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Recycled tires as coarse aggregate in concrete pavement mixtures

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Title:
Recycled tires as coarse aggregate in concrete pavement mixtures
Creator:
Zhou, Yang ( author )
Language:
English
Physical Description:
1 electronic file (16 pages). : ;

Subjects

Subjects / Keywords:
Concrete -- Additives ( lcsh )
Pavements, Concrete ( lcsh )
Crumb rubber ( lcsh )
Waste tires ( lcsh )
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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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Review:
This research evaluated the reuse potential of recycled tire chips as coarse aggregates in pavement concrete. Experimental investigation of modified pavement concrete, using different volume coarse aggregate replaced by tire chips, was completed to check the fresh and hardened concrete properties. One control mixture was designed for comparison. The coarse aggregate component of rubberized concrete was replaced by volumes of 100%, 50%, 30%, 20%, and 10% using tire-chips particles. The cementitious materials was changed from 660 lbs/cy to 570 lbs/cy to evaluate the performance. Two mixtures with 10% coarse aggregate replaced by tire chips had the best performance among all the mixtures and exceeded the 28-day compressive strength and flexural strength requirement of Colorado Department of Transportation Class P pavement concrete. The two mixtures showed high freeze/thaw durability in moderate chloride-ion penetration tests. Effects of using high-range water reducer and low-range water reducer were examined for mixtures with 10% coarse aggregate replacement. The rubberized concrete mixtures investigated in this study demonstrated ductile failure in compressive, flexural, and splitting tests instead of brit
Thesis:
Thesis (M.S.)--University of Colorado Denver.
Bibliography:
Includes bibliographic references.
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System requirements: Adobe Reader.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Yang Zhou.

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University of Colorado Denver
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
898042667 ( OCLC )
ocn898042667

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RECYCLED TIRES AS COARSE AGGREGATE IN CONCRETE PAVEMENT MIXTURES b y YANG ZHOU B.S., Northeast Forestry University, 2012 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering 2014

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ii This thesis for the Master of Science degree by Y ang Z hou has been approved for the Master of Science by Kevin L. Rens Chair Chengyu Li Frederick Rutz 4 / 29/2014

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iii Zhou, Yang ( M S Civil Engineering ) Recycled Tires as Coarse Aggregate in Concrete Pavement Mixtures Thesis directed by Professor Kevin L. Rens ABSTRACT This research e valuated the reuse potential of recycled tire chips as coarse aggregates in pavement concrete. Experimental investigation of modified pavement concrete using different volum e coarse aggreg a te replaced by tire chips was completed to check the fresh and hardened concrete properties. One control mixture was designed for comparison. The coarse aggregate component of rubberized concrete was replaced by volume s of 100%, 50%, 30%, 2 0%, and 10% using tire chips particles. The cementitious materials was c hanged from 660 lbs/cy to 570 lbs/cy to evaluate the performance. Two mixtures with 10% coarse aggregate replaced by tire chips had the best performance among all the mixtures and exce eded the 28 day compressive strength and flexural strength requirement of Colorado Department of Transportation Class P pavement concrete. The two mixtures showed high freeze/thaw durability in moderate chloride ion penetration tests. Effects of using high range water reducer and low range water reducer w ere examined for mixtures with 10% coarse aggregate replacement. The rubberized concrete mixtures investigated in this study demonstrated ductile failure in compressive, flexural, and splitting tests instea d of brittle failure as a control mixture. The form and content of this abstract are approved. I recommend its publication. Approved: Kevin L. Rens

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iv DEDICATION I dedicate this work to the persons who have believed in me and supported me the most. Through their endless love, encouragement understanding, and support throughout all the years of my educational pursuits I owe my deepest gratitude to my father, Guojun Zhou, and my mother, Ruomin Sun.

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v ACKNOWLEDGMENT S I express my sincere gratitude to my advisor, Dr. Kevin Rens, for his invaluable Coarse Aggregate in Concrete Pavement Mixtures In addition, I thank Dr. Chengyu Li and Dr. Frederick Rutz for participating on my thesis committee. I also thank my previous professor and current friend, Dr. Rui Liu, for recognizing my potential and giving me the opportunity to do this study and for his endless help and encouragement throughout the experimental program. I also express my appreciation for the technical support provided by the Laboratory at University of Colorado at Denver, including Dr. Nien Yin Chang and Tom Thuis. Additionally, I thank Mr. Dan Bentz from Bestway Concrete for the donation of coarse aggregates and Mr. Steve Calhoun from Sika for the donation of water reducers. Finally I thank all the faculty and staff of University of Colorado at Denver, Civil Engineering D epartment fo r their help and guidance throughout my educational career.

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vi TABLE OF CONTENTS CHAPTER I. INTRODUCTION ................................ ................................ ................................ ....... 1 Objectives of t his Research ................................ ................................ ..................... 3 Scope ................................ ................................ ................................ ....................... 4 Thesis Outline ................................ ................................ ................................ ......... 5 II. LITERATURE REVIEW ................................ ................................ ............................ 6 Uses of Waste Tires ................................ ................................ ................................ 6 Classification of Recycled Waste Tire Particles ................................ ..................... 7 Fresh Concrete Properties of Rubberized Concrete ................................ ................ 8 Hardened Concrete Properties of Rubberized Concrete ................................ ....... 12 Modulus of Elasticity of Rubberized Concrete ................................ ..................... 16 III. PROBLEM STATEMENT ................................ ................................ ........................ 19 IV. EXPERIMENTAL PROGRAM ................................ ................................ ................ 21 Materials for Test Specimens ................................ ................................ ................ 21 Concrete Materials ................................ ................................ .................... 21 Recycled Tire Particles ................................ ................................ ............. 21 Recycled W aste T ire S pecific G ravity E xperimental T esting and R esults ................................ ................................ ........................... 26 Admixtures ................................ ................................ ................................ 26 Type I Portland Cement ................................ ................................ ............ 27 Mixture Proportions ................................ ................................ .............................. 27 Batching of Concrete Mixture ................................ ................................ .............. 29

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vii Preparation Before Batching Concrete Mixture ................................ ....... 29 Mixing Process ................................ ................................ .......................... 30 Curing of Specimen ................................ ................................ .............................. 31 Testing of Concrete ................................ ................................ ............................... 32 Testing for Fresh Concrete Properties ................................ ...................... 32 Testing for Hardened Concrete Properties ................................ ................ 32 V. EXPERIMENTAL RESULTS AND DISCUSSIONS PHASE I .............................. 34 Batching of Trial Mixtures ................................ ................................ .................... 34 Fr esh Concrete Properties ................................ ................................ ..................... 34 Temperature of Freshly Mixed Hydraulic Cement Concrete, ASTM C 1064 ................................ ................................ ................................ ........... 36 Slump of Hydraulic Cement Concrete, ASTM C 143 ............................. 38 Unit Weight ................................ ................................ ............................... 40 Air Content ................................ ................................ ................................ 40 Hardened Concrete Properties ................................ ................................ .............. 42 Compressive Strength of Concrete Specimens, ASTM C 39 ................... 44 Flexural Strength or Modulus of Rupture, A STM C 78 ........................... 5 1 Splitting Tensile Test, ASTM C 496 ................................ ........................ 54 Rapid Chloride ion Permeability, ASTM C 1202 ................................ .... 56 Freeze thaw Durability, ASTM C 666 ................................ ..................... 60 VI. EXPERIMENTAL RESULTS AND DISCUSSIONS PHASE II ............................. 67 Fresh Concrete Properties ................................ ................................ ..................... 67 Temperature of Freshly Mixed Hydraulic Cement Concrete, ASTM C 1064 ................................ ................................ ................................ ........... 68

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viii Slump of Hydraulic Cement Concrete, ASTM C 143 ............................. 68 Unit Weight, ASTM C 138 ................................ ................................ ....... 69 Air Content of Freshly Mixed Concrete ASTM C 231 ............................ 70 Hardened Concrete Properties ................................ ................................ .............. 70 Compressive Strength of Cylinder Specimens, ASTM C 39 ................... 7 1 Modulus of Elasticity of Concrete in Compression, ASTM C 469 .......... 73 VII. CONCLUSIONS ................................ ................................ ................................ ....... 76 Results ................................ ................................ ................................ ................... 76 Summary of Fresh Concrete Properties ................................ ................................ 77 Slump ................................ ................................ ................................ ........ 77 Air Content ................................ ................................ ................................ 77 Unit Weight ................................ ................................ ............................... 77 Temperature ................................ ................................ .............................. 77 Summary of Harde ned Concrete Properties ................................ ......................... 78 Compressive Strength ................................ ................................ ............... 78 Splitting Tensile Strength ................................ ................................ ......... 78 Flexural Strength ................................ ................................ ....................... 78 Durability ................................ ................................ ................................ .. 78 Modulus of Elastic ity ................................ ................................ ................ 79 T he Effects Caused by Water Reducer ................................ ................................ 79 Recommendations ................................ ................................ ................................ 80 REFERENCES ................................ ................................ ................................ ................. 8 1

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ix APPENDIX ................................ ................................ ................................ ........................ 84 A. Product Specification Sheet................................................................................... 8 4 B. CDOT Class P Concrete Requirement..................................... ..............................9 2 C. Concrete Mixtures..................................................................................................9 4

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x LIST OF TABLES TABLE 2 .1 A STM D 6270 Terminology for Recycled Waste Tire Particles ................................ 8 4 .1 Sieve Analysis for Sand, Rocks and Tire Chips ................................ ........................ 24 4 .2 Research Design Mixtures Proportions ................................ ................................ ...... 28 4 .3 Fresh Concrete Tests ................................ ................................ ................................ ... 32 4 .4 Hardened Concrete Tests for Phase I ................................ ................................ .......... 33 4 .5 Hardened Concrete Tests for Phase II ................................ ................................ ........ 33 5 .1 Trial Mixtures Proportion after Water Adjustment ................................ .................... 35 5 .2 Water Reducer Dosage After Adjustment ................................ ................................ .. 36 5 .3 Concrete Temperatures ................................ ................................ ............................... 37 5 .4 Air Content by Pressure Meter, ASTM C231 ................................ ............................ 41 5 .5 Air Content by Rolloer Meter, ASTM C173 ................................ .............................. 41 5 .6 Compressive Strength, ASTM C 39 ................................ ................................ ........... 46 5 .7 Permeability Rating Classification ................................ ................................ ............. 58 5 .8 Rapid Chloride ion Penetration Testing Results ................................ ......................... 59 5 .9 Duribility Factor ................................ ................................ ................................ .......... 65 5 .10 Resistance to Freeze/Thaw Cycling ................................ ................................ .......... 66

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xi LIST OF FIGURES FIGURE 1 .1 A nnual Waste Tires Added to Stockpiles in Colorado ................................ ................. 2 2 .1 Typical Size and Shape of Refinements ................................ ................................ ...... 7 2 .2 Rubber Content by Total Aggregate Volume (%) ................................ ..................... 10 2 .3 Relationship between Unit Weight With Rubber Content ................................ ......... 11 2 .4 Compressive Strength f or Rubberized Concrete ................................ ........................ 14 2 .5 Durability Factor vs. Cycle Count ................................ ................................ ............. 17 2 .6 Modulus of Elasticity with Time ................................ ................................ ............... 17 4 .1 Rocks Coarse Aggregates ................................ ................................ ........................... 22 4 .2 Sand Fine Aggregates ................................ ................................ ................................ 23 4 .3 Rubber Chips Sample ................................ ................................ ................................ 23 4 .4 ASTM C 33 Grading Limits and Values for Coarse Aggregates ............................... 25 5 .1 Temperatures Measuring ................................ ................................ ............................ 37 5 .2 Zero Slump for Mixture #2 ................................ ................................ ......................... 38 5 .3 Concrete Slump and WRA ................................ ................................ .......................... 39 5 .4 Unit Weight of Concrete Mixture ................................ ................................ ............... 42 5 .5 Air Content and AEA ................................ ................................ ................................ .. 43 5 .6 Compressive Strength for Each Mixture ................................ ................................ ..... 47 5 .7 % Strength Loss of Mixtures to the Control (high cementitious content) .................. 48 5 8 % Strength Loss of Mixtures to the Control (low cementitious content) .................. 48 5 .9 Rate Gain of Compressive Strength at 28 Days ................................ .......................... 49 5 .10 Residual Strength Characteristic ................................ ................................ ............... 50

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xii 5 .11 Compressive Failure of Concrete Cylinder ................................ ............................... 5 1 5 .12 Flexural Failure of Mixture #6 ................................ ................................ .................. 52 5 .13 Flexural Strength for Each Mixture ................................ ................................ .......... 53 5 .14 Splitting Tensile Test Setup ................................ ................................ ...................... 54 5 .15 Splitting Tensile Strength for Each Mixture ................................ ............................. 55 5 .16 Splitting Tensile Test Specimen Failure ................................ ................................ ... 56 5 .17 Cell Preparation ................................ ................................ ................................ ........ 57 5 .18 Cell Preparation ................................ ................................ ................................ ........ 57 5 .19 A ir Content (Roller Meter) vs. Coulombs ................................ ................................ 60 5 .20 Chloride ion Permeability vs Air Content ................................ ................................ 6 1 5 .21 Transverse Resonant Testing Setup ................................ ................................ .......... 64 6 .1 Concrete Temperatures for Phase II ................................ ................................ ........... 68 6 .2 Concrete Slump for Phase II ................................ ................................ ....................... 69 6 .3 Unit Weight of Concrete Mixture for Phase II ................................ ........................... 69 6 .4 Air Content in Concrete Mixtures for Phase II ................................ ........................... 70 6 .5 Compressive strength for Phase II ................................ ................................ .............. 7 1 6 .6 Rate Gain of Compressive Strength for Phase II ................................ ........................ 72 6 .7 Concrete Failure for Mixture #10 ................................ ................................ ............... 73 6 .8 MOE Test Results and MOE Calculated From ACI Equation ................................ ... 74 6 .9 Modulus of Elasticity Test Setup ................................ ................................ ................ 75

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1 CHAPTER I INTRODUCTION Concrete is one of the most popular building materials used for modern construction s, such as highways, buildings, and skyscrapers. The demand for concrete will increase to about 18 billion tons a year by 2050 (Mehta 2002). At the same time, solid waste disposal is one of the major environmental issues in almost every city around the world. R oughly 4.6 billion tons of nonh azardous solid waste materials are generated every year in the United States (Amirkhanian 1994) Domestic and industrial wastes constitute almost 600 million tons of this total (Khatib and Bayomy 1999). In the United States, over 270 million di s posal tires are scraped every year (Siddique and Naik 2004). Research estimates that about 4,595.7 thousand tons of waste tires were produced in 2007 and 89.3% of them by weight were consumed in end use markets (Rubber Manufacturers Association 2009) However about 489.9 thousand tons of scrap p ed tires were still added to the existing stock piles throughout the U .S. each year. In 2009, Colorado ha d about 45 million tires stored, roughly one third of the stockpiled tires in the country and t he number of stockpiled tires is rising each year (Ayers 2009). In 2011, a total of 5,097,944 Colorado generated tires were processed in Colorado w aster tire processors and a Utah based waste tire processing facility Colorado Department of Public Health and Environment (CDPHE) reported the annual waste tires added to stockpiles in Colorado. Figure 1 1 shows decline trends in the number of waste tires added to existing stockpiles in Colorado ( CDPHE 2 011 ). In 2011, there were only 69,452 additional waste tires stockpiled compared to 604,151 tires and 572,121 tires in 2010 and 2009, respectively.

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2 Figure 1. 1 : Waste Tires Added to Stockpiles in Colorado (Adapted from CDPHE, 2011) The classification of waste tires defined by f ederal regulations is of non hazardous waste. However, the stockpiles are occupying the land resources and also are easily catching fire. The product of combustion of tires is heavy metals, oil, and other hazardous compounds. Also the stockpiles provide breeding grounds for rats, mosquitoes and other vermin (Siddique and Naik 2004). S ome innovative solutions have been developed to solve the problem s associated with stockpiling tire s. For example, t ire bales are used as road foundation and retaining wall construction and t ire shreds are useful as back fill for walls and bridge abutments. Due to the light weight of tire shreds, the horizontal pressure is reduced allow ing for thinner and less expensive construction. Also, g rounded waste tires can be used in asphalt concrete as part of asphalt binders. Plus, t ire chips can be used for thermal insulation and potentially can be used as an alternative to aggregate materials in civil engineering applications. 1,500,000 830,000 783,000 572,121 604,151 69,452 0 200,000 400,000 600,000 800,000 1,000,000 1,200,000 1,400,000 1,600,000 2006 2007 2008 2009 2010 2011 Number of Tires Year

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3 In the early 1990s, the us e of recycled waste tire particles expanded into a relatively new product called rubberized concrete which uses Portland cement as its binder (Kaloush et al. 2005; Ellis and Gandhi 2009) Researc h has shown that rubberized concrete has a very positive outlook for inception into select markets such as pavement applications (Kardos 2011) A recent research study completed by the University of Colorado at Denver for the Colorado Department of Public Health and Environment indicate d that processed crumb rubber can be used as a partial replacement for fine aggregate in Colorado Department of Transportation (CDOT) Class P pavement concrete mix (Kardos 2011) From 1 0 % to 50% replacements of sands by volum e were tested for both fresh and hardened concrete properties. The result s show ed that 20 % and 30% replacement mixtures meet CDOT Class P concrete requirements. L eaching tests were performed to evaluate the environmental sustainability of the concrete mixtures and indicated that this material would pose no threat to human health. As a potential solution to help eliminat e wa ste tires in Colorado, the reuse potential of waste tire chips as part of coarse aggregate in concrete mixture was examined in this study. Objectives of t his Research The primary objectives of this research study were to: Examine the effects of increasing the coarse aggregate replacement percentage with recycled tire chips on concrete compressive strength, split tension strength, flexural strength, mo dulus of elasticity, permeabili ty and freeze/thaw resistance ; and determine an optimum replacement percentage of coarse aggregate with recyc led tire chips for pavement concrete mixtures.

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4 Develop a concrete mixture that will incorporate waste stream materials as partial replacement for cement, rock and sand. Test tire chip concrete mixtures for fresh concrete properties (slump, air content unit weight). Test tire chips concrete for hardened concrete properties. Provide recommendations for the use of recycled tire chips as a coarse aggregate replacement in a concrete mixture designed for field implementation Examine the effects of changin g the Plastocrete 161 (low range water reducer) to Viscocrete 210 (high range water reducer) for 10 % coarse aggregate replacement concrete. Scope This study evaluated the reuse potential of wa ste tire chips as coarse aggregate in pavement concrete mixtures Two phases of experimental investigations were performed. The purpose of the first experime ntal investigation (phase I) was to obser ve the effects of increasing the coarse aggre gate replacement percenta ge with recycled tire chips on both fresh an d hardened concrete properties. Ten mixtures were batched ; and 15 0 cylinders and more tha n 40 beams were tested for the results including compressive strength, splitting tensile strength, flexural strength, and permeability The goal was to determine whic h replacement percentage would meet the requirement s specified by CDOT Class P concrete. The purpose of the second experimental investigation (phase II) was to evaluate the modulus of elasticity of the mixtures that met the CDOT requirement s Additionally,

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5 to evaluate the effect of changing water reducer on both fresh and hardened concrete properties, the water reducer was changed from low range water reducer to high range water reducer All tests were completed based on ASTM standards. Thesi s Outline Chapter I is the thesis introduction. Chapter II p resents the literature review ed re garding previous research on usages of waste tires and rubberized concrete properties including fresh and hardened concrete properties. Chapter III provides the problem statement. Chapter IV provides a detailed description of the experimental program ; including the materials for test specimens, admixtures, batching process, curing and testing for both fresh and hardened concrete properties. Chapter V presents the results of the experimental investigation for phase I and the effects of various percentage s of tire chips repl acement on concrete properties and cementitious materials content. Chapter VI discusses the modulus of elasticity of the concrete mixture with 10 % coarse aggregates with tire chips and the influence of changing water reducer. Chapter VII presents the conclusions of this study and provides recommendations for further research.

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6 CHAPTER II LITERATURE REVIEW This literature review covers the various topics researchers have investigated. Previous research conducted on rubberized concrete and utilization of scrap tires in civil engineering applications is briefly discussed. Uses of Waste Tires Waste tires that are no longer suitable for use on vehicles due to wear or irreparable damage can be recycled as aggregates in Portland cement concrete or recycled into other tires (Nehdi and Khan 2001). Shredded tires can be chosen as the filling material in school playground s Some states Alabama, Florida, Georgia, South Carolina, Virginia allow tire shreds to be used in construction of drain fields for septic systems (Environmental Protection Agency 2011 ). Tires can even be cut up into tire chips and used in garden beds to hold in water ; also, tires placed i n garden beds can prevent weeds from growing. Stockpiled tires create a huge health and safety risk to our lives. They easily catch fire, burning for months and creating substantial pollution in the air and ground. T ire piles also offer dwelling places for mosquitoes which carry diseases. A new use for waste tires involves refining them Refinements are generated in different sizes for use in a variety of applications. Figure 2 1 shows the different sizes of crumb/shredded rubber (Eldin and Senouci 1993 with permission from ASCE ) In the called rubberized concrete (Kaloush et al. 2005). Li et al. (1998) wrote, suitable

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7 for applications such as driveways, sidewalks or road construction where strength is not a high priority but greater toughness is preferred also has been found that the use of rubber particles improve s the engineering characteristics of c oncrete (Goulias et al. 1997) ; r esear ch indicates that rubberized concrete has a highly potential usage in light duty applications such as surface pavement material s and light duty structure s Figure 2 1 : Typical S ize and S hape of R efinements (With permission from ASCE) Classification of Recycled Waste Tire Particles Various ways to r euse recycled waste tires particles have been developed in recent years. American Society for Testing Material (ASTM) gives a classification of recycled waste tire particles. Table 2 .1 shows the terminology for recycled waste tire particles as defined by the ASTM D 6270 Standard Practice for Use of Scrap Tires in Civil Engineering Applications.

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8 Table 2 1 : ASTM D 6270 Terminology for Recycled Waste Tire Particles Classification Lower Limit, in(mm) Upper Limit, in(mm) Chopped Tire Unspecified dimensions Rough Shred 1.971.971.97(505050) 301.973.94(76250100) Tire Derived Aggregate 0.47(12) 12(305) Tire Shred 1.97(50) 12(305) Tire Chips 0.47(12) 1.96(50) Granulated Rubber 0.017(0.425) 0.47(12) Ground Rubber <0.017(0.425) Powered Rubber <0.017(0.425) Chopped tires dimensions are not specified in the standard ; they were cut by a cutting machine into very large pieces. The primary shredding process c an produce scrap tires with a si ze as large as 12 18 long by 2 9 wide (Siddique and Naik 2004) After secondary shredding, the rough shreds, tire derived aggregate, tire shreds and tire chips are cut down to 0. 5 to 3 Granulated ru bber, powered rubber and ground rubber are processed by the cracker mill process, granular process, or micro mill process, two stages of magnetic separation and screening (Heitzman 1992). Fresh Concrete Properties of Rubberized Concrete The fresh concrete properties usually evaluated for freshly mixed concrete are temperature, slump, air content, and unit weight. All properties and testing methods are defined by:

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9 Slump of Hydraulic Cement Concrete: ASTM C 143 Temperature of Freshly Mixed Hydraulic Cement Concrete: ASTM C 1064 Unit Weight and Air Content of Concrete: ASTM C 138 Air Content of Freshly Mixed Concrete by the Pressure Method: ASTM C 231 Air Content of Freshly Mixed Concrete by the Volumetric Method: ASTM C 173 Slump is a property that shows how flowable the concrete is. The higher the slump, the better the workability. Superplasticizer, also known as high range water reducer, can increase slump of concrete mixtures by comparison of the same concrete mixture with low range water reducer High slump concrete is usually used for slim slabs or highly reinforced structures. For heavily reinforced sections, self consolidating concrete is selected. In rubberized concrete, the fresh concrete properties are effected by the rubber p article size and quantity Khatib and Bayomy (1999) found that with rubber contents of 80% o r higher ( about 40% by total aggregate volume), the slump is near zero and the mix is not workable by hand mixing. In their research, the specimens were divided into three groups: Group A, Group B, and Group C. In Group A, only fine aggregates were replaced by crumb rubber; i n Group B, only the coarse aggregates were replaced by tire chips; i n Group C, both fine aggregates and coarse aggregates were repla ced by crumb rubber and tire chips, respectively. The results of a research completed by Aiello and Leuzzi (2010) were quite different, however; show ing that the workability of fresh concrete is slightly improved by the partial substitution of aggregate with rubber particles.

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10 Figure 2.2 ( Adapted from Khatib, 1999) shows the relationship between slump and rubber content for all groups. Figure 2. 2 : Slump vs Rubber Content (Adapted from Khatib, 1999) Kaloush et al. (2005) found that with an increasing rubber content in concrete, the unit weight decreases. W ith the use of recycled tire particles a n otable effect in the unit weight begins to occur when the percentage of replacement is higher than 20% by the volume of total aggregate used in the concrete mixture (Siddique and Naik 2004). The r esearch indicates that when 33% by volume of sand is replaced by crumb rubber, t he unit weight of rubberized concrete is reduced by approximately 10% (Li et al. 1998). Khatib found that the unit weight has a linear relation with the decreasing of rubber content. Figure 2 .3 (Adapted from Li et al. 1998) shows the decreasing relationship between unit weight and rubber content incorporated in the concrete mixtures

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11 Figure 2. 3 : Unit Weight vs Rubber Content (Adapted from Li et al., 1998) In general, with the air content increasing, the unit weight of rubberized concrete decreases uniformly. In Khatib (1999) research the rate of increase in air contents was very similar for all three testing groups : only fine aggregates were replaced by crumb rubber, only coarse aggregates were r eplaced by tire chips, both fine aggregates and coarse aggregate were replaced by crumb rubber and tire chips, respectively ; while the rubber content was less than 30% of total aggregate volume. Fedroff et al. (1996) reported that the air content in rubb erized concrete mixtures is higher than in traditional concrete mixtures This is because rubber has a hydrophobic property which repel s the surround ing water and trap s more air attached to the surface of the rubber. For traditional concrete mixtures, more air content in concrete mixture increases its durability up to approximately 9% of air content. After th is literature review about rubberized concrete, t he effect s of temperature on rubberized concr ete are not thoroughly discussed. However, this would be a noteworthy topic because temperature has a significant impact on practical concrete

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12 plac ement Aggregate warehouse s usually store the aggregate in the open air without the protect ion of shade and a t remendous amount of heat can buil d up due to the black color of tires Excessive heat results in rapid hydration of the cement paste in rubberized concrete mixture s and lead s to some difficult ies for concrete placement Generally the se are the properties of freshly mixed concrete: With the rubber c ontent increasing, the slump and unit weight decreas e Air content increases with the increasing of rubber content. Hydrophobic tendencies of waste tire particles increases the air content. High temperature due to the storage of recycled tires can result in placement difficulty. Hardened Concrete Properties of Rubberized Concrete The hardened property of rubberized concrete testing includes compressive strength, flexural strength, splitting tensile strength, rapid chloride permeability test and resistance of concrete to rapid freezing and thawing test. These tests are defined by: Compressive Strength of Concrete: ASTM C 39 Flexural Strength of Concrete: ASTM C 78 Splitting Tensile Strength: ASTM C 496 Rapid Chloride Permeability Test: ASTM C 1202 Resistance of Concrete to Rapid Freezing and Thawing: ASTM C 666 The research literature on rubberized concrete indicates a consensus regarding tire chips as the singularity in concrete mixtures and that t he compressive strength of rubberized concrete m ixtures is directly affected by the amount of recycled tire chips used in a matrix. Plus, t he particle size, surface treatment, and content are reported to

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13 have significant effect s on both compressive and tensile strength. Xi (2004) used 0.073 0.162 ( 1.85 4.12 mm) recycled rubber particles Zhang and Li (2012) used 0.039 0.093 (1 2.36 mm) particles Kaloush et al. (2005) used recycled tires with size s ranging 0.039 0.78 (1 20 mm) waste tire particles. Aiello and Leuzzi (2010) tested r ubberized concrete with the tire particle size s 0.39 0.88 (10 25 mm) All the studies evaluated the compressive, tensile, and flexural strength with certain percentage s of the aggregate replaced by recycled rubber and the mentioned conclusions were developed. S trength loss was due to the poor adhesion between the rubber particles and the surface of cement paste. Xi (2004) found that us ing the 8% silica fume pretreatment on the surface of rubber particles can improve the properties of rubber modified mortars (RMM ). On the other hand, directly using silica fume to replace equal amount (weight) of cement in concrete mix has the same effect The interfacial transition zone (ITZ) has direct influence on the performance of rubberized concrete mixtures. Research of pretreatments of rubber particles shows that several chemical treatment methods could enhance the bond between rubber particles and concrete: PAAM (polyacrylamide) pretreatment, PVA (pressure ageing vessel) pretreatment and silane pretreatment (Xi 2004). The PAAM, PVA, and silane chemical treatments could enhance the performance for ITZ. The PAAM is quite effective to improve the performance of ITZ but has an adverse effect on the rubberized concrete workability when more than 10% of total aggre gate is replaced by rubber particles by volume ; yet there is no such adverse effect on the workability of rubberized concrete by using PVA and silane pretreatment method. It has been proven that PVA is more effective than silane pretreatment (Xi 2004) Th e compressive strength decreased as the rubber content increase d: 60% of the 28 day

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14 strength was achieved at 3 days and 80% was achieved at 7 days ( Kaloush et al. 2005). In Eldin and Senouci (1993) study, when coarse aggregate was 100% replaced by tire chips, there was approximately 85% compressive strength reduction and 50% splitti ng tensile strength reduction. Previous research also shows that rubberized concrete can be used for the low strength and lightweight require ments of civil engineering applica tions. Figure 2.4 (With permission from ASCE) shows the relationship between compressive strength at the age of 7 days and 28 days and rubber content. The compressive strength with aggregates 100% replaced by rubber partical is less than 17% of the origina l concrete mixture which has no rubber particle incorporated. (Eldin and Senouci 1993) Figure 2 4 : Compressive Strength (With permission from ASCE) Compared to traditional brittle concrete mixture, rubberized concrete experience s non brittle failure during compressive, flexural, and splitting tensile strength testing. Because the rubber pieces are flexible and have a low modulus of elasticity when

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15 concrete begins to crack during flexural tests, the rubber particles act as reinforcement and keep two pieces of concrete from sudden failure. In the Kaloush et al. ( 2005 ) study, t he modulus of elasticity decreased slightly for mixture s with a low crumb rubber content. For mixtures with a high crumb rubber content, the modulus of elasticity was drastically reduced T o predict the compressive strength of rubberized concrete block with different rubber content Ling (2011) proposed the following prediction equation which is applicable within 0 % 50% for rubber content and 0.45 % 0.55 % for water cement ratio : Where = strength reduction factor for general, = strength reduction factor for 28 days = compressive strength of rubberized concrete block (MPa), =compressive strength of control concrete block (Mpa), r=rubber content by volume, =water cement ratio. For this study, i n order to constitute the durability of rubberized concrete, the abilit ies to withstand both the recycling freeze/thawing tempe rature change (ASTM C 666) and chemical permeability (ASTM C 1202) were tested to give the simulation and evaluation. The durability factor of freezing/thawing was determined by the dynamic modulus of elasticity of the concrete at 300 cycles of freezing/th awing cycles or when the dynamic modulus of elasticity reache d 60% of initial, whichever came first. The permeability of concrete was based on the amount of electrical current pass ing through the concrete slices sample ; u sually it measured at 28 days. According to Kosmatka and Panarese ( 2002) a c oncrete sample with a durability factor la r ger than 95 is considered

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16 high freezing/thawing resistant and a concrete sample with 1000 2000 coulombs pass ing through it is treated as low permeability Kardos (2011) study indicate d that for concrete with crumb rubber, the best durability is 10% replacement of sand for the highest which is 0.91, followed by 20% replacement of sand Modulus of Elasticity of Rubberized Concrete The modulus of elasticity of concre te reveals the capability of deformation under loads. Fedroff et al. (1996) found that for higher strength concretes, the stress strain curves become more linear. Gneyisi et al. (2004) found that with increasing the rubber content to 50% of the total aggr egate volume, the modulus of elasticity reduced to about 6.5 and 8.0 g pa for water cement ratios of 0.6 and 0.4, respectively ; and that t he modulus of elasticity slightly increase s with the use of silica fume. Figure 2.5 (With permission from ProQuest) shows the relationship between durability factor versus cycle count for rubberized concrete with different amount crumb rubber incorporated. Rubber content reduces the durability of concrete subjected to freeze/thaw cycling condition. The concrete mixtures with less than or equal to 20% fine aggregate replaced by crumb rubber and without recycled coarse aggregate show excellent freeze/thaw resistance. (Kardos 2011) The gain rate of rubberized concrete modulus of elasticity with different rubber content incorporated is shown in F igure 2.6 (With permission from TRB) The modulus of elasticity reduces rapidly as the rubber particle increases. (Fedroff et al. 1996).

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17 Figure 2 5 : Durability Factor vs. Cycle Count Figure 2 6 : Modulus of Elasticity with Time (With permission from TRB)

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18 The Structural Concrete Building Code (ACI 318 11) section 8.5.1 provides a prediction equation for modulus of elasticity of concrete: is the unit weight of concrete, ranging from 90 to 160 and is the compressive strength of concrete.

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19 CHAPTER III PROBLEM STATEMENT Colorado has about 45 million stockpiled tires and th at number is rising each year. Eastern Colorado lacks virgin coarse aggregates for pavement concrete mixtures. Virgin aggregates usually are shipped from Front Range quarries to Eastern Colorado projects which has resul t ed in significant transportation costs as well as a larger carbon footprint due to the mining and trucking. A recent study completed by University of Colorado at Denver (UCD) for the Colorado Department of Public Health and Environment indicates the pote ntial use of commercially processed crumb rubber as an alternative replacement for fine aggregate in CDOT Class P paving concrete mixtures. In this study, f ive mixtures with 10% 50% replacements of sand by volume were tested for both fresh and hardened con crete properties. From five replacement values, the 20% and 30% replacement mixtures met the requirement s of CDOT Class P concrete. The recycled rubber particles did not exhibit an unusual rate of strength gain behaviors with different replacement quantities. The leaching tests were performed to examine the environmental sustainability of rubberized concrete. The results showed that rubberized concrete pose s no threat to human health. The processing of crum b rubber increase s cost of concrete to $300 to $400 per ton. The expense of replacing the fine aggregates that are available in Eastern Colorado with crumb rubber is high. An alternative way is to use recycled tire chips to supplement/ replace coarse aggregate in concrete mixtures. The less effort required, the less will be the associated costs. This study examined the reuse potential of recycled tire chips as coarse aggregates in paving concrete mixtures. The use of recycled tire chips would

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20 replace the more expensive virgin coarse aggregate on the eastern plain s of Colorado. This study will help to eliminat e Colorado stockpiled waste tires.

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21 CHAPTER IV EXPERIMENTAL PROGRAM The p rimary objective of this r esearch study was to create a sustainable concrete mixture using recycled tire chips as partial replacements for coarse aggregates. The new concrete mixture was developed and examined to meet the requirement of CDOT Class P pavement concrete. This stu dy consist ed of two ph ases. In phase I, nine mixtures were batched to exam ine the performance of both fresh and hardened concrete properties. The cementitious material content was also changed to test the effect. In phase II, the mixtures that fulfill the CDOT Class P concrete requirement were modified with different types of water reducer to examine the effects. The modulus of elasticity was also investigated and compared with the results calculated by the equations provided by ACI 318 11. Materials for Test S pecimens Concrete Materials Concrete mixture consists of coarse aggregates, fine aggregates, cementitious materials admixtures, and water The design method used to proportion the concrete mixture was the absolute volume method. In this study, the increme nts of coarse aggregate volume were replaced with recycled tire chips. Figure 4.1 shows t he coarse aggregates provided by Bestway Concrete were in compliance with ASTM C 33 requirements. Fine aggregate usually consist of natural sand that were used in this study.

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22 Recycled Tire Particles Three different sizes of recycled tire chips were used in this research: 1/4 1/2 3/4 as shown in figure 4.3 They were purchased from Front Range Tire Recycle Inc. with the price of $0.18 per pound, $360 per ton. R ecycled tire chips do not have any economic advantages when compared to conventional aggregates. But as discussed in chapter II, recycled tire chips have econom ic advantages when compared to crumb rubber particles. The sieve analysis for traditional coarse aggregates fine aggregates, and recycled tire chips were performed for each size None of the single type of tire chips met the ASTM C 33 grading requirement. In order to meet the requirement of ASTM C33, a designed mix of recycled tire chips with 40% of and 60% of 1/2" was used as replacement coarse aggregate for the proportioning concrete mixture based on the sieve analysis. Figure 4 1 : Rocks Coarse Aggregates

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23 Figure 4 2 : Sand Fine Aggregates Figure 4 3 : Rubber Chips Sample L eft to R ight, R espectively According to ASTM C 33, the sieve analysis was done for all aggregates used in this study. Table 4.1 shows the sieve analysis results for both conventional aggregates and recycled tire particles. Figure 4.4 shows the ASTM C 33 g rading l imits and the sieve analysis results for c oarse a ggregates

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24 Table 4 1 : Sieve Analysis for Sand, Rocks, and Tire Chips

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25 Figure 4 4 : ASTM C 33 Grading Limits and Values for Coarse Aggregates

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26 Recycled W aste T ire S pecific G ravity E xperimental T esting and R esults It was important to determine the specific gravity value of the recycled tire chips in order to adjust the proportion in the concrete mixture containing recycled waste tire particles. The specific gravity of rubber chips was measured according to ASTC C 127 Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate. The l iterature review ed indicates that tires would float on top of water i nstead of submerg e into the water. The solution was to use a de airing chemical admixture to control the air bubbles be neath the tire chips. In this study, t he tire chips did not float when submerged initially in water No de airing chemical admixture was used through the entire specific gravity experimental testing The specific gravity of tire chips used in this study was measured to be 1.1 Admixtures The chemical admixtures used for this study were high range water reducer (HRWR), low range water reducer (LRWR), and air entraining admixture (AEA) The AEA used was Sika Air in order to maintain the specified 4 % 8% air content in the rubberized concrete mixture ; it contained a blend of high grade saponified rosin and organic acid salts. Typical amoun t s used in a concrete mixture range from 0.5 3 fl o z per 100 lbs. of cementitious material. In this study, a dosage of 0.5 fl o z per 100 lbs. was chosen to be used in each mixture. Sika Plastocrete 161, a kind of low range water reducer (LRWR), was used for determining the proportion that met the requirement of CDOT Class P pavement concrete. Sika Viscocrete 2100, a kind of high range water reducer (HRWR), was used for all the proportions that met the requirement to examine the effect of using different

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27 types of water reducer s According to the manufacture recommendation, the dosage ranges 2 6 fl o z per 100 lbs. of cementitious materials. The target slump is 2 Due to the high volume of tire chips used in some mixtures, the slump of zero was observed in some mixtures even with excessive water reducer incorporated. Type I Portland Cement An ASTM T ype I P ortland cement was used in this study. The specific gravity of this cement was 3.15 and the blaine fineness was 217 Mixture Proportions The mixture design identification ( m ix ID in Table 4 .2 ) shows the detail proportion for each mixture. For example, the first number (0.4/660/100S/ 100R/ 0TC/ P ) represents that the water cement ratio of the mixture design was 0.4 The second number (0.4/660/100S/100R/0TC/P) represents the content of cementitious materials in pounds. The third number (0.4/660/100S/100R/0TC/P) represents the percentage of sand use d for the mixture by volume. The set of values in the fourth and fifth slots represent the percentage of coarse aggregate (native rock) and the percentage of recycled tire chips, respectively. Lastly, the final number in the design identification (0.4/660/ 100S/100R/0TC/P) represents the type of water reducer used in the mixture P for Plastocrete161 (low range water reducer) and V for Viscocrete 2100 (high range water reducer) All trial mixtures proportions details were shown in t able 4.2

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28 Table 4 2 : Research Design Mixtures Proportions

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29 Batching of Concrete Mixture During 2013, batching of concrete that contained di fferent tire chips as coarse aggregate with two kinds of water reducer was completed for testing. The procedures of batching concrete were set by ASTM C 192 Making and Curing Concrete Test Specimens in the Laboratory and all processes were performed according ly Preparation B efore Batching Conc rete Mixture Coarse aggregates and fine aggregates are stored in the open air. For this study, t hey were spread on the ground under the sun for drying when it had rained the day before. After that about five days before batching they were placed in the la boratory by using wheel carts so the extra water content in the aggregates would have enough time to evaporate. This allowed the aggregates to balance out to room temperature during this time. The components of each mixture were weighed and placed in five gallon buckets. This include d the coarse aggregates, fine aggregates, tire chips, cement, and water. Before batching, samples of coarse aggregates and fine aggregates were taken and microwave dried. Using the microwave, the samples were heated three minutes each time and the weights of samples were recorded. The procedure was repeated until the weight loss was less than 0.1 gram than the previous measure. T he water content in both fine aggregates and coarse aggregates was calculated by using th is equation:

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30 Where w: water content in aggregates : weight of original sample aggregates and container : weight of dried sample aggregates and container : weight of container After determining the water content in the aggregates, the water portion of the concrete mixture could be adjusted. Admixture s such as air entrained admixture, low range water reducer and high range water reducer were measured and placed in test tube s The batching area consist ed of all the necessary tools and equipment to test fresh concrete properties. In addition, the cylinder molds and beam molds were adequately cleaned and set in the batching area for casting the concrete specimens. Mixing Process The mixing process began by thoroughly dampening the concrete mixer with water; when finished, all excessive water was dumped This prevented the wall of the concrete mixer from absorbing the water from the concrete mix. After all the excessive water was dumped, the coarse aggregates, tire chips and fine aggregates were placed into the concrete mixer. After all the aggregates were added into the mixer, the mixture was allowed to blend for three to five minutes so that all of the different kinds of aggregates were mixed evenly. The purpose of this was to prevent the various types of aggregates from sticking together. When all of the blending procedures were completed, cement was added into the mixer and blended with the aggregates for a few minutes. This was performed to prevent clumping of the cement onto the wall of the mixer. The a ir

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31 entrained admixture was added into the measured water in the bucket T hen the whole bucket of water was poured into the mixer slowly. After all the aggregates, cement, water and air entrained admixtures were placed into the mixer, the water reducer was added into the batch. Once all of the constituents had been added to the mixer, another five minutes mixing time was allowed to mix the concrete thoroughly. After the mixing was complete, all the concrete inside the mixer was placed on to a dampened wheel cart and a big cover was put on top of the wheel cart to prevent fast evaporation. Fresh concrete tests were pe rformed as soon as possible, in addition to casting the concrete into cylinders and beams by using the mold s prepared before the batching. Curing of Specimen All the specimens including cylinders and beams were moved to the curing room immediately after being cast for initial curing. The curing room was dedicated entirely to concrete specimen storage and curing. The temperature in the curing room was maintained at 23.04.0 The humidity controller of the curing room would increase the room humidity when the relative humidity drop ped below 50%. The water tanks in the curing room were equipped with heaters and an analog chart recorder with a digital temperature display. The temperature of the water in the water tank was maintained at 23.02.0 in accorda nce with ASTM C 511. The specimens were placed in the curing storage room for the 24 hours initial curing. After the initial curing, the cylinders and beams were de molded. Then c oncrete cylinders and beams were put into the water tank immediately for 100%

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32 water curing Cylinder tests were scheduled after the curing time of the 3rd day, 14th day and 28th day. Beams were tested when the curing time hit 28 days. Testing of Concrete Two phases of testing took place for each concrete mixture: freshly mix ed concrete properties and hardened concrete properties. The f resh concrete properties include d temperature, slump, unit weight, and air content; the h ardened concrete properties include d compressive strength, splitting tensile strength, modulus of rapture rapid chloride ion permeability, freeze/thaw resistance, and modulus of elasticity. The fresh concrete tests took place during the batching of the mixture and the hardened concrete tests were performed at the scheduled days. Testing for Fresh Concrete Properties Freshly mixed concrete property tests were performed immediately after the mixing procedure. F reshly mixed concrete properties of concrete are often used to evaluate the behavior of components that are in the concrete matrix. All the tests were performed in accordance with ASTM standards. Table 4 .3 shows the standard procedure and the testing time for the concrete mixtures. Table 4 3 : Fresh Concrete Tests Fresh Concrete Tests Standard Time of Test Slump ASTM C 143 At Batching Unit Weight ASTM C 138 At Batching Air Content ASTM C 231 At Batching Temperature ASTM C 1064 At Batching Testing for Hardened Concrete Properties T ests performed on hardened concrete for trial mixtures are compressive strength, splitting tensile strength, modulus of rupture, rapid chloride ion perme ability, and

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33 freeze/thaw resistance. The hardened concrete properties testing on phase II include d compressive strength and modulus of elasticity All the tests were completed in acc ordance with ASTM standard. Table 4 .4 and Table 4 .5 indicate the standard procedure s, in addition to the time th e tests were completed for the concrete mixtures. Table 4 4 : Hardened Concrete Tests for Phase I Table 4 5 : Hardened Concrete Tests for Phase II Hardened Concrete Tests Standard Time of Test Compressive Strength ASTM C 39 3,14,28 days Modulus of Rupture ASTM C 78 28 days (Class P) Freeze Thaw Resistance ASTM C 666 28 and Subsequent days Rapid Chloride Ion Penetrability ASTM C 1202 28days Splitting Tensile ASTM C 496 28 days Hardened Concrete Tests Standard Time of Test Compressive Strength ASTM C 39 3,14,28 days Modulus of Elasticity ASTM C 469 28 days

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34 CHAPTER V EXPERIMENTAL RESULTS AND DISCUSSIONS PHASE I Batching of Trial Mixtures The design plan was set. For phase I tests, m ixture #1 through mixture #9 were trial mixtures that aim ed to determine the coarse aggregates replacement percentage to satisf y CDOT Class P pavement concrete requirements. The batching of trial mixtures was completed using 100 % 50 % 30 % 20 % 10% replacements of conventional coarse aggregates. A control mixture which ha d no tire chip was batched for comparison. Water content a djustment was performed before the batching. The final proportion s for both phase I and phase II are show n in Table 5 .1 Fresh Concrete Properties Fresh concrete properties performed at the time of batching include d temperature, slump, unit weight, and air content for each mixture. When all of the materials were being mixed in the mixer, it was observed that the higher tire chips content that had been incorporated, the lower the flow ability that showed in the mix. T he amount of water reducer used in each mixture was adjusted individually during the mixing procedure in an effort to get the slump of 1 to 2 inches. The amount of water reducer used in each mixture was recorded as show n in Table 5 .2 The fresh concrete pro perty results in both metric units and U.S. units, are summarized in the following sections.

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35 Table 5 1 : Trial Mixtures Proportion after Water Adjustment

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36 Table 5 2 : Water Reducer Dosage After Adjustment Mix# Mix ID WRA L/100kg (fl oz/cwt) 1 0.4/660/100S/100R/0TC/P 0.326(5) 2 0.4/660/100S/0R/100TC/P 2.169(33.27) 3 0.4/660/100S/50R/50TC/P 0.508(7.79) 4 0.4/660/100S/70R/30TC/P 0.474(7.27) 5 0.4/660/100S/80R/20TC/P 1.17(17.99) 6 0.4/660/100S/90R/10TC/P_1 0.326(5) 7 0.4/660/100S/90R/10TC/P_2 0.326(5) 8 0.4/570/100S/70R/30TC/P 1.884(28.90) 9 0.4/570/100S/90R/10TC/P 1.71(26.24) 10 0.4/660/100S/90R/10TC/V 0.326(5) 11 0.4/660/100S/90R/10TC/P 0.326(5) Temperature of Freshly Mixed Hydraulic Cement Concrete, ASTM C 1064 The ideal temperature to place concrete is between 50 and 60F (10 16C), but should not exceed 85F (29C) (Mindess and Darwin 2003). A t emperature over 85F will cause an increase of the water evaporation in the concrete. This undesirable increased rate of evaporation is the cause of plastic shrinkage and results in internal stresses that cause cracking (Kardos 2011). To avoid the exceeded maximum recommended temperature, t he concrete mixtures were batched outside during good weathers and batched inside of lab during extreme weathers. Direct sunshine should be avoid to protect the temperature of the surface of freshly mixed concrete going over the limit. None of the mixture temperature s in this study exceeded the maximum recommended temperature. The temperatures recorded for all the mixtures are summarized in Table 5. 3

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37 Table 5 3 : Concrete Temperatures Mixture# Mixture Name Temperature in Concrete Environment Temperature Fahrenheit Fahrenheit 1 0.4/660/100S/100R/0TC/P 52 49 2 0.4/660/100S/0R/100TC/P 50 55 3 0.4/660/100S/50R/50TC/P 50 57.5 4 0.4/660/100S/70R/30TC/P 47 48 5 0.4/660/100S/80R/20TC/P 75 84 6 0.4/660/100S/90R/10TC/P_1 45 47 7 0.4/660/100S/90R/10TC/P_2 55 57 8 0.4/570/100S/70R/30TC/P 72 75 9 0.4/570/100S/90R/10TC/P 72 75 According to ASTM C 1064 Standard Test Method for Temperature of Freshly Mixed Hydraulic Cement Concrete the container should be large enough to provide at least f igure 5.1 Figure 5 1 Temperatures Measuring

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38 Slump of Hydraulic Cement Concrete, ASTM C 143 The slump values of all trial mixtures and the water reducer usage for each mixture are shown in Fig ure 5.3 The slump of concrete represents the workability of the mixture. The tire chips resulted in a less workable mixture by comparison to normal concrete (Liu 2013). It was observed that the slump for mixture #2 was zero even though the water reducer had been added excessively (figure 5.2) Mixtures that had lower cementitious materials experienced low slump and the workability was very poor. Figure 5 2 : Zero Slump for Mixture #2

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39 Figure 5 3 : Concrete Slump and WRA

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40 Unit Weight Unit weight s were tested for each mixture in accordance with ASTM C 138. The results ranged from 93 to 145 depending on the tire chips content incorporated in the mixture and the air content. A unit weight of mixtures descends as tire chip content s increase ; t h is trend was evident. The control mixture, which ha d no tire chips replacement, ha d the unit weight of 145 When the tire chips content went up to 30 % of coarse aggregate volume, the unit weight decreased to 87 % of the control mixture. Once the tire chips had replaced all the coarse aggregates in the concrete mixture, the uni t weight went down to 64 % of the control mixture. Only when the coarse aggregates content were replaced by tire chips over 30% did the unit weight change dramatically. Figure 5.4 shows the unit weight of each mixture design. Air Content Air entrained admixture was used for all nine trial mixtures. The air content was measured by pressure meter method in accordance with ASTM C 231. The s ame amount (0.5 fl oz/cwt) of air entrained admixture was used for each mixture but the air content varie d U s ing different type s of water reducer affect ed the air content in the concrete in the second phase of tests. High range water reducer increase d the air content in the concrete mixtures. Figure 5.5 shows the air content and AEA used in each mixture. As dis cussed in the literature review, rubber has the property of holding the air around ; and an 18% air content was found in mixture #2 (0.4/660/100S/0R/100TC/P).

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41 Table 5. 4 : Air Content by Pressure Meter, ASTM C231 Mixture Name Air Content % 0.4/660/100S/100R/0TC/P 5 0.4/660/100S/0R/100TC/P 18 0.4/660/100S/50R/50TC/P 11 0.4/660/100S/70R/30TC/P 10 0.4/660/100S/80R/20TC/P 3.25 0.4/660/100S/90R/10TC/P_1 6 0.4/660/100S/90R/10TC/P_2 6 0.4/570/100S/70R/30TC/P 6 0.4/570/100S/90R/10TC/P 4.75 The roller meter method was also used for part of trial mixtures to determine the air content and the results are summarized in table 5.5. Table 5. 5 : Air Content by Roll er Meter, ASTM C173 Mixture Name Air Content % 0.4/660/100S/0R/100TC/P 3.5 0.4/660/100S/50R/50TC/P 10.75 0.4/660/100S/70R/30TC/P 7.25 0.4/660/100S/90R/10TC/P_1 5.75 0.4/660/100S/90R/10TC/P_2 5.25

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42 Figure 5 4 : Unit Weight of Concrete Mixture

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43 Figure 5 5 : Air Content and AEA

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44 Hardened Concrete Properties Hardened concrete properties of rubberized concrete mixtures were performed in accordance with ASTM standards. There were 14 cylinder specimens in addition to at least 4 prismatic beams that were cast for the tests for each mixture. A total number of 126 cylinders and 36 beams were cast for phase I tests. The tests performed on the hardened concrete were: Compressive Strength: 3 cylinders at 3, 1 4, 28 days Modulus of Rupture: 2 beams at 28 days Rapid Chloride ion Permeability: 2 cylinders at 28 days Splitting Tensile Strength: 3 cylinders at 28 days Freeze/thaw R esistance: 2 beams at 28 days Compressive Strength of Concrete Specimens, ASTM C 39 The compressive strength of concrete is an important component in concrete design. Three cylinders were tested for each mixture on the respective day of age. Cylinders are 4 in diameter by 8 in length. The strength is determined by the failure uniaxial l oad (lb ) divided by the cylinder surface area ( ). According to current CDOT Class P specifications, the requirement of compressive strength is 4200 psi at the age of 28 days. An average of three cylinder compressive testing results was obtained to re present the performance of concrete at a certain age. Compressive strength of each mixture at each designed age is summarized in Table 5.6 and Figure 5.6 Figure 5.7 and Figure 5.8 indicate the compressive strength loss by comparison of control mixture at each testing day for 660 lb/cy cementitious materials mixtures and 570 lb/cy cementitious materials mixtures respectively. The compressive

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45 strength gain rage for each mixture at 3 days, 14days, and 28 days were shown in Figure5.9. The compressive valu es were obtained with the average of three specimens and the coefficient of variation was calculated for each mixture. The coefficient of variations for all mixtures lower than 2.9%, which is the precision requirement specified by ASTM C39 except mixture # 2, the mixture with 100% coarse aggregate replaced by tire chips.

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46 Table 5 6 : Compressive Strength, ASTM C 39

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47 Figure 5 6 : Compressive Strength for Each Mixture 4200psi

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48 Figure 5 7 : % Strength Loss of Mixtures to the Control (high cementitious content) Figure 5 8 : % Strength Loss of Mixtures to the Control (low cementitious content)

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49 Figure 5 9 : Rate Gain of Compressive Strength at 28 D ays 4200psi

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50 It was observed that the 10% replacement mixture #6 ( 0.4/660/100S/90R/10TC/P_1 ) met t he CDOT structural performance requirement. M ixture #7 ( 0.4/660/100S/90R/10TC/P_2 ) with the same proportion was batched and examined to meet the requirement. The repeatability was approved. Figure 5.10 demonstrates the failure mechanism of the cylinder under compression. Figure 5.11 is a concrete cylinder after compressive failure. F igure 5 10 : Residual Strength Characteristic 0 10000 20000 30000 40000 50000 60000 70000 0 20 40 60 80 100 120 140 160 Load (lbs) Time (sec) Load (lbs)

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51 (a) Mixture #6, 10% Tire Chips (b) Mixture #2, Control Mixture Figure 5 11 : Compressive Failure of Concrete Cylinder Flexural Strength or Modulus of Rupture, ASTM C 78 A minimum flexural strength of 650 psi is required by CDOT Class P pavement specifications. This is a very important parameter for pavement applications because pavement concrete slabs wil l deform under the service load and the bottom of the concrete slab tend s to rupture. Sufficient flexural strength prevent s the rupture happening under the design load. Th results show that mixture s #6, #7, #8, and #9 met the requirement of flexu ral strength. Mixture s #6 and #7, which ha d 10% coarse aggregates replaced by tire chips, reached 924 psi and 991 psi at the age of 28 days, respectively. They showed even better flexural strength than the control mixture which ha d the flexural strength 9 07 psi at the age of 28 days. Thus, i t is concluded that the flexural strength of concrete mixtures can be increased by replacing a certain level (~10%) of coarse aggregate. Mixture s #8 and #9 showed good flexural strength behavior, too

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52 However, they did not meet the requirement of compressive strength at the age of 28 days, proving them in applicable in this particular case ; though high flexural strength ma de them applicable for other cases where lower compressive strength is required such as sidewalk s Figure 5.12 demonstrates flexural failure. Figure 5. 12 : Flexural Failure of Mixture #6 Figure 5.13 shows the flexural strength for each mixture. For all of the mixtures with tire chips that had been incorporated, visual observations during the tests indicate d that all of the beams had ductile deformations instead of brittle failure. This demonstrate d that the tire chips acted as fiber reinforcement in the concrete and would not be crush ed if the concrete failed at the bot tom. Instead, once the cracking began to form, the tire chips held the two pieces of concrete and kept deforming until total failure. The flexural strength values were obtained with the average of two specimens for each mixture and the coefficient of va riation meets the precision requirement specified by ASTM C78.

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53 Figure 5 13 : Flexural Strength for Each Mixture 650 psi

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54 Splitting Tensile Test, ASTM C 496 Figure 5.14 demonstrate s the splitting tensile test set up. The results of splitting tensile tests shown in Figure 5.1 5 demonstrate a similar trend like compressive strength. As the recycled waste tire particle contents increas ed the splitting tensile strength decrease d Mixtures from #5 to #9 showed good spl itting tensile strength. The control mixture had the highest tensile strength. It was confirmed that the recycled tire particle s did not increase the tensile strength of concrete. The splitting tensile values were obtained with the average of two specimens and the coefficient of variation meets the precision requirement which is 5% specified by ASTM C496. Figure 5. 14 : Splitting Tensile Test Setup Examples of splitting tensile specimen failure for mixture #7 and mixture #8 in the test were shown in Figure 5.16

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55 Figure 5 15 : Splitting Tensile Strength for Each Mixture

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56 Figure 5. 16 : Splitting Tensile Test Specimen Failure Rapid Chloride ion Permeability ASTM C 1202 Concrete experience s damage caused by infiltration of solutions due to high permeability of concrete. So, rapid chloride ion permeability tests were performed on the concrete in this study at 28 days The ASTM C 1202 discusses procedures for monitor ing the amount of electrical current that passe s through 2 thick by 4 diameter concrete slices F or this study, t he slices were cut by a wet saw to get the 2 slice s of the concrete cylinders then a ll the slices were put in a dry vacuum desiccator for approximately 2 hours. Figure 5 .17 shows the vacuum desiccator setup. Next, deionized water was introduced to the desiccator via a tube connected to the desiccator. Once the slices were completely submerged, the tube was switched off. The c oncrete slices were kept in the water for 18 hours before the sample slices were put into the test cell s Figure 5 .18 demonstrates the cell preparation.

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57 Figure 5 17 : Vacuum Desiccator Figure 5 18 : Cell Preparation

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58 Two solutions are required for rapid chloride ion permeability testing: sodium chloride ( ) solution and sodium hydroxide ( ) solution ; t he s odium chloride solution is 3% by mass in distille d water and 0.3 molar sodium hydroxide solution is required. So, for this study the sodium chloride solution was set at one side of the cell and the sodium hydroxide solution was set at the other end T he cell set was tightened, and a 60 volt direct curr ent source was maintained across the two ends of the specimen for 6 hours. Table 5. 7 shows the classification used to determine the concrete s permeability based on the coulombs passed. Table 5 7 : Permeability Rating Classification Charge Passed (Coulombs) Chloride Ion Penetrability >4,000 High 2,000 4,000 Moderate 1,000 2,000 Low 100 1,000 Very Low <100 Negligible Two sample slices were tested for each mixture. Table 5 8 shows that the average coulombs passed two samples and all rubberized mixtures were subjected to moderate to high chloride ion penetrability at the age of 28 days except for m ixture #8 ( 0.4/570/100S/70R/30TC/P ) ; t he total coulombs passed for each specimen for mixture #8 were 5661 and 2708, respectively. Cracks were found in the slice which ha d 5661 coulombs passed for the test when the cell was being d is assembled because t he cracks might have been formed during t he preparation of the sample. I f only use the sample ha d 2708 coulombs to represent the permeability at the age of 28 days, the mixture #8 was classified at the moderate level.

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59 Table 5 8 : Rapid Chloride ion Penetration Testing Results Mixture # Mixture Name 28 day(coulombs) Classification 1 0.4/660/100S/100R/0TC/P 1785 Low 2 0.4/660/100S/0R/100TC/P 2183 Moderate 3 0.4/660/100S/50R/50TC/P 1356 Low 4 0.4/660/100S/70R/30TC/P 2889 Moderate 5 0.4/660/100S/80R/20TC/P 1516 Low 6 0.4/660/100S/90R/10TC/P_1 2257 Moderate 7 0.4/660/100S/90R/10TC/P_2 2146 Moderate 8 0.4/570/100S/70R/30TC/P 4185 High 9 0.4/570/100S/90R/10TC/P 1648 Low F igure 5.19 indicates an increase in coulombs due to an increas e in the air content by using the roller meter method. However mixture #3 (0.4/660/100S/50R/50TC/P) showed out of the trend range. So, m ore mixtures were recommended to be batched in order to investigate the abnormal point formed by mixture #3. Generally, as tire chip particles content increas es the air content increases ; and t he more air content that is entrained, the more total charges are passed. Figure 5 20 demonstrates the chloride ion permeability versus the air content entrained for each mixture. N o obvious trend was found between the total char ge passed and the air content. The air content readings from the pressure meter method were high. The r oller meter method was used to measure the air content for mixture #2 ( 0.4/660/100S/0R/100TC/P), #3 (0.4 /660/100S/50R/50TC/P), #4 (0.4/660/100S/70R/30TC/P), #6(0.4/660/100S/90R/10TC/P_1), and #7(0.4/660/100S/90R/10TC/P_2) The results are summarized in Table 5 .5.

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60 Figure 5 19 : Air Content (Roller Meter) vs. Coulombs Freeze thaw Durability, ASTM C 666 When water penetrates the holes inside of concrete and temperatures below 0 C occur, the water freezes in the concrete. Because ice has a lower density than water, the volume increase s and expands against the internal surfaces of the small holes. This forms internal stress which causes micro cracking because internal stress allows more water infiltration and, f inally would cause failure of the concrete. 0.4/660/100S/50R/50TC/P

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61 Figure 5 20 : Chloride ion Permeability vs Air Content

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62 I n accord ance with ASTM C 666 t he freeze/thaw durability of the concrete mixtures in this study was determined by the transverse resonant frequency after 300 freeze/thaw cycles Chemicals are used to modify the air content to enhance the durability of a concrete mixture. In Colorado, the temperature varies 18 F 90 F (Denver Climate Report 1981 2010). This region is subject to a large range of temperature gradients and t he freez e/thaw durability of concrete pavement is a critical parameter. For th is study two beams for each mixture were tested The y were put into the freeze/thaw chamber, which runs the temperature from 0 F to 40 F then backwards. At the age of 28 days, the bea ms were moved from the curing water tank and immediately placed in the beam holder s with fresh water surround ing the beams. All beam holders were put in the freeze/thaw chamber and run. The freeze/thaw chamber that is owned and operated by the University of Colorado at Denver Materials Laboratory completes 36 cycles in approximately one week. The determination of one cycle is from 0 F to 40 F then back to 0 F ASTM C 666 states : If, due to equipment breakdown or for other reasons, it becomes necessary to interrupt the cyc les for a protracted period, stor e the specimens in a frozen condition in such a way as to prevent loss of moisture. For Procedure A, maintain the specimens in the conta iner and surround them by ice, if possible. If it is not possible to store the specimens in their containers, wrap and seal them, in as wet a condition as possible, in moisture proof material to prevent dehydration and store in a refrigerator or cold room maintained at 0 3F ( 182C). Follow the latter procedure when Procedure B is being used. In general, for specimens to remain in a thawed condition for more than two cycles is undesirable, but a longer period may be permissible if this occurs only once or twice during a complete test.

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63 After 36 freeze/thaw cycles, all the beams were taken out and dried to SSD condition. Next, the fundamental transverse frequency was tested followed by placing the beams back in to the freeze/thaw chamber for another 36 cy cles until the cycle number hit 324. Per ASTM C 666 t he relative dynamic modulus of elasticity and the durability factor were calculated as f ollows: Where: = relative dynamic modulus of elasticity, after c cycles of freezing and thawing, percent = fundamental transverse frequency at 0 cycles of freezing and thawing = fundamental transverse frequency after c cycles of freezing and thawing Durability factor (DF): Where: DF= durability factor of the test specimen P= relative dynamic modulus of elasticity at N cycles,% N= number of cycles at which P reaches the specified minimum value for discontinuing the test or the specified number of cycles at which the exposure is to be terminated, whichever is less M=specified n umber of cycles at which the exposure is to be terminated. A photograph of the relative dynamic modulus of elasticity test process was shown in Figure 5.21.

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64 Figure 5. 21 : Transverse Resonant Testing Setup

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65 As shown in Table 5.9, mixture #2 ( 0.4/660/100S/0R/100TC/P) ha d very low durability to freeze/thaw cycling. The surface deterioration of all the concretes was observed after 324 cycles of freezing and thawing and n o significant mass loss was found except in mixture #2. However, t he concrete mixture that had 10% 50% rubber particles replaced by a volume of coarse aggregate did exhibit good resistance to freezing and thawing. Generally, as the rubber content increas ed the durability factor decrease d Table 5 9 : Duribility Factor Mixture Name Initial (Hz) Final (Hz) Durability Factor 0.4/660/100S/100R/0TC/P 2177.74 2119.145 95 0.4/660/100S/0R/100TC/P 937.5 645 11 0.4/660/100S/50R/50TC/P 1572.27 1484.375 89 0.4/660/100S/70R/30TC/P 1767.58 1728.295 96 0.4/660/100S/80R/20TC/P 1855.47 1542.97 36 0.4/660/100S/90R/10TC/P_1 1972.66 1914.06 94 0.4/660/100S/90R/10TC/P_2 1972.66 1953.13 98 0.4/570/100S/70R/30TC/P 1425.78 947.27 44 0.4/570/100S/90R/10TC/P 1386.72 917.97 44 F inal F requency was measured at 72 cycles The testing results of transverse resonant frequencies after every 36 cycles of all mixtures are shown in Table 5.10

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66 Table 5 10 : Resistance to Freeze/Thaw Cycling

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67 CHAPTER VI EXPERIMENTAL RESULTS AND DISCUSSIONS PHASE II As the result of the phase I study, the concrete mixture with 10% coarse aggregate which had been replaced by tire chips satisfied all requirement s specified by CDOT Class P pavement concrete T hus phase II of this study examined the compressive strength modulus of elasticity on rubberized concrete with 10% coarse aggregate replaced by tire chips. D ifferent types of water reducers were used to inspect the effects on concrete. Repeata bility of this rubberized concrete mixture design was again prove n The mixtures were tested, by the standards and processes set by ASTM, for fresh concrete properties including slump, air content, unit weight and temperature ; and hardened concrete prope rties including compressive strength and modulus of e lasticity. The value of modulus of elasticity of this rubberized concrete was also compared with the results of the prediction equation provided by ACI 318. Both mixture #10 (0.4/660/100S/90R/10TC/V) an d mixture #11 (0.4/660/100S/90R/10TC/P) were batched for phase II. The design mixture proportion and water reducer dosage adjustment were summarized in Table 4 2 and Table 5 .2, respectively. Fresh Concrete Properties Fresh concrete properties performed at the time of batching include d temperature, slump, unit weight, and air content for each mixture. Fresh concrete properties of mixture #11 are similar with that of mixture #6 and mixture #7. Again, the repeatability was approved. The results are summarized in the following sections.

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68 Temperature of Freshly Mixed Hydraulic Cement Concrete, ASTM C 1064 The temperatures of two mixtures are 70F and 74F, respectively. Neither mixture temperature exceeded the maximum recommended temperature. The results of tem perature are shown in Figure 6 .1. Figure 6 1 : Concrete Temperatures for Phase II Slump of Hydraulic Cement Concrete, ASTM C 143 The slump values of two mixtures are shown in Figure 6 .2. The slump of concrete represents the workability of the mixture. The tire chips resulted in a less workable mixture b y comparison to normal concrete The workability of mixture # 11 with high range water reducer was much higher than that of mixture #1 0 wit h low range water reducer. 70 74 21 23 0 10 20 30 40 50 60 70 80 0.4/660/100S/90R/10TC/P 0.4/660/100S/90R/10TC/V Fahrenheit Celsius

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69 Figure 6 2 : Concrete Slump for Phase II Unit Weight, ASTM C 138 Unit weight was tested for each mixture in accordance with ASTM C 138. The results were 142.4 and 142.8 respectively, and were consistent with the results gained from phase I. Figure 6 .3 shows the unit weight of each mixture design. Figure 6 3 : Unit Weight of Concrete Mixture for Phase II 1.25 4.75 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0.4/660/100S/90R/10TC/P 0.4/660/100S/90R/10TC/V Slump (in.) 142.4 142.8 0 20 40 60 80 100 120 140 160 0.4/660/100S/90R/10TC/P 0.4/660/100S/90R/10TC/V Unit Weight lb/cf

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70 Air Content of Freshly Mixed Concrete ASTM C 231 Air entrained admixture was used for both mixtures. The air content was measured by pressure meter method in accordance with ASTM C 231. The s ame amount of air entrained admixture was used for each mixture but the air content varie d T he use of different type s of water reducer affect ed the air content in the concrete. High range water reducer increase d the air content in the concrete mixtures. Figure 6 .4 shows the air content of each mixture. Figure 6 4 : Air Content in Concrete Mixtures for Phase II Hardened Concrete Properties Tests for hardened concrete properties of rubberized concrete mixtures were performed in accordance with ASTM. There were 20 cylinder specimens in addition to 2 prismatic beams th at were cast for the tests of each mixture. The tests performed on the hardened concrete were: Compressive Strength: 5 cylinders at 3, 14, 28 days Modulus of Elasticity: 5 cylinders at 28 days 3 6 0 1 2 3 4 5 6 7 0.4/660/100S/90R/10TC/P 0.4/660/100S/90R/10TC/V Air Content %

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71 Compressive Strength of Cylinder Specimens, ASTM C 39 For phase II of the study, five cylinders were tested for each mixture on the respective day of age. The c ylinders were 4 in diameter by 8 in length. According to current CDOT Class P specifications, the requirement of compressive strength is 4200 psi at the age of 28 days. An average of five cylinder compressive testing results was obtained to represent the performance of concrete at a certain age. The c ompressive strength of each mixture is shown in Figure 6 .5. Figure 6 5 Compressive strength for Phase II The concrete mixture with low range water reducer reached a compressive strength of 3510 psi in its 3 days age. Not much compressive strength was gained from the testing age of 3 days to the testing age of 14 days. A lar ge compressive strength increase was found between 14 days and 28 days for concrete mixture #1 0 Compared to 3510 3517 4506 3140 4025 4442 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 3 day 14 day 28 day 0.4/660/100S/90R/10TC/P 0.4/660/100S/90R/10TC/V 4200 psi

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72 the other concrete mixture, mixture #11 had a lower compressive strength during the 3 day test. It reached a much higher strength during 14 day tes t than mixture #1 0 and the rate of increase for the strength slowed. Two concrete mixtures had similar compressive strength that exceeded the Colorado Department of Transportation (CDOT) Concrete Class P specification in their 28 day testing results Figure 6.6 demonstrates the rate gain of compressive strength for Phase II Figure 6 6 : Rate Gain of Compressive Strength for Phase II A compressive strength specimen failure from mixture #10 was shown in Figure 6.7 No brittle failure was found on all mixtures with tire chips incorporated. 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 3 day 14 day 28 day 0.4/660/100S/90R/10TC/P 0.4/660/100S/90R/10TC/V

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73 Figure 6 7 : Concrete Failure for Mixture #10 Modulus of Elasticity of Concrete in Compression, ASTM C 469 The modulus of elasticity (MOE) was used to inspect the response of the concrete to load. The stiffness of the concrete was measured during this test. The MOE was obtained by attaching a low voltage displacement transducer (LVDT) to a compressormeter. As the cylinder was tested in compressi on, the data acquisition system recorded the vertical displacement and the compressive strength. The setup is shown in Figure 6.9. The stress strain curve was plotted, and the elastic modulus in compression was calculated in accordance with ASTM C 469:

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74 Where: E= chord modulus of elasticity, psi ; = stress corresponding to 40% of ultimate load; = stress corresponding to a longitudinal strain of 50 millionths, psi; = longitudinal strain produced by stress ACI 318 gives the equation for calculating the modulus of elasticity. The comparison was made to examine whether the equation provided by ACI 318 was suitable for this particular rubberized concrete mixture design. The modulus of elasticity of 28 days for ea ch mixture i s shown in Figure 6 .8 Modulus of Elasticity, ACI 318 11 Section 8.5.1 Where, = Modulus of elasticity of concrete, psi = Concrete unit weight, = Concrete compressive strength, psi Figure 6 8 : MOE Test Results and MOE Calculated From ACI Equation 3840 3560 3670 3590 0 500 1000 1500 2000 2500 3000 3500 4000 4500 0.4/660/100S/90CA/10TC/LW 0.4/660/100S/90CA/10TC/HW Test results ACI Equation Unit: ksi

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75 Figure 6 9 : Modulus of Elasticity Test Setup

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76 CHAPTER VII CONCLUSIONS Results This thesis evaluated the performance of concrete using CDOT Class P pavement concrete modified with recycled tire chips as partial coarse aggregates. The requirement of CDOT Class P pavement concrete is attached in Appendix B. The replacement of coarse aggregates by using tire chips rang ed from 10 % to 100%. T he chemical admixture dosage varie d from the pre approved CDOT Class P concrete for the mixtures proportions with more than 20% coarse aggregates replacement. For the mixture with 10% replacement, the dosages of chemical admixture remained consistent with the pre approved mixture proportion. B oth phase I and II of this study showed that a ll mixtures with 10% replacement (#6, #7, #10, #11) met the requirement s of CDOT Class P pavement concrete All the hardened concrete property test results were obtained with the average of testing specimens. The precision for all tests were checked, and met the requirement of related ASTM standard. Thus the modified concrete proportion determined can be potentially used as concrete pavement and sidewalk s in Colorado. In service monitoring would be necessary and evaluated to examine the practical performance. In total, eleven concrete mixtures were design ed batched and tested for both fresh concrete properties and hardened concrete properties. Fresh concrete properties include slump, temperature, air content, and unit weight. Hardened concrete properties include compressive strength, splitting tensile strength, flexural strength, rapid chloride

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77 ion penetration, freeze/thaw durability (in phase I ), and c ompressive strengt h and modulus of elasticity (in phase II ) Summary of Fresh Concrete Properties Slump Slump increased as the recycled tire chips decreased. The concrete mixtures with replacement of coarse aggregate more than 10 % have low workability even with excessiv e low range water reducer (Plastocrete161). U s ing high range water reducer could effectively improve the slump ; however, rapid slump loss result ed in reduced workability allow ing less time to place the concrete. Air Content The air content of each mixture was tested by the pressure meter method and some mixtures were also tested by the roller meter. The air content varie d by using consistent amount s of AEA. Generally, the air content goes up with the increase of tire chips incorporated. However, a s ignificant discrepancy of the air content measured from the pressure meter and roller meter was observed for mixture #2 ( 0.4/660/100S/0R/100TC/P). Unit Weight The u nit weight s for all mixtures tested decreased as the tire chips particle content was increa sed. The unit weight decreased linearly regardless of the cement content. Temperature Temperatures for all of the concrete mixtures did not exceed the recommended range. Temperature is not considered as an important role in the behavior in the concrete for this study.

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78 Summary of Hardened Concrete Properties Compressive Strength The compressive strength decrease d as the tire chips particle content increase d Over 30% compressive strength loss was found with 10% replacement of coarse aggregate ; and more strength loss was observed with higher replacement of coarse aggregate. All the concrete mixtures with 660lb cementitious material per cubic yard and 10% tire chips by volume of coarse aggregate fulfill ed the requirement s of CDOT Class P pavement concrete at the age of 28 days. Mixtures with lower cementitious material incorporated had lower compressive strength. Splitting Tensile Strength It was observed that the splitting tensile strength of the mixtures with tire chips was lower than that of t he control mixture The splitting tensile strength decreased by more than 18% with a 10% replacement of coarse aggregate with tire chips. Flexural Strength The flexural strength of the concrete mixtures with tire chips incorporated was observed to be higher than the flexural strength of the control concrete mixtures. The flexural strength of the mixture with 10% replacement coarse aggregate using tire chips exceeded 900 psi at the age of 28 days. The failure of the beams were ductile instead of brittle failure as a control mixture. With the tire chips content increasing, the flexural strength decrease d Durability An obvious trend of the durability factor decreas ing, with increasing the tire chips content was observed Freezing and thawing durability tests showed excellent durability

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79 factor for the 10%. Mixture #2 ( 0.4/660/100S/0R/100TC/P ) failed to complete 300 cycles of the freeze/thaw test. After 72 cycles, the relative dynamic modulus of elasticity was lower than the ASTM specified minimum value. An increase in mass loss was observed with increased percentages of tire chips content. Rapid chloride ion penetration tests showed low to moderate classification on all the mixtures as discussed in chapter V. Mixtures with 10% replacement coarse aggreg ates and higher cementitious materials showed good permeability. Concrete mixtures with lower cementitious material content is not recommended. Modulus of Elasticity Modulus of e lasticity was tested only on the mixture with 10% coarse aggregate replaced by tire chips, which satisfied all CDOT Class P pavement concrete requirements. The modulus of elasticity could be well predicted by the equation provided by ACI 318 11. T he Effects Caused by Water Reducer Two mixtures with high range water reducer (Viscocrete 2100) and low range water reducer (Plastocrete 161), respectively, were examined for this thesis. High range water reducer increase d the slump and workability obviously. However, the slump loss was rapid and the concrete place time was less. F or a concrete pavement mixture, the recommended slump range is 1 to 3 inches, which could be obtained by increasing the dosage of low range water reducer. There was no significant difference in compressive strength or in modulus of elasticity between two m ixtures. The compressive strength gained faster from the age of 3 day s to the age of 14 day s for the mixture with low range water reducer. At the 28 days age, two mixtures ha d very similar strength.

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80 Recommendations F ollowing are the recommendations for designing CDOT Class P pavement concrete modified with tire chips: Tire chips can be used as partial replacement of coarse aggregate in concrete pavement mixtures. Mixture with 10% coarse aggregate replaced ( 0.4/660/100S/90R/10TC/P ) ha d the best performance among all the tire chips incorporated mixtures. The workability of all the mixtures was low. It is recommended to use low range water reducer and to adjust the dosage to improve the slump of rubberized concrete. Additional tests are recommended to evaluate the incorporation of fly ash to improve the slump of rubberized concrete. All mixtures with 570 lbs/cy yard cementitious materials demonstrated low strengths and stiffness. It is recommended to use 660 lbs/cy or more cementitiou s materials instead of reducing the cementitious materials amount.

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81 REFERENCES Aiello, Maria Antonietta, and F. Leuzzi. 2010. Waste Ti re R ubberized C oncrete: Properties at F resh and H ardened S tate. Waste M anagement 30 ( 8 ) :1696 1704. Amirkhanian, S. and D. Manugian 1994 Construction Proceedings, ASCE 3 rd Materials Engineering Conference, Infrastructure:New Materials and Methods of Repair : 919 927. Ayers, C. State Tire Dumps Deemed Hazardous. 2009. In 7NewsDenver (Sept. 30) Available from http://www.thedenverchannel.com/news/21154774/detail.html (a ccessed October 11, 2013 ) Colorado Annual Report to the Transportation Legislation Review Committee. Denver, Colorado. Available from http://www.colorado.gov /cs/Satellite?blobcol=urldata&blobheadername1=Conten t Disposition&blobheadername2=Content Type&blobheadervalue1=inline%3B+filename%3D%222011.pdf%22&blobhead ervalue2=application%2Fpdf&blobkey=id&blobtable=MungoBlobs&blobwhere= 1251811767545&ssbinary=true Ac cessed on Feb. 28, 2013 Eldin, N. N., and A. B. Senouci. 1993. Rubber tire P articles as C oncrete A ggregate. Journal of Materials in Civil Engineering 5 (4) : 478 496. Ellis, D., and P. Gandhi. 2009 Innovative U se of Recycled T i res in Civil Engineering Applications. Melbourne, Australia: Swinburne University of Technology. Environmental Protection Agency. 2011 U.S. Scrap Tire Management Summary 2005 2009, October 2011, Civil Engineering Markets Available from http://www.epa.gov/osw/conserve/materials/tires/civil_eng.htm (accessed February 15, 2014). Fedroff, D., S. Ahmad, and B. Z. Savas. 1996. Mechanical P roperties of C oncrete with G round W aste T ire R ubber. Transportation Research Record: Journal of the Transportation Research Board 1532 ( 1) : figure 6, p.69. Reproduced with permission of the Transportation Research Board. Gambhir, M. L. 2004. Concrete T echnology Tata McGraw Hill. Available from http://www.epa.gov/osw/conserve/materials/tires/civil_eng.htm#septic (accessed December 11, 2010). Goulias, Dimitrios G., and Ali Al Hosain 1997. Non destructive E valuation of R ubber M odified C oncrete. Infrastructure Condition Assessment : Art, Science, and Practice ASCE.

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82 Gneyisi, Erhan, 2004. Properties of R ubberized C oncretes C ontaining S ilica F ume. Cement and Concrete Research 34 ( 12 ) :2309 2317. Heitzman, Michael. 1992. Design and C onstruction of A sphalt P aving M aterials with C rumb R ubber M odifier 1339. Kaloush, K. E., G. B. Way, and H. Zhu. 2005. Properties of C rumb R ubber C oncrete. Transportation Research Record: Journal of the Transportation Research Board 1914 ( 1) : 8 14. Kardos, Adam John. 2011. Beneficial U se of C rumb R ubber in C oncrete M ixtures. Masters Abstracts International 50 ( 3 ) Khatib, Zaher K., and Fouad M. Bayomy. 1999. Rubberized Portland C ement C oncrete. Journal of M aterials in C ivil E ngineering 11 ( 3 ) :206 213. Kosmatka Steven H., and William C. Panarese. 2002. Design and C ontrol of C oncrete M ixtures 14 th ed. Portland Cement Association (February 1) Li, Z., F. Li, and J. S. L. Li. 1998. Properties of C oncrete I ncorporating R ubber Ti re P articles. Magazine of Concrete Research 50 ( 4 ) :297 304. Ling, Tung Chai. 2011. Prediction of D ensity and C ompressive S trength for R ubberized C oncrete B locks. Construction and Building Materials 25 ( 11 ) :4303 4306. Liu, Riu. 2013. Recycled Tires as Coarse Aggregate in Concrete Pavement Mixtures CDOT 2013 ( 10 ) Mehta, P. Kumar. 2002. Greening of the Concrete Industry for Sustainable Development. Concrete I nternational 23 Mindess, S., J. F. Young, and D. Darwin. 200 2 Concrete Second Edition. Prentice Hall. Available from http://www.amazon.com/Concrete 2nd Edition Sidney Mindess/dp/0130646326 Nehdi, Moncef, and Ashfaq Khan. 2001. Cementitious C omposites C ontaining R ecycled T ire R ubber: A n O verview of E ngineering P roperties and P otential A pplications. Cement Concrete and Aggregates 23 ( 1 ) :3 10. Portland Cement Association 2013 Designing Mixtures to Reduce Shrinkage Potential Available from http://www.cement.org/tech/basics_shrinkage.asp (a ccessed October 19, 2013 ) Rubber Manufacturers Association. 2009. Scrap T ire M arkets in the United States : 9 th Biennial Report. Washington, DC. Available from: http://www.rma.org/download/scrap tires/market reports/US_STMarkets2009.pdf (a c cessed April 11, 2014 ).

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83 Schimizze, Richard R. et al. 1994. Use of W aste R ubber in L ight duty C oncrete P avements. Infrastructure : New Materials and Methods of Repair ASCE. Siddique, Rafat, and Tarun R. Naik. 2004. Properties of C oncrete C ontaining S crap tire R ubber : A n O verview. Waste M anagement 24 ( 6 ) :563 569. Xi, Yunping et al. 2004. Utilization of S olid W astes ( W aste G lass and R ubber P articles) as A ggregates in C oncrete. International Workshop on Sustainable Development and Concrete Technology, Beijing, China Zhang, Bo, and Guangyu Li. 2012. The A brasion resistance I nvestigation of R ubberized C oncrete. Journal of Wuhan University of Technology Mater. Sci. Ed. 27 ( 6 ) :1144 1148.

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