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Evaluation of Portland-limestone cement concretes containing high volume fly ash

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Title:
Evaluation of Portland-limestone cement concretes containing high volume fly ash
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Martin, Timothy Todd
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English
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xvi, 108 leaves : ; 28 cm

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Portland cement -- Evaluation ( lcsh )
Limestone -- Evaluation ( lcsh )
Fly ash ( lcsh )
Portland cement -- Additives -- Evaluation ( lcsh )
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bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )

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Bibliography:
Includes bibliographical references (leaves 105-108).
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Timothy Todd Martin.

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|University of Colorado Denver
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(\
EVALUATION OF PORTLAND-LIMESTONE CEMENT CONCRETES
CONTAINING HIGH VOLUME FLY ASH
by
Timothy Todd Martin
B.S., University of Colorado Denver, 2008
A thesis submitted to the
University of Colorado Denver
in partial fulfillment
of the requirements for the degree of
Master of Science
Civil Engineering
2010


This thesis for the Master of Science
degree by
Timothy Todd Martin
has been approved
by
Stephan Durham
n-z /o
Date


Martin, Timothy Todd (M.S., Civil Engineering)
Evaluation of Portland-Limestone Cement Concretes
Containing High Volume Fly Ash
Thesis directed by Associate Professor Stephan Durham
ABSTRACT
There is a global initiative aimed at reducing the impact of humans on the
environment of which the concrete industry is a large part. In order to achieve this,
current focus is being placed on the use of portland-limestone cements. U.S.
standards currently allow for a replacement of portland cement clinker up to 10% and
an increase to 15% is being considered. Canadian standards currently allow the use
of 15% limestone and Europe the maximum allowed is 35%. This research compares
the performance of concrete produced using portland-limestone cement and with
Type I/II portland cement. Additionally high volumes of fly ash were incorporated in
order to determine its effect on concretes made with portland-limestone cement. Six
concrete mixtures were designed according to Colorado Department of
Transportation (CDOT) Class P structural concrete mixture requirements: two control
mixtures, one with conventional Type Eli portland cement and one with portland-


This abstract accurately represents the content of the candidates thesis. I recommend
its publication.


limestone cement, and 4 experimental mixtures replacing portland-limestone cement
with 30%, 40%, 50%, and 60% fly ash. Testing of the fresh and hardened properties
was conducted including slump, air content, unit weight, compressive strength,
tension tests, and modulus of elasticity. Both concretes containing 100% Type I/II
cement and portland-limestone cement met the CDOT Class P strength requirements
at the required 28 days. At 56 days 3 of the portland-limestone concretes
incorporating high volume fly ash met the 28 day CDOT Class P strength
requirements. When concrete strengths were normalized for air content, the portland-
limestone cement concrete with fly ash contents up to 50% were all found to have
similar strengths with strengths substantially decreasing with 60% fly ash. The
results of this research lead to the conclusion that additional research should be
conducted into the use of high volume fly ash in concretes made with portland-
limestone cements. The feasibility of changing current concrete mixture design
practice from prescriptive requirements to performance based specifications as well
as changing performance requirements to later age strengths should also be
investigated.


DEDICATION
I dedicate this thesis to my wife. Without her constant understanding, patience, and
support, as well as her help in the lab, this thesis would never have been possible.


ACKNOWLEDGEMENT
The materials used for this research were provided by Boral Material Technologies
and Holcim Inc. Special thanks go to Brooke Smartz with Holcim Inc. for her help
during this research.
I wish to thank my advisor Dr. Stephan Durham for his support and guidance. I
would also like to thank my defense committee Dr. Kevin Rens and Dr. Fred Rutz for
their participation.
I also want to thank Adam Kardos for his help in the University of Colorado Denver
Civil Engineering Materials Testing Laboratory and Zack Ballard for his help during
batching.


TABLE OF CONTENTS
List of Figures............................................................xii
List of Tables..............................................................xv
Chapter
1. Introduction..............................................................1
1.1 Concrete.................................................................1
1.2 Concretes Environmental Impact..........................................1
1.3 Research Interest........................................................2
1.4 Thesis Overview..........................................................2
2. Literature Review.........................................................3
2.1 Overview.................................................................3
2.2 Concrete................................................................3
2.3 Cement..................................................................4
2.3.1 Cement Types...........................................................5
2.3.1.1 Portland Cement......................................................5
2.3.1.2 Blended Hydraulic Cements............................................6
2.3.1.3 Hydraulic Cements....................................................7
2.4 Environmental Impact....................................................8
2.4.1 Sustainable Development................................................8
2.5 Fly Ash................................................................10
vi


2.5.1 The Pozzolanic Reaction.................................................11
2.5.2 Effects on Concrete Properties..........................................12
2.5.2.1 Fresh Concrete Properties.............................................12
2.5.2.2 Hardened Concrete Properties..........................................13
2.5.3 High Volume Fly Ash.....................................................13
2.6 Portland-Limestone Cements...............................................17
2.6.1 Portland-Limestone Cement Production....................................18
2.6.2 Properties of Portland-Limestone Cement Concretes.......................18
2.6.2.1 Impact on Cement Hydration............................................18
2.6.2.2 Impact on Fresh Concrete Properties...................................20
2.6.2.3 Impact on Hardened Concrete Properties...............................21
2.6.2.3.1 Compressive Strength................................................21
2.6.2.3.2 Durability..........................................................23
2.6.3 Case Study............................................................24
2.7 Portland-Limestone Cements with Fly Ash..................................25
2.7.1 Durability..............................................................25
2.7.2 Compressive Strength....................................................26
2.7.3 Case Studies............................................................27
2.8 Summary..................................................................29
3. Problem Statement..........................................................30
vii


3.1 Statement
30
3.2 Research Objective........................................................30
4. Experimental Plan..........................................................32
4.1 Mixture Design............................................................32
4.1.1 Mixture Specification....................................................32
4.1.2 Concrete Mixtures.......................................................33
4.1.2.1 Cementitious Content...................................................35
4.1.2.2 Water Content..........................................................36
4.1.2.3 Coarse Aggregate Content...............................................36
4.1.2.4 Air Content............................................................37
4.1.2.5 Fine Aggregate Content.................................................37
4.1.2.6 Air Entraining Agent...................................................38
4.2 Concrete Materials........................................................38
4.2.1 Cementitious Content.....................................................38
4.2.1.1 Cement.................................................................38
4.2.1.2 Fly Ash................................................................40
4.2.2 Aggregates.............................................................40
4.2.3 Air Entraining Agent....................................................41
4.3 Concrete Mixing.........................................................41
4.4 Concrete Curing...........................................................42
viii


4.5 Concrete Testing
42
4.5.1 Fresh Concrete Properties.................................................43
4.5.1.1 Slump....................................................................43
4.5.1.2 Unit Weight.............................................................43
4.5.1.3 Air Content.............................................................44
4.5.1.4 Concrete Temperature....................................................45
4.5.2 Hardened Concrete Properties..............................................45
4.5.2.1 Compressive Strength.....................................................45
4.5.2.2 Tensile Strength........................................................46
4.5.2.2.1 Modulus of Rupture................................................... 47
4.5.2.2.2 Splitting Tension Test.................................................47
4.5.2.3 Modulus of Elasticity....................................................48
4.5.2.4 Permeability............................................................49
5. Experimental Results.........................................................51
5.1 Overview....................................................................51
5.2 Fresh Concrete Properties...................................................51
5.2.1 Slump......................................................................52
5.2.2 Air Content and Unit Weight...............................................53
5.2.3 Temperature...............................................................56
5.3 Hardened Concrete Properties..............................................57
ix


5.3.1 Compressive Strength.................................................58
5.3.1.1 Comparison of the Control Mixtures.................................61
5.3.1.2 Comparison of Compressive Strength of PLC Concretes with HVFA......62
5.3.1.3 Normalization of Compressive Strengths.............................64
5.3.2 Tensile Strength.....................................................65
5.3.2.1 Modulus of Rupture.................................................66
5.3.2.2 Splitting Tensile Strength.........................................68
5.3.2.3 Tension Tests Results..............................................72
5.3.3 Modulus of Elasticity..............................................73
5.3.4 Permeability.........................................................76
6. Economic and Environmental Benefits.....................................79
6.1 Economic Benefits......................................................79
6.2 Environmental Benefits................................................80
6.3 Recommendation........................................................80
7. Conclusion and Recommendations..........................................81
7.1 Fresh Concrete Properties..............................................81
7.2 Hardened Concrete Properties...........................................82
7.3 Recommendations........................................................83
Appendix
A. Mixture Designs........................................................85
x


B. Material Technical Data Sheets....................................91
C. Hardened Concrete Properties Test Data...........................101
REFERENCES..........................................................105
xi


LIST OF FIGURES
Figure
2.1. Portland Cement and Fly Ash at 1000X Magnification
(Kosmatka et al., 2003)................................................12
2.2. Compressive Strength versus Age (Siddique, 2004).....................14
2.3. Evolution of Hydration Products in Portland Cement Paste
(Bonavetti et al., 2001)...............................................19
2.4. Compressive Strength Comparison of PLC with Other
Composite Cements (Voglis et al., 2005)................................22
5.1. Slump Test Results and AEA Dosages....................................53
5.2. Air Content versus Unit Weight........................................55
5.3. Results of Unit Weight Tests..........................................56
5.4. Ambient Temperature versus Concrete Temperature.......................57
5.5. Compressive Strength Test Using the Forney F-401 Concrete
Testing Machine........................................................59
5.6. Compressive Strength for Control and PLC-HVFA Concrete Mixtures.......60
5.7. Compressive Strength versus Age Graph.................................61
5.8. Compressive Strength versus Age of Control Mixtures...................62
5.9. Normalized Compressive Strengths......................................65
5.10. Modulus of Rupture Test..............................................66
5.11. MOR Test Results.....................................................67
xii


5.12. MOR Test Results versus ACI Estimation...................................68
5.13. The Splitting Tension Test...............................................69
5.14. Splitting Tension Test Results...........................................71
5.15. Splitting Tension Test Results versus ACI Estimation.....................72
5.16. Tensile Strength Comparisons.............................................73
5.17. The MOE Test.............................................................74
5.18. MOE Test Results.........................................................76
5.19. RCPT Test................................................................77
5.20. RCPT Test Results........................................................78
A.l. Mix Design #1............................................................85
A.2. Mix Design #2.............................................................86
A.3. Mix Design #3............................................................87
A.4. Mix Design #4............................................................88
A.5. Mix Design #5............................................................89
A. 6. Mix Design #6............................................................90
B. l. Holcim Type Ell Cement Material Certification Report....................91
B.2. Holcim Envirocore GU Cement Material Certification Report.................92
B.3. Boral Class F Fly Ash Material Safety Data Sheet.........................93
B.4. Boral Class F Fly Ash ASTM C 618 Test Report............................96
B.5. Coarse Aggregate Laboratory Test Report...................................97
xiii


B.6. Fine Aggregate Laboratory Test Report....................................98
B.7. Eucon Air 40 Material Data Sheet.........................................99
xiv


LIST OF TABLES
Table
2.1. ASTM C 150 cement types and uses..........................................6
2.2. ASTM C 1157 hydraulic cement types and uses...............................7
2.3. Compressive strengths of concrete cylinders (Hooton et al., 2010).........23
4.1. CDOT Class P structural concrete specifications...........................33
4.2. Concrete design mixtures..................................................34
4.3. Mixture identification matrix.............................................35
4.4. Holcim Type I/II cement chemical and physical properties..................39
4.5. Holcim, Inc. ASTM C 1157 Type GU portland-limestone cement
properties................................................................40
4.6. Measure of permeability using the RCPT................................50
5.1. Summary of tests performed................................................51
5.2. Fresh concrete properties.................................................52
7.1. Comparison of CDOT Class P structural concrete specifications
with experimental results.................................................82
C.l. Average compressive strengths for all mixtures..........................101
C.2. Compressive strength test results for mixture #1........................101
C.3. Compressive strength test results for mixture #2........................102
C.4. Compressive strength test results for mixture #3........................102
xv


C.5. Compressive strength test results for mixture #4...................103
C.6. Compressive strength test results for mixture #5...................103
C.7. Compressive strength test results for mixture #6...................104
C.8. Tensile strength test results.......................................104
xvi


1. Introduction
1.1 Concrete
Concrete is present in almost every facet of our daily lives and is found in a multitude
of forms. Concrete is used in roads, bridges, sidewalks, foundations, walls, slabs,
and in many other applications. According to the Portland Cement Association
(PCA) (2010a), besides water, concrete is the most commonly used material on
earth. According to the World Business Council for Sustainable Development
(2010), for every person on earth approximately 3 tons of concrete is used on an
annual basis and concrete is used twice as much as all other building materials
combined.
1.2 Concretes Environmental Impact
Production of portland cement (PC) results in the release of approximately 0.9 pounds
of CO2 pound of cement produced (Portland Cement Association (PCA), 2010a). As
a result of the amount of CO2 released during production as well as other operations
required for the production of concrete, the concrete industry contributes
approximately 5% of the total global CO2 emissions.


1.3 Research Interest
Sustainable materials and methods are topics that are becoming more important given
the emphasis that is increasingly being placed on reducing the impact of humans on
the environment. Concrete is a factor of this impact. The use of portland-limestone
cement (PLC) is one method of reducing the concrete industrys environmental
impact that is gaining acceptance. By replacing PC clinker with limestone during
cement production CCB gases are reduced due to decreased production of PC clinker.
The use of high volume fly ash (HVFA) is another method that is also gaining
acceptance. Similar to PLC, CO2 emissions are reduced when cement content is
replaced with fly ash (FA). The use of FA, a byproduct of coal combustion, recycles
a material that would otherwise end up in a landfill. Although extensive research has
been conducted into the use of limestone in cement production as wells as the use of
HVFA in concrete, there is limited research in the use of HVFA with PLC concrete.
1.4 Thesis Overview
Chapter 1: Introduction
Chapter 2: Literature Review
Chapter 3: Problem Statement
Chapter 4: Experimental Plan
Chapter 5: Experimental Results
Chapter 6: Economic and Environmental Benefits
Chapter 7: Conclusions and Recommendations
2


2. Literature Review
2.1 Overview
The literature review serves as a background for the research that was conducted into
the use of HVFA in PLC concretes that is presented in this paper. The literature
review focused on the following subjects:
Concrete
Cement
Environmental Impact
Fly Ash
Portland-Limestone Cements
Portland-Limestone Cements with Fly Ash
2.2 Concrete
Concrete is primarily made of five main ingredients: PC, water, fine aggregate (sand),
coarse aggregate (gravel), and air. In a typical concrete mix the total volume of
concrete is approximately 7% to 15% PC, 14% to 21% water, 60% to 75% aggregate
(fine and coarse), and the final 4% to 8% consisting of entrapped and entrained air
(Kosmatka, Kerkhoff, & Panarese, 2003). Other substances are also commonly used
to influence the performance of the concrete. These include supplementary
cementitious materials (SCM) such as FA, blast furnace slag (BFS), and silica fume
3


(SF), as well as chemical admixtures such as air entraining agents (AEA), set
controlling admixtures, and plasticizers.
2.3 Cement
PC is created when cement clinker and gypsum are ground together. Clinker is made
up of a blend of calcareous materials, such as limestone, and argillaceous materials,
such as clay and shale (Kosmatka, Kerkhoff, & Panarese, 2003). After being finely
ground, these materials are fed into a kiln and heated to temperatures which
exceeding 2500F (Kosmatka, Kerkhoff, & Panarese, 2003). As a result of this
process, four major chemical compounds are produced and are the primary
components of PC clinker: tricalcium silicate (C3S), dicalcium silicate (C2S),
tricalcium aluminate (C3A), and tetracalcium aluminoferrite (C4AF). When water is
added to PC, a process known as hydration takes place which transforms the mixture
into its familiar rocklike state (Kosmatka, Kerkhoff, & Panarese, 2003). It is the
interaction of C3S, C2S, C3A, and C4AF with water during hydration that produces
these results. During hydration four primary products are formed: calcium silicate
hydrate (C-S-H), calcium hydroxide (CPI), ettringite, and monosulfoaluminate. Of
these four products, C-S-H is the major contributor to the overall strength of the
concrete, with CH and ettringite making some contribution to strength as well.
4


2.3.1 Cement Types
The American Society for Testing and Materials (ASTM) defines three broad
classifications of cement, ASTM C 150 Standard Specification for Portland Cement,
ASTM C 595 Specification for Blended Hydraulic Cements, and ASTM C 1157
Performance Specification for Hydraulic Cements (Kosmatka, Kerkhoff, & Panarese,
2003). Each classification encompasses several cement types which have different
uses in construction.
2.3.1.1 Portland Cement
ASTM C 150 is the classification that covers the PC that is commonly used in
construction in the United States. Within this classification, five major cement types
are defined as shown in Table 2.1. The cement type that is commonly used in
construction and commonly found in hardware stores is Type I/II cement which meets
the specifications for both cement types I and II. ASTM C 150 specifies a
prescriptive set of chemical and physical standards as well as a set of performance
standards that must be met for each cement type (ASTM International, 2010).
5


Table 2.1. ASTM C 150 cement types and uses.
Cement Uses
Type I Type II Type III Type IV Type V General Purpose Moderate Sultate Resistance High Early Strengths Low Heat of Hydration High Sulfete Resistance
2.3.1.2 Blended Hydraulic Cements
ASTM C 595 blended hydraulic cements (BHC) are produced by intergrinding or
blending PC with one or more SCM such as BFS, FA, SF, or other pozzolan materials
(Kosmatka, Kerkhoff, & Panarese, 2003). There are three primary types defined by
ASTM C 595: Type IS(X), Type IP(X), and Type IT (AX) (BY). X and Y are where
the percentages of SCM used in the blend are indicated. S designates the use of BFS
and P designates the use of a pozzolan such as FA (Portland Cement Association
(PCA), 2010c). IT cements are ternary blends where A and B specify the types of
SCMs that are used in the cement blend (Portland Cement Association (PCA),
2010b). BHC are typically general use cements but modifications for moderate and
low heat of hydration and moderate and high sulfate resistance applications is
possible. Like the ASTM C 150, ASTM C 595 also has an established set of
prescriptive and performance base requirements (ASTM International, 2010).
6


2.3.1.3 Hydraulic Cements
ASTM C 1157 hydraulic cements are a comparatively new specification being first
introduced in 1992 and modified again in 1998 (Tennis, 2001). Six major types of
cements are defined in this specification as shown in Table 2.2. With the hydraulic
cements, there are no chemical and physical prescriptive requirements like the ASTM
C 595 and ASTM C 150 cements. Instead, the cements must meet certain minimum
performance standards depending on their uses, similar to those specified by the other
two ASTM standards (Tennis, 2001). Because these cements only have to meet
certain performance requirements, the cement producer has the ability to design
innovative cement blends that are more environmentally friendly than traditional PC
(Van Dam, Smartz, & Laker, 2010).
Table 2.2. ASTM C 1157 hydraulic cement types and uses.
Cement Type Uses
GU General Purpose
MH Moderate Heat of Hydration
HE High Early Strengths
LH Low Heat of Hydration
MS Moderate Sulfate Resistance
HS High Sulfate Resistance
The ASTM C 1157 cements currently are not widely used in the construction
industry. Though the building codes of most states have provisions allowing the use
of these cements, most state departments of transportation do not (Van Dam, Smartz,
7


& Laker, 2010). There are two major barriers that currently inhibit the acceptance of
ASTM C 1157 cements: 1) uncertainty regarding the long-term durability of
concrete made with these cements, and 2) a lack of experience working with these
cements (Van Dam, Smartz, & Laker, 2010).
2.4 Environmental Impact
The production of cement is an energy intensive process which utilizes large
quantities of natural resources. As a result, cement manufacturing contributes
approximately 2% to the total CO2 emissions in the United States and approximately
5% worldwide (Portland Cement Association (PCA), 2010a). When considering all
greenhouse gas emissions, cement manufacturing contributes approximately 3% to
the total global emissions and 1% to the total United States emissions (Portland
Cement Association (PCA), 2010a). There are two primary sources of COi emissions
in cement production; approximately 40% is contributed by the burning of fossil fuels
and the other 60% comes from the processing of limestone (calcium carbonate) in the
kiln (Van Dam, Smartz, & Laker, 2010).
2.4.1 Sustainable Development
Going green is becoming more important with increased understanding of the human
impact on the environment and sustainable development is an important part of going
green. Sustainable development has many definitions. One that is appropriate for
8


engineering practice is meeting the needs of the present without compromising the
ability of future generations to meet their own needs (American Association of State
Highway and Transportation Officials (AASHTO), 2010). Considering the concrete
industrys contribution to green house gases and the fact that concrete is the second
most used material in construction in the world, it is important that the concrete
industry play a role in sustainable development.
P. Kumar Mehtas article Greening of the Concrete Industry for Sustainable
Development (2002) is an outline of the role of the concrete industry in going green.
He states that industrial ecology, the practice of recycling waste material from one
industry to be used in another industry, is an important role in this process. The use
of low volumes of FA, a byproduct of coal combustion, in concrete is one small way
in which the concrete industry is already practicing industrial ecology. In addition to
industrial ecology, Mehta states that the concrete industry must also adopt a holistic
approach in concrete design and construction. This requires that the industry move to
design and construct structures that are more durable. The use of HVFA is the most
promising example of how we can build concrete structures that are more durable and
resource-efficient (Mehta, 2002).
In order for the concrete industry to be a part of sustainable development,
Mehta believes that the industry has three barriers that it must overcome. The first
barrier is a restructuring of current construction practices. Currently emphasis is
placed on fast construction and low construction budgets rather than a reduction in
9


life-cycle costs. Because of this emphasis, the structures that are being built today
have a tendency to deteriorate faster which results in a considerable waste of
capital and materials (Mehta, 2002). The second barrier is the prescriptive
requirements of current building codes which focus on the materials and mixture
proportions rather than performance. The third barrier, according to Mehta, is the
focus of current engineering education and research that, like the construction
industry, focuses on the short term. Instead, education and research should focus
more on the holistic approach emphasizing durability and a reduction in long term
life-cycle costs.
2.5 Fly Ash
The use of FA in concrete mixtures has been an accepted practice for many years and
is the most widely used SCM and is estimated to be used in approximately 50% of the
ready mixed concrete (Kosmatka, Kerkhoff, & Panarese, 2003). A byproduct of the
coal combustion process, it is separated into two different classifications based upon
carbon and calcium (CaO) content (Kosmatka, Kerkhoff, & Panarese, 2003). Class F
FA typically has a low CaO content but high carbon contents (Kosmatka et al., 2003).
Class C on the other hand has a high CaO content but lower carbon contents
(Kosmatka, Kerkhoff, & Panarese, 2003). Class F and Class C FA also react very
differently in concrete mixtures. Class F is pozzolanic in nature. It requires the
presence of water and CH from the hydration process in order to react. Class C,
10


however, is considered to be pozzolanic and cementitious. The primary reason for
their differences is due to the types of coal that are used in the combustion process.
Class C FA comes from lignitic coal that is primarily found in the Western United
States and Class F FA comes from bituminous and subbituminous coal that is
primarily found east of the Mississippi River (Kosmatka, Kerkhoff, & Panarese,
2003). Class F and Class C FA also typically have different rates of dosage. Dosage
rates range from 15% to 25% and 15% to 40% for Class F and Class C FA
respectively, with the dosage rates expressed in terms of the percentage of total
cementitious materials (Kosmatka, Kerkhoff, & Panarese, 2003).
2.5.1 The Pozzolanic Reaction
The use of SCMs, such as FA in concrete mixtures, is typically used to enhance the
properties of hardened concrete by either interacting chemically with the hydration
products or by acting as inert filler. The chemical interaction takes place as a result
of the pozzolanic reaction. As shown in Equation 1.1, the silica in the SCMs reacts
with the water in the mixture and the CH from hydration to form C-S-H. As a result
CH, which is more soluble and more permeable, is replaced by C-S-H. As inert filler,
SCMs pack the voids of the concrete. These two processes result in a denser concrete
microstructure and an increase in the overall strength of the concrete. This in turn
results in a concrete that is less permeable and more durable.
11


CH + H20 + S -> C-S-H
Equation 1.1
2.5.2 Effects on Concrete Properties
2.5.2.1 Fresh Concrete Properties
FA generally has a positive impact on fresh concrete properties. FA particles are
similar in size to PC but, as seen in Figure 2.1, they are spherical in shape as opposed
to the more angular shapes of PC particle. As a result, the FA particles act like ball
bearings in the concrete mixture making it more workable and therefore easier to
place during construction than a concrete mixture with the same water-to-
cementitious ratio (w/cm) using 100% PC. The use of FA also results in a lower heat
of hydration and less bleeding and segregation (Kosmatka, Kerkhoff, & Panarese,
2003). FA also extends the setting time of concrete which in some cases is a problem
during construction.
Figure 2.1. Portland Cement and Fly Ash at 1000X Magnification
(Kosmatka et al., 2003).
12


2.5.2.2 Hardened Concrete Properties
FA generally has a positive impact on the hardened concrete properties. Concretes
containing FA have been found to improve concretes permeability, reduce alkali-
silica reactivity (ASR), and improve concretes resistance to chemical attack
(Kosmatka, Kerkhoff, & Panarese, 2003). The affect of FA on concrete strength is
somewhat mixed. FA reduces the early age strengths. However, at later ages it is
typically found to have higher strengths than concrete without FA or other SCMs.
2.5.3 High Volume Fly Ash
Currently the use of FA in concrete up to 30% replacement of PC is common practice
in the concrete industry (Crouch et al., 2007). Concretes that contain FA in quantities
greater than 30% are considered to be HVFA concretes and the use of these concretes
is gaining in popularity. The impact of HVFA on concrete is similar to that of
concrete containing normal dosage rates of FA.
The use of HVFA in concrete has a significant impact on concrete strength.
Siddique (2004) investigated four different concrete mixtures with differing amounts
of FA used in three of the mixtures. All four concrete mixtures had similar w/cm. As
seen in Figure 2.2, higher levels of FA resulted in lower compressive strengths up to
365 days. Poon et al. (2000) had similar results. They found that up to 90 days of
age, strengths in concrete mixtures with 45% replacement of FA had lower
compressive strengths than those containing 25% and 0% FA.
13


45
3
B
a>
Cl
E
v
Age (du>s)
Mixture M-l (0% llv ash- ElMsv.jrc V-2 (40% llv ash)
Mixture M-. (!5xo fly a^h QM:xrjre V-4 (50% fly ash'-
Figure 2.2. Compressive Strength versus Age (Siddique, 2004).
The reduction in concrete strength is counteracted by a subsequent reduction
in w/cm. Crouch et al. (2007) conducted a study of a typical Tennessee Department
of Transportation (TDOT) concrete mixtures using HVFA. Two concrete mixtures
were batched with Class C FA, the first with 25% FA as specified by TDOT and the
second with 50% FA. In addition, two more concrete mixtures were batched using
Class F FA, the first containing 20% FA as specified by TDOT and the second with
50% FA. The TDOT mixtures were batched with a w/cm of 0.40 for the Class C FA
mixture and 0.45 for the Class F. The HVFA mixtures had w/cm of 0.34 and 0.35 for
the Class C and Class F mixtures respectively. Their study found that despite the
reduction of w/cm, the mixtures all had similar slumps. The slump of the Class C
HVFA mixture was found to be only 0.5 inches (12.7 mm) less than the TDOT
14


mixture and the slump of the Class F HVFA mixture was found to only be 0.25
inches (6.35 mm) less than the TDOT mixture. The reduction in w/cm impacted the
results of the compressive strengths as well. Despite the higher volume of FA, the
Class C HVFA mixture was found to have higher compressive strengths at all ages
than the TDOT Class C mixture. The Class F HVFA mixture was found to have
compressive strengths that were very similar to that of the TDOT Class F mixture,
although later age strengths of the HVFA mixture were found to be lower.
The greatest benefit of using HVFA concrete is its impact on the durability of
concrete. Reduction in the quantity of PC in concrete results in reductions in drying
shrinkage and thermal contraction, both of which are responsible for cracking in
concrete (Mehta, 2002). Mehta and Langley (2000) investigated an unreinforced raft
foundation designed and built to last 1000 years for a Hindu Temple on the island of
Kauai in the Pacific Ocean. The concrete mixture was a HVFA mixture using 57%
Class F FA. Because there was no reinforcement, the volume of concrete, and the
high volume of FA, careful planning was required before construction took place. As
a result, nine months after the foundation had been placed, careful examination of
the exposed surface has shown no evidence of any cracking (Mehta & Langley,
2000). Crouch et al. (2007), in their study of the TDOT concrete mixtures, found that
the increase in FA resulted in lower absorption and lower permeability which
correlates to a higher degree of durability.
15


Research conducted at the University of Colorado Denver has shown that
there is an optimum percentage of HVFA. Liu (2010) investigated the use of post
mercury control FA in Colorado Department of Transportations (CDOT) Class D
structural concrete. A total of eight concrete mixtures were designed, batched, and
tested with differing amounts of total cementitious content and FA replacement
percentages. Two concrete mixtures were designed with a cementitious content of
660 lbs/yd3 (392 kg/m3) and with FA replacements of 30% and 50% and two mixtures
with 570 lbs/yd3 (338 kg/m3) also with FA replacements of 30% and 50%. Three
more concrete mixtures were designed with identical mixture proportions containing
615 lbs/yd3 (365 kg/m3) of cementitious materials with 40% FA replacement and one
mixture with 705 lbs/yd3 (418 kg/m3) total cementitious materials with 60% FA
replacement. Based on the results of the fresh and hardened concrete tests, Liu
(2010) determined that the concrete mixture containing 570 lbs/yd3 (338 kg/m3)
cementitious materials with 50% FA was the mixture combination that provided
optimal results. Chrismer and Durham (2010) conducted a study of HVFA in CDOT
Class P structural concrete. Four concrete mixtures were designed with a total
cementitious content of 660 lbs/yd3 (392 kg/m3) in all four mixtures with FA
replacements of 50%, 60%, 70%, and 80%. The 50% FA concrete mixture
outperformed the other three concretes overall and was the only mixture to meet the
CDOT Class P Concrete strength requirement of 4200 psi (29 MPa) at 28 days.
16


2.6 Portland-Limestone Cements
Interest in the use of PLC concrete is one that is gaining worldwide attention as
increasing pressure is placed on cement producers to reduce emissions (Blair, 2010).
PLC concretes have been used in Europe for the last 25 years where current standards
allow for a maximum of 35% replacement of PC (Cement Association of Canada,
August, 2009). In fact, currently the most popular cement used in Europe is PLC
containing up to 20% limestone (Portland Cement Assocation (PCA), 2010d). By
comparison PLC is relatively new to North America. Canada began allowing the use
of 5% limestone in PC in 1983 and in 2008 increased that limit to 15% (Blair, 2010).
In a conversation with Brooke Smartz (2010), Sustainable Products Manager at
Holcim Inc., on November 3, 2010, she stated that the current U.S. standards limit the
use of limestone to 10% but that an increase to 15% is currently under consideration.
The main benefit of using limestone is the reduction of green house gas
emissions and energy usage during the cement production process. The increase to
15% limestone in PLC produced in Canada is expected to result in a 10% decrease in
CO2 emissions (Cement Association of Canada, August, 2009). It is also expected to
reduce energy consumption by 11.8 trillion Btu and carbon dioxide emissions by
more than 2.5 million tons per year (Blair, 2010).
17


2.6.1 Portland-Limestone Cement Production
PLC is produced by intergrinding PC clinker with limestone and gypsum. Because
limestone is easier to grind than the clinker, the clinker is found to have a higher
fineness in PLC than other cements resulting in better particle size distribution
(Voglis et al., 2005). These two factors result in higher early strength gain and
reduced water demand (Voglis et al., 2005).
2.6.2 Properties of Portland-Limestone Cement Concretes
It is commonly believed that when used in PC concretes limestone acts only as inert
filler (Thomas et al., 2010). An extensive amount of research, however, shows that
limestone actually impacts the hydration process as well as the fresh and hardened
concrete properties
2.6.2.1 Impact on Cement Hydration
Hydration in PLC concretes is similar to PC concretes resulting in the formation of C-
S-H, CH, ettringite, and monosulfoaluminate. An additional hydration product,
monocarboaluminate, is formed in PLC concretes due to the presence of the
limestone and previous research has found that this effects the formation of ettringite
and monosulfoaluminate (Bonavetti et al., 2001). In concretes containing PC
ettringite is initially formed through the interaction of C3A, sulfate ions from the
gypsum, and water. When gypsum is no longer available and there is still excess
18


C3A, ettringite reacts with the C3A and water to form monosulfoaluminate. In the
case of PLC concretes, research conducted by Bonavetti et al. (2001) found that the
formation of monocarboaluminate takes place over that of the monosulfoaluminate as
shown in Figure 2.3.
Figure 2.3. Evolution of Hydration Products in Portland Cement Paste
(Bonavetti et al., 2001). E = Ettringite, Ms = Monosulfoaluminate,
Me = Monocarboaluminate, and CH = Calcium Hydroxide.
Research conducted by Tsivilis et al. (2002) found that limestone affected
other hydration products as well. They found that the limestone provided nucleation
sites which resulted in the acceleration of the production of C-S-H which results in
higher early age strengths.
19


2.6.2.2 Impact on Fresh Concrete Properties
The fresh concrete properties are important in considering the impact of PLC on
concrete. The research examined for this literature review seems to provide
contradicting results. All the research studied indicates that concretes produced with
PLC result in a decrease in water demand as a result of the increased particle size
distribution. A study conducted by Tsivilis et al. in (2000) showed that an increase in
limestone content also resulted in decreasing slumps. Sprung and Siebel reported that
concretes made with PLC had an increase in workability in comparison with
concretes made with PC (as cited in Hawkins et al., 2003, p. 5).
Research has also shown that the use of PLC in concrete reduces the amount
of bleed water released. Research by Schmidt found that PLC mortars showed a
decrease in bleed water by more than 50% when compared to PC mortars (as cited in
Hawkins et al., 2003, p. 5).
20


2.6.2.3 Impact on Hardened Concrete Properties
2.6.2.3.1 Compressive Strength
Past research examining the effect of PLC on compressive strength provide
contradicting results.
Research conducted by Tsivilis et al. (2002), four concretes produced with
PLC with limestone contents of 10%, 15%, 20%, and 35% were compared with a
fifth concrete produced with PC. Results showed that the early age strengths were
similar to the concrete with PC for limestone contents up to 20%. At seven days
compressive strengths were found to be higher than the 100% PC concrete. By 28
days the compressive strength of the PC concrete was higher than all four of the PLC
concretes. The PLC concrete with 35% limestone was found to have significantly
lower compressive strengths at all ages.
Voglis et al. (2005) compared PLC with PC and two other composite cements.
The composite cements, including the PLC, were all produced with 15% replacement
of PC clinker. The other two composite cements were made with natural pozzolana
and FA. In addition, all four cements were produced to have the same 28 day
strengths. Similar to the results of the study by Tsivilis et al. (2000), PLC was found
to have higher compressive strengths up to 7 days of age. As shown in Figure 2.4,
after 28 days, the PLC had lower compressive strengths than the other three cements.
21


(0
Q.
W
c
a>
M

>
'35
in

a.
E
o
u
1 2 7- 28 90 180 360 540
BPC
PLC
PPC
PFC
Age (days)
Figure 2.4. Compressive Strength Comparison of PLC with Other Composite
Cements (Voglis et al., 2005). PC = Portland Cement, PLC = PC +
Limestone, PPC = PC + Pozzolana, PFC = PC + Fly Ash
In research by Hooton et al. (2010) two series of concretes were produced;
three concretes with 100% cement and three concrete with 30% slag. The cements
used in each series included a PC and two PLC with 10% and 15% limestone
contents. As shown in Table 2.3, the concretes containing 30% slag had lower
compressive strengths than the concretes in the other series, it should be noted that
the PLC concretes in this series had higher strengths than the PC concrete and by 91
days the PLC with 15% limestone had the highest compressive strength followed by
the 10% limestone PLC. In the concretes containing no slag, the PLC concretes had
higher strengths than the concrete made with PC up to 91 days, at which time the
compressive strength of the PC concrete was higher than the 15% limestone PLC.
22


Table 2.3. Compressive strengths of concrete cylinders (Hooton et al., 2010).
Compressive Strength (MPa) 7 Days 28 Days 56 Days 91 Days
GU 100% 39.3 47.3 50.2 58.5
PLC 10 100% 42.6 50.7 56.8 60.2
PLC 15 100% 40.4 49.4 55.9 56.1
GU 70% Slag 30% 19.4 30.0 33.0 33.6
PLC 10 70% Slag 30% 30.0 42.6 46.2 53.4
PLC 15 70% Slag 30% 31.4 43.0 46.8 54.0
2.6.2.3.2 Durability
Research has also shown that the use of PLC had an impact on permeability as
measured by the Rapid Chloride Permeability Test (RCPT). Tsivilis et al. (2000) and
Hooton et al. (2010) found that PLC with 10% limestone performed similarly to PC.
At limestone contents of 15% and higher, they found that permeability improved.
The review of past research in regards to the impact of PLC on freeze/thaw
resistance resulted in contradictory results. Tsivilis et al. (2000) found that
freeze/thaw resistance decreased with increasing limestone content. Hooton et al.
(2010), on the other hand, concluded that freeze/thaw resistance of PLC was similar
to that of PC.
Tsivilis et al. (2000) also studied the effects of corrosion on PLC concretes in
comparison with PC concretes measuring corrosion potential, gravimetric mass loss
23


of rebar, carbonation, and porosity. Their results found that in all instances PLC
concretes performed better than PC concretes.
Hooton et al. (2010) also investigated sulfate resistance, alkali-silica reactivity
(ASR), and drying shrinkage. In the case of sulfate resistance and ASR limestone
was found to negatively impact concrete performance as indicated by increases in
mortar bar expansion with increasing limestone content. The impact of PLC on
drying shrinkage, on the other hand, was found to be similar to that of PC.
2.6.3 Case Study
Thomas et al. (2010) conducted a study on the performance of PLC concrete in a
parking lot for a ready mixed concrete plant near Gatineau, QC, Canada that was
constructed in October of 2008. Two series of concrete mixtures were designed for
this study: one with PC and the other with PLC. In each series four concrete mixtures
were produced with SCM replacements of 0%, 25%, 40%, and 50%. Field and
laboratory testing was conducted including compressive strength, RCPT, freeze/thaw
resistance, bulk-diffusion, and scaling resistance to deicing chemicals. In all cases no
significant difference was found between the PLC and PC concretes. The surface of
the concrete parking lot was inspected April of the following year and was found to
be in excellent condition with no scaling evident despite a fairly harsh winter with
numerous applications of deicing salts (Thomas et al., 2010).
24


2.7 Portland-Limestone Cements with Fly Ash
Similar research of concrete containing FA and limestone has primarily taken place
outside of the United States. This research has focused on cement mortars created
with blended cements where FA and limestone were interground with clinker and
gypsum. As a result, it was difficult to relate these studies to current practices in the
United States. In these cases, discussion of their research is limited to results found
from the compression strength of the cement mortars.
2.7.1 Durability
An important characteristic of concrete is its durability which is a determining factor
in the service life of a concrete structure. Van Dam et al. (2010) conducted research
comparing concretes made with Colorado and Utah produced ASTM C 150 Type II/V
cement, ASTM C 150 Type I/II cement, ASTM C 1157 Type GU cement, and ASTM
C 1157 Type GU cement with 20% FA. Two series of concrete mixtures were tested:
one series was made with a cementitious content of 500 lbs/yd3 (297 kg/m3) and the
second series with a cementitious content of 564 lbs/yd3 (335 kg/m3). In their
investigation factors determining the durability of concrete were tested including
sulfate resistance, ASR, freeze/thaw resistance, drying shrinkage, and permeability.
In almost all cases the test results showed that the three different mixtures from each
series performed similarly to another and in most cases differences were relatively
small regardless of cement type or content (Van Dam, Smartz, & Laker, 2010).
25


Differences were observed in the chloride permeability tests. The concretes
containing 500 lbs/yd3 (297 kg/m3) all performed similarly with the relative chloride
permeability rating found to be moderate to high. Increasing the cement content to
564 lbs/ yd3 (335 kg/m3) resulted in better performance with the concrete containing
20% FA found to have the lowest permeability at a rating of low to moderate and the
concrete containing the Type GU cements found to have higher permeability ratings
at moderate to high.
2.7.2 Compressive Strength
Compressive strength is the most widely tested and considered to be one of the most
important concrete properties. In testing the compressive strengths, Van Dam et al.
(2010) that although results varied between the concretes containing the Type II/V
cement, Type I/II cement, and the Type GU cement, the concrete containing Type GU
cement with 20% FA was found to generally have lower compressive strengths at 7
days. By 28 days the compressive strengths were found to be close or comparable
and were expected to comparable or higher at later ages.
Research conducted by Elkhadiri et al. (2002) investigated five series of
cement mixtures each series containing three different mixtures. One series was
made with standard cements: one with 100% PC and the other two were PLC cements
with 13% and 18% limestone. Two series used cements where increasing
percentages of FA was substituted for clinker in the 100% PC and the PLC with 13%
26


limestone. The last two series were made by substituting increasing percentages of
FA for the 100% PC and the PLC with 13% limestone at time of batching. Elkhadir
et al. (2002) found that compressive strengths decreased with increasing amounts of
limestone and with increasing amounts of FA.
2.7.3 Case Studies
Van Dam et al. (2010) conducted 5 case studies into the use of concretes made with
ASTM C 1157 cements with 10% limestone that also incorporated FA.
The first case study was of a concrete pavement project located in Denver,
Colorado in the Stapleton area in 2007. The concrete used for part of this project
used Type GU cement with 20% FA. The concrete was found to have compressive
and tensile strengths that exceeded the designed strengths. The project also used a
similar concrete mixture using Type Eli cement. No noticeable differences were
detected between the two concrete mixtures at the time of construction. After three
years there have been no noticeable differences in the performance of the concretes
either.
The second case study reported by Van Dam et al. (2010) was of a CDOT
project that took place near Lamar, Colorado on Highway 287. The concrete used on
the project was a CDOT Class P concrete made with Type GU cement and 20% FA.
Laboratory trial batches were made using Type GU cement and Type Eli cement.
The results of the fresh and hardened concrete properties for both concretes were
27


found to be comparable with one another. Once again no difference was noted at the
time of placement between the concrete made the Type GU cement and standard
concretes made with Type I/II cement.
The third case study was of another CDOT project using Class P concrete on
1-25 in Castle Rock, Colorado. The concrete designed for the project again used Type
GU cement with 20% FA. The tensile strength of the concrete was found to exceed
the minimum design requirements.
The fourth case study conducted by Van Dam et al. (2010) was in Morgan County,
Utah near the Devils Slide Cement Plant. The concrete used on the project was
made with Type GU cement with 20% FA and was found to exceed the compressive
and tensile design strengths.
The fifth case study was of a project in Salt Lake City, Utah on 104th South.
This particular study was a joint study with ten departments of transportation, the
Federal Flighway Administration, and the University of Utah. A trial that was
conducted for the study was the use of concrete made with Type GU cement and 25%
FA for a single days placement. This was compared to a similar concrete mixture
made with Type II/V cement that was used on the project. The strengths of the trial
concrete were found to exceed the design requirements and there were no noticeable
differences between the two concretes at the time of placement.
28


2.8 Summary
Cement production is an energy intensive process that is contributing to the human
impact on the environment. However the use of ASTM C 1157 cements and HVFA
offers a solution in reducing the impact of the concrete industry on the environment.
29


3. Problem Statement
3.1 Statement
The production of PC is an energy intensive process and is a significant factor of the
human impact on the global environment. Due to the prolific use of concrete,
reducing consumption does not seem to be an alternative at this time. In order to
reduce environmental impact, the concrete industry must find ways to reduce the
production of global warming emissions. There are two methods which have promise
in reducing the concrete industrys environmental impact: (1) replacing PC with other
more environmentally friendly products in concrete mixtures, and (2) designing
concrete mixtures that are more durable. By replacing PC with other more
environmentally friendly products, it is believed that this will reduce overall
consumption of PC and therefore reduce PC production. Producing more durable
concretes is also believed to help reduce the overall consumption of PC by reducing
the rate at which older buildings have to be replaced. The use of HVFA in
conjunction with PLC is expected to meet all of these objectives; however, very little
research has been conducted in this area.
3.2 Research Objective
The purpose of this research is to investigate the use of HVFA in PLC and its impact
on the performance of concrete. It is believed that by using FA in conjunction with
PLC, the amount of PC required in concrete mixtures will be significantly reduced
30


and yet will still meet design requirements. In addition, it is also believed that this
will produce a concrete that is more durable than what is currently being used in
construction. In order to determine if the use of HVFA in PLC will meet these
expectations, four primary objectives were defined:
Perform a literature review of related research.
Develop an experimental plan for designing and testing the concrete mixtures.
Test and compare the fresh and hardened concrete properties of the concrete
mixtures.
Based on the results of this research develop a set of recommendations for further
investigation.
31


4. Experimental Plan
During the course of this research, six concrete mixtures, two control mixtures and
four experimental mixtures, were designed and tested. All mixtures were designed
using the CDOT Class P structural concrete specifications, which is used in
pavements, as a benchmark. The fresh and hardened concrete properties were tested
for each concrete mixture and were compared to one another as well as to the CDOT
Class P requirements. In addition, modulus of elasticity (MOE), modulus of rupture
(MOR), and splitting tension tests were compared to the prediction equations found in
American Concrete Institute (ACI) 318-08 code book (American Concrete Institute,
2008).
4.1 Mixture Design
4.1.1 Mixture Specification
The CDOT Class P structural concrete for pavement mixture specification was used
in this research as a benchmark, the requirements of which are summarized in Table
4.1. For this research, however, the maximum allowed Class F fly ash content of
30% was exceeded. This was done in order to determine if the CDOT Class P
performance requirements will be met by PLC concretes with HVFA.
32


Table 4.1. CDOT Class P structural concrete specifications.
Required 28 day compressive strength 4200 psi (29 Mpa)
Minimum cementitious content 660 Ibs/yd3 (392 kg^n3)
Air content % 4-8
Water cementitious ratio (w/cm) 0.44
Minimum coarse aggregate % by weight of total aggregate 55
Minimum flexural strength at 28 days 650 psi (4.5 Mpa)
Allowable % of Class F Fly Ash by weight of total cementitious 10-30
4.1.2 Concrete Mixtures
A total of six concrete mixtures were designed for the purpose of this research: two
control mixtures and four experimental mixtures. The control concrete mixtures were
designed with 100% Type I/II PC and 100% PLC. The experimental concrete
mixtures were designed using PLC with differing replacements of FA. Past research
has shown that in concretes containing PC there is a point of decreasing rate of return
with increasing FA content. As a result, 50% FA has been found to be an optimal
percentage of HVFA in concrete. In order to determine if this holds true with PLC
concretes, the experimental concretes were designed with FA content starting at 30%,
the max allowed in CDOT Class P concrete, and increased 10% to a maximum FA
content of 60%.
All the concrete mixtures were designed using the absolute volume method as
outlined by AC1 211.1 and based on the saturated surface dry (SSD) weights. Since
33


the purpose of this research was to quantify the effects of HVFA in PLC, all mixtures
were designed using the same cementitious content, course aggregate content, w/'cm,
and air content as shown in Table 4.2. Fine aggregate content decreased with
increasing amounts of FA as required by the absolute volume design method. The
complete concrete mixture design spread sheets are located in Appendix A.
Table 4.2. Concrete design mixtures.
Mixture # 1 2 3 4 5 6
w/cm 0.44 0.44 0.44 0.44 0.44 0.44
Cement Type Eli PLC PLC PLC PLC PLC
Cement, 660 660 462 396 330 264
lbs/yd3(kg/m3) (392) (392) (274) (235) (196) (157)
Class F Fly Ash, lbs/yd3(kg/m3) 0 0 198 (117) 264 (157) 330 (196) 396 (235)
Course Aggregate, 1800 1800 1800 1800 1800 1800
lbs/yd3(kg/m3) (1068) (1068) (1068) (1068) (1068) (1068)
Fine Aggregate, 1030 1030 975 957 939 921
lbs/yd3(kg/m3) (611) (611) (578) (568) (557) (546)
Water, 290 290 290 290 290 290
lbs/yd3(kg/m3) (172) (172) (172) (172) (172) (172)
Air Content 6.0% 6.0% 6.0% 6.0% 6.0% 6.0%
AEA, fl. oz/cwt (mL/100 kg) 1.4 (91) 1.4 (91) 1.1 (72) 0.9 (59) 0.6 (39) 0.5 (33)
Each concrete mixture was given a unique mixture identification in order to
indentify each one throughout the testing duration. This mixture identification
utilized the w/cm, the equivalent number of cement bags, the percent replacement of
34


fly ash, and the cement type in that order. For example, mixture 0.44-7.0-FA0-I/II
had a w/cm of 0.44, a cementitious content equivalent to 7 bags of cement, a 0%
replacement with FA, and used Type I/II cement. Table 4.3 below summarizes the
cementitious content of all six mixtures.
Table 4.3. Mixture identification matrix.
Mix # Mixture ID w/cm Cementitious Content % FA Cement Type
1 0.44-7.0-FA0-I/II 0.44 660 lbs/yd3 0 Type I/II
2 0.44-7.0-FA0-PLC 0.44 660 lbs/yd3 0 PLC
3 0.44-7.0-FA30-PLC 0.44 660 lbs/yd3 30 PLC
4 0.44-7.0-FA40-PLC 0.44 660 lbs/yd3 40 PLC
5 0.44-7.0-FA50-PLC 0.44 660 lbs/yd3 50 PLC
6 0.44-7.0-FA60-PLC 0.44 660 lbs/yd3 60 PLC
4.1.2.1 Cementitious Content
All six concrete mixtures were designed with a total cementitious content of 660
lbs/yd3 (392 kg/m3). The two control mixtures, mixtures #1 and #2, were designed
with 100% PC and 100% PLC respectively at a total cementitious content of 660
lbs/yd3 (392 kg/m3). This was done in order to establish a performance baseline. The
four experimental mixtures were made with PLC and Class F FA. Because the focus
of this research was to determine the impact of HVFA on concrete mixtures made
with PLC, a minimum FA content of 30% was chosen based upon the maximum
35


allowed per CDOT Class P requirements. This resulted in a design of 462 lbs/yd3
(274 kg/m3) PLC and 198 lbs/yd3 (117 kg/m3) FA in concrete mixture #3. The FA
content of the other three concrete mixtures was increased at a constant rate of 10% to
a maximum of 60% FA in mixture #6. This resulted in a PLC content of 396 lbs/yd3
(235 kg/m3), 330 lbs/yd3 (196 kg/m3), and 264 lbs/yd3 (157 kg/m3) for mixtures #4,
#5, and #6 respectively and a respective FA content of 264 lbs/yd3 (157 kg/m3), 330
lbs/yd3 (196 kg/m3), and 396 lbs/yd3 (235 kg/m3).
4.1.2.2 Water Content
The water content was found based upon a w/cm of 0.44 as required by the CDOT
Class P specifications. Using Equation 4.1, the design water content was found to be
290 lbs/yd3 (172 kg/m3) for all six concrete mixtures.
water content
w/cm cernentitious content Equation 4.
4.1.2.3 Coarse Aggregate Content
As previously noted, the coarse aggregate content was kept constant for all six
mixtures in order to observe the change in performance as a result of increasing the
FA content. A coarse aggregate content of 1800 lbs/yd3 (1068 kg/m3) for all six
mixtures was used in the concrete mixture design. CDOT Class P specifications
required that coarse aggregate content is a minimum of 55% of the total aggregate.
36


The total aggregate content of all the mixtures was found to be 64% and higher. The
two control mixtures had the lowest coarse aggregate by percentage of total aggregate
at 64%, this increased to 65% for mixtures #3 and #4, and then to 66% for the final
two mixtures.
4.1.2.4 Air Content
The required air content for CDOT Class P structural concrete is between 4% and
8%. A design air content of 6% was chosen for all six concrete mixtures since this
was midway between the allowed extents.
4.1.2.5 Fine Aggregate Content
The fine aggregate content for each mixture was determined using the ACI 211.1
Absolute Volume Method. As a result, the fine aggregate content decreased with
increasing amounts of FA. Mixtures #1 and #2 were found to require the highest fine
aggregate contents at 1030 lbs/yd3 (611 kg/m3). With the addition of FA into mixture
#3 this decreased to 975 lbs/yd3 (578 kg/m3). The fine aggregate content was reduced
by 18 lbs/yd3 (10.7 kg/m3) for each of the subsequent concrete mixtures to 921
lbs/yd3 (546 kg/m3) for mixture #6.
The reduction in fine aggregate is a result of the difference in specific
gravities of the cement and FA used in the concrete mixtures. The lower specific
gravity of the FA resulted in lower fine aggregate requirements.
37


4.1.2.6 Air Entraining Agent
In order to meet the design air content of 6%, an AEA was used in all six concrete
mixtures. An initial dosage of 1.4 fluid ounces per hundred pounds of cement (fi.
oz/cwt) (91 mL/100 kg) was chosen for the two control mixtures and then reduced for
the experimental concrete mixtures due to the addition of Class F FA. The decrease
in AEA was due to the expected increase in workability of the concrete mixture
containing FA. The dosage rates for the experimental mixtures were 1.1 fl. oz/cwt
(72 mL/100 kg), 0.9 fl. oz/cwt (59 mL/100 kg), 0.6 fl. oz/cwt (39 mL/100 kg), and 0.5
fl. oz/cwt (33 mL/100 kg) for mixtures #3, #4, #5, and #6 respectively.
4.2 Concrete Materials
The materials obtained for this research were donated to the University of Colorado
Denver Civil Engineering Materials Testing Laboratory.
4.2.1 Cementitious Content
4.2.1.1 Cement
Two types of locally produced cements were used in the design of the concrete
mixtures for this research, Type I/II PC and PLC both of which were produced and
donated by Holcim, Inc. The Type I/II PC meets the ASTM C 150 specifications for
Type I and Type II PC. The PLC, part of Holcims Envirocore product line, meets
38


ASTM C 1157 specifications for Type GU cements and contains 10% limestone. The
properties of both cements are found in the Material Certification Reports located in
Appendix B.
As shown in Table 4.4 and Table 4.5, both cements have similar physical
property requirements. The Type I/II cement has additional chemical requirements
that do not apply to the Type GU PLC. The Type GU PLC also has a higher Blaine
fineness.
Table 4.4. Holcim Type I/II cement chemical and physical properties.
Item Limit Result
Chemical
C3S (%) - 59
C2s (%) - 11
c3A (%) 8 max 7
C4AF (%) - 10
C3S + 4.75 C3A(%) 100 max 92
Limestone (%) 5.0 max 3.7
Loss on Ignition 3.0 max 2.6
Insoluble Residue (%) 0.75 max 0.59
Physical
260 min
Blaine Fineness (m /kg) 430 max 414
Autoclave Expansion (%) (C 151) 0.80 max -0.02
Compressive Strength MPa (psi)
3 Days 10.0 (1450) min 31.1 (4510)
7 Days 17.0 (2470) min 37.6 (5460)
39


Table 4.5. Holcim, Inc. ASTM C 1157 Type GU portland-limestone cement
properties.
Item Limit Result
Physical
2 Blaine Fineness (m /kg) - 513
Autoclave Expansion (%) (C 151) 0.80 max 0.00
Compressive Strength MPa (psi)
1 Day - 21.4 (3100)
3 Day 10.0 (1450) min 35.4 (5130)
7 Day 17.0 (2470) min 40.8 (5920)
28 Day 28.0 (4060) min 45.9 (6660)
4.2.1.2 Fly Ash
The FA used in this research was Borals Class F FA which meets ASTM C 618
specifications. The specific gravity of the FA was 2.79. The Material Safety Data
Sheet is located in Appendix B.
4.2.2 Aggregates
The coarse and fine aggregates used in the concrete mixtures were obtained from a
Brighton, CO plant and was tested by WesTest and found to meet ASTM C 33 No.
57/67 coarse aggregate standards. WesTest also found the SSD bulk specific gravity
and absorption capacity to be 2.60 and 0.7% respectively. The nominal maximum
40


aggregate size and maximum aggregate size were found to be 1 inch and 1.5 inches
respectively.
The fine aggregate, which came from the Brighton, CO plant, was found to
meet ASTM C 33 fine aggregate standards by WesTest. The SSD bulk specific
gravity and absorption capacity were found to be 2.63 and 0.7% respectively. The
fineness modulus was found to be 2.55.
The laboratory test results for the coarse and fine aggregate are located in
Appendix B.
4.2.3 Air Entraining Agent
For all of the concrete mixtures, Eucon Air 40 AEA by Euclid Chemicals was used
and meets ASTM C 260 specifications. Chemical admixtures such as AEAs are used
to improve certain concrete properties. Use of AEA is required when the design air
content is greater than 1% to 3% that is typically entrapped in the concrete mixture
during mixing.
The technical data sheet for the Eucon Air 40 AEA is located in Appendix B.
4.3 Concrete Mixing
At the time of batching, all six mixtures were mixed using the same method. All of
the coarse aggregate was initially added to the concrete mixer followed by most of the
41


water. Approximately 1 lb of the water was withheld and mixed with the AEA.
Next, half the fine aggregate was added and the rest of the water with the AEA was
added. The mixer was started and once the water and aggregate were thoroughly
combined the cementitious materials were slowly added followed by the rest of the
fine aggregate. Once all materials were added, the concrete mixtures were thoroughly
mixed per ASTM Standard C 192; mixing for three minutes, allowed to rest for three
minutes, and then mixed again for another two minutes.
4.4 Concrete Curing.
Curing of all concrete specimens took place in a water tank in the
temperature/humidity controlled room of the University of Colorado Denver
Materials Testing Laboratory to moist cure until time of testing as required by ASTM
C 192.
4.5 Concrete Testing
In order to quantify the effects of HVFA on concrete mixtures made with PLC, the
fresh and hardened concrete properties were tested and compared.
42


4.5.1 Fresh Concrete Properties
In order to determine the effects of HVFA on concrete mixtures containing PLC, four
fresh concrete tests were performed: slump, unit weight, air content, and concrete
temperature.
4.5.1.1 Slump
The slump test, as specified by ASTM C 143, is considered to be a measurement of
the workability of concrete which is a measure of the effort required to place concrete
in its plastic state. The problem with the slump test, however, is that it does not truly
give an adequate representation of the true workability of concrete when trying to
compare concrete mixtures that are very different in overall make up. When concrete
mixtures are similar to one another, however, it is a good indicator of how easy one
concrete is to place in comparison with the other with minor changes in the concrete
mixture composition. In the case of this research, all the concrete mixtures were
identical to one another varying only in the amount of FA content or the type of
cement used. Therefore it is considered to be a reliable indication of how workable
one concrete mixture is over another in this context.
4.5.1.2 Unit Weight
Determining unit weight, as specified by ASTM C 138, is another quality control test
regularly performed on concrete. If the unit weight is found to be different than the
43


original concrete design specified, then this indicates potential issues with the
concrete mixture such as changes in materials or problems with quality control during
batching. Unit weight is also used to determine the yield of the concrete that is
batched. It is important to note that unit weight is sensitive to the amount of air
content in a concrete mixture. When air content increases unit weight will decrease
and as air content decreases unit weight will increase.
4.5.1.3 Air Content
Air content has both a positive and a negative impact on concrete. On fresh concrete,
air content is known to affect the workability of the concrete mixture. An increase in
air content will result in a more workable concrete mixture and therefore higher
slumps. In addition, air content has an impact on hardened concrete as well. The air
content positively influences hardened concrete by increasing durability. This is
especially important when concrete will be exposed to freezing and thawing
conditions such as those experienced in Colorado. Air content, however, has an
adverse affect on concrete strength and in general will reduce the compressive
strength by 5% for every 1% increase in air content. The air content was determined
using the Pressure Method as specified by ASTM C 231.
44


4.5.1.4 Concrete Temperature
Concrete temperature is important when concrete is being placed in hot or cold
weather. The concrete for this research, however, was batched in the University of
Colorado Denver Civil Engineering Materials Testing Lab so temperature was not an
important factor. The concrete temperature for each mixture was determined as
specified by ASTM C 1064.
4.5.2 Hardened Concrete Properties
The hardened concrete properties were tested during the course of this research in
order to determine the affect of HVFA on the mechanical properties of concrete
mixtures using PLC. A total of five tests were performed: compressive strength, two
tensile strength tests MOR and splitting tension, MOE, and permeability.
4.5.2.1 Compressive Strength
Of the tests performed on hardened concrete properties, compressive strength is the
most important and is the one that is the most widely used. The reason for this
importance is because concrete acts primarily in compression and is therefore
designed based on its compressive strength. In addition, almost all other hardened
concrete properties are believed to be directly related to the compressive strength of
concrete. At the time of batching, twelve 4 inch (101.6 mm) x 8 inch (203.2 mm)
(diameter x length) concrete cylinders were created for the purpose of determining the
45


affect of HFVA on the compressive strength of PLC concrete mixtures. Tests were
performed on three cylinders as specified by ASTM C 39 at 1, 7, 28, and 56 days.
The compressive strength was then determined using Equation 4.2 and then averaging
the results.
load (lbs)
compressive strength fc (psi) =------- Equation 4.2
area (in )
4.5.2.2 Tensile Strength
Concrete is weak in tension and in practice it is typically assumed that concrete is
unable to resist any tensile loading. Concrete does have some tensile strength,
however, usually found to be 7% to 11% of the compressive strength and is typically
assumed to be 10% of the compressive strength. Because it is generally assumed that
concrete is unable to resist tensile loading a minimum tensile strength is typically not
required. In some applications, however, such as Class P concrete used in pavements,
a minimum tensile strength is specified. Currently there are no effective test methods
for determining the direct tensile strength of concrete. However, there are two
methods of determining the indirect tensile strength that have been adopted by
ASTM, the MOR test and the splitting tension test.
46


4.5.2.2.1 Modulus of Rupture
MOR, also known as flexural strength, is used typically more often than the splitting
tension test and is a better measure of the tensile strength of concrete. However,
MOR typically overestimates the direct tensile strength of concrete by approximately
11% to 23% (Mindess et al., 2003). This test was performed, as required by ASTM C
78, by using third point loading. The load at failure was then used to determine MOR
(fr) as shown in Equation 4.3 and then averaging the results. In practice MOR is often
estimated using the compressive strength of concrete. Equation 4.4 is the estimation
equation from ACI 318-08 that is typically used.
fr (psi) =
load (lbs) x length (in)
width (in) x (depth (in))2
Equation 4.3
fr (psi) 7.5^ (psi)
Equation 4.4
At the time of batching two 3 inch (76.2 mm) x 4 inch (101.6 mm) x 16 inch
(406.4 mm) (width x depth x length) concrete beams were formed for each concrete
mixture to determine the MOR.
4.5.2.2.2 Splitting Tension Test
Like MOR, the splitting tension test is an estimation of the direct tensile strength of
concrete. Also similar to MOR, this test overestimates the tensile strength by
47


approximately 8% to 14% (Mindess et al., 2003). The splitting tension test, as
required by ASTM C 496, was carried out by applying a load to a concrete cylinder
lengthwise. The load at failure was then used to determine splitting tensile strength
(fct) using Equation 4.5 and then averaging the results. Similar to the MOR. the
splitting tensile strength is typically estimated in practice using Equation 4.6 from
ACI 318-08.
2 x load (lbs)
fct(psi)=---------------------------- Equation 4.5
n x length (in) x diameter (in)
fct (psi) = 6.7-y/fc (psi) Equation 4.6
At the time of batching two 4 inch (101.6 mm) x 8 inch (203.2 mm) concrete
cylinders were formed for each concrete mixture to determine the splitting tensile
strength.
4.5.2.3 Modulus of Elasticity
The MOE of concrete is considered to be a measure of the stiffness of concrete and is
typically assumed to be a linear property, although this is not the case. As in the
tensile strength, MOE is related to the compressive strength of concrete, although
material composition is known to affect MOE as well. The MOE was determined
using the chord MOE procedure as required by ASTM C 469. This requires that the
48


strain, defined as the ratio of the change of length to the original length, is graphed
versus the corresponding applied stress. Two points on this graph are then used to
determine the MOE (Ec) as shown in Equation 4.7. Similar to the MOR and splitting
tensile strengths, MOE is often estimated in engineering practice by using the
compressive strength as shown in Equation 4.8 from ACI 318-08.
Ec (psi)
stress2(psi)-stressi (psi)
strain?-strain
Equation 4.7
Ec (psi) = 57,000yf7(psi)
Equation 4.8
The two cylinders used for the splitting tension test were first used to
determine the MOE of the concrete mixtures. The cylinders were loaded to
approximately 40% of the compressive strength and the stress versus strain curve was
determined. The result for each mixture is the average of the two tests.
4.5.2.4 Permeability
Permeability is an important concrete property and is considered to be a measure of
the durability of concrete and controls the rate of entry of moisture that may contain
aggressive chemicals and the movement of water during heating or freezing
(Mindess et al., 2003). Factors such as w/cm and material composition are the main
factors which impact the permeability of a concrete mixture. Permeability is
49


determined using the rapid chloride permeability test (RCPT) as specified by ASTM
C 1202. This measures the flow of an electric charge through a concrete specimen.
The permeability of the concrete is then determined based on the measured flow as
shown in Table 4.6.
Table 4.6. Measure of permeability using the RCPT.
Charge Passed (Coulombs) Chloride Ion Penetrability
>4000 2000 4000 1000 2000 < 1000 High Moderate Low Very Low (negligible)
At the time of batching two 4 inch (101.6 mm) x 8 inch (203.2 mm) concrete
cylinders were formed for each concrete mixture to determine permeability. Two
inches (50.8 mm) were removed from either end of the concrete cylinders, prepared,
and tested as required by ASTM C 1202. The result for each mixture is the average
of two tests.
50


5. Experimental Results
5.1 Overview
The six concrete mixtures designed and batched during the course of this research
were tested as outlined in Chapter 4 and as summarized in Table 5.1.
Table 5.1. Summary of tests performed.
Test ASTM Time of Specification Testing
Fresh Concrete Properties
Slump C 143 Batching
Unit Weight C 138 Batching
Air Content C 231 Batching
Temperature C 1064 Batching
Hardened Concrete Properties
Compressive Strength C 39 1, 7, 28, and 56 days
MOR C 78 56 days
Splitting Tension C 496 56 days
MOE C 469 56 days
RCPT C 1202 56 days
5.2 Fresh Concrete Properties
The fresh concrete properties for all six batches were tested following ASTM
standards at the time of batching. Four tests were conducted including slump, air
content, unit weight, and concrete temperature. The results are summarized in Table
5.2. There are no requirements for the fresh concrete properties for CDOT Class P
structural concretes.
51


Table 5.2. Fresh concrete properties.
Mix Slump in. (mm) Air Content (%) Ambient Temp. F(C) Concrete Temp. F(C) Predicted Unit Weight lbs/ft3 (kg/m3) Measured Unit Weight lbs/ft3 (kg/m3) Difference in Unit Weight lbs/ft3 (kg/m3)
#1 1.75 (44.5) 6.0 69(21) 64(18) 140.0 (2243) 142.0 (2275) 2.0 (32)
#2 2.5 (63.5) 4.9 69(21) 63(17) 140.0 (2243) 144.2 (2310) 4.2 (67)
#3 3.25 (82.6) 9.0 74(23) 71(22) 138.0 (2211) 135.2 (2166) -2.8 (-45)
#4 6.00 (152.4) 7.9 74(23) 70(21) 137.3 (2199) 137.4 (2201) 0.1 (2)
#5 6.25 (158.8) 4.8 73(23) 71(22) 136.6 (2188) 141.2 (2262) 4.6 (74)
#6 7.25 (184.2) 4.0 74(23) 72(22) 136.0 (2179) 141.6 (2268) 5.6 (89)
5.2.1 Slump
Slump was determined using ASTM C 143 and is typically used to indirectly
determine the workability of the concrete mixture. As shown in Figure 5.1, slump
increased with change of cement type for the two control mixtures. Slump increased
0.75 inches (19 mm) from 1.75 inches (44.5 mm) for mixture #1 to 2.50 inches
(63.5mm) for mixture #2. The increase in slump as a result of the use of PLC is due
to particle size distribution. As expected, slump also increased with increasing
amounts of FA. Mixture #3, containing 30% FA, had a slump that was 0.75 inches
(19.1 mm) greater than mixture #2 at 3.25 inches (82.6 mm). At a FA content of 40%
and greater, a substantial increase in slump was observed, with mixtures #4, #5, and
52


#6 found to have slumps of 6.00 inches (152.4 mm), 6.25 inches (158.8 mm), and
7.25 inches (184.2). These results indicate that as a result of the particle size
distribution the use of PLC increases the workability of concrete. It also indicates
that FA increases workability as well and the greater the percentage of FA the more
workable the concrete mixture as a result of a decrease in water demand.
1.6
1.4 %
1.2 IS
1 d
0.8 sx
0.6 a
0.4 < fcd
0.2 0 <
Mixture
Figure 5.1. Slump Test Results and AEA Dosages.
5.2.2 Air Content and Unit Weight
Air content was obtained for each concrete mixture according to ASTM C 231. The
measured air content for each mixture was influenced by the amount of FA used, type
of cement, as well as the amount of AEA used. All but one of the mixtures was found
53


to have an air content that fell within the CDOT Class P structural concrete
specifications. Mixture #3 was found to have 9% air content, 1% higher than that
required by the Class P structural concrete specifications. This is thought to be a
result of too much AEA added at the time of batching.
The unit weight for each concrete mixture was measured as specified by
ASTM C 138. The actual unit weights of the concrete mixtures were close to that of
the design but were found to be higher than what was predicted in all cases but one.
The primary reason for the discrepancy between the predicted and measured unit
weight is believed to be due to the air content. As illustrated in Figure 5.2, the unit
weight was found to be inversely proportional to air content. As the air content
increased unit weight decreased. Human error and scale accuracy also contribute to
unit weight discrepancies.
The mixture with 30% FA was found to have the lowest unit weight, 2.8
lbs/ft3 (45 kg/m3) lower than the predicted unit weight. This same mixture, as
previously noted, was also found to have the highest air content. Mixtures #2, #5,
and #6 were found to have the greatest difference in unit weight between the
predicted and measured with the respective differences at 4.20 lbs/ft3 (67 kg/m3), 4.60
lbs/ft3 (74 kg/m3), and 5.60 lbs/ft3 (89 kg/m3) higher than the predicted unit weights.
These mixtures were also found to have the lowest air contents. The control mixture
with the Type I/II cement and the mixture with 40% FA had unit weights which were
found to be the closest to that of the predicted unit weights at a respective difference
54


Unit Weight (lbs/ft3)
of 2.00 lbs/ft3 (32 kg/m3) and 0.10 lbs/ft3 (2 kg/m3) higher than the predicted unit
weights. The predicted unit weights and the measured unit weights for each of
mixture are illustrated in Figure 5.3.
146.00
144.00
142.00
140.00
138.00
136.00
134.00
132.00
130.00
dm Unit Weight Air Content
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
Mixture
Figure 5.2. Air Content versus Unit Weight
55
Air Content (%)


146.00
Measured Unit Weight
r^>
.2/
'3
£
Mixture
Figure 5.3. Results of Unit Weight Tests.
5.2.3 Temperature
The temperature of the batched concrete mixtures was found using ASTM Standard C
1064 and in all cases was a few degrees lower than that of the measured ambient
temperature at the time of batching. The relation of ambient temperature to concrete
temperature is illustrated in Figure 5.4.
56


Mixture
Figure 5.4. Ambient Temperature versus Concrete Temperature.
5.3 Hardened Concrete Properties
In order to determine the hardened concrete properties, sixteen 4 inch (101.6 mm) x 8
inch (203.2 mm) cylinders and two 3 inch (76.2 mm) x 4 inch (101.6 mm) x 16 inch
(406.4 mm) beams were cast: twelve cylinders for compressive strength, two
cylinders for permeability testing, two cylinders for splitting tensile strength and
MOE testing, and the two beams for MOR testing. After casting, the cylinders and
beams were allowed to harden for 24 hours after which the concrete was removed
from the molds. The one day compressive strength was then determined using three
of the sixteen cylinders of each mixture. The remaining cylinders and beams were
57


placed in a water tank in the temperature/humidity controlled room of the University
of Colorado Denver Materials Testing Laboratory to moist cure until time of testing.
5.3.1 Compressive Strength
Compressive strength is the most important aspect of concrete determining the
amount of loading that a concrete structural element is able to support and is directly
related to almost all other hardened concrete properties. The 1, 7, 28, and 56 day
compressive strengths were determined using three cylinders from each mixture with
the exception of mixtures #5 and #6 where only two cylinders were used to determine
the 28 day compressive strengths. The results were compared to the 4200 psi (29
MPa) 28 day strength requirements for CDOT Class P structural concrete. The
compressive strengths were determined using a Forney F-401 concrete testing
machine as shown in Figure 5.5. Two steel retaining caps with neoprene pads were
placed at either end of the concrete cylinder before being placed into the machine.
As previously noted, the compressive strength of concrete mixtures #5 and #6
was an average of two cylinders rather than three at 28 days of age. At the time of
testing, three cylinders were broken but the data was lost shortly after testing. After
various options were considered, it was decided that the two cylinders for the splitting
tension would be used to determine the 28 day compressive strengths. Due to the
level of quality control at the time of batching and with the data from each series of
cylinder breaks showing that the difference in compressive strengths between
58


cylinders was consistently less than 500 psi, it was believed that the average of two
cylinders would provide an adequate level accuracy.
Figure 5.5. Compressive Strength Test Using the Forney F-401 Concrete
Testing Machine.
The results of the compressive strength tests show that the only concretes to
meet the CDOT Class P structural concrete design requirements were Mixtures #1
and #2. For the other four mixtures, the addition of FA resulted in a dramatic
decrease in compressive strength. The results of the compressive strength tests are
shown in Figure 5.6 and Figure 5.7,
59


Compressive Strength (psi)
6000
Current Class P concrete 28
day strength requirement.
5000 r
4000
1 7 D28 D56
*28 day strengths of
mixtures #5 and #6 are the
average of two cylinders.
3000
2000
1000
0
#2
#6
Mixture
Figure 5.6. Compressive Strength for Control and PLC-HVFA
Concrete Mixtures.
60


6000
Figure 5.7. Compressive Strength versus Age Graph.
5.3.1.1 Comparison of the Control Mixtures
The two control mixtures had the highest compressive strengths at all ages. At 28
days both mixtures had exceeded the design strength of 4200 psi (29 MPa) with
mixture #1 obtaining an average compressive strength of 4885 psi (33.7 MPa) and
mixture #2 reaching an average compressive strength of 4673 psi (32.3 MPa). The
respective average compressive strengths at 56 days were found to be 5291 psi (36.5
61


MPa) and 5129 psi (35.4 MPa). As shown in Figure 5.8, the rate of strength gain for
both concrete mixtures was similar. Between 28 and 56 days of age the rates of
strength gain were almost identical.
5.3.1.2 Comparison of Compressive Strength of PLC Concretes with HVFA
The compressive strengths of all four mixtures containing HVFA had lower average
compressive strengths than the two control mixtures. The reduction in compressive
strengths the result of the pozzolanic reaction as well as the dilution of cement
content in the concrete mixtures. The 1 day strengths of all four mixtures behaved as
expected with the average compressive strengths decreasing with increasing amounts
62


of FA with mixture #3 having the highest compressive strength and mixture # 6 the
lowest. At 7 days of age concrete mixtures #3, #4, and #6 continued this trend.
Concrete mixture #5, however, was found to have an average compressive strength
that was higher than the other three FA mixtures. At 28 days of age the compressive
strength trends once again changed. Mixture #5 was found to have the highest
compressive strength as at 7 days. However, the compressive strength of mixture #4
was found to be higher than that of mixture #3. Mixture #6 was found to still have
the lowest compressive strength. The 28 day and 56 day compressive strengths
continued this same trend, however, all four experimental concrete mixtures failed to
meet the 4200 psi (29 MPa) 28 day compressive strength requirement of Class P
concrete. The results of the compressive strength tests for mixtures #3, #4, #5, and #6
were 3181 psi (21.9 MPa), 3302 psi (22.8 MPa), 3737 psi (25.8 MPa), and 2556 psi
(17.6 MPa) respectively at 28 days. At 56 days of age, compressive strength of
mixtures #3 and #4 were almost identical at 3714 psi (25.6 MPa) and 3723 psi (25.7
MPa) respectively. As at 7 and 28 days, mixture #5 had the highest compressive
strength at 4131 psi (28.5 MPa) almost reaching the 28 day CDOT Class P concrete
strength requirement. Mixture # 6 once again had the lowest strength at 56 days with
a compressive strength of 3106 psi (21.4 MPa).
All data from the compression tests are located in Appendix C.
63


5.3.1.3 Normalization of Compressive Strengths
As previously noted, an increase in air content of 1 % typically results in a 5%
decrease in the compressive strength of concrete. Though the air content for almost
all of the concrete mixtures fell within CDOT Class P specifications, the difference in
the measured air contents was enough to affect compressive strength comparisons.
Normalizing the compressive strengths for air content was performed in order
to provide more comparable compressive strengths. As shown in Equation 5.1, the
normalized compressive strengths (NCS) were determined by subtracting the design
air content of 6% from the measured air content (AC). This was then multiplied by 5
to account for the 5% effect air content has on the compressive strength of concrete.
The measured compressive strength (MCS) was then multiplied by the result and this
product was then added to the measured compressive strength.
NCS (psi) = [(AC ,06)5]MCS + MCS Equation 5.1
As shown in Figure 5.9, normalizing resulted in a slight increase in difference
between mixtures #1 and #2. In addition, the normalized compressive strength of
mixture #3 was found to meet the CDOT Class P 28 day strength requirements at 56
days of age. The strengths of mixtures #3, #4, and #5 were also found to be more
comparable to one another with the normalized compressive strengths moderately
64


decreasing with increasing FA contents. Mixture #6 continued to show a dramatic
reduction in compressive strength in comparison to the other experimental mixtures.
l/i
Q.
CJC
8000
7000
6000
5000
Current Class P concrete 28
day strength requirement.
L.
^ 4000
w
>
1 3000
s_
Q.
£
O
U
2000
1000
1
1 Day
7 Day
28 Day
56 Day
#1
#2
#3 #4
Mixture
#5
#6
Figure 5.9. Normalized Compressive Strengths.
5.3.2 Tensile Strength
Two tests were performed in determining the tensile strength of the concrete
mixtures, the MOR test and splitting tension test. The results of the tests were then
compared to ACI equations commonly used in practice to estimate these values. In
addition, all tensile strengths results were compared to a value equal to 10% of the
compressive strength which is generally accepted to be a close approximation of the
65


direct tensile strength of concrete. All results were also compared to the 650 psi (4.5
MPa) tensile strength requirement of CDOT Class P structural concrete. All data
from the tensile strength tests is located in Appendix C.
Due to the low compressive strengths of the experimental concrete mixtures,
the tensile strength tests were not performed until 56 days of age.
5.3.2.1 Modulus of Rupture
The MOR test is performed by applying two point loads on a beam, as shown in
Figure 5.10. Two beams were formed to determine the MOR of each of the concrete
mixtures. The results were the average of the two tests. Since MOR is directly
related to compressive strength, the results were expected to be similar to those of the
compressive strength tests.
Head of
Testing Machine
Figure 5.10. Modulus of Rupture Test.
66


As shown in Figure 5.11, all concrete mixture failed to meet the tensile
strength requirements for CDOT Class P concrete. Mixtures #1 and #2 had the
highest MOR values at 595 psi (4.1 MPa) and 588 psi (4.1 MPa) respectively. As
expected, the other three experimental mixtures had lower MOR values. Mixtures #3,
#4, and #5 were found to have almost identical MOR values at 560 psi (3.9 MPa),
564 psi (3.9 MPa), and 576 psi (4.0 MPa) respectively. Mixture #6 had the lowest
MOR value at 515 psi (3.6 MPa).
Figure 5.11. MOR Test Results.
67


The measured MOR values were compared with the predicted values given by
the equation in ACI 318-08. As shown in Figure 5.12, the measured MOR values
were higher than the predicted values for all concrete mixtures.
Figure 5.12. MOR Test Results versus ACI Estimation.
5.3.2.2 Splitting Tensile Strength
As shown in Figure 5.13 the splitting tensile strength of the concrete was determined
by applying a load along the length of a concrete cylinder. Two cylinders of each
concrete mixture were tested and the average load at the time of failure was used to
determine the splitting tensile strength. As previously noted, this test was not
performed for mixtures #5 and #6.
68


Although not specifically stated in the specifications for CDOT Class P
concrete, the MOR is the most widely used test for determining tensile strength. The
factor used to multiply the square root of the compressive strength of concrete in the
ACI prediction equations for MOR is higher than the factor used for approximating
the splitting tensile strength. For these two reasons the Class P concrete tensile
69


strength requirement was reduce by the ratio of the two factors as shown in Equation
5.2.
6 7
(650psi)=581 psi Equation 5.2
Similar to MOR, the splitting tensile strength is directly related to
compressive strength and the results are expected to follow the same trend. As shown
in Figure 5.14 the splitting tensile strength for all concrete mixtures did not meet the
modified CDOT Class P 28 day tensile strength requirement. The results were also
significantly lower than the MOR results. As expected the control mixtures had the
highest strengths. The splitting tensile strengths of mixtures #1 and #2 were 484 psi
(3.3 MPa) and 444 psi (3.1 MPa) respectively. The addition of FA in the
experimental concrete mixtures resulted in a significant reduction in the splitting
tensile strength results. Mixtures #3 and #4 had strengths of 314 psi (2.2 MPa) and
325 psi (2.2 MPa) respectively.
70


700
600 ______________________________
Modified Class P concrete 28 day strength requirement.
till
#1 #2 #3 #4 #5 #6
Mixture
Figure 5.14. Splitting Tension Test Results.
The measured splitting tensile strengths were compared to the equation used
in ACI 318-08 to estimate these strengths. As shown in Figure 5.15, the measured
values were lower than the ACI estimation in all cases.
I 500
JZ
|o 400
L.
55 300
jy
I 200
h<
100
0
71


Figure 5.15. Splitting Tension Test Results versus ACI Estimation.
5.3.2.3 Tension Tests Results
The results from both the MOR and the splitting tension tests showed that all concrete
mixtures did not meet the CDOT Class P 28 day tensile strength requirements.
Figure 5.16 compares the results of both tension tests and the ACI estimation
equations. Additionally, the values corresponding to 10% of the compressive
strength are shown.
72


700
*35
a
D£
C
tZ)
£
600
500
400
300
200
100
0
ACI MOR Estimation
A -SplittingTension
I- ACI Splitting Tension Estimation
~ ' 10% Compressive Strength
0 12 3 4 5 6
Mixture #
Figure 5.16. Tensile Strength Comparisons.
5.3.3 Modulus of Elasticity
The MOE was determined by loading two cylinders from each mixture up to 45% of
the measured compressive strength. As shown in Figure 5.17, a compressometer was
installed on each cylinder and the change in length was measured at different
compressive loads. For concrete mixtures #1 through #4, the two concrete cylinders
used for determining the splitting tensile strength were first used to determine MOE.
In the case of mixtures #5 and #6 the cylinders used to determine permeability were
first used to determine the MOE.
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Figure 5.17. The MOE Test.
As in the case of MOR and splitting tension, the MOE is typically considered
to be directly related to the compressive strength and the results are expected to
follow the same trend. As shown in Figure 5.18 mixtures #1 and #2 had the highest
MOE values at 3610 ksi (24,890 MPa) and 3890 ksi (26,821 MPa) respectively. This
was opposite of what was expected with mixture #2 found to have a higher MOE than
mixture #1. As expected, the addition of FA in the experimental mixtures resulted in
74


a decrease in MOE. The MOE values of mixtures #3 and #4 had the lowest MOE
values at 3024 ksi (20,850 MPa) and 3109 ksi (21,436 MPa) respectively. The MOE
values of mixtures #5 and #6 were found to be 3556 ksi (24,518 MPa) and 3179 ksi
(21,918 MPa) respectively.
The measured MOE values for mixtures #1 through #4 were found to be
significantly lower than the equation in ACI 318-08 that is typically used to
determine the MOE of concrete. The reason for the discrepancy was due to the
loading rated used when the load was applied during testing. During the testing of
mixtures #1 through #4, two people were required, one to read the load values and
one to write down the load and displacement values. As a result the loading rate was
slow, approximately 150 to 200 pounds per second, in order to make it possible to
accurately record the measured values. This loading rate was about half of that
required by ASTM standards. A camera was used during the testing of the cylinders
for mixtures #5 and #6 in order to increase the loading rate. The camera recorded the
applied load as the change in length was read aloud from the dial indicator. This
resulted in MOE values that were comparable to the ACI prediction equation as
shown in Figure 5.18.
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5000
4000
~ 3000
it
w
O
^ 2000
1000
0
Mixture
Figure 5.18. MOE Test Results.
5.3.4 Permeability
For each concrete mixture, two concrete cylinders were used to determine
permeability at 56 days of age. Two inches (50.8 mm) were removed from the top of
each cylinder and prepared and tested as required by ASTM C 1202. Prior to testing
each specimen was subjected to a dry vacuum in a desiccator for three hours after
which time water was added while maintaining the vacuum until the specimens were
completely submerged. The vacuum was maintained for another hour after which the
vacuum was released. The specimens remained submerged under water for a
minimum of 18 hours prior to testing. When the specimens were ready for testing,
76


they were put into the test cells as shown in Figure 5.19. In one end of the cell a
prepared NaOH solution was poured and a NaCl solution was poured into the other
end. A 60 volt potential difference was maintained across the two ends of the testing
cell. The total charge passed was measured in coulombs and then related to the
permeability of the concrete.
Figure 5.19. RCPT Test.
As shown in Figure 5.20, the two control mixtures had the highest
permeabilities. Both mixtures were found to be classified as having moderate
permeability though the measured coulombs passed was higher in mixture #2 than
mixture #1 at 3003 C and 2257 C respectively. The addition of the FA resulted in a
significant reduction in the measured permeability with all four experimental
77


mixtures classified at very low permeability. The measured coulombs passed were
lowest in mixtures #3 and #4 at 444 C and 388 C respectively. Contrary to what was
expected, the measured coulombs passed increased in mixtures #5 and #6 at 524 C
and 988 C respectively. The most likely cause for the increase in permeability is due
to the use of the two cylinders of mixtures #5 and #6 for MOE testing prior to
determining permeability causing micro-cracking to occur.
-Q
£
o
3
O
U
5000
t-
4000-
3000 ^
2000 -
1000 -
i-
0
#1
High Permeability
Moderate Permeability
Lo^Permeabilit^
Very Low Permeability
U u M
#2 #3 #4 #5 #6
Mixture
Figure 5.20. RCPT Test Results.
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6. Economic and Environmental Benefits
There are important economic and environmental benefits to the use of PLC concretes
as well as HVFA in PLC concretes. These benefits, however, do not necessarily align
with current construction practice.
6.1 Economic Benefits
There is no well defined short term economic benefit to the use of PLC concretes
over the traditional cements that have been used in concrete construction for years. In
the case of Holcims Envirocore PLC, it is currently marketed at the same price as
Holcims Type I/II cement according to Brooke Smartz of Holcim, Inc (2010). As a
result, contractors will most likely not be interested in using something they have no
experience with when there are no cost savings.
The use of HVFA in PLC concretes does result in immediate cost savings of
the concrete. FA is typically about 75% of the cost of cement. In a typical concrete
mixture, cement usually costs more than all other ingredients. Replacing large
percentages of cement with FA presents a significant reduction in the upfront costs of
the concrete. The slow strength gain of HVFA concrete, however, is contrary to the
fast paced construction time tables that are typically required and may result in an
increase in construction costs as a result of this delay.
There are long term economic benefits for both PLC concretes and HVFA
PLC concretes. The research examined for the literature review showed that PLC and
79


HVFA improved the durability of concrete. The results of this research indicate that
the same holds true for the use of HVFA in PLC concretes. Improved durability
results in lower life cycle costs ultimately saving the owner money. Current
construction practice, however, focuses on construction costs and budgets rather than
the long term costs of maintenance and longevity.
6.2 Environmental Benefits
The most important benefit of using HVFA PLC concrete is the reduction of the
concrete industrys impact on the environment. The concrete industry is one of the
biggest contributors to global pollution accounting for 5% of the CO2 emissions. The
use of limestone alone is expected to reduce the C02 emissions by about 2.5 million
tons per year. The use of FA recycles an industrial byproduct that would otherwise
end up in a landfill. Ultimately, however, current construction practice is more
interested in construction costs rather than using more environmentally responsible
materials.
6.3 Recommendation
There is potential for the construction industry to realize economic benefits while at
the same time benefiting the environment. Quantitative research such as life cycle
analysis should be conducted analyzing and comparing these benefits.
80


7. Conclusion and Recommendations
This research investigated the use of HVFA in concrete using PLC. Six different
concrete mixtures were designed according to CDOT Class P structural concrete
specifications. Two control mixtures, one made with 100% Type I/II PC and one
with 100% PLC, were designed in order to establish a performance baseline for
comparison. Four experimental concrete mixtures were designed in order to study the
effects of HVFA replacement in concretes made with PLC. The fresh and hardened
concrete properties of each concrete mixture were tested and where applicable were
compared to the CDOT Class P structural concrete requirements.
7.1 Fresh Concrete Properties
Increasing FA percentages were generally found to positively affect the fresh
concrete properties.
A reduction in the required dosage of AEA was observed with increasing
percentages of FA in order to meet air content requirements of CDOT Class P
structural concrete.
Slump increased with increasing percentages of FA indicating that HVFA
improves the workability of the concrete mixture.
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7.2 Hardened Concrete Properties
The impact of HVFA on PLC concretes was found to have mixed results on the
hardened concrete properties. Table 7.1 summarizes the results in comparison with
the CDOT Class P structural concrete specifications.
Compressive strength, tensile strength, and MOE were all found to decrease
with the addition of FA.
With a design air content of 6%, FA replacement of 30% is expected to meet
the CDOT Class P 28 day strength requirements at 56 days of age.
The use of 50% FA was found to be the maximum recommended replacement
in the HVFA concrete mixtures.
Permeability was found to decrease with increasing percentages of FA
indicating that the use of HVFA in PLC concretes resulted in concrete
mixtures that were more durable than the concrete mixtures containing no FA.
Table 7.1. Comparison of CDOT Class P structural concrete specifications with
experimental results.
CDOT Class P 28
day Strength
Mixture Compression Tension
#1 Passed Passed
#2 Passed Passed
#3 Failed Failed
#4 Failed Failed
#5 Failed Failed
#6 Failed Failed
82