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Beneficial use of crumb rubber in concrete mixtures

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Title:
Beneficial use of crumb rubber in concrete mixtures
Creator:
Kardos, Adam John
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Language:
English
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xviii, 190 leaves : illustrations (some color) ; 28 cm

Subjects

Subjects / Keywords:
Crumb rubber ( lcsh )
Concrete -- Mixing ( lcsh )
Pavements, Concrete ( lcsh )
Concrete -- Mixing ( fast )
Crumb rubber ( fast )
Pavements, Concrete ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references (leaves 187-190).
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Adam John Kardos.

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Source Institution:
|University of Colorado Denver
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|Auraria Library
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All applicable rights reserved by the source institution and holding location.
Resource Identifier:
783862589 ( OCLC )
ocn783862589
Classification:
LD1193.E53 2011X K37 ( lcc )

Full Text
BENEFICIAL USE OF CRUMB RUBBER
IN CONCRETE MIXTURES
by
Adam John Kardos
B.S., Civil Engineering, University of Akron, 2007
A thesis submitted to the
University of Colorado Denver
in partial fulfillment
of the requirements for the degree of
Master of Science, Civil Engineering
2011


Copyright 2011 by Adam J. Kardos
All rights reserved.


This thesis for the Master of Science
degree by
Adam J. Kardos
has been approved
by
Cheng Yu Li
Date


Kardos, Adam John (MS, Structural, Civil Engineering Department)
Beneficial Use of Crumb Rubber in Concrete Mixtures
Thesis directed by Dr. Stephan A. Durham
ABSTRACT
The primary objective of this study was to develop a sustainable concrete mixture for
pavement applications that incorporated waste-stream materials such as fly ash,
crumb rubber "recycled tires, and recycled concrete aggregate. Fresh and hardened
concrete properties were measured on mixtures containing 15 percent cement
replacement with fly ash and sand volume replacements with crumb rubber of 10, 20,
30, 40, and 50 percent. The effects of the crumb rubber inclusion were determined by
comparing mixtures containing the crumb rubber to a control mixture with only sand
as the fine aggregate. Recycled concrete aggregate was included as a 50 percent
coarse aggregate replacement in two mixtures containing 20 and 30 percent crumb
rubber content. The mixtures were tested, by the standards and procedures set by
ASTM, for fresh concrete properties including slump, air content, unit weight and
temperature and hardened concrete properties including compressive strength, split-
tension strength, modulus of rupture, modulus of elasticity, permeability and
freeze/thaw durability.
As the crumb rubber content increased the compressive strength, split-tension,
modulus of rupture, and modulus of elasticity decreased. Freeze-thaw durability
increased, compared to the control specimen, with the 10 percent replacement of fines
for recycled waste tire particles. The results of this study determined that a 30


percent replacement of sand with crumb rubber was optimum and produced the
necessary fresh and hardened concrete properties for concrete pavement.
This abstract accurately represents the content of the candidates thesis. 1 recommend
its publication.
Stephan A. Durham


DEDICATION PAGE
I dedicate this thesis to the person who has believed in me the most. Through her
unending love and encouragement, she has supported me over the many years of my
educational pursuits, my wife of 15 years, Mrs. Jessica A. Kardos, MBA.


ACKNOWLEDGMENT
I sincerely thank my academic advisor, Dr. Stephan A. Durham for recognizing my
potential and rewarding me with the amazing opportunity to complete the Advanced
Technology Grant Program he was awarded to study the Beneficial Use of Waste
Tires for Concrete Production in Colorado. His continual advisement has guided me
to a very good understanding in structural concrete applications. In addition, I would
like to thank Dr. Kevin Rens and Dr. Cheng Yu Li for participating on my thesis
committee.
Thank you to the Colorado Department of Health and Environment for the
interest in funding this study. Other individuals that helped with this endeavor
through technical support, equipment creation, repair and use are: Tom Thuis,
Edward Moss, Randy Ray, Logan Young, M.S., Devin Eldridge, Dr. Nien Chang, Dr.
Rui Liu, Andrea Soils, M.S. and Robert W. Cavaliero, M.S.
Thank you to all those individuals and their associated companies provided
materials for the completion of the study are as follows: Jesse Dortch (Bestway
Concrete), Brandon Cook (BASF), Richard Cookson (Caliber Recycled Products),
Brooke A Smartz and Kevin Kane (Holcim Inc.), David Neel (Boral Material
Technologies), Gary Hansen (Allied Recycled Aggregates) and Dr. Angela Hagar
(City of Denver). Additionally, I would like to thank the faculty and staff of the
University of Colorado at Denver, Civil Engineering Department for their support and
guidance throughout my educational career at UCD.


TABLE OF CONTENTS
Figures.................................................................xiv
Table..................................................................xvii
Chapter
1. Introduction.....................................................1
1.1 Use of Waste-Stream Materials in Concrete........................1
1.2 Study Objective for Waste Tires in Concrete......................2
1.3 Application of Waste Tires in Concrete Study Objective
for Waste Tires in Concrete...................................4
1.4 Summary of Thesis Components.....................................5
2. Background.......................................................7
2.1 History of Recycled Waste Tire...................................7
3. Literature Review...............................................10
3.1 Preface.........................................................10
3.2 Uses of Crumb Rubber............................................10
3.3 Properties of Recycled Tires Used in Rubberized Concrete........12
3.4 Development of Mixture Designs for Rubberized Concrete..........19
3.5 Fresh Concrete Properties of Rubberized Concrete................22
3.6 Hardened Rubberized Concrete Strength Properties................27
4. Problem Statement...............................................38
viii


.38
.41
.41
.41
.42
.43
.43
.44
.44
.45
.48
.49
.53
.54
.55
.56
.57
.58
Problem Statement
Concrete Materials.....................................
Purpose of this Research Study.........................
Aggregates Required for Concrete Pavement..............
Physical Properties for Virgin Aggregates..............
Gradation for Virgin Aggregates........................
Specific Gravity for Virgin Aggregates.................
Absorption Capacity for Virgin Aggregates..............
Recycled Aggregates....................................
Sieve Analysis for Coarse Recycled Concrete Aggregate..
Specific Gravity for Coarse Recycled Concrete Aggregate ...
Sieve Analysis for Recycled Tire Particles and Virgin
Fine Aggregates.....................................
Specific Gravity for Recycled Waste Tire Particles.....
Recycled Waste Tire Specific Gravity Experimental
Testing Investigation...............................
Recycled Waste Tire Specific Gravity Experimental Testing
Recycled Waste Tire Specific Gravity Experimental
Testing Results.....................................
Terminology for Recycled Waste Tire Particles..........
Chemical Admixtures....................................
IX


.59
.62
.64
.64
.64
.65
.66
.66
.68
.69
.69
.70
.71
.72
.74
.74
.76
.76
,77
,77
Type I-II Portland Cement............................
Fly Ash.............................................
Experimental Design.................................
Design Plan.........................................
Batching of Concrete Mixtures.......................
Batching Procedure for Each Mixture.................
Preparation the Day Before Batching Concrete Mixtures
Mixing Process......................................
Curing Concrete Specimens...........................
Testing for Concrete Properties.....................
Fresh Concrete Property Tests.......................
Hardened Concrete Property Test.....................
Mixture Design Proportioning........................
Trial Proportioned Research Mixtures................
Mixture Design Identification.......................
Research Mixture Design.............................
Data Analysis.......................................
Design Summary......................................
Experimental Results................................
Batching of Trial Mixtures..........................
x


7.2 Fresh Concrete Properties........................................79
7.3 Compressive Strength of Trial Mixtures...........................81
7.4 Non-Contributing Factors in Concrete Performance.................85
7.5 Batching of Research Design Batches..............................85
7.6 Chemical Admixtures..............................................88
7.7 Testing of Fresh Concrete Properties.............................88
7.8 Slump of Hydraulic-Cement Concrete, ASTM C-143...................88
7.9 Air Content of Freshly Mixed Concrete,
ASTM C-231 and C-173.........................................91
7.10 Unit Weight, ASTM C-l 38.........................................94
7.11 Temperature of Freshly Mixed Hydraulic-Cement
Concrete, ASTM C-l064........................................98
7.12 Hardened Concrete Tests.........................................100
7.13 Compressive Strength of Cylindrical Concrete
Specimens, ASTM C-39........................................101
7.14 Evaluation of the Modulus of Elasticity,
(MOE), (ASTM C-469).........................................114
7.15 Flexural Strength or Modulus of Rupture-
(MOR), (ASTM C-78)..........................................116
7.16 Indirect-Splitting Tensile Test, (ASTM C-496)...................120
7.17 Rapid Chloride Ion Penetrability Results, (ASTM C-l202).........124
7.18 Freeze and Thaw Durability, (ASTM C-666)........................131
xi


144
150
150
151
152
154
155
155
156
156
156
157
157
157
157
158
159
159
Leaching Test, Beneficial Use of Industrial
Byproducts, (ASTM D-3987)........................
Future Work..........................................
Alley Panel..........................................
Mixture Design for Alley Panel.......................
Application of Alley Panel Mixture Design............
Application Summary for an Alley Panel Field Placement
Conclusions and Recommendations......................
Summary of Results...................................
Summary of Fresh Concrete Properties.................
Slump................................................
Air Content..........................................
Unit Weight..........................................
Temperature..........................................
Hardened Concrete Properties.........................
Summary of Strength Tests............................
Summary of Durability Tests..........................
Summary of Leachate Results..........................
Recommendation Summary...............................
Xll


Appendix
A. Product Data...................................................161
B. Concrete Mixtures..............................................171
C. Data Logs......................................................182
Bibliography............................................................187
xiii


LIST OF FIGURES
Figure
3-1 Refinement Sizes of Recycle Tires [Eldin, et al., 1993]..........11
3-2 Gradation Curves for Crumb Rubber, Coarse and
Fine Aggregate [Gesoglu, et al., 2007]......................16
3-3 Slump of Plain and Rubberized Concrete
[Gesoglu. et al., 2007].....................................21
3-4 Unit weight of plain and rubberized Concretes w/and
w/o silica fume [Gesoglu, et al., 2007].....................21
3-5 Compressive Strength Development of Plain and
Rubberized Concrete with and without Silica Fume
[Gesoglu, et al., 2007].....................................22
5-1 ASTM C-33 Grading Limits and
Values for Coarse Aggregates................................47
5-2 Acquired Crumb Rubber Sample.....................................50
5-3 ASTM C-33 Grading Limits for Fine Aggregates...................52
7-1 Compressive Strength for Trial Batches...........................83
7-2(a-c) Trial Mixtures..................................................84
7-3 Slump Test Results (ASTM C-143)..................................90
7-4 Air Content, ASTM C-231 and C-173................................93
7-5 Unit Weight, (ASTM C-138)........................................97
7-6 Concrete Temperatures, (ASTM C-1064).............................99
7-7 Actual and Normalized Compressive Strength......................103
XIV


105
106
109
110
113
113
114
115
117
119
121
122
123
124
125
126
127
129
133
136
% Strength Loss of Mixtures to the Control
% Strength Loss of Mixtures to the Control
Rate Gain of Actual Compressive Strength.
Rate Gain of Normalized Compressive Strength................
Residual Strength Characteristic............................
Compressive Failure of CR Concrete Cylinder.................
Modulus of Elasticity Test..................................
Modulus of Elasticity Test Results..........................
Modulus of Rupture, (MOR) Test Setup........................
Flexural Strength Test Results..............................
Indirect-Splitting Tensile Test Results.....................
Indirect-Splitting Tensile Test.............................
Indirect-Splitting Tensile Test Failure Curve...............
Indirect-Splitting Tensile Test Specimen Failure............
Vacuum Desiccator...........................................
RCIP Cell Preparation.......................................
Calculations for Solution Concentrations....................
Rapid Chloride Ion Penetrability Test Results...............
Materials Testing Laboratory, Rapid Freeze/Thaw Cabinet
Relative Dynamic Modulus of Elasticity Test.................
xv


7-27 Relative Dynamic Modulus of Elasticity and
Durability Factor, (ASTM C-666)...............................138
7-28 Durability Factor vs. Cycle Count..................................139
7-29 % Mass Loss vs. Cycle Count........................................142
7-30 Mix #1 Freeze/Thaw Beam after 324 freeze/thaw cycles..........143
7-31 Mix #6 Freeze/Thaw Beam after 324 freeze/thaw cycles..........144
7-32 TCLP Test Results for Volatile Organics............................148
7- 33 TCLP Test Results for Inorganics ..................................149
8- 1 Mixture Proportions for Crumb Rubber Concrete Alley Panel..........151
8-2 Performance tests for Fresh and Hardened Concrete Properties.......152
8-3 Typical Alley Cross-Section for the City and County of Denver......153
xvi


.20
.35
.42
.44
.46
.51
.53
.58
.58
.59
.60
.61
,62
.63
.63
.70
LIST OF TABLES
Refinement Sizes of Recycle Tires [Eldin, et al., 1993]..
Proportions of Concrete Mixtures in Combination
with Silica Fume and Rubber [Gesoglu, et al., 2007]
Physical Properties for Virgin Aggregates............
Physical Properties for Recycled Aggregates..........
ASTM C-33 Grading Limits and
Values for Coarse Aggregates.....................
ASTM C-33 Grading Limits and
Values for Fine Aggregates.......................
Fineness Modulus for Fine Aggregates.................
ASTM D-6270 Terminology for
Recycled Waste Tire Particles....................
BASF Air-Entraining Admixture........................
BASF Water-Reducing Admixture........................
Physical Properties for Portland Cement..............
Chemical Properties for Portland Cement..............
Identity Information for Class F Fly Ash.............
Physical Properties for Boral Class F Fly Ash........
Chemical Properties for Boral Class F Fly Ash........
Fresh Concrete Properties Tests......................
XVII


6-2 Hardened Concrete Properties Tests.................................71
6-3 Trial Mixture Designs (Fly Ash and w/cm Optimization)..............73
6- 4 Research Mixture Designs for Optimization..........................75
7- 1 Trial Mixture Proportions..........................................78
7-2 Batching and Testing Schedule for the Trial Mixtures...............79
7-3 Fresh Concrete Test Results with
Chemical Admixtures Dosages...................................80
7-4 Compressive Strength Results for Trial Batches.....................81
7-5 Research Design Mixture Proportions................................86
7-6 Batching and Testing Schedule for the Trial Mixtures...............87
7-7 Tolerance Times for Hardened Concrete
Tests, ASTM C-39..............................................87
7-8 Dosage Rates for Each Design Mixture...............................88
7-9 Actual Compressive Strength ......................................102
7-10 Normalized Compressive Strength ..................................102
7-11 Permeability Rating for Coulombs Passed...........................127
7-12 Rapid Chloride Ion Penetrability Results for Design Mixtures......128
7-13 Results for (Pc %) Relative Dynamic Modulus of Elasticity.........137
7-14 Durability Factors for Test Specimens, DF.........................139
7-15 Measureable Inorganics Values.....................................146
xviii


Chapter 1
Introduction
1.1 Use of Waste-Stream Materials in Concrete
Incorporating waste-stream materials, such as recycled tires, concrete aggregates, and
fly ash into concrete infrastructure can provide quantifiable environmental life-cycle
impact and direct cost reductions when compared with ordinary portland cement
concrete. The primary environmental savings comes from the avoided impacts of
cement manufacturing, disposal of waste tires and concrete debris in landfills, and
reduced transportation distance. The economic benefits of fly ash are evident; either
the material is disposed of at a cost or sold for an economic gain. However, the
economics of recycled aggregates (recycled waste tire and recycled concrete
aggregate) are not found in direct costs, but in the reduced transportation costs due to
the lesser distance from source to placement. Tire recycling facilities are located in
the Denver Metropolitan area. In addition, if the concrete containing the waste-
stream materials provides more durable infrastructure (i.e., longer service life), the
environmental and economic impacts increase proportionally.
In the early 1990s, recycled waste tire particles/crumb rubbers (CR) usage
expanded into a relatively new product called rubberized concrete [Ellis, et al., 2009],
[Kaloush, et al., 2005]. Rubberized concrete uses portland cement as its binder, just
1


as hot asphalt is used as the binder in asphalt concrete pavements [Kaloush, et al.,
2005], Research has shown that rubberized concrete has a very positive outlook for
inception into select markets such as surface pavement applications.
A 2009 report by Ayers and the Colorado Channel 7 News stated that
Colorado has approximately 45 million disposed tires stockpiled [Ayers, 2009]. This
amount is staggering considering there are about 135 million disposed tires stockpiled
in the United States. With such a large quantity of tires stored in Colorado compared
to other states, research is warranted to examine alternative uses for recycled tire
waste.
1.2 Study Objective for Waste Tires in Concrete
This thesis examined the reuse potential of crumb rubber recycled tires in concrete
production in Colorado. Specifically, the effects of low and high volume sand
replacement with crumb rubber on concrete properties were determined. The sand
component within concrete was replaced in 10% increments up to 50% (replacement
rates of 10, 20, 30, 40 and 50% crumb rubber). The concrete compressive strength,
split-tension strength, flexural strength, modulus of elasticity, permeability, and
freeze/thaw durability were tested in order to determine an optimum sand
replacement with crumb rubber. In addition, leaching tests were performed on the
crumb rubber concrete to determine whether any hazardous materials were leached
2


from the material. The objective of this thesis was to determine the maximum
amount of sand replacement with crumb rubber in concrete mixtures without
compromising the structural integrity of the concrete. Once a maximum replacement
rate was determined, additional mixtures were evaluated that incorporate partial
replacement of the cement, rock, and sand with fly ash, recycled concrete aggregate,
and crumb rubber respectively. This research will provide the necessary information
to determine the beneficial use of recycled tires in concrete construction in Colorado.
The primary objectives of this research study are to:
Examine the effects of increasing the sand replacement percentage with
recycled crumb rubber on concrete compressive strength, split-tension
strength, flexural strength, modulus of elasticity, permeability and freeze/thaw
resistance, and determine an optimum replacement percentage of sand with
recycled crumb rubber for concrete mixtures.
Develop a concrete mixture that incorporates waste-stream materials as partial
replacements for cement, rock and sand.
Provide recommendations for the use of crumb rubber as a fine aggregate
replacement in a concrete mixture designed for field implementation.
The primary differences between this study and past research include:
3


Replacement of sand with crumb rubber based on volume. The specific
gravity of sand is more than twice that of crumb rubber. Past research has
used a weight basis: 50 lb of sand for 50 lb of crumb rubber. In this example,
the 50 lb of crumb rubber would consume twice the volume of the sand within
the concrete mixture.
Crumb rubber with a smaller particle size (approximately 0.3mm) was used in
this study as opposed to past research where the particle sizes were greater
than 1mm.
Testing of crumb rubber concrete mixtures for fresh concrete properties
(slump, air content and unit weight). The slump measurement provides
information as to the workability (or placeability) of the concrete mixture.
Past research does not report this information.
Testing of the crumb rubber concrete for permeability. The permeability of
crumb rubber concrete has not been documented.
1.3 Application of Waste Tires in Colorado Concrete
If recycled waste tire particles are found to provide a viable material substitution in
the concrete matrix, Colorado will be provided with an alternative means in reducing
the number of tires destined for mono-landfills. An optimal concrete mixture will be
4


determined from laboratory experiments, and a concrete alley panel will be
constructed for the City and County of Denver.
1.4 Summary of Thesis Components
This thesis contains nine chapters and summarizes the use of crumb rubber as a fine
aggregate replacement in concrete mixtures. In addition, other waste-stream
materials such as fly ash and recycled concrete aggregate were utilized in mixtures to
produce a sustainable concrete mixture. The following sections, Chapter 2 consists of
a background investigation on the first applications of crumb rubber concrete in
Colorado and other regions. Chapter 3 begins by introducing crumb rubber and goes
in to a detailed investigation of past studies involving recycled waste tire particles and
concrete. Then Chapter 4 and 5 get in to the meat of the study. Chapter 4 issues the
problem statement at hand and leads into Chapter 5 to discuss the details on the
specifics on the relevance and importance of the crumb rubber concrete research.
Chapter 6 is where the knowledge gained was used to build a design plan. That
design plan will justify the results obtained from the experimental results that are
found in Chapter 7. Chapter 7 discloses the results of the characteristics learn from
various concrete tests that are by industry. Finally, Chapter 8 and 9 cover an
5


application using the conclusions found in Chapter 9. A mock plan was discussed for
crumb rubber concrete alley panel install and a discussion on some items of concern
that would need to be observed in the process.
6


Chapter 2
Background
2.1 History of Recycled Waste Tire
Disposed tires have been recycled or used in various ways for several decades. The
need to discover more ways to utilize disposed tires is more important than ever
because of the growing number of used tire stockpiles in the US. The State of
Colorado has concerns that have recently led to initiatives to fund the development of
new technologies to utilize recycle waste tires to slow the growth of these stockpiles.
Senate Bill 07-182 transferred administrative authority for the Advanced Technology
Fund from the Colorado Commission on Higher Education to the board. In addition,
the Committee makes recommendations to the board regarding the Advanced
Technology Fund Grants. The Colorado Department of Public Health and
Environments Office of Environmental Integration & Sustainability is continually
refining its recycling strategies to improve upon the disposal of materials that have a
marketable use (The Colorado Department of Public Health and Environment, 2010).
The passing of Bill 07-1288 has resulted in an award from the Advanced Technology
Grant (ATG) Program to fund a project entitled: Beneficial Use of Waste Tires for
Concrete Production in Colorado to the University of Colorado Denver.
7


Across the US, there have been several pilot programs that have used
rubberized concrete in small applications. For example, in Colorados neighboring
state, Arizona, Arizona State University (ASU) Tempe Campus has become one of
the national leaders in research involving the use of recycled tires in concrete
mixtures. Since 1999, a wave of pioneering efforts to build rubber concrete test sites
in Arizona was undertaken by ASU, Arizona Department of Transportation (ADOT),
the Arizona Department of Environmental Quality and local concrete and tire
recycling industries [Siddique, et al., 2004], In February 1999, rubber concrete was
placed for a section of sidewalk on the campus of ASU; the CR content was 40 Ib/cy
(23.73 kg/m3) of concrete. In May 2001, the ADOT Materials Group constructed a
section of parking lot in its Phoenix Division site with a design of 50 lb/cy (29.66
kg/m3) of CR at which time a routine amount of sampling and testing was performed.
The compressive strengths of cored samples were as high as 3,260 psi (22.48 MPa).
In June 2001, a wheelchair ramp on the ASU campus was constructed and had a
design of 20 lb/cy (11.87 kg/m3) of CR. In March 2002, a resident of Mesa, Arizona,
had the contractor place his patio foundation with rubber concrete consisting of 20
lb/cy (11.87 kg/m3) of CR of concrete. In March 2003, Kaloush experimented with
the use of rubber contents of 25 lb/cy (14.83 kg/m3) for a sidewalk at his home in
Scottsdale, Arizona [Kaloush, et al., 2005].
8


In 2004, Dr. VilemPetr, a professor from the Colorado School of Mines,
worked with Denver's Regional Transportation District (RTD) on a pilot project to
implement sections of curbs and gutters made with rubberized concrete at select RTD
Park N Ride locations [Carder, 2004].
Colorado is following in Arizonas footsteps as a result of House Bill 07-
1288, also known as the Recycling Resources Economic Opportunity Act, which was
signed into law on May 23, 2007 by Governor Bill Ritter. Following the passing of
the law, a 13-member Assistance Committee was established to advise the Pollution
Prevention Advisory Board in connection with the awarding of grants, loans and
rebates from the Recycling Resources Economic Opportunity (RREO) Fund.
9


Chapter 3
Literature Review
3.1 Preface
This literature review investigates the past uses and effects of recycled waste tires
used in concrete mixture design. Environmental concerns are discussed herein only
to emphasize its importance in the practice of using waste tire products in an
advantageous manner for the public's best interests. This review covers the various
topics researchers have investigated and the rubberized concrete trends that have been
discovered that has facilitated the current utilization of rubber tire chips/CR in civil
engineering applications.
3.2 Uses of Crumb Rubber
Disposed tires have been recycled or used in various ways for several decades. The
need to discover more ways to utilize disposed tires is more important than ever
because of the growing number of used tire stockpiles in the US.
New uses for disposed tires have brought about various refinements or
derivatives that are used in a variety of applications. Oftentimes, these recycled
waste tire refinements are a localized matter and are not always easily accessible for
industry use. The civil engineering industry has made a large contribution to this
10


effort by providing a means of using old tires in various refinements. Figure-3-1
illustrates the various sizes of crumb/shredded rubber.
Figure 3-1 Refinement Sizes of Recycle Tires [Eldin, et al., 1993]
In 2007, approximately 12 percent of the disposed tires used as
crumb/shredded rubber were used in civil engineering projects such as filtration
systems for water treatment, speed bumps, road base or fill for highway projects and
modified asphalt concrete pavement [Rubber Manufacturers Association, 2009]. In
the early 1990s, shredded tires/crumb rubbers usage expanded into a relatively new


product called rubberized concrete [Ellis, et al., 2009], [Kaloush, et al., 2005],
Rubberized concrete uses portland cement as its binder, just as hot asphalt is used as
the binder in asphalt concrete pavements [Kaloush, et al., 2005], Since the
conception of this new product, early research like that completed at the Hong Kong
University of Science and Technology, suggests that rubberized concrete mixtures
might be suitable for applications such as driveways, sidewalks or road constructions
where strength is not a high priority but greater toughness is preferred [Li, et al.,
1998], Such research has shown that rubberized concrete has a very positive outlook
for inception into select markets such as surface pavement applications as listed in the
above reference.
3.3 Properties of Recycled Tires Used in Rubberized Concrete
The recycled waste tire market for a particular region has typically defined the rubber
particle size used in past research projects. Early research was completed primarily
using shredded rubber particles because of the availability of the material. The crumb
rubber industry has broadened the range of available products to service a broader
market. Recent research had used the recycled waste tire particles in mixture designs
for rubberized concrete, but very little data on the usage of recycled waste tire
particles smaller than one millimeter has been completed. As refinement practices
are changed and modified for the production of recycled tire products to supply the
12


consumer markets, the availability of a broader range of particles sizes will be
available to further refine the science of rubberized concrete.
The use of shredded tires has increased since the Environmental Protection
Agency (EPA) has endorsed the use of recycled waste tires for public use since the
early 1990s. Recently, a memorandum (8P-P3T) was released by the Colorado EPA
Region 8 to address public concern as to "Potential Risks of Tire Crumb in regard to
the health risks to children. Research into the potential hazard from recycled tire
products is ongoing with each new application. However, there are concerns
remaining with the use of recycled tires. Disposed tires are known to leach a variety
of toxic elements and chemical compounds. Each brand of tire represents a unique
chemical composition. Some tires have been sitting in stockpiles for over 40 years
and the tires antidegradants are insufficient to stabilize the tire compounds resulting
in leachate from the tire rubber. However, the hazardous metals semi-volatile organic
compounds (s-VOC) and volatile organic compounds (VOCs) are known and
identified with every type of tire. This case study, like many others using waste tire
derived products, is used to evaluate whether or not a potential public health hazard
exists. In one particular case, public concern was expressed that the recycled waste
tire pieces that were used on the surfaces of children's playgrounds would adversely
affect their health. The California Office of Environmental Health Hazard
Assessment (OEHHA) completed a study based off an existing evaluation of the
13


toxicity of tire shreds literature. Californias website includes a detailed toxicology
report and potential health hazards associated with recycled waste tires[OEHHA,
2007]. Despite the consequences, a detailed investigation or an environmental impact
study should be conducted to determine potential impacts recycled tire surface-
pavements could have on the local ecology. OEHHA found 46 studies in scientific
literature that measured the release of chemicals by recycled tires in laboratory
settings and in field studies where recycled tires were used in civil engineering
applications and 49 chemicals were identified, 145 metals-tzinc, iron, manganese,
barium, lead, chromium (3) and (6), cadmium, copper, aluminum, antimony, mercury,
nickel, arsenic, selenium and cobalt)], [20_VOC-(polycyclic aromatic hydrocarbons,
aromatic nitrogen-containing, total petroleum hydrocarbons, methyl isobutyl ketone,
2-methyl naphthalene, acetone, toluene and benzene)] and [14 s-VOCs -(five different
benzothiazole, aniline, phenol, 4-(phenylamino)-phenol, phenoxazine and 2(3H)-
benzothiazolone)] -benzothiazole contaminants have been proposed as environmental
markers for tire-derived material [Kumata, 2002],
A research study completed by C.E. Pierce using CR as a lightweight
aggregate in flowable fill stated that, UASTM D 6270-98 specifies that applications
involving tire shreds should be confined to locations above the water table until it is
determined that these detectable levels are not a threat to human health [Pierce, et al.,
2002]. Incidentally, a recent study on leachate from recycled waste tire similarly
14


showed no deleterious effects to the environment [Groenevelt, et al., 1998], [Reddy,
et al., 1997]. In fact, research has shown that scrap tire rubber can absorb and retain
volatile organic compounds (VOCs) [Al-Tabbaa, et al., 1998], [Pierce, et al., 2002],
The performance of any concrete mixture is affected by the constituents that
are combined to make up the final product. Rubberized concrete has been tested with
the typical components used in traditional concrete mixtures, but with portions of the
coarse and fine aggregates substituted with recycled waste tire particles of various
sizes. Replacement quantities (1-100% by volume) and particle sizes (passing a
#40/retained on #60 sieve to cut strips of tire 3in (76mm) long) have been used to
replace the natural aggregates normally used in concrete [Pierce, et al., 2002;
Guoqiang, et al., 2004], Crumb rubber consists of particles ranging in size from
4.75mm (4 mesh) to 0.60mm (30 mesh) and lastly is powdered recycled waste tire
where particles of maximum size 0.50mm (35 mesh) but less than 0.075mm (200
mesh) [Siddique, et al., 2004]. The majority of markets define ground tire particles
passing #30 sieve as crumb rubber [Siddique, et al., 2004], Figure 3-2 shows the
gradations of recycled waste tire particles that are commonly produced and readily
available [Gesoglu, et al., 2007], Typically, shredded <0.19in (<4.75mm), is
considered a rubber tire chip product. All research that was reviewed had replaced
some portion of either fine or coarse aggregate, or both, with rubber tire chips/CR for
use in concrete mixtures. Special considerations in the concrete mixture design must
15


be taken since the specific gravity (SG) of natural aggregates is more than twice that
of recycled waste tire particles. Crumb rubber can be considered a lightweight
aggregate source due to its low specific gravity [Pierce, et al., 2002],
Figure 3-2 Gradation Curves for Crumb Rubber, Coarse and Fine Aggregate
[Gesoglu, et ah, 2007]
The use of rubber tire chips was the choice material size in the majority of
past research projects. The rubber chip size was typically greater than 0.19in
(4.75mm) and with a reported specific gravity between 1.12-1.16 [Siddique, et ah,
2004], [Ellis, et ah, 2009], A paper published in a 2009 edition of the ACI Materials
16


Journal, reported crumb rubber as having a specific gravity approximately 0.83-1.20,
which is significantly lower than the aforementioned values [Wong, et al., 2009], It is
believed that the presence of steel tire cord in the rubber tire chips would be the
potential cause of higher specific gravity values than that of the recycled waste or
variations in the type of tires that were refined and then sampled. Another
noteworthy consideration in determining the specific gravity for recycled waste tire
particles is that two different ASTMs have been used to determine the SG of recycled
waste tire particles. The standards used for coarse and fine aggregates were ASTM C-
128 and ASTM C-127 respectively. These two standards were used in all literature
involving rubberized concrete research. The other standard was ASTM D-854. The
ASTMD-854 is a standard primarily used in geotechnical research involving recycled
waste tire applications to stabilize soil. Determining an accurate SG makes a
significant difference in the yield of a mixture when a weighted portion of natural
aggregate is substituted with an equal weight of recycled waste tire, as does the size
of the recycled waste tire particles.
17


In summary, studies have shown the following trends for properties of recycled tires
used in rubberized concrete:
Determining an accurate specific gravity makes a significant difference in the
yield of a mixture when a weighted portion of natural aggregate is substituted
with an equal weight of recycled waste tire
Rubber tire chips particles have an approximate specific gravity between 1.12-
1.16 [Siddique, et al 2004], [Ellis, et al 2009]
Crumb rubber particles have an approximate specific gravity between 0.83-
1.20 [Wong, et al 2009]
Crumb rubber particles are nearly void of steel tire cord
Rubber tire chips particles likely have steel tire cord
Rubber chip size was typically greater than 0.19in (4.75mm)
Crumb rubber particles range in size from #4 US Sieve to #30 US Sieve
(4.75mm to 0.60mm)
Powdered recycled waste tires have particles of maximum size #35 US
Sieve(0.50mm) but less than #200 US Sieve (0.075 mm)
Field studies where recycled tires were used in civil engineering applications
had identified 49 chemicals, [15 metals-(zinc, iron, manganese, barium,
lead, chromium (3) and (6), cadmium, copper, aluminum, antimony, mercury,
18


nickel arsenic, selenium and cobalt)], [20_VOC-(polycyclic aromatic
hydrocarbons, aromatic nitrogen-containing, total petroleum hydrocarbons,
methyl isobutyl ketone, 2-methyl naphthalene, acetone, toluene and benzene)]
and [14 s-VOCs -(five different benzothiazoles, aniline, phenol, 4-
(phenylamino)-phenol, phenoxazine and 2(3H)-benzothiazolone)]
benzothiazole contaminants have been proposed as environmental markers for
tire-derived material [Kumata, 2002]
Recycled tire rubber is a weak aggregate regardless of size, but provides
unique mechanical properties in concrete mixtures
3.4 Development of Mixture Designs for Rubberized Concrete
Provided below is a mixture design and the results of the fresh and hardened concrete
properties tests from the [Gesoglu, et a!.] study on the Strength Development and
Chloride Penetration in Rubberized Concretes with and without Silica Fume. These
results represent a majority of the trends discovered in research and will aid in the
discussion ahead involving rubber tire particulates being placed in concrete mixtures.
Table 3-1 provides the mixture characteristics of the rubberized concrete mixtures
examined in the Gesoglu study. Table 3-1 lists the mixture designs when both silica
fume and rubber were utilized.
19


Table 3-1 Proportions of Concrete Mixtures in Combination with Silica Fume
and Rubber [Gesoglu, et al., 2007]
(\mcrcic v\/cm (Ytncnl Silica Silica Water Su]\Tj>lasnct/cr (ra\cl SjikI Ktihbcr Crumh Tiro
cries ratio tk$:/m 1 Iiiiik* fume tkj:/ ik^r/ ikp' conienl uiNvr chips
l'i ik£/m> m i in i m l C 400 n 0 inn 12 >44 OOO 0 0 0
Will 10 40 INI 12 0 t7 N04 0 0 0
4 on 0 0 ion 12 SOO XV5 5 14 4 17 7
inn 10 40 loo 12 SJO X40 > 14 5 17.0
400 0 o loo 12 xo2 705 15 41 2 54|
inn 10 10 inn 12 707 TOO 15 42 0 S2 7
400 0 o INI 12 70S 075 25 72 XX. 5
ton 10 40 inn 12 701 070 25 71 5 87.0
ton 0 0 iso 4.5 oox 025 0 0 0
27U to 40 ISO 4 5 4 oto 0 0 0
ton 0 0 ISO 4 5 *>2o X77 5 14 X ix 2
:7n IO to ISO 4 5 01 s 875 5 14 7 IX 1
ton 0 0 ISO 4.5 S2t 7X5 15 44.5 54,5
270 10 to ISO 4 5 xio 7X1 15 44 1 54 2
ton 0 o ISO 4 5 72n oo2 25 74 X 00 X
27n 10 to ISO 4 5 725 oxo 25 75.5 00.4
Figure 3-3 illustrates the affect crumb rubber has on the workability, or slump
of the concrete mixture. The workability of the concrete mixture decreased as the
rubber content increased from 0 to 25% of the total aggregate volume. As shown in
Figure 3-4, the unit weight of the rubberized concrete decreased with increasing
rubber contents. This was expected since the weight of the rubber was less than that
of the fine or coarse aggregate that it replaced.
20


Rubber content by total aggregate volume (%)
Figure 3-3 Slump of Plain and Rubberized Concrete [Gesoglu, et al., 2007]
2400
S> 2200
5.
I
Z 2000
5
1800
1600
I
I
I
w/cmo.60
5
15 25
w/om0.4(>
I JSFO
\ y; sf 10
I
I
I
I
1
1
I
I
if
Rubber content by total aggregate volume (o)
Figure 3-4 Unit weight of plain and rubberized concretes w/ and w/o silica fume
[Gesoglu, et al., 2007]
21


Figure 3-4 shows the decrease in compressive strength as rubber content was
increased to 25%. In addition, higher compressive strengths were documented when
silica fume was included in the mixture.
Q.
£
a

4>
>
£
90
80
70
60
50
40
30
20
%
I
i
10 r
o
o

ft
20 40 60
Age {dnys)
RC:0 & wflhout SF
RC:5* & without SF
RC:15*& without SF
' RC:25"o & wflhout SF
RC:0% & with SF
RCiS** & with SF
* RC: 15ao & with SF
RC:25*o & with SF
80 100
Figure 3-5 Compressive Strength Development of Plain and Rubberized
Concrete with and without Silica Fume [Gesoglu, et al., 2007]
3.5 Fresh Concrete Properties of Rubberized Concrete
The fresh concrete properties of freshly mixed hydraulic-cement rubberized concrete
are evaluated based on the test results defined by:
Unit Weight and Air Content of Concrete: ASTM C-138
Slump of Hydraulic-Cement Concrete: ASTM C-143
22


Temperature of Freshly Mixed Cement Concrete: ASTM C-1064
Sampling Freshly Mixed Hydraulic-Cement Concrete: ASTM C-172-07
Air Content of Freshly Mixed Hydraulic-Cement Concrete by the Volumetric
Method: ASTMC-173
Air Content of Freshly Mixed Hydraulic-Cement Concrete by the Pressure
Method: ASTM C-231-04
The properties for fresh concrete including, unit weight, slump and percent air
content are often used to evaluate the behavior of the constituents that make up the
concrete matrix. In Section 3.4, an example of a typical mixture design was shown to
affirm typical trends found throughout research completed using recycled tire
particles in a concrete mixture. In rubberized concrete, the size of the rubber particles
and the quantity chosen for the mixture will have a direct effect on fresh concrete
properties of the mixture. The recycled tire market for a particular region has
typically defined the rubber particle size used in past research projects. Early
research was completed primarily using shredded rubber particles. Crumb rubber/30
mesh has only recently become a common product in rubberized concrete. Research
has directed its approach primarily toward the use of the rubber chips in rubberized
concrete mixtures. There is very little data available on the usage of recycled waste
tire particles smaller than 0.039in (1mm).
23


Notable effects in the unit weight with the use of rubber tire particles
(typically 0.039in to 0.47in (1mm to 12mm)) begins to occur when replacement
values greater than 20% by volume of total aggregate were used in place of natural
aggregates [Siddique, et al., 2004], [Khatib, et al., 1999], Research produced by Li
[1998] shows that when 33% by volume of sand was replaced in a mixture with CR,
the unit weight was reduced by approximately 10%. Another report noted a reduction
in unit weight by 6 pcf (96.1kg/m3) with the addition of CR at 501b (22.68 kg)
increments [Kaloush, et al., 2005], [Pierce,2002], [Fattuhi, 1996] showing that the
addition of fly ash in the rubberized concrete further reduces the unit weight. This
same trend is seen with the use of silica fume in the featured mixture design shown in
Table 3-1 [Gesoglu, et al., 2007],
In general, as the air content increases uniformly in rubberized concrete, the
unit weight decreases. This was true when all constituents remained constant
including the natural aggregate volume and when an equal volume content of natural
aggregate was replaced with rubber. The coarse and fine natural aggregate sizes were
replaced with the respective size/gradation of rubber [Khatib, et al., 1999]. This was
shown again in reports from [Siddique, et al., 2004] also verifying [Khatib, et al.,
1999] research that higher air contents were reported without the use of air-entraining
admixtures (AEA). In addition, the report stated that both the rubber chips and CR
have the predisposition to trap air due to the rough surfaces that are created by the tire
24


refinement process. The rubber was reported to have hydrophobic tendencies causing
air to attach to the surface of the rubber particle. The use of de-airing agents can be
added to counteract these affects prior to the placement of the rubberized concrete. In
addition, it was found that after CR was subjected to ozonization, there were
increases in surface polarity, resulting in the recycled waste tire particles repelling
water [Cataldo, et al., 2010],
It is understood from traditional concrete practices that the more air in
concrete mixtures; the more durable and workable the concrete product is, up to
approximately 9% air content. Studies have shown that rubber tire particles (typically
0.039-0.472in (1-12mm) entrapped air in the mixture during the mixing process. This
happens without the use of air entraining admixtures [Khatib, et al., 1999], This
trend, which holds true for traditional concrete mixtures, does not hold for rubberized
concrete mixtures. Typically, slump follows the same trend as the unit weight of
rubberized concrete; increasing rubber content will result in a decrease in slump or a
mixture that is unfavorable. Cases where very high quantities of rubber were added,
the mixture was reported to be so unworkable that vibration techniques were needed
to consolidate the mixture, even though the air content would increase in the concrete
mixture as reported by [Khatib, et al., 1999],
After a thorough review of previous CR research, there were a few
noteworthy topics of interest that were not thoroughly discussed. The first topic, not
25


covered in this study, was whether or not the temperature of the fresh concrete
reflected the presence of the recycled waste tire particles in the mixture. The goal of
this research study was to provide a product that can be implemented effectively and
the production stream-lined at a ready-mix facility. A majority of ready-mix facilities
stockpile their aggregate in an un-shaded, open area. The exposure of the recycled
waste tire particles to the daytime sun results in the build-up of a tremendous amount
of heat due the black color exhibited by car tires. This heat will adversely affect the
behavior of the fresh rubberized concrete and will be further exaggerated as the
volume replacement increases in the mixture. Excessive heating of the mixture will
make the placement of the rubberized concrete difficult and nearly impossible to
finish due to the rapid hydration of the cement paste in the matrix.
In summary, studies have shown the following trends for fresh concrete
properties:
When there is a decrease in rubber content, the concrete mixture has increased
workability/slump and unit weight
The air content increases as the rubber content increases
When recycled waste tire is stored exposed to the sun, the heating effects
could have an adverse effect on the fresh concrete, just as most natural
aggregate would at ready-mix facilities. Further investigation is
26


recommended to determine the extent that the rubberized concrete mixture
would be affected
The unit weight will be further decreased with the use of fly ash and/or silica
fume with recycled waste tire particles in a concrete mixture
Recycled waste tire particles have hydrophobic tendencies; therefore,
increasing air content
De-airing agent is suggested for air content reduction to reduce air content
3.6 Hardened Rubberized Concrete Strength Properties
The hardened properties of rubberized concrete are evaluated based on the test results
defined by:
Compressive Strength of Concrete: ASTM C-39
Flexural Strength of Concrete: ASTM C-78
Splitting Tensile Strength: ASTMC-496
Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration/
Rapid Chloride Permeability Test (RCPT) or Rapid Chloride Ion Penetration
(RC1P): ASTM C-l202
Resistance of Concrete to Rapid Freezing/Thawing: ASTM C-666
27


There is a consensus in the rubberized concrete literature that CR presents a
singularity within the concrete matrix. The quantity of recycled waste tire particles in
a rubberized concrete mixture directly affects the compressive, flexural and tensile
strength. This characteristic, exhibited by the rubberized concrete specimen
evaluated, resulted in a loss of strength and an increase in toughness from the
replacement of natural aggregates for recycled waste tire particles or rubber chips.
[Xi, 2004] used 0.073-0.162in (1.85-4.12mm) rubber particles, [Eldin, et al., 1993]
used both recycled waste tire particles and rubber chips in separate mixtures ranging
in size from 0.079, 0.748, 1.102 and 1.496in (2, 19, 28 and 38mm). The third case
was [Kaloush, et al., 2005], who used recycled waste tire gradations that range 0.039-
0.78in (l-2mm). Each study evaluated the compressive, flexural and tensile strength
with a percentage of natural aggregate replaced with each developing the
aforementioned trend. The rubberized concrete experienced a loss in strength and an
increase in toughness. The primary cause of strength loss in rubberized concrete was
a result of poor adhesion of the cementitious products to the surface of the rubber
particles.
There have been several successful studies completed to improve upon the
interfacial transition zone (ITZ) bond between the rubber tire chips and the
cementitious material within the rubberized concrete mixture. The University of
Colorado, Boulder used a modified w/c and silica fume pretreatment on the recycled
28


waste tire particle to improve the mechanical bond. "Low water-cement ratio
significantly increases the strength of rubber-modified mortars (RMM). An 8% silica
fume pretreatment on the surface of rubber particles can improve properties of RMM.
On the other hand, directly using silica fume to replace equal amount (weight) of
cement in concrete mix has the same effect [Xi, 2004],
To the same effect, recycled waste tire particle is chemically treated to improve the
ITZ. Several chemical methods utilized to enhance the rubber particles bond are as
follows: (1) PAAM (polyacrylamide) pretreated [Xi, 2004], (2) PVA (Pressure
Ageing Vessel) pretreated [Xi, 2004], (3) silane-pretreated [Xi, 2004], (4) Sodium
Hydroxide (NaOH) soak,[Segre, et al., 2000], [Siddique, et al., 2004] and (5)
magnesium oxychloride cement (restricted applications to indoors).
A recycled waste tire particle surface treatment consisting of NaOH is
believed to hydrolyze the acidic and/or carboxyl groups of the rubber particles [Segre,
et al., 2000]. The rubber particles are submerged in solution for a period of time and
then removed from the solution and rinsed. This cost effective procedure improves
the adhesion properties of the rubber particles in the rubberized concrete matrix
[Segre, et al., 2000]. "More research is required to optimize the particle size,
percentage of rubber, type of cement, use of chemical and mineral admixtures and
29


methods of pretreatment of rubber particles on the characteristics of concrete
[Siddique, et al., 2004],
The use of PAAM, PVA and silane were proven effective to enhance the
performance of the ITZ. When recycled waste tire content was pretreated with
PAAM, the mixture exhibited poor workability when recycled waste tire consumed
more than 10 percent of total aggregate by volume. However, the use of PVA (most
effective) and silane were found to be the most effective of the chemical treatments
[Xi, 2004], The compressive and tensile strengths of the silane treated mixture were
documented to once again provide a tough rubberized concrete material and improved
compressive strengths. 'The overall results show that using proper coupling agents to
treat the surface of rubber particles is a promising technique, which produces a high
performance material suitable for many engineering applications.
Early research of rubberized concrete determined that the product was suitable
for applications requiring low strength, lightweight and energy adsorbent
characteristics [Eldin, et al., 1993], [Topcu, 1994], All research performed for
rubberized concrete experienced a non-brittle failure during the compressive, flexural
and split-tensile test, unlike conventional concrete mixtures. The properties of many
rubberized concrete specimens inherently acquired the behavior of the rubber pieces
chosen for the mixture. As the pieces of rubber tire got larger in a specimen
analyzed, it began to behave like a piece of rebar in a flexural concrete member.
30


However, these characteristics are only indicative during the splitting-tensile test.
When the concrete begins to break during the flexural test, there is less cementitious
contact within the matrix which creates a weaker material in flexure, but not the
catastrophic failure as it would be without any reinforcement. Rubber has a low
modulus of elasticity and an extensive ductile region allowing for concrete material to
be tough. "The modulus of elasticity decreased slightly for mixtures with a low CR
content. Furthermore, the modulus of elasticity was drastically reduced for mixtures
with high CR contents (the modulus was almost equivalent to that of asphalt
concrete) [Kaloush, et al., 2005].
It was also observed during the tests that it was more difficult to fully open a
waste tire fiber modified concrete column than to fully open a waste tire chip
modified concrete. This suggests that waste tire fiber modified concrete has a higher
toughness than waste tire chip modified concrete does [Guoqiang, et al., 2004], and
approximately a year later, [Kaloush, et al., 2005] conferred similar findings, such
that, the crumb rubber concrete specimens appeared to stay intact (did not shatter)
and the upper half of the specimen failed, indicating that the rubber particles absorbed
the compressive force and did not distribute it to the lower half.
The durability of a concrete specimen is evaluated by more than an individual
test standard such as compressive, flexural and tensile strengths. The tests used for
measuring a concrete mixtures ability to withstand the exposure to a variety of
31


environmental conditions are freezing/thawing (ASTM 666) and chemical attack using
(ASTM C-1202). Unfortunately there is no way to combine this experiment to
simulate conditions that are more representative to the conditions the material will
likely face in service. However, both of these tests will expose the voids within the
concrete matrix to internal-forces (tensile) and chemical attack from chloride
compounds (extremely reactive with the various constituents within the concrete) by
measuring electrical conductivity of a concrete sample. In order to constitute the
durability of a rubberized concrete mixture, conclusions must be determined from the
results of freezing/thawing (ASTM 666) and permeability using {ASTM C-1202)
testing. The porosity directly affects both of the chemicals ability to penetrate the
surface and the expansion of the freezing waters internal forces to be relieved. The
freezing/thawing (F/T) durability factor (DF) is determined from the dynamic
modulus of elasticity of the concrete measured at 300 freeze/thaw cycles or 60% of
the initial, whichever comes first. Permeability is based on the amount of current that
passes through a concrete sample, typically measured at 28 to 90 days. A concrete
sample that is highly resistant to F/T damage will have a DF of 95-100 after
completing 300 F/T cycles and a concrete sample with low permeability will pass
1000-2000 coulombs [Kosmatka, et al., 2003]. The mixture design must represent a
balance of air content to strength reduction resulting from the air voids/pores for the
desired durability requirements for its application. As previously discussed, surface
32


treatments of the CR allow for an improved cement paste adhesions. Better adhesion
of the cement paste reduces the permeability of the concrete matrix thereby
improving durability.
Approximate replacement values of rubber aggregate have been determined in
previous studies to produce a durable rubberized concrete mixture. In terms of
durability, use of concrete with the optimum amount of rubber aggregate, that is 10%
in volume, is economical and good for recycling [Topcu, 1994], Paine [2002]
investigated the use of crumb rubber as an alternative to air-entrainment for providing
(F/T) resistance in concrete. Three sizes of recycled waste tire, 0.020-0.059, 0.079-
0.315 and 0.197-0.984in (0.5-1.5, 2-8 and 5-25mm) were used. Test results showed
that there is potential for using crumb rubber as a F/T resisting agent in concrete. The
crumb rubber concrete performed significantly better under F/T conditions than plain
concrete and the performance of CR concrete in terms of scaling was similar to that
of air-entrained concrete[Siddique, et al., 2004], In general, the majority of studies
completed for rubberized concrete all resulted in mixture portions with approximately
10% and 15% ground rubber (0.079-0.236in (2-6mm) in size) that exhibited
durability factors higher than 60% after 300 freezing and thawing cycles. Flowever,
mixtures with 20% and 30% ground rubber by weight of cement could not meet the
DF requirements. Air-entrainment did not provide improvements in freezing and
thawing durability for concrete mixtures with 10, 20 and 30% ground tire rubber.
33


Each mixture exhibited increased scaling [Siddique, et al., 2004], [Savas, et al.,
1996],
The coefficient of chloride ion diffusivity (CCID) increased as w/cm and air
content increased. Test results clearly showed that CCID for all concrete increased
after F/T cycles. In addition, concrete incorporating silica fume showed the lowest
CCID and highest durability factor, regardless of curing regime, air content and
w/cm. However, fly ash concrete showed good resistance to chloride ion diffusivity
before and after F/T cycles when low w/cm as well as a proper curing and air content
were provided. Furthermore, the presence of carbon in fly ash and silica fume can
create air-void stabilization problem. Since carbon slowly adsorbs the air-entraining
admixture and inhibits further generation of microscopic air bubbles, it reduces the
total available air content in hardened concrete [Chung, et al., 2010], [Liu, 2010].
There are a limited number of studies concerning F/T and permeability of
concrete containing rubber aggregate. Recently, a study was published using silica
fume and fly ash compared against a plain concrete control sample using a variety of
w/cs and percent air contents [Chung, et al., 2010], Shown in Table 3-2 are Chungs
findings from experimental testing using ASTM C-666 and ASTM C-1202. Similar
trends were found using silica fume in the rubberized concrete mixture. The featured
rubberized concrete mixture, Table 3-2, used silica fume to evaluate the effects of
chloride penetration in the rubberized concrete [Gesoglu, et al., 2007], The addition
34


of silica fume to the concrete mixture, even as low as 10% by mass...magnitudes of
chloride penetration depth were remarkably decreasing with the use of silica fume,
especially for the rubberized concretes.
Table 3-2 Summary of Experimental Result by [Chung, et al., 2010]
Summary of experimental results.
Specimen Air content (%) Charge passed (coulombs; Coefficient of chkmde ion diffusion (x 10 1 2 m-/s] DF
28 days 56 days 91 days After F,T 28 days 56 days 91 days After FiT
04-P-6 5.9 3575.4 2714.7 2331.0 3792.0 10.71 8.43 5.71 11.39 97.1
04-SF-6 5.5 810.7 4715 3245 10208 1.29 025 0.01 1.81 98.0
04-FA-6 5.1 3087.4 20775 1004.9 3278.0 6.64 325 0.99 725 98.0
05-P-2 2.0 3039.0 - - 31392 9.71 - - 10.44 96.6
05-P-4 4.1 3557.4 - - 3784.1 11.51 - - 1181 99.5
05-P-6 5.2 3856.3 3303.3 2578.0 39745 12.07 853 7.69 12.65 96.7
05-SF-2 2.0 1044.5 - - 1163.8 418 - - 4.45 96.7
05-SF-4 4.0 1418.8 - - 1580,7 4.45 - - 4.46 100
05-SF-6 5.3 1765.7 1093.3 789.9 18765 445 1.99 1.05 5.04 100
05-FA-2 1.9 2373.7 - - 2477.3 10.67 - - 10.97 965
05-FA-4 3.8 2800.5 - - 28235 10.13 - - 1055 99.0
05-FA-6 5.0 3255.8 1549.1 1338.7 38402 10.97 4.76 366 10.97 98.6
06-P-6 5.2 3924.7 34447 2576.7 4213.8 13.71 10.97 951 13.92 98.1
0.6-SF-6 5.0 2237.7 1259.9 1055.0 2788.1 4.84 1.60 1.46 5.93 97.6
06-FA6 5.5 6104.7 3905.6 3328.1 7389.8 15.46 5.75 4.72 16.49 97.2
All values were obtained with the average of three specimens.
0,4 (water to cementitious material ratio 04.05, and 0.6) (0.5.0.6), P (Plain (silica feme, fly ash)) (ST. FA;. 2 (air content (2* *. 44 and 641) (4.6,
In summary, studies have shown the following trends for hardened concrete
properties:
Hernandez-Olivares [2002] have reported that the addition of crumb tire
rubber volume fractions up to 5% in a cement matrix does not yield a
35


significant variation of the concrete mechanical features [Siddique, et al.,
2004]
Research has not determined an optimal replacement quantity or size of crumb
rubber for compressive or flexural strengths optimization
Research has indicated that there was no brittle failure mechanism at
approximately 10% volume replacement of natural aggregates for recycled
waste tire particles
Multiple research studies indicated that compressive strength followed
opposite trends in strength development
The addition of silica fume to the concrete mixture, even as low as 10% by
mass, improved the resistance of concrete against chloride penetration,
irrespective of the amount of rubber used. Fly ash had a similar affect, but a
different quantity will need to be evaluated for an equivalent result
10 and 15% weight replacement for rubberized concrete is durable according
to ASTM 666 and ASTM C-1202.
36


Recommendations to investigate:
Research the particle size
Percentage of rubber by volume use of chemical and mineral admixtures
Methods of pretreatment or surface treatment of recycled waste tire particle
Procedure modifications to reduce adverse mechanical effects
Temperature of recycled waste tire particles at ready mix storage facilities
Evaluation of the effects of bulk storage of rubber particles on the
characteristics of concrete
Freeze-Thaw durability factor for volume replacements
Freeze-Thaw effects on scaling
37


Chapter 4
Problem Statement
4.1 Problem Statement
Tires have been recycled or used in various ways for several decades. The need to
find out more ways to utilize disposed tires is more important than ever because of
the growing number of used tire stockpiles in the US. Colorado lawmakers have
concerns that have led to initiatives to fund the development of new technologies to
utilize recycle waste tires to slow the growth of these stockpiles.
Colorado has one of three monofills within the contiguous 48 states [Ayers,
2009]. These mono-fill stockpiles will be sustained and possibly reduced over time
from Colorados rapidly growing urban districts. This is not just a localized problem
for the State of Colorado. In certain urban areas of the western United States,
population has increased 25% since 1990 [CDOLA, 2006], The demand for materials
required for the continual expansion and maintenance of the concrete infrastructure
for growing urban centers is depleting nearby virgin resources. Construction sand
and gravel operations are moving further away from highly populated urban centers
due to depletion, zoning, federal and state environmental law, and developmental
regulations. As a result, many major municipalities of the United States are currently
faced with material scarcity issues and higher emissions of greenhouse gases (GHG)
38


and costs per unit of delivered concrete due to increased transportation of the required
materials.
This study examines the use of recycled waste tire particles for use in concrete
production in Colorado. Specifically, the effects of low and high volume sand
replacement with crumb rubber on concrete properties were determined. The sand
component within concrete was replaced in 10% increments up to 50% (replacement
rates of 10, 20, 30, 40 and 50 percent crumb rubber).The concrete compressive
strength, flexural strength, indirect splitting tensile strength, modulus of elasticity,
permeability and freeze/thaw resistance were tested in order to determine an optimum
sand replacement with recycled waste tire particles. In addition, leaching tests were
performed on the crumb rubber concrete to determine whether any hazardous
materials leached from the material. The primary objective of this research study was
to determine the maximum amount of sand replacement with crumb rubber in
concrete mixtures without compromising the integrity of the concrete.
If recycled waste tire particles are found to provide a viable material substitution in
the concrete matrix, Colorado will have another avenue for dealing with its ever
growing stockpiles of disposed tires. This study developed a sustainable concrete
mixture that incorporated waste-stream materials such as fly ash, recycled concrete
and recycled waste tire particles. An optimal concrete mixture was determined from
laboratory experiments. Recommendations were made for the placement of a
39


concrete alley panel constructed for the City and County of Denver that includes the
optimum volume of crumb rubber. The success of this study will provide a means of
incorporating waste-stream materials such as recycled tires, concrete aggregates and
fly ash into concrete infrastructure, thereby providing quantifiable environmental life-
cycle impact.
40


Chapter 5
Concrete Materials
5.1 Purpose of this Research Study
This study was designed to further investigate the use of recycled waste tires within
the concrete matrix. For the mixture proportioning to be correct, it must implement
the use of all the correct material properties, specifically, the specific gravity for the
absolute volume method.
5.2 Aggregates Required for Concrete Pavement
The aggregate and the cementitious materials in the mixture design of a Colorado
Department of Transportation (CDOT) class P concrete pavement mixture are
discussed in the following sections. The design method used in proportioning the
mixture is known as the absolute volume method. In addition to the class P
proportion requirements, the remaining difference of the total volume sum is the
necessary quantity of sand for the mixture. In this study, increments of sand volume
were replaced with the recycled waste tire particles. It was necessary to find a local
accessible product that would closely emulate the volume space used by the sand.
The CDOT specifications sheet for a Class P concrete pavement is included in
Appendix A.
41


5.3 Physical Properties for Virgin Aggregates
The coarse and fine aggregate were obtained from sources local to this region of
Colorado. The University of Colorado, Denver Materials Testing Laboratory
acquired both the coarse and fine aggregate in compliance with ASTM C-33
requirements. Besides the gradation for virgin fine aggregate, the physical properties
were provided by the supplier. Table 5-1 show the properties used for the mixture
design.
Table 5-1 Physical Properties for Virgin Aggregates
Material Specific Gravity Absorption Capacity
Virgin Coarse Aggregate 2.60 1.50%
Virgin Fine Aggregate 2.63 0.70%
Bestway Aggregate provided material properties and gradation reports for the
virgin aggregates. The aggregate properties and their gradations were tested by the
supplier to verify the requirements fulfilled Class P concrete pavement specifications.
See Appendix A for the material sheets for gradation, specific gravity and absorption
capacity of the virgin aggregates.
42


5.3.1 Gradation for Virgin Aggregates
The physical property values for the virgin aggregate used in the design of the
concrete pavement mixture were specified on the test report received from Bestway
Concrete. The coarse aggregate meets the ASTM C-33 size number 57 and 67
grading requirements. In addition, the fine aggregate meets the ASTM C-33 grading
requirement for concrete pavements. An individual sieve test was not performed on
the stocked supply of virgin coarse aggregate.
5.3.2 Specific Gravity for Virgin Aggregates
The physical property values for the virgin aggregate used in the design of the
concrete pavement mixture were specified on the test report received from Bestway
Concrete. The procedure for determining the absorption capacity did not deviate
from ASTM C-128 for fine aggregates. No laboratory investigations were completed
for the specific gravity of the virgin aggregates.
43


5.3.3 Absorption Capacity for Virgin Aggregates
No laboratory investigations were completed for the absorption capacity of the virgin
aggregates.
5.4 Recycled Aggregates
The recycled coarse and fine aggregate were obtained from sources local to Denver,
Colorado. The University of Colorado, Denver Materials Testing Laboratory
acquired both the coarse and fine aggregate. The coarse aggregate used for this study
was obtained from Allied Recycled Aggregates located in Commerce City, Colorado.
They provided a recycled concrete aggregate that was produced and refined for the
requirements of a CDOT class 6 specifications for aggregate base. For the recycled
fine aggregate that will replace various portions of sand, Caliber Recycled Products
(now defunct) was located in Commerce City, Colorado. They provided the recycled
waste tire particles. Table 5-2 show the properties used for the mixture design.
Table 5-2 Physical Properties for Recycled Aggregates
Material Specific Gravity Absorption Capacity
Recycled Coarse Aggregate 2.10 5.75o
Recycled Fine Aggregate 1.08 -
44


Both suppliers for the recycled aggregates provided a general description of
the material properties and grading limits, but insisted the consumer perform and
verify the necessary material properties for the aggregate. The CDOT sheet that
shows the classification for aggregate base coarse is included in Appendix A.
5.4.1 Sieve Analysis for Coarse Recycled Concrete Aggregate
This section discusses laboratory testing of the recycled concrete aggregate. In order
to increase the use of common waste materials, a 50% replacement of the virgin
coarse aggregate with recycled concrete aggregate was utilized for two ideal
mixtures, which contain recycled waste tire particles. Performing a sieve analysis to
compare it against the virgin aggregate it replaced will ensure that class P
requirements are satisfied. It should be noted that even though the sample acquired
for this study was not modified, the distribution curve shown in Figure 5-1 with data
provided by Allied Recycle Products (Table 5-3) does not fit within the ASTM C-33
grading requirements for coarse aggregates. The curve fit of the recycled concrete
coarse aggregate provided was slightly more coarse than the virgin aggregate, but still
adequate. No adjustments were made to the aggregate gradation.
45


Table 5-3 ASTM C-33 Grading Limits and Values for Coarse Aggregates
Sieve Size % Passing
U.S (in) Metric (mm) Upper Limit Lower Limit Recycled Concrete Aggregate (RCA) Reported Coarse Aggregate Analysis Allied Aggregate Analysis (RCA)
1.5 37.5 100.0 100.0 100.0 100.0 -
1 25.0 100.0 90.0 100.0 100.0 100.0
3/4 19.0 - - 80.5 91.0 100.0
1/2 12.5 60.0 25.0 18.3 49.0 86.0
3/8 9.5 - - 5.0 30.0 73.0
4 4.75 10.0 0.0 1.2 6.0 50.0
8 2.36 5.0 0.0 1.2 8.0 38.0
46


Figure 5-1 ASTM C-33 Grading Limits and Values for Coarse Aggregates
Upper Limit Lower Limit
Recycled Concrete Aggregate (RCA) * Reported Coarse Aggregate Analysis
-X- Allied Aggregate Analysis (RCA)


5.5 Specific Gravity for Coarse Recycled Concrete Aggregate
Included in this section are the results from the preformed tests for specific gravity at
saturated surface dry and absorptions capacity for the recycled concrete aggregate.
Just as the specific gravity is needed for all other aggregates, recycled concrete
aggregate is no different. The recycled concrete aggregates specific gravity at
saturated surface dry and absorptions capacity was determined from the following
procedures laid out in ASTM C-127 and D-75 to acquiring the sample proportions.
The resulting values obtained from the tests performed were 2.10 and 5.75%
respectively. In addition to the specific gravity at saturated surface dry and
absorptions capacity results, the dry rodded unit weight was tested by procedures
defined by ASTM C-29. The result for the dry rodded unit weight was 85.81 lb/ft3
(1375.5 kg/m3).
It is noteworthy to mention that the recycled concrete aggregate was not oven
dried prior to the required 24-hour saturation. The standard indicates that oven drying
will only become significant to the resulting values when the aggregate size exceeds
2.95in (3mm).
48


5.6 Sieve Analysis for Recycled Tire Particles andVirgin Fine Aggregates
Included in this section is a summary of the gradation testing on the recycled waste
tire particles. When working with recycled waste tire in the civil engineering
industry, ASTM D-6270 provides guidance for the testing of the physical properties
and application practices. The sample of recycled waste tire was weighed to the
required quantity specified by ASTM C-53and ran through the sieve screens as shown
in Figure 5-2.
Following the sieve analysis procedures for the recycled waste tire particles, a
gradation test on the stocked concrete sand was conducted to compare to the reported
values from the supplier of the sand.
49


Figure 5-2 Acquired Crumb Rubber Sample
There was a small discrepancy, but the gradation still met the ASTM C-
iilimits as shown in Figure 5-3. The three curves in Figure 5-3 which include the
reported sand from Bestway Aggregates, actual sand analysis from the laboratory
stockpile and the recycled waste tire particles that make up the crumb rubber, all fall
within the ASTM upper and lower limits. The results of the sieve analysis are shown
in Table 5-4 and then plotted as shown in Figure 5-3.
50


Table 5-4 ASTM C-33- Grading Limits and Values for Fine Aggregates
Sieve Size % Passing
U.S (in) Metric (mm) ASTM C33 Upper Limit ASTM C33 Lower Limit Crumb Rubber Actual Sand Analysis Reported Sand Analysis
3/8 9.5 100 100 100.0 100.0 100.0
4 4.75 100 95 100.0 100.0 100.0
8 2.36 100 80 99.5 94.1 99.0
16 1.18 85 50 55.7 64.9 71.0
30 0.6 60 25 25.7 36.2 38.0
50 0.3 30 5 11.1 14.5 14.0
100 0.15 10 0 3.5 3.5 4.0
51


Figure 5-3 ASTM C-33- Grading Limits for Fine Aggregates
Upper Limit - Lower Limit o Crumb Rubber Gradation
- - Actual Sand Analysis Reported Sand Analysis


Another noteworthy condition stated by ASTM C-33 is that there cannot be
more than a 0.2 variation in fineness modulus of materials being replaced. The
acceptable range for fineness modulus is 2.3 to 3.1. The aggregate must be disposed
of, or modified to fall within the acceptable range for fine aggregates. Table 5-5
shows the obtained values for fineness modulus. The recycled waste tire particles
obtained for this study meet the requirements of ASTM C-33for fine aggregates in
concrete pavement.
Table 5-5 Fineness Modulus for Fine Aggregates
Laboratory Analysis of Reported Analysis of Analysis of Recycled Waste Tire Particles
Fineness Modulus 2.87 2.74 3.05
5.7 Specific Gravity for Recycled Waste Tire Particles
It is necessary to determine an accurate specific gravity value in order to correctly
proportion a concrete mixture containing recycled waste tire particles. As the ASTM
for tire derived aggregates only specifies the physical property tests for coarse
aggregates, the research team needed to investigate the use of the physical property
tests for fine aggregates. ASTM C-128 is not intended to be used to find the specific
gravity of lightweight aggregates. However, that does not dismiss the principles on
53


which the test was based and how it can be adapted to function as a reasonable testing
procedure for recycled waste tire particles.
5.7.1 Recycled Waste Tire Specific Gravity Experimental Testing Investigation
The specified procedure was followed just as it would be for relatively dense
aggregate particles defined by the standard; was modified and then used in the
specific gravity final testing of the recycled waste tire particles. During the testing
process, problems that pertained to the physical nature of the recycled waste tire
particles were documented. Issues included the recycled waste tire particles floating
on the water and not displacing water as required by Archimedes principle. It was
observed that some of the larger particles settled shortly after being aggressively
agitated in the volumetric flask. However, air bubbles were clearly visible while
submerged in water. Clearly, the testing process cannot continue and still acquire
good specific gravity results. The primary concern observed during the testing
process was the lack of air removal within the water and on the recycled waste tire
particles. The primary hurdle for the determination of an accurate specific gravity
value is how to remove the air trapped in and all around the recycled waste tire
particles.
54


During the literature review phase of the study, an investigation into the
physical and chemical make-up of vulcanized rubber reviled that it poses a
hydrophobic property. This entangle with the highly angular surface of the recycled
waste tire particles inhibits the air from escaping from underneath the recycled waste
tire particles floating at the surface, and the air to be released off the recycled waste
tire particles that have already settled. It was learned from other study experiences
that the batching of concrete using recycled waste tires resulted in foaming
characteristics. The solution that was used, in that study to correct the foaming
experienced, was a de-airing chemical admixture. This process of using a de-airing
chemical admixture to control foaming in fresh concrete provided an avenue to
potentially resolve the problems associated with finding the specific gravity of the
recycled waste tire particles. During the acquisition phase of materials for the study,
a de-airing chemical admixture was acquired in anticipation of foaming.
5.7.2 Recycled Waste Tire Specific Gravity Experimental Testing
A de-airing agent was implemented to resolve the issues associated with the recycled
waste tire particles floating on the water surface. This product proved to be very
instrumental in determining the specific gravity of the recycled waste tire particles. A
1:10 mixture of de-airing admixture and water was used to produce a quantity of
solution large enough to be used throughout the specific gravity testing process for
55


the recycled waste tire particles. In order for the solution to be effective and
consistent throughout the testing, the solution was stirred often. This solution was
then added to a clean and dry volumetric flask with a cap of which the mass was
determined. This measure was stored within the lab to take on the temperature
changes necessary to measure any the density changes of the 1:10 solution. This
solution was added to and subtracted from on a daily basis throughout the
experimental testing phase. A container with graduations indicating the measure of
rise and fall would have limited the error of this procedure. This would have
eliminated the need to add and subtract from the solution.
5.7.3 Recycled Waste Tire Specific Gravity Experimental Testing Results
Several trial runs were performed to evaluate any possible effects that would yield
inaccurate results. The use of the de-airing admixture in the water allowed for full
emersion of recycled waste tire particles. However, there were air bubbles still
present on recycled waste tire particles, which were further reduced when agitating
the mixture. A mass of the de-airing admixture, water and recycled waste tire
particles combined was taken following significant agitation. The mass and
calculated specific gravity was consistent with trial runs with less precision. The
value for specific gravity was calculated to be 1.06. The volumetric flask was then
capped and set aside for approximately 24 hours. Following a 24-hour set time, the
56


volumetric flask cap was removed then with the slightest agitation of the flask,
significant amounts of air surfaced requiring a small addition of solution to reach the
calibrated fill mark. A final mass was acquired in order to calculate the specific
gravity used in the concrete mixture design. That value for specific gravity was
calculated to be 1.08.
5.8 Terminology for Recycled Waste Tire Particles
From the resulting sieve analysis, ASTMD-6270 indicates that the recycled waste tire
particles do not fall within a coarse aggregate category. The tested recycled waste
tire sample primarily falls within a particle distribution range of 0.47in (12mm) to
0.017in (0.425mm) size and is called granulated rubber by ASTM D-6270. This was
ideal for the desired size and distribution needed for this study. The terminology was
specified by the aforementioned standard, which is summarized by size of particle in
the Table 5-6 below.
57


Table 5-6 ASTM D-6270 Terminology for Recycled Waste Tire Particles
Term Name Upper Limit in (mm) Lower Limit in (mm)
Chopped Tire cut into relatively larse pieces of unspecified dimensions
Roush Shred 30 X 1.97X3.94(50X50X50 ) - 30 X 1.97 X 3.94 (762 X 50 X 100)
Tire Derived Assresate (TDA) 12(305) - 0.47(12)
Tire Shreds 12(305) - 1.96(50)
Tire Chips 1.96(50) - 0.47(12)
Granulated Rubber 0.47(12) - 0.017(0.425)
Ground Rubber < 0.47 (<12) - <0.017(0.425)
Powered Rubber - - <0.017 (0.425)
5.9 Chemical Admixtures
Chemical admixtures used for this study were an air-entraining admixture (AEA) and
a water-reducing admixture (WRA).
The AEA supplied for this study was to address any unforeseeable problems
with the air content for class P concrete requirements. Table 5-7 shows the AEA
dosage range for the BASF product. Please see Appendix A for the complete BASF
product specification sheet.
Table 5-7 BASF Air-Entraining Admixture
BASF MB-AE 90
Specific Gravity 1.02
Solids Range 5.2-6.5o
.Air-Entraining Admixture 1 4-4 fl. oz. cwt (16-260 mL 100 kg)
58


The WRA specifications are for a very broad range of dosages to acquire the
desirable flow of the mixture. Table 5-8 shows the WRA broad dosage range for the
supplied BASF product. This type of product was used for reasons found during the
literature review. Even though a fairly larger particle of rubber was used by [Khatib,
et al., 1999], it was anticipated that similar results were expected with the increased
surface area due to the smaller gradation used for this project. Please see Appendix A
for the complete BASF product specification sheet.
Table 5-8 BASF Water-Reducing Admixture
BASF GLENIUM 3030 NS
Specific Gravity 1.05
Solids Range 18.3-22.3%
Water-Reducing up to 3 fl. oz./cwt (195 mL/100 kg)
Mid-Range Water-Reducing 3-6 fl. oz./cwt (195-390 mL/100 kg)
High-Range Water-Reducing up to 18 fl. oz./cwt (1170 mL/100 kg)
5.10 Type I-II Portland Cement
A type 1-11 portland cement was provided by Holcim, Inc. The specific gravity of this
cement was 3.15. The complete chemical and physical properties of the cement are
shown in Table 5-9 and 5-10. The material certification report is attached at
Appendix A.
59


Table 5-9 Physical Properties for Portland Cement
Manufacture: Holcim Type: I-II (MH) Testing Standard: ASTM C150
Result Limit
Air Content, (%) 7 12 max
2 Blaine Fineness, (m /kg) 414 260 min
430 max
Autoclave Expansion (C151), (%) -0.02 0.80 max
Assumed Standard for Specific Gravity: 3.15
Heat of Hydration: 7 days. cal/g(kJ/kg) 82 (343) N/A

Compressive Strength, psi (Mpa):
3 days 4510(31.1) 1450(10.0) min
7 days 5460 (37.6) 2470(17.0) min

Initial Vicat, (minutes) 126 45-375
Equivalent Alkalies, (%) 0.70
Mortar Bar Expansion (Cl038), (%) -0.001

The following information is based on average test data during the test period.
The data is typical of cement shipped by Holcim; individual shi pments may vary.
C3S, (%) 61
C2S, (%) 11
C3A, (%) 7
C3AF, (%) 10
60


Table 5-10 Chemical Properties for Portland Cement
Manufacture: Holcim Type: I-II (MH) Testing Standard: ASTM Cl50
Potential Phase Compositions: Result Limit
C3S, (%) 59 N/A
C2s, (%) 11 N/A
C3A, (%) 7 8 max
c3af, (%) 10 N/A
C3S + C3A, (%) 92 100 max

Si02,(/o) 19.6 N/A
A1203, (%) 4.7 6.0 max
Fe203, (%) 3.2 6.0 max
CaO. (%) 63.4 N/A
MgO, (%) 1.5 6.0 max
S03, (%) 3.4 3.0 max

Loss on Ignition, (%) 2.6 3.0 max
Insoluble Residue, (%) 0.59 0.75 max
C02, (%) 1.4 N/A
Limestone, (%) 3.7 5.0 max
CaC03 in Limestone, (%) 84 70 min
Inorganic Processing Addition 0.0 5.0 max
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5.11 Fly Ash
A Class F Fly Ash was provided by Boral Material Technologies. The identification
information for the supplied fly ash is shown in Table 5-11. The report for the
complete chemical and physical properties of the fly ash is attached at Appendix A as
well as a summary of the physical and chemical properties in table 5-12 and 5-13.
Table 5-11 Identity Information for Class F Fly Ash
Manufacturer: Boral Material Technologies
Identity: Boral Class F Fly Ash
Sample #: S-100615009
Sample Date: Mav 2010
Classification: Calcium Aluminum Silicate
Testing Standard: ASTM C618
Chemical Family: Coal Ash
62


Table 5-12 Physical Properties for Boral Class F Fly Ash
Physical Tests Results
Moisture Content, % 0.06 max 3.0
Loss on Ignition, % 0.78 max 6.0
Amount Retained on # 325 Sieve, % 18.62 max 34
Specific Gravity 2.39 N/A
Autoclave Soundness, % 0.03 max 0.8
SAI, with Portland Cement
at 7 Days, % of Control 87.10 min 75*
SAI, with Portland Cement
at 28 Days, % of Control 99.50 min 75*
Water Required, % of Control 96.30 max 105

Loose, Dry Bulk Density, lb/ft3 70.07 N/A
* Meeting the 7 day or 28 day Strength Activity Index will
indicate specification compliance.
Table 5-13 Chemical Properties for Boral Class F Fly Ash
Chemical Tests Results
Silicon Dioxide, (SiO), o 52.80 N-'A
Aluminum Oxide, (Al'O3). o 24.11 N A
Iron Oxide (Fe'O3), % 5.62 N-'A
Sum of SiO:, ATO3, Fe:03, b 82.53 min 50.0
max 70.0
Calcium Oxide, (CaO), o 9.75 N A
Magnesium Oxide, (MeO). % 2.48 N/A
Sulfur Trioxide, (SO3), % 0.32 max 5.0
Sodium Oxide, (Na'O), o 0.14 N-'A
Potassium. (K'O), % 1.17 N-'A
Total .Alkalies, (as Na'O), o 0.91 N A
Available Alkalies, (as Na'O). % - N/A
63


Chapter 6
Experimental Design
6.1 Design Plan
The primary objective of this research study was to create a sustainable concrete
mixture using recycled materials as partial replacements for cement and coarse and
fine aggregates. The optimum mixture developed will be sufficient to produce the
States most commonly used concrete mixture, a Colorado (CDOT) class P concrete
pavement. An examination of the research involving the similar concepts revealed
the potential this study has for success. The knowledge gained from this study aided
in the design process of the trial mixtures that led to the development of the final
concrete design mixtures tested during this research.
6.2 Batching of Concrete Mixtures
In the fall 2010 and spring of 2011, batching of concrete that contained recycled
waste tire particles was initiated through trial mixture design and testing. A
methodical process was adopted for all mixtures completed for this study. The
procedures set by ASTM C-/92drove many of the processes for the completion in
Making and Curing Concrete Test Specimens in the Laboratory, however the
batching varied slightly. The purpose of the variation was to attempt a mechanical
64


type treatment for the surface area of the recycled waste tire particles. This was an
attempt to improve upon the paste bond to the recycled waste tire particles.
6.2.1 Batching Procedure for Each Mixture
The constituents for each mixture design were weighed and placed into five gallon
buckets with fitted lids many days before batching of any mixture. In addition to the
weighed out portions, an unspecified quantity was stored in the same location as the
aforementioned, and in five gallon buckets with fitted lids for later adjustments of the
batch weight of each mixture. Each bucket was placed into storage until time of
batching took place. All constituents were stored within the same air handling region
of the facility where batching took place at a later date. The cementitious materials
were set aside away from moisture within the materials laboratory, in addition to the
mixing water, to maintain water temperature in accordance with ASTM C-511. An
excess quantity of water was stored for later adjustments required for mixture
batching. Storing the aggregate in buckets with fitted lids, ideally, would allow the
moisture content to stay relatively consistent with time between the batching of each
mixture. To aid in this desired result, all of the virgin coarse and fine aggregate was
placed into the curing room.
65


6.2.2 Preparation the Day Before Batching Concrete Mixtures
Before batching, samples of both the virgin coarse and fine aggregates were taken and
oven dried for approximately 24 hours. The sample of aggregate was acquired at the
approximate center of the bucket by dumping roughly half of it into another bucket,
and then returned to the storage bucket. Aggregate drying was performed in
accordance to ASTM C-566. This was done to acquire the moisture content needed
for the water adjustments in the mixture design. The aggregate samples were then
returned to the bucket from which it was acquired.
The batching area was consist with all the necessary tools and equipment to
test fresh concrete properties, in addition to the molds necessary for casting the
concrete specimens to be used later in the hardened concrete test phase of each
mixture.
6.2.3 Mixing Process
The mixing process began with thoroughly hosing out the concrete mixer and
dumping out the excess. This is in substitution of "buttering the mixer, which is
referred to in ASTM C-192. Once the excess water was emptied from the concrete
mixer, all virgin and recycled aggregates were placed into the concrete mixer. With
the aggregates loaded into the concrete mixer, they were allowed to blend for a total
of ten minutes before any other constituents are added to the mixer. The purpose of
66


this blending time is to roughen the surfaces of the waste tire aggregate to promote
cement paste bonding. When the blending time was completed, all cementitious
materials were added to the mixer then turned over a few times with the aggregate.
This was performed to prevent clumping of the cementitious material onto the walls
of the concrete mixer with the addition of the water containing the water-reducing
admixture. Once all the constituents had been added to the mixer, an additional five
minutes of mixing followed the previous ten minutes of aggregate blending totaling
approximately fifteen minutes of mixing time.
Cementitious material sticking to the walls of the concrete mix was not a
characteristic of any one type of constituent added to the mixer, but is purely
procedural in adding the constituents, and from existing hydrated cement paste on the
interior of the concrete mixer.
Once mixing was complete, contents of the mixer were emptied into a water
dampened wheel cart and used to complete the fresh concrete tests, in addition to
casting the concrete specimen molds for the hardened concrete test phase of each
mixture. Dampening the concrete mixer and the wheel cart was to compensate for
water loss of the batched mixture.
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6.3 Curing Concrete Specimens
This room is dedicated entirely for the purpose of concrete specimen storage and
curing. In the curing room, water tanks are equipped with heaters, circulating pumps
and analog chart recorder with a digital temperature display. The water tanks
maintain a uniform water temperature in accordance with ASTM C-511 for Mixing
Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing
of Hydraulic Cements and Concretes.
Accuracy of the temperature recorder is in question due to the timing of the
last calibration. The interchangeable monthly charts cannot be accounted for, which
would present an accurate account and record of the tank water temperature.
Periodically, the temperature should be checked from the partially functional chart
recorder. It can be reasonably said that the water tanks are maintained at a steady
water temperature of 72F (22C).
Control of the environmental conditions within the curing room is limited
except when the relative humidity drops below the desired 50%, in addition to
temperatures only maintained by the facilities main air handling system. When the
relative humidity drops below the desired 50%, a humidistat controlled humidifier
will be utilized to compensate. No documentation can be presented to account for the
environmental conditions in which specimens were cured and stored.
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6.4 Testing for Concrete Properties
Two main phases of testing took place on the concrete mixtures; distinguished purely
by the physical state of concrete at the time of testing, which is a fresh (plastic) state
and a hardened state. The tests for concrete properties were divided up in to fresh
concrete test and hardened concrete tests. The fresh concrete tests take place during
the batching of the mixture and the hardened concrete tests were tested at intervals
specified by ASTM.
6.4.1 Fresh Concrete Property Tests
Testing the various concrete mixtures was performed for fresh concrete properties
(slump, temperature, air content and unit weight).The properties for fresh concrete are
often used to evaluate the behavior of the constituents that make up the concrete
matrix. Table 6-1 indicates the standard procedure followed in addition to the time at
which testing was completed for the concrete mixtures.
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Table 6-1 Fresh Concrete Properties Tests
Fresh Concrete Property Tests Standard Identification Test Intervals
Slunp ASTM C-l 43 Batching Day
Concrete Temperature ASTM C-1064 Batching Day
Pressure Meter Air Content ASTM C-231 Batching Day
Roller Meter Air Content ASTM C-l '3 Batching Day
Unit Weight ASTM C-l38 Batching Day
6.4.2 Hardened Concrete Property Test
Performance testing for the crumb rubber concrete was completed in accordance to
ASTM. The tests that were performed on hardened concrete are compressive strength,
modulus of elasticity, flexural strength, indirect splitting tensile strength, permeability
and freeze/thaw resistance. The permeability of crumb rubber concrete has not been
documented. In addition to these traditional concrete tests, a leaching test was
performed in order to determine any possible contamination concerns related to field
placement and to extend the life-cycle of the recycled waste tire. Table 6-2 indicates
the standard procedure followed in addition to the time at which testing was
completed for the concrete mixture.
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Table 6-2 Hardened Concrete Properties Tests
Hardened Concrete Property Tests Standard Identification Test Intervals
Compressive Strength .ASTMC-39 1. 7.28.56.91 Days
Modulus of Elasticity in Compression ASTM C-469 28.56 Days
Modulus of Rupture .4STMC-8 28, 56 Days
Indirect Splitting Tensile ASTMC-496 28,56 Davs
Freeze and Thaw Durability ASTMC-666 28 davs and=7.5 Davs
Rapid Cliloride Ion Penetrability ASTM C-l 202 28, 56 Davs
Beneficial Use of Industrial Byproducts ASTM D-398 7 56 Davs
6.5 Mixture Design Proportioning
Proportioning is one of the unique challenges for this study. In order to establish a
consistent yield with the replacements of various constituents, the absolute volume
method was the desirable approach. However, this approach will not permit direct
proportions to the desired strength characteristics. Optimizing any concrete material
in a mixture can only be determined by completing a series of trial batches of which
will lead to further batches until desired results have been achieved.
The study began with seven concrete mixtures designs followed by nine more
that were analyzed and tested extensively. From these nine mixture designs, adequate
knowledge for the development of a concrete pavement containing crumb rubber was
achieved.
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6.5.1 Trial Proportioned Research Mixtures
The first of the mixtures that were batched was for the purpose of establishing a target
recycled waste tire particle and fly ash replacement content. The concrete mixture
designs were adjusted to obtain desirable results for replacement of the constituents.
Displayed in Table 6-3 are the seven trial rubberized concrete mixture designs.
Trial mixtures were completed in order to achieve a viable solution for a
replacement volume while meeting the CDOT requirements for a Class P concrete
used in pavements. A Class P concrete pavement also has another material
requirement that will affect the 28 day strength requirement, that requirement being
fly ash replacement of cement powder. The hardened concrete testing of the three
trial mixtures reviled to the team that 15% of Class F fly ash with a w/c of 0.35
should be used as the basis for the control beam in the study.
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Trial # Mixture ID w/cm Cementitious Content, lbs (kg) ^ 3 > < ^ > N ON 3 % Sand Volume % Crumb Rubber (CR) Coarse Aggregate (Native Rock), % Recycled Concrete Aggregate (RCA), %
1-20 .42/660/FA30/80S/20CR 0.42 660(300) 30 80 20 100 0
1-30 .42/660/FA30/70S/30CR 0.42 660(300) 30 70 30 100 0
1-40 .42/660/FA30/60S/40CR 0.42 660(300) 30 60 40 100 0
2-20 .42/660/FA0/80S/20CR 0.42 660(300) 0 80 20 100 0
2-30 .42/660/FA0/70S/30CR 0.42 660 (300) 0 70 30 100 0
2-40 .42/660/FA0/60S/40CR 0.42 660 (300) 0 60 20 100 0
3-40 . 3 8/660/F A15/60S/40C R 0.38 660(300) 15 60 40 100 0
Key: 0.35/660/FA 15/1OOS/OOC xx Denotes the optimized percentage of'crumb rubber, sand.
o
a
N
o
Table 6-3 Trial Mixture Designs (Fly Ash and w/cm


6.5.2 Mixture Design Identification
The mixture identification for each design provides details regarding the mixture. For
example, the first number (0.42/660/FA10/100S/00CR/00RCA) represents the w/cm
of the concrete mixture. The second number (0.38/660/ FA10/100S/00CR/00RCA)
represents the cementitious content in pounds of cement. The third
(0.42/660/FA10/100S/00CR/00RCA) set of numbers represent the percent
replacement of cement with fly ash (FA). The set of values in the fourth and fifth
place (0.42/660/FA 10/100S/00CR/00RCA) represent the percent replacement values
with one another of sand (S) and crumb rubber (CR). Lastly, the final number
(0.42/660/FA 10/100S/00CR/00RCA) in the mixture identification is the percent
replacement by weight of coarse aggregate with recycled concrete aggregate. Table
6-3 and Table 6-4 list each of the batches used for this study.
6.5.3 Research Mixture Design
The trial proportioned mixture results lead to mixture design proportions that can be
further refined for optimization of recyclable materials and performance. Displayed
in Table 6-4 are the eight trial rubberized concrete mixture designs.
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Mix Mixture ID \v cm Cementitious Content, lbs (kg) Fly .Ash (FA), o o Sand Volume o Crumb Rubber (CR) Coarse Aggregate (Native Rock). % Recycled Concrete Aggregate (RCA). o
1 0.35'660 FA15 lOOS OOCR OORCA 0.35 660 (300) 15 100 0 100 0
2 0 35 660 TA15 -90S 1 OCR OORCA 0.35 660 (300) 15 90 10 100 0
3 0 35 '660 FA 15 90S 1 OCR OORCA 0.35 660 (300) 15 20 80 100 0
4 0.35 660 FA15'70S30CR OORCA 0.35 660 (300) 15 70 30 100 0
5 0.35/660 FA15 -60S '40CR OORCA 0.35 660 (300) 15 60 40 100 0
6 0.35/660 FA 15 '50S'50CR OORCA 0.35 660 (300) 15 50 50 100 0
7 0.35/660 TA15 ODt.S/20CR 50RCA 0.35 660 (300) 15 80 20 50 50
8 0 35 660 TA15 Out.S 30CR 50RCA 0.35 660 (300) 15 70 30 50 50
Kev: 0.35 660 FA15 lOOS OOCR OORCA
w cm
Cement
Content
oCrunto
Rubber
and flyash determined from the laboratory trials
o Recycled
Concrete Aggregate
Ul
Table 6-4 Research Mixture Designs for Optimization


6.6 Data Analysis
Test results collected from this study were compared to past studies to determine
whether similar or even new trends developed with the crumb rubber inclusion. In
addition, it is expected that the data and experience gained through this study will be
used to provide recommendations for further developments for this material as well as
for a field implementation of the crumb rubber concrete in an alley panel located in
the City and County of Denver.
6.7 Design Summary
For this study to proceed, know how to accurately determine the specific gravity of
recycled waste tire particles used in concrete. Past researches found this process
produced a broad range of results for all the various sizes of TDA available to market.
Trial mixtures progressed while the investigation in to the crumb rubbers specific
gravity was being determined. The trial mixtures will be evaluated for compression
to determine reasonable replacement contents of recycled waste tire particles and fly
ash. The water cement ratio was adjusted at two intervals for testing. These two
intervals would lead to the water cement ratio used for the design mixtures.
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Chapter 7
Experimental Results
7.1 Batching of Trial Mixtures
Once the design plan had been set in place, the batching and testing of the trial
mixtures progressed smoothly. The batching of several trial mixtures using 20, 30
and 40% replacements of sand with a 30% replacement of cement with fly ash were
completed.
Adjustments were made accordingly to Table 7-1 to improve upon the
replacement quantity of the virgin aggregate while still being able to meet the quality
specifications for a Class P mixture. Proportioning of the trial concrete mixtures was
determined in stages as seen in Table 7-2. Throughout this chapter, the mixture under
discussion will be addressed as the mix number (Mix #), versus the designated batch
identification.
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Trial # Mixture ID wcm Cementitious Content, lbs (ks) Fly Ash (FA), % o Sand Volume o Crumb Rubber (CR) Coarse Aggregate (Native Rock). o Recycled Concrete Aggregate (RCA). o
1-20 .42 660 FA30/80S/20CR 0.42 660 (300) 30 80 20 100 0
1-30 .42 660-FA30/70S 30CR 0.42 660 (300) 30 70 30 100 0
1-40 .42/660. FA30'60S'40CR 0.42 660 (300) 30 60 40 100 0
2-20 .42/660 FA0 80S'20CR 0.42 660 (300) 0 80 20 100 0
2-30 .42 660 FA0'70S/30CR 0.42 660 (300) 0 70 30 100 0
2-40 .42/660 FA0 60S/40CR 0.42 660 (300) 0 60 20 100 0
3-40 .38 660 FA15 60S/40CR 0.38 660 (300) 15 60 40 100 0
Key; 0.35 '660/FA15'100S OOC xx Denotes tlie optimized percentage of crumb rubber, sand,
^ t \ \ *\and 11 yash determined fromthe laboratory trials
w/c
% Recycled Concrete
Aggregate
Cement .F,ly ./Sand
Content
Ash
oo
0 Crumb
Rubber
Table 7-1 Trial Mixture Proportions


Table 7-2 Batching and Testing Schedule for the Trial Mixtures
Trial Batch Identification Mix # Batcliina 7 DavTest 28 DavTest
0.42/660/FA30/80S/20CR/OORCA TR1-20
0.42 660/FA3 0 70 S/3OCR 00RCA TR1-30 10 02 10 10 09 10 10 30 10
0.42 660/FA30 60S/40CR 00RCA TR1-40
0.42 '660/FA0'80S'20CR00RCA TR2-20
0.42'660/FA0/70S'30CR 00RCA TR2-30 10 09 10 10 16/10 11 06/10
0.42 660TA0 60S40CR00RCA TR2-40
0.38'660/FAl 5/60S/40CROORCA TR3-40 IO'30'IO 11 06 10 11/27/10
7.2 Fresh Concrete Testing of Trial Mixtures
The trial mixtures were only tested for characteristics necessary to start proportioning
the design batches. In order to determine correct dosages for the design batches, fresh
concrete properties were performed for slump and air content. Table 7-3 lists the
values for slump, air content and the dosages used to improve upon the
aforementioned.
For Mix #TRl-20, Mix #TRl-30 and Mix #TRl-40, only a WRA was used
for workability. The significant increase in WRA dosage from Mix #TRl-20 to Mix
#TRl-40 was to adjust for the increased recycled waste tire particles in the mixture
which results in reduced work-ability. This was performed to improve upon how well
the mixture would flow for ease of placement and casting of laboratory molds.
No AEA was used for Mix #TRl-20, Mix #TRl-30 and Mix #TRl-40, which
did not permit the air content to move beyond 1 3% of entrapped air in the mixture.
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AEA was added to the second set of trial mixtures to improve upon what was only the
air content from the first batch, which had only entrapped air. Mixtures #TRl-30 and
#TR2-30 use the same dosage rates of WRA; however, Mix #TR2-30 included an
AEA. As a result, the air content was increased to levels that were acceptable to the
CDOT Class P requirements. AEA and WRA will enhance the effect of the other
pending the dosage of each to a mixture.
One affect was a further reduction in the water content of the last two trial
mixtures. The WRA was increased to reduce the water demand to achieve greater
strength. In addition to the lower water content making the mixtures stiffer, the
increasing volume of recycled waste tire particles resulted in a harsher mixture.
Table 7-3 Fresh Concrete Test Results with Chemical Admixtures Dosages
Mix # TR1-20 TR1-30 TR1-40 TR2-20 TR2-30 TR2-40 TR3-40
Slump, in (mm) 7.75 (197) 3.00 (76) 4.75 (121) 2.5 (64) 3.25 (83) 3.25 (83) 7.75 (197)
.Air Content, (o) 2.0 2.5 2.5 3.9 5.6 6.1 5.6
WRA. fl. oz./cwt (mL 100kg) 46.0 (1361) 9.2 (272) 20.7 (612) 9.2 (272) 9.2 (272) 20.7 (612) 29.9 (885)
AEA. fl. oz. cwt (mL 100 kg) 0.0 (00) 0.0 (00) 0.0 (00) 0.92 (27) 0.92 (27) 0.92 (27) 2.3 (68)
The results from these trial mixtures exhibit similar trends to that discovered
in the literature review except for the increase in air content with increased recycled
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waste tire particles content; however, the workability factor does correlate with
previous trends. The AEA and WRA dosage range for the design mixtures was
approximately (2.5 (73) and 18.4 (544)) fl. oz./cwt (mL/lOOkg), respectively.
7.3 Compressive Strength of Trial Mixtures
Examining the 7 and 28 day compressive strength results obtained from the first three
trials, the w/cm was reduced to 0.38 in an effort to improve upon the necessary
requirements for a Class P concrete pavement. The additional two mixtures were
evaluated using a 40% replacement of sand and 15 percent fly ash content with a
revised w/cm. Continued adjustments to the mixtures were made based upon the 7
and 28 days of age compressive strengths until proprotioning would allow for the
Class P requirements to be met.
Table 7-4 Compressive Strength Results for Trial Batches
TR1-20 psi (MPa) TR1-30 psi (MPa) TR1-40 psi (MPa) TR2-20 psi (MPa) TR2-30 psi (MPa) TR2-40 psi (MPa) TR3-40 psi (MPa)
7 days 2545(18) 2300(16) 1925 (13) 3460(24) 2855(20) 2555(18) 2710(19)
28 davs 3235 (22) 3240 (22) 2490(17) 4125(28) 3400 (23) 3190 (22) 3280(23)
Figure 7-1 displays the strength development of the 7 trial mixtures listed in
Table 7-1 that includes replacement of sand with recycled waste tire particles. A 40%
81


sand replacement with crumb rubber was used as the maximum replacement value for
the trial mixtures. This was the baseline to examine the effects of changing the
volume of fly ash and w/cm to increase the strength of the control beam. Having an
acceptable replacement quantity of fly ash for the control beam allowed for the
necessary strengths of a Class P concrete pavement to be reached with the largest
possible volume of recycled waste tire particles being used. The compressive
strengths of the seven trial mixtures are listed in Table 7-4. The 7 and 28 day strength
values along with extended values for three of the mixtures are provided in the table.
Photographs of these samples tested to failure are shown in Figure 7.1. The trend line
slopes shown for Mix #TR2-40 and Mix #TR3-40 are representative of the time in
which they were moisture cured.
82