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Rammed earth

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Title:
Rammed earth fiber-reinforced, cement-stablilized
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Simenson, Eric Walter ( author )
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English
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1 electronic file (121 pages). : ;

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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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This thesis examines the use of cement and synthetic plastic fiber additives to improve the strength of rammed earth walls. These additives can be an economical solution to increasing the strength of rammed earth, which by itself is typically a low-strength material when additives are not used. Cement can be easily incorporated into the soil mixture and it adds strength and durability to the wall. Modern fibers, such as polypropylene plastic, have high tensile strength, they are durable, and they can be incorporated into rammed earth material. The fibers can add shear strength and flexural strength to rammed earth material. Three mix designs were created: soil only, soil-cement, and soil-cement with fiber. Based on the results of this thesis, the use of cement additive in rammed earth significantly increased the compressive, shear, and flexural strength. The addition of fiber did not increase the ultimate strengths, but it did provide a secondary benefit of keeping material bound together after failure and increased residual strength after failure.
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Thesis (M.S.)--University of Colorado Denver.
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Includes bibliographic references.
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Department of Civil Engineering
Statement of Responsibility:
by Eric Walter Simenson.

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Auraria Library
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Auraria Library
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892633670 ( OCLC )
ocn892633670

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RAMMED EARTH: FIBER-REINFORCED, CEMENT-STABILIZED by ERIC WALTER SIMENSON B.S., University of Colorado Denver, 2011 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering 2013

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ii This thesis for the Master of Science degree by Eric Walter Simenson has been approved for the Civil Engineering Program by Dr. Frederick Rutz, Chair Dr. Kevin Rens Dr. Nien-Yin Chang Date: November 12th, 2013

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iii Simenson, Eric Walter (M.S., Civil Engineering) Rammed Earth: Fiber-Reinforced, Cement-Stabilized Thesis directed by Assistant Professor Dr. Frederic k Rutz ABSTRACT This thesis examines the use of cement and syntheti c plastic fiber additives to improve the strength of rammed earth walls. These additives can be an economical solution to increasing the strength of rammed earth which by itself is typically a lowstrength material when additives are not used. Cem ent can be easily incorporated into the soil mixture and it adds strength and durability to the wall. Modern fibers, such as polypropylene plastic, have high tensile strength, they are durable, and they can be incorporated into rammed earth material. The fiber s can add shear strength and flexural strength to rammed earth material. Three mix desig ns were created: soil only, soilcement, and soil-cement with fiber. Based upon the results of this thesis, the use of cement additive in rammed earth significantly incre ased the compressive, shear, and flexural strength. The addition of fiber did not i ncrease the ultimate strengths, but it did provide a secondary benefit of keeping material bou nd together after failure and increased residual strength after failure. The form and content of this abstract are approved. I recommend its publication. Approved: Dr. Frederick Rutz

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iv DEDICATION I dedicate this work to the family and friends who supported my efforts.

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v ACKNOWLEDGMENTS I would like to thank my advisor Dr. Frederick Rutz His interest in analyzing historic structures encouraged me to do the same an d follow my passion.

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vi TABLE OF CONTENTS CHAPTER I. EARTH CONSTRUCTION ............................. ................................................... ............ 1Advantages of Earth Homes ......................... ................................................... ....... 1Disadvantages of Earth Homes ...................... ................................................... ...... 2II. HISTORICAL BACKGROUND ......................... ................................................... ....... 4III. EARTH CONSTRUCTION RESEARCH .................. ................................................. 9Strength of Compacted Earth ....................... ................................................... ...... 10Soil Selection Criteria ........................... ................................................... ............. 10Direct Tensile Testing ............................ ................................................... ............ 11Structural Behavior of Rammed-Earth Walls ......... .............................................. 12Assessing the Anisotropy of Rammed Earth .......... .............................................. 12Soils Reinforced with Plastic Fiber................ ................................................... .... 13IV. MATERIALS ..................................... ................................................... ..................... 15Soil .............................................. ................................................... ....................... 15Sand and Aggregate ................................ ................................................... ........... 15Cement ............................................ ................................................... ................... 16Reinforcement ..................................... ................................................... ............... 17V. RAMMED EARTH PROCESS ........................... ................................................... ..... 18VI. OBJECTIVE OF STUDY............................. ................................................... ........... 24VII. MIX DESIGN.................................... ................................................... ..................... 25Soil Selection Requirements ....................... ................................................... ....... 25Optimum Moisture Content and Maximum Dry Density .. ................................... 32Cement and Fiber Additives ........................ ................................................... ...... 36

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vii VIII. EXPERIMENT DESCRIPTION ...................... ................................................... .... 38Unconfined Compression Test Preparation ........... ............................................... 38Direct Shear Preparation .......................... ................................................... .......... 44Modulus of Rupture Preparation .................... ................................................... .... 50IX. TEST RESULTS .................................. ................................................... ................... 53Unconfined Compression............................. ................................................... ...... 53Modulus of Elasticity ............................. ................................................... ............ 61Direct Shear ...................................... ................................................... ................. 66Modulus of Rupture ................................ ................................................... ........... 79X. CONCLUSION ..................................... ................................................... .................... 86Recommendations for Future Research ............... ................................................. 8 7REFERENCES ........................................ ................................................... ...................... 89APPENDIX .......................................... ................................................... .......................... 92New Mexico Building Code Excerpts ................. ................................................. 9 2Fiber Specifications from Manufacturer ............ ................................................. 1 04Unified Soil Classification System ................ ................................................... .. 105Gypsum Cement Specifications ...................... ................................................... 106Portland Cement Specifications .................... ................................................... ... 108

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viii LIST OF TABLES TABLE VII.1 Gradation Results from the Soil. ........... ................................................... .............. 27IX.1 Unconfined Compressive Strength for Soil Samp les. ............................................. 56IX.2 Unconfined Compressive Strength for Soil-Ceme nt Samples. ................................ 56IX.3 Unconfined Compressive Strength for Soil-Ceme nt-Fiber Samples. ...................... 57IX.4 Modulus of Elasticity for Soil-Cement Samples ................................................. ... 64IX.5 Modulus of Elasticity for Soil-Cement-Fiber S amples. .......................................... 65IX.6 Adjusted Modulus of Elasticity for Soil-Cemen t-Fiber Samples. ........................... 66IX.7 Soil Direct Shear Test Results. ............. ................................................... ................ 69IX.8 Soil-Cement Direct Shear Test Results. ...... ................................................... ......... 70IX.9 Soil-Cement-Fiber Direct Shear Test Results. ................................................... ...... 71IX.10 Soil Modulus of Rupture Test Results. ...... ................................................... ......... 81IX.11 Soil-Cement Modulus of Rupture Test Results. .................................................. .. 81IX.12 Soil-Cement-Fiber Modulus of Rupture Test Re sults. .......................................... 8 2

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ix LIST OF FIGURES FIGURE II.1 Pueblo de Taos. ............................. ................................................... ........................... 6II.2 Hakka Earth Houses. ......................... ................................................... ....................... 7II.3 Miller House. ............................... ................................................... ............................. 8V.1 Rammed Earth Forms. .......................... ................................................... ................. 19V.2 Concrete Foundation. ......................... ................................................... .................... 21V.3 Modern adobe wall............................. ................................................... .................... 22V.4 Rammed Earth Wall. ........................... ................................................... ................... 23VII.1 Sieve Stack. ............................... ................................................... .......................... 26VII.2 Liquid Limit. ............................. ................................................... ......................... 28VII.3 Casagrande Device. ......................... ................................................... .................... 29VII.4 Plastic Limit. ............................. ................................................... .......................... 31VII.5 Standard Proctor Tools. .................... ................................................... ................... 33VII.6 Air-drying Soil. ........................... ................................................... ........................ 34VII.7 Compaction Curve. .......................... ................................................... .................... 35VII.8 Polypropylene Fibers. ...................... ................................................... .................... 37VIII.1 Color of Soil-Cement and Soil. ............ ................................................... .............. 39VIII.2 Fibers in Soil. ........................... ................................................... .......................... 40VIII.3 Soil-Cement in Proctor Mold. .............. ................................................... .............. 41VIII.4 Extracted Soil-Cement Sample. ............. ................................................... ............ 41VIII.5 Capping Cylinders.......................... ................................................... .................... 43VIII.6 Unconfined Compression Sample. ............ ................................................... ......... 44VIII.7 Liner on Proctor Mold...................... ................................................... .................. 45

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x VIII.8 Liner inside Mold. ........................ ................................................... ...................... 45VIII.9 Liner filled with Soil. ................... ................................................... ...................... 46VIII.10 Pneumatic Jack. .......................... ................................................... ...................... 47VIII.11 Soil and Liner. .......................... ................................................... ........................ 48VIII.12 Cut Shear Samples. ....................... ................................................... ................... 49VIII.13 Beam Mold. ............................... ................................................... ....................... 51VIII.14 Modulus of Rupture. ...................... ................................................... .................. 52IX.1 MTS Machine. ................................ ................................................... ...................... 54IX.2 Forney Testing Machine. ..................... ................................................... ................. 55IX.3 Crushed Soil Sample.......................... ................................................... ................... 59IX.4 Crushed Soil-Cement Sample. ................. ................................................... ............. 59IX.5 Crushed Soil-Cement-Fiber Sample. ........... ................................................... ......... 60IX.6 Soil-Cement Stress-Strain. .................. ................................................... .................. 62IX.7 Soil-Cement-Fiber Stress-Strain. ............ ................................................... .............. 63IX.8 Soil Shear Stress. .......................... ................................................... ........................ 69IX.9 Soil-Cement Shear Stress. ................... ................................................... ................. 70IX.10 Soil-Cement-Fiber Shear Stress. ............ ................................................... ............. 71IX.11 Shear Stress Failure of Soil................ ................................................... ................. 73IX.12 Shear Stress Failure of Soil-Cement. ....... ................................................... ........... 74IX.13 Shear Stress Failure of Soil-Cement-Fiber. ................................................... ....... 74IX.14 Soil Direct Shear Plot. .................... ................................................... .................... 75IX.15 Soil-Cement Direct Shear Plot............... ................................................... ............. 76IX.16 Soil-Cement-Fiber Direct Shear Plot. ....... ................................................... .......... 77IX.17 Soil-Cement Modulus of Rupture. ............ ................................................... .......... 83IX.18 Soil-Cement-Fiber Modulus of Rupture. ...... ................................................... ...... 84

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xi IX.19 Soil-Cement-Fiber Modulus of Rupture Close-U p................................................ 8 4

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xii LIST OF EQUATIONS EQUATION IX.1 Unconfined Compressive Strength. ............ ................................................... .......... 53IX.2 Modulus of Elasticity. ...................... ................................................... ..................... 61IX.2 Shear Strength. ............................. ................................................... ......................... 68IX.4 Modulus of Rupture for 4-point loading. ..... ................................................... ......... 80

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xiii LIST OF ABBREVIATIONS in inch lb pound MOR modulus of rupture OMC optimum moisture content psi pounds per square inch SC soil-cement SCF soil-cement with fiber tsf tons per square foot UCS unconfined compressive strength

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1 CHAPTER I EARTH CONSTRUCTION Advantages of Earth Homes Rammed earth houses are universally available. Ea rth is a free building material and no person or company can monopolize the buildin g material. Anyone with a plot of land and a few helping hands can construct an earth en home. These homes require only simple building techniques, and materials can be lo cally sourced. Earth homes offer a sustainable housing solution for everyone in the wo rld. These houses are very durable and require little m aintenance over the life of the structure. The cost of maintaining a rammed earth can be very low. Typically, the only regular maintenance is refinishing the exterior wit h a fresh coat of plaster. This coating helps protect the wall from moisture and erosion. The soil in the wall contains no organic matter and it will not biodegrade overtime. Unlike rammed earth homes, wood homes will slowly deteriorate as the wood rots from moist ure and microorganisms. The earthen walls do not attract rodents or insects because the re is nothing in the wall for these pests to eat. Termites can cause serious problems for wo od homes, which makes earth homes an excellent choice in termite prone regions. The massive walls, usually at least 18 inches thic k, perform well in adverse weather conditions. The walls can handle high wind s, which can be beneficial in hurricane and tornado prone areas. The weight of w alls is self-anchoring against uplift forces and the thick walls are much more rigid than typical wood framed homes. Earth homes offer a natural barrier from cold temperature s and extreme fluctuations in

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2 temperature. The thick walls act as an energy coll ector and store heat from the sun. This energy is slowly radiated inside and it helps keep the indoor air temperature constant. Rammed earth homes are very quiet inside. The mas s of the walls provides exceptional insulation from outside noise. As Davi d Miller notes (Miller 1980), “Earth structures are also very quiet due to mass, added i nsulation, and double glazing. This lack of noisy and irksome furnaces, compressors, fa ns, and ducts helps contribute to peace of mind.” Many modern earth homes typically utilize radiant heat in the floors; thus, they do not have noisy forced-air furnaces fo r heating. Air-conditioning is typically not needed, even in desert climates, because the th ermal mass of the walls regulates the indoor air temperature. Disadvantages of Earth Homes Earth homes are very labor intensive to build. In areas with a high labor cost, there is a large upfront cost to construct an earth en home. The walls must be built onsite and there is no mass production of prefabricated bu ilding materials when it comes to building a rammed earth home. In developed countri es, rammed earth homes have difficulty competing with cheap building products, like wood. Wood homes can be rapidly built, which reduces costs associated with labor. Modifications are to existing rammed earth homes a re challenging. Rammed earth walls are much more permanent than typical wo od framed walls. It is not easy to cut new openings in walls for windows or doors. Th is can increase future construction costs if modifications to the structure are needed. Rammed earth is an unusual and uncommon building m aterial. It carries a stigma because people tend to think only the poor live in “mud huts”. The stigma is primarily a

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3 result of society being unfamiliar with modern ramm ed earth homes. Many examples of high-end rammed earth homes can be found in the Ame rican West. Still for many people, building a home from uncommon materials cre ates some apprehension in their mind. People might be uncertain about how the buil ding will perform or who will be qualified to inspect and service this unique struct ure. These are valid concerns and thankfully all these concerns can be addressed thro ugh education about rammed earth.

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4 CHAPTER II HISTORICAL BACKGROUND Building a shelter is a primitive instinct in huma ns. In the last several thousand years, ancient cultures across the globe built dwel lings of earth and stone. More recently, the industrial revolution brought assembly-line mec hanization that produces cheap building products of wood, steel, and concrete. As a result of the industrial revolution, the prevalence of earth buildings has declined in t he last century. A new era of earth building is on the horizon with people looking for sustainable, economical, and durable housing. This renewed interest brings challenges a s building experts must bring this ancient technology up to modern building codes and standards. Examples of rammed earth can be found all around t he world. Many of the ancient examples have disappeared as they succumbed to the forces of nature. Some of the first cities in the world were built from earth since earth was a readily available resource. Building materials in the Middle East we re scarce and they mainly consisted of earth and stone, as good timber was not abundantly available. The Tower of Babel in the seventh century B.C. was constructed of sun baked b ricks and parts of the Great Wall of China were built with rammed earth (Easton 2007). In the first century A.D., the historian Pliny the Elder documented rammed earth c onstruction in his book, “Natural History” (Bostock 1885). And then, besides, have we not in Africa and in Spa in walls of earth, known as "formaceoan" walls from the fact that they are moulded, rather than built, by enclosing earth within a frame of bo ards, constructed on either side. These walls will last for centuries, a re proof against rain,

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5 wind, and fire, and are superior in solidity to any cement. Even at this day, Spain still beholds watch-towers that were erected by Hannibal, and turrets of earth placed on the very summits of her mountains. It is from the same source, too, that we derive the substantial ma terials so well adapted for forming the earth-works of our camps and embank ments against the impetuous violence of rivers. What person, too, is unacquainted with the fact, that partitions are made of hurdles coated wi th clay, and that walls are constructed of unbaked bricks? From the Middle East, earth construction spread to parts of Africa and Asia. The Moors brought rammed earth and mud brick technology called adobe to Spain. Earth building technology then traveled to South America and eventually north to Mexico during the Spanish conquests. Prior to the arrival of the Spanish conquistadors, Native Americans, mainly the Pueblo people, used basic ear th buildings techniques throughout the American southwest around A.D. 700. Taos Puebl o community in northern New Mexico, Figure II.1, was established in the late 13th and early 14th centuries and located there is the oldest continuously occupied structure in North America (Easton 2007). It is one of the best examples of prehispanic architectur e in the Americas. It is made from adobe mud bricks and some of the walls are several feet thick. The main multistory structure consists of residential apartments that u sually have two rooms, one for sleeping/ living and the other for cooking. The primary acce ss to each apartment was by ladder through an opening on the roof. The roof entrance was designed for defensive purposes and the ladders could be removed if the village cam e under attack. Traditional doors

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6 were added later when the Spanish settled in the ar ea and spread their architectural influence. Figure II.1 Pueblo de Taos. The north side of the main structure at Taos Pueblo Photo by Captain-tucker. Used with permission. For the last several centuries different methods o f earth construction have been used throughout the world. A variation of adobe ca lled cob was common in the United Kingdom. Cob uses softball sized lumps of wet clay stacked together to form thick walls. Many examples of historic earthen buildings exist i n Rhone River valley of France. The French call rammed earth pis de terre and they used wooden forms filled with compacted layers of earth. The Chinese have used r ammed earth for thousands of years and the Hakka people of southern China currently oc cupy multistory buildings built from rammed earth, Figure II.2.

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7 Figure II.2 Hakka Earth Houses. A cluster of circular and square rammed earth homes in southern China. Photo by yaziswallow. Used with permission. More recently a significant amount of research int o rammed earth was performed by CRATerre (Center for the Research and Applicatio n of Earth) in France during the 1970Â’s to 1990Â’s under the leadership of Hugo Hoube n, Patrice Doat, and Hubert Guillard (Houben and Guillard 2008). CRATerre is s till conducting research and students can earn a graduate degree in Architecture Australia is another pioneer of modern rammed earth construction. The lack of good timber in Australia spawned a

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8 building industry focused around masonry, concrete, and earth. Both Australia and New Zealand have well established and detailed building codes for earthen structures. Even Colorado had two modern day rammed earth pion eers, Lydia and David Miller. The Millers built five houses around Greel y, Colorado during the 1940Â’s and early 1950Â’s (Miller 1980). The private residence of the Millers is shown in Figure III.3. California, Arizona, and New Mexico have many examp les of earth buildings and these states have a small, but very capable community of earth building experts. New Mexico even has a section in their current building code t hat specifies requirements for earth structures. Excerpts of the New Mexico building co de are in the Appendix. Figure II.3 Miller House. Ranch style house built with rammed earth by the Mi llers. Photo by Mother Earth News. Used with permission.

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9 CHAPTER III EARTH CONSTRUCTION RESEARCH The initial work on this thesis involved the revie w of numerous research papers, books, and other sources related to rammed earth. No published research was found on the use of plastic fiber reinforcement in rammed ea rth. Geotechnical papers discussed the use of fiber reinforcement, but these papers were n ot addressing the use of fiber reinforcement in rammed earth construction. Buildi ng a house from vertical walls of soil is a unique blend of structural and geotechnical en gineering, and relatively few research papers focus on this topic. Based upon the literature review, several research papers were selected for discussion in this thesis. These selected research papers guided the work in this thesis to a subject that had not been investigated. Specific ally, the subject of using fiber and cement together to improve the strength of rammed h ad not been thoroughly investigated. Also, there were no research papers on rammed earth that tested compressive strength, shear strength, and flexural strength in the same s tudy. The New Mexico and Australian building codes both have strength requirements, so research should focus on ways to improve the strength of rammed earth in order to me et building codes. Furthermore, research papers did not examine how fiber reinforce ment changes the material properties of rammed earth. Fiber reinforcement could be an e conomical means of increasing the strength of rammed earth. The content of the research papers that were selec ted for further discussion is summarized below. The main purpose of discussing these research papers is to help the reader understand the current body of knowledge. T he papers on rammed earth include

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10 studies on compressive strength, developing soil se lection criteria, tensile strength testing, structural behavior, anisotropic propertie s, and fiber reinforcement. Strength of Compacted Earth One study (Burroughs 2006) examined the strength o f rammed earth with varying amounts of stabilizers, like Portland cement. This study is significant due to the large number of soils tested, which numbered 104 differen t soils. The author performed 219 strength tests using varying amounts of lime, cemen t, and asphalt emulsion for stabilization. Stabilizers were added at an amount of 0-6% per dry soil weight. The strength test was unconfined compressive strength ( UCS). Each soil was tested for liquid limit, plastic limit, linear shrinkage, and gradati on. Burroughs was able to classify soils as favorable or unfavorable for stabilization. To be favorable for rammed earth construction, the UCS must be over 2 MPa (~290psi). Soils that consistently performed well had sand con tents >65%, plasticity index (PI) of <15, and a shrinkage of <6%. It was observed that these favorable soils gain relatively little compressive strength when stabilized with li me and/or cement. Unfavorable soils (<2 MPa) exhibited more strength gain when stabiliz ed, but their compressive strength still did not meet the 2 MPa criteria. Soil Selection Criteria Another study (Burroughs 2008) continued the resea rch started in the 2006 study mentioned previously. In this study by Burroughs, soil samples from other research studies were compared to the 104 samples collected by the author. Parameters for determining suitable soils for rammed earth include : clay/silt content, sand content,

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11 gravel content, liquid limit, plastic limit, plasti city index, and linear shrinkage. Optimal parameters are as followed: clay/silt content range d from 21% to 35%; sand content ranged from 30% to 70%; gravel ranged from 13% to 6 2%; liquid limit 35; plastic limit 16-19; plasticity index <15; and linear shrinkage < 6%. Linear shrinkage is the best discriminator in determining the suitability of a s oil for rammed earth and it was found that 93 of 100 samples with a LS<6% meet the 290 ps i criteria for unconfined compressive strength. In other words, soils that h ave low shrinkage generally have good strength for rammed earth walls. Gravel content an d plastic limit are the worst discriminators in determining the suitability of a soil. Direct Tensile Testing This study by Mesbah et al. (Mesbah et al. 2006) f ocused on how to test a compressed earth block containing randomly distribu ted natural fibers for reinforcement. The natural fibers were sisal fibers from the Agave plant and they ranged in length from 0.8 inches to 2.0 inches long. Natural fibers have been used throughout history as a means to reinforce earth and they are commonly foun d in adobe blocks. In this case, fibers were added at a rate of 0.5% per dry weight of soil. The authors devised a means to directly pull apart the block and test the tensile strength. It was noted that the fibers kept cracks from propagating and thus the tensile strength was increased. The longer fibers, 2 inche s, gave the blocks better residual strength after cracks formed. The fibers did not f ail, but they did pull out of the block. Overall, the fibers improved the tensile strength a nd more research is needed to determine the optimal length and quantity of fibers.

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12 Structural Behavior of Rammed-Earth Walls This study by Reddy and Kumar (Reddy and Kumar 201 1) was conducted to examine the ultimate compressive strength of full s cale rammed earth walls. This is an important study because actual full scale walls wer e tested. Previous studies reviewed for this thesis tended to focus on the testing of small cylindrical samples. This study by Reddy and Kumar draws correlations between the stre ngths of small samples and full scale walls. Three different sized specimens were tested: a prism measuring 6” long x 6” thick x 12” tall, a small wall measuring 24” x 6” x 28”, and a wall 30” x 6” x 118”. The prism had the highest average compressive strength, followed next by the small wall, and finally the wall had the lowest strength. Much of the variation between the strength of the three different specimens can be attributed to the slenderness ratio of each specimen. The walls were the most slender and this leads to b uckling as the walls deflect laterally when loaded vertically. Some important recommendations were collected fr om this study. The samples should have enough time to cure and all the samples should be roughly the same moisture content before testing. Compaction of the soil on the wet-side of the optimum moisture content (OMC) curve results in higher compressive s trength. Testing samples that are fully saturated is recommended since this approach is done in testing of masonry. Testing prisms rather than cylinders will better si mulate field conditions and this approach is done in masonry testing. Assessing the Anisotropy of Rammed Earth This study by Bui and Morel (Bui and Morel 2009) e valuates the possible anisotropic nature of rammed earth. Since monolith ic walls are constructed with layers

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13 of compacted soil, there is concern about bonding b etween layers and the variations within each layer. Layers that are too thick will not be compacted evenly. The upper portion of the layer will be more compacted than th e bottom, which means the density will be higher in the upper portion. To evaluate the rammed earth material, samples wer e loaded perpendicular to the layers. This simulated how a wall is typically loa ded from the dead loads of the building. The samples were also loaded parallel to the layers This simulated how the horizontal forces of wind or earthquakes might load a wall. T he results for compressive strength and failure modulus (the ratio between maximum stre ss and maximum deformation) were very similar. The study concluded at low stress, b efore separation of layers, the rammed earth acts as a continuous material. The possible density variation between the top and the bottom of a lift was also examined. A homogenization process determined an e quivalent elastic modulus for a layer of rammed earth. The homogenized sample was compared to a typical nonhomogenized rammed earth sample. Again, the compre ssive strengths were similar. Ultimately this study concluded rammed earth is is otropic if the layers remain bonded together. The results of this research have a significant impact on the study of rammed earth. By assuming the material is isotropi c, simplified models can be used to predict the behavior of rammed earth. Anisotropic material requires more detailed and complicated analysis. Soils Reinforced with Plastic Fiber This study by Jiang et al. (Jiang et al. 2010) com pared the engineering properties of soil reinforced with different lengths and perce ntages of polypropylene fiber. These

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14 samples were not rammed earth samples, but the stud y did provide general information on how fibers change the strength properties of soi l. Fiber lengths were 0.4 inches, 0.6 inches, 0.8 inches, and 1.0 inch. Fiber contents a s a percentage of dry soil weight were 0.1%, 0.2%, 0.3%, and 0.4%. The researchers measur ed the unconfined compressive strength and the shear strength using the direct sh ear test. It was concluded that fibers 0.6 inches or less increased both compressive strength and shear strength. Longer fibers decreased the compressive and shear strength. A fi ber content of 0.3% was the optimal content to increase both compressive and shear stre ngth. This study also examined the effect of aggregate s izes in the fiber-reinforced soil mixture. Aggregate sizes were <1mm, 1-2mm, 2-5mm, and 5-10mm. In general, increasing the aggregate size lowered the unconfine d compressive strength. The angle of internal friction peaked at 3.5mm aggregate. Cohes ion decreased as the aggregate size increased. Overall, the conclusion of this study i s polypropylene fiber can increase the strength and stability of soil.

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15 CHAPTER IV MATERIALS Soil One soil was obtained and it was the only soil use d in this experiment. The soil was a Clayey Sand (SC) as defined by the Unified So il Classification criteria. The liquid limit was 26 and the plasticity index was 6. The o ptimum moisture content (OMC) was 11.5% and the maximum dry density was 121 pounds pe r cubic foot. The optimum moisture content is the percentage of moisture in t he soil that allows for maximum density after compaction. All these tests were per formed by the author of this thesis. Linear shrinkage was not tested because Atterberg t ests indicate this was a low plasticity soil and these soils have very little shrinkage; th us, the linear shrinkage was likely below the <6% criteria defined in other research (Burroug hs 2006). This soil conformed to the ideal properties developed in other studies mention ed in this thesis. It did have a very low clay content, which means stabilization with ce ment was needed to achieve the desired strength parameters. Sand and Aggregate Sometimes it is necessary to add sand and aggregate to soil mixture. For this thesis, it was not necessary to add sand and aggreg ate. The native soil used in this project already had a high sand content; hence, its classif ication as a Clayey Sand.

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16 There are instances when sand and aggregate can im prove the rammed earth soil mixture. If the native soil was pure clay, it woul d be beneficial to add both sand and gravel. Pure clays have the tendency to shrink and swell, and this can lead to cracking in the wall. Another disadvantage of pure clay soil i s cement does not bind well with it. A general rule of thumb is the clay content of the ra mmed earth soil should be around 20 to 30 percent. It is worth noting that some studies (Burroughs 20 08, Jiang et al. 2010) have found large aggregate reduces the strength of ramme d earth. The larger material has a smaller surface area, which will reduce the frictio n surface and this can lead to lower strength in compression and shear. Gravel and other aggregate are not always used in rammed earth projects. One study (Burroughs 2008) found gravel content >13% ca n increase the strength of rammed earth. It should be noted that gravel, like pea gr avel, is typically graded to 3/8” diameter and smaller gravel can be about 1/8” diameter or la rger. Material passing through the No. 4 sieve (~1/8” diameter) is considered sand. Gr avel used in rammed earth projects is typically pea gravel or smaller, and the use of big ger aggregate is not common. Cement Type I/II Portland cement was used to stabilize th e soil. For this project, cement was used at a rate of 6% per dry soil weight. The New Mexico building code specifies a minimum of 6% cement for stabilized rammed earth. Other studies mentioned previously in this thesis have used ranges of 5% to 10% cement One author found low cement contents, ~2%, can actually lower the strength becau se the cement interferes with the

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17 inter-particle bonding of the clay (Minke 2006). T hat author and other researchers consistently find cement contents above 2% increase the strength of the soil mixture. Hydrated lime is another means of stabilization. Lime is well suited to soil with high clay content. The lime does not interfere as much with inter-particle bonding of the clay. For this study, lime was not preferred as a stabilizer because the overall clay content of the final soil mixture was only ~20%. A lso, cement seems to be the preferred method of stabilization amongst the research studie s. Reinforcement Polypropylene fiber was used in this study. The f ibers were short (0.5 inch) in length and mixed into the dry soil at a quantity of 0.3% per dry weight of soil. These parameters are based upon the study of fiber-reinfo rced soil (Jiang et al. 2010). Other studies (Consoli 1998, 2011) have used longer fiber s and incorporated greater quantities of fibers into the soil. Longer fibers have disper sion problems and tend to not mix well with the dry soil as observed by the author of this thesis. Greater quantities of fibers can lower compressive strength and shear strength. Based upon trail batches of soil with various amou nts of polypropylene fiber, it was determined that 0.3% fiber content was acceptab le for this thesis. Higher amounts tended to ball up and disperse poorly in the soil. Lower amounts resulted pockets of soil that had very little fiber reinforcement.

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18 CHAPTER V RAMMED EARTH PROCESS Earth buildings are still being built all over the world. The buildings range from simple one room homes to high-end luxury homes. Th ousands of years of refining building techniques and more recently the use of ap plied science have resulted in a construction method that is a mix of art and scienc e. Rammed earth research is ongoing at many universities throughout the world and the body of knowledge surrounding rammed earth is continuously expanding (Maniatidis and Wal ker 2003). Rammed earth is an old building technique that has benefited from modern science. The basic principle is compaction of a so il mixture into rigid forms to create monolithic walls. The soil mixture is typically ~25 % clay, ~60% sand, and ~15% gravel (Burroughs, 2008). Modern practice is to stabilize the soil mixture with about 5-10% hydrated lime or Portland cement as a percentage of the dry weight of soil. Concrete forms or other heavy duty forms are needed to withs tand the compaction force and contain the earth wall until it hardens. Typical m onolithic walls are 18 to 24 inches thick and usually limited to two stories in height.

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19 Figure V.1 Rammed Earth Forms. These plywood and steel framed forms are held toget her in the middle with steel straps. Photo by Eric Simenson. The loose soil mixture is wetted to its optimal mo isture content (OMC) and placed in a loose layer, or “lift”, about 8 inches thick. Pneumatic “pogo-stick” tampers, similar to those used in small back-fill compaction jobs, are used to compact the soil (Adobe Builder 2001). Layers that are too thick wi ll potentially have areas that are not compacted because the tamper is not powerful enough to compact deep lifts of soil. In practice, the final compacted layer typically is ab out half the thickness of the loose lift. The forms are usually left in place for a few days until the cement partially cures. Depending upon the wall thickness, the wall may tak e several months or more to fully cure.

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20 Modern rammed earth buildings can incorporate many features to improve the performance and safety of the structure. The most common features include concrete foundations and concrete bond beams at the bottom a nd top of the walls, respectively. Other design features include the use of steel rein forcement with vertical and horizontal rebar embedded in the wall. The use of rebar is rel atively uncommon in rammed earth construction and it is use in other types of earth construction techniques has not been documented. The structural performance of the buil ding can also be improved by limiting the size and location of doors, windows, a nd other openings. These basic principles are very similar to masonry design. Arc hitectural features usually include large roof overhangs to keep rain from eroding the walls. To illustrate some of these modern features, Figur e V.2 shows a typical rammed earth foundation. A keyway is constructed in the t op of the foundation to transfer shear forces. Figure V.3 shows both a concrete foundatio n and a concrete bond beam on an adobe house. Modern rammed earth and adobe walls h ave some similar features, like bond beam and concrete foundations, because buildin g codes require these features.

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21 Figure V.2 Concrete Foundation. Concrete foundation with a keyway serves as the fou ndation for a rammed earth wall. Photo by Eric Simenson.

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22 Figure V.3 Modern adobe wall. Concrete foundation and concrete bond beam on an ad obe wall. Photo by Eric Simenson. Special admixtures can be incorporated into the so il and special coatings can be applied to the finished wall to improve performance Many modern rammed earth buildings are coated with plaster and newer product s like acrylic sprays are utilized as wall coatings that provide weatherproofing. Coatin gs, like acrylic, act as waterproofing, which helps prevent the wall from eroding due to mo isture. Plaster and stucco coatings

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23 provide a durable exterior surface that takes the w ear and tear from mother nature. It is routine maintenance to restore coatings at regular intervals. Overall, the design of rammed earth buildings larg ely depends upon the soil properties and the location of the building with re gards to climate and environmental hazards. Some earth buildings are currently hundre ds of years old and they were made without the use of cement and special coatings. Ot her buildings in moist climates need additional detailing to prevent water from destroyi ng the walls. Figure V.4 Rammed Earth Wall. The plywood forms were removed after one day on thi s cement stabilized rammed earth wall in New Mexico. Photo by Eric Simenson.

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24 CHAPTER VI OBJECTIVE OF STUDY The purpose of this study was to test the engineer ing properties of rammed earth with polypropylene plastic fibers and Portland ceme nt additives. Currently, there is no published research on the use of plastic fiber rein forcement in rammed earth. The materials included a suitable soil that meets crite ria established by other researchers in peer-reviewed journals (Bryan 1988, Burroughs 2006, 2008). Additives to the soil included Portland cement Type I/II, polypropylene f iber, and water. The three mix designs for the experiment were soil, soil-cement, and soil-cement-fiber. For the soilcement and soil-cement-fiber mixes, the minimum str ength requirements were 300 pounds per square inch compressive strength and 50 pounds per square inch modulus of rupture (New Mexico Building Code 2009). According to the Australian building code, the rammed earth material was assumed to have no sh ear strength (HB 195 Standards Australia 2001). Unconfined compression, direct shear, and beam fle xure tests were performed on the three mix designs. Analysis of the test result s included comparison of ultimate strengths and also the behavior of the material dur ing testing.

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25 CHAPTER VII MIX DESIGN Finding a suitable soil is a crucial step in ramme d earth construction because the mix design consists of over 90% moist soil and the remainder being soil additives, like cement. Poor soils can be used if larger quantitie s of cement are added to increase strength. Cement is a costly additive and one of t he advantages of rammed earth construction is minimizing material cost; thus, min imizing cement is a goal for most builders. Soil Selection Requirements Several research papers (Bryan 1988; Burroughs 200 6, 2008) offer guidance on selecting soils. The soil mixture is typically abo ut 25% clay, 60% sand, and 15% gravel. The gravel content needs to be fairly small with a limited amount of material being retained on the No.4 sieve. To determine clay/sand /gravel content, dry soil was passed through a stack of sieves with progressively smalle r openings. Upon inspection, the soil for this experiment contained some percentage of cl ay and this clay portion needed to be removed from the soil before putting the soil throu gh the sieve stack. The reason for this procedure was the clay sticks on the finest sieve ( No. 200) instead of passing through it. To measure the clay content, the soil was washed th rough a No. 200 sieve. The clay content was determined by comparing the original dr y weight of the soil to the dry weight of the soil remaining on the No. 200 sieve. The so il washed through the No. 200 sieve was considered the clay portion of the soil. Below is Figure VII.1 showing the washed and dried soil sample ready for gradation through t he sieve stack.

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26 Figure VII.1 Sieve Stack. The soil sample is placed on the screen and it is s haken through progressively finer screens. For this project, approximately 3% was retained on the No.4 screen and this was considered to be the gravel fraction of the soil. Approximately 20% passed through the No. 200 sieve and this was the clay fraction. The remaining 77% was sand of various grain sizes. For this experiment, the fraction pas sing the No. 200 sieve was considered

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27 clay and not silt due to the properties exhibited d uring the Atterberg tests. Clay is cohesive and it displays predictable behaviors duri ng the Atterberg test. On the hand, silt can be unpredictable and can be very sensitive to m oisture. For example, adding one percent moisture to silt can cause it to go from a stiff soil to almost liquid. It is very difficult to perform an Atterberg test on silt. Fo r these reasons, it can be justifiably assumed that clay was in the soil and not silt. Below are the results from the gradation test and Atterberg test. Based upon these results, the soil could be classified with the Unif orm Soil Classification System. Table VII.1 Gradation Results from the Soil. Sieve Size [mm] Sieve Size Cumulative Soil Retained [g] % Retained % Passing 4.75 4 18.4 3.2 96.8 2 10 71 12.5 87.5 1.19 16 115.8 20.4 79.6 0.425 40 231.4 40.8 59.2 0.25 50 281.5 49.7 50.3 0.15 100 368.7 65.1 34.9 0.075 200 435 76.7 23.3 Pan 451.6 79.7 20.3

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28 Figure VII.2 Liquid Limit. The results of the Atterberg Liquid Limit test. As shown in Table VII.1 above, the soil for this e xperiment meets the gradation criteria explained in previous research (Bryan 1988 Burroughs 2006, 2008) for clay, sand, and gravel. The approximate ideal quantities are 20% to 30% clay, 70% to 80% sand, and a small percent of less than 10% as grave l. The soil was obtained from Pioneer Sand Company at 6379 Valmont Road Boulder, Colorado 80301. Pioneer supplies a variety of landscaping materials and they called th is soil “fill dirt”. According the supplier, it is essentially soil used for backfilli ng and it is not meant for growing plants. Figure VII.2 displays the liquid limit results fro m the Atterberg test. The test method used was ASTM D4318 “Standard Test Methods f or Liquid Limit, Plastic Limit, and Plasticity Index of Soils”. The test was perfo rmed using a standard device developed by Professor Casagrande.

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29 Figure VII.3 Casagrande Device. The standard device used to test the liquid limit o f soils. A layer of moist soil was placed smoothly into the brass cup shown in Figure VII.3. A groove was cut through the middle of the sample using a special grooving tool as specified in ASTM D4318. The test was performed by turning a crank on the Casagrande device, which drops the brass cup a stan dard distance. Each drop is called a “blow” and the total blow count was recorded when t he groove in the soil closes at which

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30 time the test was completed. As seen in Figure VII .3, a portion of the groove has closed and the test is completed. The test was performed three times using soil with different moisture contents. The liquid limit is defined as the moisture content at which it takes 25 blows to close the groove. The purpose of testing three samples is to have one point below 25 blow counts, one point near 25, and the la st point above 25. The three points should form a straight line and graphically the 25 blow count point on the line is used to determine the liquid limit. ASTM does allow a liqu id limit to be determined from testing just one sample. This procedure is necessary when a limited amount of soil is available for testing. For this thesis, 100 grams of soil wa s reserved for the Atterberg tests, which allowed three liquid limit tests and the plastic li mit test to be performed. In general, pure clays tend to have a higher liqui d limit than sandy soils and testing the liquid limit of a soil can give someone a rough idea of the suitability soil for rammed earth. Pure clays should be avoided due to their tendency to shrink and swell, which causes cracking. On the other hand, pure san d is not wanted because it has no cohesion between the sand grains and it cannot be f ormed into a wall. Suitable soil has a small fraction of clay and the remainder is sand. The sticky, cohesive property of clay helps bond together all the sand grains. Three liquid limit samples were tested at varying moisture contents to establish a linear trend line. Since the trend line closely fo llows the points, the sample at 25 blows is used to determine the liquid limit of 26% for this soil. The plastic limit was tested in accordance with A STM D4318. The test involved rolling thin ribbons of soil on a glass plate. The plastic limit is defined as the moisture content at which a ribbon of soil can be rolled 1/8 ” thick. Higher moisture contents allow

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31 the ribbons to easily be rolled. The procedure is to slowly reduce the moisture content by actively rolling the soil on the glass plate. At t he plastic limit, the soil will be at the lowest moisture content needed to form the 1/8” thi ck ribbon. The plastic limit was tested and determined to be 15. Figure VII.4 Plastic Limit. The 1/8” thick ribbon of soil has reached the plast ic limit. The plasticity index is determined by subtracting the plastic limit from the liquid limit. The plasticity index was 11. According to the Unified Soil Classification System, a soil with these gradation and Atterberg propertie s is classified as a Silty Sand/Clayey Sand with the symbol SM-SC. As previously describe d, the soil exhibited some cohesion during the Atterberg limit tests; thus, the soil is more likely a Clayey Sand (SC). Silt is non-cohesive and it can be very moisture sensitive when performing these tests. For

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32 example, some silt can have a liquid limit that is very close to the plastic limit. The unusual behavior is common with silts and this beha vior was not observed during testing for this thesis. Overall, this soil passed the gen eral requirements for rammed earth material. Optimum Moisture Content and Maximum Dry Density Upon determination of a suitable soil, the next st ep was to calculate the optimum moisture content and maximum dry density of the soi l. These values were calculated using a Standard Proctor test in accordance with AS TM D698 “Standard Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort (12400 ft-lbf/ft3)” (ASTM D698 2012). A split mold was the best choice because the compacted samples could be easily extracted from the mold. Without a split mold, the compacted sample was very difficult to remove from the mold. Typica lly, the sample would be pried out of the mold in small pieces and a composite sample of small pieces would be used to determine the moisture content. The split mold, shown in Figure VII.5, was also ne eded to prepare rammed earth samples for unconfined compression and direct shear testing. The unconfined compression samples were prepared by following the standard proctor procedure and creating a compacted cylinder of soil. Those tests are described in more detail in Chapter VIII.

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33 Figure VII.5 Standard Proctor Tools. The split mold seen on the left and the standard 5. 5 lb hammer on the right. The soil was prepared for the standard proctor test by air-drying it for 24 hours and the moisture content of the air-dried was measu red. This was the preferred procedure because it is relatively easy to spread the soil on a tarp in the laboratory or outside on a sunny day. Smaller samples can be dried more rapid ly by placing them in an oven set at a low temperature. Given the volume of soil needed for this thesis, air drying was the most practical method that satisfied the ASTM D698 standard.

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34 Figure VII.6 Air-drying Soil. The soil was dried outside on a sunny day. Five samples were prepared for the standard Procto r test and the moisture content was increased by approximately 3% for each sample. Any material larger than the No. 4 sieve was removed in accordance with the test proce dure.

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35 Figure VII.7 Compaction Curve. The compaction curve was developed using five sampl es at varying moisture contents. Based upon the test results, the optimum moisture content (OMC) was 11.5% with a maximum dry density of approximately 121 pou nds per cubic foot. The OMC is the point where the soil obtains the highest densit y when compacted. For rammed earth, it is very important to prepare soil at the OMC in order to achieve the highest density and strength. For this thesis, Portland cement was added to some of the samples being tested. When water is added to cement, a chemical process o ccurs and the water is consumed during the reaction. In effect, some portion of th e water in the soil will be lost when cement is added. For this thesis, it was decided t hat water will be added only to bring the soil to its optimum moisture content. One study (R eddy and Kumar 2011) found the optimum moisture content was slightly higher, 0.4%, for soil-cement when compared to the original soil. It was decided that increasing the moisture content for the samples

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36 containing cement would introduce a new variable an d that would make it more difficult to compare the three soil mixtures. Cement and Fiber Additives Three mix designs were used in this experiment. T he first mix was simply soil at the OMC of 11.5%. The second mix was soil at the O MC plus 6% Portland cement. The 6% Portland cement was calculated as a percentage o f the dry weight of soil. The third mix was soil at the OMC plus 6% Portland cement and 0.3% ” polypropylene fiber. The 0.3% fiber was calculated as a percentage of th e dry weight of soil. The percentage of Portland cement was specifically chosen because the NM Building Code and the research cited in this thesis used 6% as the minimum amount of cement required to stabilize rammed earth. Other r esearchers (Minke 2006) have shown lower quantities of cement can reduce strength of t he rammed earth due to chemical interaction with the cement and clay. Higher quant ities of cement will most likely increase the strength of rammed earth, but higher q uantities are not always necessary and are not economical. Typically, a suitable soil for rammed earth will easily meet strength requirements outlined in the NM Building Code when low quantities, such as 6%, of Portland cement are used. The percentage of fiber was based upon the work of other researchers (Jiang et al. 2010). Typically low percentages, such as below 1% of fiber are used in mix designs. High amounts of fiber can reduce workability as the fibers tend to impede the mixing of materials. This phenomenon was observed during tra il batching for this thesis. Several trial batches were created to test the workability of the addition of fiber to the soil. Based upon previous research and trial batches, it was co ncluded that 0.3% fiber reinforcement

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37 would be sufficient for this thesis. Smaller quant ities left pockets in the soil where there were little or no fibers. Higher quantities tended to bunch up during mixing and this could have created weak spots in the samples becaus e the fibers do not bond to each other. The 0.3% fiber generated the highest streng th samples for other researchers and the objective of this thesis was to create higher s trength rammed earth by incorporating synthetic fibers. Figure VII.8 Polypropylene Fibers. The ” long polypropylene fibers used in the fiberreinforced samples.

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38 CHAPTER VIII EXPERIMENT DESCRIPTION Three tests were performed on the three mix design s. The first test performed was unconfined compression on cylindrical samples. The second test performed was direct shear on cylindrical samples. The third tes t performed was 3-point modulus of rupture on rectangular beams. Both the unconfined compression and modulus of rupture required 6 samples of each mix per test. The direc t shear required 9 samples of each mix. Unconfined Compression Test Preparation Samples for unconfined compression were prepared in accordance with the ASTM standard “Compressive Strength of Molded SoilCement Cylinder” (ASTM D1633 2007). The samples were made by compacting s oil into a standard Proctor mold following the same procedure previously mentioned f or determining the OMC and maximum dry density. The benefit of following this procedure was the samples were uniform size and each sample received the same amou nt of compactive force. The procedure used for this experiment was to mix enough soil to make two samples at a time. Materials were mixed in a 5-gal lon bucket and stirred together with a hand trowel. Initially, larger batches were attemp ted, but the problem was the soilcement would become noticeably stiffer about 20 min utes after adding water to the dry soil-cement mixture. The stiffer soil-cement made it difficult to compact into the mold. It was determined that only two samples could be pr epared at a time before the soilcement created any issues with compaction.

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39 Figure VIII.1 Color of Soil-Cement and Soil. After adding the Portland cement, the mixture turns a gray color. The method was to mix all the materials dry then a dd water. It was much less effort to mix dry materials and materials mixed tog ether better when dry. The fibers have a tendency to clump together and extra mixing was n eeded to evenly disperse the fibers. If clumps of fibers formed, the clumps were pulled apart by hand. Mixing was completed once the gray color of the cement covered all the s oil and the original brown color of the soil could no longer be seen. Mixing of fibers was completed once random sampling of the mixture showed even dispersion of fibers throug hout the mixture.

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40 Figure VIII.2 Fibers in Soil. Fibers are randomly distributed in the soil and the cement has not been added. The soil mixes were placed into the mold in three lifts following the same procedure for the standard Proctor test. Each lift was scarified to promote bonding between the lifts. Excess material above the mold was scraped off using a beveled edge and the tops of the cylinders were made smooth as p ossible. To facilitate sample extraction from the mold, the sides were lightly lu bricated with WD-40 prior to placing any soil mix in the mold. The lubrication was nece ssary because the soil-cement mixes had a tendency to stick to the sides of the mold.

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41 Figure VIII.3 Soil-Cement in Proctor Mold. The top surface has been trimmed and sample is read y for extraction from the mold. Figure VIII.4 Extracted Soil-Cement Sample. Sample removed from mold and ready for curing proce dure.

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42 The molded samples were individually placed in sea led plastic bags and allowed to cure for 28 days in a humid concrete curing room This was somewhat of a redundant procedure. The most important step in the curing p rocedure was seal the sample in a plastic bag. This ensured no moisture was gained o r lost from the sample. Controlling the moisture was one variable that was held constan t throughout this experiment. Placing the samples in a humid curing room followed the AST M standard. The reality was the samples did not benefit from being in the humid roo m; however, it was convenient to store the samples in the curing room, which was loc ated in the laboratory where the testing was performed. In practice, it is benefici al to moist-cure soil-cement similar to moist-curing concrete. However, moisture content w as controlled throughout the experiment and kept at 11.5%, so moist-curing was n ot done on any samples. One deviation from the ASTM procedure was made in this experiment. The standard calls for submerging the cylinder in water for 4 hours prior to testing. It was decided not to do this because the soil and soil-ce ment cylinder would absorb water at different rates. There was also some concern that the soil cylinders would fall apart if they were submerged. The ASTM procedure was specif ic to soil-cement, which can handle being submerged for prolonged periods. It w as determined that since moisture was being held constant in the samples, it would ha ve been contradictory to suddenly submerged the samples immediately before testing. Prior to testing, gypsum cement (plaster) caps wer e placed on both ends of the cylinder. Several initial specimens were tested wi thout caps and the results varied significantly. The primary reason for this is the surface of the cylinders was inherently uneven and compressive load was not distributed eve nly, which leads to stress

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43 concentrations and premature failure of the specime n. Hydrocal gypsum cement was used to cap all the cylinders. The end of the cap was made smooth with a piece of glass and a small level. Figure VIII.5 Capping Cylinders. Glass plates were used to create smooth caps made o f gypsum cement.

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44 Figure VIII.6 Unconfined Compression Sample. A capped sample of rammed earth ready for unconfine d compression testing. Direct Shear Preparation The first steps in preparing the shear samples star ted with the procedure for making an unconfined compressive sample. The soil mixture was compacted into the standard Proctor mold following the same procedure previously mentioned. Once the mold was filled and leveled with the beveled edge, it remained in the mold. A small soil sample liner of stainless steel measuring 2.5 inche s in diameter and 3 inches long was placed on top of the soil in the mold. The metal l iner was then forced down into the soil, thus filling the liner with the prepared soil sampl e. This procedure is illustrated in Figures VIII.7, VIII.8, and VIII.9.

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45 Figure VIII.7 Liner on Proctor Mold. Soil sample liner ready to be driven down into the Proctor mold. Figure VIII.8 Liner inside Mold. Soil sample liner successfully driven into the Proc tor mold.

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46 Figure VIII.9 Liner filled with Soil. The liner filled with soil after the excess soil is trimmed away.

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47 Figure VIII.10 Pneumatic Jack. The jack used to extract soil sample from soil samp le liner.

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48 Figure VIII.11 Soil and Liner. A stainless steel soil sample liner and the extract ed sample. The soil filled liner was placed in a sealed plast ic bag and stored in a humid concrete curing room for 7 days. After 7 days, the soil sample was removed from the liner using a pneumatic soil extraction jack, shown in Figure VIII.10. The soil sample measuring approximately 3 inches long was then sawcut into smaller samples measuring about 0.9 inches long. Typically, one 3 inch long liner would yield two shear samples. The soil at the top and bottom of the liner was usu ally damaged and not intact, so those areas were cut off. Figure VIII.12 shows examples of the cut shear samples that are ready for testing.

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49 Figure VIII.12 Cut Shear Samples. Three shear samples have been cut from a 3 inch lon g soil sample liner. The reason for using the 2.5 inch diameter stainle ss steel soil liner was the direct shear machine has a 2.5 inch diameter shear box. O nce the samples were saw-cut, they neatly fit into the shear box. One difficulty was this experiment required all samples receive the same compactive force and it would be v ery challenging to compact soil into the shear box. The liner solved this problem becau se it was driven into a standard Proctor mold. This method ensured all shear sample s were compacted the same amount. Another issue was the soil-cement samples needed t ime to cure. It would be inefficient to compact soil-cement directly into th e shear box and wait at least a week for it to cure. There was only one shear box available and it was not practical to wait one week to test one sample when 27 samples needed to b e tested.

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50 One advantage of using the liner was multiple samp les were cut from one liner. Another advantage is soil samples in the field are collected by placing these liners into hollow stem drill rigs. Soil laboratories prepare shear samples by extracting soil out of the liner and cutting it to the desired length. Wh en possible, this experiment used industry practices that could easily be replicated by other laboratories. Shear samples were tested in accordance with ASTM standard “Direct Shear Test of Soils Under Consolidated Drained Conditions” (AS TM D3080 2011). The shear box on the direct shear machine forced a failure plane through the midsection of sample. Cutting the samples to the correct thickness ensure d the failure plane occurred through middle of the sample. A force normal to the failur e plane was applied by adding weights to a moment arm on the machine. This force was var ied and three samples were tested at three different normal forces. Modulus of Rupture Preparation Modulus of rupture beam samples were created in cu stom built rectangular forms, shown in Figure VIII.13. The testing procedure fol lowed ASTM standard “Flexural Strength of Soil-Cement Using Simple Beam with Thir d-Point Loading” (ASTM D1635 2012). The beams measured 3 inches by 3 inches by 11.25 inches. In order to achieve uniform density, the volume of the mold was calcula ted and an amount of soil mixture was weighed to fill the mold. In theory, all of th e weighed soil would fit into mold if the proper amount of compaction was applied. The soil was placed in three lifts and each lift was scarified to promote bonding between layers. T his procedure was similar to the standard Proctor procedure used to create unconfine d compression samples and direct shear samples.

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51 Figure VIII.13 Beam Mold. Laminated melamine board was used to create a mold for the modulus of rupture test. Before adding the soil, the sides were lightly gre ased with WD-40 to prevent the soil mixture from sticking to the laminated wood. Once the mold was filled, a beveled edge was used to scrap off excess soil and create a smooth surface on the top of the beam. The mold filled with soil was wrapped with plastic and the sample was allowed to cure in the mold for 7 days in a humid concrete curing room Beam samples were removed from the mold by unscrewing one side of the mold, which allowed the samples to easily be removed.

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52 Figure VIII.14 Modulus of Rupture. The loading apparatus required to perform the modul us of rupture test. The Figure VIII.14 shows a beam placed in the test ing apparatus. Steel pipes with a diameter of 1.25 inches were used instead of stee l rods as specified in the ASTM standard. The pipes were a suitable alternative be cause the soil mixes were expected to fail at very low strengths and any deflection in th e pipe would be insignificant. Stronger steel rods would be needed for testing high strengt h material.

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53 CHAPTER IX TEST RESULTS Unconfined Compression All unconfined compression tests were performed in accordance with ASTM D1633 standard “Compressive Strength of Molded Soil -Cement Cylinder” (ASTM D1633 2007) on samples that were cured 28 days. Th e unconfined compressive strength (c) is calculated by dividing the ultimate load (Pu) by the area (A) of the cylinder. c = Pu/A Equation IX.1 Unconfined Compressive Strength. The unconfined compression tests were performed us ing the MTS Model #204.63LUBT Compression Testing Machine that has a 20,000 pound capacity. In accordance with ASTM D1633, the machine was program med to apply a constant load rate of 20 10 psi per second. The load and verti cal displacement were automatically recorded with the machine’s computer software. The raw data was entered into Excel, where plots of the stress versus strain were create d for each mix design. Before testing samples in the MTS machine, several trial samples were created of each mix. The purpose of the trial samples was to understand how the samples would perform during the compression tests and the main c oncern was how the plaster caps would affect the results. It was observed that the plaster caps sometimes cracked during the early stages of the load application from appro ximately zero to 100 psi compressive stress. The cracking of the caps caused the vertic al displacement to rapidly increase

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54 during this initial phase of loading. After the in itial settlement or cracking of the cap, the stress-strain curve began to follow a linear path t hat correlated with the predicted properties of the mix designs. The results of the trial tests are not included here because they were simply used to calibrate and hone the pro cedural steps for actual testing of the mix designs. Figure IX.1 MTS Machine. MTS Machine used for unconfined compression tests. The samples of soil only were tested using the For ney Model F-40EX-F-TPILOT Compression Testing Machine following ASTM D1633 pr ocedures. These samples were the first mix design tested and the MTS machine was unavailable at the time of testing. Unfortunately this machine does not automatically r ecord data and only ultimate stress

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55 was recorded for each sample. The ultimate strengt hs of the three mix designs were still compared, but stress-strain plots for the soil only mix design were not created. Figure IX.2 Forney Testing Machine. Forney machine used for compression tests and modul us of rupture tests. Below are summary tables of the unconfined compres sion tests for each of the three mix designs. Six samples of each mix design were tested. The ultimate compressive strength is listed for each sample in p ounds per square inch. The average compressive strength of the samples, the standard d eviation, and the coefficient of variation are also listed.

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56 Table IX.1 Unconfined Compressive Strength for Soi l Samples. nn nr nr rr nr !"#$ Table IX.2 Unconfined Compressive Strength for Soi l-Cement Samples. n nnnr $ nr $ rr nr !"#$

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57 Table IX.3 Unconfined Compressive Strength for Soi l-Cement-Fiber Samples. nr nnnr $ nr $ rr nr !"#$$ The soil-cement and soil-cement-fiber samples had nearly identical average compressive strengths. This suggests that the fibe rs had little or no influence upon the compressive strength. The fibers were found to hol d cracks together after failure. The soil-cement matrix was the sole provider of strengt h in compression. The strength contribution due to stabilization with cement is cl early evident in these test results. Adding 6% Portland cement increased the compressive strength of the original soil by approximately 11 times. Numerous researchers referenced in this thesis hav e documented the increase in compressive strength when cement is added to soil. However, studies have not compared the compressive strengths between soil-cement and s oil-cement with fibers. This thesis found the average strength of soil-cement and soilcement with fibers were essentially the same, but the standard deviation and COV was lower for the soil-cement-fiber mixture indicating the fibers gave the material more predic table average strength. A larger

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58 sample size would need to be studied before conclus ively stating that fiber additives produce samples with less strength variability. The results of this test confirm the work that oth ers have already done. The primary reasons for performing this test were two-f old: 1) validate cement-stabilization is possible with the selected soil, and 2) validate th e results with other studies. Clearly, cement-stabilization occurred because the compressi ve strength greatly increased when cement was added to the soil. The results were als o similar to studies referenced in this thesis. One additional goal was achieved through p erforming compression tests and that was the cement-stabilized samples all exceeded the minimum compressive strength of 600 psi specified in the New Mexico building code. This soil and mix design would be suitable for construction in the state of New Mexic o. The failure mechanisms for the three mixes were ma rkedly different. The soil tended to slowly deform under light loading in a du ctile, plastic type behavior. Both the soil-cement and soil-cement-fiber displayed sudden, brittle failure at much higher compressive stress levels than the soil only mixtur e.

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59 Figure IX.3 Crushed Soil Sample. Failed soil sample after completion of the unconfin ed compression test. Figure IX.4 Crushed Soil-Cement Sample. Failed soil-cement sample after completion of the u nconfined compression test.

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60 Figure IX.5 Crushed Soil-Cement-Fiber Sample. Failed soil-cement-fiber sample after completion of the unconfined compression test. The soil-cement cylinders would suddenly fail with vertical cracking along the outer edges, which indicates a splitting type failu re. Once failure occurred approximately 50% of the cylinder would crumble and fall off the platen. The soil-cement-fiber cylinders also failed suddenly with vertical cracki ng; however, nearly all of the material would remain connected through the fibers and the c ylinder would remain on the platen. The fibers were not able to increase the load capac ity of the cylinder; however, they did significantly change the behavior during failure. The plaster caps influenced the failure type by restraining the ends of the cylinder. Thes e restraints forced the stress path straight-down through the cylinder. This is a know n phenomenon, so the caps were poured as thin as possible to minimize the restrain ing effect.

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61 Modulus of Elasticity From data collected during the compression testing it was possible to create stress-strain curves for the soil-cement and soil-c ement-fiber mix designs. Using ASTM standard “Static Modulus of Elasticity and Poisson’ s Ratio of Concrete in Compression” (ASTM C469 2010) the modulus of elasticity was calc ulated. The Poisson ratio was not tested because it requires a special apparatus to m easure lateral deformation of the cylinder. The modulus of elasticity (E) was calcul ated using the chord modulus of elasticity formula where S2 is the stress at 40% of the ultimate load, S1 is the stress at 1, 2 is the strain at S2, and 1 corresponds with a longitudinal strain of 0.000050 E = (S2 S1)/(2 1) Equation IX.2 Modulus of Elasticity. The following stress-strain plots were generated f rom the compression testing of the soil-cement and soil-cement-fiber mix designs.

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62 Figure IX.6 Soil-Cement Stress-Strain. The stress versus strain plots for the six soil-cem ent samples. Sample #2 and Sample #6 exhibit the characteristic initial curve shape that indicates cracking and settlement of the plaster ca p. The first portion of the curve rises at a small angle until approximately 50 psi then the c urve rises steeply. The linear elastic portion of the curve occurs after this initial port ion. To avoid recording data from the cracking of the cap, Sample #1, #3, #4, and #5 were preloaded. The preload was applied by the machine and the load was adjusted using the machineÂ’s computer controls. The preload varied from less than 40 psi to 120 psi dep ending upon condition of the plaster cap and how the platens on the machine contacted th e plaster caps.

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63 Figure IX.7 Soil-Cement-Fiber Stress-Strain. The stress versus strain plots for the six soil-cem ent-fiber samples. The preload for the soil-cement-fiber samples was much smaller. This was due to better pouring of the caps. The plaster had a tend ency to harden very quickly and within as little as 10 minutes the material was sometimes unworkable. Practice with mixing and pouring the plaster led to the creation of thinner, smoother, and more level plaster caps. These higher quality caps required less preloading because they had less of a tendency to crack and settle. Despite all this attention to de tail, Sample #4 showed larger initial strain with little loading and this indicates a potentiall y uneven cap. Sample #1 also showed some initial issues with the cap and the overall cu rve did not take the same shape as the

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64 other sample. Sample #1 reached a high strength, b ut the stress-strain curve indicates some type of anomaly with this sample. The modulus of elasticity was calculated using Equ ation IX.2. According to the ASTM standard, the initial stress is taken at a str ain of 0.00005. For this thesis, this procedure was not practical because the plaster cap s created some anomalies during the first portion of the stress-strain curves. After r eviewing the data and plots, it was decided that the initial stress/strain point would be taken where the slope of curve began to rise steeply. At this point, it was assumed that soil-c ement was behaving linearly elastically. If the initial stress/strain point was taken prior to any cracking of the plaster cap, the result was a modulus of elasticity that was unreali stically low. Table IX.4 Modulus of Elasticity for Soil-Cement S amples. n % n & 'nr(r)nr *$+ *$ *$ *$ nr rr nr !"#$

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65 Table IX.5 Modulus of Elasticity for Soil-Cement-F iber Samples. nr % n & 'nr(r)nr +*+ *+ *++ *$ nr *+ rr nr !"#$ It is should be noted that Sample #1 of the soil-c ement-fiber mix exhibited an unusual stress-strain curve. The cylinder was able to deform much more than the other samples and it was the strongest sample of the soil -cement-fiber mix. One possible explanation for this anomaly was a small portion of the cylinder may have not been fully compacted. This could happen if one of the three l ifts in the cylinder was placed too thick, which would have caused the bottom portion o f the lift to be less compacted. As the sample was tested, the testing machine compress ed the weak layer until it was fully consolidated and this caused extra deformation in t he cylinder. Regardless of the explanation, this sample was suspect and another ta ble without Sample #1 was created. Removal of outlying data was done in accordance wit h ASTM “Standard Practice for Dealing with Outlying Observations” (ASTM E178 2008 ). The ASTM standard uses statistical analysis to determine if a data point c an be classified as an outlier. In this case

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66 Sample #1 was determined to be an outlier and remov ed from the Modulus of Elasticity calculations. Table IX.6 Adjusted Modulus of Elasticity for Soil -Cement-Fiber Samples. nr % n & 'nr(r)nr *+ *++ *$ nr rr nr *+ !"#$ With Sample #1 removed, the adjusted modulus of el asticity for soil-cement-fiber mix design in Table IX.6 was very similar to the so il-cement mix design. The average modulus of elasticity for soil-cement-fiber was E = 143,213 psi and the soil-cement was E = 141,581 psi. Given the results of the compress ion tests and the calculated modulus of elasticity, it appeared that adding fibers to th e soil-cement had little or no impact on these material properties. Again, the biggest chan ges in material properties came from the addition of cement. Direct Shear Direct shear tests were performed in accordance wi th ASTM D3080 standard “Direct Shear Test of Soils Under Consolidated Drai ned Conditions” (ASTM D3080

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67 2011) on samples that were cured for 7 days. The d ecision was made to test samples a 7 days rather than 28 days due to the large number of samples needed for testing. Furthermore, it was very difficult to prepare shear samples and it was not feasible to wait 28 days in between batches given time constraints o n the project. Many of the samples were damaged during saw cutting or during extractio n from the soil sample liner. Typically the middle of the soil sample liner would yield one good, undamaged sample that could be used for testing. Originally, it was thought that one soil sample liner would yield three samples, but this proved impossible due to damage during extraction from the liner and fracturing during saw cutting. Trial samples were tested to gauge how the machine would handle soil-cement, which is much stronger than typical soil tested in this machine. It was observed that high normal force was needed to keep soil-cement samples stationary during testing. The samples had a tendency to shift in the shear box be cause the shear force was large, so a large normal force was needed to hold the sample in place. Typically for soils, a larger normal force will cause failure at higher shear for ce. In order to predict the shear strength of a material, samples were tested at diff erent normal forces and plotted in Excel. Typically for soils, a linear relationship occurs b etween shear force and normal force. Shear stress () in pounds per square inch is calculated by dividi ng the shear force (Fs) in pounds by the cross-sectional area (A) of the sample measured in square inches. Three samples were tested at the same normal stress to obtain an average shear stress for that specific normal stress. The normal stress was applied at three different stress increments. The purpose for varying the normal str ess was to create a plot of average

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68 shear stress versus normal stress. In this plot, a linear trend line was drawn and from the trend line, the cohesion and friction angle were de termined. = Fs /A Equation IX.3 Shear Strength. All shear samples were tested in accordance with A STM standard D3080 using a Forney Direct Shear Machine Model #2050 SN 814. Th e machine has an adjustable displacement rate, which was set at 0.02 inches per minute. The ASTM Standard has a range of acceptable displacement rates from 0.0001 to 0.04 inches per minute. For soils, the displacement rate is chosen based upon the time it takes the soil to consolidate. For this thesis, the soil-cement was already consolidat ed and it did not consolidate even under the large normal stress applied to the samples duri ng shear testing. The displacement rate calculation outlined in the ASTM standard was not a pplicable in this case; however, the displacement rate within the standardÂ’s range was s elected. At this rate of displacement, it took approximately 15 minutes to complete testin g on one sample. It total, 27 samples were tested. Below are the summary tables and charts for direct shear testing of the three mixes.

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69 Table IX.7 Soil Direct Shear Test Results. nnnr nnnr nnnr+ nnnr nnnr+ nnnr+ Figure IX.8 Soil Shear Stress. Plot of shear stress and normal stress.

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70 Table IX.8 Soil-Cement Direct Shear Test Results. n nnnr nnnr nnnr+ nnnr+ nnnr nnnr Figure IX.9 Soil-Cement Shear Stress. Plot of shear stress and normal stress.

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71 Table IX.9 Soil-Cement-Fiber Direct Shear Test Res ults. nr nnnr nnnr nnnr+ nnnr+$ nnnr nnnr Figure IX.10 Soil-Cement-Fiber Shear Stress. Plot of shear stress and normal stress. The soil had a friction angle of 46.4 and cohesio n of 4.8 psi. This friction angle corresponded with the typical upper limit for dense sand (Das 2008). The friction angle was calculated by taking the inverse tangent of the slope of the line and the cohesion was

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72 calculated as the y-intercept of the line. Based u pon the soil classification and the compaction applied to each sample, these results co rresponded to what would be expected for this type of soil. The soil-cement had a friction angle of 45.2 and cohesion of 47.3 psi. The friction angle remained close to the soil, but the cohesion increased nearly 10 times. The increase in cohesion came from the cement. The cem ent created much greater bonding between soil particles and this caused the cohesion to substantially increase. The soil-cement-fiber and soil-cement had similar average shear strengths at normal stresses of 111.1 psi and 138.9 psi. At a n ormal stress of 166.7 psi, the soilcement-fiber had a significantly higher average she ar stress when compared to the soilcement, 245 psi and 212 psi shear strength respecti vely. This higher shear stress caused the trend line on the soil-cement-fiber plot to ris e at a much steeper angle of 55.5. The cohesion was calculated at the point the trend line intercepts the y-axis, and in this case, the value was -2.8 psi. It is theoretically imposs ible to have a negative value for cohesion, so it is reasonable to assume this value should be zero based upon the plot. The anomaly for the soil-cement-fiber samples was likely the higher shear strength at the maximum normal stress tested. This value of 245 psi seemed unusually high and lower value that was closer to the soil-ce ment value of 212 psi would be expected given the similarity in all the test resul ts thus far. At lower normal stress, the soil-cement and soil-cement-fiber samples produced similar shear strengths. Furthermore, the unconfined compression tests and m odulus of elasticity calculations showed soil-cement and soil-cement-fiber samples ha ve very similar properties. If the average shear stress of 245 psi for the soil-cement -fiber was closer to 212 psi, the trend

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73 line for the soil-cement-fiber would be very simila r to the trend line for the soil-cement. The new trend line would create a lower friction an gle and higher cohesion, similar to the soil-cement. If shear tests were performed again, some changes could be made that might improve the results. Letting the samples cure for 28 days would give the samples additional time to gain strength. The extraction o f the samples from the liner and also saw-cutting the samples may have introduced micro-c racks that influenced the results. Stronger samples might have been able to resist pot ential cracking caused by these procedures. Additionally, cutting only one sample from the middle of the liner might yield higher quality samples. The ends of the extr acted samples always showed signs of damage and these portions were cut away, but it is possible that all the damaged material was not removed. Figure IX.11 Shear Stress Failure of Soil. Failed soil sample from direct shear testing.

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74 Figure IX.12 Shear Stress Failure of Soil-Cement. Failed soil-cement sample from direct shear testing Figure IX.13 Shear Stress Failure of Soil-Cement-F iber. The two halves are still connected together with fi ber after failure.

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75 The most significant observation between the soils tested in shear was the soilcement-fiber samples remained connected together af ter failure. The two halves of the soil-cement-fiber samples had the typical failure p lane through the middle of the sample and the fibers kept the halves connected together. Figure IX.14 Soil Direct Shear Plot. Horizontal load and horizontal displacement plot fr om direct shear testing.

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76 Figure IX.15 Soil-Cement Direct Shear Plot. Horizontal load and horizontal displacement plot fr om direct shear testing.

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77 Figure IX.16 Soil-Cement-Fiber Direct Shear Plot. Horizontal load and horizontal displacement plot fr om direct shear testing. The direct shear machine had a maximum displacemen t of 0.3 inches. Two of the soil-cement tests ended before 0.3 inches because t he shear box was not positioned to allow for maximum displacement. Luckily, the sampl es still failed and some residual strength was recorded, so the data from these sampl es was considered valid. Almost all of the curves have an initial portion where the cur ve is horizontal. This is caused by the shear box moving until it was firmly against the sa mple. Typically a slight gap existed between the sample and the shear box, so the data s howed some horizontal displacement until this gap was closed. This does not alter the maximum shear stress results. Overall, the soil-cement and soil-cement-fiber exh ibited residual strength after failure. The residual strength comes from the roug hness between the two halves of the sample sliding over each other. Three of the soilcement samples had a rapid loss of

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78 strength after failure, Sample 8tsf-01, Sample 10ts f-01, and Sample 12tsf-01. The soilcement-fiber did not have these sharp declines. It was expected that the fibers would add more residual strength because the fibers would kee p the two halves connected. It is possible that the fibers helped prevent a sudden lo ss in strength. The observation that every sample with fiber remai ned connected together after shear failure indicated the fibers were well bonded in the soil-cement matrix. The fibers have a high tensile strength of 83-96 kips per squa re inch as specified by the manufacturer (see Appendix for material data sheet) and they have a large capacity to elongate before failure. As the two halves sheared apart, the fibers were put into tension as they tried to hold the halves together. The dir ect shear machine was unable to create enough displacement to fail the fibers. After reviewing the results, it was assumed that t he residual strength of the samples would be even more dramatic if the direct s hear machine allowed for greater displacement. Alternatively, direct tensile testin g might be required to fully test the strength and limits of the fibers in the soil-cemen t. In future studies, it would be interesting to continue the test until the fibers f ailed. At that point of failure, it would be possible to analyze how much strength the fibers ac tually contributed. Overall, the ultimate shear stress of the samples came from the strength of the soil-cement matrix. The fibers appeared to influence the strength only after the ultimate shear stress of the soil/cement was reached.

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79 Modulus of Rupture The modulus of rupture (MOR) tests were performed in accordance with ASTM D1635 standard “Flexural Strength of Soil-Cement Us ing Simple Beam with Third-Point Loading” (ASTM D1635 2012). This test measures the flexural strength of beams using a four point loading apparatus. The samples were t ested using the Forney Model F40EX-F-TPILOT Compression Testing Machine. This ma chine had a large lower platen that could accommodate the size of the beams. This test is specified in the New Mexico building code and cement-stabilized rammed earth mu st have a minimum MOR of 50 psi. It was one objective to determine if the cement-sta bilized samples in this thesis met the minimum strength requirement. Performing research on a material that met building code requirements would be more relevant to the ram med earth industry than testing a material that was unsuitable for building. It was hypothesized that the fibers would increase the MOR by delaying the onset of cracking and then holding the cracks together. Using natural fibers to delay the onset of cracking was documented during direct tensile te sting research performed by other researchers (Mesbah et al. 2006). In the MOR test the bottom of the beam was put into tension and the top of the beam was in compression. Soil-cement was assumed to have relatively low tensile strength, but the fibers hav e relatively high tensile strength. It was assumed that the fibers would carry the tensile str esses; thus, the soil-cement-fiber beams would have a higher MOR than the soil-cement beams. The modulus of rupture (R) is calculated by multip lying the load (P) and span length of the beam (L) and dividing those numbers b y beam width (b) multiplied by the beam depth squared (d). It should be noted that th e span length, width, and depth are

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80 measured in inches. The load is measured in pounds force. The span length is not the overall length of the beam rather it is the distanc e between the lower supports on the beam. In accordance with the ASTM standard, the sp an length was 9.25 inches for all the specimens. R = (PL)/(bd2) Equation IX.4 Modulus of Rupture for 4-point loadi ng. It should be noted that Equation IX.4 was used to calculate the MOR for the loading setup shown in Figure VIII.14, which was th e loading setup specified by the ASTM standard. The ASTM standard calls the test a three point loading test, but the setup they specify is actually a four point loading test. The supports on the top of the beam were spaced a distance of L/3 per the ASTM sta ndard. Placing the top supports at this distance modifies the 3-point MOR equation to the 4-point MOR equation. Trial beams were not created for this test because experience had been gained using the Forney machine during the compression tes ts. Also, the ASTM standard provided an average flexural strength of 94 psi for specimens with 6% cement. This information was helpful because it provided some es timation of the expected beam strength. The machine was adjusted to provide a co nstant load rate of approximately 5 pounds per second. The ASTM standard specifies a c onstant load rate of 100 5 psi/min in the extreme fibers of the beam, which equates to approximately 5 pounds per second applied by the machine. All of the beams cracked within the middle third o f the beam. Adjustments to the MOR calculation must be made if the crack is outsid e of the middle third. Below is a summary of the modulus of rupture tests for the thr ee mixes. The maximum load was

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81 recorded by the machine and Equation IX.4 was used to calculate the MOR for each sample. Table IX.10 Soil Modulus of Rupture Test Results. nn nr nr rr !"# Table IX.11 Soil-Cement Modulus of Rupture Test Re sults. n nnnr + $$ $ nr rr !"#

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82 Table IX.12 Soil-Cement-Fiber Modulus of Rupture T est Results. nr nnnr nr rr !"# Both the soil-cement and soil-cement-fiber samples had very similar results with an average modulus of rupture of 154 psi and 151 ps i, respectively. The soil-cementfiber had a lower standard deviation and coefficien t of variation. The soil-cement-fiber beams remained bonded together even after failure, but the beams could not handle any additional loading. The fibers would stretch if ad ditional load was applied. The soil had a modulus of rupture of only 5 psi an d it could barely handle any load. The soil almost no flexural strength as was anticipated before testing. One reason for using reinforced concrete lintel over doors and windows is unstabilized rammed earth homes have virtually no flexural strength and these lintels are needed to withstand bending that occurs over the openings. The results of these tests demonstrated the benefit of adding Portland cement to increase the flexural strength.

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83 Figure IX.17 Soil-Cement Modulus of Rupture. Failed soil-cement beam from modulus of rupture tes t.

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84 Figure IX.18 Soil-Cement-Fiber Modulus of Rupture. Failed soil-cement-fiber beam from modulus of ruptu re test. Figure IX.19 Soil-Cement-Fiber Modulus of Rupture Close-Up. Fibers hold the failed beam together.

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85 Again the most significant difference between the soil-cement and soil-cementfiber was the failure mechanism. The soil-cement w ould suddenly crack and fall off the testing apparatus. The soil-cement-fiber would sud denly crack, but the fibers would hold the beam together and the beam would remain on the testing apparatus. The fibers held the beam together, but the beam could not take any additional load. The fibers did not delay the onset of cracking, wh ich was unexpected based upon the research mentioned in this thesis. As soon as a visible crack appeared, it would propagate to the top of the beam and the beam would fail. If the fibers had delayed the onset of cracking, the soil-cement-fiber beams woul d have handle more load, but this did not happen. After reviewing the results it seemed the fibers w ere not stiff enough to allow the beam to take more load. If the fibers were stiffer it is likely the crack would have not propagated as quickly and the crack would have rema ined tight. Once the beam cracked, the fibers would begin to stretch, which allowed th e crack to widen and propagate. Fiberglass or steel fibers might have increased the MOR because they are significantly stiffer than the polypropylene fibers used in this thesis.

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86 CHAPTER X CONCLUSION The initial hypothesis was the addition of fibers to the soil-cement would greatly increase the shear strength and flexural strength o f the material. For the soil-cement and soil-cement-fiber samples, the results for unconfin ed compression, shear, and flexural testing were similar. The soil-cement-fiber sample s had statistically less variation for the unconfined compression and modulus of rupture tests The sample size of six is relatively small to make statistical conclusions, b ut the evidence in this thesis suggests soil-cement-fiber material has less variation in st rength compared to soil-cement. The main difference between the soil-cement and so il-cement-fiber was the failure mechanisms. Brittle failure happened on bo th the soil-cement and soil-cementfiber. However, the material in the soil-cement-fi ber samples remained bonded together after failure. While the fiber held the material t ogether, it did not significantly increase the load capacity. The cement additive provided th e additional strength and it also made the material brittle. One possible benefit of the fibers could be in the form of safety. During failure, the material in a rammed earth wall with fiber rein forcement would remain connected together rather than falling off the wall. A soilcement wall without fiber could potentially be hazardous if large chunks of the wal l were falling down on the occupants during an earthquake or collapse. Adding fibers se ems to be a relatively easy way from a construction standpoint to gain some additional saf ety. The results were somewhat surprising in that the f iber did not increase the strengths more than the results showed. One possib le explanation is the plastic fibers are

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87 much more elastic than the soil-cement. The differ ence in engineering properties causes the soil-cement matrix to resist the entire load un til failure. After failure the fibers are stretched and begin to resist the applied load, but most material strength is gone once the soil-cement matrix cracks. This thesis explored a new topic in rammed earth r esearch and tested the strength of rammed earth with fiber and cement additives. N o previous study had been published on the use of synthetic fiber reinforcement in ramm ed earth. From the test results, the soil-cement and soil-cement-fiber mix design had ne arly identical compressive, shear, and flexural strength. The soil-cement-fiber mixtu re did have less statistical variation in the test results. The soil-cement-fiber mixture al so exhibited different behavior during failure compared to the soil-cement, and it appears that the soil-cement-fiber mixture could improve the safety of rammed earth buildings during failure or collapse. Recommendations for Future Research The use of fibers in rammed earth is a topic that must be researched more thoroughly. Currently, there is very little publis hed research on this topic and relevant research about fiber-reinforced soils is specific t o geotechnical applications and not rammed earth walls. The published geotechnical pap ers focus on a wide variety of soils and these soils are not selected specifically for t heir use in rammed earth. Future research should follow the recommended soil selection criter ia mentioned in this thesis. There are endless possibilities for conducting mor e tests on rammed earth. Testing more samples in compression, shear, and fle xure would improve the statistical analysis of the material by providing a larger data set to analyze. Other test methods, like triaxial testing, are strongly recommended. This t est would likely produce the most

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88 accurate results for compressive and shear strength Researchers have not used this test on rammed earth and one reason for this might be du e to the difficulty and time involved in performing this test. Triaxial testing might ov ercome some of the challenges mentioned in this thesis that occurred with prepari ng the shear samples. Triaxial tests could be performed on samples using the same prepar ation procedures for compression test samples outlined in this thesis. Experimenting with different mix designs is highly recommended. The use of different fiber material is a promising area of res earch. Fiberglass and steel fiber could be used instead of polypropylene fiber. These mate rials have been successfully used to increase soil and concrete strengths, but their use in rammed earth has not been explored. Studies could also examine the possibility of reduc ing the cement content when increasing amounts of fiber reinforcement are used.

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89 REFERENCES Adobe Builder (2001). “Rammed Earth, Book #9.” New Mexico ASTM. (2007). “Standard Test Methods for Compressiv e Strength of Molded SoilCement Cylinders.” ASTM D1633-07 West Conshohocken, PA. ASTM. (2007). “Standard Practice for Making and Cur ing Soil-Cement Compression and Flexure Test Specimens in the Laboratory.” ASTM D1632-07 West Conshohocken, PA. ASTM. (2008). “Standard Practice for Dealing with O utlying Observations.” ASTM E178-08 West Conshohocken, PA. ASTM. (2010). “Standard Test Method for Liquid Limi t, Plastic Limit, and Plasticity Index of Soils.” ASTM D4318-10 West Conshohocken, PA. ASTM. (2010). “Standard Test Method for Static Modu lus of Elasticity and Poisson’s Ratio of Concrete in Compression.” ASTM C469-10 West Conshohocken, PA. ASTM. (2011). “Standard Test Method for Direct Shea r Test of Soils Under Consolidated Drained Conditions.” ASTM D3080-11 West Conshohocken, PA. ASTM. (2012). “Standard Test Method for Flexural St rength of Soil-Cement Using Simple Beam with Third-Point Loading.” ASTM D1635-11 West Conshohocken, PA. ASTM. (2012). “Standard Test Method for Laboratory Compaction Characteristics of Soil Using Standard Effort (12400 ft-lbf/ft3 (600 kN-m/m3)).” ASTM D698-12 West Conshohocken, PA. Bryan, A. J. (1988). “Criteria for the suitability of soil for cement stabilization.” Building and Environment 23(4), 309-319. Bryan, A. J. (1988). “Soil/cement as a walling mate rial—I. Stress/strain properties.” Building and Environment 23(4), 321-330. Bryan, A. J. (1988). “Soil/cement as a walling mate rial—II. Some measures of durability.” Building and Environment 23(4), 331-336.

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90 Bui, Q., and Morel, J. (2009). “Assesing the anisot ropy of rammed earth.” Construction and Building Materials 23, 3005-3011. Burroughs, S. (2006). “Strength of compacted earth : linking soil properties to stabilizers.” Building Research and Information 34(1), 55-65. Burroughs, S. (2008). “Soil property criteria for rammed earth stabilization.” Journal of Materials in Civil Engineering 20(3), 264-273. Consoli, N. C., Prietto, D. M., and Ulbrich, L. A. (1998). “Influence of fiber and cement addition on behavior of sandy soil.” Journal of Geotechnical and Geoenvironmental Engineering, 124(12), 1211-1214. Consoli, N. C., Zortea, F., Souza, M. D., and Festu gato, L. (2011). “Studies on the dosage of fiber-reinforced cemented soils.” Journal of Materials in Civil Engineering, 23, 1624-1632. Das, B. (2008). Advanced Soil Mechanics Taylor and Francis, New York, NY. Easton, D. (2007). The Rammed Earth House Chelsea Green, White River Junction, VT. Houben, H., and Guillard, H. (2008). Earth Construction—A comprehensive guide Intermediate Technology Publications, London. Jaquin, P. A., Augarde, C. E., Gallipoli, D., and T oll, D. G. (2009). “The strength of unstabilised rammed earth materials.” Gotechnique 59(5), 487-490. Jiang, H., Cai, Y., and Liu, J. (2010). “Engineerin g properties of soils reinforces by short discrete polypropylene fiber.” Journal of Materials in Civil Engineering, 22(12), 1315-1322. Kaniraj, S. R., and Havanagi, V. G. (2001). “Behavi or of cement-stabilized fiberreinforced fly ash-soil mixtures.” Journal of Geotechnical and Geoenvironmental Engineering, 127(7), 574-584. King, B. (1996). Buildings of earth and straw: Structural design for rammed earth and straw bale architecture Ecological Design Press, Sausalito, CA.

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91 Maniatidis, V., and Walker, P. (2008). “Structural capacity of rammed earth in compression.” Journal of Materials in Civil Engineering 20(3), 230-238. Mesbah, A., Morel, J. C., Walker, P., and Ghavami, K. (2004). “Development of a direct tensile test for compacted earth blocks reinforced with natural fibers.” Journal of Materials in Civil Engineering 16(1), 95-98. Miller, B., and Miller, L. (1980). Manual For Building A Rammed Earth Wall SelfPublished by Authors, Greeley, CO. Minke, G. (2000). Earth Construction Handbook, WIT Press, Southampton, UK. Minke, G. (2006). Building with earth: design and technology of a sus tainable architecture. Birkhuser, Boston, MA. NM Building Code (2009). “2009 New Mexico Earthen B uilding Materials Code.” Housing and Construction Building Codes General, 14 .7.4. Reddy, B. V. V., and Kumar, P. P. (2011). “Structur al behavior of story-high cementstabilized rammed-earth walls under compression.” Journal of Materials in Civil Engineering. 23(3), 240-247. Standards Australia. (2002). The Australian earth building handbook Sydney, Australia. Walker, P. J., and Dobson, S. (2001). “Pullout test s on deformed and plain rebars in cement stabilized rammed earth.” Journal of Materials in Civil Engineering 13, 291-297

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92 APPENDIX New Mexico Building Code Excerpts

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93 TITLE 14 HOUSING AND CONSTRUCTION CHAPTER 7 BUILDING CODES GENERAL PART 4 2009 NEW MEXICO EARTHEN BUILDING MATERIALS CODE 14.7.4.1 ISSUING AGENCY: Construction Industries Division of the Regulation and Licensing Department. [14.7.4.1 NMAC Rp, 14.7.4.1 NMAC, 1-28-11] 14.7.4.2 SCOPE: This rule applies to all earthen building materia ls contracting work performed in New Mexico on or afte r January 28, 2011, that is subject to the jurisdiction of CID, unless performed pursua nt to a permit for which an application was received by CID before that date. [14.7.4.2 NMAC Rp, 14.7.4.2 NMAC, 1-28-11] 14.7.4.3 STATUTORY AUTHORITY: NMSA 1978 Section 60-13-9 and 60-13-44. [14.7.4.3 NMAC Rp, 14.7.4.3 NMAC, 1-28-11] 14.7.4.4 DURATION: Permanent. [14.7.4.4 NMAC Rp, 14.7.4.4 NMAC, 1-28-11] 14.7.4.5 EFFECTIVE DATE: January 28, 2011, unless a later date is cited at the end of a section. [14.7.4.5 NMAC Rp, 14.7.4.1 NMAC, 1-28-11]

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94 14.7.4.6 OBJECTIVE: The purpose of this rule is to establish minimum standards for earthen building materials constructi on in New Mexico. [14.7.4.6 NMAC Rp, 14.7.4.1 NMAC, 1-28-11] 14.7.4.7 DEFINITIONS: A. Amended soil means improving an unqualified soil to a qualified state with the addition of other soils or amendments. B. Amendments means additive elements to soil, such as lime, por tland cement, fly ash, etc. which are “dry-mixed” into th e main soil body as a percentage of total weight to achieve stabilization. C. Buttress means a projecting structure providing lateral sup port to a wall. The buttress shall be incorporated into the foundat ion and wall system. (Refer to figure 1 of the earthen building figures supplement). D. CEB means compressed earth block. E. Keyway means a groove on the vertical rammed earth wall s urface for interlocking purposes. Refer to figure 3 of the ea rthen building figures supplement). F. Lift means a course of rammed earth, placed within the forms, and then compacted. G. Nailer means any material rammed into the wall that serve s as an attachment device. Refer to figure 4 of the earthe n building figures supplement). H. Optimum moisture means sufficient water (generally no more than ten (10) percent) mixed into the soil to attain suffici ent compaction. I. psi means pounds per square inch. J. Qualified soil means any soil, or mixture of soils, that attains 300 psi compression strength and attains 50 psi. modulus of rupture. K. Rammed earth means qualified soil that is mechanically or manua lly consolidated to full compaction. L. Round-cap nails means fasteners that include nails or screws in combination with caps of at least three-fourths (3/ 4) inches diameter or three-fourths ( ) inch square.

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95 M. Stabilization, stabilized means qualified soils that pass the wet strength test under ASTM D1633-00 or contain a minimum of si x (6) percent portland cement by weight. Stabilization is achieved through the use of amendments. N. Wet strength compression test means an approved testing laboratory process in which a fully cured rammed earth cylinde r is completely submerged in water a minimum of four hours according to ASTM D1633-00, t hen subjected to a compression test. [14.7.4.7 NMAC Rp, 14.7.4.7 NMAC, 1-28-11] 14.7.4.8 EARTHEN BUILDING MATERIALS: A. General. The provisions of this rule, 14.7.4 NMAC, shall c ontrol the design and construction of oneand two-family dwel lings in which earthen building materials form the bearing wall system. B. Allowable wall heights for earthen structures. All earthen structures whether adobe, burned adobe, compressed earth block rammed earth or terrn, shall conform to table 1. For purposes of using table 1, height is defined as the distance from the top of the slab or top of stem wall to the unde rside of the bond beam. Table 1 ALLOWABLE WALL HEIGHTS FOR EARTHEN STR UCTURES Maximum Sds Wall Thickness Maximum Height Maximum Sds Wall Thickness Maximum Height .25 10 120” .3 10 120” 12 128 12 128 14 144 14 144 16 144 16 144 18 144 18 144 24 144 24 144 .35 10 120” .4 10 120” 12 128 12 128 14 144 14 144 16 144 16 144 18 144 18 144 24 144 24 144 10 104” 10 96” 12 128 12 112 14 144 14 136

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96 .45 16 144 .5 16 144 18 144 18 144 24 144 24 144 This table is based on two story maximum, one and t wo family residential with seismic soil site class D1. [14.7.4.8 NMAC Rp, 14.7.4.8 NMAC, 1-28-11] 14.7.4.12 RAMMED EARTH CONSTRUCTION: A. General. The following provisions shall apply. (1) Rammed earth shall not be used in any building more than (2) stories in height. The height of every wall of rammed eart h without lateral support is specified in 14.7.4.8 NMAC table 1. The height of the wall i s defined as the distance from the top of the slab or top of stem wall to the underside of the bond beam. (2) Exterior rammed earth walls shall be a minimum of eighteen (18) inches in thickness. Exception: Exterior walls th at are also designed as solar mass walls (trombe) as defined by the passive solar heating wo rksheet, dated June 2004 and prepared by the state of New Mexico energy, minerals and nat ural resources department, are allowed and shall be minimum thickness of ten (10) inches, not to exceed twelve (12) inches. They shall be fully attached to or integra ted with any adjacent structural wall and topped with a bond beam that fully attaches them to the bond beam of any adjacent structural wall as described in 14.7.4.17 NMAC. (3) Interior rammed earth walls shall be a minimum of twelve (12) inches in thickness. (4) Unstabilized rammed earth walls must be covere d to prevent infiltration of moisture from the top of the wall a t the end of each workday and prior to wet weather conditions, whether the walls are cont ained within forms or not. (5) Fully stabilized rammed earth walls may be lef t unprotected from the elements. (6) In no case shall a rammed earth wall be reduce d in thickness with back to back channels or nailers. Channels or nailers r ammed on both sides of a running wall shall not be opposite each other to avoid an hourgl ass configuration in the wall section. Channels or nailers on both sides of a running wall shall be separated from each other vertically at a distance no less than the rammed ea rth wall thickness. (Refer to figure 4 of the earthen building figures supplement).

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97 (7) An architect or engineer registered in the sta te of New Mexico shall design and seal structural portions of two-story re sidential rammed earth construction documents. (8) The general construction of the building shall comply with all provisions of the 2009 New Mexico Residential Build ing Code (NMRBC), unless otherwise provided for in this rule. (9) Passive solar structures incorporating the use of solar mass walls (trombe), direct gain arrays or sunspaces (greenhou ses) as defined by the passive solar heating worksheet, dated June 2004 and prepared by the state of New Mexico energy, minerals and natural resources department, are allo wed. B. Fireplaces. Adobe or masonry fireplaces and chimneys in ramme d earth structures shall comply with 14.7.3.18 NMAC. They shall be integrated into adjacent rammed earth walls during construction or secured t o them by suitable steel ladder reinforcement or reinforcing rods. C. Count Rumford fireplaces. Count Rumford fireplaces are allowed as provided in 14.7.3.18 NMAC. D. Stop work. The building inspector shall have the authority t o issue a “stop work” order if the provisions of this section are not complied with. E. Lateral support. Lateral support shall occur at intervals not to e xceed twenty-four (24) feet. Rammed earth walls eighteen (18) inches to less than twenty-four (24) inches thick shall be laterally supported with any one or combination of the following: A rammed earth wall of bond beam height that intersects the running wall with at least sixty (60) degrees of support (refer to a figure 5 of the earthen building figures supplement); an adobe wall of bond beam hei ght and at least ten (10) inches in width that intersects with and attaches to the runn ing wall with at least sixty (60) degrees of support (refer to figure 5 of the earthen buildi ng figures supplement); a minimum twenty 20 gauge steel frame or wood frame wall of f ull height that intersects with and attaches to the running wall with ninety (90) degre es of support, that is properly crossbraced or sheathed (refer to figure 6 of the earthe n building figures supplement); a buttress configuration that intersects the running wall at ninety (90) degrees, of adobe or rammed earth. The buttress base must project a min imum of three (3) feet (or thirty-three (33) percent of the wall height) from the running w all and support at least seventy-five (75) percent of the total wall height (refer to fig ure 7 of the earthen building figures supplement). The thickness of a rammed earth buttre ss shall be at least eighteen (18) inches. The thickness of an adobe buttress shall b e a minimum fourteen (14) inches. Rammed earth walls greater than twenty-four (24) in ches in thickness are self-buttressing and do not require lateral support provided their d esign adheres to 14.7.4.8 NMAC table 1 and the other applicable provisions of this rule.

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98 F. Openings. Door and window openings shall be designed such t hat the opening shall not be any closer to an outside corne r of the structure as follows. (1) In rammed earth walls eighteen (18) inches to less than twenty-four (24) inches thick, openings shall not be located wi thin three (3) feet of any corner of the structure. (Refer to figure 8 of the earthen buildi ng figures supplement). Exception: Openings may be located within three (3) feet of an y corner provided a buttress extending at least three (3) feet from the structure supports the corner. A continuous footing below and a continuous bond beam above, shall be provided across such openings. (2) Rammed earth walls greater than twenty-four (2 4) inches thick are self-buttressing, with no special consideration for placement of openings within the area of the wall. G. Piers. Rammed earth piers supporting openings shall meas ure no less than three (3) square feet in area and no dimension shall be less than eighteen (18) inches. (Refer to figures 9-A and 9-B of the earthen buildi ng figures supplement). [14.7.4.12 NMAC Rp, 14.7.4.12 NMAC, 1-28-11] 14.7.4.13 FOUNDATIONS: A. General. Foundation construction shall comply with applica ble provisions of the 2009 New Mexico Residential Build ing Code, and the following: a minimum of three (3) continuous #4 reinforcing rods are required in minimum 2500 psi. concrete footings supporting rammed earth walls. S tem walls shall be the full width of the wall supported above or wider to receive formin g systems. Footings shall be a minimum of ten (10) inches in depth. B. Perimeter insulation. For the purposes of placement of perimeter insulation, rammed earth walls may overhang the bea ring surface up to the thickness of the perimeter insulation, but in no case greater th an two (2) inches. C. Keyway. A key way shall be provided where the rammed eart h wall meets the foundation system. The keyway shall be e stablished at the top of the stem a minimum of two (2) inches deep by six (6) inches wi de formed at the time of the pour, and shall run continuously around the structure to include any intersecting rammed earth wall sections. The rammed earth wall shall be full y rammed into this keyway (refer to figure 2 of the earthen building figures supplement ). Exception: Placement of vertical reinforcing rods extending a minimum twelve (12) in ches into the rammed earth wall. The vertical rods shall be minimum #4, imbedded int o the concrete and spaced fortyeighty (48) inches on center, maximum. D. Concrete grade beam. Rubble filled foundation trench designs with a reinforced concrete grade beam above are allowed to support rammed earth wall

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99 construction. An architect or engineer registered in the state of New Mexico shall certify the grade beam/rubble-filled trench design portion. [14.7.4.13 NMAC Rp, 14.7.4.13 NMAC, 1-28-11] 14.7.4.14 RAMMED EARTH SOIL SPECIFICATIONS: A. General. The soil shall not contain rock more than one-and -a-half (1 1/2) inch in diameter. The soil shall not contain clay lumps more than one-half (1/2) inch in diameter. The soil shall be free of all organic ma tter. The soil shall not contain more than two (2) percent soluble salts. B. Soil compressive strength. Prior to the start of construction, fully-cured rammed earth soil samples shall be tested at an app roved testing laboratory for compressive strength. The ultimate compressive str ength of all rammed earth soil, stabilized or non-stabilized, shall be a minimum th ree-hundred (300) psi. The compressive strength report shall be submitted with the permit application. This report may be waived if the builder provides certification of compliance. The certification must be dated within one year of the date on the applica tion for the building permit. Samples tested shall be representative of soil to be used o n the project for which the permit application is submitted. C. Stabilized rammed earth soil. The following shall apply to stabilization of rammed earth soil: Asphalt emulsion may not be used for stabilization of rammed earth soil. Thorough mixing of additives to the so il may be achieved by any method that assures a complete blending to a uniform color and texture. Stabilized soil is suitable soil that contains six (6) percent or more portland ceme nt by weight or that passes ASTM D1633-00. Samples tested shall be representative o f soil to be used on the project for which the permit application is submitted. The com pressive strength report shall be submitted with the permit application. Laboratory testing shall indicate rammed earth samples attained a minimum of two-hundred (200) psi after seven (7) days. If a different soil is provided at any time during construction, i t must meet the minimum requirements outlined above, prior to use in the structure. D. Unstabilized rammed earth soil. Unstabilized rammed earth soil is that containing less than six (6) percent portland cemen t by weight or that fails to pass ASTM D1633-00. The exterior of such walls shall be prot ected with approved stucco systems or other method approved by the building official. Re fer to 14.7.4.19 NMAC for weatherresistive barrier requirements. E. Amended soil. The following guidelines shall apply when amendin g soils to attain a qualified soil. Soil shall not contain rock greater than one-and-a-half (1 1/2) inch in diameter. Soil shall not contain clay lump s greater than one-half (1/2) inch diameter. Soil shall be free of organic matter. S oil shall not contain more than two (2)

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100 percent soluble salts. Soils to be mixed shall be sufficiently dry to blend completely to one uniform color and texture. The amended soil sh all be tested prior to use as per Subsection B of 14.7.4.14 NMAC. F. Forming systems. The forming system shall be adequate to contain t he material under compaction. It shall be properly pl umbed and braced to withstand the soil pressures as well as construction activity on and a round it. G. Placement of material, compaction and curing. (1) No amount of portland cement stabilized soil w ill be mixed that will not be placed in the wall system within sixty (60) minutes of its preparation. (2) Lifts of prepared soil shall be placed in the forms in relatively even layers not to exceed 8 inches in depth. Each lift shall then be rammed to full compaction. (3) Optimum moisture content as determined to meet minimum compressive strength shall be maintained for stabil ized and unstabilized walls. (4) Work will progress, lift-by-lift, until the wo rk approaches bond beam height. (5) Forms may be stripped immediately after rammin g is completed for a section of wall, providing ramming of adjacent sect ions does not affect the structural integrity of completed walls. (6) Portland cement stabilized walls not in forms shall be lightly spraycured with water at least five (5) spaced times dur ing daylight hours. This procedure shall continue for at least three (3) days starting from the time that the wall is exposed to the elements. Exception: Rammed earth walls left in forms three (3) or more days shall not require water-spray curing. H. Placement of attachment materials. (1) Nailers: Nailers incorporated into the rammed earth wall s hall be installed as follows (Refer to figure 4 of the eart hen building figures supplement); the rammed earth wall shall not be reduced in thickness with back-to-back nailers. To avoid an hourglass configuration in the wall section, nai lers on either side of a running wall shall not be opposite each other. Nailers on eithe r side of a running wall shall be separated from each other vertically a distance not less than the rammed earth wall thickness. Nailers shall be placed onto the wall s uch that the narrow dimension of the nailer is exposed on the race of the wall prior to ramming. Nailers shall be cured and sealed against moisture penetration prior to instal lation in forms. The nailers shall not extend the full depth of the wall. Box wood nailer s are not allowed. (Refer to figure 11 of the earthen building figures supplement). The n ailer shall be no more than two (2) inches by four (4) inches by its length.

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101 (2) Channels: Channels may be incorporated into the rammed eart h wall as follows (Refer to figure 2 of the earthen buildi ng figures supplement); To avoid an hourglass configuration in the wall section, channe ls on either side of a running wall shall not be opposite each other. (Refer to figure 4 of t he earthen building figures supplement). Channels shall be no more than two (2) inches by fo ur (4) inches by their length in dimension. Vertical channels shall not be placed c loser than twelve (12) inches to a rammed earth wall finished edge or corner. [14.7.4.14 NMAC Rp, 14.7.4.14 NMAC, 1-28-11] 14.7.4.17 BOND BEAMS: A. General. The bond beam shall be secured to the rammed eart h wall. Refer to Subsections H and I of 14.7.4.16 NMAC abov e. Bond beams may be of wood or concrete construction. Bond beams shall measure six (6) inches nominal depth and extend the full width of the wall. Exception: The bond beam width may be reduced as follows: Two (2) inches maximum in an eighteen (18 ) to less than twenty-four (24) inch thick rammed earth wall, or three (3) inches maximu m in a rammed earth wall twentyfour (24) inches or greater in thickness. Bond bea ms must be continuous, running the full perimeter of the structure. Interior rammed earth or adobe walls shall be incorporated into the bond beam. Varying height bond beams shal l extend into the adjoining rammed earth wall one-half (1/2) the thickness of the adjo ining rammed earth wall. The concrete bond beam may secure anchoring and strapping device s. B. Wood bond beam construction. In addition to the general requirements of Subsection A of 14.7.4.17 NMAC, wood bond beams may be constructed as approved by the building official. Light wood bond beam cons truction may be utilized as shown in figure 10 of the earthen building figures supplemen t. C. Concrete bond beam construction. In addition to the general requirements of Subsection A of 14.7.4.17 NMAC, con crete bond beams shall be constructed of minimum twenty-five hundred (2500) p si. concrete and shall contain steel reinforcement as follows: For eighteen (18) to les s than twenty-four (24) inch thick rammed earth wall construction, a minimum of two (2 ) continuous number four (4) reinforcing rods shall be used. For walls equal to or greater than twenty-four (24) inches in thickness, a minimum of two (2) continuous numbe r five (5) reinforcing rods shall be used. Provide two (2) inch minimum reinforcement c oncrete cover over all horizontal reinforcing rods. Concrete bond beams may be used to secure anchoring and strapping devices. D. Concrete bond beam cold joints. Concrete bond beam cold joints are limited to corners of perpendicular intersections w ith other structural, full-height walls. Cold joints shall be tied into the adjoining bond b eam with three (3) number four (4) reinforcing rods. The reinforcement shall extend a minimum of twenty-four (24) inches into both portions of the concrete bond beam.

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102 [14.7.4.17 NMAC Rp, 14.7.4.17 NMAC, 1-28-11] 14.7.4.18 LINTELS OVER OPENINGS: A. General. All openings require a lintel or semi-circular ar ch over the opening. All lintels, whether of wood or concrete shall bear a minimum of twelve (12) inches into the length of the wall. Exception: Ni chos and other shaped voids as defined in 14.7.4.15 NMAC. B. Bearing limitations. Lintels shall bear a minimum of twelve (12) inche s beyond coved, splayed or rounded bearing portions o f openings that are less than the full width of the wall. (Refer to figure 15 of the earth en building figures supplement). C. Lintels over openings in stabilized rammed eart h walls. Openings less than twenty-four (24) inches in width shall not req uire a lintel or semi-circular arched opening. Openings greater than twenty-four (24) in ches in width require lintels as defined in table 4. Table 4 Concrete Lintels Over Openings in Ramme d Earth Walls (1) Wall width Lintel span Lintel depth Reinforcement (2) Reinforcement Concrete Cover (3) Uniform Load 18” 24” 6” 3#4 @ 4”o.c. 3” minimum concrete cover on all sides 1000 PLF 36” 6” 3#4 @ 4”o.c. 48” 6” 3#4 @ 4”o.c. 60” 6” 3#4 @ 4”o.c. 72” 8” 3#5 @ 4”o.c. 84” 8” 3#5 @ 4”o.c. 96” 8” 3#5 @ 4”o.c. 20” 24” 6” 3#4 @ 4”o.c. 4” minimum concrete cover on all sides 1350 PLF 36” 6” 3#4 @ 4”o.c. 48” 6” 3#4 @ 4”o.c. 60” 6” 3#4 @ 4”o.c. 72” 8” 3#5 @ 4”o.c. 84” 8” 3#5 @ 4”o.c. 96” 10” 3#5 @ 4”o.c. 24” 6” 3#4 @ 5”o.c. 36” 6” 3#4 @ 5”o.c. 48” 6” 3#4 @ 5”o.c. 60” 6” 3#4 @ 5”o.c.

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103 22” 72” 8” 3#5 @ 5”o.c. 3 1/2” minimum concrete cover on all sides 1700 PLF 84” 10” 3#5 @ 5”o.c. 96” 10” 3#5 @ 5”o.c. 24” 24” 6” 3#4 @ 6”o.c. 3” minimum concrete cover on all sides 2000 PLF 36” 6” 3#4 @ 6”o.c. 48” 6” 3#4 @ 6”o.c. 60” 6” 3#4 @ 6”o.c. 72” 8” 3#5 @ 6”o.c. 84” 10” 3#5 @ 6”o.c. 96” 12” 3#5 @ 6”o.c. 1. 3000 psi minimum concrete at approximately 28 d ays. 2. Grade 40 steel reinforcement minimum. 3. Steel reinforcement at mid-depth of lintel. [14.7.4.18 NMAC Rp, 14.7.4.18 NMAC, 1-28-11]

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104 Fiber Specifications from Manufacturer

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105 Unified Soil Classification System

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106 Gypsum Cement Specifications

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107

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108 Portland Cement Specifications