Citation
Technology, environment, resource and policy assessment of sustainable concrete in urban infrastructure

Material Information

Title:
Technology, environment, resource and policy assessment of sustainable concrete in urban infrastructure
Creator:
Reiner, Mark
Publication Date:
Language:
English
Physical Description:
xiv, 219 leaves : ; 28 cm

Subjects

Subjects / Keywords:
Concrete -- Additives ( lcsh )
Sustainable construction ( lcsh )
Infrastructure (Economics) ( lcsh )
Concrete -- Additives ( fast )
Infrastructure (Economics) ( fast )
Sustainable construction ( fast )
Genre:
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

Notes

Bibliography:
Includes bibliographical references (leaves 208-219).
General Note:
College of Engineering and Applied Science
Statement of Responsibility:
by Mark Reiner.

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:
472607655 ( OCLC )
ocn472607655
Classification:
LD1193.E53 2007d R44 ( lcc )

Full Text
TECHNOLOGY, ENVIRONMENT, RESOURCE AND POLICY ASSESSMENT
OF SUSTAINABLE CONCRETE IN URBAN INFRASTRUCTURE
By
Mark Reiner
Bachelor of Arts, History and Education, Valparaiso University 1988
Bachelor of Science, Geological Engineering, Colorado Schools of Mines 1996
Master of Science, Civil Engineering, University of Colorado at Denver 1999
A thesis submitted to the
University of Colorado at Denver Health Sciences Center
in partial fulfillment
of the requirements for the degree of
Doctor of Philosophy (Ph.D.)
College of Engineering and Applied Sciences
May 2007


by Mark Bertram Reiner
All rights reserved


This thesis for the Doctor of Philosophy
degree by
Mark Bertram Reiner
has been approved
by
Anu Ramaswami
Stephan Durham
\JU !'-j c C? Z Qd 7
Date


Reiner, Mark B. (Ph.D., College of Engineering and Applied Sciences)
Technology, Environment, Resource and Policy Assessment of Sustainable
Concrete in Urban Infrastructure
Thesis directed by Professors Anu Ramaswami and Kevin Rens
ABSTRACT
Cement production accounts for approximately one-seventh of total global CO2
emissions from all human activities. In addition, the consumption of virgin
aggregates for concrete infrastructure has created virgin material scarcity issues in
many areas of the United States. High Performance Green Concrete (HPGC) with
fly ash and recycled aggregates can help reduce the demand for material inputs and
reduce pollution outputs associated with bulk material flow of urban concrete. This
thesis quantifies the sustainability of HPGC in urban infrastructure by addressing
structural performance, environmental, economic and resource depletion impacts.
Structural (ASTM C 39) and durability tests (ASTM C 666, ASTM C 1012, ASTM
C 1202) showed that HPGC containing fly ash and 50% recycled aggregate (100%
of the coarse fraction) performed equally or better than ordinary Portland concrete
(OPC 0% fly ash and 0% recycled aggregates) with the same cementitious
content. Durability improvements were more significant with Class F fly ash than
Class C. For both Class F and C, greater percent replacement of Portland cement
with fly ash led to slower and lower strength gain, but sill within acceptable


strength criteria for CDOT Class B concrete. A baseline environmental life cycle
assessment (LCA) of OPC (with 14% Portland cement) showed emissions of 1.21
tonne C02equivalents/tonne of cement. Replacement of cement with fly ash
reduced greenhouse gas (GHG) emissions by 21% to 36% for 20% and 40%
Portland cement replacement; including fuel use for transport of fly ash and
benefits of avoided landfilling. The incorporation of 50% recycled aggregates
provided a further 5% reduction in GHG emissions.
A regional material flow analysis (MFA) and GHG inventory of the City and
County of Denver (CCoD) showed per capita concrete and aggregate use of 3.59
tonnes and 9 tonnes, respectively, and that cement usage contributed approximately
2% to CCoDs GHG footprint. HPGC (with 20% fly ash and recycled coarse
aggregates) was evaluated as a mitigation strategy with immediate cost savings,
yielding annual community-wide GHG reductions of 60,000 MTC02e (in 2005)
reducing demand for virgin aggregates by approximately 790,000 tonnes, and
direct cost savings of $2M to $4M per year.
This abstract accurately represents the content of the candidates thesis. We
recommend its publication.
Signed
Anu Ramaswami
Signed
Kevin Rens


DEDICATION
This thesis is dedicated to the women in my life: Linda, Kyla and Clarice.


ACKNOWLEDGEMENT
I recognize the contributions towards many of the insights contained within this
thesis to my advisors, Anu Ramaswami and Kevin Rens, and the support given to
me by family and friends.
I also wish to thank members of my committee for their valuable participation and
insights, especially Stephen Durham. I also wish to thank member of industry and
government that fully supported this research. The City and County of Denver and
Jim Barwick for constructing HVFA concrete elements and providing valuable
time and feedback regarding policy barriers. Bestway Ready-mix and Dan Bentz
for providing testing and empirical experience in barrier assessment. American
Coal Ash Association and Dave Goss for insights and technical advice in the fly
ash industry.


TABLE OF CONTENTS
Figures.....................................................................xiii
Tables........................................................................xv
Chapter
1. Introduction.............................................................1
1.1 What is Sustainability?..................................................1
1.2 Importance of Urban Sustainability and Infrastructure....................3
1.3 Assessment of Sustainable Concrete Materials........................5
2. Evaluating the Strength, Durability and Costs of HPGC....................9
2.1 Intellectual Contribution and Specific Objectives.......................11
2.2 Role of HPGC for Durability in Urban Sustainability.....................12
2.3 Barriers to Incorporating HPGC in Urban Infrastructure..................16
2.4 Background on Fly Ash and Fly Ash Concrete..............................19
2.4.1 Performance Assessment: Case Studies....................................21
2.5 Methodology and Results.................................................22
2.5.1 First Phase: MM Testing.................................................23
2.5.2 Second Phase: Full-Scale Testing.......................................27
2.5.3 Third Phase: Field Implementation of HPGC Structural Elements..........30


2.5.4 Phase 4: Full-Scale Regional Materials for Effect of Material Source on
Compressive Strength.......................................................35
2.5.5 Phase 5: Full-Scale Regional Materials Testing for Durability........42
__Full-Scale Compressive Strength ASTM C 39.........................45
Sodium Sulfate Expansion ASTM C 1012................................46
Rapid Chloride Permeability ASTM C 1202.............................48
Freeze-Thaw ASTM C 666..............................................51
2.6 Testing Conclusions..................................................53
2.7 Economics of HPGC....................................................55
2.7.1 Direct Cost of HPGC and Control Mixes................................56
3. Evaluating HPGC with Environmental Life Cycle Assessment.............58
3.1 Intellectual Contribution and Specific Obj ectives...................59
3.2 Background: Types of LCA.............................................60
3.3 LCA Methodology......................................................63
3.4 LCA of Concrete Infrastructure in Denver, Colorado...................68
3.4.1 LCA Infrastructure Comparison Matrix.................................68
3.4.2 Inventory of Materials Considered for Concrete LCA...................74
Material Manufacturing: Cement......................................74
Material Manufacturing: Recycled Aggregates.........................78
Material Manufacturing: Virgin Aggregates...........................81
Material Manufacturing: Fly Ash.....................................81
Material Manufacturing: LCA of transport energy.....................82
Construction: Ready-Mix Operations and Concrete Placement...........83
End-of-Life: Avoidance of Landfilling for Concrete Debris...........84
End-of-Life: Avoidance of Landfilling From Fly Ash..................86
3.4.3 First LCA: Comparing BAU to Low-level HPGC Scenarios.................88
3.4.4 Second LCA: Comparing BAU to Higher-level HPGC Scenarios.............92


3.4.5 Material Transport Costs..............................................94
3.5 End-of-Life Impacts for Recycled Concrete.............................97
3.5.1 Perceived Risks and Benefits of HPGC.................................97
3.5.2 End-of-Life of Fly Ash................................................98
Benefits of Incorporating Fly Ash...................................100
Cradle-to-Grave: Leachate of Fly Ash Compared to Fly Ash Concrete .... 100
Cradle-to-Cradle: Leachate of Crushed Fly Ash Concrete Compared to OPC
.....................................................................102
4. MFA-LCA-LCC for Resource, Environmental, and Economic Assessment 106
4.1 Intellectual Contribution and Specific Objectives....................109
4.2 Demand and Supply of Major Materials for Concrete Infrastructure.....111
4.2.1 Top-Down National-Level MFA: Cement Demand and Supply................112
4.2.2 Regional-Level MFA: Cement Demand and Supply.........................116
4.2.3 Bottom-Up Local-Level MFA: Cement Demand and Supply..................120
4.2.4 Top-Down National-Level MFA: Aggregate Demand and Supply.............123
4.2.5 Regional-Level MFA: Aggregate Demand and Supply......................125
4.2.6 Bottom-up Local-Level MFA: Aggregate Demand and Supply..............126
4.2.7 Top-Down National-Level MFA: RA Demand and Supply...................130
4.2.8 Regional-Level MFA: Recycled Aggregate Demand and Supply............132
4.2.9 Top-Down National-Level MFA: Fly Ash Demand and Supply..............133
4.2.10 Regional-Level MFA: Fly Ash Demand and Supply......................135
Future Outlook for Fly Ash Supply.....................................137
4.3 Summary of MFA in CCoD
138


5. Integrating MFA/LCA/LCC with Urban Infrastructure Materials Policy... 141
5.1 Materials and Urban GHG Mitigation Policies..........................141
5.2 Concrete in Urban GHG Inventories....................................143
5.2.1 Methodology..........................................................144
5.2.2 Results..............................................................145
5.3 Developing Material Flow Policy for GHG Mitigation...................147
5.3.1 Environmental Initiatives: Efficiency vs. Consumption................149
5.3.2 Proposed Sustainable Material Policies...............................150
5.3.3 Green Concrete.......................................................151
Precedents for Green Concrete.......................................152
Technical Performance of Green Concrete............................153
.Economics of Green Concrete........................................154
Ancillary Benefits/Costs of Green Concrete.........................158
Political Feasibility...............................................159
5.3.4 Construction and Demolition (C&D) Mandate............................159
.. Precedents of C&D Policy..........................................164
Technical Performance of a C&D Mandate.............................169
Economics of a C&D Mandate.........................................170
Political Feasibility of C&D Mandate...............................174
5.5 Current GreenPrint Policy Status.....................................174
6. Conclusions and Recommendations for Further Studies.................176
6.1 Structural Strength and Durability...................................176
6.2 LCA GHG Emissions and Material Flow Analysis of HPGC and OPC.... 178
6.3 End-of-Life Testing of HPGC and BAU..................................179
6.4 Economic Impact of HPGC and BAU......................................181


6.5 Recommendations for Future Studies Regarding Regulations Facing Coal-
Fired Power Plants................................................182
6.2.1 Economic Impact of CAMR and CAIR............................184
6.2.2 Unintended Environmental Impact of CAMR and CAIR............185
6.2.3 Change in Hazardous Classification of Fly Ash...............187
6.2.4 Follow-up Discussion Regarding CAMR and CAIR................188
Appendices
A: DISCUSSION ON LCI..............................................190
B: PRELIMINARY LCA RESULTS FOR FA REINFOCED CONCRETE..............195
C: CRMCA SURVEY...................................................205
References........................................................208


LIST OF FIGURES
FIGURE
1: Integration of Chapters................................................8
2: Compressive Strength Test Results for the 12 Mini-mix Batches.........26
3: Compressive Strength Test Results for the Full-Scale Batches..........29
4: H60 Precast Manhole and Lid (AMCOR)...................................31
5: 60 Percent Fly Ash Concrete Alley Panel (on left, OPC on right).......33
6: H60 Class C/Type III Concrete Double-tee Beam.........................34
7: Compressive Strength Test Results for Slab and Double-tee Beam........35
8: Compressive Strength Test Results ....................................37
9: Compressive Strength Test Results Comparing Cement Sources in OPC with
Virgin Aggregates with Class C Fly Ash HPGC with Recycled Aggregates.40
10: Compressive Strength Results ASTM C 39 [2005]........................45
11: Results of Sulfate Expansion [ASTM C 1012]...........................47
12: Cl202 RCPT Results...................................................50
13: Relative Dynamic Modulus of Elasticity ASTM C 666....................52
14: BEES LCC Analysis of Control and HPGC Mixes..........................56
15: Life Cycle Phases and Material Flow for Concrete in CCoD.............73
16: Percent Reduction in Energy and GHG Emissions from BAU L.............91
17: Contribution from Various Life Cycle Stages to GHG Emissions for BAU
(OPC) and HPGC with 20% Fly Ash and 50% Recycled Aggregate..........94
19: Summary of Energy and Emissions for Materials and Transport..........96
20: Percent of Maximum Allowable Concentration as Evaluated by TCLP.....102
21: Material Flows into the Urban Built Environment.....................108
22: Apparent Use of Cement by Sector and Per Capita 1984-2004...........114
23: Apparent Per Capita Consumption of Cement: 1985-2005................115
24: Population and Housing Density in Urbanized Colorado Counties.......116
25: Projected Apparent Per Capita Cement Consumption....................119
26: Regions with Net Deficits, Balances and Surpluses of Aggregates used in the
United States.......................................................124
27: Aggregate Mine Locations along the South Platte Corridor............128
28: The Temporal Movement of South Platte Corridor Aggregates...........130
29: Usage of Coal-fired Power Plant Fly Ash Wastestream.................135
30: Usage of Coal-fired Power Plant Fly Ash Wastestream.................136
31: MFA for Concrete Flow in CCoD (tonnes/year).........................138
32: Material Flow Impact of HPGC Scenarios..............................140
33: Results of Denver GreenPrint Inventory..............................146
34: GHG Mitigation Cost-Effectiveness on First Cost Basis...............154
35: Economic Performance for Varying Amounts of Fly Ash Substitution....202
xii


36: Impact of Materials in 1 m3 Reinforced Concrete
204
xiii


LIST OF TABLES
TABLE
1: Categories of sustainability...............................................2
2: ASTM C 595 blended cements................................................17
3: Mix proportions and physical properties of mini-mixes.....................25
4: Mix proportions for the full-scale tests..................................28
5: HPGC testing matrix for regional materials................................36
6: Standard deviation of fly ash replacement in concrete Classes B and D.....39
7: Standard deviation of mixes containing 50% recycled aggregate and mixes
containing 100% virgin aggregate..........................................41
8: Mix Components and Properties.............................................43
9: ASTM C 618 for Class C and Class F ashes..................................43
10: LIFE-365 predicted time to first maintenance.............................45
11: Expansion % @ 186-day and difference from control........................48
12: RCPT ratings [ASTM C 1202]...............................................49
13: Summary of 90-day RCIP Testing difference from control.................51
14: Summary of freeze-thaw at 300 Cycles difference from control...........53
15: Direct material costs of one tonne of concrete delivered to CCoD.........57
16: Identification of scenarios in first LCA analysis........................70
17: Identification scenarios in second analysis..............................71
18: LCA models used for concrete flow in CCoD................................72
19: Embodied energy and emissions of cement production.......................75
20: EIOLCA and PC A energy consumption and EIA/DOE emissions.................76
21: Input data into EIO for recycled aggregate production based on processes and
fuel consumption reported by RMCI [2006].................................79
22: Recycled concrete aggregate products, $ per tonne offset.................80
23: EIOLCA inputs for transportation mode costs per tonne-km.................82
24: Summary of EIOLCA inputs and outputs for transportation per tonne........83
25: EIOLCA inputs for 1-tonne of recycled concrete aggregates................85
26: EIOLCA inputs for avoided landfill impact for fly ash....................87
27: Input data for EIOLCA of concrete from cement, fly ash, recycled and virgin
aggregates, and ready-mix batching.......................................88
28: Summary of Life Cycle GHG Emissions from 20% Fly Ash (FA20) and 50%
Recycled Aggregate (RA50)................................................90
29: Identification scenarios in second analysis..............................93
30: Summary of second LCA analysis...........................................93
31: Summary of material transport costs for scenarios........................95
xiv


32: Recycled concrete aggregate products.................................103
33: Categories and beneficial use applications [Wisconsin DNR, 2006].....104
34: NR 538 Results ASTM D 3987 Water Leach Test........................105
35: Concrete MFA for the Denver-Aurora MSA...............................118
36: Projected concrete demand national vs. regional proxy numbers......120
37: 2006 contribution of cement to the Denver-Aurora market..............121
38: Average National C&D Debris Generation from Structures...............132
39: National CCP beneficial uses and masses..............................134
40: Projected environmental and cost benefits of HPGC for CCoD...........157
41: Secondary uses for C&D debris........................................161
42: Hazardous materials in C&D debris....................................162
43: Total disposal of debris at DADS.....................................162
44: Local government C&D ordinances in California........................166
45: States with disposal surcharges......................................168
46: CCoD regional landfill disposal costs for concrete debris 2006.....172
47: CCoD regional recycle yard disposal costs 2006.................... 173
48: Barrier issues and recommended actions for GreenPrint initiatives....175
49: Mercury speciation in landfills, cement manufacturing and coal combustion 187
50: LCA/LCI Databases and Software Considered............................194
51: 2005 Ready-mix Materials and Transport for Concrete in CCOD..........196
52: Manufacturing Life Phase Input for EIO-LCA...........................198
53: BEES Output for C02 Emissions for 1 m3 of Reinforced Concrete.......201


1. Introduction
1.1 What is Sustainability?
Sustainable development was broadly defined and coined by Gro Bruntland in 1987
as development that meets the needs of the present without compromising the
ability of future generations to meet their own needs [World Council for
Sustainable Development, 1987]. However, this definition leaves much to be
interpreted in defining what exactly our needs are; and seems to imply simply
good stewardship of our natural resources without considering other categories of
human needs. The definition of sustainability varies significantly depending on the
location and the economics of the community being described. Whereas developed
nations see the object of an environmental agenda as preservation of the planet for
future generations, the agenda of the developing nations is to preserve resources for
the comfortable survival of the present generation of people. Therefore, Hacket
[2001] gives a broader definition of sustainability that is more inclusive of human
social and cultural institutions ...the prudent use of natural, human, human-made,
social, and cultural capital to foster economic security and vitality, social and
political democracy, and ecological integrity for present and future generations.
1


Although the definition of sustainability is multi-faceted and inherently diverse,
depending on the perspective of the region being considered, there are a few broad
categories of sustainability that are emerging. Thomas and Graedel [2003]
proposed the three categories of: use of materials and energy, land use, and human
development and Ramaswami [2005] has defined infrastructure sustainability in
terms of four criteria: performance, economic sustainability, environmental and
ecosystem, and social-cultural. Definitions of sustainability by various
organizations are shown grouped by broad category on Table 1.
Table 1: Categories of sustainability
Group Social Technology Economic Environment
USEPA1 Built Environs Materials and Toxics Water, Ecology and Agriculture Energy and Environment
Natural Capital2 Built Capital Human Capital Financial Natural Capital
Hn3 Social Environmental Institutional
USIEP4 Social and Cultural Human Health Technical Performance and Safety Adaptability and Resiliency Economic Viability Environmental Ecosystems Resource Efficiency
'United States Environmental Protection Agency (USEPA):
http://www.epa.gov/nrmrl/std/seb/research/ss/abstsustain.htm
2Natural Capital, Aspen, Colorado: http://www.rmi.org/sitepages/pid564.php
United Nations Agenda 21: http://www.un.org/esa/susldev/documents/agenda21/english/agenda21toc.htm
JUrban Sustainable Infrastructure Engineering Project (USIEP), University of Colorado at Denver, Anu
Ramaswami Director [2005]
The dictionary definition of sustain (ss-st^n1) is to keep in existence, i.e. to
maintain. Sustainability therefore has an associated time element that requires a
sustainable system to be perpetual and to account for maintenance and re-
2


evaluation of function to be successful. As the material and energy demands of
future generations are unknown, the process of designing for sustainability is an
active and ongoing condition of needs assessment and problem solving [Tainter,
2006],
1.2 Importance of Urban Sustainability and Infrastructure
In 2003, for the first time in human history, more than 50% of the worlds
population was residing in urban areas versus rural settlements [UN, 2003]. The
United States Census Bureau classifies "urban" as all territory, population, and
housing units located within settlements of more than 10,000 people in a
geographic region. In developed nations such as the United States and Europe,
more than 75% of people reside in cities, with certain urban areas such as the
Colorado Front Range (CFR) region and other areas of the American West (e.g.,
Phoenix) where rapid population growth in the Greater Phoenix area has increased
by 39% (3.73% average per year) since 1995, compared to the United States
average rate of only 12% over the same period [GPEC, 2006]. Populations in
several cities in the developing world, e.g., Dhaka in Bangladesh, have increased at
unprecedented rates of more than 5% per year, placing huge demands on energy
and material resources [UN, 2003]. In the United States, the built environment
3


accounts for approximately one-third of all energy, water, and materials
consumption [USGBC, 2002],
Given these national and global trends, intelligent design and materials selection
for providing and maintaining urban infrastructure becomes critical for economic
and resource sustainability. Urban infrastructure refers to the engineered systems
that provide services pertaining to water, wastewater, energy and transport (of
human, goods and information) within an urban area [Ramaswami, 2005]. The
focus of this dissertation is on sustainable material choices in the construction of
urban infrastructure, with particular focus on the components of concrete.
Concrete is the dominate material used in construction, both in terms of gross mass
of material used as well as the energy consumed and the pollution released from
cement manufacture and installation. At the turn of the 21st century, worldwide,
cement production accounted for more than 1.6 billion tons of CO 2 released as
emissions, approximately 7% of total CO 2 emissions from all human activities
[Mehta, 2001]. Typically, CO2 emissions mirror energy consumption; however,
the production of cement involves the release of additional CO2 during
pyroprocessing, or the calcination process (conversion of calcium carbonate to
calcium oxide), which results in approximately twice the CO2 that would be
produced from energy consumption alone [CEMBUREAU, 1998]. Thus, material
4


use in urban areas, particularly concrete use due primarily to the cement content,
has far reaching impacts on environmental aspects of sustainable urban
infrastructure development.
For purposes of this dissertation, "sustainable urban infrastructure requires the
periodic evaluation of the physical condition and required function of an
infrastructure element within the community of interest. Sustainable urban
infrastructure also requires the integration of database technology with current
material science to identify synergistic wastestream materials that can provide
resiliency and durability to infrastructure while reducing the energy and
environmental impact associated with production and scarcity of virgin resources
required for perpetual maintenance and upgrading.
1.3 Assessment of Sustainable Concrete Materials
In recent years much work has been conducted on development of more
environmentally-friendly concrete materials by incorporation of materials such as
fly ash, ground granulated blast furnace slag, and foundry sand. A recognized
leader in the development of high volume fly ash concrete (HVFAC) since the
early 1980s has been the Canadian Centre for Mineral and Energy Technology
(CANMET) Materials Technology Laboratory (MTL). CANMET was also a
5


leader in recognizing the environmental benefits of fly ash concrete which led to a
partnership with the Confederation of Indian Industry (CII) to significantly increase
the use of fly ash in concrete in India to meet increasing demands for concrete
without increasing CO2 emissions and depleting natural resources.
The United States Federal Highway Administration (FHWA) has recognized the
studies by the U.S. Army Corps of Engineers (USACE), Portland Cement
Association (PCA), and the Tennessee Valley Authority regarding not only the
economic and ecological benefits that the use of fly ash in concrete provides, but
also the improved workability, lower heat evolution and permeability, and the
effect of inhibiting alkali-aggregate reaction (AAR), and enhances sulfate
resistance. In fact, the EPA guideline on the substitution of fly ash requires State
highway agencies to document the reasons for not allowing the substitution of fly
ash for cement.
However, methodologies and data elements required for a comprehensive
assessment of sustainable concrete use in urban areas are currently unknown, i.e.
how should a city integrate material science, environmental impact assessment,
resource data and policy in order to develop sustainable infrastructure? Applying
the criteria for infrastructure sustainability assessment shown in Table 1-1, the
objectives achieved in this dissertation answered the following:
6


Structural performance: Can concrete with incorporated wastestream
materials meet structural and durability requirements?
Environmental Assessment: Can the environmental impacts of sustainable
concrete be quantified for the total life-cycle reduction of greenhouse gas
(GHG) emissions ?
Ecosystem Assessment: Can sustainable concrete address issues or urban
material scarcity ?
Economics: Can an environment-friendly and resource-efficient concrete be
shown to have lower direct and indirect costs?
Social/Cultural: How can cities use the above information to develop
sustainable concrete policies that will be accepted by owner, engineer, and
contractor?
In the next four chapters, background information, objectives, preliminary results
and specific methodologies are presented for each of the study areas listed above.
The integration of the above elements is shown in Figure 1.
7


Figure 1: Integration of Chapters
To-date no study has quantified and integrated technological performance,
resource and environmental benefits, economic costs on a regional basis and
incorporated these into city-scale sustainable infrastructure policies. In this
dissertation, such an integrated quantitative approach is developed for specific
consideration of fly ash and recycled aggregate concrete implemented in the City
and County of Denver (CCoD) urban concrete infrastructure.
8


2. Evaluating the Strength, Durability and Costs of HPGC
This chapter discusses the technical performance characteristics and economics of
incorporating wastestream materials, such as recycled aggregates and fly ash, as
replacements for virgin aggregates and cement in traditional concrete mixes.
Incorporating wastestream materials into concrete infrastructure provides
quantifiable environmental life-cycle impact and direct cost reductions when
compared with ordinary Portland concrete (OPC or business-as-usual in this
dissertation). However, widespread usage of wastestream materials in new urban
concrete infrastructure (stock) requires that the mixes meet or exceed structural and
durability performance characteristics without sacrificing workability or
economics. The primary environmental savings associated with the beneficial
reuse of wastestream materials comes from the avoided impacts of cement
manufacturing, disposal of rubble in landfills, and reduced transportation distance.
The economic benefits of utilizing fly ash and recycled aggregates are directly
related to these environmental savings; either the material is transported to a
landfill and disposed of at a cost or sold to the market for an economic gain.
9


However, the economics of recycled aggregates are not found in direct material
costs, but in the reduced transportation costs due to the lesser distance from source
to placement. A cost that will continue to increase the profitability of recycled
aggregates as the distance from virgin material sources to urban centers continues
to increase.
In addition to direct material costs and environmental impact reduction, if the
concrete containing the wastestream materials provides a more durable
infrastructure, i.e. longer service life or less operation and maintenance, the
environmental and economic impacts increase proportionally. For purposes of this
dissertation, high performance green concrete (HPGC) is concrete that incorporates
recycled materials in order to create an equal or superior concrete, that:
- lowers the environmental impact of concrete production
- addresses material scarcity issues
- addresses workability issues
- performs equal or better than structural requirements, and
- provides direct material cost savings.
This chapter discusses the economic costs and the technical considerations of
incorporating recycled coarse aggregate for virgin sources and fly ash as a partial
replacement for the cement fraction of concrete to develop HPGC.
10


2.1 Intellectual Contribution and Specific Objectives
This chapter quantifies the technical characteristics of HPGC, considering a wide-
range of material replacement, i.e. up to 70% fly ash replacement and 50% recycled
aggregate. The specific objectives achieved in this chapter were the following:
Literature review of durability and compressive testing comparing fly ash
concrete with OPC.
Evaluate the barriers, perceived risks and benefits for incorporating fly ash
and recycled aggregates into urban infrastructure.
Evaluate mixes in a range of fly ash and recycled aggregate replacement
that can be provided by industry to the Colorado Front Range construction
community that will likely be accepted by engineers and decision-makers.
Evaluate the upper range of fly ash replacement that can be provided by
industry and that will likely be accepted by engineers and decision-makers.
Field Pilot Tests: Construct urban infrastructure elements to evaluate in-situ
performance, ready-mix issues, and contractor workability issues.
Lab Tests: Develop a wide range of HPGC mixes and evaluate promising
mixes to carry forward to full-scale testing. This includes structural and
durability laboratory testing of full-scale mixes.
11


Full scale structural and durability tests: Complete primary compression
strength and durability testing that best represents the physical environment
conditions of the Colorado Front Range. The durability tests included;
freeze/thaw [ASTM C666], Rapid Chloride Ion Penetration [ASTM
C1202], and sodium sulfate testing [ASTM C1012].
2.2 Role of HPGC for Durability in Urban Sustainability
Both the environmental impact and the economic cost of urban concrete
infrastructure could be further reduced by utilizing a more durable concrete mix,
thus extending the service life and requiring less replacement, rehabilitation, and
maintenance. To date, durability and high performance concrete are not necessarily
synonymous. The American Concrete Institute (ACI) defined High Performance
Concrete (HPC) as a specially engineered concrete where one or more specific
structural characteristics have been enhanced such as compressive strength.
Durability has also been defined as the ability of concrete to perform satisfactorily
with minimal maintenance over the anticipated service life of the structure [Hooton
et al, 2006], However, these definitions do not specify that durability results in an
extended service life.
12


Mehta [2003] criticized the ACI definition of HPC in that the consideration of
concrete durability is not mandatory. Aitcin [2003] provides a technical
description of HPC with regards to durability as a low waterxementitious (w/cm)
ratio concrete with an optimized aggregate-to-binder ratio to control its
dimensional stability (i.e., drying shrinkage), which receives adequate water-curing
to control autogenous shrinkage. Mehta and Aitcin [1990] incorporated durability
into HPC requirements by stating that the term HPC should be applied to concrete
mixtures possessing the following three characteristics: high workability, high
strength, and high durability. However, these definitions do not address the direct
initial cost of the mix, or the environmental impacts of a concrete mix.
Although many experts declare that fly ash concrete is more durable, there is little
research on directly estimating a predicted increased service life, or if the durability
is applicable to both types of common fly ash Class C and Class F. Mehta
(2003) states In conclusion, a combination of particle packing effect, low water
content, and pozzolanic reaction accounts for the eventual disappearance of the
interfacial transition zone in HVFA [high volume fly ash] concrete, and thus
enables the development of a highly crack-resistant and durable product.
Similarly, Horvath (2003) goes on to say While fly ash produced better, more
durable and less permeable concrete when it reaches its full strength, fly ash
content slows down initial concrete curing.
13


The United States Federal Highway Administration promotes the use of fly ash
concrete as ultimately more durable and the listed benefits included the following
[USFHWA, 2007]:
- Improved Workability: The spherical shaped particles of fly ash act as
miniature ball bearings within the concrete mix, thus providing a lubricant
effect. This same effect also improves concrete pumpability by reducing
frictional losses during the pumping process and flat work finishability.
- Decreased water demand: The replacement of cement by fly ash reduces
the water demand for a given slump. When fly ash is used at about 20
percent of the total cementitious materials, water demand is reduced by
approximately 10 percent. Higher fly ash contents will yield higher water
reductions. The decreased water demand has little or no effect on drying
shrinkage/cracking.
- Reduced heat of hydration: Replacing cement with the same amount of
fly ash (one-to-one) can reduce the heat of hydration of concrete. This
reduction in the heat of hydration does not sacrifice long-term strength gain
or durability. The reduced heat of hydration lessens heat rise problems in
mass concrete placements.
14


Increased ultimate strength: The additional binder produced by the fly
ash reaction with available lime allows fly ash concrete to continue to gain
strength over time. Mixtures designed to produce equivalent strength at
early ages (less than 90 days) will ultimately exceed the strength of
complete cement mixes.
Reduced permeability: The decrease in water content combined with the
production of additional cementitious compounds reduces the pore
interconnectivity of concrete, thus decreasing permeability. The reduced
permeability results in improved long-term durability and resistance to
various forms of deterioration.
Improved durability: The decrease in free lime and the resulting increase
in cementitious compounds, combined with the reduction in permeability,
enhance concrete durability. This affords several benefits:
o Improved resistance to Alkali silica reaction (ASR). Fly ash reacts
with available alkali in the concrete, which makes them less
available to react with certain silica minerals contained in the
aggregates.
- Improved resistance to sulfate attack. Fly ash induces three
phenomena that improve sulfate resistance:
Fly ash consumes the free lime making it unavailable to react
with sulfate
15


The reduced permeability prevents sulfate penetration into
the concrete
Replacement of cement reduces the amount of reactive
aluminates available
- Improved resistance to corrosion. The reduction in permeability
increases the resistance to corrosion.
If fly ash can improve the durability of concrete infrastructure and, thereby increase
the functional service life, the use of HPGC can have a linearly proportional impact
on material scarcity issues, environmental impact, and life-cycle costs. Therefore,
this dissertation provides strength and durability testing of regional Colorado Front
Range construction materials to evaluate the benefits of using HPGC, if any, and
identifies the issues that limit current widespread usage due to real and perceived
barriers.
2.3 Barriers to Incorporating HPGC in Urban Infrastructure
Although the replacement of Portland cement with wastestream materials, fly ash
being common, is practiced and accepted at low replacement levels, the majority of
engineers, architects, and contractors are not comfortable with specifying higher
replacement of Portland with fly ash, e.g. 20% or greater, without incentive or
16


mandate. In addition, there may be a perception that concrete construction codes
are prescriptive in the sense that there is a maximum permissible limit of fly ash
that can be specified in a concrete mix. The confusion arises from the governing
standards. Even though a blended cement standard exists, as defined in ASTM C
595, as a mixture of Portland cement and blast furnace slag (BFS) or a "mixture of
Portland cement and a pozzolan (most commonly fly ash)," many engineers and
architects do not refer or acknowledge this standard. The types of blended cements
and fly ash contents by weight, identified in ASTM C 595, are shown in Table 2.
Table 2: ASTM C 595 blended cements
Type Blended Ingredients
IP 15-40% by weight of pozzolan (fly ash)
I(PM) 0-15% by weight of pozzolan (fly ash)
P 15-40% by weight of pozzolan (fly ash)
While ASTM C 595 limits the proportion of pozzolan in cement to 40 percent by
mass, there is a performance-based cement standard ASTM C 1157 [ASTM, 2003]
that does not limit the type and the content of components in the blended cement.
The International Building Code [IBC, 2003] generally defers to ASTM C 618
[2005] in regards to fly ash content. It states that the optimum amount of fly ash or
natural pozzolan for any specific project is determined by the required properties of
the concrete and other constituents of the concrete and is to be established by
17


testing. A notable exception to performance based standards is the International
Building Code (IBC) Table R301.2(6) that restricts fly ash content to 25%
replacement for elements exposed to de-icing salts [IBC, 2003]. This restriction is
currently being re-evaluated by the IBC as it is known that fly ash decreases
permeability of concrete mixes and hence increases freeze thaw resistance.
Recently, the advantages of incorporating higher percentages of fly ash to create a
less permeable concrete mix has been recognized as beneficial for surfaces exposed
to de-icing salts, such as pavements. The Colorado Department of Transportation
(CDOT) now mandates the incorporation of a minimum of 10 percent fly ash into
the pavement concrete (Class P) as it is considered to improve durability
performance [CDOT, 2006].
Even though incorporating fly ash is assumed to improve the durability of concrete,
there is little direct evidence to quantify the increase expected in the service life of
concrete infrastructure. Also, there is little mention if one class of fly ash
outperforms the other and which, if any, should be considered more durable.
When alternative construction materials are considered for infrastructure elements,
for example OPC versus HPGC concrete, metrics are needed to ensure that
performance of the proposed material is equal or superior to conventional OPC and
meet technical specifications for the infrastructure application (e.g., bridges versus
pavements need different technical performance specifications). This chapter
18


discusses the five phases conducted as part of this dissertation to identify HPGC
mixes that would meet technical specifications to carry forward for environmental
and resource flow evaluation.
No study has specifically tested regional materials to identify the technical
performance and the environmental and economic impacts of replacing virgin
materials with the combination of fly ash and recycled aggregates for the purpose
of developing sustainable urban materials policy.
2.4 Background on Fly Ash and Fly Ash Concrete
Fly ash is a by-product of heat generation from thermal coal-fired power plants.
Fly ash [ASTM C 618] can replace Portland cement on a one-to-one mass basis and
can provide equal or superior performance up to certain replacement limits. The
chemistry of fly ash reacts with any free lime left after hydration to form calcium
silicate hydrate (CSH), which is similar to the tricalcium and dicalcium silicates
formed in OPC curing. The silica in fly ash combines with the calcium hydroxide
(CaOH, or free lime) crystals to form more CSH paste, thereby reducing micro-
cracking and creating less permeable concrete. At early ages, the fly ash in
concrete does not provide a chemical strength matrix, at later ages the fly ash does
19


form additional CSH which results in increased strength. It is the additional CSH
at later ages in FA concrete that provides a greater strength gain.
The two main types of fly ash used for concrete additives in the United States are
Class F and Class C. By definition in ASTM C 618 [2005] class F fly ash comes
from bituminous coal and class C comes from subbituminous coal. In practice
however, Class F comes from bituminous, subbituminous, and lignite coals while
class C comes from subbituminous coal [ACAA, personal communication, 2006],
Therefore, the ranking of coal by thermal value does not disclose the chemistry of
ash within these two classes. The pozzolanic properties of a good-quality fly ash
are governed primarily by its mineralogy, low carbon content, high glass content,
and 75% or more particles finer than 45 pm sieve [Malhotra and Mehta, 2002]
(ASTM C 618 05 requires a minimum of 66% passing the 45 pm sieve).
General acceptance of incorporating wastestream materials into concrete
infrastructure requires knowledge that the final mix will produce concrete with
structural and durability characteristics that meets or exceeds OPC in addition to
being environmentally safe. Despite the research cited above stating the increased
durability, the desire to include fly ash, or any waste stream product, is limited by
the perception of prescriptive limits.
20


2.4.1 Performance Assessment: Case Studies
Sustainable urban concrete infrastructure must not only provide environmental and
economic benefits, but also meet all required structural and durability performance
criteria. This section presents two recent case studies using mixes that would
classify as HPGC:
Research completed at Montana State University demonstrated that
structural grade concrete mixes can be made with even 100 percent Class C
fly ash using a 40% paste and 60% aggregate ratio and a retarder (borax) to
prevent flash set [Cross et al, 2005]. The concrete was required to have a
slump greater than 100 mm (4 in.), a setting time of 1 to 2 hours, and an 18-
hour unconfined compressive strength of at least 19 MPa (2,800 psi). The
concrete reportedly had good workability, with an average slump of 12.7
cm (5 in.) and an average set time of 2 hours. The average 18-hour and 7-
day compressive strengths were 21 and 31 MPa respectively (3,000 and
4,500 psi). [Cross et al, 2005].
The effects of the calcium oxide (CaO) and the fineness of Class F fly ash
within the range classified by ASTM C 618 [2005] were evaluated by
Bououbaa and Fournier [2002] for performance by replacing 55-60% of the
21


Portland cement on a one-to-one mass basis. The slump of the fly ash
concrete ranged from 80 to 120 mm (3.1 to 4.7 inches) and the water
cement ratio ranged from 0.43 to 0.53. The entrapped air ranged from 1.2%
to 3%. The Point Tupper Class F ash contained 4.2% CaO and a Blaine
fineness of the fly ash of 2,270 cm2/g. The Sundance Class F ash
contained 13.4% CaO and a Blaine fineness of 3,060 cm2/g. The fly ash
developed compressive strengths ranging from 34 to 62 MPa (4,931 and
8,992 psi) at 56 days. The Sundance fly ash concrete developed higher
compressive strengths than those of the Point-Tupper fly ash concrete
mainly due to the high fineness and CaO content of Sundance fly ash
[Bouzoubaa and Fournier, 2002].
2.5 Methodology and Results
In order to evaluate the viability of specifying HPGC for urban infrastructure, five
phases of structural performance testing were completed as part of this dissertation.
Phase 1: The initial testing consisted of mini-mixes (MM) that produced a
wide range of fly ash (FA) concrete mixes for compressive strength and
sulfate resistance testing.
22


Phase 2: The second phase specifically tested full-scale HPGC mixes that
would provide the highest environmental benefits to concrete urban
infrastructure.
Phase 3: The third phase constructed infrastructure elements in the CCoD
using the promising mixes identified in Phase 2 testing in order to have
empirical examples and understand workability issues.
Phase 4: The fourth phase tested full-scale mixes that included a variety of
cement sources with fly ash and recycled aggregate replacement to identify
if the cement source had a significant impact on strength.
Phase 5: The fifth, and final phase, tested the effect on durability by
including a higher range of fly ash replacement, but in percentages likely to
be accepted by engineers/owners. This phase also incorporated a higher
percentage of recycled aggregate at approximately 50% of total (100% of
coarse fraction).
2.5.1 First Phase: MM Testing
The MM test substitutes the ASTM C-128 [2004] sand moisture cone for the
ASTM C-143 [2005] concrete slump cone as a measure of workability and the
mixes are in the same proportions as a full-scale mix less the coarse aggregates.
The process was selected for quickly evaluating the effect of variables on concrete
23


systems prior to full-scale testing. Twelve MM batches were tested to encompass a
range of fly ash substitution for OPC, and water reducing admixtures that would
produce the required early and long-term strengths for potential use as pre-cast and
structural elements. The mixes were divided into three ranges of total cementitious
content (low-L, medium-M, and high-H). The total cementitious material (TCM)
for the three sets was 327-kg/m3 (550 pounds per cubic yard) for the low (L), 369-
kg/m3 (620 pounds per cubic yard) for the medium (M), and 410-kg/m3 (690
pounds per cubic yard) for the high (H). Each range of TCM content was further
divided into four total fly ash replacement percentages of 40, 50, 60, and 70 (e.g.,
L70 is a low TCM mix with 70 percent fly ash replacement). The fly ash used in
the mix was Class F obtained from the Coal Creek power plant in North Dakota
and transported to Colorado by rail. The fly ash particle diameters were 29.09
percent finer than 10 pm and 67 percent finer than 45 pm (per ASTM C 618)
[Headwaters, 2005]. In addition, Glenium 3020 HES (now known as Euclid), a
water reducing agent (WRA) was added to the mixes. The proportions used in the
12 MM tests are shown in Table 3.
24


Table 3: Mix proportions and physical properties of mini-mixes
MATERIAL H70 H60 H50 H40 M70 M60 M50 M40 L70 L60 L50 L40
kg/m3 kg/m' kg/m3 kg/m' kg/m' kg/mJ kg/mJ kg/m3 kg/m3 kg/m3 kg/m3 kg/m3
Cement 122.8 163.7 204.7 245.6 110.3 148.3 183.9 220.7 97.9 130.5 163.1 195.8
Fly Ash 286.5 245.6 204.7 163.7 258.1 221.9 183.9 147.1 228.4 195.8 163.1 130.5
WRA 12.3 16.4 20.8 24.6 11.1 14.8 18.3 22.1 9.8 13.1 16.2 19.4
Fine
Aggregate 777.0 769.8 765.3 767.4 825.7 821.4 831.4 782.8 854.5 862.9 869.5 868.8
Coarse
Aggregate 1071 1094 1083 1082 1070 1074 1063 1102 1072 1072 1061 1059
Water 122.8 115.8 128.6 132.5 118.9 117.8 121.5 124.7 124.6 124.6 122.6 123.6
Air
Content, % 0.6 0.7 0.6 0.6 0.8 1.2 1.3 1.2 0.6 0.6 1.4 1.7
w:c ratio 0.30 0.28 0.31 0.32 0.32 0.32 0.33 0.33 0.38 0.38 3.80 0.38
Note: The value represents an equivalent quantity for a full-scale mix. Coarse aggregate not used in
mini-mix tests. Computed air content based on gravimetric analysis.
Measuring compressive strength using the MM procedure is normally obtained by
50.8-mm by 101.6-mm (2-in by 4-in) cylinders. However, due to the number of
samples and because the MM trials were to be a precursor to full-mix design
strength and durability trials, smaller 50.8-mm (2-inch) cubes were tested for
compressive strength. It was anticipated that the MM strength results would be
approximately 20 percent to 30 percent higher than full-scale tests that include the
coarse aggregate fraction and are broken in larger cylinders (101.6-mm by 203.2-
mm/ 4-inch by 8-inch) due to reduced heterogeneity of the mixes.
The main criteria for selecting which of the MM mixes would be carried forward
for full-scale testing were those with the highest percentage of Portland cement
25


replacement that had little to no reduced workability issues, had 1-day compressive
strengths exceeding 10.35 MPa (1500 psi) for pre-cast work, and 28-day strengths
of 27.6 MPa (4,000 psi). The compressive strength results for the 12 mixes at 1, 3,
7, 28, and 56-day breaks are shown in Figure 2.
Figure 2: Compressive Strength Test Results for the 12 Mini-mix Batches
The performance of these mixes at early-age strength showed promising results.
All of the tests except L70 met the required structural 28-day strength of 27.6 MPa
(4,000 psi). However, L70, M70, and L60 did not meet the 1-day break strength,
required by local precast manufacturers, of 10.35 MPa (1,500 psi). Much of the
unexpected very high strengths for the passing tests were likely the result of low
26


water to cementitious ratio (wm/c) ratios, the use of smaller cubes, and the lack of
non-homogeneity usually found in larger aggregate samples.
2.5.2 Second Phase: Full-Scale Testing
The early-age compressive strength and the high volume of fly ash content led to
the selection of four mixes for full scale testing using 101.6-mm by 203.2-mm (4-
inch by 8-inch) cylinders. L50 was chosen due to the 1-day compressive strength
was 10.00 MPa (1,450 psi) and 28-day strength of 43.61 MPa (6,325 psi). M50 of
selected due to a 1-day compressive strength of 12.41 MPa (1,800 psi), and a 28-
day compressive strength was 52.40 MPa (7,600 psi). H60 mix had a 1-day
compressive strength of 12.24 MPa (1,775 psi), and a 28-day compressive strength
of 55.85 MPa (8,100 psi). The H70 mix had 1-day strength of 6.20 MPa (900 psi),
and a 28-day compressive strength of 39.99 MPa (5,800 psi). In addition to the
L50, M50, H60 and H70 mixes, three OPC mixes (0% fly ash replacement) were
included as controls for comparison purposes (L0, M0, and HO). The tests run on
all samples included; compressive strength ASTM C 39 [2005], slump ASTM C
143 [2005], air content ASTM C 231 [2004], and temperature ASTM C 1064
[2005]. All samples were compared on the basis of a 12.7 cm (5 inch) slump. In
addition, two durability tests, freeze/thaw ASTM C666 [2003] and sulfate
27


resistance ASTM Cl012 [2004] were used to evaluate M50, H60, and H70. The
proportions used in the full-scale tests are shown in Table 4.
Table 4: Mix proportions for the full-scale tests
Material H70 H60 HO M50 M0 L50 L0
kg/mJ kg/mJ kg/m' kg/m3 kg/m kg/mJ kg/m''
Cement 123.0 164.0 409.0 184.0 368.0 163.0 336.0
Class F Fly Ash 287.0 246.0 0.0 184.0 0.0 163.0 0.0
WRA 0.6 0.79 1.96 0.88 1.76 0.79 1.56
Fine Aggregate 767.0 778.0 663.0 820.0 697.0 857.0 755.0
Course Aggregate 1068.0 1068.0 1103.0 1068.0 1103.0 1068.0 1103.0
Water 126.0 128.0 143.0 129.0 146.0 139.0 135.0
Air Content,% 6.1 6.1 5.6 6.5 7.5 1.6 7.5
W/cm ratio 0.31 0.31 0.35 0.35 0.4 0.41 0.4
The mix consistency for slump was maintained between 10 cm to 15 cm (four -
inch to six inch) and the mix temperature was maintained between 15.6C to
26.7C (60F to 80F). The air content was within a reasonable range of 6.5
percent, plus or minus one percent. The H60 and H70 mixes produced the lowest
w/cm values due to the high replacement percentage of Portland cement. The
compressive strength test results for the 7 full-scales mixes at 1,3, 7, 28, and 56-
day breaks are shown in Figure 3.
28


o H70
H60
A HO
0 M50
. ... MO
- L30
LO
Figure 3: Compressive Strength Test Results for the Full-Scale Batches
The test results indicate significant differences between the MM compressive
strength results and the full-scale mix compressive strength results. The L50 mix
was the only one not to include air entrainment, for comparison purposes, which
may explain the relatively higher compressive strength when compared to the MO
mix with a similar w/cm. H60 performed slightly better than the M50 mix likely
due to the higher cementitious content and the lower w/cm and the 28-day and 56-
day compressive strengths were acceptable for all structural and non-structural
concrete applications. However, the one day strengths did not meet the stated
criteria of 10.0 MPa (1,450 psi) for precast work, but the H60 mix performed well
29


on the three day break and was deemed a good candidate mix for further evaluation
in real world applications.
Freeze-thaw and sulfate expansion durability tests were completed on M50, H60,
H70 and MO (control). For the freeze-thaw testing ASTM C-666 [2003], all
samples showed no sign of visible deterioration after over 300 cycles of freezing
and thawing. The sulfate expansion ASTM C 1012 [2004] test evaluates the
expansion of mortar bars immersed in a sulfate solution. The mortar bars were
cured until they reached a compressive strength of 20.0 1.0 MPa (3,000 150
psi), as measured before the bars are immersed in sodium sulfate. The curing times
ranged from one day for the control to nearly four weeks for the H70 mix. After
456 days (initial reading was taken October 12, 2004), the fly ash mixes generally
out-performed the control mix with the FA mixes showing essentially no expansion
and the control mix showing the highest expansion at 0.041%. These results are in
line with reported lower permeability for FA concrete.
2.5.3 Third Phase: Field Implementation of HPGC Structural Elements
The H60 mix provided excellent strength and durability results and the highest
reduction in direct material costs and environmental impact. Therefore the H60
30


design mix was selected for three field applications to see how readily industry
would accept fly ash concrete in the field.
AMCOR Precast Manhole: As part of this study, AMCOR Precast, Inc. in
Littleton, Colorado, produced a 1.83 m (72 inch height and diameter) precast
manhole and base section with a 0.255 m (10 inch) thick lid with an access hole
using the H60 mix. The final product is shown in Figure 4.
!
1 am: ur
Figure 4: H60 Precast Manhole and Lid (AMCOR)
31


The forms were stripped at one-day without steam curing and the surface texture
and appearance were considered to be good by AMCOR. The manhole included
four pipe penetrations, including a 1.22 m (48 inch) hole, and two 0.61 m (24 inch)
holes for storm sewer piping. The manhole was designed for AASHTO HS-20
traffic loading and was to be installed at a development project in Fredrick,
Colorado in the winter of 2006. However, the project was never implemented due
to contractor/owner negotiations and the manhole was never installed.
City and County of Denver Cast-in-Place Alley-Slab: The CCoD Streets
Department volunteered to use the H60 mix for an alley panel (placed on
November 9, 2004 and located between Fourth and Fifth Street, and Steel and
Adams Streets) on the condition that 28-day compressive strength be 17.24 MPa
(2,500 psi). For comparison, typical high-early cement mixes were placed next to
the H60 panel, as shown on Figure 5. These projects were significant in that the
H60 was mixed by a local ready-mix concrete batch plant and delivered by
conventional means. Prior to placing the panel, the contractor unilaterally decided
to add a significant amount of super-plasticizer to the mix to increase the slump to
approximately 18 cm (7 inches). The strengths for the alley panel were
independently tested by the CCoD inspectors and cylinders were taken at the time
of placement. Despite the high slump, the 3-day compressive strength was 21.37
MPa (3,100 psi), adequate to open the alley to traffic.
32



T7 r l./V-cV .
60% Fly Ash ; > V \'\ 0% Fly Ash L n, i,,,,,,, i
rrrrrwp^7.
:-'f. ;i'
' *1; r- i- ss *,
. ) ; '/-w -?c >

, VIf'*'
f, ;
v;,i ' > v
'1
, 'J>
v
*'v>
:' t


, s\ ; ^M.vi j !
' ' '...jjfcj*
Figure 5: 60 Percent Fly Ash Concrete Alley Panel (on left, OPC on right)
The H60 concrete required approximately 3 hours from placement to broom
finishing, compared to a one hour set for the high-early mix. There was not a
discernible color difference between the two mixes and the ready-mix contractor
commented that although the set time was longer than typical, he indicated that it
would not be a problem when placing large amounts of concrete due to the time on
site. Other than the time of initial set, he noted that the HPGC concrete was easier
to float off than the high-early strength mix and that he would have no problems
using the mix again.
33


Rocky Mountain Pre-stress T-Beam: The Rocky Mountain Pre-stress Plant
produced a prestressed structural double-tee girder and slab using the H60 mix.
For comparative purposes, the mix was modified to substitute Class C fly ash for
Class F and Type III cement (high-early) for Type I/II cement. The girder is shown
in Figure 6.
Figure 6: H60 Class C/Type III Concrete Double-tee Beam
The mix produced very satisfactory compressive strengths, particularly at the day
one breaks. The compressive strength test results for the H60 (Type C fly ash,
34


Type III cement) mix for the slab and double-tee beam were conducted by Rocky
Mountain Pre-stress at 1,7, and 28 breaks are shown in Figure 7. The double tee
girder was load tested following ACI 318-20 Strength Evaluation of Existing
Structures [2002] and performed well.
-T-Beam
-Slab
Figure 7: Compressive Strength Test Results for Slab and Double-tee Beam Utilizing 60%
Class C and Type III Cement [Source: Rocky Mountain Pre-stress]
2.5.4 Phase 4: Full-Scale Regional Materials for Effect of Material Source on
Compressive Strength
Because testing results for concrete mixes are as influenced by the variability of the
material sources as the percentages of the components used in the mixes; the fourth
phase of testing included commonly used regional materials for fly ash and
recycled aggregate and cement supplied in the Colorado Front Range. In addition,
the range of fly ash replacement for cement was evaluated at a replacement range
35


that can be met by the current industry capacity and that will likely be accepted by
engineers and decision-makers. This was essential for developing cost and
environmental impact metrics for HPGC in Chapters 3 and 4. In order to evaluate
the impact of various regional cement and fly ash sources, a preliminary evaluation
of compressive strength tests ASTM C-39 [2005] was evaluated. Table 5 was
developed to provide a matrix of mix properties and compressive strength tests for
the range of proposed HPGC mixes.
Table 5: HPGC testing matrix for regional materials
JD/s** mot*) COBCfSt* Cfsss Csmemt Tm* Tins/ Csmssffc/trms. Ms Mb P/cmsrtMs CcmmtessJpi Strsmstb. Mbs
Temoerarure.F Ai Entrainment, v. SIwnD.cm Dan of Break
3 7 14 28 56
CB30C-1 565 47 6.8 12.7 21.9 23.9 26.9 33.6
CB30C-2 565 70 6 2 3.89 20.3 26.6 32.4 365
CB40C-1 565 62 5.5 8.89 19.8 24.7 29.3 33.3
CB40C-2 Cemex 565 70 6.5 9.525 15.6 204 29.5 33.5
CB30F-1 565 57 4 1143 27.2 32.1 36.8 42.4
CB30F-2 565 71 4.8 8.89 202 24.9 33.0 37.2
CB40F-1 565 60 4.5 1016 214 271 31.0 370
CB40F-2 565 71 4.5 9.525 173 21.4 30.4 35.3
HB30C-1 565 64 6 3.255 211 268 33.2 37.0
FB40C-1 565 64 65 8.89 16.5 216 27.7 31.8
HB30F-1 565 64 46 8.89 21.3 25.8 35.6 42.0
HB40F-1 565 65 45 10.16 184 22.3 31.1 38.7
NB30C-1 565 75 5.4 635 19.0 254 32.7 34.2
NB40C-1 Mcxrrfar 565 73 57 10.16 13.7 18.7 27.8 30.1
NB30F-1 565 70 4.3 8.89 198 24.4 33.2 39.4
NB40F-1 565 74 4.3 10.16 21.1 301 35.1
CD30C-1 615 46 6 2 1016 155 26.3 30.4 316
CD40C-1 615 50 6.5 <3.97 12.1 21.1 25.9 27.4
CD40C-2 615 72 6.3 10.795 19.1 24.6 31.8 35.7
CD30F-1 men 615 52 4 8.89 t9.1 29.7 35.1 38.3
CD40F-1 615 54 42 n.16 15.7 263 31.6 34.5
CD40F-2 615 70 5 2 10.16 20.8 26.1 35.8 41.6
HD30C-1 615 65 7.5 12.065 19.2 241 297 33 3
HD40C-1 1 615 63 6.8 H.43 17.4 22.0 28.9 33.2
HD30F-1 im 615 70 42 9.525 23.5 27.8 37.2 41.9
HD40F-1 615 73 4 8.89 202 24.6 . 33.7 39.0
MD30C-1 615 69 61 8.89 21.4 26.4 32.1 34.6
W40C-1 Mocrrtari 615 70 6 11.43 18.3 23.7 31.6 353
MD30F-1 615 70 4.8 10.16 21.4 26.0 33.7 37.2
M340F-1 615 70 4.5 9.525 20.0 25.2 366 404
RCB30C-1 Cemex 565 63 66 tt.16 22.5 25.6 29.5 34.0
RCB30F-I 565 63 61 11.43 22.3 MS 36.8
Note: The ID is cement type (H for Holcim), CDOT concrete class (B for General Purpose and D
for Structural), percent fly ash replacement, fly ash class (C or F). and trial number. For example,
CD40F-1 would be composed of Cemex cement, CDOT structural class D, 40 percent replacement
of cement using Class F fly ash, and trial one.
36


CDOT concrete classes B (general purpose) and D (structural) were used as a basis
for TCM content with the three types of cement commonly used in the Colorado
Front Range (Holcim, CEMEX, and Mountain). The purpose of cement sources
and ranges being to identify if cement source had an influence on compressive
strength testing. ASTM Class C and Class F fly ash were used at 30 and 40 percent
replacements for cement in all mixes except controls. The compressive strength
results for the full-scale HPGC mixes are shown compared to OPC controls on
Figure 8 (Exhibits A through D).
Figure 8: Compressive Strength Test Results (Exhibit A: Class B 30 percent replacement;
Exhibit B: Class B 40 percent replacement; Exhibit C: Class D 30 percent replacement; Exhibit
D: Class D 40 percent replacement)
Day of Break
CB30C-2
CB30F-1
A HB30C-1
X HB30F-1
MB30C-1
o MB30F-1
+ CB0
Exhibit A: Average Compression Strength of Class B with 30 percent FA replacement
37


CB40C-2
CB40F-1
HB40C-1
X HB40F-1 l
- MB40C-1
O MB40F-1
CB0
Exhibit B: Average Compression Strength of Class B with 40 percent FA replacement
s. 70
S_ 60
f
o> 50
c
a>
£ 40
C/3
§ 30
| 20
| 10
+ + D + t
1 \ 31.0 MPa @ 28-days

X
o
+
CD30C-1
CD30F-1
HD30C-1
HD30F-1
MD30C-1
MD40F-1
CD0
20 40
Day of Break
60
Exhibit C: Average Compression Strength of Class D with 30 percent FA replacement
n
0.
2
o>
c
0>
k.
+*
(/)
o
>

<0
u
k_
Q.
E
o
o
70
60
50
40
30
20
10
0
+ + + l +
31.0 MPa @ 28-days
CD40C-2
a CD40F-2
HD40C-1
X HD40F-1
- MD40C-1
o MD40F-1
+ CD0
20 40
Day of Break
60
Exhibit D: Average Compression Strength of Class D with 40 percent FA replacement
38


The strengths for the control mixes were higher than the HPGC mixes, especially at
early ages. The strengths for the Class B control mixes appeared to level out after
28-days while the FA mixes appeared to still be gaining strength. However, all
HPGC mixes meet concrete Class B criteria by exceeding 20.7 MPa (3,000 psi) at
28-days and all concrete Class F HPGC mixes meet concrete Class D criteria by
exceeding 31.0 MPa (4,500 psi) at 28-days. The Class C ash mixes meet criteria by
56-days. The standard deviation of the HPGC mixes, as shown in Table 6,
generally resulted in a range of compressive strengths of approximately 10% at 3-
day to 6% at 28-day strengths.
Table 6: Standard deviation of fly ash replacement in concrete Classes B and D
Concrete Class Fly Ash Content 3-day Standard Deviation. MPa 28-day Standard Deviation, MPa
B 30 1.1 2.0
B 40 1.9 1.6
D 30 2.4 2.5
D 40 2.6 2.0
The effects of replacing the coarse virgin aggregate (approximately 50%) with
recycled concrete were evaluated using the 30% and 40% fly ash replacement
HPGC mixes. The compressive strengths for the recycled aggregate mixes were
compared to the mixes with virgin aggregates, as shown in Figure 9.
39


Figure 9: Compressive Strength Test Results Comparing Cement Sources (C-CEMEX, H-
Holcim. and M-Mountain) in OPC with Virgin Aggregates with Class C Fly Ash HPGC with
Recycled Aggregates (sources of cement indicated by shades of gray bars and recycled aggregate
shown by solid white bars)
Exhibit A: Class B and 30% fly ash replacement of cement
3 7 28
Day of Break
C830C WHB30C ft MB30C DC30RA50
Exhibit B: Class B and 40% fly ash replacement of cement
28
Day of Break
MB40C
HB40C
CB40C
C40RA50
The relative standard deviation in compressive strength across the mixes with 50%
recycled aggregates (RA) and mixes with solely virgin aggregates, included on
40


Table 7, ranged from 5% to 9%. The differences in compressive strengths of the
mixes by cement sources (the shaded bars on Figure 9) in the 30% and 40% FA
mixes were evaluated by the Student t-test and found not to be statistically
significant at the 5% level of significance.
Table 7: Standard deviation of mixes containing 50% recycled aggregate and mixes containing
100% virgin aggregate
n Matrix Compressive Strength (mean standard deviation), MPa
3-day 7-day 28-day
9 30%FA 18.1 1.0 25.21.4 31.41.6
9 30%FA/50%RA 15.51.4 22.71.7 28.61.3
9 40%FA 15.31.4 20.21.5 25.71.4
9 40%FA/50%RA 12.91.2 19.91.4 23.51.6
The average compressive strength of the mixes with RA compared to virgin coarse
aggregate mixes (e.g., 30%FA versus 30%FA/50%RA) at 7-days and 28-days were
also evaluated by Student t-test. At 28-days, both the 30%FA 30%FA/50%RA
and 40%FA 40%/50%RA means were marginally outside of the 95% confidence
level (above the 90% confidence level). However, the 7-day average compressive
strengths for 40%FA 40%/50%RA did not differ statistically (within the 95%
confidence level).
41


As the strength of the HPGC mixes continued to increase at 56-day testing, it was
decided to extend compression strength testing to 90-days in the next phase of
testing (Phase 5) to further evaluate this trend for fly ash concrete.
2.5.5 Phase 5: Full-Scale Regional Materials Testing for Durability
From the strength results in Phase 4, it was determined that cement source did not
have a significant influence on the results. Also, it was apparent that the strength
trends for the fly ash samples were gaining strength at a higher rate than the control
samples after the initial 28-day moist cure. Therefore, all strength and durability
testing in Phase 5 included testing to at least 90-days to further evaluate these
trends.
In the Guide to Durable Concrete [ACI Committee 201, 2002] defined durability as
concretes ability to resist weathering action, chemical attack, abrasion, and any
other process of deterioration. Therefore, the durability testing in Phase 5
followed the durability requirements of ACI 318 [2005] and tested for sodium
sulfate ASTM C 1012, corrosion protection using Rapid Chloride Permeability
ASTM C 1202, and freeze-thaw ASTM C 666.
42


Table 8: Mix Components and Properties
Materials Batch size: 0.045 m'5
Control F30 C30 F40 C40
Cement, kg 15.3 10.7 10.7 9.2 9.2
Fly Ash. kg 0.0 4.6 4.6 6.1 6.1
Aggregate. Coarse, kg 0.0 0.0 0.0 0.0 0.0
Aggregate. Recycled Coarse, kg 37.6 37.2 37.2 37.2 37.2
Aggregate, Fine, kg 45.5 46.6 47.3 46.2 47.1
Water, kg 6.4 5.5 5.5 5.5 5.5
MRWR (AT-60). ml 30.0 60.0 80.0 30.0 100.0
AEA (D-55), ml 3.0 5.8 3.8 5.8 2.5
w/cm 0.42 0.36 0.36 0.36 0.36
Air, % 6.2 5.7 7.4 6.2 7.5
Slump, cm 2.5 12.7 8.9 3.2 12.7
Unit weight, kg/m' 2264.4 2222.0 2250.3 2193.8 2165.5
Temperature. C 23.9 26.1 12.2 23.9 12.8
Ambient Temperature, C 12.8 15.6 7.2 12.8 7.2
The sources of fly ash were from the Monticello coal-fired power station in Mt.
Pleasant, Texas (Class F) and the Comanche coal-fired power station in Pueblo,
Colorado (Class C). The ASTM C 618 specifications of each ash were included in
Table 9.
Table 9: ASTM C 618 for Class C and Class F ashes
Chemical Tests Results Class F Results Class C ASTM C 618 Class F (reqd) ASTM C 618 Class C (reqd)
Sum of Si()2 A1203. Fe2()3, % 81.6.3 57.17 70 min 50 min
Calcium Oxide (CaO), % 10.83 27.67
Sulfur Trioxide (S03), % 0.43 2.18 5.0 max 5.0 max
Total Alkalies (as Na20), % 1.45 2.27
Available Alkalies (as Na20), % 0.42 1.56
Physical Tests
Loss on Ignition, % 0.67 0.26 6.0 6.0
Amount retained on No. 325 Sieve, % 23.87 11.84 34 max 34 max
Specific Gravity 2.37 2.67
Moisture Content, % 0.09 0.05 3.0 3.0
43


All mixes used South Platte virgin fine C 33 aggregate [ASTM, 2002], and all
except the control (OPC) mix used recycled concrete coarse C 33 aggregate from
the Stapleton recycling site near the Denver International Airport, provided by
Recycled Material Company Incorporated (Arvada, Colorado). The control mix
used virgin South Platte C 33 coarse material provided by Bestway Ready-mix
(Milliken, Colorado).
Prior to testing, a service life prediction model [Life-365, 2002] was run to evaluate
the effect of fly ash inclusion on service life to provide a benchmark for
comparison. The model evaluated the time required for sufficient chlorides to
penetrate the concrete cover and accumulate in sufficient quantity at the depth of
the embedded steel to initiate corrosion (2.5 cm lin), i.e., the first maintenance
prediction time by the model. Fly ash replacements of 30% and 40% (HPGC-30
and HPGC-40) were compared to OPC and OPC with a chemical corrosion
inhibitor (e.g., calcium nitrite inhibitor CNI) and the use of epoxy-coated steel.
The chloride exposure conditions (e.g. rate of chloride build up at the surface and
maximum chloride content) were modeled as a parking structure in Denver,
Colorado. The results evaluated the first maintenance as included on Table 10.
44


Table 10: LIFE-365 predicted time to first maintenance
Mix Evaluated Percent Fly Ash, % Time to First Maintenance, yrs
OPC 0 9.8
OPC-CNI 0 16.4
OPC-Epoxy Coated 0 9.8
HPGC-30 30 31.5
HPGC-40 40 54.9
Full-Scale Compressive Strength ASTM C 39
The primary criterion of HPGC is that it meets or exceeds the required structural
criteria, i.e. compressive strength. As shown on Figure 10, all mixes met the Class
B 20.7 MPa (3,000 psi) 28-day criteria [CDOT, 2006]. By 90-days, the F30 and
C30 mixes met most criteria for structural elements that specify a much higher
TCM content, reaching approximately 31 to 34 Mpa (4.5 ksi to 5 ksi). The trend
also indicates that the F30 and F40 would likely soon equal or exceed the control
strengths.
Compressive Strength
---control --f30 -o f40 -*-c30 -&-c40
Figure 10: Compressive Strength Results ASTM C 39 [2005]
45


The higher value of fineness (less retained on the No. 325 Sieve) and the higher
CaO content for the Class C ash (See Table 2.6) provided for the higher early-age
strengths. The higher aluminum and silica oxide content of the Class F ash
provided the additional source of CSH that increased longer-term strengths.
Sodium Sulfate Expansion ASTM C 1012
In the Colorado Front Range, high sulfate soils are common and have a nearly
immediate effect on the durability of in-place concrete. The degree to which
concrete, exposed to sulfate soils or water, deteriorates as a result of physical and
chemical attack is directly related to the permeability of concrete [Mehta, 2000a].
ACI 318 Table 4.3.1 [2005] classifies different levels of sulfate exposure based on
the concentration of water soluble sulfate in the soil by weight or in water (ppm)
anticipated to be in contact with the concrete. The cement types recommended
(ACI 318 R4.3) for moderate exposure included blended (IP) cement, and a
pozzolan (typically fly ash) addition to Type V in very severe exposure conditions.
For the ASTM C 1012 testing in this thesis, a Class 3 exposure (very severe) was
used to evaluate the sulfate resistance of the HPGC mixtures compared to control.
The ACI 201 standard required the use of Type V cement for exposure Class 3 with
a blend of fly ash at a replacement by mass of 25% to 35%. For this test, the
46


samples maintained Type I/1I cement in order to better evaluate the effect of the
presence and class of fly ash. The performance option requires optimizing the
cementitious materials and their amounts and requires an expansion <0.1% at 18
months to qualify as sulfate resistant in such exposure. For Class 3 exposure, the
recommendation is for w/cm to be 0.4 or below. The four HPGC mixes maintained
a 0.36 w/cm, while the control slightly exceeded the minimum with a 0.42 w/cm.
Figure 11 indicates that the expansion due to sodium sulfate at 6 months was the
lowest in the Class F fly ash mixes, with negligible results for the 30% Class F
(F30). The 30% Class C (C30) mix performed similarly to the control mix, even
exceeding the expansion at 186 days. However, at a higher replacement of cement,
the 40% Class C (C40) behaved similarly to the Class F mixes until the six month
reading where the expansion measurement was near an average between the Class
F and control mixes.
Figure 11: Results of Sulfate Expansion [ASTM C 1012] Results after 186 days of testing
indicate that the Control and C30 mixes expand at a much greater rate than the F30 and F40 mixes
and slightly more than the C40 mix
47


In terms of durability, the HPGC samples cannot be evaluated as a group. The C30
mix behaved similarly to the control and the C40 is improved, but not enough to
conclude that it provides better protection against sulfate attack. However, the
Class F samples both provided significant protection against sulfate attack when
compared to control at 186 days. The percent improvement from the control
sample is summarized in Table 11.
Table 11: Expansion % @ 186-day and difference from control
Mix Expansion (% @ 186 Days) Improvement from Control, %
Control .073 NA
F30 .005 93.5%
F40 .016 78.6%
C30 .078 -5.8%
C40 .052 28.6%
Rapid Chloride Permeability ASTM C 1202
Because of the high alkalinity in concrete, a passive layer is created around steel
and protects against corrosion from the mix water. Chloride ions, typically from
deicing salts that reach the steel will break down the passivity provided by
concrete. ASTM C 1202 Electrical Indication of Concretes Ability to Resist
Chloride Ion Penetration, often called the Rapid Chloride Permeability Test
(RCPT) and similarly referenced as AASHTO T277, passes an electrical charge, in
48


units of coulombs, as an indication of performance criteria for permeability. Table
12 provides the classification for concrete permeability per ASTM C 1202.
Table 12: RCPT ratings [ASTM C 1202]
Charge Passed (coulombs) Chloride Ion Penetrability
>4,000 High
2,000 4,000 Moderate
1,000 2,000 Low
100-1,000 Very Low
< 100 Negligible
The Minnesota Concrete Council performance specifications for low permeability
concrete requires TCM < 391 kg/m3 (658 lb/yd3), w/cm < 0.42, air 6% +/- 1%, f c
= 41.4 MPa (6 ksi) at 28 days, and ASTM C 1202 results < 1000 coulombs at 6
months and < 500 coulombs at 12 months [MCC, 2003]. The tests run for the full-
scale mixes were run for only 3 months, but the general trend indicated that the
mixes were rapidly decreasing in permeability, as shown on Figure 12. Future
RCPT testing of HPGC mixes should be conducted for a minimum of 6 months to a
year, per MCC requirements.
49


12000
Figure 12: C1202 RCPT Results
In terms of durability, the fly ash samples behaved similarly as a group. Although
the Class F ash mixes out-performed the others, all fly ash mixes showed a trend to
decreasing permeability while the control decreased at a slower rate. The percent
improvement from the control sample is summarized in Table 13.
50


Table 13: Summary of 90-day RCIP Testing difference from control
Mix Coulombs (@90 Days) Classification Improvement from Control, %
Control 4568 High NA
F30 2918 Moderate 36
F40 3172 Moderate 31
C30 4177 High 9
C40 4604 High -1
Freeze-Thaw ASTM C 666
ASTM C 666 freeze-thaw testing for concrete is a necessary durability test for
regions that experience such temperature cycles. Colorado is classified as S, or a
severe weathering region, in ASTM C 33 [2003] with special note that regions
located above 1600 m (5,000 ft) in elevation should consider higher, self-imposed
requirements for concrete performance. The ACI 318 [2005] requirements for
freeze-thaw are limited to a low w/cm ratio of 0.45 and total air content and 6%
(nominal aggregate size 1.9 cm as used in these mixes), respectively, and do not
consider the incorporation of fly ash as significant. Although the resistance to
freezing-and-thawing cycling is primarily a function of the air entrainment
[Malhotra and Mehta, 1999], fly ash does reduce the w/cm and lowers the
permeability of concrete, providing some benefit. As shown in Figure 13, the fly
ash mixes performed equally or better to the control mix at 300 cycles for the
51


control and Class F mixes, and 252 cycles for the Class C mixes (as of May 9,
2007). The requirements for ASTM C 666 are to evaluate the transverse frequency
of the mortar bars every 42 cycles (6 cycles per day) and calculate the Relative
Dynamic Modulus of Elasticity (RDME) for each sample. This is a ratio of the loss
of transverse frequency from the initial measurement. Testing is complete at 300
freeze-thaw cycles or when RDME reaches a minimum of 60% of the initial,
whichever comes first. The durability factor (DF) is the reported RDME multiplied
by the number of cycles at which RDME reaches 60% of initial. Or, as shown on
Figure 13, when the RDME reaches 300 cycles before decreasing to 60% of initial,
the final RDME at 300 cycles is reported as the DF.
# Freeze-Thaw Cycles (6 Cycles Per Day)
Figure 13: Relative Dynamic Modulus of Elasticity ASTM C 666
52


In terms of durability, the fly ash samples behaved similarly as a group. Although
the Class F ash mixes out-performed the others, all fly ash mixes showed a trend to
decreasing permeability while the control decreased at a slower rate. The percent
improvement from the control sample is summarized in Table 14.
Table 14: Summary of freeze-thaw at 300 Cycles difference from control
Mix Durability Factor Improvement from Control, %
Control 84.73 NA
F30 86.94 2.6%
F40 85.95 1.4%
C30 85.60 1.0%
C40 87.34 3.1%
2.6 Testing Conclusions
The Class F fly ash mixes provided better or equal results than the Class C mixes
and the control mix for all durability tests. The freeze-thaw tests resulted in little
difference in durability of the different mixes. Thus, all performed on an equal
basis. This was likely due to equal air entrainment more than the fly ash content of
the mixes.
53


In terms of compressive strength gain, Class C ash gained strength similarly to the
control mix and would satisfy the early strength requirements for most applications.
Class F mixes could likely be proportioned to meet most structural 28-day
requirements at 30% or less replacement, depending on the TCM. Ultimately, the
more CSH produced by the fly ash mixes, especially Class F ash, over long-term
hydration would likely surpass the control strengths with similar TCM. This
conclusion should be considered when specifying restrictive strength criteria, e.g.
35-days instead of 28-days. The environmental and economic benefits of a HPGC
mix should be considered in determining these criteria for specific applications.
Potential recommendations for CCoD would recommend a Class F fly ash at 20%
replacement of Portland cement and up to 100% of recycled aggregate for the
coarse fraction of the concrete mix for all elements and the inclusion of recycled
concrete aggregate had no negative effect on the strength or durability performance
of the mixes.
Although the Class C ash mixes did not perform as well as Class F in the durability
tests, the mixes performed equally or superior to control and are, therefore, still
classified as HPGC. The reduced expansion due to sulfate attack in the Class F
mixes were likely due to the lower lime contents than the Class C ash (10.83% CaO
for the Class F and 27.67% for Class C), as a lower pH in the pore fluid reduces
54


expansion [Malhotra and Mehta, 2002]. Concrete in contact with water and
sulfates should incorporate up to 40% Class F ash.
2.7 Economics of HPGC
As the designed service life for concrete infrastructure is typically greater than 40
years and replacement costs for concrete infrastructure are high, defining a
common study period to evaluate life-cycle cost (LCC) savings due to extended
service life would have substantial doubt. Thus, LCC methodology was only
applied to the direct material costs used in the control and HPGC mixes by
assuming that prices for goods and services change at approximately the rate of
general inflation, so that in a constant-dollar analysis the real escalation rate is zero
[USDOC/NIST, 1995],
However, as a general evaluation of LCC costs for a benchmark, the software
Building for Environmental and Economic Sustainability (BEES) Version 3.0
software [USDOC/NIST, 2003] was applied to evaluate the effects of the inclusion
of fly ash into concrete production. However, only fly ash contents of 0% (100%
Portland cement), 15%, 20%, and 35% (for slabs and all lightly reinforced) are
included in the BEES database for LCC using a real interest rate (discount factor)
of 3.5 percent [OMB, 2005]. All operation and maintenance expenses for the
55


alternatives during the period of analysis are in base year 2002 dollars. The higher
amount of fly ash substitution provided the greatest reduction in lifetime costs. The
results indicate a 10.3% reduction in LCC results for the 35% fly ash mix when
compared to 0% substitution, as shown in Figure 14.
Economic Performance
DO%Portland B'/JFIyAsh 20%FlyAsh 35%FlyAsh
ALTERNATIVES
Figure 14: BEES LCC Analysis of Control and HPGC Mixes. BEES indicates that both the
direct and future cost savings increase with increasing amounts of fly ash.
2.7.1 Direct Cost of HPGC and Control Mixes
The direct costs of the materials were considered to evaluate economic
sustainability with the additional knowledge that the anticipated service life and
reduced operation and maintenance would provide additional savings. In Table 15
below, the direct costs of the scenarios were compared.
56


Table 15: Direct material costs of one tonne of concrete delivered to CCoD
Mix Cement, $ Fly Ash, $ Coarse, $ Fine, $ Recycled Aggregate, $ Total, $ A%
Control 19.85 0.0 5.09 2.10 27.08 0.0
20% C Ash 15.85 1.60 5.09 2.10 24.64 -8.9
20% F Ash 15.85 2.08 5.09 2.10 25.12 -7.1
20% C Ash 50% Recycled 15.85 1.60 2.10 6.28 25.89 -4.5
30% C Ash 13.89 2.38 5.09 2.10 23.47 -13.2
30% F Ash 13.89 3.10 5.09 2.10 24.18 -10.6
30% C Ash 50% Recycled 13.89 2.38 2.10 6.28 24.65 -8.8
40% C Ash 11.91 3.18 5.09 2.10 22.27 -17.6
40% F Ash 11.91 4.13 5.09 2.10 23.23 -14.1
40% C Ash 50% Recycled 11.91 3.18 2.10 6.28 23.46 -13.2
Notes: Unit costs: cement $137.82/tonne [Beslway and Cemex personal communications. 2007],
Class C FA $55.13/lonne, Class F $71.66/tonne. Virgin Coarse #3/4 $11.58/lonne, virgin fine
aggregate $6.06/tonne [Bestway personal communications, 2007], Recycled #57/67 rock
$14.28/tonne [RMCI, 2007]
The direct material cost savings for the HPGC mixes ranged from 4.5% to 17.6%
less than the control, or business-as-usual (BAU) (as described in Chapter 3). In
addition, these cost savings are added to the reduced transport costs of material
flow and the environmental benefits as evaluated in Chapter 3.
57


3. Evaluating HPGC with Environmental Life Cycle Assessment
The environmental impacts of the construction sector are quite significant and
produce the most CO2 emissions in the United States through the manufacture,
transport, and use of materials [Norris, 1998], At about 300 million metric tons,
this sector creates more upstream fossil fuel CO2 emissions than the direct total
fossil fuel CO2 emissions of all federal, state, and local government electric utilities
[National Research Council, 2004]. In addition, the consumption of minerals
(construction materials and metals) account for more than 90 percent by weight of
non-food, non-fuel construction materials used in the United States [National
Research Council, 2004]. Consumption of virgin aggregate resources has created
scarcity issues in many urban areas of the United States. Furthermore, as the
transportation distance of the virgin aggregates to the urban centers increases, the
environmental impact of transportation is increasingly becoming a significant
contributor to concrete production. Horvath [2003] indicated that the energy
required to transport aggregates equals the processing energy of virgin resources at
a transport distance of approximately 5 km and exceeds the energy required for
crushing hard rock aggregates at approximately 16 km.
58


Tools such as the environmental life cycle assessment (LCA) are required to
evaluate the environmental impacts of current concrete consumption and provide
the means for comparing scenarios to evaluate policies intended to reduce
emissions associated with urban infrastructure.
3.1 Intellectual Contribution and Specific Objectives
This chapter presents a methodology to incorporate the regional manufacturing
processes and transportation information associated with concrete production and
delivery into environmental LCA models that can provide regional and local
policy-relevant information to decision-makers in Colorado. The specific
objectives to accomplish this are the following:
Evaluate the appropriate LCA models for quantifying environmental
emissions associated with concrete urban infrastructure at the regional level.
Conduct city-wide LCA of concrete to quantify environmental impact of
concrete infrastructure.
- Evaluate greenhouse gas (GHG) emissions for primary processes
and materials.
- Evaluate potential scenarios for reducing overall impact.
59


- Obtain experimental data on end-of-life for concrete containing fly
ash and recycled aggregate. End-of-life for HPGC has never been
evaluated physically or chemically for standardized beneficial
reuses.
3.2 Background: Types of LCA
LCA quantifies environmental and ecosystem impacts associated with a product
over its entire life cycle. The LCA assessment is cradle-to-grave when the
product is disposed of in the landfill or cradle-to-cradle when the product is
recycled into new materials, or for the scenarios in this study, when urban
infrastructure is recycled back into new stock (infrastructure). The LCA approach
considers all stages of a product, including; raw material acquisition, product
manufacturing, transportation, installation, operation and maintenance, and
ultimately, disposal, recycling and/or waste management termed end-of-life. The
accumulative energy associated with material extraction and manufacturing of the
materials required to produce concrete relates to the total energy of the product,
termed embodied energy. Displacing the most energy intensive element of
concrete, i.e. cement, with environmentally free wastestreams, such as fly ash,
offers opportunities to provide significant environmental and economic benefits to
the urban carbon footprint.
60


Process-based LCA Models: Currently, there are numerous LCA software tools on
the market to select from. Process-based LCA tools use the Society of
Environmental Toxicology and Chemistry (SETAC) methodology to analyze the
environmental impacts of material selection and have the ability to model each
manufacturing and transport process associated with the life-cycle of a product.
These tools vary in complexity and capability, but are primarily accounting tools
that inventory material and energy flows in a series of linked upstream
manufacturing processes to track the associated emissions and mid-point
environmental impacts. The primary limitation of process-based models are limits
on the number of upstream processes than can be included, thus only approximate
potential environmental impacts are addressed [Five Winds, 2002].
Economy-wide LCA Model: An LCA model that does not require arbitrary
boundaries is the Economic Input-Output (EIO) model [Carnegie Mellon Green
Design Institute, 2007]. The database incorporates aggregated data from all
industrial sectors according to the 1997 United States Department of Commerce
(DOC) EIO data. Input into the EIO-LCA model is economic only and is based on
producer prices for the products in terms of 1997 Dollars (USD). Economic data is
then linked to energy use and toxic releases associated with each industrial sector,
benchmarked with the US Department of Energy (DOE) national energy data and
61


the US Environmental Protection Agency's (EPA) toxic release inventory (TRI).
The primary limitation of this model results from the high level of aggregation
within the industrial sectors where individual processes cannot be evaluated, e.g.,
the difference on the environmental impact between the wet or dry kilning
processes in cement production cannot be discerned from the overall impacts
associated with concrete production. There are two major simplifications assumed
in EIOLCA. First, there is a proportional increase in all sectors, e.g., the economic
input-output model is linear, so that the effects of a $1,000 purchase from a sector
will be ten times greater than the effects of a $100 purchase from the same sector.
Second, all production facilities that make products and provide services can be
aggregated [Hendrickson et al, 2006]. This greater inclusiveness of economic
processes does raise some concerns when categories such as; Fruit and vegetable
canning and drying, Bread and bakery product, except frozen, manufacturing,
and Wineries and Distilleries adds to the overall impact, albeit a nearly negligible
contribution, of critical pollutants for cement manufacturing.
Hybrid LCA: The hybrid LCA combines a process-based model for specific
manufacturing processes where detailed inputs are known (e.g., kilning and
grinding of clinker for cement). The outputs and discharges for these processes are
then added with outputs from the economy-wide model of associated processes
62


(e.g., transport of materials) to provide for an approximation of the impact of a
product without arbitrary upstream boundaries.
In this dissertation, a hybrid-LCA methodology is used to evaluate the overall
environmental impact of HPGC and OPC infrastructure in the City and County of
Denver, Colorado (CCoD).
3.3 LCA Methodology
LCA methodology adheres to the four goals in general accordance with the
International Standards Organization (ISO) 14040 standards [2005]:
1. Goal and scope: Outlines the purpose of the study and its breadth and
depth; and, identifies the functional unit for the study.
2. Inventory analysis: Identifies and quantifies the environmental inputs and
outputs associated with a product over its entire life cycle (further
discussion in Appendix A);
3. Impact assessment: Characterizes inventory flows (inputs and outputs) in
relation to a set of environmental and health impacts; and
4. Interpretation step: Combines the environmental impacts with the goals of
the LCA study.
63


The processes involved with the manufacture and processing of fly ash (FA)
concrete (cement, aggregates and fly ash), mixing and delivery, placement and end-
of-life phases need to be modeled separately with regional industry data in order to
develop a more accurate representation of the environmental impacts of concrete
production and delivery in CCoD.
Goal and Scope: This study will utilize a hybrid LCA that combines process-based
LCA to evaluate the emissions of fuel consumed in the processing of recycled
aggregates and the kilning and grinding of clinker into cement and for the
calcination of limestone. Economy-wide EIOLCA is then combined with these
processes to determine the contribution of associated processes, such as machine
depreciation, transport and avoided emissions from not landfilling or extracting
virgin materials. The functional unit evaluated is one tonne of concrete. The
inputs into the hybrid LCA included:
- All significant processes involved in concrete production
- Distance and mode of transport for all materials and primary
sources
- Avoided emissions due to recycling aggregates and fly ash
- Cement process energy data
- Emissions due to cement calcination
64


Inventory Analysis: A description of the primary materials evaluated in this LCA
and associated processes are the following:
Portland cement: Crushed limestone, sand and shale are mixed with iron ore and
ground together to form a finely ground powder (composed mainly of calcium and
aluminum silicates). This mixture is then fused into clinkers in a single drum kiln
at approximately 1500C. The final stage is cooling where the marble-sized
clinkers are formed and then ground and mixed with a small amount of gypsum
(which regulates setting) to produce the general-purpose Portland cement.
Fly ash: Fly ash is an industrial by-product (wastestream) from modern coal fired
thermal plants that have pozzolanic properties that can substitute as a partial
Portland cement replacement in concrete. Most fly ash that is used in the CCoD
can replace cement without any additional processing requirements to meet ASTM
C 618 [AC A A, Goss, Personal Communications, 2006]. All energy associated with
the production of the fly ash is therefore assigned to the primary purpose of power
generation, and considered to be environmentally free except for the required
transport of fly ash to the ready-mix batch plants. In addition, the LCA model
included the environmental impacts avoided by incorporating the fly ash in
concrete. If not beneficially reused, fly ash is directed to a RCRA Subtitle D
monofills (discussed in Chapter 5).
65


Aggregates: Aggregates compose approximately 75% of the total mass of concrete.
The governing standard for aggregates used in concrete is ASTM C 33 [2003] that
defines the quality and size (coarse and fine) of the rock to be used. The primary
source of aggregates used in Denver is alluvial, with most of the coarse fraction
coming from the South Platte River corridor.
Water: Water, when mixed with cement (and cement with fly ash), forms a paste
that binds the aggregate together through a chemical reaction called hydration. The
water needs to be pure in order to prevent side reactions, e.g. chloride ion, from
occurring which may weaken the concrete or otherwise interfere with the hydration
process.
Landfilling: The end-of-life for the concrete infrastructure includes the scenario
that the stock is demolished and placed in a landfill after its useful life, i.e., cradle-
to-grave.
Recycled Aggregates: Another end-of-life scenario is that the concrete debris is
crushed, screened and washed to produce new aggregate used in base coarse,
vehicle tracking, structural fill and concrete products, i.e., cradle-to-cradle. The
environmental impact of reducing the strain on landfill capacity and the scarcity
issues of virgin aggregates is considered by recycling of concrete.
66


Impact Assessment: The emissions from the material processing, manufacturing,
and transport in the life cycle inventory that contribute to the total GHG and
embodied energy of concrete are accounted for during life cycle inventory.
However, the different gases accounted for in the inventory have varying impacts
on global warming, for example, additional methane in the atmosphere has an
approximately 23 times greater climate impact than the same incremental amount
of CO2 [IPCC, 2001], Therefore, each gas is represented in terms of the CO2
equivalent mass, or CO^E, that would have the same climate impact as the mass of
the individual GHG released into the atmosphere. The six gases that contribute to
GHG are:
1. carbon dioxide (CO2),
2. methane (CH4),
3. nitrous oxide (N2O),
4. hydrofluorocarbons (HFCs),
5. sulfur hexafluoride (SF6), and
6. perfluorocarbons (PFCs).
Additional LCI database sources were used as benchmarks to compare the CO2E
and energy results from the EIO and process-based LCA models, such as, the
BEES Version 3.0 software [USDOC/NIST, 2003] and the USEPAs WAste
Reduction Model (WARM) [USEPA, 2003]. WARM is a model designed to assist
67


in quantifying the GHG benefits of various waste management practices. BEES is
a LCA/LCC tool containing environmental and economic performance data for
nearly 200 products across 23 building elements (see Appendix B for a preliminary
LCA of fly ash concrete and OPC slab-on-grade unit). However, neither model
allows for regional input or much flexibility on specific product content or mode of
material transport.
3.4 LCA of Concrete Infrastructure in Denver, Colorado
The environmental sustainability of concrete infrastructure in CCoD was evaluated
by accounting the total energy (MJ) and CCLE emissions associated with the
manufacturing of concrete with environmental LCA methodology. This
methodology included the avoided energy and environmental impacts resulting
from replacing virgin materials with wastestream materials, such as fly ash and
recycled concrete aggregates, into concrete. Other avoided impacts included;
reduced material transport distance and landfill strain.
3.4.1 LCA Infrastructure Comparison Matrix
Two LCA analyses of CCoD concrete infrastructure were performed. Both
analyses considered a typical 34 MPa (5 ksi) concrete mix with 336 kg/m3 (565
68


lb/yd3 CDOT Class B) total cementitious content (TCM) and 2000 kg/m3 (3,200
lb/yd ) total aggregate content and 140 kg/m water. The scenarios are evaluated
by total energy (MJ) and total GHG emissions in metric tonnes (tonne) of C02
equivalents (MTCCLE) to analyze the embodied energy in one tonne of non-
reinforced concrete (0.43 m3 concrete by volume).
The first analysis compared two basic scenarios:
o business-as-usual (BAU) scenario that considered using ordinary
Portland concrete (OPC), i.e., 0% replacement of Portland cement
with fly ash, and a cradle-to-grave end-of-life scenario that
assumed all demolished concrete infrastructure is disposed of in the
Denver-Arapahoe Disposal Site (DADS) landfill,
o Low-level high performance green concrete (HPGC) mixes
containing a maximum of 20% replacement of Portland cement with
Class C and Class F fly ash on a one-to-one basis and a maximum of
50% recycled aggregate, i.e., 100% of the coarse fraction. The low-
level scenario was selected as this range of fly ash replacement for
Portland cement is commonly accepted by engineers, architects and
owners, and is currently considered for a city-wide policy initiative
in CCoD (discussed further in Chapter 5). The end-of-life for the
HPGC scenarios is considered cradle-to-cradle , in LCA terms, as
69


landfilling of the wastestreams are avoided by incorporating the
material into new stock. Both the BAU and HPGC scenarios were
then evaluated by material source location and mode of material
transport. The scenarios evaluated in the first LCA analysis are
defined by material content and material source location, as
included on Table 16.
Table 16: Identification of scenarios in first LCA analysis
Analysis Scenario ID Replacement. % Material Source
Fly Ash Recycled Aggregate Fly Ash Cement
First BAU_F 0 0 Florence, CO
BAU_L 0 0 Lyons, CO
FA20RA0-1 20 0 Pueblo. CO Lyons. CO
FA20RA0-2 20 0 Wheaton. WY Lyons. CO
FA20RA0-3 20 0 Underwood, ND Lyons, CO
FA20RA0-4 20 0 Mt. Pleasant, TX Lyons, CO
FA0RA50 0 50 Lyons, CO
FA20RA50 20 50 Pueblo. CO Lyons, CO
The second analysis built on the first analysis by considering the impact of a
higher-level of fly ash replacement (representative of the full-scale tests in
Chapter 2), with and without recycled aggregate, compared to the BAU
scenario. The higher-level HPGC was modeled as follows:
o Higher-level HPGC incorporated 30% and 40% replacements of
Portland cement with fly ash, again on a one-to-one basis, based on
the results of the structural and durability in Chapter 2. Recycled
70


aggregates composed 50% of total aggregates (100% of the coarse
fraction). The higher-level HPGC scenarios are identified by fly ash
(FA) and recycled aggregate (RA) replacement percentages. The
scenarios evaluated in the second LCA analysis are included on
Table 17.
Table 17: Identification scenarios in second analysis
Replacement. % Material Source
Analysis Scenario ID Fly Ash Recycled Aggregate Fly Ash Cement
FA30 30 0 Wheaton. WY Lyons. CO
Second FA30RA50 30 50 Wheaton. WY Lyons, CO
FA40 40 0 Wheaton. WY Lyons. CO
FA40RA50 40 50 Wheaton. WY Lyons. CO
The primary materials, modes and costs of transport, and processes for each life
cycle phase for LCA of concrete flows in Denver, Colorado are included on Table
18. For each process, the type of environmental LCA model used, the source of
data, and, when possible, a benchmark source is identified. The life cycle
inventory (further discussion in Appendix A) for the emissions is specific to the
United States and regional producer prices were used in the economy-wide model
to evaluate current practices.
71


Table 18: LCA models used for concrete flow in CCoD
Life-Cycle Process Notes Source Benchmark
Material Manufacturing Cement Calcination Chemical' Emissions IPCC
Kilning/ grinding Fuel Emissions2 DOE/EIA EIOLCA
Aggregates Virgin Economy-wide EIOLCA' BEES
Recycled4 Fuel Emissions2 DOE/EIA USEPA- WARM
Machine Depreciation EIOLCA
Avoided Materials EIOLCA
Transport Truck Economy-wide EIOLCA BEES
Rail Economy-wide EIOLCA US DOT
Construction Ready-mix Batching Economy-wide EIOLCA BEES
Transport Economy-wide EIOLCA
End-of-Life Landfill/ Landfill avoidance Operations Economy-wide EIOLCA USEPA- WARM
1 Emissions due lo the calcination of limestone
' Process-based emissions (national and regional)
3 All EIOLCA data input used regional producer prices for materials and transport
4 Hybrid-LCA
Items highlighted in yellow are processes developed by Mark Reiner for this thesis
The costs of materials and transport used in the EIOLCA analyses are based on
producer prices [Horvath, personal communication, 2005]. The regional unit prices
for the primary concrete materials, the year, and the transport mode are the
following:
Cement: $137.82 per tonne [Bestway and Cemex, personal
communications, 2007]
Sand and Gravel (aggregate): $7.17 per tonne [Bestway, personal
communication, 2007]
Truck transport: $0,178 per tonne/km [Glaeser et al, 2004]
72


Rail transport: $0,027 per tonne/km [Glaeser et al, 2004]

These processes, modes of transport, and associated life-cycle phases, are depicted
for the BAU and HPGC scenarios on Figure 15 (A BAU, B HPGC).
Figure 15: Life Cycle Phases and Material Flow for Concrete in CCoD. Exhibit A represents
the Business-as-Usual (BAU) scenario and Exhibit B represents the HPGC scenarios.
Material Extraction and Concrete End-of-Life
Processing Processing
Virgin Aegffeit?'
tP. Plstr* Ptv*t
'>ota; Afro'vs rprsct transport asdcucac crate lie.* :s tht uibiEmvarecuct
Exhibit A: BAU
73


Material Extractwn and Concrete End-of-Life
Processing Pro cessing
Virgin Aggregates
South Platte River
Recycled
Aggregates
Not*: Anew? rtpnsit tropoil anddailad pm lau ulheuibaiieiiniDiRUrt
1
I
!
t
I
5
l
I
I
!
t
f
Exhibit B: HPGC
3.4.2 Inventory of Materials Considered for Concrete LCA
The materials considered in both LCA analyses are inventoried below and divided
by life-cycle phase: Material Manufacturing, Construction, and End-of-Life.
Material Manufacturing: Cement
The embodied energy of cement production and the associated emissions are a
function to two processes; calcination the chemical release of CO2 from the
limestone (CaCOj) to produce the quick lime (CaO) and the combustion of fossil
74


fuel required for the extraction and transport of raw materials, kilning, and grinding
of clinker. There is a substantial range of embodied energy and emissions
associated with the manufacturing of cement depending on the efficiencies of the
plant and the national standards for cement production, as shown on Table 19.
Table 19: Embodied energy and emissions of cement production
Region Embodied Energy Emissions, CO2 mt/mt Source
World 4.8 GJ 0.814 Worrell et al, 2006
North America 5.4 GJ Worrell et al, 2006
United States 7.33 GJ Wet Kiln 6.40 GJ Dry Kiln 0.97 USEPA, Hanle, 2004
As the calcination of limestone is a significant contributor to the emissions
associated with cement manufacturing, independent of the fossil fuel energy or
efficiencies of the plant, this process was considered separately from the total
emissions. The average CO2 emissions released due to calcining limestone is
reasonably certain. The emission factor used in this analysis is the product of the
average lime fraction for clinker of 64.6 percent [IPCC, 2000] and a constant
reflecting the mass of CO2 released per unit of lime. This calculation yields an
emission factor of 0.507 tonnes of CO2 per tonne of clinker produced, which was
determined as follows:
EFciir.ker = 0-646 CqO X
44.01-
9
moie
CO-
56.08
-A-CaO
moie
CO-
= 0.507 tonnes-----;;
tonne aimer
75


The energy associated with the manufacturing processes of cement were evaluated
using average United States process data for the production of one tonne of
Portland cement from the Portland Cement Association (PCA) for 1999, 2000,
2002, and 2004 [PCA, 2006] and national emission factors from the Department of
Energy and regional for Colorado (2004) [USDOE/EIA, 2006]. These data were
then compared to the energy mix output from EIOLCA (1997) as a benchmark.
The process energy is divided by fuel type consumed in the kilning and grinding
processes in cement manufacturing and the calcination emissions are summarized
in Table 20.
Table 20: EIOLCA and PCA energy consumption and EIA/DOE emissions
ype of Fuel United States Average Energy and Emissions Regional
1997 EIOLCA1 1999 2000 2002 2004 Colorado 2004s
GJ* CO;2 3 4 GJ CO; GJ CO; GJ CO; GJ CO; GJ CO;
/fiddle )istillate 0.124 0.009 0.047 0.003 0.042 0.003 0.044 0.003 0.036 0.003 0.036 0.003
Natural Gas 2.10 0.106 0.346 0.017 0.276 0.014 0.22 0.011 0.156 0.008 0.156 0.008
'oal 4.80 0.44 3.148 0.289 3.15 0.289 3.07 0.281 2.935 0.269 2.935 0.269
etroleum Coke 0.790 0.077 0.803 0.078 0.80 0.078 0.872 0.085 0.872 0.085
Vasle Fuel 0.430 0.035 0.425 0.035 0.439 0.036 0.469 0.038 0.469 0.0.78
et Fuel 0.014 0.001
electricity 0.774 0.136 0.349 0.099 0.554 0.098 0.55 .097 0.538 0.095 0.539 0.136
"oal: talural Gas 2.29 9.1 11.4 13.9 18.8 18.8
Coal Total 0.6 0.39 0.6 0.6 0.59 0.59
lub-Tolals 8.03 0.707 5-32 0.518 5.26 0.516 5.12 0.506 5.02 0.498 5.02 0.54
:o2 Calcination 0.507 0.507 0-507 0.507 0.507 0.507
Totals 8.03 1.21s 5-32 1.025 5.26 1.023 5.12 1.013 5.02 1.01 5.02 1.05
'EIO Carnegie Mellon Green Institute http://www.eiolea.net
2 Colorado mix emission factor is 1.0046 ton C()2e/MWh compared with 0.6982 ton C02e/MWh
national average: http://www.cia.doe.gov/oiaf/l605/e-factor.html
3 Source: PCA, 2006 Table 38 Yearbook. Average energy requirements for production of one
tonne of cement (equals weighted average of 92% clinker and 8% finished cement).
4 Source: DOE, 2007 http://www.eia.doe.gov/oiaf/1605/factors.html Reported in metric tonnes.
76


5EIOLCA reports 0.215 MWh (equivalent to 0.774GJ) for electricity consumption for one tonne of
cement production. The total energy, as summed up on EIOLCA output is 7.5 GJ. Therefore,
ElOLCA assumes the 0.215 MWh is 0.215 GJ a difference of approximately 0.5 GJ. The
emissions for 0.215 MWh equals 0.774 GJ equals 0.15 mtC02e (US average). If the energy for
electricity was assumed to be 0.215 GJ then the emissions would be 0.055 tonne C02e. A
difference of 0.1 tonne/tonne. However, the total reported for the EIOLCA was 0.836. If 0.15 is
used and the sum is 0.72 then the total assumed lor calcination is 0.11 tonne/tonne If 0.055 is
used, then the sum is 0.625 and the amount assumed for calcinations is 0.211 tonne/tonne. Either
way, it is low as there should be 0.507 tonne/tonne.
The PC A emission data indicates a general trend of increased efficiencies in the
processing of cement as emissions and total energy has declined, explained by the
continuing conversion of kilns from the wet to more efficient dry processes. This
increased efficiency is significant as the coal to total energy has not declined and
the coal-to-natural gas ratios have increased steadily (as calculated on the bottom of
Table 22). However, the PCA data shows that the GHG emissions per unit, on a
whole, have remained relatively close to the one tonne MTCO^E/tonne cement or
unit per unit.
Benchmark: The EIOLCA data shows a higher embodied energy, despite the very
low ratio of coal to natural gas usage, and a higher GHG emission of 1.21
MTCO2E, approximately 20% higher than the PCA estimates. This can be
explained by the additional upstream processes that are included in the EIO
analysis (fewer boundaries). In addition to cement manufacturing, other processes
are included, such as; power generation and supply, truck transportation (of raw
77


materials for the production of cement), pipeline transportation, State and local
government electric utilities, ground or treated minerals and earths manufacturing,
and oil and gas extraction. As these processes represent the embodied energy of
cement, this provides a reasonable estimate of emissions and energy.
The emissions associated in the cement manufacturing inventory, as evaluated by
the USEPA on a national level, were estimated to be between 40.1 and 52.1 Tg
(million metric tonnes) CCFE at the 95 percent confidence level. This indicates a
range of approximately 13 percent below and 14 percent above the emission
estimate of 45.9 Tg C02 [USEPA, 2007].
Material Manufacturing: Recycled Aggregates
The data for recycled concrete aggregates were obtained from a two month project
at the Buckley Air Force Base at Aurora, Colorado performed by Recycled
Material Company, Inc. (RMC1 Arvada, Colorado) from May through June,
2006. The project involved the processing 8,919 tonnes of asphalt and 15,921
tonnes of concrete rubble stockpiled from various demolition projects as the site
was prepared for a major housing project. The project size and assortment of
rubble type and quality was considered appropriate for evaluating typical
processing energy. The machine depreciation was estimated as $6,179 (2002 USD
- base dollar) using United States Army Corp of Engineers methodology [USACE,
78


2003], or $0.25 per tonne of debris crushed and processed. The total fuel cost (all
diesel) was $8,968 at an average cost of $0.76/liter in May, 2006 [USDOE, 2007b],
or $0.36 in fuel costs per tonne of debris crushed and processed. The equipment,
fuel consumption and machine hours are included on Table 21.
Table 21: Input data into EIO for recycled aggregate production based on processes and fuel
consumption reported by RMCI [2006]
Equipment Model Used Model Year Time Operated (Hours) Total Equipment Value, $2002USD DEPR, $2002/Hr Total DEPR, $2002USD Liter/ Hr Total Fuel (Liter)
CAT Wheel Loader 980G 2001 118 $408,808 $23.34 $2,754 26.5 3130
CAT Wheel Loader 966G 2001 68 $283,778 $16.14 $1,098 22.7 1546
John Deer Wheel Loader 61 $46,477 $4.39 $268 22.7 1387
Chieftain Powerscreen, 2100, 3 Deck 2005 118 $337,452 $11.88 $1,402 37.9 4472
Hart! Startrack Crusher 2002 57.5 $0 45.5 2615
Volvo Excavator EC460 2004 19.5 $719,176 $33.71 $657 22.7 443
Totals 442 $ 6,179 $3,587
The environmental impacts of not extracting virgin resources were input as the
economic sum of the aggregate products generated from the recycled concrete
rubble. Total average revenue produced per ton of concrete rubble, assuming
equally proportionate high-end and low-end concrete as shown on Table 22 below.
79


was $8.74. The economic value of recovered reinforcing steel (rebar) from the
demolition was eliminated from consideration as the total recovered value of rebar
was $0.02/ton after environmental and hauling fees and that nearly all rebar used in
Denver infrastructure is already recycled [RMC1, 2006].
Table 22: Recycled concrete aggregate products, $ per tonne offset
Aggregate Product Cost Per Ton, $ High End Concrete Lou1 End Concrete
Percent Per Ton Total Value, $/ton Percent Per Ton Total Value, $/ton
#57 Coarse 12.95 40 5.18
-4" Fine 7.95 45 3.58
Drain Rock (3/4" x 2") 9.95 10 1.00 25 2.49
Vehicle Tracking (2"x4") 10.95 5 0.55
Class 6 Base Course (-3/4") 6.25 75 4.69
Total - 10.30 Total = 7.18
Data source: Recycled Material Company. 2006
The embodied energy of recycled concrete aggregates was considered the sum of
the energy consumed to sort, crush and screen the debris and two avoided
environmental impacts: 1) avoiding the extraction of virgin resources and 2)
avoiding landfilling of old stock. Therefore, the energy and emissions associated
with recycled aggregates and the benchmark used are discussed below in the end-
of-life phase.
80


Material Manufacturing: Virgin Aggregates
The economic input for the extraction and processing of virgin aggregate was input
into EIOLCA at $5.89 1997USD ($7.17/tonne 2006USD) and evaluated at
consuming 110 MJ/tonne and 0.0075 MTCCLE/tonne. The scarcity issues
associated with virgin aggregates are discussed in more detail in Chapter 4.
Benchmark: In BEES, coarse and fine aggregate are assumed to be crushed rock,
which tends to slightly overestimate the energy use of aggregate production. For
both coarse and fine, the energy consumed per tonne of aggregate is reported as
155 MJ. The slightly higher energy estimate (than that reported in EIOLCA) can
be explained by the higher national average ratio of crushed aggregate to alluvial
aggregates used in manufacturing concrete [USGS, 2001]. In addition, the unit cost
of aggregates in Colorado that was the input for EIO is less than the national
average, as discussed in Chapter 4.
Material Manufacturing: Fly Ash
As fly ash is a wastestream material from the coal-fired power plants, and
additional processing is not required for the sources of fly ash identified in this
LCA to meet ASTM C 618 specifications (Chapter 2), the only energy applied to
fly ash is due to mode and distance of transport.
81


Material Manufacturing: LCA of transport energy
The distance and mode of transport of material from source to final placement can
be a significant contributor to MTCCLE emissions and the overall embodied energy
of concrete infrastructure. The energy and emissions from transport were modeled
in EIOLCA and, therefore, the economic input was converted into 1997 USD. A
summary of economic inputs for transporting material by truck or rail mode of
transport in 1997USD per tonne-km is included on Table 23.
Table 23: EIOLCA inputs for transportation mode costs per tonne-km
Industry Group Sector Name NAICS Value, tonne-km VSD(Yr) CPI (Yr) 1997 $USD tonne-km
Trade. Transportation, and Information Truck Transportation 484 $0,178 (2004) 188.9 (2004) $0,151
Trade. Transportation, and Information Rail Transportation 482 $0,027 (2004) 188.9 (2004) $0,023
Costs for transport obtained from Glaeser et al. 2004 and converted to tonne-km
Benchmark: EIOLCA estimates an energy consumption of 2.5 MJ/tonne-km for
truck transport and 0.407 MJ/tonne-km for transporting materials by rail. BEES
evaluated the overall transport energy for materials by truck at 1.18 MJ/tonne-km
This difference can be attributed to the higher inclusiveness of industrial sectors
evaluated in EIOLCA and that BEES assumes highway miles and cannot be
modified to represent congestion, as EIOLCA can with higher economic inputs.
82


The EIOLCA output for energy and environmental impact of transporting one
tonne of material from the sources identified in the scenario summary in Table 16
are summarized in Table 24. The distances are road or rail km from the
manufacturer to ready-mix operations within 15 km of the Colorado State Capitol
building.
Table 24: Summary of EIOLCA inputs and outputs for transportation per tonne of material
Material Source Mode of Transport Distance, km Economic Input, USD 1997 Total Energy, MJ Total MTCOiE
Fly Ash
Pueblo. Colorado Class C Truck 188 $28.39 477 0.0601
Wheaton, Wyoming Class C Truck 285 $43.04 723 0.091
Mt. Pleasant, Texas Class F Rail 1432 $32.94 583 0.037
Underwood. ND Class F Rail 1218 $28.01 496 0.0316
Aggregate Sources
South Platte Virgin Truck 58 $8.79 148 0.0186
Recycled Aggregates Stapleton location Truck 14.5 $2.19 37 0.0464
Cement Sources
Lyons, Colorado Truck 79 $11.93 200 0.0253
Florence, Colorado Rail 177 $4.07 72 0.0046
Construction: Ready-Mix Operations and Concrete Placement
All scenarios include the process water and energy required for concrete production
added at the ready-mix batch plant and the final 15 km delivery to the State Capitol
Building for placement. EIOLCA was used to evaluate the energy and emissions
based on an economic input of $0.50/tonne of concrete for mix water ($0.40
83


1997USD) and $11.96 2006USD for the ready-mix operations ($9.52 1997USD)
[Bestway, personal communication, 2006]. EIOLCA evaluated the mix water
added 5 MJ and 0.0031 MTCO2E, while the energy and emissions from the ready-
mix process added 205 MJ and 0.0193 MTCO2E total of 210 MJ and 0.0224
MTC02E/tonne concrete.
Benchmark: The BEES estimate of ready-mix operations evaluates the added
embodied energy as 115 MJ/tonne of concrete. The higher estimate by EIOLCA
represents less upstream boundaries, but may also be attributed to a higher
economic input for ready-mix operations in Denver, compared to a national
average.
End-of-Life: Avoidance of Landfdling for Concrete Debris
The EIOLCA avoidance of disposing concrete debris (a component of construction
and demolition (C&D) debris) at DADS was estimated by the cost of disposing one
tonne of debris. The value of disposal at DADS was estimated from the disposal
fees of approximately $10.89/tonne (with an in-place density of 1.4 tonnes/m3) and
subtracting 50% profit and an estimated 20% for the royalties paid to the CCoD for
the property [Waste Management, personal communications, 2007], The EIOLCA
input for landfill avoidance was therefore evaluating to be $3.27/tonne.
84