University of Ghana http://ugspace.ug.edu.gh UNIVERSITY OF GHANA COLLEGE OF BASIC AND APPLIED SCIENCES ENGINEERING CHARACTERISTICS OF COMPRESSED EARTH BLOCKS STABILIZED WITH LIME AND COCONUT HUSK ASH BY ALBERTA AFUA YENTUMI (10518475) THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, LEGON IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF MPHIL IN ENGINEERING GEOLOGY DEGREE AUGUST 2022 University of Ghana http://ugspace.ug.edu.gh DECLARATION I therefore declare that this thesis is my own work, based on research I conducted as an MPhil student in the Department of Earth Science at the University of Ghana. It does not contain any previously published materials by another person(s), nor does it contain any materials that have been accepted for the award of any other degree at this University or elsewhere, to the best of my knowledge. All references to the works of other researchers and/or organization(s) have been duly acknowledged. …….……………………….. ……………………………… Alberta Afua Yentumi Date (Student) ………………………………. Dr. Francis Achampong Date (Supervisor) ………………………………… …………………………………… Dr. Edward Kofi Ackom Date (Co-Supervisor) II University of Ghana http://ugspace.ug.edu.gh ABSTRACT The cost of renting or owning a property in Ghana has risen considerably as a result of the country's growing population and increasing demand for housing. Expensive building materials is one of the causes of this situation. There is therefore the need to use locally available building materials to come up with innovative ways to provide sustainable housing for the citizens especially the low- income group. This research aims at investigating the engineering characteristics of compressed earth blocks stabilized with lime and coconut husk ash. Laterite blocks of size 300mm x125mm x 200mm were prepared using the following mix ratios: 0%, 5%, 10% lime, and 0%, 2%, 4% coconut husk ash (CHA). The block samples were tested for density, compressive strength, water absorption and abrasion resistance in order to observe their performance after 7, 14, 21 and 28 days of curing. Dry compressive strength increased by 38% - 110% as the amount of lime and CHA was increased in the blocks. Results show that blocks stabilized with 10% lime and 4% CHA recorded the highest compressive strength with a value of 2.53MPa which falls within the required building standards. The stabilized block samples recorded dry density values that were slightly higher than the un- stabilized block samples, as well as a higher resistance to water absorption than the un-stabilized block The durability of the blocks was determined by subjecting the blocks to abrasion resistance test. The stabilized blocks showed higher resistance as compared to the un-stabilized blocks with the blocks stabilized with 10% lime and 4% lime showed the highest resistance to abrasion of 3.0cm/g. The properties of the blocks were therefore improved by the introduction of lime and coconut husk ash. This study will be of great benefit to the construction industry since it provides a low-cost alternative to sandcrete blocks. These blocks are not only durable but also environmentally friendly. The use of coconut husk in compressed earth blocks also helps in solving regional waste disposal problem. This research will also be of benefit to low-income groups since it promotes affordable housing. III University of Ghana http://ugspace.ug.edu.gh DEDICATION This research is dedicated to God Almighty, my parents, Mr. Lucas Yentumi and Mrs. Evelyn Yentumi and my siblings, Anita Yentumi and Perpetua Yentumi. IV University of Ghana http://ugspace.ug.edu.gh ACKNOWLEDGEMENT I thank the Almighty God for his grace, favor, knowledge, and wisdom e granted me and for a successful completion of my thesis work. I am grateful to Dr. Francis Achampong, my supervisor for his expert guidance and immerse contribution to making this study a success. My heartfelt gratitude goes out to Dr. Edward Ackom, my co-supervisor, for his constructive recommendations and helpful comments in completing this final work. My heartfelt thanks go to my parents, Mr. Lucas Yentumi and Mrs. Evelyn Yentumi, as well as my grandmother, Madam Florence Gadagoe, for their affection and financial support during my studies. My appreciation goes out to Prof. Bruce Banoeng-Yakubo for the financial support to start my MPhil studies. I am also grateful to Madam Olivia Soli, Research Manager, Materials division at Ghana Highway Authority for the opportunity to carry out my laboratory analyses at the Central Materials Laboratory, Ghana Highway Authority. My sincerest gratitude goes out to the staff of the Central Materials Laboratory (Soil and aggregates division) especially Mr. Fredrick Acquah and Joseph Sosu Agbeko for their assistance throughout my laboratory work. My heartfelt thanks go to Mr. Philip Dumegah for his invaluable assistance during this study. Lastly, I would like to thank my colleagues, Andy Naah, Obed Nii Aryie, Adam Baradam, Felicia Yeboah and Yaw Kisser for their support and contributions to the success of this thesis. V University of Ghana http://ugspace.ug.edu.gh TABLE OF CONTENT DECLARATION ......................................................................................................................................... II ABSTRACT ............................................................................................................................................... III DEDICATION ............................................................................................................................................ IV ACKNOWLEDGEMENT ........................................................................................................................... V LIST OF TABLES ................................................................................................................................... VIII LIST OF FIGURES .................................................................................................................................... IX CHAPTER ONE ........................................................................................................................................... 1 INTRODUCTION ........................................................................................................................................ 1 1.1 Background ......................................................................................................................................... 1 1.2 Problem Statement .............................................................................................................................. 3 1.3 Aim and Objectives ............................................................................................................................. 4 1.4 Justification ......................................................................................................................................... 4 1.5 Project Location .................................................................................................................................. 5 1.6 Geology of the Study Area .................................................................................................................. 5 1.7 Relief and Drainage ............................................................................................................................ 6 1.8 Climate ................................................................................................................................................ 6 1.9 Vegetation and Soil ............................................................................................................................. 7 CHAPTER TWO .......................................................................................................................................... 8 LITERATURE REVIEW ............................................................................................................................. 8 2.1 Earth Construction .............................................................................................................................. 8 2.2 Earth Construction Methods ............................................................................................................... 9 2.2.1 Adobe Blocks ............................................................................................................................... 9 2.2.2 Cob ............................................................................................................................................. 10 2.2.3 Rammed Earth ............................................................................................................................ 11 2.2.4 Wattle and daub ......................................................................................................................... 12 2.2.5 Compressed Earth Block (CEB) ................................................................................................ 13 2.3 Stabilizing compressed earth blocks ................................................................................................. 14 VI University of Ghana http://ugspace.ug.edu.gh 2.3.1 Mechanical Stabilization ............................................................................................................ 15 2.3.2 Physical Stabilization ................................................................................................................. 15 2.3.3 Chemical Stabilization ............................................................................................................... 16 2.3.4 Bituminous Stabilization ............................................................................................................ 18 2.3.5 Pozzolana stabilization ............................................................................................................... 19 2.4 Compressed Stabilized Earth Blocks (CSEB) .................................................................................. 19 2.4.1 Advantages of CSEB ................................................................................................................. 20 2.4.2 Disadvantages of CSEBs ........................................................................................................... 21 2.5 Soil properties recommended for CSEB ........................................................................................... 21 2.5.1 General properties ...................................................................................................................... 21 2.5.2 Soil classification ....................................................................................................................... 22 CHAPTER THREE .................................................................................................................................... 26 METHODOLOGY ..................................................................................................................................... 26 3.1 Desk Study ........................................................................................................................................ 26 3.2 Reconnaissance Survey ..................................................................................................................... 26 3.3 Materials ............................................................................................................................................ 26 3.3.1 Soil ............................................................................................................................................. 26 3.3.2 Lime ........................................................................................................................................... 27 3.3.3 Coconut husk .............................................................................................................................. 28 3.3.4 Water .......................................................................................................................................... 28 3.4 Methods ............................................................................................................................................. 29 3.4.1 Laboratory Tests ........................................................................................................................ 29 3.5.2 Preparation of blocks ................................................................................................................. 31 3.5.3 Testing of the Blocks ................................................................................................................. 34 3.6 Data and statistical analysis .............................................................................................................. 37 CHAPTER FOUR ...................................................................................................................................... 38 RESULTS AND DISCUSSION ................................................................................................................. 38 4.1 Geotechnical properties of the Laterite Soil ..................................................................................... 38 4.2 Chemical Composition of Lime and Coconut Husk Ash (CHA) ...................................................... 40 4.3 Density of CSEBs ............................................................................................................................. 41 4.4 Compressive Strength of CEBs ......................................................................................................... 44 VII University of Ghana http://ugspace.ug.edu.gh 4.5 Water Absorption .............................................................................................................................. 47 4.6 Abrasion Resistance .......................................................................................................................... 49 4.7 Cost Analysis .................................................................................................................................... 50 4.7.1 Unit Cost of A Block ................................................................................................................. 50 4.7.2 Comparative Cost Analysis Between A Compressed Stabilized Earth Block And A Sandcrete Block .................................................................................................................................. 51 CHAPTER FIVE ........................................................................................................................................ 53 CONCLUSON AND RECOMMENDATION ........................................................................................... 53 5.1 Conclusion ........................................................................................................................................ 53 5.2 Recommendation .............................................................................................................................. 54 REFERENCES ........................................................................................................................................... 55 APPENDICES ............................................................................................................................................ 63 Appendix A: Particle Size Analysis Test ............................................................................................... 63 Appendix B: Atterberg Limit Test .......................................................................................................... 65 Appendix C: Moisture – Density Relationship ....................................................................................... 67 Appendix D: T-Test ................................................................................................................................ 70 Paired Samples Test ................................................................................................................................ 72 LIST OF TABLES Table 2. 1 Particle size classification based on the Standard (2006) .......................................................... 22 Table 3. 1 Mix Proportions ......................................................................................................................... 32 Table 4. 1 Physical properties of the soil .................................................................................................... 39 Table 4. 2 Chemical compositions of lime and coconut husk ash (CHA) .................................................. 41 VIII University of Ghana http://ugspace.ug.edu.gh Table 4. 3 Dry densities of CEBS ............................................................................................................... 42 Table 4. 4 Compressive strengths of CEBs ................................................................................................. 45 Table 4. 5 One-Way RM ANOVA summary of Compressive strength of CEBs after 28 days curing age ............................................................................................................................................................... 46 Table 4. 6 Coefficient of water absorption of CEBs ................................................................................... 47 Table 4. 7 Abrasion resistance of CEBs ..................................................................................................... 49 Table 4. 8 Unit cost of a compressed stabilized earth blocks ..................................................................... 50 Table 4. 9 Comparative cost analysis between a sandcrete blocks and compressed stabilized earth blocks .......................................................................................................................................................... 52 LIST OF FIGURES Figure 1. 1 Location map of study area ........................................................................................................ 7 Figure 2. 1 The citadel of Bam (Langenbach, 2005) .................................................................................... 9 Figure 2. 2 Adobe blocks (Jarju, 2019) ....................................................................................................... 10 Figure 2. 3 Cob structure (Danso, 2016) ..................................................................................................... 11 Figure 2. 4 Rammed earth (Danso, 2016) ................................................................................................... 12 Figure 2. 5 Wattle and daub house (Bloom, 2010) ..................................................................................... 13 Figure 2. 6 Compressed earth blocks .......................................................................................................... 14 Figure 2. 7 Granular Composition Criteria based on African Regional Standards (1996) ......................... 24 Figure 2. 8 Plasticity Criteria based on African Regional Standards (1996). ............................................. 25 IX University of Ghana http://ugspace.ug.edu.gh Figure 3. 1 Laterite soil ............................................................................................................................... 27 Figure 3. 2 Hydrated lime ........................................................................................................................... 27 Figure 3. 3 Coconut husk and ash ............................................................................................................... 28 Figure 3. 5 Particle sieve analysis ............................................................................................................... 30 Figure 3. 6 Atterberg limits test ................................................................................................................. 31 Figure 3. 7 mixing of the materials ............................................................................................................. 33 Figure 3. 8 Produced Blocks ....................................................................................................................... 33 Figure 3. 9 Compressive Strength test ........................................................................................................ 35 Figure 3. 10 Set-up diagram for capillary water absorption (Danso, 2016) ............................................... 36 Figure 4. 1 Particle size distribution curve of soil used in the study .......................................................... 40 Figure 4. 2 Dry densities of CEBs .............................................................................................................. 43 Figure 4. 3 Average dry densities of the blocks at 28 days of curing ......................................................... 43 Figure 4. 4 Compressive strength of CEBS ................................................................................................ 46 Figure 4. 5 Coefficient of water absorption of CEBs ................................................................................. 48 Figure 4. 6 Abrasion resistance of the CEBs .............................................................................................. 50 X University of Ghana http://ugspace.ug.edu.gh LIST OF ABBREVIATIONS AASHTO American Association of State Highways and Transportation Officials Al2O3 Aluminium oxide ASTM American Society for Testing and Materials BS British Standard CaO Calcium oxide CEB Compressed Earth Block CHA Coconut Husk Ash CSEB Compressed Stabilized Earth Block Fe2O3 Iron (III) oxide K2O Potassium oxide LL Liquid Limit L.O.I Lost On Ignition MDD Maximum Dry Density MgO Magnesium oxide MnO Manganese (II) oxide OMC Optimum Moisture Content PI Plasticity Index PL Plastic Limit P2O5 Phosphorus pentoxide SiO2 Silicon dioxide TiO2 Titanium dioxide XRF X-Ray Fluorescence XI University of Ghana http://ugspace.ug.edu.gh CHAPTER ONE INTRODUCTION 1.1 Background Today, both industrialized and developing countries face significant challenges in terms of sustainable development in the building construction sector. As a result of Ghana's growing population and increasing demand for housing, the cost of renting or owning a home has grown considerably in recent years. The situation has worsened because property suitable for this type of construction is becoming increasingly scarce, especially in smaller towns and cities. Most individuals, particularly those in low and moderate income, are unable to purchase them. High cost of building materials is a major factor that is contributing to this problem. Construction materials account for roughly 60% of the entire cost of a structure (Kerali, 2001). The manufacturing process for these materials is very energy demanding, unfriendly to the environment, and a source of waste (Murmu & Patel, 2018). The use of locally accessible materials and processes in the construction of building can help promote sustainable building (Dayaratne, 2018; Mazraeh & Pazhouhanfar, 2018). Earth building is the most cost-effective way to house the most people while using the fewest resources. The low energy consumption and simplicity of the manufacturing process, justifies their widespread use as a primary housing material in developing countries such as Ghana. However, earthen structures are not limited to developing countries. Several advanced nations, like France, Australia, and many European and Asian countries, continue to have a significant rural population that lives in earthen houses. 1 University of Ghana http://ugspace.ug.edu.gh Because of its minimal carbon output, low heat conductivity, and good hygroscopic qualities, Earth is recognized as an environmentally acceptable alternative (Chauhan et al., 2019 ; Valero et al., 2019). However, some disadvantages of earth building include a lack of strength and durability, as well as vulnerability to rain erosion (Arooz & Halwatura, 2018; Costa et al., 2018; Anysz & Narloch, 2019). Unfortunately, because of these issues, earth building materials have not been used in the construction industry for years and being replaced by long lasting and effective materials such as concrete and burnt bricks (Danja et al., 2017). Growing environmental concerns have resulted in a greater understanding and appreciation of the value of natural earth materials in solving many of the world's environmental and construction issues. When compared to traditional building materials, the usage of earth materials does not result in the same level of resource depletion, pollution, waste generation, or biological changes if properly managed (Bachar et al., 2015). As such, there is the need to device and present technology that can easily be implemented with the country's available resources. Manufacturing of Compressed Stabilized Earth Blocks (CSEB) is one of these technologies. Stabilizers are used in the manufacturing of CSEBs to give enough compressive strength and durability, allowing them to be used as building blocks. To stabilize the compressed earth blocks, this experimental investigation uses lime and coconut husk as partial replacements for cement in certain quantities. 2 University of Ghana http://ugspace.ug.edu.gh 1.2 Problem Statement The cost of renting or owning a property in Ghana has risen considerably over the years as a result of the country's growing population and increasing demand for housing. This is exacerbated by the fact that property suitable for this type of construction is becoming increasingly scarce, particularly in smaller towns and cities. Most people, particularly those with low and moderate incomes, are unable to acquire them. Among other things, the expense of construction materials is to blame for the scarcity and high cost of housing (Tekle, 2018). As a result, suitable and long-term low-cost housing is required in Ghana. Sandcrete block is the most accepted and widely utilized walling material in most underdeveloped countries, and cement is its primary element. The biggest issue with cement manufacture is the fact that raw materials used in its production need to be imported from other countries at a huge cost. This causes the price of cement to keep increasing as the years go by (Danso et al., 2019) Building materials made from locally available natural and renewable materials have been promoted as a means of ensuring a sustainable environment and effective use of resources. One of these alternatives is to replace cement blocks and blocks with earth blocks. As a result, the goal of this research is to come up with alternate wall-building materials. This study therefore seeks to analyze the engineering characteristics of compressed earth blocks stabilized with lime and coconut husk ash. 3 University of Ghana http://ugspace.ug.edu.gh 1.3 Aim and Objectives The aim of this study was to investigate the engineering characteristics of compressed earth blocks stabilized with lime and coconut husk ash. The specific objectives of the study are the following: 1 To produce compressed stabilized earth blocks using lime and coconut husk ash as stabilizers 2 To ascertain the geotechnical properties of compressed earth blocks improved with lime and coconut husk ash 3 To determine the compressive strength of compressed stabilized earth blocks at different ratios of lime and coconut husk ash added to laterite soil 4 To analyze the water absorption and durability of the compressed stabilized earth blocks 5 To carry out a cost comparative analysis between a conventional block and a lime and the compressed stabilized earth block. 1.4 Justification Because developing countries have limited resources, it is critical to find new ways of reducing building expenses, particularly for affordable housing, additionally to apply cheap and efficient repair and maintenance results. This is possible with the help of Compressed Stabilized Earth Blocks (CSEB), which is made from locally available resources. Because of previous failures, CSEB are not frequently used. It is crucial to make people understand that these blocks are strong and long lasting, as this will encourage the use of CSEB and benefit the underprivileged. Furthermore, the utilization of agricultural waste for block production will contribute in the solving of regional waste disposal challenges, fostering healthier environments. 4 University of Ghana http://ugspace.ug.edu.gh This research will be extremely beneficial to the construction industry because it will provide an affordable alternative to sandcrete blocks. The use of coconut husk in compressed earth blocks also helps in solving regional waste disposal problem. This research will also be of benefit to low income groups since it promotes affordable housing. 1.5 Project Location Afienya is in the Ningo-Prampram District, which spans 622.2 square kilometers. Its geographical coordinates are 50 48' 0'' N and 00 10' 0'' E. The area is located 15 kilometers east of Tema and 40 kilometers east of Accra. The Shai-Osudoku district borders it on the north, the Gulf of Guinea on the south, the Ada East district on the east, and the Kpone-Katamanso district on the west. (Ghana Statistical Service, 2014) 1.6 Geology of the Study Area The study area lies within the Accra plains. The area is underlain by ancient igneous rocks. The western boundary contains metamorphosed ancient strata, whereas the south and southeast have relatively new, unconsolidated layers. Situated in the west is the Akwapim range, which is mainly made up of quartzite, mica schist and medium-grained sandstone. The Accra plains itself are mainly occupied by the Dahomeyan gneisses and schists, which are divided into three belts running north – south across the region and consist of a westerly and easterly felsic gneiss belt separated by a mafic gneiss belt. The felsic belt consists mainly of felsic gneiss granitoids whereas the mafic gneisses are entirely garnet-amphibolite gneisses (Ghana Statistical Service, 2014). 5 University of Ghana http://ugspace.ug.edu.gh 1.7 Relief and Drainage The research site is in the heart of Accra's lowlands. The terrain is generally mild and undulating, with a low plain rising to a height of 70 meters. Throughout the area, a few notable inselbergs, isolated hills, outliers, and knolls interrupt the plains in isolated spots. The drainage system in the area is dendritic, with most streams receiving water from the Akwapim range (which also functions as a watershed) and flowing northwest to southwest into coastal lagoons. Most streams that flow across relatively flat terrain have carved out enormous valleys that remain dry for the majority of the year. Because of the seasonal nature of most streams, which is produced by high temperatures and similarly high insulation levels, a variety of artificial dams and ponds of varied sizes have been built for irrigation and recreation (Ghana Statistical Service, 2014). 1.8 Climate Afienya lies in the coastal savanna zone which is two seasonal characterizations: the rainy and dry seasons. There are two rainy seasons in the year: The main rainy season runs from April to July, while the minor season runs from September to November. May, June, and early July see the most rain. Rain falls in intensive short storms and where drainage is poor, local flooding occurs. After the rainy season, there is a long dry period that lasts from December to March. The average yearly rainfall is between 730 and 790 millimeters. Temperatures are high throughout the year, with substantial daily and seasonal changes. In the major rainy season average annual temperatures range between 25oC and 30oC while temperatures range between 27oC and 35oC in the minor season (Ghana Statistical Service, 2014). 6 University of Ghana http://ugspace.ug.edu.gh 1.9 Vegetation and Soil The study area comprises of the following: grassland, shrub land and few patches of semi deciduous forests. The study area has soils comprised of clay, sand, gravel, humus and stone. The sandy and humus quality of the soil promotes vegetable farming, while the clayey nature is used in the manufacture of bricks. The presence of this clay could however have negative effects on general construction activities (Ghana Statistical Service, 2014). Figure 1. 1 Location map of study area 7 University of Ghana http://ugspace.ug.edu.gh CHAPTER TWO LITERATURE REVIEW 2.1 Earth Construction Since time immemorial earth has been used in the construction industry in all parts of the world. This practice existed in most cultures around the world, and in certain nations, it is still the primary method of construction (Costa et al., 2016). Earth has long been utilized as a building material due to its abundance, accessibility, ease of construction, and the properties it exhibits, which imply its building performance. Earth construction has numerous advantages, including the fact that it is fireproof, regulates temperatures, and is 50% to 60% less expensive than typical cement-based construction (Adegun & Adedeji, 2017). Earth-based construction is also less harmful to the environment. When compared to traditional cement blocks, earth blocks utilize up to 30% less water in their creation (Oyelami & Van Rooy, 2016). Earth materials are also recyclable and environmentally friendly as compared to standard blocks that require fossil fuels to manufacture. The oldest known manmade earth constructions, dating back to 10 000 BC, were discovered in Mesopotamia and are made of heaped earth bricks (Vyncke et al., 2018). All around the world, there are many historical monuments composed of earthen structures. Ancient vaults that are present in the Temple of Ramses II at Gourna Egypt, the citadel of Bam in Iran (figure 2.1) and the Great Wall of China, are among the finds (Costa et al., 2016). Earth remains an essential building material up till date with an estimated 30% of the world’s population living in earth buildings (Vyncke et al., 2018). 8 University of Ghana http://ugspace.ug.edu.gh Figure 2. 1 The citadel of Bam (Langenbach, 2005) 2.2 Earth Construction Methods 2.2.1 Adobe Blocks Adobe blocks (figure 2.2) are the most popular types of earth blocks. These blocks are constructed from clay and straw or manure (Wu et al., 2012). They are produced by combining natural occurring clay, water, and sometimes fiber to create a mud-like mixture, which are set into boxes known as "forms." After the blocks are formed the form is removed and the blocks are cured for a month before they are used for building (Molla, 2012). Adobe's strength and resilience varies according to its water content. Excessive water weakens the block. 9 University of Ghana http://ugspace.ug.edu.gh The biggest advantage of adobe over the other ways is that it is the simplest approach and can be used to build a suitable housing with the least amount of construction ability. If done correctly, it can result in robust walls that are largely free of cracks (Yazew, 2015). Figure 2. 2 Adobe blocks (Jarju, 2019) 2.2.2 Cob Cob (figure 2.3), a type of ancient earthen building made of soil and straw, is comparable to adobe (Danso, 2016). Cobs are formed by kneading moist subsoil with sand and unchopped straw into solid mud loaves, then hand-ramming them together to form a self-designed structure. The mud must be hard enough to resist collapse. If the mud sags or spreads, it is either replaced or the rest of the mud is removed and re-fixed on the upper parts. The walls of the structure is best built in 10 University of Ghana http://ugspace.ug.edu.gh phases to ensure the bottom section hardens before continued, as this prevents collapsing. The walls are built in stages to allow each layer to cure before more mud is added. Treating the top surface before adding successive layers ensures that the layers stay together. Cob houses have the advantage of being simple to build and requiring little equipment. Shrinkage cracks, on the other hand, are rather common and can be quite severe (Yazew, 2015). Figure 2. 3 Cob structure (Danso, 2016) 2.2.3 Rammed Earth This approach involves piling moist subsoil into a temporary formwork and compacting it by hand or mechanically. There is no need to wait for each layer to dry out before ramming the layers together until the wall is complete. After the frame is removed, the walls are left to dry naturally. 11 University of Ghana http://ugspace.ug.edu.gh Because of the shuttering required, rammed earth (figure 2.4) is more expensive than cob. Some of them have been around for centuries (Danso, 2016). Figure 2. 4 Rammed earth (Danso, 2016) 2.2.4 Wattle and daub Wattle and daub (figure 2.5) is a technique in which hardwood strips are braided together and coated with a combination of straw and soil. To minimize shrinkage cracks after drying, a highly clayey soil is combined with straw or other vegetable fibers. The wattle and daub technique, like adobe, can be dated back many years and is common in regions of the world for providing shelter from the elements (Tekle, 2018). 12 University of Ghana http://ugspace.ug.edu.gh Figure 2. 5 Wattle and daub house (Bloom, 2010) 2.2.5 Compressed Earth Block (CEB) This method (ie CEB) (figure 2.6) is one that involves mechanically compressing soil particles into a mold to create a soil/earth block. The difference between CEB and rammed earth is that CSEB use a larger formwork to complete a wall. Compacting soil/earth in a mold improves the material's engineering qualities (Tekle, 2018). 13 University of Ghana http://ugspace.ug.edu.gh Figure 2. 6 Compressed earth blocks (www.humanitarianlibrary.org) 2.3 Stabilizing compressed earth blocks Stabilization is the process of mechanically mixing soil and stabilizing agents to create a uniform mixture, or applying a stabilizing agent to undisturbed soil and allowing it to infiltrate through soil voids to achieve contact (Abood et al., 2007). The major reasons for doing soil stabilization are as follows (Firoozi et al, 2017; Rigassi, 1985): • To decrease the volume of interstitial spaces in order to minimize porosity and increase density. • To strengthen the bonds between grains, particularly when the soil is wet. • To enhance the cohesiveness and mechanical characteristics. 14 University of Ghana http://ugspace.ug.edu.gh To increase the quality of soil blocks, a number of soil stabilization technologies are extensively utilized. The following are a few of the most common methods of stabilization. 2.3.1 Mechanical Stabilization This a method of enhancing the strength and durability of soil-aggregate mixes by changing its gradation (Afrin, 2017);(Yoder, 1957). It is also referring to the alteration of soil porosity and inter-particle friction/interlock, which can be accomplished by compaction or other mechanical techniques (Hall et al., 2012). Mechanical energy is used to compact and densify the soil by utilizing rollers, rammers, vibration methods, and, in rare cases, blasting (Afrin, 2017). The purpose of compacting soil is to increase its shear resistance, compressibility, permeability, and porosity (Lemougna et al., 2011). 2.3.2 Physical Stabilization It entails altering soil characteristics by inserting certain size ratios into the distribution of particle size of the soil. The soil texture may be changed by combining different fractions of soil particles together in a measured and controlled manner. Because the grains are packed closer together, most of the holes that existed before physical stabilization are filled. An anisotropic network is formed, which restricts grain movement in a soil. Unfortunately, unlike mechanical stabilization, the effect of physical stability alone is not long-lasting. Soil grains are easily distributed or washed away when saturated with water. Physical soil stabilization should therefore be integrated with the other methods for better outcomes (Tekle, 2018). 15 University of Ghana http://ugspace.ug.edu.gh 2.3.3 Chemical Stabilization Chemicals and emulsions are employed in chemical stabilization as an aid for compaction for soils, water repellents and binders, and to influence the behavior of clay. The additives used in chemical stabilization of soils include hydraulic binders which comprises of Portland cement, lime (Hydrated lime, quicklime, slurry), fly ash, pozzolanic. And organic binders such as polymers and organic resin. 2.3.3.1 Cement Stabilization Cement known as the go-to stabilizing agent because of its ability to cause stabilization effect all by itself (Makusa, 2013). When calcium-aluminates and calcium-silicates, and water interact, they cause hydration which creates compounds of calcium-silicate-hydrate, calcium-aluminate hydrate and calcium hydroxide, which are cementing compounds. Because of the presence of cementitious components and calcium hydroxide, cement may successfully stabilize fine-grained and granular soils as well other soil materials (Onyelowe, 2012). Hydration is a process by which cement, and water react. When cement is mixed with water it hardens up and encloses. Cement hydration is a complex process involving a complex series of unknown chemical reactions. Depending on the soil type, the content of the cement required for adequate stabilization ranges from 4% to 16% by weight (Tekle, 2018). 16 University of Ghana http://ugspace.ug.edu.gh 2.3.3.2 Lime Stabilization Lime is an inorganic mineral that contains lime. It is composed of calcium oxide and/ calcium hydroxide. Lime is a cost-effective method of soil stabilization. When lime is applied to damp soil, it loads the soil with calcium ions. The calcium ions are subsequently replaced by exchangeable cations in the soil components, such as magnesium, sodium, potassium, and hydrogen, in a process known as cation exchange. The volume of the exchange is determined by the number of exchangeable cations contained in the soil's overall cation exchange capacity. Soil grains flocculate and tend to accumulate as a result of cationic exchange and an increase in the number of electrolytes in the pore water. The accumulations in the fine fraction grow. Both the distribution of particle size and the structure of the grain are altered. Lime combines with CO2 in the atmosphere to generate weak carbonated cements. This reaction consumes some of the lime that would otherwise be available for pozzolanic reaction. The material's strength is largely due to the dissolving of clay minerals in an alkaline environment formed by the lime, as well as the recombination of the silicate and alumina in the clays with the calcium to form complex aluminum and calcium silicates, which cement the grams together. The range of lime content required for optimal stability is between 4% and 12% by weight depending on soil type, and this will increase as clay content increases (Tekle, 2018). 2.3.3.3 Fly-Ash Stabilization Fly-ash stabilization has gain popularity in recent years due to its widespread availability. When compared to other ways of soil stabilization, this process is cheap and does not consume so much time. It is a byproduct of coal-fired power plants. Fly-ash is mostly referred to as a secondary 17 University of Ghana http://ugspace.ug.edu.gh binder and, as such, cannot achieve the desired effects on soil stabilization on its own. It can however generate cementing properties when activated (Afrin, 2017). There are two known types of fly ash based on their calcium oxide (CaO) content: class C and class F fly ash. The combustion of sub-bituminous coal produces class C fly ash ashes. Class F fly ashes, on the other hand, are generated by the combustion of arithracite and bituminous coal (Reimer, 1992). 2.3.4 Bituminous Stabilization This method of stabilization involves the mixing of a particular ratio of bituminous soil material or aggregate material which will generate a stable surface (Matthew & Paul, 2018). Bitumen emulsion is classified into two types: anionic bitumen emulsion and cationic bitumen emulsion. Cationic emulsifiers are often based on long hydrocarbon nitrogen compounds such as alkyl amines. These are potent surface-active chemicals with a significant effect on surface tension. Anionic bitumen emulsions are often based on fatty acids, whose molecules are made up of long hydrocarbon chains that terminate with a carboxyl group. The "emulsifier solution" is created by reacting the anionic emulsifier with sodium hydroxide in a process known as saponification. Chemical chemicals that can enter the natural reactions of the soil and control the moisture going to the clay particles, turning the clay portion to permanent cement that binds the mass of aggregate together (Matthew & Paul, 2018). 18 University of Ghana http://ugspace.ug.edu.gh 2.3.5 Pozzolana stabilization Pozzolanas are generally made of aluminous and siliceous materials which don’t have cementing abilities and/or capabilities. However, when in a finely divided form and with moisture present, a chemical reaction with calcium hydroxide at ambient temperatures produces a by-product that possesses cementing compounds (Makusa, 2013). To attain this, the pozzolanas should be finely divided to create a large surface for effective reaction with the alkali solution. Generally, two types of pozzolanas exist which are the natural and artificial pozzolanas. Naturally, they occur as tuff, opaline shale, volcanic ash, pumicite, etc. naturally occurring pozzolanas are used in alkali-silica reactions and in dam controls. Metakaolin, silica fume, coal fly ash, slag, crushed granulated blast furnace, and other artificial pozzolanas can exist. The popularity of pozzolana being used as a temporal substitution for Portland cement or lime has increased massively over the years in the construction discipline. Pozzolana is preferred for usage in structure construction due to its ability to withstand alkali-aggregation reaction and better durability features as a result of its resistance to sulphate attack (Momade & Atiemo, 2004). In the past, pozzolana was mainly used as an additive to cement binders for mass concrete work such as the construction of dams (Kale, 1981). In recent time, there has been leading research in the use of pozzolanic materials as alternative cementing materials as a means of reducing the over dependency on cement. 2.4 Compressed Stabilized Earth Blocks (CSEB) It is a type of building material made of earth that has been uniformly mixed with a stabilizing agent, such as cement or lime, and compressed into a block. CSEBs are modern earth blocks 19 University of Ghana http://ugspace.ug.edu.gh produced in a mechanical press (Postell & Gesimondo, 2011). They are environmentally friendly, strong and long-lasting, and have great insulating capabilities. CSEB is composed of earth mixed uniformly with a stabilizing agent, such as cement or lime, and compressed into a block (Reddy et al., 2007). 2.4.1 Advantages of CSEB According to Auroville Earth Institute report (2005), some of the advantages of CSEBs are: 1. Cost efficiency: Produced locally, with a natural resource and semi-skilled labour, almost without transport, it will be definitely cost effective. 2. Energy efficient and ecofriendly: Requiring only a little stabilizer the energy consumption in a m3 can be from 5 to 15 times less than a m3 of fired bricks. The pollution emission will also be 2.4 to 7.8 times less than fired bricks. 3. Management of resources: Each quarry should be planned for various utilizations: water harvesting pond, wastewater treatment, reservoirs, landscaping, etc. it is crucial to be aware of this point: very profitable if well managed, but disastrous if unplanned. 4. Bio-degradable: Well-designed CSEB houses can withstand, with minimum of maintenance, heavy rains, snowfall or frost without being damaged. The strength and durability have been proven since half a century. 5. Market opportunity: According to the local context (materials, labour, equipment, etc.) the final price will vary, but in most of the cases it will be cheaper than fired bricks. 20 University of Ghana http://ugspace.ug.edu.gh 6. Reducing deforestation: Firewood is not needed to produce CSEB. It will save the forests, which are being depleted quickly in the world, due to short view developments and the mismanagement of resources. 7. Provide local employment: CSEB allow unskilled and unemployed people to learn a skill, get a job and rise in the social values. 2.4.2 Disadvantages of CSEBs 1. Not suitable for high-rise buildings. 2. Correct soil identification is essential. 3. Requires skilled labor. 4. Requires quality control at all stages of production to avoid low-quality products. 5. Low technical performance compared to concrete. 2.5 Soil properties recommended for CSEB 2.5.1 General properties The physical properties of soil are of great importance in the creation of CSEB. These properties determine how the soil will react to the whole stabilization process and the moulding of the blocks. Some of these properties include porosity, permeability, shrinkage, dry compressive strength among others. 21 University of Ghana http://ugspace.ug.edu.gh It is also important to control monitor the amount of clay in the soil before use in CSEBs. Increasing amounts of clay results in expansions in very high degrees when wet. This requires excessive amounts of cement to compensate for this. Vice versa also causes drastically low adhesion between the soil particles and consequently enhances the rate of breakage when demoulding the blocks. A soil containing minimum quantity of silt and clay is suitable for making the blocks. In the case where chemical additives are included in the mixture, then factors such as mineral content, metallic oxides, composition, pH levels and sulphates are of importance (Tekle, 2018). 2.5.2 Soil classification Soils can be classified in several different ways, including its function, origin, size, texture, color, and density. Soil can be classified for building purposes in two ways: plasticity index and particle size distribution analysis. Particle size analysis provides data on the soil's capability to settle tightly into a compact structure, as well as the amount of particles present whereas the plasticity index indicates the particles' cohesiveness (Tekle, 2018). 2.5.2.1 Particle Size Distribution This test determines the mass of particles present in a sample of soil. The classifications are done as gravel, sand, silt and clay. Currently, several particle size classification systems that are used in engineering. The American Society for Testing and Materials Particle Size Classification System (ASTM) which is mostly used in Ghana is illustrated below (Table 2.1). Table 2. 1 Particle size classification based on the Standard (2006) 22 University of Ghana http://ugspace.ug.edu.gh Usually, gravel is not a component in CSEB, as these large particle sizes lead to a rough finished surface. A much more suitable combination would contain clay, silt and sand sized particles. A particle size analysis will bring to light, the percentage of particles in a soil that fall into each of the above size ranges. It is critical that the soil utilized be "well graded" if dense block is to be formed. The fuller curve is the foretold distribution of the particle sizes that results in a perfectly packed form. The fuller distribution can be described as an ideal model, which is impossible in nature. Natural soil with a uniform distribution of particle size, referred to be well graded, is a suitable approximation (Tekle, 2018). The benefit of well-graded soil pertaining to compressed stabilized earth blocks is, the size distribution results in a compact structure possessing an averagely low specific surface area. A dense structure is necessary for several reasons. A closely packed arrangement will contain more touching particles, resulting in a stronger load-bearing backbone. The number and size of inter- particle voids, as well as the number of connected voids, will be reduced, lowering the porosity of the soil and hence its permeability, and thus its susceptibility to water penetration. Because the interlocking calcium silicate matrix extends through the soil voids, a more compact void system necessitates less cement to provide an equally efficient matrix (Tekle, 2018). Based on African Regional Standards (1996) and experiences from laboratory investigations, if a soil has its granular composition falling within the shaded portion of the graph below (figure 2.7), it is considered suitable for block production. Soils with granular compositions beyond the shaded area may still 23 University of Ghana http://ugspace.ug.edu.gh produce acceptable results, but it is advised that they be submitted to a series of tests to determine their suitability (African Regional Standard, 1996). Figure 2. 7 Granular Composition Criteria based on African Regional Standards (1996) 2.5.2.2 Plasticity Index The Atterberg tests are used to measure the plasticity of a soil's finer fraction. The liquid limit test estimates the percentage of water content at which soil transitions from a liquid to a plastic condition. The percentage water content at which the soil transitions from a plastic to a solid form is determined by the plastic limit test. The plasticity index, which is the water content at which the soil is considered plastic, distinguishes the plastic limit from the liquid limit. The soil's fluidity indicates the soil's cohesiveness (Tekle, 2018). 24 University of Ghana http://ugspace.ug.edu.gh Certain criteria have been set to determine the suitable plasticity of a soil for use in CSEB. According to the African Regional Standard (1996), soils that have their plasticity index falling inside the shaded portion of the graph below (figure 2.8) are said to be suitable for block production. Soils that have their plasticity index falling outside the shaded portion are also likely to give suitable results, however they should be subjected to tests to determine their suitability (African Regional Standard, 1996). Figure 2. 8 Plasticity Criteria based on African Regional Standards (1996). 25 University of Ghana http://ugspace.ug.edu.gh CHAPTER THREE METHODOLOGY 3.1 Desk Study Information on previous studies conducted on similar projects was obtained. Articles, journals, and books concerning the research topic were read and information acquired. Such information like a map of the study area, geographic coordinates, the geology of the area and the vegetation were obtained. The desk study was carried out to identify area in Accra with laterite soil deposits. Methods of stabilizing earth blocks was also researched. 3.2 Reconnaissance Survey The study area was then visited to carry out reconnaissance study in order to locate areas where laterite deposits can be found. The availability of the site was assessed, and sampling locations were identified. 3.3 Materials The materials used in this study was laterite soil, lime, coconut husk and water. 3.3.1 Soil The soil sample (figure 3.1) was obtained from Afienya area. A pit was dug using a pickaxe and a shovel and the sample was taken at a depth of 1.5m to 2.0m using the method of disturbed sampling. 26 University of Ghana http://ugspace.ug.edu.gh Figure 3. 1 Laterite soil 3.3.2 Lime Good quality commercially available lime (figure 3.4) was acquired from the local market. The chemical composition of the lime was tested in the Department of Earth Science Geochemical laboratory. Figure 3. 2 Hydrated lime 27 University of Ghana http://ugspace.ug.edu.gh 3.3.3 Coconut husk The coconut husk was collected from coconut vendors in Afienya. The coconut husks were dried in the sun for three days to remove excess moisture and burnt in a controlled environment until it was completely turned to ash. After cooling, the ashes (figure 3.3) were sieved through a 4.75mm sieve. To avoid moisture loss and contamination, the ashes were stored in airtight containers. Figure 3. 3 Coconut husk and its ash 3.3.4 Water Tap water was used throughout the research since it mixes and forms a paste that binds the aggregates together. 28 University of Ghana http://ugspace.ug.edu.gh 3.4 Methods The soil sample was subjected to laboratory examination to determine the mechanical and geotechnical qualities of the soil. The geotechnical qualities were tested at the Ghana Highways Authority's central materials laboratory, while the chemical analysis was performed at the University of Ghana's Department of Earth Science Laboratory. The tests performed include Particle size analysis, Atterberg limits, compaction test and moisture content test. Figure 3.1 illustrated the methodology followed for producing the CSEB. 3.4.1 Laboratory Tests 3.4.1.1 X-Ray Fluorescence Test The chemical composition of hydrated lime and coconut husk ash was determined using an X-Ray Fluorescence (XRF) test at the Department of Earth Science Geochemical laboratory. The percentages of oxides composed in the hydrated lime and coconut husk ash were determined. 3.4.1.2 Particle Size Analysis This test (figure 3.5) was conducted in accordance with ASTM D6913 – 04 (2009) test method. The soil sample was dried in an oven for 24 hours and lumps present were broken down with the used of the mortar and pestle. The soil sample was weighed with the use of a measuring balance and the mass recorded in grams. The sieves were positioned in ascending order of aperture size, with the largest aperture size at the top and the smallest aperture size at the bottom: 19.00mm, 9.5mm, 4.75mm, 2.0mm, 1.0mm, 0.425mm, 0.30mm, 0.15mm and 0.075mm. A pan was then placed under the last sieve to collect soil that passes through No. 200 sieve. The sample was then poured into the first sieve and shaken manually for 15 minutes. The amount of soil remaining on 29 University of Ghana http://ugspace.ug.edu.gh each sieve was weighed and documented. The weight of the soil remaining in the pan was also taken. Figure 3. 4 Particle sieve analysis 3.4.1.3 Atterberg Limit Test Atterberg limit tests (figure 3.6) are used to assess the consistency limits of soils, namely the liquid and plastic limits, from which the plasticity index can be determined. The ASTM D4318-17e1 test method was used to conduct this test. After crushing the soils, they were sieved through a #40 (0.425mm) sieve. For the liquid and plastic limits, a #40 soil passing sieve was used. Plastic and liquid limit values were used to calculate the Plasticity index. The liquid limitations were calculated using the Casagrande cup method. 30 University of Ghana http://ugspace.ug.edu.gh Figure 3. 5 Atterberg limits test 3.4.1.4 Standard Proctor Test The proctor test measures the maximum unit weight of a soil that can be compacted with a regulated compactive force at an optimum water content. The test was carried out in accordance with the ASTM D698-12 test procedure. The standard proctor test was used. The dirt was compressed with a 2.5kg rammer, which was dropped one foot into a mould containing the soil sample. The mould was filled with three equal layers of soil, each of which was subjected to 25 blows. 3.5.2 Preparation of blocks The soil sample was dried in the oven for 24 hours then sieved using a No. 4 sieve (4.75 mm). Soil that passed through the sieve was used in preparing the CSEBs. The soil was measured and spread on a mixing platform, lime and coconut husk ash were also measured and spread on the soil. In 31 University of Ghana http://ugspace.ug.edu.gh this investigation, two different lime contents, 5% and 10% and three different CHA contents, 0%, 2%, and 4% by weight of the soil-were examined for the fabrication of CSEBs. The dry material quantities utilized in each mix design were measured using a weighing balance. The soil was combined until it formed a uniform paste, the required amount of water was measured and poured on top of the paste and mixed until a homogeneous paste was formed. This procedure was repeated for each mixing batch based on the lime-CHA content. The mixture was stirred with a shovel until it was homogeneous (figure 3.7). The blocks were cast in moulds measuring 300 x 125 x 200 mm. The blocks were cured by wrapping them with wet jute bags and placed under a shed. Thirty blocks were created for each mix, making a total of two hundred and ten blocks (210). Five (5) blocks were measured after curing for 7, 14, 21 and 28 days. Each block sample was meticulously labeled for easy identification. Table 3. 1 Mix Proportions Label Laterite (%) Lime (%) CHA (%) B1 (Un-stabilized) 100% 0% 0% B2 95% 5% 0% B3 93% 5% 2% B4 91% 5% 4% B5 90% 10% 0% B6 88% 10% 2% B7 86% 10% 4% 32 University of Ghana http://ugspace.ug.edu.gh Figure 3. 6 mixing of the materials Figure 3. 7 Produced Blocks 33 University of Ghana http://ugspace.ug.edu.gh 3.5.3 Testing of the Blocks The following tests were conducted on the CSEBs, density test, compressive strength test, water absorption test. 3.5.3.1 Density Density was calculated after 7, 14, 21, and 28 days of curing in accordance with British Standard, BS EN 772:11 (2001). The blocks were dried at a constant temperature and measured until they reached a consistent mass. The dimensions of the blocks were measured using a tape measure, and the volume calculated. The weight of the blocks was estimated, and the density calculated using 𝑚 𝜌 = 𝑉 Where ρ = density m = mass v = volume 3.5.3.2 Compressive Strength Test This test was carried out in accordance with ASTM C140. Prior to testing, the surfaces of the blocks were cleaned, then two steel plates were inserted at both ends to ensure even contact and uniform loading. The strain rate is kept constant at 1.0 percent each minute. The maximum load at which failure occurred was measured and the compressive strength calculated as a ratio of the maximum load and the cross-sectional area. The values were measured in MPa. 34 University of Ghana http://ugspace.ug.edu.gh Figure 3. 8 Compressive Strength test 3.5.3.3 Water Absorption by Capillary Action This test was carried out with the purpose of assessing the ability of the block to absorb water after days of curing. Capillary testing for water absorption was carried out according to BS EN 772-11 (2001). After 28 days of curing, block samples were oven dried at 35°C until an uniform mass was achieved. Each block specimen was weighed and recorded in terms of mass. For 10 minutes, each block specimen's bedside (300 x 125 mm) was immersed in a constant head-water bath (figure 3.9) to a depth of 5 mm, and the mass of each water-absorbed block specimen was measured. The water absorption by capillarity rise was calculated using this equation; Cb 35 University of Ghana http://ugspace.ug.edu.gh = g/cm2min. Where; M1 – M2 = mass of absorbed water in grams, S = submerged surface area in centimeter square, t = duration of immersion in minutes. Figure 3. 4 Set-up diagram for capillary water absorption (Danso, 2016) 3.5.3.4 Abrasion resistance test The resistance of a lateritic block to abrasion determines its durability. The test was carried out in line with BS 3921 (1921). It was carried out in order to determine the proportion of soil particles that would be abraded from the block specimens. The blocks were placed on a wooden surface, and a wired bush was stroked 50 times in a forward and backward motion across the surface of the sample. The blocks were weighed on a balance after being brushed through, and the weight after abrasion was recorded. 36 University of Ghana http://ugspace.ug.edu.gh The abrasion coefficient is calculated using the equation. = cm2/g Where; Cu = abrasion coefficient M1-M2 = mass of the material detached by brushing S = Area of the brushed surface 3.6 Data and statistical analysis The data was entered into Excel 2016, which was then utilized to generate analysis graphics. Correlation studies were carried out to discover the correlations between the attributes of the compressed earth block specimens studied. To establish the significant difference between the control and the Lime-CHA stabilized compressed earth blocks, a One-Way Repeated Measures Analysis of Variance (One-Way RM ANOVA) test and a One-Sample t-test were performed using IBM SPSS Statistics version 20. 37 University of Ghana http://ugspace.ug.edu.gh CHAPTER FOUR RESULTS AND DISCUSSION 4.1 Geotechnical properties of the Laterite Soil The index properties of the laterite soil are displayed in table 4.1. The particle size distribution curve (figure 4.1) was generated from the sieve analysis data. The results show that the soil is a fine-grained soil with 58% fines, 8% gravel and 34% sand. The plasticity chart was utilized to accurately characterize the soil. The liquid limit, plastic limit and plasticity Index are 36%, 23% and 13% respectively. The laterite soil is classified as a lean clay (CL) under the Unified classification system and clayey soil under the American Association of State Highways and Transportation Officials (AASHTO) classification system. The soil has a Plasticity Index (PI) of 13%, which is less than the maximum value of 35% prescribed by BS 1377 (1975), indicating that it is an excellent laterite soil that is cohesive and hence easily compacted to improve the laterite's strength and durability. The Optimum Moisture Content (OMC) is 14.3% and the Maximum Dry Density (MDD) is 1990 kg/m3. The amount of water added to the CSEB mix was 14.3% of the total weight of the soil during the mixing process 38 University of Ghana http://ugspace.ug.edu.gh Table 4. 1 Physical properties of the soil Property Parameter Value Grain size distribution Gravel (%) 8 Sand (%) 34 Fines (%) 58 Atterberg Limits Liquid Limit (LL) (%) 36 Plastic Limit (PL) (%) 23 Plasticity Index (PI) (%) 13 Compaction Test Optimum Moisture Content (%) 14.3 Maximum Dry Density (kg/m3) 1990 Soil Classification Unified Soil Classification CL AASHTO Classification A- 6 39 University of Ghana http://ugspace.ug.edu.gh Figure 4. 1 Particle size distribution curve of soil used in the study 4.2 Chemical Composition of Lime and Coconut Husk Ash (CHA) The XRF test results are displayed in table 4.2. The chemical composition of CHA comprised of 34.5% Silicon dioxide (SiO2), 6.24% Aluminium oxide (Al2O3), 3.56% Iron (III) oxide (Fe2O3), 15.00% Calcium oxide (CaO), 9.49% Magnesium Oxide (MgO). According to ASTM C618 (1978) pozzolanas should have combined proportion of SiO2, Al2O3 and Fe2O3 of not less than 70%. Results of the X-ray fluorescence test showed that CHA was comprised of 34.5% SiO2, 6.24% Al2O3, 3.56% Fe2O3 which when summed does not meet the minimum requirement of 70% for pozzolanic materials. Hydrated lime is predominantly made up of CaO which comprises of 97.3%. 40 University of Ghana http://ugspace.ug.edu.gh Table 4. 2 Chemical compositions of lime and coconut husk ash (CHA) Compound Chemical Composition (%) Hydrated Lime Coconut Husk Ash (CHA) SiO2 0.21 34.5 Al2O3 0.20 6.24 Fe2O3 0.06 3.56 CaO 97.3 15.0 MgO 1.24 9.49 K2O 0.03 13.2 TiO2 0.03 0.52 MnO 0.01 0.18 P2O5 0.00 4.41 Na2O 0.00 9.05 LOI N/A N/A 4.3 Density of CSEBs The density test was conducted to determine the physical qualities of CEBs. Five block samples were tested for each mix ratio. The mean value of each test was recorded. The density was in kilograms per cubic meter (kg/m3). Figure 4.4 depicts a graphical representation of the compressed 41 University of Ghana http://ugspace.ug.edu.gh earth blocks' mean dry densities. In this investigation, the dry density of the blocks varied from 1726 kg/m3 to 1966 kg/m3. These values fall within the BS 6073 range of 1500kg/m3 – 2400kg/m3 for dense aggregates masonry units. According to the findings, there was an increase in dry density values as the number of curing days increased. The dry density mean values of the un-stabilized block samples and the Lime-CHA block samples were similar for all curing days. This suggests that the density of the block specimen did not change noticeably as a result of the addition of the lime and CHA. Danso et al. (2019) used clay pozzolana in a prior work, and the density of the specimens seemed to be about the same. This was attributable to a constant compaction rate and an identical quantity of the mix utilized for each test block sample, as corroborated by an earlier analysis (Danso et al., 2015). For samples B1, B2, B3, B4, B5, B6, and B7, the mean dry densities were 1726.25kg/m3, 1782.25kg/m3, 1823.5kg/m3, 1856kg/m3, 1838kg/m3, 1897kg/m3, and 1972kg/m3. Table 4. 3 Dry densities of CEBS Mix ratio 7days (kg/m3) 14 days (kg/m3) 21days (kg/m3) 28 days (kg/m3) B1 (control) 1632 1725 1760 1788 B2 (5% lime & 0% CHA) 1743 1788 1794 1804 B3 (5% lime & 2% CHA) 1810 1820 1826 1838 B4 (5% lime & 4% CHA) 1830 1856 1863 1875 B5 (10% lime & 0% CHA) 1827 1840 1841 1844 B6 (10% lime & 2% CHA) 1879 1902 1903 1904 B7 (10% lime & 4% CHA) 1926 1980 1989 1993 42 University of Ghana http://ugspace.ug.edu.gh 2500 2000 1500 1000 500 0 7 days 14 days 21 days 28 days Curing days B1 B2 B3 B4 B5 B6 B7 Figure 4. 2 Dry densities of CEBs 2000 1900 1800 1700 1600 B1 B2 B3 B4 B5 B6 B7 Lime-CHA Content Figure 4. 3 Average dry densities of the blocks at 28 days of curing 43 University of Ghana http://ugspace.ug.edu.gh 4.4 Compressive Strength of CEBs Results of the compressive strength test are displayed in figure 4.4. There was increasing strength as number of curing days increased. It can also be seen that all of the Lime-CHA stabilized block specimens outperformed the un-stabilized block specimens in compressive strength. The block samples containing higher amounts of lime and coconut husk showed higher compressive strength values as compared to those with lower lime-CHA content. The increase in strength is due to the stabilizers' combination with water, which creates strong and rigid hydrates, fills voids, and binds particles together independently of soil reactions (Danso et al., 2019). On the 28th day of curing, the compressive strengths of the compressed earth blocks were 1.20 MPa, 1.65 MPa, 1.87 MPa, 2.35 MPa, 2.10 MPa, 2.48 MPa, and 2.53 MPa for B1, B2, B3, B4, B5, B6, and B7, respectively. The compressive strength of all the blocks were within the prescribed minimum values for usage in structural work of 1 MPa (TS 704, 2001) and 2 MPa (Houben & Guillaud, 1994). The compressive strength of the block specimens with a 10% Lime-4% CHA (B7) composition was 110% higher than that of the un-stabilized block samples. The purpose of carrying out One-Way RM ANOVA test was to determine if there was a significant difference in compressive strength between the un-stabilized and stabilized after 28 days of curing. The test result yielded a p-value of 0.001, indicating a statistically significant difference between the un-stabilized block specimens and the Lime-CHA block samples. This means that the addition of lime and CHA to compacted earth blocks considerably improved their mechanical properties. 44 University of Ghana http://ugspace.ug.edu.gh To determine the pair where the difference occurred, a paired sample t-test was used. The results show that there is no statistically significant difference between the pairs B1-B2, B3-B5, and B4- B5. Apart from that, all the other block pairs differ significantly. Table 4. 4 Compressive strengths of CEBs Batch 7 DAYS (MPa) 14 DAYS (MPa) 21 DAYS (MPa) 28 DAYS (MPa) B1 0.67 0.74 1.00 1.20 B2 0.72 0.83 1.18 1.65 B3 0.80 0.97 1.30 1.87 B4 0.94 1.15 1.80 2.35 B5 0.86 1.11 1.66 2.10 B6 0.99 1.34 1.95 2.48 B7 1.08 1.48 2.15 2.53 45 University of Ghana http://ugspace.ug.edu.gh B1 B2 B3 B4 B5 B6 B7 3 2.5 2 1.5 1 0.5 0 7 DAYS 14 DAYS 21 DAYS 28 DAYS CURING DAYS Figure 4. 4 Compressive strength of CEBS Table 4. 5 One-Way RM ANOVA summary of Compressive strength of CEBs after 28 days curing age Sample Mean compressive Standard deviation F- value P-value strength B1 0.9275 0.2860 17.808 0.000 B2 1.0950 0.4188 B3 1.2350 0.4714 B4 1.5600 0.6414 B5 1.4325 0.5565 B6 1.6900 0.6593 B7 1.8100 0.6521 46 University of Ghana http://ugspace.ug.edu.gh 4.5 Water Absorption The ability of the bricks specimen to absorb water after being partially immersed in water for 10 minutes was studied in this test. In general, the blocks with high coefficients have a high absorption rate and consequently high porosity, whiles samples with low coefficients are less porous and absorb less water. The rate of water absorption by compressed earth block samples decreased gradually as the quantity of Lime-CHA in the block samples increased (figure 4.6). The un- stabilized block samples had the maximum water absorption of 12.2, whereas the stabilized earth blocks with 10% lime-40% CHA had the lowest water absorption of 2.94. The enhanced water absorption of CEBs could be ascribed to the stabilizer’s capacity to plug spaces between soil particles, reducing the blocks' porosity (Danso et al., 2015). Table 4. 6 Coefficient of water absorption of CEBs Sample Dry mass Wet mass (kg) Coefficient of water Mean Coefficient of Water (Kg) absorption (g/cm2min) Absorption(g/cm2min) B1 13.5 14.7 10.11 13.5 15.2 14.33 12.2 B2 12.8 14.2 11.8 11.8 12.8 14.2 11.8 B3 12.0 14.2 9.28 9.28 12.0 14.2 9.28 47 University of Ghana http://ugspace.ug.edu.gh B4 13.8 14.7 7.59 7.59 13.8 14.7 7.59 B5 13.1 14.1 8.01 8.01 13.1 14.1 8.01 B6 13.6 14.1 4.21 4.21 13.6 14.1 4.21 B7 13.9 14.3 2.94 2.94 13.9 14.3 2.94 14 12 10 8 6 4 2 0 B1 B2 B3 B4 B5 B6 B7 Lime-CHA Content Figure 4. 5 Coefficient of water absorption of CEBs 48 University of Ghana http://ugspace.ug.edu.gh 4.6 Abrasion Resistance From the results, the block samples generally showed a steady increase in their resistance to abrasion (wear) as the amount of stabilizer were increased. The un-stabilized block samples had the lowest resistance to abrasion with a value of 0.60cm2/g whiles the highest abrasion resistance value was recorded by blocks stabilized with 10% lime- 4%CHA with a value of 3.0cm2/g. The increase in abrasion resistance of the soil blocks as the stabilizers increase is attributed to the improved cementitious action between the stabilizers and that of the soil resulting in an enhanced bond strength which holds the particles in a matrix. Table 4. 7 Abrasion resistance of CEBs Sample Mean Abrasion resistance (cm2/g) B1 0.60 B2 0.86 B3 1.00 B4 1.04 B5 2.00 B6 2.25 B7 3.00 49 University of Ghana http://ugspace.ug.edu.gh 3.5 3 2.5 2 1.5 1 0.5 0 B1 B2 B3 B4 B5 B6 B7 Lime-CHA Content Figure 4. 6 Abrasion resistance of the CEBs 4.7 Cost Analysis 4.7.1 Unit Cost of A Block Table 4. 8 Unit cost of a compressed stabilized earth blocks Material Quantity Calculation Cost Laterite 1 Cement bag GHS 32.00 Lime 1 bag GHS 105.00 Coconut husk GHS 0.00 Laterite 1 4L container 32 GHS 4.00 8 Lime 1 4L container GHS 13.12 105 8 50 University of Ghana http://ugspace.ug.edu.gh Laterite 10 parts 10 x 4.00 GHS 40.00 Lime 1 part 1 x 13.12 GHS 13.12 CSEB 40 40.00 +13.12 GHS 53.12 Cost of 1 CSEB 53.12 GHS 1.32 40 Labour 10% of the unit GHS 0.13 cost of CSEB 1.32 𝑋 10 100 Water 1.32 𝑋 20 GHS 0.26 20% of the unit 100 cost of CSEB Total cost of a unit compressed earth block = 1.32+0.13+0.26 = GHS 1.70 From the calculations above, the unit cost of a compressed earth block is GHS 1.70. 4.7.2 Comparative Cost Analysis Between A Compressed Stabilized Earth Block And A Sandcrete Block The Comparative cost analysis between Compressed Stabilized Earth Blocks (CSEB) and Sandcrete blocks (SBs) for residential buildings in Ghana was conducted through quantitative and case study approaches. The estimation was done for a single room. Prices of SBs were obtained from various building materials shops in Accra. 51 University of Ghana http://ugspace.ug.edu.gh Table 4. 9 Comparative cost analysis between a sandcrete blocks and compressed stabilized earth blocks SANDCRETE BLOCKS COMPRESSED STABILIZED EARTH BLOCKS For a single room of area 12 x 12, For a single room of area 12 x 12, approximately 500 blocks will be required approximately 800 blocks will be required If a block = GHS 4.00 If a block = GHS 1.70 Then 500 blocks = GHS 2000.00 Then 800 blocks = GHS 1,360.00 The cost difference between using SB and CSEB = GHS 640.00. Results from the cost analysis shows that the cost of incurred in the use of CSEB for the construction of proposed single room is cheaper than using sandcrete blocks. The cost of production is reduced by 38%. 52 University of Ghana http://ugspace.ug.edu.gh CHAPTER FIVE CONCLUSON AND RECOMMENDATION 5.1 Conclusion The main objective of this study was to investigate the engineering characteristics of compressed earth blocks stabilized with lime and coconut husk ash. Based on the investigations and deduction from the results, the following conclusions are drawn 1. Laterite soil from Afienya shows acceptable properties in regard to its physical and chemical compositions for the production of compressed stabilized earth blocks. 2. There was no noticeable change in densities of the stabilized and un-stabilized blocks. 3. The compressive strength test results showed significant increase in strength of the stabilized blocks than the un-stabilized block. The tests further suggest a statistically significant difference in strengths based on the p-value of 0.001. 4. The water absorption results showed that the stabilized blocks absorbed less water as compared to the un-stabilized blocks which is an improvement with sample B7 being the most promising. 5. Lastly, the stabilized blocks were significantly resistant to abrasion as compared to the un- stabilized blocks with sample B7 being the most durable. 6. For practically all of the studies, the highest improvements were reported at the 10% Lime- 4% CHA contents, and hence 10% Lime-4% CHA content is recommended for usage in earthen buildings. 53 University of Ghana http://ugspace.ug.edu.gh 7. Results of the cost analysis shows that the cost incurred in the use of CSEB for the construction of the proposes single room is cheaper than using sandcrete blocks. The cost of production is reduced by 38%. 5.2 Recommendation 1. Studies should be carried out on soils from different areas to better understand the effects of lime and coconut husk ash as stabilizers. 2. The influence of lime and coconut husk ash must be considered when determining the maximum dry density to be employed in production. 3. Wet compressive strength should also be assessed to better understand the blocks performance in humid environment. 54 University of Ghana http://ugspace.ug.edu.gh REFERENCES Abood, T. T., Kasa, A. Bin, & Chik, Z. Bin. (2007). [Stabilization of silty clay soil using chloride compounds]. Engineering Science and Technology, 2(1). Adegun, O. B., & Adedeji, Y. M. D. (2017). Review of economic and environmental benefits of earthen materials for housing in Africa. In Frontiers of Architectural Research (Vol. 6, Issue 4). https://doi.org/10.1016/j.foar.2017.08.003 Afrin, H. (2017). A Review on Different Types Soil Stabilization Techniques. International Journal of Transportation Engineering and Technology, 3(2). https://doi.org/10.11648/j.ijtet.20170302.12 Ali Akbar Firoozi, C. Guney Olgun, Ali Asghar Firoozi & Mojtaba Shojaei Baghini . 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Ankara: Turkish Standard Institution. Venkatarama Reddy, B. V., Lal, R., & Nanjunda Rao, K. S. (2007). Enhancing Bond Strength and Characteristics of Soil-Cement Block Masonry. Journal of Materials in Civil Engineering, 19(2), 164–172. https://doi.org/10.1061/(ASCE)0899-1561(2007)19:2(164) Vyncke, J., Kupers, L., & Denies, N. (2018). Earth as Building Material - An overview of RILEM activities and recent Innovations in Geotechnics. MATEC Web of Conferences, 149, 1–7. https://doi.org/10.1051/matecconf/201714902001 Wu, F., Li, G., Li, H. N., & Jia, J. Q. (2012). Strength and stress–strain characteristics of traditional adobe block and masonry. Materials and Structures 2012 46:9, 46(9), 1449–1457. https://doi.org/10.1617/S11527-012-9987-Y Yazew, S. (2015). Study of Plastic Soil Cement for Flooring Application. http://thesisbank.jhia.ac.ke/id/eprint/7655 Yoder, E. (1957). Principles of Soil Stabilization: Technical Report. https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1877&context=jtrp 62 University of Ghana http://ugspace.ug.edu.gh APPENDICES Appendix A: Particle Size Analysis Test CENTRAL MATERIALS LABORATORY DRAFT FORM Date 16/06/21 WASHED SAMPLE ANALYSIS MOIST GRANDUAL Technician SOIL SAMPLE NO. SAMPLE LOCATION AFIENYA SAMPLE DESCRIPTION LATERITE MASS SAMPLE RECEIVED 1090.0 GRADING OF AIR-DRY COURSE AGGREGATE AIR-DRY MOISTURE CONTENT Sieve Mass Dry Percent Percent Passing Retained Aperture Retained Mass Retained Passing 19.00mm 19.00mm 75.0 Container No. Z - 7 53.0 Mass Moist Agg + 1531.0 Cont 37.5 Mass Dry Agg+ Cont 1501.5 26.5 Mass of container 962.0 19.0 Mass of water 29.5 Pan Mass of Dry 539.5 Aggregate Total Dry Moisture Content 5.47 Mass 63 University of Ghana http://ugspace.ug.edu.gh GRADING OF MINUS 19mm FRACTION BOWL NO. B – 9 Mass Bowl No. 867.5 Mass Bowl + air dry (moist) sub sample 1385.0 Mass air dry ( moist) sub-sample 517.5 Mass dry sample 490.7 Mass Bowl + dry sample after washing 1206 Mass dry sample after washing 338.5 Mass minus 0.075 washed away 152.2 Sieve Aperture Mass Retained Percentage Percentage Percentage Total (g) Retained (%) Passing (%) Passing (mm) Sample 19.0 0.00 0.00 100.00 100 9.5 0.00 0.00 100.00 100 4.75 36.5 7.35 92.65 93 2.00 108.0 21.74 70.91 71 1.00 45.5 9.16 61.75 62 0.425 45.5 9.16 52.58 53 0.300 26.0 5.23 47.35 47 0.150 50.0 10.07 37.28 37 0.075 28.5 5.74 31.54 32 Pan 4.5 0.91 Mass Washed 152.17 30.64 away Total 344.5 100 64 University of Ghana http://ugspace.ug.edu.gh Appendix B: Atterberg Limit Test Liquid Limit Type of test Casagrande cup liquid limit Test number 1 (27-35) 2 (23-27) 3 (22-25) Number of blows 31 27 18 Container number 511 518 544 Mass of wet soil + Container 25.13 27.34 29.58 Mass of dry soil + Container 21.23 22.58 23.98 Mass of container 9.47 9.51 9.53 Mass of water 3.9 4.76 5.6 Mass of dry soil 11.76 13.07 14.45 Moisture content 33.2 36.4 38.8 65 University of Ghana http://ugspace.ug.edu.gh 60 50 40 30 20 15 20 25 30 35 Number of blows Relationship between moisture content and number of blows Plastic Limit Type of test Plastic Limit Test number 1 2 Container number C0 H4 Mass of wet soil + Container 13.63 13.59 Mass of dry soil + Container 11.74 11.70 Mass of container 3.35 3.28 Mass of water 1.89 1.89 Mass of dry soil 8.39 8.42 Moisture content 22.5 22.4 66 University of Ghana http://ugspace.ug.edu.gh Appendix C: Moisture – Density Relationship GHANA HIGHWAY AUTHORITY FORM S1/2 DATE MATERIALS DIVISION MOISTURE –DENSITY RELATIONSHIP MINUS 19mm FRACTION SAMPLE NUMBER Mass minus 19mm Mass plus 19mm Total mass % Oversize Row Parameter Specimen Specimen Specimen Specimen Specimen Specimen Specimen Specimen 1 2 3 4 5 6 7 8 1 Container No. 2 Mass air-dry sample (g) 3 Mass water added (g) 4 Percent water added 0% 3% 6% 9% 12% 4.35% 4.35% 4.35% 5 Estimated air-dry MC (%) 6 Est. compaction MC. (%) (4) + (5) 7 Mould Number M2 M2 M2 M2 M2 M2 ST ZM8 8 Mould factor 0.4727 0.4727 0.4727 0.4727 0.4727 0.4727 0.4727 0.4727 9 Mass of mould (g) 4175 4175 4175 4175 4175 4175 4120 4092 10 Mass of mould + wet 8045 8657 8910 8748 8580 8965 8635 8296 soil. (g) University of Ghana http://ugspace.ug.edu.gh 11 Mass of wet soil. (g) 3870 4482 4735 4573 4405 4790 4515 4204 (10)- (9) 12 Wet density. 1829 2119 2238 2162 2082 2264 2134 1987 Kg/cu.m. (11) *(8) 80 13 Approx. Dry density. 1829 2057 2111 2040 1859 2170 2045 1904 100*(12)/(100+ (6)) MOISTURE CONTENT DETERMINATION 14 Oven-pan Number MKZ MAS CRO BNS UNO ORC ORS KAM 15 Mass Oven-pan (Kg) 1.205 1.203 0.835 1.049 1.188 0.853 0.800 0.926 16 Mass oven-pan + wet 1727 1728 1740 1754 1777 1755 1732 1745 soil (g) 17 Mass Oven-pan + dry 1680.5 1669.0 1617.0 1644.0 1673.5 1642.5 1615.0 1643.0 soil (g) 18 Mass of water (g). (16) 46.5 59 123 110 103.5 112.5 115 102 – (17) 19 Mass of dry soil (g). 475.5 466 782 595 485.5 789.5 815 717 (17) – (15) 20 MOISTURE 9.8 12.7 15.7 18.5 21.2 14.2 14.1 14.2 CONTENT 21 Black Calc. Air –dry MC (%) (20) –(4) 22 Dry density. 1666 1880 1934 1824 1718 1982 1870 1740 100*(12)/(100+(20)) 23 RELATIVE COMP. 100*(DD/MDD) 100% 94% 87% University of Ghana http://ugspace.ug.edu.gh 2000 MDD 1900 1800 1700 1600 8 13 OMC 18 23 Moisture Content (%) Relationship between dry density and moisture content 69 University of Ghana http://ugspace.ug.edu.gh Appendix D: T-Test Paired Samples Statistics Mean N Std. Std. Error Deviation Mean B1 .9275 4 .28605 .14303 Pair 1 B2 1.0950 4 .41877 .20938 B1 .9275 4 .28605 .14303 Pair 2 B3 1.2350 4 .47149 .23574 B1 .9275 4 .28605 .14303 Pair 3 B4 1.5600 4 .64140 .32070 B1 .9275 4 .28605 .14303 Pair 4 B5 1.4325 4 .55650 .27825 B1 .9275 4 .28605 .14303 Pair 5 B6 1.6900 4 .65934 .32967 B1 .9275 4 .28605 .14303 Pair 6 B7 1.8100 4 .65212 .32606 B2 1.0950 4 .41877 .20938 Pair 7 B3 1.2350 4 .47149 .23574 B2 1.0950 4 .41877 .20938 Pair 8 B4 1.5600 4 .64140 .32070 B2 1.0950 4 .41877 .20938 Pair 9 B5 1.4325 4 .55650 .27825 B2 1.0950 4 .41877 .20938 Pair 10 1.6900 4 .65934 .32967 B6 1.0950 4 .41877 .20938 B2 1.8100 4 .65212 .32606 Pair 11 B7 B3 1.2350 4 .47149 .23574 Pair 12 1.5600 4 .64140 .32070 B4 1.2350 4 .47149 .23574 B3 1.4325 4 .55650 .27825 Pair 13 B5 B3 1.2350 4 .47149 .23574 Pair 14 1.6900 4 .65934 .32967 70 University of Ghana http://ugspace.ug.edu.gh B6 B3 1.2350 4 .47149 .23574 Pair 15 1.8100 4 .65212 .32606 B7 Pair 16 B4 1.5600 4 .64140 .32070 B5 1.4325 4 .55650 .27825 B4 1.5600 4 .64140 .32070 Pair 17 1.6900 4 .65934 .32967 B6 B4 1.5600 4 .64140 .32070 Pair 18 1.8100 4 .65212 .32606 B7 B5 1.4325 4 .55650 .27825 Pair 19 1.6900 4 .65934 .32967 B6 B5 1.4325 4 .55650 .27825 Pair 20 1.8100 4 .65212 .32606 B7 B6 1.6900 4 .65934 .32967 Pair 21 1.8100 4 .65212 .32606 B7 71 University of Ghana http://ugspace.ug.edu.gh Paired Samples Test Paired Differences t df Sig. (2-tailed) Mean Std. Deviation Std. Error 95% Confidence Interval of the Mean Difference Lower Upper Pair 1 B1 - B2 -.16750 .13326 .06663 -.37955 .04455 -2.514 3 .087 Pair 2 B1 - B3 -.30750 .18839 .09420 -.60727 -.00773 -3.264 3 .047 Pair 3 B1 - B4 -.63250 .35743 .17872 -1.20126 -.06374 -3.539 3 .038 Pair 4 .27598 -3.660 .035 B1 - B5 -.50500 .13799 -.94415 -.06585 3 Pair 5 B1 - B6 -.76250 .37933 .18967 -1.36610 -.15890 -4.020 3 .028 Pair 6 .38117 -4.630 .019 B1 - B7 -.88250 .19059 -1.48903 -.27597 3 Pair 7 .05888 -4.756 .018 B2 - B3 -.14000 .02944 -.23369 -.04631 3 Pair 8 B2 - B4 -.46500 .23116 .11558 -.83282 -.09718 -4.023 3 .028 Pair 9 .15840 -4.261 .024 B2 - B5 -.33750 .07920 -.58956 -.08544 3 Pair 10 .25736 -4.624 .019 Pair 11 B2 - B6 -.59500 .27234 .12868 -1.00451 -.18549 -5.251 3 .013 Pair 12 .19140 -3.396 .043 B2 - B7 -.71500 .13617 -1.14835 -.28165 3 Pair 13 .12868 -3.070 .055 B3 - B4 -.32500 .09570 -.62956 -.02044 3 B3 - B5 -.19750 .06434 -.40226 .00726 3 Pair 14 B3 - B6 -.45500 .21564 .10782 -.79813 -.11187 -4.220 3 .024 Pair 15 .24090 -4.774 .017 B3 - B7 -.57500 .12045 -.95833 -.19167 3 Pair 16 .09142 2.789 .068 University of Ghana http://ugspace.ug.edu.gh B4 - B5 .12750 .04571 -.01798 .27298 3 Pair 17 B4 - B6 -.13000 .05888 .02944 -.22369 -.03631 -4.416 3 .022 Pair 18 .10551 -4.739 .018 B4 - B7 -.25000 .05276 -.41790 -.08210 3 Pair 19 .10500 -4.905 .016 Pair 20 B5 - B6 -.25750 .11587 .05250 -.42458 -.09042 -6.516 3 .007 B5 - B7 -.37750 .05793 -.56187 -.19313 3 Pair 21 B6 - B7 -.12000 .06481 .03240 -.22312 -.01688 -3.703 3 .034 University of Ghana http://ugspace.ug.edu.gh