Citation
Beneficial use of recycled materials in controlled low strength materials

Material Information

Title:
Beneficial use of recycled materials in controlled low strength materials
Creator:
Gemperline, Claire Sarah
Publication Date:
Language:
English
Physical Description:
xi, 179 leaves : illustrations ; 28 cm

Thesis/Dissertation Information

Degree:
Master's ( Master of Science)
Degree Grantor:
University of Colorado Denver
Degree Divisions:
Department of Civil Engineering, CU Denver
Degree Disciplines:
Structural engineering

Subjects

Subjects / Keywords:
Soil cement ( lcsh )
Fills (Earthwork) -- Materials ( lcsh )
Recycling (Waste, etc.) ( lcsh )
Fills (Earthwork) -- Materials ( fast )
Recycling (Waste, etc.) ( fast )
Soil cement ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references (leaves 131-136).
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Claire Sarah Gemberline.

Record Information

Source Institution:
|University of Colorado Denver
Holding Location:
Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
785241304 ( OCLC )
ocn785241304
Classification:
LD1193.E53 2011X G46 ( lcc )

Full Text
BENEFICIAL USE OF RECYCLED MATERIALS
IN CONTROLLED LOW STRENGTH MATERIALS
by
CLAIRE SARAH GEMPERLINE
B.S. Civil Engineering, University of Colorado Denver, 2008
A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado Denver
in partial fulfillment
of the requirements for the degree of
Master of Science, Structural Engineering
Civil Engineering
2011


This thesis for the Master of Science degree by
Claire Sarah Gemperline
has been approved
by
Date
Dr. Rui Liu


Gemperline, Claire Sarah (M.S. Civil Engineering)
Beneficial Use of Recycled Materials in Controlled Low Strength Materials
Thesis directed by Dr. Stephan A. Durham
ABSTRACT
Controlled low-strength material (CLSM) is a self-compacting, flowable, low
strength, cementitious material used primarily as backfill and void fill. CLSM is
primarily used as a replacement of compacted soil in cases where the application
of the later is difficult or impossible. Strength requirements are low in
comparison to typical structural concrete. This enables the use of low cost,
abundant, industrial by-products for the production of CLSM. The use of
industrial by-products in CLSM is the focus of this Thesis.
This thesis explains that the two most important properties of a CLSM are
the flowability and compressive strength. The flowability of CLSM must allow
efficient placement without segregation, while the compressive strength must
provide structural support but allow for easy excavation. Consequently, there
are minimum and maximum performance criteria for both consistency and
strength. This research investigated the effects of using recycled materials in
CLSM on the fresh and hardened CLSM properties. A total of six materials were
used to create 18 mixtures that were batched and tested. The cementitious
materials investigated were Class C fly ash and spray dryer ash; and the
aggregates tested were bottom ash, crushed glass, recycled concrete fines, and
crumb rubber. The results showed that in most cases, CLSM with acceptable
strength and flowability properties can be made using these recycled materials.


The following were observed for mixtures that achieved typical CLSM
consistency requirements.
Compressive strength increased as the Class C fly ash content increased
from 90 to 100 percent of the total cementitious content.
Compressive strength decreased as the amount of SDA content increased
from 90 to 100 percent of the total cementitious content. It is possible
that reduction in strength is due to sulfate attack.
Strength increased as the aggregate fraction of bottom ash was changed
from 25 percent to 75 percent, but decreased as the fraction was changed
from 75 to 100 percent. It is unclear if this is due to a concurrent increase
in water to cement ratio caused by adding water during batching to
maintain acceptable consistency.
The crumb rubber aggregate mixtures exhibited low unit weight, a
tendency for segregation, low strength, the lowest modulus of elasticity
measured, and was the most ductile during compression testing.
Waste glass mixtures exhibited consistency and mixing characteristics
similar to C 33 sand. The compressive strength increases as the fraction
of glass in the mixtures increased. Finely crushed concrete as aggregate
demonstrated similar fresh CLSM properties as bottom ash. Strengths for
the mixtures tested were too low to be considered useful in common
CLSM applications. It is likely that the low strengths are a consequence of
high water to cementitious ratios.
Typically the strains at yield were less than 1.5 percent except for crumb
rubber mixtures. The yield strains of crumb rubber mixtures were
typically greater than 1.5 percent indicating greater ductility than other
mixtures.


This abstract accurately represents the content of the candidates thesis. I
recommend its publication.
Approved: Dr. Stephan A. Durham
Dr. Stephan A. Durham


DEDICATION
I dedicate this thesis to my family and friends for continually supporting me; my
mother and father for showing me that giving up isnt an option, and never
doubting me and my abilities; and my brothers, sister, and sister-in-laws for the
inspiration to become an engineer.


ACKNOWLEDGMENT
I would like to thank my academic advisor, Dr. Stephan A. Durham, for his
patience, support, and the never-ending encouragement over the years. I would
like to thank Dr. Rui Liu and Dr. Rens for their support and participating on my
committee. I would like to thank Dr. Rutz for contributing to my education at the
University of Colorado at Denver. I would like to thank Dr. N.Y. Chang for his
guidance, support and kindness through the years. 1 would also like to thank
Adam Kardos, Andrea Soils, Zack Ballard, Matthew Gemperline, and Derek Chan
for their support and much appreciated help during my research.
1 would like to thank Mr. David Neel for the support, materials, and
knowledge he contributed; all of which was essential to the success of this thesis.
1 would like to thank Mr. Amster Howard for sharing his knowledge and
experience on the topic of controlled low strength materials. It was by his
suggestion that 1 was encouraged to explore this topic. 1 would like to thank MCG
Geotechnical Engineering, Inc. for financial support, which allowed me to
perform this thesis and continue with my academic career.
Additionally, 1 would like to thank the faculty and staff of the University of
Colorado Denver Civil Engineering Department for their support and guidance
throughout my academic career.


TABLE OF CONTENTS
Figures.........................................................................vii
Tables ..........................................................................ix
Chapter
1. Introduction...................................................................1
2.1.1 Cementitious Material.....................................................5
2.1.2 Aggregates................................................................7
2.3.1 Fly Ash..................................................................12
2.3.1.1 Production...............................................................12
2.3.1.2 Physical, Chemical and Reactive Properties...........................14
2.3.1.3 The Effects of Class C Fly Ash on CLSM Properties........................16
2.3.1.3.1 Flow Consistency.......................................................16
2.3.1.3.2 Bleeding and Segregation...............................................18
2.3.3.3 Air Content..............................................................19
2.3.1.3.4 Time of Set............................................................20
2.3.1.3.5 Strength...............................................................22
2.3.2 Spray Dryer Ash........................................................22
2.3.2.1 Production...............................................................22
2.3.2.2 Physical, Chemical and Reactive Properties...............................24
2.3.2.3 The Effects of Spray Dryer Ash on CLSM Properties.......................25
2.3.2.3.1 Flow Consistency.......................................................25
2.3.2.3.2 Bleeding and Segregation...............................................26
2.3.2.3.3 Air Content............................................................26
2.3.2.3.4 Time of Set............................................................27
vii


2.3.23.5 Strength............................................................27
2.3.3 Bottom Ash.............................................................29
2.3.3.1 Production...........................................................29
2.33.2 Physical, Chemical and Reactive Properties...........................30
2.3.33 The Effects of Bottom Ash on CLSM Properties.........................32
2.333.1 Flow Consistency....................................................32
2.333.2 Bleeding and Segregation............................................34
2.33.3.4 Time of Set.........................................................35
2.33.3.5 Strength............................................................36
23.4 Crushed Waste Glass as Aggregate.......................................37
23.4.1 Production...........................................................39
23.4.2 Physical and Chemical Properties.....................................40
2.3.43 The Effects of Waste Glass on CLSM Properties.........................42
23.43.1 Flow Consistency....................................................42
23.43.2 Bleeding and Segregation............................................43
2.3.433 Air Content..........................................................43
23.43.4 Time of Set.........................................................44
23.43.5 Strength............................................................45
2.3.5 Recycled Concrete as Aggregate......................................46
23.5.2 Physical, Chemical and Reactive Properties..........................47
2.3.53 The Effects of Recycled Concrete as Aggregate on CLSM Properties.....48
23.53.1 Flow Consistency....................................................48
23.53.2 Bleeding and Segregation............................................49
2.3.533 Air Content.........................................................49
2.3.533 Time of Set.........................................................49
23.53.5 Strength............................................................50
2.3.6 Recycled Crumb Rubber as Aggregate.....................................50
23.6.1 Production...........................................................50
23.6.2 Physical, Chemical and Reactive Properties...........................51
viii


2.3.6.3 The Effects of Recycled Crumb Rubber as Aggregate on CLSM Properties.... 53
2.3.6.3.1 Flow Consistency......................................................53
2.3.6.3.2 Bleeding and Segregation..............................................55
2.3.6.3.3 Air Content and Unit Weight...........................................55
2.3.6.3.4 Time of Set...........................................................56
2.3.6.3.5 Strength..............................................................56
3. Problem Statement............................................................58
3.1 Statement..................................................................58
4. Experimental Plan............................................................61
4.1 Design Summary.............................................................61
4.2 Material Properties........................................................65
4.2.1 Class C Fly Ash...........................................................65
4.2.2 Portland Cement...........................................................67
4.2.3 Spray Dryer Ash...........................................................68
4.2.4 (Virgin) Fine Aggregate...................................................69
4.2.5 (Recycled) Fine Aggregate.................................................69
4.2.5.1 Crushed Waste Glass.....................................................70
4.2.5.2 Bottom Ash..............................................................74
4.2.5.3 Recycled Concrete (RCA).................................................77
4.2.5.4 Crumb Rubber............................................................80
4.3 Experimental Design........................................................83
4.3.1 Cementitious Materials Investigation Design...............................83
4.3.2 Aggregate Replacement Investigation Design................................83
4.3.1 Mixture Batching..........................................................86
4.3.2 Curing....................................................................87
4.4 CLSM Testing...............................................................87
5. Experimental Results.........................................................89
5.1 General....................................................................89
5.2 Fresh Concrete Properties..................................................89
IX


5.2.1 Flow Consistency......................................................90
5.2.2 Air Content...........................................................95
5.2.3 Unit Weight...........................................................97
5.2.4 Bleeding and Segregation.............................................101
5.2.5 Set Time.............................................................102
5.3 Hardened CLSM Properties...............................................102
5.3.1 Compressive Strength.................................................103
5.3.2 Modulus of Elasticity................................................114
5.3.2 Relationships Between Hardened Properties and Test Variables.........118
5.3.2.1 Cementitious Materials Investigation...............................118
5.3.2.2 Aggregate Investigation............................................118
6. Conclusions and Recommendations.........................................122
6.1 Summary................................................................122
Bibilography...............................................................131
Appendix
APPENDIX A.....................................................137
APPENDIX B.....................................................155
x


FIGURES
Figures
Figure 2.1 Compressive Strength of CLSM with 3% Cement Used
(Hardjito, 2011)..............................................37
Figure 2.2 Setting and Hardening Characteristics of Sand/Glass Mixtures
(Naik, 2000)..................................................44
Figure 2.3 Compressive Strength of Glass/Fly ash CLSM Mixtures
(Naik, 2000)..................................................45
Figure 2.4 Compressive Strength of Sand/Glass CLSM Mixtures
(Naik, 2000)..................................................46
Figure 4.1 Average Crushed Glass & C 33 Sand Gradation Analysis..........73
Figure 4.2 Average Bottom Ash & C 33 Sand Gradation Analysis.............76
Figure 4.3 Average Recycled Concrete Fines & C 33 Sand
Gradation Analysis............................................79
Figure 4.4 Average Crumb Rubber & C 33 Sand Gradation Analysis.........82
Figure 5.1 Picture of a flow patty.......................................91
Figure 5.2 Average Cementitious Flow Diameters.................92
Figure 5.3 Average Aggregate Flow Diameters..............................92
Figure 5.4 Photo of a CLSM in the MTS testing machine...................104
Figure 5.5 Photo of fractured test specimen.............................105
Figure 5.6 Compressive Strength vs. Age for Class C Fly Ash (FA)........108
Figure 5.7 Compressive Strength vs. Age of Spray Dryer Ash (SDA)........109
Figure 5.8 Compressive Strength vs. Age of Bottom Ash (BA)..............109
Figure 5.9 Compressive Strength vs. Age of Crumb Rubber (CR)............110
Figure 5.10 Compressive Strength vs. Age of Recycled
Crushed Glass (RCG)..........................................110
vii


Figure 5.11 Compressive Strength vs. Age of Recycled
Concrete Aggregate (RCA)....................................Ill
Figure 5.12 28-Day Yield Strength vs. 28-Day MOE.......................117
vm


TABLES
Tables
Table 2.1 Overview of Fly Ash Constituent Compounds -
Expressed in PPM (EPA, 2011)..................................15
Table 2.2 Chemical Requirements ASTM C 618...............................15
Table 2.3 CLSM Mixtures Proportions and Fresh Properties
(Du, Kolver, and Trejo, 2002).................................18
Table 2.4 Mixture Proportions and Field Test Data (Naik, 1990)...........20
Table 2.5 Spray Dryer Ash Chemical Composition
(Naik, Singh, 1993)...........................................24
Table 2.6 Flowability and Water Content (Butalia, Wolfe & Lee, 1999).....25
Table 2.7 Flowability and Water Content
(Butalia, Wolfe, Zing & Lee 2004).............................26
Table 2.8 Flowability and Water Content (Butalia, Wolfe & Lee, 1999).....28
Table 2.9 Overview of Bottom Ash Compounds, expressed in PPM
(www.tfhrc.gov, 2011).........................................30
Table 2.10 Typical Physical Properties of Bottom Ash (FHA, 2001).........31
Table 2.11 CLSM Mixture Proportions and Fresh Properties (Du, 2002)......34
Table 2.12 Chemical Compositions of Various Color Glass
(Shaman, 2002)................................................41
Table 2.13 Flowability and Water to Cementitious Ratio...................43
Table 2.14 Mix Proportions of CLSM with Fine Recycled Concrete Aggregate
(Achtemichuk, 2008)...........................................49
Table 2.15 Typical Materials used in Manufacturing Tire (Rubber
Manufacturer's Association, 2000).............................52
IX


Table 2.16 Flowabilty, and Bleeding.........................................54
Table 2.17 Flowability, Bleeding and Initial Hardening
Time for all Mixtures............................................56
Table 2.18 Average Compressive Strength (Pierce & Blackwell 2002)...........57
Table 4.1 Colorado Department of Transportation (CDOT) Structural Backfill
Specifications (CDOT, 2011)......................................64
Table 4.2 ASTM Standards Specifications.....................................64
Table 4.3 Pawnee Class C Fly Ash Physical
and Chemical Properties..........................................66
Table 4.4 Holcim Type I-II Cement Physical and Chemical Properties..........67
Table 4.5 Chomanche Spray Dryer Ash Physical and Chemical Properties........68
Table 4.6 Testing of Recycled Materials.....................................70
Table 4.7 Fine Aggregate Properties of Waste Glass and C 33 Sand............71
Table 4.8 Fine Aggregate Properties of Bottom Ash and C 33 Sand.............74
Table 4.9 Fine Aggregate Properties of Recycled Concrete
Fines and C 33 Sand..............................................77
Table 4.10 Fine Aggregate Properties of Crumb Rubber and C 33 Sand..........80
Table 4.11 CLSM Mixture Design Matrix by % Replacement......................85
Table 4.12 CLSM Mixture Design Matrix (lb/yd3)..............................85
Table 4.13 Fresh and Hardened CLSM Properties Tested........................89
x


Table 5.1 Fresh CLSM Properties For Cementitious Replacements.........89
Table 5.2 Fresh CLSM Properties For Recycled Fine
Aggregate Replacement........................................90
Table 5.3 Cementitious Mixtures Average Flow
Consistency and w/cm ratio...................................93
Table 5.4 Aggregate Mixtures Average Flow
Consistency and w/cm ratio...................................95
Table 5.5 Measured and Calculated Unit Weights and Air Content.........98
Table 5.6 Measured and Calculated Unit Weights and Air Content.........99
Table 5.7 Cementitious Measured & Air Adjusted Theoretical
Unit Weights................................................100
Table 5.8 Aggregate Measured & Air Adjusted Theoretical
Unit Weights................................................100
Table 5.9 Penetrometer Test for SDA Mixtures..........................102
Table 5.10 Removability Modulus for Cementitious Replacements..........108
Table 5.11 Removability Modulus for Recycled
Aggregates Replacements (CDOT, 2011)...................... 108
Table 5.12 Average Compressive Strengths of Recycled Materials
Replacements................................................112
Table 5.13 28-Day Compressive Strength, Yield Stress, Yield Strain, Strain at 40
percent compressive stress, and MOE ...................................116
Table 6.1 Mixtures that achieved CLSM Consistency and Strength........127
xi


1.
Introduction
Engineering applications for controlled low-strength material (CLSM) are
continually being discovered. CLSM has been shown to improve structural
performance and expedite the construction process in multiple applications.
Examples include the use of CLSM as embedment material to support buried
flexible pipe and as backfill for retaining walls. Besides having practical
engineering application, CLSM can help to fulfill the national commitment to
effectuate sustainable development by making valued use of common waste
materials. This thesis demonstrates that CLSM can be manufactured using
industrial waste and recycled materials and thereby reduce the need to use
rapidly disappearing natural aggregates and mineral resources. Furthermore, it
is herein demonstrated that the desired strength, flowability and flexural
characteristics of CLSM can be obtained by the selective use and proper
proportioning of recycled materials.
Controlled low-strength material (CLSM) is defined by American Concrete
Institute (ACI) Committee 229 as a self-compacted cementitious material used
primarily as a backfill in place of compacted fill. CLSM is also known by other
names including flowable fill, unshrinkable fill, controlled density fill, flowable
mortar, flowable fly ash, fly ash slurry, plastic soil-cement, K-Krete, and soil-
cement slurry (ACI 1999).
CLSM is commonly specified and used in lieu of compacted fill in various
applications, especially for backfill, utility bedding, void filling, and bridge
approach support. Backfill applications include backfilling foundation walls, such
as retaining walls; or to fill both shallow and deep trenches. Utility bedding
involves the use of CLSM as a bedding material for buried water conveyance
1


pipe, electrical conduits, and other similar utilities where gravity flow of CLSM
into hard-to-reach places poses an advantage. Void-filling applications include
the filling of sewers, tunnels, shafts, basements, or other underground
structures. Bridge approach applications use CLSM as either a sub-base for the
bridge approach slab or as a structural backfill against wing-walls or other
bridge foundation elements (AC1 1999).
CLSM is commonly described as a material constructed of aggregate and
cementitious material that results in a compressive strength of 1200 psi (8 MPa)
or less. Generally, CLSM applications require unconfined compressive strength
of 200 psi (1.4 MPa) or less. The lower strength requirement is to provide easy
excavation in the event the CLSM must be removed, for example, in the event a
buried pipeline requires excavation for repair or replacement. A flowable nature
to the material is generally desired in order to facilitate placement in voids
beneath foundations, under overhanging constructions, and in the annular space
around buried pipes.
The American Concrete Institute AC1 229 committee describes CLSM as a
family of mixtures used in a variety of applications. The advantages associated
with its use include: reduced labor, reduced equipment costs, faster
construction, and the ability to place material in cramped spaces by gravity flow
(ACI 1999).
CLSM constructed using industrial by-products, such as fly ash and
foundry sand, have the positive effects of reducing landfill demand and
supporting the civil demand for sustainable development. The worlds need for
sustainable development and reduction of the waste burden on landfills
supports the need for this research and development.
The purpose of this thesis is to 1) determine if CLSM can be created using
spray dryer ash (SDA) as the principle cementations material, 2) add to the
2


growing body of knowledge regarding approximate mix proportions for CLSM
manufactured using crushed glass, bottom ash, crushed concrete and crumb
rubber as a portion or all of the aggregate, and 3) measure and compare the rate
of strength increase and the modulus of elasticity (MOE) of CLSM manufactured
from the above materials. The research presented herein investigates the effects
that the materials discussed above have on the fresh and hardened properties of
CLSM. Various proportions of the recycled materials were used in CLSM
mixtures. The mixtures for this research project consisted of aggregates
proportioned by volume and cementitious material proportioned by mass. The
control mix was a typical CLSM comprised of fine sand; cementitious material
consisting of 90 percent Class C fly ash and 10 percent cement; and a water to
cementitious ratio (w/cm) of 1.25. The test program has two components 1) the
cementitious materials investigation, and 2) the aggregate investigation.
Portland cement was mixed with either Class C fly ash or SDA using sand as a
fine aggregate. The compositions were as follows:
Class C fly ash mixtures included fly ash as 90, 95 and 100 percent of the
cementitious material.
SDA mixtures included SDA as 90, 95 and 100 percent of the cementitious
material.
Sand was replaced with either crumb rubber, bottom ash, recycled concrete
or crushed glass. Regarding aggregate compositions:
The aggregates were substituted for the sand with 25, 75 and 100 percent
replacement.
All mixtures to investigate aggregates used cementitious material
comprised of 90 percent Class C fly ash, and 10 percent portland cement.
All mixtures were designed to have 630 lbs/yd3 cementitious material except
SDA mixtures which was designed to have 750 lbs/yd3 cementations material.
3


The necessary CLSM requirement that it have a flowable consistency was
assured for all mixes by adjusting batch quantities during the batching process.
A water to cement ratio (w/cm) of 1.25 was maintained to the extent
practicable. Exceptions were necessaiy to achieve consistency requirements for
CLSM and are noted herein. All mixtures were tested for fresh and hardened
CLSM properties. The fresh CLSM properties tested included slump, unit weight
and air content. The hardened CLSM properties examined were compressive
strength, and modulus of elasticity. All testing conformed to American Society of
Testing Materials (ASTM) testing standards and all data results, details and
conclusion of findings from this research are included with this thesis.
This thesis is organized as follows: Chapter 2 presents a brief history and
literature review; Chapter 3 provides a problem statement of the research;
Chapter 4 describes the experimental plan; Chapter 5 discuses the experimental
results and Chapter 6 presents the conclusion and recommendations.
4


2.
Literature Review
The raw cementitious and aggregate materials being investigated are common
industrial and/or recycled waste. This section begins by providing a brief
summary of the nature and origin of each material, and the reasons for their
selection. This is followed by a summary, by material, of pertinent research
performed by others. Relevant material properties and CLSM investigation
considerations are also included.
2.1 Nature of the Investigated Cementitious and Aggregate Materials
The composition of early CLSM mixtures was restricted to cement, water, and
mineral aggregates such as sand and gravel. All these materials in their purest
forms are very costly, draw heavily on natural resources and/or are created by
manufacturing processes that consume large amounts of energy and thereby are
associated with environmentally significant and undesirable CO2 emissions.
Therefore, it is beneficial if sources of CLSM aggregate and cementitious material
are derived from less costly sources and sources that are less environmentally
damaging in their production. The following discussion presents a brief
summary of the materials selected for research and the rationale for their
selection.
2.1.1 Cementitious Material
The production of cement, commonly known as portland cement (PC), requires a
significant amount of energy and the use of an ever-diminishing supply of raw
materials. The production of portland cement accounted for about 3.4 percent of
5


global CO2 emissions in 2000, and the United States is the world's third largest
cement producer with production occurring in 37 states (Marland, 2003).
Carbon dioxide (CO2) is a green house gas, and is believed to be a main
contributor to global climate change. Portland cement production is a key source
of CO2 emissions, due in part to the significant reliance on coal and petroleum
coke to fuel the kiln for clinker production. Portland cement production is a
contributor to green house gases (EPA, 2004).
The concrete industry has been using coal fly ash to make high quality
concrete for many years. Fly ash is a waste by-product of coal combustion that
has found use in a wide range of construction applications, including use as a
partial replacement to cement in concrete. It's has been well established that the
use of fly ash with portland cement promotes long-term strength, durability, and
increases workability of concrete.
Fly ash is readily available at a relatively low cost. In 2001, 52 percent of
the electricity in the United States was produced by coal fired electric utilities
(ACAA, 2011). Fly ash is used mostly in portland cement concrete, but its use in
CLSM has grown considerably in recent years. Fly ash is used in combination
with portland cement in this study to create a common CLSM mix for
comparison to more innovative mixtures. It is also used in constant mixture ratio
with portland cement for mixtures that investigate aggregate selection effects on
CLSM.
A rarely used industrial by-product is spray dryer ash (SDA). In 2005 the
United States reported that 1,427,263 short tones of dry flue gas desulfurization
(FGD) material were produced and of that 159,198 short tons (or 11.15 percent)
were beneficially used (ACAA, 2005). Fly ash and SDA is known to have
pozzolanic characteristics. Pozzolans are siliceous or aluminsiliceous material
that, in finely divided form and in the presence of moisture, chemically reacts
6


with the calcium hydroxide released by the hydration of portland cement to
form calcium silicate hydrate and other cementitious compounds (PCA, 2005).
Pozzolans are generally categorized as supplementary cementitious materials or
mineral admixtures. Because spray dryer ash and fly ash have pozzolanic
characteristics, their use as cementitious material replacement in CLSM mixtures
is expected to result in desired strength and consistency.
2.1.2 Aggregates
The replacement of CLSM aggregate with recycled materials is becoming
increasingly popular. Aggregate is primarily a granular filler material within a
CLSM mixture.
Large amounts of industrial waste having a granular nature accumulate
every year in all industrial countries. These materials are, in general, unsuitable
for use in the construction industry due either to their high content of very fine
particles; or due to their poor mechanical properties. Sand is primarily used as
aggregate in CLSM mixtures. However, the availability of aggregate sources has
decreased. From the environmental perspective, the mining of aggregate
generates significant quantities of undesirable CO2 from equipment emissions.
The use of recycled materials as aggregate is expected to eliminate these
emissions and thereby improve environmental quality. There are a variety of
recycled materials that could be suitable aggregate for use in CLSM. Recycled
concrete, bottom ash, crumb rubber, and crushed glass all have promising
characteristics, are readily available, are low cost, and their use is
environmentally friendly. They are selected for use in this study for these
reasons.
7


2.1.2.1 Recycled Concrete Fines
Aggregate size particles of recycled concrete are created by crushing waste
concrete originating from demolition of civil constructions such as buildings,
sidewalks, streets, etc. Crushed concrete is separated into different size ranges
for reuse in various applications.. However, the very fine fraction is not as
desirable, demand is low, and interest in its potential use as CLSM is increasing
(Achtemich, 2009). The use of the crushed concrete fines in CLSM is expected to
reduce potential harmful effects on the environment in two ways. First, it will
reduce the disposal of fine crushed concrete and thereby reduce the use of
valuable and limited landfill space. Second, potential leaching of trace chemicals
from crushed concrete into nearby water sources would be eliminated by
encapsulation of these undesirable components in a cemented matrix.
2.1.2.2 Crushed Waste Glass
Crushed glass has recently gained attention as a potential aggregate substitute in
CLSM due to availability and low cost. Glass bottles are typically reused to make
more bottles, but when the glass cant be reused the glass is stockpiled and then
disposed in landfills. Therefore, finding a use for such glass would provide
environmental benefit by reducing landfill demand. Aggregate replacement with
crushed glass will likely be increase in future CLSM applications.
2.1.2.3 Bottom Ash
Bottom ash is another by-product of burning coal and is a common waste
produce from coal-fired power plants. It does not have the strong pozzolanic
properties of fly ash and SDA. However, its larger size, low cost, and abundance
8


makes is a good candidate for CLSM aggregate. Bottom ash is composed of the
large and small noncombustible particles that cannot be carried by the hot gases
and therefore settle at the bottom of the furnace in a solid or partially molten
condition (Hardjito, 2011}. Bottom ash is commonly sluiced from the furnaces
and often disposed in ponds. During this process the particles are pulverized to
sizes predominantly between 75 microns and 25 millimeters. Bottom ash has
successfully been used as an aggregate in CLSM mixtures. Its availability, and low
cost make it attractive as an aggregate source. However, little information is
available regarding proper CLSM mix proportions. It is investigated here to
increase this body of knowledge.
2.1.2.4 Crumb Rubber
Hard aggregate is essential to create high strengths for structural concrete.
However CLSM is a low strength material by definition. This suggests that
sources of "soft aggregate, such as crumb rubber, may be successfully used in
CLSM.
Crumb rubber is created by grinding scrap tires. The United States
produces nearly 300 million scrap tires per year (Rubber Manufacturers
Association 2006). Of these scrap tires, 14 percent are placed in landfills or
dumped in stockpiles. Hence, crumb rubber is a readily available and low cost
material and therefore an attractive CLSM aggregate replacement.
A literature review was performed to locate results of previous research
related to the use of Class C fly ash, spray drier ash, bottom ash, recycled crushed
glass, recycled concrete and/or crumb rubber in CLSM. The results of this
review are presented next.
9


2.2 Historical use of CLSM
Soil-cement has been a widely used material in geotechnical-engineering
practices for a long time. Flowable CLSM is relatively new and is different from
conventional soil-cement in that soil-cement generally is not flowable and
requires compaction.
In 1964 the U.S. Bureau of Reclamation (BOR) used CLSM in what is
thought to be its first major application (Adaska, 1997). The BOR referred to the
mixture as "plastic soil-cement, and applied it as pipe bedding to over 320 miles
of the Canadian River Aqueduct Project pipeline in northwestern Texas (Adaska,
1997). The soil used in the mixture as aggregate consisted of local sand deposits.
The estimated cost of this project was 40 percent less than expected using
conventional backfilling techniques. Also, estimates suggested use of the soil
cement increased productivity from 120 meters to 305 meters of pipe placed per
shift. Since then, CLSM has become a popular material for projects such as
structural fill, foundation support, pavement base, and conduit bedding (Du,
Folliard, Trjo, 2011).
The introduction of CLSM caught the attention of Detroit Edison
Company, who worked cooperatively with Kuhlman Corp., a ready-mix concrete
producer in Toledo, Ohio in the early 1970s. Together they created an
alternative to compacted granular fill which utilized fly ash and a concrete
batching technique. This new backfill material, called "flowable fly ash, was
used in several applications in the late 1970s (Funston, 1984). The mixture
consisted primarily of fly ash and 4 to 5 percent cement. Water was added to
attain the desired workability. In the Belle river project, it was estimated that
more than $1 million was saved by using this new material (Funston, 1984).
What made this material unique and impressive was that is remained cohesive
10


when being placed and could be shaped in unsupported steep slopes above or
underwater (Funston, 1984).
In 1977, four patents from a company known as K-Krete Inc. were issued
to Brewer et al. (Larsen, 1993). The typical K-Krete mixture was 1305 to 1661 kg
of sand, 166 to 297 kg of fly ash, 24 to 119 kg of cement, and up to 0.35 to 0.40
m3 of water per cubic meter of the product. The four patents included mixture
design, backfill technique, pipe bedding, and dike construction practice. These
patents were sold to Contech, Inc. in Minneapolis, MN, who later ceded the
patent rights to the National Ready Mix Concrete Association (NRMCA) with the
stipulation that those rights may not be used in a proprietary manner (Larsen,
1993). Since then, ready-mixed concrete producers and contactors have used
similar materials to K-Krete without patent-rights conflicts. Similar materials
have been developed and used throughout the United States and Canada.
"However, the lack of a centralized source for obtaining and disseminating
information within the marketplace appeared to cause confusion and reluctance
on the part of the engineering community to use these materials" (Du, Folliard,
Trejo, 2011). The ACI Committee 229 was establishing in 1984 under the title
"Controlled Low-Strength materials (CLSM). In 1994, the committee published a
report called "Controlled Low Strength Materials (CLSM)," which has been
referenced widely. It was revised in 1999 (Du, Folliard, Trejo, 2011).
Shortly following the development of the ACI Committee 229, different
designs were studied. Different types of mix designs were created for CLSM that
utilized recycled waste to reduce the cost. Currently there are five ASTM testing
standard available for CLSM. These are:
ASTM D 4832 Standard Test Method for Preparation and Testing of
Controlled Low Strength (CLSM) Test Cylinders
11


ASTM D 6023 Standard Test Method for Density (Unit Weight), Yield,
Cement Content, and Air Content (Gravimetric) of Controlled Low-
Strength Material (CLSM),
ASTM D 6024 Standard Test Method for Ball Drop on Controlled Low
Strength Material (CLSM) to Determine Suitability for Load Application.
ASTM D 5971 Standard Practice for Sampling Freshly Mixed Controlled
Low-Strength Material
ASTM D 6103 Standard Test Method for Flow Consistency of Controlled
Low-Strength Material (CLSM).
2.3 CLSM Development Research
This section discusses the research related to the use of recycled materials in
CLSM. Each material being researched is independently discussed and typical
material properties are presented.
2.3.1 Fly Ash
2.3.1.1 Production
Fossil fuel electric power generation produces a majority of coal combustion
residuals (CCRs). In 2009 coal generated electricity supplied approximately 45
percent of the electricity consumed in the United States (EPA, 2011). Other
industries, such as commercial boilers and mineral and grain processors that use
coal as a fuel source, also produce small quantities of CCRs. The American Coal
Ash Association (ACAA, 2011) estimates that between 100 million and 500
million tons of fly ash has accumulated in United States landfills since the 1920s
when the disposal of large quantities of fly ash in landfills began. This is likely a
12


very low estimate considering that: 1) the 2008 Kingston fly ash spill alone dumped
4,200,000 m3 of fly ash into the Emory and Clinch Rivers in Tennessee, which was
only a minor portion of the material that had been previously retained in an 84 acre
area behind a dike (en.wikipedia.org, 2011); and 2) there are many similar waste fly
ash disposal sites in the United States (en.wikipedia.org, 2011).
Coal combustion residuals are produced by coal burning power plants
and industrial boilers. The coal-fueled electric power industry generated
approximately 72.4 million tons of coal fly ash (EPA, 2011). Coal combustion
produces various forms of CCRs that are categorized by the process in which
they are generated. Fly ash is one of many CCRs that can be used as ingredients
in the manufacturing of portland cement. Exhaust gases leaving the combustion
chamber of a power plant entrain particles during the coal combustion process.
To prevent fly ash from entering the atmosphere, power plants use various
collection devices to remove it from the gases that are leaving the stack (EPA,
2011). Fly ash is the finest of coal ash particles. The use of fly ash in the United
States started in the early 1930s and today fly ash has multiple uses; one use is
to increase cement production. During cement production, fly ash can be added
to the raw material feed in clinker manufacturing to contribute specific required
constituents, such as silica, alumina, and calcium. Fly ash can also be used in non-
combustion applications as well. Fly ash's most common, and most valued, use is
as a supplementary cementitious material in concrete. It is used as a substitute
or a partial replacement for portland cement in concrete mixes. The benefits of
using fly ash in concrete are greater workability, higher strength, and increased
longevity.
Coal will continue to be an important fuel source in coming years;
therefore the quantity of fly ash produced and its beneficial reuse will also
increase. In 2008, 42.3 million tons of coal fly ash was disposed of in landfills,
13


and 58 percent generated (EPA, 2011). The research conducted herein, among
other things, increases the body of knowledge regarding the effects on the
properties of a typical CLSM mixture containing cement and fly ash.
2.3.1.2 Physical, Chemical and Reactive Properties
There are two major ASTM specified classes of fly ash produced today: Class F and
Class C. The assigned class depends on the chemical composition, which depends on
the type of coal burned. Class F fly ash is typically produced from burning anthracite
or bituminous coal, and Class C is normally produced from the burning of
subbituminous coal and lignite (FHWA, 2011). The main components of bituminous
coal fly ash (Class F) are silica, aluminum, iron oxide, and calcium oxide along with
residual, unburned carbon (EPA, 2011). Lignite and subbituminous coal fly ashes
(Class C) are characterized by higher concentrations of calcium and magnesium
oxides and, when compared to Class F fly ash, have reduced percentages of silica and
iron oxide and lower residual carbon content (EPA, 2011). Class C fly ash usually has
cementitious properties in addition to pozzolanic properties due to free lime that
causes it to gain strength when mixed with water alone. Class F is not as cementitious
when mixed with water alone. Table 2.1 presents the compounds found in fly ash
generated from the combustion of bituminous, subbituminous, and lignite coal. Table
2.2 presents the ASTM C 618 compositional requirements for Class C and Class F fly
ashes.
14


Table 2.1 Overview of Fly Ash Constituent Compounds Expressed in PPM
(EPA, 2011)
Component Bituminous Subbituminous Lignite
CM o c75 200,000-600,000 400,000- 600,000 150,000- 450,000
ai2o3 50,000 350,000 200,000- 300,000 100,000- 250,000
Fe203 100,000-400,000 40,000- 100,000 40,000 150,000
CaO 10,000- 120,000 50,000- 300,000 150,000 400,000
MgO 0 -50,000 10,000- 60,000 30,000 100,000
S03 0 -40,000 0 20,000 0- 100,000
Na20 0-40,000 0 -20,000 0 -60,000
K20 0 30,000 0 -40,000 0 -40,000
Loss of Ignition 0- 150,000 0 -30,000 0 -50,000
The fly ash used herein was Class C fly ash. Class C has pozzolanic and self-
cementing properties desired for replacement of portland cement in the CLSM
mix designs. ASTM notes that a typical cementitious design for a CLSM mix
contains 10 percent of cement. For this reason, and also because the properties
of portland cement are better controlled during manufacturing and therefore
less variable, the control mix for research presented herein used 90 percent
Class C fly ash and 10 percent portland cement. This mix proportion of
cementitious materials was also used in all mixes designed to investigate the
effects of aggregates on CLSM properties.
Table 2.2 Chemical Requirements ASTM C 618
Class F C
Silicon dioxide (Si02) plus aluminum oxide (AI2O3) plus iron oxide (Fe2O:0min, % 70 50
Sulfur trioxide (SO3), max % 5 5
Moisture content, max, % 3 3
Loss of Ignition, max, % 6 6
15


Fly ash has a lower heat of hydration than portland cement; consequently its
use will result in less heat build-up in massive placements. Large volume placements
are common when using CLSM. Therefore, the control over heat build-up afforded by
fly ash is often advantageous. The amount of heat generated is dependent upon the
chemical composition of the cement. Hydration of tricalcium aluminate and
tricalcium silicate is primarily responsible for high heat evolution. Typical portland
cement heat generation is greatest shortly after adding water whereas fly ash heat
generation is slower and lasts longer. This is because fly ash has a relatively low
surface area relative to portland cement causing the pozzolanic reaction to be slow to
start and the rate to increase several weeks after the start of hydration. For similar
reasons, strength development is slower in mixtures using large quantities of fly ash.
In 1996 Langan performed a study regarding the affects of fly ash during cement
hydration and concluded that: 1) fly ash increases the initial hydration of cement; 2)
retards hydration in the dormant and acceleration periods; and 3) accelerates
hydration after the typical portland cement acceleration period. It was also found that
fly ash retards cement hydration more significantly at high w/cm ratios. In the long
run, fly ash amended concrete demonstrates higher strength and durability.
2.3.1.3 The Effects of Class C Fly Ash on CLSM Properties
2.3.1.3.1 Flow Consistency
A flowable consistency is a critical parameter for optimizing performance and
placement characteristics of CLSM. Therefore it is critical that desired flow
requirements are achieved. The flowability of a CLSM is dependent on the
intended use of the material. The acquired flow characteristic targeted for this
study was to create an 8 to 12 inch diameter footprint, a.k.a. "patty, of the
16


slumped material using test procedure ASTM D 6103. The 8 to 12 inch
consistency criterion is suggested in ASTM D 6103 as a range typical of CLSM.
Research on CLSM containing fly ash has shown that the use of fly ash
increases the workability of the mix. CLSM mix designs may have a large
percentage replacement of cement by fly ash. Much more so than is common for
typical portland cement concrete mixtures.
Katz and Kovler (2003) investigated the use of cementitious industrial
by-products in CLSM mixtures. Three mix designs were used: one used 525
kg/m3 (885 lb/yd3) of fly ash and 53 kg/m3 (89 lb/yd3) of cement with a w/cm
of 0.51; the second mix used 519 kg/m3 (875 lb/yd3)of fly ash and 96 kg/m3
(162 lb/yd3) of cement with a w/cm of 0.50; the third mix combined 951 kg/m3
(1603 lb/yd3) of fly ash and 45 kg/m3 (76 lb/yd3) of cement with a w/cm of 0.42.
All three mixtures used sand as the fine aggregate. Water was added gradually
until the desired workability was achieved. They observed that 10 percent less
water was needed to achieve the flowability for the mixtures containing fly ash.
The acquired consistency was measured by ASTM D 6103 and resulted in an 8
inch diameter flow footprint.
Du, Folliard and Trejo (2002) researched the effects of water demand on
CLSM. Three sources of Class C fly ash three sources of Class F fly ash, three
sources of fine aggregate, and Type I portland cement were used in their study.
The water demand for their investigation was defined as the amount of water
required to obtain a flow footprint diameter between 7.9 and 9.8 inches. Table
2.3 presents the mixture proportions and the acquired flowability for mixtures
using either Class C or Class F fly ash.
17


Table 2.3 CLSM Mixtures Proportions and Fresh Properties
(Du, Kolver, and Trejo, 2002)
Mixture Type 1 cement (kg/rn3) Fly ash type Fly ash (kg/m3) Fine aggregate type Water demand (kg/m3) Flow (mm)
Mixture 1 30 Class C 180 Sand 211 200
Mixture 2 60 Class C 180 Sand 206 200
Mixture 3 30 Class C 180 Sand 206 210
Mixture 4 60 Class C 180 Sand 205 250
Mixture 5 30 Class F 360 Sand 220 200
Mixture 6 60 Class F 360 Sand 216 216
*Mixture 3 is a replicate of mixture 1, and mixture 4 is a replicate of mixture 2.
The comparison of Class C verses Class F shows that Class F requires
more ash to acquire the desired flow, where as Class requires less ash to achieve
the same flow. This is likely caused by the fact that Class F fly ash, being less
cementitious, acts in greater capacity as an aggregate than in the capacity of a
cementitious material. This is expected because Class F fly ash does not possess
the same chemical properties as Class C fly ash, as previously discussed in
Section 2.3.1.2.
2.3.1.3.2 Bleeding and Segregation
The high water demand required for CLSM mix designs increases the bleeding
and the risk of segregation of the fresh CLSM. High bleeding values have been
commonly observed with mixes containing fly ash. The large bleeding values are
18


expected for the fly ash mixes clue to the spherical shape of the fly ash particles
and their delayed setting (Ravina, 1990).
Katz and Kolver's (2003) research that was introduced in the previous
section discusses the bleeding and segregation they observed. They noted that
higher fly ash to cement ratios result in greater bleeding. Ratios of fly ash to
cement of 500/50 and 1000/50 had bleeding percentages of 3.4 percent and 4.4
percent respectively. This observation is consistent with Ravina's work
presented in the previous paragraph.
Du, Folliard and Trejo (2002) researched the effects of water demand on
CLSM. Their research demonstrated the differences in bleeding between the
Class F and Class C fly ash. A Class C fly ash to cement ratio of 180/60
demonstrated a bleeding percentage of 2.45 percent. A Class F fly ash to cement
ratio of 360/30 had a bleeding percentage of 2.92 percent. Hence, the different
classes of fly ash demonstrate similar bleeding characteristics using different
cementitious material ratios.
2.3.3.3 Air Content
Information regarding air content of CLSM mixtures containing fly ash is very
limited. Air content is commonly recorded, however seldom discussed unless
air-entraining admixtures (AEA) were specifically used.
Du, Folliard and Trejo (2002) did not use air-entraining admixtures in
their Class C fly ash mix design. The mixture had an average air content of 0.92
percent.
Naik (1991) evaluated the effects of Class C fly ash on CLSM mixtures. The
mix designs that were analyzed consisted of cement, fly ash, water, sand and pea
sized gravel. All mixtures were observed as having good workability with high
19


slumps ranging from 7.5 inches to 9.25 inches. Air content ranged between 1.0
and 2.3 percent. Table 2.4 illustrates the mixture proportions and field test done
by Naik (1991], Three out of the four mixtures (Mix 2, 3, and 4) show a linear
trend when comparing air content and w/cm. The higher w/cm has the highest
air content and the lowest w/cm has the lowest air content. Its noted that Mix 1
has the highest w/cm content and doesn't seem to fit the trend of the other
mixtures with the air content. It is noteworthy that the highest slump was also
associated with this sample. This suggests that air bubbles, as well as solid
particles, are more mobile when slumps are high thereby allowing entrapped air
to more easily exit the sample during mixing.
Table 2.4 Mixture Proportions and Field Test Data (Naik, 1990)
Mixture Mix 1 Mix 2 Mix 3 Mix 4
Cement, lb/yd3 70 81 96 129
Class C Fly Ash, lb/yd3 118 159 195 239
Water, lb/yd3 345 337 338 351
SSD Sand, lb/yd3 1728 1611 1641 1543
SSD Pea Gravel, lb/yd3 1778 1761 1813 1721
Slump, inch. 7.5 6.25 6.5 9.25
Air Content, percent 2.1 2.3 2.2 1
w/cm 1.84 1.4 1.16 0.95
2.3.1.3.4 Time of Set
The time required for the fly ash in CLSM to set is influenced significantly by the
type of fly ash and the amounts of fly ash used in the mixture. In general,
research has shown that in typical concrete mix designs fly ash retards cement
hydration in dormant and acceleration periods. Furthermore, at higher w/cm
ratios the retarding effect appears more significant than at the lower w/cm
20


ratios. CLSM mix designs have much higher w/cm ratios compared to typical
concrete mixes (Langan, 1996). Therefore, it is expected that the time of set will
be significantly delayed relative to that commonly observed for portland cement
concrete.
Folliard, Du, and Trejo (2003) study on the effects of curing conditions on
strength development of CLSM discussed the use of Class C fly ash in CLSM mix
designs. Its noted that concrete containing Class C fly ash is generally more
sensitive to curing temperature than Class F fly ash, mainly because of it
inherently higher potential for reactivity. Also, the strength development of
CLSM containing Class C fly ash was observed to be greatly affected by the curing
temperature.
McCarthy discusses the mechanisms that might cause slower time of sets
and emphasizes that CLSM strength development rate is dependent on the
curing environment (McCarthy, 1984).
The Katz and Kolver (2003) study on the utilization of industrial by-
products in CLSM mixtures showed that the greater the Class C fly ash to cement
content the higher the setting time. The mix design with a fly ash to cement ratio
of 20/1 had a setting time at 22 hours as opposed to the mix design with a fly ash
to cement ratio of 10/1, which had a 7-hour-shorter setting time of 15 hours.
Some research has investigated the effect of Class C fly ash calcium oxide
(CaO) content on the setting time of CLSM (Du, 2006). It was demonstrated that
fly ash with high calcium oxide (CaO) content (greater than 25 percent) will lead
to earlier setting and higher early strength than fly ash with lesser amounts of
CaO. The study used the needle penetration test (ASTM C 403) to evaluate time
of set of CLSM mixtures. A penetrometer approach was used herein to evaluate
the time of set.
21


2.3.1.3.5 Strength
In general, research pertaining to the effects of Class C fly ash on strength is
varied. Maintaining strength at a low level is a major objective for projects where
later excavation is required. Some mixtures that are acceptable at early age
continue to gain strength with time, making future excavation difficult. Also,
some mixtures that would achieve a desirable long-term strength have a low
short-term strength that adversely affects project schedules. For example, CLSM
used in buried pipe backfill must achieve a minimum strength before additional
fill is placed over the pipe. Therefore, strength needs depend significantly on the
use. For the remainder of this discussion, strength will refer to the strength at
28 days unless otherwise noted.
CLSM strength is dependent on the fly ash/cement ratio and w/cm ratio.
Katz and Kolver (2003) study on CLSM with Class C fly ash showed a high 28-day
compressive strength. The mix designs with fly ash to cement ratio of 10/1 and
w/cm ratio of 0.51 had a 3.5 MPa (508 lb/in2) compressive strength. The mix
design of 20/1 with a w/cm ratio of 0.42, all other things equal, had a 2.5 MPa
(363 lb/in2) compressive strength at 28 days. The mix with the highest strength
was the 5/1 with a w/cm ratio of 0.50, which had a compressive strength of 7.3
MPa (1059 lb/in2). In comparison, the mix designs used in this study targeted
the creation of CLSM exhibiting less than 200 psi (1.4 MPa) compressive
strength.
2.3.2 Spray Dryer Ash
2.3.2.1 Production
As previously discussed, fly ash is a by-product fossil fuel electric power
generation and has numerous advantages for use in the concrete industry. Spray
22


dryer ash is derived from the same source, however is less commonly used in the
construction industry due to its high sulfur trioxide (SO3) content.
Pulverized coal is generally burned during the production of energy. The
volatile matter and carbon burn off during the combustion process leaving the
coal impurities such as clays, shale, quartz, felspar, etc. mostly fused and
remaining in suspension (Naik, 1993). The fused particles are carried along with
the flue gas. When the flue gas approaches low temperatures, the fused
substances solidify to form predominately spherical particles, which are called,
fly ash (Naik, 1993). Sulfur dioxide is a gaseous product of coal combustion that
enters the atmosphere and contributes to acid rain. Flue gas desulfurization
(FGD) is employed to reduce sulfur dioxide emissions. When dry lime dust is
used for this purpose as the sorbent a solid waste product known as spray dryer
ash is produced. Butalia and colleagues implemented a laboratory-testing
program to study the suitability of spray dryer ash as flowable fill (Butalia,
1999.). Butalia showed that the relationships between strength and w/cm ratio
and cementitious material content are similar in direction to those for portland
cement. That is, strength increases with increasing cement content and
decreasing w/cm ratio. The researchers concluded that spray dryer ash is a
potentially viable cementitious material for use in CLSM and that the mixture,
with accelerators, can be controlled to provide desired early strength while
limiting long term strength to make it "diggable" (Butalia, 1999.). It was also
concluded that the load-displacement behavior, among other things, be further
investigated. This thesis measures the Youngs modulus of spray drier ash in
response to the need for more research.
Spray drier ash has been used in the construction of stabilized road base, as
a raw material for manufacturing of cement, in concrete and other cement-based
materials, and for manufacture of wallboards (Siddique, 2010). Naik (1993)
23


reported that significant amount of spray dryer ash can be used in concrete as
well as masonry products.
2.3.2.2 Physical, Chemical and Reactive Properties
Spray dryer ash has low unit weight and good shear strength characteristics and
thus hold promise for CLSM applications (Naik, 1993). Spray dryer ash by-
products consists of primarily spherical fly ash particles coated with calcium
sulfite/sulfate, fine crystals of calcium sulfite/sulfate, and unreacted sorbent
composed of mainly Ca(0H)2 and a minor fraction of calcium carbonate. The fly
ash amount varies from less than 10 percent as much as 50 percent. The spray dryer
by-products are higher in concentrations of calcium, sulfur, and hydroxide, and
lower in concentrations of silicon, aluminum, iron, etc. than is typical for
conventional Class C fly ash (Naik, 1993). Table 2.5 provides an example
chemical composition of spray dryer ash.
Table 2.5 Spray Dryer Ash Chemical Composition (Naik, 1993)
Composition Percent (%)
AI2O3 25.2
CaO 21.73
Fe2C>3 3.26
MgO 0.84
K20 1.69
Si02 21.17
Na20 3.29
S03 17.5
24


There are several dry processes for cleaning up the SO2 emissions from coal
plants. The advance systems include atmospheric fluidized bed combustion (AFBC),
lime-spray drying, sorbent furnace addition, sodium injection, and other clean-coal
technologies such as integrated coal classification combined cycle (IGCC) process.
This thesis uses a spray dryer ash (SDA) from a lime-spray drying process.
2.3.2.3 The Effects of Spray Dryer Ash on CLSM Properties
2.3.2.3.1 Flow Consistency
A flowable consistency is a very important CLSM property, and therefore it is
essential to understand how SDA, among other components, affect this behavior.
It is commonly accepted for typical concrete as well as CLSM mixtures that
consistency is predominantly controlled by the amount of water in a CLSM
mixture. A study evaluating the use of spray dryer ash in CLSM was conducted
by Butalia, Wolfe, and Lee (Butalia, 1999). Their tests results were compared to
typical CLSM mixtures. Table 2.6 presents the water content in percent along
with a flow footprint diameter measure of consistency. The results demonstrate
that an increase in water will cause an increase in flow.
Table 2.6 Flowability and Water Content [Butalia, Wolfe, & Lee 1999)
Mix# Wc (%) Flow (in)
Initial Mix
1 20 65 6
2 20 72.5 8
3 20 77 13
25


In a subsequent study, Butalia, Wolfe, Zand, and Lee (2004) researched
flowabie fill using flue gas desulfurization materials (FGDs) produced from wet
and dry desulfurization processes. The dry FGD material used in the laboratory
tests was a spray dryer ash. The flow consistency from this test is presented in
the following table, Table 2.7. The results demonstrate the same increase of flow
consistency with increasing water content.
Table 2.7 Flowability and Water Content (Butalia, Wolfe, Zang & Lee 2004)
Mix # Wc (%) Flow (mm)
1 65 150
2 72.5 200
3 77 330
2.3.2.3.2 Bleeding and Segregation
Little is written concerning the effects that spray dryer ash has on bleeding and
segregation. However, it is reasonable to assume that the bleeding and
segregation of CLSM using spray dryer ash will be similar to CLSM manufactured
using fly ash due to their similar physical properties. Fly ash and spray dryer ash
have approximately the same spherical shape and also many similar chemical
characteristics.
2.3.2.3.3 Air Content
Air content is another property that was tested in the Butalia, Wolfe, and Lee
research. However it wasn't recorded or discussed in the available reference. No
other literature was found on this subject.
26


2.3.2.3.4 Time of Set
Both of Butalia, Wolfe, and Lees investigate the time of set for CLSM mixtures
made using spray drier ash. For this research they used the penetration test in
accordance with ASTM C 403: Time of Setting of Concrete Mixtures by
Penetration Resistance. The first study, conducted in 1999, discusses how the
penetration resistance values were less than 100 lb/in2, and even after six days
resistance values were less than 200 lb/in2. Therefore, it was concluded that the
mixes exhibited slow development of penetration resistance requiring
approximately two to three weeks to reach 400 lb/in2. The characteristic slow
strength gain is common for normal CLSM mixtures. The penetration resistance
characteristics of SDA CLSM mixtures show that SDA should be suitable for
replacing conventional CLSM mixtures. The 2004 confirmed the results of the
1999 study. It was observed that spray dryer ash has a retarding effect on CLSM
time of set but doesnt seem to be substantively different from that expected of a
typical CLSM mixture.
2.3.2.3.5 Strength
The recommend value for 28-day CLSM strengths varies depending on the
intended application. Rice (1997) recommended values for 28-day strengths
range from 25 to 60 lb/in2. The minimum specified strength is intended to
provide sufficient support for construction and vehicular loads, whereas the
maximum specified strength assures that the material can be excavated. A
flowable fill having an unconfined compressive strength of 60 lb/in2 has at least
two to three times the bearing capacity of a well compacted earth backfill
(FHWA, 1995). The result from the study conducted by Butalia, Wolfe, and Lee
27


(1999) data shows that the strength of the spray dryer ash CLSM mixes
increases with curing time, it is also documented that as the water content
increased the flowability also increased. However, as the flowability increased,
the compressive strength decreased. The following table, Table 2.8 summarizes
the characteristic of each mix and their measured compressive strengths.
Table 2.8 Flowability and Water Content (Butalia, Wolfe, & Lee
1999)
Mix# Wc (%) Flow (in) Compressive Strength (lb/in2)
Initial Mix 7 (days) 14 (days) 28 (days) 60 (days) 90 (days)
1 20 65 6 10 27 35 38 51
2 20 72.5 8 8 25 27 31 34
3 20 77 13 5 18 18 24 27
It has been observed that Mixes 1 and 2 satisfied Rice's 28 day strength
recommendations. Mixes 1 and 2 are likely usable in any kind of flowable fill
applications. Mix 3's strength was less than 25 lb/in2 at 28 days and likely has
more limited applications.
Butalia, Wolfe, and Lee (1999) observed that although a 13-inch
consistency provides good workability and placeablity, high moisture content in
the spray dryer ash mix without any additive resulted in insufficient strength
development. They concluded that a flowability range of 7 to 8 in. would provide
sufficient strength and good flowability for most fill applications where spray
dryer ash is used as a cementitious material in CLSM.
In the 2004 study by Butalia, the strength gain verses water content was
evaluated and results show that compressive strength sufficient for most
28


applications can be required fora large range of mix proportions. The strength
depends chiefly on the cement and water content; the higher the cement content,
the higher the strength. As the water content increased, the strength decreased.
2.3.3 Bottom Ash
2.3.3.1 Production
Bottom ash is another by-product of fossil fuel electric power generation. As
discussed below, bottom ash is formed from burning coal. It consists of the
heavier and larger particles in flue gas that falls to the bottom of the flue and
typically ranges in size from fine sand to fine gravel. The annual production of
bottom ash is 18 million tons and the annual use is 7 million tons (ACAA, 2007).
In 2008 it was recorded that 10.4 million tons of bottom ash was landfilled and
approximately 56 percent was generated. It's low cost and availability makes its
use in CLSM desirable (ACAA, 2008).
Bottom ash is produced in a dry-bottom coal boiler from residue found in
coal-fired electric power plants. Initially, coal is pulverized and blown into a
burning chamber where it immediately ignites. About 80 percent of the
unburned material, ash, is entrained in the flue gas and is captured and
recovered as fly ash. The incombustible portion of this material not collected in
the flue as fly ash is known as dry bottom ash. It drops down to a water-filled
hopper at the bottom of the boiler or is impinge on the furnace walls (FHWA,
2011). When a sufficient amount of bottom ash drops into the hopper, it is
removed by means of high-pressure water jets and conveyed by sluiceways
either to a disposal pond or to a decant basin for dewatering, crushing, and
stockpiling for disposal or use (FHWA, 2011).
29


2.3.3.2 Physical, Chemical and Reactive Properties
Bottom ash, like fly ash, is primarily composed of silica, alumina, and iron oxide;
however, with smaller percentages of calcium and magnesium oxides, sulfates,
and other compounds than fly ash. Bottom ash composition is controlled
primarily by the source of the coal. Bottom ash derived from lignite or sub-
bituminous coals has a higher percentage of calcium oxide (Class C fly ash] than
the bottom ash from anthracite or bituminous coal (Class F fly ash)
(www.tfhrc.gov). Table 2.9 shows detailed constituent sampling results for
bottom ash as produced from the combustion of several types of coal mined
from different locations.
Table 2.9 Overview of Bottom Ash Compounds, expressed in PPM (www.tfhrc.gov)
Coal Type Bituminous Sub-bituminous Lignite
Location West Virginia Ohio Texas
Silicon Dioxide 536,000 459,000 471,000 454,000 700,000
Aluminium Oxide 283,000 251,000 283,000 193,000 159,000
Iron Oxide 58,000 143,000 107,000 97,000 20,000
Calcium Oxide 4,000 14,000 4,000 153,000 60,000
Magnesium Oxide 42,000 52,000 52,000 31,000 19,000
Sodium Oxide 10,000 7,000 8,000 10,000 6,000
Potassium Oxide 3,000 2,000 2,000 - 1,000
Bottom ash is a coarse, granular material collected from the bottom of a
coal furnace. The physical characteristics of the residuals generated depend on
the characteristics of the furnace. Typically, bottom ash is grey to black in color,
and has a porous surface structure. Bottom ashes consist primarily of angular
particles, the particles range in size from fine gravel to fine sand with very low
percentages of silt-clay sized particles (particles less than 0.075 mm). The ash is
30


usually a well-graded material, although variations in particle size distribution
may be encountered in ash samples taken from the same power plant at
different times. Bottom ash is predominantly sand-sized, usually with 50 to 90
percent passing a 4.75 mm (No. 4) sieve, 10 to 60 percent passing a 0.42 mm
(No. 40) sieve, 0 to 10 percent passing a 0.075 mm (No. 200) sieve, and a top size
usually ranging from 19 mm (3/4 in) to 38.1 mm (1-1/2 in) (FHVVA, 2011).
Bottom ash has been used as a replacement for aggregate in structural
concrete applications and in geotechnical applications, such as structural fills.
The porous surface structure of bottom ash makes the material lighter than
conventional aggregate and useful in lightweight concrete applications (EPA,
2011). Bottom ash may contain pyrites or "popcorn particles that result in low
specific gravities and high losses during soundness (i.e. freeze-thaw) testing. Due
to an inherent salt content and in some cases low pH, this material may exhibit
corrosive properties (FHWA, 1995). The specific gravity of dry bottom ash is a
function of chemical composition with higher carbon content resulting in lower
specific gravity. Bottom ash with a low specific gravity has a porous or vesicular
texture, a characteristic of popcorn particles that readily degrade under loading
or compaction. Table 2.10 lists the typical physical properties of bottom ash.
Table 2.10 Typical Physical Properties of Bottom Ash (FHWA, 1995)
Property Bottom Ash
Specific Gravity 2.1 2.7
Dry Unit Weight 720 1600 (kg/m3)
(45 100 lb/ft3)
Plasticity None
Absorption 0.8 2.0%
31


Bottom ash does not possess the same pozzolanic and cementing
properties as fly ash and, for this thesis, is investigated as an aggregate
replacement for CLSM.
2.3.3.3 The Effects of Bottom Ash on CLSM Properties
2.3.3.3.1 Flow Consistency
Hardjito, Chuan, and Tanijaya (2011) examined the effects of bottom ash on the
fresh CLSM properties. Their research focused on the practical use of bottom ash
in CLSM for various construction purposes. Cement, water, sand and fly ash and
bottom ash were studied. The research evaluated various cementitious material
mixing proportions by 1) varying the percentage of cement in the cementitious
material as 3, 6,10 and 15 percent of total wet density and 2) varying the
percentage of bottom ash in the aggregate as 0, 25, 50, 75, and 100 percent. All
the material was placed in the mixer minus half of the water. After a minute or
two of mixing, the remaining water was added and mixing continued an
additional 15 minutes. Additional water was added, followed by mixing if the
desired flowability was not initially achieved. Flowability was determined by
using the inverted slump cone test. To perform this test, the CLSM mixture was
loaded into the inverted slump cone until it was full. Then, the inverted slump
cone was lifted up so that the CLSM flowed from the base and formed a circle
(Hardjito, 2011). The diameter of the circle was measured with measuring tape.
The diameter of the circle is considered acceptable if it is within the range of 475
mm to 750 mm (29.53 inches) (Hardjito, 2011). This diameter distance is
considered adequate for most field applications of CLSM. The water content
needed to achieve the flowability based on the fly ash to bottom ash ratio for 3,
6,10, and 15 percent cement mix varied. The results showed that the required
32


water content to achieve good flowability decreases gradually as the fly ash to
bottom ash ration increases from 0:100 to 25:75 and then increases drastically
as the fly ash to bottom ash ration increases from 25:75 to 100:0, It is speculated
that this behavior is likely the consequence of effects related to the differences in
particle size distributions, particle shapes, and pozzolanic natures of fly ash and
bottom ash,
Du, Folliard, and Trejo (2002) also investigated the effects of bottom ash
as an aggregate replacement of CLSM. The flowability or constituency of the
CLSM specimens created was measured by the ASTM D6103. The experimental
program of this particular study has been described in a previous section. To
help better understand the behavior of the aggregate used in the experiment, the
uncompacted void content was analyzed for the as-received condition and
various size fractions. The researchers noted that such information is a valuable
tool for assessing the shape and surface texture of aggregates.
Higher void contents, especially for as-received materials, suggest that
additional fines in the fine aggregate or additional cementitious materials may
be required to obtain the desired workability for conventional concrete. It is
expected that higher void contents would have a similar effect on CLSM
flowability, specifically increasing the water demand. Accordingly, the high
percentage of void in the bottom ash suggests that it should need for more water
and/or more cementitious material to affect the desired flowability. The
researchers demonstrated that, compared to typical concrete sand, bottom ash
required more water. The results are presented in Table 2.11 below. The
flowability that was experienced in this study show that mixes using bottom ash,
when compared to typical CLSM mixture design using sand, requires more water
and/or more cementitious material to achieve desired flowability.
33


Table 2.11 CLSM Mixture Proportions and Fresh Properties
(Du, Folliard, Trejo 2002)
Mixture Type 1 cement (kg/m3) Fly ash type Fly ash (kg/m3) Fine aggregate type Water demand (kg/m3) Flow (mm) Total bleeding (%)
1 60 Class C 360 Bottom Ash 577 178 4.32
2 30 Class C 360 Bottom Ash 572 216 3.64
3 30 none none Bottom ash 582 127 4.35
4 60 none none Bottom ash 525 130 3.41
5 30 Class C 180 Concrete Sand 211 200 "
6 60 Class C 180 Concrete Sand 206 200 2.45
7 30 none none Concrete Sand 295 200 2.33
8 60 none none Concrete Sand 131 200 0.05
2.3.3.3.2 Bleeding and Segregation
Both bleeding and segregation were observed or calculated in the research done
by Hardjito, Chuan, and Tanijaya (2011). During literature review, it was
observed that the methods for measuring bleeding varied between researchers.
Hardjito (2011). performed the bleeding test by measuring the difference in
CLSM height following water evaporation. The bleeding test was measured in
order to obtain the height reduction of the CLSM specimen; the reduced heights
of CLSM specimens were measured on the third day after batching. The
reduction of height over the total height of the CLSM specimen is considered as
the percentage of bleeding. It was observed that the bleeding percentage of
CLSM varies from 2.31 percent to 7.25 percent. The research demonstrates that
34


the bleeding percentage of CLSM increases as the content of bottom ash is
increased; and therefore concludes that the bottom ash does have porous
properties and retains high initial moisture content. Hardjito, Chuan, and
Tanijaya (2011) explain that the initial water content is predominantly water
trapped in the pores of bottom ash, and that adds to the total available water of
CLSM mixture. The result is high amounts of free water. Within this research no
segregation was observed because fine aggregates and fillers were used in the
mixtures and the cementitious material content was great enough to hold it in
suspension. Fine particles have smaller voids between the particles, smaller
diameter, and smaller mass and are therefore inherently less likely to segregate
in a viscous paste.
2.3.3.3.4 Time of Set
The time of set for Hardjito, Chuan, and Tanijaya (2011) study was determined
using a vicat penetrometer. The general procedure follows. After mixing, the
CLSM was loaded in the penetrometer cast and water that collected on the
surface due to bleeding was removed. The vicat needle was positioned and
released. A reading of the penetration was recorded every 15 minutes.
The CLSM mixture was considered set when the penetration of the vicat
needle was less than 0.98 inches (25 mm) in 15 minutes. The results on the vicat
penetrometer method for their research was carried out for specimen with three
percent cement content and six percent cement content. The results showed that
the hardening time for the three percent cement mix varies from 5 to 6.5 hours,
whereas the hardening time for six percent cement mix varies from 4 to 6 hours.
It was observed that the overall results show that the hardening time increases
with decreasing fly ash to bottom ash ratio.
35


The researchers noted that bottom ash was very porous and that water
trapped in the pores prior to mixing is released during and after mixing causing
excessive free water and bleeding of the specimen (Kasemchaisiri,
Tangtermsirikul, 2006). It was also noted that although water due to bleeding
was removed before the hardening time testing, there is still excessive free
water trapped in the pores of bottom ash, thus causing the time for set to be
slow. Hence, the hardening time increases as the bottom ash content increases.
2.3.3.3.5 Strength
The California Bearing Ratio (CBR) machine was used to measure the unconfined
compressive strength the CLSM specimens in Hardjito, Chuan, and Tanijaya
(2011) study. The compressive strength of CLSM was tested 3, 7, 28 and 60 days
after batching.
The researchers concluded that higher quantity of cement used will
produce CLSM with higher compressive strength. This result was true for bottom
ash used as an aggregate as well as for other aggregates and was expected since
using more portland cement in CLSM is expected to cause aggregate to be more
effectively bonded together and better support the pozzolanic reaction of the fly
ash. Also, higher cement content of CLSM would have higher strength, all other
components equal, since it necessitates a lower water/cement ratio.
36


Compressive Strength of CLSM with 3% Cement Used
3
Age of CLSM (Days)
Figure 2.1 Compressive Strength of CLSM with 3% Cement Used (Hardjito, 2011)
The researchers concluded for the CLSM mixtures tested, that 3 percent
cement in the cementitious material is suitable for general-purpose backfilling
and future excavation purpose as it has low compressive strength. CLSM with 6
percent cement in the cementitious material is suitable for roadway trench
backfilling; whereas CLSM mixture with 10 percent cement in the cementitious
material is best used for structural backfill as it has higher compressive strength.
The previous figure shows the different fly ash- bottom ash portions.
2.3.4 Crushed Waste Glass as Aggregate
Glass recycling is the process of turning waste glass into usable products. Waste
glass is usually separated by chemical composition, and then, depending on the
end use and local processing capabilities, might also have to be separated into
different colors (Meyer, 2001). Glass retains its color after recycling and the
most common colors are: colorless glass, green glass, and brown/amber glass.
Glass contributes to a large amount of household and industrial waste due to its
37


weight and density. However, of the materials being recycled today, glass is still
one of the most difficult to reuse (Meyer, 2001). One of the major problems with
glass recycling is the separation of clear and colored glass and removing all of
the impurities. Post-consumer glass is often mixed -colored and containing
contaminants such as plastics, metals, and organic matter. This reduces its value
and complicates the ability to achieve the "cullet" specifications. Cullet is the
term given to crushed waste glass ready to be melted. Because of difficulties
achieving cullet specification the majority of crushed glass is landfilled. The
recycling rate in 2007 was 23.7 percent (EPA 2007). Of the 13.6 million tons of
waste glass generated that year, 10.36 million tons were landfilled and only 3.22
million tons were recycled (EPA 2007).
Closed-loop recycling is the process of collecting, sorting, transporting,
beneficiating, and manufacturing glass back into bottles; is the most common
form of glass recycling; and has costs embedded in each step of the process
(Meyer 2001). Because the post-consumer glass is of mixed color, and much of it
is broken, it cannot be easily recovered for closed-loop recycling. Therefore the
disposal of the mixed broken glass as a waste residue from the recycling process
causes a significant cost to recyclers.
Alternative solutions for disposing of mixed colored glass and glass-
containing impurities have been difficult. The basic principle of environmental
consciousness is violated when a potentially valuable resource is simply wasted
or perceived to be underutilized, especially when it uses up increasingly scarce
landfill space. Therefore, there has been a great interest in using crushed waste
glass as a fine aggregate replacement. Past research has shown that a concrete
mix containing crushed waste glass tends to lead to lower compressive
strengths, and may be particularly susceptible to alkali-aggregate reactivity
(ASR) when used with high alkali cements. Past studies took the approach of
38


grinding the waste glass into a fine glass powder and incorporating it into
concrete as a pozzolanic material. In laboratory experiments with powdered
glass suppressed the alkali reactivity of coarser glass particles as well as that of a
natural reactive aggregate. Consequently, the powdered glass undergoes
beneficial pozzolanic reactions in the concrete and could replace up to 30
percent of cement in some concrete mixes with satisfactory strength
development (Shayan 2002).
2.3.4.1 Production
Waste glass is produced through the glass recycling process, which primarily
consist of post-consumer glass. Recycling companies collect the glass from
households and commercial facilities, and then the glass is stockpiled at the
recycling plant. There the glass is separated by color. Although all glass is made
up of the same materials the type and quantity of the materials vary slightly with
different types of glass, therefore having different melting points and chemical
incompatibility (Shayan, 2002). In addition, glass will maintain its color after
recycling (Shayan, 2002). Therefore, neither brown nor amber glass is used to
manufacture clear glass, and it is important to separate the glass by color.
The process of recycling glass after the color sorting involves multiple
segments of crushing to break the glass down into smaller particles. After the
glass has successfully been crushed it travels by conveyor belt through a series
of refinements. Magnets pull out metal, and air currents remove lightweight
materials such as paper (www.es.anl.gov, 2011). Once the glass is crushed, it is
typically conveyed to a screen designed to separate the broken glass, typically a
2 inch opening. After traveling along the conveyor belt and passing the screen,
the glass is crushed and ready to be melted; at this point the material is known
39


as "cullet. However, other items passing through the screen include significant
amount of contaminates such as paperclips, caps, tabs, etc. Some cullet suppliers
use sophisticated equipment such as lasers to sort colors of crushed glass and
further remove small contaminates. Scientists continue to develop mechanisms
to improve materials sorting and, therefore, the quality of the cullet
(www.es.anl.gov, 2011). The efficiency of this process comes down to how the
glass is separated. Because, if the glass isnt properly separated the colors get
mixed and unsuitable for the use as containers then they are used for other
purposes or sent to a landfill.
2.3.4.2 Physical and Chemical Properties
Waste glass comes in a variety of different compositions. The following is a
description of the physical and chemical properties glass provides. Glass is
considered to be a unique material with the molecular structure of a liquid and
the physical characteristics of a solid. Glass sometimes is mistakenly called a
super cooled liquid, but its actually a non-crystalline solid. The molecular
structure of glass is irregular and randomly arranged. The chemical
compositions of various types of glass are listed in Table 2.12. Glass is
considered a brittle material due to its un-orderly crystalline structure (Shayan,
2002).
When used in concrete, the smooth nonporous surfaces of glass to not
promote good bonding. The result is an increased potential for failure within the
interfacial transition zone (1TZ) relative to other aggregates.
40


Table 2.12 Chemical Compositions of various color glass (Shayan, 2002)
Composition Clear Glass Brown Glass Green Glass
Si02 72.42 72.21 72.38
A1203 1.44 1.37 1.49
Ti02 0.035 0.041 0.04
Cr2C>3 0.002 0.026 0.13
Fe2C>3 0.07 0.26 0.29
CaO 11.5 11.57 11.26
MgO 0.32 0.46 0.54
Na20 13.64 13.75 13.52
K20 0.35 0.2 0.27
S03 0.21 0.1 0.07
The efficiency of glass manufacturing is dependent on the sorting of the
various colors. When the glass colors get mixed, they become unsuitable for use
as containers, and then must be used for other purposes or disposed in a landfill.
Recycled waste glass is a mix of various colored glass and impurities. The waste
glass that was used for this research was taken "as-is and unwashed. Depending
on the manufacturing plant, the material may or may not have been washed;
therefore, it may contain some remnants of sugars or other organic
contaminates. Other contaminates that werent picked up by the magnet or
vacuum during the crushing process are also present. Common contaminates are
paper, metals, and aluminum caps.
The typical average specific gravity of soda-lime glass is 2.52
(en.wikipedia. org, 2011). Considering the fact that soda-lime glass comprises
the majority of glass, it's probable to assume that the specific gravity of recycled
glass is about 2.52. Therefore, the specific gravity of waste glass is generally less
than that of natural aggregate. Consequently, it is reasonable to expect that using
41


waste glass as aggregate would lessen concrete's unit weight. Glass is not a
porous material; therefore, the expected absorption capacity is zero percent.
However, impurities in the cullet may cause a slight absorption capacity.
Different recycled glass processing facilities are likely to produce waste glass
that has varying fineness modulus and particle size distributions. Therefore the
use of crushed glass in CLSM may require carefully planned and implemented
quality control.
2.3.4.3 The Effects of Waste Glass on CLSM Properties
2.3.4.3.1 Flow Consistency
Naik and colleagues at the University of Wisconsin-Milwaukee conducted
research on the use of crushed waste glass in a CLSM (2000). Their mix design
consisted of water, cement, fly ash, and various amounts of waste glass. The
different mixtures contained glass with sand replacement levels of 30 percent to
75 percent by mass. They designed their mixtures to maintain a flow in the range
of approximately 14 +/- 2 inches (355.6 mm) in accordance with ASTM D6103.
ASTM D6103 notes that the average diameter of the patty is typically are 8 to 12
inches (203.2 to 304.8 mm). It was noted in the report that as the quantity of
glass increased, the water required remained very similar to that of sand. The
unit weight of the mixtures remained essentially unchanged because the sand
and glass had similar values of specific gravity. The w/cm ratio changed based
on the different glass proportions. Cement was the only cementitious material
used in the study. Sand was the aggregate mixed with glass. The following Table
2.13 shows the flow consistency and the w/cm ratio of the mixtures contain 0 to
80 percent crushed waste glass.
42


Table 2.13 Flowability and Water to Cementitious ratio (Naik, 2000)
Mixture Glass (%) Flow (inch) w/cm
1 0 13 0.45
2 30 13.5 0.44
3 75 12.25 0.91
The results indicated that as the quantity of glass was increased in these
mixtures, more water was required to maintain the flow. The observation can be
a result of the larger particle size and higher density of glass compared with that
of fly ash.
2.3.4.3.2 Bleeding and Segregation
Naik (2000) observed bleeding while batching CLSM mixtures containing
crushed glass. The mixtures containing crushed glass with only fly ash as the
cementitious material experienced the most bleeding. He noted that decreasing
the amount of fly ash and increasing glass content lead to increased bleeding and
segregation, observed shortly after casting the CLSM test specimens. He further
noted that this effect was greater at the higher glass and fly ash replacements. He
concluded that this observation was attributable to the decreased amount of the
cohesive material, i.e. fly ash, and increased amount of denser and larger size
glass particles compared to fly ash particles. Similar results were obtained for
CLSM containing waste glass, sand and cementitious material.
2.3.4.3.3 Air Content
Naiks (2000) research measured and reported air content for the fly ash and
glass mixtures. These ranged from 0.6 to 2.1 percent. The 80 percent glass
43


mixture had the highest percentage and the 60 percent glass mixture the lowest.
The air contents for the sand and glass mixtures increased from 0.7 percent for
mixtures having no glass to 1.9 percent for a mixtures having 75 percent glass. A
relationship between air content and the two materials is not strongly supported
by the data.
2.3A.3.4 Time of Set
The setting and hardening characteristics of the CLSM mixtures used by Naik
(2000) research was determined in accordance with ASTM D 6024. The time of
set for the fly ash and crushed glass mixtures were increasingly delayed as glass
increasingly replaced sand in the control mixture. This probably occurred due to
the decrease in the cementitious materials content of the mixture. Figure 2.2
illustrates the results from the sand and glass mixture from the Niak (2000)
study.
Mix > 1 (.1-.. MHI \s.
\flv V t. ^ "0 Vi.
Mi*' 2v Vo
w HO V,.

70 M! a -v
50 *
40 a
.01
20
10
0 21 .HI 4ft

a
50
Ajt. I!oui>
Figure 2.2 Setting and hardening Characteristics of Sand/Glass mixtures
(Naik, 2000)
44


2.3.4.3.5 Strength
Naik's (2000) research showed that the compressive strength of the fly ash and
glass mixtures increased with age. The rate of increase in compressive strength
was the highest for the mixtures containing 60 and 80 percent glass. Naik
explains that the typical CLSM mixtures behave like paste. However due to the
coarse glass in some mixtures, the CLSM had the appearance and texture of
concrete containing small aggregate. The compressive strength values of these
mixtures with and without glass ranged from 60 to 90 lb/in2 (0.4 to 0.6 MPa) at
the age of 28 days. Figure 2.3 illustrates the results Naik's study on fly ash and
glass mixtures.
Mi * \ 1 m '. U.v. !H> ' Hs Mil Mm \ 1 l,U. ML - Fh Mil
-A \h\ \ > 4M\ * ,U>-b' 1 h Mb Mm \ 4. 4r, < t;uv*. w- - H\ V-ii
Mm \ * ftO . a* K Mli Mm \ n Hir. ' t J 2 Mh
1.2 1
V u /.
V >
? (1,4
£ m
**
(U
9 (l
1
ft
1
i
14 ;K 70
Dav s
Figure 2.3 Compressive Strength of Glass/Fly ash CLSM Mixtures (Naik,
2000)
The compressive strength values of the CLSM mixtures containing glass
and sand aggregate and portland cement had similar compressive strengths as
45


CLSM mixtures containing only glass and fly ash. Compressive strengths range
from 20 to 85 lb/in2 (0.15 to 0.6 MPa) at the 28 day age. Figure 2.4 illustrates the
results from this study. The range of compressive strengths suggests that all
CLSM mixtures are likely be excavatable.
Mix v I. I.*. < Iimi' 'n.uicI Mix S-2. Of, (ilasv 70'i Sami
A Mix S-.l. "M1. t.i.iss. Ml', s.uiil
(% 0.8 0.7
0.0
u. C 4/ 0.5
b. / v * 0.4
7 i o..<
b. a. A
p 0.2
0.1
0
>
*


m
A
14 28 W
Age. day*
Figure 2.4 Compressive Strength of Sand/Glass CLSM Mixtures (Naik, 2000)
2.3.5 Recycled Concrete as Aggregate
2.3.5.1 Production
Recycled concrete used as aggregate is an example of a common construction
waste that is produced from demolishing concrete. Recycling of concrete is a
relatively simple process. For concrete to qualify for recycling it cannot contain
trash or metal objects such as rebar.
46


The concrete is typically crushed to a reasonable size for transport at the
construction site. At the recycling plant the concrete is crushed further by
primary and secondary crushers and screened to remove any contaminates
(PCA, 2011). The concrete is then graded and washed. The washed concrete is
generally stockpiled according to particle size (NMAS). Materials that do not
meet the recycling plant's requirements are either sent to another recycling
plant or landfilled (PCA, 2011).
The use of recycled aggregate will decrease the need to consume virgin
natural aggregate and simultaneously conserve landfill space. Unlike coarse
recycled concrete, fine recycled concrete aggregate has been found to have
limited use in structural concrete because it is more angular, porous, and weaker
than natural aggregate. These characteristics affect the workability, ease of
finishing and strength.
2.3.5.2 Physical, Chemical and Reactive Properties
The recycled concrete aggregate chemical and physical properties will vary
greatly depending on the source of the demolished concrete. Recycled concrete
aggregate can be purchased in various size ranges. The crushed concrete not
only contains the originating concretes coarse aggregate but also chunks of
mortar, fine aggregates and cementitious paste. This paste will also be present in
the coarse and fine aggregate in varying amounts. Chloride content may be high
when the parent material is road concrete since residual chlorides salts used to
melt snow and prevent icing may be present.
Cementitious paste and mortar contained in crushed concrete used as
aggregate reduces the specific gravity and increases the porosity of cementitious
mixtures. Higher porosity of recycled concrete aggregate leads to a higher
47


absorption (PCA, 2011). The absorption capacity of crushed concrete will
usually be higher than that of common sand and gravel due to the increased
porosity of the mortar chunks and cementitious paste surrounding the
aggregate. Typical range for absorption content is between 3 and 10 percent and
increases as the crushed concrete aggregate size decreases (www.cement.org,
2002). The physical appearance of recycled concrete is more angular than
crushed rock. Because of this characteristic it expectedly exhibits workability
problems.
2.3.5.3 The Effects of Recycled Concrete as Aggregate on CLSM Properties
2.3.5.3.1 Flow Consistency
Achtemichuk, Hubbard, Sluce, and Shehata (2009) examined the effects of fine
recycled concrete aggregate on the properties of CLSM. The workability was
evaluated using the slump flow test (ASTM D 6103). It was concluded that with
fine recycled concrete aggregate the CLSM design was mainly for applications
that involve narrow areas such as small trenches, or bedding for conduits with
small spacing, because the plastic properties of these mixtures are very
important. The mix designs consisted of fly ash, water and crushed concrete as
aggregate. Table 2.14 shows the mix proportions of the CLSM and their fresh
CLSM properties. The minimum flowability for this research was 5.9 in (150
mm).
48


Table 2.14 Mix Proportions of CLSM with Fine Recycled Concrete Aggregate
(Achtemichuk, 2009)
Fly Ash (%) w/cm Slump flow (mm)
5 2.65 120
10 1.25 119
15 0.83 132
20 0.63 108
30 0.5 141
2.3.5.3.2 Bleeding and Segregation
Segregation during the batching of RCA CLSM mixtures was a concern expressed
by Achtemichuk (2009) and avoided by adjusting water to cementitious material
ratio as needed to maintain approximately the same consistency in all tests.
2.3.5.3.3 Air Content
Air content was not specifically discussed in the Achtemichuk document.
2.3.5.3.3 Time of Set
Achtemichuk (2009) found that the fine crushed concrete used in their study
contained 0.08 percent alkalis, which were attributed, in part, to activating the
pozzalonic reaction with fly ash and slag which were used in their study as
cementitious material. They attributed the high surface area fine crushed
concrete as helping accelerate the release of alkalis from cement paste, thereby
accelerating set time.
49


2.3.5.3.5 Strength
Achtemichuk (2009) used fly ash mixed with various percentages of slag as
cementitious materials when batching, using fine crushed concrete as the sole
aggregate. Some mixtures having acceptable strength ranges resulted. As noted
earlier, the water content was adjusted to regulate consistency; therefore the
w/cm ratios for all tests varied, as did the cementitious material content.
2.3.6 Recycled Crumb Rubber as Aggregate
2.3.6.1 Production
Crumb rubber generally consists of particles ranging in size from 4.75 (No. 4
Sieve) to less than 0.075 (No. 200 Sieve). Methods commonly used to convert
scrap-tires into crumb rubber are: (i) cracker mill process, (ii) granular process
and (iii) micro-mill process (Siddique, 2009). The cracker mill process tears
apart or reduces the size of tire rubber by passing the materials between
rotating corrugated steel drums. This process produces irregularly shaped torn
particles having large surface area, The size of these particles varies from 5 to
0.5 mm (No. 4 No. 40 Sieve) and is known as crumb rubber. Crumb rubber can
be sieved to produce a wide range of particle sizes. In 2001, about 281 million
scrap tires were generated in the United State and roughly 75 percent of these
tires were reused in some type of secondary market (Rubber Manufacturers
Association 2006). Civil engineering applications, in which tires are shredded for
applications such as leachate collection in landfills or for highway embankments,
accounted for about 15 percent of scrap tires.
A nominal crumb rubber process is designed to process passenger tires
and truck tires in separate batches and can alter the mesh size of output
50


depending on customer specifications and market requirements. A magnetic
metal removal and fiber screening system are incorporated, and metal and fiber
fragments removed at various stages of the process are conveyed to central
container for later sale or disposal (Sunthonpagasit, 2002). The first part of this
process is visual inspection and sorting, and is important to ensure that the
scrap tires are suitable for processing. Passenger tires and truck tires are
separated; tires containing rims are de-rimmed. The tires are then put on a
conveying system to reduce the whole tires through shredding and granulating
down to various sizes, and then classified into three groups: coarse, mid-range,
and fine size. Not all recycled crumb rubber plants reduce the size of the
material to 40 to 80 mesh. Typically 30 mesh is the smallest size created because
smaller sizes are more difficult to isolate.
2.3.6.2 Physical, Chemical and Reactive Properties
A tire is a composite of complex elastomer formulations, fibers and steel/fiber
cord. Tires are made of plies of reinforcing cords extending transversely from
bead to bead, on top of which is a belt located below the thread. Table 2.15 lists
typical types of materials used in manufactured tires.
51


Table 2.15 Typical Materials used in Manufacturing Tire
(Rubber manufacturer's Association, 2006)
1) Synthetic rubber
2) Natural rubber
3) Sulfur and sulfur compounds
4) Phenolic resin
5) Oil
(i) Aromatic
(ii) Naphthenic
(Hi) Paraffinic
6) Fabric
(i) Polyester
(ii) Nylon
7) Petroleum waxes
8) Pigments
(i) Zinc oxide
(ii) Titanium dioxide
9) Carbon black
10) Fatty acids
11) Inert materials
12) Steel wires_______________
Crumb rubber is finely ground tire rubber from which the fabric and steel
belts have been removed. It has a granular texture and ranges in size from very
fine powder to sand-size particles. Tire chops consist of tire pieces that are
roughly shredded into 1-12 inches (2.5-30 cm) lengths (Pierce, 2002).
Pierce and Blackwell (2002) researched the characteristics of crumb rubber:
According to Humphrey (1999), some of the advantageous properties of
tire chips in civil engineering applications include low material density,
high bulk permeability, high thermal insulation, high durability, and high
bulk compressibility. When mixed with mortar or concrete, research has
shown that both compressive strength and unit weight decreases with
increasing rubber content (Goulias, 1998). Incorporating fly ash in rubber
52


mixtures further reduces unit weight (Fattuhi, 1996). Increasing rubber
content also reduced modulus of elasticity (Fedroff, 1996) and improves
ductility (Goulias, 1998). Due to its low specific gravity and unit weight
crumb rubber can be considered a lightweight aggregate for use in
concrete manufacturing. Fattuhi (1996) suggest that concrete rubber
mixtures could be used for trench filling and pipe bedding, which are
common applications for CLSM. However, research on mixing crumb
rubber in CLSM has minimal amount of literature.
2.3.6.3 The Effects of Recycled Crumb Rubber as Aggregate on CLSM
Properties
2.3.6.3.1 Flow Consistency
Pierce, and Blackwell (2002) investigated the performance of CLSM mixes using
crumb rubber exclusively as aggregate in CLSM. No sand was added to the
mixtures. The crumb rubber was a No. 30 mesh. A general-purpose fluidizing
agent commonly used for cement-sand grouts was added to three of the nine
mixtures tested to improve flowability. It was noted the higher w/cm ratios tend
to increase flowability and bleeding. Table 2.16 lists the average flowability
measured for the nine mixtures studied. Consistency was measured in
accordance with ASTM D 6103. Only two of the nine mixtures met the criterion
of a spread diameter of 8 to 12 inches (203.2 to 304.8 mm). Mixtures 1, 2 and 3
contained fluidizing agents the researchers noted that flowability increased by
40 percent when fluidizing agent was added and all other things equal. It was
concluded that Mixtures 4 and 8 could be used as CLSM in select applications
that do not require significant flowability. This contingency was in recognition
that any flow resulting in less than an 8 inch diameter footprint does not achieve
53


the ASTM minimum consistency requirement, being too stiff. Flowability
increased consistently with an increasing w/cm ratio. It is noteworthy that
Pierce and Blackwell (2002) CLSM crumb rubber mixtures required a w/cm
ratio between 1.75 and 3 to meet flowability requirements and that a fluidizing
agent was effective in increasing flowability.
Table 2.16 Flowability and Bleeding
Mixtures Flowability (cm) Bleeding (% volume)
1 0 1.3
2 20.3 1.9
3 23.9 3.7
4 16.8 4.3
5 35 10.1
6 36.3 13.8
7 31.8 9.5
8 16.8 4.6
9 >60 29.9
A study done by Wu and Tsai (2008) concluded that rubberized CLSM is
essentially not flowable without the addition of sand. No fluidizing agents were
used in their study. Wu and Tsais (2008) study indicated that, despite different
w/cm ratios, the rubberized CLSM without the addition of sand exhibited poor
workability and was unable to achieve a preferable flowability of 20 cm (8
inches). They drew the conclusion that rubber fines are poorly graded sand-like
porous materials with higher permeability and that water exchange with the
pores leads to a lower flowability.
54


2.3.6.3.2 Bleeding and Segregation
Segregation is often a concern when dealing with lightweight aggregate and
incorporating it into cement-based materials. Because of crumb rubbers low
specific gravity, it can be considered a lightweight material. As discussed in the
previous section, Pierce and Blackwell (2002) used the admixtures to increase
flowability of the mixture. Because the admixture reduced water content it also
helped to control segregation. High water contents were observed to result in
segregation. This was noted during consistency testing as an observed surface
layer of crumb rubber that developed on the surface of the tested material as it
flowed. (Pierce and Blackwell, 2002).
Bleeding depends primarily on the mixture of water content. Pierce and
Blackwell associated observations of increased bleeding with increased w/cm
ratios. To help control bleeding the mixing time and speed was increased.
2.3.6.3.3 Air Content and Unit Weight
No information was found in literature regarding the air content of CLSM that
uses crumb rubber as aggregate. However, unit weight measurements by Wu
and Tsai (2008) yielded unit weights for CLSM that ranged from 5.5 to 11.6
kN/m3 (35 to 74 lb/ft3). These values are only about 25 to 50 percent of that of a
standard CLSM or a compacted earth fill (Wu, Tsai 2008). Pierce and Backwells
(2002) investigation shows similar results. The reduction in unit weight is
primarily a function of the increase in crumb rubber content.
55


2.3.6.3.4 Time of Set
The Pierce and Blackwell (2002) investigation revealed that all mixtures set
within 24 hours. They defined set time as the earliest time for which there was
penetration resistance using a pocket penetrometer. ASTM recommends a
minimum equivalent strength of 20 lb/in2 after three days of curing. It was
recorded that all but one of their mixtures met this requirement.
Table 2.17 Flowabiiity, Bleeding and Initial Hardening Time for All Mixtures
Mixtures Flowabiiity (cm) Bleeding (% volume) Time to Reach 140 kPa (20psi)
1 0 1.3 1
2 20.3 1.9 2
3 23.9 3.7 6
4 16.8 4.3 1
5 35 10.1 1
6 36.3 13.8 1
7 31.8 9.5 1
8 16.8 4.6 2
9 >60 29.9 1
2.3.6.3.5 Strength
Pierce and Blackwell (2002) concluded that CLSM mixed with crumb rubber can
achieve sufficient strength for practical applications. Table 2.18 shows the
strengths achieved by Pierce and Blackwell. Note that Mixture 9 was not
analyzed due to a high bleeding factor. The data collected showed that the
measured compressive strengths generally fell between 30 and 300 lb/in2,
which is common for most standard CLSM. However, mixtures with strengths
56


greater than 200 lb/in2are not expected to be excavatable (ACI, 1999). Research
is not definitive regarding the influence of crumb rubber content on strength. At
a w/cm ratio of 3, strength is greatest when the crumb rubber content is 29
percent. Strength is consistently lower at both higher and lower rubber contents,
suggesting that there may be an optimum for a given w/cm ratio. The most
determinable influence on strength of cement-based material is the w/cm ratio.
Based on Pierce and Blackwell's measurements, strength generally decreases as
the w/cm ratio increases from 1.5 to 2.
Table 2.18 Average Compressive Strength (Pierce, & Blackwell 2002)
Mixtures 7-Day(kPa) 14-Day (kPa) 28-Day (kPa)
1 179 228 269
2 - 566 766
3 331 359 483
4 932 1449 2601
5 - 897 1021
6 97 469 676
7 718 897 1194
8 114 1525 -
57


3. Problem Statement
3.1 Statement
The public, industries and government have become increasingly interested in
green design and engineering in particular is moving towards more sustainable
development. The world is in a transition of improving the disposal and usage of
waste products from solid waste materials to by-products of the coal and mining
industry. Electricity is one of the most versatile and therefore the most desirable
forms of energy. The U.S. consumes the largest amount of the total electrical
power consumption in the world. In 2007, the world consumed 495 quadrillion
Btu., and of the total, the U.S. consumed 21% (energy.gov, 2011). Electric power
consumption is comprised of commercial, industrial, residential and
transportation users. The U.S. Department of Energy states that industrial use is
half of what the world consumes in electric power (energy.gov, 2011). Recycling
has a significant positive effect by reducing the amount of energy needed to
make products with new materials. When recyclables go to the landfill, more
materials must be mined, harvested or refined to replace the discarded item.
Concrete construction is one of the largest users of natural resources. The
recycling of concrete, asphalt and other solid waste materials is a great
opportunity to reduce mining, and the use of virgin materials, and minimize
landfill use.
Recycling also has economic benefits, landfill space costs money for state
and local governments, which do not receive a financial return on this
investment. Recycling, on the other hand, produces income that not only offsets
the cost of establishing recycling facilities, but also generates significant income
through tax revenues for local, state and federal governments. The use of
58


concrete has become a sustainable approach to construction. With the economy
changing and the critical need for environmental conservation, builders are
moving towards a more sustainable and innovative solutions that meet
engineering challenges while reducing labor, material cost and environmental
impact. It is for these reasons that the use of flowable fill also known as
Controlled Low Strength Material (CLSM) was chosen for further research.
CLSM is a self-compacting low strength material with a flowable
consistency that is used as an economical fill or backfill materials as an
alternative to compacted granular fill. CLSM is not concrete, nor is it used to
replace concrete. CLSM is also known as unshrinkable fill, controlled density fill
(CDF), flowable mortar, soil cement slurry, plastic cement and was known for a
while as "K-Krete. CLSM is a self-leveling material that does not require
compaction or vibration and is placed with minimal effort. When hardened the
material provides adequate strength. The ingredients may vary, but typically
consist of a mixture of soil (used as aggregate), cementitious material, and water.
The contributions of these admixtures are selected to reduce the cement
quantity, to improve the flow characteristics of the mixture and/or to optimize
the use of readily available materials. Like many other concrete products, CLSM
has many green benefits when made using industrial waste products.
The focus of this research is to create mix designs of CLSM that will
provide the use of recycled materials that are a potentially low-cost source of
aggregate. The use of these recycled materials will reduce the amount of waste
materials that end up in landfills. To fully understand the effects that recycled
materials have on the fresh and hardened properties of CLSM, the percentages of
recycled materials used ranged from 25% replacement to 100% replacement.
CLSM ideal applications are: backfill, trenches, pipe bedding, excavated tanks,
sub-bases, slope stabilization, and pavement base. These applications and others
59


require the CLSM have an acceptable compressive strength. CLSM compressive
strengths in some cases must be low enough for future excavation. The ultimate
strength, modulus of elasticity and fresh concrete properties were examined for
all mix designs. The main purpose for this research is to investigate the
advantages and disadvantages of the different percent replacement of recycled
materials, determine if they are beneficial, and conclude if specific mixtures will
result in usable CLSM.
60


4. Experimental Plan
4.1 Design Summary
The objective of this thesis is to evaluate innovative uses for common waste
materials in CLSM mixtures. To this end, the following two goals are established.
1) Determine if there is potential for CLSM to be manufactured using spray
drier ash (SDA) as the principle cementitious material by evaluating rate of
strength increase and attainment of common CLSM strength and flowability
requirements for several mixtures.
2) Measure and compare the compressive strength, and the modulus of
elasticity of CLSM mixtures manufactured using select combinations of Class
C fly ash, portland cement, SDA, crushed glass, bottom ash, recycled concrete
and crumb rubber; and thereby add to the growing body of knowledge
regarding appropriate mix proportions for CLSM manufactured using these
materials.
A standard CLSM mixture is made up of water, cement, and fine aggregate.
The ingredients that were subject to replacement with the above listed recycled
waste materials include cement and fine aggregate.
The research presented herein investigates the effects that the materials
discussed above will have on the fresh and hardened properties of CLSM.
Various proportions of the recycled materials were used in CLSM mixtures. The
mixtures for this research project consisted of aggregates proportioned by
volume and cementitious material proportioned by mass. A typical CLSM is
described in ASTM D 4832 and was selected as the control mix. It was comprised
61


of fine sand with the cementitious material consisting of 90 percent Class C fly
ash and 10 percent cement with a water to cement ratio (w/cm) of about 1.25.
The test program has two components 1) the cementitious materials
investigation, and 2) the aggregate replacement investigation. Literature review
provided information necessary to determine which waste materials may be
successfully applied to CLSM and mixture proportions likely to be successful.
Portland cement was mixed with either Class C fly ash or SDA using sand as a
fine aggregate.
Class C fly ash mixes included fly ash as 90, 95 and 100 percent of the
cementitious material.
SDA mixes included SDA as 90, 95 and 100 percent of the cementitious
material.
The sand used as control mix aggregate was replaced with either crumb
rubber, bottom ash, recycled concrete or crushed glass.
The aggregates were substituted for the sand with 25, 75 and 100 percent
replacement.
All mixes to investigate aggregates used cementitious material comprised
of 90 percent Class C fly ash, and 10 percent portland cement.
All mixes other than the SDA mixes were designed to have 630 lbs/yd3
cementitious material and to the extent practicable maintained a w/cm ratio of
1.25. The SDA mix was designed to have 750 lbs/yd3 cementitious material. As
needed, measured quantities of either water or dry mixture were added during
batching to achieve flowability requirements for CLSM. This changed some
mixture proportions slightly and is discussed in Chapter 5. All mixtures were
tested for fresh and hardened CLSM properties. The fresh concrete properties
62


tested included slump, unit weight and air content. The hardened CLSM
properties examined were compressive strength and modulus of elasticity. A
penetrometer test was used to evaluate set time for SDA mixtures. All testing
conformed to ASTM testing standards with exceptions presented in Chapter 5;
and all data results, details, conclusions, and findings of this research are
included with this thesis.
A successful CLSM must have properties defined by specific standards. The
standards of the Colorado Department of Transportation (CDOT) for typical
CLSM are herein adopted for this research with the exceptions noted below.
Mixtures that achieve the CDOT strength and consistency standards are deemed
successful.
To evaluate the effects of these recycled materials the fresh and hardened
CLSM properties of each mixture are measured and compared to each other,
CDOT and ASTM standards. A CDOT CLSM mixture is a low strength structural
material that can be used in multiple structural backfill applications. CDOT states
that structural backfill shall be composed of non-organic mineral aggregates and
soil from excavations, borrow pits, or other sources (CDOT, 2011). CDOT also
notes that fine aggregate and fly ash that do not meet the requirements
subjected in their specification manual may be used as long as testing indicates
its use is acceptable for the application. The mixtures main concern is its
flowability. The flowability requirement of a CDOT mixture is to achieve a flow
consistency that results in at least a 6 inch (152.4 mm) diameter patty of fresh
mixture when tested in accordance with ASTM D6103. Table 4.1 shows the other
specific requirements for a CDOT CLSM mixture. Table 4.2 shows the ASTM
specifications for comparison. The CDOT removability modulus (RM) and is
calculated as follows:
63


RM =
VV15 x 104 x C05
(Equation 1)
106
W=unit weight (pcf)
C=28-day compressive strength (psi)
It is expected that CLSM achieving the RM standard can be excavated with
common equipment.
Table 4.1 Colorado Department of Transportation (CDOT) Structural
Backfill Specifications (CDOT, 2011)
28-Day Compressive Strength minimum Flow Consistency Air Content
(lb/in2) (inches) (percent)
50 6 2 to 3
Table 4.2 ASTM Standards Specifications
28-Day Compressive Strength maximum 28-Day Compressive Strength typical value Flow Consistency Air Content
flb/in2) (lb/in2) (inches) (percent)
1200 50 to 100 8 to 12 entrapped .5 to 3; air entraining 15- 25
The remainder of this section is organized as follows. Section 4.2 presents
properties of the materials used in this thesis; Section 4.3 presents the
64


experimental design; and Section 4.4 presents the CLSM batching, curing, and
general testing procedures.
4.2 Material Properties
The cementitious materials used in this study are spray drier ash, Class C fly ash,
and portland cement. The aggregates used in this study are fine sand (C 33
Sand), crushed glass (recycled glass), crumb rubber, bottom ash and crushed
concrete. The properties of each are discussed in this section.
4.2.1 Class C Fly Ash
The Class C fly ash was obtained from the Pawnee Plant (Boral), just east of
Denver, Colorado. Class C fly ash was chosen rather than Class F because Class C
has stronger pozzolanic character thought to be needed to successfully replace
cement without significantly changing the total unit mass of the cementitious
material. The Class C fly ash was tested by the supplier in accordance with ASTM
C 618 and the results of this testing are shown in Table 4.3.
65


Table 4.3 Pawnee Class C Fly Ash Physical and Chemical Properties
Pawnee Class C Fly Ash
Chemical Properties Test Results ASTM C 618 Specifications
Silicon Dioxide (Si02) (%) 30.3
Aluminum Oxide (A1203] (%) 17.2
Iron Oxide (Fe203) (%) 6.66
Sum of Si02, ADO3, Fe203 (%) 54.16 70.0/50.0 min.
Calcium Oxide (CaO) (%) 29.13
Magnesium Oxide (MgO) (%) 7.45
Sulfur Trioxide (S03) (%) 2.85 5.0 max
Sodium Oxide (Na20) (%) 2.26
Potassium (K20) (%) 0.31
Total Alkalies (as Na20) (%) 2.46
Physical Properties Test Results ASTM C 618 Specifications
Moisture Content (%) 0.02 3.0 max
Loss of Ignition (%) 0.4 6.0 max
Amount Retained on No. 325 Sieve (%) 13.41 34 max
Specific Gravity - 2.77 -
Autoclave Soundness (%) 0.15 0.8 max
SAI, with portland Cement at 7 Days (%] of Control 101.9 75 min.
SAI, with portland Cement at 28 Days (%] of Control 97.8 75 min.
Water Required (%) of Control 95 105 max
Loose, Dry Bulk Density (lb/ft3] 72.03 -
66


4.2.2 Portland Cement
Type I-II portland cement was supplied by Holcim Cement Company, located in
Florence, Colorado. The cement was tested by the supplier in accordance to
ASTM C 150 and the results are shown in Table 4.4.
Table 4.4 Holcim Type 1-11 Cement Physical and Chemical Properties
Holcim Type I-II Portland Cement
Chemical and Physical Properties Test Results ASTM C 150 Specifications
Silicon Dioxide (Si02J (%) 19.6 -
Aluminum Oxide (A1203) (%) 4.7 6.0 max
Iron Oxide (Fe203) (%) 3.2 6.0 max
Calcium Oxide (CaO) (%) 63.4 -
Magnesium Oxide (MgO) (%) 1.5 6.0 max
Sulfure Tioxide (S03) (%) 3.4 3.0 max
Carbon Dioxide (C02) (%) 1.4 -
Limestone (%) 3.7 5.0 max.
Calcium Carbonate (CaC03) in Limestone (%) 84 70 min.
C3S (%) 59 -
C2S (%) 11 -
c3a (%) 7 8.0 max
c4af (%) 10 -
C3S + 4.75 C3A (%) 92 100 max
Loss of Ignition (%) 2.6 3.0 max
Blaine Fineness cm-/g 414 . 2600 4300
Air Content of PC Mortar (%) 6.3 12 max
Specific Gravity (%) 3.15 -
67


4.2.3 Spray Dryer Ash
The spray dryer ash was obtained from the Comanche Plant near Pueblo,
Colorado. The spray dryer ash that was used in this research was chosen
because of its abundance resulting from a general lack of industrial applications.
The spray diyer ash was tested by the supplier in accordance with ASTM C 618
and the results of this testing are shown in Table 4. 5.
Table 4.5 Chomanche Spray Dryer Ash Physical and Chemical Properties
Chomanche Spray Dryer Ash
Chemical Properties Test Results ASTM C 618 Specifications
Silicon Dioxide (Si02) (%) 26.21
Aluminum Oxide (A1203) (%) 15.22
Iron Oxide (Fe2C>3) (%) 4.37
Sum of Si02, Al203, Fe203 (%) 45.8 70.0/50.0 min.
Calcium Oxide (CaO) (%) 30.31
Magnesium Oxide (MgO) (%) 3.99
Sulfur Trioxide (S03) (%) 12.68 5.0 max.
Sodium Oxide (Na20) (%) 1.45
Potassium (K20) (%) 0.28
Total Alkalis (as Na20) (%) 1.63
Physical Properties
Moisture Content (%) 1.72 3.0 max.
Loss of Ignition (%) 2.47 6.0 max.
Amount Retained on No. 325 Sieve (%) 11.11 34 max.
Specific Gravity - 2.57 -
SA1, with Portland Cement at 7 Days (%) of Control 107.9 75 min.
SAI, with Portland Cement at 28 Days (%] of Control - 75 min.
Water Required (%) of Control 99.2 105 max.
68


The spray dryer ash however, did not meet the ASTM C 618 cementitious
materials specifications by not possessing the minimum allowable sum of SiCh,
AI2O3, Fe2C>3 and also by exceeding the sulfur trioxide standard.
4.2.4 (Virgin) Fine Aggregate
The fine aggregate was obtained by the University of Colorado Denver from
Bestway Concrete and other sources located in the Colorado area. The material
properties and gradation analyses were determined by WestTest Laboratories
located in Denver, Colorado. The sand was determined to meet the ASTM C 136
requirements for C 33 Fine Aggregate. The materials properties data and
complete gradation for the sand is included in Appendix B The specific gravity
for the C 33 sand is 2.63 and the absorption capacity is 0.7 percent. The fine
aggregate will be referred to as "C 33 Sand" for the remainder of this thesis.
4.2.5 (Recycled) Fine Aggregate
The bottom ash, crushed waste glass, recycled concrete fines, and the crumb
rubber used to replace aggregate in the control mix were from various sources
and were tested by methods indicated in Table 4.6 prior to use in the CLSM
mixtures.
69


Table 4.6 Testing of Recycled Materials
Fine Aggregate Test Type Performed ASTM Method
Bottom Ash Specific Gravity & Absorption Capacity ASTM C 128
Sieve Analysis (Gradation) ASTM C 136
Crushed Waste Glass Specific Gravity & Absorption Capacity ASTM C128
Sieve Analysis (Gradation) ASTM C 136
Recycled Concrete Fines Specific Gravity & Absorption Capacity ASTM C 128
Sieve Analysis (Gradation) ASTM C 136
Crumb Rubber Specific Gravity & Absorption Capacity ASTM C 128
Sieve Analysis (Gradation) ASTM C 136
4.2.5.1 Crushed Waste Glass
The crushed waste glass was obtained from Rocky Mountain Bottling Co., owned
by Miller-Coors. The waste glass was mainly produced from beer bottles with
various colors such as clear, amber and green. The glass was collected from the
hopper after it had traveled along a conveyor belt and had undergone multiple
crushings. The crushed glass also had impurities removed by a vacuum and
magnets. The waste glass was used "as received from the plant, i.e. no washing
took place. It was observed that the waste glass contained a few foreign objects
such as batteries and screws. These were removed from the material prior to
batching by a physical separation process. That is, the crushed glass was passed
through a 3/8 inch sieve to remove the undesirable objects.
Testing was performed on the waste glass to determine the absorption
capacity, specific gravity and fineness modulus. Table 4.7 shows the properties
of the waste glass and compares them to the same C 33 Sand properties.
70


Table 4.7 Fine Aggregate Properties of Waste Glass and C 33 Sand
Aggregate Property Waste Glass C 33 Sand
Absorption Capacity, (%) 0.02 0.7
Specific Gravity 2.50 2.63
Fineness Modulus 4.37 2.67
The absorption for both aggregates is low, with the waste glass
adsorption registering lower than the C 33 Sand. This can be expected because
glass is not porous and therefore does not retain water. A comparison of the
specific gravity of the waste glass to the C 33 Sand also indicates the specific
gravity of the glass is slightly lower than the sand.
Gradation analyses were performed on three independent representative
sample of waste glass. ASTM C 702: Standard Practice for Reducing Samples of
Aggregate to Testing Size was followed to obtain representative samples. This
required the waste glass to be thoroughly mixed; the pile iteratively split into
smaller piles; and two suitable piles combined for a sieve analysis. The splitting
was iterated until the two piles combined for the testing had the proper
combined weight for the analysis. The particle size distributions were consistent
with all three samples and are presented in Appendix B. The average of the
gradation analyses for the waste glass is shown alongside the gradation for the C
33 Sand on Figure 4.1. The plot is a representation of the average of three-
gradation analysis performed. The waste glass specimens did not achieve the
requirements of ASTM C 136 C 33 aggregate due to excess materials retained on
the 8, 16, and 30 sieves. The No. 200 sieve was added to the standard sieve stack
because the amount of fines in CLSM aggregate is a concern. CDOT specification
regarding fine aggregate states that 100 percent must pass the 1 inch sieve and
71


no more than 10 percent pass the No. 200 sieve. The waste glass meets this
standard.
The fineness modulus (FM) for waste glass is much higher than the C 33
Sand. The FM for fine aggregate is required for mix proportioning since sand
gradation has the largest effect on workability. In general, finer sand (lower
fineness) has a greater number of particles available to improve workability. The
fineness modulus for fine aggregate should lie between 2.3 and 3 (Mindness,
2003). The FM is used to check the consistency of grading when relatively small
changes are to be expected; but it should not be used to compare the grading of
aggregates from two different sources. Based on the test results, the waste glass
is coarser than the C 33 Sand. However, adequate workability was anticipated
because the crushed glass is a uniform relatively fine aggregate.
72


00
AVERAGE RECYCLED CRUSHED GLASS & C 33 SAND GRADATIONS
1 SIEVE ANALYSI j u.i trmaum **vi j Ml M HCHH j OPftMM u Vf A* NMChtl ""ll 16 24" 12" 8" 3" t \rr w w m *e no n OMit) mm 8 30 MO *80 00 *? HYDROMETER ANA n MAOiNM 00 IMM 4 UN *1* LYSIS im- iih MM '4 *"* 4,N PI- 0 10 W
1
i n
i \ \ \ . \ j
ASTtv C 33 _owei Limit - V* i\ \
1 cn \ 35 i \ \ \ 2 > CD r 30 C- G g s IP OS E- 7, 80 CP O X IP a. 60 70 *0 00 00
\ \ f,
> ; n SC : 0 7 55 ; M 2 ; £ 1 \ 1 - i .STM ; 331 pper 1 imit
I
ij \
i \ \
\ \
IP o ; as : a] a . i t ..... c 33 Sa id
i i
i 3ecycl 2d Cn shed 3lass

1 l \
i \ \ \ \
\
\ I
\ \ V \| Aj
\ \ \|
\ \ - j ^
18 810 >08 182 78 3T.8 18 0.8 *78 2.38 2 1.10 .428 .3 .16 .078 .037 .011 .000 006 .002 00 PARTICLE SIZE IN MILLIMETERS 1
r* ~t COBBLES GRAVEL SAND FINES
COS* j hNS C0*we MEDIA* I PNC J 1

Figure 4.1 Average Crushed Glass & C 33 Sand Gradation Analysis


4.2.5.2 Bottom Ash
Bottom ash was obtained from the Pawnee Plant (Boral), just east of Denver,
Colorado. The bottom ash and Class C fly ash were acquired from the same
production process. The bottom ash was taken from the bottom of the boiler and
included some material removed from the furnace walls. Larger pieces were
removed by passing the material over a 3/8 inch sieve. Testing was performed
on the bottom ash to determine the physical properties. Table 4.8 shows the
properties of the recycled concrete alongside the same property measurements
for the C 33 Sand for comparison.
Table 4.8 Fine Aggregate Properties of Bottom Ash and C 33 Sand
Aggregate Property Bottom Ash C 33 Sand
Absorption Capacity, (%) 7.08 0.7
Specific Gravity 2.6 2.63
Fineness Modulus 4.9 2.74
The bottom ash and the C 33 Sand have similarities and differences. The
specific gravities are very similar. However, the absorption capacities of the two
materials are significantly different. Bottom ash has a higher absorption capacity
due to its porous structure and angular shape. Water is absorbed and retained in
the porous bottom ash.
Three separate gradations were performed on the bottom ash after the
larger particles were removed by hand. ASTM C 702: Standard Practice for
Reducing Samples of Aggregate to Testing Size was used to obtain a
representative sample as previously described. The results of the three
gradation analyses are presented in Appendix B. Figure 4.2 illustrates the
comparison of the average bottom ash gradation to that of the C 33 Sand.
74


Three separate gradations were performed on the bottom ash, after the
larger particles were removed by hand. Before performing these gradations, the
bottom ash had to be sampled properly. ASTM C 702: Standard Practice for
Reducing Samples of Aggregate to Testing Size was followed for sampling. All of
the bottom ash that was obtained was dumped and mixed together, then
separated into four piles. The piles were repeatedly broken down until two
suitable piles were obtained for testing. Figure 4.2 illustrates the comparison of
the bottom ash to the C 33 sand. The practical distribution plot is an average of
three separate gradations. The gradation analysis for all three specimens did not
meet the requirements of ASTM C 136 due to excess material retained on the No.
4, No. 8, and No. 16 sieves. These results were consistent for all three samples.
The results are summarized in tables in Appendix B.
The fineness modulus (FM) for bottom ash is much higher than the C 33
sand. Therefore, based on the test result, bottom ash is a coarser material than
the C 33 sand, and may cause workability issues. However, for the CLSM
mixtures this may also not be a problem because the only aggregate being used
in a fine aggregate.
75


AVERAGE BOTTOM ASH & C 33 SAND GRADATIONS
100 na mmchm M" 24" ir 6" SIEVE ANALYSIS j 1 1/r 3*" W ** *8 #10 *18 <30 to *50 *100 *2 HYDROMETER ANALYSIS im ai/wwa* 1M)N 00 1 MN 4MH < *
\ 10 > .30 8
\ \
j \ \ \ \ \
l \
; 90 | 05 5 : s ; > a ; o | 2; ; AS* MC3 3 Low sr Lirr \ \ STM ( : 33 U jper L mil
\
\ \ \
1 £ w os h z 60 W o a 02 cu 80 70 r< 90 100 1
\
< a. i £ ;Ml Bott Ul < £ -Q ^ l \ \ 3 San i
\*
\ \
S i l \ \ \
\ \
\ \ \ y
i I
i"' y { \
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- j 1 \
18 810 J06 152 7 S 57 8 18 9 5 4 75 2.55 2 1 18 425 3 19 075 037 019 .008 .005 002 0C PARTICLE SIZE IN M1LL1M KI KRS
BOUIOERS poesies GRAVEl SAND PINES
COAAK { MNE CCMASC | MED*A j fHt

Figure 4.2 Average Bottom Ash & C 33 Sand Gradation Analysis


4.2.5.3 Recycled Concrete (RCA)
Recycled concrete was obtained from Allied Recycled Aggregate, located north of
Denver, Colorado. The aggregate was taken from a large waste pile that was
designated as recycled concrete fines. The aggregate was shoveled into buckets
from several locations on the large pile. The concrete originated from the
demolition of facilities and structures such as roads, buildings, driveways,
sidewalks, etc. Therefore the material in the pile may have been heterogeneous
with regard to material properties. The recycling plant doesn't accept any
material that contains foreign objects such as rebar. The recycled concrete fines
are considered a waste product that result from sieving crushed concrete to
obtain the larger, more valuable particles. Testing was performed on the
recycled concrete to determine the physical properties. Table 4.9 shows the
properties of the recycled concrete fines as well as the C 33 Sand fine aggregate
for comparison. The fineness modulus is derived from the average of the three
gradation tests.
Table 4.9 Fine Aggregate Properties of Recycled Concrete Fines and C 33
Sand
Aggregate Property Recycled Concrete Fines C 33 Sand
Absorption Capacity, (%) 9.7 0.7
Specific Gravity 2.62 2.63
Fineness Modulus 4.44 2.74
The specific gravity of the recycled concrete and the C 33 sand are
similar. However, the absorption capacity and the fineness modulus show that
the recycled concrete fines have a high absorption capacity, and higher fineness
77


modulus than the C 33 sand. The high absorption capacity could be a result of
the porous mortar coating on the larger particles and included mortar particles.
The high absorption results suggest CLSM may have a higher water
demand than the control mixture. The large number for the fineness modulus
indicates a coarse material. This may have a significant effect on the CLSM
workability. However, only fine, uniformly graded material is used so
workability and segregation issues were not anticipated.
Three separate gradations were performed on the recycled concrete
fines. ASTM C 702: Standard Practice for Reducing Samples of Aggregate to
Testing Size was used to obtain representative samples for gradation analyses.
The three gradation test results are presented in Appendix B. The average
gradation curve for the recycled concrete is shown with the gradation curve for
the C 33 Sand on Figure 4.3. The gradations for all three specimens did not meet
the requirements of ASTM C 136 for C 33 aggregate due to excess material retain
on the number 4, 8,16 and 30 (only two samples) sieves.
78


v£>
AVERAGE RECYCLED CONCRETE FINES & C 33 SAND GRADATIONS
I 1 Ul TNAMCMV* mi m mchm | aiaia MkCMIl 24- 12" 9" y 1 ifr 3*4" W 1 IEVE ANALYSIS U. fTAMBMB HM " M nno *1t *30 M0 960 *100 *3 HYDROMETER ANALYSIS 00 tmi 1IMI MUM
10 20 m >* 30 8 Q X 2 s X X f- 2 60 Ed O X X Leo 70 90 90 100
1 \ \ V \
\ \ \\
AS ru c I3 Low er Lirr i\

cc < S \ _L A iSTM 3 33 t pper .imit

\ ; i \
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CO * s a. £ JO \
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i \ \ \ \
t 20 j J \ > ;\ \
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v .
1 1 L...J
915 510 905 152 76 37.6 19 95 4 76 2.36 2 1.19 426 3 .15 .075 037 .019 009 005 002 001 PARTICLE SIZE IN MILLIMETERS
I BOULDERS COBBLES GRAVEL SANO FINES
iOAiwe J mkmjm j

Figure 4.3 Average Recycled Concrete Fines & C 33 Sand Gradation
Analysis


4.2.5.4 Crumb Rubber
The crumb rubber selected for this study was obtained from North West Rubber
Colorado, Inc. located in Louviers, Colorado. The rubber is identified as tire
crumb (styrene-butadiene rubber (SBR), poly Butadiene (PBD) & natural
rubber). The crumb rubber is a blend of various rubbers, carbon black and oils.
The rubber that was obtained is free of all metals and is 100 percent recycled
tire and comes in varies sizes. The crumb rubber that was used in this thesis was
collected and tested by Adam Kardos (UCD graduate student) and the results of
his testing are shown in Table 4.10 alongside the test results representing C 33
Sand.
Table 4.10 Fine Aggregate Properties of Crumb Rubber and C 33 Sand
Aggregate Property Crumb Rubber C 33 Sand
Absorption Capacity, (%) 0 0.7
Specific Gravity 1.07 2.63
Fineness Modulus 3.05 2.74
*Note: Crumb rubber results were tested and obtained from Adam Kardos, UCD Masters
Candidate, 2011.
Crumb rubber and C 33 sand have minor similarities. Crumb rubber is not
a porous material therefore has no absorption capacity while C 33 Sand has a
slight absorption capacity. The specific gravity of crumb rubber is lower than
that of C 33 sand and is only slightly greater than that of water (specific gravity
water = 1.0). When used in concrete, crumb rubber is generally considered a
lightweight concrete aggregate due to its low specific gravity. The fineness
modulus is also higher than the C 33 sand; this could be indicative of a decrease
in workability in CLSM mixtures. It was anticipated that crumb rubber could
have some trouble with both segregation and workability due to the
80


combination of mixtures having high w/cm ratios and low crumb rubber specific
gravity and high fineness modulus.
The gradation was determined as the average of analyses on two separate
representative crumb rubber samples. Adam Kardos performed the gradation
analyses as part of his more in-depth research study on the use of crumb rubber
in concrete mixtures and the results are summarized in the tables in Appendix B.
Figure 4.4 shows the average gradation curves of the crumb rubber alongside
the curve for the C 33 sand. It can be seen on the figure that the two particle size
distributions are very similar.
81


AVERAGE CRUMB RUBBER & C 33 SAND GRADATIONS
Si" 24 12 r
rrJWOAAD MTV*
OfUM
MKHII
SIEVE ANALYSIS
JUMM
T
i
1 1/2" 3M- W
e no *n no mo o *io *200
HYDROMETER ANALYSIS
1M
tun SIMM MWI
~i

Q
Id
z
<
e-
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as
H
Z
£3
O
as
a
Figure 4.4 Average Crumb Rubber & C 33 Sand Gradation Analysis


4.3 Experimental Design
The test program has two components 1) the cementitious materials
investigation, and 2) the aggregate replacement investigation.
4.3.1 Cementitious Materials Investigation Design
For the cementitious material investigation, the aggregate was sand and
cementitious material was portland cement combined with either Class C fly ash
or SDA in specific proportions. Theses mixtures are summarized as follows.
Class C fly ash mixes included fly ash as 90, 95 and 100 percent of the
cementitious material by mass.
SDA mixes included SDA as 90, 95 and 100 percent of the cementitious
material by mass.
4.3.2 Aggregate Replacement Investigation Design
For the Aggregate Replacement Investigation, the fly ash 90 percent mixture as
described above is the control mix and all investigated aggregates were
substituted for the C 33 sand in proportions described below. The C 33 sand was
systematically replaced with, bottom ash, crumb rubber, crushed glass, or
recycled concrete (RCA), in specific proportions. These mixtures are
summarized as follows.
The aggregates were substituted for the sand with 25, 75 and 100 percent
replacement by volume.
All mixes used cementitious material comprised of 90 percent Class C fly
ash, and 10 percent portland cement.
83


The targeted mix proportions are presented in Table 4.11 and Table 4.12. All
mixtures were designed to have 630 lbs/yd3 cementitious material except the
SDA mixtures, which were designed to have 750 lbs/yd3 cementitious material.
The targeted w/cm ratio was 1.25. Water or additional dry mixture components
were added during batching as necessary to achieve consistent flowability that
achieved the CDOT requirement for CLSM. Additionally, air content was not
controlled and deviated from the value presumed for design. As a consequence,
the mixture proportions actually achieved were different than those targeted.
The mix proportions achieved are presented and discussed in Chapter 5.
All mixtures were tested for fresh and hardened CLSM properties. The fresh
concrete properties tested included slump, unit weight and air content. The
hardened CLSM properties examined were compressive strength, and modulus
of elasticity. All testing conformed to ASTM testing standards and all data
results, details and conclusion of findings of this research are included with this
thesis.
84