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The Effect of Different Curing Methods on Electrical Properties of Concrete

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Title:
The Effect of Different Curing Methods on Electrical Properties of Concrete
Creator:
Alrashidi, Raid Saif
Place of Publication:
[Gainesville, Fla.]
Florida
Publisher:
University of Florida
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english
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1 online resource (91 p.)

Thesis/Dissertation Information

Degree:
Master's ( M.S.)
Degree Grantor:
University of Florida
Degree Disciplines:
Civil Engineering
Civil and Coastal Engineering
Committee Chair:
RIDING,KYLE AUSTIN
Committee Co-Chair:
TIA,MANG
Committee Members:
FERRARO,CHRISTOPHER CHARLES

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Subjects / Keywords:
electrical -- measurements
Civil and Coastal Engineering -- Dissertations, Academic -- UF
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bibliography ( marcgt )
theses ( marcgt )
government publication (state, provincial, terriorial, dependent) ( marcgt )
born-digital ( sobekcm )
Electronic Thesis or Dissertation
Civil Engineering thesis, M.S.

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Abstract:
Electrical measurements have become a popular method of assessing the transport properties of concrete because they are rapid, easy to perform, and low cost. Even though these measurements can be easily obtained, many factors can affect the results obtained such as specimen geometry, degree of saturation, temperature, pore solution composition, and curing method. There is a concern that standard moist-room curing may cause leaching, affecting the results. Thirty-eight different concrete mixtures were made and cured using two different methods to determine if curing samples in a simulated pore solution would reduce leaching and give more reliable results. Mixtures were made with different types of cement, fly ash, silica fume, slag, and metakaolin. Binary and ternary blends were used. It was found that bulk resistivity showed less issues with ion migration than surface resistivity measurements. It was also found that while curing samples in a simulated pore solution could reduce significantly leaching, surface resistivity measurements gave unreliable measurements in some cases. ( en )
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In the series University of Florida Digital Collections.
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Includes vita.
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Includes bibliographical references.
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This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Thesis:
Thesis (M.S.)--University of Florida, 2018.
Local:
Adviser: RIDING,KYLE AUSTIN.
Local:
Co-adviser: TIA,MANG.
Statement of Responsibility:
by Raid Saif Alrashidi.

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LD1780 2018 ( lcc )

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THE EFFECT OF DIFFERENT CURING METHODS ON ELECTRICAL PROPERTIES OF CONCRETE By RAID S. ALRASHIDI A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DE GREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2018

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2018 R aid S. A lrashidi

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To my lovely family and to my best friends, Waleef and Majeed

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4 ACKNOWLEDGMENTS First and foremost, I am very grateful to G od Alm ighty for his graces, blessing, and protection over my life, and for giving me strength and the ability to successfully complete this research. I would like to express my deepest gratitude for my advisor Dr. Kyle A. Riding for his extraordinary help, guidance, and motivation throughout my graduate education. He has not just made me a better engineer, but made me a successful person. Appreciation is also extended to Dr. Mang Tia, and Dr. Christopher Ferraro for serving on my supervisory committee. I wo uld also like to thank a ll my labmates and friends. Special thanks go to Abdulmajjid Alrashidy, Mohammed Almarshoud, Hossein Mosavi, Mohammed Hussain Alyami, Waleed Almasoud, and Nader Aljohani for all the support, advice, and help they have provided me. T hey have also helped me sustain a positive atmosphere in which to complete this work. Finally, I am also grateful and indebted to my beloved famil y for their unconditional love and constant support for my whole life Without all the help and encouragement from faculty, friends, and family, this work would not have been possible.

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5 TABLE OF CONTENTS ACKNOWLEDGMENTS ................................ ................................ ................................ .. 4 LIST OF TABLES ................................ ................................ ................................ ............ 7 LIST OF FIGURES ................................ ................................ ................................ .......... 8 LIST OF ABBREVIATIONS ................................ ................................ ........................... 10 ABSTRACT ................................ ................................ ................................ ................... 11 CHAPTER INTRODUCTION ................................ ................................ ................................ ........... 12 1.1 Background ................................ ................................ ................................ ... 12 1.2 Hypothesis of Research ................................ ................................ ................ 13 1.3 Research Objectives ................................ ................................ ..................... 13 1.4 Scope of the Research ................................ ................................ .................. 13 LITERATURE REVIEW ................................ ................................ ................................ 14 2.1 Introduction ................................ ................................ ................................ ... 14 2.2 Fly Ash ................................ ................................ ................................ .......... 15 2.3 Slag Cement ................................ ................................ ................................ 16 2.4 Silica Fume ................................ ................................ ................................ ... 18 2.5 Metakaolin ................................ ................................ ................................ ..... 19 2.6 Pore System and Formation Factor ................................ .............................. 20 2.7 Electrical Resistivity and Conductivity Tests ................................ ................. 22 2.7.1 Rapid Chloride Permeability Test (RCPT) ................................ ........... 22 2.7.2 Surface Resistivity ................................ ................................ ............... 24 2.7.3 Bulk Resistivity ................................ ................................ .................... 26 2.8 Factors Affecting the Resistivity Measurements ................................ ............ 27 2.8.1 Intrinsic Factors ................................ ................................ ................... 28 2.8.1.1 Water Cementitious Materials Ratio (w/cm) ................................ 28 2.8.1.2 Aggregate Size and Type ................................ ............................ 28 2.8.1.3 Sample Curing Conditions ................................ ........................... 29 2.8.1.4 Pore Solution Composition ................................ .......................... 30 2.8.2 Extrinsic Factors ................................ ................................ .................. 32 2.8.2.1 Specimen Geometry ................................ ................................ .... 32 2.8.2.2 Specimen temperature ................................ ................................ 33 2.8.2.3 Signal Frequency ................................ ................................ ......... 34 2.9 Summary ................................ ................................ ................................ ....... 35 MATERIALS ................................ ................................ ................................ .................. 37

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6 3.1 Aggregates ................................ ................................ ................................ .... 39 3.2 Mixtur es ................................ ................................ ................................ ......... 39 METHODOLOGY ................................ ................................ ................................ .......... 43 4.1 Concrete Methodology ................................ ................................ .................. 43 4.2 Concrete Mi xing ................................ ................................ ............................ 43 4.3 Fresh Concrete Properties ................................ ................................ ............ 43 4.4 Concrete Specimen Preparation ................................ ................................ ... 47 4.5 Concrete Curing ................................ ................................ ............................ 47 4.6 Simulated Pore Solution (SPS) Curing Method ................................ ............. 48 4.7 Electrical Tests ................................ ................................ .............................. 49 4.7.1 Surface Resistivity ................................ ................................ ............... 49 4.7.2 Bulk Resistivity ................................ ................................ .................... 51 RESULTS AND DISCUSSION ................................ ................................ ...................... 53 5.1 Introduction ................................ ................................ ................................ ... 53 5.2 Pore Solution Conductivity ................................ ................................ ............ 53 5.3 Corre lation between Surface and Bulk Resistivity ................................ ......... 55 5.4 Formation Factor ................................ ................................ ........................... 57 5.5 Effect of w/cm Ratio on Surface and Bulk Resistivity ................................ .... 61 5.6 Effect of SCMs on Surface and Bulk Resistivity ................................ ............ 66 5.6.1 Fly Ash ................................ ................................ ................................ 66 5.6.2 Slag ................................ ................................ ................................ ..... 68 5.6.3 Silica Fume ................................ ................................ ......................... 69 5.6.4 Metakaolin ................................ ................................ ........................... 73 CONCLUSION AND FUTURE RESEARCH ................................ ................................ 77 6.1 Summary ................................ ................................ ................................ ....... 77 6.2 Future Research ................................ ................................ ........................... 78 SURFACE AND BULK RESISTIVITY READINGS ................................ ........................ 79 LIST OF REFERENCES ................................ ................................ ............................... 82 BIOGRAPHICAL SKETCH ................................ ................................ ............................ 91

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7 LIST OF TABLES Table page 3 1 Cement and Supplementary Cementitious Material Composition as Measured by XRF ................................ ................................ ............................... 38 3 2 Coarse Aggregate Specific Gravity and Absorption ................................ ............ 39 3 3 Fine Aggregate Specific Gravity and Absorption ................................ ................ 39 3 4 Mix proportions for concrete ................................ ................................ ............... 41 4 1 Measured concret e fresh properties ................................ ................................ ... 45 5 1 Pore solution conductivity readings ................................ ................................ .... 54 5 2 Formation factor from NIST for moist curing room and SPS .............................. 59 5 3 Formation factor from measured pore solution conductivity ............................... 60 A 1 Surface and Bulk resistivity readings (moist room) ................................ ............. 79 A 2 Surface and Bulk resistivity readings (SPS) ................................ ....................... 80

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8 LIST OF FIGURES Figure page 2 1 RCPT samples during testing ................................ ................................ ............. 24 2 2 Four point wenner probe ................................ ................................ .................... 25 2 3 Bulk resistivity set up ................................ ................................ .......................... 26 2 4 The pore solution conductivity senso r ................................ ................................ 31 4 1 Determination of slump ................................ ................................ ....................... 44 4 2 Determination of unit weigh t ................................ ................................ ............... 44 4 3 Determina tion of air content ................................ ................................ ................ 46 4 4 Concrete Temperature Measurement ................................ ................................ 46 4 5 Cylinders after filled with the first layer of concrete ................................ ............. 47 4 6 The specimens were placed in a sealed container ................................ ............. 49 4 7 Oakton PC700 Meter ................................ ................................ .......................... 49 4 8 Surface resistivity meter used in this study ................................ ......................... 50 4 9 Specimen holder used in this study ................................ ................................ .... 50 4 10 Surface resistivity measurement ................................ ................................ ......... 51 4 11 Grinding samples for bulk resistivity measurement ................................ ............ 52 4 12 Bulk resistivity test ................................ ................................ .............................. 52 5 1 SR vs BR at all ages (moist room) ................................ ................................ ...... 56 5 2 SR vs BR at all ages (SPS) ................................ ................................ ................ 56 5 3 SR (moist room) vs SR (SPS) readings for all ages ................................ ........... 57 5 4 BR (moist room) vs BR (SPS) readings for all ages ................................ ........... 5 7 5 5 Form ation factor (moist room) vs SPS curing methods ................................ ...... 58 5 6 Effect of w/cm on the control mixes (moist room) ................................ ............... 62 5 7 Effect of w/cm on ternary and binary mixes (moist room) ................................ ... 62

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9 5 8 Effect of w/cm on the control mixes (moist room) ................................ ............... 63 5 9 Effect of w/cm on tern ary and binary mixes (moist room) ................................ ... 63 5 10 Effect of w/cm on the control mixes (SPS) ................................ ......................... 64 5 11 Effect of w/cm on ternary and bina ry mixes (SPS) ................................ ............. 64 5 12 Effect of w/cm on the control mixes (SPS) ................................ ......................... 65 5 13 Effect of w/cm on ternary and binary mixes (SPS) ................................ ............. 65 5 14 Effect of fly ash on surface resistivity readings (moist room and SPS) ............... 67 5 15 Effect of fly ash on bulk resistivity readi ngs (moist room and SPS) .................... 67 5 16 Effect of slag cement on surface resistivity readings (moist room and SPS) ...... 69 5 17 Effect of slag cement on bulk resistivity readings (moist room and SPS) ........... 69 5 18 Effect of silica fume on surface resistivity readings (moist room and SPS) ........ 70 5 19 Effect of silica fume on bulk resistivity readings (moist room and SPS) ............. 71 5 20 Effect of fly ash and silica fume on the different types of cement (moist room) .. 71 5 21 Effect of fly ash and silica fume on the different types of cement (SPS) ............. 72 5 22 Effect of silica fume on the different ty pes of cements (moist room) ................... 72 5 24 Effect of metakaolin on surface resistivity readings (moist room and SPS) ........ 74 5 25 Effect o f metakaolin on bulk resistivity readings (moist room and SPS) ............. 74 5 26 Effect of metakaolin on the control mixes (moist room) ................................ ...... 75 5 27 Effect of metakaolin on the control mixes (SPS) ................................ ................. 75 5 28 Effect of metakaolin on the control mixes (moist room) ................................ ...... 76 5 29 Effect of metakaolin on the control mixes (SPS) ................................ ................. 76 A 1 Surface resistivity vs bulk resistivity (Moist room) ................................ ............... 81 A 2 Surface resi stivity vs bulk resistivity (SPS) ................................ ......................... 81

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10 LIST OF ABBREVIATIONS C 100 C 100h CL F20S8 CV F10G60 F FA G HA cement M RCPT S SCMs 100 % type I/II cement with low w/cm (0.35) 100 % type I/II cement with high w/cm (0.44) Type L cem ent with a 20% of fly ash and 8% of silica fume Type V cement with a 10% of fly ash and 60% of slag cement Formation factor Fly ash Slag High Alkali cement Metakaolin Rapid chloride permeability test Silica fume Supplementary cementitious materials W/cm W ater to cementitious materials ratio

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11 Abstract of Master Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science THE EFFECT OF DIFFERENT CURING METHO DS ON ELECTRICAL PROPERTIES OF CONCRETE By Raid S. Alrashidi August 2018 Chair: Kyle A. Riding Major: Civil Engineering Electrical measurements have become a popular method of assessing the transport properties of concrete because they are rapid, easy to perform, and low cost. Even though these measurements can be easily obtained, many factors can affect the results obtained such as specimen geometry, degree of saturation, temperature, pore solution composition, and curing method. There is a concern tha t standard moist room curing may cause leaching, affecting the results. Thirty eight different concrete mixtures were made and cured using two different methods to determine if curing samples in a simulated pore solution would reduce leaching and give more reliable results. Mixtures were made with different types of cement, fly ash, silica fume, slag, and metakaolin. Binary and ternary blends were used. It was found that bulk resistivity showed less issues with ion migration than surface resistivity measure ments. It was also found that while curing samples in a simulated pore solution could reduce significantly leaching, surface resistivity measurements gave unreliable measurements in some cases.

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12 CHAPTER 1 INTRODUCTION 1 CHPATER 1.1 Background Concrete electr ical property measurement as a quality control tool has been ongoing for several decades (Sohn & Mason, 1998) (Rupnow & I cenogle, 2012) These tests use the electrical resistance as an indicator of the water and ionic penetrability of the concrete. Electricity is conducted through the concrete principally by the pore solution in the concrete pores. The higher the volume an d connectivity of the pores, the higher the electrical conductivity of the concrete. A technique has been developed recently to measure the concrete resistivity non destructively. This technique uses a four probe Wenner probe to measure the concrete surfa ce resistivity or bulk resistivity. Electrical resistivity tests such as surface and bulk resistivity have become used by the Florida Department of Transportation (FDOT), and the Louisiana Department of Transportation (LADOT) because of their simplicity. FDOT has recently become concerned that these tests do not sufficiently of supplementary cementitious materials (SCMs) is used. SCM use change the pore solution compositi on and corresponding electrical resistivity. The change in pore structure refinement rate caused by the different hydration rate of SCMs could affect the rate of leaching out of ions from the concrete during curing. Changes to the curing process could elim inate this issue. Normalization of the concrete electrical resistivity by the pore solution resistivity could account for some of the differences seen.

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13 1.2 Hypothesis of Research Curing concrete samples in a simulated pore solution can eliminate leaching and lead to more reliable electrical resistivity results. 1.3 Research Objectives The main objectives of this research project as follows: To measure the effect of using simulated pore solution to cure concrete on surface and bulk resistivity measurements. To me asure the effect of SCMs as well as the w/cm on the electrical properties of concrete with time. 1.4 Scope of the Research Thirty eight mixes with a two w/cm ratio of 0.35 and 0.44 were performed including four different types of cement, I/II, V, L, and high a lkali cement, and four SCMs, fly ash, slag, silica fume, and metakaolin were used for this research project. The surface resistivity and bulk resistivity of the concrete mixtures were measured according to AASHTO T 358 and AASHTO TP 119 respectively. Meas urements were made at 28, 56, and 91 days after mixing. Samples were made for curing in the moist room and simulated pore solution for comparison.

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14 CHAPTER 2 LITERATURE REVIEW 2 CHAPTER 2.1 Introduction Concrete is the most widely used building material in the world in part due to its favorable durability to cost ratio. Durability of concrete is substantially enhanced by the incorporation of supplementary cementitious materials (SCMs). Many SCMs are industrial byproduct that reduce the concrete greenhouse gas f ootprint (Scott & Alexander, 2016) (Borosnyi, 2016) In general, SCMs such as fly a sh, silica fume, slag cement, and metakaolin can enhance strength and durability by acting hydraulically or pozzolanicly The term hydraulic describes the material that chemically reacts with water to form a stable product under water, such as portland cement and slag cement. The term pozzolanic is a description given to a material, primarily siliceous in composition, when reacts with water, displays little cementitious properties, such as Class F fly ash, and silica fume SCMs contribute to the hydration of p ortland cement by physical phenomena and by chemical reaction. Due to pozzolanic activity and the filler effect, SCMs can enhance concrete mechanical properties and reduce the concrete penetrability (Borosnyi, 2016) (Chini, Muszynski, & Hicks, 2003) Electrical resistivity test methods have been developed to help measure the concrete resistance to fluid and ion transport. Interpretation of electrical resistivity test results for concrete durability requires an understanding of both the materials tested and the test mechanism and methods used. This literature review provides an in depth examination of typical SCMs and electrical test methods used in concrete.

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15 2.2 Fly Ash Fly Ash (FA) is a pozzolanic material that is a by product of coal combu stion for the generation of electricity. Most fly ash particles are amorphous, spherical and small in size, ranging between 1.0 and 100 m in diameter In the United States, fly ashes for use in concrete are categorized as Class F and Class C as described in ASTM C618. Classification is based on their chemical composition that depends on the type of coal burned, in which the sum of SiO2, Al2O3, and Fe2O3 should be greater than 70% for Class F fly ash, and greater than 50% for Class C fly ash (ASTM, 2010a) Although not a requirement in the standard, a primary difference betw een the Class F and Class C ashes is the amount of calcium oxide (CaO). Class C has much higher calcium content than Class F, and can have high variability of the chemical composition (Ponikiewski & (Yamei, Wei, & Lianfei, 1997) The spherical nature of fly ash particles is often improve concrete workability. (Khan, Nuruddin, Ayub, & Shafiq, 2014) Concrete workability is affected by high carbon content, in which the porous carbon particles absorb more water (Neville, 2011) As a negative side effect of fl y ash, it has been reported that higher dosages of air entrainment are required due to its adsorption to the surface of unburned carbon particles (Jolicoeur et al., 2009) Class F fly ash is also known to l ower the amount of heat hydration, which makes it very useful in mass concrete application. Class C fly ash, however, it depends on its chemical composition and can either increases or decreases the heat of hydration. Incorporation of class F fly ash can l ow early compressive strength; however, due its pozzolanic reaction, the later strength gradually improves over time (Saha, 2018) Class F fly ash can increase the sulfate resistance due to the continued reaction with hydroxides whereas Class C fly ash mixture have a greater

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16 susceptibility to reduce sulfate resistance (ACI, 2002) With respect to Alkali Silica Reaction (ASR), the use of adequate amounts of fly ashes can mitigate ASR expansion by reducing hydroxyl ions in pore water and consuming CH. However, class C fly ash may require a higher dos age than Class F fly ash to mitigate ASR because of its high chemical variability, and lower alkali binding. The use of fly ash as a partial replacement of portland cement is common. Using fly ash as an SCM can greatly improve the sulfate resistance and th e chloride permeability (X. Shi, Xie, Fortu ne, & Gong, 2012) (J. Su et.al., 2002). The combined use of fly ash with other SCMs, such as slag, whether in small or large cement substitution ratio can lead to a favorable durability performance of concrete (Ganesh Babu & Sree Rama Kumar, 2000) (Xu, 1997) The presence of fly ash can lower the alkali and hydroxide concentration in the pore solution (Vollpracht, Lothenbach, Snellings, & Haufe, 2016) The reactivity of SCMs such as fly ash is influenced by the alkalinity of pore solution of concrete. When fly ash is used as a partial replacement with cement, the alkali ( potassium and sodium ) concentrations decrease with time and result in the formation of C S H with a lower Ca/ Si ratio and alkali binding (Vollpracht et al., 2016) The pozzolanic reaction leads to C A S H phases., At longer hydration times, the concentration of hydroxides are also decreased (Hong & Glasser, 1999) (Vollpracht et al., 2016) 2.3 Slag C ement Slag cement is highly cementitious in nature, and it is a by product of the process of making steel in a blast furnace. Molten slag is rapidly q uenched whether in air or water to form glassy granules, which are then ground. Faster quenching, higher temperatures rates and higher alkali content can make the slag more reactive. Slag

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17 cement particle fineness and specific area is similar to portland ce ment particles, and has a very limited amount of crystalline material (Hadj Sadok, Kenai, Courard, & Darimont, 2011) In accordance with ASTM C989, based on the activity index, the slag is divided into three grades: grade 80, 100, and 120, in which the higher grade contributes more to the compressive strength at 7 and 28 days (ASTM, 2013a) The sulfur in su lfide form in slag cement must not exceed the allowed limit, 2.5 % (ASTM, 2013a) The initial reaction of slag is often relatively slow; therefore, setting time can be increased compared to portland cement. Slag cement reactivity is highly temperature dependent. Use of slag cement in cold weather may require heating or use of an accelerator since it hydrates very slow at low temperature. It has reported that replacing large percentages of portland cement with slag can lower the heat of hydration (Neville, 2011) The addition of slag up to 55% resulted in improved concrete workability as well as increased bleed capacity (by 30% compared to the control) with little effect on the bleeding rate (Wainwright & Rey, 2000) The reactivity of slag can influence the strength development of concrete, and in corporation of slag up to 60% can lower the compressive strength at early ages, but lead to a comparable later age compressive strength (Malagavelli, 2010a) Slag cement is effective in mitigating alkali silica reaction ASR, in which it consumes CH and binds alkalis in C S H reaction. With addition of sla increased (Malagavelli, 2010b) Slag improves the durability considerably of portland cement concrete exposed to chloride environments by improving the pore structure of

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18 concrete and increasing the material chloride binding capacity (Luo, Cai, Wang, & Huang, 2003) (Cheng, Huang, Wu, & Chen, 2005) The slag proportion in cement can affect the alkali concentration, however, if the alkali level in both slag and cli affect the alkalinity concentration of the pore solution (Chen & Brouwers, 2011) Since slag cement contains less alkali compared to the normal portland cement, it lower the potassium and sodium concentrations and reduces sulfur species, thus decreases the OH concentrations of the pore solution (Vollpracht et al., 2016) 2.4 Sili ca F ume Silica fume (SF) is a pozzolanic material that is by product of the silicon and ferrosilicon industry. Most SF particles are made up mostly of amorphous silica (SiO2 >85%) and are very small in size, typically averaging from 0.1 and 0. diameter. Silica fume acceptance is governed by ASTM C1240 (ASTM, 2012) Due to its high fineness, it reacts much faster than fly ash and slag, and may increase the water demand of concrete; therefore, it is usually accompanied with the use of superplasticizer. The high reactivity of SF can lead to a significant increase in the compr essive strength. SF is also known at mitigating ASR due to the reduction in pore solution alkalinity, therefore when it used in sufficient amounts, the expansion may be decreased to harmless level (Press & May, 1992) SF in modest quantities (3 5%) can considerably reduce the penetrability of concrete as it changes the microstructure through both chemical a nd physical pathways. Spoge et.a l ., (Song, Pack, Nam, Jang, & Saraswathy, 2010) verified a microstructure model for SF cement concrete and concluded that incorporating up to 8% silica fume in the concrete makes the microstructure of the concrete denser a nd significantly reduces the permeability. SF

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19 reduces the connectivity and size of the pores due to the growth of the secondary C S H and consumption of calcium hydroxide (Hassan, 2001) Partial replacement of the portland c ement with silica fume is known to reduce the C/S ratio of the C S H. This can reduce the chloride binding slightly by reducing the amount of chloride that adsorbs onto the surface of C S H. The presence of SF decreases the alkali and hydroxide level in th e pore solution and becomes more distinct with time when more SF reacts (Vollpracht et al., 2016) Compared to the control mix, a partial cement replacement of 5% by silica fume decreases the pore solution conductivity by 75% during the first 7 days (C. Shi, 2004) The incorporation of silica fume reduces the pH of the pore solution of concrete and increases the amount of C S H formed (M. D. A. Thomas, Hooton, Scott, & Zibara, 2012) (M. D. A. Thomas et al., 2012) Silica f ume decreases the alkali and hydroxide concentrations in the pore solution more than fly ash due to the higher reaction degree of the silica fume and higher silicon content, in which the reaction is much stronger than for fly ash. (Vollpracht et al., 2016) 2.5 Metakaolin Metakaolin (MK) is a processed kaolin clay that is calcined between 500 and 800 to create an amorphous aluminsolicate SCM. The particle size of MK is finer that the portland cement particle. It is a highly reactive aluminosilicate pozzolan that combines with calcium hydroxide to produce additional calcium silicate hydrates (C S H), aluminosilicat e hydrates (C A S H), and aluminate hydrates (C A H) (Ramezanianpour & Bahrami Jovein, 2012) MK c an significantly reduce the workability of concrete (Fras, De Rojas, & Cabrera, 2000) MK has a high silicon dioxide (SiO2) and alumina (Al2O3) content of 51.52% and 40.18% by mass, respectively. The high al umina content makes it very effective in mitigating delayed ettringite formation (DEF)

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20 (Ambroise, Maximilien, & Pera, 1994) (A. Santos Silva, 2015) The use of MK as a partial replacement of portland cement can increase the compressive strength; however, it is found that when the mix contains both metakaolin and silica fume, the higher the MK dosage, the less the increase in the compressive strength (Borosnyi, 2016) The incorporation of MK in concrete can significantly increase its resistance to the chloride penetration by decreasing the mean pore size (Ramezanianpour & Bahrami Jovein, 2012) (Y.Liu, 2012). The pozzolanic reaction of the metakaolin was found to co nsume portlandite and produce a more refined pore system (Justice & Kurtis, 2007) When using MK with concrete, the surface electrical resistance of concrete was greatly enhanced compared to the reference concrete, giving 2 4 times higher resistivity for a 15% MK dosage (Ramezanianpour & Bahrami Jovein, 2012) (Borosnyi, 2016) MK modifies the pore structure and substantially lowers the permeability of con crete resulting in increased resistance to diffusion of chloride ions and the transportation of water (Siddique & Klaus, 2009) 2.6 Pore System and Formation Factor Over the last s eve ral decades, a lot of has focused on the electrical properties of concrete as a concrete quality indicator. Electrically conductive pore solution can fill concrete pores, making the concrete electrically conductive. The electrical conductivity of the co ncrete is dependent on both the pore system and the pore solution conductivity. The concrete electrical resistivity T m), or inverse of conductivity, can be normalized by the pore solution resistivity 0 m) to give an empirical material pore system index called the Formation Factor ( F ) as shown in Equation 2 1 (Kenneth A. Snyder, 2001) :

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21 (2 1 ) F is independent of specimen size or shape and is related to the pore system as the inverse of the produc t of the concrete porosity volume and connectivity as shown in Equation 2 2 (Archie, 1942) (R. Spragg, Bu, Snyder, Bentz, & Weiss, 2013) (Spragg, 2013): ( 2 2) The Nernst Einstein relation ship can also be used to relate F and the concrete electrical resistivity to the concrete bulk effective diffusion coefficient D (m 2 /s) as shown in Equation 2 3: (Bu & Weiss, 2014) (Kenneth A. Snyder, 2001) (2 3 ) Where D 0 is the self diffusion coefficient (m 2 /s) Equation 2 2 shows how the concrete resistance against chloride penetration can be proportional to the concrete electrical properties. This r elationship is what allows concrete electrical tests to be used for concrete quality tests. The concrete pore system pore solution conductivity and consequently electrical resistivity are highly dependent on the concrete mixture characteristics such as ce mentit ious material composition, water to binder ratio, and degree of hydration (R. Spragg, Bu, et al., 2013) As the concrete hydrates with time, the microstructure and pore soluti on can also be significantly changed due to environmental conditions (R. Spragg, Bu, et al., 2013) (Spragg, 2013). Temperature, leaching of alkalis, and degree of

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22 saturation can all affect pore solution composition and electrical resistivity measurements. The pore solution resistivity can be estimated using the NIST pore solution electrical conductivity calculator (based on the mixture proportion and the alkali content), which is a vailable online http://concrete.nist.gov/poresolncalc.html experimentally by using embedded sensor into a fresh concrete (Rajabipour, Sant, & Weiss, 2007) or from pore solution extraction (B arneyback, Diamond, 1981) 2.7 Electrical Resistivity a nd Conductivity Tests Over the last few decades, different methods have been sugg ested to measure the electrical properties of concrete. (W.J. Weiss, J.D. Shane, A. Mieses, T.O. Mason, S.P. Shah, 1999)(J. Calleja, 1952). The first concrete electrical test method developed is the r apid c hloride p ermeability t est ( RCPT), standardized as ASTM C1202 (ASTM C1202, 2012) or AASHTO T277 AASHTO T277 standards. Although this test has gained wide use, it is a destr uctive test, requires a significant amount of sample preparation, and has other shortcomings that cause issues with repeatability (Riding, Poole, Schindler, Juenger, & Folliard, 2008) (K A Snyder, Ferraris, Martys, & Garboczi, 2000) Since then, other concrete electrical test methods have been developed that are non destructive and simpler to perform. These tests, while all based on the same general physic s, each have unique features and issues that merit further examination. 2.7.1 Rapid Chloride Permeability Test (RCPT) The rapid chloride permeability test (RCPT) is a popular test method that is currently performed based on the electrical concept. This test h as existed for more than three decades and was standardized as ASTM C1202 in 1991 (whiting, 1980) (Bentz, 2007)

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23 The RCPT provides a rapid indication of concrete resistance to the chloride ion penetration by measuring the total charge driven across a concrete sample by an applied 60 V electrical potential (ASTM C1202, 2012) This test method involves at least 2 days of preparation. The samples need to be cut into 2 in. thick slices and placed in a vacuum desiccator with both ends exposed. The vacuum is maintained for three hours in the desiccator, and then filled with de aired water and maintained for an addition al hour. After that, the samples should be left soaked for 18 2 hours. The 2 in. thick samples are then placed inside a testing cell with one side of the cell filled with 3.0 % sodium chloride (NaCl) and the other side filled with 0.3M sodium hydroxide ( NaOH) solutions, as shown in Figure 2 1 The electrical charge passed between the electrodes is integrated with time using readings taken every 30 minutes during the six hour testing period (ASTM C1202, 2012) Even though this test has been adopted as a standard test, there have been number of criticisms of this technique (Shane et al., 1999) (Riding et al., 2008) First, the curren t that passes through the sample is dependent on the pore solution con ductivity. For example, admixtures such as calcium nitrite corrosion inhibitors are known to increase the pore solution conductivity and charge passed (ASTM C1202, 2012) Second, the high voltage applied can lead to specimen heating, giving misleadingly high results (Shane et al., 1999) (Riding et al., 2008) Third, since it is a destructive test, it ca nnot be used again due to physical and chemical change This test has a high variability, and the precision statement in ASTM 1202 indicates that single and multilaboratory measurements will have a coefficient of variation of 12.3% and 18 %, respectively (ASTM C1202, 2012) Thus, the results from two properly conducted tests on the same material in the same lab and different l ab could differ by as

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24 much as 42% and 51%, respectively. Typically, three averaged samples are used to reduce the multilaboratory variation to 29% (Joshi & Chan, 2002) Figure 2 1 : RCPT samples during testing (Photo credit: Raid Al rashidi) 2.7.2 Surface Resistivity The surface resistivity test can be used to evaluate the electrical resistivity of a saturated concrete cylinder to provide an estimation of its permeability One of the most common techniques for measuring the surface resistiv ity is a four probe technique first developed by Frank Wenner in order to determine soil strata. It was later modified for concrete use and is often called a Wenn er probe (Wenner, 1916) In this technique, four equally spaced electrode are located on concrete surface to measure the potential difference caused by the applied current (Proceq SA, 2016) as shown in Figure 2 2 :

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25 Figure 2 2 : Four point wenner probe The electrical resistance is affected by a number of factors such as, humidity, pore solution conductivity and temperature. Therefore, care sh ould be taken when measuring the electrical resistivity, whi ch can be calculated using the E quation 2 4 : (2 4 ) Where is cm), V is the voltage measured between two inner probes ( V) I is the applied current by the two exterior probes ( A ), and a is the probe tip spacing (cm) P robe spacing must be taken into account as it will affect the obtained results. If the probe spacing is too small, a high degree of scatter can occur in the presence of the aggregate (Shahroodi, 2010) Too large of a probe spacing can lead the electrical current to penetrate more into the concrete layers (R. Polder et al., 2000) T o reduce the variance in resistivity measurements, an electrode spacing between 20mm and 70mm is typically used (Sengul & Gjrv, 2009) (Morris, Moreno, & Sags, 1996) Probe spac ing is recommended to be 1.5 times higher than the maximum aggregate size

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26 (Gowers & Millard, 1999) An electrode spacing of 1.5 inch (38 mm) is considered standard for AASHTO TP 119 (AASHTO, 2015) A precision statement for concrete surface resistivity was developed for use with LADOT and states that if two tests properly performed by a single operator should not differ from their average by more than 1 3.28%, and two tests performed by different laboratories should not vary by more than 34.55% (Rupnow & Icenogle, 2011) (R. P. Spragg, Castro, Nantung, Paredes, & Weiss, 2012) 2.7.3 Bulk Resistivity The bulk resist ivity test is a non destructive test that can be used to measure the electrical resistivity of saturated concrete to provide a rapid indication of its resistance to chloride ion penetration. This test method can use the same equipment (4 pronged Wenner pro be) as surface resistivity to measure the resistance of the cylinder with the probe tips attached to conductive plates placed on the end of the cylinder. Saturated sponges or conductive gel are typically used between the conductive plates and the ends of t h e cylinder, as shown in Figure 2 3 Figure 2 3 : Bulk resistivity set up

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27 The resistance of the saturated sponges should be measured prior to testing and subtracted from the total resistance of th e system by using the Equation 2 5 : (2 5 ) Where, R cylinder the calculated bulk resistance ( ), and R measured is the measured resistance of the probe ( ) The bulk resistivity is then calculated using the E quation 2 6 : (2 6 ) Where is the resistivity of the concrete (k .cm) and K is the geometry factor wh ich is the rati on of the cross sectional area A (cm 2 ) to the lengt h of the specimen L (cm) as shown in Equation 2 7 ( 2 7 ) A precision statement developed by LADOT indicates that the automated resistivity measureme nts within laboratory have a coefficient of variation of around of 4.36 %, and the multi laboratory coefficient of variation of 13.22 % (R. P. Spragg et al., 2012) 2.8 Factors Affecting the Resistivity Measurements The electrical resistivit y of concrete can be affected by several factors. These factors can be divided into two groups: the first group is intrinsic factors that is related to concrete characteristics such as: w/c ratio, aggregate size and type, hydration, and pore structure. The second group is extrinsic factors related to testing conditions such as spec imen geometry, temperature, moisture content, and the electrode signal frequency.

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28 2.8.1 Intrinsic Factors 2.8.1.1 Water Cementitious Materials Ratio (w/cm) Water to cement itious materials ratio (w/cm) plays an important role in the permeability o f concrete and its properties. W /cm represents the gel porosity and evaporable water in concrete. An increase in the w/cm results in a high percentage of porosity, higher pore fraction within the cement and lower electrical resistivity values, indicating a more permeable concrete (Rupnow & Icenogle, 2012) (Van Noort, Hunger, & Spiesz, 2016) 2.8.1.2 Aggregate Size and Type Most aggregates have a higher electrical resistivity than hardened cement paste because they have less por osity. Most electrical conductance occurs in the paste portion of the concrete (Azarsa & Gupta, 2017) By this same logic, higher aggregate content results in h igher electrical resistivity (Morris et al., 1996) For the same aggregate content, mixtures containing large aggregate (16 32mm) had higher resistivity compared with small particle size (0 4 mm), and three times higher than that of the cement paste (Sengul, 2014) Although most of the electrical cond uctance occurs in the paste, aggregate types can affect the properties of concrete. For the same aggregate volume percentage, electrical resistivity were higher for the crushed limestone than the rounded siliceous gravel, and the surface texture might be a possible cause for that, in which the gravel had smooth surface resulting in poor bonding (Sengul, 2014) The effect of aggregate type, content, and size should not be ignored when doing the resistivity tests. Also, when comparing the resistivity values of different concretes, they should be taken into account.

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29 2.8.1.3 Sample Curing Conditions The curing regimes and concrete composition influence the resistivity of concrete e volution with time (Presuel Moreno, Wu, & Liu, 2013) (R. Spragg, Villani, et al., 2013) The type of curing has an impact on the electrical pore solution resistivity measurements It can cause changes in rea dings by 80% (Bu & Weiss, 2014) The degree of saturation and the degree of hydration of the specimen can develop differences in resistivity measurements. The degree of hydration and saturation, the pore structure and solution through leaching can be influenced by the sample storage and curing condition (Weiss, Snyder, Bullard, & Bentz, 2012) Storing the samples underwater or saturated lime water a ffect the resistivity measurements through leaching of alkalis and can increase the degree of hydration To correct for this difference in readings, the samples cured in lime water, the average resistivity readings should be multiplied by 1.1 ( AASHTO, 2015) Increased saturation provides for more pores that can conduct electricity and increases pore solution conductivity, which effects the measured resistivity. When compared to sealed curing, storing in a satur ated lime water showed a decrease in the conductivity of the pore solution by an order of magnitude due to leaching of alkalis from the pore solution to the storage solution and less connected pore water (Bu & Weiss, 2014) Simulations of a mortar with a w/c m of 0.42 were performed with three curing conditions: a) specimens sealed on both curing and testing, b) specimens sealed during cur ing and saturated during testing, c) specimens saturated on both curing and testing (Weiss et al., 2012) (Weiss et al., 2012) (Bullard et al 2008). The results showed that the specimens that were sealed for both curing and testing had the highest resistivity while

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30 specimens sealed during the curing and saturated during testing had the lowest resistivity because of the lower degree of hydratio n. 2.8.1.4 Pore Solution Composition Pore solution analysis and composition of concrete are highly significant for understanding the ongoing hydration reactions and interpreting electrical resistivity measurements The pore solution of cementitious materials is co mposed of potassium (K + ), sodium (Na + ), calcium ( Ca 2+ ), sulfate ( SO 4 ) 2 and hydroxides (OH ) ions. Supplementary of cementitious materials (SCMs) can alter the concrete pore solution composition. in which they can consume the hydroxyl ions (OH ), which le ads to an increase the electrical resistivity compared to the referenced concrete sample (C. Shi, 2004) P ore solution expression was first u sed in 1970 by Longuet, burglen, and modified by Barneyback (Barneyback et al., 1981) This technique is performed by placing the cement paste samples into a highly pressurized die system and applying a mechanical load of up to 550 MPa T he specimen is the n squeezed to remove the pore solution. The pore solution is collected in a small syringe for measuring its composition or resistivity (Barney back et al., 1981) It is recommended that the electri cal resistivity of the pore solution be measured immediately to avoid any potential for carbonation, evaporation ( Tsui Chang, M, 2017 ) or other change in the chemical composition Another experimental method for obtaining the pore solution conductivity is a pore solution electrical conductivity sensing system. The system consists of two sensors that are made from a porous material connected to electrodes on both ends as shown in Figure 2 4 The sensor is calibrated by using differe nt salt solution such as KOH, NaOH, and NaCL to account for the moisture and temperature effect and prior to placement,

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31 the sensor should be vacuum saturated, dried to 1% relative humidity and infiltrated by a 0.4 of KOH solution (R ajabipour et al., 2007) The sensors can then be placed inside a concrete specimen during casting The fluid conductivity inside the sensor should come to equilibrium with that of the concrete pore solution. The conductivity of the sensors inside the conc rete specimens can be used to determine the pore solution conductivity (Rajabipour et al., 2007) Figure 2 4 : The pore solution conductivity sensor (Photo credit: Raid Alrashidi) The p ore solution can be estimated by using a pore solution conductivity calculator, such as http://concrete.nist.gov/poresolncalc.html in which the procedure was originally described by Taylor (1987) This method estimate s the pore solution based on the mixture proportions, degree of hydration, and the alkali content of the cementations materials (Bentz, 2007) Even though this method allows for an estimate of the pore solution conductiv ity when it is impractical to measure it has some shortcoming s. This method ac count for the reaction of sulfate that occur early in the first 24 hours Some SCMs such as silica fume can bind alkalis. The calculator estimates that 75% of the total amount of alkali from the cement ( Na+, and K+ ), fly ash, slag, and silica fume are present after the first 24 hours in the pore solution (De La Varga et al., 2014) This

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32 is a great simplification, since silica fume can release bound alkalis into the pore solution at later ages (M. Thomas, Fournier, & Folliard, 2006) ac count for all the chemical composition of all the supplementary cementitious materials such as metakaolin or emerging SCMs 2.8.2 Extrinsic Factors 2.8.2.1 Specimen Geometry Many sample geometries have been used to measure the resistivity of concrete. The resistivity of concrete ( ) can be determined by measuring the electrical resistance ( R ) and applyi ng appropriate geometry factor ( K ) converts the resistance to a r e sistivity as shown in Equation 2 8 : ( 2 8) The correction factor to measure the resistivity can be calculated using the Equation 2 9 : ( 2 9 ) Where K 1 is the geometry factor, and d is the specimen diameter (cm) This geometry correction is only valid for specimens with d/ a and L/ a M any commercial surface resistivity meters such as the Proceq Resipod automatically applies the cor rection factor K 2 given in the Equation 2 10 : ( 2 10 ) In this case, the correction factor for the surface resistivity test should be calculate d using the following Equation 2 11 :

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33 ( 2 11 ) However, if the resistivity meter displays just the measured resistance, the corre ction factor should be calculated using the Equation 2 12 : ( 2 12 ) For bulk resistivity tests (two electrode method) in which the electrical current passes through the whole cylinder to measure the resistance the resis tivity can be calculated using E quation 2 7. 2.8.2.2 Specimen temperature The temperature variation of the sample has been reported to greatly influence the measured resistivity (Michelle, Adam, Xiaorong, & Douglas, 2017) (McCarter, Starrs, & Chrisp, 2000) The temperature can affect the flow of the electrical current through the ions dissolved in the pore so lution by changing the ion mobility as well as the ion concentration in concrete (Villagrn Zaccardi, Garca, Hulamo, & Di Maio, 2009) (R. B. Polder, 2001) Higher temperature increases the movement of ions into the pore solution of concrete and decreases the electrical resistivity measurements (R. Spragg, Villani, et al., 2013) Since the temperature plays an important role in the variation of the concrete resistivity measurements, it has been proposed to account for temperature variations (Liu & Presuel Moreno, 20 14) (Villagrn Zaccardi et al., 2009) (McCarter, Chrisp, Starrs, Basheer, & Blewett, 2005) by using the Arrhe nius law as shown in Equa tion 2 13 : ( 2 13 )

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34 Where T is m) T at temp ( ), 0 is the concrete m) at reference temp (typically 23 ), R is the universal gas constant, (8.314 J/mol.k) and E is the activation energy of conduction (KJ/mol) which represents the effect of the testing temperature. E is different than the activation energy of hydration that describes the effect of temperature on the hydration process (Coyle, Spragg, Suraneni, Amirkhanian, & Weiss, 20 18) If the temperature ranges between 22.7 to 24.4 the e ffect of the temperature is not significant as the temperature factor varies from 0.97 to 1.02 (Paredes et al., 2012) (Kamtornkiat Musiket; Mitchell Rosendahl; and Yunping Xi, 2016) (R. P. Spragg et al., 2012) Nevertheless, it is mentioned th at in the AASHTO standards for a standard curing condition the concrete sample s should always be tested at standard temperature 20 to 25 (68 to 77 ) (AASHTO, 2015) However, large temperature variations are typically noticed in practice, therefore, the correction should be made when required 2.8.2.3 Signal Frequency Due to high polarization effects on the electrod es when using direct current (DC) alternating current (AC) is used to measure the electrical resistivity o f concrete (R. Polder et al., 2000) (Gowers & Millard, 1999) For the electrical resistivity measurements, the two signal AC current shapes that frequently used are sine wave or square wave (Azarsa & Gupta, 2017) The impedance spectrum in general comprises of two arc s in the high and low frequency ranges. The characteristics of the impedance spectrum at high a nd low frequencies are mainly attributed to the microstructure of concrete and the conditions at the electrode concrete interface (Layssi, H, 2009) A frequency range of 0.5 to 10 kHz is usually used for the resistivity measureme nts in the

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35 uniaxial method; however, since there are many other factors that can affect the electrical resistivity of concrete such as environment conditions, there is no uniform optimum frequency across mixtures (Layssi, H, 2009) Resistivity values are generally overestimated at frequencies below 500 Hz because of the electrode concrete interface. Compared to the 1 kHz signal frequency, using a 40 Hz signal had a 9% higher measured resistivity. (Layssi, H, 2009) 2.9 Summary This chapter has presented a literature review about the electrical properties of concrete as they become popular method and a quality control indicator. RCP test has become an old method and since it has shortcomings, the surface and bulk resistivity have been used dramatically as a non destructive and for their simplicity. However, when measuring the electrical resistivity, several factors can affect the obtained results. These factors can be summarized and divided in to two group; th e first group is the intrinsic factors include the following: W/cm: a n increase in the w/cm results in a high percentage of porosity, higher pore fraction within the cement, thus it leads to lower electrical resistivity values (Rupnow & Icenogle, 2012) (Van Noort et al., 201 6) Aggregate size a nd type : electrical resistivity is higher for mixtures having large aggregate. Curing condition : the curing regimes can highly influence the resistivity measurements due to leaching. Therefore, sealed curing still the best option since it eliminates the le aching effect. Pore structure: pore solution analysis is significant for understanding the ongoing hydration reactions and interpreting electrical resistivity measurements. Pore solution expression, sensors to put inside the fresh concrete, and NIST calcul ator are the way to obtain and estimate the pore solution conductivity. The other group is the extrinsic factors include the following:

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36 Sample geometry: many commercial resistivity meters display the resistance not the resistivity and overestimate the ob tained measurements, therefore, applying the geometry factor must be taken into account to convert the resistance to resistivity. Sample temperature: as the temperature increases, they change the ion mobility in the pore solution leading to a decrease in t he resistivity measurements (R. Spragg, Villani, et al., 2013) Therefore to account for that, Arrheni us law can be used as shown in E quation 2 13. Electrode signal frequency: resistivity values are generally overestimated at frequencies below 500 Hz because of the electrode concrete interface In general, incorporation of SCMs can enhance concrete fresh properties such as workability, setting time, and heat of hydration, and its mechanical properties such as strength. Due to their pozzolanic reaction and the filling effect, they alter the pore solution, thus the permeability is lowered.

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37 CHAPTER 3 MA T ERIALS 3 HAPTER Four different types of cements were used in this project an ASTM C150 T ype I/II, T ype IV, T ype IL11, and a T ype I cement with a high alkali content ( HA ) (ASTM, 2017) These cements with different compositions were selected to address the effect of chemical composition on measured electrical properties of concrete. ASTM C 150 (ASTM, 2007 ) Type I/II cement is the most commonly used cement in Florida AS TM C150 (ASTM, 2007) T ype V cements with a C 3 A content of 2.2% was used. The Type IL ( 11 ) used has 11% limestone fillers interground with the cement in which the The h igh alkali (HA) c ement with a Na 2 O eq content of 0.86% was procured for use The cement chemical composition is presented in Table 3 1 Four different types of supplementary cementitious materials (SCMs) were used in this study, f ly a sh, s lag cement s ilica fume, and m etakaolin to assess their effects on the concrete electrical p roperties. All cements and fly ash chemi cal compositions were measured using a Rigaku Supermini x ray fluorescence (XRF) machine. The slag cement, silica fume, and metakaolin compositions were analyzed by CTL Group. The chemical composition of SCMs used in this study are presented in Table 3 1

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38 Table 3 1 : Cement and Supplementary Cementitious Mat erial Composition as Measured by XRF Material SiO2 TiO2 Al2O3 Fe2O3 MnO MgO CaO Na2O K2O P2O5 LOI wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% wt% Cement IL(11) 19.93 0.39 4.47 3.63 0.02 0.86 64.03 0.07 0.33 0.10 5.21 Cement type V 20.83 0.21 4.1 2 3.88 0.16 0.87 66.24 0.02 0.62 0.11 2.86 Cement type I/II 21.00 0.23 5.06 3.28 0.08 0.68 66.74 0.10 0.24 0.15 3.02 High alkali cement 20.56 0.21 4.55 3.78 0.09 3.06 63.65 0.29 0.87 0.12 2.68 Class F Fly Ash 48.59 1.00 19.49 19.68 0.04 0.84 5.08 0. 83 2.09 0.12 1.88 Slag 34.1 0.58 14.04 0.59 0.25 5.45 41.27 0.23 0.24 0.01 0.47 Silica fume 87.67 <0.01 0.34 0.89 0.09 6.71 0.63 0.75 0.99 0.10 3.12 Metakaolin 52.53 1.8 42.96 1.49 <0.01 0.18 <0.01 0.05 0.14 0.15 1.46

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39 3.1 Aggregates The aggregate used in this study were selected to be representative of FDOT mixtures and are compatible with the test requirements. The No. 57 coarse aggregate used was a Miami Oolite limestone. The specific gravity and absorption were measured according to ASTM C127 (ASTM, 2015a) as shown in Table 3 2 The fine aggregate used was a natural silica sand I ts specific gravity and absorption were meas ured according to ASTM C128 (ASTM, 2015b) as shown in Table 3 3 Table 3 2 : Coarse Aggregate Specific Gravity and Absorption Bulk specific gravity dry 2.29 Bulk specific gravity SSD 2.40 Apparent specific gravity 2.56 Absorption 4.66 % Table 3 3 : Fine Aggregate Specific Gravity and Absorption Relative Density (Specific Gravity) (Oven Dry) 2.599 Relative Density (Specific Gravity) (Saturated Surface Dry) 2.605 Apparent Relative Density (Specific Gravity) 2.614 Absorption 0.22 % 3.2 Mixtures Thirty eight different concrete mixtures were made for this study, including ternary and binary cementitious mixtures with water cementitious material s ratio (w /cm) of 0.35, and 0.44 Twenty two concrete mixtures were made with an ASTM C618 (ASTM, 2010a) Class F fly ash (FA) at a 10 or 20% equivalent weight replacement of p ortlan d cement. Ten concrete mixtures were made with an ASTM C989 (ASTM, 2013a) grade 120 slag cement (G) at 30, 45, 55 or 60 % eq uivalent weight replacement of p ortland cement. Nine concrete mixtures were made with an ASTM C1240 (ASTM,

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40 2012) compliant silica fume (S ) at 4, 6, or 8 % eq uivalent weight replacement of p ortland cement. Nine concrete mixtures were made with an ASTM C618 (ASTM, 2010a) Meta kaolin at 6, 8, or 10% equivalent weight replacement of Portland cement. Table 3 4 shows the mixture proportions used in this research.

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4 1 Table 3 4 : Mix proportions for concrete weight per yd 3 (LB ) Admixtures (ml) Mix No Mix ID W/C Cement Fine aggregate Coarse aggregate FA SF S MK AEA WRDA 60 ADVA 120 1 C 100 0.35 700 1184 1680 12.0 180.7 132.5 2 C 100h 0.44 700 1190 1552 6.0 6.0 0.0 3 C F10 0.35 630 1167 168 0 70 12.0 180.7 114.5 4 C F20 0.35 560 1150 1680 140 12.0 180.7 114.5 5 C F10h 0.44 630 1145 1552 70 6.0 6.0 0.0 6 C F20h 0.44 560 1130 1552 140 6.0 6.0 0.0 7 C G60 0.35 280 1175 1680 420 12.0 180.7 212.1 8 C S8 0.35 644 1 188 1680 56 12.0 180.7 132.5 9 C M10 0.35 630 1193 1680 70 12.0 180.7 132.5 10 C F10G30 0.35 420 1172 1680 70 210 12.0 180.7 132.5 11 C F10G45 0.35 315 1164 1680 70 315 12.0 180.7 132.5 12 C F10G60 0.35 210 1156 1680 70 420 12.0 180.7 183.7 13 C F10G60h 0.44 210 1140 1552 70 420 6.0 6.0 50.6 14 C F20S4 0.35 532 1161 1680 140 28 12.0 180.7 132.5 15 C F20S6 0.35 518 1157 1680 140 42 12.0 180.7 210.8 16 C F20S8 0.35 504 1152 1680 140 56 12.0 210.8 210.8 17 C F20 S8h 0.44 504 989 1680 140 56 12.0 180.7 0.0 18 C F20M6 0.35 518 1161 1680 140 42 12.0 180.7 210.8 19 C F20M8 0.35 504 1159 1680 140 56 8.4 210.8 241.0 20 C F20M10 0.35 490 1155 1680 140 70 6.0 210.8 277.1 21 C F20M10h 0.44 490 995 1680 140 70 12.0 90.4 99.4 22 C G55S8 0.35 259 1160 1680 56 385 12.0 180.7 198.8 23 C G55M10 0.35 245 1164 1680 385 70 12.0 180.7 210.8 24 CV 100 0.35 700 1185 1680 12.0 180.7 132.5 25 CV 100h 0.44 700 1190 1552 6.0 6.0 0.0 26 C V F10G60 0.35 210 1156 1680 70 420 12.0 180.7 132.5 27 CV F20S8 0.35 504 1153 1680 140 56 12.0 180.7 132.5 28 CV M10 0.35 630 1193 1680 70 12.0 180.7 132.5

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42 Table 3 4. Continued. weight per yd 3 (LB ) Admixtures (ml) Mix No Mix ID W/C C ement Fine aggregate Coarse aggregate FA SF S MK AEA WRDA 60 ADVA 120 29 CL 100 0.35 700 1184 1680 12.0 180.7 132.5 30 CL 100h 0.44 700 1165 1552 6.0 6.0 0.0 31 CL F10G60 0.35 210 1156 1680 70 420 12.0 180.7 132.5 32 CL F20S8 0.35 5 04 1152 1680 140 56 12.0 180.7 132.5 33 CL M10 0.35 630 1192 1680 70 12.0 180.7 241.0 34 CHA 100 0.35 700 1184 1680 12.0 180.7 132.5 35 CHA 100h 0.44 700 1165 1552 6.0 6.0 0.0 36 CHA F10G60 0.35 210 1156 1680 70 420 12.0 1 80.7 132.5 37 CHA F20S8 0.35 504 1152 1680 140 56 12.0 180.7 132.5 38 CHA M10 0.35 630 1192 1680 70 12.0 180.7 241.0

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43 CHAPTER 4 METHODOLOGY 4 CHAPTER 4.1 Concrete Methodology Cylinders used for measuring concrete electrical properties were made acc ording ( ASTM, 2016) All concrete batches were made in the concrete mixing facilities at the University of Florida (UF). 4.2 Concrete Mixing Three days prior to mixing, the coarse aggrega te was soaked in a water tub and the fine aggregate was oven dried at 230F (110C). One day prior to mixing, all the materials includ ing aggregates and cementitious materials were weighed and sealed using 5 gallon buckets. On the day of mixing, the mixer was rinsed with water to clean it and then buttered with fine aggregates, cement and water to compensate for mortar loss when the fresh concrete wa s discharged from the mixer. After that, the coarse and fine aggregate were added to the mixer and mixed for 30 seconds. While the mixer was running, the cementitio u s materials and more than half of the mixing water were added. Chemical admixtures and the remaining water were added gradually over about 1 minute. The total mixing time for adding all the materials was 3 minutes, followed by a 3 minute rest, and by mixing for 2 additional minutes. After the mixing was done, the fresh concrete properties were measured. 4.3 Fresh Concrete Properties Standard concrete fresh quality control tests were performed Concrete slu mp (ASTM, 2015c) as shown in Figure 4 1 The slump was maintained

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44 between 2 and 8 in. ( 51 and 203 mm). Measured concrete fres h properties are shown in Table 4 1 Figure 4 1 : Determination of slump (Photo credit: Raid Alrashidi) The unit weight test is used to measure the density of fresh concrete for qua lity control purposes and can help pick up problems with incorrect ingredients or air content. (ASTM, 2013b) as shown in Figure 4 2 Figure 4 2 : Determination of unit weight (Photo credit: Raid Alrashidi)

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45 Table 4 1 : Measured concrete fresh properties Mix No Mix ID W/C Slump, in (mm) Air (%) Unit weight, lb/ft3 (kg/m3) Mix Temp, F (C) 1 C 100 0.35 6 (152) 3.00% 144 (2310) 74.3 (23.5) 2 C 100h 0.44 7 (165) 2.00% 142 (2280) 74.5 (23.6) 3 C F10 0.35 4 (102) 3.00% 144 (2303) 74.5 (23 .6) 4 C F20 0.35 6 (140) 4.00% 141 (2259) 75.2 (24) 5 C F10h 0.44 8 (191) 3.00% 142 (2272) 72.5 (22.5) 6 C F20h 0.44 8 (203) 3.50% 142 (2269) 72.7 (22.6) 7 C G60 0.35 5 (127) 2.00% 146 (2331) 72.1 (22.3) 8 C S8 0.35 2 (51) 3.80% 142 (2277) 72.3 (22.4) 9 C M10 0.35 3 (64) 2.80% 144 (2302) 72.7 (22.6) 10 C F10G30 0.35 5 (127) 4.50% 141 (2266) 73.4 (23) 11 C F10G45 0.35 6 (140) 3.10% 142 (2271) 72 (22.2) 12 C F10G60 0.35 8 (203) 2.50% 142 (2276) 71.8 (22.1) 13 C F10G60h 0.44 6 (152) 2.80% 140 (2249) 72.7 (22.6) 14 C F20S4 0.35 2 (51) 3.00% 143 (2284) 74.8 (23.8) 15 C F20S6 0.35 3 (64) 3.40% 142 (2282) 75.4 (24.1) 16 C F20S8 0.35 6 (152) 5.00% 141 (2262) 74.1 (23.4) 17 C F20S8h 0.44 6 (152) 1.60% 140 (2244) 72.1 (22.3) 18 C F20M6 0.35 4 (102) 3.40 % 141 (2252) 73.8 (23.2) 19 C F20M8 0.35 2 (51) 4.00% 144 (2305) 73.8 (23.2) 20 C F20M10 0.35 2 (51) 2.50% 145 (2316) 73.6 (23.1) 21 C F20M10h 0.44 6 (152) 2.00% 141 (2261) 73.9 (23.3) 22 C G55S8 0.35 3 (64) 3.50% 140 (2240) 72.5 (22.5) 23 C G55M10 0. 35 2 (51) 2.50% 140 (2240) 72.7 (22.6) 24 CV 100 0.35 3 (64) 2.75% 144 (2309) 74.7 (23.7) 25 CV 100h 0.44 6 (152) 1.50% 140 (2249) 75.4 (24.1) 26 CV F10G60 0.35 7 (178) 3.00% 142 (2278) 71.8 (22.1) 27 CV F20S8 0.35 4 (89) 4.50% 140 (2240) 73 (22.8) 28 CV M10 0.35 3 (70) 3.10% 142 (2267) 72.7 (22.6) 29 CL 100 0.35 4 (108) 3.50% 141 (2258) 76.5 (24.7) 30 CL 100h 0.44 5 (114) 4.00% 140 (2239) 76.8 (24.9) 31 CL F10G60 0.35 5 (127) 3.20% 142 (2277) 71.6 (22) 32 CL F20S8 0.35 3 (64) 4.00% 139 (2228) 75.6 (24.2) 33 CL M10 0.35 2 (38) 2.70% 144 (2307) 75.2 (24) 34 CHA 100 0.35 3 (83) 3.00% 143 (2284) 75 (23.9) 35 CHA 100h 0.44 7 (184) 2.80% 142 (2269) 75.6 (24.2) 36 CHA F10G60 0.35 5 (114) 3.20% 141 (2255) 71.8 (22.1) 37 CHA F20S8 0.35 3 (64) 4.00% 140 (2239) 74.8 (23.8) 38 CHA M10 0.35 2 (51) 2.50% 140 (2239) 74.7 (23.7)

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46 ( ASTM 2010b) as shown in Figure 4 3 Figure 4 3 : Determination of air content (Photo credit: Raid Alrashidi) The concrete fresh temperature was measured according to ASTM C1064 of Freshly Mixed Hydraulic (ASTM, 2004) as shown in Fi gure 4 4 Since the concrete mixtures were all mixed in a temperature controlled laboratory, the concrete temperature measured was between 71.6 and 75.6F (22 and 24.2C). Fi gure 4 4 : Concrete Temperature Measurement (Photo credit: Raid Alrashidi)

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47 4.4 Concrete Specimen Preparation After measuring the fresh concrete properties, 4 8 in. (100 200 mm) concrete cylinders were made acc ording to ASTM C192 procedure (ASTM, 2016) The concrete was placed into the cylinder molds in two equal layers as shown in Figure 4 5 The concrete samples were consolidated using vibration from a vibrating table. After the concrete was placed in the cy linder molds, they were finished and capped to prevent moisture loss during the f irst 24 hours after mixing. Figure 4 5 : Cylinders after filled with the first layer of concrete (Photo credit: Raid Alrashidi ) 4.5 Concrete Curing The concrete specimens were removed from molds 24 8 hours after mixing. All but three samples from each mixture were stored in a moist curing room until the y were ready for testing or further sample preparation. The moist curing room wa s kept between 70 and 77F (21 and 25C) and above 95% relative humidity.

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48 4.6 Simulated Pore Solution (SPS) Curing Method After demolding, three concrete specimens were chosen to put in a sealed container. The NIST calculator developed by Bentz and available a t ( http://concrete.nist.gov/poresolncalc.html ) was used to estimate the electrical conductivity (S/m) (inverse of the resistivity) of the concrete pore solution for each mixture. The material oxid e composition measured for each material using x ray fluorescence and given in Table 3 1 was used in the calculations. T he system degree of hydration was estim ated to be 70% in the calculations Since use of metakaolin was not an option in the calculator, and the content of K 2 O and Na 2 O for metakaolin was close to that of slag, the slag option was used instead. Therefore, after getting all the information from the calculator, the specimens were placed into six liters of a NaOH and KaOH solution in a 5 gallon bucket and sealed, as shown in Figure 4 6 A minimum of three grams per liter of Ca(OH) 2 was added to prevent calcium hydroxide leaching of the species. After that, the container was stored in a moist c uring room to maintain the temperature until they are ready for testing. On the day of testing, the surface and bulk resistivity measurements were taken, as well as the pore solution conductivity was taken by using an Oakton PC700 Meter as shown in Figure 4 7

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49 Figure 4 6 : The specimens were placed in a sealed container (Photo credit: Raid Alrashidi) Figure 4 7 : Oakton PC700 Meter (P hoto credit: Raid Alrashidi) 4.7 Electrical Tests 4.7.1 Surface Resistivity Concrete surface resistivity was measured in this project according to AASHTO T358 (AASHTO, 2011) A Proceq Resipod surface resistivity meter was used in this project, as shown in Figure

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50 4 8 The specimen holder used to mark specimen points for measurement is shown in Figure 4 9 Figure 4 8 : Surface resistivity meter used in this study (Photo credit: Raid Alrashidi) Figure 4 9 : Specimen holder used in this study (Photo credit: Raid Alrashidi) Immediately after demolding the concrete cylinders, three specimens were chosen to be used for surface resistivity testing. Four marks were made at 0, 90, 180, and 270 degree points around the circumference of the samples before the samples were placed in the fog room. On the day of testing, the samples were removed from the fog room, and kept saturated during the test ing time. The cylinder was then laid on the

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51 top of the holder and four measurements were taken around the circumference of the cylinder at 90 degree increment s with the resistivity meter as shown in Figure 4 10 This process was repeated to get the average for the eight total readings. After all the readings were taken for the three specimens, they were kept saturated to perform the bulk resistivity test. Figure 4 10 : Surface resi stivity measurement (Photo credit: Hossein Mosavi) 4.7.2 Bulk Resistivity This concrete bulk resistivity was measured according to AASHTO TP 119 (AASHTO, 2015) to provide a rapid indication of concrete mixture potential durability. The difference between bulk and surface resistivity tests is with bulk resistivity, the electrical current passes along the height (bulk) of the cylinder, while with the surface resistivity, the electrical current passes across the outer probes of the Wenner probe. Prior to testing, the concrete specimen end faces were ground with a grinding machine per (ASTM, 2013c) as shown in Figure 4 11 To measure the concrete bulk

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52 resistivi ty, the plates were attached to the probe tips of the surface resistivity meter. Every two probe tips were connected to one plate. The sponges were saturated, and their resistance was recorded to provide a correction for their resistance as described in E e was placed on the bottom plate, and the top sponge was placed on the top plate. After that, the concrete specimen was placed between the plates and the reading was taken as shown in Figure 4 12 the cylinder was taken using an infrared thermometer. These steps were performed for the other two specimens and the specimens were then placed back into the fog room until the next testing age. Figure 4 11 : Grinding samples for bulk resistivity measurement (Photo credit: Raid Alrashidi) Figure 4 12 : Bu lk resistivity test (Photo credit: Hossein Mosavi)

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53 CHAPTER 5 RESULTS AND DISCUSSION 5 CHAPTER 5.1 Introduction Thirty eight different concrete mixtures were made for this project including four types of cements and four types of SCMs materials. All samples made to measure concrete electrical resistivity properties were cured using one of two methods, moist room curing or simulated pore solution (SPS). In this study, measurements were taken at 28 days, 56 days, and 91 days to see the effect of w/c ratio, incorpor ation of SCMs, and curing me thods on the electrical properties of concrete. 5.2 Pore Solution Conductivity Based on the mix proportion and the chemical composition, the N IST pore solution c alculator was used to estimate the pore solution composition and elect rical conductivity for each mixture made In addition to measuring the solution conductivity when made, it was measured at 28, 56, and 91 days in the bucket used for curing using an Oakton PC700 Meter as shown Figure 4 7 Immediat ely before measuring the conductivity, the solution was agitated slightly to have a homogenous solution. The conductivity readings for all mixes are presented in Table 5 1 The readings indicate that for most of the mixes, the con ductivity readings are less than the estimated readings by NIST calculator and it was noticed the readings were decreased with time due to the small variability in temperature and leaching.

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54 Table 5 1 : Por e solution conductivity readings SPS readings for pore solution Conductivity S/m Mix # Mix ID NIST pore solution S/m 28 days 56 days 91 days 1 C 100 69.6 69.70 69.40 69.50 2 C 100h 48.7 53.00 52.80 53.30 3 C F10 115.8 73.70* 71.70* 71.00* 4 C F 20 158.8 72.50* 70.90* 71.00* 5 C F10h 81.8 77.80 77.60 77.00 6 C F20h 112.9 111.20 109.10 102.50 7 C G60 29.9 84.70* 85.70* 84.90* 8 C S8 73.7 71.90 70.80 70.40 9 C M10 63.2 61.70 60.10 58.80 10 C F10G30 98.2 97.50 97.10 96.30 11 C F10G45 89.2 87.2 0 87.10 87.30 12 C F10G60 89.9 88.40 88.00 87.30 13 C F10G60h 56.2 55.20 54.10 53.60 14 C F20S4 149.9 140.7 139.4 138.6 15 C F20S6 145.6 138 138.4 137.6 16 C F20S8 141.5 137.8 136.9 135.2 17 C F20S8h 100.4 91.20 86.30 82.60 18 C F20M6 155.5 118.7 11 6.7 111.7 19 C F20M8 154.4 145.8 145.5 142.7 20 C F20M10 153.3 142.3 142.1 141.9 21 C F20M10h 108.9 103.00 92.80 91.30 22 C G55S8 47.1 44.80 44.10 44.30 23 C G55M10 26.4 27.10 26.90 27.20 24 CV 100 113.9 111.10 111.20 109.20 25 CV 100h 80.4 78.80 79 .00 78.70 26 CV F10G60 93.4 92.00 91.30 88.50 27 CV F20S8 163.3 158.50 155.50 151.00 28 CV M10 103.7 100.10 96.00 92.00 29 CL 100 77.4 78.50 79.20 79.10 30 CL 100h 54.3 53.60 53.80 53.50 31 CL F10G60 82.3 80.90 81.50 80.50 32 CL F20S8 145.2 139.00 1 33.90 136.20 33 CL M10 70.3 68.80 66.30 68.40 34 CHA 100 205.1 201.30 201.00 200.60 35 CHA 100h 146.6 145.90 144.50 144.80 36 CHA F10G60 122.9 121.20 120.90 119.80 37 CHA F20S8 210.8 192.30 183.60 176.60 38 CHA M10 187.4 177.30 174.20 174.70

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55 5.3 Correla tion between Surface and Bulk Resistivity The correlations of surface and bulk resistivity readings that were obtained at 28, 56, and 91 days for the moist room and SP S curing are presented in table form in Appendix A T he resistivity readings increased wi th time for samples cured in the moist curing room for both tests due to continued hydration and leaching. F or samples cured in SPS however any increase in time was highly dependent on the mixture type and pore solution, and will be discussed in more deta ils in sections 5.5 and 5.6. For moist room and SPS curing. The bulk and surface resistivity measurements correlated very well with each othe r, as shown in Figure 5 1 and Figure 5 2 The relationship bet ween the surface resistivity tests for both curing methods is shown in Figure 5 3 Figure 5 4 shows the relationship between the bulk resistivity tests for both curing methods as well. Mixtures 22 and 23 containing 55% slag cement and silica fume or metakaolin showed much higher surface and bulk resistivity when cured with SPS than the trend found would have suggested, suggesting leaching in mixtures 22 and 23 when cured in the SPS. The lowest predicted po re solution conductivities for mixtures 7, 22 and 23. All three of these mixtures contained 55 or 60 percent slag cement without fly ash. Mixture 7 however was cured with a higher than predicted SPS conductivity and did not show the higher resistivity than the trend would predict with SPS curing, giving credence to this hypothesis. The bulk resistivity tests showed a better relationship between both curing methods due to less variation in the readings and issues with leaching.

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56 Figure 5 1 : SR vs BR at all ages (moist room) Figure 5 2 : SR vs BR at all ages (SPS) y = 0.62x R = 0.97 0 10 20 30 40 50 60 70 80 0 20 40 60 80 100 120 140 BR Moist room (K cm) SR Moist room (K cm) y = 0.92x R = 0.84 0 10 20 30 40 0 10 20 30 40 50 BR SPS (K cm) SR SPS (K cm)

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57 Figure 5 3 : SR (moist room) vs SR (SPS) readings for all ages Figure 5 4 : BR (moist room) vs BR (SPS) readings for all ages 5.4 Formation Factor In this study, the formation factor was obtained from the bulk resistivity measurements and pore solution condu ctivity using the estimated pore solution conductivity from NIST calculator and measured SPS conductivity, assuming R = 0.5385 R = 0.5096 R = 0.5199 0 5 10 15 20 25 30 35 40 45 0 20 40 60 80 100 120 140 SR SPS (K cm) SR Moist room (K cm) 28 days 56 days 91 days R = 0.8107 R = 0.8424 R = 0.8402 0 5 10 15 20 25 30 35 40 0 20 40 60 80 BR SPS (K cm) BR Moist room (K cm) 28 days 56 days 91 days

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58 equilibrium with the concrete. Table 5 2 shows the calculated formation factor for each age using the NIST calculated pore solution values for both curing methods, while Table 5 3 shows the formation factor calculated using the measured SPS conductivity values and bulk resistivity values for SPS cured samples. The mixes that were placed in the moist room exhibited a higher formation factor due to leaching impacts. Based on the results, the formation factor increases for all mixes as the time passes, and the mixes that contain 20% of fly ash and 8% of silica fume including high alkali cement (CHA F20S8) exhibited the highest formation factor amongst the mixes performed, in which higher formation factor indicates less porous concrete and lower connectivity. The ratio of the formation factor for both different curin g is 1.96 and it increases with time. Figure 5 5 shows the formation factor for all ages indicating there a good correlation between both curing methods. Figure 5 5 : Formation fact or (moist room) vs SPS curing methods R = 0.874 R = 0.8833 R = 0.8772 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 0 500 1000 1500 2000 2500 3000 Formation factor (moist room) Formation factor (SPS) 28-day 56-day 91-day

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59 Table 5 2 : Formation factor from NIST for moist curing room and SPS Mix NO Mix ID N IST Calc. Formation Factor f rom NIST for SPS curing Formation Factor from NIST for mo ist curing room 28 day 56 day 91 day 28 day 56 day 91 day 1 C 100 69.6 316 359 373 480 672 750 2 C 100h 48.7 142 169 172 211 279 381 3 C F10 115.8 466 644 851 738 1119 1444 4 C F20 158.8 676 1136 1615 1067 1879 2445 5 C F10h 81.8 234 297 369 433 507 728 6 C F20h 112.9 334 534 838 568 892 1581 7 C G60 29.9 339 516 540 680 980 1178 8 C S8 73.7 843 1268 1394 1393 2250 2549 9 C M10 63.2 871 991 1185 1377 1773 2014 10 C F10G30 98.2 714 1105 1339 1319 1890 2257 11 C F10G45 89.2 831 1160 1524 1828 2304 2693 12 C F10G60 89.9 1382 1393 1552 2097 2904 3327 13 C F10G60h 56.2 626 1037 1042 1339 1808 2356 14 C F20S4 149.9 1354 1559 2167 2399 3754 4927 15 C F20S6 145.6 1601 1953 2472 3348 4859 6219 16 C F20S8 141.5 1280 1670 2133 2684 4714 6106 17 C F20S8h 100.4 739 1126 1301 1418 2300 2956 18 C F20M6 155.5 1213 1587 2157 2363 3776 4679 19 C F20M8 154.4 1473 1403 1801 2963 3940 4845 20 C F20M10 153.3 1632 1498 1670 3315 4834 5135 21 C F20M10h 108.9 877 1257 1376 1860 2545 3508 22 C G55S8 47.1 107 7 1432 1572 1332 2393 3284 23 C G55M10 26.4 678 846 899 856 1373 1713 24 CV 100 113.9 424 459 472 703 1002 1019 25 CV 100h 80.4 190 246 226 330 440 488 26 CV F10G60 93.4 1314 1524 1526 2035 3262 3438 27 CV F20S8 163.3 1882 2195 2318 3831 5337 7776 28 CV M10 103.7 972 1076 1241 2288 2485 3276 29 CL 100 77.4 280 346 345 536 712 846 30 CL 100h 54.3 120 162 179 215 327 402 31 CL F10G60 82.3 1191 1470 1524 2852 4086 4231 32 CL F20S8 145.2 1567 2413 2177 2768 4632 5896 33 CL M10 70.3 1200 1055 1075 176 4 2019 2272 34 CHA 100 205.1 501 735 660 1110 1582 2135 35 CHA 100h 146.6 275 416 422 491 731 968 36 CHA F10G60 122.9 1317 1845 1793 2841 4006 4672 37 CHA F20S8 210.8 1985 2558 2430 5075 7686 9089 38 CHA M10 187.4 2212 1796 1668 4551 4962 5756

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60 Table 5 3 : Formation factor from measured pore solution conductivity Mix No Mix ID NIST Calc. Formation Factor from measured SPS conductivity 28 day 56 day 91 day 1 C 100 69.6 316 358 372 2 C 100h 48.7 155 1 84 188 3 C F10 115.8 297 399 522 4 C F20 158.8 309 507 722 5 C F10h 81.8 222 282 347 6 C F20h 112.9 329 516 761 7 C G60 29.9 961 1478 1532 8 C S8 73.7 822 1218 1332 9 C M10 63.2 851 942 1102 10 C F10G30 98.2 709 1092 1313 11 C F10G45 89.2 813 1133 1492 12 C F10G60 89.9 1359 1363 1507 13 C F10G60h 56.2 615 998 993 14 C F20S4 149.9 1271 1450 2003 15 C F20S6 145.6 1517 1856 2337 16 C F20S8 141.5 1246 1616 2038 17 C F20S8h 100.4 671 968 1071 18 C F20M6 155.5 926 1191 1550 19 C F20M8 154.4 1391 1322 1664 20 C F20M10 153.3 1515 1388 1546 21 C F20M10h 108.9 830 1071 1153 22 C G55S8 47.1 1025 1341 1478 23 C G55M10 26.4 696 862 926 24 CV 100 113.9 413 449 453 25 CV 100h 80.4 186 241 221 26 CV F10G60 93.4 1295 1490 1446 27 CV F20S8 163.3 1827 2090 2143 28 CV M10 103.7 938 996 1101 29 CL 100 77.4 283 355 352 30 CL 100h 54.3 118 160 176 31 CL F10G60 82.3 1171 1456 1491 32 CL F20S8 145.2 1500 2225 2042 33 CL M10 70.3 1175 995 1046 34 CHA 100 205.1 492 720 646 35 CHA 100h 146.6 274 410 417 36 CHA F10G60 122.9 1298 1815 1748 37 CHA F20S8 210.8 1811 2228 2036 38 CHA M10 187.4 2093 1670 1555

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61 5.5 Effect of w / c m Ratio o n Surface and Bulk Resistivity In order to study the effect of w/c ratio on the surface resistivity, some binary and ternary mixe s were made with the same materials at different w/cm, 0.35 and 0.44. The surface resistivity of concrete specimens was measured at 28, 56 and 91 days for both curing environments. The surface resistivity readings for the control mixes of the four types of cement, and binary and ternary mixtures for the samples cured in the moist room is shown in Figure 5 6 Figure 5 7 respectively. As expected as the w/cm increase, the resi stivity measurements decreases. For all types of cement, the resistivity increased by 20% from 28 days to 91 days, except for type 1L which only increase by 12%, indicating that the effect of limestone filler, which makes the concrete more resistant. A sim ilar trend was seen for the sample cured in SPS as moist room curing as shown Figure 5 10 and Figure 5 11 However, the two mixes that have 20%fly ash and 8% silica fume C F20S8, and 20% fly ash with 10% Metakaolin C F20M10 showed slightly showed almost no difference bet ween the low and high w/c ratio This might be because of alkali migration into the concrete, as the bulk resistivity measurements for C F20S8 had higher va lues with the lower w/cm as expected as shown in Figure 5 11 and Figure 5 13 .The C F20M10 had slightly higher values at the higher w/cm, but still within the range of acceptable results of multiple opera tors (R. P. Spragg et al., 2012) In general, for the bulk resistivity test, for the majority of the mixes, there were an increase in the resistivity over time on average of 28% for the control mixes, and 71% for the binary and ternary m ixes as shown in Figure 5 12 and Figure 5 13

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62 Figure 5 6 : Effect of w/cm on the control mixes (moist room) Figure 5 7 : Effect of w/cm on ternary and binary mixes (moist room) 0 2 4 6 8 10 12 14 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-100 C-100h CV-100 CV-100h CL-100 CL-100h CHA-100 CHA-100h Surface resistivity K cm w/cm 28 days 56 days 91 days 0 10 20 30 40 50 60 70 80 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-F10 C-F10h C-F20 C-F20h C-F10G60 C-F10G60h C-F20S8 C-F20S8h C-F20M10 C-F20M10h Surface resistivity K cm w/cm 28 days 56 days 91 days

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63 Figure 5 8 : Effect of w/cm on the control mixes (moist room) Figure 5 9 : Effect o f w/cm on ternary and binary mixes (moist room) 0 2 4 6 8 10 12 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-100 C-100h CV-100 CV-100h CL-100 CL-100h CHA-100 CHA-100h Bulk resistivity K cm w/cm 28 days 56 days 91 days 0 5 10 15 20 25 30 35 40 45 50 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-F10 C-F10h C-F20 C-F20h C-F10G60 C-F10G60h C-F20S8 C-F20S8h C-F20M10 C-F20M10h Bulk resistivity K cm w/cm 28 days 56 days 91 days

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64 Figure 5 10 : Effect of w/cm on the control mixes (SPS) Figure 5 11 : Effect of w/cm on ternary and binary mix es (SPS) 0 2 4 6 8 10 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-100 C-100h CV-100 CV-100h CL-100 CL-100h CHA-100 CHA-100h Surface resistivity K cm w/c 28 days 56 days 91 days 0 2 4 6 8 10 12 14 16 18 20 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-F10 C-F10h C-F20 C-F20h C-F10G60 C-F10G60h C-F20S8 C-F20S8h C-F20M10 C-F20M10h Surface resistivity K cm w/cm 28 days 56 days 91 days

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65 Figure 5 12 : Effect of w/cm on the control mixes (SPS) Figure 5 13 : Effect of w/cm on ternary and binary mixes (SPS) 0 1 2 3 4 5 6 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-100 C-100h CV-100 CV-100h CL-100 CL-100h CHA-100 CHA-100h Bulk resistivity K cm w/cm 28 days 56 days 91 days 0 2 4 6 8 10 12 14 16 18 20 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 0.35 0.44 C-F10 C-F10h C-F20 C-F20h C-F10G60 C-F10G60h C-F20S8 C-F20S8h C-F20M10 C-F20M10h Bulk resistivity (K cm) w/cm 28 days 56 days 91 days

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66 5.6 Effect o f S CMs o n Surface a nd Bulk Resistivity In order to study the effect of SCMs including fly ash, slag, silica fume, and m etakaolin on the surface and bulk resistivity tests most of the binary and ternary mixes were performed with low w/cm (0.35) since these mixtures are typic ally used in extremely aggressive environments 5.6.1 Fly Ash The surface resistivity readings for the mixes that contain a 10% and 20% of fly ash as well as the resistivity reading for the control mix as a comparison are discussed in this section Compared to the control mixture the fly ash did not affect the resistivity readings at age 28 days, this is due to the slow hydration process of fly ash. However, as the percentage of fly ash increased, the resistivity increased with time. Figure 5 14 presen ts also the surface resistivity readings for the moist room and SPS curing method. A similar trend was seen as the moist room for the readings here, which is th at th e fly ash did not affect the resistivity readings at age 28 days. With 20 % fly ash, the resistivity increased by 125% in the moist room, but only 73% in SPS between 28 and 91 days The control mixture increased by 22% from 28 to 91 days in the moist room, compared to only 13% in SPS. This suggests that 60 70% of the increases in resistivity readings typically seen with time in moist room cured samples could be from leaching. The bulk resistivity readings for both curing is shown in Figure 5 15 which it has almost identical trend as the surface resisti vity trend for both curing method. This supports that these tests correlate well with each other.

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67 Figure 5 14 : Effect of fly ash on surface resistivity readings (moist room and SPS) Figure 5 15 : Effect of fly ash on bulk resistivity readings (moist room and SPS) 0 5 10 15 20 25 30 0 5 10 15 20 25 Surface Resistivity (K cm) Fly ash(%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS 0 2 4 6 8 10 12 14 16 18 0 5 10 15 20 25 Bulk Resistivity (K cm) Fly ash (%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS

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68 5.6.2 Slag This section present s the surface resistivity readings for the mixes that containing a fixed 10% of fly ash, and 30%, 45% and 60% of slag a s well as the resistivity reading for the control mix as a comparison. Compared to the control, as the percentage of slag increased, the resistivity increased significantly The mixtures containing 60% slag with and without 10% fly ash showed very similar resistivity values at all ages, indicating that the fly ash had a very low degree of reaction even at 91 days, probably because of the low clinker content and calcium hydroxide consumption by the faster reacting slag mixture. Figure 5 16 presen ts the surface resistivity readings for the moist room and SPS curing method A s the percentage of slag increased, the resistivity was significantly higher than control. No significant increase in surface resistivity was seen with time for the mixtures containing slag and cured in SPS, in contrast to the increase seen in bulk resistivity as shown in Figure 5 17 This could be because of the higher effect of leaching.

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69 Figure 5 16 : Effect of slag cement on surface resistivity readings (moist room and SPS) Figure 5 17 : Effect of slag cement on bulk resistivity readings (moist room and SPS) 5.6.3 Silica Fume T he surface and bul k resistivity readings for the mixes that contain ed 20% fly ash and silica fume is shown in Figure 5 18 and Figure 5 19 respectively for samples cured 0 10 20 30 40 50 60 70 0 10 20 30 40 50 60 70 Surface Resistivity (K cm) Slag(%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 50 60 70 Bulk Resistivity (K cm) Slag (%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS

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70 in moist room and SPS The results showed that the u se of silica fume above 6% did not further increase the surface or bulk resistivity in either curing method for ternary blends. It is possible that ternary mixtures currently being used could be economized by limiting the silica fume content, while providi ng similar or even improved durability. The surface resistivity values for the mixtures containing 20% fly ash and 8% of silica fume for each of the four cement s used is shown in Figure 5 20 for samples cured in the moist room and Figure 5 21 for samples cured in SPS. Similar increases in surface resistivity were seen with time for each cement used when the samples were cured in the fog room. When the samples were cured in SPS however, the little change wa s seen with age in the surface resistivity even though increases were seen in the bulk resistivity, as shown in Figure 5 22 and Figure 5 23 This was likely caused by alkal i diffusion into the sample surface, altering the pore solution composition and reducing the surface resistivity. This illustrates the advantages of the bulk resistivity test method over the surface resistivity test method. Figure 5 18 : Effect of silica fume on surface resistivity readings (moist room and SPS) 0 10 20 30 40 50 60 70 80 0 2 4 6 8 10 Surface Resistivity (K cm) Silica fume(%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS

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71 Figure 5 19 : Effect of silica fume on bulk resistivity readings (moist room and SPS) Figure 5 20 : Effect of fly ash and silica fume on the different types of cement (moist room) 0 5 10 15 20 25 30 35 40 45 50 0 2 4 6 8 10 Bulk Resistivity (K cm) Silica fume (%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS 0 10 20 30 40 50 60 70 80 0.35 0.35 0.35 0.35 C-F20S8 CV-F20S8 CL-F20S8 CHA-F20S8 Surface Resistivity (K cm) 28 days 56 days 91 days

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72 Figure 5 21 : Effect of fly ash and silica fume on the different types of ce ment (SPS) Figure 5 22 : Effect of silica fume on the different types of cements (moist room) 0 2 4 6 8 10 12 14 0.35 0.35 0.35 0.35 C-F20S8 CV-F20S8 CL-F20S8 CHA-F20S8 Surface resistivity K cm 28 days 56 days 91 days 0 5 10 15 20 25 30 35 40 45 50 0.35 0.35 0.35 0.35 C-F20S8 CV-F20S8 CL-F20S8 CHA-F20S8 Bulk resistivity K cm 28 days 56 days 91 days

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73 Figure 5 23 : Effect of silica fume on the different types of ce ments (SPS) 5.6.4 Metakaolin Th e surface and bulk resistivity readings for the mixes that contain ed 20% fly ash and 6%, 8% or 10% of m etakaolin is shown in Figure 5 24 and Figure 5 25 respectively The results reveal that the surface resistivity increased with time by 70%, 54%, and 39% for the partial replacement of cement by 6%, 8%, and 10% of metakaolin respectively Subsequently, similar to silica fume in ternary blends, ther e was little long term benefit to using more than 6% metakaolin in the concrete mixture. The metakaolin reacts faster than the fly ash, and likely consumes significant amounts of calcium hydroxide (Olufemi, 2013) The concrete likely reaches a point where the SCMs become calcium hydroxide limited, reducing the rate of reaction and limiting the benefits of higher dosages. A comparison of mixes that contain 10% of Meta kaolin t o the control mixes of the four different types of cement used is shown in Figure 5 26 and Figure 5 27 for the surface resistivity readings. For the bulk resistivit y, the readings are shown in Figure 5 28 0 2 4 6 8 10 12 14 16 0.35 0.35 0.35 0.35 C-F20S8 CV-F20S8 CL-F20S8 CHA-F20S8 BR K cm 28 days 56 days 91 days

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74 and Figure 5 29 Metakaolin provided a significant increase in the resistivity for all cements in which it can be seen that there is no noticeable differences in the resistivity readings among the different type s of cements especially for fog room curing. Figure 5 24 : Effect of metakaolin on surface resistivity readings (moist room a nd SPS) Figure 5 25 : Effect of metakaolin on bulk resistivity readings (moist room and SPS) 0 10 20 30 40 50 60 0 2 4 6 8 10 12 Surface Resistivity (K cm) Metakaolin(%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS 0 5 10 15 20 25 30 35 40 0 2 4 6 8 10 12 Bulk Resistivity (K cm) Metakaolin (%) 28 days 56 days 91 days 28 days SPS 56 days SPS 91 days SPS

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75 Figure 5 26 : Effect of metakaolin on the control mixes (moist room) Figure 5 27 : Effect of metakaolin on the control mixes (SPS) 0 10 20 30 40 50 60 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 C-100 C-M10 CV-100 CV-M10 CL-100 CL-M10 CHA-100 CHA-M10 Surface resistivity K cm 28 days 56 days 91 days 0 5 10 15 20 25 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 C-100 C-M10 CV-100 CV-M10 CL-100 CL-M10 CHA-100 CHA-M10 Surface resistivity K cm 28 days 56 days 91 days

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76 Figure 5 28 : Effect of metakaolin on the control mixes (moist room) Figure 5 29 : Effect of metakaolin on the control mixes (SPS) 0 5 10 15 20 25 30 35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 C-100 C-M10 CV-100 CV-M10 CL-100 CL-M10 CHA-100 CHA-M10 Bulk resistivity K cm 28 days 56 days 91 days 0 2 4 6 8 10 12 14 16 18 20 0.35 0.35 0.35 0.35 0.35 0.35 0.35 0.35 C-100 C-M10 CV-100 CV-M10 CL-100 CL-M10 CHA-100 CHA-M10 Bulk resistivity K cm 28 days 56 days 91 days

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77 CHAPTER 6 CONCLUSION AND FUTURE RESEARCH 6 CHAPTER 6.1 Summary Electrical measurements has become a popular method of assessing the transport properties of concret e before of their simplicity and low cost. Even though these measurements are easy to take, many factors can affect the results obtained such as: specimen geometry, temperature, pore solution, and curing methods. Therefore, samples were made from thirty ei ght different concrete mixtures to determine if using a simulated pore solution to cure the concrete could give more consistent results than curing in a moist room. Based on the obtained results from this research the following conclusions can be drawn: Us e of supplementary cementitious materials (SCMs) causes a significant increase in the surface and bulk resistivity measurements. As the w/cm ratio increases, the electrical resistivity decreases, which indicates less permeable and more durable concrete. In consistent resistivity results with age and SCM dosage were seen for samples cured in SPS. This is likely because of the mismatch between concrete pore solution conductivity and curing water conductivity because of errors in predicting the pore solution co nductivity and changing porosity and concrete pore solution conductivity changes with continued hydration. There was little long term benefit seen when the silica fume or metakaolin dosage was increased above 6% in ternary blends.

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78 If SPS is to be used to cure concrete samples, bulk resistivity should be used instead of surface resistivity. Surface resistivity was seen to have more issues with pore solution curing water conductivity mismatch. 6.2 Future Research Based on the results presented in this study, th e following recommendations for future research are suggested: Pore solution expression is recommended to determine the validity of the NIST calculator and to determine the effects of SPS curing on the concrete pore solution. A correlation should be develo ped between the resistivity measurements and other measures of concrete transport properties such as water absorption and water permeability.

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79 APPENDIX SURFACE AND BULK RESISTIVITY READINGS Table A 1 Surface and Bulk resist ivity readings (moist room) Mix # Mix ID W/C cm) cm) 28 days 56 days 91 days 28 days 56 days 91 days 1 C 100 0.35 10.19 11.87 12.41 6.89 9.65 10.77 2 C 100h 0.44 6.82 7.44 8.31 4.33 5.73 7.82 3 C F10 0.35 9.54 13. 16 16.11 6.37 9.66 12.47 4 C F20 0.35 10.27 16.66 23.08 6.72 11.83 15.40 5 C F10h 0.44 6.86 8.36 10.73 5.29 6.20 8.90 6 C F20h 0.44 6.56 9.97 15.08 5.03 7.90 14.00 7 C G60 0.35 40.57 50.95 59.98 22.73 32.79 39.39 8 C S8 0.35 32.65 48.43 54.13 18.90 30 .52 34.59 9 C M10 0.35 38.33 46.59 49.35 21.80 28.05 31.87 10 C F10G30 0.35 22.24 29.53 35.43 13.43 19.25 22.98 11 C F10G45 0.35 30.66 40.12 48.51 20.50 25.83 30.19 12 C F10G60 0.35 42.20 54.37 59.22 23.33 32.31 37.01 13 C F10G60h 0.44 37.53 48.62 57. 18 23.83 32.17 41.93 14 C F20S4 0.35 25.02 39.31 49.65 16.01 25.04 32.87 15 C F20S6 0.35 36.49 54.74 68.67 23.00 33.37 42.72 16 C F20S8 0.35 33.33 52.73 69.64 18.97 33.31 43.15 17 C F20S8h 0.44 22.50 32.83 43.08 14.13 22.91 29.44 18 C F20M6 0.35 27.76 36.90 47.41 15.20 24.28 30.09 19 C F20M8 0.35 32.34 40.25 50.10 19.19 25.51 31.38 20 C F20M10 0.35 36.57 44.57 50.98 21.62 31.53 33.50 21 C F20M10h 0.44 27.49 33.36 42.28 17.08 23.37 32.22 22 C G55S8 0.35 55.32 90.88 121.91 28.28 50.81 69.72 23 C G55 M10 0.35 59.63 89.00 106.49 32.43 52.01 64.88 24 CV 100 0.35 9.13 10.21 10.47 6.17 8.79 8.95 25 CV 100h 0.44 6.55 6.93 7.72 4.11 5.48 6.07 26 CV F10G60 0.35 40.57 52.32 56.78 21.78 34.93 36.81 27 CV F20S8 0.35 41.59 61.37 74.79 23.46 32.68 47.62 28 CV M10 0.35 38.35 43.00 48.24 22.06 23.96 31.59 29 CL 100 0.35 10.60 11.72 11.96 6.93 9.21 10.93 30 CL 100h 0.44 6.72 6.96 7.53 3.96 6.03 7.40 31 CL F10G60 0.35 61.08 81.28 84.31 34.66 49.65 51.41 32 CL F20S8 0.35 29.73 47.84 61.03 19.06 31.90 40.61 33 CL M10 0.35 45.02 48.21 50.95 25.09 28.71 32.32 34 CHA 100 0.35 8.60 10.09 10.67 5.41 7.71 10.41 35 CHA 100h 0.44 6.04 6.53 7.25 3.35 4.99 6.60 36 CHA F10G60 0.35 38.37 49.33 53.81 23.12 32.60 38.01 37 CHA F20S8 0.35 41.75 57.66 68.05 24.08 36.46 43.11 38 CHA M10 0.35 45.31 45.77 48.34 24.29 26.48 30.72

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80 Table A 2 : Surface and Bulk resistivity readings ( SPS ) Mix # Mix ID W/C cm) cm) 28 days 56 days 91 days 28 days 56 days 91 days 1 C 100 0.35 7.82 8.50 8.85 4.54 5.17 5.36 2 C 100h 0.44 5.56 5.85 6.12 2.92 3.48 3.53 3 C F10 0.35 7.79 9.25 11.13 4.02 5.56 7.35 4 C F20 0.35 8.21 12.10 14.20 4.26 7.15 10.17 5 C F10h 0.44 4.57 5.63 6.71 2.86 3.63 4.51 6 C F20h 0.44 4.65 6.62 9.50 2.96 4.73 7.42 7 C G60 0.35 16.92 16.34 16.28 11.35 17.24 18.04 8 C S8 0.35 15.31 19.51 17.67 11.44 17.20 18.91 9 C M10 0.35 20.03 20.01 20.39 13.79 15.68 18.75 10 C F10G 30 0.35 10.00 11.77 11.33 7.27 11.25 13.63 11 C F10G45 0.35 12.95 13.63 13.71 9.32 13.00 17.09 12 C F10G60 0.35 16.20 16.75 17.51 15.37 15.49 17.26 13 C F10G60h 0.44 15.18 16.05 17.27 11.14 18.45 18.54 14 C F20S4 0.35 7.76 10.16 11.17 9.03 10.40 14.45 15 C F20S6 0.35 7.42 11.24 12.09 11.00 13.41 16.98 16 C F20S8 0.35 9.52 10.65 9.78 9.04 11.80 15.08 17 C F20S8h 0.44 10.08 12.97 14.38 7.36 11.21 12.96 18 C F20M6 0.35 9.55 11.46 12.58 7.80 10.20 13.87 19 C F20M8 0.35 8.23 9.40 9.85 9.54 9.08 11.66 2 0 C F20M10 0.35 8.63 9.71 9.75 10.65 9.77 10.89 21 C F20M10h 0.44 9.11 13.22 13.90 8.05 11.55 12.63 22 C G55S8 0.35 27.15 30.04 33.62 22.87 30.41 33.37 23 C G55M10 0.35 34.25 38.02 40.95 25.68 32.06 34.05 24 CV 100 0.35 6.20 6.57 6.60 3.72 4.03 4.15 2 5 CV 100h 0.44 4.76 4.98 5.03 2.36 3.05 2.81 26 CV F10G60 0.35 15.40 15.48 17.05 14.07 16.32 16.34 27 CV F20S8 0.35 10.77 8.83 9.55 11.52 13.44 14.19 28 CV M10 0.35 11.98 12.05 13.00 9.37 10.38 11.97 29 CL 100 0.35 7.99 7.40 7.43 3.61 4.48 4.45 30 CL 100h 0.44 5.30 5.40 5.66 2.21 2.98 3.30 31 CL F10G60 0.35 16.03 16.19 17.58 14.47 17.86 18.52 32 CL F20S8 0.35 9.53 11.13 12.93 10.79 16.62 14.99 33 CL M10 0.35 18.87 17.18 17.72 17.08 15.00 15.29 34 CHA 100 0.35 5.66 5.30 5.01 2.44 3.58 3.22 35 CHA 1 00h 0.44 4.54 4.65 4.63 1.88 2.84 2.88 36 CHA F10G60 0.35 11.70 11.80 12.75 10.71 15.01 14.59 37 CHA F20S8 0.35 7.74 7.33 9.91 9.42 12.14 11.53 38 CHA M10 0.35 7.94 8.03 7.72 11.80 9.58 8.90

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81 Figure A 1 : Surface resis tivity vs bulk resistivity (Moist room) Figure A 2 : Surface resistivity vs bulk resistivity (SPS R = 0.9785 R = 0.9732 R = 0.9739 0 10 20 30 40 50 60 70 80 90 0 20 40 60 80 100 120 140 BR Moist room (K cm) SR Moist room (K cm) 28 days 56 days 91 days R = 0.8309 R = 0.8645 R = 0.8611 0 5 10 15 20 25 30 35 40 45 0 10 20 30 40 50 BR SPS (K cm) SR SPS (K cm) 28 days 56 days 8.85

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82 LIST OF REFERENCES AASHTO. (2011). 95 11 Standard Method of Test for Surface Resistivity Indication of esist Chloride Ion Penetration. AASHTO Provisional Standards, 2011 Edition 1 8. https://doi.org/10.1520/C1202 12.2 AASHTO. (2015). TP119 15 Standard Method of Test for Electrical Resistivity of a Concrete Cylinder Tested in a Uniaxial Resistance Test. American Association of State Highway and Transportation OfficialsA 1 11. ACI. (2002). Use of fly ash in concrete Reported by ACI Comittee 232. NCHRP Synthesis of Highway Practice 96 (Reapproved), 1 34. Retri eved from http://trid.trb.org/view.aspx?id=277673 Ambroise, J., Maximilien, S., & Pera, J. (1994). Properties of Metakaolin blended cements. Advanced Cement Based Materials 1 (4), 161 168. https://doi.org/10.1016/1065 7355(94)90007 8 Archie, G. E. (1942). The Electrical Resistivity Log as an Aid in Determining Some Reservoir Characteristics. Transactions of the AIME 146 (1), 54 62. https://doi.org/10.2118/942054 G ASTM. (2004). Standard Test Method for Temperature of Freshly Mixed Hydraulic Cement Concrete. Annual Book of ASTM Standards (c), 4 6. https://doi.org/10.1520/C1064 ASTM. (2007). Standard Specification for Portland Cement. Annual Book of ASTM Standards I (April), 1 8. https://doi.org/10.1520/C0150 ASTM. (2010a). Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use. Annual Book of ASTM Standards (C), 3 6. https://doi.org/10.1520/C0618 ASTM. (2010b). Standard Test Method for Air Content of Freshly Mixed Concrete by the Pressure Method. ASTM International i 1 10. htt ps://doi.org/10.1520/C0231 ASTM. (2012). ASTM C1240 12. Standard Specification for Silica Fume Used in Cementitious Mixtures, (c), 1 7. https://doi.org/10.1520/C1240 14.2 ASTM. (2013a). Standard Specification for Slag Cement for Use in Concrete and Morta rs. ASTM Standards 44 (0), 1 8. https://doi.org/10.1520/C0989 ASTM. (2013b). Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric). ASTM International i 23 26. https://doi.org/10.1520/C0138 ASTM. (2013c). Standard Test Meth od for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete. ASTM International 23 (11), 1 7.

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83 ASTM. (2015a). C0127 Standard Test Method for Relative Density (Specific Gravity) and Absorption of Coarse Aggregate. ASTM International 5. https:/ /doi.org/10.1520/C0127 15.2 ASTM. (2015b). Standard Test Method for Relative Density (Specific Gravity) and Absorption of Fine Aggregate. ASTM International i 6. https://doi.org/10.1520/C0128 15.2 ASTM. (2015c). Standard Test Method for Slump of Hydrauli c Cement Concrete. Astm C143 (1), 1 4. https://doi.org/10.1520/C0143 ASTM. (2016). Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory. American Society for Testing and Materials 1 8. https://doi.org/10.1520/C0192 ASTM. (201 7). C 150/ C150M Standard Specification for Portland Cement. Annual Book of ASTM Standards 1 8. https://doi.org/10.1520/C0150 Ability to Resist Chloride Ion Penetration. Am erican Society for Testing and Materials. (C), 1 8. https://doi.org/10.1520/C1202 12.2 Azarsa, P., & Gupta, R. (2017). Electrical resistivity of concrete for durability evaluation: A review. Advances in Materials Science and Engineering 2017 https://doi .org/10.1155/2017/8453095 Barneyback, R. S., Diamond, S., & Lafayette, W. (1981). ( Communicated by D M Bentz, D. P. (2007). A virtual rapid chloride permeability test. Cement and Concrete Composites 29 (10), 723 731. https://doi.org/10.1016/j.cemconcomp.2007.06.006 Borosnyi, A. (2016). Long term durability performance and mechanical properties of high performance concretes with combined use of supplementary cementing materials. Construction and Building Materials 11 2 307 324. https://doi.org/10.1016/j.conbuildmat.2016.02.224 Bu, Y., & Weiss, J. (2014). The influence of alkali content on the electrical resistivity and transport properties of cementitious materials. Cement and Concrete Composites 51 49 58. https://d oi.org/10.1016/j.cemconcomp.2014.02.008 Bullard, JW, CF Ferraris, EJ Garboczi, NS Martys, PE Stutzman, and JE Terrill. (2008). Manufacturing, edited by JI Bhatty, FM Miller, and S H Kosmatka, 1311 1331. Skokie, IL: Portland Cement Association. Calleja, J. Effect of current frequency on measurement of electrical resistance of cement pastes, J. Am. Conc. Inst. 24 (1952) 329 332.

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84 Chen, W., & Brouwers, H. J. H. (2011). A method for pred icting the alkali concentrations in pore solution of hydrated slag cement paste. Journal of Materials Science 46 (10), 3622 3631. https://doi.org/10.1007/s10853 011 5278 1 Cheng, A., Huang, R., Wu, J. K., & Chen, C. H. (2005). Influence of GGBS on durabili ty and corrosion behavior of reinforced concrete. Materials Chemistry and Physics 93 (2 3), 404 411. https://doi.org/10.1016/j.matchemphys.2005.03.043 Chini, A. R., Muszynski, L. C., & Hicks, J. (2003). Determination of Acceptance Permeability Characterist ics for Performance Related Specifications for Portland Cement Concrete, (July), 1 165. Coyle, A. T., Spragg, R. P., Suraneni, P., Amirkhanian, A. N., & Weiss, W. J. (2018). Comparison of Linear Temperature Corrections and Activation Energy Temperature Cor rections for Electrical Resistivity Measurements of Concrete. Advances in Civil Engineering Materials 7 (1), 20170135. https://doi.org/10.1520/ACEM20170135 De La Varga, I., Spragg, R. P., Di Bella, C., Castro, J., Bentz, D. P., & Weiss, J. (2014). Fluid tr ansport in high volume fly ash mixtures with and without internal curing. Cement and Concrete Composites 45 102 110. https://doi.org/10.1016/j.cemconcomp.2013.09.017 Fras, M., De Rojas, M. I. S., & Cabrera, J. (2000). Effect that the pozzolanic reaction of metakaolin has on the heat evolution in metakaolin cement mortars. Cement and Concrete Research 30 (2), 209 216. https://doi.org/10.1016/S0008 8846(99)00231 8 Ganesh Babu, K., & Sree Rama Kumar, V. (2000). Efficiency of GGBS in concrete. Cement and Con crete Research 30 (7), 1031 1036. https://doi.org/10.1016/S0008 8846(00)00271 4 Gowers, K. R., & Millard, S. G. (1999). Measurement of concrete resistivity for assessment of corrosion severity of steel using wenner technique. ACI Materials Journal 96 (5), 536 541. https://doi.org/10.14359/655 Hadj Sadok, A., Kenai, S., Courard, L., & Darimont, A. (2011). Microstructure and durability of mortars modified with medium active blast furnace slag. Construction and Building Materials 25 ( 2), 10 18 1025. Hassan, Z. (2001). Binding of External Chlorides by Cement Pastes, 259 (21), 13379 13384. S H phase. Cement and Concrete Research 29 (12), 1893 1903. https://doi.org/10.10 16/S0008 8846(99)00187 8

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85 Jolicoeur, C., To, T. C., Benot, ., Hill, R., Zhang, Z., & Pag, M. (2009). Fly Ash and Chemical Mitigation. World of Coal Ash (WOCA) Conference 1 23. Joshi, P., & Chan, C. (2002). Rapid Chloride Permeability Testing. Concrete Construction World of Concrete 47 (12), 37 43. Justice, J. M., & Kurtis, K. E. (2007). Influence of metakaolin surface area on properties of cement based materials. Journal of Materials in Civil Engineering 19 (9), 762 771. https://doi.org/10.1061/(ASCE)0899 1561(2007)19:9(762) Kamtornkiat Musiket; Mitchell Rosendahl; and Yunping Xi. (2016). Fracture of Recycled Aggregate Concrete under High Loading Rates. Journal of Material s in Civil Engineering 25 (October), 864 870. https://doi.org/10.1061/(ASCE)MT.1943 5533 Khan, S. U., Nuruddin, M. F., Ayub, T., & Shafiq, N. (2014). Effects of different mineral admixtures on the properties of fresh concrete. TheScientificWorldJournal 20 14 1 11. https://doi.org/10.1155/2014/986567 Layssi, H, et. a. (2009). Electrical Resistivity of Concrete Time Dependence (October), 2 3. Liu, Y., & Presuel Moreno, F. J. (2014). Normalization of Temperature Effect on Concrete Resistivity by Method Using Arrhenius Law. ACI Materials Journal 111 (4). https://doi.org/10.14359/51686725 Liu, Y. (2012). Accelerated curing of concrete with high volume pozzolans resistivity, diffusivity and compressive strength [Ph.D. Dissertation], Florida Atlantic Univers ity, Boca Raton, Fla, USA. Luo, R., Cai, Y., Wang, C., & Huang, X. (2003). Study of chloride binding and diffusion in GGBS concrete. Cement and Concrete Research 33 (1), 1 7. https://doi.org/10.1016/S0008 8846(02)00712 3 Malagavelli, V. (2010b). High perfo rmance concrete, (October 2010), 591. McCarter, W. J., Chrisp, T. M., Starrs, G., Basheer, P. A. M., & Blewett, J. (2005). Field monitoring of electrical conductivity of cover zone concrete. Cement and Concrete Composites 27 (7 8), 809 817. https://doi.org /10.1016/j.cemconcomp.2005.03.008 McCarter, W. J., Starrs, G., & Chrisp, T. M. (2000). Electrical conductivity, diffusion, and permeability of Portland cement based mortars. Cement and Concrete Research 30 (9), 1395 1400. https://doi.org/10.1016/S0008 8846 (00)00281 7 Michelle, N., Adam, B., Xiaorong, W., & Douglas, H. R. (2017). Effects of Temperature Chemical and Mineral Admixtures, 5 (5), 1 9.

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86 Morris, W., Moreno, E. I., & Sags, A. A. (1996). Practical evaluation of resistivity of concrete in test cy linders using a Wenner array probe. Cement and Concrete Research 26 (12), 1779 1787. https://doi.org/10.1016/S0008 8846(96)00175 5 Neville, A. M. (2011). Properties of Concrete Journal of General Microbiology (Vol. Fourth). https://doi.org/10.4135/9781412 975704.n88 Olufemi, F. S. (2013). Reactivity of cement combinations containing Portland cement fly ash silica fume and metakaolin, 3 (3), 582 587. Paredes, M., Jackson, N. M., El Safty, A., Dryden, J., Joson, J., Lerma, H., & Hersey, J. (2012). Precisio n Statements for the Surface Resistivity of Water Cured Concrete Cylinders in the Laboratory. Advances in Civil Engineering Materials 1 (1), 104268. https://doi.org/10.1520/ACEM104268 Perraton, D. Aitcin, P., and Vezina,D. (1988). Permeabilities of Silica Fume Concrete, Am. Concr. Inst. Spec. Publ., vol. 108, pp. 63 84. Polder, R., Andrade, C., Elsener, B., Vennesland, O., Gulikers, J., Weidert, R., & Raupach, M. (2000). RILEM TC 154 Test methods for on site meas urement of resistivity of concrete. Materials and Structures 33 603 611. https://doi.org/10.1007/BF02480599 Polder, R. B. (2001). Test methods for on site measurement of resistivity of concrete a RILEM TC 154 technical recommendation. Construction and Building Materials 15 (2 3), 125 131. https://doi.org/10.1016/S0950 0618(00)00061 1 calcium fly ash on selected properties of self compacting concrete. Archives of Civil and Mechanical Engineeri ng 14 (3), 455 465. https://doi.org/10.1016/j.acme.2013.10.014 Press, P., & May, R. (1992). SiO 2 A1203 Fe203 SO 3 MgO Na20 K20 I g n i t i o n, 22 15 22. Presuel Moreno, F., Wu, Y. Y., & Liu, Y. (2013). Effect of curing regime on concrete resistivity and aging factor over time. Construction and Building Materials 48 874 882. https://doi.org/10.1016/j.conbuildmat.2013.07.094 Retrieved from https://www.proceq.com/uploads/tx_p roceqproductcms/import_data/files/Resipod_ Sales Flyer_English_high.pdf Rajabipour, F., Sant, G., & Weiss, J. (2007). Development of Electrical Conductivity Based Sensors for Health Monitoring of Concrete Materials Development of Electrical Conductivity Bas ed Sensors for Health Monitoring of Concrete Materials. Transportation Research Board Annual Mee (1500), 1 16.

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87 Ramezanianpour, A. A., & Bahrami Jovein, H. (2012). Influence of metakaolin as supplementary cementing material on strength and durability of con cretes. Construction and Building Materials 30 470 479. https://doi.org/10.1016/j.conbuildmat.2011.12.050 Riding, K. A., Poole, J. L., Schindler, A. K., Juenger, M. C. G., & Folliard, K. J. (2008). Simplified concrete resistivity and rapid chloride perme ability test method. ACI Materials Journal 105 (4), 390 394. Rupnow, T., & Icenogle, P. (2011). Development of a Precision Statement for Concrete Surface Resistivity. Transportation Research Record: Journal of the Transportation Research Board 2290 10. h ttps://doi.org/10.3141/2290 05 Rupnow, T., & Icenogle, P. (2012). Surface Resistivity Measurements Evaluated as Alternative to Rapid Chloride Permeability Test for Quality Assurance and Acceptance. Transportation Research Record: Journal of the Transportat ion Research Board 2290 30 37. https://doi.org/10.3141/2290 04 Saha, A. K. (2018). Effect of class F fly ash on the durability properties of concrete. Sustainable Environment Research 28 (1), 25 31. https://doi.org/10.1016/j.serj.2017.09.001 Scott, A., & Alexander, M. G. (2016). Effect of supplementary cementitious materials (binder type) on the pore solution chemistry and the corrosion of steel in alkaline environments. Cement and Concrete Research 89 45 55. https://doi.org/10.1016/j.cemconres.2016.08. 007 Sengul, O. (2014). Use of electrical resistivity as an indicator for durability. Construction and Building Materials 73 434 441. https://doi.org/10.1016/j.conbuildmat.2014.09.077 Sengul, O., & Gjrv, O. E. (2009). Effect of embedded steel on electric al resistivity measurements on concrete structures. ACI Materials Journal 106 (1), 11 18. Shahroodi, A. (2010). Development of Test Methods for Assessment of Concrete Durability for Use in Performance Based Specifications Development of Test Methods for As sessment of Concrete Durability for Performance Based Specifications. Shane, J. D., Aldea, C. D., Bouxsein, N. F., Mason, T. O., Jennings, H. M., & Shah, S. P. (1999). Microstructural and pore solution changes induced by the rapid chloride permeability tes t measured by impedance spectroscopy. Concrete Science and Engineering 1 (2), 110 119. Shi, C. (2004). Effect of mixing proportions of concrete on its electrical conductivity and the rapid chloride permeability test (ASTM C1202 or ASSHTO T277) results. Cem ent and Concrete Research 34 (3), 537 545. https://doi.org/10.1016/j.cemconres.2003.09.007

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88 Shi, X., Xie, N., Fortune, K., & Gong, J. (2012). Durability of steel reinforced concrete in chloride environments: An overview. Construction and Building Materials 30 125 138. https://doi.org/10.1016/j.conbuildmat.2011.12.038 Siddique, R., & Klaus, J. (2009). Influence of metakaolin on the properties of mortar and concrete: A review. Applied Clay Science 43 (3 4), 392 400. https://doi.org/10.1016/j.clay.2008.11.007 Silva, A. S., Ribeiro, A. B., Jalali, S., & Divet, L. (2015). The Use of Fly Ash and Metakaolin for the Prevention of Alkali Silica Reaction and Delayed Ettringite Formation in Concrete. Snyder, K. A. (2001). The relationship between the formation factor and the diffusion coefficient of porous materials saturated with concentrated electrolytes: Theoretical and experimental considerations. Concrete Science and Engineering 3 (9), 216 224. https://doi.org/10.1017/CBO9781107415324.004 Snyder, K. A., Ferraris, C., Martys, N. S., & Garboczi, E. J. (2000). Using Impedance Spectroscopy to Assess the Viability of the Rapid Chloride Test for Determining Concrete Conductivity. Journal of Research of the National Institute of Standards and Technology 105 (4), 497 509. https://doi.org/10.6028/jres.105.040 Sohn, D., & Mason, T. O. (1998). Electrically induced microstructural changes in portland cement pastes. Advanced Cement Based Materials 7 (3 4), 81 85. https://doi.org/10.1016/S1065 7355(97)00056 4 Song, H. W., Pack, S W., Nam, S. H., Jang, J. C., & Saraswathy, V. (2010). Estimation of the permeability of silica fume cement concrete. Construction and Building Materials 24 (3), 315 321. https://doi.org/10.1016/j.conbuildmat.2009.08.033 Spragg, R., Bu, Y., Snyder, K., Be ntz, D., & Weiss, J. (2013). Electrical Testing of Cement Based Materials: Role of Testing Techniques, Sample Conditioning. https://doi.org/10.5703/1288284315230 Spragg, R. P., Castro, J., Nantung, T., Paredes, M., & Weiss, J. (2012). Variability Analysis of the Bulk Resistivity Measured Using Concrete Cylinders. Advances in Civil Engineering Materials 1 (1), 104596. https://doi.org/10.1520/ACEM104596 Spragg, R., Villani, C., Snyder, K., Bentz, D., Bullard, J., & Weiss, J. (2013). Factors That Influence Ele ctrical Resistivity Measurements in Cementitious Systems. Transportation Research Record: Journal of the Transportation Research Board 2342 (2342), 90 98. https://doi.org/10.3141/2342 11 Su, J., Yang, C., Wu, W., and Huang, R. (2002). Effect ofmoisture con tent on concrete 1, pp. 117 122.

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89 Thomas, M. D. A., Hooton, R. D., Scott, A., & Zibara, H. (2012). The effect of supplementary cementitious materials on chloride binding in hardened cement paste. Cement and Concrete Research 42 (1), 1 7. https://doi.org/10.1016/j.cemconres.2011.01.001 Thomas, M., Fournier, B., & Folliard, K. (2006). Test Methods for Evaluating Preventive Measures for Controlling Expansion due to Alkali Sil ica Reaction in Concrete. University of Taxes 62. Van Noort, R., Hunger, M., & Spiesz, P. (2016). Long term chloride migration coefficient in slag cement based concrete and resistivity as an alternative test method. Construction and Building Materials 11 5 746 759. https://doi.org/10.1016/j.conbuildmat.2016.04.054 Villagrn Zaccardi, Y. A., Garca, J. F., Hulamo, P., & Di Maio, . A. (2009). Influence of temperature and humidity on Portland cement mortar resistivity monitored with inner sensors. Material s and Corrosion 60 (4), 294 299. https://doi.org/10.1002/maco.200805075 Vollpracht, A., Lothenbach, B., Snellings, R., & Haufe, J. (2016). The pore solution of blended cements: a review. Materials and Structures/Materiaux et Constructions 49 (8), 3341 3367 https://doi.org/10.1617/s11527 015 0724 1 clinker type and fineness on properties of Portland cement. Cement and Concrete Research 31 (1), 135 139. https://doi.org /10.1016/S0008 8846(00)00427 0 ground granulated blastfurnace slag (GGBS) additions and time delay on the 53 257, 2000., 22 253 257. https://doi.org/10.1017/CBO9781107415324.004 Weiss, J., Snyder, K., Bullard, J., & Bentz, D. (2012). Using a Saturation Function to Interpret the Electrical Properties of Partially Saturated Concrete. Journal of Materials in Civil Engineering 25 (8), 1097 1106. https://doi.org/10.1061/(ASCE)MT.1943 5533.0000549 Weiss, W., Shane, J., Mieses, A., Mason, T., Shah, S.(1999). Aspects of monitoring moisture changes using electrical impedance spectroscopy, in: Second Symposium on the Importance of Self Desiccation in Concrete Technology,Lund, Sweden. Wenner, F. (1916). A method of measuring earth resistivity. Bulletin of the Bureau of Standards 12 (4), 469. https://doi.org/10.6028/bulletin.282 Xu, Y. (1997). T he influence of sulphates on chloride binding and pore solution chemistry. Cement and Concrete Research 27 (12), 1841 1850. https://doi.org/10.1016/S0008 8846(97)00196 8

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90 Yamei, Z., Wei, S., & Lianfei, S. (1997). Mechanical Properties of High Performance Co ncrete Made With High Calcium High Sulfate Fly Ash. Cement and Concrete Research 27 (7), 1093 1098. https://doi.org/10.1016/S0008 8846(97)00087 2

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91 BIOGRAPHICAL SKETCH Raid Alrashidi was born in Hail, Saudi Arabia, in 1991. In 2009, he started his care er at University of Hail, where he received the degree of Bachelor of Science in civil engineering in 2014. After that, he worked as a civil engineer at Saudi Oger Company for a year and half. He then enrolled in graduate school at the University of Florid a where he received a Master of Science in civil engineering in August 2018. His research interests include durability of concrete structures.