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The Effect of Low Temperature on the Binding of External Chlorides
by
Ge-Hung Yee-Ching
A thesis submitted in conformity with the requirements for the degree of Master of Applied Science
Civil Engineering University of Toronto
© Copyright by Ge-Hung Yee-Ching (2012)
ii
The Effect of Low Temperature on the Binding of External
Chlorides
Ge-Hung Yee-Ching
Master of Applied Science
Civil Engineering
University of Toronto
2012
Abstract
Designing durable concrete structures is becoming increasingly important with emphasis being
placed on extending service life. This project focuses on the effect of low temperatures on
chloride binding, chloride binding capacity and ion-binder interactions with respect to hydroxyl
ions and pH. Three supplementary cementitious materials were used as well as two w/b ratios,
and four curing times. The effect of temperature cycling on chloride binding, binding capacity
and ion-binder interaction were also investigated. With temperatures decreasing from 23oC to -
15oC, there is a decrease in bound chloride and chloride binding capacity, with
GGBFS>GU>MK>SF being the order of binding. When temperature cycling was performed, the
binding capacity changed depending on the exposure temperature, with warmer temperatures
associated with higher binding capacities. When service life estimates were conducted using
Life-365 software, it was found chloride binding capacities determined at 23oC may not be
conservative when estimating service life in colder climates.
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Acknowledgments
I would like to thank Professor Daman Panesar for her guidance throughout this entire project,
helping and challenging me to ‘dig deeper’ and become a better researcher. Her constant
reviewing of my work and attention to detail were invaluable during the course of this project. I
would also like to thank Professor Douglas Hooton for reviewing this thesis and providing
important feedback.
During the time spent in the laboratory, I would like to especially thank Olga Perebatova for her
tireless efforts in assisting me with testing procedures, ordering materials, and helping to
troubleshoot problems when they arose. Also, I will also like to thank Tino Wang for his efforts
in assisting me throughout the testing phase of the project, and Dr. Mo Liwu for helping me with
the SEM and EDS testing.
For the raw materials used, I would like to thank Holcim Canada, SKW, and Whitemud
resources. I am also grateful to NSERC for providing funding for this project.
I would like to thank all my friends and everyone in the concrete materials research group for all
their support, helping to make my time spent here that much more enjoyable. Special mention is
made of those who I have shared an office with over the past two and a half years. In
alphabetical order: Andre, Ardavan, Eric, Mahsa, Majella, and Mila.
Finally, to my parents, who have supported me through everything that I have done, I am forever
grateful.
I have had a challenging, yet fulfilling time at the University of Toronto and I will always look
back at my time spent here in a positive light as I move on in my future endeavours.
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Table of Contents
List of Tables ................................................................................................................................ vii
List of Appendices ....................................................................................................................... xiii
Chapter 1 Introduction .................................................................................................................... 1
1.1 Background ......................................................................................................................... 1
1.2 Scope and Objectives .......................................................................................................... 3
Chapter 2 Literature Review ........................................................................................................... 4
2.1 Chloride Binding ................................................................................................................. 4
2.1.1 Chemical Binding ................................................................................................... 4
2.1.2 Physical Binding ..................................................................................................... 6
2.2 Factors Affecting Chloride Binding .................................................................................... 7
2.2.1 Supplementary Cementitious Materials .................................................................. 7
2.2.1.1 Ground Granulated Blast Furnace Slag .................................................... 7
2.2.1.2 Metakaolin ................................................................................................ 9
2.2.1.3 Silica Fume ............................................................................................. 11
2.2.2 Pore Solution Composition ................................................................................... 13
2.2.2.1 Effect of pH ............................................................................................ 13
2.2.2.2 Effect of OH- .......................................................................................... 15
2.2.3 Hydration and w/b Ratio ....................................................................................... 17
2.2.4 Temperature .......................................................................................................... 18
2.3 Methods Used to Determine Bound Chloride Content ..................................................... 19
2.3.1 Equilibrium Methods ............................................................................................ 19
2.3.2 Binding Isotherms ................................................................................................. 20
2.3.2.1 Langmuir Isotherm ................................................................................. 21
2.3.2.2 Freundlich Isotherm ................................................................................ 21
v
Chapter 3 Experimental Program .................................................................................................. 23
3.1 Overview ........................................................................................................................... 23
3.2 Materials Used .................................................................................................................. 24
3.3 Mix Designs ...................................................................................................................... 25
3.4 Casting and Curing ........................................................................................................... 26
3.5 Testing Procedure ............................................................................................................. 27
3.5.1 Sample Preparation ............................................................................................... 27
3.5.2 Equilibrium Method .............................................................................................. 27
3.5.3 Titrations ............................................................................................................... 28
3.5.4 pH Measurements ................................................................................................. 28
3.5.5 Non-Evaporable Water ......................................................................................... 29
3.5.6 Temperature Exposure .......................................................................................... 29
3.5.7 Mercury Intrusion Porosimetry ............................................................................. 30
3.5.8 Energy-Dispersive X-Ray Spectroscopy .............................................................. 30
Chapter 4 Results and Analysis .................................................................................................... 31
4.1 Preliminary Experimental Assessment ............................................................................. 31
4.2 Calculating Bound Chloride and Chloride Binding Capacity ........................................... 36
4.3 Chloride Binding ............................................................................................................... 39
4.3.1 Effect of w/b Ratio ................................................................................................ 39
4.3.2 Effect of Supplementary Cementitious Materials ................................................. 47
4.3.3 Effect of OH- Concentration ................................................................................. 54
4.3.4 Effect of pH ........................................................................................................... 62
4.4 Effect of Temperature on Chloride Binding ..................................................................... 65
4.5 Interplay Between pH, OH- and Binding Capacity ........................................................... 76
4.6 Effect of the Non-Evaporable Water Content ................................................................... 84
4.7 Effect of Seasonal Temperature Variation on Binding Isotherms .................................... 89
vi
4.8 Impact of Binding Capacities on Chloride Diffusion Coefficient and Service Life
Estimation ....................................................................................................................... 100
Chapter 5 Conclusions and Recommendations ........................................................................... 107
5.1 Conclusions ..................................................................................................................... 107
5.1.1 Effect of Temperatures Between -10oC and 23
oC on Cement Pastes
Containing GU Cement, GGBFS, MK, and SF .................................................. 107
5.1.2 Interplay between OH- Ion Concentration, pH, and Chloride Binding Capacity 107
5.1.3 Effect of Non-Evaporable Water Content on Chloride Binding ......................... 109
5.1.4 Effect of Temperature Exposure on Service Life Estimation ............................. 110
5.2 Recommendations for Future Work ................................................................................ 110
References ................................................................................................................................... 112
vii
List of Tables
Table 3-1: Summary of experimental program ............................................................................. 23
Table 3-2: Chemical composition data ......................................................................................... 24
Table 3-3: Mix designs used ......................................................................................................... 25
Table 3-4: Batching proportions ................................................................................................... 26
Table 3-5: Dilutions for chloride titrations ................................................................................... 28
Table 3-6: Temperature exposure ................................................................................................. 29
Table 4-1: Assessing variation in potentiometric titrations for 100%GU w/b 0.3 ....................... 32
Table 4-2: Assessing variation in potentiometric titrations for 100%GU w/b 0.5 ....................... 33
Table 4-3: Outlier values for titration measurements ................................................................... 34
Table 4-4: Outlier values for calculated bound chloride .............................................................. 34
Table 4-5: Sample sets that best fit Langmuir and Freundlich isotherms ..................................... 38
Table 4-6: Comparing R2 values for 7d and 56d 100%GU samples with w/b 0.5 ....................... 38
Table 4-7: Comparison of R2 values for SCMs at 23
oC ............................................................... 39
Table 4-8: Binding capacities for 7d and 56d 100%GU samples at 23oC .................................... 42
Table 4-9 Non-evaporable water content for 56d samples 0.5 w/b at 23oC ................................. 50
Table 4-10: Binding capacities for 56d 100%GU ......................................................................... 60
Table 4-11: Chloride binding capacities for 56d 100%GU at 0oC and -10
oC .............................. 61
Table 4-12: Bound chlorides at 0.1M free chloride concentration for 56d 100%GU samples .... 66
Table 4-13: Chloride binding capacities for 56d 40%GGBFS w/b 0.3 ........................................ 71
viii
Table 4-14: Chloride binding capacities for 56d 10%MK w/b 0.3 ............................................... 73
Table 4-15: Chloride binding capacities for 56d 10%SF w/b 0.3................................................. 75
Table 4-16: Interplay between variables for 56d 100%GU samples at 23oC ............................... 76
Table 4-17: Interplay between variables for 56d 40%GGBFS samples at 23oC .......................... 77
Table 4-18: Interplay between variables for 56d 10%MK samples at 23oC ................................. 78
Table 4-19: Interplay between variables for 56d 10%SF samples at 23oC ................................... 78
Table 4-20: Effect of temperature on interplay between pH, OH- and binding capacity 23
oC and
0oC using 56d 100%GU samples w/b 0.3 ..................................................................................... 79
Table 4-21: Effect of temperature on interplay between pH, OH- and binding capacity 0
oC and -
10oC using 56d 100%GU samples w/b 0.3 ................................................................................... 79
Table 4-22: Temperatures at which samples showed the highest and lowest binding capacities for
mixtures with 0.3 w/b ................................................................................................................... 80
Table 4-23: Temperatures at which samples showed the highest and lowest binding capacities for
mixtures with 0.5 w/b ................................................................................................................... 80
Table 4-24: Effect of curing time on interplay between pH, OH- and binding capacity on
100%GU w/b 0.3 .......................................................................................................................... 81
Table 4-25: Effect of curing time on interplay between pH, OH- and binding capacity 100%GU
w/b 0.5 ........................................................................................................................................... 82
Table 4-26: Cycled versus original binding capacities for 56d 100%GU .................................... 90
Table 4-27: Cycled versus original pH values for 56d 100%GU ................................................. 90
Table 4-28: Life-365 cases .......................................................................................................... 103
Table 4-29: Base case analysis for service life estimation ......................................................... 104
Table 4-30: Relative service life estimates for cases exposed to 1.0M chloride solution .......... 105
ix
List of Figures
Figure 2-1: Binding isotherm showing increased binding with increased GGBFS content
(Panesar, 2007) ............................................................................................................................... 8
Figure 2-2: Binding isotherms showing binding capacity of MK (Zibara, 2001) ........................ 10
Figure 2-3: Effect of silica content on total unbound chloride (Page & Vennesland, 1982) ........ 11
Figure 2-4: Effect of pH and w/b ratio on the total chloride content of cement paste (Tritthart,
1989) ............................................................................................................................................. 14
Figure 2-5: Influence of pH on chloride binding capacity (Song et. al., 2008) ............................ 15
Figure 2-6: Chloride and hydroxyl concentrations of pore water with different chloride cations
(Tritthart, 1989) ............................................................................................................................. 16
Figure 2-7: Effect of temperature on OH- concentration (Maslehuddin et. al., 1997) .................. 16
Figure 2-8: Effect of w/b ratio on bound chloride (Zibara, 2001) ................................................ 17
Figure 2-9: Effect of temperature on unbound chloride (Hussain & Rasheeduzzafar, 1993) ...... 18
Figure 2-10: Comparison between Langmuir and Freundlich binding isotherms (Zibara, 2001) 22
Figure 4-1: 56d 100%GU w/b 0.5 binding isotherm at 23oC ....................................................... 36
Figure 4-2: 56d 100%GU bound Cl- vs. free Cl
- at 23
oC .............................................................. 40
Figure 4-3: 7d 100%GU bound Cl- vs. free Cl
- at 23
oC ................................................................ 41
Figure 4-4: 56d 40%GGBFS bound Cl- vs. Free Cl
- at 23
oC ........................................................ 43
Figure 4-5: 56d 10%MK bound Cl- vs. Free Cl
- at 23
oC .............................................................. 44
Figure 4-6: 56d 10%SF bound Cl- vs. Free Cl
- at 23
oC ................................................................ 45
Figure 4-7: Effect of temperature on binding isotherms for 56d 100%GU .................................. 46
Figure 4-8: Effect of temperature on binding isothems for 56d 100%GU ................................... 47
x
Figure 4-9: Effect of SCMs on binding isotherms 56d samples w/b 0.5 23oC ............................. 48
Figure 4-10: Binding capacities of all 56d mix designs w/b 0.5 at 23oC ...................................... 50
Figure 4-11: Chloride binding capacities of 56d 100%GU samples at all temperatures w/b 0.5 . 52
Figure 4-12: Chloride binding capacities of 56d 40%GGBFS samples at all temperatures w/b 0.5
....................................................................................................................................................... 53
Figure 4-13: Chloride binding capacities of 56d 10%MK samples at all temperatures 0.5 w/b .. 53
Figure 4-14: Chloride binding capacities of 56d 10%SF samples at all temperatures 0.5 w/b .... 54
Figure 4-15: Bound chloride vs. OH- for 56d GU at 23
oC ........................................................... 54
Figure 4-16: Bound chloride vs. OH- all GU samples at w/b 0.5 ................................................. 56
Figure 4-17: Variation in OH- for 56d samples of all SCMs w/b 0.3 ........................................... 57
Figure 4-18: Variation in OH- for 56d samples of all SCMs w/b 0.5 ........................................... 59
Figure 4-19: OH- for 100%GU samples at all temperatures ......................................................... 59
Figure 4-20: Comparison of OH- for 100%GU samples at 0
oC and -10
oC .................................. 61
Figure 4-21: Effect of pH on bound chloride for 100%GU samples at 23oC ............................... 62
Figure 4-22: Effect of curing time on relation between bound chloride and pH for 100%GU
samples at 23oC w/b 0.5 ................................................................................................................ 63
Figure 4-23: Effect of pH on bound chloride for all SCMs at 23oC ............................................. 64
Figure 4-24: 56d 100%GU binding isotherms w/b 0.3 ................................................................. 65
Figure 4-25: 56d 100%GU binding isotherms w/b 0.5 ................................................................. 67
Figure 4-26: Variation of chloride binding capacity with temperature for 100%GU samples ..... 68
Figure 4-27: 56d 40%GGBFS binding isotherms w/b 0.3 ............................................................ 69
xi
Figure 4-28: 56d 40%GGBFS binding isotherms w/b 0.3 ............................................................ 70
Figure 4-29: 56d 10%MK binding isotherms w/b 0.3 .................................................................. 71
Figure 4-30: 56d 10%MK binding isotherms w/b 0.3 .................................................................. 72
Figure 4-31: 56d 10%SF binding isotherms w/b 0.3 .................................................................... 74
Figure 4-32: 56d 10%SF binding isotherms w/b 0.3 .................................................................... 75
Figure 4-33: Relationship between pH and free chloride for 56d samples w/b 0.5 ...................... 83
Figure 4-34: Relationship between OH- and free chloride for 56d samples w/b 0.5 .................... 84
Figure 4-35: Chloride binding capacity vs. non-evaporable water for GU mixes w/b 0.3 ........... 85
Figure 4-37: Chloride binding capacity vs. non-evaporable water for GGBFS mixes w/b 0.3 .... 87
Figure 4-38: Comparison between cycled and base 56d 100%GU samples w/b 0.5 ................... 89
Figure 4-39: Cycled vs. base 100%GU w/b 0.5 ............................................................................ 91
Figure 4-40: Cycled vs. base 40%GGBFS w/b 0.5 ...................................................................... 92
Figure 4-41: Cycled vs. base 10%MK w/b 0.5 ............................................................................. 92
Figure 4-42: Cycled vs. base 10%SF w/b 0.5 ............................................................................... 93
Figure 4-43: Effect of exposure conditions on the binding capacity of GU ................................. 94
Figure 4-44: Effect of exposure conditions on the binding capacity of GGBFS .......................... 95
Figure 4-45: Effect of exposure conditions on the binding capacity of MK ................................ 95
Figure 4-46: Effect of exposure conditions on the binding capacity of SF .................................. 96
Figure 4-47: Effect of temperature and chloride exposure on porosity ........................................ 96
Figure 4-48: Relation between difference in chloride binding capacity and difference in porosity
....................................................................................................................................................... 97
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Figure 4-49: Effect of exposure on pH of storage solution for 100%GU w/b 0.5 ........................ 98
Figure 4-50: Effect of exposure on pH for 40%GGBFS w/b 0.5 ................................................. 99
Figure 4-51: Effect of exposure on pH for 10%MK w/b 0.5 ........................................................ 99
Figure 4-52: Effect of exposure on pH for 10%SF w/b 0.5 ........................................................ 100
xiii
List of Appendices
Appendix A: Statistical analysis ................................................................................................. 117
Appendix B: Variation in pH and OH- Values ........................................................................... 118
Appendix C: EDS analysis of samples with 0.3 w/b .................................................................. 122
Appendix D: Interplay between pH, OH- and binding capacity for SCMs w/b 0.3 ................... 126
Appendix E: Interplay between pH, OH- and binding capacity for SCMs w/b 0.5 .................... 128
Appendix F: Effect of curing time on pH, OH- and binding capacity for SCMs ....................... 131
Appendix G: 0.3 w/b ratio samples cycled from 23oC to 0
oC .................................................... 134
Appendix H: Effect of exposure on pH for all SCMs w/b 0.3 .................................................... 136
Appendix I: Relation between pH and free chloride for all samples .......................................... 138
Appendix J: Relation between OH- and free chloride for all samples ........................................ 142
Appendix K: Non-evaporable water and chloride binding capacity ........................................... 146
Appendix L: LOI of raw materials and non-evaporable water contents ..................................... 149
Appendix M: Life-365 estimates of relative service life ............................................................ 153
1
Chapter 1 Introduction
1.1 Background
All structures undergo degradation over time. The ways in which this can occur vary based on
the materials used and the location of the structure. Processes responsible for such degradation
can be physical, chemical or a combination of both; with physical degradation taking place
through the action of wind, rain and snow, and chemical degradation commonly involving
carbon dioxide, sulphates or chlorides.
From the many modes of degradation mentioned, one of particular importance is related to the
corrosion of reinforcing steel when it comes into contact with chlorides. It is a well known fact
that when steel is exposed to moisture and oxygen it will corrode in the form of rust. Due to
concrete being a porous material, it does not form a permanent seal around reinforcing steel,
allowing moisture and oxygen to penetrate, with the addition of chlorides mainly in the form of
de-icing or marine salts helping to accelerate the corrosion process. Concrete is the most used
building material in the world (Kosmatka, et. al, 2002) and reinforced concrete structures are
vulnerable to degradation due to rebar corrosion. This can have serious implications on structural
integrity and service life.
The ways in which chlorides can come into contact with concrete can be grouped into two main
categories. The first category involves chlorides coming into contact with concrete from the
environment in which the concrete is located and these are referred to as external chlorides. Sea
water, deicing salts and chlorides in soil are all external chlorides. The second category involves
the presence of chlorides either in the aggregates or mix water. These chlorides are commonly
referred to as admixed chlorides. Admixed chlorides can be used as an accelerating agent in
concrete mix design, assisting in adjusting the setting time of concrete. Due to the deleterious
impact that admixed chlorides can have on corrosion however, their use is very limited.
Consequently, the focus of this study will be the impact of external chlorides.
Once external chlorides have come into contact with concrete they can enter and travel through
the pore network as a result of four transport mechanisms. These mechanisms are sorption,
2
diffusion, permeation and wick action. Sorption can be attributed to capillary suction through
unsaturated pores (Nokken & Hooton, 2002), diffusion can take place in the presence of a
chloride concentration gradient (Nokken et. al, 2004), permeation involves the ingress of
chlorides based on a pressure gradient (Zeljkovic, 2009) and wick action involves the transport
of chlorides through concrete from a saturated face to a face exposed to drying (Nokken &
Hooton, 2001).
Through the different transport mechanisms described above, chlorides are able to penetrate into
concrete and come into contact with reinforcing steel which results in corrosion. However, there
is another mechanism at work which can affect the rate at which external chlorides penetrate the
concrete. That mechanism is chloride binding. Chloride binding, as the name implies, involves
chloride being held or bound by the cementitious matrix. Due to the chlorides being held, they
cannot further penetrate into the concrete and aid in delaying the onset of corrosion. This process
is of importance as it can reduce the rate of diffusion of chlorides. The chloride binding
mechanisms are complex, consisting of chemical and physical binding processes.
To date, there has been extensive research and published literature on the influence of water-to-
binder (w/b) ratio, type of cementing material, hydroxyl ion concentration (OH-), and pH levels
on chloride binding capacity, the diffusion coefficient, and service life estimations. However,
there are relatively few reports that investigate the impact of temperatures below 23oC on
chloride binding.
3
1.2 Scope and Objectives
The key objectives of this study are:
i) To investigate the effect of temperatures between -15oC and 23
oC on chloride binding of
cement paste containing ordinary Portland cement, also known as general use cement
(GU), along with various types and amounts of supplementary cementing materials
(SCMs). In this study, ground granulated blast furnace slag (GGBFS), metakaolin (MK),
and silica fume (SF) are used.
ii) Investigate the interplay between the hydroxyl ion (OH-) concentration and pH on
chloride binding isotherms and chloride binding capacities within the temperature range
of -10oC to 23
oC.
iii) Investigate the effect of the non-evaporable water content on chloride binding capacity
through the comparison of cement pastes with two w/b ratios of 0.3 and 0.5 at various
ages, namely, 7, 14, 28 and 56 days.
iv) Investigate the effect of temperature cycling on chloride binding, ion-binder interactions,
chloride binding capacity, and service life estimation.
The significance of this research is to contribute to the understanding of the chloride binding
mechanism in particular related to reinforced concrete structures in geographic regions that
experience winter conditions. The study of chloride-binder interactions at temperatures
below 23oC is not well reported in published literature but is critical in order to yield more
accurate service life estimates of reinforced concrete structures exposed to chloride in the
form of deicing salts. Furthermore, chloride binding capacity more representative of actual
exposure conditions is critical to improve service life estimates of concrete structures,
allowing the effective allocation of resources for repair or replacement activities.
4
Chapter 2 Literature Review
2.1 Chloride Binding
Chloride binding, as the name implies, is the process whereby chloride ions become bound
within the concrete microstructure inhibiting further movement. This process is of importance
when looking at the durability of concrete. The inhibiting effect of chloride binding can delay the
onset of corrosion in reinforced concrete structures by either the cementitious and hydration
products forming different chemical compounds when exposed to chlorides, or by the adsorption
of chlorides onto the surfaces of the different hydration products. Chloride binding processes
may be classified as either chemical binding or physical binding. Chemical binding is associated
with the formation of binding products through chemical reactions involving the aluminate
compounds in cement such as tri-calcium aluminate (C3A) and chlorides to form
chloroaluminates, the most notable of which being Friedel’s salt. Physical binding describes the
adsorption process that binds chlorides to the hydrated products such as the calcium-silicate-
hydrate (C-S-H) within the microstructure of the cement paste. It is important to note that there is
no clear consensus on the mechanisms involved in both chemical and physical binding (Brown &
Bothe Jr., 2004). Both chemical and physical binding are further discussed in the following
sections.
2.1.1 Chemical Binding
Chemical binding involves the formation or alteration of hydration products upon exposure to
chlorides by means of chemical reactions. The formation of calcium chloroaluminate, better
known as Friedel’s salt, is a commonly recognized chemical binding mechanism where chlorides
react with the tricalcium aluminate (C3A) content of the cement. This reaction can be seen in
Equation 2-1 in which the bound chloride is calcium chloride (Suryavanshi et. al., 1996). The
ferrite phase, in the form C4AF forms a binding product known as calcium chloroferrite (Zibara,
2001, Roberts, 1962) which can be seen in Equation 2-2 with the aluminate phase formed
(C3AH6) being able to take part in binding reactions (Justnes, 2004). These two phases are
thought to be the most active in chemical binding with the majority of binding being dependant
on the C3A content (Yuan et. al., 2009).
5
OHCaClACOHCaClAC 223223 1010 ⋅⋅→++ ............ (2-1)
CHFHAHCHAFC ++→+ 3634 10 .............………… (2-2)
Other forms of chemical binding are worth noting due to the differences observed with the use
of either admixed or external chlorides. It was observed that with the use of admixed chlorides,
the chemical binding could occur as previously described due to the presence of un-reacted C3A
and C4AF in the mixture. When exposed to external chlorides however, chemical binding takes a
different form due to the absence of the majority of the C3A in the cement paste. The presence of
sulphates in the cement paste results in the formation of both monosulphate and ettringite. These
phases can then bind chlorides through the formation of Kuzel’s salt
3CaO.Al2O3.1/2CaSO4.1/2CaCl2.10H2O (Brown & Bothe Jr., 2004). At high chloride
concentrations however, Kuzel’s salt gets converted to Friedel’s salt which indicates that the
presence of sulphates has a more negative effect on chloride binding at low chloride
concentrations (Yuan et. al., 2009).
Chemical binding involves the creation of either calcium chloroaluminate hydrate
C3A·CaCl2·10H2O, better known as Friedel’s salt, calcium chloroferrite, C3F·CaCl2·10H2O,
which is a variation of Friedel’s salt that contains iron instead of alumina, and Kuzel’s salt,
which forms when ettringite, 6CaO·Al2O3·3SO3·32H2O, or monosulphate,
4CaO·Al2O3·SO3·12H2O, react in the presence of chlorides (Yuan et. al, 2008). The formation of
one of more of these products can be attributed to the reaction of the chlorides with the different
phases present in concrete with Kuzel’s salt being transformed into Friedel’s salt at high
concentrations of chlorides. Highlighted in Equations 2-3 and 2-4 are the mechanisms involved
proposed by Suryavanshi et. al. (1996) and Zibara (2001) related to the formation of Friedel’s
salt and calcium chloroferrite. Based on their findings, the formation of Friedel’s salt is
dependent on the amounts of C3A and C4AF present in the cement.
−+ ++↔+ OHNaCaClNaClOHCa 222)( 22 .................... (2-3)
OHCaClACOHCaClAC 223223 1010 ⋅⋅→++ .................... (2-4)
6
This reaction involves the release of OH- ions and was used as a means to explain the observed
increase in OH- ions associated with chloride binding (Suryavanshi et. al, 1996). The ferrite form
of Friedel’s salt, or chloroferrite, takes the form of OHCaClFC 223 10⋅⋅ , but under comparable
conditions, the C4AF reacts at a rate slower than that observed for C3A (Suryavanshi et. al,
1996).
Another theory was proposed where the increase in OH- ions observed was attributed to the
replacement of OH- ions in monosulphate (4CaO·Al2O3·SO3·12H2O) hydrates by Cl
- ions.
Formula (2-5) highlights the ion-exchange reaction taking place between the OH- ions and Cl
-
ions in the interlayers of the AFm hydrates as was described by Suryavanshi et. al, (1996).
−+−−+− ++−→++− OHNaClRClNaOHR ………….. (2-5)
Friedel’s salt can also be formed through precipitation. Friedel’s salt contains two
[Ca2Al(OH)62H2O]+ layers that require a negative charge in order to be stable. If the chloride
being used is NaCl, to maintain neutrality, the Cl- ions would be used, forming Friedel’s salt,
with a corresponding amount of Na+ being absorbed into phases such as the C-S-H (Jones, et al.,
2003). As the Na+ is absorbed in the C-S-H however, it would undergo another ion exchange
with the surface silanol groups, SiH3OH, releasing H+ ions in order to preserve charge neutrality.
These H+ ions would then combine with free OH
- ions in solution forming water, thereby
neutralizing the OH- (Jones, et al., 2003).
2.1.2 Physical Binding
Physical binding consists of the adsorption of Cl- ions directly to the calcium silicate hydrate (C-
S-H) sheets through Van der waals forces, with other studies investigating such theories as the
electrical double layer theory where the adsorption of chloride ions is necessary to achieve
electro-neutrality. Evidence for the binding of chlorides by the C-S-H sheets was found by
Ramachandran (1971), where after 168 hours of hydration only 78% of the chlorides used were
able to be extracted using water, with negligible amounts being extracted using alcohol.
Ramachandran (1971) determined that the chloride was either present on hydrated calcium
silicates in a chemisorbed layer, within the C-S-H interlayer spaces, or intimately bound within
the C-S-H lattice. These results were attributed to the C-S-H sheets having a positive charge
7
which would encourage adsorption of the Cl- ions. Supporting this view was another study by
Tang and Nilsson (1993) where it was found that the bound chloride content was closely related
to the C-S-H gel content regardless of the w/b ratio. As a result of these theories, the capacity of
the C-S-H layers in adsorbing chlorides is dependent on the surface area of the sheets themselves
(Zibara, 2001).
2.2 Factors Affecting Chloride Binding
2.2.1 Supplementary Cementitious Materials
There are several benefits associated with the use of Supplementary Cementitious Materials
(SCMs) in concrete. Economic, environmental and durability factors all influence their present
use. The economic and environmental benefits arise from the fact that most SCMs used such as
ground granulated blast furnace slag (GGBFS) and silica fume (SF) are all waste products of the
iron and silicon metal industries respectively. The durability factor arises due to the beneficial
changes in microstructure such as the reduction in the interfacial transition zone and the creation
of a discontinuous pore structure (Mehta & Monteiro, 2006). These benefits all arise due to the
pozzolanic reactions that occur when such materials are introduced into the concrete mix. Due to
the increasing use of such materials in concrete, it is important to understand what their possible
effects on chloride binding might be. The following sections highlight what has been previously
found concerning FA, GGBFS, SF and MK.
2.2.1.1 Ground Granulated Blast Furnace Slag
Slag is a byproduct of the iron industry, which after being water cooled and crushed, forms a
material commonly refered to as ground granulated blast furnace slag (GGBFS). GGBFS
possesses pozzolanic properties when exposed to water and an alkaline environment making it
useful as a cementitious material (Kosmatka et. al., 2002). The use of GGBFS has been shown to
increase chloride binding capacity. Research by Arya et. al. (1990), Arya and Xu (1995), Zibara
(2001), Panesar (2007) and Thomas et. al. (2011) all confirm that the use of GGBFS increases
chloride binding capacity. One reason often attributed for this increase in binding capacity is the
higher aluminate content of GGBFS when compared to GU. Luo et. al. (2003) highlighted this
trend, with improved chloride binding capacity being observed when samples were exposed to
both admixed and external chlorides. They attributed the increase in chloride binding to chemical
8
binding processes, with increased Friedel’s salt formation occurring due to the higher aluminate
content of GGBFS compared to GU. Figures 2-1 based on research by Panesar (2007) shows the
increase in bound chloride noted when 50 – 60% GGBFS is used in comparison to 0 or 25%
GGBFS as cement replacement. Although there is an increase in binding, it appears to be
disproportionate to the replacement level of GGBFS.
Figure 2-1: Binding isotherm showing increased binding with increased GGBFS content
(Panesar, 2007)
However, Zibara (2001) found that a mixture containing 25% GGBFS possessed approximately
27% higher bound chloride content compared to the control 100% GU mix. This was attributed
to the formation of secondary hydration products through hydration reactions which produces
more surface area for physical binding through adsorption. It was noted however, that the use of
admixed chlorides resulted in higher binding capacities when compared to the use of external
chlorides (Zibara, 2001).
9
Another reason attributed to the higher binding capacity of GGBFS is the dilution of sulphate
ions present in the cement. The dilution of the sulphate ions is important as when sulphate ions
are increased in GGBFS mixes to comparable levels to those in ordinary cement, the binding
capacity decreases due to the formation of AFm rather than Friedel’s salt (Xu, 1997).
Furthermore, it was noted that lower w/b ratios may hamper the utilization of the aluminate to
form Friedel’s salt, therefore the maximum effect of GGBFS additions with respect to chloride
binding may take place at higher w/b ratios (Thomas, et. al. 2011).
2.2.1.2 Metakaolin
MK is a different SCM compared to others as it is not a waste product of another industry, but
rather it is obtained through the calcining of kaolin clay at temperatures between 600°C and
800°C (Zeljkovic, 2009). The result of this is a material that is comprised primarily of silica
(SiO2) and aluminates (Al2O3). The relative quantities of each can range in value from 62.3%
SiO2 and 30.5% Al2O3 as used in research by Zeljkovic (2009) to 52.0% SiO2 and 44.7% Al2O3
used by Zibara (2001). Such variation arises depending on the source and purity of the kaolin
clay (Zeljkovic, 2009).
Similar to GGBFS, the use of MK has been associated with increased chloride binding capacity.
Work done by Bai et. al. (2003), Zibara (2001) and Coleman & Page (1997) all showed that
replacement of Portland cement with MK resulted in increased bound chloride with a reduction
in permeability of the concrete. Zibara (2001) found that samples containing 8% MK showed the
greatest binding capacity at both 0.3 and 0.5 w/b ratios. It was assumed that the chemical
composition of MK, primarily the aluminate content, is associated with an increase in binding
capacity. This is due to the hydration products formed, most notably C-S-H, calcium aluminate
silicate hydrate (C-A-S-H) and calcium aluminate hydrate (C-A-H). Results obtained by Zibara
(2001) can be seen in Figure 2-2 (8MK) where it was suggested that this increase in binding
capacity was due to the high aluminate value.
10
Figure 2-2: Binding isotherms showing binding capacity of MK (Zibara, 2001)
However, tests performed by Zibara et. al. (2008) on MK-lime mixtures, where lime was used
instead of Portland cement, showed that the binding capacity actually decreased as the MK
replacement level increased. It was found that bound chloride increased as the mass ratio of MK
to calcium hydroxide (Ca(OH)2) decreased. Such a trend was attributed to the composition of the
hydration products as the replacement level of MK changed from a 2:1 ratio consisting of two
parts MK and one part Ca(OH)2, to a 1:2 ratio, consisting of one part MK and two parts
Ca(OH)2. It was noted that a higher concentration of aluminate compounds such as
monocarboaluminate, C3A.CaCO3
.11H2O, was present at the lower MK replacement levels as
opposed to the higher replacement levels where the primary compounds were C-S-H and
stratlingite, C2ASH8.
Upon exposure to chlorides, the presence of monocarboaluminate in the 1:2 ratio samples of MK
to Ca(OH)2 allowed for increased Friedel’s salt formation at a chloride concentration of 0.1M.
However, when samples with the 2:1 ratio of MK to Ca(OH)2 were exposed to the 0.1M chloride
solution, less chloride binding took place. This difference in binding was attributed to the
preferential formation of monocarboaluminate at a higher C/A ratio as found in the 1:2 ratio
samples which is able to convert to Friedel’s salt much more readily than the stratlingite that is
formed at lower C/A ratios as found in the 2:1 ratio samples (Zibara et. al., 2008).
11
2.2.1.3 Silica Fume
SF is the byproduct of the silicon metal industry formed when high-purity quartz is reacted with
coal in an electric arc furnace (Kosmatka et. al., 2002). The SF formed in this process is
comprised of 94% - 98% silicon dioxide, SiO2. Its pozzolanic properties and small particle size
of approximately 0.1µm makes it suitable as a cementing material (Page & Vennesland, 1982).
The hydration of cement containing SF is associated with increased formation of C-S-H and a
reduction in permeability of the cement paste formed. These properties appear to be beneficial to
physical binding as was described in Section 2.1.2 due to the increase in surface area over which
adsorption can occur. However, studies on the effect of silica fume on chloride binding by
authors such as Dousti et. al. (2011), Zibara (2001), Arya et. al. (1990), Beaudoin et. al. (1990)
and Page & Vennesland (1982) found that the use of SF decreased the bound chloride content.
Results from Page & Vennesland (1982) can be seen in Figure 2-3, where as the SF replacement
level increases from 0% to 30%, the percentage of unbound chloride also increases from
approximately 40% to 85% respectively after 70 days of curing.
Figure 2-3: Effect of silica content on total unbound chloride (Page & Vennesland, 1982)
12
With silica fume replacement levels ranging from 8% (Zibara, 2001) to 30% (Page &
Vennesland, 1982), the reasons for the reduction in bound chloride was attributed to a few
mechanisms. These mechanisms involve the reduction in pH of the pore solution and the
lowering of the calcium to silica (C/S) ratio of the C-S-H formed. The reduction in pH results
from one of the mechanisms involved in the formation of secondary C-S-H. The SiO2 content of
SF requires an alkaline environment, or OH- ions, for the reaction to take place. However, after
the pozzolanic reaction is initiated by the OH- ions are themselves consumed in the reaction as
shown in Equation 2-6 resulting in a decrease in OH- ion concentration and a corresponding
decrease in pH (Larbi et. al., 1990).
OHnSiOCaOnaqOHaqCasSiO 221
2
2 )(2)()( ⋅⋅⋅=++ −+ ……….. (2-6)
The influence of silica fume on the C/S ratio and chloride binding was investigated by Zibara et.
al. (2008) using SF-lime pastes in which Ca(OH)2 was used in place of Portland Cement. Similar
to the effect on MK in Section 2.2.1.2, there was a decrease in bound chloride when the ratio of
SF to Ca(OH)2 was decreased from 2:1 to 1:2, with the 2:1 mix of SF to Ca(OH)2 binding a
negligible quantity of chloride.
Work done by Delagrave (1997) however, showed that the addition of 6% silica fume at a w/b of
0.45 did not decrease the bound chloride content, with an insignificant difference noted when
compared to a GU control sample. This was attributed to the low substitution percentage of silica
fume (6%) and the high degree of hydration (62%) that the mixture was able to attain. At a w/b
ratio of 0.25 however, the results did show a reduction in bound chloride content.
Few studies on the effect of silica fume on chloride binding found that there was an increase in
binding associated with the use of silica fume, but those that did, such as Byfors (1986),
attributed the increase in bound chloride to the increased surface area due to the formation of
hydration products such as C-S-H which would promote more adsorption or physical binding of
chloride ions.
13
2.2.2 Pore Solution Composition
Beyond the hardened microstructure and the type of material used, it is important to consider the
effect of pore solution chemistry on chloride binding. With sodium (Na), potassium (K), calcium
(Ca), sulphate (SO42-
) and OH- ions all being found in the pore solution of hydrated cement
(Buckley et. al., 2007), examination of the pore solution chemistry and its effect on chloride
binding can become complex. Coupled with the number of ions found is the transient chemistry
of the pore solution with cement hydration, which is further complicated by the presence of
SCMs, and exposure conditions such as varying temperatures and chloride ion concentrations.
The effect of pH and hydroxyl concentrations in relation to chloride binding will be discussed in
the following sections.
2.2.2.1 Effect of pH
The pH of cement pore solution changes during the hydration process. Pore solution within the
cement microstructure eventually attains a value between 12.6 and 13.5 (Neville, 1995) due to
the high Ca(OH)2 content. High pH values such as these are important in protecting steel
reinforcement from corrosion. Due to chloride binding processes taking place in this medium,
changes in the pH due to the use of different SCMs, curing times and temperatures can affect the
bound chloride content.
Research done by Tritthart (1989) and Song et. al., (2008) both show how the pH of the solution
can impact on the bound chloride. Figure 2-4 shows results obtained by Tritthart (1989) where an
increase in pH from 12.5 to 13.7 was linked to a decrease in bound chloride regardless of the
chloride concentration of the storage solution or the w/b ratio. Results from Song et. al., (2008)
can are shown in Figure 2-5 where at each chloride content, the chloride binding capacity
increased from a pH of 12.6 to approximately 12.8, after which it took on a similar trend to that
found by Tritthart (1989) where the binding capacity decreased until a pH of approximately 13.
This trend was attributed to the binder type and hydration products due to the pH being above
12.5 for all of the results.
The pH of 12.5 is of importance as it was found that the release of bound chlorides can occur at a
pH of 12.5 or lower, with the release of almost all the bound chlorides when the pH drops below
10. Associated with the release of chlorides when the pH drops is the change in the predominant
14
type of binding taking place. Above a pH of 12.5, chlorides tend to be predominantly chemically
bound. As the pH decreases from 12.5 to 10, this was where adsorption of the chlorides by the
hydration products took place, with the release of bound chlorides to free chlorides being mostly
done below a pH of 10 (Ryou & Ann, 2008).
Song et. al., (2008) did find however, that when the individual mix designs were looked at, there
appeared to be no relation found between the quantity of chloride the sample was exposed to and
the pH of the solution. These differences in pH were attributed to the properties of the different
SCMs used.
Figure 2-4: Effect of pH and w/b ratio on the total chloride content of cement paste
(Tritthart, 1989)
15
Figure 2-5: Influence of pH on chloride binding capacity (Song et. al., 2008)
2.2.2.2 Effect of OH-
When hydration of cement takes place, the concentration of OH- ions is changed affecting the pH
of the pore solution which in turn can affect the binding capacity of the cement paste. Results
obtained by Tritthart (1989) as shown in Figure 2-6 highlight the effects of different OH-
concentrations on bound chloride content when different forms of chloride such as NaCl, HCl,
CaCl2 and MgCl2 are used. When all the results are compared side by side, it can be seen that
chloride concentrations were proportional to the OH- concentration regardless of the type of
chloride used. This implies that the OH- concentration has a stronger effect on binding than the
chloride type.
Based on the results in Figure 2-6, it was theorized that chloride and OH- ions compete for
adsorption sites. It was suggested that at high concentrations, OH- ions are able to replace
chloride ions by ion exchange (Roberts, 1962). The replacement of OH- ions with chloride ions
though ion exchange is the result of the greater affinity for chloride ions by ion exchangers such
as the AFm hydrates, an example of which is monosulphate (Maslehuddin et. al., 1997). Hussain
et. al. (1995) also found similar results using GU cement samples with a 0.6 w/b ratio were
containing between 0.3% to 2.4% chlorides by weight of cement.
16
Figure 2-6: Chloride and hydroxyl concentrations of pore water with different chloride
cations (Tritthart, 1989)
Maslehuddin et. al.’s (1997) study revealed that when the influence of temperature is considered,
there is a decrease in the OH- concentration as shown in Figure 2-7. When samples were
contaminated with sodium chloride or a combination of sodium chloride and sodium sulphate,
there was a decrease in OH- concentration as the temperature increased, which would imply that
there would be a decrease in bound chloride.
Figure 2-7: Effect of temperature on OH- concentration (Maslehuddin et. al., 1997)
17
2.2.3 Hydration and w/b Ratio
Hydration and w/b ratio both play an important role in chloride binding, especially in the case of
physical binding. An increase in hydration is associated with in a more developed microstructure
that can bind more chlorides through physical adsorption to the hydrated products such as C-S-
H. With respect to the w/b ratio, research done by Zibara (2001), Delagrave et. al (1997) and
Tritthart (1989) found that a higher w/b ratio corresponds with greater bound chloride content.
Results from Zibara’s (2001) work can be seen in Figure 2-8, where for samples containing fly
ash and SF, the higher w/b ratios are associated with higher bound chloride content.
Figure 2-8: Effect of w/b ratio on bound chloride (Zibara, 2001)
The results in Figure 2-8 were attributed to reduced formation of Friedel’s salt due to the reduced
porosity and degree of hydration associated with the 0.3 w/b ratio. It was also mentioned that the
lower w/b ratio affects the adsorption capacity of the C-S-H formed due to adjustments in the
calcium to silica ratio (Zibara, 2001).
Similar results were obtained by Delegrave et. al.(1997), where samples with a w/b ratio of 0.25
bound significantly less chloride than those with a w/b ratio of 0.45. The differences in bound
chloride were attributed to the degree of hydration, with the greater hydrated gel content found in
the 0.45 w/b samples being the controlling factor. Tang and Nilsson (1993) also came to a
similar conclusion when they compared paste samples with w/b ratios ranging from 0.4 to 0.8. It
18
was noted by Delagrave (1997) however, that using the unit mass of hydrated gel to determine
the bound chloride content is not accurate due to the different C-S-H compositions that are
formed when different SCMs are used.
Arya et. al (1990) found that for Portland cement pastes, the bound chloride content continued to
increase with increasing curing time up to 84 days. However, after two days of curing, the gain
in bound chloride content was not significant. Such a trend was thought to occur due to the
chloride ions slowly reacting with ettringite to form Friedel’s salt.
2.2.4 Temperature
With respect to the environmental variables affecting chloride binding, there have been
conflicting conclusions made concerning the effect of temperature on chloride binding. Work
done by Zibara (2001), Larsen (1995), and Hussain & Rasheeduzzafar (1993) pointed to a
decrease in chloride binding with an increase in temperature. Figure 2-9 illustrates Hussain &
Rasheeduzzafar’s results which they claimed was due to the decomposition of Friedel’s salt at
higher temperatures, which in their case was 70oC. Other researchers however, claimed that
temperature only has an effect on the diffusion rate, with no effect on the amount of chloride
being bound (Nguyen et. al., 2009).
Figure 2-9: Effect of temperature on unbound chloride (Hussain & Rasheeduzzafar, 1993)
19
Arya et. al. (1990) determined that there was increased binding when the temperature was raised
from 20°C to 38°C. Although the temperature range is relatively small, the increase in binding
can be attributed to a faster rate of reaction at the increased temperatures (Arya et. al., 1990).
Zibara (2001) conditioned samples at 7oC, 23
oC and 38
oC and showed a decrease in chloride
binding with an increase in temperature. This trend was observed up to a free chloride
concentration of 0.75M after which the trend reversed, with the samples at higher temperatures
exhibiting greater binding. However, it was noted that the results at 38oC were inconclusive due
to inadequate sealing of those samples. When exposed to chloride solutions, the inadequate
sealing resulted in errors due to evaporation of solution (Zibara, 2001).
Few studies have measured chloride binding isotherms at cold temperatures, particularly below
0°C. Pure water freezes at 0°C, however, the fluid within the concrete microstructure is not pure
water. The presence of dissolved ions alters both the freezing and boiling point of water, with the
freezing point being depressed and the boiling point being increased. Microstructure also plays
an important part in determining the freezing point of pore fluids in concrete. Pigeon & Pleau
(1995) showed that as the pore size decreases from 30nm to 5nm, the freezing point at which ice
formation is possible within the pores will be depressed from approximately -3oC to -20
oC.
Coupled with this is the influence of the NaCl concentration. At a 0.1M (0.58% NaCl)
concentration, the freezing point is depressed by less than 1oC. However, at relatively higher
NaCl concentration such as 3.0M (17% NaCl), the freezing point is depressed by approximately
12oC.
2.3 Methods Used to Determine Bound Chloride Content
2.3.1 Equilibrium Methods
Equilibrium methods can take either of two forms. The first form is when a sample is immersed
in a known chloride solution, with the concentration being maintained until the changes in
chloride concentration become minimal at which equilibrium is said to be attained (Zibara,
2001). This method was performed by Tritthart (1989) where cement slabs were used to
investigate the binding of external chlorides. The second form is based on the decrease in
concentration of a known chloride solution when a sample is immersed until equilibrium is
attained. The bound chloride content is then determined based on the decrease in chloride
20
concentration. Tang and Nilsson (1993) developed a method based on this concept, with samples
being crushed to between 0.25 – 2mm in size before being immersed into known chloride
solutions. The use of crushed samples enabled equilibrium to be attained in a shorter amount of
time. The reduction in time is significant if compared to the testing done by Tritthart (1989).
Using crushed samples, Tang and Nilsson (1993), were able to attain equilibrium within 14 days
compared to the 380 days required by Tritthart (1989) for his 10mm thick cement slabs. Authors
such as Dhir et.al. (1996), Delagrave et. al. (1997), Zibara (2001), and Luo et. al. (2003) have
since used the Tang and Nilsson (1993) method to perform their research.
There are different variations of this method which all relate to the size of samples used, the
sample preparation before immersion in chloride solutions, and the length of time the samples
were immersed prior to testing. Arya et. al. (1990) used cement paste discs 49mm in diameter
and 6mm thick which were immersed in chloride solutions. Zibara (2001) used a similar method
where discs 50mm in diameter and 3mm thick were used when conditioning samples. From each
samples, 25g was used for the equilibrium procedure. These samples were then crushed and
placed in vials for testing.
However, the test method has limitations. Glass et. al. (1996) found that the equilibrium method
proposed by Tang and Nilsson overestimates the binding capacity due to the crushing of
samples. The crushing of samples would expose a greater surface area, allowing more binding
and hydration to take place than would normally be found in uncrushed samples. It has also been
said that the Tang and Nilsson method idealizes the binding process, where chlorides have access
to every grain of hydrated cement which is not always the case in real life specimens where the
pore structure may limit the chloride exposure. As a result, the binding capacities acquired using
the Tang and Nilsson method can be said to be an upper limit of what the real binding capacities
are (Jirikova & Cerny, 2006).
2.3.2 Binding Isotherms
To better describe chloride binding, adsorption isotherms, namely the Langmuir and Freundlich
adsorption isotherms can be used to describe the relationship between bound and free chlorides
at varying chloride concentrations.
21
2.3.2.1 Langmuir Isotherm
The Langmuir Isotherm is a relation that describes adsorption. This relation is used in physical
chemistry where the quantity of adsorbed particles is related to the availability of adsorption sites
and the concentration of the solution above the adsorption surface. This binding isotherm
assumes that monolayer adsorption takes place when binding occurs (Reed & Matsumoto, 1993).
The general form of the Langmuir Isotherm is as follows:
………………………. (2-6)
Where Cb and Cf are bound and free chloride concentrations respectively, with a and b being
constants that differ with temperature and binder composition.
2.3.2.2 Freundlich Isotherm
The Freundlich isotherm, similar to the Langmuir isotherm is another adsorption isotherm that
relates the amount of bound particles in relation to the concentration of the solution or gas in
contact with it. The general form of the Freundlich isotherm is as follows:
……………………. (2-7)
Where α and β are constants that differ based on the binder composition and temperature, similar
to the constants in the Langmuir isotherm.
One notable difference between the Langmuir and Freundlich isotherm is their form at relatively
high chloride concentrations as shown in Figure 2-10. The slope of the curve at high chloride
concentrations tends to approach zero for the Langmuir isotherm, whereas the Freundlich
isotherm shows an increase in bound chlorides as the free chloride concentration increases.
( )f
f
bbC
aCC
+=
1
βα fb CC =
22
Figure 2-10: Comparison between Langmuir and Freundlich binding isotherms (Zibara,
2001)
23
Chapter 3 Experimental Program
3.1 Overview
To determine the chloride binding capacity, an equilibrium method based on Tang & Nilsson
(1993) was used. Table 3-1 summarizes the different variables and test methods that were used
for this project. Crushed samples were exposed to different chloride solutions varying in
concentration from 0.1M to 3.0M. The temperatures at which the samples were stored ranged
from 23oC to -15
oC and two w/b ratios 0.3 and 0.5 were used. Four different mix designs were
used containing general use cement (GU), ground granulated blast furnace slag (GGBFS),
metakaolin (MK), and silica fume (SF).
Table 3-1: Summary of experimental program
Mix Design Variables
Materials GU, 40% GGBFS, 10% metakaolin, 10% silica fume
Curing time (days) 7, 14, 28, 56
w/b ratio 0.3, 0.5
Exposure Conditions
Chloride solutions 0.1M, 0.5M, 1.0M, 2.0M, 3.0M
Temperatures 23oC, 5
oC, 0
oC, -10
oC, -15
oC
Temperature
Exposure
23oC for 2 months 0
oC for 2 months
-15oC, -10
oC, 0
oC, 5
oC for 2 months 23
oC for 2 months
Testing Program
Cl- Potentiometric titration using Metrohm 716 DMS autotitrator with 0.01N
24
AgNO3 titrant
OH- Potentiometric titration using Metrohm 716 DMS autotitrator with 0.05M
H2SO4 titrant
pH VWR scientific model 3000 pH/mV/Temperature meter
% Non-evaporable
water
Ignition in furnace at 1100oC for 2 hours after removal of evaporable water
through oven drying at 105oC to constant mass.
3.2 Materials Used
The materials used in this project consisted of GU cement and GGBFS from Holcim Canada,
SKW SF, and MK from Whitemud Resources. The material composition of the cementing
material is summarized in Table 3-2.
Table 3-2: Chemical composition data
Constituent GU (%) GGBFS (%) MK (%) SF (%)
SiO2 19.24 37.24 61.8 97.9
Al2O3 5.43 8.7 31.8 0.28
Fe2O3 2.36 0.35 1.13 0.14
CaO 60.94 37.94 0.4 0.53
MgO 2.34 11.36 0.3 0.26
SO3 4.11 2.68 0.03 0.15
K2O 1.11 0.43 1.83 0.43
Na2O 0.22 0.43 0.19 0.06
P2O5 0.12 0.02 0.03 0.07
TiO2 0.26 0.48 0.63 -
Mn2O3 0.06 0.46 0.01 0.03
SrO 0.08 - 0.01 0.004
ZnO 0.02 - 0.01 0.34
Cr2O3 0.01 0.11 - -
Cl 0.03 0.01 - 0.07
Leco CO2 2.22 0.38 -
Leco SO3 3.95 2.16 -
Free Lime 1.1 - -
Total Alkali as Na2O 0.95 0.71 1.39 0.34
25
3.3 Mix Designs
There were four main mix designs that were used. The details of each are shown in Table 3-3.
For each mix design, w/b ratios of 0.3 and 0.5 were used.
Table 3-3: Mix designs used
Mix ID. Type GU Cement %SCM (type) w/b
100%GU_03 100% - 0.3
100%GU_05 100% - 0.5
40%GGBFS_03 60% 40% GGBFS 0.3
40%GGBFS_05 60% 40% GGBFS 0.5
10%MK_03 90% 10% Metakaolin 0.3
10%MK_05 90% 10% Metakaolin 0.5
10%SF_03 90% 10% Silica Fume 0.3
10%SF_05 90% 10% Silica Fume 0.5
The GGBFS content of 40% was chosen due to the ACI 318 requirement for deicer scaling
resistant concrete to not have a GGBFS content of over 50% (Kosmatka et. al. 2002). It was
thought that having control samples containing 0% GGBFS and samples containing 40%
GGBFS would capture the extremes of behaviour associated with the use of GGBFS. The silica
fume content of 10% was also chosen based on the requirement for deicer scaling resistance as
mentioned in the ACI 234R-06 guide for the use of silica fume in concrete. The metakaolin
content was chosen to be the same as the silica fume to enable comparison of their binding and
ion-binder characteristics.
26
3.4 Casting and Curing
Mixtures used for this project all consisted of pastes made using the cementing materials outlined
in Table 3-3. For all mixtures, distilled water was used. Materials required were batched into
plastic bags in the proportions shown in Table 3-4. The type of SCM used did not change the
batch sizes with only the w/b ratio being responsible for the differences in batch size. Batch sizes
were based on trial and error to minimize material wastage.
Table 3-4: Batching proportions
w/b ratio Binder (GU + SCM) per cylinder Distilled Water
0.3 400g 120ml
0.5 350g 175ml
The mixing was conducted using a Lancaster five speed hand mixer, with the ASTM C305-06
standard for mechanical mixing of hydraulic cement pastes and mortars of plastic consistency
being used for timing purposes only. When mixing was completed, samples were cast into plastic
cylindrical paste moulds 100mm tall by 50mm in diameter. To ensure the moulds were filled
completely with minimal air voids, they were filled in three stages. A rubber tamping rod was
used to compact the paste at each stage of filling, with the same rod being used to tap the sides of
the mould 50 to 60 times after each compaction. When the moulds were filled, the top was sealed
with a piece of clear plastic film that was held in place using a rubber band. A plastic lid was
then placed on top of the plastic film.
In order to prevent segregation of the paste the moulds were placed on a rotating wheel at 7
revolutions per minute for 24 hours and allowed to rotate end over end after casting at 23±2oC.
After 24 hours, the samples were removed from the rotating wheel, demoulded and placed in a
closed container containing saturated lime water to continue curing. Saturated lime water was
used to prevent the leaching of calcium hydroxide and to minimize carbonation of the samples.
Curing was allowed to continue for either 7, 14, 28 or 56 days at 23±2oC until testing.
27
3.5 Testing Procedure
3.5.1 Sample Preparation
To begin the sample preparation, paste cylinders were removed from curing in saturated lime
water and broken into smaller pieces using a hammer and chisel. A hammer and chisel were used
not only due to the simplicity and efficiency of the procedure, but also to eliminate the heating
effects that may be encountered if a saw was utilized. After being chiseled into smaller pieces,
the sample was then crushed manually using a mortar and pestle to achieve a particle size
between 0.25mm and 2.0mm.
After being crushed, 5.0g – 5.03g of the sample was placed in a 20ml polyethylene bottle. To
ensure a statistically adequate data set, three samples were used per mix design. When filled, the
bottles were then placed inside a vacuum oven containing silica gel to begin the drying process.
Soda lime was used to control the carbon dioxide and prevent carbonation from taking place. The
samples were then left in the vacuum oven for 3 days at 30oC during which the silica gel was
changed on a daily basis.
After 3 days of drying in the vacuum oven, the samples were placed into sealed containers in
which the relative humidity (RH) was kept at 11% using silica gel and saturated lithium chloride
solution kept in open trays within the sealed container. The RH was monitored daily using a
Vaisala humidity and temperature indicator. The samples were then left in the 11% RH
containers for 4 days after which the samples were ready for the equilibrium procedure.
3.5.2 Equilibrium Method
The equilibrium method used was based on the Tang and Nilsson (1993) method. In this study,
solutions were prepared using sodium chloride saturated with calcium hydroxide. Each solution
was made based on the molar mass of sodium chloride with 3g/L of calcium hydroxide also
being added to reduce leaching. Chloride concentrations of 0.1M, 0.5M, 1.0M, 2.0M and 3.0M
were used. For each variable that was being investigated, three replicates were used in order to
assess the standard deviation and coefficient of variation. After each polyethylene bottle was
filled with solution, it was placed in different temperature chambers, namely -15oC, -10
oC, 0
oC,
5oC and 23
oC. The samples were then left to reach equilibrium over a two week period after
which titrations were performed on the samples kept at -10oC, 0
oC, 5
oC and 23
oC. The -15
oC
28
samples remained untouched after the initial two week period and were titrated only after the
temperatures were cycled. To ensure that equilibrium had taken place, samples were titrated
prior to the end of the two week period which validated that the chloride binding process had
stabilized or reached equilibrium.
3.5.3 Titrations
Titrations were performed on the samples two weeks after being placed in contact with chloride
solution as well as four months after initial exposure, after temperature cycling had taken place.
A Metrohm 716 DMS Titrino autotitrator was used to perform the titrations, with 0.01N AgNO3
and 0.01M H2SO4 being used as the titrants for determining chloride and hydroxyl
concentrations respectively. Due to the high concentrations of the chloride solutions being
titrated, they were diluted to allow an end point to be achieved without excessive use of the
AgNO3 titrant. The dilutions used for the chloride titrations were as follows:
Table 3-5: Dilutions for chloride titrations
Initial Chloride Concentration Dilution
0.1M X 10
0.5M X 50
1.0M X 100
2.0M X 100
3.0M X 200
3.5.4 pH Measurements
A VWR scientific model 3000 pH/mV/Temperature meter was used along with a ‘VWR
sympHony electrode’ containing Ag/AgCl pH gel to carry out the pH measurements. The pH
meter was calibrated using buffer solutions of pH values 7 and 10. To perform each reading, the
electrode was inserted directly into the sample bottle with readings being taken after the meter
gave a “ready” signal. After each reading, the electrode was rinsed with distilled water and
29
carefully blotted dry using a clean laboratory wipe. The pH measurements were done on the
samples exposed to chlorides for two weeks as well as after the temperature cycling process.
3.5.5 Non-Evaporable Water
A loss on ignition procedure was carried out to determine the amount of non-evaporable water
present. For each mix design at each of the curing times mentioned, 3.0g of sample crushed to
0.25mm to 2.0mm in diameter was placed in a porcelain crucible and dried at 105oC for 24
hours. Following oven drying, the samples were placed in a furnace at 1100oC for 3 hours. After
being ignited, the samples were removed from the furnace, weighed, and the non-evaporable
water content (wn/b) determined using Equation 3-1 (Chidiac & Panesar, 2008).
( ) ( ) 1111100
105 −
−
++−
+= SCMGU
n LSCMGU
SCML
SCMGU
GU
m
m
b
w ………. (3-1)
Where m105 and m1100 represent the sample masses at 105oC and 1100
oC respectively, GU and
SCM represent the proportions of each raw material used in the mix, and the LGU and LSCM
represent the loss on ignition values for the GU and SCM respectively. For each mix design, the
SCM values used in Equation 3-1 will change based on the SCMs used.
3.5.6 Temperature Exposure
To look at the effect of changing temperature on chloride binding and the ion-binder interactions,
samples were placed in different temperatures upon being exposed to chlorides for 2 months.
After the samples were placed in their cycled temperatures, they were then allowed to sit for an
additional 2 months before being re-tested for chlorides and pH. Table 3-6 summarizes the
exposure conditions A and B.
Table 3-6: Temperature exposure
Initial Temperature Final Temperature
Exposure A -15oC, -10
oC, 0
oC, 5
oC for 2 months 23
oC for 2 months
Exposure B 23oC for 2 months 0
oC for 2 months
30
3.5.7 Mercury Intrusion Porosimetry
Mercury intrusion porosimetry was performed to determine the pore size distribution, and total
porosity of all four mix designs with 0.5 w/b ratio before and after exposure to chlorides at 0oC.
Paste specimens held in 23°C and 0°C chambers for 4 months were exposed to 1.0M chloride
solution. Prior to conducting MIP testing, a sample weighing approximately 2.0g was chiseled
out from the edge of the sample cylinder. These samples were vacuum oven dried at 38-40°C for
14 days. Mercury intrusion porosimetry tests were conducted in accordance with ASTM D4404-
84 2004. The applied pressures are related to the pore structure and pore size distribution through
the Washburn equation (Cook and Hover 1993). Despite its inherent limitations, the MIP test
was used to indicate the relative differences of the total porosity, and pore size distribution of the
mixtures tested.
3.5.8 Energy-Dispersive X-Ray Spectroscopy
Energy-dispersive x-ray spectroscopy was performed to determine the C/S ratio of the C-S-H
formed in all four mix designs. Cubic samples were sawn from the cement pastes after which
they were dried in desiccators with silica gel for 72 hours. The vacuum was kept at 100kPa
below atmospheric pressure. After this, the samples were impregnated with epoxy, allowing 24
hours for the epoxy to harden. Following this, the samples were polished with 240, 400, 600,
2400, and 4000 grit abrasive papers and then polished using two oil lubricates. One oil lubricate
contained 9 µm diamonds, and the other contained 3 µm diamonds. The final polish was done
using a 3 µm diamond pad. Following the polishing, the samples were then coated with carbon.
These samples were then tested using a JEOL JSM6610-Lv Scanning Electron Microscope
(SEM) coupled with an Oxford SDD (Silicon Drift Detector) EDX analysis detector to determine
the C/S ratio of the hydration products formed. At least three areas were analyzed per sample,
with 20 or more points being utilized in calculating an average C/S ratio.
31
Chapter 4 Results and Analysis
4.1 Preliminary Experimental Assessment
Before the main test program, an initial batch was tested to determine the variability of the
results being obtained. Due to the large number of variables being tested in this research project,
it was necessary to determine the number of samples that would be required to be tested. For the
samples containing free chloride concentrations of 0.1M, 0.5M and 1.0M stored at -10oC and -
15oC, ice was present in the storage bottle when they were removed from their temperature
chamber prior to testing. To prevent the ice from influencing the apparent ion concentrations in
solution, samples were allowed to thaw for five hours at room temperature. Tests were conducted
when there was no visually apparent ice observed. To determine the variability in the chloride
results, 100%GU samples cured for 14 days were used. These samples were exposed to chlorides
at all the temperatures mentioned in the experimental procedure, namely 23oC, 5
oC, 0
oC, -10
oC
and -15oC.
The results are shown in Table 4-1 and Table 4-2, which look at the 0.3 and 0.5 w/b ratios
respectively, using the calculated mean and standard deviation of the samples to determine the
coefficient of variation (COV) of the results. In both tables, chloride contents obtained through
potentiometric titration are represented in parts per million (ppm), with the corresponding bound
chloride values in mg Cl-/g sample.
.
32
Table 4-1: Assessing variation in potentiometric titrations for 100%GU w/b 0.3
Free
Chloride
(M)
Mean
(ppm)
Standard
Deviation
(ppm)
COV
(%)
Mean Bound
Chloride (mg
Cl-/g sample)
Standard
Deviation
(mg Cl-/g
sample)
COV
(%)
23oC
0.1 299.2 4.87 1.63 4.75 0.22 4.6
0.5 878.0 1.37 0.16 5.20 0.11 2.1
1 355.2 2.61 0.73 8.26 1.19 14.4
2 705.3 5.05 0.72 16.37 2.34 14.3
3 1053.3 8.55 0.81 26.96 3.97 14.7
5oC
0.1 293.5 7.96 2.71 5.02 0.36 7.2
0.5 835.0 5.78 0.69 9.18 0.55 6.0
1 329.8 1.51 0.46 20.00 0.71 3.5
2 695.8 6.89 0.99 20.62 3.13 15.2
3 1052.7 1.82 0.17 26.92 0.84 3.1
0oC
0.1 272.0 8.07 2.97 5.94 0.37 6.2
0.5 845.0 7.40 0.88 8.18 0.66 8.1
1 340.3 4.90 1.44 15.03 2.25 15.0
2 684.6 0.80 0.12 25.73 0.41 1.6
3 1048.4 4.92 0.47 28.88 2.28 7.9
-10oC
0.1 356.8 55.37* 15.52 3.60 0.11 3.2
0.5 891.8 7.24 0.81 3.92 0.67* 17.2
1 361.8 1.46 0.40 5.21 0.66 12.7
2 698.5 5.92 0.85 19.45 2.71 13.9
3 1034.9 10.19 0.98 35.01 4.56 13.0
-15oC
0.1 356.1 5.37 1.51 2.11 0.24 11.6
0.5 739.8 18.19 2.46 17.80 1.70 9.5
1 313.9 7.81 2.49 27.06 3.50 12.9
2 679.0 6.52 0.96 28.21 2.89 10.2
3 1070.3 4.70 0.44 18.85 2.13 11.3
* Standard deviations that may indicate a possible outlier
33
Table 4-2: Assessing variation in potentiometric titrations for 100%GU w/b 0.5
Free
Chloride
(M)
Mean
(ppm)
Standard
Deviation
(ppm)
COV
(%)
Mean Bound
Chloride (mg
Cl-/g sample)
Standard
Deviation
(mg Cl-/g
sample)
COV
(%)
23oC
0.1 285.1 3.93 1.38 5.54 0.19 3.3
0.5 837.5 3.16 0.38 9.15 0.26 2.8
1 321.3 1.16 0.36 24.47 0.62 2.5
2 692.2 4.91 0.71 23.05 2.35 10.2
3 1034.5 6.40 0.62 36.57 3.04 8.3
5oC
0.1 288.3 2.44 0.85 5.35 0.11 2.0
0.5 755.3 6.00 0.79 16.81 0.57 3.4
1 297.8 2.60 0.87 35.33 1.11 3.1
2 655.1 12.04 1.84 39.99 5.73 14.3
3 1015.3 12.09 1.19 45.02 5.75 12.8
0oC
0.1 290.2 11.40 3.93 5.26 0.50 9.5
0.5 821.4 12.31 1.50 10.66 1.16 10.9
1 297.2 0.92 0.31 35.80 0.30 0.8
2 686.9 0.98 0.14 25.35 0.57 2.2
3 1027.1 1.70 0.17 39.92 0.63 1.6
-10oC
0.1 286.3 14.50 5.06 5.46 0.70 12.9
0.5 746.8 19.12 2.56 17.71 1.82 10.3
1 298.1 7.80 2.62 35.38 3.72 10.5
2 696.9 5.09 0.73 20.65 2.41 11.7
3 1049.1 0.90 0.09 29.36 0.37 1.3
-15oC
0.1 297.6 15.35 5.16 4.91 0.74 15.0
0.5 624.2 102.79* 16.47 29.04 9.56* 32.9
1 303.1 10.10 3.33 32.83 4.77 14.5
2 695.0 6.69 0.96 21.48 3.14 14.6
3 1055.6 7.55 0.72 26.32 3.49 13.3
* Standard deviations that may indicate a possible outlier
Based on the results in Table 4-1 and Table 4-2, it was found that the chloride concentration
measurements mostly had COVs less than 5%, with only two sample sets having COVs above
10% with the responsible samples being highlighted in grey. Out of the samples highlighted
using an asterisk, it was determined that one out of the three measurements taken was an outlier,
which, when removed, the remaining two samples were within 4 ppm of each other. Table 4-3
shows the measurements taken, highlighting the outlier values.
34
Table 4-3: Outlier values for titration measurements
Temp w/b
Free
Chloride
(M)
Measurement 1
(ppm)
Measurement 2
(ppm)
Measurement 3
(ppm)
-10oC 0.3 0.1 326.6 420.7 323.1
-15oC 0.5 0.5 505.5 685.8 681.2
With the calculated bound chloride values, there was greater variation, but the majority of
samples did not exceed a COV of 15%. Only two sets of measurements exceeded 15% which
were highlighted in Table 4-1 and Table 4-2. Table 4-4 shows the measurements with the outlier
values highlighted.
Table 4-4: Outlier values for calculated bound chloride
Temp w/b
Free
Chloride
(M)
Measurement 1
(mg Cl-/g
sample)
Measurement 2
(mg Cl-/g
sample)
Measurement 3
(mg Cl-/g
sample)
-10oC 0.3 0.5 4.42 4.18 3.15
-15oC 0.5 0.5 40.08 23.23 23.81
The COVs calculated for the bound chloride values indicated that 54% of the samples had a
COV greater than 10%. However, the COVs for the ppm values obtained from the titration
procedure were much lower when compared to the calculated bound chloride, with only 8% of
samples having a COV greater than 5%. This was expected due to the multiplication effect of
converting the chloride values from ppm to mg Cl-/g sample using Equation 4-1, in which small
differences would be amplified.
Due to the variation observed in the calculated bound chloride values, an initially conservative
COV of 15% was decided to be used in further analysis. However, with the spread of COVs
ranging from 1% to 15%, using a COV of 15% would produce very conservative results when
comparing variation between samples. Based on these results, it was decided to take two
measurements would be done per sample, with a third measurement being performed if there was
a large difference between the initial two measurements. The values used in illustrations would
then be the mean of the two values measured.
35
To determine whether there are statistically significant differences when comparing the results
obtained, a T-test was utilized. A description of the T-test procedure used can be seen in
Appendix A in which the 9% COV found using this initial test batch was then used along with
the sample mean to find the standard deviation. The standard deviation obtained was then used to
find the pooled sample variances of the two samples being compared, with the results being used
to calculate the confidence interval, with appropriate values from the T-distribution table being
used.
The variation in the pH values can be seen in Appendix B, where the measurements were taken
on 56d 100%GU samples of w/b 0.3 and w/b 0.5 respectively, exposed to chloride solutions at
23oC, 5
oC, 0
oC and -10
oC. Two measurements were taken for each sample.
For the pH, there was little variation between readings. The accuracy of the pH meter was ±0.02
and when this was taken into account, repeated measurements at each free chloride concentration
were similar. The largest variation in pH, 0.03 occurred at -10oC, for the samples containing free
chloride concentrations of 0.1M, 0.5M and 1.0M. Based on these results it was thought that the
thawing period was sufficient to prevent the formation of ice altering the apparent ion
concentrations, with a single pH measurement being sufficient for samples.
The variation in OH- ion concentration was also addressed using the 56d 100%GU samples.
Three measurements were taken at each free chloride concentration and temperature with the
results being shown in Appendix B for the 0.3 w/b and 0.5 w/b ratios respectively. The COV’s
associated with the OH- concentrations were all less than 12% except for 2 samples. Due to the
variation observed, it was decided to assume a conservative COV of 12% during analysis. It was
decided to perform two measurements per sample, with a third measurement being done if there
was a large difference between the initial two measurements.
When discussing the results, the chloride binding capacities will be those associated with
exposure to 0.5M, 1.0M, and 2.0M free chloride as shown in Figure 4-1. Figure 4-1 shows the
binding isotherm for 56d 100%GU samples exposed to chlorides at 23oC.
36
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
56d 100%GU
Figure 4-1: 56d 100%GU w/b 0.5 binding isotherm at 23oC
As such, in the following analysis, the binding capacity readings that will be used are those at the
0.5M, 1.0M and 2.0M points on the binding isotherms. The reason for this is because the
chloride binding capacity is the gradient of the isotherm curve at the different points so having
the curve extend beyond both sides of the point would be beneficial in ensuring the binding
capacity is found using a representative portion of the isotherm curve.
4.2 Calculating Bound Chloride and Chloride Binding Capacity
Once the chloride concentrations of the equilibrium solutions were obtained using potentiometric
titration, the values were then used to calculate the bound chloride content using the following
equations which were obtained from work done by Tang and Nilsson (1993). Equation (4-1)
shows the main equation used to calculate bound chloride.
W
CCVC o
b
)(45.35 1−= .............. (4-1)
Where: Cb = bound chloride content (mg/g-sample)
V = volume of solution (ml)
3.0M
0.1M
2.0M
0.5M
1.0M
37
Co, C1 = initial and equilibrium concentrations of chloride solution (mol/l), respectively
W = weight of dry sample (g)
After being removed from the dessicator in which the relative humidity was maintained at 11%,
the dry weight of the samples was found through oven drying at 105°C.
Apart from calculating the bound chloride content per mass of sample used, another important
value that was obtained using the chloride binding isotherms is the chloride binding capacity
(δcb/δcf). This value shows the rate of change of bound chloride with respect to free chloride and
is important with regards to corrosion through chloride diffusion through the cement
microstructure. To obtain the chloride binding capacities, the Langmuir and Freundlich
isotherms were differentiated. The original forms of both the Langmuir and Freundlich isotherms
can be seen in Equations 4-2 and 4-4 respectively, with the differentiated forms being shown in
Equations 4-3 and 4-5, respectively.
Langmuir binding isotherm ( )
f
f
bbc
acc
+=
1 ..…..……… (4-2)
Langmuir binding capacity ( )21 f
f
b
bc
a
cc
+=
δδ
………….. (4-3)
Freundlich binding isotherm β
α fb cc = ...………… (4-4)
Freundlich binding capacity 1−
=β
βαδ
δf
f
b cc
c …………… (4-5)
Due to the differences in behaviour of the Langmuir and Freundlich isotherms stated in Section
2.3.2, a choice was necessary concerning which binding isotherm to use. To make this decision,
the coefficient of determination, or R2 value, was compared for all of the samples, with the
isotherm that provided the higher average R2 values being chosen due to its better fit with the
data. For this research, the Langmuir isotherm provided a better fit to the data and was used to
analyze the results. Table 4-5 shows the sample sets for which the Langmuir or Freundlich
38
isotherms produced a higher average R2 value with the 56d 40%GGBFS and 28d 10%SF
samples being represented equally well using either of the two isotherms.
Table 4-5: Sample sets that best fit Langmuir and Freundlich isotherms
Langmuir Equal Freundlich
7d 100%GU
28d 100%GU
7d 40%GGBFS
7d 10%MK
56d 10%MK
7d 10%SF
14d 10%SF
56d 10%SF
56d 40%GGBFS
28d 10%SF
14d 100%GU
56d 100%GU
14d 40%GGBFS
28d 40%GGBFS
14d 10%MK
28d 10%MK
It was observed that regardless of the chemical composition, the Langmuir isotherm provided a
better fit to the data for samples cured for 7 days and was used to analyze the results. Sample R2
values for the 7d and 56d 100%GU samples with a w/b ratio of 0.5 can be seen in Table 4-6.
Table 4-6: Comparing R2 values for 7d and 56d 100%GU samples with w/b 0.5
Langmuir Freundlich
a b R2 α β R
2
7d
100%GU
23oC 0.0778 -0.0562 0.975 0.0887 1.0166 0.972
5oC 0.0742 -0.1104 0.984 0.0867 1.1865 0.977
0oC 0.1152 0.061 0.986 0.1097 0.8939 0.988
-10oC 0.0159 -0.2496 0.956 0.0152 2.2281 0.913
56d
100%GU
23oC 0.2347 0.8377 0.984 0.1353 0.5641 0.992
5oC 0.2189 0.6145 0.978 0.1282 0.5684 0.971
0oC 0.3206 1.4057 0.971 0.1208 0.4361 0.931
-10oC 0.1317 0.2314 0.933 0.111 0.6725 0.962
In Table 4-6 the values shaded in grey represent the data sets best represented using the
Langmuir isotherm, while the values in the unshaded cells represent those best represented using
the Freundlich isotherm. It is noted that the R2 values for both the 7d and 56d 100%GU samples
39
were similar with a maximum of 5% difference observed for the 7d 100%GU samples kept at -
10oC. Table 4-7 compares the R
2 values of the different SCMs that were used at 23
oC. When
compared, it was found that the greatest difference in R2 values was found in the 10%MK
samples, with a 20% difference found after 7 days of curing. The least difference in R2 was
found for the 100%GU samples after 7 days of curing with a 0.31% difference. While Table 4-7
shows an equal split between those samples that are best represented by either the Langmuir or
Freundlich isotherm, the samples measured at other temperatures resulted in the findings shown
in Table 4-5.
Table 4-7: Comparison of R2 values for SCMs at 23
oC
Langmuir R2 Freundlich R
2
7d
Curing
100%GU 0.975 > 0.972
40%GGBFS 0.978 > 0.950
10%MK 0.874 > 0.701
10%SF 0.959 < 0.966
56d
Curing
100%GU 0.984 < 0.992
40%GGBFS 0.974 < 0.997
10%MK 0.883 < 0.985
10%SF 0.997 > 0.860
4.3 Chloride Binding
4.3.1 Effect of w/b Ratio
Figure 4-2 shows the chloride binding isotherms for 100%GU samples cured for 56 days and
exposed to chlorides at 23oC. It can be observed that the w/b ratio has a minimal effect on the
total bound chloride values. The mean bound chloride at 3.0M is greater for the 0.3 w/b ratio
samples compared to that of the 0.5 w/b. To confirm the similarities between the isotherms, a
student’s T-test was performed, with the results indicating that there was no statistically
significant difference between the two w/b ratios within a 95% confidence interval using a COV
of 15%. When the COV was reduced to 9%, there was no statistically significant difference
between the two w/b ratios except at 0.1M free chloride.
40
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
und
Chlo
rid
e (
mg
Cl- /g
sam
ple
)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Figure 4-2: 56d 100%GU bound Cl- vs. free Cl
- at 23
oC
At free chloride concentrations less than 0.5M the results shown in Figure 4-2 were similar to
what was found by Zibara (2001) and Tang and Nilsson (1992) where the bound chloride values
for both the 0.3 and 0.5 w/b samples were similar. At higher free chloride concentrations of 2.0M
and 3.0M however, the trend of similar bound chloride amounts remained despite what was
reported by Zibara (2001) and Tang and Nilsson (1992), where a higher w/b ratio resulted in
greater bound chloride. The similar binding amounts noted by Zibara (2001) and Tritthart (1989)
were attributed to the level of hydration their samples were able to attain. With the 0.3 and 0.5
w/b ratio samples used in this research able to attain degrees of hydration of 0.65 and 0.70
respectively through wet curing prior to chloride exposure, the theory of hydrated product being
solely responsible for bound chloride content is not accurate.
In Figure 4-3, the bound chloride contents for the 7d 100%GU samples are shown. For the 7d
samples the trend remains similar to that found for the 56d samples with similar bound chloride
amounts irrespective of the w/b ratio. Again, a student’s T-test was performed, confirming there
was no statistically significant difference between the two w/b ratios within a 95% confidence
interval using a 15% COV.
41
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Figure 4-3: 7d 100%GU bound Cl- vs. free Cl
- at 23
oC
When the binding capacities for both the 7d and 56d 100%GU samples were compared in Table
4-8, the effect of w/b ratio was minimal in terms of total bound chloride, however, it does have a
greater impact on chloride binding capacity. Regardless of the free chloride values, the chloride
binding capacities for both the w/b 0.3 and w/b 0.5 samples cured for 56 days were similar with a
maximum difference of 10.1% noted when samples were exposed to 2.0M free chloride.
However, when the chloride binding capacities for the samples cured for 7 days were compared,
the difference in chloride binding capacity between the 0.3 and 0.5 w/b ratio samples was larger
than what was found for the samples cured for 56 days. The largest difference found was a
77.7% change in chloride binding capacity when the 7d samples were exposed to 2.0M free
chloride solution. The 7d 100%GU samples show that the presence of unhydrated cementitious
material can have a large effect on chloride binding capacity, highlighting the importance of
chemical binding.
42
Table 4-8: Binding capacities for 7d and 56d 100%GU samples at 23oC
f
b
cc
δδ
at 0.5M
(mg Cl-/M g
sample)
f
b
cc
δδ
at 1.0M
(mg Cl-/M g
sample)
f
b
cc
δδ
at 2.0M
(mg Cl-/M g
sample)
w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5
7d 12.92 14.60 13.56 7.81 14.99 3.34
∆f
b
cc
δδ
11.5% 42.4% 77.7%
56d 21.79 21.57 14.01 13.31 7.33 6.59
∆f
b
cc
δδ
1.0% 5.0% 10.1%
When GGBFS, MK and SF are included, the effect of w/b ratio on bound chloride content can be
seen in Figures 4-4, 4-5 and 4-6 respectively. For the GGBFS samples shown in Figure 4-4,
those with 0.5 w/b ratio had a higher bound chloride content regardless of the free chloride
concentration. For the MK samples shown in Figure 4-5 however, as the free chloride
concentration approached 3.0M, the 0.3 w/b ratio samples began showing greatest binding. For
the GGBFS samples, a T-test revealed that there was no statistically significant difference in the
bound chloride values between the two w/b ratios within a 95% confidence interval except at
1.0M free chloride concentration. For the MK samples, there was no statistically significant
difference between the bound chloride values within a 95% confidence interval except at 0.1M
free chloride concentration where there was a statistically significant difference. For the SF
samples, it was found that there was no statistically significant difference between the two bound
chloride contents at 1.0M and 2.0M chloride concentrations within a 95% confidence interval. At
0.1M, 0.5M and 3.0M chloride samples binding more chloride when exposed to more
concentrated chloride solutions.
The reason for the binding behaviour could be due to the influence of the chemical composition
of the MK and SF in conjunction with the w/b ratio. MK, having higher aluminate content when
> < >
> > >
43
compared to GU or GGBFS, would result in greater bound chloride as the free chloride
concentration increased due to increased formation of Friedel’s salt or analogues of Friedel’s
salt. This was observed in Figure 4-5, where the w/b ratio of 0.5 would allow for the formation
of a greater amount of aluminate compounds during curing resulting in increased chloride
binding. Along with the increase in chemical binding, physical binding will also become more
dominant with the 0.5 w/b ratio allowing for greater development of the microstructure through
hydration. As the free chloride concentration in the MK samples increased to 3.0M however, the
bound chloride contents appear to reach a plateau implying that the sample has bound the
maximum amount of chloride that it can.
When a student’s T-test was performed on the results, there was no statistically significant
difference between SF samples at 1.0M free chloride. At all other free chloride concentrations,
there was a significant difference within a 95% confidence interval. At low chloride
concentrations, the 0.5 w/b ratio samples showed greater binding until the free chloride
concentration approached 1.0M after which the 0.3 w/b ratio samples showed relatively greater
binding.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Figure 4-4: 56d 40%GGBFS bound Cl- vs. Free Cl
- at 23
oC
44
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bou
nd C
hlo
rid
e (
mg
Cl- /g
sa
mple
)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Figure 4-5: 56d 10%MK bound Cl- vs. Free Cl
- at 23
oC
For the SF samples shown in Figure 4-6, the 0.5 w/b ratio resulted in reduced chloride binding
when the free chloride concentration increased beyond 1.0M. The reason for this could be due to
the influence of the SF on the composition of the C-S-H formed. SF is associated with the
formation of C-S-H with a lower C/S ratio when compared to other SCMs. The lower C/S ratio is
associated with a reduction in binding (Zibara et. al., 2008). When the 0.5 w/b ratio was used for
the SF samples, it would result in more hydration compared to the SF with 0.3 w/b ratio,
producing more C-S-H with a reduced C/S ratio. To determine this, the non-evaporable water
contents were compared. The 0.3 w/b ratio SF samples had a 0.16g/g sample non-evaporable
water content compared to the 0.5 w/b ratio SF samples which had a 0.20g/g sample non-
evaporable water content after 56 days of curing. This could then explain the reduction in bound
chloride found in the 0.5 w/b ratio samples for SF when compared to the samples with 0.3 w/b
ratio. The 0.3 w/b ratio samples, similar to what occurred for MK samples, would have been able
to bind more chloride through the incorporation of the chlorides into the microstructure as any
residual unhydrated materials began to hydrate upon exposure to the chloride solution.
45
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Figure 4-6: 56d 10%SF bound Cl
- vs. Free Cl
- at 23
oC
Figure 4-7 compares 100%GU samples kept at 23oC and 0
oC exposure temperatures. In Figure 4-
7, the samples showed a trend where reducing the temperature had little to no effect on the bound
chloride content regardless of the w/b ratio. The only difference noted was the decrease in bound
chloride for the 0.3 w/b ratio sample at 0oC as it approached 3.0M free chloride concentration.
When both the 0.3 and 0.5 w/b ratio samples at 23oC and 0
oC were compared using a T-test,
there was no statistically significant difference found between them.
46
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound
Chlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
23oC w/b 0.3
23oC w/b 0.5
0oC w/b 0.3
0oC w/b 0.5
Figure 4-7: Effect of temperature on binding isotherms for 56d 100%GU
In Figure 4-8, the influence of temperatures below freezing are compared for the 0oC and -10
oC
samples. At free chloride concentrations up to 2.0M, all the samples bind a similar amount of
chloride. At 3.0M free chloride concentration however, the 0.3 w/b ratio samples bound
noticeably less chloride when compared to the 0.5 w/b ratio samples at both 0oC and -10
oC.
Based on Figure 4-8, the bound chloride values appear to converge, with the 0.3 w/b ratio
samples binding approximately 28mg Cl-/g sample and the 0.5 w/b ratio samples binding
approximately 40mg Cl-/g sample. This indicates that the w/b ratio does have an impact on
bound chloride content as the temperature decreases. Even with crushed samples, the larger
sample pieces can have a diameter of 2mm which is large enough to have a capillary pore system
that can undergo freezing. As the water in solution freezes, it expands, filling the capillary pores,
preventing chlorides in solution from entering and coming into contact with the hydrated
cementitous material. As shown in Figure 4-8, the 0.3 w/b samples were more affected by this
effect compared to the 0.5 w/b, with reductions in bound chloride content observed.
47
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound
Chlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
0oC w/b 0.3
0oC w/b 0.5
-10oC w/b 0.3
-10oC w/b 0.5
Figure 4-8: Effect of temperature on binding isothems for 56d 100%GU
4.3.2 Effect of Supplementary Cementitious Materials
Results for the effect of the different SCMs on binding is shown in Figure 4-9 where 56d
samples with a w/b ratio of 0.5 at 23oC were compared. The order of bound chloride is
GGBFS>GU>MK>SF. Based on Figure 4-9, the GU and GGBFS samples bound similar
amounts of chloride until the free chloride concentration increased to over 0.5M in
concentration. Above 0.5M free chloride, the GGBFS samples bound the most amount of
chloride. It was expected that the GGBFS samples bind the most chloride due to its aluminate
content.
The SF samples bound the least amount of chloride compared to the GU, GGBFS, or MK
samples. These bound chloride results for SF are similar to what was found by authors such as
Arya et. al. (1990) and Zibara (2001). In their studies, the reduced bound chloride content
associated with SF was attributed to a reduction of the C/S ratio of the C-S-H formed. With
similar results found in this project, it is thought that the C/S ratio of the C-S-H is contributing to
the reduction in bound chloride content found in the SF samples when compared to the other
48
SCMs. Evidence supporting the influence of the C/S ratio was found when EDS testing was
conducted on some samples. The results can be seen in Table 4-9, with the SF samples having
the lowest average C/S ratio of 2.29 compared to the GU, GGBFS, and MK samples. The results
of the analysis can be seen in Appendix C.
Table 4-9: C/S ratios of mix designs with 0.3 w/b ratios
Mix Design Ca/Si Ratio
100%GU 8.38
40%GGBFS 8.07
10%MK 7.11
10%SF 3.77
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
100%GU
40%GGBFS
10%MK
10%SF
Figure 4-9: Effect of SCMs on binding isotherms 56d samples w/b 0.5 23oC
There is a general consensus in the literature on the important role of aluminates in chloride
binding studies (Thomas et. al. (2011), Zibara, (2001), and Dhir et. al. (1996)). However,
contrary to what was expected, the MK samples in this study did not bind the most chloride
despite the high aluminate content. With the MK samples containing approximately 8.1%
aluminates compared to the GGBFS, GU or SF samples containing 6.7%, 5.4% and 5.1%
49
aluminates respectively, it was expected that the MK samples would bind the most amount of
chloride. However, the results of this study compare favourably to those found by Zibara et. al.
(2008) in which MK-lime mixtures were investigated. It was found that an increasing MK
content was associated with a decrease in bound chlorides due to the change in the proportions of
monocarboaluminate and stratlingite formed during hydration, the effects of which were
described in Section 2.2.1.2. Coupled with the effect of increasing MK content, the 56 day wet
curing will also negate the extra aluminate that the MK would have provided due to increased
hydration, resulting in a decrease in binding being associated with an increase in hydration.
When the non-evaporable water contents of the samples were compared, it was found that the
GU samples had the greatest non-evaporable water content of 0.216g/g sample with the GGBFS
samples containing the lowest non-evaporable water content of 0.194g/g sample. All the results
can be seen in Table 4-9, and a comparison of the chloride binding capacities for all the mix
designs at 23oC can be seen in Figure 4-10. From these results it can be seen that the non-
evaporable water content of the cement paste is not a reliable indicator of the chloride binding
capacity. For the GGBFS and MK however, hydration cannot fully explain the trend observed,
where, regardless of the free chloride concentration, the GGBFS samples have the greatest
binding capacity while having the lowest non-evaporable water content. To help explain the
difference in binding capacity, the chemical composition of each material can be used.
The GU used was comprised of 19% SiO2, 5.4% Al2O3 and 61% CaO as shown in Table 3-2.
The GGBFS was comprised of 37% SiO2, 8.7% Al2O3 and 38% CaO. The MK was comprised of
62% SiO2, 32% Al2O3 and 0.4% CaO. Due to the higher aluminate content found in the MK, it
was initially thought that it would have a greater binding capacity than the GGBFS. With the
replacement levels of 40% GGBFS and 10% MK, the resulting GGBFS and MK samples
contained 6.7% and 8.1% aluminates respectively. When this was coupled with the curing time
of 2 months, the aluminate content does not have a large contribution towards the binding
capacity. Instead, the SiO2 content may play a more important role. As stated in the description
of SF in Section 2.2.1.3, the increase in SiO2 may decrease the C/S ratio of the C-S-H formed
which was found to be an important factor in chloride binding. The GGBFS used, despite having
a greater replacement level, has an equal proportion of CaO to SiO2 which would act to help
balance the C/S ratio, enabling the GGBFS samples to bind more chlorides. The MK, having
50
0.4% CaO would have less calcium content available when forming C-S-H, resulting in a
decrease in the C/S ratio and hence a decrease in the bound chloride content which is what was
noted in the results.
Free Chloride Concentration
0.5M 1.0M 2.0M
Bin
din
g C
ap
acity (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
25
100%GU
40%GGBFS
10%MK
10%SF
Figure 4-10: Binding capacities of all 56d mix designs w/b 0.5 at 23oC
Table 4-9 Non-evaporable water content for 56d samples 0.5 w/b at 23oC
Mix Design Non-Evaporable Water
Content (g/g sample)
100%GU 0.216
40%GGBFS 0.194
10%MK 0.215
10%SF 0.196
The effect of temperature on the binding capacity of the different SCMs is shown in Figures 4-
11, 4-12, 4-13 and 4-14. For the 100%GU samples shown in Figure 4-11, the binding capacity at
23oC, 5
oC and 0
oC were similar, with the 23
oC samples having the highest binding capacity of
the three at all free chloride concentrations. When the -10oC samples were looked at, exposure to
51
the lower free chloride concentration of 0.5M resulted in the lowest binding capacity. However,
as the free chloride concentration increased, eventually reaching 2.0M concentration, the binding
capacity of the -10oC samples increased relative to the rest of the samples. At 2.0M free chloride
concentration, the binding capacity of the samples exposed to chlorides at -10oC was
approximately 46% larger than that of the next highest which were the samples exposed to
chlorides at 23oC. It was thought that ice formation at -10
oC would increase the apparent chloride
concentration of the solution, increasing the bound chloride content. The ice formation would
also be coupled with a reduction in the rate of reaction due to the decrease in temperature based
on the Arrhenius equation shown in Equation 4-7.
It was observed that the introduction of the SCM resulted in different chloride binding capacities
when compared to the GU samples. For the GU and GGBFS samples in Figure 4-11 and Figure
4-12 respectively, the binding capacities for the 5oC and 0
oC samples were similar except for the
GGBFS samples exposed to 2.0M chloride solution where there was an unusually high binding
capacity noted at 0oC. The reason was thought to be due to the large bound chloride values
obtained for the samples exposed to 3.0M free chloride solution while stored at 0oC. These high
bound chloride values affect the shape of the Langmuir isotherm resulting in the high binding
capacity observed. The chloride values recorded through titration differed by less than 10%. Due
to this, the reason for the increase in binding capacity was attributed to an increase in physical
binding through chemical adsorption. Chemical binding to form analogues of Friedel’s salt will
still be present but will have a reduced effect due to the reduction in temperature. This is related
to the Arrhenius equation which relates the rate of reaction to the temperature as shown in
Equation 4-7.
RTEaAek/−= ……… (4-7)
Where k is the rate constant, T is the absolute temperature, Ea is the activation energy, R is the
universal gas constant and A is the pre-exponential factor. Based on the Arrhenius equation, a
reduction in temperature would reduce the reaction rate constant. The result of this would be a
decrease in the rate of Friedel’s salt formation. However, the effect of reducing temperature on
the rate constant as calculated using Equation 4-7 is minor. Assuming Ea, R and A are constant,
with only the absolute temperature changing, the relative differences between the k values
52
obtained for 23oC and -10
oC vary by less than 1.0%. Therefore, while being a contributing factor
to the reduction in bound chloride and chloride binding capacity, the effect of the reduction in
the rate of reaction due to temperature would be minor. For the MK and SF samples in Figure 4-
13 and Figure 4-14 respectively however, there is a marked increase in binding capacity for the
0oC samples relative to the rest at all free chloride concentrations, with the 0
oC samples having
the highest average binding capacity for both the MK and SF samples.
Free Chloride Concentration
0.5M 1.0M 2.0M
Ch
lorid
e B
ind
ing
Ca
pa
city (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
25
23oC
5oC
0oC
-10oC
Figure 4-11: Chloride binding capacities of 56d 100%GU samples at all temperatures w/b
0.5
53
Free Chloride Concentration
0.5M 1.0M 2.0M
Ch
lorid
e B
ind
ing
Ca
pa
city (
mg C
l- /M g
sa
mp
le)
0
10
20
30
40
23oC
5oC
0oC
-10oC
Figure 4-12: Chloride binding capacities of 56d 40%GGBFS samples at all temperatures
w/b 0.5
Free Chloride Concentration
0.5M 1.0M 2.0M
Ch
lorid
e B
ind
ing
Ca
pa
city (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
25
23oC
5oC
0oC
-10oC
Figure 4-13: Chloride binding capacities of 56d 10%MK samples at all temperatures 0.5
w/b
54
Free Chloride Concentration
0.5M 1.0M 2.0M
Ch
lori
de B
ind
ing
Cap
acity (
mg
Cl-
/M g
sa
mp
le)
0
5
10
15
20
25
23oC
5oC
0oC
-10oC
Figure 4-14: Chloride binding capacities of 56d 10%SF samples at all temperatures 0.5 w/b
4.3.3 Effect of OH- Concentration
Figure 4-15 shows the relation between bound chloride and the OH- ion concentration for 56d
GU samples that were stored at 23oC. For comparison, both the 0.3 and 0.5 w/b ratio samples
were included, with the labels indicating the original free chloride concentration of the solution.
OH-(mol/l)
0.06 0.07 0.08 0.09 0.10 0.11 0.12
Bound C
hlo
rid
e (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Free chloride concentrations shown on data points
Figure 4-15: Bound chloride vs. OH
- for 56d GU at 23
oC
0.1M
0.5M
1.0M 1.0M
0.5M
2.0M 2.0M
3.0M 3.0M
0.1M
55
Based on Figure 4-15, the bound chloride content increases from approximately 4 mg Cl-/g
sample to 15 mg Cl-/g sample as the OH
- concentration increases from 0.07 to 0.11 and 0.065 to
0.1 for the 0.3 and 0.5 w/b ratios, respectively. However, as the bound chloride content continues
to increase, the OH- concentration reveals that the increase in bound chloride took place at low
chloride concentrations (0.1M, 0.5M), with the OH- concentration decreasing at the higher
chloride concentrations.
The results obtained in Figure 4-15 indicate that up to a free chloride concentration of 0.5M, the
chloride ions are able to compete with the OH- ions for adsorption sites. After this point, the
increase in chloride ion concentration causes chemical binding to become dominant through ion
exchange with the AFm hydrates such as monosulphate. This results in OH- ions being able to
find adsorption sites due to the reduction in Cl- ions in solution, explaining the gradual decrease
in OH- concentration as the chloride solution concentration increases. In addition, this would
result in an increase in solubility of calcium hydroxide in the aqueous sodium chloride solutions.
At 25oC, maximum solubility was found at 1.21M NaCl solution (Johnston & Grove, 1931). This
can be seen in Figure 4-15 where the OH- concentrations all increase up to either 0.5M or 1.0M
free chloride concentration, and then decrease. This might be due to a combination of chloride
binding mechanisms taking place and the testing temperature being 23oC.
When the influence of curing time is compared, a similar trend was noticed for all the different
ages. Figure 4-16 shows the relation between bound chloride and OH- at all curing times.
56
OH- (mol/l)
0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
607d 100%GU
14d 100%GU
28d 100%GU
56d 100%GU
Free chloride concentrations shown on data points
Figure 4-16: Bound chloride vs. OH
- all GU samples at w/b 0.5
From Figure 4-16 it can be seen that for the 7d and 28d samples the peak OH- concentration is
reached at the 1.0M free chloride concentration point, whereas for the 14d samples, this peak
appears to be at the 2.0M chloride concentration point. At all ages, peak OH- concentration is
between 10 and 20 mg Cl-/g sample.
The OH- concentration was then looked at. Figure 4-17 shows the relation between the OH
-
concentration and the free chloride concentration for each mix design used at 23oC and with a
0.3 w/b ratio. Based on Figure 4-17, it can be seen that for all free chloride concentrations, the
use of GU cement produced the highest average OH- concentration and the use of SF resulting in
the lowest measured OH- concentrations. The hydration of any unhydrated SF particles which
would utilize the OH- ions as described in Section 2.2.1.3, combined with the SF samples
0.1M
1.0M
3.0M
2.0M
3.0M
3.0M
0.5M
3.0M
1.0M
0.5M
2.0M
2.0M
0.5M
0.1M
0.5M
1.0M
2.0M
1.0M
0.1M 0.1M
57
adsorbing OH- ions in the C-S-H formed would explain the low OH
- concentrations relative to
the other mix designs containing GGBFS and MK.
It was observed that for the GU, MK and SF samples, the OH- concentration increased between
0.1M and 0.5M with the values either remaining similar or decreasing as the free chloride
concentration increased. For the GGBFS samples however, the OH- concentration reached a
maximum value around 1.0M free chloride concentration after which it decreased with
increasing free chloride concentration. The reduction in OH- concentration makes sense if the
pozzolanic reactions of GGBFS, MK, and SF are taken into account. Due to the sample being
immersed, the samples with SCMs would be able to react with the calcium hydroxide present to
further hydrate. This resulted in the decrease in OH- concentration observed.
Free Chloride Concentration
0.1M 0.5M 1.0M 2.0M 3.0M
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
100%GU
40%GGBFS
10%MK
10%SF
Figure 4-17: Variation in OH
- for 56d samples of all SCMs w/b 0.3
The previously mentioned transition point in Figure 4-16 where the OH- concentration peaks for
the GU samples can still be seen when looking at the results in Figure 4-17, with the GU and SF
peak at 0.5M, and GGBFS and MK peak at 1.0M. With the SF however, the OH- values remain
similar at all free chloride concentrations ranging from approximately 0.065mol/l to 0.080mol/l.
The low OH- values obtained for SF relative to the other SCMs are due to the OH
- being utilized
in the pozzolanic reaction along with the resulting C-S-H binding less chloride due to the
58
decreased C/S ratio as was mentioned in Section 2.2.1.3. This implies that more OH- ions are
able to remain adsorbed to the hydrated products without being displaced by chloride ions
resulting in a lower OH- concentration in the equilibrium solution.
When the OH- concentrations for the samples at w/b 0.5, as shown in Figure 4-18, were
compared to the OH- values obtained for the samples at w/b 0.3, there were differences noted for
each SCM. The GU samples experienced a decrease in OH- concentration at all free chloride
concentrations with the increase in w/b ratio. This was attributed to the increase in hydration
which would allow more OH- ions to be adsorbed within the hydrated microstructure.
It was observed that the GGBFS samples with 0.5 w/b ratio had a lower OH- concentration at
1.0M free chloride concentration when compared to the OH- concentration of the GGBFS
samples with 0.3 w/b ratio. Despite the increase in solubility of calcium hydroxide at this free
chloride concentration, the 0.5 w/b ratio GGBFS samples would enable more OH- ions to
become adsorbed resulting in the reduced OH- concentration observed.
The MK samples at 0.5 w/b ratio showed a similar trend compared to the 0.5 w/b ratio GGBFS
samples. A decrease in OH- concentration at 1.0M free chloride concentration was observed with
increases in OH- concentration at 2.0M and 3.0M free chloride concentrations to levels similar to
or higher than those found in the 0.3 w/b ratio samples. The increase in OH- concentration at
2.0M and 3.0M was attributed to the increased Cl- ion concentration being able to displace the
OH- ions when being chemically bound.
When the SF samples were compared, it was noted that the OH- concentration was higher at all
free chloride concentrations when the w/b ratio was increased from 0.3 to 0.5. It was thought that
with the increased hydration associated with the higher w/b ratio, there would be less utilization
of the OH- ions to aid in hydration processes resulting in the higher OH
- concentrations found in
solution.
59
Free Chloride Concentration
0.1M 0.5M 1.0M 2.0M 3.0M
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12 100%GU
40%GGBFS
10%MK
10%SF
Figure 4-18: Variation in OH
- for 56d samples of all SCMs w/b 0.5
When the effect of temperature is included in the analysis of the effect of OH- on binding, the
results can be seen in Figure 4-19 where all the temperatures except -10oC were compared. The
corresponding binding capacity values for Figure 4-19 are shown in Table 4-10.
Free Chloride Concentration
0.1M 0.5M 1.0M 2.0M 3.0M
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
23oC
5oC
0oC
Figure 4-19: OH- for 100%GU samples at all temperatures
60
Table 4-10: Binding capacities for 56d 100%GU
Free Chloride
Concentration (M)
Temperature
23oC 5
oC 0
oC
0.1 32.58 30.40 38.75
0.5 21.79 20.41 18.39
1.0 14.01 13.28 8.96
2.0 7.33 7.13 3.61
3.0 4.53 4.37 1.90
In comparing the binding capacities in Table 4-10 to the OH- values in Figure 4-19, there is a
trend where a lower OH- concentration corresponds to a greater binding capacity for all of the
results except those at 0.1M free chloride concentration. These results can be explained based on
the ion exchange mechanism. An increase in OH- concentration corresponds to less bound
chloride due to competition for adsorption sites, with a reduced OH- concentration producing the
opposite effect. The reduction in binding capacity can also be attributed to the reduction in
temperature through a reduction in the rate of reaction. At the lower free chloride concentrations
of 0.1M, 0.5M and 1.0M this does not appear to be the case, but at higher free chloride
concentrations of 2.0M and 3.0M where chemical binding is said to control binding, there is a
decrease in binding capacity associated with the decrease in temperature from 23oC to 0
oC.
When pore freezing is taken into account at -10oC, the results for the OH
- concentrations can be
shown in Figure 4-20. It is noted that before testing the samples kept at -10oC, the sample bottles
were checked to ensure there were no visible ice crystals but there may have been ice crystals
within the sample that may have not been observed by eye. Regardless of the free chloride
concentration, the OH- values at -10
oC were always lower than those at 0
oC, with the
concentration of OH- ions at both -10
oC and 0
oC remaining similar regardless of the free chloride
concentration. The binding capacities were then compared as shown in Table 4-11.
61
Figure 4-20: Comparison of OH- for 100%GU samples at 0
oC and -10
oC
Table 4-11: Chloride binding capacities for 56d 100%GU at 0oC and -10
oC
Free Chloride
Concentration (M)
Temperature
0oC -10
oC
0.1 38.75 21.82
0.5 18.39 14.47
1.0 8.96 9.83
2.0 3.61 5.29
3.0 1.90 3.39
When looking at the binding capacities for the 0oC and -10
oC GU samples, it was observed that
at low free chloride concentrations of 0.1M and 0.5M, the binding capacity was lower for the -
10oC samples compared to the 0
oC samples. This was expected due to the reduced reaction rates
associated with the reduction in temperature coupled with partial pore freezing. At higher free
chloride concentrations of 1.0M, 2.0M and 3.0M, where there was no visible ice formed at -
10oC, higher binding capacities were measured relative to the 0
oC samples. These results are
consistent with the results for the samples exposed to chloride solutions above 0oC where a
higher OH- value was related to a lower chloride binding capacity.
62
4.3.4 Effect of pH
Tritthart (1989) found that a decrease in binding was observed as the pH of the storage solution
was increased from 12.5 to 13.7. Similarly, for this research, a decrease in bound chloride
content was observed as the pH of the solution increased although the pH range was smaller,
ranging from 12.3 to 13. Figure 4-21 shows the relation between bound chloride and the pH for
the 56d GU samples for both the 0.3 and 0.5 w/b ratios with the 0.5 w/b ratio samples showing a
higher pH associated with similar bound chloride contents for all the points measured. The 0.5
w/b ratio samples have a higher pH at all free chloride concentrations as shown in Figure 4-21.
pH
12.4 12.5 12.6 12.7 12.8 12.9
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
w/b 0.3
w/b 0.5
Figure 4-21: Effect of pH on bound chloride for 100%GU samples at 23oC
This increase in pH and resulting increase in binding was believed to be due to the relatively
greater hydration occurring due to the higher w/b ratio. The increased hydration would result in a
larger quantity of calcium hydroxide being formed. The extra calcium hydroxide would then
provide more OH- ions, thereby increasing the pH of the solution. Greater hydration would also
create extra adsorption sites at which physical binding can take place. This also holds true for all
the curing times investigated which can be seen in Figure 4-22, where the 7d, 28d and 56d GU
samples were compared.
0.1M
0.5M
1.0M
2.0M
3.0M
63
pH
12.4 12.5 12.6 12.7 12.8 12.9
Bo
un
d C
hlo
ride
(m
g C
l- /g s
am
ple
)
0
10
20
30
40
50
7d
28d
56d
Figure 4-22: Effect of curing time on relation between bound chloride and pH for 100%GU
samples at 23oC w/b 0.5
Figure 4-23 shows the influence of SCMs on the pH and bound chloride results. For all the
SCMs used, the bound chloride content decreased as the pH increased. This is in accordance
with what was found by Zibara (2001) who investigated GU, silica fume and metakaolin pastes.
The GU, GGBFS and metakaolin samples showed very similar trends in terms of the range of pH
and bound chloride values. Interestingly, the samples containing silica fume had similar pH
values to those obtained for the GU samples. However, the bound chloride content for the silica
fume samples was approximately half that of the GU samples except when the pH level
approached 12.8 where the values converged. This is in agreement with Zibara (2001) who found
that the influence of pH is greater at low chloride concentrations with decreasing influence as the
chloride concentration approaches 3.0M.
64
pH
12.4 12.5 12.6 12.7 12.8 12.9
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
100%GU
40%GGBFS
10%MK
10%SF
Figure 4-23: Effect of pH on bound chloride for all SCMs at 23
oC
Figure 4-23 shows that at similar pH levels, the SF and GU samples have differing bound
chloride values. This suggests that while the pH may have an inverse relationship with bound
chloride for the individual mix designs, the pH cannot be used to compare the bound chloride
values between mixes. This is in agreement with research done by Song et al. (2008) who stated
that binding is influenced more by the hydrated microstructure within the pH range 12.6 to 13.2,
with products of hydration such as C-S-H playing an important role. Furthermore, the bound
chloride would be released below a pH of 12.5 according to Byfors et. al (1986) resulting in an
increase in free chloride content. However, results shown in Figure 4-23 do not indicate that a
reduction in bound chloride content took place when the pH levels went below 12.5.
65
4.4 Effect of Temperature on Chloride Binding
Figure 4-24 shows the binding isotherms for the 56d GU samples at all the temperatures
measured for a 0.3 w/b ratio. The samples exposed to chlorides at 23oC bound the most chloride,
except at the 2.0M chloride concentration where the 5oC samples show greater binding. The
trend that emerged was that the lower the temperature at which samples were exposed to
chlorides, the lower the bound chloride, especially at higher free chloride concentrations. These
results are contrary to the results of Masslehudin et. al. (1997) and Hussan & Rasheeduzzafar
(1993), where an increase in temperature resulted in a decrease in binding. It is important to note
however, that the temperatures used by those researchers were significantly higher than those
used in this project, ranging from 20oC to 70
oC.
Figure 4-24 is consistent with Zibara (2001) where an increase in binding with increasing
temperature was found at 3.0M chloride concentration. However, Zibara (2001) also found that
at free chloride concentrations of 0.1M, there was a decrease in binding with increasing
temperature. Apart from the -10oC samples, this trend was not noticed as shown in Table 4-12
where from 0oC to 23
oC the bound chloride increases from 3.35 to 3.82g Cl
-/g sample
respectively.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
23oC
5oC
0oC
-10oC
Figure 4-24: 56d 100%GU binding isotherms w/b 0.3
66
Table 4-12: Bound chlorides at 0.1M free chloride concentration for 56d 100%GU samples
Temperature w/b 0.3 w/b 0.5
23oC 3.82 4.80
5oC 3.62 5.43
0oC 3.35 4.60
-10oC 8.85 5.64
Based on Table 4-12, it can be seen that for both w/b ratios, there is an increase in bound
chloride content when the temperature decreases from 0oC to -10
oC. Several mechanisms can be
linked with this. The free chloride concentration is relatively low at 0.1M, freezing of the
solution, including partial freezing within the pores of the larger sample particles can take place,
with an increase in the apparent chloride concentration occurring as a result. When this
concentrated chloride solution comes in contact with the sample, increased physical adsorption
to the hydration products takes place. Similar results were found by Panesar & Chidiac (2011)
where samples at -3oC were found to have greater binding capacity than samples at 5
oC and
13oC.
Figure 4-25 shows the binding isotherm for 100%GU paste with a w/b ratio of 0.5. The results
indicate that at 3.0M free chloride concentration, the samples exposed to -10oC and 0
oC bind
approximately 25% more compared to the 23oC and 5
oC samples. These results are similar to
what was observed by Zibara (2001), however, no specific reasoning as to why this occurs was
stated. The pH or OH- concentrations were measured to determine if they might shed some light
on what was observed. For the -10oC samples, the lowest average pH and OH
- concentrations
were obtained. However, for the samples at 0oC, the average pH was higher than that obtained
for the 23oC samples, with the average OH
- value higher than that obtained for the 5
oC samples.
Thus, the results obtained are inconclusive in determining what is causing the trend observed in
Figure 4-25 for the samples exposed to 3.0M free chloride concentration.
67
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
23oC
5oC
0oC
-10oC
Figure 4-25: 56d 100%GU binding isotherms w/b 0.5
When the influence of temperature on the chloride binding capacity of the GU samples was
taken into account, it was found that there was a general decrease in chloride binding capacity as
the temperature decreased. When the temperature decreased between 0oC and -10
oC however,
the behaviour got more complicated, with some samples experiencing an increase in chloride
binding capacity. This was attributed to the partial pore freezing effects that increase the
apparent chloride concentration. Figure 4-26 shows the change in binding capacity as the
temperature decreases.
68
Temperature
23C 0C -10C
Chlo
ride B
indin
g C
ap
acity (
mg C
l- /M g
sam
ple
)
0
10
20
30
40
0.5M Cl-
1.0M Cl-
2.0M Cl-
Figure 4-26: Variation of chloride binding capacity with temperature for 100%GU samples
The effect of temperature on the binding ability of the different SCMs was investigated. Figures
4-27, 4-28 and 4-29 show the effect of temperature on the binding isotherms of GGBFS, MK and
SF respectively. The results in Figure 4-27, comparing the bound chloride contents of GGBFS
samples at 23oC and 0
oC, indicate that samples exposed to chlorides at 23
oC show greater
binding at free chloride concentrations up to 2.0M. Between 2.0M and 3.0M free chloride
concentration however, the GGBFS samples stored at 0oC bound more chloride. A student’s T-
test showed that there was a statistically significant difference between the two temperatures
except at 2.0M free chloride concentration within a 95% confidence interval. This is attributed to
an increase in chemical binding. The extra aluminate content of the GGBFS coupled with an
increase in temperature would allow for a higher rate of formation of chemical binding products
such as Friedel’s salt.
69
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
20
40
60
23oC
0oC
Figure 4-27: 56d 40%GGBFS binding isotherms w/b 0.3
When freezing is occurs, the results can be seen in Figure 4-28 where the samples at 0oC and -
10oC are compared. When exposed to 2.0M and 3.0M free chloride solutions, the samples
exposed to chlorides at -10oC have a lower bound chloride content when compared to samples
exposed to chlorides at 0oC. A student’s T-test showed that at all free chloride concentrations,
there was a statistically significant difference between the 0oC and -10
oC samples within a 95%
confidence interval using a 15% COV. At 2.0M free chloride concentration, a 46% decrease in
bound chloride was found for the -10oC samples, with a 68% decrease in bound chloride noted
for the samples exposed to 3.0M free chlorides. The reason for this was thought to be a reduction
in Friedel’s salt production coupled with a reduction in the rate of hydration. The reduction in
temperature would result in a reduction in the rate of reaction according to the Arrhenius
equation. This reduction in the rate of reaction then has the effect of reducing Friedel’s salt
production while also reducing the rate of formation of C-S-H necessary for physical binding as
the sample hydrates while in contact with the free chloride solution. Because of the slower rate
of hydration of slag when compared to the other SCMs used in this research, the effect of
temperatures below 0oC would be more pronounced than what would be observed for the other
SCMs. This was found to be the case with the differences between the bound chlorides content
of samples tested at 0oC and -10
oC being larger than those found for GU, MK or SF. It was
70
thought that freezing within the pores of the samples could have also obstructed binding by
preventing penetration of the chloride solutions. However, at 3.0M free chloride concentrations,
there were no visible signs of freezing in the samples taking place. This agreed with what was
found by Pigeon & Pleau (1995) concerning the relation between the temperature at which ice
formation is possible, and the concentration of sodium chloride solution. It was found that at -
10oC, the 3.0M concentration would be sufficient to prevent freezing from occurring.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bou
nd
Ch
lorid
e (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
60
70
0oC
-10oC
Figure 4-28: 56d 40%GGBFS binding isotherms w/b 0.3
The binding capacities of the 56d GGBFS samples were then compared as shown in Table 4-13.
In comparing the binding capacities, it can be seen that as the free chloride concentration
increases, the binding capacity decreases for the samples kept at 23oC and -10
oC. At 0.5M free
chloride concentration, the samples at 23oC show the highest binding capacity, with the 0
oC
samples showing the lowest binding capacity. This can be attributed to the reduction in
temperature affecting the chemically bound chloride, based on the Arrhenius equation. The
samples stored at -10oC would experience partial freezing within the pores of the larger sample
pieces, creating a higher apparent chloride concentration within the pore structure. This would
explain the increase in binding capacity as the temperature decreases from 0oC to -10
oC. As the
free chloride concentration increases to 1.0M and 2.0M free chloride concentrations however,
71
the 0oC samples showed the highest binding capacity. This reflects the increase in bound
chloride observed for the 0oC samples attributed to a possible increase in physical adsorption of
chloride taking place as the temperature is reduced to 0oC.
Table 4-13: Chloride binding capacities for 56d 40%GGBFS w/b 0.3
Free Chloride
Concentration (M)
Temperature
23oC 0
oC -10
oC
0.5 19.17 11.06 15.98
1.0 16.47 15.44 8.94
2.0 12.72 34.90 4.60
Figure 4-29 shows the binding isotherms for the MK samples exposed to chlorides at 23oC and
0oC. A student’s T-test showed that there was no statistically significant difference between the
23oC and 0
oC samples at all free chloride concentrations within a 95% confidence interval using
a COV of 15%.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
60
70
23oC
0oC
Figure 4-29: 56d 10%MK binding isotherms w/b 0.3
What the bound chloride values in Figure 4-29 implied was that physical adsorption of chloride
to the hydrated microstructure was the predominant until the free chloride concentration
approached 3.0M where the bound chloride content of the 23oC samples increased.
72
Next, freezing effects were considered in Figure 4-30, where the MK samples exposed to
chloride solutions at 0oC and -10
oC were compared. It was observed that the bound chloride
content was higher for the samples stored at -10oC at free chloride concentrations of 0.1M and
0.5M. At higher free chloride concentrations however, the bound chloride content for the
samples appear similar. The student’s T-test showed that there was no statistically significant
difference between the bound chloride values at higher free chloride concentrations of 1.0M,
2.0M and 3.0M, with statistically different results obtained at 0.1M and 0.5M free chloride
concentrations.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bou
nd
Ch
lorid
e (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
60
70
0oC
-10oC
Figure 4-30: 56d 10%MK binding isotherms w/b 0.3
After looking at the bound chloride values, the binding capacities for the MK samples were then
examined as shown in Table 4-14. Similar to the GGBFS samples, an increase in free chloride
concentration decreased the binding capacity regardless of the temperature the samples were
exposed to. For the MK samples however, it was found that samples exposed to 0.5M free
chloride solution experienced an increase in binding capacity as the temperature decreased from
23oC to -10
oC. At free chloride concentrations of 1.0M and 2.0M however, the trend observed at
0.5M free chloride solution is reversed, with samples exposed to chlorides at -10oC showed the
lowest binding capacities, and the 23oC samples showing the highest binding capacities. The
73
reason for this is due to the dominance of chemical binding as the free chloride concentration
increases, with a decrease in binding capacity being consistent with a decrease in temperature.
Table 4-14: Chloride binding capacities for 56d 10%MK w/b 0.3
Free Chloride
Concentration (M)
Temperature
23oC 0
oC -10
oC
0.5 10.95 11.24 11.99
1.0 8.53 7.03 4.36
2.0 5.59 3.40 1.42
Figure 4-31 shows a comparison of the bound chloride values obtained for SF samples exposed
to chlorides at 23oC and 0
oC. Similar to the MK samples in Figure 4-29, the SF samples appear
to show similar bound chloride values for both temperatures. At free chloride concentrations of
0.1M, 0.5M and 1.0M, it was found that the samples exposed to chlorides at 0oC bound more
chlorides than samples exposed to chlorides at 23oC. At free chloride concentrations of 2.0M and
3.0M however, the opposite trend was found where the samples exposed to chlorides at 23oC
bound more chloride than samples exposed to chlorides at 0oC. To confirm this a student’s T-test
was done, that showed there was no statistically significant difference between the sample means
at 1.0M and 2.0M free chloride concentration within a 95% confidence interval using a COV of
15%.
74
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
ride
(m
g C
l- /g s
am
ple
)
0
10
20
30
40
50
60
70
23oC
0oC
Figure 4-31: 56d 10%SF binding isotherms w/b 0.3
For the -10oC samples shown in Figure 4-32, a student’s T-test showed that there is a statistically
significant difference between the bound chloride values within a 95% confidence interval using
a 15% COV. The bound chloride measured at 3.0M free chloride concentration indicated that
there is no statistically significant difference within a 95% confidence interval. The trends
observed were attributed to an increase in physical binding for samples exposed to free chloride
concentrations of 1.0M and lower, coupled with a decrease in chemically bound chloride at 2.0M
and 3.0M free chloride concentrations. At the 0.1M free chloride concentration, the water within
the pores of the larger sample pieces may have undergone freezing, increasing the apparent
chloride concentrations within the sample, resulting in greater adsorption.
75
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bou
nd C
hlo
ride
(m
g C
l- /g s
am
ple
)
0
10
20
30
40
50
60
70
0oC
-10oC
Figure 4-32: 56d 10%SF binding isotherms w/b 0.3
When the binding capacities for the SF samples were compared in Table 4-15, it was found that
samples stored at 0oC showed the highest binding capacity at lower free chloride concentrations
of 0.5M. At 23oC, samples showed higher binding capacities at higher free chloride
concentrations of 1.0M, 2.0M and 3.0M. The higher binding capacities found with samples at
23oC stored in 1.0M, 2.0M and 3.0M free chloride solutions can be explained through chemical
binding. At lower temperatures, the rates of reaction will be reduced according to the Arrhenius
equation, resulting in decreased ion-binder interaction resulting in less Friedel’s salt formation
for example, explaining the reduction in binding capacity.
Table 4-15: Chloride binding capacities for 56d 10%SF w/b 0.3
Free Chloride
Concentration (M)
Temperature
23oC 0
oC -10
oC
0.1 6.60 16.84 6.53
0.5 6.33 6.36 4.56
1.0 6.04 2.92 3.22
2.0 5.51 1.05 1.86
76
4.5 Interplay Between pH, OH- and Binding Capacity
After discussing the effect of each of the variables individually, this section is focused on the
interplay between the variables measured concerning the exposure solution composition and how
they interact to influence the chloride binding capacity of the samples. Table 4-16 shows the
comparison between free chloride concentration, pH, OH- and the binding capacities of the
100%GU samples cured for 56 days and exposed to chloride solutions at 23oC.
Table 4-16: Interplay between variables for 56d 100%GU samples at 23oC
Free Chloride
Concentration
pH OH- (mol/l) Binding Capacity
(mg Cl-/M g sample)
w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5
0.5M 12.72 12.76 0.1114 0.1012 21.79 21.57
1.0M 12.66 12.69 0.1057 0.0872 14.01 13.31
2.0M 12.56 12.59 0.1098 0.0852 7.33 6.59
Based on Table 4-16, it was observed that as the free chloride concentration increased, the pH
and binding capacity decreased for both w/b ratios. For the 0.3 w/b ratio samples, the OH-
concentrations were similar at all free chloride concentrations. The 0.5 w/b ratio samples
however, showed a decrease in OH- with increasing free chloride concentration. This was
expected however, based on the peak values of OH- concentration found in Section 4.3.3. When
the influence of w/b ratio was taken into account, there was an increase in pH, a decrease in OH-
concentration, and a decrease in binding capacity as the w/b ratio was increased from 0.3 to 0.5.
For the 0.3 w/b ratio samples, the pH decreased by 0.16 or approximately 1.3% as the free
chloride concentration increased from 0.5M to 2.0M. Binding capacity however, decreased by
14.46, or approximately 66% as the free chloride concentration was increased from 0.1M to
3.0M. From these findings, there is a non-linear relationship between the pH and binding
capacity.
The difference in OH- ion concentration can be explained by the occurrence of different chloride
binding mechanisms. For the 0.3 w/b ratio, chloride was bound through a combination of ion
77
exchange with hydroxy AFm phases, and the formation of Friedel’s salt through absorption of
chloride ions. The ion exchange mechanism with the AFm phases would result in OH- ions being
released into solution. The mechanism concerning the absorption of chloride ions to form
Friedel’s salt could then be used to explain why the OH- concentration does not increase with
increasing bound chloride. As the chloride ions are utilized to create Friedel’s salt, the Na+ ions
would then be absorbed into the C-S-H to maintain charge neutrality through ion exchange with
the surface silanol groups. The result of this would be the release of H+ ions which would then
react with the OH- in solution to form water. For the 0.5 w/b ratio samples, the dominance of this
binding mechanism can be used to explain the trend found where there is a decrease in OH- as
the free chloride concentration increases.
The pH, OH- concentration and chloride binding capacity for mixtures containing GGBFS, MK
and SF are shown in Table 4-17, Table 4-18 and Table 4-19, respectively. Based on these results,
the following observations were made concerning the interplay between the pH, OH- and binding
capacity at 23oC. For GGBFS, an increase in free chloride concentration resulted in a decrease in
pH, an increase in OH- concentration, and a decrease in binding capacity. The increase in OH
-
can be explained by the increase in total bound chloride through binding mechanisms such as ion
exchange resulting in OH- ions being released into solution.
Table 4-17: Interplay between variables for 56d 40%GGBFS samples at 23oC
Free Chloride
Concentration
pH OH- (mol/l) Binding Capacity
(mg Cl-/M g sample)
w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5
0.5M 12.73 12.74 0.0694 0.0671 19.17 23.78
1.0M 12.69 12.67 0.0871 0.0727 16.47 18.59
2.0M 12.61 12.60 0.0877 0.0874 12.72 12.19
The results for the MK samples in Figure 4-18 show that with an increase in free chloride
concentration, there is a decrease in pH and decrease in binding capacity. However, the OH-
concentrations do not follow any particular trend. The reason for this may be due to competition
78
between the different binding mechanisms taking place that result in changes in the OH-
concentration.
Table 4-18: Interplay between variables for 56d 10%MK samples at 23oC
Free Chloride
Concentration
pH OH- (mol/l) Binding Capacity
(mg Cl-/M g sample)
w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5
0.5M 12.85 12.85 0.0870 0.0847 10.95 12.30
1.0M 12.79 12.82 0.0916 0.0795 8.53 5.23
2.0M 12.70 12.71 0.0903 0.0945 5.59 1.78
For the SF samples, it was found that there was a decrease in both the pH and binding capacity as
the free chloride concentration increased. The OH- concentrations showed different trends, where
there was a decrease in OH- concentration at 0.3 w/b, with no particular trend noted for the 0.5
w/b ratio. It was also noted that the SF samples with 0.3 w/b ratio had the lowest average OH-
values when compared to the other mix designs with 0.3 w/b ratio. Hydration of the SF samples
as described in Section 2.2.1.3 can partially explain the reduction in overall OH- concentrations
as the SF samples utilize OH- ions to further hydrate, with binding mechanisms being used to
describe the variation in OH- concentration between the different free chloride concentrations.
Table 4-19: Interplay between variables for 56d 10%SF samples at 23oC
Free Chloride
Concentration
pH OH- (mol/l) Binding Capacity
(mg Cl-/M g sample)
w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5 w/b 0.3 w/b 0.5
0.5M 12.71 12.75 0.0656 0.0734 6.33 6.14
1.0M 12.65 12.69 0.0621 0.0658 6.04 3.25
2.0M 12.55 12.60 0.0528 0.0825 5.51 1.40
Next, the effect of temperature on the interplay between the pH, OH and binding capacity was
looked at. The binding capacities obtained for the 56d 100%GU samples with 0.3 w/b ratio is
79
shown in Table 4-20 and Table 4-21. From Table 4-22, it was found that as the temperature
decreased from 23oC to 0
oC, that an increase in pH, coupled with a decrease in OH
- was
associated with a decrease in binding capacity. This was found to be true at all free chloride
concentrations. When potential freezing of samples is taken into account in Table 4-21, it was
found that as the temperature decreased from 0oC to -10
oC, it was associated with a decrease in
pH, a decrease in OH- concentration at 0.5M free chloride concentration. However, at higher free
chloride concentrations of 1.0M and 2.0M the decrease in pH was associated with an increase in
binding capacity, with no clear trend in OH- concentration. Overall it was found that when
exposed to 0.5M chloride solution, GU samples at -10oC had the lowest binding capacity with
the 23oC samples showing the highest binding capacity. At higher free chloride solutions of
1.0M and 2.0M, the 0oC samples showed the lowest binding capacities. The same trend was
noted for the GU samples with 0.5 w/b ratio which is shown in Appendix E.
Table 4-20: Effect of temperature on interplay between pH, OH- and binding capacity 23
oC
and 0oC using 56d 100%GU samples w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH-
f
b
cc
δδ
pH OH
-
f
b
cc
δδ
0.5M 12.72 0.1108 21.79 12.80 0.1108 18.39
1.0M 12.66 0.1045 14.01 12.73 0.0863 8.96
2.0M 12.56 0.1086 7.33 12.63 0.1036 3.61
Table 4-21: Effect of temperature on interplay between pH, OH- and binding capacity 0
oC
and -10oC using 56d 100%GU samples w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH-
f
b
cc
δδ
pH OH-
f
b
cc
δδ
0.5M 12.80 0.1108 18.39 12.61 0.0754 14.47
1.0M 12.73 0.0863 8.96 12.60 0.0879 9.83
2.0M 12.63 0.1036 3.61 12.59 0.0871 5.29
80
The effect of temperature on the interplay between the pH, OH- and binding capacity of the
SCMs were then compared. The results of the comparisons can be seen in Appendix D and
Appendix E that correspond to the 0.3 w/b and 0.5 w/b ratios, respectively. Table 4-22 and Table
4-23 show the temperatures at which the highest and lowest resulting chloride binding capacity
was obtained for all the SCMs used at 0.3 and 0.5 w/b ratios, respectively.
Table 4-22: Temperatures at which samples showed the highest and lowest binding
capacities for mixtures with 0.3 w/b
Free Chloride
Concentration
40%GGBFS 10%MK 10%SF
Highest
f
b
cc
δδ
Lowest
f
b
cc
δδ
Highest
f
b
cc
δδ
Lowest
f
b
cc
δδ
Highest
f
b
cc
δδ
Lowest
f
b
cc
δδ
0.5M 23oC 0
oC -10
oC 5
oC 23
oC/0
oC* -10
oC
1.0M 5oC -10
oC 5
oC -10
oC 23
oC 5
oC
2.0M 0oC -10
oC 5
oC -10
oC 23
oC 5
oC
*Binding capacities for SF very similar at these two temperatures
Table 4-23: Temperatures at which samples showed the highest and lowest binding
capacities for mixtures with 0.5 w/b
Free Chloride
Concentration
40%GGBFS 10%MK 10%SF
Highest
f
b
cc
δδ
Lowest
f
b
cc
δδ
Highest
f
b
cc
δδ
Lowest
f
b
cc
δδ
Highest
f
b
cc
δδ
Lowest
f
b
cc
δδ
0.5M 23oC 0
oC 0
oC 23
oC 0
oC -10
oC
1.0M -10oC 0
oC 0
oC 23
oC 0
oC -10
oC
2.0M 0oC 23
oC 0
oC 23
oC 0
oC -10
oC
From the results shown, it can be determined that there is no set temperature at which maximum
or minimum binding capacities are achieved. From these results, it can be seen that the binding
capacities are more influenced by the supplementary cementitious material. The last variable to
investigate regarding the interplay between the pH, OH- and binding capacity is the curing time
or hydration. Table 4-24 shows the effect of curing time on 100%GU samples with w/b ratio 0.3
cured for 7 and 56 days.
81
Table 4-24: Effect of curing time on interplay between pH, OH- and binding capacity on
100%GU w/b 0.3
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH-
f
b
cc
δδ
pH OH
-
f
b
cc
δδ
0.5M 12.74 0.1044 12.92 12.72 0.1114 21.79
1.0M 12.65 0.1179 13.56 12.66 0.1057 14.01
2.0M 12.54 0.1072 14.99 12.56 0.1098 7.33
For the 56d 100%GU samples, the results indicate that the pH and OH- concentrations remain
similar for both the 7d and 56d samples as shown in Table 4-24. The 56d GU samples had a
higher binding capacity at 0.5M free chloride concentration compared to the 7d GU samples. At
higher free chloride concentrations of 1.0M and 2.0M however, the 7d GU samples showed a
higher binding capacity compared to the 56d GU samples. Hydration could be used to explain
the differences in binding capacity observed for the samples with 0.3 w/b ratio. The 56d samples
had 0.173g/g sample non-evaporable water content, compared to the 0.118g/g sample non-
evaporable water content found in the 7d samples. As a result, the 56d samples would contain
additional hydration products such as C-S-H that would help facilitate physical binding which is
dominant at lower free chloride concentrations. At higher free chloride concentrations of 1.0M
and 2.0M however, any unhydrated cementitous material in the 7d samples would contribute
towards an increase in binding capacity through chemical binding. A different trend was
observed for the samples with 0.5 w/b ratio which can be seen in Table 4-25, where at free
chloride concentrations of 1.0M and 2.0M, there was an increase in binding capacity as the initial
curing was increased to 56 days. For the 56d samples with 0.5 w/b ratio, there would be
additional hydration products formed, with greater porosity that would create additional surface
area for binding to take place when compared to the 7d samples. The hydration values support
this, with the 7d 0.5 w/b ratio samples having a degree of hydration of 52% compared to the 70%
degree of hydration found for the 56d 0.5 w/b ratio samples.
82
Table 4-25: Effect of curing time on interplay between pH, OH- and binding capacity
100%GU w/b 0.5
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH-
f
b
cc
δδ
pH OH
-
f
b
cc
δδ
0.5M 12.77 0.0868 14.60 12.72 0.1108 21.57
1.0M 12.69 0.1162 7.81 12.66 0.1045 13.31
2.0M 12.58 0.1007 3.34 12.56 0.1086 6.59
When the effect of SCMs was investigated, it was found that for the GGBFS samples at both w/b
ratios, the 56d samples had the higher binding capacities compared to the 7d samples, as shown
in Appendix D and Appendix E. This was attributed to an increase in physical binding through
the increase in hydrated products such as C-S-H.
With the use of MK, it was found that there was an overall decrease in binding capacity as the
curing time increased regardless of the free chloride concentrations as shown in Appendix D and
Appendix E. The only exception to this was seen with the 0.3 w/b ratio MK samples exposed to
0.5M free chloride, where the 56d samples had a relatively higher binding capacity. These
decreases in binding capacity with increasing hydration were attributed to chemical binding. The
7d MK samples would contain more unhydrated cementitious material that, when put into
contact with chlorides, would result in the formation of Fridel’s salt and other chloroaluminate
compounds through the different ion exchange mechanisms.
Similar to the results for the MK samples, the use of SF resulted in a decrease in binding
capacity regardless of the free chloride concentration. The decrease in binding capacity for the
0.3 w/b ratio SF samples ranged from a 6% decrease at 0.5M free chloride, to a 33% decrease in
binding capacity at 2.0M free chloride as shown in Appendix D. The 0.5 w/b ratio samples
experienced a 26% decrease at 0.5M free chloride concentration and a 77% decrease at 2.0M
free chloride concentration as shown in Appendix E. The reason for this can be associated with
SF reducing the C/S ratio of the C-S-H formed during hydration. This is associated with a
decrease in chloride binding and can help explain why the 56d SF samples have a lower binding
capacity when compared to the 7d samples.
83
When the pH values were compared for all the samples, it was found that there was a general
trend of decreasing pH associated with the increase in free chloride concentration and a decrease
in chloride binding capacity. Figure 4-33 shows a linear relation between the pH and the free
chloride concentration for all of the 56d binder systems consisting of GU, GGBFS, MK, and SF,
with a 0.5 w/b ratio. Similar results were found regardless of the curing time and w/b ratio, with
the relations for the 7d, 14d and 28d samples being shown in Appendix I. It was noted that the
linear relationship was better for the 0.5 w/b ratio samples based on the higher R2 values when
compared to the 0.3 w/b ratio samples.
When the OH- values for all the mix designs were compared, it was found that there was no
particular trend, with the pooled OH- values for the 56d samples shown in Figure 4-34 and the
rest of the results shown in Appendix J.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
56d Samples w/b 0.5
Regression Line R2 = 0.65
Figure 4-33: Relationship between pH and free chloride for 56d samples w/b 0.5
84
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
56d w/b 0.5
Figure 4-34: Relationship between OH- and free chloride for 56d samples w/b 0.5
4.6 Effect of the Non-Evaporable Water Content
As cement hydrates, its physical properties change with the formation of hydration products such
as C-S-H. Due to the changes in microstructure and composition associated with hydration, this
section takes a look at the effect of the non-evaporable water content on some of the parameters
being measured, namely, pH, OH- ions and chloride binding capacity. Non-evaporable water
content was chosen to be compared as opposed to the degree of hydration, as there is no
established mass of chemically combined water per mass of hydrated cement value, or k value,
for SCMs such as MK and SF. The results for all the loss on ignition tests is shown in Appendix
K.
Figure 4-35 shows the non-evaporable water content and the chloride binding capacities for the
GU samples with 0.3 w/b ratio exposed to 0.5M and 2.0M chloride solutions. The non-
evaporable water contents plotted correspond to the non-evaporable water contents of the GU
samples after 7, 14, 28, and 56 days of curing.
85
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
indin
g C
ap
acity (
mg C
l- /M g
sa
mple
)
0
5
10
15
20
25
0.5M NaCl Solution
2.0M NaCl Solution
Figure 4-35: Chloride binding capacity vs. non-evaporable water for GU mixes w/b 0.3
In Figure 4-35, it was observed that as the non-evaporable water content increases, the chloride
binding capacity decreases to a minimum between 0.12 and 0.15g/g sample non-evaporable
water content. After this point, the chloride binding capacity then increases with increasing non-
evaporable water content, with the samples exposed to 0.5M chloride solution attaining a higher
chloride binding capacity compared to the samples exposed to 2.0M chloride solutions.
After 7 days of curing, as shown in Figure 4-35, there would still be unhydrated cementitious
material within the sample that can readily react with chlorides to produce the higher chloride
binding capacities observed. When the samples are allowed to cure for longer periods of time,
the availability of unhydrated cementitious material will be reduced, with increased formation of
C-S-H and other products of hydration. The increased formation hydration products will help
facilitate physical binding though providing surface area over which adsorption of chloride ions
can take place, resulting in the increase in binding capacity.
When the GU samples with 0.5 w/b ratio were looked at, as shown in Figure 4-36, the samples
exposed to 0.5M chloride solution experienced the same trend found for the samples with 0.3
w/b ratio. At higher non-evaporable water contents, there will be an increase in physical binding
7d
7d
14d
14d
28d
28d
56d
56d
86
as a result of the formation of products of hydration such as C-S-H. With lower chloride
exposure concentrations being related to physical binding, the samples exposed to 0.5M chloride
solution will experience an increase in binding capacity which was observed.
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
indin
g C
ap
acity (
mg C
l- /M g
sa
mple
)
0
5
10
15
20
25
0.5M NaCl Solution
2.0M NaCl Solution
Figure 4-36: Chloride Binding Capacity vs. Non-Evaporable Water for 100%GU w/b 0.5
The samples exposed to 2.0M chloride experienced an increase in chloride binding capacity
between 0.15 and 0.18g/g sample non-evaporable water content. After this point, the chloride
binding capacity decreases with increasing non-evaporable water content. With chemical binding
being associated with exposure to more concentrated chloride solutions, it is thought that the
increased hydration would reduce the availability of unhydrated cementitious material and
aluminate containing products such as monosulphate from being utilized in chemical binding
processes. For the samples exposed to 2.0M chloride solution however, as the non-evaporable
water content increases, and the availability of unhydrated cementitious materials decreases, the
resulting decrease in chloride binding capacity.
87
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
ind
ing C
ap
acity (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
25
0.5M NaCl Solution
2.0M NaCl Solution
.
Figure 4-37: Chloride binding capacity vs. non-evaporable water for GGBFS mixes w/b 0.3
There were differing trends based on the SCM used. The results for the different SCMs can be
found in Appendix L. Figure 4-37 shows the relationship between the chloride binding capacity
and non-evaporable water content for GGBFS samples with 0.3 w/b ratio.
For the GGBFS mixes, it was found that there was an increase in chloride binding capacity
associated with an increase in non-evaporable water content at both 0.3 and 0.5 w/b ratios. The
only exception to this trend was found for the 0.3 w/b ratio samples exposed to 0.5M chloride
solution. These samples experienced an initial decrease in binding capacity between 0.10 and
0.14g/g sample non-evaporable water content after which the chloride binding capacity increased
with increasing non-evaporable water. With GGBFS samples having a higher aluminate content
compared to the GU samples, a combination of physical and chemical binding processes play an
important role in determining the chloride binding capacity. This can be seen for both samples
with the samples exposed to 2.0M chloride solution experiencing an increase in chloride binding
capacity as the non-evaporable water content increases.
For the MK samples, it was found that for both w/b ratios, there was an initial increase, then
decrease in chloride binding capacity as the non-evaporable water increased. For the 0.3 w/b
88
ratio MK samples, it was found that the chloride binding capacity increased as the non-
evaporable water content increased from 0.12 to 0.14g/g sample. After this point, as the non-
evaporable water content increased to approximately 0.155, the associated binding capacity
decreased for the samples exposed to both 0.5M and 2.0M chloride solutions. At 0.5 w/b ratio, it
was found that there was an overall decrease in chloride binding capacity as the non-evaporable
water content increased. For the samples exposed to 2.0M chloride solution however, there was
an increase in chloride binding capacity between 0.18 and 0.19g/g sample non-evaporable water
content. As the non-evaporable water content increased, however, the chloride binding capacity
decreased. For the 0.5M w/b ratio, the trend agrees with what was found by Zibara et. al. (2008)
concerning the decrease in bound chloride being attributed to an increase in MK substitution.
The higher non-evaporable water content would imply that additional hydration would have
taken place increasing the amount of hydration products such as stratlingite that do not readily
convert to Friedel’s salt, thereby reducing the chloride binding capacity.
When the SF samples were compared, it was found that for both the 0.3 and 0.5 w/b ratio
samples, the chloride binding capacity appeared to increase with increasing non-evaporable
water content. For both w/b ratios, a peak binding capacity was found when the non-evaporable
water content reached the value associated with 28 days of curing. After this point was reached,
the chloride binding capacity decreased as the non-evaporable water content decreased. It was
thought that with increasing non-evaporable water content that there would be a constant
decrease in chloride binding capacity due to the mechanisms involving the reduction in the C/S
ratio and reduction in pH of the samples. An observed increase in chloride binding capacity
means that as the SF hydrates and forms products such as C-S-H, a balance point is reached
where the benefit of additional C-S-H that would facilitate physical adsorption would be
overcome by the reduction in C/S ratio of the C-S-H formed and reduction in pH. This would
result in a decrease in chloride binding capacity as the non-evaporable water content reaches
levels associated with 56 days of curing prior to chloride exposure.
89
4.7 Effect of Seasonal Temperature Variation on Binding Isotherms
After looking at how the initial two weeks of chloride exposure can affect bound chlorides, the
effects of prolonged exposure coupled with changes in temperature will be investigated. The
cycling process was described in Table 3-1 in Section 3.1 through which samples were exposed
to chlorides for a total of four months. The objective of the cycling process is to determine the
effect of seasonal temperature changes on the chloride binding capacity. To determine the effect
of this exposure, comparisons are made between the bound chloride and binding capacities of the
samples. Figure 4-38 shows the comparison between the 56d 100%GU samples after the initial
two week period, referred to as the ‘Base’ sample, and the samples cycled from 23oC for two
months, followed by 0oC for another two months. In Figure 4-38, the cycled 23
oC sample was
compared both to the base 23oC and 0
oC samples.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
Cycled 23oC to 0
oC
Base 23oC
Figure 4-38: Comparison between cycled and base 56d 100%GU samples w/b 0.5
Based on Figure 4-38, it was observed that after being stored at 23oC for two months followed by
storage at 0oC for two months, the cycled samples experienced a decrease in bound chloride
content at higher free chloride concentrations. The samples exposed to 2.0M and 3.0M free
chloride concentrations experienced 21% and 34% decreases in bound chloride content
respectively. When the binding capacities for these two samples are compared in Table 4-26, the
90
results confirm what was observed in the binding isotherms, where the cycled samples showed
reduced binding capacities at both w/b ratios. It was noted that the decrease in binding capacity
was greater for the 0.3 w/b ratio samples compared to the 0.5 w/b ratio samples.
Table 4-26: Cycled versus original binding capacities for 56d 100%GU
Free Chloride
Concentration
(M)
56d 100%GU
w/b 0.3 w/b 0.5
Original
23oC
Cycled
23oC 0
oC
Original
23oC
Cycled
23oC 0
oC
0.5 21.79 7.20 21.57 15.49
1.0 14.01 2.38 13.31 6.54
2.0 7.33 0.76 6.59 2.23
The reason for the decrease in binding capacity was thought to be due to the interplay between
the pH, OH- and binding capacity, where the reduction in temperature from 23
oC to 0
oC would
result in an increase in pH and a decrease in OH- values. The pH values in Table 4-27 confirmed
this, where for both w/b ratios, there was an increase in pH as the temperature was reduced. This
can be due to the increased solubility of Ca(OH)2 at lower temperatures. The higher pH values
associated with the 0.3 w/b ratio samples corresponded to a larger reduction in binding capacity.
These results showed that chloride binding is affected by the immediate conditions surrounding
the samples and that the chloride content bound during the initial equilibrium period does not
remain constant, with an increase in pH being related to a decrease in binding capacity for the
100%GU samples.
Table 4-27: Cycled versus original pH values for 56d 100%GU
Free Chloride
Concentration
(M)
56d 100%GU
w/b 0.3 w/b 0.5
Original
23oC
Cycled
23oC 0
oC
Original
23oC
Cycled
23oC 0
oC
0.5 12.72 13.04 12.76 12.80
1.0 12.66 12.99 12.69 12.76
2.0 12.56 12.91 12.59 12.70
91
After looking at the effects of temperature cycling on the 56d 100%GU samples at 23oC,
comparisons between the different temperatures were looked at. Figure 4-39 shows the cycled
samples with 0.5 w/b ratio originally stored at 23oC being compared to the base samples
originally stored at 23oC and 0
oC.
When compared to the base samples, it was found that for the GU, GGBFS, and MK samples,
shown in Figure 4-40, Figure 4-41 and Figure 4-42 respectively, the 23oC to 0
oC cycling process
resulted in a decrease in bound chloride content, especially at higher free chloride concentrations
of 2.0M and 3.0M. This was true at both w/b ratios, with the graphs for the 0.3 w/b ratio samples
being shown in Appendix F. For the SF samples, the cycling process appeared to increase the
bound chloride content at both w/b ratios. This was similar to what was found by Zibara (2001),
where additional curing of samples resulted in decreased or similar binding for GU, GGBFS and
MK samples, with an increase in binding for SF samples.
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
Cycled 23oC to 0
oC
Base 23oC
Base 0oC
Figure 4-39: Cycled vs. base 100%GU w/b 0.5
92
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
20
40
60
80
100
Cycled 23oC to 0
oC
Base 23oC
Base 0oC
Figure 4-40: Cycled vs. base 40%GGBFS w/b 0.5
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (
mg
Cl- /g
sa
mp
le)
0
10
20
30
40
50
Cycled 23oC to 0
oC 10%MK
Base 23oC
Base 0oC
Figure 4-41: Cycled vs. base 10%MK w/b 0.5
93
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
un
d C
hlo
rid
e (m
g C
l- /g s
ample
)
0
10
20
30
40
50
Cycled 10%SF 23oC to 0
oC
Base 23oC
Base 0oC
Figure 4-42: Cycled vs. base 10%SF w/b 0.5
To determine the effect of seasonal variations on the chloride binding capacity of the samples,
two exposure regimes will be highlighted. Exposure A consists of samples originally being
exposed to chlorides at 0oC for two months, followed by exposure to chlorides at 23
oC for an
additional two months. Exposure B consists of samples originally exposed to chlorides at 23oC
for two months, followed by exposure to chlorides at 0oC for an additional two months. These
two cycling regimes are meant to reflect the influence of seasonal temperature variations, with
Exposure A being the temperature variation experienced when transitioning between fall and
winter, and Exposure B being the temperature variation when transitioning between winter and
spring. Figure 4-43, Figure 4-44, Figure 4-45, and Figure 4-46 show the comparisons of the two
exposure regimes for GU, GGBFS, MK and SF respectively at 0.5 w/b ratio.
For all the mix designs, it was found that Exposure A resulted in a greater chloride binding
capacity compared to Exposure B regardless of the free chloride concentration. These results
show the influence of seasonal temperature changes on the binding and unbinding of chloride
ions within the specimens.
94
Chloride Concentration (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Ch
lori
de
Bin
din
g C
apac
ity
0
2
4
6
8
10
12
Exposure A
Exposure B
100%GU
Figure 4-43: Effect of exposure conditions on the binding capacity of GU
It was noted that the GGBFS samples, as shown in Figure 4-44, experienced the largest changes
in chloride binding capacity when comparing Exposure A and Exposure B, with a 56% to 70%
decrease in chloride binding capacity observed at 2.0M and 3.0M free chloride concentrations
respectively. In comparison, the GU, MK, and SF samples subjected to Exposure B experienced
33% to 47% decreases in chloride binding capacity when compared to the samples subjected to
Exposure A.
95
Chloride Concentration (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Chlo
ride
Bin
din
g C
apac
ity
0
2
4
6
8
10
12
Exposure A
Exposure B
40%GGBFS
Figure 4-44: Effect of exposure conditions on the binding capacity of GGBFS
Chloride Concentration (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Chlo
ride
Bin
din
g C
apac
ity
0
2
4
6
8
10
12
Exposure A
Exposure B
10%MK
Figure 4-45: Effect of exposure conditions on the binding capacity of MK
96
Chloride Concentration (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Chlo
ride
Bin
din
g C
apac
ity
0
2
4
6
8
10
12
Exposure A
Exposure B
10%SF
Figure 4-46: Effect of exposure conditions on the binding capacity of SF
To further investigate the influence of temperature and chloride exposure on the samples, the
microstructure was examined using mercury intrusion porosimetry (MIP). It was previously
found by Loser et. al. (2010) that there is a linear relationship between porosity and chloride
resistance, however, in this study, the relationship between the porosity, temperature and
chloride exposure was investigated. Figure 4-47 shows the effect of temperature and chlorides on
the porosity for all the mix designs used at 23oC and 0
oC.
Tota
l P
oro
sity
(%
)
20
22
24
26
28
30
32
34
36
38
23oC no chloride exposure at 4 months
0oC in 1M chloride exposure for 4 months
100%GU 40%GGBFS 10%MK 10%SF
Figure 4-47: Effect of temperature and chloride exposure on porosity
97
For all the mix designs used, it was found that the combined effect of temperature and chloride
exposure resulted in a decrease in the total porosity of the samples. Similar to what was observed
when the chloride binding capacity values were compared, the effect of temperature and chloride
exposure had the greatest effect on the GGBFS samples, with a 23% reduction in total porosity
being observed when exposed to 1.0M chloride solution at 0oC. In comparison, the GU, MK, and
SF samples experienced a maximum reduction in porosity of 6.5% which was found with the
MK samples.
Based on these results, the differences in chloride binding capacity were plotted against the
differences in porosity for all the mix designs. The results shown in Figure 4-48, preliminarily
show a linear relation with an R2 value of 0.83 is found for the samples at 2.0M and 3.0M free
chloride concentrations. However, more data is needed in Figure 4-48 to validate that the
correlation is indeed linear. This result agrees with the work done by Loser et. al. (2010)
concerning the linear relation between porosity and chloride resistance, as a larger difference in
porosity corresponds to a larger difference in chloride binding capacity.
Change in Total Porosity
[(Porosity at 23oC)- (Porosity 0oC with Cl exposure)]
0 1 2 3 4 5 6 7 8
Ch
ang
e in
Ch
lori
de
Bin
din
g C
apac
ity
(E
xp
osu
re A
- E
xp
osu
re B
)
0
1
2
3
4
5
6
Binding Capacity at 2.0M
Binding Capacity at 3.0M
R2 = 0.83
Figure 4-48: Relation between difference in chloride binding capacity and difference in
porosity
When the chloride binding mechanisms are taken into account, the larger porosity allows for
greater physical and chemical interaction between the hydrated microstructure and the Cl- ions. It
98
was noted that when the values for the samples exposed to 1.0M free chloride concentration were
plotted, the correlation observed was not as clear, with an R2 value of 0.37 being observed. This
could be indicative of the type of binding the relation shows taking place at such chloride
concentrations. Higher free chloride concentrations are associated with chemical binding
processes, and as a result, the lower free chloride concentration of 1.0M would not produce as
good of a correlation as it is not as strongly governed by the variables being compared.
To help explain what processes may be occurring, the pH values were compared. Figure 4-49,
Figure 4-50, Figure 4-51, and Figure 4-52 compare the pH values for the cycled samples
subjected to Exposure A and Exposure B with 0.5 w/b ratios. The effects of Exposure A and
Exposure B on the samples with 0.3 w/b ratio can be seen in Appendix G.
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Figure 4-49: Effect of exposure on pH of storage solution for 100%GU w/b 0.5
For the GU samples shown in Figure 4-48, the pH values are consistently higher for the samples
subjected to Exposure B compared to those subjected to Exposure A. This was found to be the
case for all of the SCMs as shown in Figure 4-49, Figure 4-50 and Figure 4-51 respectively. The
largest difference between pH values were found for the 0.5 w/b ratio GU samples, with 1.6%
difference in pH at 1.0M free chloride concentration, and a 1.2% difference in pH at 3.0M free
chloride concentration. While the percentage differences may be small, it was found that the pH
99
of the samples can be related to the chloride binding capacity, but not necessarily the total bound
chloride content for the mix designs used.
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Figure 4-50: Effect of exposure on pH for 40%GGBFS w/b 0.5
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Figure 4-51: Effect of exposure on pH for 10%MK w/b 0.5
100
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Figure 4-52: Effect of exposure on pH for 10%SF w/b 0.5
4.8 Impact of Binding Capacities on Chloride Diffusion Coefficient
and Service Life Estimation
Determining the bound chloride content and the effects of different variables such as
temperature, SCMs, and free chloride concentration are all important in understanding the
mechanisms behind chloride binding. When it comes to application of the data obtained
however, the chloride binding capacities are of greater importance in determining the chloride
diffusion coefficient used in determining the service life of buildings and infrastructure.
Programs such as Life-365 utilize chloride diffusion coefficient to determine the time it would
take for chlorides to reach reinforcing steel and initiate corrosion (ACI Committee 234, 2006).
The diffusion coefficient used to measure chloride diffusion is based on Fick’s laws of diffusion,
more specifically, Fick’s second law of diffusion, shown in Equation 4-8, where D is the
diffusion coefficient.
x
cD
xt
c
δ
δ
δ
δ
δ
δ⋅⋅= ……………. (4-8)
101
To be able to calculate the diffusion coefficient and hence the depth of chloride penetration,
Fick’s second law must first be solved assuming that the diffusion coefficient, D, remains
constant and that it is for a semi infinite medium (Arsenault et. al., 1995). This results in
Equation 4-9 where c is the chloride concentration, c1 is the concentration of the exposed face, t
is the time of exposure and erf is the error function (Arsenault et. al., 1995).
−=
Dt
xerfctxc
21),( 1 …………… (4-9)
The chloride binding capacity derived in Section 4.1 becomes important in the determination of
the apparent diffusion coefficient which takes bound chloride into account. Due to the shape of
the binding isotherms, the apparent diffusion coefficient, DF2, is not a constant. This apparent
diffusion coefficient can be expressed as in Equation 4-10:
+
=
f
b
F
F
cc
p
DD
δδ
1
1
2 …………….. (4-10)
where p is the open porosity containing liquid, Cb and Cf are the bound and free chloride contents
respectively, fb cc δδ is the binding capacity, and DF1 is the diffusion coefficient obtained using
Fick’s first law of diffusion, shown in Equation 4-11.
x
cDJ F
eδ
δ−= ….…………. (4-11)
To obtain a better estimate of how much the service life is affected by the changes in chloride
binding capacity calculated, the program Life-365 version 2.0.2 will be used to determine the
service life estimates. Service life estimates obtained using Life-365 consist of predictions of the
initiation period and propagation period of corrosion. The initiation period describes the time
during which deleterious ions such as chlorides build up to a concentration that will allow
corrosion of the reinforcing steel to occur. Once corrosion occurs, the propagation period
describes the time taken for the reinforced concrete to reach an unacceptable state. In Life-365,
102
the length of the propagation period is always assumed to be 6 years unless epoxy coated steel is
used which would extend the propagation period to 20 years (Life-365 Consortium II, 2011).
Life-365 uses Fick’s second law of diffusion as the governing differential equation, with time
dependant changes in diffusion being taken into account through Equation 4-12.
( )m
ref
reft
tDtD
⋅= ………………. (4-12)
Where D(t) is the diffusion coefficient at time t, Dref is the diffusion coefficient at time tref, and m
is the diffusion decay index. It is important to note that in Life-365, Dref and m are chosen based
on the mix design and tref at which Dref is determined is taken as 28 days. To account for
temperature dependant changes in diffusion in Life-365, Equation 4-13 is used.
( )
−⋅=
TTR
UDTD
ref
ref
11exp ……………… (4-13)
Where D(T) is the diffusion coefficient at time t and temperature T, Dref is the diffusion
coefficient at time tref and temperature Tref, which is assumed to be 293K (20oC), U is the
activation energy of the diffusion process, assumed to be 35,000 J/mol, R is the gas constant, and
T is the absolute temperature.
To estimate the sensitivity of service life to the binding capacities reported, mix design scenarios
reported in Table 4-28 were analyzed. These cases were selected to account for the changes in
temperature between 23oC and 0
oC. For all the cases, values corresponding to a 0.5 w/b ratio
exposed to 0.5M, 1.0M, and 2.0M free chloride concentrations were selected. For all the cases,
Equation 4-10 was used along with the chloride binding capacity values calculated to obtain a
modification factor to multiply by the base diffusion coefficient in Life-365 resulting in a
modified diffusion coefficient. These modified diffusion coefficients were then used in Life-365
to determine the initiation period for corrosion.
103
Table 4-28: Life-365 cases
Case Description
1 56d GU 23oC
2 56d GU 0oC
3 56d GGBFS 23oC
4 56d GGBFS 0oC
5 56d MK 23oC
6 56d MK 0oC
7 56d SF 23oC
8 56d SF 0oC
For the eight mix design scenarios, the base diffusion coefficient was associated with the
samples that were exposed to chlorides at 23oC, with relative service lives being calculated as
shown in Table 4-29. In Life-365, the default case was used, in which the setting was for parking
garages in Toronto having a 200mm thick slab, with reinforcement having a 60mm cover depth.
It was noted that the diffusion coefficient for SF in Life-365 differed when compared to the
values for the other SCMs. Also, the diffusion decay constant, m, for the GGBFS, differed when
compared to the other SCMs in Life-365. In the analysis performed however, both the diffusion
coefficient and the diffusion decay constant were kept constant for all the cases tested. This was
done to enable the results to reflect the effect of temperature and not become a direct comparison
of the different SCMs used. Another reason for keeping both the diffusion coefficient and
diffusion decay constant similar for all cases is that there is no specific setting for MK in Life-
365. Without diffusion tests being performed in this research program, a diffusion coefficient for
the MK samples was not determined.
The service life estimates found are displayed relative to the case at 23oC, with all the cases
tested being those for samples cured for 56 days. The relative service lives displayed in Table 4-
29 and Table 4-30 highlight the effect of the change in chloride binding capacity associated with
a change in temperature from 23oC to 0
oC. A relative service life greater than 1.0 represents a
longer service life attributed to the effect of temperature on chloride binding capacity relative to
the service life obtained at 23oC. Meanwhile, a relative service life less than 1.0 represents a
shorter service life attributed to the effect of temperature on chloride binding capacity relative to
the service life obtained at 23oC. It should be emphasized that this exercise is meant to provide
104
an indication of the implication of temperature on chloride binding and in turn its effect on
service life estimates.
Table 4-29: Base case analysis for service life estimation
Case Binding
Capacity
Original
Diffusion
Coefficient
(m2/s)
Modified
Diffusion
Coefficient
(m2/s)
Service
Life
(years)
Relative
Service Life
Ratio
Relative
Service
Life
1. GU 23oC 21.57 1.3804E-11 6.1157E-13 69.1
1.691.69 1.00
2. GU 0oC 18.39 1.3804E-11 7.1180E-13 59.8
1.698.59 0.85
Table 4-30 shows the relative service life estimates obtained for the 8 cases when the binding
capacity values pertaining to the 1.0M free chloride concentration were utilized in obtaining the
diffusion coefficient. Based on Table 4-30, it was found that the relative service life decreased
for both the GU and GGBFS samples, with a 4% and 56% decrease in relative service life found
for the GU and GGBFS samples respectively as the temperature decreased from 23oC to 0
oC. For
both the MK and SF samples, there was an increase in relative service life ranging from a 22%
increase in relative service life found for the SF samples, to a 119% increase in relative service
life found for the MK samples. It is emphasized that the results are meant to show the effect of
the decrease temperature on the chloride binding capacity and the resulting change in service life
that can take place. The results from the Life-365 analysis are shown in Appendix M for the
results corresponding to exposure to 0.5M and 2.0M chloride solution.
105
Table 4-30: Relative service life estimates for cases exposed to 1.0M chloride solution
Case Binding
Capacity
Adjustment
Ratio
Original
Diffusion
Coefficient
(m2/s)
Modified
Diffusion
Coefficient
(m2/s)
Service
Life
(years)
Relative
Service
Life
1. GU 23oC 13.31 0.0699 1.3804E-11 9.6443E-13 45.1 1.00
2. GU 0oC 12.75 0.0727 1.3804E-11 1.0040E-12 43.5 0.96
3. GGBFS 23oC 18.59 0.0510 1.3804E-11 7.0451E-13 74.9 1.00
4. GGBFS 0oC 7.09 0.1236 1.3804E-11 1.7065E-12 33 0.44
5. MK 23oC 5.23 0.1606 1.3804E-11 2.2164E-12 22 1.00
6. MK 0oC 14.36 0.0651 1.3804E-11 8.9851E-13 48.2 2.19
7. SF 23oC 3.25 0.2353 1.3804E-11 3.2480E-12 13.7 1.00
8. SF 0oC 4.58 0.1793 1.3804E-11 2.4750E-12 18.1 1.22
When the results obtained from Life-365 analysis of all the cases at all three free chloride
exposure concentrations, the relative change in service life attributed to the effect of temperature
and chloride binding capacity varied from a 75% decrease associated with GGBFS samples
exposed to 0.5M chloride solution, to a 200% increase in relative service life associated with the
MK samples exposed to 2.0M chloride solution.
When GU and GGBFS samples were observed, it was found that as the temperature was
reduced, the relative service life decreased for samples exposed to 0.5M and 1.0M chloride
solutions. As the free chloride concentration increased, temperature had less of an effect on the
relative service life of the GGBFS samples. GGBFS samples exposed to 0.5M free chloride
experienced a 75% decrease in relative service life, with GGBFS samples exposed to 2.0M free
chloride showing a 57% increase in relative service life. The use of MK and SF resulted in
increases in relative service life at all free chloride concentrations as the temperature decreased
from 23oC to 0
oC. These increases in relative service life ranged from an 18% increase for the SF
samples exposed to 2.0M free chloride solution, to a 200% increase found for the MK samples
exposed to 2.0M free chloride solution. These increases in relative service life corresponded to
an increase in chloride binding capacity for both the MK and SF samples as the temperature was
reduced.
106
What these results indicate is that the combined influence of temperature and chloride binding
has an impact on service life estimates. Due to this, it was observed that the use of chloride
binding capacities obtained at 23oC will not produce conservative service life estimates if used in
calculations.
107
Chapter 5 Conclusions and Recommendations
5.1 Conclusions
This research project consisted of examining chloride binding, pH and OH- ion concentrations at
different temperatures, with samples made using SCMs including GGBFS, MK and SF. The
results were then used to address four key objectives stated in Section 1.2. The following
presents the main contributions in this thesis.
5.1.1 Effect of Temperatures Between -10oC and 23
oC on Cement Pastes
Containing GU Cement, GGBFS, MK, and SF
• After curing for 56 days and being exposed to chlorides at 23oC, the order of magnitude of
chloride binding is GGBFS>GU>MK>SF. The dominance of the GGBFS samples was
attributed to the importance of chemical binding related to the aluminate content of the mix
components, resulting in the formation of increased amounts of Friedel’s salt especially at
higher free chloride concentrations of 1.0M, 2.0M and 3.0M.
• There was a general decrease in chloride binding capacity as the temperature decreased. When
the temperature decreased between 0oC and -10
oC, the behaviour got more complicated, with
some samples experiencing an increase in chloride binding capacity. This was attributed to
the partial pore freezing effects that increase the apparent chloride concentration in remaining
unfrozen solution.
5.1.2 Interplay between OH- Ion Concentration, pH, and Chloride Binding
Capacity
• The correlation between OH- concentration and free chloride concentration is not linear in the
range of 0.1M to 3.0M free chloride concentration. Irrespective of the type of SCM and
curing time, the maximum OH- concentration is achieved at 0.5M or 1.0M free chloride
concentration. This was attributed to a combination of the pozzolanic reactions taking place
that would utilize the OH- in solution to further hydration processes, the different chloride
binding mechanisms taking place, and the solubility of calcium hydroxide.
108
• The effect of temperature on the relation between the OH- ions and the chloride binding
capacity differed with each SCM used. These effects varied to an extent where no defining
trend could be found linking the OH- ion concentration to the chloride binding capacity.
• Average OH- values for the SF samples were the lowest when compared to the other mix
designs. The low OH- values were coupled with the lowest average chloride binding
capacities observed show that while there may not be a linear trend between OH- ion
concentrations and chloride binding capacity, the reduction in overall OH- ion concentration is
related to a reduction in chloride binding capacity.
• When the exposure temperature was reduced from 23oC to 0
oC, in all cases, the pH increased.
This occurred due to the increasing solubility of Ca(OH)2 as the temperature decreased.
• GU samples experienced an increase in pH coupled with a decrease in chloride
binding capacity.
• For GGBFS samples, the increase in pH was associated with a decrease in
chloride binding capacity at 0.5M and 1.0M free chloride, and an increase in
chloride binding capacity at 2.0M free chloride.
• For MK samples, the change in chloride binding capacity resulting from the
increase in pH was influenced by the w/b ratio. When exposed to 0.5M free
chloride, the 0.3 w/b ratio samples experienced an increase in chloride binding
capacity, while samples exposed to 1.0M and 2.0M free chloride concentrations
experienced a decrease in chloride binding capacity. For the 0.5 w/b ratio
samples, an increase in chloride binding capacity was coupled with the increase in
pH.
• With SF samples, the increase in pH was coupled with a decrease in chloride
binding capacity with 0.3 w/b ratio samples, and an increase in chloride binding
capacity with 0.5 w/b ratio samples.
• When the exposure temperature was reduced from 0oC to -10
oC:
109
• The GU cement samples experienced a decrease in pH associated with a decrease
in chloride binding capacity at 0.5M free chloride, and an increase in chloride
binding capacity in 1.0M and 2.0M free chloride solutions.
• With the GGBFS samples, the decrease in pH was linked to an increase in
chloride binding capacity at 0.5M free chloride, and a decrease in chloride
binding capacity at 2.0M free chloride.
• For MK samples, the decrease in pH was linked to a decrease in chloride binding
capacity at all free chloride concentrations regardless of the w/b ratio.
• With SF samples, similar to what was found when the temperature decreased
from 23oC to 0
oC, the increase in pH was coupled with a decrease in chloride
binding capacity with 0.3 w/b ratio samples, and an increase in chloride binding
capacity with 0.5 w/b ratio samples.
5.1.3 Effect of Non-Evaporable Water Content on Chloride Binding
• For the GGBFS and MK samples, there was an overall increase in the chloride binding
capacity associated with the increase in non-evaporable water content when measured after 7
and 56 days of curing.
• For the GU and SF, when the values corresponding to 7 and 56 days of curing were
compared, there was an overall increase in chloride binding capacity with increasing non-
evaporable water content for the 0.3 w/b ratio samples, with no clear trend in chloride binding
capacity associated with an increase in non-evaporable water content for the 0.5 w/b ratio
samples.
• Irrespective of the mix design, there were no clear linear trends between the non-evaporable
water content and chloride binding capacity showing that while the degree of hydration does
have an effect on the chloride binding capacity, it is not the major controlling factor affecting
chloride binding capacity.
110
5.1.4 Effect of Temperature Exposure on Service Life Estimation
• Seasonal temperature variations have an effect on chloride binding capacity regardless of the
mix design or SCMs used and can be just as important as mix composition in determining the
chloride binding capacity. Samples initially exposed to chlorides at 0oC followed by exposure
at 23oC had a higher binding capacity compared to the samples exposed to chlorides initially
at 23oC followed by exposure at 0
oC. Seasonal temperature variations had the greatest effect
on the chloride binding capacity of cement pastes containing 40%GGBFS.
• Using Life-365 software, a decrease in temperature coupled with chloride exposure
corresponded to either a decrease in relative service life or similar relative service life for GU
and GGBFS samples. For MK and SF samples, the decrease in temperature coupled with
chloride exposure resulted in either an increase in relative service life or similar relative
service life. Utilizing chloride binding capacities obtained at 23oC or room temperature do not
yield conservative service life estimations.
5.2 Recommendations for Future Work
From the results given in Section 4.5 concerning the interplay between the pH, OH- and binding
capacity, it was found that as the temperature was reduced below 0oC, the effect of freezing
affected the observed chloride binding capacities. Each SCM behaved differently as the
temperature was reduced to -10oC. To advance understanding what may be occurring, additional
testing of chloride binding at different low temperatures such as -3oC, -5
oC, and -7
oC should be
performed to determine the effect of the onset of freezing on both the bound chloride content and
the chloride binding capacity.
Further work should be done on the effects of low temperatures on chloride penetration to
determine if changes in chloride binding capacity calculated can be related to the rate at which
chloride penetrate concrete samples at low temperatures.
The bound chloride reported here was a combination of chemically and physically bound
chlorides. Further testing should be done to determine the proportion of each type of binding that
is taking place at different temperatures to help further understand the chloride binding
mechanisms taking place.
111
Chloride binding capacities obtained from cycling seasonal temperatures should be used to
determine apparent diffusion coefficients, which can then be compared to what is currently being
used in life-cycle modeling to determine whether current estimates are conservative.
Different cycling temperatures should be used to better mimic seasonal variations in temperature.
Examples of such cycles would be samples taken from 23oC to 5
oC to represent the transition
from summer to fall, 5oC to -10
oC to represent the transition from fall to winter.
Based on the linear correlation made between the difference in chloride binding capacity and the
difference in porosity shown in Figure 4-43, it is believed that the relationship will be applicable
to any mix design regardless of the SCM used. To test this, additional mix designs must be tested
with different replacement levels of SCMs.
112
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117
Appendix A: Statistical analysis
Statistical analysis was performed using the assumed COVs found through initial test batches.
Testing for statistically significant differences between samples was done using a student’s T-
test. Using the assumed COV, the standard deviation for each sample set was found using
Equation A-1.
µ
σ=COV ……… (A-1)
Where σ is the standard deviation and µ is the mean of the samples. After finding the standard
deviation, the pooled sample variance, sp2, for both samples was then calculated using Equation
A-2.
yx
yyxx
pVV
sVsVs
+
+=
22
2 …… (A-2)
Where Vx,y are the degrees of freedom for the two sample sets being compared, and sx,y are the
standard deviations of the two sample sets. Using the pooled sample variance as well as a T-stat
obtained from the t-distribution table, a confidence interval was then found using the Equation
A-3.
( ) ( )
++−+−−
y
p
x
p
vy
p
x
p
v n
s
n
stYX
n
s
n
stYX
22
2,
22
2,
, αα …… (A-3)
Where X and Y are the mean values of the two sample sets, tv is the value obtained from the t-
distribution table and nx,y represents the number of samples in each sample set respectively. Upon
calculating the confidence interval, if the values passed through zero, it was assumed that there
was no statistically significant difference noted between the samples. This was assumed as the
mean of the difference between the sample sets could be zero.
118
Appendix B: Variation in pH and OH- Values
Variation in pH w/b 0.3
Free Cl
-
(M) pH 1 pH 2 Difference
23oC
0.1 12.78 12.76 0.02
0.5 12.72 12.72 0.00
1 12.65 12.66 0.01
2 12.55 12.56 0.01
3 12.46 12.46 0.00
5oC
0.1 12.87 12.88 0.01
0.5 12.82 12.82 0.00
1 12.75 12.77 0.02
2 12.62 12.63 0.01
3 12.54 12.56 0.02
0oC
0.1 12.86 12.87 0.01
0.5 12.79 12.8 0.01
1 12.73 12.73 0.00
2 12.62 12.63 0.01
3 12.52 12.53 0.01
-10oC
0.1 12.67 12.65 0.02
0.5 12.62 12.59 0.02
1 12.58 12.61 0.03
2 12.58 12.6 0.02
3 12.51 12.51 0.00
119
Variation in pH w/b 0.5
Free Cl-
(M) pH 1 pH 2 Difference
23oC
0.1 12.78 12.78 0.00
0.5 12.76 12.75 0.01
1 12.68 12.69 0.01
2 12.59 12.59 0.00
3 12.49 12.51 0.02
5oC
0.1 12.84 12.85 0.01
0.5 12.8 12.81 0.01
1 12.75 12.75 0.00
2 12.63 12.63 0.00
3 12.53 12.55 0.02
0oC
0.1 12.82 12.82 0.00
0.5 12.77 12.77 0.00
1 12.68 12.7 0.02
2 12.59 12.6 0.01
3 12.52 12.52 0.00
-10oC
0.1 12.6 12.62 0.02
0.5 12.61 12.59 0.02
1 12.57 12.56 0.01
2 12.57 12.54 0.03
3 12.48 12.48 0.00
120
Variation in OH- concentration w/b 0.3
Free
Chloride
(M)
Min.
(mol/l)
Max.
(mol/l)
Mean
(mol/l)
Standard
Deviation
(mol/l)
COV
(%)
23oC
0.1 0.0637 0.0807 0.0743 0.009 12.47
0.5 0.1095 0.1123 0.1108 0.001 1.29
1 0.0982 0.1131 0.1045 0.008 7.37
2 0.1063 0.1111 0.1086 0.002 2.21
3 0.0897 0.1069 0.0998 0.009 8.98
5oC
0.1 0.0953 0.0991 0.0978 0.002 2.24
0.5 0.0948 0.1106 0.1003 0.009 8.88
1 0.0925 0.0970 0.0940 0.003 2.73
2 0.0926 0.1153 0.1031 0.011 11.16
3 0.0663 0.0803 0.0717 0.007 10.42
0oC
0.1 0.0703 0.0794 0.0739 0.005 6.56
0.5 0.0972 0.1186 0.1108 0.012 10.63
1 0.0820 0.0927 0.0863 0.006 6.54
2 0.0996 0.1114 0.1036 0.007 6.57
3 0.0720 0.0795 0.0763 0.004 5.00
-10oC
0.1 0.0854 0.0988 0.0903 0.007 8.21
0.5 0.0716 0.0829 0.0754 0.007 8.62
1 0.0795 0.0985 0.0869 0.011 11.08
2 0.0814 0.0986 0.0871 0.010 11.38
3 0.0751 0.0816 0.0779 0.003 4.27
121
Variation in OH- concentration w/b 0.5
Free
Chloride
(M)
Min.
(mol/l)
Max.
(mol/l)
Mean
(mol/l)
Standard
Deviation
(mol/l)
COV
(%)
23oC
0.1 0.0611 0.0712 0.0677 0.006 8.40
0.5 0.0985 0.1026 0.1003 0.002 2.11
1 0.0839 0.0899 0.0861 0.003 3.86
2 0.0735 0.0869 0.0791 0.007 8.77
3 0.0828 0.0914 0.0867 0.004 4.98
5oC
0.1 0.0648 0.0721 0.0688 0.004 5.34
0.5 0.0639 0.0740 0.0677 0.006 8.15
1 0.0856 0.1050 0.0941 0.010 10.57
2 0.0907 0.1095 0.0983 0.010 10.07
3 0.0776 0.0832 0.0813 0.003 3.94
0oC
0.1 0.0780 0.0931 0.0840 0.008 9.50
0.5 0.0919 0.1054 0.0965 0.008 7.96
1 0.0815 0.0872 0.0847 0.003 3.44
2 0.1058 0.1071 0.1066 0.001 0.65
3 0.0838 0.1044 0.0942 0.010 10.96
-10oC
0.1 0.0540 0.0644 0.0586 0.005 9.03
0.5 0.0535 0.0589 0.0564 0.003 4.86
1 0.0517 0.0645 0.0562 0.007 12.72
2 0.0765 0.0805 0.0781 0.002 2.79
3 0.0600 0.0620 0.0607 0.001 1.85
122
Appendix C: EDS analysis of samples with 0.3 w/b
EDS analysis of GU samples
Spectrum C O Mg Al Si S K Ca Fe C/S
1 56.42 0.62 7.25 2.71 2.86 0.67 28.26 1.23 10.43
2 11.49 51.96 2 7.21 1.05 2.58 22.71 0.99 21.63
3 53.56 0.83 1.47 10.97 1.71 0.87 30.59 2.79
4 50.67 1.08 1.44 11.87 1.96 1.26 31.74 2.67
5 50.35 1.07 12.27 1.69 1.37 33.24 2.71
6 55.05 0.58 6.69 3.82 3.92 1.29 27.54 1.12 7.21
7 57.93 9.16 1.7 2.41 28.8 16.94
8 50.83 1.07 11.35 1.92 1.04 33.78 2.98
9 55.43 0.4 7.57 2.8 4.86 0.76 26.88 1.3 9.60
10 48.77 1 6.38 1.69 0.75 41.41 6.49
11 50.87 1.65 11.64 2.41 1 32.43 2.79
12 7.51 43.94 2.83 47.73 16.87
13 57.38 1.56 6.91 2.55 2.79 0.62 26.02 2.17 10.20
14 57.99 0.61 6.18 2.56 3.69 0.99 26.69 1.28 10.43
15 57.06 0.9 5.45 4.07 3.69 0.95 26.45 1.42 6.50
16 57.29 0.4 6.53 2.1 1.51 0.37 31.8 15.14
17 52.18 1.44 11.71 1.78 0.81 32.08 2.74
18 50.82 0.48 1.35 8.56 1.69 0.82 36.29 4.24
19 49.54 0.71 4.87 0.75 0.54 43.58 8.95
20 52.19 1.12 1 5.96 1.2 0.52 38 6.38
123
EDS analysis of GGBFS samples
Spectrum C O Mg Al Si S K Ca Fe C/S
1 10.18 51.75 0.6 6.54 3.11 1.44 25.29 1.1 8.13
2 58.18 8.43 4.26 8.56 1.09 0.93 18.55 2.17
3
57.56 8.31 4.48 8.32 1.4 1.14 18.79
2.26
4
50.67 0.54 1.54 13.79 1.5 1.13 30.84
2.24
5
51.4 0.55 1.59 12.93 1.87 1.25 30.4
2.35
6
51.3 0.7 1.95 11.95 2.19 1.14 30.77
2.57
7
50.97 0.6 1.87 9.76 2.09 0.8 33.91
3.47
8
50.78 1.88 1.74 12.96 1.83 1.05 29.78
2.30
9 11.91 52.31 0.62 7.3 1.83 1.29 23.86 0.88 13.04
10 59.18 8.88 1.87 2.11 27.97 14.96
11 52.94 1.25 2.51 11.07 1.8 0.95 28.49 0.98 2.57
12 50.32 0.97 2.01 12.62 1.92 1.32 30.84 2.44
13
58.23 0.47 9.29 1.71 1.21 29.1
17.02
14 6.89 57.27 8.04 0.97 1.08 25.75
26.55
15 6.38 56 1.18 7.47 1.41 0.97 25.31 1.28 17.95
16 58.33 0.77 7.97 2.6 1.57 27.52 1.24 10.58
17 6.75 45.67 0.7 0.68 3.7 0.44 42.07 11.37
18 7.48 49.82 0.81 1.18 6.93 1.29 32.49 4.69
19 47.83 0.57 0.74 3.67 0.87 46.32 12.62
20 51.53 0.69 1.66 13.8 1.22 0.84 30.26 2.19
124
EDS analysis of MK samples
Spectrum C O Na Mg Al Si S K Ca C/S
1 10.86 33.9 0.98 0.72 10.62 42.92 4.04
2 60.19 0.87 8.69 2.12 1.07 0.46 26.61 12.55
3 9.69 51.69 0.56 7.51 3.74 1.01 25.8 6.90
4 8.15 53.35 0.68 8.49 1.61 1.73 25.98 16.14
5 50.79 3.89 15.19 1.11 2.12 26.9 1.77
6 51.73 0.61 3.31 11.9 1.94 1.63 28.87 2.43
7 50.35 0.52 3.66 15.9 0.84 2.16 26.58 1.67
8 10.03 51.84 1.44 7.99 1.72 2.24 23.35 1.39 13.58
9 57.47 0.7 8.96 1.87 3.69 0.65 26.66 14.26
10 10.71 55.28 1.09 8.43 1.15 0.68 21.78 0.89 18.94
11 49.13 2.26 8.66 2.19 1.31 36.43 4.21
12 51.06 3.31 10.54 2.64 1.49 30.97 2.94
13 51.47 2.17 12.96 1.47 1.48 30.45 2.35
14 49.95 2.71 13.94 1.84 1.76 29.79 2.14
15 6.39 54.89 8.68 0.97 2.93 26.14 26.95
16 53.52 18.71 23.34 2.09 2.33 0.10
17 51.17 4.48 15.4 0.97 2.77 25.2 1.64
18 53.65 1.99 2.85 9.52 2.93 1.55 27.5 2.89
19 53.38 1.09 5.81 6.34 3.65 0.71 27.66 1.34 4.36
20 51.63 0.61 2.6 12.04 1.69 2.44 28.99 2.41
125
EDS analysis of SF samples
Spectrum C O Mg Al Si S K Ca Fe C/S
1 51.99 23.72 1.74 22.55 0.95
2 50.69 24.78 3.71 20.82 0.84
3 52.57 1.62 14.59 1.59 1.48 28.16 1.93
4 57.2 0.59 6.96 3.67 3.79 0.55 27.23 7.42
5 51.4 0.54 19.85 1.77 26.44 1.33
6 54.65 1.43 0.97 10.3 0.86 0.64 31.15 3.02
7 48.84 0.68 26.19 4.95 19.34 0.74
8 51.43 0.53 18.56 2.19 27.29 1.47
9 55.15 1.53 3.76 10.02 2.09 1.12 26.33 2.63
10 59.05 0.61 5.23 6.54 3.26 0.71 24.6 3.76
11 51.85 19.86 2.56 25.74 1.30
12 51.68 1.4 14.42 1.37 0.95 30.17 2.09
13 57.45 0.63 6.69 3.97 3.7 0.6 25.96 1.01 6.54
14 56.32 0.48 5.29 4.99 5.43 0.45 25.54 1.49 5.12
15 56.26 1.16 5.73 5.78 3.66 0.62 25.87 0.93 4.48
16 6.46 55.61 1.3 7.1 1.42 5.14 22.97 16.18
17 54.93 1.15 2.77 7.95 4.73 0.93 26.73 0.81 3.36
18 51.85 0.8 14.73 0.93 1.06 30.62 2.08
19 57.51 0.63 8.21 3.26 3.17 0.63 26.6 8.16
20 52.83 0.47 1.4 13.66 1.71 1.16 28.77 2.11
126
Appendix D: Interplay between pH, OH- and binding capacity for
SCMs w/b 0.3
56d GGBFS at 23oC and 0
oC w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.65 0.0690 19.17 12.85 0.0557 11.06
1.0M 12.62 0.0870 16.47 12.79 0.0727 15.44
2.0M 12.58 0.0880 12.72 12.69 0.0830 34.90
56d GGBFS at 0oC and -10
oC w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.85 0.0557 11.06 12.74 0.0689 15.98
1.0M 12.79 0.0727 15.44 12.74 0.0873 8.94
2.0M 12.69 0.0830 34.90 12.70 0.0792 4.60
56d MK at 23oC and 0
oC w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.85 0.0870 10.95 13.00 0.0879 11.24
1.0M 12.79 0.0916 8.53 12.93 0.0993 7.03
2.0M 12.70 0.0903 5.59 12.81 0.0941 3.40
127
56d MK at 0oC and -10
oC w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 13.00 0.0879 11.24 12.79 0.0690 11.99
1.0M 12.93 0.0993 7.03 12.79 0.0752 4.36
2.0M 12.81 0.0941 3.40 12.75 0.0868 1.42
56d SF at 23oC and 0
oC w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.71 0.0656 6.33 12.86 0.0801 6.36
1.0M 12.65 0.0621 6.04 12.78 0.0644 2.92
2.0M 12.55 0.0528 5.51 12.69 0.0646 1.05
56d SF at 0oC and -10
oC w/b 0.3
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.86 0.0801 6.36 12.61 0.0444 4.56
1.0M 12.78 0.0644 2.92 12.64 0.0603 3.22
2.0M 12.69 0.0646 1.05 12.62 0.0698 1.86
128
Appendix E: Interplay between pH, OH- and binding capacity for
SCMs w/b 0.5
56d 100%GU at 23oC and 0
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.76 0.0833 21.57 12.77 0.0965 21.46
1.0M 12.69 0.0861 13.31 12.69 0.0847 12.75
2.0M 12.59 0.0791 6.59 12.60 0.1066 5.99
56d 100%GU at 0oC and -10
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.77 0.0965 21.46 12.60 0.0564 16.61
1.0M 12.69 0.0847 12.75 12.57 0.0562 13.59
2.0M 12.60 0.1066 5.99 12.56 0.0781 9.68
56d 40%GGBFS at 23oC and 0
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.76 0.0671 23.78 12.79 0.0701 5.16
1.0M 12.70 0.0727 18.59 12.73 0.0790 7.09
2.0M 12.62 0.0874 12.19 12.64 0.0795 37.79
129
56d 40%GGBFS at 0oC and -10
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.79 0.0701 5.16 12.77 0.0749 12.93
1.0M 12.73 0.0790 7.09 12.72 0.0846 11.46
2.0M 12.64 0.0795 37.79 12.66 0.0912 9.27
56d 10%MK at 23oC and 0
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.85 0.0847 12.30 12.93 0.0917 16.16
1.0M 12.82 0.0795 5.23 12.89 0.0857 14.36
2.0M 12.71 0.0945 1.78 12.78 0.0920 11.65
56d 10%MK at 0oC and -10
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.93 0.0917 16.16 12.80 0.0580 15.39
1.0M 12.89 0.0857 14.36 12.75 0.0736 11.48
2.0M 12.78 0.0920 11.65 12.69 0.0778 7.01
130
56d 10%SF at 23oC and 0
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
23oC 0
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.75 0.0734 6.14 12.85 0.0426 7.71
1.0M 12.69 0.0658 3.25 12.77 0.0684 4.58
2.0M 12.6 0.0825 1.40 12.68 0.0748 2.23
56d 10%SF at 0oC and -10
oC w/b 0.5
Original
Free
Chloride
Solution (M)
Exposure Temperatures
0oC -10
oC
pH OH- (mol/l)
f
b
cc
δδ
pH OH- (mol/l)
f
b
cc
δδ
0.5M 12.85 0.0426 7.71 12.67 0.0567 3.22
1.0M 12.77 0.0684 4.58 12.63 0.0492 0.89
2.0M 12.68 0.0748 2.23 12.59 0.0671 0.23
131
Appendix F: Effect of curing time on pH, OH- and binding capacity
for SCMs
100%GU samples 7d and 56d w/b 0.3
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH-
f
b
cc
δδ
pH OH
-
f
b
cc
δδ
0.5M 12.74 0.1044 12.92 12.72 0.1114 21.79
1.0M 12.65 0.1179 13.56 12.66 0.1057 14.01
2.0M 12.54 0.1072 14.99 12.56 0.1098 7.33
100%GU samples 7d and 56d w/b 0.5
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH-
f
b
cc
δδ
pH OH
-
f
b
cc
δδ
0.5M 12.77 0.0868 14.60 12.72 0.1108 21.57
1.0M 12.69 0.1162 7.81 12.66 0.1045 13.31
2.0M 12.58 0.1007 3.34 12.56 0.1086 6.59
40%GGBFS samples 7d and 56d w/b 0.3
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH- (mol/l)
f
b
cc
δδ
pH OH
- (mol/l)
f
b
cc
δδ
0.5M 12.79 0.0655 14.25 12.73 0.0694 21.05
1.0M 12.73 0.0906 7.32 12.69 0.0871 11.52
2.0M 12.63 0.0589 2.96 12.61 0.0877 3.30
132
40%GGBFS samples 7d and 56d w/b 0.5
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH- (mol/l)
f
b
cc
δδ
pH OH
- (mol/l)
f
b
cc
δδ
0.5M 12.80 0.0715 14.24 12.74 0.0671 13.25
1.0M 12.73 0.0807 4.85 12.67 0.0727 5.04
2.0M 12.63 0.0641 1.54 12.60 0.0874 1.62
10%MK samples 7d and 56d w/b 0.3
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH- (mol/l)
f
b
cc
δδ
pH OH
- (mol/l)
f
b
cc
δδ
0.5M 12.87 0.0958 10.05 12.85 0.0870 10.95
1.0M 12.83 0.1056 10.43 12.79 0.0916 8.53
2.0M 12.72 0.0873 11.26 12.70 0.0903 5.59
10%MK samples 7d and 56d w/b 0.5
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH- (mol/l)
f
b
cc
δδ
pH OH
- (mol/l)
f
b
cc
δδ
0.5M 12.87 0.0839 18.07 12.85 0.0847 12.30
1.0M 12.80 0.0845 12.11 12.82 0.0795 5.23
2.0M 12.71 0.0768 6.67 12.71 0.0945 1.78
133
10%SF samples 7d and 56d w/b 0.3
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH- (mol/l)
f
b
cc
δδ
pH OH
- (mol/l)
f
b
cc
δδ
0.5M 12.63 0.0580 6.74 12.71 0.0656 6.33
1.0M 12.58 0.0622 7.19 12.65 0.0621 6.04
2.0M 12.46 0.0614 8.21 12.55 0.0528 5.51
10%SF samples 7d and 56d w/b 0.5
Original
Free
Chloride
Solution (M)
Curing Time
7d 56d
pH OH- (mol/l)
f
b
cc
δδ
pH OH
- (mol/l)
f
b
cc
δδ
0.5M 12.68 0.0565 8.35 12.75 0.0734 6.14
1.0M 12.62 0.0594 7.51 12.69 0.0658 3.25
2.0M 12.49 0.0745 6.19 12.60 0.0825 1.40
134
Appendix G: 0.3 w/b ratio samples cycled from 23oC to 0oC
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bou
nd
Ch
lorid
e (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
Cycled 23oC to 0
oC
Base 23oC
Base 0oC
Cycled vs. Base 100%GU w/b 0.3
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
60
70
Cycled 23oC to 0
oC
Base 23oC
Base 0oC
Cycled vs. Base 40%GGBFS w/b 0.3
135
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bo
und
Chlo
rid
e (
mg
Cl- /g
sam
ple
)
0
10
20
30
40
50
Cycled 23oC to 0
oC 10%MK
Base 23oC
Base 0oC
Cycled vs. Base 10%MK w/b 0.3
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
Bound C
hlo
ride (
mg C
l- /g s
am
ple
)
0
10
20
30
40
50
Cycled 23oC to 0
oC 10%SF
Base 23oC
Base 0oC
Cycled vs. Base 10%SF w/b 0.3
136
Appendix H: Effect of exposure on pH for all SCMs w/b 0.3
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Effect of exposure on pH of cycled 56d 100%GU w/b 0.3
X Data
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Effect of exposure on pH of cycled 56d 40%GGBFS w/b 0.3
137
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Effect of exposure on pH of cycled 56d 10%MK w/b 0.3
Free Chloride Concentration
1.0M 2.0M 3.0M
pH
12.0
12.2
12.4
12.6
12.8
13.0
13.2
Exposure A
Exposure B
Effect of exposure on pH of cycled 56d 10%SF w/b 0.3
138
Appendix I: Relation between pH and free chloride for all samples
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
56d Samples w/b 0.3
Regression line R2 = 0.47
Relationship between pH and free chloride for 56d samples w/b 0.3
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
28d Samples w/b 0.3
Regression line R2 = 0.61
Relationship between pH and free chloride for 28d samples w/b 0.3
139
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
28d Samples w/b 0.5
Regression line R2 = 0.74
Relationship between pH and free chloride for 28d samples w/b 0.5
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
14d Samples w/b 0.3
Regression line R2 = 0.49
Relationship between pH and free chloride for 14d samples w/b 0.3
140
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
14d Samples w/b 0.5
Regression line R2 = 0.63
Relationship between pH and free chloride for 14d samples w/b 0.5
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
7d Samples w/b 0.3
Regression line R2 = 0.45
Relationship between pH and free chloride for 7d samples w/b 0.3
141
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
pH
12.4
12.6
12.8
13.0
13.2
7d Samples w/b 0.5
Regression line R2 = 0.53
Relationship between pH and free chloride for 7d samples w/b 0.5
142
Appendix J: Relation between OH- and free chloride for all
samples
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
56d w/b 0.3
Relationship between OH- and free chloride for 56d samples w/b 0.3
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
28d w/b 0.3
Relationship between OH- and free chloride for 28d samples w/b 0.3
143
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
28d w/b 0.5
Relationship between OH- and free chloride for 28d samples w/b 0.5
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
14d w/b 0.3
Relationship between OH- and free chloride for 14d samples w/b 0.3
144
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
14d w/b 0.5
Relationship between OH- and free chloride for 14d samples w/b 0.5
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
7d w/b 0.3
Relationship between OH- and free chloride for 7d samples w/b 0.3
145
Free Chloride (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
OH
- (m
ol/l)
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
7d w/b 0.5
Relationship between OH- and free chloride for 7d samples w/b 0.5
146
Appendix K: Non-evaporable water and chloride binding capacity
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
indin
g C
ap
acity (
mg C
l- /M g
sa
mple
)
0
5
10
15
20
25
0.5M NaCl Solution
2.0M NaCl Solution
Chloride Binding Capacity vs. Non-Evaporable Water for 40%GGBFS w/b 0.5
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
ind
ing C
ap
acity (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
0.5M NaCl Solution
2.0M NaCl Solution
Chloride Binding Capacity vs. Non-Evaporable Water for 10%MK w/b 0.3
147
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
ind
ing C
ap
acity (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
0.5M NaCl Solution
2.0M NaCl Solution
Chloride Binding Capacity vs. Non-Evaporable Water for 10%MK w/b 0.5
Non-Evaporable Water (g/g sample)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
indin
g C
ap
acity (
mg C
l- /M g
sa
mple
)
0
5
10
15
20
0.5M NaCl Solution
2.0M NaCl Solution
Chloride Binding Capacity vs. Non-Evaporable Water for 10%SF w/b 0.3
148
Non-Evaporable Water (%)
0.08 0.10 0.12 0.14 0.16 0.18 0.20 0.22
Ch
lorid
e B
ind
ing C
ap
acity (
mg C
l- /M g
sa
mp
le)
0
5
10
15
20
0.5M NaCl Solution
2.0M NaCl Solution
Chloride Binding Capacity vs. Non-Evaporable Water for 10%SF w/b 0.5
149
Appendix L: LOI of raw materials and non-evaporable water contents
LOI values of raw materials
Mix
Composition Replicates
Original
Sample
(g)
After
Ignition
(g)
Loss on
Ignition
(g)
Loss on
Ignition
(%)
Mean
Loss on
Ignition
(%)
1 1.0148 0.9894 0.0254 2.50
2.513 100%GU 2 1.0285 1.0024 0.0261 2.54
3 1.0892 1.062 0.0272 2.50
1 1.0028 0.9793 0.0235 2.34
2.392 40%GGBFS 2 1.0035 0.9794 0.0241 2.40
3 1.0033 0.9789 0.0244 2.43
1 1.0046 0.9898 0.0148 1.47
1.486 10%MK 2 1.0061 0.9911 0.015 1.49
3 1.0118 0.9967 0.0151 1.49
1 1.0004 0.9778 0.0226 2.26
2.305 10%SF 2 1.0125 0.9889 0.0236 2.33
3 1.0237 0.9999 0.0238 2.32
150
Non-evaporable water contents for all samples
Mix w/b Curing
(days) Replicate
Crucible
Mass (g)
Original
Sample
(g)
Total
Initial
Mass (g)
After
Oven
Drying (g)
M105 (g)
After
Ignition
(g)
M1100
(g)
Non-Evap.
Water (g/g
sample)
0.3 7
1 14.2745 3.0183 17.2928 16.8365 2.562 16.5107 2.2362 0.117
100%GU 2 14.2664 3.0072 17.2736 16.8211 2.5547 16.4954 2.229 0.117
3 14.6687 3.0263 17.6950 17.2426 2.5739 16.9144 2.2457 0.117
0.3 14
1 14.2691 3.0625 17.3316 16.9261 2.657 16.5191 2.25 0.151
100%GU 2 14.2765 3.0154 17.2919 16.8912 2.6147 16.4913 2.2148 0.151
3 14.6704 3.0123 17.6827 17.2857 2.6153 16.8856 2.2152 0.151
0.3 28
1 15.3652 3.0067 18.3719 17.9959 2.6307 17.5642 2.199 0.166
100%GU 2 15.9143 3.0237 18.938 18.5603 2.646 18.1234 2.2091 0.168
3 13.5126 3.017 16.5296 16.1545 2.6419 15.72 2.2074 0.167
0.3 56
1 14.2806 3.008 17.2886 16.9273 2.6467 16.4814 2.2008 0.172
100%GU 2 14.2815 3.0758 17.3573 16.9857 2.7042 16.5295 2.248 0.173
3 16.248 3.0837 19.3317 18.9616 2.7136 18.5037 2.2557 0.173
0.3 7
1 15.3619 3.0148 18.3767 17.8991 2.5372 17.6153 2.2534 0.098
40%GGBFS 2 16.4723 3.0529 19.5252 19.0423 2.57 18.7528 2.2805 0.099
3 17.5423 3.0543 20.5966 20.1136 2.5713 19.8254 2.2831 0.099
0.3 14
1 16.474 3.025 17.6807 19.0799 2.6059 18.7244 2.2504 0.129
40%GGBFS 2 15.3628 3.0347 18.9325 17.978 2.6152 17.6208 2.258 0.130
3 17.5435 3.0162 16.5368 20.1419 2.5984 19.7874 2.2439 0.129
0.3 28
1 16.4773 3.0161 19.4934 19.0995 2.6222 18.7161 2.2388 0.142
40%GGBFS 2 17.5465 3.0246 20.5711 20.1776 2.6311 19.7913 2.2448 0.143
3 12.1703 3.0655 15.2358 14.8372 2.6669 14.4471 2.2768 0.142
0.3 56
1 14.6764 3.0043 17.6807 17.2958 2.6194 16.8759 2.1995 0.162
40%GGBFS 2 15.9185 3.014 18.9325 18.5487 2.6302 18.1277 2.2092 0.161
3 13.5172 3.0196 16.5368 16.1555 2.6383 15.7324 2.2152 0.162
0.3 7
1 14.7393 3.0442 17.7835 17.3219 2.5826 17.0044 2.2651 0.113
10%MK 2 12.1636 3.0064 15.1700 14.7149 2.5513 14.4022 2.2386 0.112
3 14.4567 3.0364 17.4931 17.0345 2.5778 16.7179 2.2612 0.113
0.3 14
1 12.164 3.0303 15.1943 14.7817 2.6177 14.407 2.243 0.139
10%MK 2 14.7407 3.0107 17.7514 17.3431 2.6024 16.9709 2.2302 0.139
3 14.4583 3.0298 17.4881 17.0773 2.619 16.7028 2.2445 0.139
0.3 28
1 16.2433 3.0026 19.2459 18.8511 2.6078 18.4537 2.2104 0.151
10%MK 2 14.2739 3.0182 17.2921 16.8989 2.625 16.4966 2.2227 0.153
3 14.673 3.0176 17.6906 17.2998 2.6268 16.8978 2.2248 0.152
0.3 56
1 15.3679 3.0032 18.3711 17.9808 2.6129 17.5791 2.2112 0.153
10%MK 2 14.7504 3.0262 17.7766 17.384 2.6336 16.9795 2.2291 0.153
3 14.4667 3.0453 17.512 17.1193 2.6526 16.7114 2.2447 0.153
151
0.3 7
1 13.5074 3.0300 16.5374 16.0626 2.5552 15.7533 2.2459 0.109
10%SF 2 16.2400 3.0138 19.2538 18.7829 2.5429 18.4747 2.2347 0.110
3 15.9105 3.0822 18.9927 18.5094 2.5989 18.1964 2.2859 0.109
0.3 14
1 16.241 3.0207 19.2617 18.839 2.598 18.4728 2.2318 0.135
10%SF 2 15.9121 3.0168 18.9289 18.5078 2.5957 18.1406 2.2285 0.136
3 13.5096 3.0367 16.5463 16.1238 2.6142 15.7549 2.2453 0.135
0.3 28
1 14.2797 3.0667 17.3464 16.9413 2.6616 16.5409 2.2612 0.148
10%SF 2 14.4648 3.0003 17.4651 17.0705 2.6057 16.6768 2.212 0.149
3 14.7478 3.0007 17.7485 17.3541 2.6063 16.9601 2.2123 0.149
0.3 56
1 16.4812 3.0038 19.485 19.0836 2.6024 18.675 2.1938 0.157
10%SF 2 17.5497 3.0131 20.5628 20.1619 2.6122 19.7513 2.2016 0.157
3 12.1734 3.068 15.2414 14.8356 2.6622 14.4176 2.2442 0.157
Mix
Composition w/b
Curing
(days) Replicate
Crucible
Mass (g)
Original
Sample
(g)
Total
Initial
Mass (g)
After
Oven
Drying (g)
M105
(g)
After
Ignition
(g)
M1100
(g)
Non-Evap.
Water (g/g
sample)
0.5 7
1 14.2484 3.0121 17.2605 16.5948 2.3464 16.232 1.9836 0.153
100%GU 2 8.5306 3.0577 11.5883 10.9107 2.3801 10.545 2.0144 0.152
3 9.2955 3.0166 12.3121 11.6431 2.3476 11.2838 1.9883 0.151
0.5 14
1 8.9452 3.0507 11.9959 11.3586 2.4134 10.9248 1.9796 0.189
100%GU 2 9.3836 3.0011 12.3847 11.7591 2.3755 11.3319 1.9483 0.189
3 8.9353 3.014 11.9493 11.3235 2.3882 10.8939 1.9586 0.189
0.5 28
1 9.3722 3.0115 12.3837 11.7888 2.4166 11.3265 1.9543 0.206
100%GU 2 8.9468 3.0245 11.9713 11.3774 2.4306 10.9111 1.9643 0.206
3 8.5335 3.0167 11.5502 10.9603 2.4268 10.4951 1.9616 0.206
0.5 56
1 8.8853 3.0342 11.9195 11.3402 2.4549 10.8555 1.9702 0.215
100%GU 2 8.5327 3.052 11.5847 11.0045 2.4718 10.5156 1.9829 0.215
3 8.9482 3.0102 11.9584 11.3925 2.4443 10.9077 1.9595 0.216
0.5 7
1 8.8805 3.0441 11.9246 11.1794 2.2989 10.8879 2.0074 0.117
40%GGBFS 2 14.9062 3.0856 17.9918 17.2373 2.3311 16.9397 2.0335 0.118
3 9.2801 3.0419 12.322 11.5711 2.291 11.2827 2.0026 0.116
0.5 14
1 9.2805 3.0559 12.3364 11.6422 2.3617 11.2693 1.9888 0.158
40%GGBFS 2 8.8812 3.0259 11.9071 11.217 2.3358 10.8489 1.9677 0.158
3 9.2951 3.0188 12.3139 11.6287 2.3336 11.2614 1.9663 0.158
0.5 28
1 9.3857 3.0494 12.4351 11.7665 2.3808 11.3654 1.9797 0.173
40%GGBFS 2 8.9373 3.0252 11.9625 11.3014 2.3641 10.9018 1.9645 0.174
3 14.9089 3.0304 17.9393 17.2778 2.3689 16.8774 1.9685 0.174
0.5 56
1 9.297 3.0116 12.3086 11.6591 2.3621 11.2264 1.9294 0.194
40%GGBFS 2 9.3874 3.0578 12.4452 11.7854 2.398 11.3465 1.9591 0.194
152
3 9.2843 3.0054 12.2897 11.6414 2.3571 11.2104 1.9261 0.194
0.5 7
1 8.9341 3.0136 11.9477 11.2587 2.3246 10.8951 1.961 0.157
10%MK 2 9.3824 3.0189 12.4013 11.7101 2.3277 11.3484 1.966 0.155
3 8.9442 3.0173 11.9615 11.2717 2.3275 10.9107 1.9665 0.155
0.5 14
1 8.9547 3.0133 11.968 11.3313 2.3766 10.9056 1.9509 0.189
10%MK 2 8.6979 3.0025 11.7004 11.0653 2.3674 10.641 1.9431 0.189
3 9.3694 3.018 12.3874 11.7481 2.3787 11.3226 1.9532 0.189
0.5 28
1 8.9574 3.041 11.9984 11.3668 2.4094 10.9167 1.9593 0.200
10%MK 2 8.7019 3.007 11.7089 11.0893 2.3874 10.6429 1.941 0.200
3 9.2817 3.0374 12.3191 11.6979 2.4162 11.2464 1.9647 0.200
0.5 56
1 8.9385 3.0004 11.9389 11.3188 2.3803 10.8655 1.927 0.205
10%MK 2 9.374 3.0312 12.4052 11.7794 2.4054 11.3198 1.9458 0.206
3 8.905 3.0028 11.9078 11.0894 2.1844 10.6335 1.7285 0.233
0.5 7
1 8.9535 3.0143 11.9678 11.2396 2.2861 10.8809 1.9274 0.157
10%SF 2 8.6966 3.036 11.7326 10.9991 2.3025 10.64 1.9434 0.155
3 9.3686 3.0605 12.4291 11.6873 2.3187 11.3275 1.9589 0.154
0.5 14
1 8.5315 3.0103 11.5418 10.8546 2.3231 10.4413 1.9098 0.186
10%SF 2 14.9067 3.0739 17.9806 17.2815 2.3748 16.8566 1.9499 0.188
3 14.2496 3.0221 17.2717 16.5863 2.3367 16.1691 1.9195 0.187
0.5 28
1 8.8829 3.006 11.8889 11.2087 2.3258 10.7832 1.9003 0.193
10%SF 2 9.2962 3.0162 12.3124 11.6329 2.3367 11.2056 1.9094 0.193
3 14.252 3.0394 17.2914 16.6105 2.3585 16.1783 1.9263 0.194
0.5 56
1 14.912 3.0074 17.9194 17.2434 2.3314 16.8129 1.9009 0.196
10%SF 2 14.2544 3.0781 17.3325 16.6412 2.3868 16.2009 1.9465 0.196
3 8.9595 3.0036 11.9631 11.2893 2.3298 10.8606 1.9011 0.195
153
Appendix M: Life-365 estimates of relative service life
Life-365 Analysis for Samples Exposed to 0.5M Chloride Solution
Case Binding
Capacity
Adjustment
Ratio
Original
Diffusion
Coefficient
Modified
Diffusion
Coefficient
Service
Life
(years)
Relative
Service
Life
GU 23oC 21.57 0.0443 1.3804E-11 6.1157E-13 69.1 1.00
GU 0oC 18.39 0.0516 1.3804E-11 7.1180E-13 59.8 0.85
GGBFS 23oC 23.78 0.0404 1.3804E-11 5.5706E-13 81 1.00
GGBFS 0oC 5.15 0.1623 1.3804E-11 2.2404E-12 20.2 0.25
MK 23oC 12.3 0.0752 1.3804E-11 1.0383E-12 42.2 1.00
MK 0oC 16.16 0.0583 1.3804E-11 8.0464E-13 53.3 1.26
SF 23oC 6.14 0.1400 1.3804E-11 1.9325E-12 29.6 1.00
SF 0oC 7.71 0.1148 1.3804E-11 1.5842E-12 35.3 1.19
154
Life-365 Analysis for Samples Exposed to 1.0M Chloride Solution
Case Binding
Capacity
Adjustment
Ratio
Original
Diffusion
Coefficient
Modified
Diffusion
Coefficient
Service
Life
(years)
Relative
Service
Life
GU 23oC 13.31 0.0699 1.3804E-11 9.6443E-13 45.1 1.00
GU 0oC 12.75 0.0727 1.3804E-11 1.0040E-12 43.5 0.96
GGBFS 23oC 18.59 0.0510 1.3804E-11 7.0451E-13 74.9 1.00
GGBFS 0oC 7.09 0.1236 1.3804E-11 1.7065E-12 33 0.44
MK 23oC 5.23 0.1606 1.3804E-11 2.2164E-12 22 1.00
MK 0oC 14.36 0.0651 1.3804E-11 8.9851E-13 48.2 2.19
SF 23oC 3.25 0.2353 1.3804E-11 3.2480E-12 13.7 1.00
SF 0oC 4.58 0.1793 1.3804E-11 2.4750E-12 18.1 1.22
155
Life-365 Analysis for Samples Exposed to 2.0M Chloride Solution
Case Binding
Capacity
Adjustment
Ratio
Original
Diffusion
Coefficient
Modified
Diffusion
Coefficient
Service
Life
(years)
Relative
Service
Life
GU 23oC 6.59 0.1317 1.3804E-11 1.8183E-12 25.7 1.00
GU 0oC 5.99 0.1431 1.3804E-11 1.9755E-12 24 0.93
GGBFS 23oC 12.19 0.0758 1.3804E-11 1.0468E-12 51.6 1.00
GGBFS 0oC 37.79 0.0258 1.3804E-11 3.5591E-13 81 1.57
MK 23oC 1.78 0.3593 1.3804E-11 4.9595E-12 13.4 1.00
MK 0oC 11.65 0.0791 1.3804E-11 1.0915E-12 40.2 3.00
SF 23oC 1.40 0.4170 1.3804E-11 3.8412E-12 14 1.00
SF 0oC 2.23 0.3097 1.3804E-11 5.3436E-13 16.5 1.18