INCLUSION OF SUSTAINABLE MATERIAL AND MATERIAL USE POLICY INTO THE INTERNATIONAL ENERGY CONSERVATION CODE:
A CASE FOR STRUCTURAL MATERIAL REQUIREMENTS
Bachelor of Science Civil Engineering, University of Iowa, 1996
A thesis submitted to the University of Colorado at Denver in partial fulfillment of the requirements for the degree of Master of Science Civil Engineering
Chad Michael Carr
This thesis for the Masters of Science degree by Chad Michael Carr has been approved
Carr, Chad Michael (M.S. Civil Engineering)
INCLUSION OF SUSTAINABLE MATERIAL AND MATERIAL USE POLICY INTO THE INTERNATIONAL ENERGY CONSERVATION CODE: A CASE FOR STRUCTURAL MATERIAL REQUIREMENTS
Thesis directed by Professor Kevin L. Rens, PhD, PE
The 14 different International Building codes do not include any requirements addressing non-renewable resource depletion or environmental protection, except for the International Wildland-Urban Interface Code, new in 2006. However, this code does not address building material use. The International Building Codes are the standard by which most jurisdictions in the United States are regulated. The most relevant building code dealing with structural material conservation is the International Energy Conservation Code. This thesis investigated the inclusion of new proposed requirements into the International Energy Conservation Code that address sustainable material use and conservation. Two new requirements were proposed. The first was a waste management program requirement for building construction projects. This type of requirement has proved very successful in California where construction site waste management programs are required in most jurisdictions. The first proposal requirement was developed by review of 20 previous and 2 new waste
management case studies, where cost comparisons were made and recycling success rates were examined. The second proposed requirement was a partial cement replacement requirement for structural concrete mixes. Fly ash and slag have proven to be very successful in partially replacing cement in concrete to the benefit of the environment. Seven previous case studies, along with one new case study were reviewed for the second proposed requirement.
This abstract accurately represents the content of the candidates thesis. I recommend its publication.
Kevin L. Rens
I would like to express my appreciation to Dr. Kevin L. Rens for his support and encouragement over the past years.
Thanks to Stephan Durham and Anu Ramaswami for taking the time to participate in my thesis committee.
I would also like to extend my gratitude to Nicole Ellison and Nick Ereckson for assisting me in information gathering throughout this process.
Many thanks also to Neenan Company for their cooperation and patience with me on the Fort Collins Police Services Project.
Finally, I would like to thank my family, friends, and especially my wife Kristy for their support and sacrifices.
2.1 International Energy Conservation Code History...............8
2.2 Current Material Use Requirements...........................10
2.3 Industrial Impact of a Cement Replacement
2.4 Design Community Behavior...................................18
2.5 Environmental Sustainability................................19
3.1 Recycled Steel Requirement...................................25
3.2 Recycled Supplemental Cement Material in Concrete
3.3 Site Waste Disposal/Recycling Program Requirement...........28
4.1 Economic Issues.............................................32
4.2 Technical Issues............................................34
4.3 Contractor Issues
4.4 Structural Challenges........................................39
5. Previous Studies and Research..................................42
5.1 Previous Site Waste Management Program Case Studies..........42
5.2 Previous Case Studies of Fly Ash and Slag Use................61
5.3 Availability of Concrete Mixes with Supplemental Cement
6. New Case Studies (Fort Collins Police Services and Medical
Center of the Rockies).......................................97
6.1 Recycled Steel Criteria (Fort Collins Police Services)......101
6.2 Recycled Supplemental Cement Material Criteria
(Fort Collins Police Services)..............................102
6.3 Recycled Cementitious requirement effect on cost and schedule... 104
6.4 Structural Performance of High Volume Fly Ash Concrete (Fort
Collins Police Services)....................................106
6.5 Waste Disposal/Recycling Program Criteria (Fort Collins Police Services and
Medical Center of the Rockies)..............................109
6.6 Waste Recycling Achievements (Fort Collins Police Services
and Medical Center of the Rockies)..........................112
6.7 Waste Management Program Effect on Cost and Schedule
(Fort Collins Police Services)..............................116
6.8 Energy Conservation Analysis (Fort Collins Police Project)
7.0 Proposed Code Requirements..................................123
7.1 First Code Development Cycle Waste Management Proposal....123
7.2 Second Code Development Cycle Waste Management
7.3 First and Second Code Development Cycle
Supplemental Cement Use Proposal..........................126
7.4 Supporting Case Study Data for Code Additions.............127
7.5 Code Acceptance Requirements..............................132
8. Summary and Conclusions...................................135
A. Medical Center of the Rockies LEED Scorecard............138
B. Fort Collins Police Services Case Study Data............141
C. BEES Analysis Data......................................161
D. Life 365 LCA Data for Previous Fly Ash Case Studies.....163
B. Previous Waste Management Case Studies..................183
C. Previous Fly Ash Use Case Studies.......................186
LIST OF FIGURES
1. World Production of Hydraulic Cement by Region.......................6
2. Annual Coal Combustion Waste Product Use In the U.S..................16
3. World Population 1950-2050............................................22
4. U.S. Population Projected Growth 2000-2100...........................23
5. U.S. Coal Mines and Facilities.......................................35
6. United States Western Region Coal Fired Power Plants.................36
7. Building Material Flow Diagram........................................45
8. Recycled Materials (% of Total Wastestream)..........................60
9. Cost of Recycling vs. Landfilling....................................61
10. BEES Analysis of Embodied Energy for Concrete Mixes
with 0%, 15%, and 20% Fly Ash......................................66
11. BEES Analysis of CCF Release for Concrete Mixes
with 0%, 15%, and 20% Fly Ash......................................67
12. Fort Collins Police Services Rendering...............................99
13. Medical Center of the Rockies Aerial View During Construction........101
14. Grade Walls Poured with 20% Fly Ash Concrete. (Fort Collins Police
15. Core Wall Construction (Fort Collins Police Services)................107
16. Drilled Pier (Fort Collins Police Services)..........................108
17. Recycling Bins (Fort Collins Police Services)......................110
18. Recycling Bins Labeled by Material Type
(Medical Center of the Rockies).....................................112
19. Concrete Wash Out Area (Fort Collins Police Services)..............114
20. Concrete Embodied Energy Analysis (Fort Collins Police Services
21. Concrete CO2 Release Analysis (Fort Collins Police Services BEES
22. Percent Recycled Projects Over 30,000 Square Feet.................124
23. Percent Recycled Projects Under 30,000 Square Feet................125
B.l Fort Collins Police Drilled Pier Concrete Mix Design................144
B.2 Fort Collins Police Drilled Pier Concrete Field Test Data...........144
B.3 Fort Collins Police Site Work Concrete Mix Design...................145
B.4 Fort Collins Police Site Work Concrete Field Test Data..............145
B.5 Fort Collins Police Drilled Slab on Deck Concrete Mix Design........146
B.6 Fort Collins Police Slab on Deck Concrete Field Test Data...........146
B.7 Fort Collins Police Interior Slab on Grade Concrete Mix.............147
B.8 Fort Collins Police Interior Slab on Grade Concrete Field Test......147
B.9 Fort Collins Police Walls and Columns Concrete Mix Design...........148
B. 10 Fort Collins Police Walls and Columns Concrete Field Test.........148
B. 11 Life 365 LCA Analysis Output (Fort Collins Police Services
100% Portland cement Concrete)....................................159
B. 12 Life 365 LCA Analysis Output (Fort Collins Police Services
20% Fly Ash Concrete)............................................160
C. l Concrete Mix CO: Release Analysis Comparison....................161
C. 2 Concrete Mix Embodied Energy Analysis Comparison..................162
D. 1 Life 365 LCA Analysis Output (Little Mountain 0% Fly Ash
D.2 Life 365 LCA Analysis Output (Little Mountain Reservoir
40% Fly Ash Concrete)..............................................165
D.3 Life 365 LCA Analysis Output (Little Mountain Reservoir
50% Fly Ash Concrete)..............................................166
D.4 Life 365 LCA Analysis Output (Bayview High Rise
0% Fly Ash Concrete)...............................................167
D.5 Life 365 LCA Analysis Output (Bayview High Rise
20% Fly Ash Concrete)..............................................168
D.6 Life 365 LCA Analysis Output (Bayview High Rise
33% Fly Ash Concrete)..............................................169
D.7 Life 365 LCA Analysis Output (Government of Canada Building
0% Fly Ash Concrete)...............................................170
D.8 Life 365 LCA Analysis Output (Government of Canada
25% Fly Ash Concrete)..............................................171
D.9 Life 365 LCA Analysis Output (BC Gas 0% Fly Ash Concrete)...........172
D.10 Life 365 LCA Analysis Output (BC Gas 20% Fly Ash Concrete).........173
D.l 1 Life 365 LCA Analysis Output (BC Gas 40% Fly Ash Concrete)........174
D.12 Life 365 LCA Analysis Output (Two Folsom 0% Fly Ash Concrete)... 175
D. 13 Life 365 LCA Analysis Output (Two Folsom 33% Fly Ash Concrete).. 176
LIST OF TABLES
1. State Initiatives for Sustainable Construction of Government Funded
2. Construction and Demolition Material Break Down...................44
3. Waste Management Case Study Review List...........................47
4. Concrete Mix Designs for Little Mountain Reservoir................70
5. Table 5 Durability and Permeability Properties for
Little Mountain Reservoir.........................................71
6. Life 365 Life Cycle Cost Analysis (Little Mountain Reservoir)....72
7. Concrete Mix Designs for the Bayview at Coal Harbour High Rise
8. Fly Ash Use for the The Bayview at Coal Harbour High Rise
9. Compressive Strength Averages for 15% and 50% Fly Ash Mix
10. Life 365 Life Cycle Cost Analysis (Bayview High Rise Apartment)...78
11. Trial Concrete Mix Designs for the Government of Canada Building..79
12. Compressive Strength Test Result Summary for the Government
of Canada Building................................................80
13. Set Time for Trial Mixes for the Government of Canada Building....81
14. Life 365 Life Cycle Cost Analysis (Government of Canada Building).82
15. Concrete Pour Data for the BC Gas Operations Center Construction......85
16. Life 365 Life Cycle Cost Analysis (BC Gas Operations Centre)..........86
17. Concrete data for the Two Folsom Project..............................87
18. Life 365 Life Cycle Cost Analysis (Two Folsom)........................88
19. Concrete mix designs for the University of Colorado at Denver Study...90
20. Concrete Mix Compressive Strength Test Results for the University
of Colorado at Denver Study...........................................91
21. Previous Fly Ash Case Studies Summary................................93
22. LEED Materials & Resources Point Summaries
for Fort Collins Police Services and Medical Center of the Rockies..98
23. Life 365 Life Cycle Cost Analysis (Fort Collins Police Services).....106
24. Waste Recycling Statistics for Fort Collins Police Services From
Start of Construction through August 2006...........................113
25. Waste Recycling Statistics for Medical Center of the Rockies
From Start of Construction through December 2005......................115
26. Waste Management Cost Data (Fort Collins Police Services)............117
27. Fort Collins Police Services Concrete Analysis Summary...............121
28. Proposed Supplemental Cement Material (SCM) Requirements.............126
A. l LEED Scorecard as of June 2006 (Medical Center of the Rockies).......138
B. l LEED Scorecard as of October 2006 (Fort Collins Police Services).....141
B.2 Fort Collins Police Services Concrete Test Results....................149
The current International Energy Conservation Code (IECC) addresses the design of energy-efficient building envelopes, and installation of energy efficient mechanical, lighting and power systems through requirements emphasizing performance (IECC, 2003). There is no mention of material use in this description. In the preface to the code, the following quote is found. The International Energy Conservation Code, in this 2003 edition is designed to meet these needs through model code regulations that will result in the optimal utilization of fossil fuel and nondepletable resources in all communities, large and small. Why does this code fail to address one of the largest energy waste contributors in the construction industry? Why are non-renewable resource conservation issues not included in our building codes? The non-sustainability of the present rate of resource consumption, and the environmental effects from raw material extraction, dictate that changes need to be made sooner rather than later.
So, what needs to be considered in developing enforceable criteria that change the behavior of the construction industry? Standards can be developed and included in International Codes to compliment programs such as Leadership in Energy & Environmental Design (LEED) in enforcing a change in the way industry approaches material use. This thesis investigates, through case studies
and research, the obstacles and benefits of requiring recycled structural materials in building construction and requiring waste management programs on construction sites to conserve energy and benefit the environment.
LEED is a credit based rating system which incorporates sustainable construction into a complete building design approach. LEED is overseen by the United States Green Building Council (USGBC), which is a coalition of business and academic professionals, in all sectors of the building industry. LEED is a relatively new system that has grown tremendously in the past 10 years and includes 2,969 registered building projects as of March 2006 (HPAC, 2006). LEED certification is achieved by registering with the USGBC, and satisfying prerequisites and standard criteria for the level of certification desired. The levels of certification out of 69 maximum points are as follows:
Certified (28 32 points)
Silver (33 38 points)
Gold (39 51 points)
Platinum (52 69 points)
The LEED point categories and possible available points in each are as follows:
Sustainable Sites (14 points)
Water Efficiency (5 points)
Energy & Atmosphere (17 points)
Material & Resources (13 points)
Indoor Environmental Quality (15 points)
Innovation & Design Process (5 points)
The USGBC certification committee completes a review of substantiated data in a required format from the project to determine the level of certification met (USGBC, 2004). Examples of actual LEED checklists are shown in Tables A.l and B.l in the appendix.
LEED requires recycled materials be used to earn certain points towards certification. The owner can decide weather to pursue these particular points on a project pursuing certification. There are many other areas in which a building can achieve different levels of LEED certification without resorting to recycled material use. Materials and resources make up 20% of the total available points (USBGC, 2005). The only prerequisite for recycled material use on a LEED certified project is storage and collection of recyclables on site. This will be discussed later. The LEED system almost always achieves some material recycling or reuse in the certification process. However, there are many opportunities for recycled material use which are ignored due to material preference, lack of initiative, or ignorance. This falls on the design team, owner, and contractor to various degrees depending on the project. LEED project success is based on a point system. Once a certification level goal is decided, and the particular points to be achieved are identified, all other potential energy saving ideas may be ignored.
Environmental sustainability is a relatively new movement in modem building construction in North America. Research and interest in this topic has
grown rapidly in the last two decades. Building codes have been very slow in incorporating sustainable building material use and building practices. While LEED has been instrumental in bringing about change in the building industry, it remains voluntary in the private sector where it is relatively seldom used. LEED also has many loopholes in material use which allows the contractor and owner to step around certain potentially environmentally beneficial material use choices. Any actual or perceived potential added cost is met with great resistance. However, incorporating requirements into building codes would force owners, designers, and contractors to address this issue. First, requirements have to be developed that are reasonable to implement, with little potential for added cost, and significant enough to have a measurable effect on environmental sustainability. Any proposed requirements need to be gradual.
Two main objectives for this thesis are to propose well substantiated:
Partial cement replacement requirements for inclusion into the IECC.
Waste management requirements for inclusion into the IECC.
Cement does not account for a large proportion of the energy used in the lifetime of a building structure. The embodied energy of structural materials accounts for only about 10% of a buildings life time energy consumption (ISE, 1999). The embodied energy includes the energy consumed by all of the processes used to extract, process, manufacture, and implement the use of the product. The majority of this energy is in the form of fossil fuels. Buildings account for over 30% of the raw materials used in the United States and approximately 30% of the solid waste stream (EPA, 2006). Most importantly, the construction and operation of buildings account for approximately 30% of the greenhouse gas emissions released into the atmosphere each year in the U.S.
(EPA, 2006). Altogether, approximately one ton of carbon dioxide is released into the atmosphere for every ton of cement produced. There is approximately 1.5 billion tons of cement produced every year worldwide. This constitutes 7 to 8 percent of all of the carbon dioxide produced annually worldwide (Shell, 2001). The demand for cement production is expected to double within 25 years due to the expected acceleration of development and rapid population growth of many third world countries. This current growth trend is shown in Figure 1. This
includes China, which produces approximately one third of the Worlds cement alone (Mehta, 1998). Reducing cement production by supplementing concrete mix designs with recycled materials, such as fly ash and slag, would have a major impact on the global warming problem.
1930 1940 1950 1960 1970 1980 1990 2000 2002 2004
Figure 1 World Production of Hydraulic Cement by Region.
The Environmental Protection Agency (EPA) introduced a new initiative titled Coal Combustion Products Partnership which promotes fly ash and slag use (EPA, 2006). The EPA does not classify fly ash or slag as a hazardous waste. However, there is some concern in the agency over the threat fly ash poses to groundwater. This is because approximately 70% of fly ash generated ends up as waste in special dedicated landfills (DOE, 2006). Stock piles of fly ash can leach
out trace amounts of harmful elements (Reiner, 2006). Fly ash and ground-granulated blast furnace slag are already commonly used in standard concrete mixes throughout the world. Concrete producers typically keep the amount of fly ash and slag low (10% to 20%) to avoid required modification of current field practices for concrete placement, and due to direction from designers and contractors. The maximum level of cement replacement typically used for standard concrete mixes in North America is in the range of 30% for fly ash and 35% for slag. Very often, no recycled material such as ash or slag is used in the mix despite efforts by the EPA to promote its use.
The chemical composition of fly ash is very similar to Portland cement, with the difference between the two being the relative amounts of compounds in each. The American Standard for Testing Materials (ASTM) contains two classes of fly ash used in concrete in the United States. These are Class F and Class C. Class F fly ash must have more than 70% of silica, alumina, and iron oxide while Class C must have at least 50% of these oxides according to ASTM C 618 (2005). However, fly ash mineralogy and particle size have a much greater effect on concrete properties than does the chemistry (Mehta, 1998). The amount of calcium in the fly ash is much more significant than the oxides noted above.
Class C usually has higher early strength due to its higher levels of calcium oxide, while Class F fly ash tends to offer more resistance to sulfate attack, and typically has higher long term compressive strength (Mehta, 1998).
Current American Concrete Institute (ACI) and Canadian Standards
Association (CSA) specifications place no maximum limit on fly ash or slag use in concrete mixes unless the mix is to be used for elements that will be exposed to salts or deicers. For these applications, fly ash is limited to 25% and slag 50%. The International Building Code (IBC, 2003) has the same requirements. Lack of direction on fly ash and slag use in concrete is an impediment to concrete sustainability.
2.1 International Energy Conservation Code History
In order to propose a policy change to the IECC, some background on where the original version of the code came from is useful. The first energy conservation code to be used nationwide in the United States grew out of the international energy crisis of the early 1970s. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) published ASHRAE Standard 90-75 Energy Conservation in New Building Design in 1975, and revised in 1977 (Heldenbrand, 1999). The original report was later published as the Model Energy Code by the Council of American Building Officials (CABO) in 1977 (Heldenbrand, 1999). This original energy conservation code has only recently been turned over to the IECC. CABO assigned all rights and responsibilities to the International Code Council (ICC), which published the first version on the IECC in 1998. The ICC has three statutory members: Building
Officials and Code Administrators International, Inc., International Conference of
Building Officials, and Southern Building Code Congress International. The consolidation of these three bodies into the ICC is pending. The code has continued to be developed and maintained by the ICC since 1998. The code became part of the International Code Family developed and published in 2000.
There are now 14 different building codes in the International Code Family. Each of these 14 codes addresses a different aspect of building design and construction. For example, there is an International Residential Code, and International Electrical Code, and so on. These codes have become the standard in building design in the United States. The focus of this thesis is the International Energy Conservation Code. This code was chosen because building material conservation results in the conservation of energy, which benefits the environment. This code seems to be the most relevant, as none of the other codes include sustainable construction policy in their content.
The International Code Family includes these 14 building codes:
International Building Code
International Residential Code
International Fire Code
International Plumbing Code
International Mechanical Code
International Fuel Gas Code
International Energy Conservation Code
International Private Sewage Code
International Performance Code
International Code Council Electrical Administration
International Property Maintenance Code
International Zoning Code
International Existing Buildings Code
International Wildland-Urban Interface Code
2.2 Current Material Use Requirements
Currently there are no recycled material use requirements in the International Building Codes or any of the material codes such as the ACI.
ASTM Cl 157 (2003) does not place any restrictions on the amount or type of cement or ash material used for concrete mixes. This ASTM standard is a performance specification covering hydraulic cements for both general and special applications. Cement is classified by type (Type I, II, III, IV, or V) based on specific requirements for general use, high early strength, sulfate attack resistance, heat of hydration, and low reactivity with alkali-reactive aggregates. ASTM C618 (2005) states that the optimum amount of fly ash is project specific, and to be established by testing. No limits are stated in this standard. ASTM C595 (2005) limits the amount of pozzolan (fly ash) in cement to 40 percent by mass.
The use of recycled or otherwise low impact construction materials is totally voluntary in most jurisdictions. There are several jurisdictions which have implemented requirements as mentioned above. However, these are in the minority. There are only 16 states with comprehensive green building initiatives in the public sector as shown in Table 1 (Pew, 2006). There were approximately
2,969 building projects registered with LEED nationwide as of March 2006. Not all registered projects achieve certification.
Table 1 State Initiatives for Sustainable Construction of Government
Funded I uildings (PEW, 200< 5)
State Initiative State Initiative
Arizona LEED Required Michigan LEED Required
Arkansas LEED or Green Globes Recommended New Mexico LEED Required
California LEED Required New Jersey LEED Recommended
Colorado LEED Required New York LEED Recommended
Connecticut LEED Required Rhode Island LEED Required
Hawaii LEED Required Pennsylvania LEED Recommended
Maine LEED Required Washington LEED Required
Maryland LEED Required Green Globes Req. Wisconsin LEED Required
While green building initiatives are growing nationwide, practices vary widely. Implementation of green building practices was much more common for public construction projects, while the majority of construction is in the private sector. For example, 30% of the 2,969 registered projects were government projects (HPAC, 2006). The EPA now requires all new government buildings to obtain LEED certification (EPA, 2006). Many city and state governments have this requirement as well. Cities such as Denver. Colorado and Seattle, Washington now require new government buildings over a certain size to achieve a Silver level of LEED certification. Seattle requires LEED certification for government buildings over 5,000 square feet. Denver requires LEED for all new government
buildings. The growth of LEED participation is being greatly aided by public entities.
2.3 Industrial Impact of a Cement Replacement Requirement
Industrial activities have long been the subject of criticism for environmental matters. Industry as relates to this thesis included all companies that contribute directly to the extraction, production and construction of buildings. Again, the focus of this study was primarily those which contribute to steel and concrete structures. These being the most commonly used non-renewable structural materials used in the construction of buildings. Some examples of these industries are mining, chemical producers, steel producers, concrete suppliers, pre-cast concrete manufacturers, and construction companies. Industry is very organized and influential to the building codes content. Any attempt to get structural material requirements into the IECC would have to consider the impact to industry. Industries will most certainly be involved in the review and final content of any added provisions.
Industries involved in the production of concrete were of primary concern to this thesis. The proposed goal was to research the minimum requirement for recycled material use in concrete as a replacement for a portion of the cement. Such a requirement would impact several industries. Obviously this would impact the concrete suppliers and the construction companies. Less obviously
this would impact certain mining and chemical companies as well. The pre-cast concrete industry would also be affected greatly by such a requirement. Some of these potential impacts are discussed further below.
The chemical industry is mainly involved with admixtures in concrete mixes. The amount of fly ash, slag or other recycled material affects the chemistry of the mix. Concrete admixtures are placed in one of five categories. These are air entraining, accelerating, water reducing and set controlling, flowing concrete admixtures, and finally miscellaneous. For example, when fly ash is added to a concrete mix, the silica in the fly ash reacts with the calcium hydroxide crystals on the concrete aggregate. The product of this reaction is a calcium silicate hydrate paste which results in concrete that is less permeable and more durable (Mehta, 1998). However, this same reaction also slows the set up time somewhat, and reduces the bleed water available for finishing. Chemical admixtures are introduced in carefully designed mixes to remedy these issues.
The type and quantity of admixtures depends on the desired mix properties and the characteristics of the other mix ingredients such as the cement, sand, and aggregates. One common type of admixture used is a superplasticizer to increase the workability of the mix for the lower water content. These can be relatively expensive. The addition of a partial cement replacement requirement to the building codes would not adversely affect the chemical producers financially, nor would it cause a switch towards a proprietary product. There are several concrete
mix companies with proprietary mixes of their own with high volumes of fly ash. Most proprietary mixes include at least one chemical admixture already. The added material requirement could only cause an increase in use of these admixtures, if any change at all. Some examples of current proprietary mixes in use are the Lafarge Corporations Agila mix and Aggregate Industrys Delvo hydration stabilization mix. Both of these mixes have one or more proprietary chemical admixture. Chemical companies are very reluctant to publicize chemical admixture constituents or manufacturing processes. For this reason, it is difficult to calculate the effect chemical admixture production has on the overall energy savings of fly ash and slag use in concrete. However, chemical admixtures are used in small quantities, typically constituting only .005% to .2% of the total concrete mass. For this reason, the embodied energy of the admixtures does not significantly affect the total embodied energy of the mix. Therefore, mineral admixture use in concrete, such as fly ash and slag, greatly reduces the total embodied energy of concrete, even when additional chemical admixtures are introduced. The introduction of chemical admixtures can offset the cost savings of using fly ash and slag to some degree. The environmental effects of increased chemical admixture use seem to be minimal due to the inert nature of concrete once cured. Superplasticizers (water reducing admixtures) are the most commonly used for concrete mixes containing fly ash or slag. There has been some concern over the potential release of formaldehyde from these
admixtures. However, the amounts are considered very small and insignificant by the EPA. The main constituents in this type of admixture are lignosulphonates, melamine sulphonates, naphthalene sulphonates, and polycarboxylates. None of these constituents have been labeled acutely toxic (Deutsche Bauchemie, 2005).
The mining industry is responsible for the extraction of coal for coal fired electric power plant use. Coal extraction and production increases in the United States each year and is expected to continue increasing in the future. For example, 1,114 million tons of coal was produced in the United States in 2005.
In 1995 the production was 1,032 million tons and 883.6 million tons in 1985 (NMA, 2005). A decline in coal production in the United States is not anticipated for many years according to the U.S. Geological Survey, which predicts this to occur sometime late this century.
Fly ash is produced as a byproduct of burning coal for electric power production. The amount of fly ash produced from burning coal is around 55 to 60 million tons per year in the United States. Only around 30% of this fly ash gets used (DOE, 2006). The remaining ash is deposited in landfills creating environmental concerns. Figure 2 shows the disparity between coal combustion product (CCP) production and recycling. There was an estimated 600 million tons of fly ash produced worldwide in 2000 (Malhotra, 1999).
Produced Landfilled Produced Recycled Recycled Coal Combustion Waste Product
Figure 2 Annual Coal Combustion Waste Product Use in the U.S.
A building code requirement which increases fly ash demand would be favorable to the mining and electric power industries, creating a demand for this waste, and saving disposal costs. The main obstacle to providing fly ash to the concrete industry is temporary storage, and adequate distribution of the useful fly ash to the demand locations. This will be discussed more in section 4.2. The iron ore mining industry would also have favorable consequences from such a requirement since slag can also be used to replace cement. Blast furnace slag is a byproduct of steel production form Iron Ore. A demand for this waste product would be favorable to both the mining and steel industries. An increase in demand would result in an increase in cost, if fly ash and slag production growth does not keep up with increases in demand. However, cement currently is substantially more expensive than these products. A rise in cement replacement product prices would not necessarily increase the cost of concrete. The key would
be to keep the requirement levels of fly ash and slag modest at first to ease the transition.
The greatest impact of a partial cement replacement requirement would be on the concrete industry itself. This includes the concrete mix producers as well as the pre-cast industry. Large commercial producers of concrete such as LaFarge and Aggregate Industries already produce and market high volume fly ash mixes. Fly ash is already used quite commonly in standard concrete mixes worldwide to varying degrees. A minimum recycled materials requirement would force concrete producers to adjust their business models somewhat. Concrete producers would have to develop more dependent and streamlined relationships with fly ash and slag producers. This would result in more industrial waste recycling due to the increased demand.
The pre-cast industry would stand to benefit from a partial cement replacement requirement. The pre-cast industry has an advantage over the ready mix industry in that pre-cast concrete is placed in a more controlled environment which leads to greater material and energy efficiency. The drawback of increased curing times for fly ash and slag use is of much less concern to pre-cast manufacturers than it is to ready mix producers. This is because delayed set times can cause costly delays in construction schedules for cast-in-place concrete, where as this is a more addressable concern for the more flexible pre-cast manufacturing plant operations. Additional storage area can usually be found to
accommodate larger numbers of pre-cast concrete elements undergoing the curing process. Fly ash and slag use levels proposed in this thesis are low enough to avoid significant set up time delay issues for pre-cast manufacturing.
2.4 Design Community Behavior
The building design community is an integral part of the construction process. This community includes architects, structural, mechanical, electrical and civil engineers as well as other landscaping and interior design professionals. This thesis involves structural building materials only. Therefore, only the architectural, structural engineering and civil engineering disciplines are discussed.
The design community is charged with all aspects of design and material specification for building projects. These design disciplines are also very involved in construction administration in conjunction with the general contractor. There is great potential for architects and engineers to affect change in how buildings are constructed. The LEED organization was founded by the design community. However, few design professionals are willing to devote time out of the project design budget to voluntarily incorporate sustainable material requirements. This typically only occurs when owner driven. The owner needs to be educated on life cycle costs in order for this to occur. The design team can justify costs to the owners by completing life cycle cost analyses. However, this
takes extra time and expertise, cutting into profitability of design firms working with a fixed budget. Additional fee would often be required for this service to be completed. Owners tend to look only at first cost, which can work against sustainable initiatives. If requirements were included in the building code, these issues would be addressed on every project. The percentage of new building projects using the LEED system is very small. There were only 337 LEED certified (2969 registered) buildings worldwide as of September 2006 (HPAC, 2006). This number is growing rapidly, but has a long way to go before being a significant contributor to global environmental sustainability.
2.5 Environmental Sustainability
Human activity is the primary cause of the recent global warming according to most climate scientists. The EPA agrees that the Earths climate is warming, and human activity is largely the cause (EPA, 2006). This finding has recently been further substantiated by a study of glacier melting in Greenland headed by Eric Rignot, a glaciologist with NASAs Jet Propulsion Laboratory at the California Institute of Technology. The results in this study were released in February 2006. It found that Greenland lost 22 cubic miles of ice in 1996 and 54 cubic miles in 2005. They found glacial melting has increased on average 28.5 percent in each of the last ten years (Roach, 2006). Glaciers all over the world are decreasing in size, or disappearing. For example, the glacier atop Mount
Kilimanjaro in Tanzania has decreased over 80% in size since 1912. This glacier is expected to disappear by 2015 (Lemonick, 2006). Another example is the damage to coral reefs around the globe. Studies have shown global warming is the main contributor to coral bleaching. About one third of the Worlds coral reefs have been severely damaged, and about half of the remaining reefs would be lost by 2030 if current trends continue (Diamond, 2005). This is significant since coral reefs are habitat for a disproportionate number of the Worlds marine species. At a 2005 conference in Exeter, England, a group of 200 leading climatologists agreed that as little as a 3.5 degree Fahrenheit average increase in the Earths surface temperature from pre-industrial levels would result in a risk of dangerous climate change. It was also noted that the planet Earth is already more than half way to this temperature change (Goodell, 2006). Nineteen of the twenty hottest years on record have occurred since the 1980s (Kluger, 2006). The carbon dioxide levels in the worlds atmosphere are the highest they have been in the last 650,000 years, and levels are increasing 200 times faster than at any time in that same period, according to the Intergovernmental Panel on Climate Change (Black, 2005). The dangers of climate change include local desertification, intense storms, and other drastic changes in ecosystems. The evidence supporting the relationship between human activity and global climate change is overwhelming.
In addition to climate change, the rate of raw material extraction is on a non-sustainable pace according to most environmental scientists. For example, one quarter of the Earths remaining forests will be converted to other uses within the next 50 years at present rates (Diamond, 2005). Diamond also notes that the worlds major energy sources of readily accessible oil, natural gas, and coal will be depleted within a few decades. Further reserves will be deeper underground and increasingly expensive to extract resulting in more environmental costs. This includes aggregate for concrete. For example, sand and gravel operations continue to move farther away from city centers in the United States. This is due to several factors including aggregate depletion (Reiner, 2006).
This is just a small sample of the overwhelming evidence of global climate change and environmental degradation reported by scientists worldwide. With the worlds ever increasing population and the growth of third world economies towards first world economic consumption levels, extraction levels and environmental impacts will only increase worldwide in the future. Figure 3 shows that the Worlds population is expected to increase another 50% surpassing 9 billion by the year 2050 (U.S. Census, 2006). The U.S. population has doubled in size since 1950, and is expected to continue to grow well into the future as shown in Figure 4 (U.S. Census, 2006). So what can be done to affect change in the course of the environments deterioration? With the magnitude of impact
building construction has on our environment, changes in building codes can have a substantial future benefit.
World Population: 1950-2050
1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050
Source: U.S. Census Bureau, International Data Base, April 2005 version.
Figure 3 World Population 1950-2050
(In millions) 600 -r-
Figure 4 U.S. Population Projected Growth 2000-2100
Adding structural material requirements would decrease the impact of building construction on the environment in two major ways. First, replacing cement and other energy intensive materials with recycled materials will reduce greenhouse gases and conserve energy and water. Fly ash reduces the amount of water required in a concrete mix by 2% to 10% depending on the amount of ash used. Second, construction and demolition waste recycling will reduce landfill flow and provide construction material producers with additional resources for manufacturing new materials. This also conserves energy and reduces the level of virgin material extraction. With building construction accounting for over 30 percent of raw material extraction in the United States, and cement production accounting for 7 to 8 percent of annual CO2 emissions worldwide (Shell. 2001), requirements such as those described above would have a significant benefit to society.
The ultimate goal of this thesis was to contribute to encouraging the construction industry to be sustainable and non-threatening to our environment.
In order to achieve this goal, some practical well substantiated objectives had to be met.
The first objective was to propose a recycled partial cement replacement requirement. Even a small amount of required material, such as 5%, would make a very significant difference in the carbon footprint of concrete production. For example, when the local Denver building code allows 0% to 20% fly ash in place of cement, the majority of contractors choose not to incorporate fly ash at all. A different message would be sent as to sustainable material use, if the requirement was 5% to 20% rather than the 0% to 20% requirement.
The second objective was to get some basic sustainable structural building material requirements, such as recycling, into the IECC. The materials focused on were steel and concrete. Steel and concrete are the two most commonly used building materials next to wood. Recycled wood products can not be used for typical wood saw cut lumber. Therefore, a recycled wood requirement was not proposed in this thesis. However, recycled wood is used to make wood chips which are used to make structural wood products such as oriented strand board
and glue laminated beams. Wood waste accounts for approximately 17% of the total waste placed in landfills in the United States (EPA, 2005). Also, wood is a renewable resource. A certified wood requirement would certainly further the larger goals of this study. The largest and most respected of these certifications is the Forest Stewardship Council label. The Forest Stewardship Council is an international non-profit organization which oversees certification of forest land.
Achievement of these two objectives would increase energy and material conservation from the volunteering minority to a mandatory majority. These requirements will have to be included into codes eventually. The present practices are not sustainable as previously discussed. The sooner society forces these changes to take place, the higher the quality of life will be provided for future generations, and the less problematic the situation will become. These environmental problems will resolve themselves in one way or another.
However, an orderly and gradual resolution, in lieu of allowing the resolution to occur catastrophically in the future is more desirable
3.1 Recycled Steel Requirement
A possible recycled steel requirement was investigated to determine the feasibility of including a minimum percentage recycled steel content requirement for structural steel members. In order for such a requirement to be considered for adoption into the International Code, there would have to be a benefit to such a
provision. Steel is already the most recycled material in North America. The rate of recycled steel use for wide flange beams and plates is approximately 97.5% in North America and the average recycled steel percentage in reinforcing bars for concrete is approximately 63% (Steel Recycling Institute, 2005). Therefore, a recycled steel requirement would have little or no effect on the rate of recycled steel use for these members. The rate of recycled steel use is determined by the steel market and the two processes by which steel is made. Both processes use old steel to make new. These two processes are the Basic Oxygen Furnace (BOF), and the Electric Arc Furnace (EAF). The BOF process uses 25 to 35 percent recycled steel. The EAF process uses nearly 100% recycled steel (Steel Recycling Institute, 2005). These two processes complement each other in the market place. The EAF process relies on steel created from the BOF process, since the BOF process brings in new steel material to the cycle to account for the growth of steel in use. Because recycled steel use is inherent to the method of production, it does not make sense to apply a recycled steel content requirement to the building codes. However, it does make sense to require steel waste to be salvaged and recycled from construction and demolition. Because nearly all steel can be reused to make new steel with an economic benefit to all parties involved, a waste management program requirement for steel would be easy to implement. The use of scrap steel to make new steel is much cheaper and energy efficient than mining virgin ore. There is not enough scrap in the market place to supply
enough steel based on steel use worldwide. Thus, it is still necessary to continue to mine virgin ore to make new steel. There will be no recycled steel use requirement pursued in this study for these reasons. The LEED program includes recycled steel use in the recycled material use credit. Steel is a good example of a successful sustainable building material.
3.2 Recycled Supplemental Cement Material in Concrete Requirement
The first objective, as it pertains to supplemental cement material (SCM) use in concrete, was to determine optimum requirements based on sustainability, performance, availability, and cost. These requirements must also be acceptable to the International Code Committee, and stand up to rigorous resistance and multiple arguments against code inclusion. Because the International Energy Conservation Code was the target of proposals developed in this study, new requirements must be shown to adequately conserve energy. The proposal must be specific enough to be defended against potential arguments against it. The best way to do this was to break down each potential argument and provide statistical and anecdotal evidence convincing enough to merit serious consideration. The proposal was a relatively modest use of SCMs in concrete mix designs in order to introduce these types of requirements into the code gradually allowing time for industry adjustment.
3.3 Site Waste Disposal/Recycling Program Requirement
The second objective was to introduce a potential waste management program requirement that could be added to the building codes. The recycling of construction and demolition waste conserves energy by saving energy used to extract, transport, and produce virgin material for new products. This is even true when the energy used to transport and reprocess the recycled waste is taken into consideration (Sheehan, 2001). Waste recycling and reuse also saves raw materials and landfill space. The 20 previous case studies reviewed, and the 2 new case studies developed show that waste management programs are successful, cost effective, and relatively easy to implement.
There is an abundance of case studies and information reports that show overwhelmingly waste management programs significantly reduce energy use and resource extraction while reducing landfill waste streams. Most studies also show an economic benefit to these programs. This thesis does not attempt to collect and summarize this mountain of data. Most of this information is readily available in libraries and on the internet. This thesis focused on 20 case studies for a base of information to determine optimum waste management requirements for inclusion into the International Energy Conservation Code.
Several obstacles were identified that interfere, or prevent energy conservation measures from taking place in building construction. The State of California recently implemented a study to identify what needs to be done to facilitate more green building practices in the State. The California Integrated Waste Management Board (CIWMB) oversaw this study completed by Strategies Inc. and VITETTA Public Management Consulting. This was a far reaching and in depth study involving California State and local regulators, designers, developers and contractors. This study found several obstacles to building green. The three most popular reasons for not building green were ignorance by the owner or developer, lack of financial incentive for the builder, and lack of product information and resources (Davis, 2001).
Most owners are not educated about sustainable construction practices and materials. This is a serious obstacle because most projects which attempt to implement sustainable construction practices do so in response to the owners request. The owner is not likely to push for energy conserving measures in construction unless he or she has some knowledge of the benefits and costs for doing this. Participants in the California study identified the following evidence as required to convince owners to build green; case studies of green material use,
environmental effects resulting from building construction and operations, capital and operating costs for different green features, and the effect of green building construction on occupant productivity (Davis, 2001). In addition, education on life cycle cost is needed. The complexity of todays building codes increase the confusion in the industry. Interpretation of vague code provisions can often hinder the implementation of sustainable construction practices. Another impediment identified in this study was lack of information on green building products. Participants surveyed in the study commonly stated that unavailable information on such products often forced projects to depend on specialized consultants, which adds to project cost. Participants identified high volume fly ash concrete as a green building material that often is abandoned due to ignorance of builders and building officials. However, the study found that once a product became well known, it had few problems being utilized (Davis, 2001).
While nearly all case studies and research shows that building green is cost effective for the end user or owner, there is little or no cost benefit to the builder. The builder often has even higher cost than for typical construction, since almost all of the added cost is up front on a project. The economic benefit seen by the owner is accrued over time. For example, optimizing energy performance of the building would result in energy cost savings over the life of the structure. Much of the added up front cost is paid by the contractor and not passed on to the owner. The owner is often not willing to fully compensate a
builder to include things like a waste management program or less available green" building materials. The cost of setting up a recycling program, or the added time in the schedule to find the best building materials is usually not met with an increase in money to the contractor from the owner. Transferring economic benefit to the contractor for first time costs needs to be addressed.
Product information for sustainable building products is not well marketed, or easy to locate according to responses of participants in the study. A consequence of this is skepticism by owners and contractors resulting in low use of these types of products. High fly ash content concrete was noted as a good example of a green building material that is under utilized due to this ignorance of sustainable building products (Davis, 2001).
Solutions to these obstacles noted in the California study included public grants, marketing efforts, tax subsidies for builders and even fast track permitting for green projects. If certain high impact sustainable building requirements were clearly stated in the building code, many of these problems would be alleviated. Confusion over building code provisions would be reduced. The building design and construction process would not rely as heavily on owner initiative.
Provisions clearly defined in the building code would cause green building practices to go mainstream. An effective solution to lack of owner initiative is often owner education. The owner needs to be educated on sustainable building tactics and life cycle cost analysis of the various options. This type of education
could potentially be provided by government, community organizations, or the local design community.
4,1 Economic Issues
One of the main requirements for proposal acceptance into the International Codes, is that it shall not necessarily increase cost (IECC, 2003). The cost issues are different for waste management programs than they are for SCM requirements. Costs can be incurred by many different players in the building industry when new requirements are to be met. The most common argument against requiring waste management programs on construction sites is the cost and time involved in the initial organization and set up (Davis, 2001). Some localities have readily available recycling companies that can quickly get a site set up for recycling, and find end uses for the materials. However, some regions of the country have very modest support systems recycling of construction waste. For instance, the LEED case study for the Colorado Courts project in Santa Monica, California noted that an estimated $10,000 premium was paid by the city to have construction waste recycled (USGBC, 2003). This case study will be further discussed in section 5. To defend against this argument, any new proposal must take this into consideration. Once included as a building code requirement, waste recycling programs would become common place thus creating a new demand for recycling services. New demand would spark an
increase in the number of available recycling services in all regions where these new provisions are enforced. The good example was found in the State of California where construction site waste management programs are now mandatory for most localities to help meet the state mandated recycling requirement of 50% of all waste generated. Because of this requirement, California far exceeds other states in recycling service availability and recycling business entrepreneurship. The state of California diverted only 10% of its waste from the landfill in 1990. By mandating a 50% recycling goal to be reached over time, the state now recycles 52% of its waste and has grown the recycling industry into a very valuable part of the state economy (CIWMB, 2004). The waste management program proposed would need to start with a modest requirement that phases in more stringent recycling requirements over time allowing for the infrastructure to develop. This would minimize the up front cost while sparking initiative for increased recycling.
The economic studies behind the use of supplemental cement materials in concrete have generally shown that fly ash and slag are less expensive than cement. However, this cost savings is very often not passed on to the contractor. The concrete mixes with fly ash or slag will usually cost the contractor the same as 100% Portland cement mixes. The potential for cost comes in with availability and effect on construction schedules. The issue of schedule is the number one cost factor. It has been shown in case studies researched here that fly ash use at
rates of 10% to 30% typically have an insignificant effect on early strength and set time, thus not affecting the construction. This will be discussed further in the section 5.
4.2 Technical Issues
The availability and quality of fly ash is very significant to viability of a potential fly ash use requirement. Coal fly ash producers have to be able to supply and distribute an adequate amount of the acceptable types of fly ash. Shortages do occur in the U.S. in certain regions under particular conditions. For example, the Centralia, Washington plant is the primary provider of fly ash for concrete in the Northwest region of the United States. Figures 5 and 6 illustrate the distribution of coal production and coal fired power plants in the western United States. When this plant has a temporary shut down, or problem with fly ash quality, it can greatly affect the ability of contractors in this region to meet fly ash requirements. Distribution of ash, slag, and cement are all dependent on train lines to some extent. Due to supply and distribution challenges, any proposed fly ash requirement would have to be somewhat modest and flexible. A requirement of 5% to 15% recycled supplemental cement materials requirement would be more reasonable rather than attempting to require more ambitious levels. Storage of fly ash is another issue that poses a challenge to enacting fly ash use requirements. It costs money to store fly ash between the time it is generated and
the time it is placed into a concrete mix. Due to the cycle of high and low levels of construction in the northern United States, the ability of power plants and concrete producers to store fly ash is critical to adequate distribution. Figures 5 and 6 show the distribution of coal activity in the U.S.
Figure 5 United States Coal Mines and Facilities (USGS, 2006)
In order for fly ash to get used efficiently, it must be stored or shipped to where construction activity remains high throughout the year in the southern regions of the country. This causes variations in price and quality for ready mix producers. The solution to this issue lies in the investment in infrastructure in the
industry as well as coordination and cooperation between the various power plants and concrete producers (ACAA, 2005).
Figure 6 United States Western Region Coal Fired Power Plants (Western Region Ash Group, 2006)
Fly ash quality is also a concern affecting fly ash supply. Recently enacted Federal regulations require a reduction in nitrous oxide emissions from coal fired power plants per the EPAs Title IV acid rain program resulting in more unburned carbon in the waste ash (EPA, 2005). Higher levels of carbon in fly ash make it less suitable for use in concrete (Buckley, 2005). There is
technology which can separate unbumed carbon from fly ash. However, this technology is relatively new and expensive to implement. New Federal regulations requiring reduced mercury emissions also affect fly ash quality for use in concrete. This ruling by the EPA was called the Clean Air Mercury Rule finalized in 2005 (EPA, 2005). There is also technology available for capturing mercury without increasing fly ash carbon content. However, this new technology is not required to be used currently, and is more expensive than older technology. (Buckley, 2005)
The final quality issue is the variability of coal ash based on origin and generation process. The western United States typically produces a higher quality ash for concrete use because of its lower sulfur and carbon content (Buckley, 2005). Another impediment is obtaining Class C ash versus Class F ash when the fly ash type is dictated by the project specifications. One idea to alleviate this problem is the use of hybrid ash containing a mixture of both ash classes. This would allow concrete producers to alleviate shortages of one ash type by supplementing it with the other. Hybrid ashes are not currently covered by ASTM, however these are being developed on a performance based standard (Buckley, 2005). Fly ash quality issues warrant flexibility in supplemental cement material type requirements.
4.3 Contractor Issues
Significant resistance will come from the construction industry on any potential code change. The contractor almost always bears the most hidden cost for new building policies or procedures. In order for a construction company to be profitable, the project must be run efficiently. Any new construction procedure or use of unfamiliar building materials can slow down the construction progress and add cost. This is the main point of resistance by the construction industry.
The superintendent on most any construction project will plan the job to be complete at the agreed on schedule at the least cost. Any additional research or set up is usually strongly resisted by the contractor unless mandated and paid for by the owner. If sustainable construction requirements were codified, owners would be forced to negotiate with contractors on these issues. The only added cost for implementing these types of requirements would be at the start of construction. As construction progresses, costs would be recouped by the savings involved in reducing the amount of waste to be hauled to the landfill, or the reduced cost of the concrete, for example. The construction industry is open to green building practices in most cases as long as their total cost on a project is not increased without compensation. When contractors feel assured they will not incur hidden costs, and have resources available to meet the expectations of the job, they will offer much less resistance to these types of changes.
4.4 Structural Challenges
There are many published studies documenting the structural performance of fly ash and slag as partial cement replacements in concrete. Fly ash has been shown to enhance workability and provide superior durability while creating a higher compressive strength mix long term (Mehta, 1998). The environmental benefits have already been stated. The structural performance differences causing issues between typical standard concrete mixes and mixes which contain fly ash or slag fall into four categories. These include scaling from exposure to deicers, delayed time of set, lower early strength, and finishing. All of these issues can be resolved with the proper concrete mix and placement. A cost savings is typically achieved for levels of fly ash that will be proposed in this study since fly ash and slag are less expensive than cement.
Much research has been completed on fly ash and slag use in concrete. Research shows that all of the four issues stated above can be resolved resulting in a mix with superior performance at less cost in most cases. Very few instances of structural problems have been shown to occur with typical fly ash use levels. These levels would be fly ash in the range of 15% of the total cement material. When fly ash levels exceeding this range are used, structural issues do arise if these mixes are not designed or implemented properly. The most significant structural issues for these mix designs are during construction. However, if fly
ash and slag levels are kept low enough for certain building elements, these problems can easily be avoided.
The first issue listed above is scaling from exposure to deicers. The International Building Code limits fly ash use to 25% for concrete which will be exposed to deicers or salt (ICC, 2003). When this requirement is followed, scaling is not a significant issue provided finishers use techniques suitable for fly ash concrete. Delayed time of set is probably the most difficult barrier to overcome in the use of supplemental cement materials. Problems with this issue can be avoided with a proper concrete mix design utilizing admixtures to decrease set time, or a reduction in the level of SCM's used for suspended concrete elements. Lower early strength can be dealt with in much the same way as the delayed set time issue. Strategic use of the high levels of fly ash in building elements where early strength is not critical, along with lower levels of fly ash where early strength is more critical, is also an effective strategy for mitigating this problem. Finishing difficulty is a complaint from contractors sometimes heard when a high volume fly ash mix is used for slabs. Fly ash concrete tends to have less bleed water, and therefore tends to stick to the trowel. Finishers are familiar with more bleed water at the surface of flatwork during finishing. Increased workability does not necessarily mean that it is easier to finish. Fly ash actually improves workability relative to a mix without fly ash at the same water cement ratio. This is due to the spherical particle shape of fly ash (Bouzoubaa et
al, 2005). If ACI-305 finishing methods are followed correctly, and water reducing admixtures are used appropriately, problems with finishing fly ash concrete can be minimized. Concrete with fly ash replacing a portion of cement is more workable and easier to consolidate than 100% Portland cement mixes under vibration consolidation (Bouzoubaa et al, 2005). Concrete mixes utilizing fly ash are also easier to pump through the dispensing hose, as they increase the flow-ability of the mix as well. It has been found that both classes of fly ash improve concrete workability (FHWA, 1999). Concrete with fly ash is more durable because fly ash decreases the amount of water required due to finer pores in the hydrated cement paste. This decreases permeability, in turn decreasing corrosion (Bouzoubaa et al, 2005). Finally, limiting the use of fly ash in slab mix designs to 15% or so usually turns this into a non-issue. Structural issues introduced by the use of fly ash and slag in concrete can be dealt with in cost effective ways.
5. Previous Studies and Research
The first group of 20 case studies were gathered and reviewed, as shown in Table 3, to provide a base of knowledge for data available to date on waste management and recycling programs. These case studies were found by researching internet sites of various state and city governments, and environmental organizations. Case studies were reviewed for data and anecdotal evidence.
The second group of 7 previous case studies contained detailed data on fly ash or slag use as a partial cement replacement in structural concrete mixes.
These case studies are listed in Table 21. A purpose of this exercise was to gain a basis for comparison to new case studies developed in this thesis. This data was also analyzed for the purpose of using as additional evidence to support proposals identified in this thesis.
5.1 Previous Site Waste Management Program Case Studies
The first group of twenty previous case studies shown in Table 3, were limited to new commercial and public construction in North America. Case studies were also chosen by the type of data recorded and the extent to which that data was available for review. Limited success was achieved in an attempt to
gather complete recycling material and cost data on these case studies. Data from selected case studies was collected, tabulated and compared graphically.
LEED requires a waste management and recycling program as a prerequisite in order to achieve certification for a project. Not all of the case studies researched have been involved in LEED. Various materials were included in these programs depending on the specific project. In order to identify materials to target for recycling in the building code, information was gathered from these case studies on the ability of contractors to have the particular material recycled. Recycling services for the material must be readily available in all parts of the country, and uses must be found for the product produced from recycling the material. Cost impact was also be determined when data was available. Finally, recycling and reuse of material must be found to conserve energy and benefit the environment.
From case study research, it was learned that California and Washington State are at the forefront of construction site waste recycling in the United States. Some jurisdictions in California and Washington already have requirements and specifications in place for both commercial and residential construction. Data from construction activities in these areas provide a basis for determining what requirements work and benefit the environment. These are discussed below in this section. Case studies from several different states across the country were used. For a list of all 20 previous waste management program case studies
reviewed in this study see Table 3. According to available published information, the average composition of construction and demolition debris in the U.S. (EPA, 2005) and California (Recycle Works, 2005) is shown in Table 2.
Table 2 Construction and Demolition Material Break Down
Material United States California
Concrete and mixed rubble 40-50% 23.3%
Wood 20-30% 27.4%
Drywall (Gypsum Sheathing) 5-15% 13.4%
Metals 1-5% 8.8%
Note: Not all materials included in studies are shown.
It should be noted that this data is for demolition projects as well as new
construction projects for roadways and buildings. This data gives a basis for
comparison for individual project case study research. Construction waste reuse
and recycling will be defined for this thesis as the following:
Reuse: Construction waste that would otherwise be disposed of in a landfill,
or incinerated that is reused in a way that benefits the end user
Recycling: Construction waste that is sent to a materials recovery facility to be sorted and prepared into marketable commodities for manufacturing.
The building material flow diagram in Figure 7 illustrates the life cycle of
building materials from the extraction of virgin material through disposal as waste
or recycled material, usually after building demolition. The important thing to
point out is the large amount of energy used to extract and manufacture virgin
materials. Recycling and reuse of waste materials allows for this phase of the
cycle to be bypassed, thus saving energy and waste. The sustainability measures proposed aim to reduce the amount of waste generated by construction, and conserve energy expended in raw material extraction and processing.
Figure 7 Building Material Flow Diagram
The U.S. EPA has a specification developed for construction site waste management plans called Section 01690 (EPA, 2006). These specifications are required to be followed for all EPA work. In this specification separate collection containers are required on site for untreated lumber, gypsum wallboard, paper and cardboard, plastics, metals, glass, and one for other salvageable materials. It is
proposed that a specification similar to this be included in the International Energy Conservation Code.
San Mateo County, California now requires a site waste management plan for all large construction and demolition projects per county ordinance. This was in response to the Integrated Waste Management Act passed in the State of California in 1989 which required all California communities to achieve a construction and demolition diversion rate of 50% by the year 2000, as discussed in 4.1. San Mateo requires a waste management plan for any new structure that is equal to or greater than 2,000 square feet. Waste management plans are also required for larger demolition and remodel work. The county ordinance requires these types of projects to recycle or reuse 100% of inert solids which includes asphalt, brick, concrete, dirt, fines, rock, sand, soil, and stone. It also requires a minimum of 50% of all other materials to be diverted from disposal (Recycle Works, 2005). The county requires a waste management plan application to be filled out in order to receive a building permit. Attached to the application is a list of recycling and salvage businesses in San Mateo County. Next to each business, the type of materials the facility accepts is noted along with location and contact information. The ordinance enforced in San Mateo County is very rare in the United States. Instituting a waste management plan on a construction site is almost always voluntary across the United States. This would change quickly if similar requirements were added to the International Code.
The 20 previous studies reviewed offer a comprehensive guide to help determine what materials might be good candidates for application of waste recycling requirements. These studies also aid in determining the cost effect and the success rate of implementing waste management programs on building construction sites.
Table 3 Waste Management Case Study Review List
Building Project Project Location Square Feet of Construction Percent of Total Waste Recycled Net Cost Savings LEED Certification
Madison Gas and Electric Company Wisconsin >30,000 75.35 $103,651 None
Epic Systems Corporation Verona Wisconsin >30,000 73.8 Not Available None
BC Cancer Agency Research Centre British Columbia >30,000 98.5 Not Available Gold
EPA Campus at Research Triangle Park North Carolina 1,170,000 80 Not Available None
Alliant Energy Worldwide H.Q. Wisconsin 325,000 75.69 $15,826 None
Douglas High School Massachusetts 137,000 57 $31,812 None
The EPA National Computer Center North Carolina 95,322 90 Not Available Silver
Harley Davidson Motor Wisconsin 81,629 76.4 $10,000 Certification
New England Regional Lab North Carolina 70,400 51 $10,210 Gold
Affiliated Engineers Inc. Wisconsin 52,000 70.4 $42 Certification
William and Flora Hewlett Foundation Headquarters California 48,000 69 Not Available Gold
Champlain College Campus Library Vermont 35.000 22 $2,852 None
Kent Pullen Regional Communications.& Emerg. & Coord. Cnt Washington 34,900 86 Not Available Certification
Schlitz Audubon Nature Center Wisconsin 34,000 76.68 $6,500 Certification
Colorado Court Affordable Housing California 30,200 75 Not Available Gold
Fisher Pavilion Washington 14,000 86 Not Available Certification
Waukesha County Retzer Nature Center Wisconsin 8,242 82.17 Not Available None
Mary Meyer Corp. Expansion Vermont 7,020 38 $3,125 None
Middlebury College recycling facility Vermont 5,272 21 $165 None
Iowa South Central Environmental Education Center Iowa 4,000 28 -$300 None
construction sites in North America. Descriptions of the 20 previous waste management case studies shown in Table 3 are as follows:
Madison Gas and Electric Company: This project was the Madison Gas and Electric West Campus Cogeneration Facility constructed in Madison, Wisconsin. This facility consisted of 180 million dollar electric power plant which provided 150,000 megawatts of electricity to the Madison area each year. The main building was built with steel framed construction. Materials recycled included metal, wood, concrete, cardboard and plastic. The majority of the waste recycled was concrete and metal at 42% and 23% of the waste stream respectively. Metal waste made up the majority of the cost savings by selling steel H-piles and copper scrap metal. It was noted that 2,037 tons of waste material was diverted from the landfill.(WasteCap, 2005).
Pellitteri Waste Systems was the primary waste and recycling hauler for this project. Bins were set up on site with signs to indicate the material type for each bin. It was noted that the program involved educating workers about the recycling program and its goals, as well as distributing handouts to job site personnel. This project had a recycling rate over 75% at a cost savings of $103,651. This case study was also developed by WasteCap Wisconsin, Inc. (WasteCap, 2005).
Epic Systems Corporation Verona Business Campus: This office building case study was developed by WasteCap Wisconsin for a business
campus constructed in Verona, Wisconsin. This project had a 65% recycling rate by weight. The materials recycled included 730.16 tons of wood, 312.59 tons of scrap metal, 587.8 tons of concrete, and 242.5 tons of gypsum sheathing. Cardboard and other commingled material was also recycled. This project used nearly all gypsum sheathing waste as a soil amendment in nearby farmland. The building campus construction was completed in September 2005 (WasteCap, 2005).
The BC Cancer Agency Research Centre: This case study was completed by the Green Building Council. Finished in March 2005, this project consisted of 231.000 square feet of medical office and research space located in Vancouver, British Columbia, Canada. Nearly all types of construction materials were recycled resulting in 98.5% of construction waste being recycled or reused. Recycled waste use was not described in the published literature. The building was constructed with steel and concrete framing (CGBC, 2003).
EPA Campus at Research Triangle Park: This campus included several facilities contributing more than 1.1 million square feet of floor space. This project was completed in May 2002 with an estimated cost of $273 million. Construction waste materials specified for recycling were land clearing debris, concrete, masonry, rock, clean soil, asphalt, metals, untreated wood, gypsum sheathing, cardboard, paper, plastic and beverage containers. This project had an 80% recycling rate. The case study was completed by the U.S. EPA. There was
no LEED certification for this campus. The silver certification applied to the Computer Center only which will be discussed below. The building structures were generally built with steel framing and slab on deck floor systems. All natural site material cleared for construction was reused on site. Cut down timber was shredded for mulch, excavated rock was crushed for use as structural fill, and excavated topsoil was stock piled for reuse (EPA, 2001).
Alliant Energy Worldwide Headquarters: This was a 325,000 square foot office building in Madison, Wisconsin. This was a steel structure with a precast concrete facade. The building was completed in April 2002. The waste management program targeted cardboard, paper, concrete, gypsum sheathing, metal, wood, styrofoam and glass and plastic bottles for recycling. The case study was completed by WasteCap Wisconsin, Inc. (WasteCap, 2002).
Green Valley Disposal was hired to haul and dispose of waste. Green Valley Disposal was also involved in determining where certain materials would be recycled, and how they would be used. Clearly marked waste bins were set up on site to separate waste. Cardboard, paper, and other commingled items were hauled to a recycling center for shipping to markets. Waste metal was hauled to a local scrap metal recycler. Gypsum sheathing waste was hauled to a local farm for use as a soil amendment. Concrete was hauled off site for recycling as well. This project had a recycling rate over 75% at a cost savings of $15,827. (WasteCap, 2002).
Douglas High School: This building was a steel framed, 37,000 square foot school in Douglas, Massachusetts. The building was completed in August 2003. The waste management program targeted cardboard, concrete, gypsum sheathing, metal, and wood for recycling. The case study for this project was developed by the Massachusetts Department of Environmental Protection (MDEP, 2003).
Consigli Construction hauled all of the gypsum sheathing scrap boards to G-P Gypsum Corporation in Newington, New Hampshire, some 100 miles away. G-P payed Consigli $11 to $12 per ton for the sheets, and converted them into new wall board. Consigli saved $2,891 on gypsum sheathing recycling alone. Clearly marked waste bins were set up on site to separate waste. This project had a 57% recycling rate at a cost savings of $31,812. The majority of this savings came from concrete reuse on site which saved the contractor approximately $22,800 by avoiding disposal costs (MDEP, 2003).
EPA National Computer Center: This is one of the largest computer centers in the United States. The center opened in January 2002. This building is a steel framed 95,322 square foot office building in Research Triangle Park, North Carolina. Nearly all types of recyclable construction waste material were recycled with a landfill diversion rate of approximately 90%. A break down of recycled material end uses was not published. This case study was completed by the U.S. EPA (USBG, 2003).
Harley Davidson Motor Company Product Development Center Office Expansion: WasteCap Wisconsin Inc. completed this case study for an 81,629 square foot steel framed building in Wauwatosa, Wisconsin. Bins were set up on site and clearly marked by material type which included cardboard, metal, untreated wood, gypsum sheathing, and concrete. Recycled concrete made up the largest percentage by weight at approximately 35% of the waste stream. The overall recycling rate was listed at 76.40% by weight at a cost savings of over $10,000. Over 30 tons of Gypsum sheathing was hauled to a local farm where it was used as a soil amendment. The gypsum sheathing acts similar to agricultural gypsum providing calcium and sulfur to soils. WasteCap Wisconsin, Inc. was responsible for organizing and overseeing the waste management plan. Waste Management, Inc. was the primary hauler of waste materials (WasteCap, 2003).
EPA New England Regional Laboratory: This case study was for the U.S. EPA New England Regional Laboratory (NERL) located in North Chelmsford, Massachusetts, completed in 2001. The case study was completed by Building Green Inc. The building was completed in 2001. This project was approximately 72,000 square feet of steel framed, single story building space including a laboratory, administrative office space, a hazardous material storage building and boat storage. This project achieved a Gold rating in the LEED system and won several prestigious awards for environmental sustainability.
Research into the results of this case study reveals a successful waste recycling program (WBDG, 2005).
A construction site recycling program was required for LEED certification, therefore a waste management and recycling program was set up. Recycling bins were set up on site and labeled for designated waste materials. Several different types of materials were recycled including wood, cardboard, wallboard, metal, and concrete. The general contractor for this project was Erland Construction headquartered in Massachusetts, and recycling services were provided by Graham Waste Service. Graham Waste Service operates in Massachusetts and southern New Hampshire. This company provided the bins as well as pick up and delivery to the appropriate recycling facilities. Over half of the solid waste generated by the site was diverted from the landfill and recycled. The foreman of Erland Construction was quoted as saying, subs were pretty helpful about getting on board with recycling. At first laborers didn t understand why we were doing it, but once you got the rhythm, it was easy". This project had a 51% recycling rate and had a cost impact of $4,050 in savings for the project (WBDG, 2005).
Affiliated Engineers Inc.: This project case study was a steel framed office building for Affiliated Engineers Inc. This building was 52,000 square feet of office space in Madison, Wisconsin completed in April 2002. This project was given a recycling grant from the Department of Natural Resources in January
2002. Materials recycled included metal, wood, gypsum, cardboard, Styrofoam, clean fill, and beverage containers (WasteCap, 2002).
Green Valley Disposal was also the waste and recycling hauler for this project. Bins were set up on site with signs to indicate the material type for each bin. It was noted that four tons of fill were hauled to a local fill site at no charge to the contractor. Interviews with the workers on site expressed that separating material on site was simple once the habit was instilled. It was also stated that the presence of multiple dumpsters for waste disposal was more convenient than a single dumpster. This project had a recycling rate of approximately 70% at a slight cost savings (WasteCap, 2002).
William and Flora Hewlett Foundation Headquarters: The headquarters was a two story 48,000 square foot building with underground parking located in San Mateo County, California. The building was completed in April 2002. The waste management program recycled 69% of construction waste materials. A material breakdown was not provided for review. The case study for this project was completed by The Green Building Council (Recycle Works, 2006)..
Champlain College Campus Library: The new campus library for Champlain College in Burlington, Vermont was completed by the Vermont Department of Environmental Conservation Waste Management Division. The building was constructed with conventional steel framing. Fourteen tons of brick
and concrete were recycled, in addition to cardboard. This project concluded in May 1998. (VDEC, 1998).
Kent Pullen Regional Communications & Emergency Coordination Center: The Center was a steel framed 34,900 square foot facility located in King County, Washington. This project was completed in 2003. Recycled materials included untreated wood, metal, gypsum sheathing, cardboard, and concrete as well as commingled items and paper. This project had an 86% recycling rate by weight. Recycled material end uses were not reported in the published data. Recycled material totaled 130 tons (King County, 2003).
Schlitz Audubon Nature Center: This case study, developed by WasteCap Wisconsin was for a 34,000 square foot building located in Milwaukee, Wisconsin. The building structure was made up of a wood frame with siding and stone veneer. The recycling rate for construction waste was over 78% by weight. Recycled materials include cardboard, metal, untreated wood, gypsum sheathing, concrete, and other commingled items. Fifteen tons of gypsum was used as a soil amendment and 24 tons of concrete was hauled to a concrete recycling facility, crushed, and reused as aggregate for new road projects. The contractor saved approximately $6,542 in disposal costs which was about a 42.5% savings over disposing 100% of waste in landfills. This project was completed in March 2003 (WasteCap, 2003).
Colorado Court Affordable Housing: This steel framed building construction case study was developed by the USGBC. The Colorado Courts project served as a demonstration project by the City of Santa Monica, California as preparation for the city to meet a new recycling ordinance. Because recycling is not yet common in this city, and space was very limited for recycling bins, an estimated $10,000 premium was paid to have the projects construction waste recycled (Global Green, 2003). It was noted in this same study that once recycling services were in place, projects save money rather than having to pay a premium for construction waste recycling. A breakdown of recycled material types and its end use was not provided in the published literature.
Fisher Pavilion: This case study was completed by the USGBC. The building was built with concrete and steel construction. Materials recycled included cardboard, paper, wood, metals, and gypsum sheathing. It was noted that the project had an 82% overall recycling rate (DOE, 2003).
Waukesha County Retzer Nature Center: This Center was an 8,242 square foot addition located in Waukesha County, Wisconsin, and was completed in May 2005. It also involved the demolition of two walls from the existing building. The new building was constructed with wood and concrete. WasteCap Wisconsin Inc. developed this case study. The recycled materials were as follows: cardboard, scrap metal, untreated wood, and concrete. WasteCap Wisconsin documented the program and interviewed several people involved in
the project. Most of the materials to be recycled were handled by Waste Management Inc. The Waukesha County Recycling Specialist was quoted as saying We have had excellent cooperation from the general contractor, Creative Constructors, who had done some recycling on other construction sites.''1 This project had an over all recycling rate of 82% by weight. Concrete made up over 85% of the recycled materials on this site by weight, and was hauled to a local mining pit for reuse. Other recovered materials were hauled to local recycling centers (WasteCap, 2005).
Mary Meyer Corporation Corporate Office Expansion: This case study was for a 7,000 square foot office building, with an additional 3,300 square feet of remodeled area. The building was located in Townshend, Vermont. This study was also developed by the Vermont Department of Environmental Conservation Waste Management Division. The contractor instituted a reuse program to utilize waste products from the remodeled portion. The reuse program saved the contractor rental, hauling and disposal fees. Wood, concrete, and scrap metal were all recycled on this project (VDEC, 2002).
Middlebury College Recycling Facility: This case study for a recycling facility in Middlebury, Vermont was developed by the Vermont Department of Environmental Conservation Waste Management Division. Materials Recycled included wood, cardboard and scrap metal. The project superintendent held
weekly meetings with subcontractors in which recycling was addressed. This project was completed in May 2002 (VDEC, 2002).
South Central Iowa Solid Waste Agency Environmental Education Center: Completed in November 2003, this study was completed with grant money from the Iowa Department of Natural Resources. This 2,000 square foot building was constructed with conventional wood framing on a concrete foundation. It was noted that the biggest problem was making sure subcontractors properly sorted the waste material. It was also noted that recycling waste on this project increased disposal costs by approximately $300. This project also had problems finding markets for gypsum sheathing. However, markets for wood, cardboard and metal were readily available in this rural area. The building was completed in November, 2003 (Grabner-Kerns, 2004).
Case Study Summary: These previous 20 case studies showed how waste reuse and recycling often saves cost, and instills a sense of pride in owners and laborers. Construction waste included cardboard, wood, gypsum sheathing, metals, concrete, glass, plastics, paper, and several other types of materials.
Figure 8 shows a breakdown based on material type, which illustrates the average portions of the various materials in the waste streams of these case studies, for which data was available. Savings generally ranged from $0 to $10,000 with a few exceptions. The savings was actually much greater for some of the very large projects that found markets for waste products. Figure 9 shows a breakdown of
the average cost ratio of reuse or recycling over disposal cost for each major material type. This figure shows that all major structural materials cost less on average to recycle than to dispose of in landfills for 5 of the previous 20 case studies that had this data available. Recycling rates were generally over 50%, except for a few of the smaller projects. These 20 previous case studies helped to identify a minimum level of recycling that could potentially be included into the
IECC. This proposed requirement is further described section 7.
<Â£ 15.00 0)
2 10.00 a>
By Weight By Volume
Wood Cardboard Metals Concrete/Fill Gypsum
1. Graph based on 11 of the 20 case studies for which data was available. Figure 8 Recycled Materials (% of Total Wastestream)1
1. Graph based on 5 of the 20 case studies for which data was available. Figure 9 Cost of Recycling vs. Landfilling1
5.2 Previous Case Studies of Fly Ash and Slag Use
Seven additional case studies summarized in Table 21, were reviewed for information to support the partial cement replacement objective of this thesis. Case studies for slag use were not included in this thesis because research on slag as a SCM is not as well developed as fly ash. New case studies for slag use have been initiated by EcoSmart, Inc. to gain experience and knowledge for slag as a cement material. According to the Slag Cement Association, slag is now widely available for use in concrete mixes in the United States east of the Mississippi
River. Slag blended cement shipments have increased steadily over the past 10 years. The total U.S. slag cement shipments increased over 300% between 1996 and 2005. This constituted nearly 3.5 million metric tons of slag cement in 2005 (SCA, 2006). The Slag Cement Association attributes this growth to wider availability of slag for use in concrete and the growing interest in sustainable construction.
LaFarge North America has a large slag operation in the Midwestern United States. Slag is obtained from the Ispat-Inland Steel plant in Indiana. It is then trucked to the Lafarge plant in Chicago for processing. This facility makes blended cement called NewChem from slag. Over 120,000 tons (108,840 metric tons) of slag was used to make this product in 2005. This is just one example of the widespread use of slag as a cement material (Lafarge, 2006). Slag has been used as a cement supplement for many years and its use as a cement supplement continues to grow.
The purpose of researching the following 7 additional fly ash case studies was to build a base of evidence to support a proposed minimum fly ash use requirement into the IECC. Any proposal of this significance must be supported by overwhelming statistical and anecdotal evidence in order to be considered by the code officials. This is especially true for a major change to concrete requirements, since concrete is the oldest and most widely used construction material. Fly ash has been used routinely as a cement supplement in structural
concrete mixes for many years. Numerous case studies containing fly ash use in concrete have been published worldwide since the Canada Center for Mineral and Energy Technology (CANMET) study in 1985 (Mehta, 1998). This is evident in research into this topic. Typical rates of fly ash use in the United States are 0% to 20% of the cement materials in the concrete mix. The question to be answered remains; how much fly ash is an optimal amount to propose as a minimum requirement? The goal would be to require as much as possible without causing potential structural performance issues or cost increases. The fly ash case studies selected for research and presentation in this study were carefully selected for their quality and relevance to large commercial building projects.
The Kyoto Protocol was signed by Canada in December 1997. This International Agreement requires Canada to reduce its greenhouse gas emissions to 6% below 1990 levels (Sage, 2004). To achieve this lofty goal, the Canadian government instituted Action Plan 2000 which is a package of measures aimed at reducing the countrys gas emissions. The EcoSmart Foundation, Inc. is a nonprofit society in Canada advised by several industrial and governmental entities. Its purpose was to develop and manage activities that implement more sustainable practices in the building industry. EcoSmart is one of the primary organizations involved in supporting Canadas efforts on the building construction side of this plan. In fact, it was noted in one case study that high volume fly ash concrete has become known as EcoSmart concrete in Canada. Action Plan 2000 aims to
increase the use of supplemental cement material use to 25% on average for concrete use across Canada (Sage, 2004). Several of the fly ash case studies reviewed for this thesis were developed by EcoSmart.
The fly ash case studies found for reference in this study had fly ash replace cement at rates of 15% to 70%. Seven different case studies were reviewed for mix design data, mix test data, and anecdotal evidence of issues encountered in fly ash use during construction. Four of these were developed by EcoSmart, Inc. for projects in British Columbia, Canada. These case studies show that while fly ash concrete typically works well when implemented properly, there are some negative aspects to its use when levels of fly ash reach a high level under certain conditions. Review of these studies reveals the need to keep minimum supplemental cement material requirements modest due to the potential problems that may be introduced for contractors with little experience in high volume fly ash mixes. Any proposed minimum to be included in the International Codes would have to be a safe amount for inexperienced contractors to utilize in building construction.
In order to analyze the fly ash case studies for energy conserv ation, CO: releases, and cost implications, software tools had to be found that were acceptable to the concrete industry, accurate, and comprehensive in scope. Two such software models were used. These were Building for Environmental and Economic Sustainability (BEES), and Life 365. BEES was developed by the
National Institute of Standards and Technology for the purpose of providing the building industry with a tool to compare economic and environmental costs between building products. The tool developed is computer software with a built in data base for various building products compiled by various building material associations and consultants. This software has been developed over the course of several years, and included very thorough analysis of all aspects of building material acquisition, production, transportation, and construction in a life cycle analysis. This software has been developed in coordination with the EPA and Harvard University (NIST, 2003). It has become the benchmark for building material economic and environmental comparisons in the United States.
A life cycle analysis (LCA) was also completed for the previous fly ash case studies reviewed utilizing Life 365 software produced by the Silica Fume Association, Master Builders, and Grace Construction Products. There are several life cycle analysis software programs on the market. The consortium that currently oversees Life 365 is seeking to have this software adopted as the industry consensus model with refinements from ACI Committee 365. This software performs life cycle cost analysis of reinforced concrete.
A BEES analysis was performed on case studies where concrete quantities were available. BEES will allow analysis of fly ash levels of 15% and 20% only, along with a 100% Portland cement mix. Concrete mix designs with fly ash levels other than these two percentages were determined through linear
interpolation. The values in Figures 10 and 11 were used to provide the basis for interpolation to determine BEES analysis embodied energy and C02 release values for various levels of fly ash use. These figures included three different concrete mix designs with different rates of fly ash use.
Embodied Energy by Fuel Usage
FI Feedstock Energy | Fuel Energy
100% Portland Cement 20% Fly Ash Cement
15% Fly Ash Cement
Category 100% OPC 15%FlyWall 20%FlyWall
Feedstock Energy 1.36 1 37 1 38
Fuel Energy 5031 47.33 46.33
Sum 51.67 48.70 47 71
Figure 10 BEES Analysis of Embodied Energy for Concrete Mixes with 0%, 15%, and 20% Fly Ash
Figure 10 illustrates the decrease in embodied energy realized by replacing a portion of the cement with fly ash. The more fly ash used, the less embodied energy required to produce and place the mix. The feedstock energy is the amount of raw material embodied energy used, and the fuel energy is the fossil fuel energy consumed by the equipment used in the extraction, manufacturing,
transportation and placement of the mix. Figure 11 shows the benefit to the environment from this same fly ash use. The more fly ash used, the larger the reduction in CCF gas released in production and placing of the concrete mix. See Table 21 for a list of previous fly ash case studies reviewed in this thesis along with a summary of BEES analyses completed.
Global Warming by Life-Cycle Stage
| 4,000 *
n Raw Materials Acquisition | | Manufacturing FI Transportation use End of Life
15% Fly Ash Cement
Note: Lower values are better
Category 100% OPC 15%FlyWall 20%FlyWall
1. Raw Materials 4902 4448 4296
2. Manufacturing 22 22 22
3. Transportation 340 340 340
4. Use 0 0 0
5. End of Life 0 0 0
Sum 5263 4809 4658
Figure 11 BEES Analysis of CO2 Release for Concrete Mixes with 0%, 15%, and 20% Fly Ash
A Life 365 life cycle cost analysis was also completed on the 7 previous fly ash case studies where relevant to the project. The analyses performed were
specific as to building regional location, exposure condition, and concrete element type. A 38mm (1 Vfe) concrete cover around steel reinforcing bars was assumed. This is a common required cover depth for concrete placed in forms and exposed to earth and weather, as is very often the case with walls and slabs (ACI, 2005). Slabs and walls were chosen as the element type, as these make up the vast majority of concrete placed. The Life 365 software only considers high salt, deicers, and weather exposure conditions such as in parking garages or near the Ocean. The relevant exposure condition assumed for each project is noted in the LCA summary table for each case study. The Life 365 LCA analyses show significant cost savings for all projects analyzed. The level of cost savings would only be realized for the concrete with the exposure conditions noted. Concrete not exposed to weather would have less cost savings. However, all of the fly ash concrete placed would realize a net cost savings due to the equal or lower first cost and lower life cycle cost of fly ash concrete relative to 100% Portland cement mixes in all exposure conditions. Summary tables of Life 365 LCA results are included in each case study discussion where relevant. Reference Figures D.l through D.l3 for complete Life 365 output for the previous fly ash case studies discussed below.
Little Mountain Reservoir: This case study in Vancouver, B.C. was completed by EcoSmart, Inc., with the goal of using the largest amount of fly ash feasible for the project. This structure is a water reservoir with a capacity of 175
million liters. Approximately 27,000 cubic meters (35,314 cubic yards) of concrete was used in total including the flowable concrete fill placed below the foundations. This project replaced approximately 41.5% of the Portland cement that would have been used with fly ash. Construction of this structure took place in both warm and cold months. This study noted that 20 to 25% fly ash replacement for cement in concrete in British Columbia was normal, and larger volumes of fly ash have drawn mixed reactions from contractors. Fly ash volumes were adjusted throughout the structure according to the time of year the section was constructed. Lower volumes of fly ash were used in the winter months due to slower set up time under cold conditions. There were also specific mixes used for different types of structural elements to facilitate constructability of the structure. Several important issues were addressed in this study, and are discussed below (Sukumar et al, 2004).
The first issue to consider was the concrete mix designs developed by Lafarge Canada, Inc., who also supplied the concrete to the site. A superplasticizer admixture was used in the high volume fly ash mixes. The concrete mix design specification for walls and columns called for 35% minimum fly ash while 30% minimum fly ash was specified for structural slabs. Actual mix designs used ranged from 40 to 57.7% fly ash for both mix specifications. The design strength for these mixes was 35 MPa (5076 psi). The mix design details are shown in Table 4.
Table 4 Concrete Mix Designs for Little Mountain Reservoir1 _________(Sukumar, et al, 2004)______________________________
Mixture ID GVRD3 GVRD4 GVRD5 GVRD6
Portland Cement 228kg/m3 (3841b/yd3) 200kg/irf (3371b/yd3) 195kg/m3 (3291b/yd3) 200kg/m3 (3371b/yd3)
Fly Ash 152kg/mJ (2561b/yd3) 180kg/mJ (3031b/yd3) 195kg/m' (3291b/yd3) 180kg/m3 (3031b/yd3)
Total Aggregates 1850kg/m3 (31181b/yd3) 1830kg/m3 (30841b/yd3) 1805kg/nf (30421b/yd3) 1830kg/nf (30841b/yd3)
Water 130kg/m3 (2191b/yd3) 130kg/rrf (2191b/yd3) 130kg/m (2191b/yd3) 130kg/m-' (2191b/yd3)
Air Content 5-8% 5-8% 5-8% 5-8%
Superplasticizer As Required As Required As Required As Required
1. Mix designs for the flowable fill placed under t le foundation are not shown.
All of the mixes utilized Type Cl fly ash which is defined by the Canadian Standards Association A3000. This type of fly ash would be considered a Type F in the U.S. system. All of the mixes utilized Type 10 cement also per the CSA which is equivalent to a type I cement under the U.S. System. Fifty six day strength data ranged between 40.2 and 60.7 MPa (5830 to 8800 psi) for the slab mixes which was significantly higher than the required design strength of 35 MPa (5076 psi). This was based on 65 tests. The 56 day strength for the wall and column pours ranged from 35.2 to 56.2 Mpa (5104 to 8150 psi) which also satisfied the specified strength. These results were based on 46 tests. Initial and final set times were also recorded for the wall pours and compared to a mix with 100% Portland cement. The initial set was defined as 600 psi (4.1 MPa) penetration resistance, and final set was defined as 3600 psi (24.8 MPa)
penetration resistance. Based on test results in the field, the final set time for form stripping took around 13 hours, opposed to around 8 hours for a typical 100% Portland cement mix (Sukumar et al, 2004).
There were other concrete issues noted in the study. Concrete with these high levels of fly ash tends to be sticky compared to 100% Portland cement mixes. This was not a problem in walls and columns since the concrete was easily vibrated and consolidated into place and no problem to pump. The concrete was also tested for durability and permeability. This project had very high standards for these two properties due to the required water containment and hydrostatic loading. The high volume fly ash mixes were found to be superior to concrete mixes with no fly ash in these areas. Table 5 shows how the slab and wall concrete tested for durability. The high resistivities indicate this concrete will have good resistance to rebar corrosion. The low boiled absorption and permeability show the concrete placed will resist water penetration very well.
Table 5 Durability and Permeability Properties for Little Mountain
Reservoir (Sukumar, et al, 2004
Properties Slab Concrete Wall Concrete Test Procedure
Resistivity ohm-cm 26,600 18,600 ASTMC1202
RCP, coulombs 789 1,150 ASTMC1202
Permeability Rating very low low ASTMC1202
Boiled Absorption % 3.7 5.8 ASTM C642
Vol. permeable voids % 8.7 12.8 ASTM C642
Unit mass, wet kg/nr 2459 (4144 lb/yd3) 2335 (3935 lb/yd3) ASTM C642
All specifications for the mixes in these two areas were met. Concluding remarks in this study included that the concrete on this project proved to be excellent in terms of workability, durability properties, strength and finish While fly ash is less expensive than cement, the cost savings was not passed on to the contractor for this project. The cost ended up nearly the same as if it were a conventional mix project. The concrete supplier stated the reason for the lack of cost savings was that the high volume fly ash concrete required more effort in the mixture proportioning, quality control testing, and manufacturing process due to the originality of the mix designs. Overall, the project was very successful according to the parties involved (Sukumar et al, 2004).
After reviewing this case study, a Life 365 LCA analyses was completed for the concrete used on this project. The results are shown in Table 6. This table shows a cost savings of over $40 per square meter for fly ash use over the 75 year life of the structure. Note, that the time to first repair of the structure is nearly doubled with the 40% to 50% fly ash mix is used in lieu of a 100% Portland cement mix for the exposure condition noted
"able 6 Life 365 Life Cycle Cost Anab Ksis (Little Mountain Reservoir)
Concrete Mix Used Exposure Condition Assumed Life Cycle Cost Savings over 75 Year Life Time to First Repair
100% Portland Cement 1.5km from Coast $0 17.1 years
40% Fly Ash 1,5km from Coast $40.47/m- ($3.76/ftz) 35.6 years
50% Fly Ash 1.5km from Coast $54.83/ m2($5.09/fr) 46.2 years
Bayview High Rise Apartment: This project at Coal Harbour in Vancouver, British Columbia was a 30 story building which was used as a case study developed by EcoSmart, Inc. for the Greater Vancouver Regional District (GVRD) Air 2000 Program. This program was in response to Canadas Action Plan 2000. 11,630 nr (15,219 yd3) of concrete were used on this project. The purpose of this study was to investigate high volume fly ash use in high rise construction. High rise construction requires a rigid schedule of shoring and reshoring to construct each level up the building. Longer set up times can have a more significant effect on schedule in high rise construction than more typical concrete construction. An extensive and in depth study was completed prior to construction of this building to determine the most cost efficient use of fly ash and construction methods to minimize cost and construction duration (Busby, 2002).
Several aspects of fly ash use were studied before construction began.
Each building element was considered for use of fly ash taking into consideration concrete volumes, construction method modifications, and effect on schedule.
One of the first exercises implemented was testing of trial mixes to determine the effectiveness of accelerating admixtures. The goal was to create high volume fly ash concrete mixes with set times close to conventional concrete mixes with no fly ash. It was concluded that the use of the admixture Polarset by Grace Products, had no significant effect on concrete set times when 40% fly ash was used. While this does not rule out the possibility of achieving more conventional
set times using accelerators by other producers, this study showed that many accelerators may not achieve the desired effect when fly ash levels reach this range. This result forced the contractor to plan a modified construction sequence due the longer expected set times (Busby, 2002). See Table 7 for revised specifications for concrete mixes based on this study at the preliminary phase.
Table 7 Concrete Mix Designs for the Bay view at Coal Harbour High Rise
Apartment Building (Busby, 2002)
Stripping Mixture ID WC Ratio Slump Maximum Aggregate % Fly Ash 28 Day Strength
Footings Core 0.50 80 mm (3.15 in) 40 mm (1.57 in) 40 30 MPa (4321 psi)
Footings Other 0.50 80 mm (3.15 in) 40 mm (1.57 in) 40 25 MPa (3626 psi)
Slabs Parkade On Grade 0.50 70 mm (3.15 in) 20 mm (0.79 in) 20 25 MPa (3626 psi)
Slabs -Suspended Parking Slabs 0.40 70 mm (3.15 in) 20 mm (0.79 in) 15 35 MPa (5076 psi)
Slabs Exterior On Grade 0.45 70 mm (3.15 in) 20 mm (0.79 in) 20 32 MPa (4641 psi)
Slabs Podium and Tower 0.45 70 mm (3.15 in) 20 mm (0.79 in) 15 25 MPa (3626 psi)
Toppings 0.45 70 mm (3.15 in) 20 mm (0.79 in) 15 20 MPa (2900 psi)
Walls & Columns Floor P3 to 8 0.45 80 mm (3.15 in) 20 mm (0.79 in) 15 40 MPa (5800 psi)
Walls & Columns Floors 8 to 12 0.45 80 mm (3.15 in) 20 mm (0.79 in) 15 35 MPa (5076 psi)
Walls & Columns Floors 12 to 16 0.45 80 mm (3.15 in) 20 mm (0.79 in) 20 30 MPa (4351 psi)
Walls & Columns Other 0.45 80 mm (3.15 in) 20 mm (0.79 in) 20 25 MPa (3626 psi)
The complete concrete mix designs were not disclosed by the concrete supplier for this case study. The reason stated for this was to protect the design for proprietary reasons. This is quite common among large concrete suppliers with unconventional mixes due to cost of developing and testing these types of mixes. It should be noted that the contractor met or exceeded the minimum required fly ash specified with no additional cost. The actual percentages of fly ash used for the different concrete elements are in Table 8.
Table 8 Fly Ash Use for the The Bayview at Coal Harbour High Rise
Apartment (Busby, 2002)
Building Mixture ID Estimated Concrete Volume Placed (M'1) Actual % Fly Ash Used
Footings Core 570 (745 yd*) 45
Footings Other 430 (562 yd'1) 45
Slabs Parkade on Grade 210(275 yd3) 20
Slabs Suspended Parking 90 018 yd-1) 33
Slabs Exterior on Grade 1770 (2315 yd''1) 20
Slabs Podium and Tower 4630 (6055 yd1) 15-25
Toppings 140(183 yd1) 45
Walls and Columns Floors P3 to 8 830 (1085 ydJ) 33
Walls and Columns Floors 8 to 12 250 (327 yd1) 33
Walls and Columns Floors 12 to 16 250 (327 ydJ) 33
Walls and Columns All Others 2460 (3217 yd1) 33
The actual amounts of fly ash used were based on a number of variables
including temperature and schedule. Notice, the only building elements where the
amount of fly ash used varied was the tower slabs, walls and columns. The tower slabs made up the largest amount of concrete at 40% of the total concrete used. The reason less fly ash was used for some of the slabs was due to temperature changes throughout the construction schedule. The 15% mix was used during the winter months when the average temperature was dipping below 9 degrees Celsius (48 degrees F.). The tower was built using a fast track 3 day cycle. Although the tower columns and walls had a lower specified minimum required fly ash percentage, a significantly higher level of fly ash was used consistently through the building. A lower fly ash percentage was specified for the lower floor levels due to the higher 28 day strength required at these levels. This project used fly ash very successfully once adjustments were made to the criteria (Busby, 2002).
A type C fly ash was used throughout the project which typically would perform better than type F fly ash at achieving higher early strength. However, the type C fly ash used on this project had a lower calcium content than typical type C ash, and therefore behaved similar to a type F ash. CSA type 10 Portland Cement was used which is equivalent to a type I in the U.S. system. Higher early strengths were seen for the lower fly ash mixes as shown in Table 9.
Table 9 Compressive Strength Averages for 15% and 50% Fly Ash Mix
Designs (Busby, 2002)
Time Strength (15% Fly Ash) Strength (50% Fly Ash)
7 days 20MPa (2900 psi) 16MPa (2320 psi)
28 days 29MPa (4206 psi) 27MPa (3916 psi)
56 days 32MPa (4641 psi) 34MPa (4931 psi)
The data above is an estimate of the typical strengths seen for a 25 MPa (3626 psi) mix design. This shows the higher fly ash use results in lower early strength followed by more rapid strength gain after 7 days.
The concrete placers stated that the mixes with higher levels of fly ash replacement were more workable that mixes with little or no fly ash. There were no special procedures required to finish slabs with fly ash replacement levels in the 15% to 33% range. The tower slabs were preheated before and immediately after placement to hasten setting time which is normally done for this type of construction cycle on a high rise building. The contractor also commented the fly ash had a positive effect on the appearance of architecturally exposed concrete while also creating a smoother finish than traditional mixes. There was no thorough cost analysis completed to compare concrete construction costs for this project to an estimate of total concrete construction cost using conventional concrete mixes. However, fly ash is already used at modest levels by most concrete producers in Canada, and by many concrete suppliers in the United States due to its material cost benefit. The contractor commented that high levels of fly ash in high rise construction slabs could have a potentially high additional
cost because, the cost of the modified forming system would far out weigh the cost savings from using large amounts of fly ash. This case study demonstrated that higher volumes of fly ash work well for most concrete elements in high rise construction. However, it also showed that fly ash replacing cement in structural slabs in high rise construction should probably be kept at 15% to 25% maximum to avoid high additional costs in the forming system and length of schedule (Busby, 2002).
After reviewing this case study, a Life 365 LCA analyses was completed for the concrete used on this project. The results in Table 10 show that a significant savings in the parking structure concrete will be realized over 75 years due to the 20% and 30% fly ash levels used for this structure.
Table 10 Life 365 Life Cycle Cost Analysis (Bayview High F Jse Apartment)
Concrete Mix Used Exposure Condition Assumed Life Cycle Cost Savings over 75 Year Life Time to First Repair
100% Portland Cement Parking Garage $0 16.2 years
20% Fly Ash Parking Garage $17.29/m" ($1.60/ft2) 22.0 years
33% Fly Ash Parking Garage $28.49/nr ($2.64/ft2) 28.6 years
Government of Canada Building: This project in Yellowknife, NT (Northwest Territories) case study was reviewed for fly ash use. This building was chosen for study by the Public Works and Government Services Canada to further the knowledge base of fly ash use in concrete. This building is a 4 story
office building with a construction cost of 28 million dollars Canadian. This project did achieve a Silver LEED certification. A study of different concrete mixes with partial cement replacement was completed prior to construction in order to support a specification to be written for concrete on this project. This building successfully utilized a significant amount of fly ash as a partial cement replacement in all concrete mixes (Babuin & Robson, 2004).
The trial mix design study completed prior to construction was very helpful in determining the proper amount of fly ash to use on this project. Three different trial batches with different amounts of cement replacement were tested. The fly ash amounts used were 25%, 35% and 45% of the total cement materials. The target compressive strength of all three of the mix designs was 25 MPa (3626 psi). Type 10 cement and type Cl fly ash was used for all three mix designs as shown in Table 11.
Table 11 Trial Concrete Mix Designs for the Government of Canada
Building (Babuin & Robson, 2004)
Material 25% Mix 35% Mix 45% Mix
Water 164 kg/m3 158kg/m3 158 kg/m3
Cement 225 kg/m* 195kg/m3 165 kg/m3
Fly Ash 75 kg/m3 105kg/m3 135 kg/m3
Coarse Aggregate 980kg/m3 985kg/nr 985kg/m3
Sand 1013 kg/m3 1010kg/m3 990kg/m3
Slump 80 mm 80 mm 80 mm
Air Content 2.0% 2.0% 2.0%
Yield 1.0 m3 1.0 M3 1.0 M3
Note: A water reducing admixture called Polyheed 997 developed by Degussa Construction Chemicals was also added in the same proportion to each mix. This admixture was added at a rate of 650 mL per 100 kg of cement.
Cylinders were made from each of the trial mixes for compressive strength testing according to CSA A23.2-3C as shown in Table 12.
Table 12 Compressive Strength Test Result Summary for the Government
of Canat a Building (Babuin & Robson, 2004)
Age Avg. Compressive Strength (MPa)1 25% Fly Ash Avg. Compressive Strength (MPa)1 35% Fly Ash Avg. Compressive Strength (MPa)1 45% Fly Ash
3 days 22.2 18.18 13.1
7 days 29.0 26.9 24.7
14 days 36.4 32.8 32.1
28 days 43.4 38.7 36.4
56 days 45.7 44.9 44.2
1. The average compressive strength results are based on 2 sets of cylinders.
These test results were used to develop a specification for the project. Note, that all of the mix designs far exceeded the 25 MPa (3638 psi) 28 day strength target. These results show that the mix designs were quite conservative exceeding the design strength by 45% to 73% as shown in Table 12.
The initial time of set was also tested for the 3 mixes. Early strength for stripping of forms for floor slabs was important to meet schedule. The set times were based on the ASTM C403 (2003). A set of cylinders was cured at room temperature while the other set of cylinders was cured at 5 to 8 degrees Celsius (41 to 47 degrees F.) as shown in Table 13.
Table 13 Set Time for Trial Mixes for the Government of Canada Building ________(Babuin & Robson, 2004)______________________________
Fly Ash Replacement Initial Set Time 22C Initial Set Time 5 to 8C
25% 540 min 710 min
35% 560 min 960 min
45% 615 min 980 min
The initial set time is probably the most important obstacle to overcome in the use of high levels of fly ash to replace cement in concrete mixes. This is especially true in cold weather. The test results above and the final conclusions of this case study demonstrate the importance of this issue in implementing these types of mixes. Note that the increase in set time for the 45% fly ash mix over the 25% fly ash mix was about 13.8% at room temperature, but increased to 38% in the cold weather curing simulation. It should be noted, this case study also stated that fly ash use for slab-on-grade slabs is ranges from 15% to 25% for the majority of work in Alberta, Canada, and that very few of the mixes have trouble reaching the 28 day compressive strength (Babuin & Robson, 2004). This demonstrates that fly ash is implemented in cold weather without serious issue, on a regular basis, when early strength is not a concern. Fly ash use in cold weather is problematic once fly ash levels exceed about 25% to 30% for load bearing and self supporting elements.
The contractor and structural engineer decided to use a 20% minimum requirement for the fly ash specification for all concrete mixes based on the findings of these trial mix designs. Mix designs in the range of 25% on average
were used. The major concern was set time and 28 day strength. Another concern was the increased possibility of surface finish defects such as minor crazing and dusting for slabs. This is a more common problem in slabs with high volumes of fly ash in dry climates due to the increased cure time. The combination of the longer cure time and dry climate can cause surface drying while the slab cures slowly, resulting in these defects. This can be avoided with misting water on the slab during curing. This case study brought to light some of the common potential problems of replacing large amounts of cement with fly ash under certain field conditions.
After reviewing this case study, a Life 365 LCA analyses was completed for the concrete used on this project. The results shown in Table 14 show that by replacing 25% of the cement with fly ash in the parking structure, the owner will save over $22 per square meter of area over the 75 year life of the structure.
Table 14 Life 365 Life Cycle Cost Analysis (Government of Canada Building)
Concrete Mix Used Exposure Condition Assumed Life Cycle Cost Savings over 75 Year Life Time to First Repair
100% Portland Cement Parking Garage $0 19.1 years
25% Fly Ash Parking Garage $22.14/nT ($2.05/ft2) 28.7 years
BC Gas Operations Centre: This project in Surrey, BC was also commissioned by the GVRD, and developed by EcoSmart. This is a 15,980 nr (172,000 sq. ft.) office building with an additional 3,995 nr (43,000 sq. ft.) of
underground parking. This structure was built with over 10,300 cubic yards of concrete. The concrete on this project utilized fly ash to replacement cement at levels of 20% to 40%. This case study gives in depth information on concrete construction with significant amounts of fly ash used for a typical large office building (Rice, 2000).
Much of the concrete was exposed for this building, which required more attention to concrete appearance and finishing than for a typical office building. This building utilized exposed concrete shear walls with punched window openings to resist lateral wind and seismic design loads. The original goal after schematic design for the project was to use 40% fly ash content in place of cement overall. This amount was chosen as an amount that was reasonable to achieve, while significantly above the typical level used. The structural engineer noted that the actual concrete mix designs used are usually designed by the concrete supplier in coordination with the contractors input. The design team for this project had to consider many aspects of the concrete design and construction that are not necessarily typical. Therefore, the structural engineer and owner had much more input. (Rice, 2000).
The different aspects considered were strength, durability, workability, economics, variability, color, curing time, and finishing. The typical design strength for mixes on this project was 30 Mpa (4350 psi). This was specified as the 56 day strength in lieu of the typical 28 day strength due to the slower strength
gain of high volume fly ash concrete. The stripping strength was specified at 10 Mpa (1450 psi) for architectural concrete and 8 MPa (1160 psi) for columns, slabs and beams. Durability was not a concern, since concrete with fly ash has superior durability compared to 100% Portland cement mixes. The contractor commented that the fly ash concrete was more workable than conventional mixes. The contactor also noted that the cost of fly ash was about one half the cost of cement, and also required less labor to place due to its superior workability. The variability and color of the architectural concrete was a concern. It was determined that the source of cement and aggregates had a greater effect on color than did the fly ash. It was noted that the fly ash caused the concrete to have a warmer color than the plain grey cement color if the concentration is high enough. The curing time and finishing were the two most significant factors in deciding how much fly ash to use. The concerns over these issues were much the same as for the Government of Canada Building. The longer set time of the 40% mix became problematic right away at the beginning of construction. The contractor made a decision to not use concrete with fly ash at temperatures less than 10 degrees Celsius (50 F). The same concern with slab surface defects in high volume fly ash concrete was addressed on this project as with the Government of Canada Building. The contractor advised using a double wide trowel for finishing slabs which can ride over the top of waves in the surface of the slab allowing for a smoother more uniform finish. Although the use of high levels of fly ash as
a cement replacement brought new challenges to the construction of the building, the contractor was able to work through the issues and gain experience in the use of these types of mixes. The contractor now advocates the use of fly ash, and became involved in using 55% fly ash in the subsequent project stating they felt comfortable and confident in its use. The contactor suggested that more education needs to be given to suppliers, placers, and finishers in order to facilitate more fly ash use (Rice, 2000). The fly ash and cement statistics for this project are shown in Table 15.
Table 15 Concrete Pour Data for the BC Gas Operations Center
Construction (Rice, 2000)
Mix Fly Ash Content Fly Ash Wt. Cement Wt. Concrete Used
R1534 20% 55 kg/m3 220 kg/m3 6.0 m3
R2034 20% 59 kg/m3 236 kg/m3 10.0 m3
R2099 20% 60 kg/m3 240 kg/m3 4.8 m3
R3034 20% 75 kg/m3 300 kg/m3 385.6 m3
R3035 20% 73 kg/m3 292 kg/m3 488.8 m3
R3035W 20% No Data No Data 10.6 m3
R3036 20% 82 kg/m3 328 kg/m3 7.2 m3
T3025 20% 60 kg/m3 240 kg/m3 1,227.8 m3
T3034 20% No Data No Data 38.0 m3
T3035 20% No Data No Data 288.0 m3
R3536 23% 106 kg/m3 355 kg/m3 351.2 m3
M2045 40% 104 kg/m3 156 kg/m 216.8 m3
M3015 40% 135 kg/m3 203 kg/m3 97.6 m3
M3034 40% 130 kg/m3 195 kg/m3 3,979.2 m3
M3036 40% 105 kg/m3 158 kg/m3 621.2 m3
M3043 40% 110 kg/m3 165 kg/m3 212.0 m3
All Other 0% 0 kg/m3 Varied 6,664.6 m3
Note, over 818 metric tons (900 tons) of fly ash were used on this project saving approximately 818 metric tons of carbon dioxide form being released into the atmosphere. After reviewing this case study, a Life 365 LCA analyses was completed for the concrete used on this project. The Life 365 results in Table 16 indicate a significant savings in life cycle cost, as the rate of fly use increases for portions of the structure exposed to salts and deicers. The 40% fly ash mix design also results in a doubling of the time to first repair over a 100% Portland cement mix, in the exposed condition application.
Table 16 Life 365 Life Cycle Cost Analysis (BC Gas Operations Centre)
Concrete Mix Used Exposure Condition Assumed Life Cycle Cost Savings over 75 Year Life Time to First Repair
100% Portland Cement Parking Garage $0 16.2 years
20% Fly Ash Parking Garage $17.29/nr ($1.60/ft2) 22.0 years
40% Fly Ash Parking Garage $40.3 l/m2 ($3.74/ft2) 33.7 years
Two Folsom: This is a large office building in the San Francisco Bay area, which utilized several different blended cement mixes in the range of 15% to 50% fly ash. This structure was a 15 story, 50,167 m2 (540,000 sq. ft.) building with a concrete frame. This case study reports very few delays in the construction schedule due to set up time of high volume fly ash concrete. No special cure was used for slabs with 15% to 33% fly ash cement mixes. A 7 day wet cure was used
for slab-on-grade which contained a 50% fly ash cement mix. The contractor was quoted as saying properly proportioned HVFA concrete is adaptable to current building practices". The contractor also stated they would use HVFA concrete again in the future. This project did not have the cold temperature concerns that were found in the EcoSmart, Inc. case studies in Canada. No significant problems were reported for this project which utilized 9,175 nr (12,000 cubic yards) of concrete containing 20% or more fly ash as cement material (Headwater, 2001). The breakdown of fly ash used is shown in Table 17.
Table 17 Concrete data for the Two Folsom Project (Headwaters, 2001)
Application Area** Fly Ash Content In Place Volume Design Strength
Working Slab 33% 955.7m1 (1,250 yd") 20.67MPa (3,000 psi)
Shear Wall Foundation 33% 1,777.6m-1 (2,325 yd:^) 34.45MPa (5,000 psi)
Other Foundations 50% 1,490.9m'* (1,950 yd1) 34.45MPa (5,000 psi)
Basement Perimeter Walls* 20% 1,529m1 (2,000 yd1) 27.56MPa (4,000 psi)
Slab on Grade 50% 2.600m1 (3,400 yd1) 27.56MPa (4.000 psi)
Columns 33% 57m1 (75 yd1) 34.45MPa (5,000 psi)
Miscellaneous Curbs/Pads 33% 516m1 (675 yd3) 20.67MPa (3,000 psi)
Metal Deck Slabs 33% 248m1 (325 yd3) 27.56MPa (4.000 psi)
* Shotcrete application.
** Not all concrete elements are included.
Note, approximately 2,270 metric tons (2,500 tons) of fly ash were used on this project saving approximately 2540 metric tons (2,800 tons) of carbon dioxide form being released into the atmosphere. After reviewing this case study, a Life 365 LCA analyses was completed for the concrete used on this project. The
results are shown in Table 18, and again reveal the cost savings are great over the life of the structure, for parking garage concrete elements utilizing significant rates of cement replacement with fly ash.
Table 18 Life 365 Life Cycle Cost Analysis (Two Folsom)
Concrete Mix Used Exposure Condition Assumed Life Cycle Cost Savings over 75 Year Life Time to First Repair
100% Portland Cement Parking Garage $0 36.5 years
33% Fly Ash Parking Garage $30.44/m" ($2.83/ft2) 61.9 years
Madera Project: This case study demonstrates the use of high volume fly ash concrete in small structures. This project was a model home built in Gainesville, Florida, and designed in part by the University of Floridas Energy Extension Service to promote resource efficient construction(ISG Resources Inc., 2003). The foundation for this building utilized a high volume fly ash mix with a 21 MPa (3000 psi) design strength. No admixtures were used in this mix. Finishers were able to get on the slab on grade within one hour of the pour completion and had no problems with the workability or finish. Sixty one cubic meters (80 cubic yards) were placed in the building foundation with a boom pump. The concrete mix used a 40% class F fly ash and 60% type II cement as cementing materials. The 28 day strength test results exceeded the 21 MPa (3000 psi) design strength. Approximately 16.3 metric tons (18 tons) of fly ash was