<%BANNER%>

Effect of High Curing Temperatures on the Strength, Durability and Potential of Delayed Ettringite Formation in Mass Con...


PAGE 1

EFFECT OF HIGH CURING TEMPERATURES ON THE STRENGTH, DURABILITY AND POTENTIAL OF DE LAYED ETTRINGITE FORMATION IN MASS CONCRETE STRUCTURES By LUCY ACQUAYE A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2006

PAGE 2

Copyright 2006 by LUCY ACQUAYE

PAGE 3

This document is dedicated to David and Anna.

PAGE 4

iv ACKNOWLEDGMENTS My sincere gratitude goes to Dr. Abdol Chini whose constant advice, encouragement, patience and dedication to my graduate studies has resulted in this dissertation. Dr. Chini admitted me into this distinguished university and program where all my academic and professional goals were met and exceeded. He was the committee chair for both my masters thesis and doctoral diss ertation, and his kindness and inspiration have sustained me throughout my studies. Dr. Chin i provided outstanding academic and professional guidance during my doctoral studies and gave me wonderful opportunities to excel academi cally and professionally. The research reported here was spon sored by the Florida Department of Transportation (FDOT). Sincere appreciation is due to the FDOT State Materials Office Concrete Lab employees in Gainesville and Richard DeLorenzo for his guidance and help in sampling and testing concrete specimens. My sincere thanks go to Barbara Beatty of the FDOT chemical lab for her support My sincere thanks go to Dr. Jo Hassel for her constant encouragement and financial assistance during my doctoral studies. My thanks also go to members of my doctoral committee for their help in completing this di ssertation. I am grateful to the faculty and staff at the Rinker School of Building Construction for providing a stimulating environment for my graduate studies. My tha nks go to the faculty of the Department of Building Technology, Kwame Nkrumah Univers ity of Science and Technology, Ghana, for their support throughout my studies.

PAGE 5

v I am utterly grateful to G od for all the wonderful blessi ngs in my life. I am very grateful to my parents for all the sacrifices they made to se e me to such great heights and for their constant support. I am grateful to my siblings who supported and expanded my dreams. I am grateful to my husband, Mark for his support and encouragement. I wish to thank my children David and Anna, whose in terest in mamas homework spurred me on to complete this dissertation.

PAGE 6

vi TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................iv LIST OF TABLES.............................................................................................................ix LIST OF FIGURES...........................................................................................................xi ABSTRACT.....................................................................................................................xi v CHAPTER 1 INTRODUCTION........................................................................................................1 Background...................................................................................................................1 Objectives and Scope of Research................................................................................5 Research Methodology.................................................................................................6 Importance of Research................................................................................................7 2 LITERATURE REVIEW.............................................................................................8 Introduction................................................................................................................... 8 Cement Hydration.........................................................................................................9 Effect of Curing Temperatur e on the Microstructure of Hydrated Cement Paste......12 Dense Shell of Hydration Products.............................................................................14 Effect of Curing Temperature on Co ncrete Strength Development...........................15 Effect of Temperature on the Durability of Concrete.................................................17 Fly ash and Slag in Concrete......................................................................................19 Delayed Ettringite Forma tion (DEF) in Concrete......................................................22 3 RESEARCH METHODOLOGY...............................................................................27 Introduction.................................................................................................................27 Degree of Hydration...................................................................................................28 Introduction.........................................................................................................28 Methodology........................................................................................................29 Calculations to Determine the Degree of Hydration...........................................35 Problems Encountered in the Experimental Process...........................................35 Mass Concrete Experiments.......................................................................................42 Compressive Strength..........................................................................................44

PAGE 7

vii Resistance to Chloride Penetration......................................................................44 Time to Corrosion................................................................................................45 Density and Percentage of Voids in Hardened Concrete....................................45 Microstructure analysis Sca nning Electron Microscope (SEM)......................46 Introduction..................................................................................................46 Signals of Interest.........................................................................................46 SEM Use in Concrete...................................................................................48 Experimental Work......................................................................................48 Sample Preparation for SEM Examination..................................................49 4 TEST RESULTS AND DISCUSSION......................................................................51 Introduction.................................................................................................................51 Phase 1 Determination of Degree of Hydration......................................................51 Phase 2 Tests of Mass Concrete..............................................................................57 Degree of Hydration Results...............................................................................63 Compressive Strength Results.............................................................................65 Resistance to Chloride Ion Penetration...............................................................68 Density and Percentage of Voids Results............................................................69 Time to Corrosion Results...................................................................................72 Phase 3 Microstructural Analysis...........................................................................74 SEM Observations of Plain Cement Mixes.........................................................74 Effect of Curing Temperature on the Presence of Ettringite Crystals..........74 Effect of Curing Duration on the Amount of Ettringite Crystals formed....75 SEM Observations of Fly Ash Mixes..................................................................78 Introduction..................................................................................................78 Effect of Curing Temperature on the Presence of Ettringite Crystals..........79 Effect of Curing Duration on the Amount of Ettringite Crystals formed in Voids...................................................................................................80 SEM Observations of Slag Mixes.......................................................................82 Introduction..................................................................................................82 Effect of Curing Temperature on the Presence of Ettringite Crystals..........83 Effect of Curing Duration on the Amount of Ettringite Crystals formed....83 5 CONCLUSIONS AND RECOMMENDATIONS.....................................................87 Introduction.................................................................................................................87 Conclusions.................................................................................................................87 Research Implications for Mass Concrete Structures.................................................92 Recommendations.......................................................................................................93 APPENDIX A CONCRETE MIX DESIGNS.....................................................................................96 Mix 1 Plain Cement Mix.........................................................................................96 Mix 2 18% Fly Ash Mix..........................................................................................97

PAGE 8

viii Mix 3 Plain Cement Mix.........................................................................................98 Mix 418% Fly Ash Mix............................................................................................99 Mix 5 Plain Cement Mix.......................................................................................100 Mix 6 50% Slag Mix..............................................................................................101 Mix 7 Plain Cement Mix.......................................................................................102 B ADDITIONAL SEM IMAGES................................................................................103 Part 1 Mix 1:Plain Cement Only Mix (0%FA)......................................................103 Part 2 Mix 2: 18% Fly Ash Mix.............................................................................109 Part 3 Mix 3: 50% Slag Mix..................................................................................112 LIST OF REFERENCES.................................................................................................115 BIOGRAPHICAL SKETCH...........................................................................................119

PAGE 9

ix LIST OF TABLES Table page 2.1 Major Compounds of Portland Cement.....................................................................9 2.2 Measured Porosity....................................................................................................18 2.3 Results of compressive st rength and AASHTO T-277 test......................................21 2.4 AASHTO T-277 tests for charge passed..................................................................22 2.5 Rate of chloride diffusion ppm/day (avera ge of three replicates, Norwegian test)..22 3.1 Properties of Cement and Fly ash............................................................................30 3.2 Properties of Blast furnace slag ASTM C 989-97b, AASHTO M302...................30 3.3 Mix proportions of paste mixes................................................................................31 3.4 Time to 70% hydration in plain cement mix............................................................37 3.5 Concrete Mix 1 0% Fly Ash (Isothermal Curing).................................................38 3.6 Binders used in mass concrete mixes by the FDOT.................................................41 3.7 Mixture Proportions for F DOT Class IV mass concrete..........................................43 4.1 Nonevaporabe water content for vari ous Fly ash mixes Lam et al. (2000)..............54 4.2 Degree of hydration results for plain cement mixes................................................55 4.3 Degree of hydration for 18% fly ash mixes.............................................................56 4.4 Degree of hydration for 50% fly ash mixes.............................................................57 4.5 Degree of hydration for cement and blast furnace slag mixes.................................57 4.6 Summary of Plastic Proper ties of Fresh Concrete...................................................58 4.7 Results of concrete mixes M1 and M2.....................................................................58 4.8 Results of concrete mixes M3 and M4.....................................................................59

PAGE 10

x 4.9 Results of concrete mixes M5 and M6.....................................................................60 4.10 Results of concrete mixes M7 and M8.....................................................................61 4.11 Summary of Results of concrete mixes M1 M2, M3 and M4................................62 4.12 Summary of Results of concre te mixes M5, M6, M7 and M8.................................63 4.13 Compressive strength as a ratio of 28-day samples cured at 73oF..........................66 4.14 Compressive strength as a ratio of the 28-day samples cured at 73oF....................67 5.1 Compressive strength samples cured isothermally..................................................89 5.2 RCP for samples cured isothermally........................................................................90 5.3 Compressive strength for adiabatically cured samples............................................90 5.4 RCP and Ettringite Formation fo r adiabatically cured samples...............................93

PAGE 11

xi LIST OF FIGURES Figure page 2.1 External thermal cracking........................................................................................10 2.2 Internal thermal cracking.........................................................................................11 2.3 Effect of curing temperature on concrete strength development.............................16 2.4 Pore size distribution with age for 30% Fly ash mix...............................................20 3.1 Paste samples cast in one-ounce polypropylene screw cap jars...............................32 3.2 Oven used to cure samples at 200F.........................................................................32 3.3 Samples cured in four-ounce pol ypropylene jars after demolding..........................33 3.4 Samples crushed in mechanical crusher...................................................................33 3.5 Approximately 3 grams of samples weighed...........................................................34 3.6 Samples removed after ignition at 1832F...............................................................34 3.7 Curing tanks used for samples at elevated temperatures..........................................36 3.8 Degree of hydration (wnu = 0.23)............................................................................37 3.9 Compressive strength results....................................................................................38 3.10 Rapid Chloride Permeability (RCP) results.............................................................39 3.11 Degree of hydration based on adiabatic curing (wnu = 0.23)..................................42 3.12 Different interactions of an electron beam (PE) with the solid target. BSE = backscattered electrons, SE = secondary electrons, X = x-ray, AE = auger electrons...................................................................................................................47 3.13 The EDAX analysis of gel showing calcium, sulfur, and aluminum peaks typical for ettringite..................................................................................................49 3.14 Mortar samples mounted on stubs for SEM examination........................................50

PAGE 12

xii 4.1 Degree of hydration for 0%FA and 18%FA mixes..................................................64 4.2 Degree of hydration for 0%BFS and 50%BFS mixes..............................................65 4.3 Compressive strengths fo r 0%FA and 18%FA mixes..............................................66 4.4 Compressive strengths for 0%BFS and 50%BFS mixes..........................................67 4.5 Chloride Ion Penetration resu lts for 0%FA and 18%FA mixes...............................68 4.6 Chloride Ion Penetration resu lts for 0%BFS and 50%BFS mixes...........................69 4.7 Density for 0%FA and 18%FA mixes......................................................................70 4.8 Density for 0%BFS and 50%BFS mixes..................................................................70 4.9 Percentage of voids for 0%FA and 18%FA mixes..................................................71 4.10 Percentage of voids fo r 0%BFS and 50%BFS mixes..............................................72 4.11 Time to Corrosion results for all mixes....................................................................73 4.12 The RCP at 91days expressed in terms of Time to Corrosion unit..........................73 4.13 Well-defined Monosulphate (M) crystals in a void..................................................76 4.14 Void with clusters of Ettringite (E) crystals.............................................................76 4.15 Void containing both Monosulphate (M) and Ettringite (E) crystals.......................77 4.16 Voids containing Ettringite (E) some appear almost full of it.................................77 4.17 Void completely filled with fibrous Ettringite (E)...................................................78 4.18 Void containing hexagonal plates of Monosulphate (M).........................................80 4.19 Void showing Monosulphate (M) transformed into Ettringite (E)..........................81 4.20 Clusters of Fibrous Et tringite (E) in void.................................................................81 4.21 Sample with empty air Voids (V)............................................................................84 4.22 Higher magnification of 4.32...................................................................................84 4.23 Sample with empty air Void (V)..............................................................................85 4.24 Reacting Slag (S) particle with Ettringite (E) formed..............................................85 4.25 Slag particle completely covered with Ettringite (E)...............................................86

PAGE 13

xiii B.1 Void with monosulphate (M), no ettringite found.................................................103 B.2 Close-up view of Figure B.1..................................................................................104 B.3 Void with ettringite (E) and monosulphate (M).....................................................104 B.4 Void with ettrin gite (E) crystals.............................................................................105 B.5 Void showing monosulphate and the early formation of ettringite (E) crystals....105 B.6 Void showing ball of ettringite (E) crystals...........................................................106 B.7 Void showing balls of ettringite (E) crystals..........................................................106 B.8 Voids showing ettringite (E ) crystals some almost full.........................................107 B.9 Voids showing ettringite (E) and monosulphate crystals.......................................107 B.10 Ettringite (E) crystals in and around vicinity of void.............................................108 B.11 Ettringite (E) crystals in void.................................................................................108 B.12 Fly ash particle w ith reaction around rim...............................................................109 B.13 Fly ash particle w ith reaction around rim...............................................................109 B.14 Void containing monosulphate...............................................................................110 B.15 Void containing ettringite crystals.........................................................................110 B.16 Close up view of ettringi te crystals in Figure B.15................................................111 B.17 Reacting fly ash particle.........................................................................................111 B.18 Slag particles showing some early reaction...........................................................112 B.19 Slag particles show ing reaction on surface............................................................112 B.20 Slag particle show ing reaction on surface..............................................................113 B.21 Slag particle show ing reaction on surface..............................................................113 B.22 Ettringite formed around surf ace of reacting slag particle.....................................114 B.23 Close-up view of Figure B.22................................................................................ 114

PAGE 14

xiv Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy EFFECT OF HIGH CURING TEMPERATURES ON THE STRENGTH, DURABILITY AND POTENTIAL OF DE LAYED ETTRINGITE FORMATION IN MASS CONCRETE STRUCTURES By Lucy Acquaye May 2006 Chair: Abdol Chini Major Department: Design, Construction and Planning The Florida Department of Transportation (FDOT) has in recent years recorded high core temperatures of 170oF 200oF during curing of mass concrete elements. Frequent reports of such high temperatures have raised concerns of the strength and durability of concrete cured at such high temperatures. Additional concerns have been raised of the possibility of e xpansions of the hardened concrete from delayed ettringite formation (DEF) and its subsequent dete rioration. FDOT specifies a maximum differential temperature of 35oF between the core and exterior of mass concrete elements during curing to avoid cracking from high ther mal stresses and a s horter service life of the structure. However no limit is specified for the maximum curing temperature. This dissertation investigated the effects of high temperatures on the strength, durability and potential of delayed ettringite fo rmation in mass concrete mixes.

PAGE 15

xv Using typical FDOT Class IV mass concre te mixes it was found that elevated curing temperatures resulted in lower later-a ge strengths. Blending the cement with fly ash and slag resulted in increased strength and durability when compared to the plain cement mixes for all curing durations and temperatures. Investigating the potential of delayed ettringite formation in the concrete mixes cured at elevated temperatures and the eff ect of permeability on the onset and amount of ettringite formed showed that: 1. At room temperature curing no ettring ite was observed when samples were examined microscopically using a sc anning electron microscope (SEM) at 7, 28 and 91 days, notwithstanding having the highest permeability values. 2. At elevated curing temp eratures of 160 and 180oF, the plain cement mixes had high permeability values and microscopic examination showed ettringite crystals in void spaces at 28 days. At 91 days these samples showed voids almost fill ed with the crystals. 3. Concrete mixes containing 18% fly as h and 50% slag and cured at the elevated temperatures resulted in much lower permeability. The low permeability of the blends delayed the onset of ettringite formation as well as the amount formed when compared to the plain cement mixes. This was particularly evident in the slag mixes.

PAGE 16

1 CHAPTER 1 INTRODUCTION Background In recent years, Florida Department of Transportation (FDOT) has recorded high core temperatures of 170 – 200oF during curing of mass c oncrete structures. Mass concrete structures as define d in the FDOT Structures Desi gn Guidelines is “any large volume of cast-in-place or precast concrete w ith dimensions large enough to require that measures be taken to cope with the generation of heat and at tendant volume change so as to minimize cracking" (FDOT, 2002). Although a definite size has not been determined, a concrete member, which is 2 ft to 3 ft th ick, is considered to be mass concrete. In its mass concrete specifications, FDOT does not set a limit on the maximum core temperature during curing. F DOT however in its specifica tion for mass concrete, limits the differential curing temperature between the core and exterior of the mass concrete to 35oF. Limiting the deferential temperature is sp ecified to avoid cracking due to excessive thermal stresses in the concrete. Cracking due to thermal behavior may cause loss of structural integrity and monolithic action, or may cause excessive seepage and shortening of the service life of the c oncrete structure or may be esthetically objectionable (American Concrete Institute (ACI), 1999) The high core temperatures were recorded in mass concrete structures cured in accordance with maintaining the maxi mum differential temperature of 35oF throughout the curing period. These high temperatures have raised concerns on the effects of high curing temperatures on the strength and dur ability of mass concre te structures. Of

PAGE 17

2 additional concern is the potenti al of delayed ettringite form ation (DEF) in the hardened concrete when cured at such high temperatur es and its associated deterioration of the concrete structure. Ettringite in Portland cement systems is the first hydrate to crystallize during the first hour of placing the concrete At high curing temper atures (>160F), the ettringite becomes unstable and decomposes only to reform later in the hardened concrete in the presence of moisture with associated cracking of the structur e. Concretes cured at temperatures above 160oF are susceptible to DEF in the hardened concrete. Isolated cases of expansion and cracking from DEF have o ccurred in some in-sit u concretes of large section and high cement content in the U.K. These in-situ concretes were cast in the summer months and the possible early p eak temperature was between 185 and 200oF. The cracking took between 8 and 20 years to manifest itself (Hobbs, 1999). The cementwater reaction during the hydration of cement is an exothermic reaction. Due to the low diffusivity of heat from concre te, it acts as a insulator and in a large concrete mass, the heat liberated from the reaction can accu mulate and lead to high temperatures. A study by Tarkhan (2000) of mass concrete specifications used by state highway agencies in the United States found that nine highway agencies of the forty-three respondents had mass concrete specifications. Highway agencies of Illinois and Kentucky specified a maximum curing temperature of 160oF. A maximum differential temperature of 35oF was specified by eight of the nine highway agencies with mass concrete specifications. 65% of all respondents believed th at there is a need for further research into the effects of high curing temperature on concrete properties. Reasons cited to limit the maximum curing temperature of mass concrete elements included: Avoid reduction of later age strength,

PAGE 18

3 Minimize swelling and shrinkage cracking, Increase the durability of the concrete and Decrease the formation of dela yed ettringite (DEF) in the hardened concrete and its subsequent damage. There are several known potential causes of cracking in concrete. One is excessive stress due to applied loads and another is cr acks due to drying shri nkage or temperature changes in restrained conditions. Mass concrete is often subject to both of these stresses; therefore, prevention of cracking is a vital cons ideration in the design of these structures. However, during the construction process, the most pressing item is the control of drying shrinkage and differential temperature. The ri se in temperature of mass concrete depends on the initial concrete temper ature and volume to surface area ratio. Furthermore, the increase in temperature is affected pr edominantly by the chemical composition of cement, with C3A (Tricalcium Aluminate) and C3S (Tricalcium Silicate) being the compounds primarily responsible for elevated temperature development. The watercement ratio, fineness of the cement, concrete mixture temperature and temperature of curing are also contributors to the developm ent of heat. When the water-cement ratio, fineness, or curing temperature is increased, the heat of hydra tion is increased. The rate and amount of heat generated are important in any concrete construction requiring considerable mass. The heat accumulated must be rapidly dissipated in order to impede a significant rise in concrete temperature at the center of the structure. The excessive rise in concrete temperature is undesirable since the concrete will harden faster at an elevated temperature and any non-uniform cooling of th e concrete structure may create stresses due to thermal contraction.

PAGE 19

4 The current method of preventing cracking in mass concrete is to maintain a temperature differential (betw een the surface and the core) of no more than 35F. Control of temperature gain is po ssible (Kosmatka and Panarese 1994) through the following: Low-heat-of-hydration Portland or blended cement Reductions in the initial concrete temperat ure to approximately 50F by cooling the concrete ingredients Cooling the concrete through the use of embedded cooling pipes during curing Low lifts: 5 ft or less during placement. Pozzolans: the heat of hydration of pozzo lan is approximately 25 to 50% that of cement. When the massive concrete specified has high cement contents (500 to 1000 lb. per cu yard), many of the above mentioned plac ing methods cannot be used. For concretes that are often used in mat foundations a nd power plants good placing methods (Kosmatka and Panarese, 1994), are the following: Place the entire concrete section in one continuous pour Avoid external restraint from adjacent concrete elements Control internal differential thermal strains by preventing the concrete from experiencing excessive temperature differen tial between the internal concrete and the surface. In order to control the internal temperature differential, the concrete is insulated to keep it warm (tenting, quilts, or sand on polyet hylene sheeting). Studies have shown that the maximum temperature differential (MTD) be tween the interior a nd exterior concrete should not exceed 35F to avoid surface cracking. The Florida Department of Transporta tion Standard Specifications Section 450 allows the maximum curing temperature of 158 to 176F for accelerated curing of pre-

PAGE 20

5 stressed concrete elements. However, accel erated curing is conducted under suitable enclosures with a controlled environment to avoid thermal shock and minimize moisture loss. These conditions do not exist in mass concrete operations and such high temperatures may have detrimental effects on concrete properties. It is therefore necessary to revisit the current specificati on for mass concrete, and examine the need for additional provisions. The provisions that need to be reconsidered are maximum internal concrete temperature and/or maximu m concrete placing temperature. Objectives and Scope of Research The objectives of this diss ertation were as follows: To determine the effects of concrete curi ng temperature on the strength and durability of concrete, using typical FDOT Class IV mass concrete mixes. To determine the effects of fly ash and slag on the strength and durability of concrete cured at elevated temperatures. To determine the propensity of typical F DOT class IV mass concrete mixes to DEF when cured at elevated temperatures. To determine the effect of permeability of the concrete microstructure on the onset and amount of ettringite formed. To determine the effect of replacing part of the cement with fly ash or slag on the onset and amount of ettringite crystals fo rmed in samples cured at the elevated temperatures. The concrete used for this research will be typical class IV FDOT mass concrete mixes. The use of fly ash and slag as partia l replacement of cement is known to increase the durability and strength of concrete. Th ere is little information available on its influence on ettringite formation in concre te cured at elevated temperatures. This

PAGE 21

6 dissertation reports findings on how the strengt h and durability of concrete cured at the elevated temperatures. Additionally by the use of Scanning electron Microscope, this dissertation presents findings on ettringite formation in c oncrete curried at elevated temperatures and how this is influenc e by the addition of fly ash and slag. Research Methodology This dissertation was conducted by performing the following tasks: 1. Performed a state of the ar t review of work reported on heat generation in mass concrete and measures taken to avoid cracks and premature deterioration of concrete. 2. Evaluation of the effects of concrete te mperature on the properties of hardened concrete. The evaluation included the fo llowing tests: compressive strengths, rapid chloride permeability, time to corrosion, volume of permeable voids, and microstructure analysis using the S canning Electron Micros cope (SEM). a. Class IV Structural concrete mixe s, consisting of 18% replacement by weight of cement with class F fly as h, were used. Specimens required for the above mentioned tests were cast at room temperature and stored in water tanks where they were subjected to different curing temperatures (73 to 200F). b. Other mixes tested were similar to Pa rt a, except that 50% of cement was replaced by slag. Molds were cast a nd stored as explained in part a. 3. Analyzed the test results and determine the maximum internal concrete temperature above which the concrete pr operties will be affected (later age strength reduction, durab ility problems, and DEF).

PAGE 22

7 4. Examination of the current FDOT mass c oncrete specifications and suggest, if necessary, the requirement for maxi mum curing temperature or maximum concrete placement temperature. Importance of Research The research presented in this dissertati on will provide information on the effect of elevated curing temperatures on the strength and durability of typical class IV FDOT mass concrete mixes. Additionally information from this research will serve as a basis to decide if the specification for mass concrete used by FDOT should specify a limit on the maximum curing temperature. Fly ash and slag are used in typical class IV mass concrete and this research will show their effect at high curing temperatures on the strength and durability of the concrete and the potential of DEF formation.

PAGE 23

8 CHAPTER 2 LITERATURE REVIEW Introduction This chapter presents a state-of-the-a rt review of literature on how strength, durability and formation of delayed ettringite (DEF) in concrete are affected by high curing temperatures. In massive concrete st ructures, high curing temperatures result from a combination of heat produced by the hydration of concrete and the relatively poor heat dissipation of concrete. Although various measures are implemented to limit the maximum temperatures in mass concre te, a high core temperature of 200oF has been recorded in Florida for a mass concrete st ructure cast during the summer. While such concrete meets the specification of mainta ining a maximum differential temperature of 35oF between the core and surface of the mass c oncrete structure, of major concern is what happens to the strength, durability and DE F in the concrete when subjected to such high curing temperatures. This chapter reviews how heat is genera ted in concrete from the hydration of cement. Cracking of concrete due to the heat as well as the microstructure formed under such high temperature curing is examined. Th e influence of the microstructure formed under high curing temperatures on the strength and durability of conc rete are presented. To improve the quality of concrete struct ures cured under high temperatures, other cementitious materials such as fly ash and blast furnace slag have gained increasing use in mass concrete structures. The effects on the microstructure of conc rete due to the use of such materials and the influence on streng th and durability of ma ss concrete structure

PAGE 24

9 are reviewed. A final review is presente d on how high curing temperatures makes hardened concrete structures susceptible to damage from the formation of delayed ettringite (DEF). Cement Hydration The compounds of Portland cement (see Table 2.1) are nonequilibrium products of high temperature reactions in a high-ener gy state. When ceme nt is hydrated, the compounds react with water to acquire stab le low-energy states, and the process is accompanied by the release of energy in the form of heat (Mehta and Monteiro, 1993). Cement acquires its adhesive property from its reaction with water by forming products, which possess setting, and hardening properties. Table 2.1 Major Compounds of Portland Cement Name of compound Oxide composition Abbreviation Tricalcium Silicate Dicalcium Silicate Tricalcium Aluminate Tetracalcium Aluminoferritte 3CaO.SiO2 2CaO.SiO2 3CaO.Al2O3 4CaO.Al2O3.Fe2O3 C3S C2S C3A C4AF The heat generated from the hydration of cement causes a rise in temperature of concrete. If this rise occurred uniformly th roughout a given concrete element without any external restraint, the element would e xpand until the maximum temperature has been reached. The concrete will then cool down with uniform contraction as it loses heat to the ambient atmosphere. This uniform expansion and contraction will result in no thermal stresses within the concrete element. Accord ing to Neville (1997), restraint exists in all but the smallest of concrete members. These thermal restraints result in external and internal cracking of the concrete. Figure 2.1 shows an example of temperature change,

PAGE 25

10 which causes external cracking of la rge concrete mass. The critical 20oC (35oF) temperature difference occurs during cooling (FitzGibbon, 1976). Figure 2.1 External thermal cracking In massive concrete structures, internal re straint occurs from the inability of the heat to dissipate quickly from the core of the member due to the low thermal diffusivity of the concrete. A temperature differential is set up between the core of the concrete and the surface due to the accumulation of the heat from the hydration process. The unequal thermal expansion in the various parts of the concrete member results in stresses, compressive in one part and tensile in the ot her. Cracking of the su rface results when the tensile stresses at the surface of the element due to the expansion of the core exceed the tensile strength of the concrete. Accordi ng to FitzGibbon (1976), the cracking strain of concrete is reached when an inte rnal thermal differential of 20oC (36oF) is exceeded. Figure 2.2 shows a pattern of temperature ch ange, which causes internal cracking of a large concrete mass. The critical 20oC (36oF) temperature is reached during heating but Crack condition as surface cools too fast 20 o C Core temp. Surface temp. 4 days 3 2 1 20 o C 40oC 60oC 80oC 20 o C Core temp. Surface temp. 4 days 3 2 1 20 o C 40oC 60oC

PAGE 26

11 cracks open only when the interior has cool ed through a greater temperature range than the exterior. Figure 2.2 Internal thermal cracking Cracking due to thermal behavior may cau se loss of structural integrity and monolithic action or may cause extreme seep age and shorten the service life of the concrete structure. Various measure are undertak en to reduce the temperature rise in large concrete pours. Notable among these measures include: o The prudent selection of a low-heat-g enerating cement system including pozzolans; o The reduction of the cementitious content; o The careful production control of aggregate gradations a nd the use of large-size aggregates in efficient mixe s with low cement contents; Crack initiated but does not open until core cools through greater range than surface 20 o C Core temp. Surface temp. 4 da y s 3 2 1 20 o C 40oC 60oC

PAGE 27

12 o The precooling of aggregates and mixing wate r (or the batching of ice in place of mixing water) to make possible a low concrete temperature as placed; o The use of air-entraining admixtures and chemical admixtures to improve both the fresh and hardened proper ties of the concrete; o Coordinating construction schedules with seasonal changes to establish lift heights and placing frequencies; o The use of special mixing and placing equi pment to quickly place cooled concrete with minimum absorption of ambient heat; o Dissipating heat from the hardened conc rete by circulating cold water through embedded piping; o Insulating surfaces to minimize thermal diff erentials between the interior and the exterior of the concrete. Despite the application of the above-men tioned measures to control temperature rise in concrete, maximum core temperatures of 200oF have been recorded in Florida. This high temperature have been reached while satisfying the specification for mass concrete of maintaining a maximu m temperature differential of 35oF between the core and the surface of the concrete structure. Of increasing concern is the effect on the properties of concrete when subjected to su ch high curing temperatures. An examination of the microstructure of concrete formed at high curing temperatures is reviewed next. Effect of Curing Temperature on the Microstructure of Hydrated Cement Paste Verbeck and Helmuth (1968) found the reacti ons between cement and water to be similar to any other chemical reaction, pro ceeding at a faster rate with increasing temperature. This rapid initial rate of hydr ation at higher temperatures they theorize retards subsequent hydration of the cement producing a non-uniform distribution of the

PAGE 28

13 products of hydration within th e paste microstructure. At high temperatures, there is insufficient time available for the diffusion of the products of hydr ation away from the cement particles due to the low solubility and diffusivity of the products of hydration. This results in a non-unifor m precipitation of the products of hydration within the hardened cement paste. The results of a calorimetric study on the early hydration of cement as reported by Neville (1997) indicate that a heat evolution peak occurs at about 6 to 8 hours after the initialization of the hydration process at normal temperatures This was revealed from early hydration reactions of cement, using the conduction calori meter (Verbeck and Helmuth, 1968). During this period, the cemen t undergoes very rapid reactions with 20 percent of the cement hydrating over a 2 or 3hour period. At an elev ated temperature of 105oF, these reactions are accelera ted with as much as 30 to 40 percent of the cement hydrating in a 2-hour period. At steam curing temperatures, 50 percent or more of the cement hydrates in an hour or less. Products of cement hydration have low solubi lity and diffusivity and at high curing temperatures, the rapid hydration does not allow for ample time for the products to diffuse within the voids. This results in a high concentration of hydration products in a zone immediately surrounding the grain. This forms a relatively impermeable rim around the cement grain, which subsequently retard s any subsequent hydration (Verbeck and Helmuth, 1968). This situation does not occur in normal temperature curing where there is adequate time for the hydration products to diffuse and precipitate relatively uniformly throughout the interstitial space among the cem ent grains. The coarse pore structure in

PAGE 29

14 the interstitial space from the high temperatur e has a detrimental effect on the strength of concrete. Further evidence from Goto and Roy ( 1981) confirms the observation by Verbeck and Helmuth (1968) of retardation of subse quent cement hydration at high temperatures. In an examination of the structure of the hydrated cement paste subjected to high temperatures in its early life, Goto and Roy (1981) found out that curing at 60oC (140oF) resulted in a much higher volume of pores la rger than 150nm in diameter compared with curing at 27oC (81oF). These large pores make the conc rete susceptible to deterioration from harmful substances, which are easily tr ansported through the c oncrete structure. A study by Kjelsen et al (1990) of the micros tructure of cement pa stes hydrated at temperatures ranging from 41 – 122oF (5 – 50oC) using backscattered imaging found that the low curing temperatures resulted in a uniform distribution of hydration products and fine self-contained pores. Elevated temperatures on the other hand resulted in a nonuniformly distributed hydration products and coarse, interconnected pores. The microstructure of the hydrated cement paste formed at high cu ring temperatures affect the strength and durability of the concrete. Th e large interconnected pores resulting from high temperature curing does not make for dur able concrete structures. Since strength resides in the solid parts of a material, the presence of voids as a consequence of high curing temperature are detrimental to the strength of the concrete. Dense Shell of Hydration Products Kjellsen, Detwiler and Gjrv (1990) suppor t the concept that a dense shell of hydration products surrounding the cement grains is formed at higher curing temperatures. Hydration products are more uni formly distributed at lower temperatures. In addition, at higher temperat ures of curing there are five phases as opposed to the

PAGE 30

15 standard four phases at lower temperatur es. The five phases are unhydrated cement, calcium hydroxide, two densitie s of C-S-H and pores. The st rength of the material is greatly affected by the uniformity of the microstructure. At the elevated temperatures the C-S-H close to the grains is much denser and stronger. However, the intervals between the cement grains determine the strength of the concrete. Therefore curing at elevated temperatures has a harmful effect on the later-age strength of concrete. Additionally elevated curing temperatures according to Kjellsen, Detwiler and Gjrv (1990) result in increased porosity. Kjellsen, Detwiler and Gjrv (1990) further noted that C3S pastes that were cured at higher temperatures (50100C) had a coarser stru cture, including an increase of large pores, over those cured at 25 C. Even steam curing (97C) resulted in coarser pore structure. The difference in porosity is attributed mostly to the difference in volume of pores of radius 750-2300 A. For plain cement pastes of equal water-cement ratios cured to the same degree of hydrati on, the higher the curing temperature the greater the total porosity. The results indicate th at large pores have th e greatest effect on permeability. Permeability is a contributing component to most durability problems, therefore it is suggested that higher curing temperatures pos sibly reduce the durability of plain cement concretes. Effect of Curing Temperature on Concrete Strength Development The strength of concrete is its ability to resist stress without failure. Strength of concrete is commonly consider ed its most valuable propert y. Strength usually gives an overall picture of the quality of concrete because it is directly related to the structure of the hydrated cement paste (Neville, 1997). A rise in curing temperature according to Neville (1997) speeds up the hydration process so that the structure of the hydrated cement paste is established early. Although a

PAGE 31

16 higher temperature during placi ng and setting increas es the very early strength, it may adversely affect the strength from 7 days (Nev ille, 1997). This is because the rapid initial hydration according to Verbeck and Helmuth ( 1968) appears to form products of a poorer physical structure, probably more porous, so that a proportion of the pores will always remain unfilled. Since the voids do not contribute to the strength of concrete, a low temperature with slow hydration will re sult in a uniform dist ribution of hydration products within the inters titial space and high strengt hs at latter ages. A fast hydration of cement from high curing temperatures will result in a high early strength due to more hydration products be ing formed. At latter ages however, the retardation in hydration as a result of a dense shell around the hydrating cement grains will result in a more porous structure a nd reduced strengths as shown in Figure 2.3 (Verbeck and Helmuth, 1968). Figure 2.3 Effect of curing temperatur e on concrete strength development

PAGE 32

17 Effect of Temperature on the Durability of Concrete According to ACI Committee 201, durability of Portland cement concrete is defined as its ability to resi st weathering action, chemical at tack, abrasion, or any other process of deterioration. Durable concrete will retain its original form, quality, and serviceability when exposed to its envi ronment. Although designers of concrete structures have been mostly interested in the strength charact eristics of concrete, durability issues in concrete technology have been brought to the forefront in recent times as a result of the premature failure of nondurable concrete structures. The pore structure of the concrete dete rmines the ease with which deleterious harmful substances such as chloride ions are transported into the concrete. Harmful substance such as chloride ions in concre te attack and corrode the steel resulting in premature failure of the structure. High curi ng temperatures in conc rete result in porous concrete. This is because the low diffusivity of the hydration products does not allow for uniform distribution at high curing temperatur es due to the faster reaction rate. These hydration products precipitate in the vicinity of the cement grains resulting in a more porous concrete. At low cu ring temperatures, the hydrat ion products are uniformly distributed within the interstitial spaces making it difficult for deleterious harmful substances to be transported into the concrete Kjellsen et al. (1990) performed an inve stigation of the pore structure of plain cement pastes hydrated at 41, 68 and 122oF (5, 20 and 50oC respectively). The specimens were tested when they reached 70% hydrati on, a time marking adequate development of the microstructure. Two techniques used to measure porosity in this study were mercury intrusion and backscattered el ectron images. They theorized that during hydration at elevated temperatures cement hydration proceed s more rapidly. Subsequently since the

PAGE 33

18 cement has low solubility and low diffusibilit y, cement hydration products are not able to disperse at a significant distance from the cement grain in the limited time provided at high temperature curing. This causes areas of dense hydration produc ts that act as a barrier, preventing further hydra tion. When there is a de velopment of dense hydration product there is also a development of greater volume of large pores and a coarser pore structure. The large pores correspond to a re duction in the modulus of elasticity of the concrete indicating increased cracking as it is exposed to structural stresses. The curing temperature clearly affected the pore structure of hydr ated cement paste as shown in Table 2.4. The higher curing temper ature resulted in a greater quantity of larger pores as well as an increase in the total porosity. These results are in agreement with the observation by Goto a nd Roy (1981) that curing at 60oC (140oF) resulted in a much higher volume of pores larger than 150nm in diameter compared to curing at 27oC (81oF). These larger pores make the concrete more susceptible to attack by harmful substances since they provide an easier pa thway through the concrete. Permeability is a contributing factor to various kinds of durability problems, therefore suggesting that high curing temperatures could reduce the durability of plain cement concretes. The increased permeability also leads to increased water intr usion to the reinforcing steel and promoting an increase to the rate of corrosion of the members. Table 2.2 Measured Porosity Curing temperature Porosity (MIP + HP) Porosity (BSEI) Standard deviation 41F 33.2% 4.27% .818% 68F 34.2% 10.93% 1.086% 122F 35.7% 15.11% 1.881%

PAGE 34

19 Campbell and Detwiler (1993) explain that th e durability of concrete is a primary contributor to its satisfactory performance. Agencies typically control the durability of concrete by restricti ng the water-cement ratio to 0.45 or less. However, the curing process is often overlooked, though it also aff ects the durability of the concrete. A basic principle noted is that the Po rtland cement concretes resistan ce to penetration by chloride ions is reduced due to coarsening of the cem ent paste pore structure. Specifying a low water-cement ratio provides limited effectiveness in bettering the performance of the concrete. Fly ash and Slag in Concrete Class F fly ash is an artificial pozzolanic material, which possesses no cementitious value, but in finely divided form, in the presence of moisture, chemically reacts with calcium hydroxide from the Portland cem ent reaction to form compounds possessing cementitious properties. The fly ash reaction products closely resemble the calcium silicate hydrate produced by hydration of Po rtland cement (Neville, 1997). The fly ash reaction does not start until sometime after mi xing. According to Fraay et al (1989), the glass material in fly ash is broken down only when the pH value of the pore water is at least about 13.2. The increase in alkalinity required for the fly ash reaction is achieved through the reaction of the Po rtland cement. At high temper atures, the fly ash reaction takes place sooner due to the increased hydration rate of the cement. Prior to the reaction of the fly ash particles, they act as nuclei for the precipitation of the cement hydration. When the pH of the pore water becomes hi gh enough, the products of reaction of fly ash are formed on the fly ash particles and in thei r vicinity. With the passage of time, further products diffuse away and precipitate within th e capillary pore system, this result in a reduction of the capillary porosity and consequen tly a finer pore structure (Fraay et al,

PAGE 35

20 1989). Figure 2.8 shows the changes in pore size distribution determined by mercury porosimetry, in cement paste containing 30 percent of Class F fly ash by means of total cementitious material (Fraay et al, 1989). The cement paste becomes increasingly denser after the initiation of the po zzolanic reaction of fly ash. Figure 2.4 Pore size distribution with age for 30% Fly ash mix Slag is a waste product in the manufactur e of pig iron. Chemically, slag is a mixture of lime, silica and alumina, the same oxides that make up Portland cement (Neville, 1997). Compared to the fly ash, fine ly ground granulated blast-furnace slag is self-cementing. It does not require calcium hydroxide to form cementitious product such as calcium silicate hydrates. When used on its own, the amounts of hydration products formed by the blast-furnace slag is insufficient fo r application of the material to structural purposes. Used in combination with Portla nd cement, the hydration of the slag is accelerated in the presence of calcium hydr oxide and gypsum (Mehta and Monteiro, 1993). The beneficial effects of slag arise form the denser microstructure of the hydrated cement paste, more of the pore space is filled with the hydration products than in cement only mixes.

PAGE 36

21 Supplementary cementing materials are sugge sted to increase the performance of the concrete. Campbell and Detwiler inve stigated the optimum mix design for satisfactory strength and durability of steam-c ured concrete with 0 .45 water-cement ratio and various compositions of Canadian Type 10 cement (ASTM Type I) with slag and silica fume. The compressive strength of the cylinders after 18 hours of steam curing and one day of moist curing were compared. The results as shown in Table 2.5 reveal that slag is effective in reducing the rate of ch loride ion diffusion and therefore increasing the durability of the concrete. However the mixes with silica fume and slag, or silica fume alone were more durable. Table 2.3. Results of compressive strength and AASHTO T-277 test Mix no. Description Compressive strength MPa Total Charge passes, coulombs, average of three slices Rating M1 Control:100% PC 27.3 11130* M2 30% Slag 25.3 7800 M3 40% Slag 27.9 7690 M4 50% Slag 28.9 4500 High M5 5.0% SF 32.6 1780 Low M6 7.5% SF 33.3 910 M7 10.0% SF 36.4 290 M8 30% Slag; 7.5% SF 28.5 350 M9 40% Slag; 7.5% SF 31.3 200 M10 30% Slag; 10% SF 34.5 150 Very Low *Extrapolated value. Detwiler, et al. (1994) inve stigated the chloride penetration of 0.4 and 0.5 watercement ratio concretes containing either 5 percent silica fume or 30 percent slag (substitution by mass) cured at elevated temperatures. They found that higher curing temperatures resulted in great er penetration of chloride i ons. In addition, at any given

PAGE 37

22 temperature, both the silica fume and slag c oncretes performed bette r than the Portland cement concrete. Their studies showed that the use of pozzolanic materials is more effective than lowering the water-cement ra tio from 0.5 to 0.4 in improving the resistance to chloride ions (Tables 2.6 and 2.7). Table 2.4 AASHTO T-277 tests for charge passed Mix w/c 73F 122F 158F Portland Cement .40 .50 5700 9800 12,000† 13,000† 18,000† 16,000† 5 % Silica Fume .40 .50 1500 1800 3000 3400 4100 13,000 30% Slag .40 .50 1300 1700 1500 2200 4300 5400 *Charge(coulombs) passed in 6 hr for concrete s cured at constant te mperatures indicated to degree of hydration of approximately 70 percent. †Extrapolated values. These tests were terminat ed before the full 6 hr had elapsed due to excessive temperature increases. Table 2.5 Rate of chloride diffusion ppm/day (average of three replicates, Norwegian test) Concrete w/c 73F 122F 158F Plain Cement .40 .50 10 13 12 15 34 38 5 % Silica Fume .40 .50 4 3 7 5 12 22 30% Slag .40 .50 3 6 4 7 13 18 Delayed Ettringite Formation (DEF) in Concrete In the early 1980’s, Heinz and Ludwig (1987) observed that prec ast units made of high strength concrete that had been heat treated during production, showed damage of the structure connected with a loss of strengt h. These damages occurred in those building components which for several years had b een subjected to open-air weathering and

PAGE 38

23 therefore to frequent satu ration. The damage was charac terized by crack formation emerging from the edges of the building comp onents as well as a loss of bond between the cement paste and the coarse aggregates. The damage was attributed to the late formation of ettringite in the hardened conc rete. Delayed ettringite formation (DEF) is the destructive development of ettringite in concrete, months or years after placement in an environment where moisture exposure is frequent (Hime and Marusin, 1999). DEF is a worldwide phenomenon having been found in railway ties (sleepers) produced in Germany, Finland, The United States, Aust ralia and South Africa (Hobbs 1999, Heinz & Ludwig 1987, Hime & Marusin, 1999). Ettringite (C6ASH32) in Portland cement systems is the first hydrate to crystallize during the first hour of placing the concrete. This is because of the high sulpfate/aluminate ratio in the solution phase during the first hour of hydration. The precipitation of early ettringite contributes to stiffening (l oss of consistency), setting (solidification of the paste) and early strength development. Later, after depletion of sulfate in the solution when the aluminate concentration goes up again due to renewed hydration of C3S and C4AF, ettringite becomes unstable a nd is gradually converted into monosulfate (C4ASH18) which is the final product of Po rtland cements containing more than 5 percent of C3A (Mehta & Monteir o, 1993). At high curing temperatures, the decomposed ettringite reforms in the hardened concrete in the presence of moisture with the resultant expansion and deterioration of the concrete. In a study of expansions in mortar samples subjected to higher curing temperatures, Lawrence (1995) found that the minimum curing temperatures for expansion lie between 65 and 70oC. The primary ettringite is unstable when cured at this te mperature due to the am ount of alkalis in the

PAGE 39

24 pore liquid. If the concrete is exposed to such temperatures, primary ettringite will not be formed and that which was formed prior to such a heat treatment will decompose (Stark & Seyfarth, 1999). Under moist conditions, at or below room temperature, ettringite again becomes the stable phase and may cause DEF (Heinz, Kalde, Ludwig & Ruediger, 1999). The microsturcture of concretes and mortar s after expansion is characterized by the presence of bands of ettringite around aggr egate particles and with in cracks, pores and voids in the cement paste (Scrivener & Lewis, 1999). The expansive process in DEF is marked by enlargement of the affected conc rete and the developm ent of gross cracking. In extreme cases, the concrete becomes cr umbly and soft, proving evidenced of the destruction of the effectiveness of th e cement paste binder (Diamond, 1996). DEF is not only limited to precast concrete units, recent observations of DEF in large sections of in-situ conc rete have been made in the U.K. (Johansen & Thaulow, 1999). DEF whether formed as a result of st eam curing or from high core temperature from larger sections of concrete cast in-s itu has been found by Diamond (1996) to exhibit similar crack patterns and micros tructural features. The observed crack pattern is that of a network with component crack segments runnin g partly along aggregate peripheries (rim cracks), but generally connecting through se gments running through the cement paste (paste crack). Two opposing sc hools of thought exist as to how DEF leads to expansion of the concrete. The homogeneous paste ex pansion theory (Johansen & Thaulow, 1999), maintains that the paste expands and the DEF is deposited in the gaps created between the aggregates and the paste as the aggregates do not expand. This theory is refuted by many writers among them Diamond (1996) who main tain that crystal pressure from the

PAGE 40

25 formation of ettringite better explains the e xpansion and subsequent deterioration of the concrete. The expansion associated with the forma tion of ettringite is influenced by the microstructure of the material in which it is deposited and the amount of pore space available (Taylor, Famy & Scrivener, 2001). So me of the ettringite produced is deposited freely in available space and does not contribute to expansi on. Thus, the expansion does not depend simply on the amount of ettringite produced. Additionally, expansion depends on the quality of the pore space. A given amount of ettringite will produce more expansion if the pores in whic h it is deposited are small and poorly connected than if they are large and more highly connected. SEM examination at 180 days and 5 y ears of concrete cured at various temperatures showed the follo wing (Stark & Seyfarth, 1999): o For normally cured concrete, there was no ev idence of ettringite at 180 days but at 5 years the concrete showed a dense struct ure with fine ettrin gite needles covered the pore surfaces, without filling the por es completely. An accumulation of ettringite in the available spaces due to transportation processe s took place within the time interval. o At 180 days samples cured at 60oC showed small needle-like crystals evenly distributed on pore surfaces and in in terfaces between aggregate and hardened cement paste. At 5 years the ettringite found was in larger crystals and in substantially larger amounts than found at 180 days. The concrete was crack-free comparable to the normally cured concrete The concrete was in tact with no hint

PAGE 41

26 of damage, indicating that the existence of ettringite in internal damages of hardened concretes is not an indicati on of damaging ettringite formation. o Samples cured at 90oC showed large ettringite crys tals in structurally damaged areas and on surfaces of pores. After 5 years, the concrete was completely interspersed with microcracks. Pores, microcracks and interfaces were completely filled with new phase formations of ettringite.

PAGE 42

27 CHAPTER 3 RESEARCH METHODOLOGY Introduction This chapter presents the materials, mixtur es, and test methods used to evaluate the effects of elevated curing temperatures on the strength, durability and formation of Delayed Ettringite (DEF) in mass concrete. The work was divided into three phases as follows: In phase 1, three mixes of pastes comprising plain cement, cement with 18% fly ash and cement with 50% fly ash were cured at temperatures of 73, 160 and 200oF for various durations to determine the age at which a maturity of 70% degree of hydration of the cement was attained. Once th is age was determined for the various mixes and curing temperatures, mass concrete with binders in the same proportions as in the paste would be made and tested wh en they reached 70% degree of hydration. This would ensure that all the mass concrete properties would be determined at the same maturity and make for easy compar ison. Difficulty in establishing and exact time to reach 70% degree of hydration as well as inability to reach th is maturity in the cement/fly ash mixes resulted in using the curing durations of 7, 28 and 91 days as the bases of comparing the mass concrete properties. In phase II, four FDOT Class IV mass conc rete mixtures were made and cured at temperatures of 73oF, 160oF and 180oF for durations of 7, 28 and 91 days. The concrete samples were tested to determine the following properties: Compressive strength – ASTM C 39 (ASTM 1996)

PAGE 43

28 Resistance to chloride penetr ation – ASTM C 1202 (ASTM 1994) Time to Corrosion – FM 5-522 Density and percentage of voids – ASTM C 642 (ASTM 1997) Phase III. This phase involved microstructu re analysis of the mass concrete by the aid of a scanning electron microscope. Mo rtar samples sieved from the concrete mixes were subjected to the same curing regi me. At each test age, the mortar samples were removed and placed in methanol to stop further hydration of the cement. After a minimum of 7 days in the methanol, inches thick wafers were cut from the samples. These wafers were fractured and ex amined to determine the presence or lack of ettringite crystals. Degree of Hydration Introduction A well-hydrated Portland cement paste consis ts mainly of calcium silicate hydrates, calcium sulphoaluminate hydrates and calcium hydroxide (Metha and Monteiro, 1993). When the cement paste is ignited to a temperature of 1832oF (1000oC), the nonevaporable water chemically combine in the hydration pr oducts is released. The degree of hydration is a measure of the nonevaporable water content of the paste expressed as a percentage of the nonevaporable water content of fullyhydrated cement paste. The nonevaporable water content of fully-hydrated cement paste is 0.23 grams of water per gram of cement (Basma et al, 1999). For this study a degree of hydration of 70% was decided as the maturity level at which the mass concrete properties would be determined. The choice of 70% degree of hydration was based on a study by Kjellsen et al (1990) who found that the time required to attain this level of matur ity is not so long as to be im practical to replicate in the

PAGE 44

29 laboratory. Additionally, by this point, the rate of hydration has slowed enough that small variations in curing time will not result in si gnificant error making for easy comparison of the various samples. Methodology Tables 3.1 and 3.2 show the chemical co mposition and physical properties of the cement, fly ash and blast furnace slag used in the study. The Portland cement used was AASHTO Type II. Described here are the methods applied to determine the time to attain 70% degree of hydration for three paste mixes isothermally cured at temperatures of 73, 160 and 200F. The three paste mix designs tested are as follows 1. Plain cement paste mix 2. Cement and 18% Fly ash paste mix 3. Cement and 50% Fly ash paste mix

PAGE 45

30 Table 3.1 Properties of Cement and Fly ash Chemical Composition Portland Cement Fly Ash % Silicon Dioxide (SiO2) 20.6 % Aluminum Oxide (Al2O3) 5.1 % Ferric Oxide (Fe2O3) 4.7 86.9 % Magnesium Oxide (MgO) 0.7 % Sulfur Trioxide (SO3): 3.2 0.2 % Tricalcium Silicate (C3S) 50.0 % Tricalcium Aluminate (C3A) 5.6 % Total Alkalis as Na2O 0.52 % Insoluble Residue 0.12 Loss of Ignition (%) 1.5 3.2 Physical Properties Fineness: Blaine (m2/kg) 341 #325 Sieve 34% Time of Setting (Gilmore): Initial (Minutes) Final (Minutes) 145 235 Fly ash activity index: 7 Days – 69% 28 Days – 78% Compressive Strength (PSI) – ASTM C-150: 3 Days 3200 7 Days 4070 Table 3.2. Properties of Blast furn ace slag –ASTM C 989-97b, AASHTO M302 Chemical Analysis % Silicon Trioxide (SiO3) 2.3 % Sulfide Sulfur 0.9 Slag Activity Index 7 Days 28 Days 96% 132% Physical Properties Fineness: #325 Sieve (45um) 2% Compressive Strength (PSI): 7 Days STD Average 7 Days Slag Average 28 Days STD Average 28 Days Slag Average 4750 4380 5900 7810 Blast furnace slag produced by Lafarge in Tampa

PAGE 46

31 Table 3.3. Mix proportions of paste mixes Mix design Cement (lbs) Fly Ash (lbs) Water (lbs) w/b ratio Mixing Water F 18% fly ash at 73F 3.540 .777 1.77 .41 73 18% fly ash at 160F and 200F 5.057 1.110 2.53 .41 136 50% fly ash at 73F 2.467 2.467 2.02 .41 73 50% fly ash at 160F and 200F 3.083 3.083 2.53 .41 136 The proportions of materials used in the paste mixes are shown in Table 3.3. The pastes were made in accordance to ASTM C 305-99. The procedures followed to determine the degree of hydration were as follows: a. Three samples each was made of each paste mix to be tested at each curing period and temperature. Samples at 73F were tested at ages of 1, 3, 7, 10, 14, 28 and 56 days. Samples at 160 and 200F were tested at ages of 1, 3, 7, 10 and 14 days. b. The water used for samples cured at 160F and 200F was preheated to 136F, to produce a cement paste with temperature of approximately 98F. This was done to reduce the time for samples cured at 160 a nd 200F to be in equilibrium in the curing environment. c. Samples were cast in 1-ounce polypropylene screw cap jars (1.78 cubic inches) as shown in Figure 3.1. The polypropylene ja rs offer high temperature resistance up to 275F for short period s and 212F continuously. Each jar was capped and placed in watertight bags, which were submerged in a bucket of water. The watertight bags were used to ensure th at during the first 24 hours of curing no additional water was permitted to affect the designated water cement ratio. The water in the buckets for samples cu red at 160 and 200F was preheated to approximately 100F to ensure a short time la g to attain the elevated temperatures in the ovens as shown in Figure 3.2.

PAGE 47

32 Figure. 3.1 Paste samples cast in on e-ounce polypropylene screw cap jars. d. The samples cured at 73F were placed in watertight bags immersed in water and cured in a moisture room kept at 100% humidity and 73F, water. Figure 3.2. Oven used to cure samples at 200F e. After 24 hours, the samples were demolded, placed in four-ounce polypropylene jars as shown in Figure 3.3 and placed in their curing environment to continue the isothermal curing for the remaining curing duration.

PAGE 48

33 Figure 3.3 Samples cured in four-ounce polypropylene jars after demolding f. At the end of curing duration three samp les for each mix and temperature were removed and placed in methanol. Samples cured at 160 and 200F were cooled to room temperature before placing in the me thanol. This was done to avoid igniting the methanol. The samples were placed in the methanol to stop further hydration of the cement. g. After at least 7 days in the methanol, the samples were removed and wiped clean. The samples were then crushed in a mechanical crusher (see Figure 3.4). The crushed sample was then pulverized. Figure 3.4 samples crushed in mechanical crusher

PAGE 49

34 h. Approximately 3 grams of the pulverized sample was then weighed as shown in Figure 3.5. The scale used was accurate to 1/10,000 of a gram. The samples were dried for 24 hours in an oven maintained at 2215F (105C ) to remove the evaporable water from the sample. After removal from the oven the samples were cooled to room temperature and the weight was recorded as w1. i. The samples were then ignited for 45 mi nutes at 1832F (1000C) to remove the nonevaporable water chemically combined in the hydration products. The samples were cooled to room temperature and the weight recorded as w2. Figure 3.6 shows samples removed from the oven after ignition. Figure 3.5 Approximately 3 grams of samples weighed. Figure 3.6 Samples removed after ignition at 1832F.

PAGE 50

35 Calculations to Determine the Degree of Hydration The calculation of the degree of hydration was based on the formula given by Zhang et al (2000). The nonevaporable water content, wn was cal culated according to the following equation: wn = (w1 – w2) rfc w2 (1 rfc) rfc = pf rf + pc rc The degree of hydration was determined as a ratio of wn / wnu wnu nonevaporable water content per gram of fully hydrated cement 0.23 w1 weight of the sample after drying w2 weight of the sample after ignition pf weight percent of fly ash in the mix, 18% and 50% pc weight percent of cement in the mix rf loss of ignition of fly ash 4.7% rc loss of ignition of cement 2.1% Problems Encountered in the Experimental Process Various problems were encountered during the experimental process to determine the degree of hydration of the paste samples. These problems and how they were resolved is presented below. 1. The oven used to cure samples at 160F fa iled five days into the curing process requiring a new oven to be used. 2. Some of the samples kept cured in the ovens at 160 and 200F lost the water in which they were immersed during the c ourse of the curing duration. Cracking of the jar covers and evaporati on of the water caused this.

PAGE 51

36 3. To resolve the above problems, curing tanks as shown in Figure 3.7 were used in place of the ovens for the elevated temp erature curing. These tanks were filled with water maintained at 160 and 200F. 4. The degree of hydration tests were re peated based on curing for elevated temperatures in the curing tanks. The resu lts of the degree of hydration are shown in Figure 3.8. Figure 3.7 Curing tanks used for samp les at elevated temperatures.

PAGE 52

37 Degree of hydration Isothermal curing20 30 40 50 60 70 80 90 13710142856 Duration (days)Hydration (%) 0% FA 73F 0% FA 160F 0% FA 200F 18% FA 73F 18% FA 160F 18% FA 200F 50% FA 73F 50% FA 160F 50% FA 200F Figure 3.8 Degree of hydration (wnu = 0.23) Based on the results of the degree of hydration shown in Figure 3.8, samples made from the cement fly ash paste mixes did not attain a 70% degree of hydration for the temperatures and curing durations used in th is test. The times to reach 70% degree of hydration in the plain cement mix was established as shown in Table 3.4. Table 3.4 Time to 70% hydration in plain cement mix Curing Temperature (oF) Duration (approximate) 73 160 200 7 3 3 Based on the durations in Table 3.4, samp les of FDOT Class IV mass concrete (Mix 1 – appendix) based on the paste mix we re made and cured isothermally following the curing conditions used for the paste samp les. Three samples were tested for each temperature to determine the compressive strength in accordance with ASTM C 39 – 96. Compressive strength results are presented in Table 3.5 and Figure 3.9.

PAGE 53

38 Table 3.5 Concrete Mix 1 – 0% Fly Ash (Isothermal Curing) Compressive strength (psi) RCP (coulombs) Temp (oF) 70% DH 28 Days 90 Days 70% DH 28 Days 73 6,839 7,472 8252 5,845 4,720 160 4,621 4,963 5616 8,763 7,110 200 2,910 2,872 2636 9,756 11,070 Concrete 0% FA (ISO) Compressive strength2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 70% DH28 Days90 Days Curing duration (days)Compressive strength (psi) 73F 160F 200F 7 days 3 days 3 days Figure 3.9. Compressive strength results Figure 3.9 shows a substantial decrease in compressive strength of samples cured isothermally at 160 and 200oF compared to samples cured at room temperature. This is specially pronounced for 200oF curing temperature where co mpressive strength of a 90 days old sample is less than a 3 days old sa mple. The reduction in compressive strength of samples cured at elevated temperatures mi ght be due to high temperature changes (100 to 200oF) as the freshly mixed concrete is intr oduced into the high temperature curing environment and thermal shock to concrete.

PAGE 54

39 Concrete 0% FA (ISO) RCP2,000 4,000 6,000 8,000 10,000 12,000 70% DH28 Days Curing duration (days)Couloumbs 73F 160F 200F 3 days 7 days 3 days Figure 3.10 Rapid Chloride Permeability (RCP) results Figure 3.10 shows the RCP results of the concrete samples cured isothermally at 160oF and 200oF compared to samples cured at room temperature (73oF). Samples cured at the high temperatures recorded high char ges passing through the samples indicating reduced durability for the conc rete. The samples cured at 200oF showed reduced durability from 7 days to 28 days as the charged passed increased over the curing duration. At 28 days, the samples cured at 73oF had the least current passing indicating better durability than the samples cured at 200oF, which recorded the highest charges passing at 28 days. With the drastic reduction in compressive strength of the mass concrete samples cured at the elevated temperatures, the e xperimental set-up was changed as follows: 1. The curing was done adiabatically to simu late conditions as in mass concrete cured in the field. All the samples were introduced to the curing environment approximately 6 hours after the start of th e mixing process. Samples at 160F and 180F were introduced into th e curing tanks at 80F after which the heat was

PAGE 55

40 turned on. The curing temperature of 160 F was attained within 2 days after which the heat was turned off. The 180 F tank attained the maximum temperature after about 2 days after which the heat was turned off. The lids of the curing tanks were kept on whilst the temperatur e cooled to 73F within approximately two weeks of turning the heat off in both tanks. 2. The maximum temperature was reduced from 200 to 180F. 3. A review of mass concrete mixes used by the FDOT, was undertaken to examine the proportions of binders commonly used by the department. The results as shown in Table 3.6, indicated that 80 pe rcent of the cement/fly ash mixes had 0.18 and 0.20 of the cement replaced by fly as h. Two (2) per cent of the cement /fly ash mixes had a fly ash replaceme nt of 0.40. Based on this review, the proportion of fly ash replacement for the mass concrete tests was limited to 18 percent 4. The samples were then transferred to the mo isture room into curing baths, as were the 73 samples. Lime was then added to the water at this point in the curing cycle. 5. Following the change in the curing c onditions, new tests were conducted to determine the time to achieve 70% degr ee of hydration for the mix. The results from this test are shown in Figure 3.11. 6. As can be observed in Figure 3.11, the curves were very erratic making it difficult to establish the duration to attain matu rity of 70% degree of hydration in the various mixes. This led to the use of curing durations of 7, 28 and 91 days as the bases to compare the mass conc rete properties in this study.

PAGE 56

41 7. At specified curing durations, mass concrete samples described in the next section were tested and the degree of hydration of the cement was determined for that age and curing temperature. Table 3.6 Binders used in mass concrete mixes by the FDOT BINDERS USED IN MASS CON CRETE DESIGNS IN FLORIDA A. Cement mixes Proportion of Cement Number of mixes % Cement Mixes % Total mixes 1.00 10 100 11 B. Cement / Fly Ash mixes Proportion of fly ash Number of mixes % Cement/ Fly ash Mixes % Total mixes 0.18 18 32 21 0.19 6 11 7 0.20 21 37 24 0.21 1 2 1 0.22 5 9 6 0.30 1 2 1 0.35 2 4 2 0.39 2 4 2 0.40 1 2 1 Total 57 100 66 C. Cement / Blast Furnace Slag mixes Proportion of Slag Number of mixes % Cement/Slag Mixes % Total mixes 0.50 11 55 13 0.60 2 10 2 0.70 7 35 8 Total 20 100 23 SUMMARY Binder Number of Mixes % of Mixes Cement 10 11 Cement/ Fly Ash 57 66 Cement/Slag 20 23 Total 87 100

PAGE 57

42 Degree of hydration Adiabatic curing20 30 40 50 60 70 80 123456789101428 Duration (days)Hydration (%) 0% FA 73F 0% FA 160F 0% FA 180F 18% FA 73F 18% FA 160F 18% FA 180F Figure 3.11 Degree of hydration base d on adiabatic curing (wnu = 0.23) Mass Concrete Experiments Two typical FDOT Class IV concrete with fly ash or slag as the supplementary cementitious material to cement were used in the mass concrete tests (See appendix A). The goal of the tests was to determine the effects of elevated curing temperate on the strength and durability of concrete properties. Four mixes with different proportion of cement, fly ash and blast furnace slag as s hown in Table 3.7, were made and tested. The tests were repeated. The mixe s tested were as follows: o 0% Fly ash mixes (Mix 1 and Mix 3) o 18% Fly ash mixes (Mix 2 and Mix 4) o 0% Blast furnace slag mixes (Mix 5 and Mix 7) o 50% Blast furnace slag mixes (Mix 6 and Mix 8)

PAGE 58

43 Table 3.7. Mixture Proportions for FDOT Class IV mass concrete Saturated Surface-Dry Weights, lb/cu yd Mixture Cement Fly ash Slag Fine aggregate Coarse aggregate Air Entrainer (Darex) Admixture (WRDA) Water w/b ratio Mix 1 & 3 Mix 2 & 4 Mix 5 & 7 Mix 6 & 8 744 610 660 330 134 330 936 918 1076 1066 1746 1729 1794 1785 4 oz 4 oz 5 oz 5 oz 24.4 oz 24.4 oz 33.0 oz 33.0 oz 305 305 267 267 0.41 0.41 0.40 0.40 Samples made from the various mixes were cured adiabaticlly as before described. All the samples were mechanically vibrated during their preparat ion. After casting in their molds, the samples were kept in watert ight bags for 24 hours after which they were demolded and placed directly in the curing wate r. Samples cured at 73F were kept in the moisture room. The heat in the 160 and 180F tanks was turned off after the maximum temperature was attained. Cooling of the ta nks to a temperature of approximately 73F occurred over a 14-day period. The samples in the curing tanks were transferred into the moisture room and placed in limewater. Samp les cured at 73F were also places in limewater at this time. Various tests were performed on the mass concrete samples after 7, 28 and 91 days of curing. The tests performed were: 1. Determination of degree of hydration 2. Compressive strength – ASTM C 39 (ASTM 1996) 3. Resistance to chloride penetr ation – ASTM C 1202 (ASTM 1994) 4. Time to Corrosion – FM 5-522 5. Density and percentage of voids – ASTM C 642 (ASTM 1997)

PAGE 59

44 6. Microstructure analysis Compressive Strength The compressive strengths of the samples we re determined at curing durations of 7, 28 and 91 days. The compressive strengths were determined according to ASTM C 3993a, Standard Test Method for Compressive Stre ngth of Cylindrical Concrete Specimens by the FDOT physical laboratory. Twenty-seven 4” diameter x 8” cylinders were molded for each mix. Nine samples for each mix were tested at 7-, 14-, and 28-days age three for each curing temperature. Resistance to Chloride Penetration Each mix cured at the 73, 160 and 180F wa s tested at 28-, an d 91-days age to determine its ability to resist the chloride-ion penetration. Th e rapid chloride permeability for each sample was estimated following ASTM C 1202-94, Standard Test Method for Electrical Indication of Concrete’s Abili ty to Resist Chloride-Ion Penetration In this test, the chloride-ion penetrability of each sample was determined by measuring the number of coulombs that can pass through a sample in 6 hours. This provided an accelerated indication of concrete’s resistance to the pe netration of chloride-ions, which may corrode steel reinforcement or prestressed strands. Si x 4” diameter x 8” cylinders of each mix, two for each curing temperature were tested at 28-, and 91-days age. A 2” thick disc was sawed from the top of each cylinder and used as the test specimen. It has been determined that the total charge passed is related to the resistance of the specimen to chloride-ion penetration. The surface resistivity of each sample to the penetration of chloride ions was measured at the curing durations from the re maining portions of the samples used in the rapid chloride permeability tests.

PAGE 60

45 Time to Corrosion The time to corrosion test determines the duration of time for reinforcement within a sample to corrode. The time to corrosion was determined according to Florida Method of Test for An Accelerated Laboratory Me thod for Corrosion Testing of Reinforced Concrete Using Impressed Current. The samples used in this test were cylinders of 4” diameter x 6” long. Nine samples were made for each mix three for each curing temperature. Each sample contained a #4 re inforcing bar, 12” long. The bottom of the reinforcing bar was elevated by 0.75” from the bottom of th e mold. Fresh concrete was placed in each mold and each mold was overfill ed. The apparatus that had the reinforcing bars attached to it was placed over the cylin ders. The apparatus was then placed on an external vibrator that caused the reinforcing bars to submerged into the overfilled fresh concrete when the vibrator was turned on. Afte r vibration, a trowel wa s used to slope the overfilled top of the mold at a 15-degree angl e from the outer rim of the sample to the center of the sample. After 28 days of curing, the samples were further cured in a solution of 3% NaCl after which they were teste d. The tests were performed at the Florida Department of Transporta tion Corrosion Laboratory. Density and Percentage of Voids in Hardened Concrete The density and percentage of voids fo r each mix and curing temperature were determined at curing durations of 7, 28 and 91 days. The tests were done according to ASTM C 642 97, Standard Test Method for Density, Absorption, and Voids in Hardened Concrete by the FDOT physical laborator y. Approximately 800 grams of each sample was tested.

PAGE 61

46 Microstructure analysis – Scanning Electron Microscope (SEM) Introduction A microscope provides the ability to see mu ch finer details of an object than is possible to the naked eye. The scanning electron microscope (SEM), which became commercially available in the 1960s, permits the observation and characterization of heterogeneous organic and i norganic materials on a nanom eter (nm) and micrometer (um) scale (Goldstein et al, 1992). The reso lution of a microscope is the smallest separation between two points in an object that can be distinc tly reproduced in the image. Today’s SEM has achieved a resolution better than 10nm, an improvement by a factor about 103 relative to a light microscope (Sarkar, Aimin and Jana, 2001). The popularity of the SEM stems from its capability of obtai ning three-dimensional-like images of the surfaces of a very wide range of materials. Signals of Interest In the SEM, the area to be examined or microvolume to be analyzed is irradiated with a finely focused beam, which may be swept in a raster ac ross the surface of the specimen to form images or may be static to obtain an analysis at one position (Goldstein, Newbury, Joy, Lyman, Echlin, Lifshin, Sawyer and Michael, 1992). When a beam of primary electrons strikes a bulk solid, the el ectrons are either refl ected (scattered) or absorbed, producing various signals (Figure 3.12) The types of signals produced include secondary electrons (SE), backscattered electron (BSE), characteristic x-rays and othe r photons of various energies. These signals are obtained from specific emission volumes within the sample and can be used to examine many characteristics of the sample s such as composition and topography. The intensity of the backscattered electrons is proportional to the at omic number of the

PAGE 62

47 elements in the sample. More electrons are scattered from higher atomic number elements, and, in an image appear brighter than low atomic number elements which appear darker in an image. Backscat tered electrons therefore respond to the compositional variations in the sample and en able the distinctions of the various phases based on the differences in th eir average atomic numbers. Figure 3.12. Different interactions of an electron beam (PE) with the solid target. BSE = backscattered electrons, SE = secondary electrons, X = x-ray, AE = auger electrons Secondary electrons are loosely bound outer shell electrons from the sample atoms which receive sufficient kinetic energy during in elastic scattering of the beam electrons to be ejected from the atom and set in motion (G oldstein et al, 1992) Secondary electrons have a shallow escape depth and collecting them as an imaging signal enable high topographical resolution of the sample to cl early distinguish between the various shapes of the phases in the sample. Measuring th e energy and intensity distribution of the characteristic x-ray signals generated by th e focused electron beam enables chemical analysis of the specimen. This chemical analysis is done using the SEM’s adjunct microanalytical unit, commonly known as th e energy dispersive xray analyzer (EDAX), (Sarkar, Aimin and Jana, 2001). Characteristic x-rays are analyzed to yield both the

PAGE 63

48 qualitative identification and quantitative comp ositional information from regions of the specimen as small as a micrometer in diameter. SEM Use in Concrete Most of the properties of concrete are ev aluated according to standard procedures. The SEM does not fall under the realm of any st andard procedure. It is a relatively new technique which is yet to be universally accep ted by the concrete technologist. One of the first applications of SEM was in the study of concrete hydration in the early 1970s (Sarkar, Aimin and Jana, 2001). The chief in terests one has in st udying concrete under SEM are to study the effects of deterior ation of concrete or its performance characteristics, qualitative phase identificati on, grain morphology, distribution pattern and association with other phases (Sarkar, Aimin and Jana, 2001). Experimental Work The scanning electron microscope used in this research was the SEM JSM 6400. All analyses were conducted at the Major An alytical and Instrumentation Center at the University of Florida. The SEM analysis was used to determine the presence of ettringite crystals in voids of mortar samples sieved from the concrete mixes. The signals of interest used in this study when the el ectron beam impinged on the specimen were secondary electrons and characteristic x-ra ys. Because of the different morphological features characteristic of th e phases, they could be iden tified by secondary electron images. This avoided the use of thin or polis hed sections using back scatter (BS) electron which may wash out or grind out ettringite nests and introduc e artifacts such as cracks. Moreover with SE techniques, crevices and both sides of “hills” are revealed. Fly ash particles used in some of the mixes are cl early revealed by SE techniques, while BS procedures may reveal them primarily as voids because of their poor backscattered

PAGE 64

49 electron yield (Hime, Marusin, Jugovic et. Al 2000). Measuring the energy and intensity distribution of the characterist ic x-rays enabled a chemical analysis of the samples to confirm the various phases identified in the secondary electron image. Energy Dispersive Analysis of the X-rays (EDAX) was used to confirm or deny the presence of the ettringite. EDAX of an ettringite mass has a “step” pattern of the aluminum, sulfur and calcium peaks as shown in Figure 3. 13 (Hime, Marusin & Jugovic, 2000). Figure 3.13 The EDAX analysis of “gel” show ing calcium, sulfur, and aluminum peaks typical for ettringite Sample Preparation for SEM Examination The samples used for the microstructural an alysis were made from mortar sieved from the concrete mixes. The samples were cured adiabatically as the mass concrete samples. After 24 hours in watertight bags, the samples were demolded from the twoounce jar and placed directly in the curing environment. At the end of the curing period, the samples were removed from the curing ta nk and placed in methanol to stop further hydration. After at least 7 days in the methanol, the samples were removed and finely cut into ” thick wafers. The samples were th en placed in an oven maintained at a

PAGE 65

50 temperature of 230F for 24 hours to remove a ll the evaporable water, not used in the hydration process. The samples were stored in a desiccator after removal from the oven. To obtain very good images using the SEM and avoid the introduction of cracks or removal of any ettringite nests, cutting of the surface of the sample was avoided, instead pieces were fractured and the fractured surfaces were analyzed. The fractured pieces were cut and coated with carbon. Since the samples were non-conducting, coating was necessary to eliminate or reduce the electric charge th at builds up rapidly in a nonconducting specimen when it is scanned by a beam of high-energy electrons. Figure 3.14 shows mortar samples mounted and ready for examination in the SEM Figure 3.14. Mortar samples mounted on stubs for SEM examination

PAGE 66

51 CHAPTER 4 TEST RESULTS AND DISCUSSION Introduction This chapter presents results of the expe rimental work conducted to determine the maximum curing temperature to avoid durabili ty problems and the formation of delayed ettringite in mass concrete. The st udy was conducted in three phases: 1. Phase 1 involved tests to determine the tim e to achieve a maturity of 70% degree of hydration of cement in mass concrete mixes with cement, fly ash and blast furnace slag as the cementitious materials. 2. Phase 2 involved tests of two FDOT Class IV mass conc retes at temperatures of 73, 160 and 180F for 7, 28 and 91 days. Vari ous tests were performed on the concrete to evaluate the effect of th e curing conditions on the strength and durability of the concrete. 3. In phase 3, mortar samples prepared from the sieved mass concrete mixes were subjected to the same curing conditions. The samples were then examined under a scanning electron microscope to determine the formation or otherwise of delayed ettringite. Phase 1 – Determination of Degree of Hydration The results for the degree of the hydration for the different mixes tested are shown in Tables 4.2 through Table 4.5. Initially, all ca lculations for the degree of hydration were based on the fact that the nonevaporable wa ter content for 1 gram of fully hydrated

PAGE 67

52 cement was 0.23 grams of water. This value was found to be inapplicable to cement blends with fly ash or slag. Scanning Electron Microscope (SEM) obs ervations by Maltais & Marchand (1997) for pastes some incorporating fly ash as a 10, 20 and 30 per cent replacement of cement and cured at 68 and 104F showed that the fly ash did not react before at least 28 days. Although the fly ash did not react during the first days of curing, their test results indicated that it could not be considered as a totally inert material. Despite the very little pozzolanic activity, Maltais and Marchand (1997 ) found out that the presence of fly ash appeared to increase the mort ar nonevaporable water content at early days. This increase was attributed to an acceleration of the early cement hydration in the presence of fly ash. Two reasons for the acceleration of cement hydration in the presence of fly ash are physical and chemical effects. o Physical o The addition of fly ash tends to increa se the number of fine particles in the system. The presence of these fine particles contributes to increase the density of the matrix making for better hydration of the cement. o The replacement of cement particles by fly ash is also believed to increase the available space in the floc stru cture created by the cement grains. o The fine particles provide additiona l nucleation sites for cement hydration products. o Chemical o According to Maltais and Marchand (1997) the acceleration of cement hydration in the presence of fly ash is mainly related to the preferential

PAGE 68

53 adsorption of calcium ions on the fly ash particles. The phenomenon contributes to decrease the calcium ion concentration in the liquid phase, which subsequently favors the dissolution of calcium phases from the cement grains. Fly ash reacts with the calcium hydroxide formed from the hydration of the cement. The reduction in calcium hydroxide content fo rm the pozzolanic react ion will not enable a value of 0.23 to be a good estimate of th e degree of hydration. The pozzolanic reaction will reduce the amount of calcium hydroxide a nd replace it with hydrates formed by the pozzolanic reaction. The amount of water released from a mole weight of the hydrates is less than the amount of water released form a mole weight of calc ium hydroxide due to its large molecular weight. A more reliable estimate was determined for the cement fly ash mixes after hydrating paste at 73F in the moisture room for 1 year and calculating the nonevaporable water content. The new valu es for the nonevaporable water content for the cement and fly ash mixes were as follows: o 0.19 for cement and 18% fly ash mix with w/b ratio of 0.41 o 0.15 for cement and 50% fly ash mix with w/b ratio of 0.41. These values for the nonevaporable water content are comparable to that determined for various mixes of fly ash by Lam et al. (2000) and shown in Table 4.1 below.

PAGE 69

54 Table 4.1. Nonevaporabe water content for va rious Fly ash mixes Lam et al. (2000) w/b Fly ash replacement (%) *Wnu at 90 days 0.3 0.3 0.5 0.5 25 55 25 55 0.19 0.15 0.18 0.15 Calculated from ratio of Wn / Degree of hydration Legend: Degree of Hydration results o IOP –Isothermal curing of paste samples in oven o (Row # 1, 6, 14, 16, 17, 24, 25, 36, 37, 40, 41, 44, 45, 48, 49) o ITP –Isothermal curing of paste samples in tanks o (Row # 2, 7, 15, 18, 19, 26, 27, 38, 39, 42, 43, 46, 47, 50, 51) o ATM – Adiabatic curing of mortar samples in tank o (Row # 3, 8, 11, 20, 21, 28, 29, 32, 33) o ATC – Adiabatic curing of mortar sieved from concrete in tank o (Row # 4, 5, 9, 10, 12, 13, 22, 23, 30, 31, 34, 35, 52, 53, 54) o C & F Calculation of degree of hydra tion based on total cement and fly ash content and the nonevaporable water conten t at full hydration after curing for 1 year at 73oF. the nonevaporable conten t for 1 gram of 18%FA mix was determined to be 0.19 and that for the 50%FA was determined to be 0.15. o C – Calculation of degree of hydration ba sed on cement solely responsible for the hydration products formed assuming no reac tion of fly ash. NA designation is applied to durations and temperatures fo r which fly ash reaction is assumed to have started, invalidating an extension of this calculation.

PAGE 70

55 o C & S Calculation of degree of hyd ration based on total cement and blast furnace slag content and the nonevaporabl e water content at full hydration of 0.23 as for plain cement mixes. Table 4.2. Degree of hydration resu lts for plain cement mixes Curing Duration (days) Mix Temp Row Mix design 1 2 3 4 5 6 7 8 9 10 14 28 56 91 1 IOP – 0% .41w/c 58 67 70 71 71 73 74 2 ITP – 0% .41 w/c 56 64 69 71 77 78 79 3 ATM – 0% .41 w/c 52 60 60 64 61 62 61 62 70 63 68 70 4 ATC – 0% .41 w/c 59 64 69 73 5 ATC – 0% .40w/c 54 64 62 6 IOP – 0% .41w/c 68 72 75 73 72 69 69 7 ITP – 0% .41 w/c 68 72 76 76 81 79 79 8 ATM – 0% .41 w/c 60 73 68 71 67 69 67 69 74 68 70 71 9 ATC – 0% .41 w/c 61 61 66 160 10 ATC – 0% .40w/c 62 59 61 11 ATM – 0% .41 w/c 60 73 71 71 68 68 67 69 74 73 70 68 12 ATC – 0% .41 w/c 59 63 69 180 13 ATC – 0% .40w/c 60 59 60 14 IOP – 0% .41w/c 73 75 80 78 75 75 76 0% 200 15 ITP – 0% .41 w/c 65 69 73 73 75 74 74

PAGE 71

56 Table 4.3. Degree of hydration for 18% fly ash mixes Curing Duration (days) Mix Temp Row Mix design 1 2 3 4 5 6 7 8 9 10 14 28 56 91 16 C 63 65 75 78 76 79 NA17 IOP – 18% FA 60 63 73 75 74 76 79 18 C 51 65 70 75 81 84 NA19 ITP – 18% FA 50 63 68 72 78 82 80 20 C 51 58 60 63 61 60 61 64 73 69 69 73 21 ATM – 18% FA 49 55 59 61 60 58 59 62 70 66 67 70 22 C 55 64 NA 73 23 ATC – 18% FA 54 62 76 24 C 78 81 84 NA NANANA25 IOP – 18% FA 75 78 81 83 82 78 76 26 C 73 78 80 NA NANANA27 ITP – 18% FA 70 75 77 79 81 83 82 28 C 61 71 74 75 73 71 70 NA NA NA NANA29 ATM – 18% FA 59 69 72 73 71 69 68 70 69 72 72 71 30 C 65 NANA 160 31 ATC – 18% FA 63 64 73 32 C 59 71 73 75 71 73 71 NA NA NA NANA33 ATM – 18% FA 56 69 72 73 69 70 69 70 69 75 73 71 34 C 63 NANA 180 35 ATC – 18% FA 61 68 70 36 C 80 84 84 NA NANANA37 IOP – 18% FA 78 81 81 83 82 81 84 38 C 68 70 74 NA NANANA18% 200 39 ITP – 18% FA C&F 66 68 71 73 75 79 77

PAGE 72

57 Table 4.4. Degree of hydration for 50% fly ash mixes Curing Duration (days) Mix Temp Row Mix design 1 2 3 4 5 6 7 8 9 10 14 28 56 91 40 C 58 68 80 82 84 86 NA41 IOP – 50% FA 44 53 61 63 65 66 64 42 C 50 70 78 84 94 102NA73 43 ITP – 50% FA 38 53 60 65 71 78 76 44 C 80 80 82 NA NANANA 45 IOP – 50% FA 61 62 63 64 63 66 68 46 C 86 88 88 NA NANANA 160 47 ITP – 50% FA 65 67 67 71 74 78 75 48 C 86 88 86 NA NANANA 49 IOP – 50% FA 66 67 66 64 65 68 61 50 C 70 80 78 NA NANANA 50% 200 51 ITP – 50% FA 53 61 59 60 66 67 68 Table 4.5. Degree of hydration for cement and blast furnace slag mixes Curing Duration (days) Mix Temp Row Mix design 1 2 3 4 5 6 7 8 9 10 14 28 56 91 73 52 ATC – 50% SL C & S69 78 81 160 53 ATC – 50% SL C & S84 86 82 50% 180 54 ATC – 50% SL C & S82 85 84 Phase 2 – Tests of Mass Concrete Table 4.6 provides a summary of the plastic properties of the mass concrete mixes tested. Tests for each mix included determination of the degree of hydration, compressive strength, time to corrosion, rapid chloride permeability, de nsity and the percentage of voids at curing durations of 7, 28 and 91 da ys and curing temperatures of 73, 160 and 180oF. The test for each mix was repeated a nd the average results for each mix is provided in Tables 4.7 and 4.8.

PAGE 73

58 Table 4.6. Summary of Plastic Pr operties of Fresh Concrete. Test # Mixture Concrete Temperature (oF) Air Temperature (oF) Slump in Air Content % Workability w/b ratio 1 72 72 2 70 70 3 72 72 4 Mix 1 Mix 2 Mix 3 Mix 4 Mix 5 Mix 6 Mix 7 Mix 8 75 75 69 70 74 74 75 73 71 70 6.50 5.00 6.50 7.50 5.25 3.25 4.00 2.75 4.0 2.0 4.5 2.5 6.0 3.9 5.50 3.00 Good OK Good Good Good Sticky Good Stiff 0.41 0.41 0.41 0.41 0.40 0.40 0.40 0.40 Table 4.7. Results of concrete mixes M1 and M2 Temp DurationHydrationComp Density Voids RCP ResistivityCorrosion Test # Mix ID (oF) (days) (%) (psi) (lbs/ft3) (%) (coulombs) (kohms/cm)(days) 7 56 6048 28 66 6860 155.70 16.00 5507 8.63 12 73 91 70 7457 155.70 16.30 4456 11.07 7 56 5992 28 60 6051 157.10 16.70 8701 7.16 8 160 91 63 6280 156.50 16.00 6693 8.28 7 56 5761 28 67 5790 159.05 15.95 9317 8.46 5 M1 (0% Fly Ash) w/c = 0.41 slump = 6.5" 180 91 66 6037 156.50 15.80 7695 8.27 7 49 6610 28 58 7770 161.20 16.75 5014 9.04 14 73 91 58 8517 159.90 15.90 2285 17.84 7 62 6942 28 61 7149 162.15 16.60 2470 21.33 9 160 91 60 7810 160.30 16.70 1701 29.80 7 57 6660 28 62 7069 162.15 16.90 2646 19.42 9 1 M2 (18% Fly Ash) w/c = 0.41 slump = 5.0" 180 91 61 7437 160.70 16.20 1822 23.06

PAGE 74

59 Table 4.8. Results of concrete mixes M3 and M4 Temp DurationHydration Comp Density Voids RCP ResistivityCorrosion Test # Mix ID (oF) (days) (%) (psi) (lbs/ft3) (%) (coulombs) (kohms/cm)(days) 7 61 5800 154.20 16.30 28 61 6387 156.30 15.30 5616 11.22 15 73 91 69 7043 152.20 14.50 4531 12.18 7 66 5567 155.30 15.90 28 62 5613 155.10 16.20 8565 8.42 5 160 91 70 5957 155.20 15.80 6851 9.78 7 61 5323 155.80 16.00 28 59 5353 155.20 15.80 10459 8.85 7 M3 same as M1 (0% Fly Ash) w/c = 0.41 slump = 6.5" 180 91 72 5343 154.10 15.50 7370 9.12 7 58 6320 159.70 16.60 28 66 7173 159.40 16.00 5331 10.83 27 73 91 93 8220 158.10 15.70 2272 18.95 7 64 6647 161.40 16.80 28 66 6570 160.40 17.40 2626 21.33 15 160 91 86 7180 158.90 15.80 1872 26.09 7 64 6247 159.00 17.40 28 74 6643 158.70 17.10 2360 18.67 15 2 (repeat of test 1) M4 same as M2 (18% Fly Ash) w/c = 0.41 slump = 7.5" 180 91 90 7187 158.90 15.80 1923 22.13

PAGE 75

60 Table 4.9. Results of concrete mixes M5 and M6 Temp Duration Hydration Comp Density Voids RCP ResistivityCorrosion Test # Mix ID (oF) (days) (%) (psi) (lbs/ft3) (%) (coulombs) (kohms/cm)(days) 7 50 4780 156.2 14.7 28 63 5673 150.0 14.0 5850 9.84 18 73 91 63 6310 152.4 14.2 4105 12.1 7 54 4783 155.6 15.8 28 58 4673 152.9 15.1 10108 7.93 11 160 91 62 4903 153.7 16.6 7770 8.45 7 55 4830 155.1 15.7 28 61 4673 151.9 14.9 8996 11.45 14 M5 (0% Slag) w/c = 0.40 slump = 5.25" 180 91 65 4707 155.9 15.8 9233 9.65 7 69 5293 161.5 16.0 28 80 7165 158.5 14.7 2845 17.88 42 73 91 83 8003 157.5 14.1 2114 24.50 7 80 6790 161.4 16.0 28 84 6877 159.3 15.1 1919 21.68 16 160 91 84 7617 158.5 14.3 1662 25.90 7 80 5853 161.4 15.5 28 84 6273 158.7 14.7 2689 18.49 11 3 M6 (50% Slag) w/c = 0.40 slump = 3.25" 180 91 87 7180 159.5 15.0 1753 25.00

PAGE 76

61 Table 4.10. Results of concrete mixes M7 and M8 Temp Duration Hydration Comp Density Voids RCP ResistivityCorrosion Test # Mix ID (oF) (days) (%) (psi) (lbs/ft3) (%) (coulombs)(kohms/cm)(days) 7 57 5760 152.3 12.3 28 65 6733 155.7 13.6 4430 11.34 21 73 91 61 7307 152.4 12.3 3960 12.5 7 69 5947 151.4 11.9 28 60 5653 156.3 14.3 8135 7.93 11 160 91 60 5890 154.4 14.0 7119 8.45 7 64 5450 152.5 11.8 28 57 5430 154.8 14.7 6175 10.97 7 M7 same as M5 (0% Slag) w/c = 0.40 slump = 4.0" 180 91 54 5373 153.7 14.0 8347 9.05 7 69 5770 155.5 12.8 28 75 8303 159.8 15.3 2540 19.45 85 73 91 79 9003 155.7 12.6 1890 22.54 7 87 7307 156.3 12.0 28 87 7470 160.5 14.4 1943 23.67 22 160 91 80 8230 156.1 12.9 1481 27.00 7 83 6567 155.4 11.8 28 85 6883 160.8 14.9 2105 20.55 44 4 (repeat of test 3) M8 same as M6 (50% Slag) w/c = 0.40 slump = 2.75" 180 91 80 7370 157.3 12.1 1802 24.76

PAGE 77

62 Table 4.11. Summary of Results of conc rete mixes M1 M2, M3 and M4 Temp Duration Hydration Comp Density Voids RCP Resistivity Corrosion Mix ID (oF) (days) (%) (psi) (lbs/ft3) (%) (coulombs) (kohms/cm) (days) 7 59 5924 154.20 16.30 28 64 6624 156.00 15.65 5562 9.93 14 73 91 69 7250 153.95 15.40 4494 11.63 7 61 5780 155.30 15.90 28 61 5832 156.10 16.45 8633 7.79 7 160 91 67 6119 155.85 15.90 6772 9.03 7 59 5542 155.80 16.00 28 63 5572 157.10 15.88 9888 8.66 6 M1 & M3 (0% Fly Ash) w/c = 0.41 180 91 69 5690 155.30 15.65 7533 8.70 7 54 6465 159.70 16.60 28 62 7472 160.30 16.38 5173 9.94 20 73 91 76 8369 159.00 15.80 2279 18.40 7 63 6795 161.40 16.80 28 64 6860 161.30 17.00 2548 21.33 12 160 91 73 7495 159.60 16.25 1787 27.95 7 61 6454 159.00 17.40 28 68 6856 162.15 17.00 2503 19.05 12 M2 & M4 (18% Fly Ash) w/c = 0.41 180 91 70 7312 159.80 16.00 1873 22.60

PAGE 78

63 Table 4.12. Summary of Results of c oncrete mixes M5, M6, M7 and M8 Temp Duration Hydration Compressive Density Voids RCP Resistivity Corrosion Mix ID (oF) (days) (%) (psi) (lbs/ft3) (%) (coulombs) (kohms/cm)(days) 7 54 5270 154.3 13.5 28 64 6203 152.9 14.2 5140 10.59 20 73 91 62 6808 152.4 13.3 4033 12.3 7 62 5363 153.5 13.9 28 59 5163 154.6 14.7 9122 7.93 11 160 91 61 5397 154.1 15.3 7445 8.45 7 60 5140 153.8 13.8 28 59 5052 153.4 14.8 7586 11.21 11 M5 & M7 (0% Slag) w/c = 0.40 180 91 60 5040 154.8 14.9 8794 9.35 7 69 5532 158.5 14.4 28 78 7734 159.2 15.0 2693 18.67 64 73 91 81 8503 156.6 13.4 2002 23.52 7 84 7049 158.9 14.0 28 86 7174 159.9 14.8 1919 21.68 19 160 91 82 7924 157.3 13.6 1572 26.45 7 82 6210 158.4 13.7 28 85 6578 159.8 14.8 2689 18.49 28 M6 & M8 (50% Slag) w/c = 0.40 180 91 84 7275 158.4 13.6 1778 24.88 Degree of Hydration Results The degree of hydration was determined fr om mortar samples sieved from the concrete mixes. The samples were cured adia batically for the same durations as the mass concrete samples. At the e nd of the curing durations, the hydration process was stopped by immersion in methanol and then tested to determine the degr ee of hydration. Figures 4.1 and 4.2 show the results of the hydration tests.

PAGE 79

64 Degree of Hydration (0%FA & 18%FA)50 55 60 65 70 75 80 72891 Duration ( Days)Hydration (%) 0% FA 73F 0% FA 160F 0%FA 180F 18% FA 73F 18%FA 160F 18%FA 180F Figure 4.1. Degree of hydration for 0%FA and 18%FA mixes Addition of Fly ash increases the degree of hydration at early ages for the samples cured at the higher temperatures. Higher curi ng temperatures have not been effective however in increasing the degree of hydration at early age for the mix without fly ash. At later ages, the degree of hydration for the fly ash mix is hi gher than that without fly ash at all curing temperatures. The de gree of hydration for the fly ash mix at later ages is highest in the samples cured at 73oF and decr eases with increasing curing temperature.

PAGE 80

65 Degree of Hydration (0%BFS & 50%BFS)50 55 60 65 70 75 80 85 90 72891 Duration ( Days)Hydration (%) 0%BFS 73F 0% BFS 160F 0%BFS 180F 50%BFS 73F 50%BFS 160F 50%BFS 180F Figure 4.2. Degree of hydration for 0%BFS and 50%BFS mixes Addition of slag as seen in Figure 4.2, resulted in a drastic increase in the degree of hydration over the mix without slag at both early and later ages for all curing temperatures. The slag mixes cured at highe r temperatures showed a much higher degree of hydration at early ages, however at later ages all curing temper atures had reach to about the same degree of hydration. Compressive Strength Results The compressive tests were performed on tw enty-seven different cylinders for each mix. Nine samples of each mix were tested at curing durations of 7, 28 and 91 days from the mixing date. Three samples each were tested for three different temperatures of 73, 160 and 180oF. The compressive strengths were de termined in accordance with ASTM C39-93a. Figures 4.3 through 4.7 show the resu lts of the compressive strength for the different mixes and curing conditions.

PAGE 81

66 Compressive strengths (0%FA & 18%FA)5000 5500 6000 6500 7000 7500 8000 8500 9000 72891 Duration ( Days)PS 0% FA 73F 0% FA 160F 0%FA 180F 18% FA 73F 18%FA 160F 18%FA 180F Figure 4.3. Compressive strength s for 0%FA and 18%FA mixes Table 4.13. Compressive strength as a ra tio of 28-day samples cured at 73oF Temperature (oF) Mix Duration (days) 73 160 180 7 0.89 0.87 0.84 28 1.00 0.88 0.84 0% FA 91 1.09 0.92 0.86 7 0.87 0.91 0.86 28 1.00 0.92 o.92 18% FA 91 1.12 1.00 0.99 Higher curing temperatures resulted in lo wer strength for all ages and mixtures except fly ash mix at 7 days age, which had a higher strength at the 160F as shown in Figure 4.3 and Table 4.13. Addition of fly ash increased the strength at all ages and curing temperatures when compared to th e mix without fly ash, mirroring the higher degree of hydration of the fly ash mixes over the plain cement mixes. The highest strength at later age was recorded for the fly ash mix cured at 73oF, which also had the highest degree of hydration at this age.

PAGE 82

67 Compressive strengths (0%BFS & 50%BFS)4000 5000 6000 7000 8000 9000 72891 Duration ( Days)PSI 0%BFS 73F 0% BFS 160F 0%BFS 180F 50%BFS 73F 50%BFS 160F 50%BFS 180F Figure 4.4. Compressive strength s for 0%BFS and 50%BFS mixes Table 4.14. Compressive strength as a rati o of the 28-day samples cured at 73oF Temperature (oF) Mix Duration (days) 73 160 180 7 0.85 0.86 0.83 28 1.00 0.83 0.81 0% Slag 91 1.10 0.87 0.81 7 0.71 0.91 0.80 28 1.00 0.93 0.85 50% Slag 91 1.10 1.02 0.94 Higher curing temperatures resulted in incr eased early age strength in the slag mix but reduced later age stre ngth as seen in Figure 4. 4 and Table 4.14. Higher curing temperatures in the mix without slag generally resulted in a decrease in both early and later age strength. The mix with slag had hi gher strengths at all curing durations and temperatures compared to the mix without the slag. This observa tion agrees with the higher degree of hydration in the sl ag mix over the mix without slag.

PAGE 83

68 Resistance to Chloride Ion Penetration Six samples of each mix were tested at 28 and 91 days, two for each curing temperature. The tests were done in accord ance with ASTM C 1202-94. Results of this test are shown for the various mixes in Fi gures 4.5 and 4.6. The blended cement mixes were observed to have a higher resistance to chloride ion penetr ation than the plain cement mixes as shown by the lower char ges passing through during the test. Chloride Ion Penetration RCP (0%FA & 18%FA)1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 2891 Duration ( Days)Coulombs 0% FA 73F 0% FA 160F 0%FA 180F 18% FA 73F 18%FA 160F 18%FA 180F Figure 4.5 Chloride Ion Penetration results for 0%FA and 18%FA mixes As shown in Figure 4.5 above, at higher cu ring temperatures, the mixes without fly ash, had higher chloride pe netration at both 28 and 91 days. For the fly ash mixes however higher curing temperatures resulted at much reduced chloride ion penetration at 28 days although their influence on chloride pene tration at 91 days was about the same as curing at 73oF. Overall, the fly ash mixes had lower chloride ion penetr ation at all curing durations and temperatures when comp ared to the mixes without fly ash.

PAGE 84

69 Chloride Ion Penetration RCP (0%BFS & 50%BFS)1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 2891 Duration ( Days)Coulombs 0%BFS 73F 0% BFS 160F 0%BFS 180F 50%BFS 73F 50%BFS 160F 50%BFS 180F Figure 4.6. Chloride Ion Penetration results for 0%BFS and 50%BFS mixes The mix without slag as seen in Figure 4.6, showed increased RCP values at higher temperatures. The RCP values for the slag mi xes were not much affected by the curing temperatures. Overall, RCP values for the slag mixes were considerably reduced when compared to the mixes without slag at all curing temperatures and durations. Density and Percentage of Voids Results Two samples of each mix for each curing temperature weighing approximately 800g were tested at 7, 28 and 91 days to dete rmine the density and percentage of voids. Figure 4.7 shows the density for the plain cement and fly ash mixes. Figure 4.8 shows the density for the blast furnace slag mix.

PAGE 85

70 Density (0%FA & 18%FA)150.00 154.00 158.00 162.00 166.00 170.00 72891 Duration ( Days)Density (lbs/cuft) 0% FA 73F 0% FA 160F 0%FA 180F 18% FA 73F 18%FA 160F 18%FA 180F Figure 4.7 Density for 0%FA and 18%FA mixes The mix with fly ash showed a higher dens ity at all curing temp eratures and curing durations, than the mix without it as seen in Figure 4.7. The curing temperature of the concrete had a minimal influence on the resulting density. Density (0%BFS & 50%BFS)150.0 152.0 154.0 156.0 158.0 160.0 72891 Duration ( Days)Density (lbs/cuft) 0%BFS 73F 0% BFS 160F 0%BFS 180F 50%BFS 73F 50%BFS 160F 50%BFS 180F Figure 4.8. Density for 0%BFS and 50%BFS mixes

PAGE 86

71 Addition of slag has increas ed density for all curing te mperatures and ages. Higher curing temperatures have sligh tly increased density at 91 days for mixes with and without slag as seen in Figure 4.8. Percentage of voids (0%FA & 18%FA)15.00 15.50 16.00 16.50 17.00 17.50 72891 Duration ( Days)Voids (%) 0% FA 73F 0% FA 160F 0%FA 180F 18% FA 73F 18%FA 160F 18%FA 180F Figure 4.9. Percentage of voids for 0%FA and 18%FA mixes At 7 days, the fly ash mixes had a highe r percentage of voids at all curing temperatures when compared to the mix without fly ash as shown in Figure 4.9. The percentage voids in the fly ash mixes is higher in the samples cured at elevated temperatures. For both mixes with and wit hout fly ash, the percentage of voids at 91 days was least in the samples cured at 73oF.

PAGE 87

72 Percentage of voids (0%BFS & 50%BFS)13.0 13.5 14.0 14.5 15.0 15.5 72891 Duration ( Days)Voids (%) 0%BFS 73F 0% BFS 160F 0%BFS 180F 50%BFS 73F 50%BFS 160F 50%BFS 180F Figure 4.10. Percentage of voids for 0%BFS and 50%BFS mixes At 7 days, the mixes with slag showed a lower percentage of voids in the samples cured at the elevated temperatures, however, this situation was reversed at 91 days in which the percentage of voids was lower in the samples cured at 73oF. At all curing temperatures and durations, the mix without sl ag cured at 73oF had the least percentage of voids as seen in Figure 4.10. Time to Corrosion Results The corrosion results for each mix and curing temperature is presented individually as an average of three samples. The results as shown in Figure 4.11 indicate the increase in the concrete durability by the use of slag. The use of fly ash also increased the time to corrosion when compared to the plain cement mixes, but to a sma ller extent. Increasing the curing temperature for all the mixes re sulted in reduction of time to corrosion.

PAGE 88

73 Time to Corrosion (TTC) Impressed current0 10 20 30 40 50 60 70 0% Fly Ash0% Slag18% Fly Ash50% Slag Mix DesignsDuration (days) 73 F 160 F 180 F Figure 4.11. Time to Corrosion results for all mixes RCP (91 days) Expressed in terms of TTC unit0 10 20 30 40 50 60 70 0% Fly Ash0% Slag18% Fly Ash50% Slag Mix designsDuration (days) 73 F 160 F 180 F Figure 4.12. The RCP at 91days expressed in terms of Time to Corrosion unit Three parameters were used in this research to study the durability of the concrete: 1. Percentage of voids 2. Rapid chloride permeability (RCP) and 3. Time to corrosion (TTC) – Impressed current The following observations were made in relating these parameters:

PAGE 89

74 a. The percentage of voids determined for the various samples did not have much variation in the values an d could not be used to establish differences in the durability of the mixes. b. The RCP and TTC tests exhibited similar results for the plain cement mixes (0% FA and 0% BFS), that is both tests s howed reduction in durability when curing temperature increased (see Figures 4.11 and 4.12). c. The mixes with the Fly ash and slag showed conflicting durability results from the RCP and TTC tests as seen in Figur es 4.11 and 4.12. The TTC test indicated better durability for the samples cured at 73oF (Figure 4.11), whereas the RCP test showed that the Fly ash and slag mixes had better durability at the higher curing temperatures. Phase 3 – Microstructural Analysis SEM Observations of Plain Cement Mixes Effect of Curing Temperature on the Presence of Ettringite Crystals 1. None of the plain cement mixes cure d at room temperature showed the presence of ettringite crystals (Fi gure 4.13). These samples had the highest permeability rates. However the high permeability values had no effect on ettringite formation. This observation agrees with a threshold temperature of 160oF is required during curing for ettrin gite to reform in the hardened concrete. 2. For the plain cement mixes cured at th e elevated temperatures of 160 and 180oF, there was no observation of ettringite crystals when examined microscopically after 7 days of curing.

PAGE 90

75 3. For the plain cement mixes cured at th e elevated temperatures of 160 and 180oF, ettringite was present when they were examined at 28 and 91 days (Figures 4.14 & 4.16). These samples had higher permeability values when compared to the room cured samples. Effect of Curing Duration on the Am ount of Ettringite Crystals formed 1. At the elevated curing te mperatures of 160 and 180oF well-formed balls of ettringite crystals were seen in the voids when examined at 28 days. 2. The high permeability of the samples cured at the elevated temperatures facilitated the formation and transportation of ettringite within the microstructure of the hardened samples. Voids observed partially filled with ettringite when examined at 28 days showed an increased amount of the ettringite crystals when examined at 91 days. Figures 5 and 7 show voids completely filled with ettringite when examined at 91 days, a direct consequence of the increased permeability.

PAGE 91

76 Figure 4.13 Well-defined Monosulphat e (M) crystals in a void Figure 4.14. Void with clusters of Ettringite (E) crystals M 0%FA 73F –28days 2500x E 0%FA 160F –28days 350x

PAGE 92

77 Figure 4.15. Void containing both Monosulphate (M) and Ettringite (E) crystals Figure 4.16. Voids containing Ettringite (E ) some appear almost full of it. E 0%FA 160F –91days 300x M E 0%FA 180F – 28days 220x E

PAGE 93

78 Figure 4.17. Void completely filled with fibrous Ettringite (E) SEM Observations of Fly Ash Mixes Introduction Calcium hydroxide crystals formed by the hydrating cement constitute 20 to 25 percent of the volume of so lid in the hydrated phase (N eville, 2004). Calcium hydroxide is water-soluble and may leach out of harden ed concrete, leaving voids for ingress of water. Through its pozzolanic properties, fl y ash chemically combines with calcium hydroxide and water to produce C-S-H, whic h fills in the spa ces between hydrating cement particles, thus reducing the risk of leaching calcium hydroxide. The long-term reaction of fly ash refines the pore structure of concrete and reduces the permeability (ACI 232.2R-96, 1999). At normal temperatures, little pozzolani c activity from fly ash occurs after 28 days of cu ring (Malhotra and Ramezanianpour, 1994), this is evident in 0%FA 180F – 91days 2000x E

PAGE 94

79 the almost identical permeability values for the fly ash mixes and the plain cement mixes at 28 days cured at room temperatures. At the elevated temperatures however the pozzolanic activity occurs sooner and this is evident in the much lower permeability of the fly ash mixes cured at the elevated temper atures when compared to the plain cement mixes. At the elevated curing temperatures, the permeability values of the plain cement mixes is about 3 times more than those of the fly ash mixes. Effect of Curing Temperature on the Presence of Ettringite Crystals 1. The fly ash samples cured at room temp erature did not show the presence of ettringite even though the RCP test i ndicated the higher pe rmeability values when compared to the fly ash mixes cured at the elevated temperatures. 2. At the elevated temperature curing of 160oF, ettringite was not present when examined at 28 days as shown in Figure 4.18. The low permeability of these samples will inhibit the ingress of water and the formation of ettringite. At 91 days however thes e samples showed the presence of ettringite crystals in the void spaces. 3. Ettringite was observed at 28 days in the fly ash samples cured at 180oF (Figure 4.19) just as in the plain cemen t mixes. These samples have almost identical permeability values to the fly ash samples cured at 160oF. While the samples cured at 160oF did not show ettringite at 28 days, the higher curing temperature of 180oF will account for th e observation of the ettringite in the higher cured samples.

PAGE 95

80 Effect of Curing Duration on the Amount of Ettringite Crystals formed in Voids 1. At 28 days, the ettringite formed in the voids of samples cured at 180oF was not as big and in well-formed balls as the crystals seen in the equivalent plain cement mixes. 2. At 91 days, examination of the fly ash samples cured at 180oF showed ettringite crystals in pore spaces (F igure 4.20). The amount of ettringite observed was increased from that observed in these samples at 28 days. These pores however were not entirely filled with the ettringite when compared to the equivalent plain cement mixes. Figure 4.18. Void containing hexagona l plates of Monosulphate (M). 18%FA 160F – 28days 800x M

PAGE 96

81 Figure 4.19. Void showing Monosulphate (M ) transformed into Ettringite (E) Figure 4.20. Clusters of Fibrous Ettringite (E) in void 18%FA 180F – 28days 4300x E M 18%FA 180F – 91days 80x E

PAGE 97

82 SEM Observations of Slag Mixes Introduction Slag is a waste product in the manufactur e of pig iron. Chemically, slag is a mixture of lime, silica, and alumina, the same oxides that make up Portland cement, but not in the same proportions (Neville, 2004) The permeability of mature concrete containing slag is greatly reduced when comp ared with concrete not containing slag. As the slag content is increa sed, permeability decreases. The pore structure of the cementitious matrix is changed through the re actions of slag with the calcium hydroxide and alkalis formed during the Portland cement hydration. Pores in concrete normally containing calcium hydroxide in part get fill ed with calcium silicate hydrate. Permeability of concrete depends on its porosity and poresize distribution. Wh ere slag is used, reduction in the pore size has been noted prior to 28 days after mixing (ACI 233R-95, 1999). Miller and Conway (2003) examined the eff ectiveness of using slag to prevent DEF expansions in mortar made from expansive cements. One year into the study, they found that 5% slag substitution reduced or delaye d, but did not eliminate expansions at curing temperatures above 167oF (75oC). Expansion was however completely absent when 17.5% slag substitution was used. Substitution of the cement by slag did not have any adverse effect on the strength of the mortar cured at 194oF (90oC) which showed superior strength at all ages for all mixes with 30% slag substitution (Miller and Conway, 2003). This was also evident in compressive strength tests of the mixes used in this study which showed higher strengths for the slag mixes cu red at elevated temperatures (Chini and Acquaye, 2005). The beneficial e ffect of added slag in reducing expansions from DEF may have to do with the reduced pH of the por e solution. Ettringite is more stable below

PAGE 98

83 pH of 12.5 and the slag may reduce the pH to the region where ettr ingite stability is enhanced. If there is less decomposition at th e elevated temperature, less ettringite may potentially form later, when its formation may lead to volume instability (Miller and Conway, 2003). Effect of Curing Temperature on the Presence of Ettringite Crystals 1. At all curing temperatures, the slag mixes had the lowest permeability values of the mixes tested. 2. No ettringite was observed at 28 days in the slag samples cured at the elevated temperatures (Figures 4.21 and 4.23). The slag samples had the least permeability values when compared to equivalent plain cement and fly ash mixes. 3. At 91 days, slag mixes cured at the elevated temperatures showed the presence of ettringite. Inclusion of 50% slag was the most effective at delaying the onset of the ettringite. However by 91 days, these ettringite crystals were observed in the void spaces Effect of Curing Duration on the Am ount of Ettringite Crystals formed 1. The amount of ettringite in the voids observed at 91 days in the elevated cured samples was in much smaller amounts than in the fly ash or plain cement mixes. They could only be se en at very high magnifications as shown in Figure 4.22. 2. Some ettringite crystals were formed on the surfaces of slag particles as seen in Figures 4.24 and 4.25

PAGE 99

84 Figure 4.21. Sample with empty air Voids (V) Figure 4.22 Higher magnification of Figure 4.32 50%BFS 160F – 28days 450x V E M 4800x 50%BFS 160F – 91days

PAGE 100

85 Figure 4.23. Sample with empty air Void (V) Figure 4.24. Reacting Slag (S) particle with Ettringite (E) formed 50%BFS 180F – 28days 300x V 50%BFS 180F – 91days 500x S E

PAGE 101

86 Figure 4.25 Slag particle completely covered with Ettringite (E) 50%BFS 180F – 91days 900x E

PAGE 102

87 CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS Introduction This dissertation investigated the effect s of elevated curing temperatures on the strength, durability and potential of delayed ettringite formation (DEF) in typical FDOT Class IV mass concrete mixes. The three conc rete mix designs tested were plain cement mixes, mixes with 18% fly ash and mixes with 50% slag. The durability of the concrete was evaluated through a measure of the permeab ility of the concrete. Higher permeability values indicated a greater ease of ingress of deleterious material and a less durable concrete. Two curing cycles were used for the elevated temperature curingisothermal and adiabatic curing. Samples cu red isothermally at the el evated temperatures were placed in tanks set at the elevated temperatur es immediately after casting. In the adiabatic curing cycle, samples were introduced to the elevated curing temperature environment, 6 hours after casting. In the adia batic curing cycle, the tank s were initially set at 80oF and the elevated temperatures of 160 and 180oF were attained within 2 and 2 days respectively. The adiabatic curing cycles were set to simulate appr oximate conditions of mass concrete cured in the field. Conclusions Table 5.1 is a summary of the compressive strengths of plain cement mixes cured isothermally and Table 5.2 gives the permeability values of these samples. Summaries of results of the compressive strength, permeability and ettringite formation in samples cured adiabatically are sh own in Tables 5.3 and 5.4. Comparing the strength and

PAGE 103

88 permeability of the isothermally and adiabatically cured samples, the following conclusions were observed: 1. There was a substantial decrease in co mpressive strength of plain Portland cement concrete samples cast and stor ed immediately in water tanks under isothermal curing temperatures of 160 and 200oF compared to samples cured at room temperature 73oC. This reduction was 34 and 62% for 28-day compressive strength for samples cured at 160 and 200oF, respectively. In addition, RCP test of these samples showed a significant increase in permeability of concrete cured at high temperature. 2. When plain Portland cement concrete samples were subjected to the adiabatic curing cycle, there was a moderate reduction in 28-day compressive strength of samples cured at elevated temperatures compared to samples cured at room temperatur e. The reduction was approximately 15% and 18% for samples cured at temperatures of 160 and 180oF, respectively. However, there was stil l a significant increase in permeability of concrete measured through the RCP test. 3. Adiabatic curing of fly ash cement concrete samples (18% fly ash by weight) resulted in 8% reduction of 28-day compressive strength for samples cured at 160oF and 180oF compared to those cured at room temperature. However, permeability of concrete measured by RCP test improved noticeably at higher curing temp eratures suggesting that at higher temperatures the fly ash becomes effective much earlier and reduces the

PAGE 104

89 RCP values. At normal curing temperature the RCP reducing effect of fly ash becomes effective after approximately two months. 4. When 50% (by weight) of Portland cement is replaced by blast furnace slag, the 28-day compressive strength of samp les cured adiabatically at elevated temperatures reduced by 7.and 15% for curing temperatures of 160oF and 180oF compared to those cured at room temperature. Results of compressive strength tests and RCP tests reveal ed that addition of blended cement improves strength and durability of concrete. Table 5.1. Compressive strength samples cured isothermally COMPRESSIVE STRENGTH (PSI) Plain cement mix Temp (F) Value 28 days 91 days Avg* 7472 8252 StaDev 304 276 73 95%C.I.348 319 Avg* 4963 5616 StaDev 276 624 160 95%C.I.319 711 Avg* 2872 2636 StaDev 276 406 200 95%C.I.319 464 Avg* – Average of 3 samples, SD – Standard Deviation, C.I. – 95% Confidence Interval

PAGE 105

90 Table 5.2. RCP for samples cured isothermally RAPID CHLORIDE PERMEABILITY (RCP) Plain cement mix 28 days Temp (F) Value Coulomb Rate Avg* 4720.0 SD 74.0 73 95%C.I. 103 High Avg* 7110.0 SD 410.0 160 95%C.I. 568 High Avg* 11070.0 SD 503 200 95%C.I. 698 High Avg* – Average of 2 samples, SD – Standard Deviation, C.I. – 95% Confidence Interval Table 5.3. Compressive strength fo r adiabatically cured samples COMPRESSIVE STRENGTH (PSI) Plain cement mix 18% Fly ash mix 50% Slag mix Temp (F) Value 7 days 28 days 91 days 7 days 28 d ays 91 days 7 days 28 days 91 days Avg* 5924 6624 7250 6465 7472 8369 5532 7734 8503 SD 363.0 363.0 290.0 305.0 406.0 232.0 348.0 638.0 595.0 73 95%C.I. 290 290 232 247 319 189 290 508 479 Avg* 5780 5832 6119 6795 6860 7495 7049 7174 7924 StaDev 305.0 334.0 305.0 334.0 406.0 406.0 348.0 392.0 392.0 160 95%C.I. 247 276 247 261 334 334 276 319 305 Avg* 5542 5572 5690 6454 6856 7312 6210 6578 7275 StaDev 261.0 348.0 435.0 247.0 276.0 218.0 450.0 406.0 305.0 180 95%C.I. 203 276 348 203 218 174 363 319 247 Avg* – Average of 6 samples, SD – Standard Deviation, C.I. – 95% Confidence Interval

PAGE 106

91 Relating the mix design, curing temperature, duration of curing and the concrete permeability to the amount and onset of formati on of ettringite crystals in the samples cured adiabatically, the following conclusions were drawn from Table 5.4: 1. Samples cured at room temperature, resu lted in high permeability values for each respective mix. However no ettringite crystals were observed in these samples when examined microscopically. This observation agrees with the fact that a threshold curi ng temperature of about 160oF is needed for ettringite to reform in the hardened concrete in the pr esence of moisture. 2. For samples cured at the elevated temperatures, the plain cement mixes had the highest permeability values and the la rgest amount of ettringite crystals observed in void spaces when examined at 28 and 91 days. The amount of ettringite increased with increas ed curing temperature and duration. 3. Addition of 18% fly ash and 50% slag reduced the permeability of the concrete mixes. At room temperature the slag mixes had the least permeability values at 28 days due to the early reaction of slag within this time. The fly ash mixes did not show much reduction in permeability values at 28 days when cured at room temperature. 4. Addition of fly ash and slag resulted in much reduced permeability values for samples cured at the elevated temperatures. The reduced permeability resulted in the delay of the onset of the ettringite and the amounts formed in the blended mixes. 5. The 50% slag was better at delaying the onset on the ettringite in the samples cured at 180oF so that at 28 days no et tringite was observed. At

PAGE 107

92 160oF however, both the 18% fly ash a nd 50% slag were effective at delaying the onset of ettr ingite prior to 28 days. Research Implications for Mass Concrete Structures. This research has very important implica tions for mass concrete structures. These include: a. The samples used in this study were smaller allowing for easier penetration of water. b. This fact notwithstanding, the fly ash and slag were beneficial in delaying as well as limiting ettringite formation in the hardened concrete. c. In mass concrete structures, the high temperatures will be at the core of the structure and the dense structures resulting from the addition of slag and fly ash may prevent the ingress of water to such potential spots for ettringite formation in the hardened structure. d. Additionally, the modification of the pore solution by adding fly ash and slag may prevent ettringite forma tion in the hardened concreted and the associated expansion and deterioration.

PAGE 108

93 Table 5.4. RCP and Ettringite Formati on for adiabatically cured samples RAPID CHLORIDE PERMEABILITY (RCP) and ETTRINGITE FORMATION (EF) Plain cement mix 18% Fly ash mix 50% Slag mix 28 days 91 days 28 days 91 days 28 days 91 days Temp (oF) Value (RCP) RCP (Coulomb) EF # RCP (Coulomb) EF # RCP (Coulomb) EF # RCP (Coulomb) EF # RCP (Coulomb) EF # RCP (Coulomb) EF # Avg* 5,562 4,494 5,173 2,279 2,692 2,002 SD 236 159.0 205 135 239 290 95%C.I. 231 156 201 132 234 284 73 Rate High No High No High No Mod No Mod No Mod No Avg* 8,633 6,772 2,548 1,787 1,931 1,572 SD 1,189 348 242 176 164 182 95%C.I. 1165 341 237 173 160 178 160 Rate High Yes <50% High Yes <50%Mod No Low Yes <50% Low No Low Yes <50% Avg* 9,888 7,532 2,503 185 5** 2,329 1,778 SD 1,270 1,236 221 64 283 204 95%C.I. 1245 1211 217 72 278 200 180 Rate High Yes >50% High Yes >50%Mod Yes <50% Low Yes <50% Mod No Low Yes <50% RCP Avg* –Average of 4 samples, SD – Standard Deviation, C.I. – 95% Confidence Interval ** – Average of 3 samples EF # Presence of ettringite in sample and per centage of void space filled with crystals formed: < 50% less than 50% of a void filled with ettringite > 50% greater than 50% of a void filled with ettringite Recommendations The objective of this disser tation was to investigate th e performance of Portland cement concretes cured at elevated temperatur es using typical FDOT Class IV concrete mixes. This was to determine if repor ted high curing temperatures (170 to 200oF) in FDOT mass concrete projects have detrimen tal effects on strength, durability and other physical/chemical properties of concrete. This research was also conducted to determine if limits placed on the differential temperat ures curing should be extended to include

PAGE 109

94 limits on the maximum core curing temperature. Based on findings of this dissertation it is recommended that: 1. Use of fly ash or slag as a cement replacement should be required in mass concrete since these fly ash and slag reduce the detrimental effect of high curing temperature on strength and durability of pure cement concrete. 2. When fly ash and slag are used as a cement replacement, based on ideal laboratory conditions and accurate batc hing proportions there was an 8 to 15% reduction in compressive strength due to elevated curing temperatures. However, this loss could be inflated considerably if the concrete was produced at a batch plant with wider mixer proportions tolerances and the ever-present potential of unmetered water in the mix. 3. This research also showed that when the pure cement concrete specimens were placed in preheated curing tank s as soon as they were molded and cured under constant temp eratures of 160 and 200oF, their compressive strengths were signif icantly decreased (34 and 62% for 160 and 200oF, respectively) and their permeability were increased. 4. Use of fly ash or slag as a cement replacement in the blended concretes cured at the elevated temperatures resulted in low permeability values, which delayed the onset and amount of ettringite formed in the microstructure. 5. Formation of delayed ettringite in samples 28 days and older where temperature was 160 and 180oF is a point of concern and more study is needed to look at the microstructural analysis of samples cured at

PAGE 110

95 temperatures more than 160oF, specifically for detection of delayed ettringite formation. 6. More research is needed to evaluate the effects of other proportions of fly ash and slag. Future research should al so evaluate the effect of varying sample sizes on the observations made as well as observing the samples over a much longer study period.

PAGE 111

96 APPENDIX A CONCRETE MIX DESIGNS Mix 1 – Plain Cement Mix

PAGE 112

97 Mix 2 – 18% Fly Ash Mix

PAGE 113

98 Mix 3 – Plain Cement Mix

PAGE 114

99 Mix 418% Fly Ash Mix

PAGE 115

100 Mix 5 – Plain Cement Mix

PAGE 116

101 Mix 6 – 50% Slag Mix

PAGE 117

102 Mix 7 – Plain Cement Mix

PAGE 118

103 APPENDIX B ADDITIONAL SEM IMAGES Part 1 Mix 1:Plain Cement Only Mix (0%FA) Figure B.1 Void with monosulpha te (M), no ettringite found M 0%FA 73F –91days 170x

PAGE 119

104 Figure B.2 Close-up view of Figure B.1 Figure B.3 Void with ettring ite (E) and monosulphate (M) M 0%FA 73F –91days 1800x E 0%FA 160F –28days 1000x M

PAGE 120

105 Figure B.4 Void with ettringite (E) crystals Figure B.5 Void showing monosulphate and the ear ly formation of ettringite (E) crystals E 0%FA 160F –91days 700x M 0%FA 160F –91days 950x E

PAGE 121

106 Figure B.6 Void showing ball of ettringite (E) crystals Figure B.7 Void showing balls of ettringite (E) crystals E 0%FA 160F –91days 1800x E 0%FA 180F –28days 3000x

PAGE 122

107 Figure B.8 Voids showing ettringite (E) crystals some almost full Figure B.9 Voids showing ettringite (E) and monosulphate crystals E 0%FA 180F –28days 220x M 0%FA 180F – 91days 500x E E E

PAGE 123

108 Figure B.10 Ettringite (E) crystals in and around vicinity of void Figure B.11 Ettringite (E) crystals in void E 0%FA 180F –91days 1400x E 0%FA 180F – 91days 2300x

PAGE 124

109 Part 2 Mix 2: 18% Fly Ash Mix Figure B.12 Fly ash particle with reaction around rim Figure B.13 Fly ash particle with reaction around rim 18%FA 73F – 91days 1200x F 18%FA 160F – 91days 650x F

PAGE 125

110 Figure B.14 Void containing monosulphate Figure B.15 Void containi ng ettringite crystals 18%FA 160F – 28days 800x M 18%FA 180F – 91days 80x E

PAGE 126

111 Figure B.16 Close up view of ettr ingite crystals in Fig B.15 Figure B.17 Reacting fly ash particle 18%FA 180F – 91days 800x E 18%FA 180F – 91days 650x F

PAGE 127

112 Part 3 Mix 3: 50% Slag Mix Figure B.18 Slag particles s howing some early reaction Figure B.19 Slag particles showing reaction on surface 50%BFS 73F – 28days 850x S 50%BFS 73F – 91days 1000x S S

PAGE 128

113 Figure B.20 Slag particle showing reaction on surface Figure B.21 Slag particle showing reaction on surface 50%BFS 180F – 28days 800x S 50%BFS 160F – 28days 150x S

PAGE 129

114 Figure B.22 Ettringite formed around surface of reacting slag particle Figure B.23 Close-up view of Figure. B.22 50%BFS 180F – 91days 1000x E 50%BFS – 180F – 91days 350x E

PAGE 130

115 LIST OF REFERENCES American Concrete Institute, (ACI) Manual of Concrete practice, Pa rt 1: Materials and General Properties of Conc rete, Detroit, Michigan, 1999. ACI 232.2R-96, Use of fly ash in concrete, AC I Manual of Concrete practice, Part 1: Materials and General Properties of C oncrete, 34 pp. (Detroit, Michigan, 1999). ACI 233R-95, Granulated Blast-Furnace Slag as a Cementitious Constituent in Concrete, ACI Manual of Concrete practice, Part 1: Ma terials and General Properties of Concrete, 18 pp. (Detroit, Michigan, 1999). Basma, A., Barakat S., and Al-Oraimi, S., “Prediction of Cement Degree of Hydration Using Artificial Neural Networks” ACI Materials Journal Vol. 96, No.2, pp.167-172, 1999. Campbell, G. and Detwiler, R., “Development of Mix Designs for Strength and Durability of Steam-Cured Concrete” Concrete International 37-39, 1993. Chini, A.R., and Acquaye, L., “ Effect of Elevated Concrete Temperatures on the Strength and Durability of Concrete ,” Materials and Structures/Mat eriaux et Constructions. Vol. 38, No. 281 pp. 673-679, August/September 2005. Detwiler, R., Fapohunda, C., and Natale, J., “Use of Supplementary Cementing Materials to Increase the Resistance to Chloride Ion Penetration of Concretes Cured at Elevated Temperatures” ACI Materials Journal Vol.91, No.1, pp. 63-66, 1994. Diamond, S., “Delayed Ettringite Forma tion – Processes and Problems ”, Cement and Concrete Composite. Vol. 18, pp. 205215, 1996. FitzGibbon, M.E. “Large pours –2, heat generation and control”. Concrete, Vol.10, No. 4, pp. 33-5. Dec.1976, London. Florida Department of Transportation, “ Structures Design Guidelines (LRFD),” 2002. Fraay, A.L.A., Bijen J.M., and de Hann Y.M. “The reaction of fly ash in Concrete; A critical examination”. Cement and Concrete Research. Vol 19, No. 2, pp. 235-46, 1989. Goldstein, J., Newbury, D., Joy, D., Lyman, C ., Echlin, P., Lifshin, E., Sawyer L., and Michael, J. Scanning Electron Microscopy and X-ray Microanalysis. A text for Biologists, Material scientists and Geologists. Plenum Press, New York 1992

PAGE 131

116 Goto, S., and Roy, D.M. “ The effect of w/c ratio and curing temperature on the permeability of hardened cement paste ”. Cement and Concrete Research. Vol. 11, No. 7, pp. 575-9, 1981. Heinz, D., Kalde, M., Ludwig, U., and Ruediger, I., “ Present State of Investigation on Damaging Late Ettringite Formation (DLEF) in Mortars and Concretes ,” ACI SP-177, Bernard Erlin (Editor), American Concrete Institute, Farmington Hills, MI, 1999, pp. 114. Heinz, D., and Ludwig, U., “ Mechanism of Secondary Ettrin gite Formation in Mortars and Concrete Subjected to Heat Treatment, ” ACI SP-100, John M. Scanlon (Editor), American Concrete Institute, Framington Hills, MI, 1987, pp. 2059-2071. Hime W.G., and Marusin S. L., “ Delayed Ettringite Format ion: Many Questions and Some Answers ,” ACI SP-177, Bernard Erlin (Editor), American Concrete Institute, Farmington Hills, MI, 1999, pp. 199-206. Hime, W.G., Marusin, S.L., Jugovic, Z.T., Ma rtinek, R.A., Cechner, R.A., and Backus, L.A. “Chemical and Petrographic Analyses and ASTM Test Procedures for the Study of Delayed Ettringite Formation.” Cement, Concrete, and Aggregates. CCAGDP. Vol. 22 No. 2. pp. 160-168 December 2000. Hobbs D.W., “ Expansion and Cracking in Concrete Asso ciated with Delayed Ettringite Formation, ” ACI SP-177, Bernard Erlin (Editor), American Concrete Institute, Farmington Hills, MI, 1999, pp. 159-177. Johansen V., and Thaulow N., “ Heat Curing and Late Formation of Ettringite ,” ACI SP177, Bernard Erlin (Editor), American Conc rete Institute, Farmington Hills, MI, 1999, pp. 199-206. Kjellsen K.O., Detwiler R.J., and Gjorv O.E. “ Pore Structure of Plain cement pastes hydrated at different Temperatures”. Cement and Concrete Research. Vol. 20, pp. 927933, 1990a. Kjellsen K.O., Detwiler R.J., and Gjorv O.E. “ Development of Microstructure in plain hydrated at different Temperatures”. Cement and Concrete Research. Vol. 21, pp. 179189, 1990b. Kosmatka, S., and Panarese, W. “ Design and Control of Concrete Mixtures,” thirteen edition, Portland cement Associ ation, Skokie, Illinois, 1994. Lachemi, M. and Aitcin, P., “Influence of Ambient and Fresh Concrete Temperatures on the Maximum Temperature and Thermal Gradi ent in a High Performance Concrete Structure” ACI Materials Journal (94)(2)(1997) 102-110.

PAGE 132

117 Lam L., Wong, Y.L., and Poon, C.S. “ Degree of hydration and gel/space ratio of highvolume fly ash systems ”, Cement and Concrete Research. Vol. 30, 474 756, 2000. Lawrence C.D., “ Mortar Expansions due to Delayed Ettringite Formation. Effects of Curing Period and Temperature ”. Cement and Concrete Research. Vol. 25, pp. 903-914, 1995. Maltais, Y., and Marchand, J., “Influence of Curing Temperature on Cement Hydration and Mechanical Strength Development of Fly ash mortars ”, Cement and Concrete Research. Vol. 27, No. 7, pp. 1009-1020, 1997. Mehta, P.K., and Monteiro, P.J.M., “Concrete: Microstructure, Properties, and Materials”. The McGraw-Hill Companies, Inc., 1993. Neville, A. M. ‘Properties of Concrete’.4th Edition, John Wiley & Sons Inc., 1997 Neville, A. M. “Properties of Concrete”. 4th Edition, John Wiley & Sons Inc., 2004. Miller M.F., and Conway, T.,” Use of Ground Granulated Blast Furnace Slag for Reduction of Expansion Due to Delayed Ettringite Formation ,” Cement, Concrete, and Aggregates, CCAGDP, Vol, 25, No. 2, December 2003, pp. 59-68 Sarkar, L.S., Aimin, X., and Jana, D. “ Scanning Electron Microscopy, X-Ray Microanalysis of Concrete ,” in Handbook of Analytical Te chniques in Concrete Science and Technology. Ramachandran, V.S., and Bea udoin, J.J. (Editors), Noyes Publication, US, 2001, pp. 231-273. Scrivener, K.L., and Lewis, M.C., “ Effect of Heat Curing on Expansion of Mortars and Composition of Calcium Silicate Hydrate Gel ,” ACI SP-177, Bernard Erlin (Editor), American Concrete Institute, Farmington Hills, MI, 1999, pp. 199-206. Stark, J and Bollmann, K. “ Delayed Ettringite Formation in Concrete”. BauhausUniversity Weimar / Germany Stark, J and Seyfarth, K., “ Ettringite Formation in Hard ened Concrete and Resulting Destruction ,” ACI SP-177, Bernard Erlin (Editor) American Concrete Institute, Farmington Hills, MI, 1999, pp. 125-140. Tarkhan, S.B. Degree of Hydration for Ce ment Paste with Fly ash at Elevated Temperatures. Master’s Thesis University of Florida, 2000. Taylor, H.F.W., Famy, C., and Scrivener, K.L., “ Delayed Ettringite Formation ”. Cement and Concrete Research. Vol. 31, pp. 683-693, 2001. Verbeck, G.J., and Helmuth R.A. Structures and physical properties of cement paste”. Proc. 5th Int. Symp. On the Chemistry of Cement, Tokyo, Vol. 3, pp. 1-32, 1968.

PAGE 133

118 Zhang, Y.M., Sun W., and Yan, D. H., ‘ Hydration of high-volume fly as h cement pastes’ Cement and Concrete Composites Vol. 22, pp. 445 – 452, 2000.

PAGE 134

119 BIOGRAPHICAL SKETCH Lucy Acquaye has a Bachelor of Scie nce degree in Building Technology from Kwame Nkrumah University of Science and Technology. She taught courses in construction materials and methods the univers ity after her bachelo r’s degree. In 1998, she was awarded a J.J. Fulbright Scholarship to attend the University of Florida, USA, where she graduated with a Master of Sc ience in Building Cons truction in August 2000. Since August 2003, she has been a graduate inst ructor at the Rinker School of Building Construction where she has taught courses in Construction Drawing and Construction Mechanics. Lucy will graduate with a PhD in Building Construction in May 2006.


xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID E20101119_AAAACQ INGEST_TIME 2010-11-19T16:24:25Z PACKAGE UFE0013837_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
FILES
FILE SIZE 821458 DFID F20101119_AABQZX ORIGIN DEPOSITOR PATH acquaye_l_Page_052.jp2 GLOBAL false PRESERVATION BIT MESSAGE_DIGEST ALGORITHM MD5
ff6c11e3afc379b4932c7f691687dcc0
SHA-1
4fe330840d37f95ff0bc3b1c152c6d9129555002
67433 F20101119_AABRGG acquaye_l_Page_027.jpg
e026e87e164cd84bc7219641408152e7
6b64d7007b5a68cf4d227209f3bfa32acd5043ff
33739 F20101119_AABRFS acquaye_l_Page_008.jpg
ad9448903c7d69bfe4a7e25b4a63e1b9
7215eb5700d3de0e52e0b50d16e93c80331dc37a
1051950 F20101119_AABQZY acquaye_l_Page_121.jp2
37b88bd4bc7a7ea31c732385bfc16f95
41d22e630caff0451b30d3ab7163ee9dcb9303de
68917 F20101119_AABRGH acquaye_l_Page_028.jpg
ce8eb091cc1f78bcdec7e53072397ada
c1a82c556148d29d8cfee907b358445341b6a890
66991 F20101119_AABRFT acquaye_l_Page_009.jpg
6e56f9e23c073d35b637862516b60f15
758e009791a0cf973fa217918d0554c792aa13a5
1813 F20101119_AABQZZ acquaye_l_Page_023.txt
2cc0df2735cf77bd42a57c9aaa53971e
d5728492a1cf5cdc4cef0ef300cc9257de1b5d40
72500 F20101119_AABRGI acquaye_l_Page_029.jpg
42cc4aec888848131db9d8d0a7afba0e
63f0028e7fbcceeb7289d1eb9e10cab554471796
81573 F20101119_AABRFU acquaye_l_Page_012.jpg
2510713e643e71492e641f28b201c5b0
c712503211a9001e8a26b9b7ad1377558010eff3
73611 F20101119_AABRGJ acquaye_l_Page_030.jpg
b20b65192cfbc0149f284e89429c6e5d
1a09fe47e7855da9c184154281dc9f19c0fbabf5
71431 F20101119_AABRFV acquaye_l_Page_013.jpg
8651c68db8cf064f8e0703467ada7fc8
9192b38f39733a3670c85a29fe0e26930c725e31
73819 F20101119_AABRGK acquaye_l_Page_034.jpg
e636a9edf4d2c4e12260c53e22bb8624
60149e7803a64a0417a22cd3f36a9051aa5682d5
56809 F20101119_AABRFW acquaye_l_Page_014.jpg
af5d566e4e6ba0e79693fc6918c46e7b
9d78d2fcddae6bcc81cbe776320051577b613b60
66620 F20101119_AABRHA acquaye_l_Page_059.jpg
0434e80dfda76967b74fcafd85e13261
1e593ea1b4dfd65a04f6bc7ee720be9b791a8333
63468 F20101119_AABRGL acquaye_l_Page_035.jpg
40ef75b8aa1c10af988787048e89cd00
a275d4b4f4f167b32a3e49715ffb24dcb3b7b59b
53098 F20101119_AABRFX acquaye_l_Page_015.jpg
7935f82a63da09d276541398427da741
9207ec1506ab9335cab0d1da326251a6c5443d1d
66678 F20101119_AABRHB acquaye_l_Page_060.jpg
97060368e7ba3c1a94b93a9f3c8d5c4d
079fef7d6a7e524159e127c57f2b3423ec94cd33
66751 F20101119_AABRGM acquaye_l_Page_036.jpg
335840230e697bbb6a7237694699348a
4bf891f895867154ffe4c4ddc283c0bdc326fc43
63423 F20101119_AABRFY acquaye_l_Page_016.jpg
35bbe85a0773247475feccef3c4db5e1
5d4937db49636e0bde6b0cce8108b1db5dd5738f
70685 F20101119_AABRHC acquaye_l_Page_061.jpg
171fce4d406e9110b880ebe853310fe5
e97f9545e5dafde6106d4b8a03293a17107e6cb6
72739 F20101119_AABRGN acquaye_l_Page_038.jpg
8f8c198fce8c50cdcee90cd130a2e856
8cd293b92f5840ddbe541e50116ae0b7619af28f
72660 F20101119_AABRFZ acquaye_l_Page_017.jpg
019ce810c0689f624f7a1139094dd9eb
485f60c62dc55a7759a49a593f5281d8e8d0d9a4
62532 F20101119_AABRGO acquaye_l_Page_040.jpg
5dcb80e9dc2bb81812e51ac3ae67ab52
f6419b843dd548067c2fcbac1e00ae190adbb407
63516 F20101119_AABRHD acquaye_l_Page_062.jpg
1cf1ea861a594fe4259fdaf18cda1844
f6c8b3e08e5654d01719a7a1699c8f2559ec193d
23021 F20101119_AABRGP acquaye_l_Page_041.jpg
04b5734195bfd2941e5c145552863609
a3af1c1577e1d1d8ddb81e068b1f07f034965424
70545 F20101119_AABRHE acquaye_l_Page_063.jpg
56f857ca30ee4acc481351e16d94fc42
820e9073404fd5091b9197af4ccc453981c55aff
59069 F20101119_AABRGQ acquaye_l_Page_042.jpg
c31104156b5a7d3dbbf5c7cdc47871d9
e08010655bdf488fe13f3e3ecea39dfe8158ecf1
65183 F20101119_AABRHF acquaye_l_Page_064.jpg
095ec49e7c4446cc09a5777738bf37b1
d637aeda841edf00ed68f1fb42ae2c27d2d45f6f
33102 F20101119_AABRGR acquaye_l_Page_044.jpg
c3e31685ba6f6535f4253aa395105667
6a872b460de473b344c036eed120c3f438e1b662
45485 F20101119_AABRHG acquaye_l_Page_065.jpg
f2cad783b174935a9412c84c8c26d500
07270ef938e673019d0eabd0d4eafb3b86986c5e
55308 F20101119_AABRGS acquaye_l_Page_045.jpg
a6c634f56c9cea677a8129cea5ff37c6
b50f80bc5fc02ccc5820cb2cbb5e18d3c63185d9
53567 F20101119_AABRHH acquaye_l_Page_066.jpg
86289b84b0418e7bc109e6d98f4491eb
fd115ba14d7131bd4d96968df50c1844fe038156
68807 F20101119_AABRGT acquaye_l_Page_046.jpg
e092173dab484a96da18662320598191
aebec0ecfd106daf6ba1cef8aea6e87745511e12
60448 F20101119_AABRHI acquaye_l_Page_067.jpg
b871735487b08b8c38fe739161bdf2e4
ebdb4fda8a37af77a862d9576110426679b9370d
53169 F20101119_AABRGU acquaye_l_Page_049.jpg
11c39f7156c3443af9a2bb3a35a349ca
b17ff15857e7d0ff18140b801b6f5d8e325dda38
59706 F20101119_AABRHJ acquaye_l_Page_070.jpg
bcbf5833a6532a9633b49e55ef9fe8f0
b3a3e8ca035909cb1b7dc5712a48d04916fda1bc
32981 F20101119_AABRGV acquaye_l_Page_051.jpg
e91582c5f3cc78dd8b9cabd8e87ca627
3d917990e504c46685d0389812b66431713fbabb
79236 F20101119_AABRHK acquaye_l_Page_072.jpg
414dfed43e88ac8f33413a2b8cdee915
ef559a8326104c1cda00bb5ef03608e4de2b8bb3
65413 F20101119_AABRGW acquaye_l_Page_054.jpg
73511e414f105d6b43f10466c8c7fa3b
a528c3fc780b9c3205ad33f1b82f03833327b769
48928 F20101119_AABRHL acquaye_l_Page_074.jpg
a9af11fb0964b025cc6fcd3a8bbfecce
c4d78537f4db07bd90fa1930b3195e5dde7af46b
61152 F20101119_AABRGX acquaye_l_Page_055.jpg
f4235d05340d719eb7b35c0366cb0e22
3171d89175b94442b188ad3ba7543aff407c3351
58126 F20101119_AABRIA acquaye_l_Page_096.jpg
babb875850f43db7b75e3992c6a6dedd
3bfeb1034c524d1fa5876c8a53967d5ada4b4003
48702 F20101119_AABRHM acquaye_l_Page_075.jpg
1f45c7b33c113718ff54cd4709f6eb6a
b0f05bffe5ec92444375eac84d1c24f65ca2ea39
57328 F20101119_AABRGY acquaye_l_Page_056.jpg
817846d5213a1b6d5cbed38f8f167ab3
819ce7d89b0ba2a93f724118d331a6073e547531
71313 F20101119_AABRIB acquaye_l_Page_097.jpg
6df76ee794b60cf60a9efb48d690864c
2cf6512a30f2824e6cb72369a3e5ad8ee211f3aa
50658 F20101119_AABRHN acquaye_l_Page_076.jpg
1eacc143506119a3761d26cf041a15d7
b25f0950a87ca02d4475f2ead59a11488042b911
56336 F20101119_AABRGZ acquaye_l_Page_057.jpg
cb0ced53edccb2f7e88b5a7985055c23
13151c53089e63985b1f16c043d3b7ed4dfdcb90
52095 F20101119_AABRIC acquaye_l_Page_099.jpg
fe239071a8a367243735a6bac3ced2a8
0e40726d00f7c2f820df746d7e73e93316d30c7e
48015 F20101119_AABRHO acquaye_l_Page_077.jpg
8e9def99e6b2f2acb5edd90b84e3bea6
918dcf9cc9d594e5010cccf31cf9d7bcb71f1d7e
48855 F20101119_AABRID acquaye_l_Page_100.jpg
ca94aa81c2019a397ba486a8f5cd4ce7
bb28b4a1cd680cee4d30739c5c04cc9669134831
63502 F20101119_AABRHP acquaye_l_Page_078.jpg
31323e346fd365131dad8c1178555cf5
b6b3dfb4cff2ef28570a5a12011db39e81028a97
44661 F20101119_AABRHQ acquaye_l_Page_079.jpg
25dfca0c348cbbbf9b6bab6df6febbf8
c149509fab33b2f00662589f20a7d1f881f934af
34056 F20101119_AABRIE acquaye_l_Page_101.jpg
b49c6d1da67ff05b5f08a435b00b4bcd
d220e51ac2aae523760db7850d768647a4b113a2
60196 F20101119_AABRHR acquaye_l_Page_080.jpg
11609d6e557bd9263553d7693849076f
7690babc6e4a2e6f909a411c95a8ac9fce73b4e1
62131 F20101119_AABRIF acquaye_l_Page_102.jpg
25b6c45851d9f16c3e6b80f910b04956
3f8b52eaeaf5a96e7d5d569ceb4e95be431fbd7b
60753 F20101119_AABRHS acquaye_l_Page_081.jpg
a9a6b99d82db25501602eec83c35eb23
1c607ebc9681f376ac3d4096de63ec109b501117
59133 F20101119_AABRIG acquaye_l_Page_103.jpg
8827af5ed17eb16ee82b6f96a4b4a166
2d1273ef4f89039a7f0f31f25d7e732faa3e2d80
66392 F20101119_AABRHT acquaye_l_Page_083.jpg
4bb552d5020dddf28a68b5ad0504bef8
e9adeeaafea3107d0780227e1ca88106f0e35d1d
44951 F20101119_AABRIH acquaye_l_Page_104.jpg
5c1c2db74675efe9b8b7f921359476ba
b793e711877a355af516b8e38d795a750552f513
54601 F20101119_AABRHU acquaye_l_Page_085.jpg
23c633637e3b1263096b3da034a39983
146e6bcc1587b49aefbeb060be73eb9f9c99b102
63635 F20101119_AABRII acquaye_l_Page_105.jpg
3b59c64b9239096dbb37d46fa1e7f771
14501d9b1ee1f4547f7ec49fdaa07b5f03dd79d4
48308 F20101119_AABRHV acquaye_l_Page_086.jpg
0bb405138e26c629e426c30aaf6f5238
58caa9c1c23640e36d0b70e5230a11b2021f2008
62932 F20101119_AABRIJ acquaye_l_Page_106.jpg
1bde9c5ac08e0931b657cc76f9627bc3
79c46479cbdf46f3decd1812cd31d633ea423657
57819 F20101119_AABRHW acquaye_l_Page_089.jpg
ddd1a39134f3ba8a6fdb627a5486b300
5b8c20540d2c2fc4e11a26840037e5f0d0a26b86
40866 F20101119_AABRIK acquaye_l_Page_107.jpg
f76b83e9288ae9b921156c0adad2d02d
d1c695c83abc5715c08f520a23cb2aee5ec0c6b6
40617 F20101119_AABRHX acquaye_l_Page_090.jpg
ec2cc1d0372da3080dcedb98ec6ae2c4
02812441eeb7119d164759a8ce433e1ee86f9dcc
51566 F20101119_AABRJA acquaye_l_Page_129.jpg
dcaf2c556079f643cc5892a9db63f5c5
0b8aed8fb6e39cca1d928183ff7184e8a6aa7cec
86384 F20101119_AABRIL acquaye_l_Page_108.jpg
5b236cfbd410c344a8de5c9c5659990a
d9f42ce4eefb27baa6a1dcac4f79ac5aaf367ce6
80283 F20101119_AABRHY acquaye_l_Page_092.jpg
327da32b61a310610366155639d24427
121a7d56d3e059daefb2d61acaba3367c99bc8bf
88467 F20101119_AABRJB acquaye_l_Page_131.jpg
146706e6e7c69cbab134828af4b39900
e207343d91cba60adf9e360c2681ac5b57a2df95
19624 F20101119_AABRIM acquaye_l_Page_110.jpg
72e2d8af942de443161d0e44762a0420
e14ce4ec62bafe929b7ec16c1a83932c7498ed6a
58996 F20101119_AABRHZ acquaye_l_Page_094.jpg
c1087e909530d29d10ffa775dd517844
36701998b69a0836f6f09746428b02475d28d418
86588 F20101119_AABRJC acquaye_l_Page_132.jpg
a5490b0e45689edda9fccfbc63ddc99d
26f489eaa38439398375a1563bf2c0492e6202d1
51890 F20101119_AABRIN acquaye_l_Page_111.jpg
dc2ea4fbfd05cea45ca85bd2e94767da
e4c982bc21430c3bc22820bacbbc2ea86cc01180
14493 F20101119_AABRJD acquaye_l_Page_133.jpg
4c6f4b4dc3d20863761b4e61266ad99d
3cdf97b37c9fb2b35914583357c942257fb0b4d6
50331 F20101119_AABRIO acquaye_l_Page_112.jpg
702a7e2dde9a4018c27b73e89f4e561d
469f044ee80908cee715cdecae06707fdb2649b2
27572 F20101119_AABRJE acquaye_l_Page_001.jp2
d48210bb0e210826db6f65971069ef80
5e69b412c1e75334b087873d3acaa518f5968164
51090 F20101119_AABRIP acquaye_l_Page_114.jpg
0f668aafe866d4054430e9afb48a49d8
5ed6f290fc74a704fdf89d023aad68ddf8eba0dc
56438 F20101119_AABRIQ acquaye_l_Page_116.jpg
f9c26a39979549a88fdc98d56082cec5
90a00e67a568ecfa10e3f75a656e03a80acc43a6
5814 F20101119_AABRJF acquaye_l_Page_002.jp2
582010670b17dc8ff2dc594710fc768c
f54c7286b291a499abecf5f4151f6152cc6a1b7b
54303 F20101119_AABRIR acquaye_l_Page_117.jpg
2681755a341e021893b60a0c3fd164db
1b5027912450b41f1f2c2e5d35fa823848963472
6202 F20101119_AABRJG acquaye_l_Page_003.jp2
9923761e318b04c437df444c9761a740
89fd5b34ec44d8fb000a14f4cb21673bdd0727d7
44665 F20101119_AABRIS acquaye_l_Page_119.jpg
0a7df401e4ed6564667388cdd9f30b78
aa2a5bcd0d148a8bb3eed20ca686d8cba8f0f256
92910 F20101119_AABRJH acquaye_l_Page_004.jp2
fbd8431c6f82c3e4370918f03a29d261
2252f6d593985070ce630cb5c4af896e4c28eb46
62626 F20101119_AABRIT acquaye_l_Page_120.jpg
35b1099f67fb494ab8d5f7486c542302
4406a336813edee7c2a55c2cb7fd53ae467c528f
29459 F20101119_AABRJI acquaye_l_Page_005.jp2
b6d60594a0d49723fca5b11a804d17dd
1fe5ec3534a71ff67bbac20bf4a9ea98b62dc316
64073 F20101119_AABRIU acquaye_l_Page_122.jpg
9bf5406bb355732e144bec68df9a7510
7e422f83827ff09a06e27c0e1f74ae3faca35acd
1051985 F20101119_AABRJJ acquaye_l_Page_006.jp2
f67b1a54b36ce6ee1261ad2e9fb40391
0bd2086565a72bb8edd5b92429c0f3c86d98d654
55451 F20101119_AABRIV acquaye_l_Page_123.jpg
16dda184a889c166159e795462a8d5a2
d6fa43c434f63eb9abf6cdab3a82bb6207336a9e
976127 F20101119_AABRJK acquaye_l_Page_010.jp2
098653b304908660075b99b0afae396e
48002a87d18f6dd54f4830f974927c5d44311a5c
68169 F20101119_AABRIW acquaye_l_Page_125.jpg
cfd458ccba1f50f29dba2e62246afb06
7ab00e45825885c1ee2d4d191e3d5ee78966c80f
1051982 F20101119_AABRJL acquaye_l_Page_012.jp2
554ff8839be327c5f37173342f19ab26
19d8004d36e1f144592548d3b2332841e74c885f
61733 F20101119_AABRIX acquaye_l_Page_126.jpg
7865868b6f57e6d82bc9ddc0deb019c5
926a004ac2b9220e3edcbf47cc4773b9913b3ee3
860588 F20101119_AABRKA acquaye_l_Page_031.jp2
1002b2dea320d7d450d58f67eeee00dd
ee0049b5c80c45f2cf569497aaaf31669937fdcf
1051986 F20101119_AABRJM acquaye_l_Page_013.jp2
ac172bc85cc5ab059543e0b57b307b66
0c719d7c9067474b1826dbaca697a18856e2d61e
61755 F20101119_AABRIY acquaye_l_Page_127.jpg
98e1df82c4b48917a0ec638627d39b23
eb46a7a8fe144c10de32b6e43013476276aed3b8
111362 F20101119_AABRKB acquaye_l_Page_032.jp2
4447e7e7273575f634cad0406ea19ac8
6c4d0c97191dc78e0db6ca454915c191d073d0b7
111200 F20101119_AABRJN acquaye_l_Page_017.jp2
41956c5a15b49bea9884b4b2eb859251
145d4b6df1ae58fd8ceb3f013b642cb4800cd7c6
66076 F20101119_AABRIZ acquaye_l_Page_128.jpg
0ea5af7653a1919f5e285f58fbd41341
634d9cb0c5440ca7247d618ce77b3a75f7f145b5
99251 F20101119_AABRKC acquaye_l_Page_033.jp2
fdab1ac548f7a897351d1b1a527af842
451916ce791388609350f629c71044208fc7c694
102601 F20101119_AABRJO acquaye_l_Page_018.jp2
a6ce4456a2745423ab86d52a186253f2
9ba1bdec3a9a15e56291285751c6da28934cf1ab
111507 F20101119_AABRKD acquaye_l_Page_034.jp2
13836c677310563776129f205eabaadf
c558220bb4da111f289cd4c4e4eb018b9f457226
97827 F20101119_AABRJP acquaye_l_Page_019.jp2
0f19a380d3f6c6b7c88d13cc980df94e
aae61a9b98b321c63ffe4c36ef89640eab1231ad
891821 F20101119_AABRKE acquaye_l_Page_035.jp2
0928079f657a2b3853c07527291ac72a
e995572f9de287f710235cb081cd08e5fc23214a
97433 F20101119_AABRJQ acquaye_l_Page_020.jp2
f49a27cbd5e45648e4cdd2e023f4198c
88f790de927c8021e4925f9250ead711967ecfd0
91830 F20101119_AABRKF acquaye_l_Page_036.jp2
9729880a96818a0d5bfce507a6ccd666
52fb28eaa04068f6a5a799fa93d481652d21cc85
91759 F20101119_AABRJR acquaye_l_Page_021.jp2
7de1cef13c9d0fd44326efda4231a9c9
16219b253bed1967db4a25b0b7f192adc7c095cf
48513 F20101119_AABRJS acquaye_l_Page_022.jp2
b02513f1ce7becda23e11c7263664b13
5ebe7bb6ba131433b1e597125f92c77d86a79e50
86341 F20101119_AABRKG acquaye_l_Page_037.jp2
f8ba27426a50374903d24e37824c6a9f
ba7569efc33d484a067884c146dca3c264c53b42
93092 F20101119_AABRJT acquaye_l_Page_023.jp2
9260978f9d7c8e4c1458f9a0b635360a
669fac71ea99b165e8f348057b147f28f355c74c
110883 F20101119_AABRKH acquaye_l_Page_039.jp2
03218926ef2aa93f6145449a448d8811
2f66f03c2cf7913491b75b5294f806d9fb0e93a2
94020 F20101119_AABRJU acquaye_l_Page_024.jp2
4cf5655b3d93afaba97c5c557f0aa525
05de785ff09ad85dee22682bb918387555fdc17f
94358 F20101119_AABRKI acquaye_l_Page_040.jp2
496787a46bee5bf00af6d66c43503aab
a17e8d696fb65504b75678f1f321154c13e63b7c
814145 F20101119_AABRJV acquaye_l_Page_025.jp2
39d879d270be7651144758871f2a3f56
989f13bde628a891b8cd045fbf6ee991a16416a6
28731 F20101119_AABRKJ acquaye_l_Page_041.jp2
a85404cda595a3442b7eff2e65b88d3e
ddd8fd9271b28e4495fbac95d75dcd299460580b
100808 F20101119_AABRJW acquaye_l_Page_027.jp2
32ad6440c669386cbccc7f79d6955986
52d0f15324c3ece659aa7992fb6746c970dda666
86635 F20101119_AABRKK acquaye_l_Page_042.jp2
e91d15f3afceaff88b64acdbb2a0a654
d7eb8d998668005f5ef49ff7ebe2e6b8c06f4a72
101610 F20101119_AABRJX acquaye_l_Page_028.jp2
7bb72efe3f460653f159803fb888cbe6
978db1cd10db24ce50b10445c9a7cd97f636c4bb
90243 F20101119_AABRLA acquaye_l_Page_067.jp2
23eb5f28c2fac9fc2575193cedb17bbb
f07fd8458cf4354fa7eb01cd11e0a8d9846177f3
98422 F20101119_AABRKL acquaye_l_Page_043.jp2
08cdf3f43d99ebe28bd0fcd6816d4c83
320f19b9e17de4e199bc5a90a4fcbb0a730007e4
109496 F20101119_AABRJY acquaye_l_Page_029.jp2
09c0a44ceea559470a0c7fa109a41808
48b7cf0fd8abbbe481ff7f81e7c7efedf833ebe5
78561 F20101119_AABRLB acquaye_l_Page_068.jp2
1efc66379da0ea0ad3e3cb1a47b0a826
c4d193f3db27f458d457e5eb9cc6f9b3b5449e85
63829 F20101119_AABRKM acquaye_l_Page_045.jp2
7951ef826df07d6d3f9c3807fbc32911
8122c3e13f15e8f0c3eacfb9aa86bec1abd3dabd
112549 F20101119_AABRJZ acquaye_l_Page_030.jp2
9f3246824fcc0dc655592fc2113d4559
88b4fb3cefeb614015ca83b56de7d69d26123c9a
671830 F20101119_AABRLC acquaye_l_Page_070.jp2
d80ac55b815d0b6f4f346492513d44ad
e3b908f773ab715a10cb98f43290af6fba39a17e
689232 F20101119_AABRKN acquaye_l_Page_047.jp2
0bc2cada7f4ca656dd2e21f2d9c18336
011bf1b256318ef8fd917d5ee00fad5f0e805e6a
775598 F20101119_AABRLD acquaye_l_Page_073.jp2
6bd50ef7d7e8f3fdc12651d3e5221dbb
d8e9c542eeefd2a6bfac6e00c9c4e94033a8559d
750989 F20101119_AABRKO acquaye_l_Page_048.jp2
7c46771829e00537c0b6ac37633b8814
3de6eb190f30031878c89419c7d83f3f48701cfb
52894 F20101119_AABRLE acquaye_l_Page_075.jp2
1c8c066838284e9369bb34943c950d01
90f0f52c14116949a89c9db332c572129d18f92d
914386 F20101119_AABRKP acquaye_l_Page_049.jp2
e0583394eb4ceae08ad0abf06f796853
1692d73e0a3cde944052284ce54a966f7dfd624c
54396 F20101119_AABRLF acquaye_l_Page_076.jp2
a720eae967f5bc88e404155fb942105c
cda9fa6fc7d2f76e300f030268a45c11c20aa188
649915 F20101119_AABRKQ acquaye_l_Page_051.jp2
1123d46611bfc3bac3914958e7b1b433
d08f3266584d27da277cb85ef1ca2945bc812800
54009 F20101119_AABRLG acquaye_l_Page_077.jp2
74df780db0515d2e501ec3c1a49e726a
06a9a61110522b18792768cdfbb24f7e37499a06
729296 F20101119_AABRKR acquaye_l_Page_053.jp2
837203175a733c97043822cca5ff6700
122f3716dd262dc396d6c036b25bcec75d1366d9
89726 F20101119_AABRKS acquaye_l_Page_055.jp2
4720153342101ea9c57180400f11b7e4
8fe05a5fb538180c62a60f7269e80aba9b1a1a2a
76812 F20101119_AABRLH acquaye_l_Page_078.jp2
c3d48fa62fa7d52f67a103e476a595c4
f25b6441c605d7d7f2363309d5c3b9c013b3b711
57254 F20101119_AABRKT acquaye_l_Page_056.jp2
cbe26210997a04836047bdef1d87803d
e0537cff0acc7a70b3f7cd4b95ef548f6dc2f575
546200 F20101119_AABRLI acquaye_l_Page_079.jp2
61a4baac4585198b2351b1e770b1b56c
b3e99189e43baa8d69f9039d8d282b78fc04f72a
700594 F20101119_AABRKU acquaye_l_Page_057.jp2
7aa625f39a4f0d43a19f9d848b013e0b
d82b830477ba86e0a2683701a454ec847dccf1a6
779073 F20101119_AABRLJ acquaye_l_Page_080.jp2
68bec7eee6666e3c24b4bbb756e0c16b
aaefe4cac7527796b7d0e764a3cb3392c5abbe23
916927 F20101119_AABRKV acquaye_l_Page_058.jp2
4871c4fb6ea47b736e619e8f7e25cebc
eb6691a0d7bf90c98387e2eda7ab8625f512a7f4
741548 F20101119_AABRLK acquaye_l_Page_081.jp2
1ec55c3cb1a76777d350adf0693d19dd
bed37062b6bee98a62789cd4e31f6a07cfa5bdb1
108325 F20101119_AABRKW acquaye_l_Page_063.jp2
f49d4fec766deb2dcdaa5033495cf563
b322579f86b1d2c72e8666f34df0fd5be228db53
664423 F20101119_AABRMA acquaye_l_Page_101.jp2
d447862abc3e1aa1fcca5dce459ddc1a
6f90cb0c30669b7ba0a0fa5caf1405f1a589804b
720722 F20101119_AABRLL acquaye_l_Page_082.jp2
286cf92a48ca952350854f3817377aa3
6d3521e9d3269f7a56c997c2f5f6e0945122fba3
865379 F20101119_AABRKX acquaye_l_Page_064.jp2
e972b94273f4414c813527d25547a000
5c010d774c2327b373cebe694bbbd65d0c91390c
92750 F20101119_AABRMB acquaye_l_Page_102.jp2
b15094f5e4be10dde65443dd20f2345c
a312666a1c5e97041d9e124ede4d866582774906
827771 F20101119_AABRLM acquaye_l_Page_083.jp2
1df6290038ce443758ffc42f0c1de858
0e0b62178b16b46f756f4a1447923af493fc897f
672600 F20101119_AABRKY acquaye_l_Page_065.jp2
34ea1c139fd97d195d16d1a623696cc2
611affef3fb252fe9128c493a5b143349477fbe1
59230 F20101119_AABRMC acquaye_l_Page_104.jp2
3048495f0a56ba8640d7a9a9aea97d7f
244b35b718a7057d3e7d992f11ba51a85840da42
676288 F20101119_AABRLN acquaye_l_Page_084.jp2
bba6c284cf26f40e611b6b75faa10e0f
bb120a5fab14dbf39cdb588f76c4e03194f1f6a0
78552 F20101119_AABRKZ acquaye_l_Page_066.jp2
6d4b04eb8300795dacc6811512bd561e
226a720288fd94689327dc94e26d325069517bc1
72813 F20101119_AABRMD acquaye_l_Page_105.jp2
74ef392ffcc6c0af73619b229659db66
b22dcd66adeb328e478db98837bb54899a840906
763907 F20101119_AABRLO acquaye_l_Page_087.jp2
ec57846f292733386ea952911e063a71
eee945a2f812833f451ffcdc72c7f96f09cd294f
94757 F20101119_AABRME acquaye_l_Page_106.jp2
71e1fe575598a074bc329940e053c8e3
340090e86413997d44cb1ca97505cfa14415cd35
609870 F20101119_AABRLP acquaye_l_Page_088.jp2
c1c0eae14f53f2d294bbd0b81a1073c6
12d365dc843e079eda1e805caec0f842e57f3f5a
103824 F20101119_AABRMF acquaye_l_Page_108.jp2
8625899ab43917cb69e731ebb871d2e9
26dff2b9ea063cae61ba494f13ac5d285d743a83
84205 F20101119_AABRLQ acquaye_l_Page_089.jp2
9ef7afe294a87c96bedf3b07ba71a187
c973c80a89aaa9197a8d615e6268c1d42bcbc867
89471 F20101119_AABRMG acquaye_l_Page_109.jp2
9fcf3388e13c688408c3c86069dbd31c
aac5c39367aa5f08a6afeeb9afaf5bb32b5f3fda
1051874 F20101119_AABRLR acquaye_l_Page_091.jp2
4bcc5dc8588fb269ef272daa51e84425
98005939fae9eddb3e11a69e7d5669daae29d735
23604 F20101119_AABRMH acquaye_l_Page_110.jp2
6d4d0c06f1785ac1131fc45b73b2ecba
a6dcfaf3fba9e588d1a6cebc4d471282c66a9ae9
1051879 F20101119_AABRLS acquaye_l_Page_092.jp2
efed7e2b0d7e4fb04ac43698456ed7de
bd7ed5d4f30fa7113322677a2a438ea8ea1d1868
88255 F20101119_AABRLT acquaye_l_Page_094.jp2
16300da3a0d377d82e6cb6f25d131e65
cc56ba0396777da47f900832dfbac97892e9e17f
831157 F20101119_AABRMI acquaye_l_Page_112.jp2
c7ab8ed7f6c10aa5434bbc324108c3e1
8ba8d64ac6596b03d2533724b2e70fba0591d082
1022479 F20101119_AABRLU acquaye_l_Page_095.jp2
eaeb1ca91d03b6ee79b6b9be219b973f
d52859da0203c18d70bc9121f017d28e8a242a2f
850353 F20101119_AABRMJ acquaye_l_Page_113.jp2
c618bbfb9e9c21a64e4ebe87f68c9247
31a5e6bb4d8fcdc6ae7aed059975177936dd7bec
1051869 F20101119_AABRLV acquaye_l_Page_096.jp2
da1b7080b29f841b7feb3a18e39710e4
4d894e1d4da412da11ecd603a30f2dfad5d2572c
849897 F20101119_AABRMK acquaye_l_Page_114.jp2
ed296a63736bac2bebc9c8df69eb4c50
6351d0b848826a84b78cb8df6bb28bf6a24ff7ff
107953 F20101119_AABRLW acquaye_l_Page_097.jp2
19913dd779e1aed6bc9abcdf74b59991
93c89a49bef5695fa3f9673d794da236f2933dd7
907254 F20101119_AABRML acquaye_l_Page_117.jp2
233515571224b7e9b09a812610dd9515
97d959c0ceb74091194581afc4f4c372ce01c330
80212 F20101119_AABRLX acquaye_l_Page_098.jp2
5d2e2201c746136689e8b4b2283810ff
0f9e34537a4a557138ecd7b0e11eceacefba0bc3
1053954 F20101119_AABRNA acquaye_l_Page_004.tif
40d70d138bf513c2c6886fcf7bf95e2a
ec073620871d0911de23a2641bc4a1a5ef45a88e
735783 F20101119_AABRMM acquaye_l_Page_118.jp2
dc109030ef6330150f3cfd0fd1882ae9
cb60eada955fc0699e9d4cd1b95e9775418f240b
1051947 F20101119_AABRLY acquaye_l_Page_099.jp2
9e651687a8864d90e12e43ec4ff4c4ef
4c300f9dca235bd6ef83fafd06c89b2606068714
25271604 F20101119_AABRNB acquaye_l_Page_008.tif
74d9d144128d72accc4170349d796549
62b2e58d0816f198eebdb57f331843c2f7021ecc
1051965 F20101119_AABRMN acquaye_l_Page_119.jp2
8461c42c1c81091d9555bad889c35536
9d8a036c378735341cc9d3cc83312e4201747a10
992072 F20101119_AABRLZ acquaye_l_Page_100.jp2
dae9da3c94dacc36ed284b40a32fbc08
4d85f1ffdc176e354a22cdc82061c736a9f8e4b2
F20101119_AABRNC acquaye_l_Page_010.tif
a444b91b2acee08dd391c11a89015458
faea2bc0760020f21df3e1654c5418b809e6cc73
1051922 F20101119_AABRMO acquaye_l_Page_122.jp2
adf701b3dea20355882d634abe3ff6e1
6695ebc3db8e1aebb4833a64483fb5ad9ee82c1f
F20101119_AABRND acquaye_l_Page_011.tif
2fc3c9b5031bd96afea7c22baa483a39
0f1f5dc5f9d7f9fd566a4705e306f1b917a1a823
1051972 F20101119_AABRMP acquaye_l_Page_123.jp2
68c7283dceb1565bb6ae7cb950e68680
23f43b1c603dd3fb5c927e9424ed400d61f82e8c
F20101119_AABRNE acquaye_l_Page_016.tif
ae0d13c121f2b3e93b664f11835f8635
1d92701593974a86a9c711021cc8a6172cf3d12a
1051966 F20101119_AABRMQ acquaye_l_Page_124.jp2
5e78eaa534412fee97ab44580c8cda42
2bfa135b734e20249e1a5396574c43dc8340a5dd
F20101119_AABRNF acquaye_l_Page_018.tif
842fce56e7720f9b88c95f681c610f3d
7cfc845ab083f91b44b4f48c6b3a96acc699a252
1051834 F20101119_AABRMR acquaye_l_Page_125.jp2
aa463e3d501ed7a03faaab65d62ffa50
ff5d5ed108a3f46f3553a1b728d921f7fcc01daa
F20101119_AABRNG acquaye_l_Page_019.tif
d05b73294179925d50bc796e20da036f
3e123d346476d71c105aacc58850a08fad069161
1051976 F20101119_AABRMS acquaye_l_Page_126.jp2
63fd5a071af9684ae5eea2570a7bf311
0fa72070f20ef30ae949c2227f2fd791809203dd
F20101119_AABRNH acquaye_l_Page_020.tif
122bd95187071797c96ceaa319296157
016f3bf861bc15c251575a7a72359ecc5c797769
1051825 F20101119_AABRMT acquaye_l_Page_127.jp2
b593607d8172523a1f3c5747e02f63d1
edbf0eea6dff6e4b4d735a96fb5a015c6b373be2
F20101119_AABRNI acquaye_l_Page_021.tif
8af50df7d5317d416740f402d4d4b695
bf8aec621bf75e86736878d08f18be6106ffec0b
1051920 F20101119_AABRMU acquaye_l_Page_128.jp2
dada0ebdd8fa1d9925dc8e889ab3ed6e
39034071dd9ec4e1855223ca050a7140b75f9629
1051955 F20101119_AABRMV acquaye_l_Page_129.jp2
328c1afd0f1a66dae150a2b72fa51b3c
9efe65e9d792456c734e3603a9a89ae035c62a2a
F20101119_AABRNJ acquaye_l_Page_023.tif
59896f07a194acf9993b149fa3c3e2f9
ffe26d1472c0b951a40736f2ed7753afefa5f16e
119827 F20101119_AABRMW acquaye_l_Page_130.jp2
34bc2d59d8d7824d7ca8695c9063540f
4f816b73ac3db8d299e472d3fe1224bf3830590b
F20101119_AABRNK acquaye_l_Page_025.tif
691f6f4efb1fef7a39a7b3dcee9fa689
0869a0291290a302abd1d91f706219f76bf3b633
135451 F20101119_AABRMX acquaye_l_Page_132.jp2
e81b3e86075871e582538c9f64931ebd
8867f878890e59d49c045151c72baccd784cfe5d
F20101119_AABROA acquaye_l_Page_049.tif
ad3f3ff1ec7dd981db324529af6da0d8
a5018361253297935330780f6a6a914dd1a007c8
F20101119_AABRNL acquaye_l_Page_026.tif
b41b15836876d4dadc75f16759b2c3e0
0b99ef831aeaba81e64e07332499cbf78702bb3c
F20101119_AABROB acquaye_l_Page_053.tif
46185709974b5f9763459085953623a9
5ea41990fd401cc98be058047dd0f205d5cee1a5
F20101119_AABRNM acquaye_l_Page_027.tif
6033660512554730111c2eeeef66889a
77e52bb5e04082da3f65f6c960c8e154b4d8b6d9
F20101119_AABRMY acquaye_l_Page_002.tif
62a6b0d5662366619393bbd9707a64a9
51d504f4a1c12fb98746c6672a64f1f0822f7739
F20101119_AABROC acquaye_l_Page_054.tif
2421ba8ac6a4484f83e87dffa40191c8
f6c9545784b71b09e5936fe9b27cffe81e21418b
F20101119_AABRNN acquaye_l_Page_028.tif
1c865cb254cc5640dc12b588118b18c5
72bd219b401465026160f2893736a27b4490a689
F20101119_AABRMZ acquaye_l_Page_003.tif
98888d3f727b0b609869b53d4262b64d
02946bab3d565f3bc651cbca950358d91c50afb8
F20101119_AABROD acquaye_l_Page_055.tif
8d4db9abbce2e2c662d52a95da16e08e
6d9b5936f35cae227b0446cedde5c84d3ee850ed
F20101119_AABRNO acquaye_l_Page_029.tif
8100df6c42afd98fbf6cf77fddae2360
4348b38dbaec3ee02af03a9985709eba6ba218ce
F20101119_AABROE acquaye_l_Page_056.tif
4c73ca617ae664415a42f58446a4894f
d8ed09a7be81f058fe909c8d8fd023b91fda7cab
F20101119_AABRNP acquaye_l_Page_032.tif
37a71ae52655c589857b4c99f2c02e75
544ec88379c9bb896bf0aa7cb4015bbd15c4402d
F20101119_AABROF acquaye_l_Page_058.tif
1790414a2df589714c2bfad98736e9f0
f2acba382cf45e80f14975afd95aa01dc0b5322d
F20101119_AABRNQ acquaye_l_Page_033.tif
ea04cc9421394470835a51daca0929f9
0e5086eec88f97da3ca0664885f50107943bead2
F20101119_AABROG acquaye_l_Page_059.tif
c71d8d968dc6406be07e3825ca788fdc
39381c2c27f860cee9767356308bf68204cd0932
F20101119_AABRNR acquaye_l_Page_034.tif
b2514983420ba8b9e21aa70bcc402369
9c5104689c59b8e262e3f445187d4710b7db03f8
F20101119_AABROH acquaye_l_Page_060.tif
52ef36df4d0d64cb47534f3061d7500c
fc7eed0991c0ac4f3d6d924752a7bef327711471
F20101119_AABRNS acquaye_l_Page_035.tif
c02b22f0f1e326917f1abde456c04bde
ac41df487005e29aa58b0ab1733df2c15910519a
8423998 F20101119_AABROI acquaye_l_Page_062.tif
60ac55d407ac5b74a657d467310cc372
55e940784b815c7e644e8aa5e8f949a8dd1576d3
F20101119_AABRNT acquaye_l_Page_036.tif
3b488aa7df930c6797eb44a1cfece4ca
00feb25da82967b4ef7b333d92dc909a45a606ea
F20101119_AABROJ acquaye_l_Page_064.tif
88dada68a354d20d1e282f2e79a714f1
e6e08ec8b5e1e82993c5753072ff960e01831e40
F20101119_AABRNU acquaye_l_Page_037.tif
37d89dc1129dc6e7908ccf9a93a3c92e
3fde1c2a88f04ad2bcddb0dc8dbf2d15f03aba3c
F20101119_AABRNV acquaye_l_Page_039.tif
21d946afc92aed9e8f7195cebee7f5cd
234ee16451a1fddde6c1ddea70466418842ab1bb
F20101119_AABROK acquaye_l_Page_067.tif
792f44e44691057033eb38d9d6a6c4b6
0289a72200b8a58b8714fbc29cc08eb2d06e6a81
F20101119_AABRNW acquaye_l_Page_043.tif
ab44b6d9076ec8ae57ffe820ed5e53d5
3d5a4752c01bf0fdfc24a5ff5c43861fb45a8ef3
F20101119_AABROL acquaye_l_Page_068.tif
3303989ca5f0218022238beb97e262e2
fab6f940a41c61d14ad5ea8c5952932391cca1cb
F20101119_AABRNX acquaye_l_Page_044.tif
102d2c76cd04f3ca29d1be30da3b81b7
432efa70cd56c336c4b973f914625b58d6793aa9
F20101119_AABRPA acquaye_l_Page_087.tif
228b74d6b274720942316952f60990a1
ef643da2de9456d6d57f573eccd83c562252603f
F20101119_AABROM acquaye_l_Page_070.tif
24da14734b5801504fa4a9910368aba2
7ca4a074ea5ddc660b491586a474635efa981bff
F20101119_AABRNY acquaye_l_Page_045.tif
9c6c16344b0fc192b57a9c4abe5bcb1c
0b59c5de4a801d3f58ab6e5d4e40145c3a6dffd1
F20101119_AABRPB acquaye_l_Page_089.tif
30431a88bbc90ea22a2aa0782a4398a0
e7d0b8328bfbdf2da5e7c85a1799a3837b326285
F20101119_AABRON acquaye_l_Page_071.tif
dda2e8fa0194d4b925f3d3b3fc550cb2
3e9b48ef4cffe4b0ade54d5fa827a91255306972
F20101119_AABRNZ acquaye_l_Page_046.tif
c4653ac1f89a284cb7bfd553c089820a
41aabd5f073cd843b624b5581d0b3fb7e2c628e8
F20101119_AABRPC acquaye_l_Page_091.tif
babe16ea74e8920e9604edf81e44b8d4
49c8e5886a26f9d6dc3b694d8b4a0cea93a1e40d
F20101119_AABROO acquaye_l_Page_072.tif
c7a057835ad04c751eb98f487f351cad
16cbc91ca3fe2fe6b0269fc2bb73b59f7d7e01fd
F20101119_AABRPD acquaye_l_Page_092.tif
462b7c47c4d4d6171de133edd3bc763e
1cbabb1135074f2eeaf3269fdf639389269cbfbf
F20101119_AABROP acquaye_l_Page_073.tif
a7c1cea52f114517cc4b8a8dd826cab8
d67fef1fbd786f73f352377f250c62d52ed8787e
F20101119_AABRPE acquaye_l_Page_093.tif
87f4e24871315f517278a58730921f47
705729ca098e213591cb55a11eed2851f498ed80
F20101119_AABROQ acquaye_l_Page_075.tif
13163c9f585a3ae32d33f79587e120c1
130193d57e1a2ead28de6ef02a835a52396eeb4a
F20101119_AABRPF acquaye_l_Page_094.tif
847bf7c994e2a9266c225743f9dc1105
2a81df0d4241395993180bf3b8e801428b652c0d
F20101119_AABROR acquaye_l_Page_078.tif
ae03a67b6728a8974fce5018911f34d0
7767c57d5e5c228ccc958d3ffe6cfcc3839c78a4
F20101119_AABRPG acquaye_l_Page_096.tif
38c92e43e20e59bca89920fa1916a867
5134a04d2087008d3fb92ff1d66d6e34e4895400
F20101119_AABROS acquaye_l_Page_079.tif
0120eb463c963ec802647cae381a5cff
9ac66f5b6894519f318eb616a40c0e3e4c8353f8
F20101119_AABRPH acquaye_l_Page_097.tif
245d2ffd49d4057c6a3cce5b5024c204
a4a192193c3d10f4142613c507bd9ccc99c13e6e
F20101119_AABROT acquaye_l_Page_080.tif
075c44ce0ed8cba3fc822ac3b52cfcdb
ccbe87a7592a4bdc964f1d6837357fb656d96262
F20101119_AABRPI acquaye_l_Page_098.tif
0f072dd0f0948b2aa83c501513f187da
0fb2a798e18b675bc3d794a3d407c522692fd120
F20101119_AABROU acquaye_l_Page_081.tif
1dd2a00d914c9b276cebbce600f94ade
d45b0d154750ce1d3c50e84bd88cce8fcb52cb5c
F20101119_AABRPJ acquaye_l_Page_101.tif
3c0ffeb53623cbcb9157b17161591a4b
11f0f9a5e937790b68ac2095b485a8af44f3433d
F20101119_AABROV acquaye_l_Page_082.tif
70f2abc6a1f40a54bc91a5a230f1b474
9222915bfb2867387374d44a503ce0466fe829bc
F20101119_AABRPK acquaye_l_Page_102.tif
aa0120ff5562ee904918161c9eac204f
b2e8576b174f6007dc765d5a78d2d94097646a2a
F20101119_AABROW acquaye_l_Page_083.tif
a631ddd98707eb0d3c4b2b8194e776ed
92d210837a220ff1f29a3b78db4f41b2b64d6267
F20101119_AABROX acquaye_l_Page_084.tif
5e8af4e0f3cd3da6d6b25b424c25b971
e66cea66d1db390cdfa51c990cb475ac48e4735f
F20101119_AABRQA acquaye_l_Page_127.tif
9f40016d401129ca375676d5b2dbc54a
b9fe7a4e56390e8488ab5c5d65793a110ef20fe6
F20101119_AABRPL acquaye_l_Page_103.tif
f28465ec6463400403820e5987c1a900
d92f3483b3dbcf0a01c6cff6d5c90b5c9c7b02d3
F20101119_AABROY acquaye_l_Page_085.tif
720b1486b2641fe13e8a2aa1f9bc8e02
ec424f1b814a4992531f76aec85c437be26f7a75
F20101119_AABRQB acquaye_l_Page_128.tif
f3052a0431f2280ea88d94a4dba818ec
8fc51dac6c597aa3ad4b2587f5aafe0e0d618cc5
F20101119_AABRPM acquaye_l_Page_104.tif
8c1d015e440d22d52b26bd8436932fc7
0566d5b0cc6a81b3b54f0f9821dae37338a3c605
F20101119_AABROZ acquaye_l_Page_086.tif
8f6e6a746cedab3c94dc806de29ab530
01c18be7a03fceefa795630204e9fd135f764bda
F20101119_AABRQC acquaye_l_Page_130.tif
309f0011ec5d1c319b36a2ffa770cbb6
6c656ac3ad89a94492ed6bf7fc8f2392637ae89c
F20101119_AABRPN acquaye_l_Page_105.tif
9fbc24918008fea1a59a23ba556589eb
e396c4642ebe712e5eda404ac7f7fa389c37525e
F20101119_AABRQD acquaye_l_Page_131.tif
dd787d1f961d0f827a848d9c4b5f3122
40ffd68f87ab0ce1e8490a37b0613892ce7a6b3b
F20101119_AABRPO acquaye_l_Page_106.tif
3bf1cc255526737dc8a7c498d0900103
533f39e0005635f743a2f751ff69429bca1c86a4
F20101119_AABRQE acquaye_l_Page_132.tif
cbf399968c2841cea0794c35efc70206
c4da81f9d25053cc6b7a7ac41f4af250612face6
F20101119_AABRPP acquaye_l_Page_108.tif
dd00cdf4f99931cad087c101644c6700
865c90ad9314702aa3c91b32482ee978f6cf8279
F20101119_AABRQF acquaye_l_Page_133.tif
5b746d521be539335915cba3eb94f09c
25c7bb2134837f6c7f1713939616ef824c0d4f20
F20101119_AABRPQ acquaye_l_Page_111.tif
96f8546563ec9e94c34c0d6674b942c7
ccfc55ef2e32715de7588fa347c394c41c60e43e
F20101119_AABRQG acquaye_l_Page_134.tif
393bd2518e852fc0f6e941869b0e3c80
0df31fea3e3e62316176e76c57da6866539bfd50
F20101119_AABRPR acquaye_l_Page_112.tif
ef503fc40492e997fac9a83f2f14a186
e581e25a4b4b6ae4e531ec34cba0547fd0eb5061
9490 F20101119_AABRQH acquaye_l_Page_001.pro
18346d05c51864f140719428343bd08a
2539f677f833f8db4fd99a4fb2c342ec2abda2f8
F20101119_AABRPS acquaye_l_Page_114.tif
a7570b9c9d93400f24952e1eacace777
606a36bfbe7db7205f7b4292dde87f637803022e
1098 F20101119_AABRQI acquaye_l_Page_002.pro
cf0eee9da57f851ea7a6c27e2ad0905d
96bf46993c799296f680465144cd1b3596c2cddd
F20101119_AABRPT acquaye_l_Page_115.tif
bda09740028b3b4c23f38fa23b71442d
c1758cfffc90c6d3cfa50685cb756847d88d9354
41662 F20101119_AABRQJ acquaye_l_Page_004.pro
db7e007a0c01c45864e5b99457cb81fc
46996136129b1623489e6c6b3d8ebe33ec7fe0eb
F20101119_AABRPU acquaye_l_Page_116.tif
125b4712a0aeb41a318edf7ed72c0a46
75238cb6244a0d834e06f5e0f221650259c37a22
99123 F20101119_AABRQK acquaye_l_Page_007.pro
99b505cd0bbc2b5d7b2b66e9648aba57
b29907f24ede34c8d9c3a9e2e5520926886b54b6
F20101119_AABRPV acquaye_l_Page_117.tif
49ca87049dfd5e09034a292e904b26ff
70bcb388423facfaa78f8a9de8f06559b1afd2b2
25942 F20101119_AABRQL acquaye_l_Page_010.pro
95e4ab0888300fabae6c5e5cb67b253e
f7bcb25b65e089b798130a8e3949bc83259b863f
F20101119_AABRPW acquaye_l_Page_121.tif
f074feec071a7a3b51fd89e7e9f8ba90
26e51c9237b975f9dacc22e08f77a4e21ebc2ae2
46020 F20101119_AABRRA acquaye_l_Page_037.pro
a9023fbab5bad819b38cc2e137ea9821
a405a31f19d5a1781bc8feb3dfd6342054889e36
F20101119_AABRPX acquaye_l_Page_122.tif
42fe66e13fd0097214248060841ae8d0
cf9872e2b71e9c4e9d4f941f183ddee3e102b89b
50213 F20101119_AABRRB acquaye_l_Page_039.pro
e11459b2632af3e7e2d5d72ecc49b7f2
5de2c02f128b4772192398741cdcaa602c2a3190
56033 F20101119_AABRQM acquaye_l_Page_011.pro
095e8769c793a020fa7eb830c4d1b6f9
128cabd3c9a688d47db744d52106fd6d486cf6e2
F20101119_AABRPY acquaye_l_Page_124.tif
a6128544119ee5e68839349419d2aae8
ebd32104c29b551a69ac9101a343d2e31ed067c6
42912 F20101119_AABRRC acquaye_l_Page_040.pro
beb41435ab74ad40b4cb184391006f2f
6ef81458b5c59db9bd7181be2f55fa2bbba96e41
35245 F20101119_AABRQN acquaye_l_Page_014.pro
a6ac81085b684916d0a0c71e66a00b25
c8febc118dc06bc3a38b1458561a53906979e5fe
F20101119_AABRPZ acquaye_l_Page_126.tif
5f8880d04fac27f1beefcc5499ddb89d
a8b40f5f6274681889136991d3bc1d53d4a1e2c6
11799 F20101119_AABRRD acquaye_l_Page_041.pro
0e104266902daf0618a53754cd5d2840
ec06d80e4f7c53f42cfd88be43c47f4da56a4436
34647 F20101119_AABRQO acquaye_l_Page_015.pro
4b20c8bcf8928110efa298c3224191e9
d52cd3deca2af32220b4ed30e38c9821cf30ef39
44705 F20101119_AABRRE acquaye_l_Page_043.pro
c96aaf4c792a8e34a7c0f0ccafd78ba5
7e75b1cdce1cc928eacc5995e7d2c2088941aa72
51219 F20101119_AABRQP acquaye_l_Page_017.pro
5ad1fa67f55ea33caa2fbb2bf0a55791
1bbfed52bbc4d6f8fe8b0d8adbddb0af8afbfe33
19228 F20101119_AABRRF acquaye_l_Page_044.pro
8a759116a09bafe09caf83b40fb1a7a9
c7b403cda7df8f08061bd2b9ee8c1e1a4b8bed2d
41461 F20101119_AABRQQ acquaye_l_Page_021.pro
99bc749bb528306d89a48b0fb35cf44d
917c9dffb0a71f85b2a2d8ea5423e37e57f69c0c
47493 F20101119_AABRRG acquaye_l_Page_046.pro
553c9abf71a40633fb88e72db6b633d3
ddb959025fa5352e9c3d6be77b3a80e738fb8afd
21057 F20101119_AABRQR acquaye_l_Page_022.pro
8c611aeae8e1d4b9c9211b7ad4d99953
d95c3cce13c4f3d1bc4a0a12b949d4beba55344c
13429 F20101119_AABRRH acquaye_l_Page_047.pro
24929ea4b27caf6167568801d2967b34
d1ce20dbb0644f2eb23bb9e32d6d0762ac08387d
43103 F20101119_AABRQS acquaye_l_Page_023.pro
33139043cf94c5b0bccb251e5f190f7f
06209e7ab7c870ab18c1e2352bda61e1af414424
17685 F20101119_AABRRI acquaye_l_Page_048.pro
88e589c666236d5122b8381d2e4faf24
985c3c2b3c84293b0de162abe7aea8f772b90e64
44008 F20101119_AABRQT acquaye_l_Page_024.pro
3fc909eed4a61d2170ff4e35dfacc639
5b9026afd165743b45d82c752f282419296745fe
20444 F20101119_AABRRJ acquaye_l_Page_049.pro
1e21084222d889ee565c905a51b605ad
d833509b8c188afcc72cd7684e28a997168ab9f4
47713 F20101119_AABRQU acquaye_l_Page_028.pro
b35cc4d73faaead9ae5ed4b99b5d5d2e
6932adc74fcec4e690ca5c7cb218868a0259d9f2
33337 F20101119_AABRRK acquaye_l_Page_050.pro
688b463183122f818090d52b2d125e3d
82da9236b8d986bdbd8a1f7c53dd043c87848f4f
50856 F20101119_AABRQV acquaye_l_Page_029.pro
bdb7e052d563f7c62b467f39e7584d0d
51ef4148a497ec9d6818800a147616883377a989
11961 F20101119_AABRRL acquaye_l_Page_051.pro
970ac77455d3a665a530241c8204e4be
808f9bc98ccd0df6260c9c75382eb8781dbc539e
52469 F20101119_AABRQW acquaye_l_Page_032.pro
95db34ad74ff2275b8ae7b9ebdc63bde
dedbca04962c8b5f24ef039515155ded79ef364d
37609 F20101119_AABRRM acquaye_l_Page_054.pro
8e7c0e50420d1abb32ef0e6bb2fe7cfa
3367f43a28af2f339bb5f3fe0a6f30f37d3d62a9
47158 F20101119_AABRQX acquaye_l_Page_033.pro
790678cc867e25a99476cafc80a151ce
ad645190a0b17322e24e086b117606c375d33542
35407 F20101119_AABRSA acquaye_l_Page_074.pro
04e1525e41df1a91c43934fb957c288e
9635a678f5878148fd46df41bc563de5c61911ec
36455 F20101119_AABRQY acquaye_l_Page_035.pro
c10dfffc5dd52d7604f97ee271a3f325
b3e75a8c541d18a015055db7eabe30980037de5e
35444 F20101119_AABRSB acquaye_l_Page_076.pro
f83ab83f842e93b6a642ca64dc41a20b
4316fd2261005e2c8178796051b06e8cf0017be7
30755 F20101119_AABRRN acquaye_l_Page_057.pro
d5c69d25c8a6a6416de44b833ae0576f
7c546665f263810dcf5f480f70ad0d73303c1044
46105 F20101119_AABRQZ acquaye_l_Page_036.pro
d9321ccba2c9d6295eb3d905c5235baf
12e62d420284aedecc3a609718c6b61d8e5f6121
32390 F20101119_AABRSC acquaye_l_Page_077.pro
9398f6dfff58f98ddff449c3f648402b
c6f532f68f93ba953d447fbb0fbe0fc596825cbc
42611 F20101119_AABRRO acquaye_l_Page_058.pro
a9937bff748a779f13497167f3efcff8
d09e2dc33bbbbf433582f3ed8ac0f7fd029bd2ae
44874 F20101119_AABRSD acquaye_l_Page_078.pro
dede7dd62de291b64d36cbcad9c07dc2
ce7ac579245232f48fffdc6d1903450307753e38
45656 F20101119_AABRRP acquaye_l_Page_059.pro
f87e7bd80f33f287191a44d5f3d888e5
f0ae5eaf30a91138832d864a00ec6d20a08ec280
35341 F20101119_AABRSE acquaye_l_Page_080.pro
6c30aa8d045c5b378d792e03f1732e58
0ae1b6df50df712c371535a58c61c06d3586b5f4
47964 F20101119_AABRRQ acquaye_l_Page_061.pro
f8ad0007d5a0678fe3601feecc380ca4
9faa1dbfd3d9bb5b6e992cdd8a6214f44e8c8c97
32781 F20101119_AABRSF acquaye_l_Page_082.pro
ee22387e6bb220dc56182a4eac818479
d17cb9a4e9283fa4e50f90d5d6cc8087e13e9dc4
39805 F20101119_AABRRR acquaye_l_Page_062.pro
f98fe5627982fdb4ffd5b7db9d97e7f8
cb25816815400cb2f5cb211b288475267bfbadab
38384 F20101119_AABRSG acquaye_l_Page_083.pro
2dc2ed51879999fa11993981866e828e
2a001ecfcd7c37514baba26ab76fc6634115b90f
49744 F20101119_AABRRS acquaye_l_Page_063.pro
96c46319c9616b195b7be0b4a33500e5
eb9c3d88bad20f1bd6262aa488e991055637df4e
26186 F20101119_AABRSH acquaye_l_Page_084.pro
4b6d816b9236b4799ccc9dc568264150
a1e4f131f064dd38b993d225b1c845400da8456a
37950 F20101119_AABRRT acquaye_l_Page_064.pro
37854aa4b0f1522008aef66e91e8a012
0efdfc4f8d0e39620a35265ccb18cf09c93f06ea
28506 F20101119_AABRSI acquaye_l_Page_085.pro
208fbe8b3dbc1de57fca6e816eb035d5
0add565775c0faae33f11304eab7eeb5ba279bfb
21754 F20101119_AABRRU acquaye_l_Page_065.pro
e2a1f74d582e8993c58daafdb962be60
a8d8d9803e04f072fb9234ebd2a5599b85bdd9f9
26175 F20101119_AABRSJ acquaye_l_Page_086.pro
991274fe62e83caa9cfa64f008d88e97
0b33cd6a294c16ecaef67cd128de6145bf845f4c
34357 F20101119_AABRSK acquaye_l_Page_087.pro
fe7ed07523429301a1897c9b15fa12eb
8a7a89c3f512028c108888a3bb9a048d0794c627
35382 F20101119_AABRRV acquaye_l_Page_066.pro
fb19ae142a0be10e20984f4c087903a6
95c5ebf573f9b4f0fb9e7fcba9538dc102c1c174
20541 F20101119_AABRSL acquaye_l_Page_088.pro
d464f65dbba2d50a5e575611e1ba32d8
4e525fb3b454590a57e56038529d3abbc445e47e
37968 F20101119_AABRRW acquaye_l_Page_069.pro
42f3fdd5c6e241dd16506edbefb08d39
2c50318f0a6b33dd8582d442c4b138bc2889c3fb
62016 F20101119_AABRTA acquaye_l_Page_108.pro
0f908ea07096bb72b227f0aeed43f00b
bed6af208cb8ff5de33721cbaeee735a376950c3
25158 F20101119_AABRSM acquaye_l_Page_090.pro
d226286990050a96c28eed0581a6021a
6231bd0142ea24ab5071b6f93c35fdbe504342cb
36915 F20101119_AABRRX acquaye_l_Page_070.pro
dcb1e0ba3bdb7b8dbfafb2463e9b6a39
b09f2cf940aff18f12dbdf6e5c6190e86cba3820
40695 F20101119_AABRTB acquaye_l_Page_109.pro
de6edad5795934ebb554c93912a9180d
3e6807161b4822a88a868bf043bbb95bac3367f4
4203 F20101119_AABRSN acquaye_l_Page_091.pro
6e4ceeab062b30622ecf63b366d0aa9d
8a82902562146fca85adc6a01c36a1594b66c134
7912 F20101119_AABRRY acquaye_l_Page_071.pro
43bb0b34d7c4dec3eeb2eacb69903ebd
5327c2bd9420c7a08e2c737b194c52b6b1b558d0
9421 F20101119_AABRTC acquaye_l_Page_110.pro
90831967d9119efaf061059237c8b21d
7bdefc8914681adc48941ef2a0155c40bff627a1
52992 F20101119_AABRRZ acquaye_l_Page_073.pro
ddc9da9f282dfe41b2f801dc40be3566
3fe25a659947e1b331f0e51e965dff8952650878
38608 F20101119_AABRTD acquaye_l_Page_112.pro
65b610cb471ddb8fa87ca983f35e3d15
1755142eb221f675e3e8555b0a21dd12e752b35a
4464 F20101119_AABRSO acquaye_l_Page_092.pro
72fec254f09ddb77d0cafba7223fc9da
d0ceaf8083417331a8b670f214ee8b7838192e21
30419 F20101119_AABRTE acquaye_l_Page_113.pro
208803e6b1f4cefb984640d7a91975e4
c4099d9da702f61e5bedadf8b08b72ee451f958f
24067 F20101119_AABRSP acquaye_l_Page_093.pro
9a189f4613558c0903c9ad10ff8b909a
24d50aeefc9d828d0bc4b6a2c265e28900446012
30581 F20101119_AABRTF acquaye_l_Page_114.pro
4ed89bf6cdaa5f86d185afe45bf6a305
54647c0bdcf96f11a2a23c1f72bfee1fa93e2029
40336 F20101119_AABRSQ acquaye_l_Page_094.pro
0e35f3b45e71b0fd11225bac899d51ae
807fd4016058f4206a038afaaff996abc41ecc02
31947 F20101119_AABRTG acquaye_l_Page_116.pro
ca9afb47cac61076a535b59b03549fae
58ff977679fb2e628dc6e8dea17c3adce54d6be0
18513 F20101119_AABRSR acquaye_l_Page_095.pro
87e912dadc41fbd6f9b7f3ef2a6dbb9c
3df3f58759e5333401b3f585aa711cf3d3c62e73
25132 F20101119_AABRTH acquaye_l_Page_117.pro
854040e8cf405c8a5c11c0496ab8c133
452b1b7757ffe30f7b2ab6a0c1feea3c340a2d8a
5195 F20101119_AABRSS acquaye_l_Page_096.pro
52866b8c93ef3aad1c024a9207c20e9a
0295ebeb1ebf78a97d26d471cf570c00edadbd90
3932 F20101119_AABRTI acquaye_l_Page_118.pro
a02ab3f59c3205edea555e521233595d
5da43c8d2e3cbd1c45f251a2f252e0ace73359bd
49400 F20101119_AABRST acquaye_l_Page_097.pro
24c00c4d9fc5612257f88c96173c55da
d76ba7b4f7517891eadb79cdb931e4c91c577173
2952 F20101119_AABRTJ acquaye_l_Page_119.pro
91f42d1cfd08928d238ae21588a22d4f
72cb94f0ae70ab55a33c7582e254e8dba83dff0d
36074 F20101119_AABRSU acquaye_l_Page_098.pro
d2145c6c151a09aaf9ecbfc1e08f1cbd
1fc9d26744bfa73cfb6f990e64ee894d18ca9831
4805 F20101119_AABRTK acquaye_l_Page_120.pro
717407ea77df762031924077ed67def0
c6db9589da1676f12f8c9edcd6f8bc8a06c70d84
4353 F20101119_AABRSV acquaye_l_Page_100.pro
21925821274a77c102d88e6539357a15
857d207a719c8d594b46aa8dd1d4c82160b66ef4
4338 F20101119_AABRTL acquaye_l_Page_121.pro
bebfce2b0cb847d0d93b5844b21f6c06
2783cdd8bcc0edb23e2fb0017d1332a98e515372
4957 F20101119_AABRSW acquaye_l_Page_101.pro
0af0bea6cf69b76f8487dcc35911a81e
8b61a99e8922e0ab5d962df11e3ee8ca9afc5566
5196 F20101119_AABRTM acquaye_l_Page_122.pro
edc053f723fa279547fb2e4cbd89e381
c6d9691890e08095b0b55b667d25bd2dd5fd9cd0
41923 F20101119_AABRSX acquaye_l_Page_102.pro
b5be914389ca1af6c099cd47c3cd1fe3
6306ef5b259dbb8757046bc0576f7e9853a9b398
3140 F20101119_AABRUA acquaye_l_Page_006.txt
5f0700b9daec5c10b27e526765f125a6
c21d6e235e433fc9ea76b9e2fff51038175307e9
4827 F20101119_AABRTN acquaye_l_Page_123.pro
870462aa3f713ee7a733eda8a4a88afb
2c9ac17880172f1e89738aab457c49f99790cbe8
43626 F20101119_AABRSY acquaye_l_Page_106.pro
7818303a3ac7c296ea7bbd0aa312abaf
f346629b1e70e66f35cc0cc7476c8c0b92a9b636
4111 F20101119_AABRUB acquaye_l_Page_007.txt
dd9f74df2c35ee36609b828b912835c6
5920412e3e2d01297e4548568d47af79d24a7762
3564 F20101119_AABRTO acquaye_l_Page_125.pro
3cc896a61ac623c1b1639c5fea612214
f1176f0a6f049d9a51c535336599441e7f7f9aab
26252 F20101119_AABRSZ acquaye_l_Page_107.pro
7dffeaf79143f8770df723c4cf604e5a
f12e268a11bfd97cc065e9e73d9ad6eb9d6fd1bf
1391 F20101119_AABRUC acquaye_l_Page_008.txt
2ba432343e6bee17a46b89c496be6969
51df44c99f4cce28670955a586d8af75e788e51d
2172 F20101119_AABRUD acquaye_l_Page_009.txt
d5babb2f86808c6bb95b93a38c3cdcc3
79a417924b991c96b88a288b881eb73eb62e31fa
3295 F20101119_AABRTP acquaye_l_Page_126.pro
1ff3d40c3b055e6fb5476dbcd5c4717e
18268793d37958bc8bfce2f94143df9527c3043e
1026 F20101119_AABRUE acquaye_l_Page_010.txt
b6789280bf8003037864658ec5a4149d
ab799c8f26e8a71943ce793cc7d4bf6749f85e1b
4301 F20101119_AABRTQ acquaye_l_Page_128.pro
38e2eff86fb512cf21e36e185591a616
2a4a261a6b892ef03f007907647e0fe51a18e381
2238 F20101119_AABRUF acquaye_l_Page_011.txt
44088ced02cac8cb3162fccecbdbdecb
e90b157f36a200181b3e3aae0a3dfbde26bfe3c8
5286 F20101119_AABSAA acquaye_l_Page_053thm.jpg
5aca1ee726c02f11fd79e058ff7625e7
139ac22976913112c50bf45a5716cb068f288e79
4028 F20101119_AABRTR acquaye_l_Page_129.pro
8c6e183e661fa2f7318e37e4113bfe8d
e48efb838f620f5830316c92f7b1aaaf0e3cd65a
2633 F20101119_AABRUG acquaye_l_Page_012.txt
55351e199cd7b6636ce136ad3a0a7dd8
0a5c4fc3060e212c1283175e5c0d0fea07ce0291
21177 F20101119_AABSAB acquaye_l_Page_054.QC.jpg
1f5e9cbad71e59e3fdbf81dae119b32f
0ebca8c320a2c04370a56404b53217e84fb841e7
55309 F20101119_AABRTS acquaye_l_Page_130.pro
84bd494b692e90742b74f6b422d59f48
e404c8125ca2e2ceb02b3cd609d6cfee224f8108
2584 F20101119_AABRUH acquaye_l_Page_013.txt
22b09f2087906a6a508ada86bc970c49
6361e258464708d22cb5b521817ec932016dc3a4
20031 F20101119_AABSAC acquaye_l_Page_055.QC.jpg
44eab9432d5249ed4df9d82f854a01cd
af135cb10563270714568070a97cdb971ebc4034
60691 F20101119_AABRTT acquaye_l_Page_131.pro
a58ef9065a5c6287b7f54ed1b1804e56
afb5f3f52b9c62c66e1753722fa60a7a5f177556
1589 F20101119_AABRUI acquaye_l_Page_014.txt
fd8bf93c69fc0bc394fe8959a8ace65d
e3570869ecec2534f20206603124d6f9d5597833
5717 F20101119_AABSAD acquaye_l_Page_055thm.jpg
20c0198ae13d2baaae42b66c8f7e7a75
6e0609f1a59f3dbae8e906ef061783f7536ef0cc
61886 F20101119_AABRTU acquaye_l_Page_132.pro
09cde5c681a263af3b70952e2f6dfb98
1b5cd628c187ff3fa971597fd1801a95670bb0ef
1537 F20101119_AABRUJ acquaye_l_Page_015.txt
84985d8def4572356db28e5de7343000
e8327f134ccbcb3eb727f9f364569b4030228f74
18557 F20101119_AABSAE acquaye_l_Page_056.QC.jpg
660f3c9ac99506f33cc259717dcbbedc
a9b7b56bf500650083d04b415c994368f841266f
4209 F20101119_AABRTV acquaye_l_Page_133.pro
57319219f22b80eb28b7fe4078be70e3
c6c820ae2306aa80e35cd1541f4f5caa8ff3986d
2025 F20101119_AABRUK acquaye_l_Page_017.txt
49580cecb50345d0ae47674939e391f6
667600389312ae0fad0937c2d8420f0c8d4ed84c
5403 F20101119_AABSAF acquaye_l_Page_056thm.jpg
e2c230b19d8bf6c12222d54ecaccc8c7
e6505782e451219dffef72b2a227584803fc01c1
515 F20101119_AABRTW acquaye_l_Page_001.txt
7964d079934ddb59f5185e54c00d4539
3b889dbcbcd191f30161a834d2efe1d76d3a4893
1886 F20101119_AABRUL acquaye_l_Page_018.txt
8de749d70d8516810a87163ec0885148
9808f61e6f3f2248669eeb954b1281cc2b0a6897
18464 F20101119_AABSAG acquaye_l_Page_057.QC.jpg
85d307745dcccdfda997a89d567d3182
9c5162c63d272f9c0ae9ccdb176ae84c247d7e26
107 F20101119_AABRTX acquaye_l_Page_002.txt
8ad7847996ce4eb7d0ee877e774a1b8b
e29142e604a31a086973581b38231285b20d6601
1766 F20101119_AABRVA acquaye_l_Page_040.txt
f8bcfff7a01dccdaf0257f5ab4024ed8
ec3a0ce69ea9fbb7a5344bfdbff31edb0c98f27c
1819 F20101119_AABRUM acquaye_l_Page_019.txt
7591f549d8b33b1145f53ca9fff80490
6213d6b0a8b9d7a1a578ee7b2e3da5780b21bab6
4975 F20101119_AABSAH acquaye_l_Page_057thm.jpg
ce46d97a82ea26091ca6c33058006bdb
04cdf7510ffd530202adb389ae8c039b0313b731
110 F20101119_AABRTY acquaye_l_Page_003.txt
ed25f3e0bb2e0254742cc1d96b86173c
02bc513bea7b844ad1661bd579edbd4b9357cc68
1841 F20101119_AABRVB acquaye_l_Page_043.txt
332c07a10d9902cd9ebcb664a8326225
c8a9934f02fc2621ddbcdc41254a9254377a1fc8
1843 F20101119_AABRUN acquaye_l_Page_020.txt
7923e18bf53142124114cdc1308216ea
1b2d17e06a25b2afa112c0c3ab78fee0d1dd76d2
6387 F20101119_AABSAI acquaye_l_Page_058thm.jpg
0523e91abd84f628ef1fdadb56facb78
a4a82e4836f24ae2c2c18e8d0812a799213adbb7
501 F20101119_AABRTZ acquaye_l_Page_005.txt
5599e6ae7be3f00d78e978567cbba8d3
5625fe76071a621e5cddd37b841746cabc5e0834
2220 F20101119_AABRVC acquaye_l_Page_045.txt
65025be3269ec9bb98c4f23e3d647340
1ad1c4b2e88cb9b225ffed3bf481dae85450c0b5
1846 F20101119_AABRUO acquaye_l_Page_024.txt
479558b39254f807699f1db46a6ef1a5
01edde1535ef40113d3398d3e2471031c45cd6e7
21911 F20101119_AABSAJ acquaye_l_Page_059.QC.jpg
6f7a84e1c971e94affddad4bcfaa8e46
9c44b868cf9697fa3a32ad9debc3d440581a5653
2128 F20101119_AABRVD acquaye_l_Page_046.txt
9e30caed30690880cbf80a14e792b2e0
65d417f8891d8831792716fe586f9bd56d046d43
1621 F20101119_AABRUP acquaye_l_Page_025.txt
b8f8a5be518f6cf2dd107d781383d8d1
a918fdc9c7956c968d0d7dc32bda4f9208f2680a
20844 F20101119_AABSAK acquaye_l_Page_060.QC.jpg
63a9067c8ff4197c1b09550cff4576d2
213c9856b682bc459b68df031b2bead798fc5ee3
781 F20101119_AABRVE acquaye_l_Page_048.txt
862a58dc7235ecd5aa43d802f54ea8ff
b72ab8b2b8eb8ee0cadf68686d1dba070062e77c
5987 F20101119_AABSAL acquaye_l_Page_060thm.jpg
c8fe3857a96783530ebc30e7176ab4a5
e0ac750e34cbf0956a8d7007c60359da2938f040
927 F20101119_AABRVF acquaye_l_Page_049.txt
0feb6aae38732f5d76e3221810a2ed16
1a9bb84f4f04d947210249be271504a52cb07ff3
1274 F20101119_AABRUQ acquaye_l_Page_026.txt
0b3dc0d030367c3cb2f7cc1e1f2bbe06
3d2d68d06785a3f7a49d77ddb69957fd830541b1
15938 F20101119_AABSBA acquaye_l_Page_074.QC.jpg
5e660127bc8703d4460397587a53065c
b1cb3d1999c6bd6ccb46be1e2f2cf99f8af0a143
22467 F20101119_AABSAM acquaye_l_Page_061.QC.jpg
32786abc7904bf159704a3305b876c91
d3e213977148cd93fb0c61b49ac667dc032871ee
1423 F20101119_AABRVG acquaye_l_Page_050.txt
08dd74e59c0851df0f83d88300551c17
a9602d30cbc8f9492f7f16e1512c95f70b8fe5d5
F20101119_AABRUR acquaye_l_Page_028.txt
86e423a3a1cf901a7c691b70b25f043d
c38bbcab2ee361cbd7f35ccbc57befd1f92be22f
15741 F20101119_AABSBB acquaye_l_Page_075.QC.jpg
c115564e342683d4d95c13cebe871a79
fb02ae5f7bf963701456195b4eea782b1dda15ed
6313 F20101119_AABSAN acquaye_l_Page_061thm.jpg
5591bce23edbcc003875b831bc8e981c
53b645aeb9862fa1e6ea5cc595d99bea7342286c
1393 F20101119_AABRVH acquaye_l_Page_053.txt
32aaf1d5a0d01d6273bbdf5256843ec4
92d81bad213c29097a0b44a4e3251d8d77a589f4
2041 F20101119_AABRUS acquaye_l_Page_029.txt
c33a466308664af324e96ec9c6a7e558
14ff668a7ff18bf4f01f471b867f40e69ad0ba0a
17142 F20101119_AABSBC acquaye_l_Page_076.QC.jpg
a43442408abd708ec9d0214faf747f9e
cfd0deb168c4954df4637f3da18d1562841c9bc8
20549 F20101119_AABSAO acquaye_l_Page_064.QC.jpg
de03ca05367cb6c3b07398d62c424882
3f91cfbe402f2b35ca38d40a030f9e38c716bbcb
1760 F20101119_AABRVI acquaye_l_Page_054.txt
9cc68b403bd3416b70e9661cf2e06eb3
ebd7d313cb330ca871a7a0b3c3510a5e6efbea31
2086 F20101119_AABRUT acquaye_l_Page_032.txt
60d5feec529c3920a3a98cd0f1dffc78
c7e479a11447661bc3423976af68c048d7db6c25
4791 F20101119_AABSBD acquaye_l_Page_076thm.jpg
bfb7d786425eb4de7e0e13351f7fd0bc
0dd8f31b772fe318141a97450f772d995583c582
14532 F20101119_AABSAP acquaye_l_Page_065.QC.jpg
4f2fbde01a240340408c9a48d8d69c92
d0f754da36cf44bbd44fc0187245516c6ca8e75b
1710 F20101119_AABRVJ acquaye_l_Page_055.txt
cb8989f5f2961864a4ec96efa1b38301
1255b6aa01353869b88da964e80fac5f8b0c3dbb
1949 F20101119_AABRUU acquaye_l_Page_033.txt
954dfa9c2de4b1cff7ba9fde54f7ecc1
64ebaaf957783c0a10c84cc0cc8eb5a589f41888
15138 F20101119_AABSBE acquaye_l_Page_077.QC.jpg
794b197d75dde4fec0ab31109ac9fbdb
24620c4db3f35cb36c7158d550d09205f2a7d1b5
4535 F20101119_AABSAQ acquaye_l_Page_065thm.jpg
7eed8f2cdadc5e8607076e7eb175329c
3a2b2a9134e3101896a13400619742d6ec5559bd
2144 F20101119_AABRVK acquaye_l_Page_056.txt
dfdc0e845a6f0dd3729f40649596ca9f
1146c1138f4446948b53ca48e101430ce5444a87
2102 F20101119_AABRUV acquaye_l_Page_034.txt
d0150fd2d67fa1946e24afc32f6c653e
90dab27356d3edbe1864c9a31f84508b8584ca4b
20560 F20101119_AABSBF acquaye_l_Page_078.QC.jpg
ba6461f8bda1982c8e82052412a061a4
781f0a973bdc4054a09abc8ae692293dd3b6f2be
17544 F20101119_AABSAR acquaye_l_Page_066.QC.jpg
1fa700adf891196643771b8d62a786c6
28501ac9df5e48962be43a424799a57b598611ab
1534 F20101119_AABRVL acquaye_l_Page_057.txt
ed5f5f3bc0ec1eb675db00b2b382ec3c
b93e62b6eedd871a16160b2c9e3bf491892a91fc
2233 F20101119_AABRUW acquaye_l_Page_036.txt
612859903c58893e2174ef44d5d1e19c
4390ccbdb72d0cb3bdb81d32e49a2eefba49f9f3
14364 F20101119_AABSBG acquaye_l_Page_079.QC.jpg
e1212376fd9ff4b1143932b59a273f00
46b516b54e250915f264548cb87cab9a09c3a6f0
5117 F20101119_AABSAS acquaye_l_Page_066thm.jpg
5f338ab17bd597033504f7ca93b69dc0
6c8600c19b930f369e1e33caeb9bb60783696824
1786 F20101119_AABRWA acquaye_l_Page_075.txt
d81373c4c909d449a182cc4b8d4fd8a1
0534039677d2eb45b7de0ba016e67985ea15622a
2004 F20101119_AABRVM acquaye_l_Page_058.txt
8602e851be7b8f28fe31e497d06a866d
fae44fd117572e03eaca178890cc329fb71edfbc
2249 F20101119_AABRUX acquaye_l_Page_037.txt
c20202933d2b81411497ce0a8fce076e
6e2f5d226b43a81dd5ca3dee9f0246e45ab71bdd
18624 F20101119_AABSBH acquaye_l_Page_080.QC.jpg
ec9cd0ecaed0d3ff0992857f0a70a9a1
1a12b4ffeae3a31b9b9d47c487625a1625ae0f56
19993 F20101119_AABSAT acquaye_l_Page_067.QC.jpg
479d690bd8d7b5ca88936fb6dcacdeca
b3cbef1cabc4dd154ce0cdb07eb569942c22af07
1253 F20101119_AABRWB acquaye_l_Page_079.txt
24becf12ab14c78e2e19b08927a45b43
013503ce7ebf10da55aed29fb865a51d69f395c1
F20101119_AABRVN acquaye_l_Page_059.txt
cdfc86185e6cb72cf307f97399e13468
da33e7e615c546c6006ffa7c2c6fd5abb2c4e6dd
1997 F20101119_AABRUY acquaye_l_Page_038.txt
0fbfd9ddba07fc8b29a223b07f1d51fc
9bf9826435dc88d3aa0f59df424e00c35a3a47a0
5283 F20101119_AABSBI acquaye_l_Page_080thm.jpg
31a128bb24f8a97240449f88c7985108
ff115386c5f8f8753f125d31331375e6ab8eda89
F20101119_AABSAU acquaye_l_Page_068thm.jpg
a2a712e80efa7d9413d3b478977581ff
1b6d3e992b5a748ff92a6f097633bf96de28246a
1680 F20101119_AABRWC acquaye_l_Page_080.txt
c0849e24986745ac42b43eea696ff38a
605a7fe3651d58247984eef406bbb20bee3a2d9a
1757 F20101119_AABRVO acquaye_l_Page_060.txt
269f989a977c4adca3429e6e3cf32478
5f17e736b6fa41682ee5de51e1242c24a65156aa
1977 F20101119_AABRUZ acquaye_l_Page_039.txt
d59de11620f789d4ba67641966208730
802ab331a6dd3a0f859de26f06eeafcfd9be2a89
19840 F20101119_AABSBJ acquaye_l_Page_081.QC.jpg
62793ab4ef6d7de46b8675aefe16c5be
fdecb5aff9e6ecd25824618a6ad677305e4302f1
18016 F20101119_AABSAV acquaye_l_Page_069.QC.jpg
98a986ca85407dca8aeda5e7493b1343
96395fc5f8e9d1b00b3fb7a38f99ea5f07938710
1942 F20101119_AABRWD acquaye_l_Page_082.txt
a35a76309352952e23eb5d685b951f7a
722af0e01ca0197c5d682fe92993b0551c3035df
1895 F20101119_AABRVP acquaye_l_Page_061.txt
532e15dc7c4ceefba1e9e403fd455eed
72daaa6583b605a3251fe6f9c4dcc43c897e3f0f
5423 F20101119_AABSBK acquaye_l_Page_081thm.jpg
ccee4c0f470c080c542b5f80381a2ae1
cff6312fe87d7051b2410ef4e6550ae41f0ed3a2
5024 F20101119_AABSAW acquaye_l_Page_070thm.jpg
4731e462ed27bcff6455ff022a55887b
12716108229e7946b3585010f55664e9c9b50d88
1787 F20101119_AABRWE acquaye_l_Page_083.txt
7f8a2183ab42c041645e418edb1a2687
b55bbdc53e1d2311550135f4e6d23a360284b764
1782 F20101119_AABRVQ acquaye_l_Page_062.txt
521d108180a60d7b83af017a773fa4bf
1834d0a3ee42dda9ebf0afb51858210240721e18
18841 F20101119_AABSBL acquaye_l_Page_082.QC.jpg
10da48c13831785eaab62010abce1b69
63a783caddf95636d7d8f3be2436c0ec536d7b11
5526 F20101119_AABSAX acquaye_l_Page_071thm.jpg
3de45c5e4ccdd87ee21af30ceecfd0c5
e1a249168e34ad107eb7ba84b5ff726170d9f28d
1642 F20101119_AABRWF acquaye_l_Page_085.txt
5fc9cd767020024e053d577a5e084081
d7f4ac2ec6afe19dedba41c46cc819e587ea0f88
5919 F20101119_AABSCA acquaye_l_Page_092thm.jpg
756aeaf622dd2cc118d59c744a7933ba
523743fdb5c2326c1a7161fd895ebb13751436ed
5259 F20101119_AABSBM acquaye_l_Page_082thm.jpg
4892f6bce484de8efdf0d2a7e7a1ddc4
a38c578914aa11786a3245027cda6a88f9d7a1ee
24114 F20101119_AABSAY acquaye_l_Page_072.QC.jpg
4ba8d3970066327cc0d8938fd571d8fe
f19e0d767b2c373e0978a8216735bb1bd62da117
1655 F20101119_AABRWG acquaye_l_Page_087.txt
01517a51e56b7b48b57484f1e0cf8300
1bc51d57ccb5d6c3d46898f8e02dcfaa311143d8
1957 F20101119_AABRVR acquaye_l_Page_063.txt
808e48e93157128e3be1052cca6fa03b
3666578835a8604ee82de059b679c8880c57e4cf
5917 F20101119_AABSCB acquaye_l_Page_093thm.jpg
dd67c8bba055060e55cf496ac1c34568
e2104ad4307b4ddb6fd01a97299a77a4a5c7a25a
20075 F20101119_AABSBN acquaye_l_Page_083.QC.jpg
928e59d901a815bc8e9d6257ed15808b
78a6e18a06d13fe6be644975d8886d301ddd6d72
6126 F20101119_AABSAZ acquaye_l_Page_073thm.jpg
b1a6a873a3b0af10c01dd16eba8332ee
7d8325799e6af99b981fbe0fcb2917ed76df4f20
984 F20101119_AABRWH acquaye_l_Page_088.txt
9a328d1ea269645a022e7098eb975123
ae00231d7b1a0808382e49f7ba94e360f26cf7a4
870 F20101119_AABRVS acquaye_l_Page_065.txt
ef14e67e20d43b67444286456e827180
76ac1638d38f0d4347a6f84ba49122cac91efb4b
19549 F20101119_AABSCC acquaye_l_Page_094.QC.jpg
56c5bef4517c5e524a7196687f66f516
23d146ec239264dca38dc79503b8c1e098c9f1f5
5818 F20101119_AABSBO acquaye_l_Page_083thm.jpg
df4a2ad3999bcecbb31d8321e95a30bf
5017f498a236684102fd0ccebb1c231eb501f6da
170 F20101119_AABRWI acquaye_l_Page_091.txt
b4d128a20a50a770f3c9a0bf2ef31c69
58835bba101bf24969a4a1abe731b158bdf1bbba
1594 F20101119_AABRVT acquaye_l_Page_066.txt
f8248c03fc3a74554feac8abdf633413
a98f0712e433caf18073a4729f872a96ff22e9a7
5570 F20101119_AABSCD acquaye_l_Page_094thm.jpg
ab5edb3ab43deb6a657d7287c95e1883
4fc6cc569daf516864137cb6b69c4f50ed9b4384
17464 F20101119_AABSBP acquaye_l_Page_084.QC.jpg
73cd394cb58d940fd1bfef0ea12d6a5e
4749558b96687228a33bd7e76b019c1efe899de3
220 F20101119_AABRWJ acquaye_l_Page_092.txt
f24ca3d0bbf494892b8e68708a94165c
fefe40882b45dff8af4f3f3f4d9aaac95f28efed
1754 F20101119_AABRVU acquaye_l_Page_069.txt
5849bc6fc54a1054e12f6f165aded890
fa32f5b87e0811ca505018f988ed8d26645bfca4
17628 F20101119_AABSCE acquaye_l_Page_095.QC.jpg
3bdd0568ef4e6484b305130f0be55dfa
383c01e8dd42fc7bea71019fb689b4071152ecd1
4952 F20101119_AABSBQ acquaye_l_Page_084thm.jpg
e31d8b70f3a1bf3c84de08697235209c
2f4a3cae8632f5dbb248931266e30957684a6630
988 F20101119_AABRWK acquaye_l_Page_093.txt
86adac34db7c04090926b57254db0f87
a35ce4c57e9e2a737a2bca9897bdd51480d8b8dd
1947 F20101119_AABRVV acquaye_l_Page_070.txt
b6f7fe2ce2e916310cf475ace870dd8d
06b22c9e1de011696e5d4757467b3c8b751e3e09
5158 F20101119_AABSCF acquaye_l_Page_096thm.jpg
cd328da4dc5e37c3d5df3882a30fdfcd
5762722586fb60a5097d3864d36e9f10359a875b
16721 F20101119_AABSBR acquaye_l_Page_085.QC.jpg
69bab315f72cdf9ee5b57630245d99c5
e6f92ba9fb9fc299bb15483aeb0d82df43e868f9
1774 F20101119_AABRWL acquaye_l_Page_094.txt
f3e6ad2a57620f9410c17e772fe2e0b5
dd7c0ea58014c9af9b0e195f1dfe5b275eed1724
367 F20101119_AABRVW acquaye_l_Page_071.txt
01beb0819b86c5b5bb39e455e688aa0d
e8c69c9d4626f795d07abde282e7a5ec3e6094f6
23029 F20101119_AABSCG acquaye_l_Page_097.QC.jpg
b5d8e3a9aaf68c52e39c198fcd52e8bf
7e3f65429245dadb93ef5d7597b7ebcac237ec30
5143 F20101119_AABSBS acquaye_l_Page_085thm.jpg
f14c46fcecedc0bcd74b8fba7ccb8504
c8e5b67916586194dc47bd883a600744fd66eabe
F20101119_AABRWM acquaye_l_Page_097.txt
219e685b3325dec0ebffd296205abd37
dd4b200df70be146507f885c7400df6af99a18c5
1271 F20101119_AABRVX acquaye_l_Page_072.txt
9c6dea662395a9a914f16559e1d122a9
98eab6fbc963dc23908e708ff35573d5f94f15d8
1486 F20101119_AABRXA acquaye_l_Page_114.txt
77d680563457ff00892ea01f77616420
53a2c36f234b07c7e6af3d9475d31bbc2e804f12
6348 F20101119_AABSCH acquaye_l_Page_097thm.jpg
6e253635199b4fd935dd2c6aaa69759b
91a99517e574b2b54348b7e9ded7e482f035a98a
15565 F20101119_AABSBT acquaye_l_Page_086.QC.jpg
786f571d75c1cea5992cc3ba14ddddd4
c602e9e293b6784c85c47ff0f7a7ada4dc092131
1612 F20101119_AABRWN acquaye_l_Page_098.txt
b82c93a00c23cd1c3a9637767b8e1689
d85ae5b3c51937a603e8627772f21fa2806b7e36
2937 F20101119_AABRVY acquaye_l_Page_073.txt
6f7ddb6707363e794788dcf9cb46a17d
50b91829b87c482367c591831c8a04986ff6f01e
1538 F20101119_AABRXB acquaye_l_Page_115.txt
7f884288bad0feaf9f6160082367d695
0aba4aee5dbba429d62b2807b5f827c61576e159
18195 F20101119_AABSCI acquaye_l_Page_098.QC.jpg
a8cebe90736050a7d8fcca9c95e5146e
d598297fff42473644e22aad57043a0244374f2c
19826 F20101119_AABSBU acquaye_l_Page_087.QC.jpg
249eff407de0dd14637f8fc8a35824dd
4e06ef4294141be0843b347b2460a618ee1b1c5f
150 F20101119_AABRWO acquaye_l_Page_099.txt
f19a1d9f6b291b890b08d52ae509e6f5
bffa5b3018d88c108d602672d807ecf0e5fd2cad
1801 F20101119_AABRVZ acquaye_l_Page_074.txt
39ff3ce30821129b787c1de518417b76
af5c3b80d36ec535bf985428fe4f28c214e1f359
1516 F20101119_AABRXC acquaye_l_Page_116.txt
1dfd308c0aa1897cf1bb6808d75dc326
b1219e95524dec5a74caa3e18b0dd9d55f711930
5411 F20101119_AABSCJ acquaye_l_Page_098thm.jpg
8aa3bac4080dededde48b283d567d8f5
ae87d13b7faa944fcd845596d181d846d1c2f75b
5556 F20101119_AABSBV acquaye_l_Page_087thm.jpg
3b374e26f74f83f0a37053bc458ee9b1
0a82b0884198a3c017021eae23b2e552d110edbb
178 F20101119_AABRWP acquaye_l_Page_100.txt
21e411eb39d565f93fde945c6c61ac93
1bd371d872259216e970e2f7360855d592347892
1301 F20101119_AABRXD acquaye_l_Page_117.txt
ce8e2826f7a76fdb3e034a9d9aca1893
5147fc83d5fa86242b98e485bb19623800d28c54
5385 F20101119_AABSCK acquaye_l_Page_099thm.jpg
20e41afbf6a5f3a05053db412838165f
233576c4f7b6aa0502eed8278dc37c0d645689fd
4587 F20101119_AABSBW acquaye_l_Page_088thm.jpg
0be17555a51726cf0224bf453ba68898
1cbfb7ae42af232dfeefb03e641da93d695d8530
216 F20101119_AABRWQ acquaye_l_Page_101.txt
5bce89f2985007acd20c03b6b695be7b
5b785a9636e05f0f43ec5467c1bd21263ec64455
159 F20101119_AABRXE acquaye_l_Page_119.txt
9a199bb8409cd64602d40bc9a19c370c
f5de7b7f4b5e540ff12618742c11c754fa3ba3d0
4794 F20101119_AABSCL acquaye_l_Page_100thm.jpg
ee945ea508def68cf9322ba808cfd7e5
94c4dd3d900e5bdacccea534c57b1085db8434c5
19310 F20101119_AABSBX acquaye_l_Page_089.QC.jpg
5fab2aee2400c7a21122f49d95814abe
f1033f68e06e2463f871ea0652997a446ebe1045
1521 F20101119_AABRWR acquaye_l_Page_104.txt
0ddd0e9ca18b2a4c7e6cc8cf8c206370
c00a3a613f2cf72f77c7d4e8024f3406b5fe5e03
192 F20101119_AABRXF acquaye_l_Page_120.txt
580a59e6fa2aae5e4ad4cfae02db9a2d
4ffaca578e084a42875216f0ade9f20e4bf72a45
6477 F20101119_AABSDA acquaye_l_Page_110.QC.jpg
e56459502204a00cd96e674111cfbe42
d89344ed61a419952964d184cbf8a3dfdad9ec90
10584 F20101119_AABSCM acquaye_l_Page_101.QC.jpg
097fc06c2b4de8771b7b75beb3dfbb6f
67814b5ad7b8df0fbedbc1321962707e72daf6d9
4081 F20101119_AABSBY acquaye_l_Page_090thm.jpg
82530542b956a9e08635d0358a8aefa4
4883f8293471dfe2877492cc1e2864c9ec3752c1
277 F20101119_AABRXG acquaye_l_Page_121.txt
6e691299217f9482342600f25a7f24be
f4d5a4059b869b6bccfbe83e596a88177a20772c
2132 F20101119_AABSDB acquaye_l_Page_110thm.jpg
41f5d734a396277cee764c4830f6f310
6a0a36f1c497a7453da03e3cb53bc93570f489f6
3240 F20101119_AABSCN acquaye_l_Page_101thm.jpg
28e8504a83f5925f22e7b25c0cf848c7
9b5423298af41d25250bacb323fa71b9d110926d
17794 F20101119_AABSBZ acquaye_l_Page_091.QC.jpg
5400a005cd19908257e81611e2a426a8
7a94458e38613ffc6886422469a2dfd4008aa9b9
276 F20101119_AABRXH acquaye_l_Page_123.txt
39807cd08ed5c1787858e9927620a3ec
891d9f11f4c5e388fae3f69967858e7e30297780
1733 F20101119_AABRWS acquaye_l_Page_105.txt
4b01c4daced8f8d95fe7e7092840c657
d77034c9c48a426aeea7dfd5da6320d282bc676a
14948 F20101119_AABSDC acquaye_l_Page_111.QC.jpg
1c3537f1b69d421a2a80b4291243483d
e82da9a3c0c9de162c56defa0268af18dfdf7b38
5760 F20101119_AABSCO acquaye_l_Page_102thm.jpg
4695be94d6bb4001ba7ed13e32a65d01
968a2d52296861efc954d9fb473a44a9b5a55258
1155 F20101119_AABRAA acquaye_l_Page_090.txt
111ad57965207cace056e8defe6ef372
1e6c2bed5e8fcc9e582b8acc390164565f5ac7bc
20109 F20101119_AABQUG acquaye_l_Page_102.QC.jpg
7dbc8b6871fe3f79bb36f4a73f3dc8c1
bd484a973e04ccb3c6407a06f937a42078cca4ed
206 F20101119_AABRXI acquaye_l_Page_126.txt
9cd3c21664ce56e14a547706e597a301
9c82aef8bb99703210457519c7ad93c3330724a5
1165 F20101119_AABRWT acquaye_l_Page_107.txt
ec616997db73c6aa131399b145465ca1
b97e31a88b9ef23f11c1dd8f9d4c5e0cdd33404b
4308 F20101119_AABSDD acquaye_l_Page_111thm.jpg
42995103a76b4fdb5a32be8994c62cab
ec95e08a32de5af64ac0f68d975e7ded806baa9e
18997 F20101119_AABSCP acquaye_l_Page_103.QC.jpg
249848fb206661372d57ec2fbc1e4d16
150e15f1e1be2fa489fa3c2e8ab983aa3a20fc17
22165 F20101119_AABRAB acquaye_l_Page_036.QC.jpg
815dbef445d370823b11515884fc7ae3
c3158870e6a475b31626ee6939e6c25b13b81066
39359 F20101119_AABQUH acquaye_l_Page_103.pro
363ed060e933a78bcb337ceecc1f6339
1336fb172176929a3d40a8f08e4c7d39ffbc4888
208 F20101119_AABRXJ acquaye_l_Page_127.txt
f0c8d025fc424c19cfa6f712cec85042
20efc87f1e8d0a62245f0ba67f8dbf134fd410b1
3204 F20101119_AABRWU acquaye_l_Page_108.txt
a49207b7c28f191468a9466f94096006
c2995757eca143104a77f980df9795782058251e
14710 F20101119_AABSDE acquaye_l_Page_112.QC.jpg
be1b69c869fd0f81a93b10840cca42ab
53707c1abc374855ac13b47945b57d33bbc68957
5549 F20101119_AABSCQ acquaye_l_Page_103thm.jpg
ef80fa70dc2a0e5fe6353f581e0e7f81
cc13590bbd4ef4ae291b20d15b1527c3200da0b6
F20101119_AABRAC acquaye_l_Page_091.jpg
40dbd0200e5815bf7d5a5c4accb9a693
a94a3d9ea1dde923e8ca36fce713bd3a3dbd494a
38550 F20101119_AABQUI acquaye_l_Page_089.pro
7e8ac9ac5678ee21325bd06741943132
5abcb5cb127e19361ef569be7727d853a55bd634
2145 F20101119_AABRXK acquaye_l_Page_130.txt
d9847e1454eef74284365d6eba0c15c3
cfa1b019bb6cafa959dc44cef6a7366c04fee51f
1860 F20101119_AABRWV acquaye_l_Page_109.txt
4749fa18929c992e1f0939e222dd4c7c
71ba3e087b294245473e89b6c1472d49e0ecc555
4131 F20101119_AABSDF acquaye_l_Page_112thm.jpg
a6511da2bd7b5b5946f1723ba727da97
996fe795f823c19d5b5298e5c5994f699466680b
4191 F20101119_AABSCR acquaye_l_Page_104thm.jpg
d3799e0c2d1dfe549dec68ab60c6826e
594ea5b9243c15bc26100ea0f17c89f4d8466ef1
16775 F20101119_AABRAD acquaye_l_Page_099.QC.jpg
0ca22c45fbf9783d68488e4b8c1962d7
98d31030c25c56480cf9d054d1b13e99a89c1767
110380 F20101119_AABQUJ acquaye_l_Page_038.jp2
ed661f98117e8d05d174222525c20736
f9f9f5685714b635b869cee0510096fd57e3a07e
2348 F20101119_AABRXL acquaye_l_Page_131.txt
dcbf296f198058508783105298b375b5
14ff073dbb09e26bda58cfcb1ed2d12c64e464ea
431 F20101119_AABRWW acquaye_l_Page_110.txt
916483e9df1e144b0ac6af0c28456d39
1557ba4b36148e112f4d7f17c2c2e92a743cd790
4227 F20101119_AABSDG acquaye_l_Page_113thm.jpg
b5ec616fbbd442c0f119b0939e84e27d
c0df84d3ffb13dbe01b8faa183a15836db1be713
20252 F20101119_AABSCS acquaye_l_Page_105.QC.jpg
7f879ea010458df40abb076cef1a059a
8d115e84ff96d4047a9be95fe5c07447f40cab91
17786 F20101119_AABRAE acquaye_l_Page_053.QC.jpg
56e4551c56605bce64aebdbe3c9021f3
c1b306cf8ecff74fd39885e736cda8f611caf10e
2578 F20101119_AABRYA acquaye_l_Page_008thm.jpg
ff47c9ab4eb327d130cb070d63d7907f
bcb6dfc6849f973ded4a441b7fa403eb2d891157
54505 F20101119_AABQUK acquaye_l_Page_098.jpg
800fee7df1f1c06058462018f8dc3b9e
c0a6dfd50d37b9edc0c8944eabd0fde1381a629a
2393 F20101119_AABRXM acquaye_l_Page_132.txt
2bb46ce0109a80ec21dc90787efe4774
f8b5ad2864e8eb617820f4825a4440b40dcafabc
1634 F20101119_AABRWX acquaye_l_Page_111.txt
b1023a1327a214537e98caebafd4ecb1
c49625fa94e831995f976606e3bf8a1616100220
4181 F20101119_AABSDH acquaye_l_Page_114thm.jpg
60e1e4986f963735d1213c7dcb6c1de5
154bc0d4276d27b17f591f09aca0b594826d54d1
5319 F20101119_AABSCT acquaye_l_Page_105thm.jpg
7a5b0eefb474699adf2838e89ce61be0
3bfa5bd201df2ae0df24d7b375312f06470e01fa
11172 F20101119_AABRYB acquaye_l_Page_010.QC.jpg
cb996ea88a9eb89f8a89ab3c7821de2f
76690aa7eef10b80cadd09ad32c466e64be5f182
29353 F20101119_AABQUL acquaye_l_Page_031.pro
92e26c84f32a641a18bd5d1b9d609635
02c243fc6ff61b3099525e2b84455a7ebd68f8ee
205 F20101119_AABRXN acquaye_l_Page_133.txt
c2b8aade2c13da0dff6de00605856f43
3ed2224a33eb80491178edc3fbbeb062c5e1637c
1768 F20101119_AABRWY acquaye_l_Page_112.txt
9e6f17ba902a84b843263bf02726fdd8
f9a391b2c4fae7d0a129768826a7ca17bca1615c
67456 F20101119_AABRAF acquaye_l_Page_093.jpg
4019edf2cc95c29040b11fb23b8ef246
2d00cb1c2b6a2bd46652920f75659a962e74bf67
16561 F20101119_AABSDI acquaye_l_Page_115.QC.jpg
a682b5b0087ee9aeaf54a64d9274fd0d
4f2cff7b6688b5aa17c2bda46bfc4edd49e29a1f
5846 F20101119_AABSCU acquaye_l_Page_106thm.jpg
36f362ad99140e3cbbffa2b9a2176184
e466209935c13ae4b3d9d9a7d8ee758da5f3965f
2610 F20101119_AABQVA acquaye_l_Page_001thm.jpg
f456d581a9b261527874ea2bd00f0acd
f38e97c268d3b1255c2b9e586aea856dfcfb1290
F20101119_AABRYC acquaye_l_Page_011.QC.jpg
41c86d4c04d7607c1a6c20a6f01e8b45
38cff78a1740b4f33c05183155fa061e3ab26cc6
15359 F20101119_AABQUM acquaye_l_Page_113.QC.jpg
189671444353e533739805dca9f0f0af
2eba723205419ddbf5b9553f04e353dc127bab28
762 F20101119_AABRXO acquaye_l_Page_134.txt
2b520feefdf79fe35051c214f423312c
da63e76cf49f07bd7d69a429daee619605db4298
1363 F20101119_AABRWZ acquaye_l_Page_113.txt
5bcb8d2be642a2bc3f1a18f7190dbe52
186dc55b9ef6cda702989c5d68fcbffd90b5ede7
13509 F20101119_AABRAG acquaye_l_Page_107.QC.jpg
56e28a68c5acba03d79c17146168eb36
dc0079f30da72f1d90a7680c467bc79e5714e9be
4552 F20101119_AABSDJ acquaye_l_Page_115thm.jpg
9900a993a0a034eac455e23db15bd818
5ba4438d225472daedd2f2bc313044ff6e30fefd
4156 F20101119_AABSCV acquaye_l_Page_107thm.jpg
a8f1cf0fca018678a2ecfd4d5715aa9a
d991f995ce16eaf3ea52a7623b721bd5160acfdd
1967 F20101119_AABQVB acquaye_l_Page_076.txt
c83bbd477a01a5dc0b9af0d41d0a287e
a455af2be64c8a2c139d886fcef32d15da6717ed
5444 F20101119_AABRYD acquaye_l_Page_011thm.jpg
a14889461d5aa318290e9d245a7c0a76
19ebbbbcd446e46bdc81ec87cfe327154fd24404
253 F20101119_AABQUN acquaye_l_Page_096.txt
cefc5425c34dfac435f801d53e8f7c9f
4cd0e73145f155bc57b89518b5e18e7ec1b1d3ea
5354499 F20101119_AABRXP acquaye_l.pdf
353fa8ef1b8a48a68acf5113cb5094df
acd0501f523403c66b3f10ba6e4bc0b746dc3df8
F20101119_AABRAH acquaye_l_Page_040.tif
ef83143f1e2562c4c4e0b3567cd0ac97
41ec8074ecfde4376069ec779066ffe31941f6f1
16718 F20101119_AABSDK acquaye_l_Page_116.QC.jpg
4ed8a7eceaf768f7659eac3e2788013a
15425455aba3d126a30c2e117534dc92f31c5ae9
26485 F20101119_AABSCW acquaye_l_Page_108.QC.jpg
7dd1df6bdd761a95796ef58dffaf4f6f
39537d1daa9547853799756b6cd21435dcae8ba8
F20101119_AABQVC acquaye_l_Page_099.tif
f44eca9f9ddeca7ad583df0386800467
856c28c7b09d650fe44b5a8ba71557e35022dabf
20445 F20101119_AABRYE acquaye_l_Page_013.QC.jpg
e89fd67663aed4c581c2e5834a85f46d
4572a2898030480b9492b7db4d0d7ca43158db98
23570 F20101119_AABQUO acquaye_l_Page_017.QC.jpg
7a061f0fa96a0cdf58f18a72517f82d3
60a8d25b4893ff317440bc56e3bc4632a470eb79
8045 F20101119_AABRXQ acquaye_l_Page_001.QC.jpg
ba305e7cd6a8e20d862157b8aa9e93c1
8a5822dba99463204a05eaf2adc5f2190e9fd9ca
93849 F20101119_AABRAI acquaye_l_Page_016.jp2
e5f55c8ad5051f89a0d45b1cea6713cd
9e830a638a34bd76a49ad7515e0da0fc3ad259d4
4629 F20101119_AABSDL acquaye_l_Page_116thm.jpg
813e79920a425d8457f5883d81b4e4f0
287075861e5bb22cd32c49c9d024caede3c3c782
7679 F20101119_AABSCX acquaye_l_Page_108thm.jpg
ee4ce9b0adae9b7a4717f783b9361b57
c3e45786b97b1b84548da4584957e8d9fa33c2c5
1797 F20101119_AABQVD acquaye_l_Page_103.txt
8f53401bb2e5a33727cf2fcf013b45cf
858f72b2346f32b01175ec4e3f75467a5728e6ab
5684 F20101119_AABRYF acquaye_l_Page_013thm.jpg
20fee755949ba9e08d0b3ed15a581184
032c972c76356c4a1a68bdfab6e7e83b5cfbc841
F20101119_AABQUP acquaye_l_Page_007.tif
8ea775d2e72e5258e7a1e08fb924bf0d
92d5cc7d21bc5f39a738ffc6e85cd9c0759e68ae
3357 F20101119_AABRXR acquaye_l_Page_002.QC.jpg
741a6415a0f21ccb6324bd993d0f29b8
83cd7ed090469d3a2f993d949ab2facfabc87a3b
F20101119_AABRAJ acquaye_l_Page_118.tif
6d793fcabb2a313a90e35a4f9368ac9e
0aaf7f0cb113e4d873f01764bb6953846ddb2d82
6011 F20101119_AABSEA acquaye_l_Page_125thm.jpg
e68562c234a1e010186e7d826a196bb4
a09c0de563fd5636efbb32df9c0f05d9bae7d9dc
16627 F20101119_AABSDM acquaye_l_Page_117.QC.jpg
5db02d72db5d5ba4a6364ccfddbcbff8
d7854064e387e98053af668ba4289030bbb00f57
19063 F20101119_AABSCY acquaye_l_Page_109.QC.jpg
4b7f7ca1667315d94167f947f346834a
39ef26e3853fac6d830b580110f16ed4934934db
24637 F20101119_AABQVE acquaye_l_Page_131.QC.jpg
99e5f64d57a6488deed40e60b034aa16
9a0d597b24ee59be5c0d3bee39e1a23282682ddd
20243 F20101119_AABRYG acquaye_l_Page_016.QC.jpg
e44f23ebbd195c1aa86edd7a48fb1a01
c2c6c129c64cbf761a37d1403811e0152adf449c
37244 F20101119_AABQUQ acquaye_l_Page_052.pro
ced6127bd3bfdae621d44ff4481690f0
a2cddcdc9b477a21b5b83cf7a94ba986e1388dab
1390 F20101119_AABRXS acquaye_l_Page_002thm.jpg
d182681b46d78fa20799464a8e86947d
a2f8c9aa04c509bb0ca3426477f734767169423c
78724 F20101119_AABRAK acquaye_l_Page_015.jp2
02752466819bad6f70c47aea4be9dc4c
e49beea12aecf1934e56b64628acc928af16aada
18260 F20101119_AABSEB acquaye_l_Page_126.QC.jpg
d298ae52a0d49d87abc01b14e4b874b7
4c74d5b12e493465798839079b5575f7a072c863
4710 F20101119_AABSDN acquaye_l_Page_117thm.jpg
58f13f8ce3c7502f48d5132784fe9c8f
85fe0e80fa6b628a255b9f8acbe37500a9eec485
5433 F20101119_AABSCZ acquaye_l_Page_109thm.jpg
bc7611a1fc3959fb1528fc4b2defecf5
00ab982b114bf41f580a98eebbf0adf2ea65914a
530 F20101119_AABQVF acquaye_l_Page_041.txt
d2cf6fcfea9f316c0949fa53f7dfb919
280d91d933d04a9ce98434c8df773c6a0f20abb3
5700 F20101119_AABRYH acquaye_l_Page_016thm.jpg
d8b79cc6e4431fa0dc53b27ee89c6d20
2927efb3f0e7394b481bd710095c0ee72dc2fab6
55000 F20101119_AABRAL acquaye_l_Page_084.jpg
e40b2c4fd5a9f6d970af82023f14da8f
45da72c4a87b2f1eae4fc4ec3b8e564ed34b4255
18888 F20101119_AABSEC acquaye_l_Page_128.QC.jpg
07324741bea77cf5ca5fd51261994e03
24e0ee3f083fd386c34db0af0044a184c5eed378
10231 F20101119_AABSDO acquaye_l_Page_118.QC.jpg
5e5cb342127a2722ffe21140b6ac23c3
9090ad3484804a9f2da2dd1fa75dc88665be284d
17050 F20101119_AABQVG acquaye_l_Page_014.QC.jpg
78967e178d29f489f40a2585366be3c7
4825f18a61a08c466f7cb9f9841e94a25a0d87f8
6129 F20101119_AABRYI acquaye_l_Page_018thm.jpg
904a816c34326544cb56e3196f149d34
d33ca354aa42c60cf581ea93e7dffafad3a073a2
F20101119_AABQUR acquaye_l_Page_038.tif
d4d0ae5c9131e9954de72435b33936a4
d8f2b9b0e98a89a5035b212e138c5e3e14ea9027
F20101119_AABRXT acquaye_l_Page_004.QC.jpg
b10a605abcaed5c864f01926fac22f4f
d4aaf8692afcbc734c50a362cc0dc21a7c35ae3f
3209 F20101119_AABRBA acquaye_l_Page_003.QC.jpg
8c53ff6ab86752491c4fa65785c1e53d
bd4d46a824189161228b86328025eb1be1901e0a
494 F20101119_AABRAM acquaye_l_Page_051.txt
344c143e5d60c3a55aca28edda0750b3
d4796934f17a1c2c5b9859d8e6cc2531251bdac5
5546 F20101119_AABSED acquaye_l_Page_128thm.jpg
7404fcca82198a9de1ee9b7dbf1ff150
6b7717000d7c83e0eaa7f57fce97b87f932b6f07
3329 F20101119_AABSDP acquaye_l_Page_118thm.jpg
b490805ed1fce7f18b9446bf948f5598
e6a811659d4a5342402db858ab8ebe7d898cf22e
4998 F20101119_AABQVH acquaye_l_Page_014thm.jpg
d5d4d20814f9aa9bb6ed884b219327fb
80f6b06db4ec0ff14b11145cefd532ccfd81f007
21538 F20101119_AABRYJ acquaye_l_Page_019.QC.jpg
559acd8f8b7c78deb060ad7759a9c435
c65c0ccb08501da433852e24904084fa85f211d9
15074 F20101119_AABQUS acquaye_l_Page_114.QC.jpg
67e18d1c30d9541b4aa41cb91fbd0d65
ec1d918aef95e63008221fe4d3f07cc9d9a3f06e
5647 F20101119_AABRXU acquaye_l_Page_004thm.jpg
8b0d2dd8592fcde04e646f7c58d90a4b
e1666acc5ce7926b3f39fd38f58e5ce8f5666cb7
F20101119_AABRBB acquaye_l_Page_057.tif
b49bc2ca58faa483ef5248151de47255
81ab035a71fd770c16a682b18f2ba3f99b8b2b4f
51861 F20101119_AABRAN acquaye_l_Page_121.jpg
e7a26fce385cc33e03abc2db727c176e
b8117e090ea436f5bb3dc78649336a6c6e356d06
23004 F20101119_AABSEE acquaye_l_Page_130.QC.jpg
cb7aa951e9ef5f9efd0810c5a629f7ec
1ea931792f80a4343943a86b2255df51b09c776b
14363 F20101119_AABSDQ acquaye_l_Page_119.QC.jpg
1b5b5415bc70d17b773f5c8c1b17e49e
07f9651f7949df1194755f0c02b4140c3040c10f
1272 F20101119_AABQVI acquaye_l_Page_031.txt
76ee5b5b1718daf072d60575b02674d5
5219d626c537ce1c1454a3cb3e4a3b007509e351
6152 F20101119_AABRYK acquaye_l_Page_019thm.jpg
94741006e5cda39d4c4bd615966c6b68
a73a84ef79711c3949f3814b4168b1b66b83039b
57737 F20101119_AABQUT acquaye_l_Page_090.jp2
f348bd1361d7fdbb1744226192ef3b6e
bbf278b1df721c99f384c864934ad86860761e6c
7958 F20101119_AABRXV acquaye_l_Page_005.QC.jpg
dfd3dcb2eecee94fbcfe7c39eeea1ee4
6a3a49100d27b04e282c681805058090dc610658
3916 F20101119_AABRBC acquaye_l_Page_077thm.jpg
2190a3f21ad4d8dfe47381ccb6362abd
f57fe3ac1dedc8430a434b196cf3cb7e4c569c49
78418 F20101119_AABRAO acquaye_l_Page_130.jpg
93c493a24c3d837b8f85d76256faf28e
6dd1e6661e45a780d80ef6d8850e36c46c218347
6238 F20101119_AABSEF acquaye_l_Page_130thm.jpg
c967a7ab2a492cad00ff7588c76d4a04
708592fed6ae0f9c8869a74dd62667931d71ce15
15933 F20101119_AABSDR acquaye_l_Page_121.QC.jpg
28e50f4355881d2674610f0210ef6460
436c00cb2acb36894326cf1415faa46f809703c3
20772 F20101119_AABQVJ acquaye_l_Page_093.QC.jpg
0fe624e769c088fef44d1c4816dc06b6
e8a0df7d4c836bbdef3c7c193d4698f404aad359
21535 F20101119_AABRYL acquaye_l_Page_020.QC.jpg
52086f6881157843f24394fd5c792fc1
22fdf8e9a5d4409d67c05834e591f68ff6680bd0
78200 F20101119_AABQUU acquaye_l_Page_069.jp2
668a05975a4cb22410351e7751deb335
b605452b3de5b68c946b12106826bbb28b0d67cd
2492 F20101119_AABRXW acquaye_l_Page_005thm.jpg
efecc3416bafff17e657c183e8b37ee3
cd9da270f9ba62b53a9ec1f4fd391afdccf77715
55713 F20101119_AABRBD acquaye_l_Page_069.jpg
e4deeedbfeb36df29b20fa2ba53b42de
526e56393d317f3b9da39b74dd967f911ccd52a5
14038 F20101119_AABRAP acquaye_l_Page_047.QC.jpg
fc57ecf35aed974d43c93a27a39b4d75
9f9552cdbe310e2b121b40bd1e67e11f63ea5b8d
6748 F20101119_AABSEG acquaye_l_Page_131thm.jpg
5abc17104f47c653bc2cbe9559d98077
f5e026c46262265b41c44605017505e839711fb0
4929 F20101119_AABSDS acquaye_l_Page_121thm.jpg
4c3703f72c121fbb3a2106ea5aff0d9c
092f1444948aa3e90ee11e52abc8745db6fc3bd5
6554 F20101119_AABRZA acquaye_l_Page_032thm.jpg
761b7a36d32de706d3bc3049dcac369f
824a92a9a19093bc20b6a1f8827b8ded2555ec3a
5758 F20101119_AABRYM acquaye_l_Page_021thm.jpg
95889231a59941fe8774889ab28b738f
cde9c0df0f96edf159d0bef44b6e7c8054e7ae00
69091 F20101119_AABQVK acquaye_l_Page_058.jpg
e2c6a3b681f97b94bda3759324148aba
1182beae99769f8bd74507e90cad697f07c5506f
6471 F20101119_AABQUV acquaye_l_Page_029thm.jpg
8abb658e371c5d3b6a46345f78fcbe24
fd2145b70bd0346605b4229da5672af91c8b47c6
4823 F20101119_AABRXX acquaye_l_Page_006thm.jpg
817f869b5b7f5c0de565bacdebbf7dbc
7e57b20b3aebc55cad17b86bf52dddb7fc0781c7
23799 F20101119_AABRBE acquaye_l_Page_012.QC.jpg
1a4b1464a73eaf33ebae51da4880c600
215f03e879d3c69fadcea78e391cdc2643994f52
757095 F20101119_AABRAQ acquaye_l_Page_008.jp2
84b8b4666e969a25e9d9ccf4241cc99e
8fdc640ba9a664412359bb7548987486e9d406c2
7009 F20101119_AABSEH acquaye_l_Page_132thm.jpg
d7ad13a5eff3f59476be85bebff992f5
c7ba84e6dea9bd98d6ce38d7ace0e64a6352da8c
18057 F20101119_AABSDT acquaye_l_Page_122.QC.jpg
407c2741dd06c5b4996c27af5af8bfe6
3d6ad78676f32cf3face0942453e91e861713a2e
22425 F20101119_AABRZB acquaye_l_Page_033.QC.jpg
4465c774ee3066e4ce7443de6cef3cd5
998c8b6aef230356f29e539c7ea1fb177db44a06
3557 F20101119_AABRYN acquaye_l_Page_022thm.jpg
181020d600c9d97807d7f95458e233de
c0c869fbc3c516a6d611a8f24f23bce4bcde9440
41932 F20101119_AABQVL acquaye_l_Page_055.pro
14ab1b98507fc0ee35b6d7a24e02528f
4b89c8232132920b79cd90d548af02066e67fb8d
98123 F20101119_AABQUW acquaye_l_Page_046.jp2
dd5e0fac7e98c67e7271c55e6e38e6ab
6b21b9bda88c13151e4e2ef5d6944ab5776d1c35
24529 F20101119_AABRXY acquaye_l_Page_007.QC.jpg
0e7b85c86ac4f3b04e088fcddad63491
7627e2d163536fbd257e9116b06124ee1d7aaced
44444 F20101119_AABRBF acquaye_l_Page_026.jpg
d154f39c52068f571668f3a5524e2aeb
5c3f4136966af92270352cc3d73c61271be6871b
14914 F20101119_AABRAR acquaye_l_Page_088.QC.jpg
98fd48f24e35e50c64905500292a9c4d
a08016cb1adc5aa8d4524d0bb7ee06a70a0162cf
4574 F20101119_AABSEI acquaye_l_Page_133.QC.jpg
fb4ce635553a6faddcd77eb2b2c11149
5324b243adf8bbcc2cc23b211d10b87fe1387d7b
5243 F20101119_AABSDU acquaye_l_Page_122thm.jpg
4777b4df755c7e24a9ce2fc07f65edae
83bd46e399d82bca28ac74dcbfdd6ad03bd7cb72
24300 F20101119_AABRZC acquaye_l_Page_034.QC.jpg
d0e0b890b4337c33e8131aa7c5aea36f
62a6b3ac898a9f51b9f468420fbdd4173ea48bef
21152 F20101119_AABRYO acquaye_l_Page_024.QC.jpg
2ae2a131498bb85f9933eccd7a045c67
e154a95b6d004cf442eb453c00d43e4ccf88df0d
22346 F20101119_AABQVM acquaye_l_Page_092.QC.jpg
075444f271b025b89963f5eb7552ad8c
81f60ae94350367f5561567745f455611ee92748
34263 F20101119_AABQUX acquaye_l_Page_075.pro
07ddbcfd3218efe861c254e30963628c
e316fe32c15c99a4d075272693ab7ed17e2bc816
6028 F20101119_AABRXZ acquaye_l_Page_007thm.jpg
038a4b40e4c5cfa7acffeec31a994daf
2ae3263f7d17edbcb455b5cff77a837acb6614b9
F20101119_AABRBG acquaye_l_Page_050.tif
e2d2ba2e553bb7f70ad983a0a124660f
6a5f64014674bd4d4064fec1b8d09188ddac50bb
1490 F20101119_AABQWA acquaye_l_Page_068.txt
2ec0a27b5bcc8f8306b0dcfb267a285d
16420f04df50a65165962dc66f706d9dcd17cb54
6120 F20101119_AABRAS acquaye_l_Page_020thm.jpg
a9d97894215bb776cbb861b867da4411
43b345aebc6b47c2ea9f7e3ec0f5ea8825f852e5
1743 F20101119_AABSEJ acquaye_l_Page_133thm.jpg
c39745a5f40f6dff63c736d8dfa0e5a9
abab7653d7716d6e0f79773788288439492b3298
17149 F20101119_AABSDV acquaye_l_Page_123.QC.jpg
8493e5f6f682eb821e86aebb6807b054
7742a956abe9bf69f9b37e05d644619c0f1f90ee
20134 F20101119_AABRZD acquaye_l_Page_035.QC.jpg
544e53a36a0caa8a565756e3940fef82
17e7a90cf06d23be59065d7c7c614564058dae4e
6039 F20101119_AABRYP acquaye_l_Page_024thm.jpg
5589e93f518b85988d4d77f496835fa1
227ace9d22e831480c659336559dc4790f419800
13937 F20101119_AABQVN acquaye_l_Page_104.QC.jpg
fcd2510ba422c32458ba03c4b5f28421
267ada83f0a4aa5ebbf4ac5d071b3e9210884333
4450 F20101119_AABQUY acquaye_l_Page_074thm.jpg
e44fc87c7e03519f598a95c4501bc45f
0596560b96d8049b1a5354eca6c489a9b08cbb15
F20101119_AABRBH acquaye_l_Page_022.tif
7b45bb5474d4796341be803522ebc45e
497dd45c8254625b74e58ac43aaf2f3399c43ead
F20101119_AABQWB acquaye_l_Page_024.tif
041e172d5cf3f157937c1943d0ba3c13
c592ee1d3ab95d34d02e1401ca19386966d68cbb
38062 F20101119_AABRAT acquaye_l_Page_010.jpg
ab114f2dcf929af0be5aec72389f6751
01881da5e80b251f3c086ca19a3958e9be59e816
10835 F20101119_AABSEK acquaye_l_Page_134.QC.jpg
031743c5350bf833b611a3fdd247cf1a
d03003d81175ed96de65ba99a6c05c22cbf2cb66
5547 F20101119_AABSDW acquaye_l_Page_123thm.jpg
d136079f80625c8d7662bbe772d47c20
864fb877cb0dd229e799814b1a31a3a08ac53661
5842 F20101119_AABRZE acquaye_l_Page_035thm.jpg
579b9d1859af450c5f76717cc88977ae
38bbfdea6a8f2a2d01ebdb2950d9ba99205ebea6
19207 F20101119_AABRYQ acquaye_l_Page_025.QC.jpg
45f5ff449352fef51a75c5e9eb0ec034
1cf17434ee152f00417fbfcc04c3ae522e1f68c2
F20101119_AABQVO acquaye_l_Page_067thm.jpg
ea74b15d7591946c83a008fa5df33630
27097f460e99c3987b1a9c5698efa4486bd97e96
F20101119_AABQUZ acquaye_l_Page_078thm.jpg
13d7d55f3b45b3e534a83935f06e6bef
4e3abf1ce6b8d8f057808762beede369c81e4ce6
133142 F20101119_AABRBI acquaye_l_Page_131.jp2
8d04a9f39e80d5d2f2ae7560666bc97d
3a231f7847d6e404cf4e0ece46f919aac1d2b837
6613 F20101119_AABQWC acquaye_l_Page_034thm.jpg
f0fa102b56e8ac9ebd666776b9a79f60
879b430ff35f66813c4b4cecae4cb82dfb6ff93d
4423 F20101119_AABRAU acquaye_l_Page_047thm.jpg
81256ced1fd0bb92d6a8a8e805803f64
edfebaffd4c9a2955107c5ae28be4f71332cd05e
3230 F20101119_AABSEL acquaye_l_Page_134thm.jpg
1d23a75166e3219111fa91a56d111e54
8cd3c12672cd62291148fea1c1383608aedf9239
16489 F20101119_AABSDX acquaye_l_Page_124.QC.jpg
d982c5ce1ae6857db89f93a13e89184e
bffbac5388d491bfbadf9d613c3013d0f22c26f9
6208 F20101119_AABRZF acquaye_l_Page_036thm.jpg
7739a104cec919c0c44530d32e6351a7
c9633acf526748ef0fc1c1dd97eb85679b33d6a0
5696 F20101119_AABRYR acquaye_l_Page_025thm.jpg
7578b59a858c47da27881269e4488be5
7ac0d965c5b7ea562cb1b06cb21674d1bbf24d29
1790 F20101119_AABQVP acquaye_l_Page_102.txt
9e145da9a5db524de2e57e0e606d6f00
5a74379b0e32b9da251e66f3eeb82ef31b0b5ca5
60718 F20101119_AABRBJ acquaye_l_Page_031.jpg
7c98b87399f0bd98758849783c446487
1787802e7eeb523a1aded0e26ab5298fecd35915
2078 F20101119_AABQWD acquaye_l_Page_030.txt
cf37abbd5aaddb27df18c20487664415
37ddcbf1e45f5bbe8b29bfe8fd400539a44bb96a
1096 F20101119_AABRAV acquaye_l_Page_084.txt
d05dc81c7592e4b25dca6c2e7843531c
afae6dc5c1e2450aad9f89d9a72c18e699701426
155636 F20101119_AABSEM UFE0013837_00001.mets FULL
5d550590f4325dd7fb3bf00ce01dbf9a
74d8cd249b9c1b0ca17ed64a6e53fc4d75a778e0
5326 F20101119_AABSDY acquaye_l_Page_124thm.jpg
9ddce20bb653e41d25e156f4e7fd7de2
5d1e35965694297e623bcb15668ce7283a67c0cc
20454 F20101119_AABRZG acquaye_l_Page_037.QC.jpg
757291a737a511910dc17203154991fa
8da2a611a6af6bef43dfeb7f4add129329095fc2
14662 F20101119_AABRYS acquaye_l_Page_026.QC.jpg
233191fef63941c6c416663014454516
85e65bd313f54bf43b9016dc7173d875eab90179
5655 F20101119_AABQVQ acquaye_l_Page_126thm.jpg
03b0fcb91be78f7743dec9c635b008b4
bb460c34ea95e5416fff0fdda2713950447cbb89
5642 F20101119_AABRBK acquaye_l_Page_023thm.jpg
54283ed7284d63a58c1e472dc3488198
2a8644ed15b7bf63d33a90abfd956a0363e573cb
F20101119_AABQWE acquaye_l_Page_107.tif
4d12169f43df0244c80222163f65191e
7baf1de3f6e813857f56ad1f4bfb9f5c38f319d0
34657 F20101119_AABRAW acquaye_l_Page_025.pro
2ee98f88452b75805cce03c37ee1f580
1455e9c53d360ca7668024e7271bc2d6bd7d9fd7
20001 F20101119_AABSDZ acquaye_l_Page_125.QC.jpg
64868e7f4b70b345549fd54a13acd6a1
5c042112ffb2026bcd4a908c2ab02a357c549625
5958 F20101119_AABRZH acquaye_l_Page_037thm.jpg
59f0fe5b94902f129fe70fd52bb21cf2
a19080e39121f34376fe52c2126519b59030e297
4698 F20101119_AABRYT acquaye_l_Page_026thm.jpg
74f63fc31b772df79b830d0f19122c65
cf4bb536a1396ccfbb8982c5b8aaef53a930345c
43866 F20101119_AABQVR acquaye_l_Page_134.jp2
d28bbb1a0c17fcdc1be97dfd773b6d17
c2ffbee80c1d4011db9adc8902718e5912b59977
F20101119_AABRBL acquaye_l_Page_120.tif
e654fe23e28e1d21b2d2f77eabdd1d24
d497a8198943844fe545bdc23e265e348d977cbf
17774 F20101119_AABQWF acquaye_l_Page_068.QC.jpg
4545ad69b205ad8c695b3fdedbce44e5
dbea9fe5247a61da53a2c50979d16689e1af4b44
624047 F20101119_AABRAX acquaye_l_Page_085.jp2
9c134df718deba385c55080961980409
be663dfd54324d3b457be4d5388bbb4884c3f6a3
23665 F20101119_AABRZI acquaye_l_Page_038.QC.jpg
9608074b83044e8006159bfda3119a9d
31058604b3ee5536b52ea9334b045e67935b0f41
F20101119_AABRCA acquaye_l_Page_069.tif
fd77df68dcba338458817af2d538bf1a
65c7ccd20a27f65a0b5135cb27cecfaff9c7e39a
12627 F20101119_AABRBM acquaye_l_Page_133.jp2
946cccb98f956191417d3fbc62714f44
ab6238ccfc50ab90fec6c59cbc75d74a64847594
55073 F20101119_AABQWG acquaye_l_Page_009.pro
b39f2fbe606de8db06841d419cbc927b
df1ec1127fe275712b692b93845ae8a5eb7dcf76
76341 F20101119_AABRAY acquaye_l_Page_006.pro
30411ff3777e13c09170c44c17652715
87e89bf799ad3a83c84a3bccc5ed3452f92cbec2
6495 F20101119_AABRZJ acquaye_l_Page_038thm.jpg
76db4ce69f9a2508a59480993cd4de47
d52f7c9a616509a0fea820ae683d8f99eac74e1e
21730 F20101119_AABRYU acquaye_l_Page_027.QC.jpg
7dd8ff42ac3f4a0d101b50324327f51e
edc1e72407f6eabb84a158852bd47a3fb9c726c5
72398 F20101119_AABQVS acquaye_l_Page_071.jpg
78cb7432c4fccae12dd60af1a623f1ef
3d68f1e5035e2728be26a041b6cff00f208fafff
F20101119_AABRCB acquaye_l_Page_042.tif
3e2880303127a6c21feab48da0154634
f2f4cc0bb6e3a91ea9afe020d0db1cdd5c14884c
24106 F20101119_AABRBN acquaye_l_Page_026.pro
c5a06658c64b6493a095a036ee2fa69f
50f43c698044faa15215bae3bf2f8bc19845854a
31034 F20101119_AABQWH acquaye_l_Page_105.pro
e76f98ad8c9993691dc8bb0bb96fde9c
5d6d0fea804c0fc376b18a489fd328210ea74199
10674 F20101119_AABRAZ acquaye_l_Page_003.jpg
9ca3695d87f78f4774fbe6f6f68f34cf
df613d44a909baac0753559a13820d15b04c1306
23399 F20101119_AABRZK acquaye_l_Page_039.QC.jpg
3d0c5053bffed0a8ba00028b6818b573
fb770e397efeddfdd1e34440d71294662d81e6e9
6232 F20101119_AABRYV acquaye_l_Page_027thm.jpg
868db600064c330da96d2056c94a15bc
4916b87212c02e4b344f250a5fa15faf90155804
F20101119_AABQVT acquaye_l_Page_125.tif
843d480b0cf4eb554b02b51ac6834ac9
ded4bf21de76ff8ca4ff5d767f64c4d5306c4c4e
63086 F20101119_AABRCC acquaye_l_Page_023.jpg
20e12abbad327de03da5d31e60989e7f
099033f17f417539f284ce87422778ab768e1d2a
45098 F20101119_AABRBO acquaye_l_Page_019.pro
4835c88cae03d06b3ef8274ef5de33d0
95181b047ff0267a12ec8fa3b8a13946623d5204
99422 F20101119_AABQWI acquaye_l_Page_060.jp2
aa96e9e6da8ac94d54385ba219f8cad5
0f144cf053d629fe3878c3a99a512cbcaf474e85
6604 F20101119_AABRZL acquaye_l_Page_039thm.jpg
0c5941b8ffb72d2181fb25b2440ba831
34ec065bfb3829845f6f0cbe104dc891278df899
22079 F20101119_AABRYW acquaye_l_Page_028.QC.jpg
71c374fbfcd571492867f94f89486f92
a264acbf58feb7b0e97a664b7c1541f102c0623f
18010 F20101119_AABQVU acquaye_l_Page_134.pro
e6b4202cd938cb43568b608175a592f1
5c0aae738bd4e9ea9ea51c8040fee37634b53dc1
5426 F20101119_AABRCD acquaye_l_Page_095thm.jpg
637d3df796efbcdc959c334ecca2ae2d
9da540331b4ea717e7c511cfd8f1a0019f64882c
20789 F20101119_AABRBP acquaye_l_Page_106.QC.jpg
428de6f0e58f0348cee888932c3e7c33
28ac872250fe7191abb7250188543223244f6d1a
20062 F20101119_AABQWJ acquaye_l_Page_023.QC.jpg
ce62a1ed33a094be4e3563e1ebc82b99
f3a52e0b1ce5e8dab34db6ef997ea15280672ac1
19912 F20101119_AABRZM acquaye_l_Page_040.QC.jpg
c4e69880afe33fe428371daa87a283e0
778c24870f267a0f5152747d2d7dbf5811121e49
6307 F20101119_AABRYX acquaye_l_Page_028thm.jpg
0fb50970fa782f341b67cdb6244b577c
747a44212f891c64447ab11971c99054a60d9ef6
60340 F20101119_AABQVV acquaye_l_Page_025.jpg
24bab09d24c8ef7c030fa91e2eed7c27
acd2c1da7cde9982c662afb39a1e9be5955de862
44186 F20101119_AABRCE acquaye_l_Page_060.pro
ceaa1df694f38249ab3b7686f37f4663
50f4520e754acff4a5a780b3a85a391410e511cf
46442 F20101119_AABRBQ acquaye_l_Page_027.pro
3daec51055e6074bcb8b7422e9254624
a805a43fbff966df4272f665839b0ee0c162a8f1
969673 F20101119_AABQWK acquaye_l_Page_062.jp2
6f38ce826d2244e71136d899fd12e493
3c42995ac9317483a016b324b746fc2621615364
7707 F20101119_AABRZN acquaye_l_Page_041.QC.jpg
674645ecaecaf14dcbc1a74235c9c16d
6a2cd78a5eb138f27455ce64e981cadb46694081
23385 F20101119_AABRYY acquaye_l_Page_029.QC.jpg
54930aeb6cfbaab178312336942eee57
54e99de44c5f7bc6200d8b9de69241119f80c804
41359 F20101119_AABQVW acquaye_l_Page_067.pro
4ca2a40b19838ad8cc0a55750735b00e
a69eb4ee7c670eb06a49cdda6134f9e6653ef114
1785 F20101119_AABRCF acquaye_l_Page_064.txt
9b40fb860aaa445e31db78c3714b606d
1a73c7835ca36e5ac7ab00d1114c15e3eaa02e55
1636 F20101119_AABRBR acquaye_l_Page_081.txt
a4c484c5c51e377a73ee38e665a3bca3
daf6a665c4db4834eb6bcf461587b75e197b77d1
15522 F20101119_AABQWL acquaye_l_Page_048.QC.jpg
14c9df23a48b6e5b7e5fc37712fa94cc
6c481b97531594d2d447ce3ecebe5b4ce83deb7e
2432 F20101119_AABRZO acquaye_l_Page_041thm.jpg
0ab35012f1d3863ef5615d69f422b88e
5b7f4dcb11e29b83aee5269b65c7117fb66e5b14
24387 F20101119_AABRYZ acquaye_l_Page_030.QC.jpg
1fc1b0f93f1136e1da647671f45a6f24
7d4cd4efc88dd2cfa8cb6779f034f5add6a8e4cc
F20101119_AABQVX acquaye_l_Page_074.tif
f23a3d1994622d784d373476a963609a
f31b2c30c3cdeae5948e17ab20a9c800d057d7d9
F20101119_AABRCG acquaye_l_Page_113.tif
b058ea3d6ddfbdfc4e0db139a7793b8e
e5773206937b7db31196c110086ec56faa3a3972
F20101119_AABQXA acquaye_l_Page_011.jp2
3cbcb5bef7b450a761108cff8d718451
e56bef429917ceb48bdf4904b97fd7b59003a016
1824 F20101119_AABRBS acquaye_l_Page_021.txt
b7497157d64ef49e304be21e30429568
32d45c113dc7d502b02933238c346a6ee12926de
31715 F20101119_AABQWM acquaye_l_Page_008.pro
40154fafcbb6265748168fba0c6bf818
6eb1ed1bdd961746330b1e3fd9da22b9500e940a
5539 F20101119_AABRZP acquaye_l_Page_042thm.jpg
91457fde994495d84a30ed6777056896
48f3115a23d8c345aaa72ab5ce28536212bab389
19084 F20101119_AABQVY acquaye_l_Page_042.QC.jpg
477728056288f187d00cfd4eaa55c84b
6a72e1e6f421bb40158807824c1a274793d9fcee
22272 F20101119_AABRCH acquaye_l_Page_071.QC.jpg
c8748b2bcb2f4b6a0caeaef091c6a6ed
98a5dd227347580a2c6c6bfecd2a67d1a11cebfc
54741 F20101119_AABQXB acquaye_l_Page_095.jpg
face1d2aca91a44af4e2dfeef6031f16
82b8e266f2872c586bc138428a48b8fa98a24e7c
944316 F20101119_AABRBT acquaye_l_Page_116.jp2
5d4d0d1436f46ca81df9bc3311a00c12
a03f18d6b778ccdbd4b5e177ffa88fb079cf9859
5693 F20101119_AABQWN acquaye_l_Page_124.pro
fa24aebf9b3c8196f5224f613dcf5899
75bfec90cabf303f7ba55eaf15d9e4d0900f6918
21503 F20101119_AABRZQ acquaye_l_Page_043.QC.jpg
b626f46803c9f6e03458e2ff67ede173
2a6053d1083ef7de2b99ca3c5364a2eeed8514d3
6469 F20101119_AABQVZ acquaye_l_Page_012thm.jpg
ae68d03aa9aa7927cc6290465ea71b78
6aa23db293a4e2448d2b9ab72d98abbfcb5c9d00
5466 F20101119_AABRCI acquaye_l_Page_091thm.jpg
99fafaed1702683605b1cc09d846ba4f
db88b8b7b8eb7793062023f7cd824bfe570038ab
193 F20101119_AABQXC acquaye_l_Page_118.txt
1dbf82ece2cd0129faf8284a937630a5
ac8af41beeb792fe7b882e5551b7525403a6da06
227 F20101119_AABRBU acquaye_l_Page_124.txt
199e7b81a25a656f7dcc10f7699fd7a6
20b1080ca04ec86978acd234e6d82322857ac2e3
5609 F20101119_AABQWO acquaye_l_Page_089thm.jpg
c7752291459261d4ac3f3fb4810c21f4
b7f27aae67460a55754f503c2b558a7d634b4033
11208 F20101119_AABRZR acquaye_l_Page_044.QC.jpg
b8c28a20cee2941f8939181f1eee384b
63e4641dbf6ebafacd57e70fb007a783ec7592b0
4892 F20101119_AABRCJ acquaye_l_Page_015thm.jpg
b38be69069bac2549b604b5fb770e44e
0b98418fe42c8efd5a7130ac54842d4e7be66d45
F20101119_AABQXD acquaye_l_Page_031thm.jpg
fa47256ee6b78fda6ea68a2aa5681eff
ad8872984aaa33965a7bc7a056d65d30b3fcdd27
894 F20101119_AABRBV acquaye_l_Page_022.txt
51c1682f05af39fcc924739a86c0dd62
54686f8f5d1ef3f5c04243bb8a2fd7a549913c1a
F20101119_AABQWP acquaye_l_Page_099.pro
d60402936cc91ec8d10169b62bed0341
de3823ee126b5cdf3c8d99ab4f7398f29d5853cf
4950 F20101119_AABRZS acquaye_l_Page_045thm.jpg
2a08b21147055ef880874b29fb8c7e81
6c4e7ce41c12effdcf8a2b52c36968f489294940
25511 F20101119_AABRCK acquaye_l_Page_104.pro
a504db2728f6326bd4dbf58f28c0ddaa
b8d77b8027154e421d1c665075e9332f29bba5f3
58449 F20101119_AABQXE acquaye_l_Page_053.jpg
7fe37796d4f5521686fef4de1d284735
17c37318cf30ad9e9a43669ec6a25fc9a011e3e6
44788 F20101119_AABRBW acquaye_l_Page_088.jpg
a059a6340e1c36c2f771f53c4d41d13a
c923955c6e523d8f4e2cd5392ec086cb4e5dec60
45549 F20101119_AABQWQ acquaye_l_Page_044.jp2
cb7dcda832ae160abebdecb61ddedbbc
3a90b864e7e86b1814b9a2e71fc00dd2b44fbbef
21951 F20101119_AABRZT acquaye_l_Page_046.QC.jpg
0309a20d416e1fcc7b0aae547ab2a1f3
cbcf43171fd38e5357042bcb572aa8abb1a6aa42
F20101119_AABRCL acquaye_l_Page_014.tif
21f93a2d092d0cf1c03147eb285b0099
57b566498fbad49bd469e0735fd79974f37ed3ae
55652 F20101119_AABQXF acquaye_l_Page_074.jp2
441b09d4fd8c6bf6689f5861219d2394
c84d6c274beed51fdbf2aa1422169d463fef4067
59356 F20101119_AABRBX acquaye_l_Page_082.jpg
7064e324873f4f1095884e65049e1746
4751bd01cd2f3e1cd2ff113939e66b9533f07db9
F20101119_AABQWR acquaye_l_Page_088.tif
9f2e885cfc075ed3486e668e9b4a7f32
769ebb0c2596c18d49b7b904e9d8327f7668cbba
6354 F20101119_AABRZU acquaye_l_Page_046thm.jpg
ddc46ce3407d1a27fbbc5ea9a724db4e
21ac898446a02f8e865d42afb846352cc6dec4c1
923555 F20101119_AABRCM acquaye_l_Page_072.jp2
bad17962c890fd01e6cbff0360626766
f66df201dad61d4aa7b912807aed469dbed6d1ad
17591 F20101119_AABQXG acquaye_l_Page_015.QC.jpg
42ada0614b99321fd94b57f09688983f
197dd78f80e178f60f01ca66e1e1cbe13abba2b6
35477 F20101119_AABRBY acquaye_l_Page_068.pro
59cb9417bd89d1f9a72f671065671dad
9836b37ba19a45f776fefbcebe13492050472020
17683 F20101119_AABQWS acquaye_l_Page_006.QC.jpg
e905641ef07138af718981e2af1dbdfb
73f96f810f4d1c6c18633d5b707c2088cc430aea
1688 F20101119_AABRDA acquaye_l_Page_004.txt
a8e8e46c68d344cbe106dd911c6385ae
16fdc2187f61aa47b9ebfccf204f676f7fc34288
5942 F20101119_AABRCN acquaye_l_Page_064thm.jpg
8dfbc3860e90933905af344bec866d57
ecca2696b538ada5c296eabbbdd4de6ee8f83cc3
237 F20101119_AABQXH acquaye_l_Page_122.txt
ce9924d7659cc04877126a4fe676f84e
49f53b946c32dd4eb9b23b9a00d7759217d932ea
4704 F20101119_AABRBZ acquaye_l_Page_119thm.jpg
3c33c2d57017fa8d046894bc18354d53
44009399ba6e271b8a6ee10bec24001d16050552
F20101119_AABRDB acquaye_l_Page_035.txt
179a87e020355a4c404066e799e13238
db06f4d2a06878e4f2e4f7c49094196349fd71b7
4795 F20101119_AABRZV acquaye_l_Page_048thm.jpg
1fbfb80bdb4e5e9941fd0536ce87731e
48b68eddf183f2c598103bfdd6b4dc3857a28258
63555 F20101119_AABRCO acquaye_l_Page_052.jpg
66f2278daec5986786ad47f3fe8d2110
1f081016c87d7267ea965cef280cf671f80839dd
60716 F20101119_AABQXI acquaye_l_Page_087.jpg
bab9776a4ba1e6f207e2bb8b2a3255a3
76cb85afe58fedfc03a893733ea47834bc3abdf8
32738 F20101119_AABQWT acquaye_l_Page_134.jpg
2b3edf12827109beeaeece142433f7e8
0692cb0169e2b1425dee9273772e4359ce1785b9
F20101119_AABRDC acquaye_l_Page_041.tif
70169715958323685d836090ad2f5975
f3e9029d52573512aca96d9808cedfae5b93e99b
17432 F20101119_AABRZW acquaye_l_Page_049.QC.jpg
6ac6c985dde4f8e6443a3b85e7458f61
84a161a1a0cd77cc2de1fd244d851210f66225f2
1724 F20101119_AABRCP acquaye_l_Page_089.txt
61c40fc0d80f58e1e869b062769bcebc
578e8ee4d5d25062d2d749d7720882b015e406da
F20101119_AABQXJ acquaye_l_Page_110.tif
b0550547ceb678fc679155cd80510402
64c0b073609b4dc6a0ad49e7e7e6d647844e5c98
1051889 F20101119_AABQWU acquaye_l_Page_120.jp2
801a41f55b10274b7c6a9c37c60e776d
6ea4ae099e744a531fa953a34bf6b0e332e4668b
F20101119_AABRDD acquaye_l_Page_006.tif
ee96009d235ca1edd943e290c0d81bad
8e7259bd5cf07695afdefd672e8fe3ccf4ec1c02
5309 F20101119_AABRZX acquaye_l_Page_049thm.jpg
81fd10a42cf69900c47afeb82396c093
3d651dbe0f007f01ea31d200580c9798e31601c1
88982 F20101119_AABRCQ acquaye_l_Page_103.jp2
9aea1e2c1e8123f1a3f038d4f691de87
5b60bd358c77d581efdeddfe5481ce3fe4af18f4
22231 F20101119_AABQXK acquaye_l_Page_058.QC.jpg
9084ba8a45f2fc91ac430cb43f86a2b4
4c32c181b237fbd13ca2628cbb70973a1f14e170
47626 F20101119_AABQWV acquaye_l_Page_018.pro
49b6e9e893e16547110f29714d5e245a
bfe5547654289bd5d6ba3a66c5ffcaa694336d2f
38816 F20101119_AABRDE acquaye_l_Page_056.pro
7695d4dd4683c44919401b4a1cb85fb3
53698035f6fe151dfa08cc67c05a29825cda2054
4750 F20101119_AABRZY acquaye_l_Page_050thm.jpg
f7d5311ca47a7487e555c8357173b661
c2b087b120ac88c403f57a72e894c7abc3155b31
11793 F20101119_AABRCR acquaye_l_Page_022.QC.jpg
d062829efb5086a1c1fdc68eb2ec668a
fc59682061ea5f58f86077d3af75ede2a408afa4
1919 F20101119_AABQXL acquaye_l_Page_077.txt
0f45181b68bbc07d1cb1942bad5a6bc1
d66b87e07d4d720f867e18a798fb3f3c1002fbb3
6569 F20101119_AABQWW acquaye_l_Page_072thm.jpg
897c8ec37c7e54554402f1701a9beb47
f9d96c6f5bf77d00cac39ac3867bc94f1d939fc6
45321 F20101119_AABRDF acquaye_l_Page_020.pro
951823ee3a8d7e3aecf3b104a1c6ec8c
0ffcdd1774fe4504633a686ef501da3b60d17da9
10992 F20101119_AABRZZ acquaye_l_Page_051.QC.jpg
5ae0deaf59c91fc163114997f757535f
90bf1c99ed439d58fa56a080b69166f9439decdf
163 F20101119_AABQYA acquaye_l_Page_129.txt
8843be11f2704cfe728d25b59ad58b35
f6fabcb176e5859d65191635b32e99ba1c648c5d
F20101119_AABRCS acquaye_l_Page_012.tif
12ebfc9a535532298ce7fc9c2e10016f
bb6692d45ab82d0a6815401ece90b03b9022f240
F20101119_AABQXM acquaye_l_Page_106.txt
46cd049b5a36afd475ad32e4e6b5beed
db741ee61326b05f4096e163a136f4a322b887d2
52876 F20101119_AABQWX acquaye_l_Page_034.pro
f140b138958d550be1dbaec1919bbbf8
d9ded254c3996c612f2f6adc6bb75356f9febc8a
101793 F20101119_AABRDG acquaye_l_Page_059.jp2
3e328c9df53c00853126327bea6d2aee
a6808ae38b0f7b321a3c6169d80b9f0a0cc123a8
3682 F20101119_AABQYB acquaye_l_Page_051thm.jpg
5e68f2c69b434368651c36e35ce22f5b
b47ed8feec62e2648339dd0cf4f26ae9823f8247
37879 F20101119_AABRCT acquaye_l_Page_045.pro
50a49ad95d6d11960ec162fca22ff732
ec63e8c1c39c67e3e4b94b803b1fcf6743afbd1f
20452 F20101119_AABQXN acquaye_l_Page_052.QC.jpg
4326e8059f65bcad5d7b143f252501b6
38cda2f04d45dda94f733aebd1760b253f362e2d
53484 F20101119_AABQWY acquaye_l_Page_068.jpg
d7378a7f5a56a5a537a5fc747a3a73aa
e509ed55a2a2d58d2829bc3c75aeb7d9ca7d1e37
16937 F20101119_AABRDH acquaye_l_Page_096.QC.jpg
14745e95255bdce8c3165f60ae9c827b
c89d189e7839e8c32556db62c44f94532a7e146c
58968 F20101119_AABQYC acquaye_l_Page_109.jpg
a46eebb9a4a1be44832bffaf2445d180
74005efe7bdf987bd02ac27eeea0989af53b4c82
20012 F20101119_AABRCU acquaye_l_Page_009.QC.jpg
a75a231cd7d4aec19b569c051c5c51a3
4e641be651e3cc78fdaedc69cd16969f008f4d81
F20101119_AABQXO acquaye_l_Page_095.tif
ff4de4cb40c769f86574d0fe9c1e1dd3
37cbfb27907b99713a30c2d8af2c188c28571efa
15839 F20101119_AABQWZ acquaye_l_Page_129.QC.jpg
f52fe7cb30ef6ab726660690bfc256df
6ed8caeb56e1bfd455077eb52aac882cf2946bc0
66128 F20101119_AABRDI acquaye_l_Page_013.pro
1e1316b254245d7871cf576eb3c73303
760269fbd3fff23341ef1c705f60cc857d065fd2
5376 F20101119_AABQYD acquaye_l_Page_009thm.jpg
a3bc2de1f47cccef4de52431b52f5d58
fbba369eaad0ed5d6c4853cc66bdab1f15461118
4799 F20101119_AABRCV acquaye_l_Page_127.pro
6caaf1b333a0403261ab1b414a33dc49
732717f3c8f2ab7043f28fd906c44d2964ad8c78
18639 F20101119_AABQXP acquaye_l_Page_070.QC.jpg
e60c6c040f74ec076046235dbcfd867b
d30662c0f21eec36254d1dfcbdbca3104216d252
19350 F20101119_AABRDJ acquaye_l_Page_120.QC.jpg
23538f945445e2eace32566891ad85cb
a3ac6f85a582c601afc51801784658343007ebd1
F20101119_AABQYE acquaye_l_Page_076.tif
037e5ba15cf57f993c7d118c9dc499a2
c9d118ff9e827b6405d8f0df97da40509bfde652
6489 F20101119_AABRCW acquaye_l_Page_017thm.jpg
5e59ff3eccdede0b47385edd54255db9
c4019c5ba4c5aadaf99a433c9ed615ad861a4fdb
43115 F20101119_AABQXQ acquaye_l_Page_016.pro
e9a34c855a3f91d549c18163061f709a
58d5e8d2c00bbf8a92099905b7841eaf77cbb6c4
F20101119_AABRDK acquaye_l_Page_066.tif
05be4c309815b3fc422e00218543bf13
7a4292efb63b1a1e9a055695f236ada20877aa05
233 F20101119_AABRCX acquaye_l_Page_128.txt
85f231354d90d7bf57803efbab7ae49a
0c66d7926b06401894169e54113a9815293af841
F20101119_AABQXR acquaye_l_Page_005.tif
8a71ec47a367e7271a5131b043ee82ac
36b14316a3fc3d368014e075201a2b7fbdb28cba
15633 F20101119_AABRDL acquaye_l_Page_050.QC.jpg
c50740542f86e2b66eeb81d7c5b760b3
09e0915e14d1b54c7d70635b4eaa3f5064f3a47d
5207 F20101119_AABQYF acquaye_l_Page_069thm.jpg
48dc325d29f66dbb5a6ddb80523781ad
9de865734fbacd25e5fa7bfe60cffd4b8b05efe6
20793 F20101119_AABRCY acquaye_l_Page_073.QC.jpg
6bc4e5d07b36d73d207659ee065cce11
fba94eda1554e89bad7ab9418658a8786e9bafd3
73518 F20101119_AABQXS acquaye_l_Page_050.jp2
d66607d4f645388c786cfe39c13f8dbe
39097f0e85e6f0a0235f94e95b7133169bab5f03
4955 F20101119_AABREA acquaye_l_Page_129thm.jpg
5a8f3f406f71fc35b251662e9935286c
5517f4445fa5f0dc9db7e236808edf5de507abd4
52523 F20101119_AABRDM acquaye_l_Page_030.pro
18d42e6c61371353b986f209f1fc720d
4a7c223bb31e9ef72eb1c42ca9001ef65954a4e7
623 F20101119_AABQYG acquaye_l_Page_047.txt
8063788814e9b8e3bafb689a5e8bf3cd
5ef271d043c751b2999c0cdf7cccffecc5d5574a
F20101119_AABRCZ acquaye_l_Page_016.txt
e2bdc3623987b4624a99b6f47f8978c5
e4a4804192cf89db045cfe0eecfa491046cf30a2
40975 F20101119_AABQXT acquaye_l_Page_047.jpg
4b06cad36c518fc09ca60054b94847e9
e61e2f00dc313d83207731d3b406ae624e0e1308
25413 F20101119_AABREB acquaye_l_Page_072.pro
76dad0d7813ee4c13774ef35c30d5a08
b7257bf280eee908eedba5216ab40ed18d2d57e2
F20101119_AABRDN acquaye_l_Page_061.tif
9b349151f833d66d47972cf9e037b379
adf685201e99eb2e5b18e028eef636a90927acd5
1341 F20101119_AABQYH acquaye_l_Page_086.txt
2bda1d96ea8245bbd0dbdf3d9d14543c
85b0ca90005325516247add8b3e065b0b5d984c9
6496 F20101119_AABREC acquaye_l_Page_063thm.jpg
a67bc5cd3ef88f03389c9ddffc66e247
16a57db61cc5a0463c7fee278041cea9836fbdb4
32119 F20101119_AABRDO acquaye_l_Page_111.pro
32849b6f569d10bbfaa44dad3feace3a
7cf87218bed928325303b49a58c2c9a7d88c257f
18956 F20101119_AABQYI acquaye_l_Page_127.QC.jpg
8d7c5d9b865506b9b773fbb366b1454d
b1c429198aab1d4247b4b11b2c2fea165ef77256
F20101119_AABQXU acquaye_l_Page_109.tif
2ae2dcad2c715c85f8c4c6dcb676795b
acccf2dcdf249d0ab6f3333c9fc91c8c898c60af
6119 F20101119_AABRED acquaye_l_Page_059thm.jpg
58d04f38a3cf6b42b678f4d9fd124204
a49ae788ce86fdf1a6f422d0efdffbd6af0ab3fb
6215 F20101119_AABRDP acquaye_l_Page_033thm.jpg
44646ebb241d66ffc57c9bc544a1ca10
0e6732ea5167e1af017121ba3e137301b4693651
F20101119_AABQYJ acquaye_l_Page_015.tif
d5f44fb65e5f3f7d8618e684fc5fa8ac
acea31cbe8a10beb5e3cb388c0030e25d6ba6dfb
1960 F20101119_AABQXV acquaye_l_Page_052.txt
62dcf20162e895ccb841027ade3564a3
044fcd4c69689fe2bc1204a8eacacc457b396627
23477 F20101119_AABREE acquaye_l_Page_063.QC.jpg
c0e561208294a3577aec5962ffd4e3a1
61dcb071756e5b6827a0ebc9aa0ca9c3b373f029
F20101119_AABRDQ acquaye_l_Page_031.tif
7d62ed926300fee4f0c68807d6e47d39
026f84ea244f28dc4830da8437af769971b28a0d
F20101119_AABQYK acquaye_l_Page_047.tif
1194054d2b3e20529977d645b8f3fcfc
eb29cdf93c85822a0ce77b578918654b1ba754ab
19970 F20101119_AABQXW acquaye_l_Page_062.QC.jpg
b338b3b9fddf52c48b62d9483cd5f9bf
ae08639e459a4e8d779ee047d9e17254d111f733
104872 F20101119_AABREF acquaye_l_Page_061.jp2
0bf29b6aca0b788e751655758c69ba69
3d0004281e8421071ea369ec10a86efbd0a8cc30
F20101119_AABRDR acquaye_l_Page_013.tif
a356197545be742befd186cd7b2aecad
06c96c943bf5d9da1d8a6a4f34460e556b28bed6
31582 F20101119_AABQYL acquaye_l_Page_081.pro
1720e4fcaa4dd89344cead8630333127
24947de21ad03d08eff6b01362b550b13006326c
34514 F20101119_AABQXX acquaye_l_Page_118.jpg
34a9324c489dbc88445a976a9a670494
e11c33aeb55b69297832eebbc66077eb142c658f
F20101119_AABREG acquaye_l_Page_009.tif
869e04e931e08f64b70b0357659c0820
62bab9722e696c49dac728f005c38cf2b59f3b56
4608 F20101119_AABQZA acquaye_l_Page_086thm.jpg
ae0a649eb70ebd5cce5af5e68eade928
d86cfc31b4a2b8d1cd72ebbcedffe09776593386
8467 F20101119_AABRDS acquaye_l_Page_008.QC.jpg
97dc678ebf5cc5b43305f6b025a91dff
d685f00ee915e795ddaf8e12ac33bc930659ee6b
54458 F20101119_AABQYM acquaye_l_Page_115.jpg
849a5da4a4ce61f4c7ac0e3e623f93e8
9baf42a6c83f4a0794e2c98a8316c339a4b54e3f
F20101119_AABQXY acquaye_l_Page_048.tif
cfa70c658f7f5f30c77a96a280dbd05d
6387edb4c07ce8f6c80d468cbd9abb704169ee69
10443 F20101119_AABREH acquaye_l_Page_002.jpg
c411c7daaccf757289762a4ed711ebd8
eebdc2b7746e8d4cf26140bfc5a364e341bbb6ee
F20101119_AABQZB acquaye_l_Page_123.tif
45738a7688e95740198451aad982ce78
7b155bb33c33bab3f67c4f1c69687d9c6fbe81ba
589319 F20101119_AABRDT acquaye_l_Page_086.jp2
e14edf4a7d65e477787e66aa68344fd7
a724af31999976a5dfe4c8b3ecb592ffdb9de345
50061 F20101119_AABQYN acquaye_l_Page_050.jpg
bc4043188c1ec20c8d55347cc4154677
e21a0072d0931aa67c01724f5e67543141ce8a16
4475 F20101119_AABQXZ acquaye_l_Page_075thm.jpg
b9e7297311ca8a7e615783451fa96fdc
54a17d09c910146a91af5bbc9d19d455bdbb2d11
760381 F20101119_AABREI acquaye_l_Page_071.jp2
ab8136b63281d9ca3d4f7109b30177a4
acc7235e93970df5cd3daf91cb27198095ba5206
31122 F20101119_AABQZC acquaye_l_Page_053.pro
0f10dba1fb6a68e60c0dcb791b450b6f
7f3f98e7d8799f09afc38ea0ef3fe682e2580bea
1051973 F20101119_AABRDU acquaye_l_Page_009.jp2
d061dfb80349511e360d61e2e179e157
00c4352ceeba0b5b118210d8e27116d858d0e250
F20101119_AABQYO acquaye_l_Page_001.tif
fc60856b75896cc32a3147b73a598d5d
4fb44958cd316e2f424bc5734c1bd4dd9968e783
F20101119_AABREJ acquaye_l_Page_090.tif
000130b239861f30ed74a30a4f6bc81d
81756ff45264e9b71a15469559be31020da30b04
25229 F20101119_AABQZD acquaye_l_Page_132.QC.jpg
87b6d0b0d4d6ef6147ed436eb6216af1
61cd49a8477751a9a4d21270bfecded4b34eb0a2
F20101119_AABRDV acquaye_l_Page_007.jp2
91f616575c770fc16b936c1115cf32ae
59d59cf2c4ae392807eec853ea9a2286b29af16f
F20101119_AABQYP acquaye_l_Page_030.tif
3d9ee81605b37cbff411dcbe620b61cf
b36e1c862ab7730bdad78274fbec5ac2e759120b
F20101119_AABREK acquaye_l_Page_051.tif
e0aaee7559cc1cbdc1ac4b5660303405
c9d8b84b30566824443465a80fe9bbee92874207
4094 F20101119_AABQZE acquaye_l_Page_079thm.jpg
3dbd8878b895a87c299b6da43ae25652
8f541826e297394e2d142855c4ffad88d8f3c1b8
69355 F20101119_AABRDW acquaye_l_Page_011.jpg
1b278331f979f77c53bd37efde6790d1
17c8b12796f134f046f126d6da53f26f1b3f00e3
19357 F20101119_AABQYQ acquaye_l_Page_031.QC.jpg
785a380a617f5ebf55854c8108a78a2e
b75a899f7307ebaadaf6ba0fdbda6324a79986e5
F20101119_AABRFA acquaye_l_Page_017.tif
5a9bd8b54089a3efaed4ba5c6386e342
62731c72f8dc6f9ef4d1f0bc06cc1ce269d15e71
50847 F20101119_AABREL acquaye_l_Page_038.pro
c487edf4671b6aa6a39650548efbb713
78525719c1ec6183a73b4d2c2b47099b466783ab
6737 F20101119_AABQZF acquaye_l_Page_030thm.jpg
4effa1eb19d3aadb455523b2b34a1598
0640b57cfc987849a4cb605a92901637ee79a311
844600 F20101119_AABRDX acquaye_l_Page_054.jp2
4f2ea0ff5e25ccef998ad0d31434df6e
0065ff18ec18c18a35585fb91b1d8c6f92653d96
F20101119_AABQYR acquaye_l_Page_054thm.jpg
56a625ec252ba1ce5e18ac39ebb4a0ec
6ef6ddcb9f8d31f570155ff516fbb1154e1d2340
63652 F20101119_AABREM acquaye_l_Page_037.jpg
bdd107b9f87cdb8e688e646c0621b6b5
875a630b0d1e5aee47e422b7086957de54608f56
F20101119_AABQZG acquaye_l_Page_077.tif
2f95ca3c25a6f7826ec051ad6879a0fb
917b9452e9e5ebc495d8d111bf64faeaa7bc7fc6
F20101119_AABRDY acquaye_l_Page_093.jp2
8dbdab495801187a58c620cffc55015d
f2c9e635456f829aca5fe2b2881498178c9c4344
23718 F20101119_AABQYS acquaye_l_Page_032.QC.jpg
9d50da1b950777d4027c14f627f308a8
90b9cffc83582109784573f54684f13491787133
F20101119_AABRFB acquaye_l_Page_065.tif
b4f4586394c871908b838a1059cf2db9
a0141c8d8ab168200f7e213483098098eaa24b5d
F20101119_AABREN acquaye_l_Page_100.tif
3ac7d9d190495bc065c6857f393e2625
84891992d24d0f3c2a1e39342391b8f33120bd8a
1374 F20101119_AABQZH acquaye_l_Page_003thm.jpg
9995bf109c762555e5812ba0d4f415c1
2619bce718101cf885c021df5e6a665cd20eb24b
19828 F20101119_AABRDZ acquaye_l_Page_021.QC.jpg
62227782d7e48e6e9cd6f29299d2c4a8
97797ef718eab119750e30098881585cfd406ea4
1904 F20101119_AABQYT acquaye_l_Page_027.txt
32bda459e1a05c348b035ceb0f780e58
1258c9163652246f7f9e4ea74798f2aca80973b4
68135 F20101119_AABREO acquaye_l_Page_033.jpg
a4b17f8152a37ef9af78cabab0cdb8a5
27a8e2c26977cb03ed67e3b5cc6893d25432afd0
5859 F20101119_AABQZI acquaye_l_Page_127thm.jpg
e06a7d3a59d556d98b8c706ab819b3ab
67cd8246591113d6b17ad33f40f9772c4a6eddc8
3337 F20101119_AABQYU acquaye_l_Page_010thm.jpg
eaae00ed49756e80d0d7f2e9a94bc2b5
611a2980e38f730dc0d360d7d6c6aa040f78be46
58205 F20101119_AABRFC acquaye_l_Page_107.jp2
8ec3a1b59f1d7f38f8442ad848754f3e
83f9b0f237a31a57db8e075f4d927ad3fbb7e8a7
21804 F20101119_AABREP acquaye_l_Page_018.QC.jpg
29a6b783ad6a58af7c923fc1fd91a17d
ee79f86ea94f1217ac756301224542cccd460b9d
13750 F20101119_AABQZJ acquaye_l_Page_090.QC.jpg
ccf72a27dd34bc8d64cccdd46fa23542
b386a0f1c57be1ddff1bc7674c614d2af2d1ffb1
863171 F20101119_AABRFD acquaye_l_Page_111.jp2
9899aa71ac6aaa11ac8d03f7d89f86c8
706f114222079fe92807c514f796d6752970c970
F20101119_AABREQ acquaye_l_Page_119.tif
fd7473ad7e8433c8ee337fc78d7e3f6e
af1c49a4ea99e2f737294512af2523af36805e16
147 F20101119_AABQZK acquaye_l_Page_125.txt
0ee67ad483fa72390bd91c8d982f2ecb
85f5d942dfe302bbfbd09994432388ca54fc1cc5
46359 F20101119_AABQYV acquaye_l_Page_048.jpg
11e684e811974cdeb59f873e81c7998e
adc13af1408cfcbc815bb77e953a4ed6d23ac386
17295 F20101119_AABRFE acquaye_l_Page_045.QC.jpg
b3c6ab0dcaf12514d32866b6609bed2c
6a75d3f716d2120357f6fa641aebe2cab0ad3b57
65069 F20101119_AABRER acquaye_l_Page_073.jpg
b2d13633868afefaf434b74571973d3a
924d9976fd7e44ddc40ad940841adc973577e74d
5459 F20101119_AABQZL acquaye_l_Page_062thm.jpg
2f711020f51eda26c4a78b668bd9ca74
bf36d75a3b3ace73c3493eb803326d101a5b7a59
F20101119_AABQYW acquaye_l_Page_129.tif
f31c85ce620b8e5afd15d03147454820
2111cad6c00e659f695b9f0f44dfaa67abdb5dd7
F20101119_AABRFF acquaye_l_Page_067.txt
a99e163fce9ffde27419090460656d12
6f2d15efd8cf732bea3e8539820dc153f41e396b
792 F20101119_AABRES acquaye_l_Page_044.txt
3b7cf6944640ec6ac58c80328c7c52dc
13ae207c48ed90281b2cef4ef0e9e2147c72d6b6
5669 F20101119_AABQZM acquaye_l_Page_052thm.jpg
aab6a5d97bf0f13182ee62425166f1d9
e280f3ce607bb70b23447d5447028901dba157ba
25205 F20101119_AABQYX acquaye_l_Page_079.pro
a3e2378aa698c545f41ce7d3bb25181d
7b9e5344cf7b38c23d917604910776ce080d3134
1458 F20101119_AABRFG acquaye_l_Page_003.pro
b859ef488b550b8b417cc17eb2c8c997
22f556bf1889fd19e2fbf7d8a93ffaae280048ff
859 F20101119_AABRET acquaye_l_Page_095.txt
8d9a5708e3db29da9c3e746b9d4b39ec
48b5084b26a5daf317def2beca017c777c3c5926
12401 F20101119_AABQZN acquaye_l_Page_005.pro
293e287e60f18bcf7108b2134acd9fea
cfba02734ab6c3c7e56f5cc6cebb515888e218a4
619286 F20101119_AABQYY acquaye_l_Page_026.jp2
a6c488788337acdfde77849b4094004c
5972f0fd61128a1f13ff9a8384b9566c65865b10
5981 F20101119_AABRFH acquaye_l_Page_040thm.jpg
15d25cf35d7c24c44aa92dca0518885d
d05b74f78f954e5f8c0003e80ae5e3658e5befcd
F20101119_AABREU acquaye_l_Page_063.tif
9d2e22d0cd4227cdee4d3821f180e410
a6f23782d002035de4391b952057ff03efd51a0e
32281 F20101119_AABQZO acquaye_l_Page_115.pro
4acc81f870d9ad63205aa07e11551310
b9b98a9a9fdef9800516f1ce9582dafef833f36d
6144 F20101119_AABQYZ acquaye_l_Page_043thm.jpg
bd044c822d07d774f1c41c3f42450877
4c0f6fed78d7ac117679032fd5468f6792f7f581
F20101119_AABRFI acquaye_l_Page_052.tif
627c169639e3d08cee907c3d67898668
b913efbbcc2662097dd2bb69280353ff28382fe9
3508 F20101119_AABREV acquaye_l_Page_044thm.jpg
aa2629afa4691a34c6ffea14d84d8f53
ff4ca7ddd1c0d9b5210f36a7e64c97b139304f78
5920 F20101119_AABQZP acquaye_l_Page_120thm.jpg
364f7f6b4e233f08affadd717a059cd0
99da82e3e6e9c8b510d6072284afce4fc2e69dc0
1705 F20101119_AABRFJ acquaye_l_Page_042.txt
ebf9e598f9d821f9afad18d8acbe4717
9216f63f40d89198595f7c2904511a14dcaddcc4
73709 F20101119_AABREW acquaye_l_Page_032.jpg
a1bf86f202c5f723247a20ecc9d77ae9
c9cc7f82e35dedd92fe42a086e9eefb4dc9d6374
26194 F20101119_AABQZQ acquaye_l_Page_001.jpg
3dd4ad5b5c918a1098578105b49a34a1
aee6c3e18c32e08e2f12cf19342a859b6084c155
50837 F20101119_AABRFK acquaye_l_Page_113.jpg
78727a0bc12481206a3eba9950bd4aaf
53ea2b395d423d97a090a67e0762701109ef10c7
52952 F20101119_AABREX acquaye_l_Page_124.jpg
a4130a0b3d22da7ed22113b9219ac7ca
544d72fc4262856a0889a26fcd35780a7c9c6988
911789 F20101119_AABQZR acquaye_l_Page_115.jp2
d873c3e3f5207d754e418d8fd01623c5
38015e8e81c29b0847409be73bd94358f1ac2ef3
67572 F20101119_AABRGA acquaye_l_Page_018.jpg
3d4efdf1728d3fa958407ec932081af7
385c746d9a9c9589dd5b3596f81f619198379026
201755 F20101119_AABRFL UFE0013837_00001.xml
ce6312a5ea01cdedd613e780b70ace57
a5d341d88b0ab58aa030a0dee04281e7892ebf0c
39178 F20101119_AABREY acquaye_l_Page_042.pro
57106c7793a765accd490763e0d998e5
5154fa89dcdd83d549c6d8fb43700d6e3bf4e9b3
78892 F20101119_AABQZS acquaye_l_Page_014.jp2
105e77422ef75c461c1ffb8b95314dba
6b8bdd215c8ddedf96168b6fff9f9b1c19577cb2
64195 F20101119_AABRGB acquaye_l_Page_019.jpg
453c09f08799286f538c05294d280bf0
a1abb9b992428e5a948396747532b26f6ea68745
67592 F20101119_AABREZ acquaye_l_Page_012.pro
e32b426ea7ce1af2947685ffef110edf
48fb87dfc996d2623408ab4d9ab36fad8a7d1fe2
65096 F20101119_AABQZT acquaye_l_Page_043.jpg
d1cb12b89767127429f76a94274eac99
641b4aa88780ada92e4ffa25af59c20727d17436
15627 F20101119_AABQZU acquaye_l_Page_100.QC.jpg
1596ae9c144e4ae0c1afad6a9942d7ef
e92ec90b6e98e72d0af747c36d41a1b4b090d6f8
64422 F20101119_AABRGC acquaye_l_Page_020.jpg
a05ccc352d470832105d60b2a117942f
272f350146f68cede3b2b99486d57ce75f5eb3ea
62672 F20101119_AABRFO acquaye_l_Page_004.jpg
d9a3869c4e561b8ba329bf52d3dae491
431d12750b963926c54bc9bef7bfb14920e0397a
72715 F20101119_AABQZV acquaye_l_Page_039.jpg
8a182a02fbbb224edcb4a2e44ba3889d
82f41a08ec62f957d7f36ca1f44c93b0654d9cb8
61026 F20101119_AABRGD acquaye_l_Page_021.jpg
c760197ad7530346df89bcf0e1facdcf
a5a2a519fb97d1fe7a4e48aa2daa05f11ec9bbf9
23766 F20101119_AABRFP acquaye_l_Page_005.jpg
3c2de7d994ecde143f4b56003ca06616
6eb13436d5b63a8091ee46bece7b767b0a3f0135
34741 F20101119_AABRGE acquaye_l_Page_022.jpg
6202612535703c679b9817876e43c385
e08c2c57060a53396c7b2aa6fc0a33711edf40c2
71228 F20101119_AABRFQ acquaye_l_Page_006.jpg
44f2d44bdd4f4e1019dd5cf8bcb9df4d
45b8c4845b0e9f6e3d2233913910f3e28517f80f
2359 F20101119_AABQZW acquaye_l_Page_078.txt
9b38d1ecc0ffce6177edec22c67625c4
7ea1142fd3758a537503073d9a9d4c4c6ee9534e
63541 F20101119_AABRGF acquaye_l_Page_024.jpg
08652dc138e680f8189a4ae7d4a48c7c
39a52da3dc585830168ec18ffe57175cc3884177
97280 F20101119_AABRFR acquaye_l_Page_007.jpg
8dff85da8f09d40fba0d108f4a3d5c11
6d5055dc9cfcb34d05f3c6260e79e408431fad26


Permanent Link: http://ufdc.ufl.edu/UFE0013837/00001

Material Information

Title: Effect of High Curing Temperatures on the Strength, Durability and Potential of Delayed Ettringite Formation in Mass Concrete Structures
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0013837:00001

Permanent Link: http://ufdc.ufl.edu/UFE0013837/00001

Material Information

Title: Effect of High Curing Temperatures on the Strength, Durability and Potential of Delayed Ettringite Formation in Mass Concrete Structures
Physical Description: Mixed Material
Copyright Date: 2008

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0013837:00001


This item has the following downloads:


Full Text












EFFECT OF HIGH CURING TEMPERATURES ON THE STRENGTH,
DURABILITY AND POTENTIAL OF DELAYED ETTRINGITE FORMATION IN
MASS CONCRETE STRUCTURES













By

LUCY ACQUAYE


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2006

































Copyright 2006

by

LUCY ACQUAYE

































This document is dedicated to David and Anna.















ACKNOWLEDGMENTS

My sincere gratitude goes to Dr. Abdol Chini whose constant advice,

encouragement, patience and dedication to my graduate studies has resulted in this

dissertation. Dr. Chini admitted me into this distinguished university and program where

all my academic and professional goals were met and exceeded. He was the committee

chair for both my master's thesis and doctoral dissertation, and his kindness and

inspiration have sustained me throughout my studies. Dr. Chini provided outstanding

academic and professional guidance during my doctoral studies and gave me wonderful

opportunities to excel academically and professionally.

The research reported here was sponsored by the Florida Department of

Transportation (FDOT). Sincere appreciation is due to the FDOT State Materials Office

Concrete Lab employees in Gainesville and Richard DeLorenzo for his guidance and help

in sampling and testing concrete specimens. My sincere thanks go to Barbara Beatty of

the FDOT chemical lab for her support

My sincere thanks go to Dr. Jo Hassel for her constant encouragement and financial

assistance during my doctoral studies. My thanks also go to members of my doctoral

committee for their help in completing this dissertation. I am grateful to the faculty and

staff at the Rinker School of Building Construction for providing a stimulating

environment for my graduate studies. My thanks go to the faculty of the Department of

Building Technology, Kwame Nkrumah University of Science and Technology, Ghana,

for their support throughout my studies.









I am utterly grateful to God for all the wonderful blessings in my life. I am very

grateful to my parents for all the sacrifices they made to see me to such great heights and

for their constant support. I am grateful to my siblings who supported and expanded my

dreams. I am grateful to my husband, Mark for his support and encouragement. I wish to

thank my children David and Anna, whose interest in "mama's homework" spurred me

on to complete this dissertation.
















TABLE OF CONTENTS

page

A C K N O W L E D G M E N T S ................................................................................................. iv

LIST OF TABLES ........... .... ......... ........... ........... .... ......... ............ .. ix

LIST OF FIGURES ......... ......................... ...... ........ ............ xi

ABSTRACT ........ .............. ............. ...... ...................... xiv

CHAPTER

1 IN TR OD U CTION ............................................... .. ......................... ..

B background ............................ ............ .... .................. ............... .
O objectives and Scope of R esearch.......................................... ........... ............... 5
R research M methodology ................. .... ...................... .... ........ ................ .6
Im portance of R research ........................................................... ............... ............. 7

2 L IT E R A TU R E R E V IE W .................................................................. .....................8

In tro d u ctio n .................................................................................. 8
C em ent H ydration ..................................... ... ........... ...... .. ...................... 9
Effect of Curing Temperature on the Microstructure of Hydrated Cement Paste......12
D ense Shell of H ydration Products........................................................ .................. 14
Effect of Curing Temperature on Concrete Strength Development...........................15
Effect of Temperature on the Durability of Concrete...............................................17
Fly ash and Slag in Concrete ............. ....... ....................................................... 19
Delayed Ettringite Formation (DEF) in Concrete ............................................... 22

3 RESEARCH M ETHODOLOGY ........................................ .......................... 27

In tro d u ctio n .......................................................................................2 7
D degree of H ydration ............................................... ........ ................. 28
In tro d u ctio n ................................................................................................... 2 8
M methodology ................ ............................... ..................29
Calculations to Determine the Degree of Hydration .............................. 35
Problems Encountered in the Experimental Process............... ............ .....35
M ass C concrete Experim ents ............................................... ............................ 42
C om pressiv e Strength ............................................................... .....................44









Resistance to Chloride Penetration......................... ......................... 44
Tim e to C orrosion........... ....................... .. .................... .. ...... ............45
Density and Percentage of Voids in Hardened Concrete ...............................45
Microstructure analysis Scanning Electron Microscope (SEM) ....................46
Intro du action .............................................................4 6
Signals of Interest ................................................... .. .. ........ .... 46
SEM U se in C concrete ........................................................ ............... 48
E xperim ental W ork ................................................... ............... ... 48
Sample Preparation for SEM Examination .............. ............... 49

4 TEST RESULTS AND DISCUSSION ........................................ ...............51

Introduction ................. ......... ...................................... ..... .......... .51
Phase 1 Determination of Degree of Hydration ............................................... 51
Phase 2 Tests of M ass Concrete ..................................................... ............. 57
D egree of H ydration R results .................................... ............................ ......... 63
Com pressive Strength R esults................................... ............................. ....... 65
Resistance to Chloride Ion Penetration .................................... ............... 68
Density and Percentage of Voids Results.........................................................69
Time to Corrosion Results ......... ............... ................... 72
Phase 3 M icrostructural A analysis ...................................................... ................. .74
SEM Observations of Plain Cement M ixes..................................................... 74
Effect of Curing Temperature on the Presence of Ettringite Crystals..........74
Effect of Curing Duration on the Amount of Ettringite Crystals formed ....75
SEM Observations of Fly Ash Mixes ..............................78
In tro d u ctio n ......................... ..... .... .. ....... .. .............................7 8
Effect of Curing Temperature on the Presence of Ettringite Crystals..........79
Effect of Curing Duration on the Amount of Ettringite Crystals formed
in V o id s ................................................. ................ 8 0
SEM Observations of Slag M ixes ............................................ ............... 82
In tro d u ctio n ......................... ..... .... .. ....... .. .............................8 2
Effect of Curing Temperature on the Presence of Ettringite Crystals..........83
Effect of Curing Duration on the Amount of Ettringite Crystals formed ....83

5 CONCLUSIONS AND RECOMMENDATIONS ............... .................... ..........87

Intro du action ...................................... ................................................ 87
C on clu sion s ........................ ....... .... .... .... .. ..................................... 87
Research Implications for Mass Concrete Structures ..........................................92
Recom m endations....... ........ .............................. .. .... ......... ........ 93

APPENDIX

A CON CRETE M IX D E SIGN S......................................................................... ...... 96

M ix 1 P lain C em ent M ix ........................................ ...................... .....................96
M ix 2 18% Fly A sh M ix ..................................................................... 97









M ix 3 P lain C em ent M ix .............................................................. .....................98
M ix 4- 18% F ly A sh M ix ......... ................................................................... ......... 99
M ix 5 Plain C em ent M ix ............................................... ............................ .. 100
M ix 6 50% Slag M ix .......... ... ........................ ........ ... .... ................. 101
M ix 7 Plain C em ent M ix ............................................... ............................ 102

B ADDITIONAL SEM IMAGES............................. ................... .................. 103

Part 1 Mix 1:Plain Cement Only Mix (0%FA) ............................................... 103
Part 2 Mix 2: 18% Fly Ash Mix........ ....... .... ....................................... 109
Part 3 M ix 3: 50% Slag M ix ......... .............................................. ............... 12

LIST O F R EFEREN CE S ... .... ............................................................ ............... 115

BIOGRAPHICAL SKETCH ...... ........ ................... ............................ 19







































viii
















LIST OF TABLES


Table page

2.1 Major Compounds of Portland Cement .... ................ ....................9

2 .2 M measured P orosity ............................................................................ ...... 18

2.3 Results of compressive strength and AASHTO T-277 test...................................21

2.4 AASHTO T-277 tests for charge passed...... ....................... ............22

2.5 Rate of chloride diffusion ppm/day (average of three replicates, Norwegian test)..22

3.1 Properties of Cem ent and Fly ash ........................................ ........................ 30

3.2 Properties of Blast furnace slag -ASTM C 989-97b, AASHTO M302...................30

3.3 M ix proportions of paste m ixes ............... ........... ................................................31

3.4 Time to 70% hydration in plain cement mix................................. ...... ............ ...37

3.5 Concrete Mix 1 0% Fly Ash (Isothermal Curing)...................... ....................38

3.6 Binders used in mass concrete mixes by the FDOT..................................... 41

3.7 Mixture Proportions for FDOT Class IV mass concrete........................................43

4.1 Nonevaporabe water content for various Fly ash mixes Lam et al. (2000)..............54

4.2 Degree of hydration results for plain cement mixes .............................................55

4.3 Degree of hydration for 18% fly ash mixes ...... .................................... 56

4.4 Degree of hydration for 50% fly ash mixes ...... .................................... 57

4.5 Degree of hydration for cement and blast furnace slag mixes .............. ...............57

4.6 Summary of Plastic Properties of Fresh Concrete. .............................................58

4.7 Results of concrete mixes Ml and M2................................. ...............58

4.8 Results of concrete mixes M 3 and M 4 ... .................. .. ........................ ............ 59









4.9 Results of concrete mixes M5 and M6.................. ...... ...............60

4.10 Results of concrete mixes M 7 and M 8......... ...... ..... ................ .. ............. 61

4.11 Summary of Results of concrete mixes Ml M2, M3 and M4.............................62

4.12 Summary of Results of concrete mixes M5, M6, M7 and M8.............................63

4.13 Compressive strength as a ratio of 28-day samples cured at 73oF ........................66

4.14 Compressive strength as a ratio of the 28-day samples cured at 73oF ....................67

5.1 Compressive strength samples cured isothermally ..............................................89

5.2 RCP for sam ples cured isotherm ally ................................... .......... ................... 90

5.3 Compressive strength for adiabatically cured samples ........................................90

5.4 RCP and Ettringite Formation for adiabatically cured samples.............................93
















LIST OF FIGURES


Figure p

2.1 External therm al cracking ............................................... ............................. 10

2.2 Internal therm al cracking ......................................................... .............. 11

2.3 Effect of curing temperature on concrete strength development ...........................16

2.4 Pore size distribution with age for 30% Fly ash mix ............................................20

3.1 Paste samples cast in one-ounce polypropylene screw cap jars.............................32

3.2 Oven used to cure samples at 200F ............... .................... .................32

3.3 Samples cured in four-ounce polypropylene jars after demolding .....................33

3.4 Sam ples crushed in m echanical crusher........................................ .....................33

3.5 Approximately 3 grams of samples weighed. .................................. ...............34

3.6 Samples removed after ignition at 18320F. ................................... ............... 34

3.7 Curing tanks used for samples at elevated temperatures............... ...................36

3.8 Degree of hydration (wnu = 0.23)................. ......... .. ........ ........ 37

3.9 Compressive strength results ......... .............. .... ............... 38

3.10 Rapid Chloride Permeability (RCP) results .................................. ............... 39

3.11 Degree of hydration based on adiabatic curing (wnu = 0.23)..............................42

3.12 Different interactions of an electron beam (PE) with the solid target. BSE =
backscattered electrons, SE = secondary electrons, X = x-ray, AE = auger
e le c tro n s .......................................................................... 4 7

3.13 The EDAX analysis of "gel" showing calcium, sulfur, and aluminum peaks
typical for ettringite .................. .................................. .... .. ........ .... 49

3.14 Mortar samples mounted on stubs for SEM examination.............. .. ................50









4.1 Degree of hydration for 0%FA and 18%FA mixes...............................................64

4.2 Degree of hydration for 0%BFS and 50%BFS mixes............... .... .............. 65

4.3 Compressive strengths for 0%FA and 18%FA mixes............................................66

4.4 Compressive strengths for 0%BFS and 50%BFS mixes............... ...................67

4.5 Chloride Ion Penetration results for 0%FA and 18%FA mixes.............................68

4.6 Chloride Ion Penetration results for 0%BFS and 50%BFS mixes...........................69

4.7 D ensity for 0% FA and 18% FA m ixes ................................................. ................70

4.8 Density for 0%BFS and 50%BFS mixes....................................... ............... 70

4.9 Percentage of voids for 0%FA and 18%FA mixes ...............................................71

4.10 Percentage of voids for 0%BFS and 50%BFS mixes ...........................................72

4.11 Time to Corrosion results for all mixes....................... ....................73

4.12 The RCP at 91days expressed in terms of Time to Corrosion unit..........................73

4.13 Well-defined Monosulphate (M) crystals in a void...............................................76

4.14 Void with clusters of Ettringite (E) crystals..............................................76

4.15 Void containing both Monosulphate (M) and Ettringite (E) crystals......................77

4.16 Voids containing Ettringite (E) some appear almost full of it ...............................77

4.17 Void completely filled with fibrous Ettringite (E)................................................78

4.18 Void containing hexagonal plates of Monosulphate (M) ........................................80

4.19 Void showing Monosulphate (M) transformed into Ettringite (E) ..........................81

4.20 Clusters of Fibrous Ettringite (E) in void ...... ......... ...................................... 81

4.21 Sam ple w ith em pty air V oids (V) ........................................ ........................ 84

4.22 Higher m agnification of 4.32 .............................................................................84

4.23 Sam ple w ith em pty air Void (V) ..................................................... ............ 85

4.24 Reacting Slag (S) particle with Ettringite (E) formed............................................85

4.25 Slag particle completely covered with Ettringite (E)............................................86









B.1 Void with monosulphate (M), no ettringite found ..............................................103

B .2 Close-up view of Figure B .1 ................................................... .................. 104

B.3 Void with ettringite (E) and monosulphate (M).....................................................104

B.4 Void with ettringite (E) crystals................................ ........................ ......... 105

B.5 Void showing monosulphate and the early formation of ettringite (E) crystals ....105

B.6 Void showing ball of ettringite (E) crystals ................................. .....................106

B.7 Void showing balls of ettringite (E) crystals........................................................106

B.8 Voids showing ettringite (E) crystals some almost full ......................................107

B.9 Voids showing ettringite (E) and monosulphate crystals....................................107

B.10 Ettringite (E) crystals in and around vicinity of void............................................ 108

B 11 E ttringite (E ) crystals in void ........................................................................ ... 108

B.12 Fly ash particle with reaction around rim.................................... ............... 109

B.13 Fly ash particle with reaction around rim.................................... ............... 109

B 14 V oid containing m onosulphate..................................... ............................ ........ 110

B 15 V oid containing ettringite crystals ................................... ................................... 110

B. 16 Close up view of ettringite crystals in Figure B.15..............................................111

B 17 Reacting fly ash particle .................................................... .... ............... 111

B.18 Slag particles showing som e early reaction ..........................................................112

B. 19 Slag particles showing reaction on surface ...................................................112

B.20 Slag particle showing reaction on surface..........................................................113

B.21 Slag particle showing reaction on surface..........................................................113

B.22 Ettringite formed around surface of reacting slag particle...................................114

B .23 Close-up view of Figure B .22...................................................... .............. 114















Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

EFFECT OF HIGH CURING TEMPERATURES ON THE STRENGTH,
DURABILITY AND POTENTIAL OF DELAYED ETTRINGITE FORMATION IN
MASS CONCRETE STRUCTURES

By

Lucy Acquaye

May 2006

Chair: Abdol Chini
Major Department: Design, Construction and Planning

The Florida Department of Transportation (FDOT) has in recent years recorded

high core temperatures of 170F 200F during curing of mass concrete elements.

Frequent reports of such high temperatures have raised concerns of the strength and

durability of concrete cured at such high temperatures. Additional concerns have been

raised of the possibility of expansions of the hardened concrete from delayed ettringite

formation (DEF) and its subsequent deterioration. FDOT specifies a maximum

differential temperature of 35F between the core and exterior of mass concrete elements

during curing to avoid cracking from high thermal stresses and a shorter service life of

the structure. However no limit is specified for the maximum curing temperature. This

dissertation investigated the effects of high temperatures on the strength, durability and

potential of delayed ettringite formation in mass concrete mixes.









Using typical FDOT Class IV mass concrete mixes it was found that elevated

curing temperatures resulted in lower later-age strengths. Blending the cement with fly

ash and slag resulted in increased strength and durability when compared to the plain

cement mixes for all curing durations and temperatures.

Investigating the potential of delayed ettringite formation in the concrete mixes

cured at elevated temperatures and the effect of permeability on the onset and amount of

ettringite formed showed that:

1. At room temperature curing no ettringite was observed when samples were

examined microscopically using a scanning electron microscope (SEM) at

7, 28 and 91 days, notwithstanding having the highest permeability values.

2. At elevated curing temperatures of 160 and 180F, the plain cement mixes

had high permeability values and microscopic examination showed

ettringite crystals in void spaces at 28 days. At 91 days these samples

showed voids almost filled with the crystals.

3. Concrete mixes containing 18% fly ash and 50% slag and cured at the

elevated temperatures resulted in much lower permeability. The low

permeability of the blends delayed the onset of ettringite formation as well

as the amount formed when compared to the plain cement mixes. This was

particularly evident in the slag mixes.














CHAPTER 1
INTRODUCTION

Background

In recent years, Florida Department of Transportation (FDOT) has recorded high

core temperatures of 170 200F during curing of mass concrete structures. Mass

concrete structures as defined in the FDOT Structures Design Guidelines is "any large

volume of cast-in-place or precast concrete with dimensions large enough to require that

measures be taken to cope with the generation of heat and attendant volume change so as

to minimize cracking" (FDOT, 2002). Although a definite size has not been determined, a

concrete member, which is 2 ft to 3 ft thick, is considered to be mass concrete.

In its mass concrete specifications, FDOT does not set a limit on the maximum core

temperature during curing. FDOT however in its specification for mass concrete, limits

the differential curing temperature between the core and exterior of the mass concrete to

35F. Limiting the deferential temperature is specified to avoid cracking due to excessive

thermal stresses in the concrete. Cracking due to thermal behavior may cause loss of

structural integrity and monolithic action, or may cause excessive seepage and shortening

of the service life of the concrete structure or may be aesthetically objectionable

(American Concrete Institute (ACI), 1999)

The high core temperatures were recorded in mass concrete structures cured in

accordance with maintaining the maximum differential temperature of 35F throughout

the curing period. These high temperatures have raised concerns on the effects of high

curing temperatures on the strength and durability of mass concrete structures. Of









additional concern is the potential of delayed ettringite formation (DEF) in the hardened

concrete when cured at such high temperatures and its associated deterioration of the

concrete structure. Ettringite in Portland cement systems is the first hydrate to crystallize

during the first hour of placing the concrete. At high curing temperatures (>160F), the

ettringite becomes unstable and decomposes only to reform later in the hardened concrete

in the presence of moisture with associated cracking of the structure. Concretes cured at

temperatures above 160F are susceptible to DEF in the hardened concrete. Isolated cases

of expansion and cracking from DEF have occurred in some in-situ concretes of large

section and high cement content in the U.K. These in-situ concretes were cast in the

summer months and the possible early peak temperature was between 185 and 200F.

The cracking took between 8 and 20 years to manifest itself (Hobbs, 1999). The cement-

water reaction during the hydration of cement is an exothermic reaction. Due to the low

diffusivity of heat from concrete, it acts as a insulator and in a large concrete mass, the

heat liberated from the reaction can accumulate and lead to high temperatures.

A study by Tarkhan (2000) of mass concrete specifications used by state highway

agencies in the United States found that nine highway agencies of the forty-three

respondents had mass concrete specifications. Highway agencies of Illinois and Kentucky

specified a maximum curing temperature of 160F. A maximum differential temperature

of 35F was specified by eight of the nine highway agencies with mass concrete

specifications. 65% of all respondents believed that there is a need for further research

into the effects of high curing temperature on concrete properties. Reasons cited to limit

the maximum curing temperature of mass concrete elements included:

* Avoid reduction of later age strength,









* Minimize swelling and shrinkage cracking,

* Increase the durability of the concrete and

* Decrease the formation of delayed ettringite (DEF) in the hardened concrete and its
subsequent damage.

There are several known potential causes of cracking in concrete. One is excessive

stress due to applied loads and another is cracks due to drying shrinkage or temperature

changes in restrained conditions. Mass concrete is often subject to both of these stresses;

therefore, prevention of cracking is a vital consideration in the design of these structures.

However, during the construction process, the most pressing item is the control of drying

shrinkage and differential temperature. The rise in temperature of mass concrete depends

on the initial concrete temperature and volume to surface area ratio. Furthermore, the

increase in temperature is affected predominantly by the chemical composition of

cement, with C3A (Tricalcium Aluminate) and C3S (Tricalcium Silicate) being the

compounds primarily responsible for elevated temperature development. The water-

cement ratio, fineness of the cement, concrete mixture temperature and temperature of

curing are also contributors to the development of heat. When the water-cement ratio,

fineness, or curing temperature is increased, the heat of hydration is increased. The rate

and amount of heat generated are important in any concrete construction requiring

considerable mass. The heat accumulated must be rapidly dissipated in order to impede a

significant rise in concrete temperature at the center of the structure. The excessive rise

in concrete temperature is undesirable since the concrete will harden faster at an elevated

temperature and any non-uniform cooling of the concrete structure may create stresses

due to thermal contraction.









The current method of preventing cracking in mass concrete is to maintain a

temperature differential (between the surface and the core) of no more than 35F. Control

of temperature gain is possible (Kosmatka and Panarese, 1994) through the following:

* Low-heat-of-hydration Portland or blended cement

* Reductions in the initial concrete temperature to approximately 50TF by cooling the
concrete ingredients

* Cooling the concrete through the use of embedded cooling pipes during curing

* Low lifts: 5 ft or less during placement.

* Pozzolans: the heat of hydration of pozzolan is approximately 25 to 50% that of
cement.

When the massive concrete specified has high cement contents (500 to 1000 lb. per

cu yard), many of the above mentioned placing methods cannot be used. For concretes

that are often used in mat foundations and power plants good placing methods (Kosmatka

and Panarese, 1994), are the following:

* Place the entire concrete section in one continuous pour

* Avoid external restraint from adjacent concrete elements

* Control internal differential thermal strains by preventing the concrete from
experiencing excessive temperature differential between the internal concrete and the
surface.

In order to control the internal temperature differential, the concrete is insulated to

keep it warm (tenting, quilts, or sand on polyethylene sheeting). Studies have shown that

the maximum temperature differential (MTD) between the interior and exterior concrete

should not exceed 35F to avoid surface cracking.

The Florida Department of Transportation Standard Specifications Section 450

allows the maximum curing temperature of 158 to 1760F for accelerated curing of pre-









stressed concrete elements. However, accelerated curing is conducted under suitable

enclosures with a controlled environment to avoid thermal shock and minimize moisture

loss. These conditions do not exist in mass concrete operations and such high

temperatures may have detrimental effects on concrete properties. It is therefore

necessary to revisit the current specification for mass concrete, and examine the need for

additional provisions. The provisions that need to be reconsidered are maximum internal

concrete temperature and/or maximum concrete placing temperature.

Objectives and Scope of Research

The objectives of this dissertation were as follows:

* To determine the effects of concrete curing temperature on the strength and durability

of concrete, using typical FDOT Class IV mass concrete mixes.

* To determine the effects of fly ash and slag on the strength and durability of concrete

cured at elevated temperatures.

* To determine the propensity of typical FDOT class IV mass concrete mixes to DEF

when cured at elevated temperatures.

* To determine the effect of permeability of the concrete microstructure on the onset

and amount of ettringite formed.

* To determine the effect of replacing part of the cement with fly ash or slag on the

onset and amount of ettringite crystals formed in samples cured at the elevated

temperatures.

The concrete used for this research will be typical class IV FDOT mass concrete

mixes. The use of fly ash and slag as partial replacement of cement is known to increase

the durability and strength of concrete. There is little information available on its

influence on ettringite formation in concrete cured at elevated temperatures. This









dissertation reports findings on how the strength and durability of concrete cured at the

elevated temperatures. Additionally by the use of Scanning electron Microscope, this

dissertation presents findings on ettringite formation in concrete curried at elevated

temperatures and how this is influence by the addition of fly ash and slag.

Research Methodology

This dissertation was conducted by performing the following tasks:

1. Performed a state of the art review of work reported on heat generation in mass

concrete and measures taken to avoid cracks and premature deterioration of

concrete.

2. Evaluation of the effects of concrete temperature on the properties of hardened

concrete. The evaluation included the following tests: compressive strengths,

rapid chloride permeability, time to corrosion, volume of permeable voids, and

microstructure analysis using the Scanning Electron Microscope (SEM).

a. Class IV Structural concrete mixes, consisting of 18% replacement by

weight of cement with class F fly ash, were used. Specimens required for

the above mentioned tests were cast at room temperature and stored in

water tanks where they were subjected to different curing temperatures (73

to 2000F).

b. Other mixes tested were similar to Part a, except that 50% of cement was

replaced by slag. Molds were cast and stored as explained in part a.

3. Analyzed the test results and determine the maximum internal concrete

temperature above which the concrete properties will be affected (later age

strength reduction, durability problems, and DEF).









4. Examination of the current FDOT mass concrete specifications and suggest, if

necessary, the requirement for maximum curing temperature or maximum

concrete placement temperature.

Importance of Research

The research presented in this dissertation will provide information on the effect of

elevated curing temperatures on the strength and durability of typical class IV FDOT

mass concrete mixes. Additionally information from this research will serve as a basis to

decide if the specification for mass concrete used by FDOT should specify a limit on the

maximum curing temperature. Fly ash and slag are used in typical class IV mass concrete

and this research will show their effect at high curing temperatures on the strength and

durability of the concrete and the potential of DEF formation.














CHAPTER 2
LITERATURE REVIEW

Introduction

This chapter presents a state-of-the-art review of literature on how strength,

durability and formation of delayed ettringite (DEF) in concrete are affected by high

curing temperatures. In massive concrete structures, high curing temperatures result from

a combination of heat produced by the hydration of concrete and the relatively poor heat

dissipation of concrete. Although various measures are implemented to limit the

maximum temperatures in mass concrete, a high core temperature of 200F has been

recorded in Florida for a mass concrete structure cast during the summer. While such

concrete meets the specification of maintaining a maximum differential temperature of

35F between the core and surface of the mass concrete structure, of major concern is

what happens to the strength, durability and DEF in the concrete when subjected to such

high curing temperatures.

This chapter reviews how heat is generated in concrete from the hydration of

cement. Cracking of concrete due to the heat as well as the microstructure formed under

such high temperature curing is examined. The influence of the microstructure formed

under high curing temperatures on the strength and durability of concrete are presented.

To improve the quality of concrete structures cured under high temperatures, other

cementitious materials such as fly ash and blast furnace slag have gained increasing use

in mass concrete structures. The effects on the microstructure of concrete due to the use

of such materials and the influence on strength and durability of mass concrete structure









are reviewed. A final review is presented on how high curing temperatures makes

hardened concrete structures susceptible to damage from the formation of delayed

ettringite (DEF).

Cement Hydration

The compounds of Portland cement (see Table 2.1) are nonequilibrium products of

high temperature reactions in a high-energy state. When cement is hydrated, the

compounds react with water to acquire stable low-energy states, and the process is

accompanied by the release of energy in the form of heat (Mehta and Monteiro, 1993).

Cement acquires its adhesive property from its reaction with water by forming products,

which possess setting, and hardening properties.

Table 2.1 Major Compounds of Portland Cement
Name of compound Oxide composition Abbreviation

Tricalcium Silicate 3 CaO. SiO2 C3S

Dicalcium Silicate 2CaO.SiO2 C2S

Tricalcium Aluminate 3CaO.A1203 C3A

Tetracalcium Aluminoferritte 4CaO.Al203.Fe203 C4AF



The heat generated from the hydration of cement causes a rise in temperature of

concrete. If this rise occurred uniformly throughout a given concrete element without any

external restraint, the element would expand until the maximum temperature has been

reached. The concrete will then cool down with uniform contraction as it loses heat to the

ambient atmosphere. This uniform expansion and contraction will result in no thermal

stresses within the concrete element. According to Neville (1997), restraint exists in all

but the smallest of concrete members. These thermal restraints result in external and

internal cracking of the concrete. Figure 2.1 shows an example of temperature change,









which causes external cracking of large concrete mass. The critical 20C (35F)

temperature difference occurs during cooling (FitzGibbon, 1976).


800C
SCrack condition as
surface cools too fast
60( C




S2 0 Core temp.

200C
Surface temp.


1 2 3 4 days

Figure 2.1 External thermal cracking

In massive concrete structures, internal restraint occurs from the inability of the

heat to dissipate quickly from the core of the member due to the low thermal diffusivity

of the concrete. A temperature differential is set up between the core of the concrete and

the surface due to the accumulation of the heat from the hydration process. The unequal

thermal expansion in the various parts of the concrete member results in stresses,

compressive in one part and tensile in the other. Cracking of the surface results when the

tensile stresses at the surface of the element due to the expansion of the core exceed the

tensile strength of the concrete. According to FitzGibbon (1976), the cracking strain of

concrete is reached when an internal thermal differential of 200C (360F) is exceeded.

Figure 2.2 shows a pattern of temperature change, which causes internal cracking of a

large concrete mass. The critical 200C (360F) temperature is reached during heating but









cracks open only when the interior has cooled through a greater temperature range than

the exterior.

-Crack initiated but does
not open until core cools
through greater range
than surface
600C -




400C

Core temp.

200C Surface temp.





1 2 3 4 days

Figure 2.2 Internal thermal cracking

Cracking due to thermal behavior may cause loss of structural integrity and

monolithic action or may cause extreme seepage and shorten the service life of the

concrete structure. Various measure are undertaken to reduce the temperature rise in large

concrete pours. Notable among these measures include:

o The prudent selection of a low-heat-generating cement system including

pozzolans;

o The reduction of the cementitious content;

o The careful production control of aggregate gradations and the use of large-size

aggregates in efficient mixes with low cement contents;









o The precooling of aggregates and mixing water (or the watching of ice in place of

mixing water) to make possible a low concrete temperature as placed;

o The use of air-entraining admixtures and chemical admixtures to improve both the

fresh and hardened properties of the concrete;

o Coordinating construction schedules with seasonal changes to establish lift

heights and placing frequencies;

o The use of special mixing and placing equipment to quickly place cooled concrete

with minimum absorption of ambient heat;

o Dissipating heat from the hardened concrete by circulating cold water through

embedded piping;

o Insulating surfaces to minimize thermal differentials between the interior and the

exterior of the concrete.

Despite the application of the above-mentioned measures to control temperature

rise in concrete, maximum core temperatures of 200F have been recorded in Florida.

This high temperature have been reached while satisfying the specification for mass

concrete of maintaining a maximum temperature differential of 35F between the core

and the surface of the concrete structure. Of increasing concern is the effect on the

properties of concrete when subjected to such high curing temperatures. An examination

of the microstructure of concrete formed at high curing temperatures is reviewed next.

Effect of Curing Temperature on the Microstructure of Hydrated Cement Paste

Verbeck and Helmuth (1968) found the reactions between cement and water to be

similar to any other chemical reaction, proceeding at a faster rate with increasing

temperature. This rapid initial rate of hydration at higher temperatures they theorize

retards subsequent hydration of the cement producing a non-uniform distribution of the









products of hydration within the paste microstructure. At high temperatures, there is

insufficient time available for the diffusion of the products of hydration away from the

cement particles due to the low solubility and diffusivity of the products of hydration.

This results in a non-uniform precipitation of the products of hydration within the

hardened cement paste.

The results of a calorimetric study on the early hydration of cement as reported by

Neville (1997) indicate that a heat evolution peak occurs at about 6 to 8 hours after the

initialization of the hydration process at normal temperatures. This was revealed from

early hydration reactions of cement, using the conduction calorimeter (Verbeck and

Helmuth, 1968). During this period, the cement undergoes very rapid reactions with 20

percent of the cement hydrating over a 2 or 3-hour period. At an elevated temperature of

105F, these reactions are accelerated with as much as 30 to 40 percent of the cement

hydrating in a 2-hour period. At steam curing temperatures, 50 percent or more of the

cement hydrates in an hour or less.

Products of cement hydration have low solubility and diffusivity and at high curing

temperatures, the rapid hydration does not allow for ample time for the products to

diffuse within the voids. This results in a high concentration of hydration products in a

zone immediately surrounding the grain. This forms a relatively impermeable rim around

the cement grain, which subsequently retards any subsequent hydration (Verbeck and

Helmuth, 1968). This situation does not occur in normal temperature curing where there

is adequate time for the hydration products to diffuse and precipitate relatively uniformly

throughout the interstitial space among the cement grains. The coarse pore structure in









the interstitial space from the high temperature has a detrimental effect on the strength of

concrete.

Further evidence from Goto and Roy (1981) confirms the observation by Verbeck

and Helmuth (1968) of retardation of subsequent cement hydration at high temperatures.

In an examination of the structure of the hydrated cement paste subjected to high

temperatures in its early life, Goto and Roy (1981) found out that curing at 600C (140F)

resulted in a much higher volume of pores larger than 150nm in diameter compared with

curing at 270C (81F). These large pores make the concrete susceptible to deterioration

from harmful substances, which are easily transported through the concrete structure.

A study by Kjelsen et al (1990) of the microstructure of cement pastes hydrated at

temperatures ranging from 41 122F (5 50C) using backscattered imaging found that

the low curing temperatures resulted in a uniform distribution of hydration products and

fine self-contained pores. Elevated temperatures on the other hand resulted in a non-

uniformly distributed hydration products and coarse, interconnected pores. The

microstructure of the hydrated cement paste formed at high curing temperatures affect the

strength and durability of the concrete. The large interconnected pores resulting from

high temperature curing does not make for durable concrete structures. Since strength

resides in the solid parts of a material, the presence of voids as a consequence of high

curing temperature are detrimental to the strength of the concrete.

Dense Shell of Hydration Products

Kjellsen, Detwiler and Gj0rv (1990) support the concept that a dense shell of

hydration products surrounding the cement grains is formed at higher curing

temperatures. Hydration products are more uniformly distributed at lower temperatures.

In addition, at higher temperatures of curing there are five phases as opposed to the









standard four phases at lower temperatures. The five phases are unhydrated cement,

calcium hydroxide, two densities of C-S-H and pores. The strength of the material is

greatly affected by the uniformity of the microstructure. At the elevated temperatures the

C-S-H close to the grains is much denser and stronger. However, the intervals between

the cement grains determine the strength of the concrete. Therefore curing at elevated

temperatures has a harmful effect on the later-age strength of concrete. Additionally

elevated curing temperatures according to Kjellsen, Detwiler and Gj0rv (1990) result in

increased porosity. Kjellsen, Detwiler and Gj0rv (1990) further noted that C3S pastes

that were cured at higher temperatures (50-100C) had a coarser structure, including an

increase of large pores, over those cured at 250C. Even steam curing (97C) resulted in

coarser pore structure. The difference in porosity is attributed mostly to the difference in

volume of pores of radius 750-2300 A. For plain cement pastes of equal water-cement

ratios cured to the same degree of hydration, the higher the curing temperature the greater

the total porosity. The results indicate that large pores have the greatest effect on

permeability. Permeability is a contributing component to most durability problems,

therefore it is suggested that higher curing temperatures possibly reduce the durability of

plain cement concretes.

Effect of Curing Temperature on Concrete Strength Development

The strength of concrete is its ability to resist stress without failure. Strength of

concrete is commonly considered its most valuable property. Strength usually gives an

overall picture of the quality of concrete because it is directly related to the structure of

the hydrated cement paste (Neville, 1997).

A rise in curing temperature according to Neville (1997) speeds up the hydration

process so that the structure of the hydrated cement paste is established early. Although a










higher temperature during placing and setting increases the very early strength, it may

adversely affect the strength from 7 days (Neville, 1997). This is because the rapid initial

hydration according to Verbeck and Helmuth (1968) appears to form products of a poorer

physical structure, probably more porous, so that a proportion of the pores will always

remain unfilled. Since the voids do not contribute to the strength of concrete, a low

temperature with slow hydration will result in a uniform distribution of hydration

products within the interstitial space and high strengths at latter ages.

A fast hydration of cement from high curing temperatures will result in a high early

strength due to more hydration products being formed. At latter ages however, the

retardation in hydration as a result of a dense shell around the hydrating cement grains

will result in a more porous structure and reduced strengths as shown in Figure 2.3

(Verbeck and Helmuth, 1968).




IIF
Aje of Cnrte: 000










S2000
SU


Curling Tempervture-*


Figure 2.3 Effect of curing temperature on concrete strength development









Effect of Temperature on the Durability of Concrete

According to ACI Committee 201, durability of Portland cement concrete is

defined as its ability to resist weathering action, chemical attack, abrasion, or any other

process of deterioration. Durable concrete will retain its original form, quality, and

serviceability when exposed to its environment. Although designers of concrete

structures have been mostly interested in the strength characteristics of concrete,

durability issues in concrete technology have been brought to the forefront in recent times

as a result of the premature failure of nondurable concrete structures.

The pore structure of the concrete determines the ease with which deleterious

harmful substances such as chloride ions are transported into the concrete. Harmful

substance such as chloride ions in concrete attack and corrode the steel resulting in

premature failure of the structure. High curing temperatures in concrete result in porous

concrete. This is because the low diffusivity of the hydration products does not allow for

uniform distribution at high curing temperatures due to the faster reaction rate. These

hydration products precipitate in the vicinity of the cement grains resulting in a more

porous concrete. At low curing temperatures, the hydration products are uniformly

distributed within the interstitial spaces making it difficult for deleterious harmful

substances to be transported into the concrete

Kjellsen et al. (1990) performed an investigation of the pore structure of plain

cement pastes hydrated at 41, 68 and 122F (5, 20 and 50C respectively). The specimens

were tested when they reached 70% hydration, a time marking adequate development of

the microstructure. Two techniques used to measure porosity in this study were mercury

intrusion and backscattered electron images. They theorized that during hydration at

elevated temperatures cement hydration proceeds more rapidly. Subsequently since the









cement has low solubility and low diffusibility, cement hydration products are not able to

disperse at a significant distance from the cement grain in the limited time provided at

high temperature curing. This causes areas of dense hydration products that act as a

barrier, preventing further hydration. When there is a development of dense hydration

product there is also a development of greater volume of large pores and a coarser pore

structure. The large pores correspond to a reduction in the modulus of elasticity of the

concrete indicating increased cracking as it is exposed to structural stresses.

The curing temperature clearly affected the pore structure of hydrated cement paste

as shown in Table 2.4. The higher curing temperature resulted in a greater quantity of

larger pores as well as an increase in the total porosity. These results are in agreement

with the observation by Goto and Roy (1981) that curing at 600C (140F) resulted in a

much higher volume of pores larger than 150nm in diameter compared to curing at 27C

(81 F). These larger pores make the concrete more susceptible to attack by harmful

substances since they provide an easier pathway through the concrete. Permeability is a

contributing factor to various kinds of durability problems, therefore suggesting that high

curing temperatures could reduce the durability of plain cement concretes. The increased

permeability also leads to increased water intrusion to the reinforcing steel and promoting

an increase to the rate of corrosion of the members.

Table 2.2 Measured Porosity
Curing temperature Porosity (MIP + HP) Porosity (BSEI) Standard deviation

410F 33.2% 4.27% .818%
680F 34.2% 10.93% 1.086%
1220F 35.7% 15.11% 1.881%









Campbell and Detwiler (1993) explain that the durability of concrete is a primary

contributor to its satisfactory performance. Agencies typically control the durability of

concrete by restricting the water-cement ratio to 0.45 or less. However, the curing

process is often overlooked, though it also affects the durability of the concrete. A basic

principle noted is that the Portland cement concretes resistance to penetration by chloride

ions is reduced due to coarsening of the cement paste pore structure. Specifying a low

water-cement ratio provides limited effectiveness in bettering the performance of the

concrete.

Fly ash and Slag in Concrete

Class F fly ash is an artificial pozzolanic material, which possesses no cementitious

value, but in finely divided form, in the presence of moisture, chemically reacts with

calcium hydroxide from the Portland cement reaction to form compounds possessing

cementitious properties. The fly ash reaction products closely resemble the calcium

silicate hydrate produced by hydration of Portland cement (Neville, 1997). The fly ash

reaction does not start until sometime after mixing. According to Fraay et al (1989), the

glass material in fly ash is broken down only when the pH value of the pore water is at

least about 13.2. The increase in alkalinity required for the fly ash reaction is achieved

through the reaction of the Portland cement. At high temperatures, the fly ash reaction

takes place sooner due to the increased hydration rate of the cement. Prior to the reaction

of the fly ash particles, they act as nuclei for the precipitation of the cement hydration.

When the pH of the pore water becomes high enough, the products of reaction of fly ash

are formed on the fly ash particles and in their vicinity. With the passage of time, further

products diffuse away and precipitate within the capillary pore system, this result in a

reduction of the capillary porosity and consequently a finer pore structure (Fraay et al,










1989). Figure 2.8 shows the changes in pore size distribution determined by mercury

porosimetry, in cement paste containing 30 percent of Class F fly ash by means of total

cementitious material (Fraay et al, 1989). The cement paste becomes increasingly denser

after the initiation of the pozzolanic reaction of fly ash.

300

S-Age:
S240 -
S< I week



120


601 year


0.0010.01 O.1.
Pore Diameter pm


Figure 2.4 Pore size distribution with age for 30% Fly ash mix

Slag is a waste product in the manufacture of pig iron. Chemically, slag is a

mixture of lime, silica and alumina, the same oxides that make up Portland cement

(Neville, 1997). Compared to the fly ash, finely ground granulated blast-furnace slag is

self-cementing. It does not require calcium hydroxide to form cementitious product such

as calcium silicate hydrates. When used on its own, the amounts of hydration products

formed by the blast-furnace slag is insufficient for application of the material to structural

purposes. Used in combination with Portland cement, the hydration of the slag is

accelerated in the presence of calcium hydroxide and gypsum (Mehta and Monteiro,

1993). The beneficial effects of slag arise form the denser microstructure of the hydrated

cement paste, more of the pore space is filled with the hydration products than in cement

only mixes.










Supplementary cementing materials are suggested to increase the performance of

the concrete. Campbell and Detwiler investigated the optimum mix design for

satisfactory strength and durability of steam-cured concrete with 0 .45 water-cement ratio

and various compositions of Canadian Type 10 cement (ASTM Type I) with slag and

silica fume. The compressive strength of the cylinders after 18 hours of steam curing and

one day of moist curing were compared. The results as shown in Table 2.5 reveal that

slag is effective in reducing the rate of chloride ion diffusion and therefore increasing the

durability of the concrete. However the mixes with silica fume and slag, or silica fume

alone were more durable.

Table 2.3. Results of compressive strength and AASHTO T-277 test
Total Charge passes,
Compressive strength coulombs, average of three
Mix no. Description MPa slices Rating
M1 Control:100% PC 27.3 11130*
M2 30% Slag 25.3 7800
M3 40% Slag 27.9 7690 High
M4 50% Slag 28.9 4500
M5 5.0% SF 32.6 1780 Low
M6 7.5% SF 33.3 910
M7 10.0% SF 36.4 290

M8 30% Slag; 7.5% SF 28.5 350
Very Low
M9 40% Slag; 7.5% SF 31.3 200
M10 30% Slag; 10% SF 34.5 150

*Extrapolated value.




Detwiler, et al. (1994) investigated the chloride penetration of 0.4 and 0.5 water-

cement ratio concretes containing either 5 percent silica fume or 30 percent slag

(substitution by mass) cured at elevated temperatures. They found that higher curing

temperatures resulted in greater penetration of chloride ions. In addition, at any given










temperature, both the silica fume and slag concretes performed better than the Portland

cement concrete. Their studies showed that the use of pozzolanic materials is more

effective than lowering the water-cement ratio from 0.5 to 0.4 in improving the resistance

to chloride ions (Tables 2.6 and 2.7).

Table 2.4 AASHTO T-277 tests for charge passed
Mix w/c 730F 1220F 158F
Portland .40 5700 12,000? 18,000?
Cement .50 9800 13,000f 16,000f
5 % Silica Fume .40 1500 3000 4100
.50 1800 3400 13,000
30% Slag .40 1300 1500 4300
.50 1700 2200 5400

*Charge(coulombs) passed in 6 hr for concretes cured at constant temperatures indicated
to degree of hydration of approximately 70 percent.
tExtrapolated values. These tests were terminated before the full 6 hr had elapsed due to
excessive temperature increases.


Table 2.5 Rate of chloride diffusion ppm/day (average of three replicates, Norwegian
test)
Concrete w/c 730F 1220F 158F
Plain .40 10 12 34
Cement .50 13 15 38
5 % Silica Fume .40 4 7 12
.50 3 5 22
30% Slag .40 3 4 13
.50 6 7 18



Delayed Ettringite Formation (DEF) in Concrete

In the early 1980's, Heinz and Ludwig (1987) observed that precast units made of

high strength concrete that had been heat treated during production, showed damage of

the structure connected with a loss of strength. These damages occurred in those building

components which for several years had been subjected to open-air weathering and









therefore to frequent saturation. The damage was characterized by crack formation

emerging from the edges of the building components as well as a loss of bond between

the cement paste and the coarse aggregates. The damage was attributed to the late

formation of ettringite in the hardened concrete. Delayed ettringite formation (DEF) is

the destructive development of ettringite in concrete, months or years after placement in

an environment where moisture exposure is frequent (Hime and Marusin, 1999). DEF is a

worldwide phenomenon having been found in railway ties (sleepers) produced in

Germany, Finland, The United States, Australia and South Africa (Hobbs 1999, Heinz &

Ludwig 1987, Hime & Marusin, 1999).

Ettringite (C6ASH32) in Portland cement systems is the first hydrate to crystallize

during the first hour of placing the concrete. This is because of the high

sulpfate/aluminate ratio in the solution phase during the first hour of hydration. The

precipitation of early ettringite contributes to stiffening (loss of consistency), setting

(solidification of the paste) and early strength development. Later, after depletion of

sulfate in the solution when the aluminate concentration goes up again due to renewed

hydration of C3S and C4AF, ettringite becomes unstable and is gradually converted into

monosulfate (C4ASHis) which is the final product of Portland cements containing more

than 5 percent of C3A (Mehta & Monteiro, 1993). At high curing temperatures, the

decomposed ettringite reforms in the hardened concrete in the presence of moisture with

the resultant expansion and deterioration of the concrete. In a study of expansions in

mortar samples subjected to higher curing temperatures, Lawrence (1995) found that the

minimum curing temperatures for expansion lie between 65 and 70C. The primary

ettringite is unstable when cured at this temperature due to the amount of alkalis in the









pore liquid. If the concrete is exposed to such temperatures, primary ettringite will not be

formed and that which was formed prior to such a heat treatment will decompose (Stark

& Seyfarth, 1999). Under moist conditions, at or below room temperature, ettringite

again becomes the stable phase and may cause DEF (Heinz, Kalde, Ludwig & Ruediger,

1999).

The microsturcture of concretes and mortars after expansion is characterized by the

presence of bands of ettringite around aggregate particles and within cracks, pores and

voids in the cement paste (Scrivener & Lewis, 1999). The expansive process in DEF is

marked by enlargement of the affected concrete and the development of gross cracking.

In extreme cases, the concrete becomes crumbly and soft, proving evidenced of the

destruction of the effectiveness of the cement paste binder (Diamond, 1996).

DEF is not only limited to precast concrete units, recent observations of DEF in

large sections of in-situ concrete have been made in the U.K. (Johansen & Thaulow,

1999). DEF whether formed as a result of steam curing or from high core temperature

from larger sections of concrete cast in-situ has been found by Diamond (1996) to exhibit

similar crack patterns and microstructural features. The observed crack pattern is that of a

network with component crack segments running partly along aggregate peripheries (rim

cracks), but generally connecting through segments running through the cement paste

(paste crack). Two opposing schools of thought exist as to how DEF leads to expansion

of the concrete. The homogeneous paste expansion theory (Johansen & Thaulow, 1999),

maintains that the paste expands and the DEF is deposited in the gaps created between

the aggregates and the paste as the aggregates do not expand. This theory is refuted by

many writers among them Diamond (1996) who maintain that crystal pressure from the









formation of ettringite better explains the expansion and subsequent deterioration of the

concrete.

The expansion associated with the formation of ettringite is influenced by the

microstructure of the material in which it is deposited and the amount of pore space

available (Taylor, Famy & Scrivener, 2001). Some of the ettringite produced is deposited

freely in available space and does not contribute to expansion. Thus, the expansion does

not depend simply on the amount of ettringite produced. Additionally, expansion depends

on the quality of the pore space. A given amount of ettringite will produce more

expansion if the pores in which it is deposited are small and poorly connected than if they

are large and more highly connected.

SEM examination at 180 days and 5 years of concrete cured at various

temperatures showed the following (Stark & Seyfarth, 1999):

o For normally cured concrete, there was no evidence of ettringite at 180 days but at

5 years the concrete showed a dense structure with fine ettringite needles covered

the pore surfaces, without filling the pores completely. An accumulation of

ettringite in the available spaces due to transportation processes took place within

the time interval.

o At 180 days samples cured at 600C showed small needle-like crystals evenly

distributed on pore surfaces and in interfaces between aggregate and hardened

cement paste. At 5 years the ettringite found was in larger crystals and in

substantially larger amounts than found at 180 days. The concrete was crack-free

comparable to the normally cured concrete. The concrete was intact with no hint






26


of damage, indicating that the existence of ettringite in internal damages of

hardened concretes is not an indication of damaging ettringite formation.

o Samples cured at 900C showed large ettringite crystals in structurally damaged

areas and on surfaces of pores. After 5 years, the concrete was completely

interspersed with microcracks. Pores, microcracks and interfaces were completely

filled with new phase formations of ettringite.














CHAPTER 3
RESEARCH METHODOLOGY

Introduction

This chapter presents the materials, mixtures, and test methods used to evaluate the

effects of elevated curing temperatures on the strength, durability and formation of

Delayed Ettringite (DEF) in mass concrete. The work was divided into three phases as

follows:

S In phase 1, three mixes of pastes comprising plain cement, cement with 18% fly

ash and cement with 50% fly ash were cured at temperatures of 73, 160 and 200F for

various durations to determine the age at which a maturity of 70% degree of

hydration of the cement was attained. Once this age was determined for the various

mixes and curing temperatures, mass concrete with binders in the same proportions as

in the paste would be made and tested when they reached 70% degree of hydration.

This would ensure that all the mass concrete properties would be determined at the

same maturity and make for easy comparison. Difficulty in establishing and exact

time to reach 70% degree of hydration as well as inability to reach this maturity in the

cement/fly ash mixes resulted in using the curing durations of 7, 28 and 91 days as

the bases of comparing the mass concrete properties.

S In phase II, four FDOT Class IV mass concrete mixtures were made and cured at

temperatures of 73F, 160F and 180F for durations of 7, 28 and 91 days. The

concrete samples were tested to determine the following properties:

o Compressive strength ASTM C 39 (ASTM 1996)









o Resistance to chloride penetration ASTM C 1202 (ASTM 1994)

a Time to Corrosion FM 5-522

a Density and percentage of voids ASTM C 642 (ASTM 1997)

Phase III. This phase involved microstructure analysis of the mass concrete by the

aid of a scanning electron microscope. Mortar samples sieved from the concrete

mixes were subjected to the same curing regime. At each test age, the mortar samples

were removed and placed in methanol to stop further hydration of the cement. After a

minimum of 7 days in the methanol, 14 inches thick wafers were cut from the

samples. These wafers were fractured and examined to determine the presence or lack

of ettringite crystals.

Degree of Hydration

Introduction

A well-hydrated Portland cement paste consists mainly of calcium silicate hydrates,

calcium sulphoaluminate hydrates and calcium hydroxide (Metha and Monteiro, 1993).

When the cement paste is ignited to a temperature of 1832F (1000C), the nonevaporable

water chemically combine in the hydration products is released. The degree of hydration

is a measure of the nonevaporable water content of the paste expressed as a percentage of

the nonevaporable water content of fully-hydrated cement paste. The nonevaporable

water content of fully-hydrated cement paste is 0.23 grams of water per gram of cement

(Basma et al, 1999).

For this study a degree of hydration of 70% was decided as the maturity level at

which the mass concrete properties would be determined. The choice of 70% degree of

hydration was based on a study by Kjellsen et al (1990) who found that the time required

to attain this level of maturity is not so long as to be impractical to replicate in the









laboratory. Additionally, by this point, the rate of hydration has slowed enough that small

variations in curing time will not result in significant error making for easy comparison of

the various samples.

Methodology

Tables 3.1 and 3.2 show the chemical composition and physical properties of the

cement, fly ash and blast furnace slag used in the study. The Portland cement used was

AASHTO Type II. Described here are the methods applied to determine the time to attain

70% degree of hydration for three paste mixes isothermally cured at temperatures of 73,

160 and 200F. The three paste mix designs tested are as follows

1. Plain cement paste mix

2. Cement and 18% Fly ash paste mix

3. Cement and 50% Fly ash paste mix










Table 3.1 Properties of Cement and Fly ash
Chemical Composition Portland Cement Fly Ash
% Silicon Dioxide (SiO2) 20.6
% Aluminum Oxide (A1203) 5.1 86.9
% Ferric Oxide (Fe203) 4.7
% Magnesium Oxide (MgO) 0.7
% Sulfur Trioxide (SO3): 3.2 0.2
% Tricalcium Silicate (C3S) 50.0
% Tricalcium Aluminate (C3A) 5.6
% Total Alkalis as Na20 0.52
% Insoluble Residue 0.12
Loss of Ignition (%) 1.5 3.2
Physical Properties
Fineness: Blaine (m2/kg) 341 #325 Sieve 34%

Time of Setting (Gilmore): Fly ash activity index:
Initial (Minutes) 145 7 Days 69%
Final (Minutes) 235 28 Days 78%

Compressive Strength (PSI) ASTM C-150:
3 Days 3200
7 Days 4070



Table 3.2. Properties of Blast furnace slag -ASTM C 989-97b, AASHTO M302
Chemical Analysis
% Silicon Trioxide (Si03) 2.3
% Sulfide Sulfur 0.9
Slag Activity Index
7 Days 96%
28 Days 132%

Physical Properties
Fineness: #325 Sieve (45um) 2%
Compressive Strength (PSI):
7 Days STD Average 4750
7 Days Slag Average 4380
28 Days STD Average 5900
28 Days Slag Average 7810

Blast furnace slag produced by Lafarge in Tampa









Table 3.3. Mix proportions of paste mixes
Mix design Cement Fly Ash Water w/b Mixing Water
(lbs) (bs) (lbs) ratio F

18% flyashat730F 3.540 .777 1.77 .41 73
18% fly ash at 160F and 200F 5.057 1.110 2.53 .41 136
50% fly ash at 730F 2.467 2.467 2.02 .41 73
50% fly ash at 160F and 200F 3.083 3.083 2.53 .41 136


The proportions of materials used in the paste mixes are shown in Table 3.3. The

pastes were made in accordance to ASTM C 305-99. The procedures followed to

determine the degree of hydration were as follows:

a. Three samples each was made of each paste mix to be tested at each curing period

and temperature. Samples at 73F were tested at ages of 1, 3, 7, 10, 14, 28 and 56

days. Samples at 160 and 200F were tested at ages of 1, 3, 7, 10 and 14 days.

b. The water used for samples cured at 1600F and 200F was preheated to 136F, to

produce a cement paste with temperature of approximately 98F. This was done to

reduce the time for samples cured at 160 and 200F to be in equilibrium in the

curing environment.

c. Samples were cast in 1-ounce polypropylene screw cap jars (1.78 cubic inches) as

shown in Figure 3.1. The polypropylene jars offer high temperature resistance up

to 2750F for short periods and 212F continuously. Each jar was capped and

placed in watertight bags, which were submerged in a bucket of water. The

watertight bags were used to ensure that during the first 24 hours of curing no

additional water was permitted to affect the designated water cement ratio. The

water in the buckets for samples cured at 160 and 200F was preheated to

approximately 100F to ensure a short time lag to attain the elevated temperatures

in the ovens as shown in Figure 3.2.




















Figure. 3.1 Paste samples cast in one-ounce polypropylene screw cap jars.



d. The samples cured at 73F were placed in watertight bags immersed in water and

cured in a moisture room kept at 100% humidity and 73F, water.























Figure 3.2. Oven used to cure samples at 200F

e. After 24 hours, the samples were demolded, placed in four-ounce polypropylene

jars as shown in Figure 3.3 and placed in their curing environment to continue the

isothermal curing for the remaining curing duration.


















Figure 3.3 Samples cured in four-ounce polypropylene jars after demolding

f. At the end of curing duration three samples for each mix and temperature were

removed and placed in methanol. Samples cured at 160 and 200F were cooled to

room temperature before placing in the methanol. This was done to avoid igniting

the methanol. The samples were placed in the methanol to stop further hydration

of the cement.

g. After at least 7 days in the methanol, the samples were removed and wiped clean.

The samples were then crushed in a mechanical crusher (see Figure 3.4). The

crushed sample was then pulverized.

i:1


Figure 3.4 samples crushed in mechanical crusher









h. Approximately 3 grams of the pulverized sample was then weighed as shown in

Figure 3.5. The scale used was accurate to 1/10,000 of a gram. The samples were

dried for 24 hours in an oven maintained at 221+5F (105C) to remove the

evaporable water from the sample. After removal from the oven the samples were

cooled to room temperature and the weight was recorded as wl.

i. The samples were then ignited for 45 minutes at 1832F (1000C) to remove the

nonevaporable water chemically combined in the hydration products. The samples

were cooled to room temperature and the weight recorded as w2. Figure 3.6

shows samples removed from the oven after ignition.












Figure 3.5 Approximately 3 grams of samples weighed.
















Figure 3.6 Samples removed after ignition at 18320F.









Calculations to Determine the Degree of Hydration

The calculation of the degree of hydration was based on the formula given by Zhang et al

(2000).

The nonevaporable water content, wn was calculated according to the following equation:

Wn = (wI -W)
w2 (1 rfc)

rfc = pf rf + pc rc

The degree of hydration was determined as a ratio of
Wn / wnu

wnu nonevaporable water content per gram of fully hydrated cement 0.23
wi weight of the sample after drying
w2 weight of the sample after ignition
pf weight percent of fly ash in the mix, 18% and 50%
pc weight percent of cement in the mix
rf loss of ignition of fly ash 4.7%
re loss of ignition of cement 2.1%



Problems Encountered in the Experimental Process

Various problems were encountered during the experimental process to determine

the degree of hydration of the paste samples. These problems and how they were resolved

is presented below.

1. The oven used to cure samples at 1600F failed five days into the curing process

requiring a new oven to be used.

2. Some of the samples kept cured in the ovens at 160 and 200F lost the water in

which they were immersed during the course of the curing duration. Cracking of

the jar covers and evaporation of the water caused this.









3. To resolve the above problems, curing tanks as shown in Figure 3.7 were used in

place of the ovens for the elevated temperature curing. These tanks were filled

with water maintained at 160 and 200F.

4. The degree of hydration tests were repeated based on curing for elevated

temperatures in the curing tanks. The results of the degree of hydration are shown

in Figure 3.8.


Figure 3.7 Curing tanks used for samples at elevated temperatures.











Degree of hydration Isothermal curing

90
80 _--- 0% FA 73F
.--. --0% FA- 160F
-., -". --,--0% FA- 200F
60r .--.---18 FA-73F
0 50 x
40 ...--- -. -.A .. ...18% FA-160F
>' 0 -A~--e-...--^.S~-~---'
I --...---18% FA-200F
30 -
x' -..---50% FA-73F
20
2-.e.-50% FA-160F
1 3 7 10 14 28 56
-. -50% FA 200F
Duration (days)



Figure 3.8 Degree of hydration (wnu = 0.23)

Based on the results of the degree of hydration shown in Figure 3.8, samples made

from the cement fly ash paste mixes did not attain a 70% degree of hydration for the

temperatures and curing durations used in this test. The times to reach 70% degree of

hydration in the plain cement mix was established as shown in Table 3.4.

Table 3.4 Time to 70% hydration in plain cement mix
Curing Temperature
oF)g Duration (approximate)
(OF)
73 7
160 3
200 3


Based on the durations in Table 3.4, samples of FDOT Class IV mass concrete

(Mix 1 appendix) based on the paste mix were made and cured isothermally following

the curing conditions used for the paste samples. Three samples were tested for each

temperature to determine the compressive strength in accordance with ASTM C 39 96.

Compressive strength results are presented in Table 3.5 and Figure 3.9.










Table 3.5 Concrete Mix 1 0% Fly Ash (Isothermal Curing)
Compressive strength (psi) RCP coulombss)
Temp (F) sig (s
70% DH 28 Days 90 Days 70% DH 28 Days
73 6,839 7,472 8252 5,845 4,720
160 4,621 4,963 5616 8,763 7,110
200 2,910 2,872 2636 9,756 11,070


Concrete 0% FA (ISO) Compressive strength




7 days


3 days

3 days
A A


S9,000
S8,000
E 7,000
| 6,000
. 5,000
c 4,000

E
3,000
o 2,000
0


70% DH 28 Days
Curing duration (days)


-D-73F
-0--160F
-A-200F


90 Days


Figure 3.9. Compressive strength results

Figure 3.9 shows a substantial decrease in compressive strength of samples cured

isothermally at 160 and 200F compared to samples cured at room temperature. This is

specially pronounced for 200F curing temperature where compressive strength of a 90

days old sample is less than a 3 days old sample. The reduction in compressive strength

of samples cured at elevated temperatures might be due to high temperature changes (100

to 2000F) as the freshly mixed concrete is introduced into the high temperature curing

environment and thermal shock to concrete.










Concrete 0% FA (ISO) RCP

12,000

10,000 7 days
8 3 daysG-_ E 73F
E 8,000
0 3 days --- 160F
6,000 -- 200F

4,000

2,000
70% DH 28 Days
Curing duration (days)


Figure 3.10 Rapid Chloride Permeability (RCP) results

Figure 3.10 shows the RCP results of the concrete samples cured isothermally at

160F and 200F compared to samples cured at room temperature (73F). Samples cured

at the high temperatures recorded high charges passing through the samples indicating

reduced durability for the concrete. The samples cured at 2000F showed reduced

durability from 7 days to 28 days as the charged passed increased over the curing

duration. At 28 days, the samples cured at 730F had the least current passing indicating

better durability than the samples cured at 2000F, which recorded the highest charges

passing at 28 days.

With the drastic reduction in compressive strength of the mass concrete samples

cured at the elevated temperatures, the experimental set-up was changed as follows:

1. The curing was done adiabatically to simulate conditions as in mass concrete

cured in the field. All the samples were introduced to the curing environment

approximately 6 hours after the start of the mixing process. Samples at 1600F and

180F were introduced into the curing tanks at 800F after which the heat was









turned on. The curing temperature of 160F was attained within 2 days after

which the heat was turned off. The 180F tank attained the maximum temperature

after about 212 days after which the heat was turned off. The lids of the curing

tanks were kept on whilst the temperature cooled to 73F within approximately

two weeks of turning the heat off in both tanks.

2. The maximum temperature was reduced from 200 to 1800F.

3. A review of mass concrete mixes used by the FDOT, was undertaken to examine

the proportions of binders commonly used by the department. The results as

shown in Table 3.6, indicated that 80 percent of the cement/fly ash mixes had

0.18 and 0.20 of the cement replaced by fly ash. Two (2) per cent of the cement

/fly ash mixes had a fly ash replacement of 0.40. Based on this review, the

proportion of fly ash replacement for the mass concrete tests was limited to 18

percent

4. The samples were then transferred to the moisture room into curing baths, as were

the 73 samples. Lime was then added to the water at this point in the curing cycle.

5. Following the change in the curing conditions, new tests were conducted to

determine the time to achieve 70% degree of hydration for the mix. The results

from this test are shown in Figure 3.11.

6. As can be observed in Figure 3.11, the curves were very erratic making it difficult

to establish the duration to attain maturity of 70% degree of hydration in the

various mixes. This led to the use of curing durations of 7, 28 and 91 days as the

bases to compare the mass concrete properties in this study.










7. At specified curing durations, mass concrete samples described in the next section

were tested and the degree of hydration of the cement was determined for that age

and curing temperature.

Table 3.6 Binders used in mass concrete mixes by the FDOT
BINDERS USED IN MASS CONCRETE DESIGNS IN FLORIDA
A. Cement mixes
Proportion of Cement Number of mixes % Cement Mixes % Total mixes
1.00 10 100 11

B. Cement / Fly Ash mixes
Proportion of fly ash Number of mixes % Cement/ Fly ash Mixes % Total mixes
0.18 18 32 21
0.19 6 11 7
0.20 21 37 24
0.21 1 2 1
0.22 5 9 6
0.30 1 2 1
0.35 2 4 2
0.39 2 4 2
0.40 1 2 1
Total 57 100 66

C. Cement / Blast Furnace Slag mixes
Proportion of Slag Number of mixes % Cement/Slag Mixes % Total mixes
0.50 11 55 13
0.60 2 10 2
0.70 7 35 8
Total 20 100 23

SUMMARY
Binder Number of Mixes % of Mixes
Cement 10 11
Cement/ Fly Ash 57 66
Cement/Slag 20 23
Total 87 100











Degree of hydration Adiabatic curing

80
70 0 O% FA 73F
60- 4-1 O0% FA-160F
X .J.* x----*^ 0%FA 180F
.2 50 .
50 ... < --x-- ---x ... 18% FA-73F
S40 ..o... 18% FA-160F
30 ...D... 18% FA-180F
20
1 2 3 4 5 6 7 8 9 10 14 28
Duration (days)



Figure 3.11 Degree of hydration based on adiabatic curing (wnu = 0.23)

Mass Concrete Experiments

Two typical FDOT Class IV concrete with fly ash or slag as the supplementary

cementitious material to cement were used in the mass concrete tests (See appendix A).

The goal of the tests was to determine the effects of elevated curing temperate on the

strength and durability of concrete properties. Four mixes with different proportion of

cement, fly ash and blast furnace slag as shown in Table 3.7, were made and tested. The

tests were repeated. The mixes tested were as follows:

o 0% Fly ash mixes (Mix 1 and Mix 3)

o 18% Fly ash mixes (Mix 2 and Mix 4)

o 0% Blast furnace slag mixes (Mix 5 and Mix 7)

o 50% Blast furnace slag mixes (Mix 6 and Mix 8)









Table 3.7. Mixture Proportions for FDOT Class IV mass concrete
Saturated Surface-Dry Weights, lb/cu yd
Fine Coarse Air Entrainer Admixture
Mixture Cement Fly ash Slag aggregate aggregate (Darex) (WRDA) Water w/b ratio

Mix 1 & 3 744 936 1746 4 oz 24.4 oz 305 0.41

Mix 2 & 4 610 134 918 1729 4 oz 24.4 oz 305 0.41

Mix 5 & 7 660 1076 1794 5 oz 33.0 oz 267 0.40

Mix 6 & 8 330 330 1066 1785 5 oz 33.0 oz 267 0.40




Samples made from the various mixes were cured adiabaticlly as before described.

All the samples were mechanically vibrated during their preparation. After casting in

their molds, the samples were kept in watertight bags for 24 hours after which they were

demolded and placed directly in the curing water. Samples cured at 730F were kept in the

moisture room. The heat in the 160 and 180F tanks was turned off after the maximum

temperature was attained. Cooling of the tanks to a temperature of approximately 73F

occurred over a 14-day period. The samples in the curing tanks were transferred into the

moisture room and placed in limewater. Samples cured at 730F were also places in

limewater at this time.

Various tests were performed on the mass concrete samples after 7, 28 and 91 days

of curing. The tests performed were:

1. Determination of degree of hydration

2. Compressive strength ASTM C 39 (ASTM 1996)

3. Resistance to chloride penetration ASTM C 1202 (ASTM 1994)

4. Time to Corrosion FM 5-522

5. Density and percentage of voids ASTM C 642 (ASTM 1997)









6. Microstructure analysis

Compressive Strength

The compressive strengths of the samples were determined at curing durations of 7,

28 and 91 days. The compressive strengths were determined according to ASTM C 39-

93a, Standard Test Methodfor Compressive Siir egthl of Cylindrical Concrete Specimens,

by the FDOT physical laboratory. Twenty-seven 4" diameter x 8" cylinders were molded

for each mix. Nine samples for each mix were tested at 7-, 14-, and 28-days age three for

each curing temperature.

Resistance to Chloride Penetration

Each mix cured at the 73, 160 and 180F was tested at 28-, and 91-days age to

determine its ability to resist the chloride-ion penetration. The rapid chloride permeability

for each sample was estimated following ASTM C 1202-94, Standard Test Methodfor

Electrical Indication of Concrete's Ability to Resist Chloride-Ion Penetration. In this test,

the chloride-ion penetrability of each sample was determined by measuring the number of

coulombs that can pass through a sample in 6 hours. This provided an accelerated

indication of concrete's resistance to the penetration of chloride-ions, which may corrode

steel reinforcement or prestressed strands. Six 4" diameter x 8" cylinders of each mix,

two for each curing temperature were tested at 28-, and 91-days age. A 2" thick disc was

sawed from the top of each cylinder and used as the test specimen. It has been determined

that the total charge passed is related to the resistance of the specimen to chloride-ion

penetration. The surface resistivity of each sample to the penetration of chloride ions was

measured at the curing durations from the remaining portions of the samples used in the

rapid chloride permeability tests.









Time to Corrosion

The time to corrosion test determines the duration of time for reinforcement within

a sample to corrode. The time to corrosion was determined according to Florida Method

of Test for An Accelerated Laboratory Method for Corrosion Testing of Reinforced

Concrete Using Impressed Current. The samples used in this test were cylinders of 4"

diameter x 6" long. Nine samples were made for each mix three for each curing

temperature. Each sample contained a #4 reinforcing bar, 12" long. The bottom of the

reinforcing bar was elevated by 0.75" from the bottom of the mold. Fresh concrete was

placed in each mold and each mold was overfilled. The apparatus that had the reinforcing

bars attached to it was placed over the cylinders. The apparatus was then placed on an

external vibrator that caused the reinforcing bars to submerged into the overfilled fresh

concrete when the vibrator was turned on. After vibration, a trowel was used to slope the

overfilled top of the mold at a 15-degree angle from the outer rim of the sample to the

center of the sample. After 28 days of curing, the samples were further cured in a solution

of 3% NaCl after which they were tested. The tests were performed at the Florida

Department of Transportation Corrosion Laboratory.

Density and Percentage of Voids in Hardened Concrete

The density and percentage of voids for each mix and curing temperature were

determined at curing durations of 7, 28 and 91 days. The tests were done according to

ASTM C 642 97, Standard Test Method for Density, Absorption, and Voids in

Hardened Concrete, by the FDOT physical laboratory. Approximately 800 grams of each

sample was tested.









Microstructure analysis Scanning Electron Microscope (SEM)

Introduction

A microscope provides the ability to see much finer details of an object than is

possible to the naked eye. The scanning electron microscope (SEM), which became

commercially available in the 1960s, permits the observation and characterization of

heterogeneous organic and inorganic materials on a nanometer (nm) and micrometer

(um) scale (Goldstein et al, 1992). The resolution of a microscope is the smallest

separation between two points in an object that can be distinctly reproduced in the image.

Today's SEM has achieved a resolution better than 10nm, an improvement by a factor

about 103 relative to a light microscope (Sarkar, Aimin and Jana, 2001). The popularity

of the SEM stems from its capability of obtaining three-dimensional-like images of the

surfaces of a very wide range of materials.

Signals of Interest

In the SEM, the area to be examined or microvolume to be analyzed is irradiated

with a finely focused beam, which may be swept in a raster across the surface of the

specimen to form images or may be static to obtain an analysis at one position (Goldstein,

Newbury, Joy, Lyman, Echlin, Lifshin, Sawyer and Michael, 1992). When a beam of

primary electrons strikes a bulk solid, the electrons are either reflected (scattered) or

absorbed, producing various signals (Figure 3.12)

The types of signals produced include secondary electrons (SE), backscattered

electron (BSE), characteristic x-rays and other photons of various energies. These signals

are obtained from specific emission volumes within the sample and can be used to

examine many characteristics of the samples such as composition and topography. The

intensity of the backscattered electrons is proportional to the atomic number of the









elements in the sample. More electrons are scattered from higher atomic number

elements, and, in an image appear brighter than low atomic number elements which

appear darker in an image. Backscattered electrons therefore respond to the

compositional variations in the sample and enable the distinctions of the various phases

based on the differences in their average atomic numbers.

PE


BSE
X S I



V-, Electron
range
Diffusion cloud ran


Figure 3.12. Different interactions of an electron beam (PE) with the solid target. BSE =
backscattered electrons, SE = secondary electrons, X = x-ray, AE = auger
electrons

Secondary electrons are loosely bound outer shell electrons from the sample atoms

which receive sufficient kinetic energy during inelastic scattering of the beam electrons to

be ejected from the atom and set in motion (Goldstein et al, 1992). Secondary electrons

have a shallow escape depth and collecting them as an imaging signal enable high

topographical resolution of the sample to clearly distinguish between the various shapes

of the phases in the sample. Measuring the energy and intensity distribution of the

characteristic x-ray signals generated by the focused electron beam enables chemical

analysis of the specimen. This chemical analysis is done using the SEM's adjunct

microanalytical unit, commonly known as the energy dispersive x-ray analyzer (EDAX),

(Sarkar, Aimin and Jana, 2001). Characteristic x-rays are analyzed to yield both the









qualitative identification and quantitative compositional information from regions of the

specimen as small as a micrometer in diameter.

SEM Use in Concrete

Most of the properties of concrete are evaluated according to standard procedures.

The SEM does not fall under the realm of any standard procedure. It is a relatively new

technique which is yet to be universally accepted by the concrete technologist. One of the

first applications of SEM was in the study of concrete hydration in the early 1970s

(Sarkar, Aimin and Jana, 2001). The chief interests one has in studying concrete under

SEM are to study the effects of deterioration of concrete or its performance

characteristics, qualitative phase identification, grain morphology, distribution pattern

and association with other phases (Sarkar, Aimin and Jana, 2001).

Experimental Work

The scanning electron microscope used in this research was the SEM JSM 6400.

All analyses were conducted at the Major Analytical and Instrumentation Center at the

University of Florida. The SEM analysis was used to determine the presence of ettringite

crystals in voids of mortar samples sieved from the concrete mixes. The signals of

interest used in this study when the electron beam impinged on the specimen were

secondary electrons and characteristic x-rays. Because of the different morphological

features characteristic of the phases, they could be identified by secondary electron

images. This avoided the use of thin or polished sections using backscatter (BS) electron

which may wash out or grind out ettringite nests and introduce artifacts such as cracks.

Moreover with SE techniques, crevices and both sides of "hills" are revealed. Fly ash

particles used in some of the mixes are clearly revealed by SE techniques, while BS

procedures may reveal them primarily as voids because of their poor backscattered










electron yield (Hime, Marusin, Jugovic et. Al, 2000). Measuring the energy and intensity

distribution of the characteristic x-rays enabled a chemical analysis of the samples to

confirm the various phases identified in the secondary electron image. Energy Dispersive

Analysis of the X-rays (EDAX) was used to confirm or deny the presence of the

ettringite. EDAX of an ettringite mass has a "step" pattern of the aluminum, sulfur and

calcium peaks as shown in Figure 3.13 (Hime, Marusin & Jugovic, 2000).


VERT = 5000 COUNTS DISP =1
Ca
OXIDE
FORMULA PERCENT

S AI,O, 15.09
S10, 1.02
SSO 36.87
CaO 47.02
AlCa
0
1 2 3 4 5 6 7 8 9
Range = 10.230 keV


Figure 3.13 The EDAX analysis of "gel" showing calcium, sulfur, and aluminum peaks
typical for ettringite

Sample Preparation for SEM Examination

The samples used for the microstructural analysis were made from mortar sieved

from the concrete mixes. The samples were cured adiabatically as the mass concrete

samples. After 24 hours in watertight bags, the samples were demolded from the two-

ounce jar and placed directly in the curing environment. At the end of the curing period,

the samples were removed from the curing tank and placed in methanol to stop further

hydration. After at least 7 days in the methanol, the samples were removed and finely cut

into /4" thick wafers. The samples were then placed in an oven maintained at a









temperature of 230 F for 24 hours to remove all the evaporable water, not used in the

hydration process. The samples were stored in a desiccator after removal from the oven.

To obtain very good images using the SEM and avoid the introduction of cracks or

removal of any ettringite nests, cutting of the surface of the sample was avoided, instead

pieces were fractured and the fractured surfaces were analyzed. The fractured pieces were

cut and coated with carbon. Since the samples were non-conducting, coating was

necessary to eliminate or reduce the electric charge that builds up rapidly in a non-

conducting specimen when it is scanned by a beam of high-energy electrons. Figure 3.14

shows mortar samples mounted and ready for examination in the SEM


Figure 3.14. Mortar samples mounted on stubs for SEM examination














CHAPTER 4
TEST RESULTS AND DISCUSSION

Introduction

This chapter presents results of the experimental work conducted to determine the

maximum curing temperature to avoid durability problems and the formation of delayed

ettringite in mass concrete. The study was conducted in three phases:

1. Phase 1 involved tests to determine the time to achieve a maturity of 70% degree

of hydration of cement in mass concrete mixes with cement, fly ash and blast

furnace slag as the cementitious materials.

2. Phase 2 involved tests of two FDOT Class IV mass concretes at temperatures of

73, 160 and 180F for 7, 28 and 91 days. Various tests were performed on the

concrete to evaluate the effect of the curing conditions on the strength and

durability of the concrete.

3. In phase 3, mortar samples prepared from the sieved mass concrete mixes were

subjected to the same curing conditions. The samples were then examined under a

scanning electron microscope to determine the formation or otherwise of delayed

ettringite.

Phase 1 Determination of Degree of Hydration

The results for the degree of the hydration for the different mixes tested are shown

in Tables 4.2 through Table 4.5. Initially, all calculations for the degree of hydration were

based on the fact that the nonevaporable water content for 1 gram of fully hydrated









cement was 0.23 grams of water. This value was found to be inapplicable to cement

blends with fly ash or slag.

Scanning Electron Microscope (SEM) observations by Maltais & Marchand (1997)

for pastes some incorporating fly ash as a 10, 20 and 30 per cent replacement of cement

and cured at 68 and 104F showed that the fly ash did not react before at least 28 days.

Although the fly ash did not react during the first days of curing, their test results

indicated that it could not be considered as a totally inert material. Despite the very little

pozzolanic activity, Maltais and Marchand (1997) found out that the presence of fly ash

appeared to increase the mortar nonevaporable water content at early days. This increase

was attributed to an acceleration of the early cement hydration in the presence of fly ash.

Two reasons for the acceleration of cement hydration in the presence of fly ash are

physical and chemical effects.

o Physical

o The addition of fly ash tends to increase the number of fine particles in the

system. The presence of these fine particles contributes to increase the

density of the matrix making for better hydration of the cement.

o The replacement of cement particles by fly ash is also believed to increase

the available space in the floc structure created by the cement grains.

o The fine particles provide additional nucleation sites for cement hydration

products.

o Chemical

o According to Maltais and Marchand (1997) the acceleration of cement

hydration in the presence of fly ash is mainly related to the preferential









adsorption of calcium ions on the fly ash particles. The phenomenon

contributes to decrease the calcium ion concentration in the liquid phase,

which subsequently favors the dissolution of calcium phases from the

cement grains.

Fly ash reacts with the calcium hydroxide formed from the hydration of the cement.

The reduction in calcium hydroxide content form the pozzolanic reaction will not enable

a value of 0.23 to be a good estimate of the degree of hydration. The pozzolanic reaction

will reduce the amount of calcium hydroxide and replace it with hydrates formed by the

pozzolanic reaction. The amount of water released from a mole weight of the hydrates is

less than the amount of water released form a mole weight of calcium hydroxide due to

its large molecular weight. A more reliable estimate was determined for the cement fly

ash mixes after hydrating paste at 730F in the moisture room for 1 year and calculating

the nonevaporable water content. The new values for the nonevaporable water content for

the cement and fly ash mixes were as follows:

o 0.19 for cement and 18% fly ash mix with w/b ratio of 0.41

o 0.15 for cement and 50% fly ash mix with w/b ratio of 0.41.

These values for the nonevaporable water content are comparable to that

determined for various mixes of fly ash by Lam et al. (2000) and shown in Table 4.1

below.









Table 4.1. Nonevaporabe water content for various Fly ash mixes Lam et al. (2000)
w/b Fly ash replacement *Wnu at 90 days
(%)
0.3 25 0.19
0.3 55 0.15
0.5 25 0.18
0.5 55 0.15
Calculated from ratio of Wn / Degree of hydration



Legend: Degree of Hydration results

o IOP -Isothermal curing of paste samples in oven

o (Row # 1, 6, 14, 16, 17, 24, 25, 36, 37, 40, 41, 44, 45, 48, 49)

o ITP -Isothermal curing of paste samples in tanks

o (Row # 2, 7, 15, 18, 19, 26, 27, 38, 39, 42, 43, 46, 47, 50, 51)

o ATM Adiabatic curing of mortar samples in tank

o (Row # 3, 8, 11, 20, 21, 28, 29, 32, 33)

o ATC Adiabatic curing of mortar sieved from concrete in tank

o (Row # 4, 5, 9, 10, 12, 13, 22, 23, 30, 31, 34, 35, 52, 53, 54)

o C & F Calculation of degree of hydration based on total cement and fly ash

content and the nonevaporable water content at full hydration after curing for 1

year at 73oF. the nonevaporable content for 1 gram of 18%FA mix was

determined to be 0.19 and that for the 50%FA was determined to be 0.15.

o C Calculation of degree of hydration based on cement solely responsible for the

hydration products formed assuming no reaction of fly ash. NA designation is

applied to durations and temperatures for which fly ash reaction is assumed to

have started, invalidating an extension of this calculation.










o C & S Calculation of degree of hydration based on total cement and blast

furnace slag content and the nonevaporable water content at full hydration of 0.23

as for plain cement mixes.

Table 4.2. Degree of hydration results for plain cement mixes
Curing Duration (days)
Mix Temp Row Mix design Curing Duration (days)
1 2 3 4 5 6 7 8 9 10 14 28 56 91
1 IOP 0%.41w/c 58 67 70 71 71 73 74 -
2 ITP 0%.41 w/c 56 64 69 71 77 78 79 -

73
3 ATM 0%.41w/c 52 60 60 64 61 62 61 62 70 63 68 70 -
4 ATC 0%.41w/c 59 64 69
5 ATC 0%.40w/c 54 64 62

6 IOP 0%.41w/c 68 72 75 73 72 69 69
7 ITP 0%.41 w/c 68 72 76 76 81 79 79

0% 160
8 ATM 0%.41 w/c 60 73 68 71 67 69 67 69 74 68 70 71 -
9 ATC-0%.41w/c 61 61 66
10 ATC 0%.40w/c 62 59 61

11 ATM-0%.41w/c 60 73 71 71 68 68 67 69 74 73 70 68 -
180 12 ATC 0%.41w/c 59 63 69
13 ATC-0%.40w/c 60 59 60


14 IOP- 0%.41w/c 73 75 80 78 75 75 76 -
15 TP .41 65 -20069 73 7375 74 -
15 ITP 0% .41 w/c 65 69 73 73 75 74 74













112 3 4 5


Curing Duration (days)


6 7 8 9


10 14 28 56


63 65 75 78 76 79 NA
60 63 _73 75 74 76 79
51 65 70 75 81 84 NA


50 63 I- I- 68 -


- 72 78 82 80 -


Table 4.3.


18%










'able 4.4. Degree of hydration for 50% fly ash mixes


Table 4.5. Degree of hydration for cement and blast furnace slag mixes
Curing Duration (days)
Mix Temp Row Mix design Curing Duration (days)
1 2 3 4 5 6 7 8 9 10 14 28 56 91
73 52 ATC-50%SL C&S 69 78 -81

50% 160 53 ATC-50%SL C&S 84 86 82

180 54 ATC-50%SL C&S 82 85 84


Phase 2 Tests of Mass Concrete

Table 4.6 provides a summary of the plastic properties of the mass concrete mixes

tested. Tests for each mix included determination of the degree of hydration, compressive

strength, time to corrosion, rapid chloride permeability, density and the percentage of

voids at curing durations of 7, 28 and 91 days and curing temperatures of 73, 160 and

180F. The test for each mix was repeated and the average results for each mix is

provided in Tables 4.7 and 4.8.








58



Table 4.6. Summary of Plastic Properties of Fresh Concrete.
Concrete Air Slump Air Content Workability w/b ratio
Test Mixture Temperature (F) Temperature in %
# (F)

Mix 1 75 72 6.50 4.0 Good 0.41
Mix 2 75 72 5.00 2.0 OK 0.41

Mix 3 69 70 6.50 4.5 Good 0.41
2 Mix 4 70 70 7.50 2.5 Good 0.41

Mix 5 74 72 5.25 6.0 Good 0.40
3 Mix 6 74 72 3.25 3.9 Sticky 0.40

Mix 7 75 4.00 5.50 Good 0.40
71
4 Mix 8 73 2.75 3.00 Stiff 0.40
70



Table 4.7. Results of concrete mixes Ml and M2

Test # Mix ID Temp Duration Hydration Comp Density Voids RCP Resistivity Corrosion
S(Testd# Mix ID(b/f) (ulombs) kohms
(F) (days) (%) (psi) (Ibs/flt3) (%) coulombss) (kohms/cm) (days)


M1
(0% Fly Ash)
w/c = 0.41
slump = 6.5"


M2
(18% Fly Ash)
w/c = 0.41
slump = 5.0"


28 66 6860 155.70 16.00 5507 8.63 12


7457


155.70 16.30 4456


11.07


7 56 5992 -
160
160 28 60 6051 157.10 16.70 8701 7.16 8

91 63 6280 156.50 16.00 6693 8.28

7 56 5761 -
180
28 67 5790 159.05 15.95 9317 8.46 5

91 66 6037 156.50 15.80 7695 8.27


7 49 6610 -
73 161.20 16.75 5014 14
28 58 7770 161.20 16.75 5014 9.04 14


8517 159.90 15.90 2285


17.84


7 62 6942 -
160
160 28 61 7149 162.15 16.60 2470 21.33 9

91 60 7810 160.30 16.70 1701 29.80

7 57 6660 -
180 28 62 7069 162.15 16.90 2646 19.42 9
28 62 7069 162.15 16.90 2646 19.42 9


7437 160.70 16.20 1822


23.06








59



Table 4.8. Results of concrete mixes M3 and M4

Test# MiID Temp Duration Hydration Comp Density Voids RCP Resistivity Corrosion
Test# Mix ID
(F) (days) (%) (psi) (Ibs/f3) (b/) %) coulombss) (kohms/cm) (days)

7 61 5800 154.20 16.30
737 156.30 15.30 5616 11.22 15
28 61 6387 156.30 15.30 5616 11.22 15


M3 same as
M1
(0% Fly Ash)
w/c = 0.41
slump = 6.5"


M4 same as
M2
(18% Fly Ash)
w/c = 0.41
slump = 7.5"


7 66 5567 155.30 15.90
160 28 62 5613 155.10 16.20 8565 8.42 5

91 70 5957 155.20 15.80 6851 9.78

7 61 5323 155.80 16.00
180
180 28 59 5353 155.20 15.80 10459 8.85 7

91 72 5343 154.10 15.50 7370 9.12


1)
7 58 6320 159.70 16.60
733 159.40 16.00 5331 10.83 27
28 66 7173 159.40 16.00 5331 10.83 27


8220 158.10 15.70 2272


18.95


7 64 6647 161.40 16.80
160
160 28 66 6570 160.40 17.40 2626 21.33 15

91 86 7180 158.90 15.80 1872 26.09

7 64 6247 159.00 17.40
180
28 74 6643 158.70 17.10 2360 18.67 15


7187 158.90 15.80 1923


2
(repeal
of test


7043 152.20 14.50 4531


12.18


t


22.13








60



Table 4.9. Results of concrete mixes M5 and M6


Mix ID Temp Duration Hydration Comp Density Voids RCP Resistivity Corrosion
Test# Mix ID
(F) (days) (%) (psi) (Ibs/ft3) (%) coulombss) (kohms/cm) (days)

7 50 4780 156.2 14.7


M5
(0% Slag)
w/c = 0.40
slump = 5.25"


M6
(50% Slag)
w/c = 0.40
slump = 3.25"


73
28 63 5673 150.0 14.0 5850 9.84 18

91 63 6310 152.4 14.2 4105 12.1

7 54 4783 155.6 15.8
160
160 28 58 4673 152.9 15.1 10108 7.93 11

91 62 4903 153.7 16.6 7770 8.45

7 55 4830 155.1 15.7
180
28 61 4673 151.9 14.9 8996 11.45 14


4707 155.9 15.8


9233


7 69 5293 161.5 16.0
73158.5 14.7 2845 17.88 42
28 80 7165 158.5 14.7 2845 17.88 42


8003 157.5 14.1


2114


24.50


7 80 6790 161.4 16.0
160
28 84 6877 159.3 15.1 1919 21.68 16

91 84 7617 158.5 14.3 1662 25.90

7 80 5853 161.4 15.5 -
180 28 84 6273 18.7 14.7 2689 18.49 11
28 84 6273 158.7 14.7 2689 18.49 11


7180 1S9.S 1S.0 2S.00


7180 159.5 15.0


25.00








61



Table 4.10. Results of concrete mixes M7 and M8

Test# MiID Temp Duration Hydration Comp Density Voids RCP Resistivity Corrosion
Test # Mix ID) (ulombs) (kohms/cm) (ys
(F) (days) (%) (psi) (Ibs/ft3) (%) coulombss) (kohms/cm) (days)


VI7 same as ME
(0% Slag)
w/c = 0.40
slump = 4.0"


VI8 same as ME
(50% Slag)
w/c = 0.40
slump = 2.75"


7 57 5760 152.3 12.3
73
28 65 6733 155.7 13.6 4430 11.34 21

91 61 7307 152.4 12.3 3960 12.5

7 69 5947 151.4 11.9
160
160 28 60 5653 156.3 14.3 8135 7.93 11

91 60 5890 154.4 14.0 7119 8.45

7 64 5450 152.5 11.8


180


28 57 5430 154.8 14.7 6175 10.97 7

91 54 5373 153.7 14.0 8347 9.05



7 69 5770 155.5 12.8

28 75 8303 159.8 15.3 2540 19.45 85


155.7 12.6 1890


22.54


7 87 7307 156.3 12.0
160
160 28 87 7470 160.5 14.4 1943 23.67 22

91 80 8230 156.1 12.9 1481 27.00

7 83 6567 155.4 11.8


180


28 85 6883 160.8 14.9 2105 20.55 44


157.3 12.1 1802 24.76


4
(repeat of
test 3)


157.3 12.1 1802


24.76








62



Table 4.11. Summary of Results of concrete mixes M M2, M3 and M4

Mix ID Temp Duration Hydration Comp Density Voids RCP Resistivity Corrosion
Mix ID
(F) (days) (%) (psi) (bs/ft3) (%) coulombss) (kohms/cm) (days)
7 59 5924 154.20 16.30
73 28 64 6624 156.00 15.65 5562 9.93 14
91 69 7250 153.95 15.40 4494 11.63
M1 & M3 7 61 5780 155.30 15.90
(0% Fly Ash) 160 28 61 5832 156.10 16.45 8633 7.79 7
w/c = 0.41
91 67 6119 155.85 15.90 6772 9.03
7 59 5542 155.80 16.00
180 28 63 5572 157.10 15.88 9888 8.66 6

91 69 5690 155.30 15.65 7533 8.70


7 54 6465 159.70 16.60
73 28 62 7472 160.30 16.38 5173 9.94 20

91 76 8369 159.00 15.80 2279 18.40

M2 & M4 7 63 6795 161.40 16.80
(18% Fly Ash) 160 28 64 6860 161.30 17.00 2548 21.33 12
w/c = 0.41
91 73 7495 159.60 16.25 1787 27.95
7 61 6454 159.00 17.40
180 28 68 6856 162.15 17.00 2503 19.05 12

91 70 7312 159.80 16.00 1873 22.60











Table 4.12. Summary of Results of concrete mixes M5, M6, M7 and M8

MiID Temp Duration Hydration Compressive Density Voids RCP Resistivity Corrosion
Mix ID
(F) (days) (%) (psi) (Ibs/ft3) (%) coulombss) (kohms/cm) (days)
7 54 5270 154.3 13.5
73 28 64 6203 152.9 14.2 5140 10.59 20
91 62 6808 152.4 13.3 4033 12.3
M5 & M7 7 62 5363 153.5 13.9
(0% Slag) 160 28 59 5163 154.6 14.7 9122 7.93 11
w/c = 0.40
91 61 5397 154.1 15.3 7445 8.45
7 60 5140 153.8 13.8
180 28 59 5052 153.4 14.8 7586 11.21 11
91 60 5040 154.8 14.9 8794 9.35


7 69 5532 158.5 14.4
73 28 78 7734 159.2 15.0 2693 18.67 64
91 81 8503 156.6 13.4 2002 23.52

M6 & M8 7 84 7049 158.9 14.0
(50% Slag) 160 28 86 7174 159.9 14.8 1919 21.68 19
w/c = 0.40
91 82 7924 157.3 13.6 1572 26.45
7 82 6210 158.4 13.7
180 28 85 6578 159.8 14.8 2689 18.49 28

91 84 7275 158.4 13.6 1778 24.88



Degree of Hydration Results

The degree of hydration was determined from mortar samples sieved from the


concrete mixes. The samples were cured adiabatically for the same durations as the mass


concrete samples. At the end of the curing durations, the hydration process was stopped


by immersion in methanol and then tested to determine the degree of hydration. Figures


4.1 and 4.2 show the results of the hydration tests.










Degree of Hydration (0%FA & 18%FA)

80
75 x -- 0% FA- 73F
70 .- 0% FA-160F
6 ---- 0%FA 180F
65 .
E 18% FA- 73F
S60 ~- 18%FA- 160F
55 -o -18%FA- 180F
50
7 28 91
Duration ( Days)


Figure 4.1. Degree of hydration for 0%FA and 18%FA mixes

Addition of Fly ash increases the degree of hydration at early ages for the samples

cured at the higher temperatures. Higher curing temperatures have not been effective

however in increasing the degree of hydration at early age for the mix without fly ash. At

later ages, the degree of hydration for the fly ash mix is higher than that without fly ash at

all curing temperatures. The degree of hydration for the fly ash mix at later ages is

highest in the samples cured at 73oF and decreases with increasing curing temperature.










Degree of Hydration (0%BFS & 50%BFS)

90
85 : 0 -*- 0%BFS-73F
0 80-
80 x-- 0% BFS- 160F
75
75 -A- 0%BFS 180F
70 x
.65 x 50%BFS 73F
%60 =- 50%BFS-160F
55 -o 50%BFS- 180F
50
7 28 91
Duration (Days)


Figure 4.2. Degree of hydration for 0%BFS and 50%BFS mixes

Addition of slag as seen in Figure 4.2, resulted in a drastic increase in the degree of

hydration over the mix without slag at both early and later ages for all curing

temperatures. The slag mixes cured at higher temperatures showed a much higher degree

of hydration at early ages, however at later ages all curing temperatures had reach to

about the same degree of hydration.

Compressive Strength Results

The compressive tests were performed on twenty-seven different cylinders for each

mix. Nine samples of each mix were tested at curing durations of 7, 28 and 91 days from

the mixing date. Three samples each were tested for three different temperatures of 73,

160 and 180F. The compressive strengths were determined in accordance with ASTM

C39-93a. Figures 4.3 through 4.7 show the results of the compressive strength for the

different mixes and curing conditions.











Compressive strengths (0%FA & 18%FA)


x X









7 28 91
Duration (Days)


-*-0% FA 73F
--0% FA- 160F
--0%FA- 180F
-x -18% FA-73F
18%FA- 160F
18%FA-180F


Figure 4.3. Compressive strengths for 0%FA and 18%FA mixes

Table 4.13. Compressive strength as a ratio of 28-day samples cured at 73oF
Mix Duration Temperature (F)
Mix
(days) 73 160 180

7 0.89 0.87 0.84
0% FA 28 1.00 0.88 0.84

91 1.09 0.92 0.86


7 0.87 0.91 0.86
18% FA 28 1.00 0.92 0.92

91 1.12 1.00 0.99



Higher curing temperatures resulted in lower strength for all ages and mixtures

except fly ash mix at 7 days age, which had a higher strength at the 160F as shown in

Figure 4.3 and Table 4.13. Addition of fly ash increased the strength at all ages and

curing temperatures when compared to the mix without fly ash, mirroring the higher

degree of hydration of the fly ash mixes over the plain cement mixes. The highest

strength at later age was recorded for the fly ash mix cured at 73oF, which also had the

highest degree of hydration at this age.


9000
8500
8000
7500
C 7000
6500
6000
5500
5000







67



Compressive strengths (0%BFS & 50%BFS)

9000

8000 0%BFS 73F
-E-0% BFS 160F
7000
7000 -- 0%BFS 180F
a6000 50%BFS 73F
6000
S__ 50%BFS 160F
5000 -- -o -50%BFS- 180F

4000
7 28 91
Duration ( Days)


Figure 4.4. Compressive strengths for 0%BFS and 50%BFS mixes

Table 4.14. Compressive strength as a ratio of the 28-day samples cured at 73oF
Mx Duration Temperature (OF)
Mix
(days) 73 160 180

7 0.85 0.86 0.83
0% Slag 28 1.00 0.83 0.81
91 1.10 0.87 0.81

7 0.71 0.91 0.80
50% Slag 28 1.00 0.93 0.85
91 1.10 1.02 0.94


Higher curing temperatures resulted in increased early age strength in the slag mix

but reduced later age strength as seen in Figure 4.4 and Table 4.14. Higher curing

temperatures in the mix without slag generally resulted in a decrease in both early and

later age strength. The mix with slag had higher strengths at all curing durations and

temperatures compared to the mix without the slag. This observation agrees with the

higher degree of hydration in the slag mix over the mix without slag.









Resistance to Chloride Ion Penetration

Six samples of each mix were tested at 28 and 91 days, two for each curing

temperature. The tests were done in accordance with ASTM C 1202-94. Results of this

test are shown for the various mixes in Figures 4.5 and 4.6. The blended cement mixes

were observed to have a higher resistance to chloride ion penetration than the plain

cement mixes as shown by the lower charges passing through during the test.


Chloride Ion Penetration RCP (0%FA & 18%FA)

10000
8000 0--0% FA- 73F
S7000- --0% FA- 160F
7000
E 6000 0%FA- 180F
o 5000- 18% FA- 73F
L 4000
S4000 18%FA- 160F
3000
2000 -- -- 18%FA-180F
1000
28 91
Duration (Days)


Figure 4.5 Chloride Ion Penetration results for 0%FA and 18%FA mixes

As shown in Figure 4.5 above, at higher curing temperatures, the mixes without fly

ash, had higher chloride penetration at both 28 and 91 days. For the fly ash mixes

however higher curing temperatures resulted at much reduced chloride ion penetration at

28 days although their influence on chloride penetration at 91 days was about the same as

curing at 730F. Overall, the fly ash mixes had lower chloride ion penetration at all curing

durations and temperatures when compared to the mixes without fly ash.











Chloride Ion Penetration RCP (0%BFS & 50%BFS)


--0%BFS- 73F
---0% BFS- 160F
A 0%BFS 180F
-- 50%BFS 73F
--- 50%BFS 160F
o 50%BFS- 180F


Duration ( Days)



Figure 4.6. Chloride Ion Penetration results for 0%BFS and 50%BFS mixes

The mix without slag as seen in Figure 4.6, showed increased RCP values at higher

temperatures. The RCP values for the slag mixes were not much affected by the curing

temperatures. Overall, RCP values for the slag mixes were considerably reduced when

compared to the mixes without slag at all curing temperatures and durations.

Density and Percentage of Voids Results

Two samples of each mix for each curing temperature weighing approximately

800g were tested at 7, 28 and 91 days to determine the density and percentage of voids.

Figure 4.7 shows the density for the plain cement and fly ash mixes. Figure 4.8 shows the

density for the blast furnace slag mix.


10000
9000
8000
7000
6000
5000
4000
3000
2000
1000


E3 --- -- --
U-










Density (0%FA & 18%FA)

170.00

166.00 --0% FA- 73F
S--0% FA- 160F
S162.00 0%FA- 180F

U 158.00 18% FA- 73F
10 18%FA- 160F
S154.00 -o 18%FA-180F

150.00
7 28 91
Duration ( Days)


Figure 4.7 Density for 0%FA and 18%FA mixes

The mix with fly ash showed a higher density at all curing temperatures and curing

durations, than the mix without it as seen in Figure 4.7. The curing temperature of the

concrete had a minimal influence on the resulting density.


Density(O%BFS & 50%BFS)

160.0 -_ _
S158 -.o --0%BFS- 73F
158.0
S- 0%BFS -160F

156.0
156.0 --0%BFS- 180F

154.0 x 50%BFS 73F
.-
50%BFS 160F
) 152.0
S- --o 50%BFS- 180F

150.0
7 28 91
Duration ( Days)


Figure 4.8. Density for 0%BFS and 50%BFS mixes










Addition of slag has increased density for all curing temperatures and ages. Higher

curing temperatures have slightly increased density at 91 days for mixes with and without

slag as seen in Figure 4.8.


Percentage of voids (0%FA & 18%FA)

17.50
17.00 ______ -0% FA- 73F
-. -.- 0% FA- 160F
S16.50 -0%FA 180F
U,
0 16.00 -x 18% FA- 73F
18%FA-160F
15.50 18%FA-180F
15.00
7 28 91
Duration ( Days)


Figure 4.9. Percentage of voids for 0%FA and 18%FA mixes

At 7 days, the fly ash mixes had a higher percentage of voids at all curing

temperatures when compared to the mix without fly ash as shown in Figure 4.9. The

percentage voids in the fly ash mixes is higher in the samples cured at elevated

temperatures. For both mixes with and without fly ash, the percentage of voids at 91

days was least in the samples cured at 73oF.










Percentage of voids (0%BFS & 50%BFS)

15.5

15.0 0 O%BFS- 73F
-- 0% BFS 160F
V 14.5 x 0%BFS- 180F

0 14.0 -x- 50%BFS- 73F
13.5 50%BFS 160F
135 o --50%BFS- 180F
13.0
7 28 91
Duration ( Days)


Figure 4.10. Percentage of voids for 0%BFS and 50%BFS mixes

At 7 days, the mixes with slag showed a lower percentage of voids in the samples

cured at the elevated temperatures, however, this situation was reversed at 91 days in

which the percentage of voids was lower in the samples cured at 73oF. At all curing

temperatures and durations, the mix without slag cured at 73oF had the least percentage

of voids as seen in Figure 4.10.

Time to Corrosion Results

The corrosion results for each mix and curing temperature is presented individually

as an average of three samples. The results as shown in Figure 4.11 indicate the increase

in the concrete durability by the use of slag. The use of fly ash also increased the time to

corrosion when compared to the plain cement mixes, but to a smaller extent. Increasing

the curing temperature for all the mixes resulted in reduction of time to corrosion.












Time to Corrosion (TTC) Impressed current


70
60
> 50
3 40
0 30
5 20
20
10
0


073 F
0160 F
0180 F


i-



0% Fly Ash 0% Slag 18% Fly Ash 50% Slag
Mix Designs


Figure 4.11. Time to Corrosion results for all mixes


RCP (91 days) Expressed in terms of TTC unit


70
60
, 50
S 40
40
. 30
I 20
20
10
0


i




0% Fly Ash 0% Slag 18% Fly Ash 50% Slag
Mix designs


073 F
E160 F
0180 F


Figure 4.12. The RCP at 91days expressed in terms of Time to Corrosion unit

Three parameters were used in this research to study the durability of the concrete:


1. Percentage of voids


2. Rapid chloride permeability (RCP) and


3. Time to corrosion (TTC) Impressed current


The following observations were made in relating these parameters:









a. The percentage of voids determined for the various samples did not have much

variation in the values and could not be used to establish differences in the

durability of the mixes.

b. The RCP and TTC tests exhibited similar results for the plain cement mixes (0%

FA and 0% BFS), that is both tests showed reduction in durability when curing

temperature increased (see Figures 4.11 and 4.12).

c. The mixes with the Fly ash and slag showed conflicting durability results from the

RCP and TTC tests as seen in Figures 4.11 and 4.12. The TTC test indicated

better durability for the samples cured at 73oF (Figure 4.11), whereas the RCP

test showed that the Fly ash and slag mixes had better durability at the higher

curing temperatures.

Phase 3 Microstructural Analysis

SEM Observations of Plain Cement Mixes

Effect of Curing Temperature on the Presence of Ettringite Crystals

1. None of the plain cement mixes cured at room temperature showed the

presence of ettringite crystals (Figure 4.13). These samples had the highest

permeability rates. However the high permeability values had no effect on

ettringite formation. This observation agrees with a threshold temperature

of 160F is required during curing for ettringite to reform in the hardened

concrete.

2. For the plain cement mixes cured at the elevated temperatures of 160 and

180F, there was no observation of ettringite crystals when examined

microscopically after 7 days of curing.









3. For the plain cement mixes cured at the elevated temperatures of 160 and

1800F, ettringite was present when they were examined at 28 and 91 days

(Figures 4.14 & 4.16). These samples had higher permeability values when

compared to the room cured samples.

Effect of Curing Duration on the Amount of Ettringite Crystals formed

1. At the elevated curing temperatures of 160 and 180oF well-formed balls of

ettringite crystals were seen in the voids when examined at 28 days.

2. The high permeability of the samples cured at the elevated temperatures

facilitated the formation and transportation of ettringite within the

microstructure of the hardened samples. Voids observed partially filled with

ettringite when examined at 28 days showed an increased amount of the

ettringite crystals when examined at 91 days. Figures 5 and 7 show voids

completely filled with ettringite when examined at 91 days, a direct

consequence of the increased permeability.










()', FA '3F -28dais


Figure 4.13 Well-defined Monosulphate (M) crystals in a void


Figure 4.14. Void with clusters of Ettringite (E) crystals































Figure 4.15. Void containing both Monosulphate (M) and Ettringite (E) crystals


igure 4.16. Voids containing Ettringite


some appear almost full of it.

































Figure 4.17. Void completely filled with fibrous Ettringite (E)


SEM Observations of Fly Ash Mixes

Introduction

Calcium hydroxide crystals formed by the hydrating cement constitute 20 to 25

percent of the volume of solid in the hydrated phase (Neville, 2004). Calcium hydroxide

is water-soluble and may leach out of hardened concrete, leaving voids for ingress of

water. Through its pozzolanic properties, fly ash chemically combines with calcium

hydroxide and water to produce C-S-H, which fills in the spaces between hydrating

cement particles, thus reducing the risk of leaching calcium hydroxide. The long-term

reaction of fly ash refines the pore structure of concrete and reduces the permeability

(ACI 232.2R-96, 1999). At normal temperatures, little pozzolanic activity from fly ash

occurs after 28 days of curing (Malhotra and Ramezanianpour, 1994), this is evident in


I









the almost identical permeability values for the fly ash mixes and the plain cement mixes

at 28 days cured at room temperatures. At the elevated temperatures however the

pozzolanic activity occurs sooner and this is evident in the much lower permeability of

the fly ash mixes cured at the elevated temperatures when compared to the plain cement

mixes. At the elevated curing temperatures, the permeability values of the plain cement

mixes is about 3 times more than those of the fly ash mixes.

Effect of Curing Temperature on the Presence of Ettringite Crystals

1. The fly ash samples cured at room temperature did not show the presence of

ettringite even though the RCP test indicated the higher permeability values

when compared to the fly ash mixes cured at the elevated temperatures.

2. At the elevated temperature curing of 160F, ettringite was not present

when examined at 28 days as shown in Figure 4.18. The low permeability

of these samples will inhibit the ingress of water and the formation of

ettringite. At 91 days however these samples showed the presence of

ettringite crystals in the void spaces.

3. Ettringite was observed at 28 days in the fly ash samples cured at 180F

(Figure 4.19) just as in the plain cement mixes. These samples have almost

identical permeability values to the fly ash samples cured at 160F. While

the samples cured at 160F did not show ettringite at 28 days, the higher

curing temperature of 180F will account for the observation of the

ettringite in the higher cured samples.









Effect of Curing Duration on the Amount of Ettringite Crystals formed in Voids

1. At 28 days, the ettringite formed in the voids of samples cured at 1800F was

not as big and in well-formed balls as the crystals seen in the equivalent

plain cement mixes.

2. At 91 days, examination of the fly ash samples cured at 1800F showed

ettringite crystals in pore spaces (Figure 4.20). The amount of ettringite

observed was increased from that observed in these samples at 28 days.

These pores however were not entirely filled with the ettringite when

compared to the equivalent plain cement mixes.


== M L 18" FA 160F 28days


Figure 4.18. Void containing hexagonal plates of Monosulphate (M).































Figure 4.19. Void showing Monosulphate (M) transformed into Ettringite (E)


18",F.\ 180F 91dal s


Figure 4.20. Clusters of Fibrous Ettringite (E) in void


18%FA 180F 28days









SEM Observations of Slag Mixes

Introduction

Slag is a waste product in the manufacture of pig iron. Chemically, slag is a

mixture of lime, silica, and alumina, the same oxides that make up Portland cement, but

not in the same proportions (Neville, 2004). The permeability of mature concrete

containing slag is greatly reduced when compared with concrete not containing slag. As

the slag content is increased, permeability decreases. The pore structure of the

cementitious matrix is changed through the reactions of slag with the calcium hydroxide

and alkalis formed during the Portland cement hydration. Pores in concrete normally

containing calcium hydroxide in part get filled with calcium silicate hydrate. Permeability

of concrete depends on its porosity and pore-size distribution. Where slag is used,

reduction in the pore size has been noted prior to 28 days after mixing (ACI 233R-95,

1999).

Miller and Conway (2003) examined the effectiveness of using slag to prevent DEF

expansions in mortar made from expansive cements. One year into the study, they found

that 5% slag substitution reduced or delayed, but did not eliminate expansions at curing

temperatures above 167F (75C). Expansion was however completely absent when

17.5% slag substitution was used. Substitution of the cement by slag did not have any

adverse effect on the strength of the mortar cured at 1940F (90C) which showed superior

strength at all ages for all mixes with 30% slag substitution (Miller and Conway, 2003).

This was also evident in compressive strength tests of the mixes used in this study which

showed higher strengths for the slag mixes cured at elevated temperatures (Chini and

Acquaye, 2005). The beneficial effect of added slag in reducing expansions from DEF

may have to do with the reduced pH of the pore solution. Ettringite is more stable below









pH of 12.5 and the slag may reduce the pH to the region where ettringite stability is

enhanced. If there is less decomposition at the elevated temperature, less ettringite may

potentially form later, when its formation may lead to volume instability (Miller and

Conway, 2003).

Effect of Curing Temperature on the Presence of Ettringite Crystals

1. At all curing temperatures, the slag mixes had the lowest permeability

values of the mixes tested.

2. No ettringite was observed at 28 days in the slag samples cured at the

elevated temperatures (Figures 4.21 and 4.23). The slag samples had the

least permeability values when compared to equivalent plain cement and fly

ash mixes.

3. At 91 days, slag mixes cured at the elevated temperatures showed the

presence of ettringite. Inclusion of 50% slag was the most effective at

delaying the onset of the ettringite. However by 91 days, these ettringite

crystals were observed in the void spaces

Effect of Curing Duration on the Amount of Ettringite Crystals formed

1. The amount of ettringite in the voids observed at 91 days in the elevated

cured samples was in much smaller amounts than in the fly ash or plain

cement mixes. They could only be seen at very high magnifications as

shown in Figure 4.22.

2. Some ettringite crystals were formed on the surfaces of slag particles as

seen in Figures 4.24 and 4.25























Figure 4.21. Sample with empty air Voids (V)


F%


Figure 4.22 Higher magnification of Figure 4.32











50"oBFS 180F 28days


Figure 4.23. Sample with empty air Void (V)


Figure 4.24. Reacting Slag (S) particle with Ettringite (E) formed


- -dP W