Control of Early Age Shrinkage Cracking in Reinforced

Home , Concrete plant

CONTROL OF EARLY AGE SHRINKAGE CRACKING IN REINFORCED

CONCRETE BRIDGE DECKS

A Thesis

Presented to

The Graduate Faculty of The University of Akron

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

Mohamed Essili

August, 2017 CONTROL OF EARLY AGE SHRINKAGE CRACKING IN REINFORCED

CONCRETE BRIDGE DECKS

Mohamed Essili

Thesis

Approved: Accepted:

______Advisor: Department Chair Dr. Anil Patnaik Dr. Wieslaw K. Binienda

______Committee Member: Interim Dean of the College Dr. Craig Menzemer Dr. Donald J. Visco

______Committee Member: Exec. Dean of the Graduate School Dr. Ping Yi Dr. Chand K. Midha

______Date

ii ABSTRACT

Early-age shrinkage cracking is commonly observed in many concrete bridge decks in the state of Ohio and elsewhere around the United States. Cracking increases the effects of freeze-thaw damage, spalling, and corrosion of steel reinforcement, thus resulting in premature deterioration and structural deficiency of the bridges. In this study, some of the main causes of the early-age cracking in the decks are identified, and several concrete mix design proportions were developed and evaluated in order to prevent or minimize the shrinkage cracking. Different admixtures (SRAs and CRAs) as well as polypropylene fibers were considered and the effects of these materials were evaluated. A series of concrete shrinkage, mechanical property and freeze-thaw tests were performed. The outcomes of this study identify optimum materials to be used in concrete mixes as appropriate mitigation strategies in order to reduce or eliminate early-age shrinkage cracking and thus help minimize shrinkage-associated cracking in concrete bridge decks, potentially leading to overall reduction in bridge deck maintenance costs.

iii ACKNOWLEDGEMENTS

I would like to express my deepest gratitude to my advisor, Dr. Anil K. Patnaik for his excellent guidance throughout my graduate studies. I am grateful for his patience, continuous support and enthusiasm at all the time in my research.

My sincere appreciation is also extended to the following individuals who made it possible for me to complete my graduate research:

 ODOT SME’s: Mr. Perry Ricciardi, and Dr. Waseem Khalifa.

 Samantha Althoff – Micromeasurements.

 Ricky Sherman – Darwin Chambers.

 David Mcvaney, University of Akron.

 Kimberly Stone, Department of Civil Engineering, University of Akron.

 UA Graduate Students: Mohamed Habouh, Srikanth Marchetty, Sourav Khatua,

Abdulla Alzlfawi, Umang Pawar and Sunil Gowda

 My family and friends for their support and encouragement as I pursued my

graduate studies

iv TABLE OF CONTENTS

LIST OF FIGURES…………………………………….…………………………………ix

LIST OF TABLES……………………………….…….………………………..………xiii

CHAPTER

I.INTRODUCTION ...... 1

1.1. Problem Statement ...... 1

1.2. Objective And Scope ...... 3

1.3. Organization ...... 4

II.LITERATURE REVIEW ...... 5

2.1. Allowable Crack Widths ...... 5

2.2. Classification Of Cracks In Reinforced Concrete Members ...... 6

2.2.1. Cracks Dependent On Applied Loadings ...... 8

2.2.2. Cracks Independent Of Loading ...... 8

2.2.2.1. Plastic Shrinkage ...... 9

2.2.2.2. Autogenous Shrinkage ...... 11

2.2.2.3. Drying Shrinkage ...... 12

2.3. Factors Related To Shrinkage Cracking In Concrete Bridge Decks ...... 13

2.3.1. Material And Mix Design Factors ...... 14

2.3.1.1. Cement Type ...... 14

2.3.1.2. Water-To-Cement Ratio ...... 14

2.3.1.3. Cement Content ...... 14

2.3.1.4. Concrete Strength ...... 15

v 2.3.1.5. Slump ...... 15

2.3.1.6. Admixtures ...... 15

2.3.1.7. Air Content ...... 17

2.3.1.8. Concrete Mixes ...... 17

2.3.1.9. Aggregate Type And Size ...... 17

2.3.2. Construction And Environmental Factors ...... 18

2.3.2.1. Weather ...... 18

2.3.2.2. Curing ...... 19

2.3.2.3. Structural Design Factors ...... 19

2.4. Effect Of Using Sras And Cras To Control Shrinkage Cracking ...... 20

2.4.1. Definition And History ...... 21

2.4.2. Function And Theory ...... 22

2.4.3. Application Techniques ...... 23

2.4.4. Material Properties ...... 23

2.4.5. Previous Research On Sra And Cra ...... 24

2.4.5.1. State Dots ...... 25

2.4.5.2. Other Researchers ...... 27

2.5. Use Of Fibers To Control Shrinkage Cracking ...... 29

2.6. Testing Methods ...... 32

2.6.1. Unrestrained (Free) Shrinkage Test ...... 32

2.6.2. Restrained Shrinkage Tests (Ring Tests) ...... 33

2.6.3. Plastic Shrinkage (Panel) Test ...... 34

2.6.4. Freeze-Thaw Durability Of Concrete ...... 36

vi 2.7. Summary Of Literature Review ...... 39

III.EXPERIMENTAL PROGRAM ...... 42

3.1. Introduction ...... 42

3.2. Materials ...... 43

3.2.1. Cementitious Materials ...... 43

3.2.2. Aggregates ...... 43

3.2.3. Chemical Admixtures ...... 45

3.2.4. Polypropylene Fibers ...... 46

3.3. Concrete Mixes ...... 47

3.4. Testing Program ...... 51

3.4.1. Concrete Mixing Procedure ...... 52

3.4.2. Fresh Concrete Properties ...... 53

3.4.3. Mechanical Testing ...... 55

3.4.3.1. Compressive Strength And Split Tensile Strength Test ...... 55

3.4.3.2. Flexural Tensile Strength Test ...... 56

3.4.4. Shrinkage Tests ...... 57

3.4.4.1. Plastic Shrinkage Panel Test ...... 57

3.4.4.2. Free Shrinkage Test ...... 60

3.4.4.3. Restrained Shrinkage Ring Test ...... 62

3.4.5. Freeze-Thaw Testing ...... 66

IV.TEST RESULTS ...... 69

4.1. Introduction ...... 69

4.2. Fresh Property Tests ...... 69

vii 4.3. Mechanical Properties Tests...... 70

4.3.1. Compressive Strength Test ...... 70

4.3.2. Split Tensile Strength Test ...... 72

4.3.3. Flexural Strength Test ...... 73

4.4. Shrinkage Tests ...... 75

4.4.1. Plastic Shrinkage (Panel) Test ...... 75

4.4.2. Free Shrinkage Test ...... 78

4.4.3. Restrained Shrinkage Test ...... 81

4.5. Freeze Thaw Tests ...... 84

V.CONCLUSIONS AND RECOMMENDATIONS ...... 88

5.1. Conclusions ...... 88

5.2. Recommendations ...... 89

REFERENCES ...... 90

APPENDIX ...... 90

viii LIST OF FIGURES

Figure 1.1 Early-age Shrinkage Cracking in Concrete Bridge Decks ...... 2

Figure 1.2 Transverse Cracking Caused by Drying Shrinkage in Concrete Bridge Decks 3

Figure 2.1 Classification of cracks in reinforced concrete members (Patnaik et al, 2014) 7

Figure 2.2 Common causes for cracking in concrete structures. (TRC E-C107, 2006) ..... 7

Figure 2.3: Factors related to cracking in concrete bridge decks (Patnaik and Baah, 2014)

...... 13

Figure 2.4 Effect of SRA on Concrete Drying Shrinkage ...... 24

Figure 2.5 Effect of CRA Compared To Conventional SRA ...... 29

Figure 2.6 Effect of Polypropylene Fibers on Crack Width ...... 30

Figure 2.7 -Typical Plot of Crack Patterns of Test Slabs Without Fibers (Left) And With

0.3 Kg/M3 (0.5 Lbs/yd3) Monofilament Fibers (Right) (Patnaik et al, 2007) ...... 31

Figure 2.8 Free Shrinkage Test Specimen (ASTM C 157) ...... 32

Figure 2.9 Free Shrinkage Test Setup ...... 33

Figure 2.10 Ring Test Setup According to Different Standards ...... 34

Figure 2.11 Panel Test Setup (Kraai, 1985) ...... 34

Figure 2.12 Shrinkage Panel Forms (Patnaik et al, 2007) ...... 36

Figure 2.13 Freeze-Thaw Test Apparatus ...... 37

Figure 2.14 Comparison of Plain and Fiber Reinforced Concretes Under Freeze-Thaw

(Balaguru and V. Ramakrishnan, 1986) ...... 38

Figure 3.1 TUF-STRAND SF Polypropylene Fiber ...... 47

Figure 3.2 Slump Test Apparatus ...... 54

ix Figure 3.3 Air Content Test Apparatus ...... 54

Figure 3.4 Compressive Strength Testing ...... 55

Figure 3.5 Split Tensile Strength Testing ...... 56

Figure 3.6 Flexural Tensile Strength Testing ...... 57

Figure 3.7 Preparation of Test Panels ...... 58

Figure 3.8 Testing of the Panels ...... 59

Figure 3.9 Shrinkage Panel Test ...... 59

Figure 3.10 Free Shrinkage Specimen Molds ...... 61

Figure 3.11 Free Shrinkage Specimens ...... 61

Figure 3.12 Measurement of Free Shrinkage using ASTM C490 ...... 62

Figure 3.13 Dimensions of Used Ring vs. AASHTO Standard Ring ...... 63

Figure 3.14 Ring Specimen Molds ...... 63

Figure 3.15 Casting of Concrete Rings ...... 64

Figure 3.16 Shrinkage Specimens Placed in Environmental Chamber ...... 65

Figure 3.17 Shrinkage Specimens Connected to Data Acquisition System ...... 65

Figure 3.18 Freeze-Thaw Specimens inside the Chamber...... 66

Fig. 3.19 Freeze-Thaw Specimens’ Tray ...... 67

Figure 3.20 Curing Of Freeze-Thaw Specimens ...... 67

Figure 3.21 Resonance Frequency Test ...... 68

Figure 3.22 Freeze-Thaw Cycle ...... 68

Figure 4.1 Compressive Strength of Different Mixtures ...... 71

Figure 4.2 Split Tensile Strength of Different Mixtures ...... 73

Figure 4.3 Flexural Strength Test Data ...... 74

x Figure 4.4 Panel Test Results...... 76

Figure 4.5 Typical Crack Distribution in Non-Fiber Mixtures ...... 77

Figure 4.6 Typical Crack Distribution in Fiber-Reinforced Mixtures ...... 77

Fig. 4.7 Free shrinkage in Non-fiber Mixtures ...... 78

Figure 4.8 Free shrinkage in Fiber-Reinforced Mixtures ...... 78

Figure 4.9 Free Shrinkage Tendency Diagrams ...... 79

Figure 4.10 Strains in non-Fiber Ring Specimens ...... 82

Figure 4.11 Strains in Fiber-Reinforced Ring Specimens ...... 82

Fig. 4.12 Cracking in Control Specimen at 10-11 Days ...... 83

Figure 4.13 Cracking in SRA Specimen at 14-15 Days ...... 83

Figure 4.14 Tendency Diagrams for Freeze-Thaw ...... 85

Figure 4.15 Damage in non-fiber Freeze-thaw Specimens after 60 cycles ...... 86

Figure 4.16 Damage in fiber-reinforced Freeze-thaw Specimens after 60 cycles ...... 86

Figure A.1 Free Shrinkage in The Control Mix ...... 98

Figure A.2 Free Shrinkage in The SRA Mix ...... 98

Figure A.3 Free Shrinkage in The CRA Mix ...... 99

Figure A.4 Free Shrinkage in The Fibers Mix ...... 99

Figure A.5 Free Shrinkage in The Fibers + SRA Mix ...... 100

Figure A.6 Free Shrinkage in The Fibers + CRA Mix ...... 100

Figure A.7 Restrained Shrinkage in The Control Mix (2 Rings) ...... 101

Figure A.8 Restrained Shrinkage in The SRA Mix (2 Rings) ...... 101

Figure A.9 Restrained Shrinkage in The CRA Mix (2 Rings) ...... 102

Figure A.10 Restrained Shrinkage in The Fibers Mix (2 Rings) ...... 102

xi Figure A.11 Restrained Shrinkage in The Fibers+SRA Mix (2 Rings) ...... 103

Figure A.12 Restrained Shrinkage in The Fibers+CRA Mix (2 Rings) ...... 103

Figure A.13 Flexure in Control Specimen #1 ...... 104

Figure A.14 Flexure in Control Specimen #2 ...... 104

Figure A.15 Flexure in SRA Specimen #1 ...... 105

Figure A.16 Flexure in SRA Specimen #2 ...... 105

Figure A.17 Flexure in CRA Specimen #1 ...... 106

Figure A.18 Flexure in CRA Specimen #2 ...... 106

Figure A.19 Flexure in Fiber Specimen #1 ...... 107

Figure A.20 Flexure in Fiber Specimen #2 ...... 107

Figure A.22 Flexure in Fiber+SRA Specimen #2 ...... 108

Figure A.23 Flexure in Fiber+CRA Specimen #1 ...... 109

Figure A.24 Flexure in Fiber+CRA Specimen #2 ...... 109

xii LIST OF TABLES

Table 2.1 Allowable Crack Widths from ACI 224R-01 (2008) ...... 6

Table 2.2 Classification of Non Load-Independent Cracking (TRC E-C107, 2006) ...... 9

Table 2.3: Design Factors Affecting Bridge Deck Cracks (Shing and Abu-

Hejleh, 1999) ...... 20

Table 3.1 Properties and Chemical Contents Of Cement ...... 43

Table 3.2 #8 Coarse Aggregate Gradations (Sieve Analysis)...... 44

Table 3.3 Fine Aggregate Gradation (Sieve Analysis) ...... 44

Table 3.4 Mixes Used For Plastic Shrinkage Panel Test ...... 49

Table 3.5 Mixes Used For All Other Tests ...... 50

Table 3.6 Fresh and Hardened Property Tests ...... 51

Table 4.1 Compressive Strength Test Data (psi) ...... 71

Table 4.2 Split Tensile Test Data (psi) ...... 72

Table 4.3 Flexural Strength Test Data ...... 74

Table 4.4 Panel Test Results ...... 76

Table 4.5 Free Shrinkage Results ...... 80

Table 4.6 Restrained Shrinkage Results ...... 81

xiii CHAPTER I

INTRODUCTION

1.1.Problem Statement

Cracking in reinforced concrete bridge decks continues to be a statewide problem in

Ohio. A study by the National Cooperative Highway Research Program (NCHRP) reported that there were more than 100,000 bridges in US suffering from early transverse cracks

(Krauss and Rogalla 1996). Bridge decks in Ohio continue to suffer greatly from this problem. Previous investigations have indicated that several bridges across the state are experiencing cracking widths over 10 times the maximum limit allowed by ACI-224

(Ganapuram et. al, 2012).

Concrete is by its nature a quasi-brittle material with a low capacity for deformation under tensile stresses. Mechanical loading, deleterious reactions, and environment loading can result in the development of tensile stresses in concrete. These tensile stresses all too frequently result in cracking that can adversely affect the performance of concrete.

The most common cause of cracking in concrete bridge decks stems from distress caused by shrinkage. Most shrinkage cracking occurs early in the bridge’s life right after construction, and continues to affect the bridge’s performance throughout its service life.

The presence of early-age cracking in concrete bridge decks increases the effects of freeze- thaw damage, spalling due to sulfate and chloride penetration, and corrosion of steel

1 reinforcement, thus resulting in premature deterioration and structural deficiency of bridges. There is a great need to reduce the extent of this cracking and thereby prevent deterioration.

Over the years, several solutions have been devised to mitigate the problem of shrinkage cracking. Fibers and Shrinkage Reducing Admixtures (SRA) have been used extensively to combat the cracking problem. And most recently, Crack Reducing

Admixtures (CRA) have been introduced. More details on the performance of these materials and their effect on concrete can be found in literature.

Figure 1.1 Early-age Shrinkage Cracking in Concrete Bridge Decks

Figure 2.2 Transverse Cracking Caused by Drying Shrinkage in Concrete Bridge Decks

1.2.Objective and Scope

In this work, a literature review was conducted in order to investigate the causes of different types of shrinkage as well as their effects on bridge performance. Attention was focused on the use of SRAs, CRAs and fibers to prevent or slow down the progression of shrinkage-induced cracks in reinforced concrete bridge decks. The effects of these materials on other concrete properties such as freeze-thaw durability, compressive strength and flexural strength were also studied.

1.3.Organization

Five chapters are included in this thesis. Chapter one introduces the problem statement and objectives of this study. Chapter two provides a literature review on the past research related to the early-age shrinkage cracking. Chapter three presents the experimental program that was adopted. Chapter four summarize the test results of the different concrete mixes under mechanical tests, shrinkage conditions and freeze-thaw conditions, respectively. Finally chapter five offers concluding remarks and recommendations as well as future research plans.

4 CHAPTER II LITERATURE REVIEW

2.1.Allowable Crack Widths

In order to mitigate the effects of cracks on reinforced concrete bridge decks, the design of reinforced concrete members must make sure that crack widths do not exceed the allowable limits under normal service conditions. The cracking of a reinforced concrete slab at service loads should not impact the appearance of the structure or lead to corrosion of the embedded reinforcement.

Widening of cracks due to loading as well as freeze-thaw action can lead to severe effects on the performance of reinforced concrete. Wide cracks allow deleterious materials such as chemicals from deicing salts to penetrate the concrete cover and cause corrosion of the reinforcing steel, leading to concrete spalling.

ACI Committee 224 states that crack widths equal to or greater than 0.007 in. can cause deterioration related to durability when bridge decks are exposed to de-icing chemicals.

According to these guidelines, crack widths in the range 0.01 to 0.015 in. are acceptable from aesthetic considerations (ACI 224R-01). The maximum reasonable crack widths are shown in Table 2.1.

5 Table 2.1 Allowable Crack Widths from ACI 224R-01 (2008) Crack Width Exposure Condition in. mm

Dry air or protective membrane 0.016 0.41

Humidity, moist air, soil 0.012 0.30

Deicing chemicals 0.007 0.18

Seawater and seawater spray, wetting and 0.006 0.15 drying

Water-retaining structures 0.004 0.10

2.2.Classification of Cracks in Reinforced Concrete Members

Reinforced concrete cracks could be classified in three different ways as shown in

Figure 2.1: (Patnaik et al, 2014).

i. Cracks that are dependent on applied loadings,

ii. Cracks independent of loading, and iii. Cracks based on orientation.

Figure 2.1 Classification of cracks in reinforced concrete members (Patnaik et al, 2014)

TRC E-C107 classifies the causes of reinforced concrete cracking into two main categories; before and after hardening as illustrated in Figure 2.2. (TRC E-C107, 2006).

Figure 2.2 Common causes for cracking in concrete structures. (TRC E-C107, 2006)

Cracks that occur before hardening, primarily due to settlement or shrinkage, construction movements, and excessive evaporation of water, are called plastic cracks.

Plastic cracking can be predominantly eliminated through close attention to the mixture design, material placement, and curing. Cracks that occur after the concrete has hardened

7 may be due to a variety of reasons. These cracks may be due to mechanical loading, moisture and thermal gradients, chemical reactions of incompatible materials (e.g., alkali- aggregate reactions) or environmental loading (e.g. freezing of water in unsound aggregate or paste).

2.2.1. Cracks Dependent on Applied Loadings

According to Leonhardt (1977), cracks formed in reinforced concrete members can be classified into two main categories: (i) cracks caused by externally applied loads and

(ii) cracks that occur independently of the loads. Flexural cracks and inclined shear cracks are the two main types of cracks caused by externally applied loads.

2.2.2. Cracks Independent of Loading

While the commonly held belief is that external loading is responsible for generating the majority of the tensile stresses in a material, much of the cracking in concrete can be traced to an intrinsic volumetric instability or the deleterious chemical reactions. The volume instability results in response to moisture, chemical, and thermal effects. In addition, various deleterious chemical reactions involving the constituents of concrete or embedded materials can play significant roles causing localized internal expansions. Table

2.2 provides a summary of cracks due to environmental conditions, and discusses when they are most likely to occur.

Table 2.2 Classification of Non Load-Independent Cracking (TRC E-C107, 2006)

2.2.2.1.Plastic Shrinkage

Plastic shrinkage is associated with the evolution of shrinkage at the concrete surface.

Plastic shrinkage occurs within the first few hours after placement of the fresh concrete while still in the forms. Concrete bridge decks are more prone to this type of shrinkage because of the relatively high concrete surface exposed to dry air (Nawy, 1996). The primary cause of "plastic shrinkage" cracks is the rapid evaporation of water from the surface of the concrete. Immediately after the concrete has been placed, the particles within the concrete begin to settle. When the particles settle, the water within the concrete

9 displaces and rises to the top. This process is better known as "bleeding." Not all of the water within the concrete displaces. Under most weather conditions, some of the water on the surface of the concrete evaporates. The rate of evaporation depends on factors such as the temperature of the concrete, temperature of the air, relative humidity, and wind velocity surrounding the concrete. When the rate of evaporation of water from the surface of concrete exceeds its bleeding rate the surface begins to dry resulting in high capillary stress development near the surface (Cohen et al. 1989). Plastic shrinkage cracks typically occur on horizontal surfaces exposed to the atmosphere. These cracks are different from other early cracks because they are deeper and wider. Plastic shrinkage cracks are typically two to four inches deep and approximately one-eighth inch wide. They may also extend several feet in length adopting a crow’s-foot pattern. These cracks form before any bond has developed between the aggregate particles and mortar. Therefore, the cracks tend to follow the edges of large aggregate particles or reinforcing bars and never break through the aggregate particles. Although plastic shrinkage cracks usually do not impair the structural performance of the slab, cracks in some building floors have been blamed for leakage.

Mitigation Strategies: In order to reduce plastic shrinkage, the rate of water evaporation should be minimized. According to research studies performed by the Departments of

Transportation of Ohio, Minnesota, Idaho and Nevada; it is recommended to wait for ideal conditions, put up windbreaks, shade the deck, or apply a fog mist or evaporation retarder film as soon as possible after pouring and rapidly complete the finishing of the deck

(Schmeckpeper and Lecoultre, 2008) (MDOT,2011). NDOT recommends the implementation of SCC/SCA in concrete mix design. However, proper curing should be ensured. NDOT also recommends the addition of SRA to the concrete mix, but requires

10 that the implementation of the SRA in environments of moderate to severe freezing and thawing must be done cautiously (Ah-sha et al. 2001).

2.2.2.2.Autogenous Shrinkage

When cement consumes water for hydration purposes, it takes up less space than the cement and water particles separately before hydration, causing autogenous (self- generated/chemical) shrinkage. The main reason behind autogeneous shrinkage is low w/c

(Neville, 1995). As long as the water-to-cement ratio is greater than about 0.42, drying shrinkage is the dominant volume change and autogenous shrinkage only represents about

5 percent of the total shrinkage . However, as the water-to-cement ratio decreases, the autogenous shrinkage increases and can reach 50 to 400 microstrain, as much as half of the total shrinkage for water-to-cement ratios of 0.30. Autogenous shrinkage is especially detrimental to concrete because it occurs during the first several days of hydration when the concrete is still in a plastic or low strength state. By delaying the time in which the initial hydration occurs, by adding retarders or pouring during cold weather, autogenous shrinkage has more time to occur and can become increasingly severe. (Schmeckpeper and

Lecoultre, 2008) (Brown et al. 2001) (TRC E-C107, 2006).

Mitigation Strategies: Autogenous shrinkage can be largely prevented by avoiding extremely low water-to-cement ratios (below 0.40) and high paste volumes, keeping the surface of the concrete continuously wet; conventional curing by sealing the surface to prevent evaporation is not enough and water curing is essential. With wet curing, water is drawn into the capillaries and the shrinkage does not occur. Note that autogenous shrinkage

11 is separate from and additional to conventional drying shrinkage, which will start when water curing ceases. (The Concrete Society, 2006).

2.2.2.3.Drying Shrinkage

Drying shrinkage is primarily an issue related to the cement paste and depends strongly on the amount of water present in the concrete mixture before hardening (plastic state) and remaining after hardening (hardened state). There are three main mechanisms of drying shrinkage: capillary stress, disjoining pressure, and surface tension. Each of these mechanisms is dominant in a different range of relative humidity. The most relevant range of relative humidity for field conditions is 45%-90%. In this range the capillary stress mechanism is the most dominant. As water evaporates, the tensile stresses that were confined to the surface tension of the water are transferred to the walls of the capillary pores (Brown et al. 2001). Full-depth drying shrinkage cracks typically begin to form at a restrained 400 microstrain and usually develop above the uppermost transverse bars

(Babaei & Fouladgar, 1997). Since the drying occurs over a period of time, creep acts beneficially to relieve the stress build up caused by drying and reduce drying shrinkage cracks. A Minnesota study suggests that the rate of shrinkage, not the ultimate shrinkage, has more of an affect on the amount of drying shrinkage cracks that develop (French et al,

1999). Factors affecting drying shrinkage are ambient relative humidity, temperature, wind velocity, and time of exposure.

Mitigation Strategies: Drying shrinkage can be prevented by reducing the volume of the cement paste, water-cement ratio, water content, better combined aggregate gradation, or pozzolans such as Class F fly ash, minimization of poorly graded fine aggregates and by

12 using Type II cement (Babaei & Fouladgar, 1997) ;(French et al, 1999); (Brown et al.

2001); (TRC E-C107, 2006). The addition of SRA can also reduce drying shrinkage by as much as 50 to 60 percent (Nmai et al, 1998); (Ah-sha, 2001).

2.3.Factors Related to Shrinkage Cracking in Concrete Bridge Decks

Patnaik and Baah (2014) classified the Factors related to cracking in bridge decks into the following groups (Figure 2.3):

• Material and mix design factors;

• Construction and environmental factors;

• Structural and foundation issues;

• Traffic related factors; and

• Other factors, including age of the bridge.

Figure 2.3 shows the categories of factors related to cracking in bridge decks, and the types of cracks that belong to each category.

Figure 2.3: Factors related to cracking in concrete bridge decks (Patnaik and Baah, 2014)

2.3.1. Material and Mix Design Factors

Several material and mix design factors are related to shrinkage cracking in concrete bridges. These factors are discussed in greater detail in the following subsections.

2.3.1.1.Cement Type

The type of cement used plays an important role in reducing shrinkage cracking.

Several researchers and state DOTs recommend the use of cement type II and avoiding finely ground cement and Type III cement in warm weather conditions. Concrete with lower cement content and Type II cement has a lower risk of cracking than that with Type

I cement, because Type II cement has a lower heat of hydration (TRS1105, 2011); (Shing and Abu-Hejleh, 1999); (Krauss and Rogalla, 1996).

2.3.1.2.Water-to-Cement Ratio

The water-to-cement ratio also affects the concrete strength. With a given amount of cement, a higher water-to-cement ratio produces more cement paste generating a weaker yet more workable concrete. The lowest possible water-to-cement ratio to meet the workability requirements will minimize the cracking tendency by reducing shrinkage

(McDonald, Krauss, and Rogalla 1995).

2.3.1.3.Cement Content

Minimizing the cement content has a positive direct effect on reducing and controlling shrinkage cracking. Using smaller amounts of cement decreases the heat generated from hydration resulting in low thermal shrinkage. Concrete with less cement exhibits less

14 drying and autogenous shrinkage (TRC E-C107, 2006); (Darwin et al, 2004). Colorado

DOT recommends a limit on cement content to a maximum of 470 Ib/yd3 or lower if possible (1999).

2.3.1.4.Concrete Strength

It may seem that high early strength of concrete may reduce cracking but since the strength gain of concrete is usually accompanied by a gain in modulus of elasticity, it can’t be easily said that higher strength reduces cracking. There is no general agreement among studies that considered this factor. Schmitt and Darwin (1995), (1999) noticed increased cracking with increased compressive strength. Shing and Abu Hejleh (1999) also recommended against fast strength gain in deck concrete. Krauss and Rogalla (1996) recommended the use of concrete with low early strength. On the other hand, Ramey et al.

(1997) recommended increasing compressive strength.

2.3.1.5.Slump

Schmitt and Darwin (1995) noted that cracking increases with increasing slump. This could be a result of the effect of increased slump on settlement cracking or the effects of a higher water and/or cement content corresponding to the increase in slump. Issa (1999) attributed cracking of concrete to use of high slump concrete.

2.3.1.6.Admixtures

Admixtures may have both positive and negative effects on deck cracking. (TRC E-

C107, 2006). Chemical admixtures, except air-entraining admixtures, should conform to

15 the requirements of AASHTO specification M194, which lists the following types of admixtures:

Type A—water-reducing;

Type B—retarding;

Type C—accelerating;

Type D—water-reducing and retarding;

Type E—water-reducing and accelerating;

Type F—water-reducing, high-range; and

Type G—water-reducing, high-range, and retarding.

Water-reducing admixtures are particularly beneficial in increasing workability while maintaining a constant w/cm or maintaining workability while lowering the w/cm. This facilitates the development of a workable concrete mix for which a maximum w/cm is specified. In projects with closely spaced or congested reinforcement, the use of high- range, water-reducing admixtures help concrete flow around these obstructions without segregation (NCHRP Synthesis-333, 2004). Retarding admixtures reduce the rise in temperature of the concrete and may be used to reduce the potential for thermal shrinkage cracking. Retarders are particularly useful when the ambient temperature is expected to reach or exceed 24°C (75°F). Water reducers are used because they result in reduction in the amount of mix water and resulting drying shrinkage. Shrinkage reducing admixtures may also be used for some applications to reduce shrinkage by as much as 50% (Weiss and

Berke, 2002).

2.3.1.7.Air Content

Air content is usually used to increase freeze thaw durability of concrete. But it may be advantageous to use high values of air content in moderate and warm climates. Cheng and Johnson (1985) observed that increase in air content reduces cracking. Schmitt and

Darwin (1999) even noticed significant decreases in cracking with air content more than

6% and recommend at least 6% air content. French et al. (1999) recommend air content of

5.5-6%. On the other hand, Stewart and Gunderson (1969) found no relationship between air content and cracking, which in recent times has been disproved.

2.3.1.8.Concrete Mixes

Concrete mixtures made using higher cement contents are very conducive to cracking by producing higher heat of hydration, greater shrinkage, higher modulus of elasticity, and lower creep. Frequent use of high strength concretes in the construction industry tends to encourage increased cement contents increasing the cost of the mixture and increasing cracking. TRC E-C107(2006) highly recommends proper planning during materials selection and mixture proportioning, a crack-resistant concrete having lower cement content, which still meets durability and performance specifications, can be produced.

2.3.1.9.Aggregate Type and Size

Aggregate type and size influence the strength, elastic modulus, shrinkage and creep.

Both aggregate quantity and quality should be carefully examined when designing a crack resistant deck mixture. Increasing aggregate content will allow a reduction in the paste content while reducing the mixture component that is most susceptible to shrinkage and

17 thermal stresses (TRC E-C107). Suggestion on aggregate from prior studies include using largest possible size of aggregate, maximizing aggregate volume and using low shrinkage aggregate to reduce cracking (Babaei and Purvis, 1994; Krauss and Rogalla, 1996; French et al., 1999; PCA, 1970).

2.3.2. Construction and Environmental Factors

2.3.2.1.Weather

The weather during placement of the concrete bridge deck can affect the tendency for cracking. An acceptable temperature range for deck casting is recommended to be between

40o F to 90o F. Also, concrete placement should be avoided on days when the temperature range between high and low temperature exceeds 50o F, because additional thermal stresses will be produced in the deck (French et al. 1999). In addition, thermal stresses can be generated when concrete is cast on girders in cold weather due to the differences in temperature of the girders and the heat of hydration of the concrete deck. In hot weather and on windy days, rapid surface evaporation can lead to plastic shrinkage cracks or drying shrinkage cracks. By monitoring the evaporation rate, precautions can be taken to reduce concrete moisture losses using sunscreens, windbreaks, fog mist, and chemical curing films

(McDonald, Krauss, and Rogalla 1995); (Schmitt and Darwin, 1995). Early evening or night casting can also help to reduce the cracking tendency.

2.3.2.2.Curing

The curing process is very important to eliminate plastic shrinkage cracking and to reduce drying shrinkage cracking. In the early stages of concrete curing, the hydration process is relatively slow and requires the cement to be saturated with water. If water is allowed to evaporate from the surface, the concrete will not acquire any additional strength.

Immediately after finishing the deck, wet curing of the concrete should begin. Curing can be accomplished by ponding water on the deck or by covering the deck with wet burlap covered with plastic sheeting. The deck must remain wet until the curing process is complete. The longer the deck is cured, the higher the concrete strength, the lower the shrinkage, and the less likely transverse cracks will form. From studies performed by

McDonald et al. (1995), moist curing is recommended to last at least seven days.

2.3.2.3.Structural Design Factors

The severity of deck cracking depends, to a certain extent, on the structural aspects of bridge decks. Table 2.3 shows design factors affecting stringer supported bridge deck cracks.

Table 2.3: Design Factors Affecting Bridge Deck Cracks (Shing and Abu- Hejleh, 1999)

2.4.Effect of Using SRAs and CRAs to Control Shrinkage Cracking

The use of SRAs to control shrinkage cracks in concrete is a relatively new concept

(Nmai et al, 1998). SRAs were first introduced in Japan in 1982. In 1985, U.S. Patent

Number 4,547,223 was granted to Goto et al. for developing the main component of SRA which is polyoxyalkylene alkyl ether, a lower alcohol alkyleneoxide adduct. And finally In

1996, Berke et al. patented the product in the U.S. Shrinkage-reducing admixtures provide an effective method of reducing the strains caused by shrinkage and the resulting stresses while maintaining the original concrete mixture proportions and mixing requirements relatively unchanged (Berke et al, 1997).

2.4.1. Definition and History

Whittmann (1976) explained the reasons behind plastic shrinkage cracking in concrete surface. According to his research, the evaporation of bleed water on the surface of concrete creates air-liquid menisci in the liquid between the solid particles on the surface. These menisci cause tensile stress to develop in the pore fluid, leading to shrinkage. The viscous nature of the material at these early ages causes the majority of the shrinkage to occur in the vertical direction. As the system shrinks, the pore fluid is brought to the surface and evaporates (Whittmann, 1976). SRA works by reducing the surface tension of the pore water and thus lowering plastic shrinkage (Lura et al., 2006). This decrease of surface tension in the pore fluid in the SRA mixtures results in less evaporation, reduced settlement, reduced capillary pressure, and lower crack-inducing stresses at the topmost layer of the mortar. Therefore SRA reduces the potential for the development of plastic shrinkage cracks.

The mechanisms responsible for drying shrinkage are not yet fully understood; however, its occurrence is mainly attributed to capillary stresses (L’Hermite, 1988). When pore water evaporates from capillary pores in hardened concrete during drying, tension in the liquid is transferred to the capillary walls, resulting in drying shrinkage (Foliard and

Berke, 1997). For a given pore size distribution, the internal stress generated upon

21 evaporation is proportional to the surface tension of the pore water solution. SRAs reduce drying shrinkage by lowering the surface tension of pore water in hardened concrete. Thus, upon evaporation from capillary pores during drying, there is less tendency for shrinkage and resultant stresses.

2.4.2. Function and Theory

Berke, 1997). For a given pore size distribution, the internal stress generated upon

22 evaporation is proportional to the surface tension of the pore water solution. SRAs reduce drying shrinkage by lowering the surface tension of pore water in hardened concrete. Thus, upon evaporation from capillary pores during drying, there is less tendency for shrinkage and resultant stresses.

2.4.3. Application Techniques

There are two ways of applying SRA. One is to simply either brush it or spray it on top of the concrete surface, called the impregnation method or topical application. The second method is to integrate it in the mix during the mixing of concrete separately from any other admixtures. It has been found that the integration method provides much better results in reducing drying shrinkage (Ah-Sha, 2001). Nmai (1998) also noticed that drying shrinkage was reduced by about 50 to 60 percent when a 7.5 kg/m3 dosage of SRA was added integrally.

2.4.4. Material Properties

Shrinkage-reducing admixtures (SRA) are commercially available in the US. For this project, BASF MasterLIFE SRA 035 is considered. BASF recommends that the SRA be added in a typical dosage range between 0.5- 1.5 gal/yd3 (2.5 to 7.5 L/m3). However, dosages outside of this range may be required depending on the level of shrinkage reduction needed. BASF also strongly recommends that drying shrinkage testing be performed to determine the optimum dosage for each application and each set of materials.

The SRA contains no water, but the usual high rate of addition requires an adjustment in water content. For this reason, the manufacturer specifies that the mix water content should

23 be reduced to account for the quantity of SRA used. If the delayed addition method is used, mixing at high speed for 3-5 minutes after the addition of SRA admixture will result in mixture uniformity. The SRA does not substantially affect slump; however, it may increase bleed time and bleed ratio (10% higher). It may also delay time of set by 1-2 hours depending upon dosage and temperature. Compressive strength loss is also minimal when

SRA is used according to BASF. BASF warns that concrete applications exposed to freezing and thawing environments must be pre-approved and require field trials prior to use of the SRA.

Figure 2.4 Effect of SRA on Concrete Drying Shrinkage

2.4.5. Previous Research on SRA and CRA

A wide variety of tests have been implemented to evaluate the shrinkage and cracking behavior of concrete. Due to its simplicity, the ring test is the most widely used

24 for cracking tendency (Tritsch et al, 2005). Plate tests are also used to evaluate plastic shrinkage in fresh concrete immediately exposed to drying. The geometry of the plates limits the mixes to a small coarse aggregate or none at all. The small cross sections in the linear tests also restrict the size of the coarse aggregate (Kraai, 1985). Some of the linear tests require complicated instrumentation that monitors shrinkage and applies a tensile force to restrain the specimen (Paillère, Buil, and Serrano, 1989). In contrast to other tests, ring tests allow actual concrete mixes to be evaluated under restraint that is similar to the restraint caused by girder systems on bridge decks. Instrumenting the rings with strain gages allows the strain development to be monitored and provides an accurate indication of time-to-cracking. With the ring test, several mixes can be evaluated under the same conditions to determine which mix exhibits the best shrinkage and cracking behavior.

2.4.5.1.State DOTs

Oregon: In 2013, a research project carried out by Oregon’s DOT investigated the shrinkage threshold limits and testing protocols for ODOT high performance concrete mixes. Several testing methods were implemented including ASTM C157 test for free shrinkage and ASTM C 1581 and AASHTO PP34-98 for restrained shrinkage. Results showed that when incorporating SRA alone or a synergistic mixture of SRA and FLWA, the cracking resistance of ODOT HPC was significantly improved. The HPC with a combination of SRA and LWFA showed the most significant benefits in improving the cracking resistance (Ideker et al, 2013).

California: A study was performed by Maggenti et al (2013) for CalTrans on the combined effects of addition of SRA and Fibers to the concrete mix for the purpose of shrinkage control. It was found that the addition of SRAs to meet the Caltrans shrinkage performance

25 requirements (0.030% at 28 days and 0.045% at 180 days) led to “a dramatic reduction in cracking”. Upon inspection, several decks constructed using SRAs between 2002 and 2008 were reported to be free of visible cracking. According to CalTrans reports, the use of

SRAs could eliminate the need to specify low-strength concrete, long curing times, a low w/cm, or large aggregates.

Kansas and Missouri: A joint study by the state DOTs of Kansas and Missouri in

2005 found that adding a shrinkage-reducing admixture to concrete significantly reduces free shrinkage and restrained shrinkage rate, but also makes achieving consistent concrete properties (i.e., air content) difficult, thus requiring more air entraining admixtures

(Tritsch, 2005).

Nevada: Results from a research program conducted by NDOT recommend the implementation of the SRA in environments where moderate and severe freezing and thawing is not a concern. It also recommended that the maximum addition rate to not exceed 2.5% by weight of cementitious material. In addition, the SRA concrete should be designed at a minimum targeted compressive strength of 31 MPa (4500 psi) at 28 days, with a maximum W/C ratio not exceeding 0.45. NDOT warns that the implementation of

SRA in environments of moderate to severe freezing and thawing must be done cautiously.

Moreover, NDOT strongly encourages using a minimum of 7% plastic air content. It also recommends addition of Fly ash to SRA concrete in order to achieve desirable performance in resisting chloride ion penetration (Ah-Sha et al, 2001).

Hawaii: HDOT’s usage of SRA began in early 2001 in the construction of the

Keaiwa Stream Bridge on Hawaii Island. SRA of 96 oz per cubic yard in a concrete bridge deck was implemented to reduce shrinkage in lieu of the 30-day delayed poured closure

26 strip. To determine its effectiveness and the effects of reinforcing, a research project was undertaken by HDOT to monitor the shrinkage strains in the Keaiwa Stream bridge deck and in eight 36 x36 x 8 inch concrete specimens. These specimens were categorized into two groups, with and without the SRA and varying amounts of steel reinforcements of 0.3 to 1.2 percent. Vibrating strain gages were used to monitor shrinkage, strain and creep for one year. Results showed a 60% reduction in shrinkage in the unreinforced test specimens with SRA. Creep was also reduced by 30 percent. The reinforced sections also showed reductions in shrinkage and creep (Carnate, 2014).

2.4.5.2.Other Researchers

Many other researchers have studied the effects of SRA on concrete. Berke et al. found that shrinkage reduction is directly related to the SRA addition rate as a percentage of the mixing water. Furthermore, data on large-scale field experiments show that substantial reduction in cracking is obtained for concretes treated with SRA (1997).

Palacios and Puertas (2007) found that SRA reduced the shrinkage by up to 85 and 50% when the alkali activated slag mortar specimens were cured at relative humidities of 99 and

50%, respectively. Shah et al. found that a major advantage of SRA was the delay of cracking in ring specimens from restrained shrinkage. The age of the first visible crack depended on the amount of SRA. Cracks in concrete mixes with an SRA of 1 percent formed at around 10 to 15 days. Concretes with an SRA of 2 percent showed significantly improved cracking performance as compared with plain concrete, showing first cracks at about 48 days (Shah et al., 1997).

Bentz et al. found that addition of SRA to concrete can reduce the surface tension by a factor of two, significantly decreasing the strains from autogenous shrinkage (Bentz,

2008); (Bentz et al, 2001). It was also found that the addition of the SRA results in less evaporation, reduced settlement, reduced capillary tension, and lower crack-inducing stresses at the topmost layer of the mortar, greatly mitigating the effects of plastic shrinkage

(Bentz, 2008); (Mora-Ruacho et al, 2009). However, a serious drawback of SRA is that it increases the freezable water content of cement pastes cured under saturated conditions at early ages, which may have negative implications for the early-age frost resistance of these materials (Bentz, 2007; 2008). Rajabipour et al. (2008) explored the possible negative side effects of SRA. They found that the addition of SRA reduces the polarity of mixing water.

Lowering the affinity of alkalis to dissolve and ionize in the mixing water. The reduced alkalinity of the pore fluid was found to greatly slow down the rate of cement hydration and can contribute to retardation in hydration and strength development of concrete containing SRA. They recommend a delayed addition of SRA (e.g., addition of SRA to concrete at job site instead of addition during the initial mixing at concrete plant) which can be beneficial in alleviating the hydration retardation (Rajabipour et al., 2008).

A recent study by Nmai et al. (2014) showed that SRAs have minimal, if any, effect on crack width when cracking occurs. A new admixture was proposed that is capable of reducing not only drying shrinkage but also initial crack width, should cracking occur. This innovative crack-reducing admixture (CRA) is based on a specialty alcohol alkoxylate and it is being marketed under the trade name MasterLife CRA 007 admixture. The effects of the CRA on the properties of concrete, particularly setting time and strength, are similar to the effects of SRAs. Therefore, depending on dosage, as well as on concrete and ambient temperatures, setting time may be slightly delayed. In addition, a slight reduction in strength may occur depending on dosage of the CRA. Compared with conventional SRAs,

28 the CRA has been shown to provide internal stress relief in ASTM C1581/C1581M ring test, as a result, it changes the mode of failure in the ring test from a sudden release of all the compressive strain in the inner ring to a gradual release of the compressive strain. The net benefit of the internal stress relief provided by the CRA is a greater delay in the time- to-cracking in the ring test and an initial crack width of about 0.004 in. (0.1 mm) compared to 0.04 in. (1 mm) in untreated concrete and SRA-treated concrete specimens. Figure 2.5 demonstrates the effect of CRA on shrinkage behavior.

Figure 2.5 Effect of CRA Compared To Conventional SRA

2.5.Use of Fibers to Control Shrinkage Cracking

Grzybowski and Shah (1990) conducted shrinkage tests using ring specimens to study the effects of fibers on concrete shrinkage properties. Two types of fibers (steel and polypropylene), amounts of fibers (0.1 to 1.5 percent by volume), age of concrete (2 hr or

4 days), and period of drying (up to six weeks) under a given environment {40 percent relative humidity and 20 C (68 F)} were studied. It was found that while fiber addition did

29 not significantly decrease the overall amount of shrinkage, it can substantially reduce crack widths resulting from restrained drying shrinkage.

Figure 2.6 Effect of Polypropylene Fibers on Crack Width

Patnaik et al. (2007) evaluated the effect of newly developed high tenacity monofilament polypropylene fiber on the plastic shrinkage of concrete. The crack reduction potential of the fiber was studied using cement-rich concrete and the performance of the fiber was compared with that of three other presently available fibers. Performance of these fibers was evaluated by comparing the area of plastic shrinkage cracks developed in control slabs (with no fibers) with the crack area of fiber reinforced concrete slabs.

Results showed that that the new fiber with fiber length of about 18 mm [¾ inch], and a fiber dosage of 0.593 kg/m3 [1.0 lb/yd3] was most effective in reducing the plastic shrinkage cracks in concrete.

Figure 2.7 -Typical Plot of Crack Patterns of Test Slabs Without Fibers (Left) And With 0.3

Kg/M3 (0.5 Lbs/yd3) Monofilament Fibers (Right) (Patnaik et al, 2007)

Research by Qian & Stroeven (2000) shows that short fiber types greatly increase the number of fibers used in the concrete, and are usually used to decrease cracking and increase durability. While long fibers aim more often to increase mechanical properties of the concrete. Addition of hybrid fibers created synergy in the concrete and leaded to similar significant improvements in monofiber reinforced concrete having the higher total fiber content. A study by Aly et. al, (2008) suggests that the addition of PP Macro fibers may have an adverse effect on free shrinkage, increasing it in comparison to non-fiber concrete mixtures. One explanation is that concrete mixtures that incorporated PP fiber are more permeable and hence more vulnerable to drying, as evidenced by more moisture lost during the period of drying than companion mixtures without fibers. That effect was noticed to be further amplified in mixtures containing slag.

2.6.Testing Methods

2.6.1. Unrestrained (Free) Shrinkage Test

Tests to measure the unrestrained shrinkage of concrete are widely used and often performed simultaneously with restrained shrinkage tests. Several test methods have been developed, including those that use rectangular and ring-shaped specimens. The most common procedure is described in ASTM C 157, “Standard Test Method for Length

Change of Hardened Hydraulic-Cement Mortar and Concrete.” It is a common method to determine the shrinkage by measuring the length change of hardened concrete prisms

75mm × 75mm × 285mm (3 × 3 × 11.25 in). In this test method, rectangular concrete prisms are cast with gage studs at either end. A length comparator is used to measure shrinkage relative to an initial reading. Figures 2.6 and 2.7 demonstrates the test setup.

Figure 2.8 Free Shrinkage Test Specimen (ASTM C 157)

Figure 2.9 Free Shrinkage Test Setup

2.6.2. Restrained Shrinkage Tests (Ring Tests)

Over the last few decades, the shrinkage ring test has been frequently used as a testing technique to identify potential cracking risks of certain concrete and mortar mixtures. In the restrained ring test, a concrete ring is cast around an inner steel ring. The steel ring restrains the shrinking concrete, producing an internal pressure on the concrete ring, which causes tensile hoop stresses to develop in the concrete. When the tensile stresses minus the relaxation due to creep exceed the tensile strength of the concrete, cracking will occur. The steel ring can be instrumented to monitor the strain development and determine time to cracking. There are two standard testing procedures based on similar principles (as shown in Figure 1.7): ASTM C1581- 2009 and AASHTO T334-08. The major difference is the concrete thickness. The thickness of the concrete ring specimen for

ASTM C1581 is 1.5 in, and the thickness for the AASHTO T334 ring is 3 in. Factors such as aggregate source and gradation, aggregate-paste bond, cement type, cement content,

33 water content, mineral admixtures, fiber reinforcement, and chemical admixtures can be evaluated. The test does not predict concrete cracking in actual service, but rather compares the relative cracking potential of different mixes.

Figure 2.10 Ring Test Setup According to Different Standards

2.6.3. Plastic Shrinkage (Panel) Test

Kraai (1985) proposed a test to determine the cracking potential due to drying shrinkage of concrete. The test makes use of flat concrete specimens exposed to severe drying conditions, thereby increasing the cracking tendency of the concrete. The specimens are 2x3 ft and ¾ in. thick.

Figure 2.11 Panel Test Setup (Kraai, 1985)

The cracking potential in the concrete mix is determined by comparing the cracking of two test panels exposed simultaneously to a set of severe conditions designed to cause cracking. One panel is a control panel; the other is a similar panel except that a single parameter is altered to study its effect. The second panel could also be made identical in materials but then be subjected to different temperature or drying conditions.

For the control panel those influences on drying shrinkage cracking are chosen that are thought to maximize the amount. In one recent version of the test the following conditions were applied to the control panel for this purpose:

The concrete test specimen is only 3/4 inch thick, but the exposed top surface is

2x3 feet to accelerate the rate of evaporation and shrinkage. Because the specimen is only

3 ⁄4 inch thick, no coarse aggregate is used in the panel (Kraai, 1985). After 24 hours of drying, the concrete panels are inspected and crack lengths and widths are measured.

Relative cracking potential is determined by comparing the test panel with the control panel.

The mixes tested contained 418 kg/m3 (705 lb/yd3) of cement and a high water- cement ratio, 0.70. Kraai found that cracking began around one hour after drying was initiated and most of the cracking occurred within 4 hours (1985).

Figure 2.12 Shrinkage Panel Forms (Patnaik et al, 2007)

2.6.4. Freeze-Thaw Durability of Concrete

One of the most damaging actions affecting concrete is the abrupt temperature change

(freeze-thaw cycles). There are 2 types of deterioration of concrete structures by cyclic freeze-thaw, one is surface scaling, characterized by the weight loss. In addition to internal crack growth characterized by the loss of dynamic modulus of elasticity (Shang et al,

2013). ASTM test standard C-666 (AASHTO T-161) studies in detail the testing procedures for concrete in freeze-thaw conditions. The test focuses on measuring the two main symptoms of damage experienced by concrete during freeze thaw.

Scaling damage is measured using scales to determine the amount of weight loss.

Internal damage is determined using ASTM procedure C215 for fundamental transverse resonant frequency of concrete. Figure 2.13 demonstrates the test setup.

Figure 2.13 Freeze-Thaw Test Apparatus

The test method covers the determination of the resistance of concrete specimens to rapidly repeated cycles of freezing and thawing in the laboratory by two different procedures: Procedure A, rapid freezing and thawing in water. And procedure b, rapid freezing in air and thawing in water. Both procedures are intended for use in determining the effects of variations in the properties of concrete on the resistance of the concrete to the freezing-and-thawing cycles.

The test consist of a suitable chamber or chambers in which the specimens may be subjected to the specified freezing-and-thawing cycle, together with the necessary refrigerating and heating equipment and controls to produce continuously, and automatically, reproducible cycles within the specified temperature requirements. The specimens are arranged such that each specimen is surrounded by between 1 and 3 mm of

37 water at all times. ASTM C666 specifies that the specimens should be subjected to 300 cycles of freeze-thaw, with their scaling and freeze-thaw properties measured every 30 cycles.

Balaguru and Ramakrishnan (1986) compared the performance of fiber reinforced concrete specimens with plain concrete specimens and found that their behavior under freeze-thaw loading is essentially similar. For the same air content, freeze-thaw durability was the same for both plain and fiber reinforced concrete. The research also found an increase in the water absorption after the concretes were subjected to freezing and thawing.

That increase is smaller in the case of fiber concretes, indicating that fiber concretes were less permeable both before and after freeze-thaw damage. Figure 2.14 compares the performance of fiber-reinforced concrete under freeze-thaw with plain concrete.

Figure 2.14 Comparison of Plain and Fiber Reinforced Concretes Under Freeze-Thaw (Balaguru

and Ramakrishnan, 1986)

Berkowski and Kosior-Kazberuk (2015) further studied the effect of different types of steel and polypropylene fibers on the surface scaling resistance of concrete subjected to cyclic freezing and thawing in the presence of deicer salt. The test parameters included fiber type and dosage, and the type of concrete surface subjected to freezing and thawing.

Both the cut and cast surfaces of specimens were tested. The dispersed steel reinforcement was found to improve the scaling resistance significantly. However, the effectiveness of fibers was related to their shape and dimensions. With steel fibers showing greater efficiency than Polypropylene fibers.

2.7.Summary of Literature Review

 Shrinkage is the most common cause of early age cracking in bridge decks

 The two main types of shrinkage are plastic (before hardening) and drying shrinkage

(after hardening)

 The rate and severity of shrinkage are affected by several factors, these factors can be

attributed to material properties, construction practices and design factors.

 Shrinkage cracking is caused mainly by tensile stresses in the capillary walls caused by

the pore fluid. When these tensile stresses exceed the concrete’s modulus of rupture,

cracking occurs.

 SRAs were first introduced in the 1980s in Japan as a solution to the concrete shrinkage

problem.

 SRAs reduce shrinkage by lowering the surface tension of pore water in both plastic

and hardened concrete. Thus, upon evaporation from capillary pores during drying,

there is less tendency for shrinkage and resultant stresses.

 There are two methods of application of SRA to concrete: one is impregnation or

topical application, the other is the integration of SRA into the mix.

 Two testing methods can be used to determine the shrinkage of concrete, one is through

the measurement of cracking due to restrained shrinkage using the ring test, the other

is the measurement of volume change using the free (unrestrained) shrinkage test.

 Other test methods exist that could effectively measure shrinkage, with the panel test

being the most prominent.

 Over the years, several state DOTs as well as various researchers studied the effects of

SRA on concrete. In general, SRA greatly enhanced the shrinkage behavior of concrete,

lowering the amount of shrinkage by as much as 50-80%. However, other side effects

are a cause of some concern These effects include lowered compressive strength,

reduced freeze-thaw durability and retardation of cement hydration.

 SRAs were also found to possess minimal, if any, effect on crack width once cracking

occurs.

 In 2014, a new product was introduced. Known as CRA (Crack reducing admixture),

this new product was shown to provide internal stress relief in the concrete, causing

greater delay in the time-to-cracking and a highly reduced crack width.

 Fiber is also commonly used to mitigate shrinkage cracking in concrete. Its effect when

used in combination with SRAs is generally positive. The addition of SRA delays the

time of cracking and the addition of fiber reduces the crack opening.

 Another problem facing concrete bridge decks is the deterioration due to freeze-thaw.

Frost damage is considered to be a typical material deterioration in the concrete

structures subjected to external environmental conditions.

 Research indicates that the use of fibers has mixed effects on concrete freeze-thaw

durability. The effect of fiber depends on type, shape and length of the fiber.

CHAPTER III

EXPERIMENTAL PROGRAM

3.1.Introduction

This chapter includes the evaluation of restrained concrete ring specimens, free shrinkage prism specimens, plastic shrinkage panel specimens and freeze-thaw specimens in order to compare the shrinkage cracking, freeze-thaw durability and mechanical properties of several concrete mixes. Three individual preliminary tests were performed to evaluate the experimental procedures. The testing program involves a series of concrete mixes evaluated while subjected to the same environmental conditions.

Most specimens used concrete cast with a Type I portland cement, slag and limestone coarse aggregate that were cured for 24 hours prior to the initiation of drying.

Freeze-thaw specimens were placed in a curing tank filled with lime water for a period of

10 days. The program involves six mixes; a control mix, 2 mixes similar to the control mix but with SRA and CRA, respectively, and three more mixes similar to the previous with fibers. The mixes are based upon typical bridge deck mixes from the Ohio Department of

Transportation (ODOT) with minor modifications to suit the lab testing conditions.

3.2.Materials

3.2.1. Cementitious Materials

Two types of cementitious materials are used for this program. Type I portland cement, provided by Cemex plant in Fairborn, OH, and Grade 100 slag provided by Lafarge

Holcim plant in Cleveland. The slag has a specific gravity of 2.89.

Table 3.1 Properties and Chemical Contents Of Cement

Type I Portland Cement Specific 3.15 Gravity SiO2, % 1.5

Al2O3, % 0.9

Fe2O3, % 0.3

CaO, % 53.1

MgO, % 0.8

SO3, % 0.1

Loss on Ignition 2.6

Limestone 3

3.2.2. Aggregates

Limestone coarse aggregates were provided by W L Tucker Supply Company in

Cuyahoga Falls, OH. Coarse aggregate of #8 size was used in this study. The specific gravity of the aggregate is 2.67. The gradation of the coarse aggregates is presented in

Table 3.2.

Table 3.2 #8 Coarse Aggregate Gradations (Sieve Analysis)

Comulative % Sieve Passing

½” 100

3/8” 98.5

1/4” 67.8

#4 37.7

#8 3

#16 0.4

Fine aggregate was provided by W L Tucker Supply Company in Cuyahoga Falls,

OH. The fine river sand aggregate met ODOT sand requirements. The specific gravity of fine aggregate is 2.65. The detailed gradation is listed in Table 3.3.

Table 3.3 Fine Aggregate Gradation (Sieve Analysis)

Comulative % Comulative % Sieve Retained Passing 3/8” 0 100

1/4” 0.5 99.5

#4 1.8 97.7

#8 13.4 84.3

#16 23.3 61

#30 18.8 42.2

#50 24.5 17.7

#100 13.6 4.1

#200 1.9 2.2

3.2.3. Chemical Admixtures

Five types of chemical admixtures were used in this study: air entraining admixture

(AEA), Type A water reducer (WR), high range water reducing admixture (HRWRA), shrinkage reducing admixture (SRA), and Crack Reducing Admixture (CRA).

EUCON Air Mix 200 air-entraining admixture from Euclid chemical company was used to ensure proper air content in all the concrete mixes (between 6% and 7%). According to the information from the product instructions, it is a concentrated aqueous solution of modified resins used for proper air control under a wide range of temperatures. The adding amount is decided by the recommended addition rate from the product instructions and adjusted according to common practice.

EUCON WR-91 Type-A water-reducing admixtures from Euclid Chemical

Company is adopted to achieve the desired slump value (around 6-8 in.) as well as reducing the water content in all concrete mixes. It is a liquid, water-reducing and plasticizing admixture for concrete. It is intended for use in applications prone to shrinkage cracking especially concrete floors and bridge decks. Its adding rate is also determined according to the product instructions and adjusted by common practice.

EUCON 1037 Type-F high-range water-reducing admixtures from Euclid

Chemical Company was adopted to achieve adequate workability in the fiber-reinforced mixes as well as reducing the water content. It is a polycarboxylate-based admixture specifically designed for concrete industry, and is formulated without added chlorides. It provides excellent slump increase and retention in low water to cement ratio concrete. Its adding rate was also determined according to the product instructions and adjusted by common practice.

Masterlife SRA-035 shrinkage-reducing admixture from BASF Chemical Products was added to two mixes to test its effects on reducing concrete drying shrinkage. It was developed specifically to reduce drying shrinkage of concrete and mortar, and the potential for subsequent cracking. It functions by reducing capillary tension of pore water, a primary cause of drying shrinkage. The amount to be added was decided by the recommended dosage from the product instructions and adjusted after several trials. When shrinkage reducing admixture (SRA) is added, the same amount of water is taken out.

Masterlife CRA-007 crack-reducing admixture from BASF Chemical Products was added to two mixes to test its effects on reducing concrete drying shrinkage and subsequent cracking. It is an innovative crack-reducing admixture that is specifically formulated to reduce the magnitude of drying shrinkage and minimize the potential for cracking.

Compared to a shrinkage reducing admixture, MasterLife CRA 007 crack-reducing admixture provides enhanced performance through significant reduction in the potential for shrinkage cracking, and reduced initial crack widths if cracking does occur. The adding amount to be added was decided from the recommended dosage from the product instructions and adjusted according to trials. When crack reducing admixture (CRA) is added, the same amount of water is taken out.

3.2.4. Polypropylene Fibers

TUF-STRAND SF Polypropylene fiber by Euclid Chemical Company was used for this study. It is a polypropylene / polyethylene synthetic macro-fiber used in a wide variety of applications. The fiber complies with ASTM C1116 Standard Specification for Fiber

Reinforced Concrete and Shotcrete, and specifically designed to provide equivalent tensile and bending resistance similar to conventional reinforcement requirements. It provides

46 enhanced flexural toughness, impact and abrasion resistance and will also help mitigate the formation of plastic shrinkage cracking in concrete. The fiber has specific gravity of 0.92, typical length of 2”, Aspect ratio of 74, typical tensile strength between 87-94 ksi, modulus of elasticity 1380 ksi, and it has a distinctive white color. The dosage rates will vary depending upon the reinforcing requirements and the product instructions and adjusted according to trials.

Figure 3.1 TUF-STRAND SF Polypropylene Fiber

3.3.Concrete Mixes

A variety of concrete mixes were used to evaluate the effects of the use of shrinkage reducing admixture, crack reducing admixture and polypropylene fiber on shrinkage and cracking as well as mechanical and fresh concrete properties and freeze-thaw durability.

The preliminary testing used a basic concrete mix expected to have normal cracking tendency. In this program, the ODOT mix represents a typical concrete mix for bridge decks used by the agency.

Some modifications have been performed to that mix in order to make it more suitable for lab testing conditions. The rest of the mixes in those programs were developed in the laboratory. The water-cement ratio (w/c) is held constant at 0.5 for the control mixes to ensure high cracking potential. Values of 0.6 and 0.48 were used for the shrinkage panel mixes and mixes with SRA and CRA, respectively. The mixes developed in the laboratory had a target air content of 6 to 7%, a target slump of 150 mm (6 in.), and contain maximum aggregate size 3/8”. The cement content was 450 lb/yd3 and slag content 150 lb/yd3 for all the mixes, except for the shrinkage panel mixes which had high cement content of 960 lb/yd3 in order to initiate shrinakge.

Details of mixing, casting, curing, and drying are presented in Section 3.4. Tables

3.4 and 3.5 show the different mixes used in this study.

Table 3.4 Mixes Used For Plastic Shrinkage Panel Test

Series Series Series II Series III Series V Series I IV VI Material (SRA (CRA (Fibers + (Control) (PP (Fibers + 1gal/yd3) 1gal/yd3) SRA) Fibers) CRA)

Cement Type I 960 960 960 960 960 960 (lb/yd3)

#8 Limestone Aggregate 1185 1185 1185 1185 1185 1185 (lb/yd3)

River Sand 1185 1185 1185 1185 1185 1185 (lb/yd3)

Water (lb/yd3) 576 576 576 576 576 576

W/C Ratio 0.6 0.6 0.6 0.6 0.6 0.6

BASF Masterlife ___ 1 ______1 ___ SRA 20 (gal/yd3)

BASF Masterlife CRA 007 ______1 ______1 (gal/yd3)

PolyPropylene ______10 10 10 Fibers (lb/yd3)

Table 3.5 Mixes Used For All Other Tests

Series Series Series II Series III Series V Series I IV VI Material (SRA (CRA (Fibers + (Control) (PP (Fibers + 1gal/yd3) 1gal/yd3) SRA) Fibers) CRA)

Cement Type I 450 450 450 450 450 450 (lb/yd3)

Slag Grade 100 150 150 150 150 150 150

#8 Limestone Aggregate 1750 1750 1750 1750 1750 1750 (lb/yd3)

River Sand Fine Aggregate 1195 1195 1195 1195 1195 1195 (lb/yd3)

Water (lb/yd3) 300 288 288 300 288 288

W/C Ratio 0.5 0.48 0.48 0.5 0.48 0.48

Eucon WR 91 Water Reducer 20 20 20 20 20 20 (oz/yd3)

Eucon AM 200 Air Entrainer 4.5 4.5 4.5 4.5 4.5 4.5 (oz/yd3)

Eucon 1037 High range Water ______40 40 40 Reducer (oz/yd3)

BASF Masterlife ___ 1 ______1 ___ SRA 20 (gal/yd3)

BASF Masterlife CRA 007 ______1 ______1 (gal/yd3)

PolyPropylene ______10 10 10 Fibers (lb/yd3)

3.4.Testing Program

This section describes the test methods used in this study for the determination of fresh, hardened, shrinkage and freeze-thaw properties in concrete mix designs. A number of tests is conducted in order to evaluate several early age properties for each mix.

According to the state of the concrete when it is being tested, these tests can be put into two stages: (1) fresh concrete tests, and (2) hardened concrete tests.

Fresh concrete property tests evaluate the following properties of concrete: air content and slump. The hardened concrete property tests can be further divided into three sub-classes. The first one is about the early-age properties, such as the compression strength of concrete, the flexural strength of concrete, and the split tensile strength of concrete. The second is the plastic and drying shrinkage of concrete, which include panel shrinkage, free shrinkage and the restrained ring shrinkage. The third one focuses on testing the freeze-thaw durability of different mixes, measured by two properties: weight loss and resonance frequency change. The candidate mixture(s) with the best overall mechanical, shrinkage cracking resistance, and freeze-thaw resistance are picked in order to develop a concrete mix performance matrix. For each concrete mix, the tests considered in this study are summarized in Table 3.6.

Table 3.6 Fresh and Hardened Property Tests

Concrete property Testing Method Fresh Concrete Properties Slump ASTM C 143/AASHTO T 119 Air Content ASTM C 231/AASHTO T 152 Hardened Concrete Properties Compressive Strength ASTM C 39/AASHTO T 22 Split Tensile Test ASTM C 496 Flexural Shear Strength ASTM C 78/AASHTO T97 Plastic Shrinkage Shrinkage Panel Test (Literature) Drying Shrinkage (Free) ASTM C 157 AASHTO T 160 Drying Shrinkage (Restrained) ASTM C1581 AASHTO PP34-99 Freeze-Thaw Durability ASTM C666 AASHTO T-161

3.4.1. Concrete Mixing Procedure

Using the mix proportions outlined in Tables 3.4 and 3.5, twelve mixes were made.

The details of mixing and casting are given below.

All mixing was done in a 0.15 m3 [5.0 ft3] capacity mixer. The cementitious materials, aggregates, chemical admixtures and fibers were all weighed accurately and kept in separate plastic containers. Butter mix was done first. Then, coarse aggregate was placed in the mixer. The sand and two thirds of water were then added and mixed for one minute.

Type I cement and grade-100 slag were then added along with the remaining one third of the water. All chemical admixtures were diffused into the mixing water shortly before addition. For fiber-reinforced mixes, the fibers were added last after mixing and the ingredients were mixed for three minutes, which was followed by a three minute rest period. The final mixing was done for two minutes so that the fibers distributed evenly.

Since the mixes were of a flowing consistency, both mixing and placing were carried out without any problems. Some minimal vibration was needed to ensure that the concrete was adequately set. In fiber-reinforced mixes, the fibers distributed uniformly and well. There was no segregation or balling of the fibers in any of the mixes. Six different batches were made on a single day for panel tests, while the other mixes were divided into two phases. The first phase consisted of Series I through III, no fibers were used on that phase. The second phase consisted of all fiber-reinforced mixes and used Series IV through

VI. After each mixing, the mixing drum was thoroughly cleaned and a butter mix was made before the next mix. All the mixes were done under identical conditions. Because of higher cement and water content as well as the use of Superplasticizers, the slump achieved in each batch was greater than 150 mm [6 inches]. No reduction in slump due to the addition of fibers was detected, mainly due to the use of Type-F HRWR. The fresh concrete test results were documented.

3.4.2. Fresh Concrete Properties

Slump was tested for every trial mix design following the standards of ASTM C143

Standard Test Method for Slump of Hydraulic-Cement Concrete. Results from the test are summarized in Chapter 4. Figure 3.2 shows the test apparatus.

Figure 3.2 Slump Test Apparatus

All Mixes are also tested for air content according to ASTM C231 Standard Test

Method for Air Content of Freshly Mixed Concrete by the Pressure Method. Results for the test are summarized in Chapter 4. Figure 3.3 shows the test apparatus.

Figure 3.3 Air Content Test Apparatus

3.4.3. Mechanical Testing

Six cylinders with diameter of 4 inches and 8 inches high were made for each of the mixes according to the ASTM procedures. They were tested at 3, 15 and 28 days of curing to determine compressive strength and at 28 days for the split tensile strength for all mixes. Additional 4x4x14 in. prisms were cast to determine flexural tensile strength for each mix at 28 days.

3.4.3.1.Compressive Strength and Split Tensile Strength Test

ASTM C 39/AASHTO T 22 was used to determine the compressive strength of the concrete mixes. For every mix, six cylinder specimens of 4 in. diameter x 8 in. height were cast. Two were tested at the age of 3 days, and the rest at 28 days. The test was conducted using a hydraulic machine (Fig. 3.4) at a constant load rate of 30-40 psi/s. Then, the specimens were loaded till failure, with all displacements and loads data being recorded.

Figure 3.4 Compressive Strength Testing

Figure 3.5 Split Tensile Strength Testing

3.4.3.2.Flexural Tensile Strength Test

ASTM C 78/AASHTO T97 procedures are followed for measuring the flexural strength of the concrete beam specimens. The concrete beam has a dimension of 4 in x 4 in x 14 in. A 12 in. span is used, which made the height of the beam of 4 in., i.e., 1/3 of the span, as demonstrated in Figure 3.6. This test was conducted using Instron 5960 hydraulic machine, using the loading rate of 125-175 psi/min.

Figure 3.6 Flexural Tensile Strength Testing

3.4.4. Shrinkage Tests

3.4.4.1.Plastic Shrinkage Panel Test

Tests were conducted using 25 mm [1 inch] thick slabs that were 0.9 meter (3 ft.) long and 0.6 meter (2 ft.) wide. The slabs were restrained around the perimeter using wire mesh. The slab size selected was similar to the slab size currently used in literature for plastic shrinkage testing of concrete.

Since it is a qualitative comparative study, the slab size would not influence the test results. Slabs are placed on a flat surface (laboratory floor) and subjected to a wind velocity of 22 km/hour [14 mph], using high-velocity fans. Six slabs, (one for each trial mix) were made and tested simultaneously under identical environmental conditions. Therefore, a true comparison of shrinkage cracking was obtained. Wire mesh along with rebar was used at perimeter to achieve restraint to ensure the panels do not shrink freely.

The test set-up is shown in Figure 3.7. The figure shows the molds prepared prior to placing the concrete. One mold was used for control concrete (without admixtures or

57 fiber) and the other five were used for concrete mixed with fiber and admixtures. Freshly mixed concrete was placed in the molds with proper care to fill it around the wire mesh that was placed at side runners at the periphery. The concrete was lightly tamped and leveled with trowels. The top surface of the concrete slabs was then finished with a straight edge wooden float. To maintain consistency in the surface finish of all the test slabs, the same research assistant finished all the test slabs of the project.

Figures 3.8 and 3.9 show the preparation and testing of the panels. Results were taken after 24 hours of testing, crack widths and distributions were measured for all panels and tabulated in Chapter 4.

Figure 3.7 Preparation of Test Panels

Figure 3.8 Testing of the Panels

Figure 3.9 Shrinkage Panel Tests

Since the main objective was to study the influence of admixtures and fiber addition on the plastic shrinkage, it was necessary to make the concrete with a very high potential for shrinkage cracking. The testing conditions such as the ambient temperature, the humidity and the wind velocity of 22 km/hour [14 mph] were kept constant for each set of test slabs. A high cement content as well as high water-cement ratio (0.6) were used to maximize the cracking potential.

3.4.4.2.Free Shrinkage Test

The free shrinkage test was carried out following ASTM C157/C157M and

AASHTO T160 “Length Change of Hardened Hydraulic-Cement Mortar and Concrete”.

Three 3 in x 3 in x 11.25 in prisms were cast using the same concrete batch for both the free shrinkage and restrained shrinkage specimens in every mix design. The prisms were cast into steel molds manufactured specifically for length change tests and supplied by

Humboldt. Each mold has a replaceable gage stud at each end, providing the gage length of 10 in. specified by ASTM C490. Figure 3.10 shows the molds before casting the specimens. The prisms were placed in the environmental chamber at the same time as the ring specimens, and they were demolded 24 hours after casting.

The temperature inside the chamber was maintained at 23 ± 1oC. And the relative humidity at 50 ± 4%. A shrinkage frame with electronic dial gage was used to monitor the free shrinkage, as shown in Fig. 3.12. The dial meter was installed to record the shrinkage value at different ages. The specimen’s initial shrinkage values are measured using the shrinkage frame immediately after demolding and before placement into the chamber.

Readings are then taken every 24 hours for the first 7 days, and then at 14, 21, and 28 days.

Figure 3.10 Free Shrinkage Specimen Molds

Figure 3.11 Free Shrinkage Specimens

Figure 3.12 Measurement of Free Shrinkage using ASTM C490

3.4.4.3.Restrained Shrinkage Ring Test

The restrained shrinkage test adopts the AASHTO ring and follows the standards

AASHTO PP34-99 “Estimating the Cracking Tendency of Concrete”. Test apparatus was fabricated with a modified ring with smaller thickness than the originial.

Structural steel pipe conforming to ASTM A 501 or A 53M/A 53 12-in. extra- strong pipe with an outside diameter of 324 mm (12 ¾ in.) and wall thickness 13 mm ( 1/2 in.) is used for fabricating the inner steel ring (see Figs. 3.13 and 3.14).

Figure 3.13 Dimensions of Used Ring vs. AASHTO Standard Ring

Figure 3.14 Ring Specimen Molds

Figure 3.15 Casting of Concrete Rings

The outer ring was made of Sonotube board provided by Whitecap Supply. It has an inside diameter of 406 mm (16 in.). Two strain gages were mounted on the inner surface of the steel ring at equidistant points at midheight. Data acquisition equipment from Vishay

Company was used for the strain instrumentation, and it automatically recorded each strain gage every 60 minutes independently. Data acquisition was made using a Vishay

Measurements Group System-9000 DAQ connected to a PC with StrainSmart software installed (See figure 3.17).

Wooden forms were made of 21 in. by 21 in., 3/4 in. thick plywood sheet, and the top surface was covered with polyurethane sheet to ensure that the concrete rings are able to shrink freely.

Two ring specimens were cast for each mix design, both were 6 in. tall rings. The outer forms are removed at an age of 12 hours, and then the specimens are moved to the conditional room (Fig. 3.16) with a constant air temperature of 23 ±1oC and 50 ± 4 %

64 relative humidity. Temperature and humidity were maintained using an environmental chamber provided by Darwin Chambers Company in St. Louis, MO. The data from the strain gages was recorded every 60 minutes, and review of the strain and visual inspection of cracking was conducted daily.

Figure 3.16 Shrinkage Specimens Placed in Environmental Chamber

Figure 3.17 Shrinkage Specimens Connected to Data Acquisition System

3.4.5. Freeze-Thaw Testing

The primary objective of this part of the investigation was to evaluate durability characteristics of ODOT concrete mixtures containing SRA and CRA using the freezing and thawing of concrete test (ASTM C 666 procedure A). The secondary objective was to compare the performance of the fiber reinforced concrete mixes with polypropylene fiber compared to that of control mixes.

Figure 3.18 shows the test specimens inside the chamber. A freeze-thaw chamber model TH-055 supplied by Darwin chambers was used for this study. Each specimen was placed inside a galvanized steel tray fabricated specifically for freeze-thaw testing. Figure

3.19 demonstrates the tray dimensions.

Figure 3.18 Freeze-Thaw Specimens inside the Chamber

Fig. 3.19 Freeze-Thaw Specimens’ Tray

All specimens were 11.25x3x3 in. The tray’s dimensions are slightly larger to allow for all the faces to be covered by at least 1/8” of water at all times. Specimens were cured by submerging for 14 days in a tank filled with lime water as shown in figure 3.20.

Figure 3.20 Curing Of Freeze-Thaw Specimens

After curing, initial readings of weight and resonance frequency were taken for each specimen (Figure 3.21). Specimens are then moved to the freeze-thaw chamber where they were placed inside the tray and covered with a 5% salt solution. The temperature changed between -15oC and 15oC over a cycle of 12 hours. Reading for weight loss and change in resonance frequency were taken every 10 cycles (5 days). The test was stopped after 60 cycles (30 days). Figure 3.22 shows the cycle time.

Figure 3.21 Resonance Frequency Test

Figure 3.22 Freeze-Thaw Cycle

CHAPTER IV

TEST RESULTS

4.1.Introduction

The performance of concrete mix designs using materials for reducing early age shrinkage is reported in this chapter. All mixes were based off ODOT concrete mix design, which serves as a benchmark mix. In this chapter, the test results for concrete mixes using different materials are presented. The mixes were tested for mechanical properties such as compressive strength, split tensile strength and flexural strength. Plastic, free, and drying shrinkage properties were also evaluated. And finally, freeze-thaw properties for each mix were determined.

4.2.Fresh Property Tests

The slump test and air content test were conducted as quality control of concrete fresh properties. The slump test follows ASTM C 143/AASHTO T 119 “Slump of hydraulic cement concrete and for air content test”. The pressure method was used to measure the air content. The method follows AASHTO T 152/ASTM C 231 “Air Content of Freshly-mixed Concrete by the Pressure Method”.

The slump test results were between 6.5 in. and 8.5 in., and the air content test results were from 6.5% to 8.6%. Because of the slightly high w/c ratio in addition to several chemicals being added to the concrete mix, it was difficult to limit the preferable slump to between 5 to 6 in. for some concrete mixes.

The addition of SRA and CRA did not seem to have any significant effect on either the slump or air content. All mixes achieved desirable flow and were placed and compacted without problems. When using fiber-reinforcement, the addition of superplasticizer was required in order to maintain desirable workability. Fiber-reinforced mixtures had slightly higher slump than non-fiber mixtures. And the air content was similar to that of non-fiber mixtures.

4.3.Mechanical Properties Tests

The compressive strength, split tensile strength, and flexural strength were tested for each concrete mix design.

4.3.1. Compressive strength test

ASTM C 39/AASHTO T 22 “Compressive Strength of Cylindrical Concrete

Specimens” was followed for the compressive test of concrete cylinder specimens.

Specimens were tested for compressive strength at 3, 15 and 28 days. The compressive strength test results were relatively low compared to the minimum ODOT 28-day compressive strength requirements of around 5,000 psi, this is due to the high water/cement ratio (48-50%) used in the different mixes to ensure maximum shrinkage potential. The test results are presented in Table 4.1 and graphically in Figure 4.1.

Table 4.1 Compressive Strength Test Data (psi)

Mixture Series I Series II Series III Series IV Series V Series VI

3 days 1682 2019 3049 1640.5 1885 2905

15 days 2828 3293 5009 2720 2807 4118

28 days 2977 3625 5149 2742 3003 4838

Control SRA CRA Fiber F-SRA F-CRA

6000

5000

4000

3000

2000 COMPRESSIVE STRENGTH (PSI) STRENGTHCOMPRESSIVE

1000

0 3 days 15 days 28 days

Figure 4.1 Compressive Strength of Different Mixtures

The comparison among the different mixes shows that the addition of SRA leads to a slight increase in compressive strength at all ages (around 20%). This can be mainly due

71 to the lower water content specified by the producer, and conforms to observations from literature. The addition of CRA, however, leads to a much more significant increase in compressive strength (between 65-70%) at all ages, which is more than can be accounted for by only the reduction in water content.

Fiber-reinforced mixtures were found to have relatively lower compressive strength at early ages. This conforms to observations by Aly et. al (2008) in which it was concluded that the use of polypropylene fibers in concrete mixtures containing slag can cause a reduction in mechanical properties.

4.3.2. Split tensile strength test

ASTM C496 “Standard Test Method for Splitting Tensile Strength of Cylindrical

Concrete Specimens” is followed for split tensile test of cylinder specimens. The test results are presented in Table 4.2 and shown graphically in Fig. 4.2.

Table 4.2 Split Tensile Test Data (psi)

Split Tensile Strength (Psi)

Without Fibers With Fibers

Control 282 269

SRA 365 342

CRA 433 408

Split Tensile Strength (psi) w/o fibers Split Tensile Strength (psi) w/ fibers

500

450

400

350

300

250

200

150 28 DAYS SPLIT STRENGTH DAYS 28 TENSILE 100

0 Control SRA CRA

Figure 4.2 Split Tensile Strength of Different Mixtures

Results from split tensile test reflect those of compressive strength test, with mixtures containing CRA having strength significantly higher than those of Control and

SRA. Fiber-reinforced mixtures also suffer from reduced split tensile strength compared to those without fibers.

4.3.3. Flexural strength test

AASHTO T 97/ASTM C 78 “Standard Method of Test for Flexural Strength of

Concrete (Using Simple Beam with Four-Point Loading)” is followed for the flexural strength test of beam specimens. The flexural strength of all the concrete mix designs at 28 days were tested. The test results are shown in Table 4.3 and also graphically in Figure 4.3.

Table 4.3 Flexural Strength Test Data

F + F + Mixture Control SRA CRA Fibers SRA CRA

Load At Failure (lbs) 2760 2729 3610 3081 2786 3316

28-days Modulus of 518 512 677 578 522 622 Rupture (psi)

800

700

600

500

400

300

200

days Modulusof Rupture (psi)

- 28 100

0 Control SRA CRA Fibers F + SRA F + CRA

Figure 4.3 Flexural Strength Test Data

Results from flexural strength test are generally higher than split tensile test.

Mixtures containing CRA have a significantly higher strength than those of Control and

SRA. Fiber-reinforced mixtures show a much better performance than non-fiber mixtures.

SRA mixtures seem to have slightly lower strengths compared to control.

4.4.Shrinkage Tests

Three tests on shrinkage properties of all the concrete mixes are conducted: plastic shrinkage test, free shrinkage and restrained shrinkage tests. The panel tests show the mix susceptibility to plastic shrinkage cracking during the first 24 hours. The free shrinkage test shows the basic shrinkage property of concrete without any restraint; while the restrained shrinkage test illustrates the combination of concrete tensile strength and shrinkage properties and relatively mimics the condition of concrete deck being restrained by supports.

4.4.1. Plastic Shrinkage (Panel) Test

The average crack widths and lengths were measured for all the cracks that appeared on the top surface of each test slab after 24 hours. The longer duration was chosen to make sure that all the cracks had developed and stabilized. The crack widths were measured at a number of locations along the length of each crack. The lengths of the crack were measured for each crack. Area of each crack was calculated by multiplying the length of the crack by the average width. Total crack area for a given slab was calculated by summing the areas of all the cracks on the slab. The crack area of control slab was considered as 100 percent for comparison of the effectiveness of the materials. The crack areas of the other panels were expressed as a percentage of the crack area of the corresponding control slab. Table 4.4 shows the results of panel testing. Crack widths and distributions are shown in Figure 4.4. Crack distributions for different mixes are shown in

Figures 4.5 and 4.6.

Table 4.4 Panel Test Results

Mix Series I Series II Series III Series IV Series V Series VI Maximum Crack 0.04 0.03 0.012 0.007 0.012 0.007 Width (in.) Crack Density 0.181 0.103 0.05 0.06 0.024 0.022 (in/in2) % Reduction 0 43 72 67 87 88 in Crack Density

Figure 4.4 Panel Test Results

Figure 4.5 Typical Crack Density in Non-Fiber Mixtures

Figure 4.6 Typical Crack Density in Fiber-Reinforced Mixtures

4.4.2. Free Shrinkage Test

Free shrinkage test follows AASHTO T 160 (ASTM C 157) “Length Change of

Hardened Hydraulic Cement Mortar and Concrete”. Free shrinkage data are collected at 1,

2, 3, 4, 5, 6, 7, 14, 21, and 28 days, respectively, from which the free shrinkage tendency diagrams are drawn for all concrete mixes. The free shrinkage data is listed in Table 4.5, and their tendency diagrams are shown in Figs. 4.7 to 4.9.

0 0 5 10 15 20 25 30 -0.0001 -0.0002 -0.0003 -0.0004 -0.0005 Free Free Shrinkage -0.0006 -0.0007 -0.0008 Time, Days

Control SRA CRA

Fig. 4.7 Free shrinkage in Non-fiber Mixtures

0 -0.0001 0 5 10 15 20 25 30 -0.0002 -0.0003 -0.0004 -0.0005

-0.0006 Free Free Shrinkage -0.0007 -0.0008 -0.0009 Time, Days

Fiber F-SRA F-CRA

Figure 4.8 Free shrinkage in Fiber-Reinforced Mixtures

0 0 5 10 15 20 25 30

-0.0001

-0.0002

-0.0003

-0.0004

-0.0005 Free Free Shrinkage

-0.0006

-0.0007

-0.0008

-0.0009 Time, Days

Control SRA CRA Fiber F-SRA F-CRA

Figure 4.9 Free Shrinkage Tendency Diagrams

Table 4.5 Free Shrinkage Results day Series I Series II Series III Series IV Series V Series VI

0 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000 0.00000000

1 -0.00005900 -0.00002400 -0.00000976 -0.00001463 0.00000000 0.00000000

2 -0.00014000 -0.00005900 -0.00003902 -0.00008780 -0.00003902 -0.00002000

3 -0.00020000 -0.00009300 -0.00007805 -0.00017073 -0.00007805 -0.00002900

4 -0.00026000 -0.00012000 -0.00011220 -0.00023902 -0.00011707 -0.00004900

5 -0.00031000 -0.00014000 -0.00014634 -0.00030244 -0.00014634 -0.00006800

6 -0.00037000 -0.00017000 -0.00017073 -0.00037561 -0.00020488 -0.00013000

7 -0.00042000 -0.00021000 -0.00020000 -0.00045366 -0.00023415 -0.00015000

14 -0.00060000 -0.00036000 -0.00030244 -0.00065366 -0.00042927 -0.00032000

21 -0.00064000 -0.00039000 -0.00031707 -0.00071707 -0.00053659 -0.00038000

28 -0.00067000 -0.00041000 -0.00032683 -0.00077073 -0.00055610 -0.00041000

Figures 4.7 through 4.9 show that the use of SRA and CRA reduces the amount of free shrinkage at 28 days by 38% and 52%, respectively, the use of CRA seems to greatly reduce the amount of shrinkage during the first 2-3 days, with minimal or no shrinkage occurring during this period. The use of fibers, while effective in reducing the amount of shrinkage for the first 7-10 days, was found to cause a slight increase in free shrinkage at later ages.

This can be explained through the work of Aly et. al,(2008) in which it was found that the use of polypropylene fibers in concrete mixtures containing Slag can result in adverse effects, causing increased shrinkage and decreased mechanical properties compared to non-fiber mixtures. This is due to the increase in nano-porosity, this micro- pore-structure that is influential on the rate of drying shrinkage. The high porosity is likely due to the increase in mesoporous zone at the vicinity of PP fibers.

4.4.3. Restrained Shrinkage Test

ASTM C1581 / AASHTO PP34-99 Cracking Tendency Using a Ring Specimen is followed for the restrained shrinkage test. The test results are presented in Table 4.6 as well as Figures 4.10 to 4.13.

Table 4.6 Restrained Shrinkage Results

Non-fiber-reinforced Fiber-Reinforced

Time of First Crack Width Time of First Crack Width Crack (Days) (in.) Crack (Days) (in.) Control 10-11 0.02 none none

SRA 14-15 0.01-0.012 none none

CRA none none none none

Restrained Shrinkage (µɛ) – Non-Fiber Mixtures 60

0 µstrain 0 100 200 300 400 500 600 -20

Shrinkage, -40

-60

-80 Time (Hours)

Control SRA CRA

Figure 4.10 Strains in non-Fiber Ring Specimens

Restrained Shrinkage (µɛ) – Fiber-Reinforced Mixtures 0 0 100 200 300 400 500 600 -10 -20 -30 -40 -50 -60

Shrinkage,µstrain -70 -80 -90 -100 Time (Hours)

Fiber F-SRA F-CRA

Figure 4.11 Strains in Fiber-Reinforced Ring Specimens

Fig. 4.12 Cracking in Control Specimen at 10-11 Days

Figure 4.13 Cracking in SRA Specimen at 14-15 Days

Of the six mixtures used in this study, the control mix was the first to crack at around 10-11 days, followed by the SRA mix at 14-15 days. Figures 4.12 and 4.13 show the crack in the rings at aforementioned ages. With the SRA mix having less crack width than the control. No cracks were found in the CRA mix after 28 days.

In fiber-reinforced mixtures, none of the rings showed cracking by the end of the testing period of 28 days. The use of SRA and CRA was found to reduce the strains due to shrinkage by 40-50% and 60-70%, respectively, the use of CRA seems to greatly reduce the strains due to shrinkage during the first 2-3 days, with minimal or no shrinkage occurring during this period. The use of fibers was found to cause an increase in strains due to shrinkage which still conforms to findings by Aly et. al (2008).

4.5.Freeze Thaw Tests

Freeze-thaw test follows AASHTO T 161 (ASTM C-666) “Test for Resistance of

Concrete to Rapid Freezing and Thawing”. Weight loss and resonance frequency data were collected every 10 cycles (5 days), from which the freeze-thaw resistance tendency diagrams were drawn for all concrete mixes. The freeze-thaw tendency diagrams are shown in Fig. 4.14. Visual comparison of damage due to freeze-thaw is demonstrated in Figures

4.15 and 4.16.

Figure 4.14 TendencyDiagrams Freeze for

Thaw

Figure 4.15 Damage in non-fiber Freeze-thaw Specimens after 60 cycles

Figure 4.16 Damage in fiber-reinforced Freeze-thaw Specimens after 60 cycles

While some weight loss due to surface scaling was detected in all specimens, the resonance frequency for all specimens remained relatively unchanged throughout the test duration, implying that no internal damage was occurring. This is due to all mixes having a high air content (6-8%).

Results from freeze-thaw tests show that the use of SRA and CRA has no significant impact on the damage due to Freeze-Thaw. The addition of CRA seems to relatively increase scaling in both fiber and non-fiber mixtures compared with SRA. With

86 the effect being less in fiber-reinforced mixtures. The addition of Polypropylene fibers was found to slightly reduce the weight loss for all mixes, which implies improved resistance to scaling in fiber-reinforced mixtures compared to those without fibers.

CHAPTER V

CONCLUSIONS AND RECOMMENDATIONS

The goal of this study was to find the mitigation strategies for early-age shrinkage cracking in concrete bridge decks. A comprehensive literature is first conducted. Based on the literature and also the recommendations from the ODOT, 3 new materials were evaluated. One of the current ODOT concrete mix was used as benchmark for comparisons with other new materials developed in this study. Fresh properties, hardened properties, and shrinkage properties were evaluated for all the concrete mixes. The conclusions and recommendations are presented in this chapter.

5.1.Conclusions

Based on the experimental evaluation of different mix designs done in this study, the following conclusions are obtained.

1- The use of CRA gives the best results for reducing both restrained and free

shrinkage in comparison to traditional SRA as well as the control mix.

2- Mixtures containing CRA also possess significantly better mechanical properties

than the control mix.

3- A side effect of using CRA is a slight increase in scaling due to freeze-thaw. That

effect can be reduced using fibers and adequate air content.

4- The use of fibers in mixtures containing slag leads to a marginal increase in both

free and restrained shrinkage at later ages as well as a reduction in mechanical

properties.

5.2.Recommendations

Based on the comprehensive experimental program conducted in this study, the following recommendations are suggested for improved concrete design to mitigate the shrinkage cracking in concrete.

1- CRA is recommended for use in concrete mixes to mitigate early-age shrinkage

cracking in concrete bridge decks. Shrinkage resistance as well as mechanical

properties are significantly improved.

2- Adequate air content as well as fibers should be provided when using CRA in order

to resist scaling due to freeze-thaw.

3- Polypropylene fibers are recommended for use in bridge decks in order to reduce

cracking due to shrinkage as well as provide adequate resistance to damage due to

freeze-thaw.

4- To ensure best performance against shrinkage, Mixes containing polypropylene

fibers should avoid using slag, if possible.

REFERENCES

AASHTO PP34-98 (1998). “Standard Practice for Estimating the Crack Tendency of Concrete,” AASHTO Provisional Standards, pp. 179-182.

ACI 224.1R-93, (Reapproved 1998) “Causes, Evaluation and Repair of Cracks in Concrete Structures,” ACI Committee 224, American Concrete Institute, Farmington Hills, MI.

Ah-Sha, H. H., Sanders, D. H., & Saiidi, M. S. (2001). Early Age Shrinkage and Cracking of Nevada Concrete Bridge Decks (No. RDT01-010,).

Aly, T., Sanjayan, J. G., & Collins, F. (2008). Effect of polypropylene fibers on shrinkage and cracking of concretes. Materials and Structures, 41(10), 1741-1753.

ASTM C 157-04, (2003). “Standard Test Method for Length Change of Hardened Hydraulic-Cement, Mortar, and Concrete,” 2003 Annual Book of ASTM Standards, Vol. 4.02, American Society for Testing and Materials, West Conshohocken, PA.

ASTM C 1581-04, (2004). “Standard Test Method for Determining Age at Cracking and Induced Tensile Stress Characteristics of Mortar and Concrete under Restrained Shrinkage,” ASTM International, West Conshohocken, PA.

ASTM C494 / C494M-15a, Standard Specification for Chemical Admixtures for Concrete, ASTM International, West Conshohocken, PA, 2015

Baah, P. (2014). Cracking Behavior of Structural Slab Bridge Decks (Doctoral dissertation, The University of Akron).

Baah, P., Ricciardi, P., Khalifa, W., and Patnaik, A., (2014) “Cracking Behavior of Three Span Structural Slab Bridge Decks,” 9th International Conference on Short an Medium Span Bridges, July 15-18, Calgary, Canada.

Baah, P., Ricciardi, P., Khalifa, W., and Patnaik, A., (2014) “Cracking Behavior of Structural Slab Bridge Decks,” Ohio Transportation Engineering Conference (OTEC), October 28-29, Columbus, U.S.A.

Babaei, K., & Fouladgar, A. M. (1997). Solutions to concrete bridge deck cracking. Concrete International, 19(7).

Babaei, K., and Purvis, R., (1994) “Prevention of Cracks in Concrete Bridge Decks: Report on Laboratory Investigation of Concrete Shrinkage,” Research Project No. 89-01, Pennsylvania Department of Transportation, Harrisburg, PA.

Balaguru, P. N., & Ramakrishnan, V. (1986, May). Freeze-Thaw Durablity of Fiber Reinforced Concrete. In Journal Proceedings (Vol. 83, No. 3, pp. 374-382).

Bentz, D. P. (2007). Ten observations from experiments to quantify water movement and porosity percolation in hydrating cement pastes. Transport Properties and Concrete Quality: Materials Science of Concrete, American Ceramic Society, Westerville, OH, 3- 18.

Bentz, D. P. (2008). A review of early-age properties of cement-based materials. Cement and Concrete Research, 38(2), 196-204.

Bentz, D. P., Geiker, M. R., & Hansen, K. K. (2001). Shrinkage-reducing admixtures and early-age desiccation in cement pastes and mortars.Cement and concrete research, 31(7), 1075-1085.

Berke, N. S., Dallaire, M. P., Hicks, M. C., & Kerkar, A. (1997). New developments in shrinkage-reducing admixtures. ACI Special Publication,173.

Berkowski, P., & Kosior-Kazberuk, M. (2015). Effect of Fiber on the Concrete Resistance to Surface Scaling Due to Cyclic Freezing and Thawing. Procedia Engineering, 111, 121-127.

Brown, M.D., Sellers, G., Folliard, K.J., and Fowler, D.W., (2001) “Restrained Shrinkage Cracking of Concrete Bridge Decks: State-of-the-Art Review,” Center for Transportation Research, The University of Texas at Austin, FHWA/TX-0-4098-1.

Carnate, G. (2014). Shrinkage Reducing Admixture Usage in Hawaii Bridge Decks, Article retrieved from http://www.concretebridgeviews.com/i77/Article3.php

Cheng, T., & Johnston, D. (1985). Incidence Assessment of Transverse Cracking in Concrete Bridge Decks: Structural Considerations—Vol I. North Carolina Department of Transportation, 85-002.

Cohen, M. D., Olek, J., and Dolch, W. L., (1990) “Mechanism of Plastic Shrinkage Cracking in Portland Cement and Portland Cement Silica Fume Paste and Mortar,” Cement and Concrete Research, Vol. 20, pp. 103-119.

Darwin, D., Browning, J., & Lindquist, W. D. (2004). Control of cracking in bridge decks: observations from the field. Cement, concrete and aggregates, 26(2), 148-154.

Grzybowski, M., & Shah, S. P. (1990). Shrinkage cracking of fiber reinforced concrete. Materials Journal, 87(2), 138-148.

Folliard, K. J., & Berke, N. S. (1997). Properties of high-performance concrete containing shrinkage-reducing admixture. Cement and Concrete Research, 27(9), 1357- 1364.

French, C. E., Eppers, L. J., Le, Q. T. C., & Hajjar, J. F. (1999). Transverse Cracking in Bridge Decks: Summary Report (No. MN/RC-1999-05,).

Holland, T. (1999). Using shrinkage-reducing admixtures. Concrete Construction, 44(3), 15-18.

Ideker, J. H., Fu, T., & Deboodt, T. (2013).Development of Shrinkage Limits and Testing Protocols for ODOT High Performance Concrete(No. FHWA-OR-RD-14-09).

Issa, M. A. (1999). Investigation of cracking in concrete bridge decks at early ages. Journal of Bridge Engineering, 4(2), 116-124.

Janssen, D. J., & Snyder, M. B. (1994). Resistance of concrete to freezing and thawing (No. SHRP-C-391).

Kraai, P. P. (1985). A proposed test to determine the cracking potential due to drying shrinkage of concrete. Concrete construction, 30(9), 775-778.

Krauss, P. D., and Rogalla, E. A., (1996) “Transverse Cracking in Newly Constructed Bridge Decks,” NCHRP Report 380, Transportation Research Board, National Research Council, Washington, D. C., USA.

Leonhardt, F., (1977) “Crack Control in Concrete Structures,” IABSE Surveys, S-4/77, pp. 1-26.

L'Hermite, R. (1988). Mathematical modeling of creep and shrinkage of concrete. Z. P. Bazant (Ed.). Chichester: Wiley.

Lura, P., Mazzotta, G. B., Rajabipour, F., & Weiss, J. (2006, March). Evaporation, settlement, temperature evolution, and development of plastic shrinkage cracks in mortars with shrinkage-reducing admixtures. In K. Kovler (Ed.), Int. RILEM-JCI Seminar on Concrete Durability and Service Life Planning (ConcreteLife'06).

Lura, P., Pease, B., Mazzotta, G. B., Rajabipour, F., & Weiss, J. (2007). Influence of shrinkage-reducing admixtures on development of plastic shrinkage cracks. ACI Materials Journal, 104(2).

Maggenti, R., Knapp, C., & Fereira, S. (2013). Controlling Shrinkage Cracking. Concrete international, 35(7).

McDonald, D. B., Krauss, P. D., and Rogalla, E.A., (1995) “Early-Age Transverse Deck Cracking,” Concrete International. Vol. 17, No. 5, pp. 49.

Mora-Ruacho, J., Gettu, R., & Aguado, A. (2009). Influence of shrinkage-reducing admixtures on the reduction of plastic shrinkage cracking in concrete. Cement and Concrete Research, 39(3), 141-146.

Nawy, E. G. (1996). Fundamentals of high strength high performance concrete. Addison- Wesley Longman.

Neville, A. M. (1995). Properties of concrete.

Nmai, C. K., Tomita, R., Hondo, F., & Buffenbarger, J. (1998). Shrinkage reducing admixtures. Concrete International, 20(4), 31-37.

Nmai, C. K., Vojko, D., Schaef, S., Attiogbe, E. K., & Bury, M. A. (2014). Crack- Reducing Admixture. Concrete international, 36(1).

Paillere, A., Buil, M., & Serrano, J. J. (1989). Effect of fiber addition on the autogenous shrinkage of silica fume. ACI Materials Journal,86(2).

Ramakrishnan, V., Zellers, R., & Patnaik, A. K. (2007). Plastic shrinkage reduction potential of a new high tenacity monofilament polypropylene fiber. Special Publication, 243, 49-62.

Palacios, M., & Puertas, F. (2007). Effect of shrinkage-reducing admixtures on the properties of alkali-activated slag mortars and pastes. Cement and concrete research, 37(5), 691-702.

Portland Cement Association (1970) “Durability of Concrete Bridge Decks,” Final Report of a Cooperative Study, No. EB067.01E. 1970.

Qian, C.X. & Stroeven, P. (2000). Development of hybrid Polypropylene-Steel Fiber Reinforced Concrete, Cement and Concrete Research, Vol. 30, No.1, pp. 63-69, ISSN0008 8846.

Rajabipour, F., Sant, G., & Weiss, J. (2008). Interactions between shrinkage reducing admixtures (SRA) and cement paste's pore solution. Cement and Concrete Research, 38(5), 606-615.

Ramey, G. E., Wolff, A. R., and Wright, R. L., (1997) “Structural Design Actions to Mitigate Bridge Deck Cracking,” Practice Periodical on Structural Design and Construction, Vol. 2, No. 3, pp. 118-124.

Russell, H. G. (2004). NCHRP Synthesis of Highway Practice 333: Concrete Bridge Deck Performance. Transportation Research Board of the National Academies, Washington, DC.

Sato, T., Goto, T., & Sakai, K. (1983). Mechanism for reducing drying shrinkage of hardened cement by organic additives. CAJ Review, 52-54.

Schmeckpeper, E. R., & Lecoultre, S. T. (2008).Synthesis into the Causes of Concrete Bridge Deck Cracking and Observations on the Initial Use of High Performance Concrete in the US 95 Bridge over the South Fork of the Palouse River (No. N08-05).

Schmitt, T. R., and Darwin, D., (1995) “Cracking in Concrete Bridge Decks,” Report No. K-TRAN: KU-94-1, Final Report, Kansas Department of Transportation.

Shah, S., Marikunte, S., Yang, W., & Aldea, C. (1997). Control of cracking with shrinkage-reducing admixtures. Transportation Research Record: Journal of the Transportation Research Board, (1574), 25-36.

Shang, H. S., & Yi, T. H. (2013). Freeze-thaw durability of air-entrained concrete. The Scientific World Journal, 2013.

Shing, P. B., & Abu-Hejleh, N. (1999). Cracking in Bridge Decks: Causes and Mitigation (No. CDOT-DTD-R-99-8,).

Tomita, R., Takeda, K., & Kidokoro, T. (1983). Drying shrinkage of concrete using cement shrinkage reducing agent. CAJ Review, 198-201.

Transportation Research Circular E-C107, (2006) “Control of Cracking in Concrete – State of the Art,” Transportation Research Board Report, Oct.

Tritsch, N., Darwin, D., & Browning, J. (2005). Evaluating Shrinkage and Cracking Behavior of Concrete Using Restrained Ring and Free Shrinkage Tests. The Transportation Pooled Fund Program Project No. TPF-5 (051).

Weiss, W. J., & Shah, S. P. (2002). Restrained shrinkage cracking: the role of shrinkage reducing admixtures and specimen geometry. Materials and Structures, 35(2), 85-91.

Weiss, W. J., and Berke, N. S., (2002) “Admixtures for Reducing Shrinkage and Cracking,” Early-Age Cracking in Cementitious Systems – State of the Art Report (A. Bentur, ed.).

Wittmann, F. H. (1976). On the action of capillary pressure in fresh concrete. Cement and Concrete Research, 6(1), 49-56.

Zhuang, J. (2009). Evaluation of Concrete Mix Designs to Mitigate Early-age Shrinkage Cracking in Bridge Decks (Doctoral dissertation, Washington State University).

APPENDIX

Acceptable ODOT Mix Design

Free Shrinkage - Control Mix 0 0 5 10 15 20 25 30 -0.0001

-0.0002

-0.0003

-0.0004

Shrinakge -0.0005

-0.0006

-0.0007

-0.0008 Time, Days

CN-1 CN-2

Figure A.1 Free Shrinkage in The Control Mix

Free Shrinkage - SRA Mix 0 0 5 10 15 20 25 30 -0.00005 -0.0001 -0.00015 -0.0002 -0.00025

Shrinkage -0.0003 -0.00035 -0.0004 -0.00045 -0.0005 Time, Days

SRA-1 SRA-2

Figure A.2 Free Shrinkage in The SRA Mix

Free Shrinkage - CRA Mix 0 0 5 10 15 20 25 30 -0.00005

-0.0001

-0.00015

-0.0002 Shrinkage

-0.00025

-0.0003

-0.00035 Time, Days

CRA-1 CRA-2

Figure A.3 Free Shrinkage in The CRA Mix

Free Shrinkage - Fibers Mix 0 0 5 10 15 20 25 30 -0.0001

-0.0002

-0.0003

-0.0004

-0.0005 Shrinkage -0.0006

-0.0007

-0.0008

-0.0009 Time, Days

Fiber-1 Fiber-2

Figure A.4 Free Shrinkage in The Fibers Mix

Free Shrinkage - F-SRA Mix 0 0 5 10 15 20 25 30 -0.0001

-0.0002

-0.0003

-0.0004

Shrinkage -0.0005

-0.0006

-0.0007

-0.0008 Time, Days

F-SRA-1 F-SRA-2

Figure A.5 Free Shrinkage in The Fibers + SRA Mix

Free Shrinkage - F-CRA Mix 0 0 5 10 15 20 25 30 -0.00005 -0.0001 -0.00015 -0.0002 -0.00025

Shrinkage -0.0003 -0.00035 -0.0004 -0.00045 -0.0005 Time, Days

F-CRA-1 F-CRA-2

Figure A.6 Free Shrinkage in The Fibers + CRA Mix

100

Control Mix 50

0 0 50 100 150 200 250 300 350 400

-50 µ -100

-150 Shrinkage,

-200

-250

-300 Time, Hours

R1-S1 R1-S2 R2-S1 R2-S2

Figure A.7 Restrained Shrinkage in The Control Mix (2 Rings)

SRA Mix 60

0 0 50 100 150 200 250 300 350 400 450

-20 Shrinkage,µ

-40

-60

-80 Time, Hours

R3-S1 R3-S2 R4-S1 R4-S2

Figure A.8 Restrained Shrinkage in The SRA Mix (2 Rings)

101

CRA Mix 10

0 0 100 200 300 400 500 600 -10

-20

-30

Shrinkage,µ -40

-50

-60

-70 Time, Hours

R5-S1 R5-S2 R6-S2

Figure A.9 Restrained Shrinkage in The CRA Mix (2 Rings)

Fiber Mix 0 0 100 200 300 400 500 600 -20

-40

-60

-80 Shrinkage, Shrinkage, µ -100

-120

-140 Time, Hours

R1-S2 R2-S1 R2-S2

Figure A.10 Restrained Shrinkage in The Fibers Mix (2 Rings)

102

F-SRA Mix 0 0 100 200 300 400 500 600 -20

-40

-60

Shrinkage,µ -80

-100

-120 Time, Hours

R3-S1 R3-S2 R4-S1 R4-S2

Figure A.11 Restrained Shrinkage in The Fibers+SRA Mix (2 Rings)

F-CRA Mix 5

0 0 100 200 300 400 500 600 -5

-10

-15

-20

Shrinkage,µ -25

-30

-35

-40 Time, Hours

R5-S1 R5-S2 R6-S2

Figure A.12 Restrained Shrinkage in The Fibers+CRA Mix (2 Rings)

103

Figure A.13 Flexure in Control Specimen #1

Figure A.14 Flexure in Control Specimen #2

104

Figure A.15 Flexure in SRA Specimen #1

Figure A.16 Flexure in SRA Specimen #2

105

Figure A.17 Flexure in CRA Specimen #1

Figure A.18 Flexure in CRA Specimen #2

106

Figure A.19 Flexure in Fiber Specimen #1

Figure A.20 Flexure in Fiber Specimen #2

107

Figure A.22 Flexure in Fiber+SRA Specimen #2

108

Figure A.23 Flexure in Fiber+CRA Specimen #1

Figure A.24 Flexure in Fiber+CRA Specimen #2

109

110