technical worth [6].

Research centers, Industrialists, entrepreneurs and builders have developed a very

sophisticated body of knowledge, making this technology competent to the present

construction technologies. Compressed Earth Building production meets scientific

requirements for product quality control, from identification, selection and extraction of the

earth used, to quality assessment of the finished block, thanks to procedures and tests on

the materials, which are now standardized. This scientific body of knowledge ensures the

quality of the material. Simultaneously, the accumulated experience of builders working on

a very large number of sites has also enabled architectural design principles and working

practices to emerge and today these form practical points of reference for architects and

entrepreneurs, as well as for contractors.

The setting up of compressed earth block production units, whether on a small-scale or at

industrial level, in rural or urban contexts, is linked to the creation of employment

generating activities at each production stage, from earth extraction in quarries to building

work itself. The use of the material for social housing programs, for educational, cultural or

medical facilities, and for administrative buildings, helps to develop societies' economies

and well-being.

Compressed earth block production forms part of development strategies for the public and

the private sector, which underline the need for training and new enterprise, and thus

contributes to economic and social development. This was the case in the context of a

program on the island of Mayotte, in the Comoros archipelago, for the construction of

housing and public buildings, a program today regarded as an international reference. The

use of Compressed Earth Blocks which followed the setting up of an island production

industry proved to be pivotal in Mayotte’s development, founded on a building economy

generating employment and local added value in monetary, economic and social terms.




Housing programs are often integrated into a strategy of development. One must consider

not only the direct benefits of the program (number of improved dwellings) but also its

effects on the local economy. An organization can produce compressed earth block on the

site itself or encourage local entrepreneurship by subcontracting teams. In any case,

vocational training provided during a program is a benefit for the community housing

programs can provide an opportunity to set up a local industry if appropriate materials such

as compressed earth block as preferred to materials based on imported components.

2.6.3 The future of compressed earth block

Earth as a building material undoubtedly presents certain outstanding shortcomings,

however, it also has important assets, which compensate any disadvantages, that could be

corrected. The shortcomings, principally low mechanical characteristics, unsatisfactory

resistance to weathering and liability to volume changes especially in the case of clayey

soils, can be corrected by combining chemical and mechanical action. Excellent

stabilisation results have been obtained on very different materials with various stabilisers

[7]. However, it is essential to guarantee quality of the compressed earth block by proper

mix design and adopting appropriate stabiliser to the earth to be treated; to carry out the

work in compliance with well established rules.

The research centers in India Auroville, CRATerre in France, and the Hydraform Company

in South Africa have made great progress on compressed earth block; thanks to scientific

research, experimentation, and architectural achievements which form the basis of a wide

range of technical documents and academic and professional courses. A major effort is now

being devoted to the question of norms and this should help to confer ultimate legitimacy

upon the technique in the coming years.

2.7 Social acceptance

Another key to success in an earth building is the social acceptance of the dwellings by

their future inhabitants. They generally ask for a ‘modern’ look, i.e. a house made of sand

cement blocks. But at the same time, the traditional way of life must be preserved and

attention has to be paid to the local climatic conditions, especially in hot countries. The




compressed earth block looks modern. Its flexible size and shape allows it to be used to

achieve many different types of masonry and so to build houses of any style. In hot

countries, and even more in those with a wide thermal variation, a compressed earth block

wall creates a truly comfortable living environment compared to sand, cement based

materials. Occasionally, a social reluctance to use the compressed earth block can be

encountered when the compressed earth block has been too strongly associated with low

cost or “cheap” building. Social acceptance depends a great deal on how it is presented to

the population. Organizations have an active part to play in this respect, as well as political

decision makers. The involvement of architects and engineers in this process is also

necessary.

2.8 Comparison of compressed earth block with other building

materials

Compressed earth blocks represent a considerable improvement over traditional earth

building techniques. When guaranteed by quality control, compressed earth block products

can very easily bear comparison with other materials such as the sand-cement block or the

fired brick as shown in Table 2.2 below.

Table 2.2 Properties of compressed stabilised earth blocks versus other walling materials

[4].

Property

Compressed

Stabilised

Earth

Blocks

Fired

clay

bricks

Calcium

silicate

bricks

Dense

concrete

blocks

Aerated

concrete

blocks

Lightweight

concrete

blocks

Wet

compressive

strength

(MPa )

1-40

5-60

10-55

7-50

2-6

2-20

Moisture

movement

(%)

0.02-0.2

0.00-0.02

0.01-0.035

0.02-0.5

0.05-0.10

0.04-0.08

Density

(kg/m3)

1700-2200 1400-2400 1600-2100 1700-2200 400-950 600-1600

Thermal

conductivity

w/moC

0.81-1.04

0.70-1.30

0.10-1.60

1.00-1.70

0.10-0.20

0.15-0.70

Durability

against rain Good to very

poor

Excellent

to very

poor

Good to

moderate

Good to

poor

Good to

moderate

Good to poor




2.8.1 Compressive strength

The compressive strength of compressed stabilised earth blocks (i.e. the amount of pressure

they can resist without collapsing) depends upon the soil type, type and amount of

stabiliser, and the compaction pressure used to form the block. Maximum strengths

(described in MPa) are obtained by proper mixing of suitable materials and proper

compacting and curing.

Several different minimum values of 28-day wet compressive strength, all above 1.0 MPa

are proposed; some of the recommendations by different authors for the minimum

compressive strength of compressed stabilised soil block include 1MPa, 1.4 MPa, from 1.4

to 2MPa and 2MPa [10].

In practice, typical wet compressive strengths for compressed stabilised earth building

blocks may be less than 4MPa. It is a strength suitable for many building purposes. It also

competes favorably, for example, with the minimum British Standard requirements of

2.8MPa for precast concrete masonry units and load bearing fired clay blocks, and of

5.2MPa for bricks [4].

Where building loads are small (e.g. in the case of single storey constructions), a

compressive strength of 1MPa to 4MPa may be sufficient. Many building authorities

around the world recommend values within this range.

2.8.2 Density and thermal properties

Normally compressed stabilised earth blocks are denser than a number of concrete masonry

products such as aerated and lightweight concrete blocks. While having densities within the

range of various types of bricks e.g. clay, calcium silicate and concrete bricks (see Table

2.2). The high density of compressed stabilised earth blocks may be considered as a

disadvantage due to its dead weight on the structure and when the blocks have to be

transported over long distances; however, it is of little consequence when they are produced

at or near the construction site. Low density compressed stabilised earth blocks have an

advantage over high density ones of acting as better thermal insulators. This is particularly




advantageous in hot dry climates where extreme temperatures can be moderated inside

buildings made of compressed stabilised earth blocks.

2.8.3 Moisture movement

Building materials with high porosity when used for wall construction may expand slightly

in wet and dry conditions. Such movements may result in cracking and other defects to the

building. Expansion of compressed stabilised earth blocks may vary according to the

properties of the soil; some soils expand or shrink more than others.

The addition of a stabiliser will reduce this expansion. In general, however, there may be

greater movement in structures built with compressed stabilised earth blocks than those

using alternative construction materials (see Table 2.2). Proper block manufacture and

construction methods, however, will reduce such movement.

Moisture movement is denoted in terms of linear percentage. It is worth mentioning that

moisture movement becomes especially important when two materials with different

movement properties are used in a building. Differential movement results in stress, which

may break the bond between the materials, or cause other damage. For example, cement

renderings often peal off earth walls or poorly compressed stabilised earth blocks because

of their different expansion properties.

2.8.4 Durability, Maintenance and Appearance

As a rule soil blocks containing stabilisers show greater resistance to extreme weather

conditions [4]. Blocks of the same size, when made of a sufficiently good quality and shape

with a high quality finish, can be used for fair-faced walling. Their appearance depends

upon soil colors, particle size, and degree of compaction used. With high quality blocks

external or even internal rendering should not be necessary. A white wash finish applied

directly to the blocks as a render coat could be used to reduce solar gain.




It should be noted that compressed stabilised earth blocks, in common with other types of

blocks and bricks, would need adequate steel reinforcement if used in areas prone to

earthquakes or cyclones etc.

Termites, bacteria, fungi and fire do not present a particular hazard for compressed

stabilised earth blocks. However, organic material in the soil may weaken the strength of

the block.

27

CHAPTER THREE

CONCEPTUAL REVIEW

3.1 General Where there is a demand for improving traditional building materials made of raw earth,

compressed earth block may provide an answer since the production methods are

technically accessible to the local labor, and because laying the block requires only

elementary masonry skills [11].

Compressed earth block is regular in shape and size and can be used in prestigious

buildings as well as in social building programs. It can be produced in small-scale village

workshops as well as in medium or large-scale urban plants.

In the early of the development of the compressed earth block technique, the attention of

researchers was focused mainly on the strength of the blocks and the design of presses. But

experience has shown the importance of other production parameters such as selection and

preparation of the soil. Failures were generally due to an underestimation of some

production parameters or due to an improper building design. Since the beginning of the

80’s great stress has been laid on vocational training in the filed of production and building

techniques at every level. Technical data obtained on sites or from researches have been

put into practice.

Improving existing equipment and developing new tools specific to the compressed earth

block is one way of assisting the spread of the technique. Another key to a successful

dissemination is the development of managerial tools at workshop level as well as for the

implementation of large-scale programs [11]. Furthermore, research and further

development has still to be done in the field of building norms, standards and technical

manuals to facilitate the introduction of the technique to the formal building sector.

3. Conceptual Review


3.2 Properties and analysis of soil for soil cement block

3.2.1 General properties

Soil is the result of the transformation of the underlying rock under the influence of physical,

chemical and biological processes related to biological and climatic conditions [14].It is

found deposited on the surface of the earth and may consists of many different types. The

variation in the soils present at the surface can be attributed to a series of natural effects

working on the area over time. On the very surface of the soil one typically finds material

with a large amount of organic compounds. This is unsuitable for block manufacture and can

usually be distinguished by a musty smell especially on heating [15]. Material underneath

this organic layer is much better as it usually contains a cross section of particle sizes and

includes a proportion of small soil particles called “fines”. These are usually defined as

particles passing a 75µm mesh and consist of silt and clay. Clay is necessary in block

production because it aids the workability of the mixture, increasing levels of consolidation

and improving green strength. Larger particles “sands” found in soil can generally be

assessed as minerals that are silicas, silicates or limestones. Soil has a proportion of water

and air that fill the gaps between adjoining particles in the soil. This gives natural soil a non-

homogenous and porous nature.

Systems for identifying some major characteristics have been developed to define different

ranges of soil characteristics. The most common of these is the size distribution of the soil

particles. The physical characteristics that can define a sample of soil includes color, shape,

apparent bulk density, specific bulk density, size or texture, moisture content, porosity or

voids ratio, permeability, effective surface area, adhesion, specific heat capacity, dry strength

and linear contraction [15].

Chemical properties are also sometimes of interest particularly when a chemical additive is

used. These chemical properties include the composition, mineral content, metallic oxides,

pH levels and sulphates in the soil [15, 16].

Soil characteristics and climatic conditions of an area must be evaluated before

manufacturing soil building blocks. A dry climate, for example, needs different soil blocks



from those used in temperate, rainy or tropical areas. All soils are not suitable for every

building need [4].

With so many different characteristics that one could discover about a sample of soil, it

would be foolhardy to try and discover them all in every situation that soil is to be used for

making compressed stabilised soil block. Only a small number of characteristics are of real

relevance to the scientist testing the soil. The chemical composition of the soil is of little

importance once the absence of unstable compounds and organic matter has been established.

The physical properties are of greater interest for making compressed stabilised soil block as

these will help to determine its ease of mixing, forming, de-moulding, porosity, permeability,

shrinkage, dry strength and apparent bulk density. Controlling or monitoring the clay fraction

is important in making compressed stabilised soil blocks. Too much clay results in

unacceptably high expansion upon wetting, requiring excessive amounts of cement to attune

this. Too little clay causes low adhesion between particles and hence causes high breakage

rates on de-moulding of the compressed stabilised soil block [15]. The basic material,

however, required to manufacture compressed stabilised earth building blocks is a soil

containing a minimum quantity of silt and clay so as to facilitate cohesion [4].

Optimum fines content for making compressed stabilised soil block was suggested by the

United Nations to be about 25% of which more than 10% is clay. A more useful range of

particle sizes suitable for building with earth block is given in as follows [15]:

Sand/fine gravel: 40 - 75%

Silt: 10 - 30%

Clay: 15 - 30%

From the literature it is unclear how much a change of say ±5% to the clay content will have

on the overall performance of the compressed stabilised soil lock. Controlling the moisture

content in the mixture is also important, but generally the production manuals use a simple

drop test to determine an acceptable range. The accuracy of this test is fairly low and what

effect the possible variation in the moisture has on the finished product is not clear.



The detrimental characteristic of expansion and contraction of a compressed stabilised soil

block can only occur if three characteristics are present: “Clays” and “Porosity and

Permeability” and “Moisture differential”. If any one of those is absent then expansion and

contraction will not occur, (ignoring thermal expansion and contraction).

We need clay to be present in compressed stabilised soil block and it is impossible in

humid climates to avoid moisture differentials so that the only characteristics that we can

seek to reduce are the porosity and permeability.

Using a suitable soil for soil-cement block production will result in [4]:

- Strong blocks, namely those that after curing possess high wet strength and erosion

resistance.

- Handle able blocks that immediately upon demoulding can be transferred to a

curing area without a high breakage rate.

- Block that will not seriously distort or crack during curing.

- Blocks, which will not expand and contract excessively in the building if subjected

to wetting and drying cycles.

Specifically disqualified soils are:

- Those containing high excessive organic impurity.

- Those, which are highly expansive.

- Those containing excessive soluble salts e.g. gypsum and chalk.

3.2.2 Classification of soil

Soils are classified in many different ways: by their use, origin, size, texture, color and

density [3]. For building purpose soil can be generally characterized in two ways, by a

particle size distribution analysis and by a plasticity index. The particle size analysis will

give information on the soil ability to pack into a dense structure and the quantity of fines

present (combined silt and clay fraction), while the plasticity index gives an idea of

cohesion of the fines [17].



3.2.2.1 Classification by grain size

All soils consist of disintegrated rock, decomposed organic matter and soluble mineral

salts. Soil types are graded according to particle size using a system of classification widely

used in civil engineering. The classification of soils based on grain size, according to the

Ethiopian Building Code of Practice, EBCS and ASTM, are summarized as shown in Table

3.1 and 3.2 respectively.

Table 3.1 Soil classification according to particle size in mm EBCS 7[18].

Particle Size

Basic soil type Coarse Medium Fine

Stone 60-200(1)

> 200(2)

-- --

Gravel 20-60 6-20 2-6

Sand 0.6-2 0.2-0.6 0.06-0.2

Silt 0.02-0.06 0.006-0.02 0.002-0.006

Clays <0.002 mm

[1]

Cobbles [2]

Boulders

Table 3.2 The grain size classification based on the ASTM D 2487 Standards [14]:

Pebbles Gravel Sand Silt Clay

200 to 20 mm 20 to 2mm 2 to 0.006mm 0.06 to 0.002 mm 0.002 to 0mm

Gravel is not usually used in soil- cement production, as the large particle size may lead to

a poor (rough) surface finish. A suitable soil will contain a mixture of sand, silt and clay

sized particles. The properties of each of these three fractions influence the properties of

the block and will be discussed below. [

A particle size analysis will determine the fraction of a soil’s particles that fall with in each

of the above size bands. If dense block is to be produced, it is important that the soil used is

“well graded”. The theoretical distribution of particle sizes to provide a perfectly packed

structure is called the fuller curve [17]. The fuller distribution is an ideal model and never



occurs naturally. However, a natural soil which has an even distribution of particle size,

termed well graded is a good approximation.

The fuller curve is based upon the assumption that all of the particles are spherical and that

the largest particles just touch each other, while there are enough intermediate particles to

fill the voids between the largest, but without holding them apart.

The value of a well-graded soil for soil cement is that such a distribution of sizes gives a

dense structure with a low specific surface area. A dense structure is important for several

reasons. A densely packed arrangement will have a higher number of contacting particles,

giving a better load-bearing skeleton. The number and size of the inter-particle voids will

be reduced as will the number of linked voids, these will reduce the porosity of the soil and

hence also its permeability, thereby reducing susceptibility to water penetration. As the

interlocking calcium silicate matrix extends through the soil voids, a more compact void

system requires less cement to provide a matrix of equal efficiency.

Similarly if it is imagined that cement coats the surfaces of soil particles, a high specific

surface area soil will need high amount of cement for blinding, or a lower specific surface

area soil will require less cement to provide the same particle surface coverage and

consequently the same strength and durability.

The upper and lower limit to the soil’s grading also need to be considered. A soil may be

considered well graded with a uniform distribution of particles from fine silt to coarse sand

(coarse soil). The coarse soil will have a lower specific surface area than the fine soil, as

the same mass of soil will contain fewer and larger particles. From the above consideration

of specific surface area, it might be concluded that the more coarse soil would produce

strong blocks with lower cement content than that needed for the fine soil. This is however

only the case when the blocks are kept within the mould to cure.

A coarse soil containing no fines (silt and clay) is non-plastic and will not have sufficient

cohesion to retain its shape on ejection from the mould or to allow easy transportation to

the curing area [17]. The coarse soil could be considered to be a form of sand-cement



containing large voids (a result of the lack of fines). Large voids would increase the

porosity of the block and lead back to the common sand-cement problem of rapid drying

before the cement has had time to adequately cure. Such a soil would be considered well-

graded but still be unsuitable for soil-cement block production.

Conversely a well-graded fine soil, containing little sand but high clay content, would have

a high specific surface area and expansive behavior. The high clay content would give the

soil cohesion and stability on ejection from the mould, but the high specific surface area

would require a large amount of cement to provide reasonable particle coverage.

Thus, a suitable soil will be well graded but certain other limits should also be imposed: the

largest particle size present should not be sufficiently large to cause a poor surface finish.

Sufficient fines (silt and clay) should be present to allow handleability on demoulding but

not enough to blind the small quantity of cement to be used.

3.2.2.2 Classification by plasticity (Fine content)

The silt and clay content of a soil are responsible for soil cohesion and it is these fines that

provide the fresh blocks with handleability until the initial set of the cement has occurred.

The degree of cohesion provided to the block is dependent both on the fines present and the

degree of compaction used to form the block.

In general terms, a low-pressure moulding process will require higher fines content than a

high pressure moulding process. This is because increased compaction will force the soil

particles into more intimate contact, thus strengthening the fresh compact.

However, the fines, in particular the clay fraction can also lead to blinding of the cement as

a result of their high surface area. The approximate surface area of fine sand and medium

silt are 0.023 and 0.23 square meters per gram, while for three major clay groups, kaolinite,

illite and montmorillonite this increases to 10, 100 and 1000 square meters per gram

respectively [17].

The fines also affect the final cured block’s expansion on wetting. Clay usually exists in

small agglomerations, which expand in three dimensions on wetting as water penetrates

some of the numerous individual particle boundary fissures. The expansions of the clay



fraction must be largely restrained by the calcium silicate matrix in order to minimize

expansion and contracting of the cured block, on reported wetting and drying. Hence for

durability the clay fraction should be as small as possible to allow the lowest cement

content. It might be expected form the large difference between the specific surface areas

of the three clay types mentioned above that different clays significantly differing

expansions characteristics on wetting. This is the case, in general as the surface area of the

clay fraction rises, so does the amount it will expand on wetting. As a result the type of clay

as well as the quantity present will affect the block [17].

The fine fraction can be seen to be helpful to the block production process but to adversely

affect the wet strength and durability of the final cured block. The quantity and type of clay

should therefore be considered important soil parameters.

The quantity of fines may be measured by using one of the sedimentation tests, however

the clay type present is very difficult to determine without highly complex tests. In fact it is

not necessary to know the clay type present but it is important to know the properties

exhibited by the clay.

The Atterburg tests defining liquid limit, plastic limit and plasticity index are used to

quantify the plasticity of the finer fraction of a soil (only particles less than 0.425 mm are

tested). These tests measure the percentage water contents at which the soil passes from a

liquid state to a plastic state (liquid limit) and from a plastic state to a solid state (plastic

limit). The numerical difference between the liquid and plastic limit (the plasticity index)

thus gives the range of water content over which the soil may be considered plastic. As

plasticity is dependent on the soil cohesion, it has been found that this index reflects the

cohesive characteristics of the soil. Furthermore as cohesion is largely dependent on the

specific surface area of the fines, these plasticity limits also reflects the expansiveness of

the soil. A soil with a low plasticity index will display low cohesion and usually low

expansion on wetting, while a high index soil will display the reverse.



3.3 Suitable soil for soil cement block

A suitable soil should not contain organic material or excessive soluble salts, which would

interfere with the setting of the cement. Its sand fraction should be well graded to provide a

densely packed load-bearing skeleton for the block and its largest size particle should be

small enough to give a smooth surface finish. The fine fraction should be just sufficient to

provide enough cohesion to the fresh block to prevent damage on ejection and

transportation from the mould. Too large fines content will either require large cement

content for adequate stabilisation or will reduce the durability and wet strength of the final

cured block. The cohesion of the fresh block will depend on the compaction pressure used

and the type as well as the quantity of clay present in the fines.

From the above it should now be possible to see the role that each of the soil’s component

fractions plays in a soil-cement block and the importance of selecting a suitable soil. If the

soil available on site appears unsuitable, it should be remembered that natural soil exists in

distinct strata with differing compositions. If the different strata are adequately tested then

it is a comparatively simple operation to mix suitable masses of two or more strata to

produce an acceptable soil [17].

3.4 Available criteria for soil suitability

Selecting a suitable type of earth can take place in the field using parameters, which are the

fruit of experience acquired in the course of operational practice. If any doubt persists,

laboratory identification tests should be carried out.

It is not an exhaustive review but rather included as indication of the variation between

authors and as a warning that such criteria should be used as a guide in initial soil selection

rather than as a rigid set of rules. Some of the criteria based only on particle size while

others use criteria based solely on the Atterburg limits (plasticity index). In general it

would be wise to consider both [17].



3.4.1 Criteria based on African Regional Standards

A. Granular composition

In order to decide whether a soil sample is suitable for soil cement block production or not,

one should determine the particle size distribution. From such test results and previous

practical experiences, one can get indication on the suitability of the soil sample in

question.

Based on African Regional Standards and experiences from laboratory investigations, if the

granular composition of soil falls with in the limits of the recommended shaded area of Fig.

3.1, the soil is usually considered as suitable for stabilised soil block production. Types of

earth the granular composition of which fall out side the shaded area may still give

acceptable results, but it is recommended that they be subjected to a series of tests enabling

their suitability to be assessed.

Fig.3.1 Diagram of texture [19].



B. Plasticity

Additional tests such as liquid and plastic limits can also be made. Such test results will

give indication about the plasticity (workability) of the soil in question. If plasticity of the

soil fall preferably with in the limits of the recommended shaded area of the diagram of

plasticity as shown in Fig. 3.2 below, the soil is considered suitable for soil cement block

production. Types of earth the plasticity of which fall out side the shaded area may still

give acceptable results, but it is recommended that they be subjected to a series of tests

enabling their suitability to be assessed.

Fig.3.2 Diagram of Plasticity [19].



3.4.2 Criteria based on Spence, R.J.S & Cook, D.J.1983, Building

Materials in Developing Countries

The suitability criteria of soil for soil cement block production have variations between

different authors. Spence and Cook are among the authors who set the criteria on soil

cement block production. Space and Cook include a graphical plot on a triangular U.S.

Bureau of public roads particle size graph roughly between the limits:

Sand: 90 - 60 silt: 25-0 clay: 25-0

A. Triangular chart for particle size classification of soils:

If the granular composition of soil falls with in the limits of the recommended shaded area

of Fig. 3.3, the soil is usually considered as suitable for stabilised soil block production.

Shaded area indicates soil most suitable for soil stabilisation.

Fig.3.3 Triangular chart for particle size classification [17].



B. Atterburg limit criteria for soil stabilisation

If plasticity of the soil fall preferably with in the limits of the recommended shaded area of

the plasticity chart as shown in Fig. 3.4 below, the soil is considered suitable for soil

cement block production. From Fig 3.4 is applicable only to the fraction of soil finer than

0.4 mm, roughly between the limits; Plasticity index 0- 22 %, liquid limit 7-40%.

Fig 3.4 Plasticity chart [17].

3.5 Tests for soils

3.5.1 Types of tests

Prior to soil cement block production there are three main types of tests, which may be

conducted: Field tests, Laboratory tests and trial production tests [8].

First, field tests can divide the soils in to two categories. These categories are suitable and

unsuitable and if suitable in to potential high and low cement classes [17].



Second, Laboratory tests can be used to characterize the soils by particle size distribution,

plasticity or other numerical measures for relation to the selection criteria (see section 3.4)

and enable simple soil modification by blending [17].

Most small- scale manufacturers of blocks, especially those producing blocks at a rural

building site, have little or no access to laboratory facilities and in particular accurate mass

measurement to 0.01g. For these block makers, judicious use of the field tests, the

shrinkage test, production trials and past experience has to suffice.

The laboratory tests are appropriate where medium or large- scale production is planned,

where minimizing cement content is especially important or when soil cement block

making is moving into a new area.

Third, trial production tests can be carried out on manufactured blocks to check that the

final block properties required (dry strength, wet strength and durability) can be achieved.

3.5.1.1 Field tests

Field tests are for preliminary site surveying to identify if the soils are most likely suitable

and so restrict the number of soils to be more rigorously assessed by laboratory tests or trial

production. The tests will provide a rough idea of a soil’s grading and plasticity and also

indicate whether a soil contains significant organic matter (reject outright), a majority of

gravel, a majority of sand or a majority of fines. They may also be able to distinguish

whether silt or clay is a more significant fraction of the fines. They are generally fairly easy

to perform and often require little or no experimental equipment, making them very simple

to implement.

Simple field tests which are performed to get an indication of the composition of the soil

sample includes: smell test, nibble test, touch test, sedimentation test, adhesion test,

washing test, linear shrinkage test, dry strength test, water retention test, consistency test

and cohesion test [4].



However field tests are frequently reported, with out acknowledging the reliance they place

on the operator’s senses. Interpretation of the results is a skilled operation. Consider for

example the dry strength test, the prepared soil sample is crushed between the fingers and

the ease of crushing is taken as a measure of the soil’s clay content. For a novice operator

the ease of crushing the soil and comparing the clay content is difficult but a skilled

operator may compare the ease of crushing with that of soils he/ she has previously tested

and hence arrives at a more precise conclusion.

Tests that rely on personal judgment are open to differing interpretation between operators

and depend on the operator’s skill for their accuracy. Training and experience of field tests

may provide a fact, quite accurate determination of the soil’s characteristics.

All of the test results observed (both the good and the bad), plus the location and depth of

the soil samples in question should be recorded in case it is later necessary to use a soil for

blending which on preliminary examination had been rejected [17].

3.5.1.2 Laboratory tests

The laboratory tests establish numerical values for certain soil parameters, primarily the

percentage distribution of the different sizes of soil particles present and the plasticity

limits. These values are subsequently used to determine the best available soil or

domination of soils. All of these tests rely on accurate weighing and or some form of

laboratory equipment scales with a resolution higher than one thousandth of the chosen

sample weights is desirable. There are four main types of tests: The sieving test,

sedimentation test, Atterburg limit test and compaction test.

The sieving tests separate the different size fractions of the soil in to discrete parts thereby

indicating the soil’s particle grading. The silt and clay fraction are too small to particle

grading. The silt and clay fractions are too small to be easily separated by sieving and as

such are normally reported as a combined fraction [11]. The larger particles may be

separated in to a number of size fractions, depending on the number of sieve seizes

available, according to the EBCS and ASTM particle classification boundaries, given in



section 3.2.2.1. A full laboratory analysis would give the percentage by weight of each of

these size bands.

The sedimentation tests if correctly conducted have the ability to separate the larger sand

and gravel size fraction from the combined fines fraction and under favorable circumstance

to further distinguish the combined fraction in to separate silt and clay fraction [16, 18].

However the simplest test, the glass-jar sedimentation test, is usually included under field-

tests because visual discrimination of the silt/ clay boundary may not be possible. In this

case the test can only be used to give an idea of the general relative proportions of sand and

fines.

In its coarsest form the glass- jar sedimentation test provides no more information than a

sieving test and although less accurate, it does not require any mass measurement. Further,

although the sedimentation time is long the operator time required to conduct the test is less

than that for a sieving test [17].

The Atterburg or plasticity tests define the soil’s liquid limit, plastic limit and plasticity [16,

17]. The Atterburg limits allow the soils plasticity characteristics to be related to the criteria

given in section 3.4 above.

The shrinkage test is a test of the soil’s contraction on drying and gives a combined

measure of the soils’ particle grading, plasticity and clay type. It gives an overall idea of the

soils behavior and suitability for stabilisation.

The degree of contraction may be thought of as a measure of the expansive force, which the

soil stabiliser will have to withstand when a manufactured block is exposed to water. The

degree of contraction is then taken as a measure of the quantity of stabiliser required. The

shrinkage test may be used as a straightforward method of determining a soil’s suitability

for use where more complex testing is not possible or not justified for small- scale

production. However it must be remembered that this test gives no direct information on

the soil’s constituent parts and as such will not allow easy soil modification [17]. It was

empirically designed for used with the CINVA RAM, a low- pressure (2MPa) manual-



compaction-moulding machine developed by VITA. It was intended to gauge the amount

of stabiliser required for a given soil compacted with this machine. It is very suitable for

small- scale production if soil modification is not considered cost effective but it must be

used in conjunction with tests on trial blocks.

It should be remembered from the above discussion of soil suitability that the compaction

pressure used to compact the block does affect the soil requirements. The shrinkage test

was empirically calibrated for the CINVA-RAM (2MPA) and is not directly applicable to a

machine operating at a different compacting pressure. In general if the machine compacts

to a higher pressure then the cement content may be reduced for a given soil shrinkage, or

alternatively the range of acceptable soil shrinkage values may be increased [17].

If the results from these are to be useful, a great deal of time and care must be taken. This

point is seldom mentioned. These tests appear simple to carry out and they produce

numerical values, which are relatively easy to interpret, but they are not proofed and will

produce misleading results if not carefully performed. The sedimentation tests in particular

are very delicate, requiring time and practice to be perfect. In general soil tests are subject

to two accuracy limitations: experimental care and measurement resolution.

3.6 Soil as a building material

Some form of soil covers virtually the whole land surface of the earth. This soil is usually

readily processed with simple hand tools into an easily mouldable material, which

possesses good compressive strength when dry. Given soil’s widespread availability, it is

not surprising that it was traditionally widely used as a building material.

The major drawback to building with soil is its susceptibility to water. A soil wall may be

considered as a load-bearing skeleton of silt and sand glued together by clay. This glue-like

behavior when dry is caused by micro droplets of water, which exist at clay particles

interfaces.

Clay particles are usually electro statically charged as a result of surface ion substitution.

The charge tightly bonds a thin adsorbed layer of water to the particles surface. The

bonding is sufficiently strong for some adsorbed water to remain even at oven drying



temperatures (105-110°C). At the point of contact between two adjacent particles, micro

droplet of water can exist where the two adsorbed water layers come into contact. These

micro droplets generate both surface and capillary tension forces, which hold the clay

particles together. However when any significant quantity of water is absorbed into empty

soil pores, the droplets increase in size and the capillary and surface tension forces reduced,

causing the soil to quickly soften and subsequently swell. On repeated wetting and drying

the outer surfaces of a soil wall expand and contract more quickly than the main body. In a

comparatively short time this leads to cracking and spalling of the outer surfaces and low

durability for the wall. Moreover if the wall becomes saturated with water the compressive

strength may fall sufficiently to allow complete collapse [17].

There are many methods to reduce a soil’s susceptibility to weakening by water. These fall

in to the following broad categories:

i) Protecting the wall from exposure to water,

ii) Reducing the permeability of the wall by increasing the soil density,

iii) Making the soil water-repellant by the addition of a water proofing agent and

iv) Providing a secondary cementitious- type strength mechanism which is largely

unaffected by water [17].

3.7 Soil stabilisation

There are several methods of soil stabilisation widely used to improve construction quality.

Some of the major stabilisation techniques are described below.

3.7.1 Mechanical stabilization

Mechanical stabilisation involves tamping or compacting the soil by using a heavy weight

to bring about a reduction in the air void volume, thus leading to an increase in the density

of the soil. The main effects of compaction on the soil are to increase its strength and

reduce its permeability. The degree of compaction possible, however, is affected greatly by

the type of soil used, the moisture content during compaction and the compression effort

applied. Best results can be obtained by mixing the correct proportions of sand and clay in

a soil [4].



More recent developments for roads and embankment construction have led to compacting

soil with vibrating rollers and tampers. Tampers and block-making presses are also used for

single storey constructions. The major drawback of mechanically compressed stablised

earth blocks is their lack of durability especially in places of moderate to high rainfall.

Manual stabilisation or compaction methods vary from foot treading to hand tamping

equipment, with compacting pressures varying between 0.05 to about 4MPa. Mechanical

equipment may achieve compacting pressures of several thousand MPa [4].

Within the civil engineering industry there are several methods of compaction that are used

in ground stabilisation that use methods of static, vibration and dynamic blows to compact

soil. Block compaction uses similar methods and similar technology only on a smaller scale

and typically compaction takes place in a confined space rather than in unconfined open

areas [15]. Block compaction has predominantly used vibration or slow steady squeezing

(quasi-static) compaction to achieve the desired levels of soil consolidation. Until very

recently the dynamic element used in block manufacture has been limited to the

compression piston coming into contact with the surface of the soil at some speed followed

by static pressure being applied to the material

The following three figures (Fig 3.5, 3.6, 3.7) demonstrate the different types of

compaction, the particle intimacy around the optimum moisture content (O.M.C.), and the

relationship between moisture content and achieved density for different compaction

energies.



Fig.3.5 Unconfined, semi-confined and confined compaction [15].

Fig.3.6 Diagram of particle intimacy around the optimum moisture content [15].



Fig.3.7 Optimum moisture content for soil at different compaction energies [15].

Improved levels of compaction have a significant effect on the compressive strength of the

sample and on the effectiveness of the cement stabiliser added. If a compressed stabilised

soil block could be compacted to a higher density, then for the same ultimate strength the

cement content could be reduced. The trade off is an increased energy cost for a reduction

in chemical additives [15]. Another thing that is apparent is the possible miss match of

moisture contents desired for optimum compaction for a given energy and optimum

moisture content for cement curing.

3.7.2 Cement stabilisation

Cement as a stabilising material is well researched and understood and its properties are

clearly defined. From different types of cement, Portland cement is readily available in most

urban areas, and usually available in semi-urban areas, as it is one of the major components



for any building construction. Earlier studies have shown that cement is a suitable stabiliser

for use with soil in the production of compressed stabilised soil Block.

Cement is mainly composed of Lime (CaO) and Silica (SiO2), which react with each other

and the other components in the mix when water is added. This reaction forms combinations

of Tri-calcium silicate and Di-calcium silicate referred to as C3S and C2S in the cement

literature [20]. The chemical reaction eventually generates a matrix of interlocking crystals

that cover any inert filler (i.e. aggregates) and provide a high compressive strength and

stability.

Fig. 3.8 below attempts to illustrate how these crystals actually give the material strength.

The basic mechanism is friction of point contacts between the particles taking place at a

microscopic level. The duration of time for this reaction to take place is not precisely defined.

There is however the definition of the “critical time” after which further working of the mix

causes breaking of the crystals that have formed but before the total matrix has gained

strength. The flow chart that follows shows the reaction and their effect with respect to time.



Fig.3.8 Crystalline cement growth in sandcrete [21]

Cement is usually mixed with an aggregate to form concrete. The aggregate is usually inert

filler that makes up the bulk of the material, and the cement coats the aggregate in the gaps

[20]. The concrete industry has recognized that the achieved strength of concrete is highly

dependent on the quantity of voids present in the mixture before curing. The presence of 5%

air voids will reduce the strength of a concrete mix by about 30% and even 2% voids can

result in a drop of strength of more than 10% compared to a sample with 0% voids present

[20]. To aid the particle intimacy, different aggregate grades are mixed together giving a

spectrum of particle sizes that reduces the quantity of air voids in the material.

The water used to mix the concrete plays an important role both in placing the material and in

achieving strength. The quantity of water used is typically calculated using an appropriate

water-cement ratio.



Very low water-cement ratios yield a highly unworkable mixture and more water has to be

added to form the mixture into the desired shape. Additional water is called the free-water

content and is calculated from the Slump or Vebe test.

This water does not form part of the chemical reaction and will eventually evaporate from the

concrete leaving voids of air throughout the material [20]. In order to keep the free-water as

low as possible concrete can be compacted or vibrated to aid workability and consolidation.

Portland cement hydrates when water is added; the reaction produces a cementitious gel

that is independent of the soil. This gel is made up of calcium silicate hydrates; calcium

aluminate hydrates and hydrated lime. The first two compounds form the main bulk of the

cementitious gel, whereas the lime is deposited as a separate crystalline solid phase. The

cementation process results in deposition between the soil particles of an insoluble binder

capable of embedding soil particles in a matrix of cementitious gel. Penetration of the gel

throughout the soil hydration process is dependent on time, temperature and cement type.

The lime released during hydration of the cement reacts further with the clay fraction

forming additional cementations bonds. Soil-cement mixes should be compacted

immediately after mixing in order not to break down the newly created gel and therefore

reduce strengthening. The basic function of cementation is to make the soil water-resistant

by reducing swelling and increasing its compressive strength.

With respect to the general processes of cementation, penetration and binding mentioned

above, many factors must be considered. Processes may also vary between different types

of soils. Cement is considered a good stabiliser for granular soils but unsatisfactory for

clays. Generally cement can be used with any soil type, but with clays it is uneconomical

because more cement is required. The range of cement content needed for good

stabilisation is between 3% and 18% by weight according to soil type [4].

Findings have shown that there is a relationship between linear shrinkage and cement

content needed for stabilisations. Table 3.3 below shows that the cement to soil ratio ranges

between 5.56% and 8.33% for measured shrinkage variations of between15mm to 60mm

[4].



Table 3.3 Cement to soil ratio [4].

Measured shrinkage (mm)

Cement to soil ratio

Under 15 1:18 parts (5.56%)

15 – 30 1:16 parts (6.25%)

30 – 45 1:14 parts (7.14%)

45 – 60 1:12 parts (8.33%)

It may be noted that for a given shrinkage the cement to soil ratio is a function of the

compaction effort exerted. For example, a CINVA RAM machine exerts a compaction

pressure of about 2MPa by increasing this pressure to about 10MPa the cement content can

be reduced to between 4% and 6% for soil with shrinkage of up to 25mm. Over this

shrinkage value, 6% - 8% cement would need to be used for effective stabilization

3.7.3 Lime stabilisation

One major alternative binder to cement is lime. By adding lime to the soil for stabilisation,

four basic reactions are believed to occur: Cation exchange, flocculation and

agglomeration, carbonation, and pozzolanic reactions [4].

The pozzolanic reaction is believed to be the most important and it occurs between lime

and certain clay minerals to form a variety of cementitious compounds, which bind the soil

particles together. Lime can also reduce the degree, to which the clay absorbs water, and so

can make the soil less sensitive to changes in moisture content and improve its workability.

Lime is a suitable stabiliser for clay soils. Lime is cheaply available than Portland cement

in Ethiopia and is produced locally in traditional kilns. However, some improvements still

need to be made in its production and processing.

It is estimated that up to 40% of cement used in building construction in masonry mortars

could be saved through the use of lime and other lime associated binders. The advantages

that lime has over Portland cement are that it requires less fuel to manufacture and requires

relatively simple equipment to make. It is therefore more suitable for village scale

production and use [7].



When lime is used as a stabiliser instead of cement, the quantity of stabiliser required has

been increased. However, research at the United Kingdom Building Research

Establishment shows that such increment is not necessary if a sufficiently high compacting

effort is applied on a high clay content soil. The reduction in the volume of air voids brings

the lime and soil particles into closer contact and the stabilising reactions can take place

more easily. Tests show that wet compressive strengths of between 3MPa and 3.5MPa may

be achieved with compacting efforts in the range of 8 - 14MPa [4].

3.7.4 Bitumen stabilisation

There are two ways whereby bitumen can stabilise soil. The first way is a binding process

that increases soil strength particularly in granular soils. Generally, small amounts of

bitumen (2% to 6%) give the soil cohesion. When these percentages are exceeded the

bitumen tends to act as a lubricant separating the particles and thus reducing the strength.

The second way is when the bitumen acts as a water repellent. The two mechanisms usually

occur together in any soil but to different degrees, depending on the type of soil. Soils

suitable for bituminous stabilisation are sandy soils. Clays need large amounts for good

results [4].

The main disadvantages of bituminous materials as stabilisers are:

• They are not a traditional building material in most developing countries,

• Bituminous materials are expensive to import,

• Preparation costs are high (heating, storing and mixing),

• Heat can have an adverse effect on their binding properties, particularly in hot

countries.

3.7.5 Gypsum stabilisation

Gypsum is a traditional material found in many Mediterranean and Middle Eastern

countries. The earliest civilizations used gypsum for building purposes, mainly for plasters

and mortars. The advantage that gypsum has over Portland cement and lime is that it

requires a low calcinations temperature (about 1/7th

of that needed for cement and 1/5th

of

that needed for lime). Besides its agricultural and chemical uses, the main use of gypsum in



Ethiopia is in the production of Portland cement where it retards the setting of the cement.

Gypsum is a good stabiliser for sandy soils.

3.7.6 Pozzolanas stabilisation

Pozzolanas are fine silica and alumina rich materials which when mixed with hydrated lime

produce cementitious materials suitable for stabilisation and construction needs. Pozzolanas

are found in their natural state as volcanic ash or pumice or it can be man made [20].

3.7.7 Other stabilisers

Traditionally, many stabilisers such as animal dung, ant hill materials, bird droppings, plant

extracts and animal blood, have been used for the manufacture of compressed stablised

earth building blocks. These waste materials generally consist of nitrogenous organic

compounds, which help bind together soil grains. Chopped straw, grasses and natural

organic fibers, although not active stabilisers, they are used as reinforcement materials to

reduce linear shrinkage problems, which occur with soil that has high clay content.

3.8 Rationale of soil cement

Soil on its own can be used for construction, but unless it is protected from water the

resulting building will not be very durable in any but the driest climates, as has been

described above. Cementitious stabilisation in combination with densification gives soil

both wet strength and erosion resistance. Densification or compaction reduces the soils

permeability and enhances the secondary cementitious bonding mechanism. Portland

cement is the most commonly used stabiliser and at present usually the cheapest. Lime and

lime pozzolan stabilisation are growing in popularity because, unlike cement, lime may be

produced economically by small scale batching kilns. How ever at present the quality of

lime produced by such small-scale kilns is highly variable and liable to change from one

batch to another.

Soil cement is produced by dry mixing a suitable soil with a small quantity of cement and

remixing the product with a specific quantity of water [the criteria for suitable soil is



discussed above but it should be noted that two or more unsuitable soils may be combined

by simple mixing to produce one more successful soil]. The resulting damp soil is normally

compressed in a mould, ejected and subsequently wet cured for 3-4 days then damp cured

for twenty-eight days before incorporation in a building. In many ways soil- cement may be

seen as a simpler version of sand-cement, not requiring the sand to be first separated from

other soil constituents. Sand-cement is widely used, though variable in quality as a result of

poor curing [17].

Soil cement blocks produced with compression are in general denser and hence less porous

than sand cement. The resultant reduction of moisture loss during curing leads to a greater

consistency in quality for soil cement.

The minimum amount of cement required to stabilise a block depends on the type of soil,

the degree of compression and the final application for the blocks. Generally the interest is

to minimize the cement content to below 10%. Given suitable conditions, blocks cement

contents as low as 3% are possible.

The exact mechanism by which a small content of cement may stabilise a large mass of soil

is not fully understood. A typical Portland cement is made up of 54.1% tricalcium silicate

(C3S). This is in keeping with most of the published concrete literature and is acceptable,

allowing these simple equations to be given as illustrations instead of the more complicated

fully balanced chemical equations] and 16.6 % dicalcium silicate (C2S) [20].

In the presence of damp soil these components hydrate to form mono and dicalcium silicate

hydrate gels (CSH and C2SH, see equation below). These gels then slowly crystallise in to

an insoluble interlocking matrix throughout the soil voids binding the soil particles

together. As the matrix is insoluble it gives a strength mechanism that works to restrain the

softening and swelling of the unaffected soil, thereby dramatically reducing the weakening

effect of water. The interlocking calcium silicate fibers may be seen when a cured soil

cement sample is examined under an electron microscope [17].



Making the approximate assumption that C3S2H3 (Calcium silicate hydrate) binding gel, is

the final product of the hydration of both C3S and C2S, the reactions of hydration can be

written (as a guide, although not as exact stoichiometeric equation) [20] and results in the

release of free lime (CH) according to the reaction:

2C3S+6H=C3S2H3+3Ca (OH) 2---------------------------------- [3.1]

2C2S+4H=C3S2H3+Ca (OH) 2---------------------------------- [3.2]

The free lime then reacts further with the clay fraction (pozzolanic reaction) by the removal

of silica from the clay minerals and subsequently forms more calcium silicate gel that also

gradually crystallizes.

In summary, soil cement is a building material which has superior strength and erosion

resistance compared to unstabilised soil, with out incurring the cost of the large quantities

of cement found in concrete.

4. Properties of Materials,

Mix Proportions and Tests


CHAPTER FOUR

PROPERTIES OF MATERIALS, MIX PROPORTIONS AND

TESTS

4.1 Introduction

In this chapter the materials used in the investigation are described with respect to their

sources, and their physical and chemical properties. All laboratory investigations on

materials are carried out in the A.A.U, Faculty of Technology construction materials and

soil mechanics laboratory, Selam Technical and Vocational center and Geological Survey

of Ethiopia Geochemical laboratory.

4.2 Soil

The soil used in this investigation was brought from Kara area, which is about 20km East

of Addis Ababa. It was found out with different sizes and deleterious substances. It was

then pulverized, and sieved to the appropriate size. The physical properties and chemical

compositions of the soil are given in Table 4.1 and Table 4.2 below respectively.

Table 4.1 Physical properties of the soil

NO Physical Properties Values

1 Specific gravity 2.61

2 Natural moisture content 14.87%

3 Optimum moisture content 19%

4 Maximum dry density 1610kg/m

3

5 Silt content 16.25

6 Clay content 13.75

7 Sand content 70%

8 Linear shrinkage 7.14%

9 Liquid limit 31.91%

10 Plastic limit 25.75%

11 Plasticity index 6.16%

Table 4.2 Chemical composition of the soil Chemical oxides of the soil and their chemical Composition

SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O MnO H2O LOI TiO2 P2O5 SO3 Cl- pH

65.32 15.27 7.68 <0.01 0.18 1.59 4.08 0.17 0.19 4.06 0.4 <0.01 0.07 <0.01 6.75




4.3 Cements

In this research work five mixes are prepared using Mugher Portland pozzolana cement and

9 mixes are prepared using Messobo Portland cement. Portland pozzolana cements were

produced by Mugher and Messobo cement factory and comply with the requirements of

Ethiopian standards. The chemical composition of the cements is shown in Table

4.3.below.

Table 4.3 Composition and properties of cements produced in Ethiopia [22].

Mean Chemical Oxides of Clinker (%) Cement

Source CaO SIO2 Al2 O3 Fe2O3 MgO SO3

Mugher 65.61 21.26 5.76 3.79 0.95 1.08

Messobo 66.36 21.50 5.21 4.03 1.26 0.68

Dire Dawa 65.81 22.31 4.95 4.03 1.84 0.70

Mean Chemical Compounds of Clinker (%) Cement

Source C3S C2S C3A C4AF Total %of

Silicates

Mugher 58.3 17.0 8.9 11.5 95.7 75.3

Messobo 64.0 13.3 7.0 12.3 96.6 77.4

Dire Dawa 57.4 20.7 6.3 12.3 96.6 78.1

Mean Chemical Oxides of OPC (%) Cement

Source CaO SIO2 Al2O3 Fe2O3 MgO SO3

Mugher 63.38 21.36 4.89 3.92 1.27 2.54

Messobo 63.94 20.50 4.75 3.70 1.31 2.41

Mean Chemical Compounds of OPC (%) Cement

Source C3S C2S C3A C4AF Total %of

Silicates

Mugher 50.04 23.48 6.32 11.91 91.76 73.52

Messobo 60.41 13.19 6.32 11.27 91.20 73.61

Mean Chemical Oxides of Pozzolana (%) Cement

Source SIO2 Al 2 O3 Fe2 O3 CaO MgO SO3

Mugher 64.58 2.27 0.97 4.04 15.17 0.00

Messobo 54.80 8.83 10.55 8.14 6.22 0.03

Dire Dawa 68.10 11.32 4.82 1.50 0.63 0.00

Cement

Source

Pozzolana

included in

PPC (%)

Gypsum Content

in cement (%)

Pozzolana

Type

Cement Type

Produced

Specific

Gravity

OPC 3.15 Mugher 28.3 4-5 Pumice

PPC N/a

OPC 3.15 Messobo 25.0 5 Volcanic

Basalt PPC 2.75

Dire Dawa 25.0 5 Pumice PPC N/a




4.4 Water

Throughout the investigation tap water, which is supplied by the Addis Ababa water supply

system of the city, is used.

4.5 Mix proportion

Providing detailed technical and economic information on the production of compressed

stabilised earth blocks by assessing the potential of local materials i.e. types of cement and

soil is the purpose of this investigation. Thus two types of cement from manufacturers, and

a soil sample from Kara area of Addis Ababa are selected and prepared. To this effect the

following test programs, are followed. The mix proportions are made based on literature

recommendations.

1. The first series of mixes (5 in number) are conducted to compare the difference in

compressive strength values with age, rate of strength development of the block

produced using Mugher Portland pozzolona cement. They are made with 24% of water

and cement content of 4%, 6%, 8%, 10% and 12% by weight of soil. The Mix

proportions are given in Table 4.4 below.

Table 4.4 Mix proportions for the 1st series

Mix code Cement

(Kg)

Water

(%)

Soil

(kg)

MG4 4 24 100.45

MG6 6 24 100.45

MG8 8 24 100.45

MG10 10 24 100.45

MG12 12 24 100.45

2. The second series of mixes (5 in number) are conducted to compare the difference in

compressive strength values with age, rate of strength development of the block

produced using Messobo Portland pozzolona cement. They are made with 24% water

and cement content of 4%, 6%, 8%, and 10%&12% by weight of soil. The Mix

proportions are given in Table 4.5 below.




Table 4.5 Mix proportions for the 2nd series

Mix code Cement

(Kg)

Water

(%)

Soil

(Kg)

MO4 4 24 100.45

MO6 6 24 100.45

MO8 8 24 100.45

MO10 10 24 100.45

MO12 12 24 100.45

3. The third series of mixes (4 in number) are conducted to compare the effects of mould

pressure on the compressive strength of the sample and on the effectiveness of the

cement stabiliser. They are made with 4MPa, 6MPa, 8MPa and 10MPa pressure mould

and cement contents of 6%, 8%, 10% and12% by weight of soil. The mix proportions

are given in Table 4.6 below.

Table 4.6 Mix proportions for the third series

Mix code Cement

(Kg)

Mould pressure

(MPa)

C6P4 6 4

C6P6 6 6

C6P8 6 8

C6P10 6 10

C8P4 8 4

C8P6 8 6

C8P8 8 8

C8P10 8 10

C10P4 10 4

C10P6 10 6

C10P8 10 8

C10P10 10 10

C12P4 12 4

C12P6 12 6

C12P8 12 8

C12P10 12 10




4.6 Specimen preparation Since the preparation of specimens was considered to be one of the most important stages

in the execution of the experiments, extra care had been taken with the soil, cement mix,

moisture content, compression, curing, and sizing of the samples.

The high levels of accuracy, reliability and consistency demanded by the experiments be

maintained throughout the testing regimes, and for all the different types of tests conducted.

Specimen preparation describes the raw materials used, the mix proportions, addition of

moisture, the compression method used, the curing regime, and the dimensions of the

samples.

Literature indicates that an ideal soil would have an optimum raw materials composition of:

sand 75%, fines (silt and clay) 25% of the fines, at least not less than 10% has to be clay

[10]. The actual mix then used consisted of: Sand 70%, Silt 16.25% and Clay 13.75%.

A shrinkage test and a simplified sedimentation test were used to confirm the limits for the

different constituents [10]. Proportioning the mix of the soil raw material with the cement

stabiliser was done in varying quantities, by percent weight of cement from 4% by weight

in 2% increments up to 12% by weight of the soil as follows: 4%, 6%, 8%, 10% and 12%.

A total of two hundred four blocks of average dimension 220*220*115 mm were

subsequently made in this manner for three series of tests.

The constituent parts of the mixed soil preparations were separately weighed using an

accurate and sensitive electronic weighing machine accurate to ±0.05g. To improve on the

degree of mix, a mechanical mixer had to be used.

To produce the blocks, a pre-installed M7 E380 machine designed on the quasi-static

compression principal was used for the entire samples see (Fig 4.1). Before filling the

mould for each compression, the mould lining was lightly oiled with used engine oil.

The soil was carefully poured into the mould, all pre-weighed, packed and sealed in light

transparent plastic bags. After each pouring, the soil was leveled in the mould. The use of

the M7 E380 machine was based on the operational manual of the machine.




The blocks were compressed by the pumping action of the side pump up to 10 MPa. The

hydraulic pressure was released using the flow valve screw causing the hand pump to

become slack. The mould cover (Top ram) was then moved upwards to expose the green

block, which was, then demoulded. The green blocks were then carefully removed and put

over base plates, and immediately placed in plastic bags and left to cure in the shade. The

dimensions and the weights of the green blocks were recorded.

Fig.4.1 M7 E380 machine [23].

Curing of the blocks consisted of two distinct phases described herein as primary and

secondary phases. The curing time, temperature, duration, and moisture conditions were of

particular interest to the experiment. Primary curing, whose purpose is to ensure that

moisture is retained in the block, and not lost rapidly, was done for a period of five days.

Laboratory dry conditions were used with curing temperatures of 22-24 °C. After five days,

the blocks were noticeably lighter in color than when demoulded. Each of the blocks were

marked using permanent ink markers in each case to clearly show the percentage cement

content, moulding pressure, date and time of production, and an identification number. This

decision to mark individual blocks was to be found very useful later on. In order to enable

the blocks to further achieve strength, secondary curing was allowed to continue for a

further fifty-one days. The clearly marked blocks were placed side by side and covered




with a large polythene sheet. This was done to slow down evaporation and to protect the

blocks from external interference. The blocks were then left to dry in this manner under

laboratory air conditions.

4.7 Tests on blocks

Different separate tests and experiments, all of which have direct bearing with the

investigation of the effects of stabilisation and moulding pressure on the strength and

performance of blocks, were selected and conducted. The tests include the wet and dry

compressive strength tests and the water absorption test. Although the wet and dry

compressive strength tests and the water absorption tests are both now standard

performance tests widely described and used for stabilised soils, they were originally

developed for concrete blocks and fired bricks.

4.7.1 Compressive strength test

The compressive strength of the blocks is perhaps their most important property. The

compressive strength values give an overall picture of the quality of the block and are an

indication of the hardness of the hydrated cement paste that binds the various particles

together. The main aim of the compressive strength tests was to determine the wet

compressive strength values of the blocks. It is the wet compressive strength value, which

is normally lower than the dry compressive strength, which is used in the structural design

of buildings. The compressive strength test done is a standard test based on ASTM

standards, Volume 04.08, Soil and Rock, 1996.

After the 7, 14, 28 and 56 days curing period, the blocks of average dimension

22×22×11.5cm is measured and weighed. The main compression equipment used was the

Concrete Testing Machine with a maximum load of 100KN. The machine is certified and

calibrated for the test duration by Hydraform Company South Africa. Figure 4.2 shows a

photographic record of the compressive strength test taken during the experiment.

Three blocks in each category of varying cement content from 4% in increments of 2% up

to12% were tested for wet compressive strength. Each block sample of dimension

22×22×11cm was soaked for 24 hours or overnight in ordinary tap water. They were then




removed and kept aside for 30 minutes to let the extra surface water to drip off. The

samples were then carefully placed within the set marking pins of the compression-testing

machine.

Fig. 4.2 Compressive strength testing

The crushing load was then continuously applied without shock to the sample at a rate of

3.5 MPa per minute till failure [24], and in this way the maximum crushing load was

obtained for each sample. The wet compressive strength was then calculated in each case

from the ratio of the maximum load and the cross sectional area of the block in N/mm2.

4.7.2 Water absorption test

The aim of the water absorption test was to determine the percentage moisture absorption

capacity of the block samples. Block samples were weighed in the laboratory dry condition

(Wd) and, immersed in water for 24 hours, removed and weighed again (WW). An accurate

electronic weighing machine was used in case, to an accuracy of 0.05g. The percentage

moisture absorption by weight was calculated from the formula:




Mc = Ww – Wd x 100 (%)………………………………………… [4.1]

Wd

Where:

Mc = percentage moisture absorption (%)

Ww= mass of wetted sample (g)

Wd = mass of dry sample (g)

Through the water absorption test, it should be possible to determine the ability and extent

to which blocks can absorb moisture. Knowledge of the water absorption levels of blocks

could serve as useful criteria for setting limits and for investigating possible ways of

reducing the same in order to improve on the durability of blocks.

The apparatus consisted of an accurate weighing balance, a stop watch and a water trough

with a capacity to hold up to 2 fully immersed blocks. The entire test took two days to

complete mainly due to the overnight soaking of the block samples in water. This test helps

to investigate the effect of water absorption of stabilised soil blocks during the rainy

season. The recommended maximum water absorption value of blocks is from 15% to the

maximum value of 20% [10].

65

CHAPTER FIVE

TEST RESULTS AND DISCUSSIONS ON THE SUITABILITY OF

SOIL SAMPLE FOR THE PRODUCTION OF COMPRESSED

STABILISED SOIL BLOCK

5.1 Introduction

The use of a suitable soil is fundamental to successful production of compressed cement

stabilised soil block. Since soil from the Kara area of Addis Ababa is used to compressed

stabilised earth block production, this area was the prime target for investigation and

testing. The following report examined the process of soil selection for the purpose of soil

cement block production. Soil suitable for soil cement block production is then considered

from a particle grading and plasticity viewpoint, with due consideration to the underlying

mechanisms responsible for strength and durability.

In general the literature concerned with soil testing provides a number of suitable tests but

does not provide a logical testing plan for their implementation. The following section

discusses and analyzes soil laboratory test results for soil suitability. From this discussion it

is hoped that the reader may be able to appreciate the need for different scales of soil

testing. A full laboratory analysis includes soil grading, plasticity, and chemical

composition. In this case a soil sample from the Kara area of Addis Ababa considered

suitable by the field test selection process is taken to the Addis Ababa University, Faculty

of Technology, Civil Engineering Department and Geological Survey of Ethiopia

Geochemical laboratories and relevant soil tests are conducted.

Based on the results of soil testing, trial blocks by using different content and type of

cement is produced and the block is tested for 7th

day, 14th

day, 28th

day and 56th

day

compressive strength and water absorption capacity.

5. Test Results and Discussions on the

Suitability of Soil Sample for the

Production of Compressed Stabilised Soil Block


5.2 Laboratory tests and results on soil sample

Laboratory tests conducted provide more precise detailed information on the soil gradation

and plasticity. This information helps to check the suitability of the soil based on the

selection criteria given in Section 3.3 and 3.4.

With so many different characteristics that one could discover about a sample of soil, it

would be unwise to try and discover them all in every situation that soil is to be used for

making compressed stabilisied soil block. In this research work only a small number of

characteristics that are of real relevance to the production of compressed cement stabilised

soil block is considered. The physical properties are of greater interest for making

compressed stabilised soil block as these will help to determine its ease of mixing, forming,

de-moulding, porosity, permeability, shrinkage, dry strength and apparent bulk density.

The soil sample is generally characterized in two ways, by a particle size distribution

analysis and by plasticity index. The particle size analysis gives information on the soil

ability to pack in to a dense structure and the quantity of fines present (combined silt and

clay fraction), while the plasticity index gives an idea of the cohesion of the fines.

5.2.1 General classification

The laboratory tests conducted helps to establish numerical values for the soil sample

parameters, primarily the percentage distribution of the different sizes of the soil particles

present and the plasticity limits. These values are subsequently used to determine the

suitability of the soil sample for block production.

A) Particle size distribution

The combined sieving and hydrometer tests separated the different size fractions of the soil

sample into discrete parts thereby indicating the soil's particle grading. The results of these

tests are plotted in Figure 5.1 below. Detail raw data's and test results are given in

(Appendix A1.5, A1.6 &A1.7).





GRAIN SIZE ANALYSIS OF SOIL

0

10

20

30

40

50

60

70

80

90

100

0.001 0.01 0.1 1 10 100

GRAIN DIAMETER

PE

RC

EN

T P

AS

SIN

G

2

1.18

0.6

0.3

0.15

0.075

0.0328

0.0209

0.0123

0.0087

0.0062

0.0044

0.0031

0.0023

0.0019

0.0013

Fig. 5.1 Particle size distribution of soil from Kara area

From the above curve, actual composition of the soil from the Kara area of Addis Ababa is

grouped as follows: Sand -70%, Silt -16.25% and Clay -13.75%.

Based on this result, now it is possible to check the suitability of the soil by using different

techniques as per the literature.

A.1 Based on African Regional Standard (ARS)

As per ARS 680:1996 Code of practice for the production of compressed earth blocks

recommendations, if the granular composition of the soil fall with in the shaded area on the

diagram of texture as shown in Fig. 3.1, it gives satisfactory result.

The gradation curve of the soil sample from the Kara area shown in Fig. 5.1 above falls

completely with in the shaded area of the diagram of texture as shown in Figure 5.2 below.

This implies that the sample soil chosen fulfills this requirement.





Fig 5.2 Particle size distribution of the sample soil on the diagram of Texture

A.2 Based on Space and Cook modifications on a triangular U.S Bureau of public

roads particles size graph

The shaded area in Fig 3.3 indicates soils most suitable for stabilisation. Soil sample from

Kara area which has a composition of (70% sand, 16.25%silt and 13.75% clay) as plotted

“1” in Fig 5.3 below falls with in the shaded area is an indicator for the soil’s suitability for

soil cement block production.

2

3

1 Upper bound Curve

Lower bound curve

Gradation curve





Fig 5.3 Triangular chart for particle size classification of soil sample from Kara area

Both ARS and Space and Cook modifications on a triangular U.S Bureau of public roads

particles size graph indicated the suitability of the soil from the Kara area of Addis Ababa

for compressed stabilised soil block production.

The suitability criteria of soil for soil cement block production have variations between

different authors. It is better to take such criteria as a guide in initial soil selection rather

than as a rigid set of rules. Some authors recommend in the criteria based on solely on

atterburg limits. As per the recommendation of the literature survey the researcher checked

the suitability by using both criteria. The following section discusses on the criteria based

on the atterburg limits of the soil sample.

B) Atterburg limit criteria (Plasticity)

The Atterburg or plasticity tests define the moisture content at which the soil passes from a

liquid state to plastic state and from plastic state to a solid state; these boundary points are

the liquid and plastic limits respectively. The atterburg limits allow the soil plasticity

characteristics to be related to the suitable soil selection criteria given above in section 3.4.

1 = Sand- 70%

Silt -16.25%

Clay-13.75%

1





The plastic limit and liquid limit tests described in the appendix A1.3 and A1.4 are

prepared by using method of ASTM D 2216-92. The linear shrinkage test which is a test of

the soil’s contraction on drying and believed to give a combined measure of the soils’

particle grading, plasticity and clay type is conducted based on BS 1377-2:1990. It gives an

overall idea of the soils behavior and suitability for stabilisation. Atterburg limit test results

of the soil sample are given in Table 5.1 below but full test measurements and data records

are described in appendix A1.3 and A1.4.

Table 5.1 Atterburg limit test results of soil sample from Kara Area

Atterburg limits Value

Plastic limit 25.78

Liquid limit 32.4

Plasticity index 6.62

Shrinkage limit 7.15

Based on these results we can check the suitability of the sample soil for soil cement block

production. The following two sections area the criterias based on the atterburg limits of

the soil sample.

B.1 Based on African Regional Standard (ARS)

The soil sample is checked for suitability in the plasticity chart as shown below by using

the atterburg limit values from Table 5.1 above. The plasticity index of 6.62 and liquid

limit of 32.4 falls at point “1” in the plasticity chart of Fig 5.4 below. Point “1” is located in

the shaded area, which indicates the suitability of the Kara area soil for soil cement

production.





Fig 5.4 Diagram of Plasticity

B.2 Spence, R.J.S & Cook, D.J.1983 Building Materials in Developing

Countries

The soil sample is checked for suitability in the plasticity chart below by using the

atterburg limit values from Table 5.1 above. The plasticity index of 6.62 and liquid limit of

32.4 falls at point 1 in the plasticity chart as shown in fig 5.5 below. Point 1 is located in

the shaded area, which indicates the suitability of the soil for soil cement production.

1111 Point 1

Plasticity index=6.62

Liquid limit = 32.4





Fig 5.5 Plasticity chart

5.2.2 Soil compaction test

After the above index properties of the soil sample are quantified, the soil is considered as

suitable for further testing. The first test to be performed by the researcher was the

compaction test. The general meaning of soil compaction in soil mechanics is to press soil

particles tightly together by expelling the air from void spaces between the particles. It is

also cheap and effective way to improve the properties of a soil sample. The amount of

compaction is quantified in terms of dry density (dry unit weight) of the soil.

The usual practice in a construction project to determine the optimum moisture content and

maximum dry density is to perform laboratory compaction tests. A common compaction

test in the laboratory is known as Standard Proctor test. The Standard Proctor Compaction

was carried out on the soil sample from the Kara area using ASTM D 698 Method A and

the result is plotted in Fig 5.6 and detail measurements and raw data’s are given in

Appendix A1.8.

1

Point 1

Plasticity index=6.62

Liquid limit = 32.4





Fig 5.6 Proctor compaction curve

Point “A” in the above curve shows the maximum dry density (MDD) and optimum

moisture content (OMC) of the soil. MDD and OMC are 1610kg/m3 and 19% respectively.

The compaction effort is the primary factor affecting maximum dry density and optimum

moisture content for a given soil type. In this particular case compaction of the soil sample

was conducted by using M7 E380 Hydra form machine using 10MPa system pressure. The

optimum moisture content was determined by using the ideal block length for a given soil

type. The amount of moisture content used to produce this ideal block length is taken as

optimum moisture content. The ideal block length was 22cm and the amount of water

required to get this length was 24%.

5.3 Chemical analysis

From the literature chemical properties of the soil (the composition, mineral content,

metallic oxides, pH levels and sulphates) are of interest particularly when a chemical

additive is used. Since cement is to be used as a stabiliser the chemical analysis of Soil

from Kara area was conducted at Geological survey of Ethiopia, Geochemical laboratory.

The ultimate goal was to get the chemical components of the soil and to gain insight into

COMPACTION CURVE

1420

1440

1460

1480

1500

1520

1540

1560

1580

1600

1620

10 12 14 16 18 20 22 24 26 28 30

MOISTURE CONTENT

DR

Y D

EN

SIT

Y

Series1

A





the reactions occurring in Portland cement soil mixtures. Soil of Kara area found (20km)

east of Addis Ababa was investigated and the results are expressed in Table 4.2 above and

Appendix 2. From the chemical components we can see that the amount of SiO2 (65%) is

an indication of the composition of sand in the soil. Soil silica and alumina react with

cement to form a cementing agent. SiO2 and Al2O3 from soil react with CaO from cement

and water. This implies that given sufficient cement, soil properties control results. The

higher the silica contents in the soil the more active the soil and better reactive. Chemical

and organic contents of the soil hinder hydration reaction. Even though organic content and

low pH of the soil do not in them selves constitute a definite indication of poorly reacting

soil, 6.75 pH level and low organic content (2.03%) of the Kara area soil helps to consider

the soil as good reacting soil because sandy soil with the organic content greater than 2% or

having a pH lower than 5.3 will generally not react normally with cement. Other important

property of Kara area soil is its small percentage of SO3 (0.07%), which is important to

reduce the amount of sulphates to be produced.

5.4 Summary

The report examined the process of soil selection for the purpose of soil cement block

production. Soil suitable for soil cement block production is considered from a particle

grading and plasticity viewpoint and its chemical composition, with due consideration to

the underlying mechanisms responsible for strength and durability. To this effect soil in the

Kara area of Addis Ababa is examined and numerical values of basic physical property

parameters are determined in Addis Ababa University Civil Engineering Department

laboratories and the chemical compositions of the soil are determined in Geological Survey

of Ethiopia Geochemical laboratories. Based on these laboratories results, the suitability of

this soil for soil cement block production is evaluated. The suitability criteria of soil for soil

cement block production have variations between different authors but in this research

work the suitability of soil is tested by using African Regional standards and Space and

Cook criteria. The particle grading and plasticity results of the soil in question fall with in

the acceptable rages on both criteria and then the soil is accepted and passed for further

investigation.

75

CHAPTER SIX

TEST RESULTS AND DISCUSSIONS ON THE PRODUCED

COMPRESSED CEMENT STABILISED SOIL BLOCK

6.1 Introduction

Tests and experiments on blocks are necessary to measure the block properties upon which

durability is dependent like strength, water absorption and to monitor the blocks

performance in conditions, which simulate the cause of the deterioration. The tests will

provide experimental results and data from which general and localized trends could be

identified, and from which comparisons can be made with theoretical predictions or other

available data. The tests also would provide an opportunity with which the validity of

currently held beliefs could be tested, and any agreements or departures from the norm

spotted. It is expressed early that translating the experimental data into information to

facilitate the potential improvement of production and the performance of blocks would be

the broad objective of this thesis.

6.2 Compressive strength

There are several manufacturing variables that could affect the performance of blocks.

These include soil type, cement content, compaction pressure, moisture content, and curing

method. In the experiments conducted it was decided that of these several variables, only

the cement content be varied while all the other parameters would remain fixed. The reason

for this decision and approach was based on the fact that it was the stabiliser content,

which, according to the literature on stabilised soils, was significantly responsible for the

improvement in strength, dimensional stability and durability of blocks.


Produced Compressed Stabilised Soil Block


6.2.1 Effects of cement and cement content on the compressive

strength of soil blocks

The 7th

, 14th

, 28th

and 56th

days mean compressive strength values of compressed soil

blocks stabilised with Messobo and Mugher pozzolana cement contents of 4%, 6%, 8%,

10% and 12% are shown in Table 6.1 and Table 6.2 below and all the raw data’s of cube

compressive strength test results are presented in a tabulated form in Appendix 3 and in a

graphical form in Fig 6.1 and Fig 6.2 below.

Table 6.1 Mean compressive strength of soil cement blocks using Mugher PPC

Mean compressive strength [MPa] Mix code

7 days 14 days 28 days 56 days

MG4 0.3 0.6 1 1.25

MG6 0.6 1.3 1.5 2.23

MG8 1.1 1.8 2.1 3.2

MG10 1.4 2.1 2.6 4.03

MG12 1.5 2.5 3.5 5.03

Effects of cement content on the compressive

strength of CSEB

00.5

11.5

22.5

33.5

44.5

55.5

0 2 4 6 8 10 12 14

Cement content (%)

Co

mp

ress

ive

Str

en

gth

(Mp

a)

7th day

14th day

28th day

56th day

Fig 6.1 Effects of cement content on the compressive strength of soil block using

Mugher PPC




Table 6.2 Mean compressive strength of soil cement blocks using Messobo PPC

Mean compressive strength [MPa] Mix code

7 days 14 days 28 days 56 days

MO4 0.15 0.7 0.8 1.0

MO6 0.4 1.0 1.6 1.85

MO8 1.0 1.3 2.3 2.9

MO10 1.3 1.7 3 3.2

MO12 1.7 1.8 3.4 4

Fig 6.2 Effects of cement content on the compressive strength of Soil

Block using Messobo PPC

From these results general and localized trends can be recognized. According to the

tabulated results in Appendix 3 and 4, it would be reasonable to conclude that for a given

constant compaction pressure, an increase in absolute compressive strength can be achieved

by increasing the cement content. This increment in cement content results in deposition of

cement gel between soil particles. The interlocking cement gel between the soil particles

binds the soil particles together and creates high strength. The results also show that from

the blocks produced at the varying cement contents from 4% in increments of 2% up to

12% at constant compressive pressure of 10MPa, all the blocks except blocks produced by

4% cement have 28 day wet compressive strength values well above most of the

Effects of cement content on compressive

Strength of CSSB

0 0.5

1 1.5

2 2.5

3 3.5

4 4.5

0 2 4 6 8 10 12 14

Cement content (%)

Co

mp

res

siv

e

S

tren

gth

(M

Pa)

7th Day

14th Day

28 th Day

56th Day




recommended minimum values for use in structural work as per the literature. According to

the literature, several different minimum values of 28-day wet compressive strength, all

above 1.0 MPa are proposed; but the 56 day wet compressive strength of all the blocks

produced in this research are well above the minimum recommended values.

From the graphical presentation of the results shown above in Fig 6.1 and 6.2, the rate of

increase in strength can be approximated. The graph reveals that the absolute increase in

compressive strength appears to remain constant but then increases less at the lower cement

contents but more at the higher cement contents. For instance, when the Mugher cement

content is doubled from 4% to 8% at constant compaction pressure, a compressive strength

increase of 110% is achieved; further doubling of the cement content from 6% to 12%

would produce a projected increase in wet compressive strength of up to 135%.

Table 6.3 Rate of increase in compressive strength for Mugher cement content increment

Mix

code

Cement content

(%)

28th day

compressive

Strength(MPa)

Compressive

strength

% Increase

MG4 4 1 -

MG6 6 1.5 50

MG8 8 2.1 40

MG10 10 2.6 24

MG12 12 3.5 35

Table 6.4 Rate of increase in compressive strength for Messobo cement content increment

Mix

code

Cement content

(%)

28th day

compressive

Strength(MPa)

Compressive

strength

% Increase

MO4 4 0.8 -

MO6 6 1.6 100

MO8 8 2.3 44

MO10 10 3 30

MO12 12 3.4 14




6.2.2 Comparison of compressive strength of soil cement block made

using Mugher and Messobo Portland pozzolana cements

There are only three operating cement factories in Ethiopia. Mugher and Messobo Cement

factories produce both ordinary Portland and Portland pozzolana cements (OPC and PPC)

while the Dire Dawa cement factory produces only PPC. Mugher and Messobo cements are

distributed through out the country markets and Dire Dawa PPC is distributed around Dire

Dawa area.

The annual production capacity of these three cement factories is about 1.6 Million Tons

and of which 15% is OPC and the rest is PPC. The physical and chemical compositions of

cements produced from these three factories are summarized in Table 4.2.

Due to availability and cost in the market, the researcher used only Mugher and Messobo

Portland pozzolana cements as a stabiliser in this research work. For the production of

Mugher and Messobo Portland pozzolana cements, the factories used different type and

amount of pozzolanic materials as shown in Table 4.2, which in turn has an effect on the

physical and chemical properties of the cement produced. These differences in the physical

and chemical properties of Mugher and Messobo Portland pozzolana cements is thought to

have a different stabilisation effect on compressed earth block. In this section detailed

analysis of the test results is undertaken from the point of view of determining the

comparative effect of each cement type on the variable under investigation. To check these

effects different trial mixes are prepared as shown in Table 4.4 and 4.5.The results of tests

are shown in appendixes and the 56 day compressive strength comparison curves are

shown in Fig 6.3 below.

From Fig 6.3 it is observed that the 56th

day compressive strength of the compressed

stabilised soil blocks by using these two cements revealed that stabilising by using Mugher

Portland pozzolana cement has better compressive strength than using Messobo Portland

pozzolana cement and the percentage differences are given in Table 6.5 below.




Fig 6.3 Comparison of the 56th

day compressive strength of CSEB using Messobo and

Mugher cement

Table 6.5 Comparison of the 56th

day compressive strength of CSEB by using Mugher

and Messobo PPC as stabilisers.

Cement content by weight of soil and compressive strength of

CSSB in MPa

Cement type

4% 6% 8% 10% 12%

Mugher 1.25 2.23 3.2 4.03 5.03

Messobo 1 1.85 2.7 3.2 4

difference 20 17 16 20 20 %٭

Taking Mugher as reference٭

6.3 Effects of compaction pressure on compressive strength of

soil block

Although the stabiliser content could be responsible for binding, sealing, reinforcing and

imparting flexibility to the block, compaction pressure could contribute towards increasing

the densification and thereby reducing voids. The stabiliser increases the compressive

strength and impact resistance of the block, as well as reducing its tendency to swell and

shrink; by sealing all voids and pores and providing a waterproofing film. The stabiliser

Compressive Strength of CSEB using Mugher

and Messobo PPC

0 1 2 3 4 5 6

0 5 10 15

Cement Content (%)

56

th d

ay

Co

mp

res

siv

e

Str

en

gth

(M

Pa

)

Mugher PPC

Messobo PPC




may help to reduce cracking; conversely, by reinforcing the soil, the stabiliser may reduce

excessive expansion and contracting. The effect of stabilisation is greatly increased when

the soil is compacted. In the previously conducted experiments, all blocks were compacted

prior to curing to a compaction pressure 10 MPa, a value considered to be high enough to

produce the best possible quality blocks. In practice however, Most CSEB producers

including Selam Technical and vocational center used to compaction pressure values much

less than 10 MPa. In subsequent experiments to follow, both the compaction energy and the

cement content will be varied. The stabiliser used in this experiment was Messobo Portland

pozzolana cement. This is because of availability and cost currently on the market; it is

only Portland pozzolana cement, which is widely available and used in most parts of the

Ethiopia. It is likely to remain the stabiliser of choice due to its well-established reliability,

availability and quality record.

From the literature, improved levels of compaction have a significant effect on the

compressive strength of the sample and on the effectiveness of the cement stabiliser added.

The researcher proved this fact in the laboratory by using different compaction pressure

and cement content according to the mix proportion and design given in section 4.5. Fig 6.4

and Table 6.6 below indicate test results of the relationship between cement content,

compaction pressures and 28-day compressive strength of the soil cement block. The full

laboratory test result of this test is given in Appendix 5, 6, 7 and 8.

Fig 6.4 Effects of compaction pressure on compressive strength of CSSB

EFFECTS OF COMPACTION PRESSURE ON

COMPRESSIVE STRENGTH OF CSEB

0

1

2

3

4

0 2 4 6 8 10 12 14

CEMENT CONTENT (%)

28

TH

DA

Y

CO

MP

RE

SS

IVE

ST

RE

NG

TH

(M

Pa

)

4Mpa

6Mpa

8Mpa

10Mpa




Table 6.6 Effects of compaction pressure on the 28th

day compressive strength of CSEB

COMPACTION PRESSURE AND

COMPRESSIVE STRENGTH OF

CSEB (MPa)

CEMENT

CONTENT

(%) 4 6 8 10

6 0.1 0.9 1.2 1.7

8 1.3 1.65 2.1 2.6

10 1.4 2.2 2.6 2.75

12 1.8 2.4 2.95 3.4

According to the tabulated results in Table 6.6 above the compressive strength of CSEB is

tested for various cement content samples ranging from 4% to 12% by differing the

confining pressure from 4% to 10% with an interval of 2Mpa for all cement content of

samples. The results of this test proved that compaction pressure have an effect on the

compressive strength of soil cement block. The higher the compaction pressure the higher

the compressive strength. When the compaction pressure is doubled from 4MPa to 8MPa at

constant cement content of 8, 10 and 12, a compressive strength is increased by 62%, 86%

and 64%, respectively.

6.4 Water absorption

The experimental results of the water absorption test are tabulated in Appendix 9, and

shown in a graphical form in Fig 6.5. Fig 6.5 shows the effect of cement content increase

on the water absorption capacity of the block.

According to the tabulated results in Appendix 9, the mean water absorption values for the

various samples tested range from 9.8% for the 12% cement content samples to 15.81% for

the 4% cement content samples. From the literature the recommended maximum water

absorption value for blocks is below15%.

According to Appendix 9, an increase in cement content has the effect of reducing the

water absorption value of the blocks produced at constant compaction pressure. A doubling




of the cement content from 4% to 8% results into a reduction in mean water absorption of

10%. A further doubling of cement content from 6% to 12% is projected to reduce the

mean water absorption by 30%. This shows that the increase in cement content results into

a reduction in water absorption.

In practice, water can gain access to the block either in liquid phase in the case of rainwater

infiltration or suction from a wet surface, or in the vapor phase in the case of condensation

or adsorption, but leaves the block almost exclusively in the vapor phase through

evaporation. Therefore the water content of the wall should be determined not only by its

contact to water sources but also with its water vapor balance i.e., evaporation minus

condensation and adsorption. Given that the block undergoes seasonal cycle with maximum

water content in the rainy season and minimum water content in the dry season, such cycles

constitute an added complexity in analyzing the moisture balance and therefore any

remedial steps that could be taken.

EFFECTS OF CEMENT CONTENT ON THE

ABSORPTION CAPACITY OC CSEB

6

8

10

12

14

16

18

2 4 6 8 10 12 14

CEMENT CONTENT(%)

AB

SO

RP

TIO

N C

AP

AC

ITY

(%)

Fig 6.5 Effects of cement content on the absorption capacity of soil cement block

6.5 Summary Stabilisation of soil for the production of compressed stabilised soil blocks improves the

performance characteristics of soil block. In this research work, by using soil from Kara

area of Addis Ababa and Portland pozzolana cements from Mugher and Messobo cement

factories, three different series of mixes are prepared and more than 200 soil cement blocks




are produced. By using these test blocks, different standard performance tests are

conducted at Selam technical and vocational center. The effects of varying the cement

content with 2% from 4% to 12 % on the performance of soil block, the effects of

compaction pressure on the quality of soil cement block, the effects of different local

stabilisers (Mugher and Messobo PPC), the effects of cement content on the absorption

capacity of soil cement blocks are also examined. Based on the results obtained the

following points are concluded:

• The performance characteristics of soil blocks are improved by cement stabilistaion.

• Increment of cement content increases the compressive strength and decreases the

absorption capacity of soil cement block.

• Increment of the compaction pressure improves the compressive strength of soil

cement block.

• The effects of local stabilisers (Mugher and Messobo pozzolana cements) are

examined and comparisons are made.

• The 56th

day compressive strength of compressed cement stabilised soil block is

much higher than the 28th

day.

85

CHAPTER SEVEN

ECONOMIC ANALYSIS OF CEMENT STABILISED

COMPRESSED EARTH BLOCK

7.1 Production cost of cement stabilised compressed earth

block

In this research work, the production cost of compressed stabilised soil block are based on

Hydraform M7 E380 Machine and relevant data’s of working conditions are taken from

Selam Technical and Vocational center. Prices of raw materials used for the production of

the blocks are from the current price indexes of construction materials and the quantity of

materials needed are calculated based on the optimum mix design of this research.

Two typical cases have been considered for the cost calculation. These are the production

on site and Block yard.

1. On site production: the production is done on construction site. This case has the

minimum physical set up: simple store room and light production shed. This

physical set ups could be re-used by the owner at the end of the project. The soil is

extracted from the site.

2. Blockyard production: The production is done with durable facilities and a good

set up. The store room, office and production shed are movable, so that they can be

re-used several times after wards. The blockyard site is located in the countryside

and it has a quarry.

7.2 Parameters that influence the production cost of CSEB

1.Machine life span This represents the total number blocks, which can be

produced by the press: About 1.5 million blocks can be

produced by using M7 E380 Hydraform block making

machine over a period of 5 years with proper maintenance.

7. Economic Analysis of Compressed Cement

Stabilised Soil Block Versus Other

Conventional Building Materials


2.Daily production It varies with the block size. In the case of 220×220×115 cm

block the daily production ranges from 1200 to 1500. In this

research work 1200 blocks per day are taken as the daily

production.

3.Annual production It is the monthly production (26 days) over a period of 11

months. Every year, one month is deducted for the

maintenance of the equipment.

4.Equipment cost

Main equipments and machineries: Hydraform Block Making

Machine (M7 E 380), Pan Mixer, Motor, Soil crusher, Soil

sieve, Wheel barrow, Water Can and Plastic sheet .The detail

cost of the equipment is given in the Appendix 10.

5. Buildings &

Infrastructure

On-site production: It needs simple store room 15m2 and a

simple production shed 75m2. It could be re-used at the end of

the project, for another purpose.

Blockyard: Moveable office 10m2, moveable store room 20m

2,

moveable production shed 75m2. They would be moved and re-

used at the end of the exercise or project.

6. Maintenance

This is the total cost of the maintenance during the lifespan of

the press. It includes the daily maintenance and the yearly

repairs, once in a year. It is a lump sum given according to the

experience in Selam (proper maintenance).

7.3 Details for cost calculation

7.3.1 Variable costs

1. Labor This includes workers salaries.

2. Water It represents, about 20% of the mix. It would vary with the soil

quality.

3. Cement 6% cement (by weight) is taken as optimum for the cost

calculations.





4. Soil The cost includes the selected soil type excavation, loading

unloading and transportation costs.

5. Maintenance per

CSEB

Maintenance cost over the lifespan of the press divided by the

total production.

7.3.2 Fixed costs

1. Investment cost This corresponds to the interest of the loan taken from a bank

2. Equipment

depreciation

This is calculated on the lifespan of the press (for about 1.5

million blocks); on average it serves for 5 years. The lifespan

depends on the daily productivity with one type of block.

Therefore, the depreciation can be estimated as 20% per year.

3. Buildings

depreciation

On-site production: they can be re-used at the end of the

project for another purpose. They have only a little value and

their depreciation is evaluated to 50%.

Blockyard and Research Center: they would be moved at the

end of the exercise and re-used several times. Therefore, their

depreciation is evaluated to 5%.

7.3.3 Profit Margin

1. On-site

production

There is no profit margin, as the blocks are not for sale but for

use on the project site.

2. Blockyard

Production

This margin should allow some profit, which would be re-

invested at the end of the exercise to start another similar

enterprise.

7.4 Unit cost

For both production on site and blockyard, when fixed and variable costs are added

together and this total sum is divided by the number of blocks produced, it gives the unit

cost as shown in Table 7.1 and 7.2.This enables the price of the blocks to be set at sensible

level, by adding a profit margin to the unit cost.





Table 7.1 On-site /Cost calculation table for (220x220x110 mm) block using 6% cement

COST CALCULATION ON-SITE PRODUCTION

Daily production (blocks) 1200

Annual production (blocks) 343,000

Equipment cost (Hydraform machine with Accessories) 165,000

Buildings and infrastructure cost 20,000

VARIABLE COSTS Cost/unit Units Cost/block

Labor per day (Man/day) 10 9 0.075 6.98%

Soil per day (11.25m3 per 1200 blocks) 6.67 11.25 0.063 5.87%

Cement per day (6%=6.03Qt. per

1200 blocks)

150 6.03 0.754 70.20%

Maintenance per block 0.014 1 0.014 1.3%

Total variable Costs 0.906 84.36%

Fixed Costs Total

cost(Birr)

Cost/Block

(Birr)

Investment cost (interest) 4% 185,000 0.022 2.05%

Equipment depreciation (Press lifespan) 20% 165,000 0.096 8.94%

Building depreciation (site duration) 50% 20,000 0.029 2.7%

Miscellaneous 2% 0.021 1.96%

Total fixed costs 0.168 15.64%

Total cost price per block 1.074 100%

Note: Factory cost of Mugher PPC =108.69birr

VAT+ Transportation cost (30%) =32.60birr

Total = 141.30birr/Qt.

Factory cost of Messobo PPC =100.00birr

VAT+ Transportation cost (45%) = 45birr

Total = 145birr/Qt





Table 7.2 Blockyard /Cost calculation table for (220x220x110 mm-) block using 6%

cement

COST CALCULATION Blockyard production



Equipment cost (Birr) 165,000

Buildings and infrastructure cost(Birr) 60,000

VARIABLE COSTS Cost /

unit

Units Cost/block


Soil per day (11.25m3 per 1200 blocks) 31.67 11.25 0.296 22.77%

Cement per day (6% = 6.03Qt. per 1200

blocks)

150 6.03 0.754 58%


Total variable costs 1.14 87.69%

Fixed Costs Total cost Cost/Block

Investment cost (interest) 4% 225,000 0.026 2%

Equipment depreciation (Press lifespan) 20% 165,000 0.096 7.38%

Building depreciation (site duration) 5% 60,000 0.010 0.77%

Miscellaneous 2% 0.025 1.92%

Total fixed costs 0.16 12.31%

Total cost price per block 1.3 100%

Profit margin 20% 0.26

Selling price 1.56

Infrastructure is large

The soil cost includes digging and sieving on

site

The Block yard is assumed to be 10 km

away from the quarry and soil transport

cost is taken as 25 Birr/m3






Total = 145birr/Qt





7.5 Sensitivity Analysis

Sensitivity analysis is used to evaluate the effects of change in the variable and fixed costs

on the final cost of the soil block. This prevents one being caught unaware if costs increase

or if productivity falls. The following comments are driven from this sensitivity analysis

and Table 7.3 and Fig 7.1 shows the effects of cement content on the final cost of the soil

cement block.

7.5.1 Comments on how the parameters influence the cost of CSEB

Two production

cases:

On-site and

Blockyard

On-site production uses small facilities with low overheads. Thus it is

a low cost case. The other case has larger physical set-ups. The

blockyard has the larger overheads and the soil is delivered by lorry.

Thus the cost is high. This shows that on-site production is the

cheapest but has the disadvantage of scattered production. The

blockyard case is a middle way, and presents a lot of advantage.

Daily production This influences, substantially, the production cost of the block. For

example, if the productivity of interlocking blocks could be increased

from 1200 to 1400 blocks per day (without decreasing their quality),

the blocks would be 14% cheaper. Note that increasing the given

outputs is difficult, since they are near the maximum.

Annual production The number of months worked yearly has very little influence on the

production cost. Working one month more or less will change the

production cost by not more than 2 %.

Investment cost and

Maintenance cost

For each case considered, this variable has a small influence on the

production cost of the block. Doubling the investment and

maintenance cost will increase the production cost of the block by 3%.

Depreciation cost This also has an influence on the production cost of the block.

Doubling the depreciation cost will increase the production cost of the

block by more than 7 %.

Labor cost This influences substantially the production cost of the block. An

increase of 25% for the labor cost will increase the production cost of

the block by about 1.5 %.





Soil cost It influences substantially the production cost of the block an increase

of 25% for soil will increase the production cost of the block by 5.7

%.

Cement cost This has a high influence on the production cost of the block: an

increase of 25% will increase the production cost of the block by more

than 14.5%.

Overheads and

miscellaneous

This has a little influence on the production cost of the block:

doubling the miscellaneous costs will increase the production cost of

the block by less than 2%.

Profit

margin

Its base, for a healthy unit should be determined. For this research

work 20% is determined as profit margin.

Table 7.3 Effects of cement content on the cost of soil cement block

Cement

content (%)

by weight

Cement

content

kg/Block

Cost/Block

(Birr)

56 days wet Compressive

Strength (MPa)

4 0.335 1.33 1.25

6 0.502 1.56 2.23

8 0.67 1.83 3.2

10 0.837 2.08 4.03

12 1.005 2.33 5.03

EFFECT OF CEMENT CONTENT ON SOIL CEMENT

COST

0

0.5

1

1.5

2

2.5

0 0.2 0.4 0.6 0.8 1 1.2

CEMENT CONTENT IN KG/BLOCK

CO

ST

OF

A B

LO

CK

Fig.7.1 Sensitivity test chart





Table 7.4 Cost calculation for (200x200x400) mm HCB “Class C”

COST CALCULATION HCB production



Equipment cost with accessories 22900


VARIABLE COSTS Cost

per

unit

Units Cost/block


Sand per day (4.1m3 per 1200 blocks) 150 4.1 0.51 10.69%

Red sand per day (6.17m3 per 1200 blocks) 70 6.17 0.36 7.55%

Crushed stone 00 per day (1.03m3) 185 1.03 0.16 3.35%


Cement per day (28.6Qt. per 1200 blocks) 150 28.6 3.58 75.05%


Total Variable Costs 4.74 99.37%


Investment Cost (interest) 4% 82900 0.009 0.19%

Equipment Depreciation (Press lifespan) 20% 22900 0.013 0.27%

Building Depreciation (site duration) 5% 60,000 0.0087 0.18%

Miscellaneous 2% 458 0.001 0.02%

Total Fixed costs 0.0317 0.66%

Total cost price per block 4.77 100.00%


Selling Price 5.72






Total = 145birr/Qt





Table 7.5 Cost calculation for (200x200x400) mm HCB “Class B”

COST CALCULATION HCB production



Equipment cost with accessories 27000


VARIABLE COSTS Cost per

unit

Units Cost/block


Sand per day (3.82m3 per 1200 blocks) 150 3.82 0.48 7.93%

Red sand per day (3.82m3 per 1200

blocks)

70 3.82 0.223 3.69%



Cement per day (35.3Qt. per 1200

blocks)

150 35.3 4.41 72.89%


Total Variable Costs 6.02 99.50%


Investment Cost (interest) 4% 82900 0.009 0.15%

Equipment Depreciation (Press lifespan) 20% 22900 0.013 0.21%

Building Depreciation (site duration) 5% 60,000 0.010 0.17%

Miscellaneous 2% 458 0.001 0.02%

Total Fixed costs 0.033 0.55%

Total cost price per block 6.05 100.00%


Selling Price 7.26






Total = 145birr/Qt





7.6 Comparison of compressed stabilised soil block with hollow

concrete blocks per m2 area of wall

The first question a potential user will ask is weather a building built with compressed

stabilised earth block is more economical than one built with any other material. First of

all, one must consider the type of building. In luxury villa, the cost of the wall building

materials accounts very little of the total cost. Choosing the compressed stabilised earth

block to build a prestige villa is mainly a question of thermal comfort and of taste. But in

the case of low cost houses, such as those social housing programs, the cost of walls is a

major component of the total cost; as per the literature survey it accounts 30%of the total

building cost. This implies that the choice of building materials and the wall building

techniques are more critical.

The use of hollow concrete blocks is increasing rapidly in every part of the world. But there

thermal performance is poor and there cost is very dependent on the local cost and

availability of cement. Further more HCB wall always requires plastering and/or rendering.

To make a realistic comparison, it was important to consider a complete section of wall

including the cost of plastering and structural elements. In this research, wall made of HCB

plastered on both sides in one hand and HCB wall pointed on both sides on the other hand

compared with dry stacked compressed stabilised soil blocks wall varnished on both sides

per m2 area of wall and cost comparisons are prepared and tabulated in Table 7.6 below.

According to Table 7.6 the cost of HCB wall plastered and painted internally and externally

costs 204.06 Birr per m2

but one m2

of CSEB wall varnished both internally and externally

costs 91.4 Birr. This implies that the cost of CSEB wall is 55.2% cheaper than HCB.

.





Table 7.6 Comparison of CSEB with Hollow Concrete Blocks per m2 area of wall

No Description

Hollow

concrete block

(HCB) blocks

Per m2

Plastered and

painted (out

side &inside)

(Birr)

Hollow concrete

block (HCB)

blocks Per m2

Pointed (out side

& inside)

(Birr)

Dry stack

Soil blocks

(plastered

internally)

Per m2

(Birr)

Dry stack

Soil blocks

Per m2

(Birr)

1 Block 74.36 74.36 62.40 62.40

2 Mortar for fixing 21.70 21.70 --- ---

3 Plastering 50.00 --- 25 ---

4 Pointing --- 20.00 --- ---

5 Painting 24.00 --- 12.00 ---

6 Varnish -- --- 7.00 14.00

7 Labor 34.00 22.00 23.00 15.00

8 Total walling cost 204.06 138.06 129.40 91.40

Percentage 0 -32.35 -36.59 -55.2

Note:

In this table comparison is made on CSEB and HCB wall. The building elements ( Soil cement blocks)

have a compressive strength of 2MPa or equivalent to Class “C” HCB. As per the out comes of this

research, increasing the cement content in the compressed stabilised soil block yields a better

compressive strength of the block. Cost comparison for structural/load bearing wall (wall constructed

from Class “A” and “B” HCBS) can be made with better % of cement in the Compressed Stabilised Soil

block.

8. Conclusions and Recommendations


CHAPTER EIGHT

CONCLUSIONS AND RECOMMENDATIONS

The conclusions and Recommendations that could be drawn from the results of these

research and experiments are wide ranging and are summarized as follows:

8.1 Conclusions

1. Stabilisation of soil block using Portland pozzolana cement fulfills a number of

objectives that are necessary to achieve a lasting structure from locally available

soil. Some of these are: better mechanical characteristics (leading to better

compressive strength), better cohesion between particles (reducing porosity

which reduces changes in volume due to moisture fluctuations).

2. Increase in cement content results in an increase in the compressive strength

value of blocks made at the same constant compaction pressure. For instance, by

using 10 MPa compacting pressure, increasing the cement content from 4% to 8

% yields 110 % increment in compressive strength of the block.

3. Increase in cement content could be a more effective method of increasing

compressive strength values than an increase in compaction pressure and the

final wet strength reached by a block is much more sensitive to variations in the

cement content than to densification.

4. The investigation of this thesis has revealed that many different factors are

responsible for ensuring a good bond between the cement and the particles

mixed within it. These requirements not only affect the components of the

mixture used, how it is prepared, delivered into its final state, but also

subsequent curing times and environmental conditions of the finished product.

5. The amount of water for the soil-cement mixture needs to be carefully

controlled. There needs to be sufficient moisture for the cement to fully hydrate



but no excess of water which would reduce the final density, increase porosity

and reduce final strength.

6. The moisture absorption capacity of the block could be significantly correlated

to its durability. Increase in the cement content of block results into a reduction

of its water absorption capacity.

7. The cost and technical performance comparison between compressed stabilised

soil block and hollow concrete block has revealed that compressed stabilised

soil block is interesting by the social and economical impact it will bring to

local people. In the case of low cost housing, the technologies are really more

affordable by (55%) than the conventional ones used (HCB).

8. From literature the best soil composition for soil-cement is 75% sand, 25% silt

and clay, of which more than 10% is clay. In this research, Soil from Kara area

of Addis Ababa with a composition of Sand 70%, Silt 16.25% and Clay -

13.75% is used as a raw material for soil cement. This composition yielded a

sandcrete product after mixed with cement and exhibited good structural

characteristics. Unfortunately, soil with these exact characteristics will not be

found easily near every potential building site and so one of the following two

things must be done. Either the soil is tested and the required parts added to

make the ideal soil, or a compromise is made and a slightly higher percentage of

cement is used to ensure a satisfactory outcome whatever the type of soil is

used.

9. The two types of Portland pozzolana cements used for stabilisation, Mugher

PPC and Mossebo PPC showed more or less equivalent technical performance

at 28 day, irrespective of their chemical composition, but Mugher PPC has

shown better stabilisation effect based on the 56th

day compressive strength of

blocks.



8.2 Recommendations

1. Occasionally, a social reluctance to use the compressed earth block can be

encountered when the compressed earth block has been too strongly associated with

low cost or “cheap” building. Social acceptance depends a great deal on how it is

presented to the population. Organizations have an active part to play in this

respect, as well as political decision makers. The involvement of Architects and

Engineers in this process is also necessary.

2. The results of this research work have revealed that compressed stabilised soil block

can be used as an alternative wall making material. Significant cost cut can be

achieved in low cost housing projects especially town houses and duplex buildings.

Any concerned body can use this material as an alternative wall making material

with proper quality control.

3. The use of compressed stabilised soil block as a walling material in Ethiopia has

shown different defects. These defects include time related loss of quality of the

block under direct or indirect influence of environment. This can be reduced by

proper quality control during production; Plastering of the first two courses of the

wall and increasing the overhangs of the roof.

4. Improvements to the durability of blocks can only become possible when most of

the currently unanswered questions are settled. The most probable likely answer

will lie in ways to achieve higher inter particle bonding and the exclusion of the

damaging effects of moisture.

5. In Ethiopia especially in the central, northeast, northwest and in the southern eastern

rift valley area it is believed that the soil is suitable for the soil cement block

production. Suitable soil selection using laboratory tests may be expensive for

small-scale production. Adoption of simple field test methods and trial block

production can be the best solution.

Department of Civil Engineering

99

6. Premeditated further research will still be needed to test refine and validate the

findings contained in this report with a view to developing a reliable long-term

durability model.

7. Further research on different type of soil including clay soils is very important due

to availability and diversity of these soil types. A more detailed account of the

interaction between cement and clay and why too much clay in the mixture is

detrimental to the effectiveness of the cement is another topic for further

investigation.

8. Chemical and organic contents of soil that hinder hydration reaction and how to

treat these unsuitable soils are further research topics for better understand.


100

REFERENCES

1. Mathewos consult in collaboration with The Federal Urban Planning Institute

(FUPI) and Urban Development Capacity Building office, Ministry of Works and

Urban Development of Ethiopia, Urban upgrading and Renewal manual, 2006

2. Appropriate Technology in Civil Engineering, proceedings of conference held by

the Institute of Civil Engineers, Tomas Telford, Ltd. London, April 1981

3. Dr.-Ing. Abebe Dinku, Associate Professor of Civil Engineering, A text book of

Building Construction, Addis Ababa University, 2007

4. Doctor. E.A.Adam in collaboration with Professor A.R.A.Agib, Compressed

stabilized Earth Block Manufacture in Sudan, UNESCO, Paris, July 2001

5. A.K.LAL, Hand book of Low Cost Housing, New Age International (p) Ltd. March

1995

6. Vincent Rigassi, Craterre-ERG, Compressed Earth Blocks: Manual of production,

A publication of the Deutsches Zentrum fur Entwicklungtechnologien-Gate Volume

1,1985

7. Appropriate Building Materials for Low Cost Housing African region, proceedings

of a symposium held in Nairobi Kenya from 7 to 14 November 1983, E.&F.N.Spon

Ltd, London 1985

8. Ethiopian Ministry of Finance and Economic Development, A Plan for Accelerated

and Sustained development to end poverty (PASDEP), (2005/06-2009/10)

9. Cebtex, Compressed Earth Block Construction

Http://Cebtex.Com

10. A.G.Kerali, Working paper, Destructive effects of moisture on Long-Term

Durability of Stabilised Soil Blocks, Development Technology Unit, University of

Warwick, January 2000, http://www.eng.warwick.ac.uk/DTU/

11. CRATerre, The Basics of Compressed Earth Blocks, A publication of the Deutsches

Zentrum fur Entwicklungtechnologien-Gate, 1991

12. Satprem Maïni, Building with Earth in Auroville, A case study, Auroville Earth

Institute, India, April 2005.


101

13. Satprem Maïni, Modernity of Earthen Architecture, presentation on National

Alternative Building materials workshop Addis Ababa, Ethiopia, Feb, 2006

14. Satprem Maimi, Production and use of Compressed Stabilized Earth Blocks,

Auroville Earth Institute, India, March 2006

15. David Edward Montgomery, Dynamically-compacted cement stabilised soil blocks

for low-cost walling, University of Warwick, School of Engineering, January 2002

16. Craig, R.F, Soil mechanics, E & FN Spon, 1997.

17. D. E.M. Gooding, Soil testing for soil cement block preparation, DTU Working

paper No.38, 1993, http://www.eng.warwick.ac.uk/DTU/

18. Ethiopian Building Code Standard: Foundations, EBCS-7, Ethiopian Ministry of

Works and Urban Development, Addis Ababa, 1995.

19. African Regional Standards, Compressed Earth Blocks Standards, CDI and

CRATerre-Publications, 1998.

20. A.M. Neville, Properties of concrete, ELBS with Addison Wesley Longman, fourth

edition, 1996

21. David Edward Montgomery, Stabilised soil research progress report, University of

Warwick, School of Engineering, 1998. http://www.eng.warwick.ac.uk/DTU/

22. Birhanu Bogale, Comparison of concrete Durability as produced by various

cements manufactured in Ethiopia, MSc Thesis, AAU, February 2007.

23. Hydraform Training manual. www.Hydraform.com

24. ASTM, Annual book of ASTM Standards, Volume 04.08,Soil and Rock, 1996


102

APPENDIX ONE

SOIL INDEX PROPERTIES TEST RESULTS

Soil Testing Laboratory Table A1.1 Natural moisture content Determination

Method used ASTM D 2216

Sample no: Project: M.Sc.Thesis

Boring No Location: Addis Ababa Kara area

Depth Date: April 30/2007

Description of Sample: sandy soil

Tested by: Asmamaw Tadege

Determination No: 1 2 3 Container (Can)no. 31 76 26

Weight of Can+moist soil,W1(g) 51.176 43.798 51.3

Weight of Can+dry soil,W2(g) 46.546 40.129 46.737

Weight of can,Wc(g) 15.414 15.715 15.671

weight of water,ww(g) 4.63 3.67 4.57

weight of dry soil,ws(g) 31.13 24.41 31.06

Moisture content, ω 14.87 15.03 14.71

ω=14.87%

Table A1.2 Specific Gravity Test Method used ASTM D 854



Depth Date: May 12 /2007



Determination No: 1 2 3 weight of pycnometer+soil+water(m3) 167.79 167 163.18

weight of pychnometer+water(m4) 149.29 148.28 144.79

weight of pychnometer+Soil (m2) 79.54 78.64 75.09

weight of pychnometer(m1) 49.59 48.55 45.1

Temprature,T(°C) 23 23 23

specific gravity 2.61 2.64 2.58

Average specific Gravity 2.61

Appendix One


Table A1.3 Plastic Limit Determination

Method used ASTM D 2216-92

Sample no: Project: M.ScThesis

Depth Location: Addis Ababa Kara area

Description of Sample: sandy soil Date: June 14/2007


Determination No: 1 2 3 Can no 36 80 40

Weight of can+Moist soil, W1 (g) 22.262 24.9634 12.2203

Weight of can+Dry soil, W2 (g 20.9029 22.9985 11.09

Weight of can, Wc (g) 15.568 15.7085 6.5545

Weight of water, Ww (g) 1.3591 1.9649 1.1303

Weight of dry soil, Ws (g) 5.3349 7.29 4.5355

Water content, ω (%) 25.48 26.95 24.92

Plastic content (%) 25.78

Table A1.4 Liquid Limit Determination

Method used ASTM D 2216-92



Description of Sample: sandy soil Date: June 14/2007


Determination No: 1 2 3 Number of drops 17 26 31

Can no 10 4 15

Weight of can+Moist soil,W1(g) 22.72 23.00 26.04

Weight of can+Dry soil,W2(g 18.61 19.01 21.35

Weight of can,Wc(g) 6.39 6.56 6.48

Weight of water,Ww(g) 4.11 3.99 4.69

Weight of dry soil,Ws(g) 12.22 12.45 14.87

Moisture content, ω (%) 33.60 32.08 31.55

Liquid limit

Series1, 17, 33.6

Series1, 26, 32.22

Series1, 31, 31.55

31

31.5

32

32.5

33

33.5

34

0 5 10 15 20 25 30 35No of Blows

Mo

istu

re c

on

ten

t

Appendix One


Table A1.5 Hydrometer Analysis/ Grain-Size Analysis

Method used ASTM D 422



Depth Date: May 19-20/2007



Date

Time

Hydrometer

Reading Temperature °c

Composite

correction

May 19,2007 8.15 A.M

8.17 A.M 1.019 20 0.002

8.20 A.M 1.018 20 0.002

8.30 A.M 1.016 20.5 0.002

8.45 A.M 1.015 21 0.002

9.15 A.M 1.014 21 0.002

10.15 A.M 1.013 22 0.002

12.15 P.M 1.012 22 0.002

4.15 P.M 1.011 21 0.002

8.15 P.M 1.0105 20 0.002

May 20,2007 8.15 A.M 1.01 20 0.002

Table A1.6 Sieve analysis of fine aggregate

Weight of oven dry sample for Hydrometer analysis = 100gm

Percentage of sample passing sieve no 10 = 100%

Calculated weight of total Hydrometer analysis sample=100gm

Sieve size[mm] Weight

retained(gm)

Weight

passed(gm)

Total

percentage

passing

2 0 100 100

1.18 9 91 91

0.6 23 68 68

0.3 24 44 44

0.15 9 35 35

0.075 5 30 30

Pan 30

Appendix One


Table A1.7 Hydrometer Analysis /Grain-Size Analysis

Method used ASTM D 422 Project: M.Sc. Thesis Tested by: Asmamaw T.

Types of Hydrometer analysis used 151H Location: Addis Ababa, Kara area Date: May 19-20/2007

Specific gravity of soil =2.61 Description of Sample sandy soil

Weight of oven dry Sample = 100gm

Amount of Dispersing agent used 40gm/Liter

Data

Timemm

mmmmm

mmmmm

mmmmm

mmmmm

m

Elapsed

time, T

in min

nmmm

mmmm

m

Actual

hydrometer

Reading

Composite

Correction

Hydromete

r reading

with

composite

Correction

Temperature

°C

Effective

depth of

Hydrometer

L,cm

Value

of

K

Diameter

of Soil

particle

(mm)

Soil in

suspension

i.e. % of

soil finer)

(%)

May19

/2007

8.15AM

0

8.17 AM 2 1.019 0.002 1.017 20 11.3 0.0138 0.0328 27.47

8.2 AM 5 1.018 0.002 1.016 20 11.5 0.0138 0.0209 25.88

8.3 AM 15 1.016 0.002 1.014 20.5 12.1 0.0137 0.0123 22.64

8.45 AM 30 1.015 0.002 1.013 21 12.3 0.0136 0.0087 21.02

9.15 AM 60 1.014 0.002 1.012 21 12.6 0.0136 0.0062 19.41

10.15AM 120 1.013 0.002 0.011 22 12.9 0.0134 0.0044 17.79

6.15 PM 240 1.012 0.002 1.01 22 13.1 0.0134 0.0031 16.17

10.1PM 480 1.011 0.002 1.009 21 13.4 0.0136 0.0023 14.56

2.15 PM 720 1.0105 0.002 1.0085 20 13.6 0.0138 0.0019 13.75

May20

/2007

8.15AM 1440 1.01 0.002 1.008 20 13.7 0.0138 0.0013 12.94

Appendix One


Table A1.8 Compaction Test

Method used ASTM D 698 Method A



Description of Sample: sandy soil Date: 21/06/2007


Moisture content determination

Trial

No.

Weight of

Compacted

Soil+Mould

wsm(gm)

Weight

Of

Mould

Wm (g)

Weight of

Compacted

Soil (g)

Wet

Density

wetץ

Can

no

Weight of

Wet soil+

Can, W1

(g)

Weight

of

dry soil+

can,W2(g)

Weight

of

water,

Ww(g)

Weight of

can,Wc(g)

Weight

of

Dry

soil

Ws (g)

Moisture

Content

W(%)

Dry

Density,

dry ע

7215 5602 1613 1.67 63 55.78 50.4 5.38 15.6 34.8 15.46 1.45

7215 5602 1613 1.67 A36 54.36 49.05 5.31 15.51 33.54 15.83 1.45

13 7215 5602 1613 1.67 C10 51.58 46.47 5.11 13.84 32.63 15.66 1.45

7404 5602 1802 1.87 1 60 53.21 6.79 15 38.21 17.77 1.59

7404 5602 1802 1.87 48 60 53.92 6.08 16 37.92 16.03 1.61

16 7404 5602 1802 1.87 A10 60 52.86 7.14 15 37.86 18.86 1.57

7450 5602 1848 1.92 D7 60 52.57 7.43 15 37.57 19.78 1.60

7450 5602 1848 1.92 C23 60 52.14 7.86 13 39.14 20.08 1.60

19 7450 5602 1848 1.92 D8 60 52.2 7.8 15 37.2 20.97 1.59

7442 5602 1840 1.91 D16 60 51.21 8.79 16 35.21 24.96 1.53

7442 5602 1840 1.91 C9 60 50.66 9.34 14 36.66 25.48 1.52

22 7442 5602 1840 1.91 C19 60 51.19 8.81 14 37.19 23.69 1.54

7405 5602 1803 1.87 35 83.39 68.71 14.68 15.6 53.11 27.64 1.47

7405 5602 1803 1.87 C11 83.3 68.66 14.64 14.13 54.53 26.85 1.48 25

7405 5602 1803 1.87 C33 93.52 76.15 17.37 13.76 62.39 27.84 1.46

Notes: D = B-C ; E = D/963 ; I = G-H ; K = H-J; L = I/K×100 ; M = (E/(100+L)×100

Appendix One


APPENDIX TWO

CHEMICAL ANALYSIS OF SOIL

108

APPENDIX THREE

COMPRESSIVE STRENGTH TEST RESULTS USING MUGHER PPC

Table A3.1 Blocks Compressive Strength Tests Result using 4% Mugher PPC

Date Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

Mpa

Average

Strength

MPa

1 9/7/2007 16/7/2007 7 20.3×22.1×11.6 1844.7 0.3

2 9/7/2007 16/7/2007 7 20.7×22.1×11.6 1771.36 0.2

3 9/7/2007 16/7/2007 7 20.4×22.1×11.6 1845.23 0.3

0.3

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

Weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 23/7/2007 14 20.3×22.1×11.6 1806.27 0.5

2 9/7/2007 23/7/2007 14 20.4×22.1×11.6 1816.53 0.6

3 9/7/2007 23/7/2007 14 20.3×22.1×11.6 1810.41 0.6

0.6

Date Marking

Casted

Tested

Age in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 20.6×22.1×11.6 1761.00 0.8

2 9/7/2007 06/08/2007 28 20.5×22.1×11.6 1769.60 1.0

3 9/7/2007 06/08/2007 28 20.6×22.1×11.6 1761.00 1.0

1.0

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 03/09/2007 56 21×22.1×11.6 1690.3 1.2

2 9/7/2007 03/09/2007 56 21×22.1×11.6 1708.9 1.3

3 9/7/2007 03/09/2007 56 21.2×22.1×11.6 1711.18 1.2

1.25

Appendix Three


Table A3.2 Blocks Compressive Strength Test Results using Mugher 6 % PPC

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

Mpa

Average

Strength

MPa

1 9/7/2007 16/7/2007 7 20.5×22.1×11.6 1864.76 0.5

2 9/7/2007 16/7/2007 7 20.9×22.1×11.6 1866.39 0.6

3 9/7/2007 16/7/2007 7 21.2×22.1×11.6 1867.56 0.7

0.6

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

Weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

Mpa

1 9/7/2007 23/7/2007 14 21.8×22.1×11.6 1837.86 1.2

2 9/7/2007 23/7/2007 14 20.3×22.1×11.6 1844.69 1.4

3 9/7/2007 23/7/2007 14 21.1×22.1×11.6 1839.12 1.4

1.3

Date Marking

Casted

Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 20.7×22.1×11.6 1790.20 1.5

2 9/7/2007 06/08/2007 28 21×22.1×11.6 1801.8 1.5

3 9/7/2007 06/08/2007 28 20.9×22.1×11.6 1791.7 1.4

1.5

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

Mpa

Average

Strength

MPa

1 9/7/2007 03/09/2007 56 20.8×22.1×11.6 1762.85 2.3

2 9/7/2007 03/09/2007 56 20.5×22.1×11.6 1769.62 2.1

3 9/7/2007 03/09/2007 56 20.3×22.1×11.6 1748.62 2.3

2.23

Appendix Three


Table A3.3 Blocks Compressive Strength Test Results using 8% Mugher PPC

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 16/7/2007 7 20.4×22.1×11.6 1873.9 1

2 9/7/2007 16/7/2007 7 20.9×22.1×11.6 1885.06 1.1

3 9/7/2007 16/7/2007 7 20.2×22.1×11.6 1870 1.2

1.1

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 23/7/2007 14 21.3×22.1×11.6 1831.34 1.7

2 9/7/2007 23/7/2007 14 20.7×22.1×11.6 1846.74 1.8

3 9/7/2007 23/7/2007 14 21.9×22.1×11.6 1828.74 1.8

1.8

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.1×22.1×11.6 1793.20 2.0

2 9/7/2007 06/08/2007 28 21.1×22.1×11.6 1793.20 2.1

3 9/7/2007 06/08/2007 28 20.6×22.1×11.6 1780.00 2.2

2.1

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 9/7/2007 03/09/2007 56 21.1×22.1×11.6 1756.27 3.2

2 9/7/2007 03/09/2007 56 21.1×22.1×11.6 1756.27 3.1

3 9/7/2007 03/09/2007 56 20.9×22.1×11.6 1754.41 3.3

3.2

Appendix Three


Table A3.4 Blocks Compressive Strength Test Results using 10%Mugher PPC

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 16/7/2007 7 20.7×22.1×11.6 1846.74 1.3

2 9/7/2007 16/7/2007 7 20.4×22.1×11.6 1931.26 1.4

3 9/7/2007 16/7/2007 7 20.3×22.1×11.6 1876.94 1.4

1.4

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 9/7/2007 23/7/2007 14 21×22.1×11.6 1857.51 2

2 9/7/2007 23/7/2007 14 21.1×22.1×11.6 1848.7 1.9

3 9/7/2007 23/7/2007 14 21.8×22.1×11.6 1839.7 2.2

2.1

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 20.6×22.1×11.6 1836.8 2.5

2 9/7/2007 06/08/2007 28 20.6×22.1×11.6 1836.8 2.7

3 9/7/2007 06/08/2007 28 21×22.1×11.6 1838.9 2.6

2.6

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 03/09/2007 56 20.2×22.1×11.6 1795.9 4.1

2 9/7/2007 03/09/2007 56 20.7×22.1×11.6 1771.36 3.8

3 9/7/2007 03/09/2007 56 20.7×22.1×11.6 1771.36 4.2

4.03

Appendix Three


Table A3.5 Blocks Compressive Strength Test Results using 12%Mugher PPC

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 16/7/2007 7 21.9×22.1×11.6 1888.04 1.4

2 9/7/2007 16/7/2007 7 21.7×22.1×11.6 1869.49 1.5

3 9/7/2007 16/7/2007 7 21.1×22.1×11.6 1899.47 1.5

1.5

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 23/7/2007 14 22.3×22.1×11.6 1806.27 2.5

2 9/7/2007 23/7/2007 14 23×22.1×11.6 1841.7 2.5

3 9/7/2007 23/7/2007 14 22.8×22.1×11.6 1818.22 2.6

2.5

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.8×22.1×11.6 1807.2 3.3

2 9/7/2007 06/08/2007 28 22×22.1×11.6 1808.5 3.5

3 9/7/2007 06/08/2007 28 21.7×22.1×11.6 1797.6 3.5

3.5

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 03/09/2007 56 22.1×22.1×11.6 1729.75 4.5

2 9/7/2007 03/09/2007 56 22.2×22.1×11.6 1765.05 5.3

3 9/7/2007 03/09/2007 56 22.4×22.1×11.6 1758.83 5.3

5.03

113

APPENDIX FOUR

COMPRESSIVE STRENGTH TEST RESULTS USING MESSOBO PPC

Table A4.1 Blocks Compressive Strength Test Results using 4% Messobo PPC

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 02/7/2007 7 19.6×22.1×11.6 1880.73 0.1

2 25/06/07 02/7/2007 7 20.6×22.1×11.6 1846.23 0.2

3 25/06/07 02/7/2007 7 20.2×22.1×11.6 1861.71 0.1

0.15

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 09/7/2007 14 20.1×22.1×11.6 1814.53 0.8

2 25/06/07 09/7/2007 14 20.3×22.1×11.6 1806.27 0.7

3 25/06/07 09/7/2007 14 20.8×22.1×11.6 1800.76 0.7

0.7

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 25/06/07 23/7/2007 28 19.5×22.1×11.6 1720.34 0.6

2 25/06/07 23/7/2007 28 19.9×22.1×11.6 1705.36 0.8

3 25/06/07 23/7/2007 28 20.4×22.1×11.6 1682.68 0.9

0.8

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 20/08/2007 56 20.4×22.1×11.6 1606.2 1.0

2 25/06/07 20/08/2007 56 19.5×22.1×11.6 1600.32 1.0

3 25/06/07 20/08/2007 56 20×22.1×11.6 1638.3 0.9

1.0

Appendix Four


Table A4.2 Blocks Compressive Strength Test Results using 6% Messobo

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

Mpa

1 25/06/07 02/7/2007 7 20×22.1×11.6 1852.86 0.33

2 25/06/07 02/7/2007 7 20.7×22.1×11.6 1856.16 0.4

3 25/06/07 02/7/2007 7 20.2×22.1×11.6 1854.49 0.35

0.4

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 09/7/2007 14 20.5×22.1×11.6 1826.7 1

2 25/06/07 09/7/2007 14 20.6×22.1×11.6 1817.83 1

3 25/06/07 09/7/2007 14 20.3×22.1×11.6 1827.9 1

1.0

Date Marking

Casted

Tested

Age In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 23/7/2007 28 20.8×22.1×11.6 1725.34 1.5

2 25/06/07 23/7/2007 28 20.1×22.1×11.6 1766.02 1.5

3 25/06/07 23/7/2007 28 19.9×22.1×11.6 1783.77 1.6

1.6

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 20/08/2007 56 20.0×22.1×11.6 1638.32 1.7

2 25/06/07 20/08/2007 56 20.2×22.1×11.6 1660.72 1.8

3 25/06/07 20/08/2007 56 20.1×22.1×11.6 1649.58 2.0

1.85

Appendix Four



Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 02/7/2007 7 20.2×22.1×11.6 1852.86 0.8

2 25/06/07 02/7/2007 7 20.5×22.1×11.6 1856.16 1.0

3 25/06/07 02/7/2007 7 20.1×22.1×11.6 1853.95 1.0

1.0

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

Mpa

1 25/06/07 09/7/2007 14 19.9×22.1×11.6 1842.57 1.2

2 25/06/07 09/7/2007 14 20.6×22.1×11.6 1836.77 1.2

3 25/06/07 09/7/2007 14 20.9×22.1×11.6 1829.07 1.4

1.3

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 23/7/2007 28 21.2×22.1×11.6 1784.78 2.3

2 25/06/07 23/7/2007 28 20.5×22.1×11.6 1769.62 2.5

3 25/06/07 23/7/2007 28 20.5×22.1×11.6 1769.62 2

2.3

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 25/06/07 20/08/2007 56 20.3×22.1×11.6 1671.76 2.7

2 25/06/07 20/08/2007 56 20.2×22.1×11.6 1699.35 2.8

3 25/06/07 20/08/2007 56 20.3×22.1×11.6 1690.97 2.7

2.7

Appendix Four



Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 02/7/2007 7 21.5×22.1×11.6 1886.88 1.2

2 25/06/07 02/7/2007 7 20.8×22.1×11.6 1856.61 1.4

3 25/06/07 02/7/2007 7 21.1×22.1×11.6 1879.26 1.2

1.3

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 09/7/2007 14 22×22.1×11.6 1826.27 2

2 25/06/07 09/7/2007 14 21.6×22.1×11.6 1823.97 1.6

3 25/06/07 09/7/2007 14 21.2×22.1×11.6 1821.58 1.5

1.7

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

Mpa

1 25/06/07 23/7/2007 28 20.8×22.1×11.6 1781.6 3

2 25/06/07 23/7/2007 28 20.9×22.1×11.6 1791.74 3

3 25/06/07 23/7/2007 28 21.2×22.1×11.6 1766.38 2.5

3.0

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 25/06/07 20/08/2007 56 20.6×22.1×11.6 1704.21 3.5

2 25/06/07 20/08/2007 56 20.7×22.1×11.6 1790.20 3.0

3 25/06/07 20/08/2007 56 20.5×22.1×11.6 1693.5 2.9

3.2

Appendix Four


Table A4.5 Blocks Compressive Strength test results using 12% Messobo PPC

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 02/7/2007 7 21.8×21.1×11.6 1986.59 1.7

2 25/06/07 02/7/2007 7 20.4×21.1×11.6 1988.63 1.8

3 25/06/07 02/7/2007 7 20.7×21.1×11.6 1986.96 1.7

1.7

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 09/7/2007 14 20.6×21.1×11.6 1923.82 1.7

2 25/06/07 09/7/2007 14 21.1×21.1×11.6 1936.32 1.8

3 25/06/07 09/7/2007 14 21×21.1×11.6 1945.54 1.8

1.8

Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 25/06/07 23/7/2007 28 21.4×21.1×11.6 1890.08 3.4

2 25/06/07 23/7/2007 28 21.4×21.1×11.6 1870.99 2.5

3 25/06/07 23/7/2007 28 20.7×21.1×11.6 1788.64 3.4

3.4

Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 25/06/07 20/08/2007 56 21.9×21.1×11.6 1790.96 4.2

2 25/06/07 20/08/2007 56 21.5×21.1×11.6 1805.28 3.9

3 25/06/07 20/08/2007 56 20.5×21.1×11.6 1813.62 3.8

4.0

118

APPENDIX FIVE

EFFECTS OF COMPACTION PRESSURE ON THE COMPRESSIVE STRENGTH

OF SOIL BLOCK BY USING 6% CEMENT

Table A5.1 Block compressive strength test result by using compaction pressure of 4MPa.

Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength MPa

Average

Strength MPa

1 9/7/2007 06/08/2007 28 25×21.1×11.6 1666.9 0.1

2 9/7/2007 06/08/2007 28 24.5×21.1×11.6 1667.6 0.1

3 9/7/2007 06/08/2007 28 24×21.1×11.6 1668.7 0.2

0.1


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

Weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 23.1×21.1×11.6 1715.6 0.9

2 9/7/2007 06/08/2007 28 23.7×21.1×11.6 1741.1 0.9

3 9/7/2007 06/08/2007 28 23.2×21.1×11.6 1723.3 1.0

0.9


Date Marking

Casted

Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 23.6×21.1×11.6 1800.4 1.0

2 9/7/2007 06/08/2007 28 22.8×21.1×11.6 1809.9 1.2

3 9/7/2007 06/08/2007 28 23.1×21.1×11.6 1802 1.2

1.2


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m

3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.8×21.1×11.6 1799.2 1.8

2 9/7/2007 06/08/2007 28 22.3×21.1×11.6 1795.5 1.5

3 9/7/2007 06/08/2007 28 22×21.1×11.6 1791.4 1.7

1.7

119

APPENDIX SIX




Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 22.1×21.1×11.6 1737.8 1.3

2 9/7/2007 06/08/2007 28 22.1×21.1×11.6 1756.3 1.3

3 9/7/2007 06/08/2007 28 22.5×21.1×11.6 1717.82 1

1.3


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

Weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.8×21.1×11.6 1799.2 1.5

2 9/7/2007 06/08/2007 28 21.9×21.1×11.6 1809.6 1.8

3 9/7/2007 06/08/2007 28 22.4×21.1×11.6 1829.6 1.6

1.65


Date Marking

Casted

Tested

Age In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.7×21.1×11.6 1845.1 2.0

2 9/7/2007 06/08/2007 28 21.5×21.1×11.6 1862.3 2.0

3 9/7/2007 06/08/2007 28 21.4×21.1×11.6 1878.8 2.2

2.1


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21×21.1×11.6 1906.6 2.5

2 9/7/2007 06/08/2007 28 20.9×21.1×11.6 1896.2 2.75

3 9/7/2007 06/08/2007 28 20.4×21.1×11.6 1908.3 2.5

2.6

120

APPENDIX SEVEN




Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 23.1×21.1×11.6 1715.6 1.0

2 9/7/2007 06/08/2007 28 23.3×21.1×11.6 1736.0 1.4

3 9/7/2007 06/08/2007 28 22.8×21.1×11.6 1765.0 1.5

1.4


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.5×21.1×11.6 1805.3 1.8

2 9/7/2007 06/08/2007 28 21.4×21.1×11.6 1851.9 2.5

3 9/7/2007 06/08/2007 28 21.7×21.1×11.6 1801.5 2.1

2.2


Date Marking

Casted

Tested

Age In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 20.3×21.1×11.6 1932.1 3.0

2 9/7/2007 06/08/2007 28 20.6×21.1×11.6 1884.2 2.5

3 9/7/2007 06/08/2007 28 20.1×21.1×11.6 1912.1 2.4

2.6


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 20.8×21.1×11.6 1885.7 2.5

2 9/7/2007 06/08/2007 28 20.8×21.1×11.6 1905.3 2.7

3 9/7/2007 06/08/2007 28 20.8×21.1×11.6 1905.3 3.0

2.75

121

APPENDIX EIGHT




Date

Marking

Casted Tested

Age

in

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 22.7×21.1×11.6 1727.8 1.5

2 9/7/2007 06/08/2007 28 22.5×21.1×11.6 1761.4 1.9

3 9/7/2007 06/08/2007 28 22.7×21.1×11.6 1731.6 2.0

1.8


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.6×21.1×11.6 1834.8 2.5

2 9/7/2007 06/08/2007 28 21.8×21.1×11.6 1836.7 2.2

3 9/7/2007 06/08/2007 28 21.5×21.1×11.6 1836.2 2.5

2.4


Date Marking

Casted

Tested

Age In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 20.8×21.1×11.6 1885.7 3.0

2 9/7/2007 06/08/2007 28 20.8×21.1×11.6 1964.2 2.8

3 9/7/2007 06/08/2007 28 20.6×21.1×11.6 1896.1 3.0

2.95


Date

Marking

Casted Tested

Age

In

days

Dimension

L×W×H

Unit

weight

Kg/m3

Compressive

Strength

MPa

Average

Strength

MPa

1 9/7/2007 06/08/2007 28 21.1×21.1×11.6 1917.0 3.5

2 9/7/2007 06/08/2007 28 21.2×21.1×11.6 1936.3 3.2

3 9/7/2007 06/08/2007 28 21.4×21.1×11.6 1927.2 3.5

3.4

122

APPENDIX NINE

WATER ABSORPTION TEST RESULT

Table A9.1 Water absorption test result of soil cement block

Cement

content

Sample WW Wd Absorption

Wc

Absorption

1 9492 8165 16.25 4

2 9476 8214 15.36

15.81

1 9629 8522 12.99 6

2 9610 8324 15.45

14.22

1 9991 8717 14.61 8

2 9970 8774 13.63

14.12

1 10285 9038 13.76 10

2 10251 9021 13.63

13.76

1 10189 9303 9.52 12

2 10142 9213 10.08

9.8

123

APPENDIX TEN

COST OF M7 E 380 MACHINERY AND ACCESSORIES

TABLE A10.1 Cost of Haydraform machine and its accessories

Quantity Unit Description Unit Price

(Birr)

Total price

(Birr)

1

1

M7 E 380 Machinery

Block tester

Air Freight

93,534.15

4,035.85

41,356.38

138,926.38

1 PNONS1 Soil mixer

Overall dimension (lxwxh)

mm (2100x950x100) mm

Capacity up to 200lit

16,400.00 16,400.00

1 PNONS1 Motor 2.2kw 960 rpm 1,500.00 1,500.00

1 PNONS1 Soil crusher with out motor

Overall size (lxwxh) mm

(1130x1550x1520) mm

Capacity more than 2m3

Per hr.

6,700.00

6,700.00

1 PNONS1 Motor power, 11kw,

1400rpm`

2,300.00 2,300.00

1 PNONS1 Soil sieve (9100

x1091x1495) mm mainly

made of RHS angle iron,

flat iron and wire mesh

1075.00 1075.00

1 PNONS1 Wheel Barrow 500.00 500.00

Total

167,401.38

124

APPENDIX ELEVEN

PICTURES

asmamaw tadege

Documents