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Effect of Fiber Types on the Mechanical Properties and Permeability of High Strength Concrete

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Title:
Effect of Fiber Types on the Mechanical Properties and Permeability of High Strength Concrete
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KIM, BYOUNGIL ( Author, Primary )
Copyright Date:
2008

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Alcohols ( jstor )
Cellulose fiber ( jstor )
Cements ( jstor )
Compressive strength ( jstor )
Compressive stress ( jstor )
Specimens ( jstor )
Steels ( jstor )
Stress tests ( jstor )
Tensile strength ( jstor )
Tensile stress ( jstor )

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University of Florida
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University of Florida
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Copyright Byoungil Kim. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
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2/28/2007
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649810170 ( OCLC )

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EFFECT OF FIBER TYPES ON THE MECHANICAL PROPERTIES AND PERMEABILITY OF HIGH STRENGTH CONCRETE By BYOUNGIL KIM A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING UNIVERSITY OF FLORIDA 2006

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Copyright 2006 by Byoungil Kim

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I dedicate this work to my loving wife , Yookyung, whose tireless support never waned despite years of weekends commuting the leng th of Florida while I worked to achieve this goal.

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ACKNOWLEDGMENTS I would like to acknowledge my graduate advisor, Dr. Andrew J Boyd, for his guidance and support throughout my research. I would also like to thank Dr. Reynaldo Roque and Dr. Mang Tia for their advice and assistance in performing the work and analysis of this thesis. Special thanks go to Mr. George Lopp for his support in the laboratory and his valuable advice. My deepest thanks go to all the members of the Civil Engineering materials group for their friendship and support during the past two years. They include Sungho Kim, Yanjun Liu, Mahir Dham, Eddie Roske, Xiaoyan Zheng, Chulseung Koh, Alvero Guarin, and Jaeseung Kim. I would like to express a very sincere appreciation to all my family and wife’ family for their love, support, and encouragement. iv

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TABLE OF CONTENTS page ACKNOWLEDGMENTS .................................................................................................iv LIST OF TABLES ...........................................................................................................viii LIST OF FIGURES .............................................................................................................x ABSTRACT .....................................................................................................................xiv CHAPTER 1 INTRODUCTION........................................................................................................1 1.1Background..............................................................................................................1 1.2 Objectives...............................................................................................................2 1.3 Scope.......................................................................................................................2 1.4 Research Plan..........................................................................................................2 2 LITERATURE REVIEW.............................................................................................4 2.1 Principles of Fiber Reinforced Concrete................................................................4 2.1.1 Fiber Reinforced Concrete...........................................................................4 2.1.2. Role of Fibers in Cement Composite..........................................................5 2.1.3 Fiber Mechanism..........................................................................................5 2.1.4 Fracture Toughness......................................................................................6 2.1.5 Fiber-Cement Paste Interface.......................................................................6 2.1.6 Stress-Strain Behavior..................................................................................6 2.2 Mechanical Behavior of Fiber Reinforced Concrete..............................................7 2.1.1 Compressive Strength...................................................................................8 2.1.1.1 Steel fiber reinforced concrete...........................................................8 2.1.1.2 Synthetic fiber reinforced concrete..................................................10 2.1.2 Splitting Tensile Strength...........................................................................11 2.1.2.1 Steel fiber reinforced concrete.........................................................11 2.1.2.2 Synthetic fiber reinforced concrete..................................................12 2.3 Water Permeability...............................................................................................13 2.3.1 Introduction................................................................................................13 2.3.2 Permeability of Concrete............................................................................13 2.3.2 Factors Affecting the Permeability of Concrete.........................................15 2.3.2.1 W/C-ratio..........................................................................................15 v

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2.3.2.2 Cement type......................................................................................15 2.3.2.3 Aggregate type.................................................................................15 2.3.3.4 Maximum aggregate size.................................................................16 2.3.3.5 Curing condition...............................................................................17 2.3.3.6 Fiber type..........................................................................................17 3 DESCRIPTION OF EXPERIMENT PROGRAM.....................................................19 3.1 Characterization of Constituent Materials............................................................19 3.1.1 Cement........................................................................................................19 3.1.2 Coarse Aggregates......................................................................................19 3.1.3 Fine Aggregates..........................................................................................20 3.1.4 Chemical Admixtures.................................................................................20 3.1.5 Fibers..........................................................................................................21 3.2 Mix Proportions for the Matrix.............................................................................22 3.3 Mixing and Curing Procedures.............................................................................23 3.3.1 Mixing Procedure.......................................................................................23 3.3.2 Curing Procedure........................................................................................25 3.2 Fresh Concrete Properties.....................................................................................25 3.2.1 General.......................................................................................................25 3.2.2 Workability.................................................................................................26 3.2.2.1 Slump test (ASTM C 143)...............................................................26 3.2.2.2 Inverted slump cone test (ASTM C 995).........................................26 3.2.2.3 Vebe test (ASTM C 1170)...............................................................28 3.2.3 Air Content (ASTM C 1170)......................................................................29 3.2.4 Temperature and Unit Weight....................................................................29 4 MECHANICAL TESTS.............................................................................................30 4.1 Objectives.............................................................................................................30 4.2 Compression Tests................................................................................................30 4.2.1 Experimental Program................................................................................30 4.2.2 Test Apparatus and Procedure....................................................................31 4.3 Splitting Tensile Tests..........................................................................................33 4.3.1 Experimental Program................................................................................33 4.3.2 Test Apparatus and Procedure....................................................................34 4.4 Permeability Test..................................................................................................36 4.4.1 Experimental Program................................................................................36 4.4.2 Preparation of Test Specimens...................................................................36 4.4.3 Testing Procedure.......................................................................................37 4.4.4 Method of Measuring Rate of Flow...........................................................39 4.4.5 Determination of Coefficient of Permeability............................................39 4.5 Density, Absorption, and Voids in Hardened Concrete.......................................40 4.5.1 Experimental Program................................................................................40 4.5.2 Procedure....................................................................................................41 4.5.2.1 Oven-dry mass..................................................................................41 4.5.2.2 Saturated mass after immersion.......................................................42 vi

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4.5.2.3 Saturated mass after boiling.............................................................42 4.5.2.4 Immersed apparent mass..................................................................43 4.5.3 Calculation..................................................................................................43 5 TEST RESULTS AND ANALYSIS..........................................................................44 5.1 Introduction...........................................................................................................44 5.2 Fresh Properties....................................................................................................44 5.3 Compression Tests................................................................................................51 5.3.1 Compression Test Results..........................................................................51 5.3.1.1 Fiber influence on the compressive strength....................................51 5.3.1.2 Fiber influence on the elastic modulus.............................................53 5.3.1.3 Stress versu s strain response............................................54 5.4 Splitting Tensile Strength Tests............................................................................56 5.5 Volume of Voids...................................................................................................60 5.5.1 Tests Results and Data Analysis.................................................................60 5.5.2 The Effect of Volume of Voids on the Splitting Tensile Strength.............61 5.5.3 The Effect of Volume of Voids on the Compressive Strength...................65 5.6 Permeability Test..................................................................................................65 5.6.1 Permeability Test Results...........................................................................65 5.6.2 The Effect of Compressive Strength on Permeability................................70 5.6.3 The Effect of Volume of Voids on Permeability........................................74 6 SUMMARY AND CONCLUSIONS.........................................................................75 6.1 Summary of Test Results......................................................................................75 6.2 Conclusions...........................................................................................................76 APPENDIX A COMPRESSION TESTS............................................................................................78 B SPLITTING TENSILE STRENGTH TESTS............................................................90 LIST OF REFERENCES...................................................................................................97 BIOGRAPHICAL SKETCH...........................................................................................100 vii

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LIST OF TABLES Table page 3-1 Chemical and Mineralogical Composition..................................................................19 3-2 Aggregate Gradation, Coarse Aggregates...................................................................20 3-3 Aggregate Gradation, Fine Aggregates.......................................................................21 3-4 Properties of Fibers Used............................................................................................22 3-5 Material and Mix Proportions (Class II/V)..................................................................24 4-1 Number of Specimens Tested......................................................................................31 4-2 Number of Specimens Tested......................................................................................34 4-3 Number of Specimens Tested......................................................................................37 4-4 Number of Specimens Tested......................................................................................42 5-2 Plastic Properties for Class V Concrete.......................................................................45 5-3 The Average Values of f' c and E c Obtained for Class II Concrete..............................51 5-4 The Average Values of f' c and E c Obtained for Class V Concrete..............................52 5-5 The Average Values of f spt and f' c Obtained for Class II Concrete.............................58 5-6 The Average Values of f spt and f' c Obtained for Class V.............................................59 5-7 The Values of Volume of Voids and f spt Obtained for Class II Concrete...................62 5-8 The Values of Volume of Voids and f spt Obtained for Class V Concrete...................63 5-9 Summary of the Values of K and f' c Obtained for Class II Concrete..........................69 5-10 Summary of the Values of K and f' c Obtained for Class V Concrete........................70 A-1 Summary of the Values of f' c and E c Obtained for Class II Concrete.........................78 A-2 Summary of the Values of f' c and E c Obtained for Class V Concrete........................79 viii

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B-1 The Values of f spt and f' c Obtained for Class II Concrete............................................90 B-2 The Values of f spt and f' c Obtained for Class V Concrete...........................................91 ix

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LIST OF FIGURES Figure page 2-1 Typical Types of Stress and Strain Curve in Compression...........................................7 3-1 Different Fibers Used. A) PP, B) PVA, C) Cellulose, D) Hooked Steel.....................21 3-2 Inverted Slump-Cone time Test Setup.........................................................................27 3-3 Vebe Time Test Setup.................................................................................................28 4-1 Test Set-up Used to Measure the Stress-Strain Response in Compression. A) Test Machine, B) Sample Condition................................................................................32 4-2 Test Set-up for Measurement of Elastic Modulus. A) Test Machine, B) Sample Condition..................................................................................................................33 4-3 Test Set-up for Splitting Tensile Test. A) Test Machine, B) Sample Condition.........35 4-4 Water Permeability Test. A) Test Set up, B) Test Apparatus......................................37 4-5 Schematic Diagram of Water Permeability Flow Fixture...........................................40 4-6 Measurement of Flow Rate in Water Permeameter.....................................................41 5-1 Slump Results for Class II Concrete............................................................................46 5-2 Slump Results for Class V Concrete...........................................................................47 5-3 Inverted Slump-Cone vs Vebe Time Results for Class II Concrete............................47 5-4 Inverted Slump-Cone vs Vebe Time Results for Class V Concrete............................48 5-5 Slump vs Inverted Slump-Cone Time for Class II and Class V Concretes.................48 5-6 Slump vs Vebe Time Class II and Class V Concretes.................................................49 5-7 Vebe Time vs Inverted Slump Cone Time Class II and Class V Concretes...............49 5-8 Air Content Results for Class II Concrete...................................................................50 5-9 Air Content Results for Class V Concrete...................................................................50 x

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5-10 Ultimate Compressive Strength for Class II Concrete..............................................53 5-11 Ultimate Compressive Strength for Class V Concrete..............................................54 5-12 Elastic Modulus, E c for Class II and Class V Concretes...........................................55 5-13 Average Stress vs Strain Response of Class II Concrete...........................................56 5-14 Average Stress vs Strain Response of Class V Concrete..........................................57 5-15 Splitting Tensile Strength for Class II Concrete........................................................59 5-16 Splitting Tensile Strength for Class V Concrete.......................................................60 5-17 Volume of Voids for Class II Concrete.....................................................................64 5-18 Volume of Voids for Class V Concrete.....................................................................64 5-19 f spt vs Volume of Voids for Class II Concrete-Control Samples...............................65 5-20 f spt vs Volume of Voids for Class II Concrete-Fiber Samples...................................66 5-21 f spt vs Volume of Voids for Class V Concrete-Control Samples...............................66 5-22 f spt vs Volume of Voids for Class V Concrete-Fiber Samples..................................67 5-23 Compressive Strength vs Volume of Voids for Class II and V Concretes................67 5-24 Coefficient of Permeability for Class II Concrete.....................................................71 5-25 Coefficient of Permeability for Class V Concrete.....................................................71 5-26 Coefficient of Permeability vs Compressive Strength for Class II Concrete............72 5-27 Coefficient of Permeability vs Compressive Strength for Class V Concrete............73 5-28 Relationship between Permeability and Compressive Strength for Class II and Class V Concretes....................................................................................................73 5-29 Relationship between Permeability and Compressive Strength for Class II and Class V Concrete......................................................................................................74 A-1 Stress vs Strain Response for Plain Concrete-Class II Concrete................................80 A-2 Stress vs Strain Response for Polypropylene Fibers-Class II Concrete.....................80 A-3 Stress vs Strain Response for Polyvinyl Alcohol Fibers-Class II Concrete...............81 A-4 Stress vs Strain Response for Cellulose Fibers-Class II Concrete.............................81 xi

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A-5 Stress vs Strain Response for Steel Fiber-Class II Concrete......................................82 A-6 Stress vs Strain Response for Plain Concrete-Class V Concrete................................82 A-7 Stress vs Strain Response for Polypropylene Fibers-Class V Concrete.....................83 A-8 Stress vs Strain Response for Polyvinyl Alcohol Fibers-Class V Concrete...............83 A-9 Stress vs Strain Response for Cellulose Fibers-Class V Concrete.............................84 A-10 Stress vs Strain Response for Steel Fibers-Class V Concrete..................................84 A-11 Compressive Failure of Plain Concrete for Class II Concrete..................................85 A-12 Compressive Failure of Polypropylene Fibers for Class II Concrete.......................85 A-13 Compressive Failure of Polyvinyl Alcohol Fibers for Class II Concrete.................86 A-14 Compressive Failure of Cellulose Fibers for Class II Concrete...............................86 A-15 Compressive Failure of Cellulose Fibers for Class II Concrete...............................87 A-16 Compressive Failure of Plain Concrete for Class V Concrete.................................87 A-17 Compressive Failure of Polypropylene Fibers for Class V Concrete.......................88 A-18 Compressive Failure of Polyvinyl Alcohol Fibers for Class V Concrete.................88 A-19 Compressive Failure of Cellulose Fibers for Class V Concrete...............................89 A-20 Compressive Failure of Steel Fibers for Class V Concrete......................................89 B-1 Splitting Tensile Failure of Plain Concrete for Class II Concrete..............................92 B-2 Splitting Tensile Failure of Polypropylene Fibers for Class II Concrete....................92 B-3 Splitting Tensile Failure of Polyvinyl Alcohol Fibers for Class II Concrete.............93 B-4 Splitting Tensile Failure of Cellulose Fibers for Class II Concrete............................93 B-5 Splitting Tensile Failure of Steel Fibers for Class II Concrete...................................94 B-6 Splitting Tensile Failure of Plain Concrete for Class V Concrete..............................94 B-7 Splitting Tensile Failure of Polypropylene Fibers for Class V Concrete...................95 B-8 Splitting Tensile Failure of Polyvinyl Alcohol Fibers for Class V Concrete.............95 B-9 Splitting Tensile Failure of Cellulose Fibers for Class V Concrete............................96 xii

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B-10 Splitting Tensile Failure of Steel Fibers for Class V Concrete.................................96 xiii

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Abstract of Thesis Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Engineering EFFECT OF FIBER TYPES ON THE MECHANICAL PROPERTIES AND PERMEABILITY OF HIGH STRENGTH CONCRETE By Byoungil Kim August 2006 Chair: Andrew J. Boyd Major Department: Civil and Coastal Engineering This study describes an experimental investigation into the relationships among strength, voids and permeability of concrete resulting from the addition of different fibers. The fiber volume fractions considered in this study were 0.5% for polypropylene fibers, 0.75% for polyvinyl alcohol fibers, 0.1% for cellulose fibers, and 0.89% for hooked steel fibers, commonly used in Florida industry. Tests on the mechanical properties included compressive strength, elastic modulus, and splitting tensile strength. The durability tests included volume of voids and water permeability. The fresh fibrous mixes were characterized by their slump, inverted slump-cone time, Vebe time, air content, and unit weight. The addition of PP, PVA, and hooked steel fibers greatly decreased the fresh mix workability. High permeable voids resulting from the incorporation of PP, PVA, and cellulose fibers resulted in a lower splitting tensile strength than plain concrete mixes. Hooked xiv

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steel fibers showed the highest splitting tensile strength among all concrete mixes, regardless of volume of voids. The incorporation of PP, PVA, and steel fibers slightly increased the compressive strength and modulus of elasticity. This increased strength affected the resistance to water penetration rather than the effect of the amount of porosity. The Class II concrete having a lower compressive strength than the Class V concrete showed lower resistance to water penetration. Among all the fiber types, the hooked steel fibers having high modulus, elongation, and tensile strength showed the highest resistance to water penetration. xv

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CHAPTER 1 INTRODUCTION 1.1 Background Since ancient times, fiber reinforcement has been used to reinforce brittle materials. Straw was used to reinforce sun-baked bricks, and horsehair was used to reinforce masonry mortar and plaster. A pueblo house built around 1540, believed to be the oldest house in the United States, is constructed of sun-baked adobe reinforced with straw (ACI, 1996). Currently, a wide range of engineering materials (including ceramics, cement, plastics, and gypsum products) incorporate fibers to enhance composite properties. The enhanced properties include tensile strength, elastic modulus, crack resistance, crack control, durability, fatigue life, resistance to impact, plastic shrinkage and settlement, expansion, thermal characteristics, and fire resistance (ACI, 1996). Considerable research, development, and application of FRC are taking place throughout the world. Industry interest and potential business opportunities are evidenced by continued new developments in fiber reinforced construction materials. These new developments are reported in numerous research papers, international symposia, and state-of-the-art reports issued by professional societies. Steel and synthetic fibers have been the most prevalent in highway applications. They have been used in pavements, bridges, median barriers, retaining walls, pipe, and shotcrete. Specifiers continuously state they are looking for improved performance and life cycle costs (AASHTO-AGC-ARTBA Joint Committee, 2001). 1

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2 1.2 Objectives The following were the primary objectives of the study presented in this thesis: Evaluate the influence of fiber addition for a variety of fiber types, on the properties of fresh and hardened concrete. Determine correlations among strength, void content and permeability results from laboratory experiments for the various fiber types. 1.3 Scope This study focuses on the experimental investigation of the behavior of fiberreinforced concrete. The properties investigated include workability, air content, compressive strength, splitting tensile strength, volume of voids, and permeability. 1.4 Research Plan The following items constitute the research plan for this study: A literature review covering past research into the durability of fiber reinforced concrete. Four fiber types were selected for study: Dramix ZP 305 hooked-collated steel fiber from Bekaert, STRUX 90/40 monofilament polypropylene / polyethylene blend fiber from Grace Construction Products, RF 4000x30 monofilament polyvinyl alcohol fiber from Kuraray, and Buckeye UltraFiber 500 TM pressed-squared virgin cellulose fiber from Durafiber. These fiber types are commonly used in Florida industry and are purported to affect the mechanical and durability properties. Ten mixtures were designed to evaluate the plastic and hardened properties of fiber reinforced concrete, divided into two concrete classes as per Florida Department of Transportation (FDOT) specification. The classes investigated were Class II (w/c-0.44) and Class V (w/c-0.37). Two kinds of control samples were cast to evaluate the affection of fibers. First, plain concrete mixes were performed for each Class. Then, additional concrete samples before adding fibers were taken out and cast when the fiber mixes. The following laboratory tests were used to ascertain plastic properties of FRC. The slump test has been found to be an inappropriate method to measure workability of FRC so other methods were chosen. The Vebe Test (ASTM C 1170) and Inverted Slump Cone (ASTM C 995) were used to quantify FRC workability. The Air Content Test (ASTM C 1170) was performed to ensure that the introduction of fibers did not result in the entrapment of unwanted air voids within the concrete that could result in crack initiation or increased permeability.

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3 The following laboratory tests were used to ascertain the mechanical properties of FRC: compressive strength, modulus of elasticity, and splitting tensile strength. The following laboratory test was used to ascertain durability performance: volume of voids and water permeability test. The data was analyzed and the relationships between strength, voids and permeability were made.

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CHAPTER 2 LITERATURE REVIEW Primarily organized into steel and synthetic fibers, this literature review was undertaken in order to understand the mechanical and durability properties of FRC that affect strength, energy absorption and water permeability. The characteristics of various fibers and the behavior of concrete reinforced with each of these fibers are discussed herein. It was also important to review previous studies concerning the performance of fiber-reinforced concrete based on steel, polypropylene, polyvinyl alcohol, and cellulose reinforcements. 2.1 Principles of Fiber Reinforced Concrete 2.1.1 Fiber Reinforced Concrete Fiber reinforced concrete is a concrete mixture containing short discrete fibers that are uniformly distributed and randomly oriented in three dimensions. Fiber material can be steel, cellulose, carbon, polypropylene, glass, nylon, polyester, etc. A fiber contributes to the load-carrying capacity of a body which consists of a fiber embedded in a surrounding matrix. The load is transferred through the matrix to the fiber by shear deformation at the fiber matrix interface. This load transfer generally arises as a result of the different physical properties of the fiber and the matrix (e.g., the different modulus of elasticity values of the fiber and the matrix). Expressions for the variation of in shear stress along the fiber matrix interface and the tensile stress in the fiber can be obtained by considering the equilibrium of forces acting on an element of the fiber. Variations in the mechanical properties and geometry of both the fiber and the matrix result in different 4

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5 failure mechanisms for the composite (e.g., pull-out of fibers from the matrix) (Beaudoin, 1990). 2.1.2. Role of Fibers in Cement Composite The incorporation of fibers into a brittle hydrated cement matrix serves to increase the fracture toughness of the composite by the resultant crack arresting processes and normally increases the tensile and flexural strengths. A high fiber tensile strength is essential for a substantial reinforcing action. A high ratio of fiber modulus of elasticity to matrix modulus of elasticity promotes stress transfer from the matrix to the fiber. Fibers having large values of failure strain give high extensibility in composites. Problems associated with fiber debonding at the fiber-matrix interface are prevented by fibers possessing a lower Poisson’s ratio. In practice most fibers have surface flaws due to handling, processing, manufacturing, and ageing, etc. Defects on the surface of fibers can the strength properties of the composite. The strength reduction due to the presence of flaws varies with fiber length and diameter (Beaudoin, 1990). 2.1.3 Fiber Mechanism Fibers work with concrete to utilize two mechanisms: the spacing mechanism and the crack bridging mechanism. The spacing mechanism requires a large number of fibers well distributed within the concrete matrix to arrest any existing micro-crack that could potentially expand and create a sound crack. For typical volume fractions of fibers, utilizing small diameter fibers to micro fibers can ensure the required number of fibers for micro crack arresting. The second mechanism, crack bridging, requires larger straight fibers with an adequate bond to concrete. Steel fibers are considered a prime example of this fiber type and are commonly referred to as large diameter fibers or macro fibers.

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6 Benefits of using large steel fibers include impact resistance, flexural and tensile strengths, ductility, and fracture toughness (Bayasi et al., 1989). 2.1.4 Fracture Toughness A major role of fibers in fiber-reinforced cement composite is to provide toughness, i.e. increasing the energy consumed by for the fracture processes. In general, fibers serving as crack arrestors or barriers increase the tortuosity of an advancing crack. Two processes that increase the value of the fracture energy are fiber pull-out and fiber debonding, which are considered to be energy dissipating processes applicable to brittle materials (Kelly, 1970). Pull-out work is defined as the work done against sliding friction in extracting fibers from a broken matrix, and debonding as the work done in destroying the bond between fiber and matrix. 2.1.5 Fiber-Cement Paste Interface The nature of the fiber-cement interface is particularly complicated, since there may be a chemical reaction between the cement and some types of fibers. Generally, an increase in bond strength results in increased crack resistance. In common practice, the better bond strength is achieved by using a reinforcement having a rough surface, which needs more frictional energy during pull-out. 2.1.6 Stress-Strain Behavior Idealized stress-strain curves for cement matrices reinforced with discontinuous fibers have been presented by several authors. The curves generally contain three distinct regions as shown in Figure 2.1 (Beaudoin, 1990). Region 1: In the first region, the load is carried by both the fibers and the matrix. Stress is transferred to the fibers when cracking in the matrix occurs. Stress is transferred back from the fibers into the matrix in regions away from the crack.

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7 Region 2: In cement composites, multiple fractures of the matrix usually occur in the second region as the fiber failure strain generally exceeds that of the matrix. Significant strain, cracking and energy absorption takes place in this region. Stress transfer alternates between the matrix and the fibers resulting in formation of fine cracks. Region 3: In the third region, the matrix no longer contributes significantly to the load carrying capacity of the composite as stress ceases to be transferred from the fibers back into the matrix. Additional stress is carried by the bridging fibers. Interfacial bond strength and fiber properties control composite failure. Region 2 Plain Concrete Stress Steel Fiber Synthetic Fiber Region 1 Region 3 Strain Figure 2-1 Typical Types of Stress and Strain Curve in Compression 2.2 Mechanical Behavior of Fiber Reinforced Concrete Concrete made with Portland cement has certain characteristics: it is relatively strong in compression but weak in tension and thus tends to be brittle. The weakness in tension can be overcome by the use of conventional rod reinforcement and to some extent by the inclusion of a sufficient volume of certain fibers. The use of fibers also alters the

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8 behavior of the fiber-matrix composite after it has cracked, thereby improving its toughness. 2.1.1 Compressive Strength ACI Committee 544 (1989) reported that the presence of fibers alters the mode of failure of cylinders by making the concrete less brittle. Significant post-peak strength is retained with increasing deformation beyond the maximum load. Fibers usually have only a minor effect on compressive strength, slightly increasing or decreasing the test result. Since smaller cylinders give higher strengths for conventional concrete and promote preferential fiber alignment in FRC, small cylinders with long fibers may give unrealistically high strengths. The compressive properties of fiber-reinforced concrete (FRC) are relatively less affected by the presence of fibers as compared to the properties under tension and bending. The influence of fibers in improving the compressive strength of the matrix depends on the use of mortar or concrete having coarse aggregates and on the magnitude of compressive strength. Studies prior to 1998 including those of Williamson (1974) and Naaman et al. (1974) showed that with the addition of fibers there is an almost negligible increase in strength for mortar mixes; however for concrete mixes, strength increases by as much as 23%. 2.1.1.1 Steel fiber reinforced concrete Fanella and Naaman (1985) conducted that the effect of a comprehensive evaluation of the stress-strain properties of steel fiber reinforced mortar (concrete) in compression. Three volume contents (1, 2, and 3%) and three aspect ratios (47, 83, and 100) were evaluated in combination with three mortar matrices of increasing compressive

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9 strength. The steel fibers were smooth and brass-coated. The results showed a slight improvement in compressive strength ranging from 0 to 15% at best. Naaman et al. (1993) reported that the effect of adding 1% by volume of 1.2 in. (30 mm) hooked steel fibers with an aspect ratio of 60 slightly increased the compressive strength in comparison with the control mix (17%), resulting in a much larger area under the stress-strain curve and thus indicating a substantial increases in ductility and energy absorption to failure. On the other hand, the addition of 2% by volume of 1.2 in (30 mm) hooked steel fibers with an aspect ratio of 60 caused significant increases in the compressive strength. In comparison with the control mix, there was an average increase of 30% in compressive strength. The coarse aggregate was crushed limestone with a maximum size of 0.5 to 0.75 in and the w/c ratio was 0.34. Poon et al. (2004) reported that the use of steel fibers at the level of 1% resulted in a small increase of about 3% in the compressive strength. The steel fibers used were hooked fibers with a length of 25 mm and an aspect ratio of 60. However, Ding and Kusterle (2000) reported different results from the previous study. The steel fiber contents for compressive strength tests were 20, 40 and 60 kg/m 3 ; fiber length of 30 mm, diameter of 0.5 mm. The hooked end fiber had an aspect ratio of 60. The results showed that adding 20 kg/m 3 by volume slightly increased the compressive strength (1.8%). On the other hand, other fiber volume fractions slightly decreased the compressive strength (i.e., 9% for 40 kg/m 3 and 3% for 60 kg/m 3 by volume). In addition, the improvement in strength does not always increases with a larger dosage of fibers material.

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10 2.1.1.2 Synthetic fiber reinforced concrete Malhotra et al. (1995) studied the mechanical properties of polypropylene fiber reinforced concrete. Fibrillated polypropylene fiber, 1.55-in in length, was used. The fiber contents were 4 kg/m 3 (0.44%) and 5 kg/m 3 (0.54%) of the mixed concrete by volume. The incorporation of the fibers in the concrete had, in general, no significant effect on the compressive strength, although there were a few exceptions. Yao et al. (2000) also observed that there was no significant improvement in the compressive strength with using smooth and straight polypropylene fiber when the fiber content was 0.5% and the length was 15 mm. In 2003, Choi et al. published the results of compressive strength of polypropylene fiber reinforced concrete (PFRC). A monofilament fiber 0.90 mm in diameter and 50 mm in length was used. The fiber contents were 1.0% and 1.5% of the mixed concrete by volume. This polypropylene fiber has a “wavelength” shape and is collated in small bundles for rapid introduction into concrete mixtures. Plain concrete samples failed explosively at their peak load while PFRC samples broke with vertical cracks on the surface of the sample at about 70-85% of the peak load. The average compressive strength showed that the polypropylene fiber did not contribute to the increase of the compressive strength. However, the strains according to peak load increased significantly, as did the toughness. Naaman et al. (1993) reported that mixes containing 1% or 2% by volume of polypropylene fibers showed deterioration in the compressive stress-strain response when compared with the control mix using 0.75 in length. Unlike the steel fiber mix at 1% and 2% volume fraction, the polypropylene mix at 1% and 2% volume fraction showed a significantly lower ductility. They concluded that this lower ductility may be attributed to

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11 the low elastic modulus of the polypropylene fibers and their poor bonding properties in comparison with steel fibers. Leung et al. (2005) investigated that the addition of 0.5% polypropylene fiber measuring 15 mm in length and 0.5% polyvinyl alcohol fiber measuring 12 mm in length decreased the compressive strength about 10% for PP and 15 % for PVA fibers in comparison with plain concrete. They explained that the incorporation of small diameter fibers into the mix makes compaction more difficult, and hence, more entrapped air remains in the final specimen. However, Song et al. (2005) found that the addition of PP fibers having a 19 mm length and a concentration of 0.6 kg/m 3 slightly improved the compressive strength by 5.8% in comparison with plain concrete. 2.1.2 Splitting Tensile Strength ACI committee 544 reported that results from the splitting cylinder tensile strength test (ASTM C 496) for FRC specimens are difficult to interpret after the first matrix cracking and should not be used beyond the first crack because of unknown stress distributions after the first crack. The precise identification of the first crack in the split cylinder test can be difficult without strain gauge or other sophisticated means of crack detection, such as acoustic emission or laser holography. The relationship between splitting tensile strength and direct tensile strength or modulus of rupture has not been determined. 2.1.2.1 Steel fiber reinforced concrete Yao et al. (2003) investigated the mechanical properties of concrete containing steel fiber at 0.5% fiber volume fraction. The steel fibers were hooked end and 30 mm in length. The authors found that the addition of steel fiber increased strength about 9% in comparison with average plain concrete values. Shaaban and Gesund (1993) carried out

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12 splitting tensile tests with 6x12 in specimens containing 1 in corrugated steel fibers with a tensile strength of 180 ksi (1240 MPa.). The fiber contents used were 0, 79, 157, 235, and 313 lbs/yd 3 of concrete. The test results showed that steel fiber can significantly enhance the tensile strength of concrete. The load at first crack was used in the splitting tensile test for determining the tensile strength of SFRC. 2.1.2.2 Synthetic fiber reinforced concrete Al-Tayyib et al. (1998) also reported that little improvement has been achieved in the tensile strength of PFRC. The tensile strength of PFRC mixes is 2-8% higher than that of PC mixes due to the inclusion of polypropylene fibers with 0.8 in fibrillated bundles when 0.2% by volume of concrete was used in the PFRC mixes. Choi et al. (2005) found that the average splitting tensile strength of PFRC increased by approximately 20-50%, which is 9% to 13% of its compressive strength. This result is due to the reinforcing fiber’s role to resist cracking and spalling across the failure plains. Moreover, the addition of polypropylene fibers largely increased the ductility of the concrete, which is described as the amount of strain until the failure point. It was noticed that the stress-strain curves of PFRC are linear up to the first crack, known as the proportional limit, which directly corresponded with the first macro-crack that happened. Following this, the stress sharply dropped and then, the strain continued to increase, the stress increased again to a second peak. This process was repeated several times, until the final failure. These results were due to the fiber’s additional roles in tensile and ductility within the FRC. A monofilament fiber 0.90 mm in diameter and 50 mm in length was used. The fiber contents were 1.0% and 1.5% of the mixed concrete by volume.

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13 On the other hand, Yao et al. (2003) studied the mechanical properties of polypropylene fiber at 0.5% fiber volume fraction. The PP fibers were smooth and straight with a 15 mm length. They found that the addition of polypropylene fiber decreased splitting tensile strength by 5% in comparison with plain concrete. 2.3 Water Permeability 2.3.1 Introduction The permeability of concrete plays a very important role in influencing the durability of a concrete structure. First, it controls the rate of water flow, which can cause disruption to the concrete upon freezing. Secondly, it controls the rate of the flow of chemicals, such as chloride ions, which reduce the pH of the concrete and increase the rate of corrosion of the steel reinforcement in concrete structures. Therefore, the permeability of concrete to water is a property of interest to nearly all designers of concrete structures (Tyler et al. 1961). 2.3.2 Permeability of Concrete Permeability is the ease with which liquids or gases can travel through the concrete. This is an important property affecting the water tightness of liquid-retaining structures, resistance to chemical attack, development of hydrostatic pressure in the interior of the concrete mass, and ingress of moisture into the concrete wall which affects its thermal insulation properties (Neville et al. 1987, 1971). Neville et al. (1971) points out that movement of water through a concrete of certain thickness can be caused not only by a head of water but also by a humidity differential between the two sides of the concrete or by osmotic effects. We should distinguish between permeability and absorption. Absorption is normally measured by drying a specimen to a constant weight, immersing it in water and measuring the increase

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14 in weight as a percentage of dry weight, so that absorption represents the maximum holding capacity of water in relation to a prescribed condition of dryness. Permeability, on the other hand, is concerned with flow through the concrete. The flow of water through concrete is essentially a flow through a porous body, but the problem is far from simple. Both the cement paste and the aggregate contain pores, and, in addition, the concrete as a whole may contain voids due to incomplete compaction or to bleeding. These voids may occupy a fraction of 1% to 10% of the volume of the concrete. Since aggregate particles are enveloped by the cement paste in fully compacted concrete, it is the permeability of the paste that has the greatest effect on the permeability of concrete. The pores in the cement paste are gel pores and capillary pores. The gel pores constitute about 28% of the paste volume, and the capillary pores between 0% and 40%, depending on the water/cement-ratio (w/c-ratio) and the degree of hydration (Neville 1971, 1981). The permeability of concrete is not a simple function of its porosity but depends also on the size, distribution, and continuity of the pores. Thus, although the cement gel has a porosity of 28%, its permeability is only about 2.75 x 10 -14 in/sec. This is due to the extremely fine texture of hardened cement paste. The pores and the solid particles are very small and numerous, while in rocks the pores are fewer in number but are much larger and lead to a higher permeability. The water can flow more easily through the capillary pores than through the much smaller gel pores. The cement paste as a whole is 20 to 100 times more permeable than gel itself. It follows that the permeability of cement paste is controlled by its capillary porosity. Since the capillary porosity of cement paste decreases with age, permeability also decreases (Neville 1971, 1981).

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15 2.3.2 Factors Affecting the Permeability of Concrete 2.3.2.1 W/C-ratio The permeability of concrete is dependent mainly on the capillary pores in the cement paste. Concretes with lower w/c ratio result in a lower volume of the capillary system than those with higher w/c (Neville 1981). Therefore, w/c is one of the major factors affecting the permeability of concrete. Powers et al (1954) studied the permeability of Portland cement paste and found that the higher the water to cement ratio, the higher the permeability. The permeability coefficient of hardened paste ranges from 0.1 x 10 -12 to about 120 x 10 -12 cm/sec for water/cement-ratios ranging from 0.3 to 0.7. 2.3.2.2 Cement type The type of cement used affects the permeability insofar as it influences the rate of hydration: the more rapid-hardening the cement, the earlier the age at which the permeability is reduced to some desirable value (Neville 1971). The permeability of concrete is affected also by the properties of the cement used. For the same water to cement ratio, coarser cement leads to a higher porosity than finer cement. However, the long-term porosity and permeability are unaffected by the type of cement used (Powers et al. 1954, Neville 1971). This is because the degree of hydration would be approximately equal. 2.3.2.3 Aggregate type The aggregate used in concrete has a substantial impact on the permeability of concrete. Neville (1981) stated that the difference between the permeability of cement paste and of concrete containing a paste of the same w/c ratio is appreciable as the permeability of the aggregate itself affects the behavior of the concrete. If the aggregate has a very low permeability, its presence reduces the effective area over which flow can

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16 take place. Furthermore, since the flow path has to circumvent the aggregate particles, the effective path becomes considerably longer so that the effect of aggregate in reducing the permeability may be considerable. Generally, however, the influence of the aggregate content in the mix is small and since the aggregate particles are enveloped by the cement paste, in fully compacted concrete, it is the permeability of the paste that has the greatest effect on the permeability of the concrete. Nymae (1985) concluded that the aggregate in concrete can have two opposing effects on permeability. The aggregate particles can obstruct the flow path resulting in reduced permeability, while a cracked interface between hydrated cement and aggregate and also the porosity of the aggregates can increase the permeability of the concrete. 2.3.3.4 Maximum aggregate size The maximum aggregate size also influences the permeability of concrete. The larger the maximum aggregate size for a given water to cement ratio, the higher the permeability of concrete, probably because of the relatively large water voids developed on the underside of the coarser aggregate particles (Troxell 1968). Murata (1965) also found that the diffusion coefficient of mass concrete with coarse aggregate exhibiting a maximum size of 4 inches was on the average about 7 times and 16 times those of concrete with maximum aggregate sizes of 1.6 inches and 1 inch, respectively. The Gradation of the aggregate also influences the permeability of concrete. A well-graded aggregate is more important from the standpoint of water-tightness than it is from the standpoint of strength, since a well-graded aggregate will produce a denser concrete (Troxell 1968).

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17 2.3.3.5 Curing condition The permeability of concrete is decreased when the proportion of cement hydrated is increased. Continued hydration of the cement results in gel development which reduces the size of voids. Therefore, a continued moist curing will decrease the permeability of concrete (Troxell 1968). Powers et al (1954) found that the chemical reaction between the constituents of Portland cement and water progressively replaces the original cement minerals with hydration products, principally cement gel. The volume of the cement gel produced by hydrating the cement is approximately 2.3 times the volume of the cement. The gel not only replaces the original cement minerals but also tend to fill the original water-filled space. Within a week the coefficient of permeability of cement paste (w/c = 0.7) dropped to about one one-hundred-thousandth of its initial value. By the twenty-fourth day, it had dropped to less than a millionth of its initial value. They also found that the specimens which had been allowed to dry after removal from moist-curing condition and the resaturation of dry specimens will result in increased permeability as compared with those which are not subjected to drying and resaturating before being tested. This is because the stresses arising from differential shrinkage caused small cracks on the surface of the specimens. 2.3.3.6 Fiber type As mentioned above, Leung et al. (2005) investigated the water permeability test with Steel, PP, and PVA fibers by adding a 0.5% volume fraction of fibers. The results indicate high variability of the permeability coefficient among the same types of specimens. Based on the results on compressive strength tests, they pointed out that the porosity in the PP and PVA fiber-reinforced specimens except steel fibers may be higher

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18 than in the plain specimens, which would mean that the permeability for the plain concrete should be the lowest. However, this is not the case in general. The lower permeability for some fiber reinforced specimens may be due to the presence of fibers that reduce internal microcracking (e.g., due to shrinkage) in the cementitious matrix and hence improve resistance to water penetration. They also observed that the permeability coefficient for steel fibers having the highest strength represented the highest value.

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CHAPTER 3 DESCRIPTION OF EXPERIMENT PROGRAM This chapter is divided into four sections, specifically the characterization of constituent materials, mixture proportions, mixing and curing procedures, and fresh properties. 3.1 Characterization of Constituent Materials 3.1.1 Cement AASHTO cement type II was used to achieve a high rate of strength development and to resist an aggressive medium (i.e., seawater, wet and dry conditions, etc.). The compounds contained are described in Table 3-1. Table 3-1 Chemical and Mineralogical Composition Chemical CompositionSiO2Al2O3Fe2O3CaOMgOSO3Na2OK2OMineralogical CompositionC3SC2SC3AC4AFValue (%)20.475.194.4963.491.12.55Value (%)54.350.0530.2817.9776.15713.66 3.1.2 Coarse Aggregates The coarse aggregate used in this research was crushed limestone with a maximum size of 0.375 in (9.5 mm). The reason for choosing a relatively small-size aggregate was 19

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20 to improve the efficiency of fiber reinforcement. In SFRC application, it is generally recommended that the length of the fiber be at least twice the maximum size of the aggregate. In this study, 1.2 in steel fibers were used. The bulk specific gravity of the coarse aggregate was 2.28, the bulk specific gravity at the SSD was 2.40, and the apparent specific gravity was 2.59. The absorption of the coarse aggregate was 5.18%. The gradation results for the coarse aggregates, as obtained from tests performed at the FDOT laboratories according to ASTM C33, are given in Table 3-2. Table 3-2 Aggregate Gradation, Coarse Aggregates Sieve SizeActual Weight Retained (g)Cumulative Percentage RetainedCumulative Percentage Passing1/2 in.0.0001003/8 in.31.00298No.4730.205347No.81231.609010No.161314.20964No.501330.20973 3.1.3 Fine Aggregates The fineness modulus for the fine aggregate was 2.39 and the specific gravity was 2.648 BSG OD , 2.650 BSG SSD , and 2.658 ASG. The Absorption of the fine aggregate was 0.18%.Gradation results for the sand, as obtained from tests undertaken in the FDOT laboratories according to ASTM C 33, are given in Table 3-3. 3.1.4 Chemical Admixtures Two water reducing admixtures were used in this study. The first was WRDA 60, which produces typically 8-10% water reduction and set retardation. The addition rate of WRDA 60 was 195 to 390 ml/100kg (3 to 6 fl oz/100lbs). The second water reducer was ADDA 140 superplasticizer, which is a high range water-reducing admixture.

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21 Table 3-3 Aggregate Gradation, Fine Aggregates Sieve SizeActual Weight Retained (g)Cumulative Percentage RetainedCumulative Percentage PassingNo.41.100100No.89.80397No.1658.701585No.30165.804456No.50300.507921No.100369.50982 Addition rates of ADVA 140 superplasticizer can vary with type of application, but will normally range from 390 to 1300 ml/l00kg (6 to 20 fl oz/100 lbs) of cement. 3.1.5 Fibers Polypropylene, polyvinyl alcohol, cellulose and steel fibers were used in this study. The pictures and properties of these fibers are summarized in Figure 3-1 and Table 3-4. The fibers were selected from the four different manufactures i.e., BEKAERT, DURAFIBER, GRACE, and KURARAY. A) B) C) D) Figure 3-1 Different Fibers Used. A) PP, B) PVA, C) Cellulose, D) Hooked Steel

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22 Table 3-4 Properties of Fibers Used ManufactureBEKAERTGRACEDURAFIBERKURARAYProduct NameDramix ZP 305STRUX 90/40Buckeye UltraFiber 500TMRF 4000x30Fiber TypeHooked-collatedMonofilamentSquare-pressedMonofilament Length (in)1.21.550.0831.19Diameter (in)0.0220.0170.026Modulus (GPa)2009.529Tensile Strength ksi(MPa)160(1104)90(620)116(800)Aspect Ratio (l/D)559045Specific Gravity7.850.920.81.3AbsorptionNoneNoneDosage (lb/yd3)1207.750.516.43Polyvinyl AlcoholFiber MaterialSteel Polypropylene/ Polyethylene BlendVirgin Cellulose 3.2 Mix Proportions for the Matrix Synthetic fiber mix dosages above 4 lbs/yd 3 (2.4 kg/m 3 ) require a reduction in the coarse aggregate and an increase in the mortar fraction to accommodate the additional surface area of the synthetic fiber added. The synthetic fiber mix dosages used in this study were 7.75 lbs/yd 3 for polypropylene, 16.43 lbs/yd 3 for polyvinyl alcohol, and 1.5 lbs/yd 3 for cellulose. Thus, the volume of the coarse aggregate was reduced by adjusting for each of the above synthetic fiber volumes. Steel fiber-reinforced concrete within the dosage range of 20-40 lbs/yd 3 (12-24 kg/m 3 ) will seldom create a need to adjust the mix

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23 design. The mix should be reviewed from 4065 lbs/yd 3 (24-39 kg/m 3 ). At and above 65 lbs/yd 3 (39 kg/m 3 ), some adjustment to the mix design is required. The steel fiber mix dosages in this study were 120 lbs/yd 3 . The volume of the coarse aggregate was consequently reduced to adjust for the steel fiber volume (AASHTO-AGC-ARTBA Joint Committee, 2001). The materials used in the study were: (1) AASHTO Type II Portland cement which meets ASTM 150 specifications, (2) 3/8 in (9.5 mm) maximum size of coarse aggregate crushed limestone, (3) natural sand with a specific gravity of 2.648 at SSD and fineness modulus of 2.39, (4) polypropylene fiber with a specific gravity of 0.92, (5) polyvinyl alcohol fiberwith a specific gravity of 1.3, (6) cellulose fiber with a specific gravity of 0.8, (7) steel fiber with a specific gravity of 7.85, (8) admixtures WRDA 60, and ADVA 140 provided by Grace Construction Products. The mix proportions used in this study were applicable to concrete that has a normal weight and a moderate compressive strength of 31 MPa (Class II), and 45 MPa (Class V) at 28 days. A series of ten concrete mixes were prepared with and without fibers. The fiber addition rates were 7.75 lbs/yd 3 for polypropylene fibers, 16.43 lbs/yd 3 for polyvinyl alcohol fibers, 1.50 lbs/yd 3 for cellulose fibers, and 120 lbs/yd 3 for steel fibers corresponding to fiber contents of 0.5%, 0.75%, 0.1%, and 1% by volume respectively. Table 3-5 summarizes the mix designs for FRC. 3.3 Mixing and Curing Procedures 3.3.1 Mixing Procedure Each batch was mixed in a pan mixer with a maximum capacity of 16 ft 3 at the FDOT concrete mixing laboratory. The limestone aggregate was batched at a saturated, surface-wet condition. Saturation was attained by soaking the aggregate in water for at

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24 Table 3-5 Material and Mix Proportions (Class II/V) Mix Type PCPPPVACelluloseSteelW/C0.44/0.370.44/0.370.44/0.370.44/0.370.44/0.37Cement (lbs/yd3)611/752611/752611/752611/ 752611/ 752Water (lbs/yd3)269/278269/278269/278269/278269/278Coarse Aggregate (lbs/yd3)1444/14301424/14101414/14001439/14251407/1393Fine Aggregate (lbs/yd3)1490/13621490/13621490/13621490/13621490/1362Fiber Content (lbs/yd3)None7.7516.431.5120Air Target (%)33333Water Reducer (oz)33.833.833.833.833.8High Range WR (oz)120.3120.3120.3120.3120.3 least 5 days. Standard 4 x 8 in plastic cylinder molds were prepared for compression, splitting tension, permeability, absorption, and volume of voids testing for control mixes. However, when the plastic fiber was mixed, the 23 x 13 x 8 in wooden molds were used in place of the 4 x 8 in plastic cylinder molds to ensure proper distribution of the fibers throughout the blocks. These blocks were cored after 14 days during of moist curing. The following mixing sequence was used for all mixes. First, gravel and sand were mixed for approximately 1 minute. Then 50 % of water was added and the mixture was mixed for 1 minute to allow absorption by the fine aggregate. Next, then cement was added and the remaining water containing the set retarder and high-range water reducing admixture Mixing continued for another 2 minutes. All component materials (except

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25 fibers) were added, to ensure proper and uniform mixing. Finally, fibers were added to the mix. Altogether, the mixing time took approximately 3-4 minutes to guarantee homogenous fiber distribution and to minimize segregation and balling. After completion of the batch, the mix was poured into the appropriate molds, which were then placed on a vibrating table. The vibrating process was continued for approximately 1-2 minutes. 3.3.2 Curing Procedure Curing of all FRC specimens was carried out as follows: after placement, the specimens were kept in their plastic or wood molds for 24 hours and covered with a plastic sheet; the specimens were then removed from their molds and moved to the moisture curing room, which was maintained at 100 percent relative humidity and 72 F (23 C) until the time of testing. However, the coring blocks were moved to UF concrete laboratory and allowed to cure immersed in fresh water for another 2 weeks after coring. The specimens consisted of 28 cylinders for plain concrete and 40 cylinders for plastic fiber concrete, including an additional 10 control cylinders cast before adding plastic fibers using a vibrating table. 3.2 Fresh Concrete Properties 3.2.1 General Immediately after mixing, the concrete was tested for slump (ASTM C 143), air content (ASTM C 231), inverted slump cone time (ASTM C 995), Vebe time (ASTM C 1170), and unit weight (ASTM C 231). Measuring the plastic properties of FRC requires a different approach than with more typical concrete because the slump loss does not necessarily mean that there is a corresponding loss of workability, especially when vibration is used during placement. The Vebe and inverted slump cone tests have been developed specifically to evaluate the workability of FRC.

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26 3.2.2 Workability One shortcoming of using fibers in concrete is a reduction in workability. The workability of FRC is affected by fiber aspect ratio and volume fraction as well the workability of plain concrete. As the fiber content or aspect ratio of the fiber increases, the slump decreases. Most researchers limit V f to 2.0% and l/D to 100 to avoid unworkable mixes. In addition, some researchers have limited the fiber reinforcement index [V f *(l/D)] to 1.5 for the same reason. To overcome the workability problems associated with FRC, modification of concrete mix design is recommended. 3.2.2.1 Slump test (ASTM C 143) The slump test is a common, convenient, and inexpensive test, but it may not be a good indicator of workability for FRC. However, the slump test was measured with and without fiber during the mixing procedure. A sample of freshly mixed concrete was placed and compacted by rodding in a mold shaped as the frustum of a cone. The mold was raised, and the concrete allowed to subside. The vertical distance between the original and displaced position of the center of the top surface of the concrete is measured and reported as the slump of the concrete. 3.2.2.2 Inverted slump cone test (ASTM C 995) This test has been developed specifically to measure the workability of FRC. It effectively measures the mobility or fluidity of the concrete under internal vibration. The test is not suitable for flowable mixtures of FRC because the concrete tends to run through the cone without vibration. This test method provides a measure of the consistency and workability of fiber-reinforced concrete. Figure 3-1 shows the inverted slump-cone time test setup.

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27 Figure 3-2 Inverted Slump-Cone time Test Setup Except for the standards related to internal vibration, the procedure was carried out according to ASTM C 995 as follows: The bucket was dampened and was placed on a level, rigid, horizontal surface free of vibration and other disturbances. The cone was dampened and was placed in the positioning device, where it was level. From the sample obtained, the cone was filled in three layers, each approximately one third of the volume of the cone. Each layer was lightly leveled with a scoop or trowel to minimize the entrapment of large voids and the surface of the top layer was stroked off by means of a screeding and rolling motion of the tamping rod. Protruding fibers which inhibit screeding were removed by hand. One third of the volume of the cone corresponded to a depth of 5.875 in. (149 mm); two thirds of the volume corresponded to a depth of 9.375 in. (237 mm). Then, an external vibrator and a stopwatch were started simultaneously. The stopwatch was stopped when the cone became empty, which occurred when an opening became visible at the bottom of the cone. When the cone became plugged during

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28 the test, or failed to empty because of an excess of material that has fallen through during filling, the result was disregarded and a new test was done on another portion of the sample. The time needed for the mix to flow out of the cone was recorded. 3.2.2.3 Vebe test (ASTM C 1170) This test method is intended to be used for determining the consistency and density of stiff to extremely dry concrete mixtures. The following procedure was used for all mixes: When the consistometer was installed on an unbending, horizontal and smooth surface, the cylinder mold was put on the vibrating table and secured using the special screws. The conical mold was dampened, and put into the cylinder mold, and the funnel was positioned over the cylinder mold. The screw of the rotating arm was tightened so that the tunnel avoided the mold lifting. After the concrete was prepared, the conical mold was filled in three steps with 25 strokes of a tamping rod distributed uniformly over Figure 3-3 Vebe Time Test Setup

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29 the whole surface. The conical mold was lifted vertically, avoiding sideways or torsional movements. The rotating arm was moved so that the transparent disk was above the concrete surface, and the disk was lowered until it touched the concrete. The transparent disk was left free and the fixing screw on the holding bar was unscrewed so that it moved freely inside the cylinder and touched the concrete, which was then compacted. Then, the vibrating table was operated and the timer was pressed. As soon as the transparent surface was completely covered by the fresh concrete, the timer and the vibrating table were stopped. This time is the vebe time and represents the workability of concrete. 3.2.3 Air Content (ASTM C 1170) This test was done to confirm that the addition of fibers did not result in the entrapment of unwanted air voids within the concrete that could result in crack initiation or increased permeability. Both effects would lead to decreases in durability performance. 3.2.4 Temperature and Unit Weight The initial temperature and unit weight of the fresh fiber reinforced concrete mixes were also measured. The unit weight was measured according to ASTM C 29/C 29M standard procedures, using the 0.25 ft 3 base portion of the pressure meter. The unit weight was taken after the sample was properly vibrated. The initial temperature was taken using a thermometer marked from 0 to 100F.

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30 CHAPTER 4 MECHANICAL TESTS This chapter describes the mechanical and durability tests that were designed to evaluate the different mechanical properties of FRC. 4.1 Objectives The objectives for this experiment were to verify properties of hardened FRC containing fiber types used in the industry. The fiber contents studied in this experiment were 0.5% for polypropylene, 0.75 % for polyvinyl alcohol, 0.1% for cellulose, and 1% for steel fiber by volume. Generally, a relatively low fiber content of less than 1% seems to have a small positive influence on the concrete, and a fiber content of more than 2% may create difficulty in mixing and achieving uniform distribution of the fibers. However, the fiber contents used in this study were arrived at through discussion with industry representatives and are reasonable fiber contents for practical applications. 4.2 Compression Tests 4.2.1 Experimental Program The compression tests were subdivided into two groups: (1) Class II concrete, consisting of 0.44 w/c ratio FRC mixes containing four types of fibers with different fiber volume fractions (0.5% for polypropylene, 0.75% for polyvinyl alcohol, 0.1% for cellulose, and 1% for steel); (2) Class V concrete, consisting of 0.37 w/c ratio FRC mixes with the same fiber volume fractions and types as the class II concretes.

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31 Standard cylindrical specimens were prepared for control mixes on the 28 th day. For each plastic fiber mix, two 8 in x14 in x23 in. blocks were prepared to ensure proper distribution of the fiber evenly throughout the blocks. Each block was cored to produce a series of 4 in x8 in. cylinders on the 14 th day. Additionally, three 4 in x8 in. control cylinders were cast before adding fibers to the mix, and the compression tests were performed with and without fibers for each fiber mixture design. Six specimens were tested for each parameter. Table 4-1 shows the number and size of specimens tested for each mix and the type of test performed. Table 4-1 Number of Specimens Tested FiberPCII/VControl03PPII/VPolypropylene0.533PVAII/VPolyvinyl Alcohol0.7533CELLII/VCellulose0.133STEELII/VHooked Steel0.8933Fiber Volume Fraction Vf (%)Number of Specimens Tested4 x 8 inCompression TestControl33333MOEMix TypesConcrete ClassesFiber Types 4.2.2 Test Apparatus and Procedure For each test, two types of methods were used: (1) a nondestructive method to measure the static modulus of elasticity (E c ) and (2) a destructive method to produce the stress-strain curve. Figures 4.1 and 4.2 display the setups used for stress-strain curve tests and the elastic modulus, specifically. The load was measured by a load cell, while the deformation was measured using linear voltage differential transducers (LVDT) for the elastic modulus test. The stress-strain curve in compression was obtained for all cylinders, tested at a controlled a displacement rate of 0.025in/min in the UF laboratory. The curve provided information on strength and ductility. The three curves obtained from

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32 the three identical cylinders of each concrete class were combined to acquire the average stress-strain curves for the concrete classes. Average curves for each concrete class were compared to clarify the influence of time, fiber content, fiber type, and specimen conditions. A) B) Figure 4-1 Test Set-up Used to Measure the Stress-Strain Response in Compression. A) Test Machine, B) Sample Condition. The elastic modulus test was performed on 4 in x8 in specimens. The fixture used for this type of test (Fig. 4.2) consisted of two aluminum rings separated by temporary bracing that held the top and bottom rings apart at a gauge length of exactly 5.5-in. To allow for free movement of the rings, the bracing was removed after the two rings were fixed to the concrete cylinder. When the specimen was placed on the lower platen or bearing block of the testing machine with the strain-measuring equipment attached, the axis of the specimen was carefully aligned with the center of thrust of the spherically-seated upper bearing block. As the spherically-seated block was brought slowly to bear upon the specimen, the movable portion of the block was rotated gently by hand so that uniform seating was obtained. The movement between the two rings was measured by LVDT. A 500 kip capacity Test Mark Industries testing machine equipped with a swivel head platen was used for all tests. Each specimen was loaded by the load-controlled

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33 method at a rate of 400-500 lbs/sec, and the load was increased up to 40% of the anticipated strength, which was assumed to be equal to the strength of the control specimen. When the target load was reached, it was immediately reduced to zero at the same rate at which it was applied. This loading cycle was completed three times for each specimen. Once the elastic modulus test was completed, the rings were removed and the cylinder was tested up to failure. The collected data were averaged, and various plots were obtained for each specimen and for an average of each series. A) B) Figure 4-2 Test Set-up for Measurement of Elastic Modulus. A) Test Machine, B) Sample Condition. 4.3 Splitting Tensile Tests 4.3.1 Experimental Program The splitting tensile tests were subdivided into two groups: (1) Class II concrete, consisting of 0.44 w/c FRC mixes containing four types of fibers with different fiber volume fractions (0.5% for polypropylene, 0.75% for polyvinyl alcohol, 0.1% for cellulose, and 1% for steel); (2) Class V concrete, consisting of 0.37 w/c FRC mixes containing the same fiber volume fractions and types such as the Class II concretes. Standard cylindrical specimens were prepared for control mixes on the 28th day. For each plastic fiber mix, two 8 in x14 in x23 in blocks were prepared to ensure efficient

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34 distribution of the fiber evenly throughout the blocks. Each block was cored to produce a series of a 4 in x 8 in cores after 14 days of moist-curing. Additionally, three 4 in x 8 in cylinders were cast before adding fibers during the mixing and splitting tensile tests were performed with and without fibers for each fiber mixing. Six specimens were tested for each parameter. Table 4-2 shows the number and size of specimens tested for each mix and the type of test performed. Table 4-2 Number of Specimens Tested PCII/VControl0PPII/VPolypropylene0.5PVAII/VPolyvinyl Alcohol0.75CELLII/VCellulose0.1STEELII/VHooked Steel0.89333333Control3Splitting Tensile TestFiberMix TypesConcrete ClassesFiber TypesFiber Volume Fraction Vf (%)Number of Specimens Tested4 x 8 in33 4.3.2 Test Apparatus and Procedure Three standard cylindrical 4 in x 8 in test specimens were prepared to determine the splitting strengths after 28 days. This was obtained directly from the load recorded by using a 600 kip capacity FORNEY testing machine. The setup for the splitting tensile tests is shown in Figure 4.3. Before testing, the diameter and length of the each test specimen were determined to nearest 0.01 in. (0.25 mm) by averaging three diameters measured near the ends and the middle of the specimen and two lengths of the specimen on the two ends.

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35 A) B) Figure 4-3 Test Set-up for Splitting Tensile Test. A) Test Machine, B) Sample Condition. In accordance with the ASTM C496-01 procedure for splitting tensile strength determination, diametral lines were drawn on each end of the specimen using a suitable device to ensure that they were in the same axial plane, and then two pieces of hard wood measuring 0.25 in x 0.75 in x 8 in were placed 180 apart along the longitudinal axis of each cylinder, as shown in Fig. 4.3. This was done to avoid any stress concentrations that might result along the line of application of the load. The load was applied continuously and without shock, at a constant rate within a range 100 to 200 lbs/sec until failure of the specimen. The maximum applied load indicated by the testing machine at failure was recorded. The splitting tensile strength was computed as follows: ldPfst2 Where: f st = splitting tensile strength, in psi P = maximum applied load, in lbf l = length of cylinder, in inches d = diameter of cylinder, in inches.

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36 4.4 Permeability Test 4.4.1 Experimental Program Water permeability tests were subdivided into two groups: (1) Class II concrete, consisting of 0.44 w/c FRC mixes containing four types of fibers with different fiber volume fractions (0.5% for polypropylene, 0.75% for polyvinyl alcohol, 0.1% for cellulose, and 1% for steel); (2) Class V concrete, consisting of 0.37 w/c FRC mixes having same fiber volume fractions and types such as Class II concretes. Standard cylindrical specimens were prepared for control mixes on the 28th day. The top inch of the cylinder was then sliced off and the next 2 inched was used in the permeability test. Table 4-3 shows the number and size of specimens tested for each mix and the type of test performed. 4.4.2 Preparation of Test Specimens The test specimens were cylindrical samples measuring 4 inches in diameter and 2 inches in height, and were made by cutting 4 in x 8 in cast cylinders at 1 and 3 inches from the top surface. The circumferences of the test specimens were roughed and wire-brushed until all loose particles were removed. Care was taken to ensure that the surfaces of the test specimens were dry. A 1-inch thick layer of epoxy (Sikadur 32, Hi-Mod) was applied around the curved side of the test specimen by means of a casting mold. The casting mold was 6 inches in diameter by 2 inches in height and was bolted down to a steel plate. The inner surface of the casting mold and the top surface of the steel plate were coated with a very thin layer of a release agent. The side of the specimen was first coated with a thin layer of epoxy. The specimen was then placed in the center of the casting mold, and the remaining gap between the casting mold and the test specimen

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37 Table 4-3 Number of Specimens Tested PCII/VControl0PPII/VPolypropylene0.5PVAII/VPolyviny Alcohol0.75CELLII/VCellulose0.1STEELII/VHooked Steel0.89Mix TypesConcrete ClassesFiber TypesFiber Volume Fraction Vf (%)33333PermeabilityNumber of Specimens Tested4 x 2 in was filled with epoxy. A vibrator was used to eliminate air bubbles from the epoxy. When the epoxy had hardened, the test specimen was removed from the casting mold. Any amount of epoxy which may have adhered to the top and bottom surfaces of the test specimen was removed. Figure 4.4 shows a picture of a prepared concrete specimen coated with epoxy on the side. A) B) Figure 4-4 Water Permeability Test. A) Test Set up, B) Test Apparatus 4.4.3 Testing Procedure The prepared test specimen was placed into the permeability apparatus by following these steps: 1. The test specimen was placed on the center of the base plate.

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38 2. A neoprene gasket was placed on the specimen. 3. The acrylic tube was placed on the neoprene gasket. 4. Another neoprene gasket was placed on the acrylic tube. 5. The top plate was placed on the neoprene gasket and bolted to the base place with four 3/8-inch diameter rods. 6. A torque of approximately 10 to 12 foot-pounds was applied to all bolts, and this needed to be checked periodically in order to ensure the same torque during the entire period of testing The permeability apparatus was then connected to the manometer tube using the following procedure: 7. The valve for the manometer tube was turned off. 8. The manometer tube was attached to the connection at the center of the top plate of the permeability apparatus. 9. Pressure was applied to the main pressure line and maintained at 40 psi by the regulating valve, which controlled the pressure from the air compressor. 10. The water reservoir was connected to the pressure regulator through one of the two quick connections of the water reservoir, and a pressure of 42 psi was maintained. 11. The other quick connection of the water reservoir was connected to the quick connection at the top plate of the permeability apparatus, and water was injected into the permeability apparatus and manometer tube by opening the manometer valve slowly until the water in the manometer tube reached the top level. The valve was then turned off, and the permeability apparatus was disconnected from the water reservoir. 12. The air bubbles trapped inside the permeability apparatus were released through the quick connection at the top plate. At this stage, the permeability test could be started by simply opening the manometer valve to connect the 40 psi air pressure line to the manometer. The water levels in the manometer tube and the time at the start of the test were recorded. Possible leakage of water between the epoxy and the side of the test specimen was checked. The test was continued if no leakage was found. When the water level in the manometer tube reached a low level, additional water was added to the manometer tube from the water reservoir. The process of refilling the manometer tube was the same as the process of initial filling as described earlier.

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39 4.4.4 Method of Measuring Rate of Flow The amount of water flowing into a test specimen was measured by reading the water level of the 0.1-inch manometer tube at least once per day. A plot of the cumulative amount of water flowing into the test specimen vs time was drawn for each test specimen, in order to determine when a steady state flow condition was reached. A steady state flow condition was reached when the flow rate did not change with time. The steady state condition was usually reached within a time frame of about 10 to 21 days, but the specific time was dependent upon many factors such as the w/c and curing conditions. The test was continued for about 7 to 10 days beyond the steady flow condition. The average rate of inflow in the last 7 to 10 days was used as the rate of flow for the test specimen. 4.4.5 Determination of Coefficient of Permeability A specimen flow fixture that produces one dimensional water flow from one cylindrical face to the other, previously developed by Soongswang et al. (1988), was used to secure each specimen for testing (see Figures 4.5-4.6). The Plexiglas ring above the sample is essentially a chamber filled with pressurized water. The opposite side of the sample is exposed to ambient pressure conditions. Therefore, a pressure gradient is formed across the sample and water is forced to flow through it. The coefficient of permeability of a test specimen is computed from the net rate of inflow by using the following equation, which is based on Darcy’s Law: PAHQKv Where H is the height (thickness) of mortar specimen (in), A is the cross-sectional area of the specimen (in 2 ), P is water pressure in psi, is density of water in lb/in 3 , Q v is the volumetric flow rate (in 3 /sec):

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40 tAhQtubev)( Where is the change of permeant liquid level in the metering tube (in), is the inner cross-sectional area of the metering tube (in h tubeA 2 ), and t is the duration of time—under steady state conditions—over which the change of liquid height occurred. h 25.4 mm(1.0 in) 19.1 mm(0.75 in)Water inflowWater outflowSteel bolts Epoxy coating(to seal side of sample)Rubber gasket ringsPlexiglas plateEpoxycollar EpoxycollarCylindrical mortar specimen 19.1 mm(0.75 in) Cylindrical plexiglas ring Plexiglas plate102 mm (4 in.)diameter specimen25mm mm (1 in.) wideepoxy collar 25mm mm (1 in.) wideepoxy collar Figure 4-5 Schematic Diagram of Water Permeability Flow Fixture 4.5 Density, Absorption, and Voids in Hardened Concrete 4.5.1 Experimental Program Density, absorption and void ratio tests were subdivided into two groups: (1) Class II concrete, consisting of 0.44 w/c FRC mixes containing four types of fibers with different fiber volume fractions (0.5% for polypropylene, 0.75% for polyvinyl alcohol, 0.1% for cellulose, and 1% for steel); (2) Class V concrete, consisting of 0.37 w/c

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41 Air pressure source Initial Water Level (@ time = 0)Final Water Level (@ time = t) Change in heightover timeWater exits at ambient conditions (1 atm pressure)Water permeabilityfixtureMetering tube with known inner cross-sectional area Figure 4-6 Measurement of Flow Rate in Water Permeameter FRC mixes having the same fiber volume fractions and types as the Class II concretes. Standard cylindrical specimens were prepared for control mixes on the 28th day. When the fiber was mixed, three control samples were made before adding fibers, and another three fiber samples were cast after adding fibers. A total six samples were cast and middle of each cylinder was cut into a 3 in thick disk. Table 4-4 shows the number and size of specimens tested for each mix and the type of test performed. 4.5.2 Procedure 4.5.2.1 Oven-dry mass When the specimens with and without fiber were cut to 3 in thickness from the 4 in x 8 in cylinders, the mass in the surface dried condition was determined and the specimens were dried in an oven at a temperature of 100 to 110 for at least 24 hours. After each specimen was removed from the oven, it was allowed to cool in dry air to a

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42 Table 4-4 Number of Specimens Tested PCII/VControl0PPII/VPolypropylene0.5PVAII/VPolyvinyl Alcohol0.75CELLII/VCellulose0.1STEELII/VHooked Steel0.89Mix TypesConcrete ClassesFiber TypesFiber Volume Fraction Vf (%)Number of Specimens Tested4 x 3 inVolume of Voids TestControlFiber333333333 temperature of 20 to 25C, and its mass was again determined. If the difference between values obtained from two successive values of mass exceeded 0.5% of the lesser value, the specimens was returned to the oven for an additional 24 hour drying period, and the procedure was repeated until the difference between any two successive values was less than 0.5% of the lowest value obtained. This last value was designated mass A. 4.5.2.2 Saturated mass after immersion After the determination of mass A, the dried specimen was immersed in water at approximately 21C for at least 48 hours and until two successive values of mass of the surface-dried sample at intervals of 24 h showed an increase in mass of less than 0.5% of the larger value. Surface moisture was removed with a towel, and the mass was determined. The final surface-dry mass after immersion was designated mass B. 4.5.2.3 Saturated mass after boiling The surface-dry specimen after immersion was placed in a suitable receptacle, covered with tap water, and boiled for 5 hours. It was allowed to cool for at least 14 hours until reaching to a final temperature of 20 to 25C. Surface moisture was removed with a towel and the mass of the specimen was determined. The soaked, boiled, and surface

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43 dried mass was designated mass C. 4.5.2.4 Immersed apparent mass After immersion and boiling of the specimen, it was suspended by a wire and the apparent mass in water was determined. This apparent mass was designated mass D. 4.5.3 Calculation By using the values for mass determined in accordance with the procedure described in the above section, the following were made: Absorption after immersion, % = [(B-A)/A] x 100 Absorption after immersion and boiling, % = [(C-A)/A] x 100 Bulk density, dry = [A/(C-D)] = g 1 Bulk density after immersion = [B/(C-D)] Bulk density after immersion and boiling = [C/(C-D)] Apparent density = [A/(A-D)] = g 2 Volume of permeable pore space (voids), % = (g 1 -g 2 )/g 2 x 100 Where: A = mass of oven-dried sample in air, g B = mass of surface-dry sample in air after immersion, g C = mass of surface-dry sample in air after immersion and boiling, g D = apparent mass of sample in water after immersion and boiling, g g 1 = bulk density, dry, Mg/m 3 and g 2 = apparent density, Mg/m 3 = density of water = 1 Mg/m 3 = 1 g/cm 3

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CHAPTER 5 TEST RESULTS AND ANALYSIS 5.1 Introduction The test results and analysis will be presented categorically in the following order: fresh properties, compression, splitting tension, volume of voids and water permeability. 5.2 Fresh Properties This section discusses the results obtained from the fresh property tests conducted at the day of mixing for all FRC mixes. The results of fresh property tests showing the relationship between mix types are given in Table 5-1 and 5-2. The results comparing each fresh property test for different fiber types are plotted using bar charts. The slump test was used to monitor the consistency of FRC. The slump test was used to monitor the consistency of FRC. Figures 5-1 and 5-2 show the slump test results and demonstrate the reduction of fresh mix workability resulting from the addition of fibers. The reduction range for each fiber was 4.5 – 7.0 in. for PP, 4.25 5.50 in. for PVA, 1.25 3.50 in. for cellulose, and 2.50 4.75 -in. for hooked steel fibers, relative to control samples tested from the same mixture before adding fibers. Among the fiber types, the addition of cellulose fibers resulted in the lowest slump loss. However, it shows a high slump loss when it compared by fiber volume fraction. Inverted slump-cone time and Vebe time were measured to evaluate the mobility or fluidity of the mixtures because the slump test is not a good indicator of workability for FRC. Both of these vibration-type tests measured essentially the same characteristic of 44

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45 the freshly mixed concrete. There is a significant decrease of workability for FRC when adding PP, PVA, and hooked steel fibers from the Figures 5-3 and 5-4. Table 5-1 Plastic Properties for Class II Concrete withoutwith withoutwith PC5.751525.1068/73136.28Mix 18.501.503.20140.08Mix 16.501.009974.703.20139.84Mix 26.501.504.20138.88Mix 16.501.508564.204.20139.76Mix 25.003.754.90138.72Mix 17.505.751013.703.90139.52Mix 23.250.753.10144.72Mix 13.250.758794.002.80144.72Mix 2Steel72/79Mix #PP75/76PVA77/75Cell68/75Fiber TypesSlump (in) Inveted Slump (s)Vebe Time (s) Air Content (%)Air/Mix Temp. ()Unit Weight (lb/ft3) Table 5-2 Plastic Properties for Class V Concrete withoutwith withoutwith PC3.253243.4070/73142.72Mix 17.752.00142.50Mix 16.251.757863.002.90143.20Mix 28.504.25143.70Mix 18.002.756742.702.00143.04Mix 27.504.003.40140.88Mix 17.754.501622.703.40142.08Mix 27.002.502.70145.44Mix 16.501.755952.802.40146.00Mix 2PP68/75PVA68/73Fiber TypesSlump (in) Unit Weight (lb/ft3)Mix #Air Content (%)Air/Mix Temp. ()Cell68/73Inveted Slump (s)Vebe Time (s) 75/76Steel Figures5-5 and 5-6 show the curvilinear relationship between the Vebe time with vibration and the slump obtained under static test conditions, slump and inverted slump-cone time. The flattening of the FRC curve above 4.5 or 5.0 in. slump indicates that for these mixtures, there is no improvement in workability as slumps increase beyond about 4.50 in. On the other hand, Figure 5-7 show a linear relationship illustrating direct proportionality between the Vebe time and the inverted slump cone time. The exact

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46 nature of the relationships shown in Figures 5-5, 5-6, and 5-7 will vary from one type of concrete to another depending on maximum aggregate size and gradation, fiber concentration, type and aspect ratio, and air content. Figures 5-8 and 5-9 indicate that the addition of PP, PVA, and hooked steel fibers showed a lower air content than the plain concrete mixes and control samples made before adding fibers. However, the cellulose fibers slightly increased the entrapped air contents in comparison with the air contents measured before adding fibers for concrete classes. SteelCellPVAPPPC0123456789Mix TypesSlump (inch) Without Fiber With Fiber Figure 5-1 Slump Results for Class II Concrete

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47 SteelCellPVAPPPC0123456789Mix TypesSlump (inch) Without Fiber With Fiber Figure 5-2 Slump Results for Class V Concrete PCPPPVASteelCell0102030405060708090100110Mix TypesTime (sec) Inverted Slump Time Vebe Time Figure 5-3 Inverted Slump-Cone vs Vebe Time Results for Class II Concrete

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48 CellSteelPVAPPPC0102030405060708090100110Mix TypesTime (sec) Inverted Slump Time Vebe Time Figure 5-4 Inverted Slump-Cone vs Vebe Time Results for Class V Concrete y = 1.90x2 29.74x + 118.53R2 = 0.9202040608010012001234567Slump (in)Inverted Slump Cone Time (sec) Class II Class V Figure 5-5 Slump vs Inverted Slump-Cone Time for Class II and Class V Concretes

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49 y = -3.46Ln(x) + 7.51R2 = 0.970123456789100123456Slump (in)Vebe Time (sec) 7 Class II Class V Figure 5-6 Slump vs Vebe Time Class II and Class V Concretes y = 12.34x 1.98R2 = 0.8402040608010012002468Vebe Time (sec)Inverted Slump Cone Time (sec) 10 Class II Class V Figure 5-7 Vebe Time vs Inverted Slump Cone Time Class II and Class V Concretes

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50 SteelCellPVAPPPC23456Mix TypesAir Content (%) Without Fiber With Fiber Figure 5-8 Air Content Results for Class II Concrete PCPPPVACellSteel12345Mix TypesAir Content (%) Without Fiber With Fiber Figure 5-9 Air Content Results for Class V Concrete

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51 5.3 Compression Tests 5.3.1 Compression Test Results Tables 5-3 and 5-4 summarize the average values of the compressive strength, f’ c , and elastic modulus for both concrete classes tested on the 28 th day. Table 5-3 The Average Values of f' c and E c Obtained for Class II Concrete Average47898.20S.D1510.28C.O.V3.163.36Average47828.378.16S.D760.210.27C.O.V1.582.493.34Average48328.348.41S.D1680.150.48C.O.V3.481.775.73Average46747.647.84S.D1750.260.36C.O.V3.733.434.62Average51908.499.26S.D660.030.13C.O.V1.280.341.39Mix TypesSpecimen IDModulus of Elasticity (ksi)Compressive Strength (ksi)ControlFiberPCPPPVACelluloseSteel 5.3.1.1 Fiber influence on the compressive strength The experimental results from the compressive strength tests of all fiber mixes appear in Figures 5-10 and 5-11. The addition of the polypropylene fibers (at a level of 0.5% by volume with a length of 1.55-in. and an aspect ratio of 90) slightly reduced the compressive strength for the Class II concrete but somewhat increased the compressive strength about 5% for Class V. Similar results have been reported by Leung et al (2005) and Yao et al (2000). The use of polyvinyl alcohol fibers (at a fiber volume fraction of 0.75% with a length of 1.19-in and an aspect ratio of 45) resulted in a small increase in the compressive

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52 Table 5-4 The Average Values of f' c and E c Obtained for Class V Concrete Average50989.66S.D530.39C.O.V1.044.03Average51539.9710.13S.D1090.260.32C.O.V2.122.573.16Average51679.8910.10S.D980.090.30C.O.V1.890.932.93Average50349.569.17S.D1610.300.62C.O.V3.193.106.71Average53149.7610.19S.D1730.150.28C.O.V3.261.512.77PPControlFiberSpecimen IDModulus of Elasticity (ksi)Compressive Strength (ksi)PVASteelCelluloseMix TypesPC strength for both concrete classes in comparison with the plain concrete mixes. Similar results have been reported by Leung et al (2005). The addition of 0.89% steel fibers by volume (with a length of 1.2-in and an aspect ratio of 55) aids in converting the properties of brittle concrete to that of a ductile material. The compressive strength of steel fiber-reinforced concrete was improved by 13% for Class II and 5% for Class V over the control concrete. On the other hand, the addition of 0.1% cellulose fibers had negative effects on the compressive strength for both mixes when compared with plain concrete mixes. However, it can be observed from Figure 10 that the compressive strength of the cellulose fiber is slightly higher than that of plain concrete samples made before adding fibers. It also can be seen from Figures 5-10 and 5-11 that the compressive strength of the cellulose fiber concrete was much lower than other fiber types.

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53 The improvements in compressive strength came principally from the fibers interacting with the advancing cracks. When withstanding an increasing compression load, the fibrous concrete cylinders may develop lateral tension, thus initiating cracks and propatating those cracks. As the advancing crack approached a fiber, the debonding at the fiber-matrix interface began due to the tensile stresses perpendicular to the expected path of the advancing crack. As the advancing crack finally reached the interface, the tip of the crack encountered a process of blunting because of the already present debonding crack. The blunting, blocking, and even diverting of the crack allowed the fibrous concrete cylinders to withstand additional compressive load, thus upgrading their compressive strength over the non-fibrous control concrete (Song et al 2005). SteelCellPVAPPPC6789101112Mix TypesUltimate Strength (ksi) Without Fiber With Fiber Figure 5-10 Ultimate Compressive Strength for Class II Concrete 5.3.1.2 Fiber influence on the elastic modulus The purpose of this section is to compare the variation in elastic modulus between

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54 the various fiber mixes. Figure 5-12 shows the results of the modulus of elasticity for concrete Classes II and V. The PP and PVA fiber mixes showed no significant differences from the control mixes. However, the mixes containing cellulose represented PCPPPVACellSteel6789101112Mix TypesUltimate Strength (ksi) Without Fiber With Fiber Figure 5-11 Ultimate Compressive Strength for Class V Concrete a decrease in E c of about a 2-3% from the control mix, whereas the steel fiber mix showed a 4-9% higher elastic modulus than that of the plain concrete mixes. Generally, the results indicate that the addition of hooked steel (0.89%), polypropylene (0.5%), and polyvinyl alcohol (0.75%) fibers have only a slight effect on the ascending breach of the stress strain curve of the composite. 5.3.1.3 Stress versus strain response This section focuses on the effect of fiber types on the stress-strain response of all FRC mixes. Figure 5-13 compares the average stress-strain curves of Class II concrete mixes tested on the 28th day. It can be observed that little ductility can be expected

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55 following the peak load for control, PVA (0.75%), and cellulose (0.1%) fibers. The compressive strength of these concretes dropped after reaching their peak load. Figure 5-13 clearly shows that the mix containing the hooked steel fibers leads to PCPPPVACellSteel3000350040004500500055006000Mix TypesEc (ksi) Class II Class V Figure 5-12 Elastic Modulus, E c for Class II and Class V Concretes the highest compressive strength and the largest area under the stress-strain curve. The addition of hooked steel fibers increases the post-peak ductility and energy absorption capacity of concrete in compression, but has a relatively small effect on the peak compressive stress. The strain at peak compressive stress tends to increase with hooked steel fiber reinforcement. The mix including polypropylene fibers shows a lower strength than that of other mixes. However, it is observed that the area under the curve is much larger, thus indicating a substantial increase in ductility and energy absorption to failure for concrete from Figure 5-13.

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56 Figure 5-14 shows the average stress-strain curves of the Class V concrete mixes tested on the 28 th day. The performance of Class V concrete was similar to that of Class II concrete until reaching the peak load. Although the hooked steel fibers show the highest strength of all Class V mixes, it does not indicate a post behavior bridge effect, and the strength sharply dropped after failure. 0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) PC-II PP-II-0.5% PVA-II-0.75% Cell-II-0.1% Steel-II-1% Figure 5-13 Average Stress vs Strain Response of Class II Concrete 5.4 Splitting Tensile Strength Tests This section discusses the results obtained from the splitting tensile and compressive strength tests conducted at one day on all FRC mixes. Tables 5-5 and 5-6 summarize tabulated values for each individual specimen. The results comparing the splitting tensile for different test series are plotted using bar charts. Figure 5-15 compared all FRC mixes for Class II concrete. When analyzing Figure 5-15, it can be observed that the PP and PVA fibers give the lowest splitting tensile

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57 0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) PC-V PP-V-0.5% PVA-V-0.75% Cell-V-0.1% Steel-V-1% Figure 5-14 Average Stress vs Strain Response of Class V Concrete strengths compared with all other mixes. The PP and PVA fiber mixes cause a 10% and 9% reduction in f spt relative to the plain concrete mix. It is observed that cellulose fibers have little effect on the splitting tensile strength when compared with plain concrete. However, the hooked steel fibers containing 0.89% by volume give the highest average splitting tensile strengths compared with all other mixes and increase the strength by 10% for plain concrete mix and by 17% for control samples made before adding fibers. Figure 5-16 compares splitting tensile strengths of all FRC mixes for Class V concrete. It can be seen that the PP and PVA have the lowest splitting tensile strengths compared with all other mixes. The PP and PVA fiber mixes caused a 17% reduction in f spt relative to the plain concrete mix. It is also observed that cellulose fibers reduced the splitting tensile strength by 8% when compared with plain concrete. However, the cellulose fiber increased the f spt by 17% when compared with control samples made

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58 before adding fibers. The hooked steel fiber mix containing 0.89% by volume shows the highest average splitting tensile strengths compared with all other mixes and increases the strength by 4% for plain concrete mix and by 21% for control samples made before adding fibers. Table 5-5 The Average Values of f spt and f' c Obtained for Class II Concrete ControlFiberAverage721.838204.13S.D15.65224.93C.O.V2.172.74Average637.56653.468092.07S.D38.1863.33272.93C.O.V6.029.693.37Average636.21657.918407.59S.D33.338.32482.14C.O.V5.235.825.73Average649.36666.807697.42S.D33.6229.21362.18C.O.V5.184.384.71Average647.86784.749261.99S.D16.7317.94129.03C.O.V2.582.291.39Mix TypeSpecimen IDSplitting Tensile Strength (psi)Compressive Strength (psi)SteelPCPPPVACellulose It can be generally observed that the average splitting tensile strengths of PP, PVA and cellulose fiber mixes (except hooked steel fibers) showed a lower strength than the control mixes. However, it can be seen that the average splitting tensile strength of PP (excluding Class V), PVA, and cellulose fiber mixes showed a higher strength than the control samples made prior to adding fibers.

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59 Table 5-6 The Average Values of f and f' Obtained for Class V spt c Concrete ControlFiberAverage781.279659.32S.D14.04317.57C.O.V1.803.29Average670.88651.8210129.48S.D12.819.08319.80C.O.V1.912.933.16Average628.89648.5610096.38S.D14.0124.46295.57C.O.V2.233.772.93Average625.74721.909165.38S.D27.1312.14615.24C.O.V4.331.686.71Average647.86808.8110193.49S.D16.7342.17282.72C.O.V2.585.212.77CelluloseSteelMix TypeSpecimen IDSplitting Tensile Strength (psi)Compressive Strength (psi)PCPPPVA SteelCellPVAPPPC500550600650700750800850900Mix TypesSplitting Tensile Strength (psi) Without Fiber With Fiber Figure 5-15 Splitting Tensile Strength for Class II Concrete

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60 PCPPPVACellSteel500550600650700750800850900Mix TypesSplitting Tensile Strength (psi) Without Fiber With Fiber Figure 5-16 Splitting Tensile Strength for Class V Concrete 5.5 Volume of Voids 5.5.1 Tests Results and Data Analysis This section discusses the results obtained from volume of voids and splitting tensile strength tests conducted at one day on all FRC mixes. Tables 5-7 and 5-8 summarize tabulated values for each individual specimen. The results comparing the volume of voids for different fiber types are plotted using bar charts. From Figures 5-17 and 5-18, it can be seen that the volume of voids of plain concrete mixes in both Class II and V have the lowest values (12.97% for Class II and 12.19% for Class V), and these low values show the highest splitting tensile strength of FRC mixes. The addition of PP fibers increased the permeable voids in concrete (14.26% for class II and 12.77% for class V), and also resulted in about a 10 17% lower splitting

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61 tensile strength than plain concrete mixes, as described in Figures 5-17 and 5-18. When compared with the control samples cast before adding PP fibers, the increased permeable voids of PP control samples (13.80% for class II, and 12.32% for class V) also show a lower splitting tensile strength than that of the plain concrete mixes. The results of PVA fibers showed a similar trend with PP fibers as described in Figures 5-17 and 5-18. The addition of PVA fibers increased the permeable voids in concrete (13.55% for Class II and 13.60% for Class V) and caused the reduction of the splitting tensile strength (9% for Class II and 17% for Class V) in comparison with plain concrete. Hooked steel fiber mixes showed a 0.85% reduction compared to Class II plain concrete and a 0.89% increase compared to Class V plain concrete and resulted in the highest splitting tensile strength in both concrete classes, regardless of the volume of voids from the Figures 5-17 and 5-18. 5.5.2 The Effect of Volume of Voids on the Splitting Tensile Strength Figure 5-19 compared the splitting tensile strength to volume of voids for control samples of Class II concrete. The high voids in the control fiber samples reduced the splitting tensile strength by 6-8%. Figure 5-20 compares the splitting tensile strength to volume of voids for fiber samples of Class II concrete. Fiber samples having higher permeable voids (excluding steel fibers) also reduced the splitting tensile strength by 7-10%. These steel fibers with low voids compared to the plain concrete mix indicate the highest f spt in the all mixes. Figure 5-21 compares the splitting tensile strength to volume of voids for the Class V control samples. Figure 5-21 shows that the high voids in control fiber samples reduced the splitting tensile strength by 14-20%.

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62 Table 5-7 The Values of Volume of Voids and f spt Obtained for Class II Concrete ControlFiberControlFiberControl113.03722.00Control212.88737.39Control313.00706.10Average12.97721.83S.D0.0815.65C.O.V0.612.17Control113.8314.23659.30725.84Control213.7214.31653.78608.26Control313.8514.23590.59626.28Average13.8014.26637.56653.46S.D0.070.0538.1863.33C.O.V0.510.326.029.69Control113.2913.50604.50655.44Control213.1113.59633.24697.41Control313.0313.55670.90620.89Average13.1413.55636.21657.91S.D0.130.0533.3038.32C.O.V1.010.335.235.82Control113.8013.41645.97696.18Control213.1513.67617.56666.46Control313.4213.61684.55637.77Average13.4613.56649.36666.80S.D0.330.1433.6229.21C.O.V2.431.005.184.38Control112.9012.19692.58781.14Control213.0112.18681.88804.21Control312.9811.98669.56768.88Average12.9612.12681.33784.74S.D0.060.1211.5317.94C.O.V0.440.981.692.29Volume of Voids (%)Splitting Tensile Strength (psi)CellMix TypeSpecimen IDSteelPCPPPVA Figure 5-22 compares the splitting tensile strength to volume of voids for the Class V fiber samples. The PP and PVA fiber mixes showing high voids reduced the splitting tensile strength by 17%. The cellulose fiber mix had a 12.22% volume of voids (slightly higher over plain concrete) and indicated the reduction of f spt by 8%. The steel fiber mix

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63 having a volume of voids 1% higher than plain concrete mix indicated the highest f spt in the all mixes. Table 5-8 The Values of Volume of Voids and f spt Obtained for Class V Concrete ControlFiberControlFiberControl112.16790.41Control212.37765.11Control312.05788.30Average12.19781.27S.D0.1614.04C.O.V1.331.80Control112.2812.81680.45672.34Control212.4212.77656.34648.51Control312.2712.74675.84634.61Average12.3212.77670.88651.82S.D0.080.0412.8019.08C.O.V0.680.271.912.93Control112.9713.48630.34671.60Control212.8713.68642.12622.89Control312.8513.63614.89651.20Average12.9013.60628.89648.56S.D0.060.1014.0124.46C.O.V0.500.772.233.77Control112.6912.11613.61726.26Control212.4712.38606.79708.18Control312.4812.17656.81731.26Average12.5512.22625.74721.90S.D0.120.1427.1312.14C.O.V0.991.164.331.68Control113.1413.10636.54845.43Control213.2513.01593.02762.70Control313.1513.10632.24818.31Average13.1813.07620.60808.81S.D0.060.0523.9842.17C.O.V0.460.403.865.21Splitting Tensile Strength (psi)Mix TypePCPPPVACellSteelVolume of Voids (%)Specimen ID

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64 10.511.011.512.012.513.013.514.014.5PCPPPVACellSteelMix TypesVolume of Voids (%) Without Fiber With Fiber Figure 5-17 Volume of Voids for Class II Concrete 11.011.512.012.513.013.514.0PCPPPVACellSteelMix TypesVolume of Voids (%) Without Fiber With Fiber Figure 5-18 Volume of Voids for Class V Concrete

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65 5.5.3 The Effect of Volume of Voids on the Compressive Strength Figure 5-23 shows that the relationships between compressive strength and volume of voids in harden concrete. It can be observed that there are no significant correlations between the two values. The compressive strength for Class V concrete having higher values than that for Class II concrete shows the same values at the 13% voids. It means that an increase of permeable voids resulting from the addition of fibers does not largely affect the compressive strength of FRC rather than the affection of splitting tensile strength. 500550600650700750800850900PCPPPVACellSteelMix TypesSplitting Tensile Strength (psi)1112131415Volume of Voids (%) Class II-Splitting Tensile Strength-Control Class II-Volulme of Voids-Control Figure 5-19 f spt vs Volume of Voids for Class II Concrete-Control Samples 5.6 Permeability Test 5.6.1 Permeability Test Results The permeability results for all tested specimens are shown in Tables 5-9 and 5-10. The results indicate a high variability in the permeability coefficient among the same

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66 500550600650700750800850900PCPPPVACellSteelMix TypesSplitting Tensile Strength (psi)1112131415Volume of Voids (%) Class II-Splitting Tensile Strength-Fiber Class II-Volulme of Voids-Fiber Figure 5-20 f spt vs Volume of Voids for Class II Concrete-Fiber Samples 500550600650700750800850900PCPPPVACellSteelMix TypeSplitting Tensile Strength (psi)1112131415Volume of Voids (%) Class V-Splitting Tensile Strength-Control Class V-Volume of Voids-Control Figure 5-21 f spt vs Volume of Voids for Class V Concrete-Control Samples

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67 500550600650700750800850900PCPPPVACellSteelMix TypeSplitting Tensile Strength (psi)1112131415Volume of Voids (%) Class V-Splitting Tensile Strength-Fiber Class V-Volume of Voids-Fiber Figure 5-22 f spt vs Volume of Voids for Class V Concrete-Fiber Samples y = -0.53x + 16.07R2 = 0.167.07.58.08.59.09.510.010.511.010.011.012.013.014.015.0Volume of Voids (%)Compressive Strength (ksi) Class II Class V Figure 5-23 Compressive Strength vs Volume of Voids for Class II and V Concretes

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68 types of specimens, which is quite common for permeability measurements. The results comparing the water permeability for different fiber types are shown in Figures 5-24 and 5-25. It can be discovered that the water permeability of plain concrete mixes has average values of 4.11x10 -13 m/s for Class II and 3.45x10 -13 m/s for Class V. The mix including Class II PP fibers shows a high variability in the coefficient of permeability. The highest coefficient of permeability of 14.70x10 -13 m/s is excluded due to high variability. The remaining coefficients of shows a 8 % reduction of water permeability in spite of the high volume of voids. On the other hand, the coefficient of permeability for Class V indicates a 30% decrease in water penetration. The addition of PVA fibers shows similar trend to PP fibers. The coefficient of permeability in concrete to average values of 3.82x10 -13 m/s for Class II (slight lower values than plain concrete). The low coefficient of permeability for Class V (2.42x10 -13 m/s) indicates a 30% reduction in comparison with plain concrete. PVA fibers also have a higher volume of voids than plain concrete. The inclusion of cellulose fibers for Class II shows different results than other fibers. Class II concrete cellulose fibers indicate the highest water permeability in the FRC mixes. On the other hand, the Class V cellulose fibers largely reduce the water penetration about 13% in comparison with plain concrete. The addition of steel fibers for Class II shows the lowest permeability and has a 34% lower coefficient of permeability. Class V concrete steel fibers have a 20% lower the water penetration (excluding the outliner specimen) and higher volume of voids than plain concrete.

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69 Figures 5-24 and 5-25 show that the addition of fibers improves the samples to resist water penetration. However, Class V concrete indicates more a definite reduction in water permeability resulting from the addition of fibers. Among the fibers, hooked steel fibers make the samples the largest reduction in water permeability. Table 5-9 Summary of the Values of K and f' c Obtained for Class II Concrete Control13.548.12Control24.797.98Control34.008.51Average4.118.20S.D0.630.28C.O.V15.343.36PP0.5%13.487.87PP0.5%214.708.42PP0.5%34.088.20Average7.428.16S.D6.310.27C.O.V85.053.34PVA0.75%13.658.25PVA0.75%23.978.95PVA0.75%33.848.02Average3.828.41S.D0.160.48C.O.V4.245.73CE0.1%14.168.18CE0.1%24.507.90CE0.1%34.237.46Average4.307.84S.D0.180.36C.O.V4.104.62ST1%13.209.37ST1%22.739.30ST1%32.809.12Average2.919.26S.D0.250.13C.O.V8.661.39Mix TypeSpecimen IDCoefficient of Permeability (x10-13 m/s)Compressive Strength (ksi)PVAPCPPSteelCellulose

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70 Table 5-10 Summary of the Values of K and f' c Obtained for Class V Concrete Control13.269.21Control23.169.88Control33.929.89Average3.459.66S.D0.410.39C.O.V11.914.03PP0.5%12.259.94PP0.5%22.7210.50PP0.5%32.009.95Average2.3310.13S.D0.360.32C.O.V15.683.16PVA0.75%12.2510.21PVA0.75%22.629.76PVA0.75%32.3710.32Average2.4210.10S.D0.190.30C.O.V7.842.93CE0.1%13.208.67CE0.1%22.828.97CE0.1%32.959.86Average2.999.17S.D0.190.62C.O.V6.476.71ST1%13.999.91ST1%22.2310.48ST1%32.0910.19Average2.7710.19S.D1.060.29C.O.V38.262.80Mix TypesSpecimen IDCoefficient of Permeability (x10-13 m/s)Compressive Strength (ksi)PVAPPPCSteelCellulose 5.6.2 The Effect of Compressive Strength on Permeability Figure 5-26 compares the compressive strength to the coefficient of permeability for Class II concrete. From Figure 5-26, the highest coefficient of permeability in the cellulose fiber mix is related to the lowest compressive strength and the coefficient of

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71 1.01.52.02.53.03.54.04.55.0PCPPPVACellSteelMix TypesK (x10-13m/s) Class II Figure 5-24 Coefficient of Permeability for Class II Concrete 1.01.52.02.53.03.54.04.55.0PCPPPVACellSteelMix TypesK (x10-13m/s) Class V Figure 5-25 Coefficient of Permeability for Class V Concrete

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72 permeability of the PP and PVA fiber mixes, which have values slightly lower than plain concrete, show almost the same or slightly higher compressive strength. On the other hand, the steel fibers having the highest compressive strength indicate the lowest permeability among all fiber mixes. 6.06.57.07.58.08.59.09.510.010.511.011.512.0PCPPPVACellSteelMix TypesUltimate Strength (ksi)1.01.52.02.53.03.54.04.55.0K (x10-13 m/s) Class II-Compressive Strength Class II-Coefficient of Permability Figure 5-26 Coefficient of Permeability vs Compressive Strength for Class II Concrete From Figure 5-27, it is clear that the coefficients of permeability in all fiber mixes are lower than that of the plain concrete mix. The coefficients of permeability of the PP and PVA fiber mixes, having similar values, show higher compressive strengths than that of plain concrete. On the other hand, the steel fiber mix, having a compressive strength similar to the PP and PVA fibers, indicates the lowest permeability of among all fiber mixes. There appears to be a curvilinear relationship between water permeability and compressive strength, as shown in Figure 5-28. Generally, Class V concrete, having higher compressive strength than that of Class II concrete shows the lower permeability.

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73 6.06.57.07.58.08.59.09.510.010.511.011.512.0PCPPPVACellSteelMix TypesUltimate Strength (ksi)1.01.52.02.53.03.54.04.55.0K (x10-13 m/s) Class V-Compressive Strength Class V-Coefficient of Permability Figure 5-27 Coefficient of Permeability vs Compressive Strength for Class V Concrete y = -3.29Ln(x) + 12.89R2 = 0.797.07.58.08.59.09.510.010.511.01.01.52.02.53.03.54.04.55.0Coefficient of Permeability (x10-13m/s)Compressive Strength (ksi) Class II Class V Figure 5-28 Relationship between Permeability and Compressive Strength for Class II and Class V Concretes

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74 5.6.3 The Effect of Volume of Voids on Permeability The permeable voids in harden concrete also affect the permeability. However, the volume of voids is based on the absorption concept different from the water penetration. There are no significant correlations between the air content and permeability. It means that the addition of fibers having different properties affect the resistance of water penetration rather than the affection of permeable voids to control the rate of water flow. y = 0.23x + 12.24R2 = 0.071112131415161.52.02.53.03.54.04.55.05.56.0Coefficient of Permeability (x10-13m/s)Volume of Voids (%) Class II Class V Figure 5-29 Relationship between Permeability and Compressive Strength for Class II and Class V Concrete

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CHAPTER 6 SUMMARY AND CONCLUSIONS 6.1 Summary of Test Results An experimental program was performed examining the effects of fiber type on concrete properties in both the fresh and hardened states. The fresh fibrous concrete was characterized by its slump, inverted slump-cone time, Vebe, and air content. Compressive stress-strain curves, modulus of elasticity, splitting tensile strength, volume of voids, and water permeability tests were used as representatives of the hardened physical and mechanical properties. The fiber types and dosage rates by volume included in this study were polypropylene (0.5%), polyvinyl alcohol (0.75%), cellulose (0.1%), and hooked steel (0.89%). The polypropylene, polyvinyl alcohol, cellulose, and steel fiber mixes manifested the reductions in fresh-mix workability resulting from the slump, the inverted slump-cone time and the Vebe time tests. The slump was in inverse proportion to the inverted slump-cone time and the Vebe time. There was not a large enhancement in workability after the slump increased beyond about 4.5 or 5.0 in. A linear correlation was observed from the results between the Vebe time and inverted slump-cone time test. The air contents resulting from the addition of polypropylene, polyvinyl alcohol, and steel fibers were about 1.0-1.5% lower than those of plain concrete mixes. However, when compared with the air contents of the control samples that were tested before adding plastic fibers, the difference of the air contents were negligible. The inclusion of cellulose fibers showed a slight increase in air content in both concrete classes. These decreased or increased air contents are directly related to the unit weight results. The mix containing hooked steel fibers showed an average increase in compressive strength of almost 13% for Class II concrete and 5% for Class V concrete. Also, reinforcing a concrete matrix with hooked steel fibers significantly improved the ductility beyond the peak stress for Class II concrete. The polypropylene and polyvinyl alcohol fiber mixes showed no important changes in the compressive 75

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76 strength and ductility in both concrete classes. Only the Class II mix of polypropylene fibers showed ductility beyond the peak stress on the stress-strain graph. The compressive strength of the cellulose fibers indicated the lowest values in all FRC mixes. Among all fiber mixes, the incorporation of hooked steel fibers induced the highest splitting tensile strength which was also higher than that of the plain concrete mixes. On the other hand, other fiber mixes, such as polypropylene, polyvinyl alcohol, and cellulose fibers had a similar trend. Although these fibers definitely reduced the splitting tensile strength in comparison with the plain concrete mixes, they showed a small increase in strength when compared to the control samples made before adding fibers. The volume of voids of polypropylene, polyvinyl alcohol, and cellulose fibers in Class II concrete was normally about 0.5-1% higher than that of the plain concrete mix. These slightly higher permeable void volumes are connected to lower the splitting tensile strength. Plastic fiber samples also have high voids in comparison with the control samples made prior to adding fibers. However, there was no significant reduction in splitting tensile strength due to the addition of fiber. The volumes of voids of hooked steel fibers is 0.85% lower than that of the plain concrete mix for Class II and 0.88% higher than that of plain concrete mix for Class V. In spite of the volume of voids, the addition of hooked steel fibers showed much higher strength than other mixes. The Class V concrete showed a trend similar to that of the Class II concrete. The PP and PVA fibers having similar compressive strength in comparison with plain concrete for Class II showed that there was no significant change in water permeability. On the other hand, the cellulose fibers having the lowest compressive strength indicate the highest coefficient of permeability in Class II mixes. The steel fibers having the highest compressive strength indicated the lowest coefficient of permeability. Among all fiber mixes, the steel fibers largely improved resistance to water penetration. The Class V concrete mixes having lower coefficient of permeability in comparison with Class II showed a more definite relationship between the compressive strength and permeability. The PP, PVA and steel fiber mixes, having higher compressive strength than that of plain concrete mix, improved the resistance to water penetration. 6.2 Conclusions The following conclusions can be drawn from the investigations performed in this study. 1. The inclusion of PP, PVA, cellulose, and hooked steel fibers decreases the workability of fresh concrete; this effect is more pronounced for fibers with a higher aspect ratio. However, the effect of PP, PVA, and hooked steel fibers on fresh mix workability, as represented both by inverted slump-cone time and Vebe

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77 time, seem to be insignificant. Cellulose fibers cause the lowest slump loss values when compared with the other fibers. 2. At an aspect ratio of 55 and a fiber volume fraction of 0.89 percent, hooked steel fibers having high modulus, elongation, and tensile strength generate compressive, splitting tensile strength and energy absorption capacities which are higher than those of PP, PVA, and cellulose fibers regardless of volume of voids, although the effect of fiber reinforcement on compressive and tensile strength is relatively small. 3. The splitting tensile strength of PP, PVA, cellulose, and steel fiber-reinforced concrete ranges from approximately 7% to 9% of its compressive strength. There was no significant improvement in splitting tensile strength by the PP, PVA, cellulose, and hooked steel fibers. 4. The addition of PP, PVA, and cellulose fibers resulting in high permeable voids shows a lower splitting tensile strength in comparison with plain concrete mixes. 5. The incorporation of PP, PVA, and steel fibers normally enhance resistance to water permeability in spite of high permeable voids in comparison with control samples. The high permeability of Class II compared to Class V results in a lower compressive strength. Among all fiber types, the hooked steel fibers showed the highest resistance to water penetration.

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APPENDIX A COMPRESSION TESTS Table A-1 Summary of the Values of f' c and E c Obtained for Class II Concrete Control147688.12Control246507.98Control349508.51Average47898.20S.D1510.28C.O.V3.163.36PP0.5%147558.327.87PP0.5%248678.208.42PP0.5%347238.608.20Average47828.378.16S.D760.210.27C.O.V1.582.493.34PVA0.75%148568.258.25PVA0.75%249878.518.95PVA0.75%346538.268.02Average48328.348.41S.D1680.150.48C.O.V3.481.775.73CE0.1%146527.558.18CE0.1%245127.437.90CE0.1%348597.937.46Average46747.647.84S.D1750.260.36C.O.V3.733.434.62ST1%152508.529.37ST1%252028.499.30ST1%351198.479.12Average51908.499.26S.D660.030.13C.O.V1.280.341.39Mix TypesSpecimen IDCompressive Strength (ksi)Modulus of Elasticity (ksi)FiberControlSteelPCPPPVACellulose 78

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79 Table A-2 Summary of the Values of f' c and E c Obtained for Class V Concrete Control150849.21Control250539.88Control351569.89Average50989.66S.D530.39C.O.V1.044.03PP0.5%150329.969.94PP0.5%252449.7310.50PP0.5%3518410.249.95Average51539.9710.13S.D1090.260.32C.O.V2.122.573.16PVA0.75%152739.8410.21PVA0.75%2508010.009.76PVA0.75%351489.8310.32Average51679.8910.10S.D980.090.30C.O.V1.890.932.93CE0.1%149329.358.67CE0.1%249509.438.97CE0.1%352199.909.86Average50349.569.17S.D1610.300.62C.O.V3.193.106.71ST1%154609.6110.48ST1%251239.919.91ST1%353609.7710.19Average53149.7610.19S.D1730.150.28C.O.V3.261.512.77PCSteelCellulosePVAPPMix TypesSpecimen IDModulus of Elasticity (ksi)Compressive Strength (ksi)ControlFiber

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80 Class II-Plain Concrete0246810120.0000.0020.0040.0060.0080.010StrainStress (ksi) Figure A-1 Stress vs Strain Response for Plain Concrete-Class II Concrete Class II-Polypropylene 0.5%0246810120.0000.0020.0040.0060.0080.010StrainStress (ksi) Figure A-2 Stress vs Strain Response for Polypropylene Fibers-Class II Concrete

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81 Class II-Polyvinyl Alcohol 0.75%0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-3 Stress vs Strain Response for Polyvinyl Alcohol Fibers-Class II Concrete Class II-Cellulose 0.1%0246810120.0000.0020.0040.0060.0080.010StrainStress (ksi) Figure A-4 Stress vs Strain Response for Cellulose Fibers-Class II Concrete

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82 Class II-Hooked Steel 1%0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-5 Stress vs Strain Response for Steel Fiber-Class II Concrete Class V-Plain Concrete0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-6 Stress vs Strain Response for Plain Concrete-Class V Concrete

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83 Class V-Polypropylene 0.5%0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-7 Stress vs Strain Response for Polypropylene Fibers-Class V Concrete Class V-Polyvinyl Alcohol 0.75%0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-8 Stress vs Strain Response for Polyvinyl Alcohol Fibers-Class V Concrete

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84 Class V-Cellulose 0.1%0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-9 Stress vs Strain Response for Cellulose Fibers-Class V Concrete Class V-Hooked Steel 1%0246810120.0000.0020.0040.0060.0080.010Strain Stress (ksi) Figure A-10 Stress vs Strain Response for Steel Fibers-Class V Concrete

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85 Figure A-11 Compressive Failure of Plain Concrete for Class II Concrete Figure A-12 Compressive Failure of Polypropylene Fibers for Class II Concrete

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86 Figure A-13 Compressive Failure of Polyvinyl Alcohol Fibers for Class II Concrete Figure A-14 Compressive Failure of Cellulose Fibers for Class II Concrete

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87 Figure A-15 Compressive Failure of Cellulose Fibers for Class II Concrete Figure A-16 Compressive Failure of Plain Concrete for Class V Concrete

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88 Figure A-17 Compressive Failure of Polypropylene Fibers for Class V Concrete Figure A-18 Compressive Failure of Polyvinyl Alcohol Fibers for Class V Concrete

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89 Figure A-19 Compressive Failure of Cellulose Fibers for Class V Concrete Figure A-20 Compressive Failure of Steel Fibers for Class V Concrete

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APPENDIX B SPLITTING TENSILE STRENGTH TESTS Table B-1 The Values of f spt and f' c Obtained for Class II Concrete ControlFiberControl1722.008117.67Control2737.397982.24Control3706.108512.47Average721.838204.13S.D15.65224.93C.O.V2.172.74PP0.5%1659.3725.847873.67PP0.5%2653.78608.268415.60PP0.5%3590.59626.288201.27Average637.56653.468092.07S.D38.1863.33272.93C.O.V6.029.693.37PVA0.75%1604.5655.448252.01PVA0.75%2633.24697.418948.31PVA0.75%3670.9620.898022.46Average636.21657.918407.59S.D33.338.32482.14C.O.V5.235.825.73CE0.1%1645.97696.188176.18CE0.1%2617.56666.467899.16CE0.1%3684.55637.777458.04Average649.36666.807697.42S.D33.6229.21362.18C.O.V5.184.384.71ST1%1666.33781.149365.29ST1%2633.73804.219303.31ST1%3643.52768.889117.36Average647.86784.749261.99S.D16.7317.94129.03C.O.V2.582.291.39Mix TypesSpecimen IDSplitting Tensile Strength (psi)PPPVACellCompressive Strength (psi)PCSteel 90

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91 Table B-2 The Values of f spt and f' c Obtained for Class V Concrete ControlFiberControl1790.419210.20Control2765.119875.31Control3788.309892.14Average781.279659.32S.D14.04317.57C.O.V1.803.29PP0.5%1680.45672.349935.20PP0.5%2656.34648.5110498.58PP0.5%3675.84634.619954.65Average670.88651.8210129.48S.D12.819.08319.80C.O.V1.912.933.16PVA0.75%1630.34671.6010207.20PVA0.75%2642.12622.899761.42PVA0.75%3614.89651.2010320.53Average628.89648.5610096.38S.D14.0124.46295.57C.O.V2.233.772.93CE0.1%1613.61726.268673.72CE0.1%2606.79708.188967.11CE0.1%3656.81731.269855.30Average625.74721.909165.38S.D27.1312.14615.24C.O.V4.331.686.71ST1%1666.33845.4310476.37ST1%2633.73762.709910.93ST1%3643.52818.3110193.18Average647.86808.8110193.49S.D16.7342.17282.72C.O.V2.585.212.77Mix TypesSpecimen IDSteelPCPPPVACellSplitting Tensile Strength (psi)Compressive Strength (psi)

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92 Figure B-1 Splitting Tensile Failure of Plain Concrete for Class II Concrete Figure B-2 Splitting Tensile Failure of Polypropylene Fibers for Class II Concrete

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93 Figure B-3 Splitting Tensile Failure of Polyvinyl Alcohol Fibers for Class II Concrete Figure B-4 Splitting Tensile Failure of Cellulose Fibers for Class II Concrete

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94 Figure B-5 Splitting Tensile Failure of Steel Fibers for Class II Concrete Figure B-6 Splitting Tensile Failure of Plain Concrete for Class V Concrete

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95 Figure B-7 Splitting Tensile Failure of Polypropylene Fibers for Class V Concrete Figure B-8 Splitting Tensile Failure of Polyvinyl Alcohol Fibers for Class V Concrete

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96 Figure B-9 Splitting Tensile Failure of Cellulose Fibers for Class V Concrete Figure B-10 Splitting Tensile Failure of Steel Fibers for Class V Concrete

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LIST OF REFERENCES AASHTO-AGC-ARTBA Joint Committee, “The Use and State-of-the-Practice of Fiber Reinforced Concrete,” American Concrete Pavement Association, 2001. American Concrete Institute (ACI) Committee 544, “State-of-the-Art Report on Fiber-Reinforced Concrete,” (ACI 544.1R-96), American Concrete Institute, Detroit, 1996. American Concrete Institute (ACI) Committee 544, “Measurement of Properties of Fiber-Reinforced Concrete,”(ACI 544.2R-89), American Concrete Institute, Detroit, 1989. American Society for Testing and Material (ASTM) C 1116-03, “Standard Specification for Fiber-Reinforced Concrete and Shortcrete,” Annual Book of ASTM Standards, 2003, Vol. 04.02, American Society for Testing and Material (ASTM), West Conshohocken, Pa. American Society for Testing and Material (ASTM) C 39/C 39M-01, “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimen,” Annual Book of ASTM Standards, 2003, Vol. 04.02, American Society for Testing and Material (ASTM), West Conshohocken, Pa. American Society for Testing and Material (ASTM) C 231-97, “Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method,” Annual Book of ASTM Standards, 2003, Vol. 04.02, American Society for Testing and Material (ASTM), West Conshohocken, Pa. American Society for Testing and Material (ASTM) C 496-96, “Standard Test Method for Splitting Tensile Strength of Cylindrical Concrete Specimen,” Annual Book of ASTM Standards, 2003, Vol. 04.02, American Society for Testing and Material (ASTM), West Conshohocken, Pa. American Society for Testing and Material (ASTM) C 995-94, “Standard Test Method for Time of Flow of Fiber-Reinforced Concrete through Inverted Slump Cone,” Annual Book of ASTM Standards, 2003, Vol. 04.02, American Society for Testing and Material (ASTM), West Conshohocken, Pa. American Society for Testing and Material (ASTM) C1170-91, “Standard Test Method for Determining Consistency and Density of Roller-Compacted Concrete Using a Vibrating Table,” Annual Book of ASTM Standards, 2003, Vol. 04.02, American Society for Testing and Material (ASTM), West Conshohocken, Pa. 97

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98 Al-Tayyib, A.J., Al-Zahrani, M.M., Rasheeduzzafar and Al-Suaimani, G.J., “Effect of Polypropylene Fiber Reinforcement on the Properties of Fresh and Harden Concrete in the Arabian Gulf Environment,” Cement and Concrete Research, 1988, Vol. 18, pp. 561-570. Beaudoin, J.J., Handbook of Fiber-Reinforced Concrete Principles, Properties, Developments and Applications. Noyes Publications, Park Ridge, New Jersey, NJ, 1990. Bayasi, Z., Bhatachary, R., and Posey, M., “Fiber Reinforced Concrete: Basics and Advancement,” Proceeding, Symposium on Advancements in Concrete Materials, Bradley University, 1989, Vol. l, pp.1-27. Choi, Y., and Yuan, R.L., “Experimental Relationship between Splitting Tensile Strength and Compressive Strength of GFRC and PFRC,” Cement and Concrete Research, 2005, Vol. 35, pp. 1587-1591. Ding, Y., and Kusterle, W., “Compressive Stress-Strain Relationship of Steel-Reinforced Concrete at Early Age,” Cement and Concrete Research, 2000, Vol. 30, pp. 1573-1579. Fanella, D. A., and Naaman, A. E., “Stress-Strain Properties of Fiber Reinforced Concrete in Compression,” ACI Journal, 1985, Vol. 82, No. 4, pp. 475-483. Kelly, A., “Interface Effects and the Work of Fracture of a Fibrous Composite,” Pro. R. Soc, London Ser. A., 1970, Vol. 319, pp. 95-116. Leung, C. K. Y., Lai, R., and Lee, A. Y. F., 2005,” Properties of Wet-Mixed Fiber Reinforced Shotcrete and Fiber Reinforced Concrete with Similar Composition,” Cement and Concrete Research, 2005, Vol. 35, pp. 788-795. Naaman, A. E., Al-khairi, F. M., and Hammoud, H., Mechanical Behavior of High Performance Concrete, 1993, Vol. 6: “High Early Strength Fiber Reinforced Concrete (HESFRC),” Strategic Highway Research Program, Nation Research Council, Washington, D.C., xix, pp. 37-73. Naaman, A.E., Moavenzadeh, F., and McGarry, F., “Probabilistic Analysis of Fiber Reinforecd Concrete,” Journal of Engineering Mechanics, 1974, Vol.100, No.EM2, pp. 397-413. Neville, A. M., and Brooks, J. J., Concrete Technology. Longman Scientific & Technical, England, 1987. Neville, A. M., Hardened Concrete: Physical and Mechanical Aspects, American Concrete Institute, Detroit, MI and the Iowa State University Press, Ames, Iowa, 1971.

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99 Nymae, B. K., “Permeability of Normal and Lightweight Mortars,” Magazine of Concrete Research, 1985, Vol. 11, No. 4, pp. 44-48. Malhotra, V. M., Carette, G. G., and Bilodeau, A., “Mechanical Properties and Durability of Polypropylene Fiber Reinforced High-Volume Fly Ash Concrete for Shotcrete Application,” ACI Materials Journal, 1994, Vol. 91, No. 5, pp. 478-486. Murata, J., “Studies on the Permeability of Concrete” RILEM Bulletin (Paris), New Series, 1965, No. 29, pp. 47-54. Poon, C.S., Shui, Z.H., and Lam, L., “Compressive Behavior of Fiber Reinforced High-Performance Concrete subjected to Elevated Temperatures,” Cement and Concrete Research, 2004, Vol. 34, pp. 2215-2222. Powers, T. C., Copeland, L. E., Hayes, J. C., and Mann, H. M., “Permeability of Portland Cement Paste,” ACI Journal, 1954, Vol. 50, pp. 285-298. Song, P. S., Hwang, S., and Sheu, B. C., “Strength Properties of nylonand Polypropylene-Fiber-Reinforced Concretes,” Cement and Concrete Research, 2005, Vol. 35, pp. 1546-1550. Shaaban, A. M., and Gesund, H., ” Splitting Tensile Strength of Steel Fiber Reinforced Concrete Cylinders Consolidated by Rodding or Vibrating,” ACI Materials Journal, 1993, Vol. 90, No. 4, pp.366-369. Soongswang, P., Tia, M., Bloomquist, D., Meletiou, C., and Sessions, :L., “Efficient Test Setup for Determining the Water-Permeability of Concrete,” Transportation Research Record, 1988, Vol., 1204, pp. 77-82. Tyler, I. L., and Erlin, B., ”A Proposed Simple Test Method for Determining the Permeability of Concrete,” Journal of the PCA Research and Development Laboratories, 1961, Vol. 3, No. 3, pp. 2-7. Troxell, G. E., Davis, H. E., and Kelly, J. W., Composition and Properties of Concrete, 2 nd Edition, McGraw-Hill Civil Engineering Series, New York, NY, 1968. Williamson, G.R., “The Effect of Steel Fibers on the Compressive Strength of Concrete,” Fiber Reinforced Concrete, SP-44, American Concrete Institute, 1974, Detroit, MI, pp. 195-207. Yao, W., Li, J., and W, K., “Mechanical Properties of Hybrid Fiber-Reinforced Concrete at Low Fiber Volume Fraction,” Cement and Concrete Research, 2003, Vol. 33, pp. 27-30.

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BIOGRAPHICAL SKETCH The author was born in 1976 in Gyeongsan, Daegu. He graduated with a Bachelor of Science in architecture engineering from the Yeungnam University in February 2003. He then completed a Master of Engineering in civil and coastal engineering from the University of Florida in August 2006. 100