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Characterizing Compressed Earth Bricks Based on Hygrothermal Aging and Wind-Driven Rain Erosion

Permanent Link: http://ufdc.ufl.edu/UFE0043055/00001

Material Information

Title: Characterizing Compressed Earth Bricks Based on Hygrothermal Aging and Wind-Driven Rain Erosion
Physical Description: 1 online resource (63 p.)
Language: english
Creator: EXELBIRT,JOSEPH
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: ACCELERATED -- BRICKS -- COMPRESSED -- CONSTRUCTION -- DEVELOPING -- EARTH -- ERROSION -- NATIONS -- SUSTAINABILITY -- SUSTAINABLE
Building Construction -- Dissertations, Academic -- UF
Genre: Building Construction thesis, M.S.B.C.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Building Construction CHARACTERIZING COMPRESSED EARTH BRICKS BASED ON HYGROTHERMAL AGING AND WIND-DRIVEN RAIN EROSION By Joseph Exelbirt May 2011 Chair: Esther Obonyo Cochair: Charles Kibert Major: Building Construction The rapidly increasing demand for affordable housing in developing countries has highlighted the need for sustainable housing options, especially given the inadequate supply of traditional building materials. While advances in the design and use of compressed earth bricks (CEBs) present a viable solution to this dilemma, there have been significant concerns about their durability in tropical environments. The objective of this research is to evaluate the durability of CEBs using hygrothermal aging and wind-driven rain (WDR) erosion tests. Hygrothermal aging was performed by exposing different CEBs samples to 100?C and 100% humidity for 7 days and then conducting an analysis using scanning electron microscopy (EDS), which determined that Soil Cement CEB showed the least deviation in the chemical reaction of the focal elements. The WDR erosion test revealed that the soil cement CEB had the least erosion from the rest of the CEBs. In conclusion, the stability of CEBs appears to vary depending on the constituent ingredients and stabilization techniques used. Based on this research it was shown that there is a correlation between elemental composition and erosion levels of the CEBs. The CEB that has the least microstructural change at the elemental level had the least erosion levels from the exposure to WDR acceleration.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by JOSEPH EXELBIRT.
Thesis: Thesis (M.S.B.C.)--University of Florida, 2011.
Local: Adviser: Obonyo, Esther.
Local: Co-adviser: Kibert, Charles J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043055:00001

Permanent Link: http://ufdc.ufl.edu/UFE0043055/00001

Material Information

Title: Characterizing Compressed Earth Bricks Based on Hygrothermal Aging and Wind-Driven Rain Erosion
Physical Description: 1 online resource (63 p.)
Language: english
Creator: EXELBIRT,JOSEPH
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2011

Subjects

Subjects / Keywords: ACCELERATED -- BRICKS -- COMPRESSED -- CONSTRUCTION -- DEVELOPING -- EARTH -- ERROSION -- NATIONS -- SUSTAINABILITY -- SUSTAINABLE
Building Construction -- Dissertations, Academic -- UF
Genre: Building Construction thesis, M.S.B.C.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Building Construction CHARACTERIZING COMPRESSED EARTH BRICKS BASED ON HYGROTHERMAL AGING AND WIND-DRIVEN RAIN EROSION By Joseph Exelbirt May 2011 Chair: Esther Obonyo Cochair: Charles Kibert Major: Building Construction The rapidly increasing demand for affordable housing in developing countries has highlighted the need for sustainable housing options, especially given the inadequate supply of traditional building materials. While advances in the design and use of compressed earth bricks (CEBs) present a viable solution to this dilemma, there have been significant concerns about their durability in tropical environments. The objective of this research is to evaluate the durability of CEBs using hygrothermal aging and wind-driven rain (WDR) erosion tests. Hygrothermal aging was performed by exposing different CEBs samples to 100?C and 100% humidity for 7 days and then conducting an analysis using scanning electron microscopy (EDS), which determined that Soil Cement CEB showed the least deviation in the chemical reaction of the focal elements. The WDR erosion test revealed that the soil cement CEB had the least erosion from the rest of the CEBs. In conclusion, the stability of CEBs appears to vary depending on the constituent ingredients and stabilization techniques used. Based on this research it was shown that there is a correlation between elemental composition and erosion levels of the CEBs. The CEB that has the least microstructural change at the elemental level had the least erosion levels from the exposure to WDR acceleration.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by JOSEPH EXELBIRT.
Thesis: Thesis (M.S.B.C.)--University of Florida, 2011.
Local: Adviser: Obonyo, Esther.
Local: Co-adviser: Kibert, Charles J.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2011
System ID: UFE0043055:00001


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1 CHARACTERIZING COMPRESSED EARTH BRICKS BASED ON HYGROTHERMAL AGING AND WIND DRIVEN RAIN EROSION By JOSEPH EXELBIRT A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUI REMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN BUILDING CONSTRUCTION UNIVERSITY OF FLORIDA 2011

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2 2011 Joseph Exelbirt

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3 To my wife Michele and my daughters Rachel, Leah and Tasha

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4 ACKNOWLEDGMENTS I would like to thank my fam ily and frien ds for their support and encouragement I would also like to thank my professors at the M.E. Rinker, Sr. School of Building Construction at the University of Florida for bestowing their knowledge of the construction industry and to the Team t hat has made t his research so rich and broad. Special appreciation goes to Dr. Charles Kib ert who imparted the foundation and knowledge of sustainability on to me I wish to thank Dr. Esther Obonyo who patien tly guided me in the thesis journey Lastly, I wish to thank Dr. Siobhan M atthews, who although being long distance, has been always there to assist me

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5 TABLE OF CONTENTS page ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 ABSTRACT ................................ ................................ ................................ ..................... 9 CHAPTER 1 INTRODUCTION ................................ ................................ ................................ .... 11 2 LITERATURE REVIEW ................................ ................................ .......................... 14 2.1 Advantages and Disadvantages of Building with Earth ................................ .. 15 2.1.1 Advantages ................................ ................................ .......................... 15 2.1.2 Disadvantages ................................ ................................ ..................... 16 2.2 Earth Building Techniques ................................ ................................ ............. 17 2.2.1 Earth Building Techniques ................................ ................................ ... 17 2.2.1 Rammed Earth ................................ ................................ .................... 17 2.2.2 Molded Earth ................................ ................................ ....................... 18 2.2.3 Adobe Molding ................................ ................................ ..................... 19 2.2.4 Stacked Earth (Cob) ................................ ................................ ............ 20 2.2.5 Compressed Earth Bricks (CEB) ................................ ......................... 20 2.3 Factors affecting the deterioration of CEBs ................................ .................... 21 2.3.1 Physical, Chemical, and Biological Deterioration ................................ 21 2.3.2 Hygrothermal Deterioration ................................ ................................ 22 2.3.3 Wind Driven Rain Erosion ................................ ................................ ... 23 2.4 Principle s of Stabilization ................................ ................................ ............... 25 2.4.1 Soil Stabilization ................................ ................................ .................. 25 2.4.2 Principles of CEB Stabilization ................................ ............................ 25 2.4.3 Cebs and Mechanical Stabilization ................................ ...................... 26 2.4.3 CEB Stabilization Techniques Using Machines ................................ ... 26 2.4.4 Stabilizers Used in CEBs ................................ ................................ ..... 27 2.4.4.1 Cement stabilization ................................ ............................... 27 2.4.4.2 Lime stabilization ................................ ................................ .... 28 2.4.4.3 Other stabilizers ................................ ................................ ...... 29 2.5 Summary ................................ ................................ ................................ ........ 30 3 METHODOLOGY ................................ ................................ ................................ ... 35 3.1 CEB Formulation and Fabrication ................................ ................................ .. 35 3.2 Hygrothermal Aging ................................ ................................ ........................ 36 3.3 WDR Erosion ................................ ................................ ................................ 36

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6 4 RESULTS ................................ ................................ ................................ ............... 43 4.1 Hygrothermal Aging ................................ ................................ ........................ 43 4.2 WDR Erosion ................................ ................................ ................................ 44 5 DISCUSSION AND CONCLUSION ................................ ................................ ........ 54 5.1 Summary ................................ ................................ ................................ ........ 54 5.2 Discussion ................................ ................................ ................................ ...... 54 5.2.1 Compressed Earth Bricks ................................ ................................ .... 55 5.2.2 Evaluate Hygrothermal Performance ................................ ................... 55 5.2.3 Simulat ion of Wind Driven Rain Erosion ................................ .............. 56 5.3 Conclusions ................................ ................................ ................................ .... 57 5.4 Further Research ................................ ................................ ........................... 59 LIST OF REFERENCES ................................ ................................ ............................... 61 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 63

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7 LIST OF TABLES Table page 3 1 Mix design for the bricks ................................ ................................ ..................... 38 3 2 Compressive strength of the bricks ................................ ................................ .... 38 3 3 Mineral composition of materials ................................ ................................ ........ 38 4 1 EDS results from hygrothermal aging ................................ ................................ 47 4 2 Evaluation for EDS results from hygrothermal aging ................................ .......... 48 4 3 WDR brick erosion test results ................................ ................................ ........... 49

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8 LIST OF FIGURES Figure page 2 1 Castillo,10 th century ................................ ................................ ............................ 31 2 2 Manual rammed earth technique ................................ ................................ ....... 31 2 3 Shaping a granary, Nigeria ................................ ................................ ................. 32 2 4 Hier oglyph, Egypt. ................................ ................................ .............................. 33 2 5 Tomb of Queen Hatshepsut, Egypt. ................................ ................................ ... 33 2 6 Handmade adobe, India ................................ ................................ ..................... 34 2 7 ................................ ................................ ...... 34 3 1 CINVA type CEB manual machine ................................ ................................ ..... 39 3 2 JEOL scanning electron m icroscope model 6400 ................................ ............... 39 3 3 Schematic for erosion rig ................................ ................................ .................... 40 3 4 ................................ ........................ 40 3 5 Experimental WDR erosion rig ................................ ................................ ........... 41 3 6 Release valve and psi gauge ................................ ................................ .............. 41 3 7 Jet nozzle ................................ ................................ ................................ ........... 42 4 1 Magnitude of change for all elements ................................ ................................ 50 4 2 Magnitude of change for C, Ca,O, Si ................................ ................................ .. 50 4 3 Soil cement lime fluid ................................ ................................ .......................... 51 4 4 Interlocking soil cement lime fluid ................................ ................................ ....... 51 4 5 Soil cement ................................ ................................ ................................ ......... 52 4 6 Soil cement lime ................................ ................................ ................................ 52 4 7 Soil cement fiber ................................ ................................ ................................ 53

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9 Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science in Building Construction CHARACTERIZING COMPRESSED EARTH BRICKS BASED ON HYGROTHERMAL AGING AND WIND DRIVEN RAIN EROSION By Joseph Ex elbirt May 2011 Chair: Esther Obonyo Cochair: Charles Kibert Major: Building Construction The rapidly increasing demand for affordable housing in developing countries has highlighted the need for sustainable housing options, especially given the inadequ ate supply of traditional building materials. While advances in the design and use of compressed earth bricks (CEBs) present a viable solution to this dilemma, there have been significant concerns about their durability in tropical environments. The obje ctive of this research is to evaluate the durability of CEBs using hygrothermal aging and wind driven rain (WDR) erosion tests. Hygrothermal aging was performed by exposing different CEBs samples to 100C and 100% humidity for 7 days and then conducting a n analysis using scanning electron microscopy (EDS) which determined that Soil Cement CEB showed the least deviation in the chemical reaction of the focal elements T he WDR erosion test revealed that the s oil c ement CEB had the least erosion from the rest of the CEBs In conclusion, the stability of CEBs appears to vary depending on the constituent ingredients and stabilization techniques used B ased on t his research it was show n that there is a correlat ion between elemental composition and erosion levels of

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10 the CEB s. T he CEB that ha s the least microstructural change at the elemental level had the least erosion levels from the exposure to WDR acceleration.

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11 CHAPTER 1 INTRODUCTION In recent years developing nations have been facing an exponential demand for affordable housing, for which neither conventional industrialized techniques nor traditional industrial building materials like brick, concrete and steel are in adequate supply (Minke 200 6 ). Current conditions have been worsening ; co nventional building materials have remained scarce, housing demand has risen and the urgency to provide immediate practical solutions ha ve become more acute. Adequate shelter is one of the most important basic human needs, and p rovision s of housing for low income population s ha ve been a very difficult requirement to meet, since land and construction costs are typical ly beyond the means of both the rural and urban poor ( Adam 2001 ) It is therefore necessary to seek ways to reduce construction costs, as well as implementing sustainable and effective solutions. Such objectives can be achieved partially through the production and use of locally available earth as a principal building material (Minke, 2006) and the promotion of building with compressed earth bricks (CEB s ). Eart h as a natural building material is practical and affordable and it is available in most regions of the world. Earth is frequently used and transformed in place, and can be obtained directly from the footprint building site making its use even more appro pri ate due to the significant reduction or elimination of transportation costs Further, e arth has several key advantages over more conventional building materials as it is an inherently ecological ly material it has excellent thermal mass properties that can maintain comfortable interior temperatures within dwellings, granaries and other structures without the need for mechanical heating or cooling. Additionally, u sing earth

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12 as a building material requires little embodied energy for its processing, and earth structures are virtually entirely recyclable. At the end of its life cycle, as Rael (2008) reducing construction waste and the need for construction and demolition landfills. Lastly, the local population benefits from more direct and indirect employment opportunities through the use of earth based construction techniques over imported and other industri al construction materials Despite the above advantages, CEBs do have some deficiencies, especially when used in tropical environments, characterized by frequent and intense rainfall and long periods of high relative humidity which prematurely compromise their integrity This is due to the fact that CEBs are produced mainly from soil as the bulk ingredient, which is notorious for being prone to erosion and disintegration in water. Under the severe conditions often experienced in the humid tropics, soil b ased brick s often show considerable defects even over short periods of time. Consequently, the maintenance costs or even early rebuilding costs of deteriorated CEBs structures in such environments are undesirable and un sustainable. Because of the huge p otential for CEB use in all climates including those with high rainfall and high ambient humidity s tudying the durability of C E B s of varying composition is a major research concern, s ince increasing the long term durability of the brick s can be the key t o the ir widespread implementation and acceptance in geographical regions where affordable housing is desperately needed

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13 The research discussed in this paper is a subset of a NSF funded SGER: A project carried out in Tanzania and the United States (University of Florida) in 2008 2010. This thesis focuses on the hygrothermal aging and WDR erosion experiments carried out at the University of Florida in 2010. Background inf ormation and various aspects of research activities and results can be accessed at: http://web.dcp.ufl.edu/obonyo/SGERResearch.html The aim of this thesis is to characterize hygrothermal agi ng and wind driven rain erosion in CEBs of several common compositions through laboratory acceleration test methods. The specific obje c tives of this research are: 1. C onduct a litera ture review of CEB s and assess the factors affecting deterioration specifica lly, hygrothermal aging and wind driven rain erosion. 2. Evaluate the hygrothermal performance of several compositions of CEBs. 3. C onduct an accelerated t est to simulate wind driven rain erosion on these CEBs Chapter 2 contains a literature review that addre sses earth building techniques factors affecting the deterioration of CEBs, and stabilization techniques for CEBs Chapter 3 provides the methodology used to conduct this research. Chapter 4 provides the results of the laborat ory experiments performed. Finally, Chapter 5 discusses and analyzes the laboratory results, provides a conclusion of the research and results and provides recommendations for further research.

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14 C HAPTER 2 LITERATURE REVIEW Earth as a construction material has been used for thousan ds of years by civilizations all over the world. Many different techniques and methods have been developed, which vary according to the local climate and environment, as well as local traditions and customs (Houben & Guillaud, 1994). Globally, and in most hot arid and temperate climates, earth has been widely used as the preferred building material for vernacular architecture. Even today, academics, authors, builders, writers and architects have noted that between one third and one half of the population of the planet lives in buildings constructed of earth (Rael, 2008). Traditional earth construction materials have proven to be suitable for a wide range of buildings, and with earth being one of the few abundant materials that has not gone through the proces s of industrialization, it has a great potential for increased use in the future of ecologically and economically sustainable construction and development ; by disseminating a modern and progressive approach in areas where earth construction has been consid ered less successful as it has been in hot and humid climates (Houben & Guillaud, 1994). While traditional earth architecture presents several challenges due to climatic variability, compressed and stabilized earth bricks offer a potential remedy for many of could indeed be implemented for a foundation for Rural and Urban Sustainable Engineering of the developing nations and their diverse and growing populations.

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15 2.1 Advan tages and Disadvantages of Building with Earth The perceived hegemony of the industrialized world has for decades been directly responsible for causing an inferiority complex among earth building cultures. Today, the most common building material on the pl society, the phenomenon of abandoning its earth building traditions creates a significant risk of depleting precious na tural resources such as forest wood used for brick firing and an unsustainable and unaffordable investment in construction projects using industrially produced materials such as concrete, which often performs poorly in developing nations 2001) and in doing so, also causes the regrettable loss of traditional cultural knowledge and heritage. While it is true that the makeup of soil, which differs from one place to another, makes it difficult to create material standards for earth and building co des for earth buildings (Rael, 2008), its potential cannot be overlooked with the considerable benefits of earth construction, namely ecological and economic sustainability. 2.1.1 Advantages Given the long term vitality of soil based construction material s in human history, it is not surprising that these materials offer several advantages, some of which have been alluded to in earlier sections. The principal advantages of CEBs include their ability to insulate against thermal extremes, their very low cost of construction and transportation, greatly reduced environmental pollution, their recyclability; their relatively low technological complexity (which allows for do it yourself construction); and their marked preservation of timber and other materials, re ducing ecological degradation through mining and deforestation (Minke, 2006).

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16 Soil is available in large quantities in most regions of the world and is easily accessible to low income groups. In some locations, earth is the only material available and it r equires simple, low cost equipment to produce building materials. Even with the addition of stabilizers does not drastically weaken these key advantages, and CEBs are suitable as a construction material for the majority of many common architectural design s. Lastly, CEBs are highly competitive against their more conventional alternatives in their fire resistance and are virtually non combustible (Adam, 2001). 2.1.2 Disadvantages The perceived lack of durability of earth building techniques has created a b arrier to its use and adaptation in modern construction industries. Physical disadvantages of building materials constructed from soil commonly include their reduced durability if not regularly maintained and properly protected, particularly in areas affe cted by medium to high rainfall, their low tensile strength (being particularly poor in their resistance to bending moments and seismic activity, and their limited applicability only in compression (e.g. bearing walls, domes and vaults), their low resistan ce to abrasion and impact if not sufficiently reinforced or protected, and perhaps most notably their low acceptability amongst most social groups (being considered by many to be a second class and generally inferior building material). On account of these problems, earth as a building material lacks institutional acceptability in most countries and as a result building codes and performance standards have not been fully developed, despite highly redeeming qualities and potential for technological developm ent through stabilization techniques and augmented construction (Adam, 2001).

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17 2. 2 Earth Building Techniques 2. 2 .1 Earth Building Techniques The following sections will discuss different types of earth building techniques. These include rammed earth, mold ed earth, adobe molding, stacked earth, and compressed earth bricks. The relative strengths and weaknesses of each technique will also be discussed. 2.2.1 Rammed Earth Earth construction and techniques have been known for over 9000 years. Earth was used as the primary building material in all early ancient cultures for homes and communal structures. Early Stone and Bronze Age archeological remains found in China are rammed earth structures. Further, the technique can be traced across the world and through out history. Indeed, compressed soil based architecture is known to have been utilized on all human occupied continents, and in every early human culture, with examples being known from all kinds of human occupied and agricultural structures such as farm s, granaries, houses, chateaux and fortresses (Figure 2 1 ). Rammed earth structures include entire villages in North Africa, the majority of the Great Wall of China, most buildings in the Himalayan regions of Tibet, Bhutan, Nepal and Ladakh, and widesprea d examples from native North and South America (Minke, 2006). Modern rammed earth is also often known by its French name, pis de terre which was first used in Lyon, France, in 1562. In this technique, earth is compressed between parallel wooden plates th at are later removed and are extended farther to work on another section of the wall (Figure 2 2) A slightly dampened mixture of earth containing appropriate amount of clay, grit and sand is poured into the molds or

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18 formwork one layer at a time and compre ssed in place to form a homogenous monolith wall (Rael, 2008). As with all earth construction techniques, the process begins with soil selection. The soil necessary for rammed earth building techniques is preferably sandy or gravely rather than clayey. Onc e excavated, the soil is thoroughly sieved and the larger rocks are removed. If the natural soil is too dry, it should be moistened and mixed to produce a uniformly damp mixture. The mixture is then poured into a form in thin layers and then rammed to incr ease its densit y. The resulting structure is highly stable in most circumstances (Auroville 2011 ). Technologically advanced techniques are based on the same principles, though the traditional wooden rammer has been replaced by pneumatic rammers, and the heavy wooden formworks have evolved into light composite ones, made of plywood, steel or aluminum. Pneumatic rammers, dump loaders, mixers, ban conveyors, etc., have been introduced, which have allowed for faster building and provide a finish of more cons istent quality (Auroville 2011 ) Furthermore, rammed earth has spread to regions where it is not vernacular, and where traditional techniques have been lost due to performance requirements of local regulatory building codes. Technical standards have been prescribed by experts in the field where an ideal mixture is 15 to 18 percent clay mixed with 23 percent coarse aggregate, 30 percent sand, and 32 percent silt: but because clay provides good cohesion, mixes with up to 30 percent clay are possible (Rael, 2008). 2.2.2 Molded Earth Direct shaping makes use of plastic earth and does not require a mold or formwork. Plastic earth is shaped, much as a potter would do it. The quality of the soil,

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19 its preparation and the water consistency are known only to the bui lders, and is highly variable. This technique also allows for a very fluid and varied architecture. This technique requires that builders have the proper knowledge regarding soil quality in order to control shrinkage as the walls dry, and is indeed an art form (Figure 2 3). The molded earth technique has been and is still used a great deal in Africa, in the Sahel, as well as in many equatorial regions. Beautiful examples can be seen in Cameroon, where shaped earth has been used for houses and granaries. Nat ural and traditional stabilizers have been used in countries like Nigeria and Ghana, and other countries of this region. Builders either used plants or vegetable juice, or boiled seeds or other plant parts to prepare natural glues, which were then added to the soil. Unfortunately, most of this knowledge has been lost over the years under the guise of endangered, becoming increasingly scarce over time. 2.2.3 Adobe Molding Sundri ed clay brick, called adobe, is undoubtedly one of the oldest building materials used by humankind, with the oldest identified adobes produced around 9,000 often with straw added. After being cast, they are left to dry in the sun. They are traditionally either hand shaped or shaped in parallel piped wooden molds (Figure 2 4) The Spanish name adobe comes from the Egyptian hieroglyph (Figure 2 5), meaning brick. It has passed al When Arabs until it in modern Spanish. It was then incorporated into French and English.

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20 The adobe techniqu e is made either by filling molds with a pasty soil mixture or by throwing moist lumps of earth into them (Figure 2 6) Different types and sizes of molds can be used, and are usually made from timber. The throwing technique is commonly used in all develop ing countries. The greater the force with which the mixture is thrown, the better its compaction and dry strength. The surface is smoothed either by hand or by a timber piece, trowel or wire partition and stacking. One person can typically produce between 300 and 500 bricks per day. Adobe, as ancient as it is, it is still used around the globe, and its production has been industrialized, standardized and codified by many local building authorities (Minke 2006). 2.2.4 Stacked Earth (Cob) Plastic soil is usua lly formed in balls, which are freshly stacked one on top of the in France. This technique is still used in Africa, India and in Saudi Arabia, where elaborated architectural examples can be seen. Shibam, the historic capital of Southern Yemen, was built with a combination of cob and adobe (Figure 2 7). It has Educational, Scientific and Cultural Organisation as a world heritage site (Auroville 2011). 2.2.5 Compressed Earth Bricks (CEB) With the advent of the industrial revolution, natural earth construction techniques dwindled, but following the Second World War, material and resource sh ortages brought earth construction back as a possible compensation for many construction needs. With the introduction of massive road construction, techniques for earth stabilization with cement were developed and implemented. These techniques carried ove r to traditional

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21 earth brick production, increasing its density and making CEBs stronger and more durable. The late 1980s saw a significant interest in CEBs in both developed and developing countries. This increased interest in CEBs came at a time when the construction sector was developing performance based specifications for building materials (Heathcote, 2007). 2. 3 Factors affecting the deteriorat ion of CEBs Naturally, the usefulness of CEBs depends on the durability of the bricks themselves. Durabili material when exposed to the environment undergoes deterioration over a period of time, and the rate of deterioration affecting a material can be internal and external (Avrami et al., 2008). The internal factors that affect deterioration could be related to material composition and production methods and the external factors causing deterioration from en vironmental influences. These often act on a material simultaneously and manifest themselves in the form of physical, chemical and biological deterioration (Kuhnel, 2004). 2.3.1 Physical, Chemical, and Biological Deterioration There are several factors that cause CEBs to physically deteriorate. These include fluctuating temperatures, which often act together with ambient air humidity, ground moisture, and rain. This results in the weakening of intragranular bonds which in turn causes fissures in the bl ock fabric and makes the blocks more susceptible to weathering (Kuhnel, 2004). Bricks that are susceptible to weathering are more prone to water absorption, further accelerating the degradation process.

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22 Absorption of water causes swelling in the fabric an d evaporation causes shrinkage in the block (Ren and Kagi,1995). As water percolates, any unstabilized portion can be expected to dissolve, thus leading to softening of the earth fabric with a direct impact on the surface strength. Any loose material on the surface of the block is usually washed away with this force, causing pitting in the blocks, which makes them vulnerable to further erosion (Kerali, 2000). Heathcote (2002) in his study showed that the predominant cause of deterioration of earth wall s was due to erosion caused by WDR. T emperature fluctuation is also responsible for causing physical deterioration in the CEBs. Such fluctuations can occur in ambient temperatures or can be caused by direct sunlight and the resulting thermal loading, both o f which result in expansion, but also contraction through shrinkage and drying of the brick fabric (Kerali, 2000). Consequently, there is a fractional reduction in the volume of the bricks, destabilizing the structures built thereof. Deterioration in CEBs can also be caused due to chemical activity which includes the deterioration due to sulphate attack from acid rain, chemical leaching, and sa lt crystallization of the CEBs (Larbi, 2004). 2.3.2 Hygrothermal Deterioration Deterioration of CEBs due to mo isture absorption and temperature change can be defined as hygrothermal deterioration. The service life of CEBs is strongly related with how the material composition of the CEBs respond to heat, air, and moisture absorption changes (Kunzel, 1995). CEBs ca n be characterized as being comprised of only a few components, each with an expected performance capability to withstand moisture and recurring water penetration dependent and independent on the climatic conditions in which the CEBs are used. The mechanis ms by which CEBs redistribute and transport

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23 moisture must be taken into consideration for the potential for moisture induced damages (Karagiozis, 200 2 ). Since water is a solvent, all CEBs will eventually have water related damage, some will be as soon as t hey have been built while others may take a considerable time. However, the water contained in the original brick will also dry out, and this dehydration will affect its strength. The drying rate of a CEB depends on the loads to which the CEBs has been ex posed and drying rate performance characteristic combine with water penetration represent hygrothermal performance (Karagiozis, 2002). Hygrothermal loads on the other hand, include contributions from loads caused by wind driven rain, mechanical pressur es, wind pressures, stack effect, vapor diffusion, liquid diffusion, sorption and suction storage, and temperature dependent sorption capabilities as well as evaporation condensation characteristics. At all times, the thermal transport is fully coupled to moisture transport and can be related to the quality and durability of the materials and their associated mechanical, chemical, and hygrothermal properties which are a variable function of time and the environment to which they are exposed (Karagiozis, 2 00 2 ). 2.3.3 Wind Driven Rain Erosion When wind occurs simultaneously with rain, it causes an angled rainfall vector research is governed by a range of parameters inc luding environment topology, wind speed, wind direction, turbulence intensity, rainfall intensity, raindrop size distribution and rain event duration. This large number of parameters and their variability make the quantification of WDR an extremely complex area of research. Field experimental methods and measurements of WDR science have virtually remained unchanged since

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24 the 1930s and have been commonly performed for research purposes only (Blocken and Carmeliet, 2004). Simulation research was conducted b y Cytrin who developed a rain simulation test in 1955 to evaluate the resistance to the forces of driving rain setting up a format of water pressure and exposure to time suggesting an equivalent factor of 10 years of rainfall. In 1970, Wolfskill developed a shower spray test in which he measured the erosion of stabilized soils and correlated the depth of the pitting to the capacity of the principles, but developed a soil r atio measuring the test erosion depth related to rain precipitation (Heathcote, 2002). In 1990, Ola and Mbata developed a vertical spray test with pressures ranging from 6 psi to 65 psi and water flows of 2 gallons per minute to 12.25 gallons per minute re spectively, and correlating to annual rainfalls of 25 inches to 275 inches in a period of compaction and /or cement content were increased (Heathcote, 2002). In the 1970s, an inc reased interest in earth based construction motivated the Commonwealth Experimental Building Station in Australia to develop an accelerated erosion test which is the name of the document. The test is based on spraying the face of a sample for a period of one hour or until the sample is penetrated (Heathcote, 2002). a horizontally mounted nozzle. Specimens are mount ed in the rig in the same orientation as proposed for wall construction. A shield ensures that only a limited area

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25 of block face is subjected to the water spray. During testing, the spray may be stopped every 15 min to assess performance. The depth of pit ting is measured using a 3/8in diameter flat ended rod. The erosion rate is expressed as the pitting depth per minute of exposure time (Walker, 2004). 2. 4 Principles of Stabilization 2.4.1 Soil Stabilization In the field of road construction, techniques o f improving soil durability with additives that modify soil properties have been used widely since the 1920s. These techniques, known as soil stabilization techniques, have the effect of increasing durability and creating erosion resistant soil. The resu lt is structures that can withstand the impact of a variety of damaging environmental influences, such as temperature fluctuations, humidity moisture and mechanical pressure D ifferences in the durability of soil that has been stabilized can be signi fica nt, as reported by Adam: esistance can help prevent structural failures brought about by clay and silt expansion and contraction, which can cause crumbling of surface coatings. Further t he strength of a soil can be increased 400% to 500% with the use of the stabilization include increasing the soil density as well as adding stabilizing agents, which either react with the soil grains or bind them together (Adam, 2 001). 2.4.2 Principles of CEB Stabilization The strength of CEBs is also strongly affected by quality control procedures. These range from soil sampling practices to methods of manufacturing. Attention to a wide variety of factors is required: for exampl e, the strength and durability of bricks can be improved through soil testing, gradation, optimum amount of clay in the soil, optimum

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26 amount of water while making the bricks, compression force applied and curing conditions. The primary ingredient that all ows a soil to be used effectively in construction is clay, which offers a cohesive effect by binding other fractions. However, the tendency of clay to disintegrate can be problematic, which is why stabilization techniques are so important for the durabilit y of CEBs (Adam, 2001). 2.4.3 C EB s a nd Mechanical Stabilization A technique for stabilizing CEBs is known as mechanical stabilization. This refers to the use of machines to compact and compress bricks, which reduces the air void volume in the CEBs. By i ncreasing soil density, compacting and compression make s the bricks more resistant to wind and rain erosion. During this process, attention must be paid to the type and proportions of soil used, the moisture content during compaction, and the effort appli ed in compression, because each of these factors has a significant effect on the resulting density and durability of the CEBs. In particular, mechanical stabilization aims to achieve the correct proportions of sand and cla y so that the bricks will be less permeable and thus more durable. Specific methods of mechanical stabilization include foot treading as well as the use of hand tamping equipment. These methods can achieve compacting pressures ranging as high as several thousand MN/m2 as a result of us ing mechanical equipment. (Adam, 2001). 2.4.3 CEB Stabilization Techniques Using Machines There are three types of manual presses that can be used with CEBs. These presses trace their origins to a device commonly known as the CINVA Ram, which is made up of a steel box and a lever (Rael, 2008). These three presses all share the same basic design as the CINVA Ram: the light mechanical press, the light hydraulic press, and the heavy mechanical press.

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27 Light mechanical presses are relatively easy to construc t and to repair. Other strengths of this type of press include being lightweight, easy to use, cost efficient and durable. Although they usually have only one molding module that can exert low pressures, they are still one of the best available presses o f their type, which is why many countries manufacture and use them despite their low production output (Houben and Guillaud, 1994). Another press that is considerably more productive than the CINVA Ram type is the light hydraulic press. Despite their s mall size, these presses can apply pressures of up to 10MN/m2 by using a hydraulic piston instead of the swivel and rod system of the CINVA Ram. As a result, the light hydraulic press can yield CEBs with a density that is as much as 20% greater than regul ar CEBs, thus allowing for expansive soil compressions. (Houben and Guillaud, 1994). Finally, there are heavy mechanical presses, which are characterized as industrial grade. These presses utilize long lasting pressure and have interchangeable molds. The ir design results in greater efficiency higher compression and density, as well as increased production capacity. (Houben and Guillaud, 1994 ). 2.4.4 Stabilizers Used i n C EBs There are several types of stabilizing agents that are commonly used in buildin g CEBs. These include cement, lime, bitumen, gypsum, and pozzolanas. Each of these stabilizers will be discussed in the following sections. 2.4.4.1 Cement stabilization As previously mentioned, compressed earth bricks are particularly susceptible to ero sion caused by water. However, adding cement to CEBs helps to make the bricks

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28 water resistant. This happens because the cement actually limits the amount of swelling caused by water, and it also adds strength to the bricks: Cementation can make soil wate r resistant through the limitation of swelling and the augmentation of compressive strength. When ordinary Portland cement hydrates when water is added, a cementitious gel is produced that is independent of the soil. This gel is made up of calcium silicate hydrates and calcium aluminate hydrates, which make up the bulk of the gel, and hydrated lime, which is deposited as a separate crystalline solid phase. This cementation process which varies with time, temperature, soil type, and cement type deposits an insoluble binder between the particles of the soil, which embeds them in a matrix of cemetitious gel. At the same time, the lime released during cement hydration forms additional cementitious bonds as it reacts with the clay particles. (Adam, 2001). Rese arch suggests that optimal levels of stabilization occur when the bricks contain between 3% and 18% of cement content by weight. The correct percentage of cement to use depends primarily on the soil type, since the amount of linear shrinkage affects the c ement content that is needed for stabilization ( Minke 2006 ). 2.4.4.2 Lime stabilization One limitation of using of cement a s a stabilizer is that it does not work well with clay soils. However, using lime is a stabilizing agent that can be used effecti vely to stabilize clay soils. There are several stabilizing effects that lime may have, including cation exchange, flocculation and agglomeration, carbonation, and pozzolanic reactions. The pozzolanic reaction has a particularly stabilizing effect because it binds soil particles together as various cemetitious compounds are formed. The addition of lime serves to make clay less absorbent of water; thus, the clay soil becomes more

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29 manageable and less susceptible to variations in moisture content (Adam, 2001 ). Minke ( 2006 ) offers this description of the stabilizing effects of lime: If there is sufficient humidity, then an exchange of ions takes place in the loam with lime as stabilizer. The calcium ions of the lime are exchanged with the metallic ions of th e clay. As a result, stronger agglomerations of fine particles occur, hindering the penetration of water. Furthermore, the lime reacts with the CO2 in the air to form limestone. (Minke, 2006 ) Therefore, lime can also be used as a stabilizer in CEBs. 2.4. 4.3 Other stabilizers There are several other stabilizers that can be used in CEBs. For example, bitumen is ideal for sandy soils. In granular soils, it is possible to increase both the cohesion and strength of earth bricks by adding even small amounts o f bitumen (2 6%). Another advantage of bitumen is that it repels water. Some soil types may experience both of these advantages to differing extents. However, the amount of bitumen needed for clay soils is quite large. There are also several disadvanta ges to using bitumen: for expensive to import and transport, require heating, storing and preparation which increase costs; and in hot climates, heat can have an adverse effect on their binding Yet another stabilizing ingredient is gypsum, which is a material that has been traditionally used in many Mediterranean and Middle Eastern countries, especially in early civilizations. Gypsum works parti cularly well as a stabilizer for sandy soils. Finally, pozzolanas can also be used, and they are most effective when combined with hydrated lime. These substances are found naturally in volcanic ash or pumice;

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30 alternatively, they can be produced from fin ely ground recycled fire clay bricks and mudstone. Pozzolanas are notably rich in silica and alumina. (Adam, 2001). 2. 5 Summary From the above literature review, a number of conclusions can be made. Earth based construction technology has a long history ; technologies like adobe, rammed earth, molded earth and stacked earth, have been successful in hot and arid climates throughout the world and for millennia. The review also shows that when CEBs are stabilized, they improve their physical structure and b ehave better in humid climates as compared to other methods of building It is also established that even under normal conditions, durability of the CEBs will be affected by environmental exposure. This condition worsens when the bricks are exposed to hy grothermal conditions and WDR, since the primary agents that weaken the brick fabric are water, temperature, and chemical action within the brick. Water related action causes the brick fabric to weaken due to factors like wetting and surface abrasion due to rainwater. When combined with temperature fluctuations, this causes the fabric to weaken further, resulting in cracks in the bricks. The literature review shows that when soil is mechanically stabilized, particularly with cement and other additives, i t increases the strength and durability of the bricks to some extent, depending on the combination of additives and soil selection. Hygrothermal aging and WDR erosion testing provide the investigation of how specific changes occur and how the environment affects CEBs in the field in an accelerat ed research format

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31 Figure 2 1 Castillo,10 th century (Auroville Earth Institute, 2011). Figure 2 2 Manual rammed earth technique (Auroville Earth Institute, 2011).

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32 Figure 2 3. Shaping a g ranary, Nige ria (Auroville Earth Institute, 2011).

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33 Figure 2 4 Hieroglyph, Egypt (Auroville Earth Institute, 2011). Figure 2 5 Tomb of Queen Hatshepsut, Egypt (Auroville Earth Institute, 2011).

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34 Figure 2 6 Handmade adobe India (Auroville Earth Ins titute, 2011). Figure 2 7

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35 CHAPTER 3 METHODOLOGY The objective s of this study are : 1) T he characteriz ati on of four types of CBSs that were subjected to hygrothermal aging and 2) C o nduct an d evaluate an acc elerated test to simulate wind driven rain erosion on CEBs based on the Bulletin 5 test rig To evaluate the hygrothermal impacts to the CEBs, s canning electron microscope (SEM) and Energy dispersive X ray analysis (EDS) were util ized EDS is a technique used to identify the elemental composition of a sample or small area of interest on the sample. During EDS, a sample is exposed to an electron beam inside a SEM. These electrons collide with the electrons within the sample, causi ng some of them to be knocked out of their orbits. The vacated positions are filled by higher energy electrons which emit x rays in the process. By analyzing the emitted x rays, the elemental composition of the sample can be determined tracking changes in minerals that were known to be originally present (Sem Lab,Inc.). 3.1 CEB Formulation a nd Fabrication The NSF funded SGER project concluded that the optimum formulation s for the fabrication of the CEBs used in this study were: 1) Soil Cement Lime Fluid: 1 00lb of soil, 5lb of cement, 5lb of lime 2.5lb of Aeonian Brick Stabilizer 2) Soil Cement: 100lb of soil, 7lb of cement, 3) Soil Cement Lime: 100lb of soil, 5lb of cement, 7lb of lime 4 ) Soil Cement Fiber: 100lb of soil 5lb of, cement, 1lb of fiber (Tab le 3 1). The refore these four CEB formulations were used in this research and a fifth brick : a factory produced interlocking brick was also included in the research as a control. The CEBs were fabricated using a Terra Block manual block press based on the CinvaRam design (Figure 3 2 ) The CEBs were tested for compressive strength (Table 3 2).

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36 3.2 Hygrothermal Aging Many studies in this area conduct testing on hygrothermal aging by quantifying the impact of cyclic loading. Specimens are therefore assessed f ollowing exposure to wet and dry cycles ( Obonyo 2011). In this study, the focus was on the water induced chemical changes following exposure to heat. To achieve this goal, the specimens were aged through being subjected to elevated heat and moisture con ditions based on the provisions of the ASTM C1560 03 Standard Test Method for Hot Water Accelerated Aging of Glass Fiber Reinforced Cement Based Composites. The hygrothermal aging performance of the CEB types as outlined in section 3.1 were assessed by pla cing them in a climate control chamber. The specimens were first cu t in a 2in by 2in by 1in cubes out of a whole brick then placed in water and exposed to high temperature (100C) and ( 100% humidity ) for 7 days The samples were subsequently dried, and t hen crushed using a pestle and mortar prior to SEM/EDS analysis to determine the extent of chemical composition alteration resulting from the hygrothermal aging process. The SEM/EDS characterization was conducted using a JEOL Scanning electron m icroscope m odel 6400 ( Figure 3 2 ) at the Major Analytical Instrumentation Center (MAIC), at the University of Florida. The chemical reactions that were expected to take place were based on the mineral composition of the CE Bs (T able 3 3) 3 .3 WDR Erosion The WDR erosio n accelerated testing rig used in this study is a modified version assembled for experimental and preliminary testing based on an adaptation of the UTS using provisions of various ASTM Standard Erosion Testing. The three tests employed in this study were the Cavitation Erosion Test using vibratory apparatus (ASTM G 32),

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37 the Liquid Impingement Erosion Test (ASTM G 73), and the Erosion of Solid Materials by a Cavitating Liquid Jet Test (ASTM G 134). Precedence for this approach can be found in the accelerat ed erosion testing done on different materials by Dynaflow, Inc. ( Dynaflow, Inc., 201 1; Obonyo 2011). Figure 3 3 shows a schematic of the test rig for this research and figure 3 4 shows a working modified Bulletin 5 UTS developed by Heathcote. The foll owing modifications were made to the Bulletin 5 rig: a pre s sure washer was used instead of a high flow water pump, and the component of the pressure washer were adapted to measure psi pressure and a release valve was use d to control water flow and reduce p ressure (Figure s 3 5, 3 6,3 7 ). The specimens were placed with their external face surface exposed to four inch diameter water spray the nozzle tip of the pressure washer with a cone spray nozzle setting The nozzle was positioned 20 inches f rom the face of the samples and water was sprayed at a setting of 300psi and 40 gallon per hour water flow and 600psi with 60 gallons per hour water flow respective ly to verify two levels/strengths Readings are taken every 15 minutes to establish the dep th of erosion to assess the resilience of the five brick types Depth of erosion was measure d with a visual inspection for pitting and a .25in rod was placed in the cavity and marked at the original face level for deeper erosion levels

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38 Table 3 1. Mix design for the bricks Types of brick Mixing proportion Proportion in lb Soil Cement 14.3:1'(soil: cement) 100lb of soil : 7lb of cement Soil Cement L ime 20:1:1.4' (Soil :Cement: lime) 100lb of soil : 5lb of cement : 7lb of lime Soil Cement F ib er 20:1:0.2' (Soil :Cement: fiber) 100lb of soil : 5lb of cement : 1lb of fiber Soil Cement L ime F luid 20:1:1:0.5' (Soil: cement: lime: fluid) 100lb of soil : 5lb of cement : 5lb of lime 2.5lb of Aeonian fluid Table 3 2 Compressive strength of the bri cks Types of Brick Compressive strength (psi) Soil Cement 1100 Soil Cement Lime 1200 Interlocking Block 1400 Soil Cement Fiber 1150 Soil Cement lime fluid 1000 Table 3 3 Mineral composition of materials Materials Mineral composition Lime (hydrated ) Calcium, Oxygen, Calcium Hydroxide Portland C ement Tricalcium Silicate, Dicalcium Silicate, Tricalcium Aluminate and Calcium aluminoferrite Soil Fe, Al, Phosphate, Inorganic Phosphorus, Aloxides, and apatite

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39 Figure 3 1 CINVA type CEB manual mac hine (Terra Block 2011) Figure 3 2 JEOL s canning electron m icroscope model 6400 (University of Florida, 2011)

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40 Figure 3 3 Schematic for erosion rig Figure 3 4 UTS WDR erosion rig ( Heathcote 200 2 )

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41 Figure 3 5 Experimental WDR erosion rig Photo c ourtesy of Joseph Exelbirt Figure 3 6 Release valve and psi gauge. Photo c ourtesy of Joseph Exelbirt

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42 Figure 3 7 Jet nozzle Photo courtesy of Joseph Exelbirt

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43 CHAPTER 4. RESULTS 4.1 Hygrothermal Aging Table 4 1 provides the results from the chemical characterization which identifies the microstructural reactions the samples experienced as the procedur e of water immersion and heat exposure to 100C temperatures in an oven for 7 days. These results show the microstructural profile of the original samples and the changes that occurred to the samples due to the aging process. Table 4 2 p r o vides an evaluati on of the magnitude of change at the elemental level the samples underwent from the aging process with the change s being represented as total percentage of accumulation or loss Figure 4 1 and figure 4 2 demonstrates the magnitude of change the trend of the elemental changes the different CEB type s and how some of the gains and losses are significant whil e others are insignificant. Upon examination of these tables and graphs, the following can be identified : The percentage content and microstructural cha nges that magnesium aluminum t ita nium and iron display ed were relatively s mall and t he percentage content and microstructural changes of the remaining elements : c arbon, o xygen, s ilica and c alcium displayed relative higher value s and are as follows: In the soi l cement l ime f luid CEB the aging process caused a significant loss of c arbon and a substantial accumulation of o xygen remainder elements, s ilica and c alcium show a proportionate increase, although not as considerable. In the soil c ement CEB the aging process did not trigger significant movement in any of the four mentioned elements

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44 In the s oil c ement l ime CEB the aging process caused a significant loss of c a lcium ; in fact it is the CEB wherein the loss of c alcium is most prominent. The remain ing three elements of c a rbon o xygen and s ilica show a proportionate increase though not drastic. In the s oil c ement f iber CEB the aging process caused significant o xy gen and s ilica loss and a moderate c arbon relative proportionate increase ; c ncrease is the most prominent of all the elements in this CEB type 4.2 WDR E rosion The purpose of the erosion tests was to determine which bricks would withstand WDR erosion. The test utilized a pressure washer nozzle with two settings: 300 psi of water pressure and 600 psi of water pressure The result was that only two of the brick types were capable of withstanding the water pressure without significant deterioration The factory produced interlocking CEB demonstrated the least degree of erosion, foll owed by the soil cement CEB which showed minimal cumulative erosion Thus, the soil cement outperformed the rest of the CEBs that were included in the study. T he resu lts of these tests are shown in Table 4 3 The following sections discuss the results of the tests to measure pitting and erosion, an d the accompanying images reveal the depth of erosion and offer visual evidence of the differences in material composition of the CEB s tested. The results will be divided into sections that address each type of brick: soil cement l ime f luid, f actory p roduced i nterlocking, s oil cement, s oil cement lime and s oil c ement f iber. Soil cement l ime f luid CEB had an initial erosion depth of 0.6in after the first 15 minutes of exposure to 10 gallons of water stream at the 300psi setting and culminating in 1.0 in erosion depth with a total of 4 0 gallons of water after 60 minute exposure When

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45 exposed to the 600psi setting, the initial erosion depth was 0.7in with a total of 15 gallons of water exposure. At the end of the 60 minute and 60 gallons of water exposure cycle, 1.2in erosion depth was recorded ( Figure 4 3 ) Factory p roduced i nterlocking CEB had a minimal initial erosion depth after the first 15 minutes of exposure to 10 gallons of water stream at the 300psi setting a nd did not show any pitting after 30 minutes of exposure and 2 0 gallons of water stream to the remainder of the 60 minute cycle and total water exposure of 40 gallons Similar results were recorded with minimal initial erosion depth after the first 30 minu tes of exposure to 45 gallons of water stream at the 6 00psi setting and did not show any pitting there after to the remainder of the 60 minute cycle and 60 gallons of water exposure (Figure 4 4 ). Soil c ement CEB had an initial erosion depth of 0. 005 in after the first 15 minutes of exposure to 10 gallons of water stream at the 300psi setting and culminating i n 0 .0 25 in erosion depth with a total of 40 gallons of water after 60 minute exposure. When exposed to the 600psi setting, the initial erosion depth was 0 020 in with a total of 15 gallons of water exposure. At the end of the 60 minute and 60 gallons of water exposure cycle 0.035 in erosion depth was recorded ( Figure 4 5 ) Soil cem ent l ime CEB had an initial erosion depth of 0. 70 in after the first 15 minutes of exposure to 10 gallons of water stream at the 300psi setting and culminating in 0. 8 5 in erosion depth with a total of 40 gallons of water after 60 minute exposure. When exposed to the 600psi setting, the initial erosion depth was 0. 8 0 in with a total of 15 gallons of water exposure. At the end of the 60 minute and 60 gallons of water exposure cycle, 1.0 in erosion depth was recorded (Figure 4 6 ).

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46 Soil c ement f iber CEB had an initial erosion depth of 1 .0in after the first 15 minutes of exposure to 10 gallon s of water stream at the 300psi setting and culminating in 1 6 in erosion depth with a total of 40 gallons of water after 60 minute exposure. When exposed to the 600psi setting, the initial erosion depth was 1 .0in with a total of 15 gallons of water exposur e. At the end of the 60 minute and 60 gallons of water exposure cycle, 2. 2 in erosion depth was recorded (Figure 4 7 ).

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47 Table 4 1 EDS r esults from hygrothermal a ging Types of Sample Chemical Original Samples Aged Samples Element (%) Atomic (%) Element (%) Atomic (%) Soil C ement L ime F luid C 16.7 24.8 8.8 13.9 O 45.3 54.4 51.6 63.5 Mg 1.1 0.9 0.3 0.2 Al 4.2 3.0 4.5 3.2 Si 9.0 6.1 10.3 6.9 Ca 18.4 9.0 21.1 10.8 Ti 0.6 0.2 1.2 0.5 Fe 4.3 1.4 1.9 0.7 Soil Cement C 9.1 14.8 10.2 16.3 O 51.7 62.8 51.3 61.5 Mg 1.6 1.2 0.4 0.3 Al 3.7 2.6 5.4 3.8 Si 11.2 7.8 13.6 9.3 Ca 19.7 9.6 15.4 7.4 Ti 0.3 0.1 0.6 0.2 Fe 2.1 0.7 2.4 0.8 Soil Cement L ime C 6.8 11.0 11.1 17.3 O 50.3 63.8 52.3 61.5 Al 2.4 1.8 4.3 3.0 Si 9.9 6.8 15.9 10.5 S 0.4 0.3 0.6 0.4 Ca 25.7 13.7 13.3 6.3 Fe 2.2 0.8 1.8 0.6 Soil Cement Fiber C 14.7 21.6 17.7 26.5 O 54.2 59.9 46.5 53.5 Mg 0.1 0.1 0.1 0.1 Al 4.3 2.8 4.3 3.0 Si 21.1 13.3 14.0 9.3 Ca 3.7 1.6 12.8 5.9 Ti 0.3 0.1 0.6 0.2 Fe 1.3 0.4 3.0 1.0

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48 Table 4 2 Evaluation for EDS results from hygrothermal a ging Types of Sample Chemical Original Samples Aged Samples Difference Value of Change Element (%) Element (%) Original Aged (%) (%) SCLF C 16.7 8.8 7.9 47 SC C 9.1 10.2 1.1 12 SCL C 6.8 11.1 4.3 63 SCF C 14.7 17.7 3 20 SCLF O 45.3 51.6 6.3 14 SC O 51.7 51.3 0.4 1 SCL O 50.3 52.3 2 4 SCF O 54.2 46.5 7.7 14 SCLF Mg 1.1 0.3 0.8 73 SC Mg 1.6 0.4 1.2 75 SCL n/a SCF Mg 0.1 0.1 0 0 SCLF Al 4.2 4.5 0.3 7 SC Al 3.7 5.4 1 .7 46 SCL Al 2.4 4.3 1.9 79 SCF Al 4.3 4.3 0 0 SCLF Si 9 10.3 1.3 14 SC Si 11.2 13.6 2.4 21 SCL Si 9.9 15.9 6 61 SCF Si 21.1 14 7.1 34 SCLF Ca 18.4 21.1 2.7 15 SC Ca 19.7 15.4 4.3 22 SCL Ca 25.7 13.3 12.4 48 SCF Ca 3.7 12.8 9.1 246 SCLF Ti 0.6 1.2 0.6 100 SC Ti 0.3 0.6 0.3 100 SCL n/a SCF Ti 0.3 0.6 0.3 100 SCLF Fe 4.3 1.9 2.4 56 SC Fe 2.1 2.4 0.3 14 SCL Fe 2.2 1.8 0.4 18 SCF Fe 1.3 3 1. 0 77

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49 Table 4 3 WDR brick erosion test results CEB Pressure (psi) Distance (in) Wate r (gal) Time (min) Erosion (inches) Soil Cement Lime Fluid 600 20 15 15 0.7 in 600 20 15 30 0.8 in 600 20 15 45 1.0 in 600 20 15 60 1.2 in 300 20 10 15 0.6 in 300 20 10 30 0.7 in 300 20 10 45 0.9 in 300 20 10 60 1.0 in Factory Produced Inte rlocking 600 20 15 15 0.005 in 600 20 15 30 0.010 in 600 20 15 45 no change in depth 600 20 15 60 no change in depth 300 20 10 15 < 0.005 in 300 20 10 30 no change in depth 300 20 10 45 no change in depth 300 20 10 60 no change in depth Soil Cement 600 20 15 15 0.020 in 600 20 15 30 0.025 in 600 20 15 45 0.030 in 600 20 15 60 0.035 in 300 20 10 15 0.005 in 300 20 10 30 0.010 in 300 20 10 45 0.020 in 300 20 10 60 0.025 in Soil Cement Lime 600 20 15 15 0.8 0 in 600 20 15 30 0.9 0 in 600 20 15 45 0.95 in 600 20 15 60 1.00 in 300 20 10 15 0.70in 300 20 10 30 0.75in 300 20 10 45 0.80in 300 20 10 60 0.85in Soil Cement Fiber 600 20 15 15 1.00 in 600 20 15 30 1.40 in 600 20 15 45 1.80 in 600 20 15 60 2.20 in 300 20 10 15 1.0 0 in 300 20 10 30 1.2 0 in 300 20 10 45 1.40 in 300 20 10 60 1.60 in

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50 Figure 4 1. Magnitude of change for all elements Figure 4 2. Magnitude of change for C, Ca, O, Si

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51 Figure 4 3. Soil cement lime fluid. Photo c ourtesy of Joseph Exelbi rt. Figure 4 4. Interlocking soil cement lime fluid Photo c ourtesy of Joseph Exelbirt.

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52 Figure 4 5. Soil cement. Photo c ourtesy of Joseph Exelbirt. Figure 4 6. Soil cement lime. Photo c ourtesy of Joseph Exelbirt.

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53 Figure 4 7 Soil c ement f iber Photo c ourtesy of Joseph Exelbirt.

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54 CHAPTER 5 DIS CUSSION AND CONCLUSI ON 5.1 Summary The principal objective of this thesis was to measure the effects of hygrothermal loads and exposure to wind driven rain erosion on the performance of different types of CEBs. Practices in the manufacturing of CEBs as well as existing trends and studies in the field of soil stabilization were reviewed. The main concern with the use of earth based bricks was durability in hot and humid climates with high annual rainfall, a limitation which interferes with the usefulness and expanded use of CEBs in these regions. The performance of CEBs also varies widely according to the makeup of the soil, the manufacturing and stabilization techniques used, and the climate in which they are used. One common concern about the use of CEBs in humid climates is that earth based bricks may not be able to resist hygrothermal loads and WDR erosion as well as conventional building materials. In order to examine the effects of deterioration and erosion in such environments, this study provided a scenario that aimed to replicate and exceed the conditions found in the humid tropics. A series of CEBs were fabricated based on field parameters, and the durability of these CEBs was then evaluated thro ugh accelerated environmental simulations. These simulations enabled the researcher to assess and characterize damage that could potentially be caused by hygrothermal loads of extreme heat and humidity and extreme wind driven rain (WDR). 5. 2 Discussion T he stated objectives in this study were achieved as described in the following sections. The original objectives, as expressed in Chapter 1, were: 1. Conduct a literature review of CEBs

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55 2. Evaluate the effects of hygrothermal aging on CEBs, and 3. Evaluation the e ffects of wind driven rain erosion. 5.2.1 Compressed Earth Bricks A literature review was conducted to explore the history of earth building techniques and to gain a greater understanding of the current trends in earth construction, which are characterize d by rapid growth and great potential. This objective was reached through the extensive review of existing literature in Chapter 2. Recent studies about earth construction techniques and current practices in the manufacturing of CEBs, the factors that cau se deterioration CEBs, and techniques for so il stabilization were presented. 5.2.2 Evaluate Hygrothermal Performance Hygrothermal performance of the CEBs was achieved by conducting an accelerated hygrothermal aging procedure that entailed subjecting CEB samples to 100% humidity and 100C heat to simulate extreme tropical environmental and weather factors affecting CEBs. The EDS results provided data about the microstructural variations from CEB samples that were exposed to aging and contrasted them with virgin samples. Since all samples were exposed to the same test parameters, the variation in the composition of the bricks before and after the test offered evidence of changes due to the exposure to heat and water. These variations in the elements that were recorded during the EDS analysis revealed that the effects of the tests varied by the type of CEB. These varying effects are most likely due to differences in composition of the CEB including the soil and the stabilizers used. The elements that sho wed the greatest fluctuations due to the aging process were carbon, oxygen, calcium and silica. These changes did not occur in all of the four

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56 sample types, and the detected levels of each element increased in some cases and decreased in others. This is t o be expected because the soil type and the presence of stabilizers both influence the ability of the brick to withstand effects of heat and water. Similar results were found by Obonyo when samples were exposed to the same testing parameters: The SEM EDS analysis it is clear that the chemical changes occurring within the microstructure can be directly linked to the existence of specific stabilizers which and how the CEBs reaction to the aging process. For example, the inclusion of lime triggers chemical r eactions that increase after one month of exposure increases carbon and calcium while decreasing oxygen and silica. Over the same time period, the chemical reactions that occur when fiber is included in the mix reduce carbon content by over 1/3 while sign ificantly increasing the oxygen, silica and calcium content. Although previous research recommended the inclusion of both lime and fiber for the case study context it is also clear that their use could result in both desirable and undesirable effects depe nding on how the mineralization of the organic inclusions affects hydration based chemical reactions ( Obonyo 2011) the fluctuations in constituent elements that will result fr om exposure to heat and water. For this reason, the composition of CEBs plays an important role in their potential durability. 5.2.3 Simulation of Wind Driven Rain Erosion The third objective, which was to determine the erosion levels due to WDR, was achi eved by conducting accelerated simulation tests with a modified spray rig based on test and an analysis was then conducted comparing the rates of erosion on different brick samples. The results showed that different methods of stabilization affect the capacity of the CEBs to withstand WDR loads. Since the methodology used provided a set of

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57 parameters in which the WDR acceleration was constant and the CEB samples differed fr om one another, the test results also showed that each brick reacted to the loads differently. The CEB that performed the best was the factory produced interlocking brick, which showed very little erosion. The reason is because it is manufactured with hig h compression equipment and the soil composition and stabilizer used have been developed for commercial use and high standards. The soil cement CEB did not perform as well as the factory produced interlocking CEB, but its performance was exceptional compar ed to the rest of the CEBs. The reason for this performance can be attributed to the stabilizer chosen, which in this case was cement. The cement lime and cement lime fluid CEBs performed similarly in the tests conducted, but unlike soil cement bricks, the ir erosion results show the potential for this type of CEB composition to deteriorate in the field under conditions of wind storms coupled with heavy rains. As for the soil cement fiber CEB, the erosion was the most significant when compared with the rest ( Kosmatka et al ., 2 002). This has implications for the strength of the chemical bonds: anges that accompany variations in fiber moisture content can Kosmatka et al., 2002 ). 5. 3 Conclusions A number of conclusions can be made from the results of this study. Among the chief historic limitations to the use of CEBs in developing countries of tropical climate

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58 are their ability to withstand frequent driving rain and high ambient temperature with high ambient humidity. Due to the fact that insufficient data has existed to d ocument the advantages of some CEB construction methods over others, expansion and increased use of this ancient technology has been slow. By promoting the development of CEB manufacturing techniques, including improved soil selection and more advanced typ es of manufacturing methods and stabilization techniques, CEBs can have a significant and sustainable impact to the housing needs of the developing nations in tropical climates. Properly stabilized CEBs, with appropriate climate based technological modifi cations and adaptations, can be an optimal choice for constructing several types of structures in parts of the world that have been historically unable to utilize this construction material. Due to the readily available and abundant soil supply which cons capacity to create more stable indoor climates, and their economic advantage s over walls made of other industrially manufactured materials such as fired bricks or concrete. The resu lts from this research support the advancement in the research and improvement of C E Bs E lectron microscopically techniques were used to demonstrate preliminary data on the microstructural and chemical changes in CEBs that were triggered by exposure to ext reme environmental weather simulation of extreme heat and humidity. The purpose for characteriz ing the se microstructural changes and reactions support the understanding of how the compositions of CEBs withstand extreme climatic exposure s

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59 Further the results for the erosion test provide useful information as to erosion resistance and some predictability to the service life for different types of CEBs. Clearly, CEBs that display ed minor da mage caused by the erosion test had a formulation that can be used to benchmark as an exemplary prototype for further research and application. And the performance of CEBs can be optimized through establishing correlations as seen in this study where the CEB with the least erosion had the least elemental variation in the EDS results, thus a direct link between these changes and desirable physical or mechanical properties can be established. Finaly, these experiments provide a preliminary and experimental tool that can be developed with further scientific research that can be applied to predict life expectancy and the ability to estimate CEB performance and expected service life. As additional data is collected and R&D protocols and testing methods are adopted, CEB construction certainly may expand into parts of the world which could benefit most from this simple, economical and ecologically conservative technology. 5.4 Further Research This study focused on hygrothermal exposure and the consequential damages to the structure of the bricks tested as well as the potential erosion caused by wind-driven rain. However, further and more comprehensive research should be conducted. For example, similar tests can be conducted on the bricks that are currently stored outside at the Rinker School yard at the University of Florida a location known for its relatively high humidity and annual rainfall. These CEB have been exposed to natural weathering for more than a year, and these results can be contrasted with the data from this study which employed simulated conditions. Another line of future research could address the effects of alternate stabilizers, such as bitumen, polymers, and chemical additives used

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60 in the concrete and road construction industry There are also additional fiber treatment options that could be investigated, such as fiberglass and treated wood fibers. Protective coatings are another variable that could potentially affect durability and should be studied. Finally, the testing of hygrothermal aging and the resulting chemical changes could be quantified over a longer period of time. This kind of analysis can be used to evaluate the effectiveness of soil selection, stabilizer selection, and method of brick compression, in order to identify the ideal composition of the CEBs, specifically in terms of the correct proportions of earth and stabilizers for each particular soil type.

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61 LIST OF REFERENCES Adam, E.A.. (2001). Compressed stabilized earth block manufacture in Sudan. Available: ht tp:// unesdoc.unesco.org/images/0012/001282/128236e.pdf Last accessed March 16 2011. Auroville Earth Institute, http://earth auroville.com Last accessed March 16, 2011. erra literature review: An overview of research Institute, Los Angeles. driven rain research in building and Industrial Aerodynamics 92(13) ; Pg. 1079 1130. Dynaflow, Inc., http://www.dynaflow inc.com/Services/matr&d.htm Last accessed April 4, 2011. University of Technology, Sydney. Houben, H. & Guillard, H.,(1994) Intermediate Technology Publications, London. Karagiozis, A.,(2002) ormance study phase I Oak Ridge National Laboratory Kerali, A. brick s University of Warwick, School of Engineering 2001. K osmatka S. H., Kerkhoff, B. & P anarese W. C. ( 2002 ). Design a nd control of concrete mixtures Skokie, Ill, Portland Cement Association. material information Science and Earth Observation,Material Characterization 53 ; Pg 171 180. components based on PhD thesis, Fraunhofer Institute of Building Physics. ioration of brick Construction and Building materials 18 ; Pg 299 307.

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62 Architecture Birkhuser Publishers for Architecture. Printed in Germany Obonyo, E. (2011). Developing enhanced, lignocellulosic fiber reinforcement for low cost, cementitious, construction materials ending second review for Architectural Engineering and Design Management Obonyo, E ., 2011. "Optimizing the p hysical, m echan ical and h ygrother mal p erformance of c ompressed earth b ricks" Sustainability 3 ( 4 );Pg. 596 604 weatherability of Building materials 16 ; Pg 163 172. R New York. Ransom, W. H. ( 1963 ) Research Station, London. Sem Lab, Inc., http://www.sem lab.com Last accessed March 16, 2011 Walker J. P., (2004) Earth Block Masonry ; Pg. 497 506.

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63 BIOGRAPHICAL SKETCH Joseph Exelbirt was born in C ali Colombia in 19 67 A t the age of ten he moved with his family to Israel and the at age of thirteen they relocated to Miami, Florida where he graduated from N orth M iami B each Senior High School and t he n pursued an undergraduate degree in Political Science at Tel Aviv University in Israel. Upon graduation, he worked in the diamond industry as the quality control officer of a major diamond manufacturer in the Ramat Gan Diam o nd District. After a brief relocation back to the United States Joseph retu rned to Colombia where he earne d an MBA from INALDE a Harvard affiliated institution Upon reentering the workforce, and advancing though the t extile i ndustry for several years, he gained experience from manufacturing of commodity prime materials to supplying the retail industry. Upon returning to the United States in 19 96 he worked in various fields to broaden his professional background and was e mployment with Dean Witter (finance) and W e ichert Best B each of Miami Beach F L (real e state ). Having a great interest in construction industry Joseph chose to enter into this occupation from the botto m up, and built his credentials being involved in residential and commercial remodeling project s. This j ourney led him to Gainesville FL to pursue a master s degree in sustainable building construction from the University of Florida With h is wife Michelle and three daughters supporting him through the journey he is looking forward to a vibrant career with in a n organization committed to sustainable developme nt with aspirations of implementing his expertise in international management and direction