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Open Access Theses & Dissertations

2018-01-01

Utilization Of Digital Image Correlation TechniqueIn Asphalt TestingAlejandra EscajedaUniversity of Texas at El Paso, ale.escajeda56@gmail.com

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UTILIZATION OF DIGITAL IMAGE CORRELATION

TECHNIQUE IN ASPHALT TESTING

ALEJANDRA ESCAJEDA

Master’s Program in Civil Engineering

APPROVED:

Soheil Nazarian, Ph.D., Chair

Imad Abdallah, Ph.D.

Calvin M. Stewart, Ph.D.

Charles Ambler, Ph.D.

Dean of the Graduate School

Copyright ©

by

Alejandra Escajeda

2018

UTILIZATION OF DIGITAL IMAGE CORRELATION

TECHNIQUE IN ASPHALT TESTING

by

ALEJANDRA ESCAJEDA, B.S.C.E.

THESIS

Presented to the Faculty of the Graduate School of

The University of Texas at El Paso

in Partial Fulfillment

of the Requirements

for the Degree of

MASTER OF SCIENCE

Department of Civil Engineering

THE UNIVERSITY OF TEXAS AT EL PASO

December 2018

iv

Acknowledgements

I would like to express my gratitude for my thesis advisor, Dr. Soheil Nazarian, for constant

support and advice through my undergraduate and graduate careers. His guidance made all this

possible for me, and I hope for the future generations too. It was an exceptional experience to

research under his supervision. I would like to thank Dr. Imad Abdallah as well, for being

instrumental in the progress of the research, for believing in me, and for giving me the opportunity

to work at such prestigious lab. I also express my deepest gratitude to Dr. Calvin Stewart, with a

sincere thank you for the time, wisdom and teachings shared with me, as well as for the opportunity

to utilize his specialized laboratory equipment. Another big thanks to Sergio Rocha for supporting

me in the functionality of the laboratory machines and equipment. I also want to thank Jose

Garibay for helping me collect the necessary material. Special thanks to the student staff members

of the asphalt team, Victor Garcia, Luis F. Cordoba, Esteban Fierro, and Jose Lugo, for keeping

the lab processes running smoothly.

Of course, this would not have been possible without the support of my friends, Diana

Cabrera, Melissa Escalante, Luis Lemus, and Ivan Ramirez, thank you very much for your

friendship and your advice, I will never forget it. I would also like to thank Juan F. Gonzalez

because he was able to support me through my writing process.

Special thanks to my family (in Spanish):

Gracias a mis padres, Julio Escajeda y Silvia Figueroa por siempre guiarme y apoyar todos

mis sueños.

v

Abstract

Over 90% of the roads in the United States are paved with hot mix asphalt (HMA). These

asphalt pavements include many mix types, such as permeable friction course (PFC), stone mastic

asphalt (SMA) and conventional dense graded mixes. The performance of the HMA is an

important factor in pavement design programs used by many departments of transportation. The

type of HMA selected not only influences the performance of the pavement structure, but also the

pavement’s life cycle cost. The performance life of an HMA mix is to be studied further with

experimental data in order to contribute and expand on the current limited empirical data.

The study presented herein uses digital image correlation (DIC) to capture the strain and

displacement data during testing of the specimens. DIC was utilized to analyze specimens tested

with the overlay tester (OT) test, indirect tensile test (IDT), and semicircular bending (SCB) test.

The objective of this study is to present the use of DIC as an alternative to traditional analysis with

physical extensometers and to demonstrate the feasibility of non-contact analysis.

vi

Table of Contents

Acknowledgements ........................................................................................................................ iv

Abstract ............................................................................................................................................v

Table of Contents ........................................................................................................................... vi

List of Tables ............................................................................................................................... viii

List of Figures ................................................................................................................................ ix

Chapter 1: Introduction ....................................................................................................................1

1.1 Background .......................................................................................................................1

1.2 Problem Statement ............................................................................................................3

1.3 Objective ...........................................................................................................................3

1.4 Thesis Organization ..........................................................................................................3

Chapter 2: Literature Review ...........................................................................................................5

2.1 Indirect Tensile Test .........................................................................................................5

2.2 Overlay Tester ...................................................................................................................5

2.3 Semicircular Bending Test ................................................................................................6

2.4 Dynamic Modulus .............................................................................................................6

2.5 Digital Image Correlation .................................................................................................6

Chapter 3: DIC Methodology and Study of Materials .....................................................................8

3.1 Materials .........................................................................................................................12

3.2 Dynamic Modulus Test ...................................................................................................14

Chapter 4: Indirect Tensile Test .....................................................................................................18

4.1 Test Protocol ...................................................................................................................18

4.2 Test Results .....................................................................................................................18

4.3 IDT Recommended Practices .........................................................................................29

Chapter 5: Overlay Tester ..............................................................................................................32

5.1 Testing Specifications .....................................................................................................32

5.2 DIC Test Results .............................................................................................................34

5.3 OT Recommended Practices ...........................................................................................40

vii

Chapter 6: Semicircular Bending Test ...........................................................................................42

6.1 Testing Specifications .....................................................................................................42

6.2 DIC Test Results .............................................................................................................43

6.3 SCB Recommended Practices.........................................................................................48

Chapter 7: Summary and Conclusions ...........................................................................................50

7.1 Summary .........................................................................................................................50

7.2 Test Comparison for the Material’s Modulus .................................................................50

7.3 Conclusion ......................................................................................................................51

7.4 Recommendations and Future Work ..............................................................................52

References ......................................................................................................................................53

Appendix ........................................................................................................................................55

A. Synthetic IDT ...................................................................................................................55

B. OT.....................................................................................................................................65

C. SCB ..................................................................................................................................69

D. Master Curves Data ..........................................................................................................75

Vita 76

viii

List of Tables

Table 3.1: Type C Sieve Analysis................................................................................................. 12

Table 3.2: Testing Matrix ............................................................................................................. 13

Table 3.3 Dynamic Modulus Test Results .................................................................................... 16

Table 4.1 Modulus data represented by a linear fit, the modulus values are the slopes of the lines

....................................................................................................................................................... 29

Table 4.2 Statistics generated from the modulus values for the two methods .............................. 30

Table 5.1 Modulus data obtained in the OT by using the regression lines of Figure 5.4 and Figure

5.8.................................................................................................................................................. 41

Table 5.2 Statistics calculated for the modulus calculated with the bottom, middle, and top

extensometers ................................................................................................................................ 41

Table 6.1 Moduli values obtained for the synthetic specimen using the SCB test ....................... 48

Table 6.2 Statistics for the synthetic specimen under SCB testing ............................................... 49

Table 7.1 IDT Test Results ........................................................................................................... 50

Table 7.2 OT Test Results ............................................................................................................ 51

Table 7.3 SCB Test Results .......................................................................................................... 51

Table 7.4 DM Test Results ........................................................................................................... 51

ix

List of Figures

Figure 1.1 a) Fatigue Cracking (Fidalgo n.d.), b) Rutting (Arjun n.d.), c) Thermal Cracking

(Shannon 2015) ............................................................................................................................... 2

Figure 3.1 Painted speckled pattern process ................................................................................... 9

Figure 3.2 DIC Calibration Card .................................................................................................... 9

Figure 3.3 DIC Testing Setup ....................................................................................................... 10

Figure 3.4 Extensometer Placement a) IDT b) SCB c) OT .......................................................... 11

Figure 3.5 Synthetic Polyurethane Specimens.............................................................................. 14

Figure 3.6 Dynamic Modulus Testing Setup ................................................................................ 15

Figure 3.7 Master curve from Dynamic Modulus data, taken from the table in Appendix D. All

three specimen’s data were taken to create the master curve. ...................................................... 17

Figure 4.1 IDT Specifications from the ASTM standard which shows the diagram of an IDT

strength-loading fixture (ASTM International 2017) ................................................................... 19

Figure 4.2 Machine set-up (Ramos 2015) for the IDT as specified by ASTM ............................ 19

Figure 4.3 Progression of the specimen used in the IDT, from initial stage to painted with the

speckle pattern .............................................................................................................................. 20

Figure 4.4 IDT Synthetic Machine Data for the loads applied on the specimen over time .......... 20

Figure 4.5 Extensometer Placement for the IDT .......................................................................... 21

Figure 4.6 Strain vs Time: comparing the length of the extensometers as well as their placement

....................................................................................................................................................... 22

Figure 4.7 IDT Stress vs Strain Synthetic Material ...................................................................... 23

Figure 4.8 IDT Load over time data obtained from the machine at varying temperatures for

different tests (IDT1 to IDT3)....................................................................................................... 24

x

Figure 4.9 IDT DIC Strain Result ................................................................................................. 25

Figure 4.10 Complete test results using DIC analysis .................................................................. 27

Figure 4.11 IDT DIC results at different temperatures only for the loading portion.................... 28

Figure 5.1 OT Layout with dimensions specified as well with imagery to depict the set-up

(Ramos 2015) ................................................................................................................................ 32

Figure 5.2 OT Gluing Methodology (Ramos 2015) ..................................................................... 33

Figure 5.3 DIC Data obtained with extensometers for a) Strain vs Time and b) Stress vs Strain 35

Figure 5.4 OT Stress vs Strain ...................................................................................................... 36

Figure 5.5 OT Machine Data ........................................................................................................ 36

Figure 5.6 OT DIC Strain Progression ......................................................................................... 37

Figure 5.7 OT Type C Stress vs Strain ......................................................................................... 38

Figure 5.8 OT Stress vs Strain Loading ........................................................................................ 39

Figure 6.1 SCB Testing Schematic (Chong, Kuruppu and Kuszaul 1984) .................................. 42

Figure 6.2 SCB set-up that shows how the machine and the speckled pattern specimen are placed

(Ramos 2015). ............................................................................................................................... 43

Figure 6.3 SCB Machine Data ...................................................................................................... 44

Figure 6.4 SCB Synthetic Stress vs. Strain ................................................................................... 45

Figure 6.5 SCB DIC Strain Results .............................................................................................. 46

Figure 6.6 DIC and Machine Data Results ................................................................................... 47

Figure 6.7 SCB Stress vs Strain .................................................................................................... 47

1

Chapter 1: Introduction

Digital Image Correlation (DIC) is a non-contact remote sensing technique that captures

strains and displacement without installing sensors on the specimen (Ramos 2015). The

measurements are performed by cameras that are installed in a closed environment that do not

come in contact with the specimen at any point during the test. This remote sensing technique

tracks the speckled pattern painted on the specimen in the series of photographs taken with the

camera throughout the test at specific times and with a set frame rate. The focus of this thesis is to

demonstrate the use of DIC as a technique that can provide strain and deformation fields in a non-

contact manner.

1.1 BACKGROUND

Flexible pavements comprise over 90 percent of the roads paved in the United States.

Flexible pavement system consists of the following three layers: asphalt, base, and subgrade. This

layered system allows the loading applied at the top of the HMA mix to spread throughout the

layers below.

The HMA mix is considered a viscoelastic material with properties dependent on loading

rate and temperature. The HMA mix is characterized by key components such as the quality of

the binder, aggregates, air voids, binder content, and aggregate geometry. The base layer consists

of an aggregate mix that allows load distribution and allows the drainage of the system. The bottom

layer, known as the subgrade, provides the foundation of the system and it is composed of the

existing soil in the area.

Flexible pavements are built to provide pavements that are smooth and can withstand

vehicle loads. However, due to loading over time, the flexible pavement exhibits certain types of

distress, such as fatigue cracking, rutting, and thermal cracking, as shown in Figure 1.1.

2

Figure 1.1 a) Fatigue Cracking (Fidalgo n.d.), b) Rutting (Arjun n.d.), c) Thermal Cracking

(Shannon 2015)

Fatigue cracking is caused by constant traffic loading, mainly by the tire-pavement

interaction creating cracks that begin in the surface, which is also known as “top down cracking”

(Pavement Interactive n.d.). After constant loading the longitudinal cracks will connect and create

an alligator pattern as seen in Figure 1.1a. For such failure to occur, the pavement must experience

high levels of stress in a concentrated area. Such failure can potentially lead to asphalt breakdown

and water penetration to the system which causes further damage (Arjun n.d.).

Another type of damage is known as rutting, as seen in Figure 1.1b. Rutting is an

indentation in the road due to wheel loading. Because of load exerted on the pavement by the

vehicles, the asphalt is displaced away from said loads (Hajj et al., 2008). These pavement failures

are primarily caused by inadequate compaction, fragile mix design mixture, and not having a thick

enough layer (Chong et al., 1984).

Thermal cracking, represented in Figure 1.1c, occurs due to temperature differences

experienced by the pavement, where the asphalt shows hardening due to low temperatures and

softening due to high temperatures (Arjun n.d.).

Standards are established by organizations such as TxDOT and the American Society for

Testing and Materials (ASTM) to assess the performance of HMA mixes. Three of the most

common testing protocols used are the Indirect Tensile Test (IDT), Overlay Tester (OT), and

Semicircular Bending Test (SCB). IDT test is utilized to examine the materials’ response to

vertical loading, deformation, and fracture properties (ASTM International 2017). The OT was

developed to analyze the HMA response to repeated stress concentration and the crack propagation

3

from the bottom of the specimen (Bennert 2009). Lastly, SCB is used to determine the fracture

toughness of the material (Kim et al., 2015).

1.2 PROBLEM STATEMENT

IDT, OT, and SCB are used to characterize material response. Due to the lack of repeatability

of the results and the inability to capture reliable parameters, an alternate analysis technique is

investigated. With the use of DIC, it is possible to capture the complex stress and strain

distributions by analyzing the video (created from pictures taken during the testing) with tools

from DIC, it lets us capture data with digitally placed extensometers that allows us to compare it

to other data obtained from non-DIC analysis with physically placed extensometers. This to prove

that DIC will capture data that traditional analysis captures using digital techniques, without the

need of repeated testing.

1.3 OBJECTIVE

The objectives of this study are to present the use of DIC, to assess its repeatability, and to

analyze its compatibility with traditional analysis methods by physically placing extensometers on

the specimen. To achieve these objectives, the following activities were carried out:

1. Tested a Type-C HMA mix and a polyurethane grade 95A material using the IDT, OT,

and SCB tests at varying temperatures (4.4 °C, 25 °C, and 37.8 °C).

2. Placed virtual extensometers in the analysis stage to track the parameters that are

unseen to traditional analysis outside of DIC. These unseen parameters are:

displacements in the x, y, and z directions, strain field evolution, strain vectors, and

principle strains.

3. Placed digital extensometers throughout the specimens to understand the variability of

the results, and its dependency on the placement of the extensometers.

1.4 THESIS ORGANIZATION

The thesis is divided into nine chapters starting with chapter one, this chapter that

introduces the topic. Chapter 2 focuses on the literature review describing the following concepts

4

and tests: Overlay Tester, Indirect Tensile Test, Semicircular Bending Test, Dynamic Modulus

Test, and Digital Image Correlation. Chapter 3 presents the study’s methodology and a detailed

specification regarding the testing material. Chapters 4, 5, 6, and 7 present the testing results and

analysis for the tests carried out. Previously mentioned tests were performed for both HMA and

synthetic material. It is important to note that Chapter 4, which presents the Indirect Tensile Test,

will contain the results for all the tested temperatures, 4.4 °C, 25 °C, and 37.8 °C, because there are

standard testing temperatures; whereas the following chapters will have the data for 25 °C, as well

taken from the standard testing temperatures, the remaining results regarding the other

temperatures will be presented in the Appendix. Chapter 8 will include a test result comparison.

The final chapter contains a summary of the project, recommendations and future work.

5

Chapter 2: Literature Review

2.1 INDIRECT TENSILE TEST

The IDT was created to determine the Poisson’s ratio and the stiffness of the materials

(Roque, et al. 1998). According to the American Society for Testing and Materials (ASTM), IDT

test consists of vertically loading the specimen to failure and calculating its strength. The type of

loading induces tension in mid specimen which ultimately cause the material to crack. Yi-Qui et

al. (2012) successfully obtained parameters unseen to traditional testing outside DIC, during IDT

testing that aided in the investigation of the specimen deformation and fracture properties. DIC

uses virtual extensometers to further understand the complex behavior of asphalt samples during

testing. Further information is presented in Chapter 4.

2.2 OVERLAY TESTER

OT was developed in the 1970’s with its primary objective to model the pavement

displacements that are caused from temperature-induced stress (Germann and Lytton 1979). A

specimen sized 6 in. (150 mm) long, 3 in. (75 mm) wide, and 1.5 in. (38 mm) high is glued to two

steel plates, one plate is fixed, and the other plate moves. OT is a displacement-control test that

measures the number of cycles to failure (Zhou and Scullion 2003) . Bennert et al. (2011), Bennert

(2009), and Hajj et al. (2008), among others, rated OT as a reliable test for identifying HMA crack

resistance . Garcia and Miramontes (2015) stated that the repeatability of cycles to failure was of

concern due to several operational issues such as the torque applied to the specimen while being

attached to the plates, the glue quantity, the glue curing time, and time between specimen testing

and preparation. Ramos (2015) showed a favorable comparison between the lab data and the

displacements and strains obtained from the DIC.

6

2.3 SEMICIRCULAR BENDING TEST

Chong et al. (1984) developed the SCB Test to characterize the cracking resistance

potential of the material in a three-point bending test. The specimen contains a notch at the base

of the specimen to ensure crack propagation at the center of the specimen. According to Lim et al.

(1993), the test is utilized for the determination of the stress intensity in mode I and a combination

of mode I and II. The SCB is perceived as a powerful tool that allows further fracture asphalt

resistance evaluation (Zhong, et al. 2005). Reyes et al. (2016) indicated that SCB test exhibited

consistency, repeatability, simplicity, and the ability to obtain multiple specimens from one field

core, versus the IDT, which obtains more parameters at the cost of a longer period of time, and in

turn leads to a preferred analysis in DIC.

2.4 DYNAMIC MODULUS

The dynamic modulus test is widely utilized and accepted as a testing procedure by various

transportation agencies and research laboratories. According to AASHTO TP62-07, the dynamic

modulus test requires the following: testing at least two specimens with a 6 in. (156 mm) height

and 4 in. (102 mm) diameter, at four temperatures ranging from 40 °F to 100 °F (4.4 °C to 37.8

°C), and at six loading rates ranging from 25 Hz to 0.1 Hz. This test serves primarily to obtain the

modulus of the material, in comparison, the other tests were performed to obtain the modulus and

more, hence why some of the other tests were preferred. For further explanation, please refer to

Chapter 7.

2.5 DIGITAL IMAGE CORRELATION

DIC is a non-contact tool used primarily for analyzing the results of the IDT, OT, DM,

and/or SCB tests. DIC allows for adding analysis tools digitally, such as extensometers in this case,

7

after a test has run and as many times as desired, which in turn yields different results. This

technology allows the measurement of displacements and strains; also, it allows a more detailed

study of the materials cracking and fracture phenomena (Safavizadeh et al., 2018). Ramos (2015)

suggested that the DIC method allowed the user to validate the predictions done through finite

element models. Yates et al. (2010) demonstrated through the use of DIC the crack stability of

growing cracks and the closure of those cracks in certain testing environments. Zhou et al. (2007)

also utilized DIC to monitor the crack growth during the OT tests. In summary, DIC is a technique

used for the comparison of other testing technique in order to validate and further understand the

asphalt mechanism and behavior during testing.

8

Chapter 3: DIC Methodology and Study of Materials

This study utilized the Vic-3D software, created by Correlated Solutions, Inc. This software

allows the calculation of the following: displacements in the x, y, and z directions, strain field

evolution, strain vectors, and principle strains. The idea of DIC is that its software (Vic-3D) has

the option of creating a video from the pictures captured during the test, and the field evolution of

the contour of the specimen (Correlated Solutions 1998). In the contour, a gradient of different

colors symbolizes the probability of where the specimen will crack from. This contour varies

throughout the duration of the video. The software tracks each pixel’s deformation throughout the

test and compares it to the original pixel location. The software works by taking a series of pictures

while testing, and the software compares the subsequent deformed images to the reference image.

For the software to capture the movement, the specimen must be prepared with a random

speckle pattern. Figure 3.1 shows the spray-painted speckled pattern method. The specimen is

painted with white paint and then with black paint the speckled pattern is created by lightly tapping

the canister tap which in turn aids in pixel detection. DIC system uses the two calibrated cameras

to take pictures (or frames) of the test in motion. After the specimen is placed in the test bench,

the DIC system is calibrated with calibration cards by aligning the cards with the specimen and

lightly moving the cards until the system accepts the configuration. These cards help the software

to determine the correct position of the camera setup to ensure that the data obtained will be

reliable.

The software uses an algorithm to determine which pictures from both cameras are chosen

to create the final video in which the digital tools can be placed to obtain the desired parameters.

9

Figure 3.1 Painted speckled pattern process

To ensure accurate data acquisition, the pictures need to be calibrated, this is done with a

calibration card, which is included in the software package. Figure 3.2 shows the calibration card.

Figure 3.2 DIC Calibration Card

10

The calibration card, which must closely match the size of the object being analyzed (in

this case the specimen) and the size of the speckled pattern, is moved around the testing area with

precise and subtle movements while approximately 20 images are captured. Vic-3D software

processes the images to provide a calibration score in pixels. A lower score is considered better. If

the calibration score is not accepted by the software, the set up should be adjusted and the

calibration process must be repeated.

Figure 3.3 shows the equipment setup and camera placement. Adequate placement is

essential for error reduction during testing. The images were captured with two Point Gray GRAS-

20S4M-C with 17-mm-lense cameras that were mounted on a tripod. According to the Vic-3D

manual, the angle between the two cameras should be 25° or greater. It is important to maintain

the set up during the calibration and testing. The calibration will not be valid if the setup is changed

during testing.

Figure 3.3 DIC Testing Setup

11

Once the frames are captured, they are processed in the VIC-3D software. The software

can output the displacement in the x, y, z direction, strain in the x and y direction, shear strain,

major and minor principle stains, and the principle strain angle. The software also allows the user

place virtual extensometers to calculate the strain along a certain length. Figure 3.4 shows the

extensometer placement for the three performed tests, IDT, OT, and SCB. For the following study,

the extensometers where strategically placed depending on the test.

Figure 3.4 Extensometer Placement a) IDT b) SCB c) OT

IDT

OT

SCB

12

3.1 MATERIALS

The study consisted of performing three different tests with one mix at three different

temperatures. The mix utilized for this study is a dense graded mix with a binder content of 4.7%

using a PG 70-22 binder. Table 3.1 shows the mix gradation. A description of the test, temperature,

and air voids is provided in

Table 3.2.

Table 3.1: Type C Sieve Analysis

Sieve Size Percent Passing

1” 100.0

3/4” 99.3

3/8” 82.4

No. 4 52.7

No. 8 36.9

No. 30 18.6

No. 50 14.0

No. 200 5.6

13

Table 3.2: Testing Matrix

Test Temperature °C

(°F) ID Air Voids (%)

OT

4.4 (40)

Specimen 1 6.6

Specimen 2 6.4

Specimen 3 6.3

25 (70)

Specimen 4 6.2

Specimen 5 6.0

Specimen 6 6.3

37.8 (100)

Specimen 7 6.1

Specimen 8 6.3

Specimen 9 6.0

IDT

4.4 (40)

Specimen 10 6.9

Specimen 11 6.1

Specimen 12 6.0

25 (70)

Specimen 13 6.5

Specimen 14 6.1

Specimen 15 6.9

37.8 (100) Specimen 16 6.0

Specimen 17 6.1

14

Specimen 18 6.1

SCB

4.4 (40)

Specimen 19 6.5

Specimen 20 6.4

Specimen 21 6.3

25 (70)

Specimen 22 6.7

Specimen 23 7.0

Specimen 24 6.8

37.8 (100)

Specimen 25 6.3

Specimen 26 6.4

Specimen 27 6.5

A synthetic Polyurethane grade 95A was also used in this study. The homogeneity of these

materials allows for a less complex analysis and its ability to see the loading and unloading of a

material. Figure 3.5 shows the synthetic specimens. The synthetic material had a nominal modulus

of elasticity of 7,300 psi and a Poisson’s ratio of 0.25.

Figure 3.5 Synthetic Polyurethane Specimens.

3.2 DYNAMIC MODULUS TEST

The dynamic modulus (DM) test was performed following the ASTM D3497-79 standard

for comparison of the dynamic moduli with those that we obtained with DIC in the previous tests

IDT

SCB

OT

15

(IDT, OT, and SCB). Figure 3.6 shows the testing set-up. Three specimens with a 6 in. (156 mm)

height and 4 in. (102 mm) diameter were tested at the following temperatures: 4.4 °C (40 °F), 21.1

°C (70 °F), 37.8 °C (100 °F), and 54.4 °C (130 °F). Each specimen at each temperature was subject

to sinusoidal axial compression loadings at frequencies of 25 Hz, 10 Hz, 5 Hz, 1 Hz, 0.5 Hz, and

0.1 Hz. The dynamic modulus was calculated from the recoverable axial strain response of the

material. The strain is obtained from the three gauges placed around the specimen.

Figure 3.6 Dynamic Modulus Testing Setup

The master curves for the specimens are included in Appendix D. This study focused on

the results from frequencies of 0.5 Hz and 0.1 Hz to have a comparable loading frequency as that

used in the other tests. The master curves were generated from the table located in the Appendix

“D. Master Curves Data

16

Table 3.3 shows the dynamic modulus results, average, and covariance for three specimens

tested under 4.4 °C (40 °F), 21.1 °C (70 °F), and 37.8 °C (100 °F).

17

Table 3.3 Dynamic Modulus Test Results

Specimen Number 4.4 °C (40 °F)

DM 0.5 Hz (psi) DM 0.1 Hz (psi)

1 1,679,000 1,265,000

2 1,711,000 1,299,000

3 1,564,000 1,188,000

Average 1,651,333 1,250,667

Coefficient of

Variation 0.038224 0.037128

21.1 °C (70 °F)

DM 0.5 Hz (psi) DM 0.1 Hz (psi)

1 555,000 358,400

2 541,000 346,100

3 497,100 312,500

Average 531,033 339,000

Coefficient of

Variation 0.046449 0.057226

37.8 °C (100 °F)

DM 0.5 Hz (psi) DM 0.1 Hz (psi)

1 143,100 78,400

2 129,200 69,200

3 112,600 58,400

Average 128,300 68,667

Coefficient of

Variation 0.097177 0.119304

18

Figure 3.7 Master curve from Dynamic Modulus data, taken from the table in Appendix D. All

three specimen’s data were taken to create the master curve.

1

10

100

1000

10000

0.00001 0.01 10 10000

Dy

na

mic

Mo

du

lus,

Ksi

Frequency, Hz

54.4 °C 37.8 °C 21.1 °C 4.4 °C

19

Chapter 4: Indirect Tensile Test

The purpose of this chapter is to present the test protocol and results for the IDT tests on

the synthetic specimen and the hot mix asphalt specimens at three different temperatures of 4.4 °C

(40 °F), 25 °C (70 °F) and 37.8 °C (100 °F).

4.1 TEST PROTOCOL

The IDT tests were performed following the ASTM D693 standard. The specimens had a

diameter of 6 in. (150 mm) and a thickness of 2.5 in. (64 mm). The loading rate is 1.97 in./min (50

mm/min). Figure 4.1 shows the testing schematic from the ASTM standard and Figure 4.2 depicts

the physical setup by Ramos (2015) that was used as the basis for this test. Figure 4.3 displays the

progression of specimen preparation used in the IDT. The specimen was first spray painted white

and then painted with a black speckled pattern. The asphalt specimens were conditioned to the

following temperatures before testing: 4.4 °C (40 °F), 25 °C (70 °F) and 37.8 °C (100 °F), whereas

the synthetic specimen was conditioned to 25 °C (70 °F).

4.2 TEST RESULTS

The synthetic specimen was loaded from 100 lbf to 500 lbf, this load range was chosen

since it was observed that at 1,000 lbf the synthetic specimen would crack. These limits were set

to have a safe range and to not exceed the force than what the HMA mix specimen can handle.

The synthetic specimen was used to determine where to place the extensometers and to see how it

behaved depending on their placement. Figure 4.4 shows the load versus time. For the synthetic

study, only the results for the 500-lbf loading will be presented. The results for the other loading

forces are included in Appendix A.

20

Figure 4.1 IDT Specifications from the ASTM standard which shows the diagram of an IDT

strength-loading fixture (ASTM International 2017)

Figure 4.2 Machine set-up (Ramos 2015) for the IDT as specified by ASTM

21

Figure 4.3 Progression of the specimen used in the IDT, from initial stage to painted with the

speckle pattern

Figure 4.4 IDT Synthetic Machine Data for the loads applied on the specimen over time

The post-processing of the test consisted on the placement of the virtual extensometers as

mentioned in Chapter 3. Figure 4.5 shows how the virtual extensometers where placed in DIC to

analyze the test results. The strain was estimated with those extensometers (see Figure 4.6).

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14 16 18

Load

(lb

f)

Time (sec)

100 lbf200 lbf300 lbf400 lbf500 lbf

22

Figure 4.5 Extensometer Placement for the IDT

With this tool and using the length of the extensometer, the strain is calculated as follows

in which “𝐿” is the length, “∆𝐿” is the change in length, and “𝜀” is strain:

𝜀 = ∆𝐿

𝐿

The extensometer placement is a key to capture what is happening during the test. The

vertical extensometers placed in the IDT measure: 3 in. (76 mm), 4 in (102 mm), and 5 in (127

mm). The horizontal middle extensometers measure 4 in. (102 mm) and the top and bottom

measure 3 in. (76 mm), both the top and bottom extensometers are placed 0.6 in. (16 mm) from

the edge of the specimen.

Figure 4.6 shows the variations of the vertical and horizontal strain versus time obtained

from the extensometers. A similar increasing linear pattern for the varying length and placement

direction of the extensometers can be seen, this is due to the increasing load applied with respect

to time, and the strain calculated. The 3 in. extensometer does not experience the complete load

from the top to bottom exerted on the specimen since it just captures the strain concentration at the

middle of the specimen; hence, the magnitude of the strain in low compared to its counterparts of

4 and 5 in. From these results, a trendline is possible which would aid in the prediction of the

length and placement of the extensometer. With these prediction lines we can assume that by using

IDT

(4.1)

23

5 in. extensometer (reaching from the edges of the specimen) we can observe the complete

behavior of the specimen under test.

Figure 4.6 Strain vs Time: comparing the length of the extensometers as well as their placement

Utilizing both the machine and DIC data, the user can create the stress versus strain curves.

In this study, two methods were used to calculate the stress. The first (Method I) is done by using

the general formula for calculating stress which depicted in Equation 4.2, and the strain was

calculated from the use of the virtual extensometers. In the second method (Method II), the

relationships proposed by Roque and Buttlar (1994) as depicted in Equations 4.3 through 4.7 were

used:

𝜎 = 𝑃

𝐴

where 𝜎 is the stress, 𝑃 is the applied load, 𝐴 is the area of a circle which is the shape of the IDT

specimen (𝐴 = 𝜋 ∗ 𝑟2 for this case).

𝜎𝑥 = 2𝑃

𝜋𝑡𝐷(𝐶𝑠𝑥)

𝐶𝑠𝑥 = 0.948 − 0.01114 (𝑡

𝐷) − 0.2693(𝜐) − 1.436 (

𝑡

𝐷) (𝜈)

-0.02

-0.015

-0.01

-0.005

0

0 2 4 6 8 10 12 14 16 18 20

eyy

Vertical Extensometer

5 in4 in3 in

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0 2 4 6 8 10 12 14 16 18 20ex

xTime (sec)

Horizontal Extensometer

Bottom

Middle

Top

(4.3)

(4.4)

(4.2)

(4.2)

24

𝜀𝑥 = 𝐻𝑀

𝐺𝐿∗ 1.072 ∗ 𝐶𝐵𝑋

𝐶𝐵𝑋 = 1.03 − 0.0189 (𝑡

𝐷) − 0.081(𝜐) (

𝑡

𝐷) + 0.089 (

𝑡

𝐷)

2

𝜈 = −𝜀𝑙𝑎𝑡𝑒𝑟𝑎𝑙

𝜀𝑎𝑥𝑖𝑎𝑙

where, 𝑡 is the thickness, 𝐷 is the diameter, and 𝐻𝑀 is the measured horizontal deflection.

Figure 4.7 shows the stress strain curves obtained from the two methods. From the first

method, the utilized strain is from the horizontal extensometer at the middle of the specimen. The

slope of the line through the stress-strain curve corresponds to the modulus of the specimen. Even

though both methods yield moduli that are in the range of the nominal modulus of 7,300 psi for

the synthetic specimens, the modulus from Method II is more rigorous.

Figure 4.7 IDT Stress vs Strain Synthetic Material

y = 6,247x

R² = 0.9954

y = 9,484x

R² = 0.99490

5

10

15

20

25

30

0 0.0005 0.001 0.0015 0.002 0.0025 0.003

Str

ess

(psi

)

exx

METHOD I

METHOD II

(4.7)

(4.5)

(4.6)

25

The same procedure used for the synthetic material was done for the asphalt material.

Figure 4.8 shows the variations of load with time for all the testing temperatures. More force is

sustained at lower temperatures.

Figure 4.9 shows the strain progression in the x-direction for one specimen tested at 25 °C.

The spectrum of colors acts as an indicator to where more strain is present. The red color indicates

a higher strain while the purple color indicates a lower strain. The first two frames show the

behavior at the start of the test; on the first frame, the purple coloration observed throughout the

specimen signifies that it is at rest and that no strain is present. Frame two shows how strain is

beginning to be present in the specimen, right at the contact points with the machine, located at

the top and bottom central parts of the specimen. Frame three shows the specimen under the

maximum load, strain begins to propagate with greater magnitude throughout the specimen at this

stage. Frames four and five correspond to the post failure conditions after the maximum load has

been applied. Again, the strain has propagated through the specimen with greater magnitude as

0

1000

2000

3000

4000

5000

6000

7000

0 5 10

Fo

rce

(lb

f)

Time (sec)

IDT 4.4oC

0 5 10

Time (sec)

IDT 25oC

0 5 10Time (sec)

IDT 37.8oC

IDT 1 IDT 2 IDT 3

Figure 4.8 IDT Load over time data obtained from the machine at varying temperatures for

different tests (IDT1 to IDT3)

26

seen in the color spectrum. The load concentration occurs near the top and bottom plates which

yields the strain fields visible in the figure.

Figure 4.9 IDT DIC Strain Result

Figure 4.10 shows the representative data of the test, compared to Figure 4.11 which only

shows the loading portion of the test. Results are similar between same temperature specimens,

but they differ greatly between different temperatures.

At colder temperatures, the specimen becomes hardened which leads to a sparser data set

since the specimen loses elasticity and is more resistant to cracks, hence, the data varies greatly

since this type of testing in conjunction with DIC analysis is not optimized to perform under low

temperatures which may skew the data. which is the result of a quicker test and a shorter window

for obtaining data, compared to its higher temperature counterpart (i.e. 4.4 °C vs 25 °C or 37.8

°C). A decrease in testing time leads to obtaining less information about the specimen, since

sometimes the colder specimen shows no signs of cracking, leading to the data shown in the Figure

4.10 for the 4.4 °C specimen.

27

At higher temperatures -as shown in Figure 4.10 for 25 °C and 37.8 °C- the data from the

tests analyzed with DIC is similar in a way that it could be fitted into a pattern. A greater amount

of data could be obtained from these tests since these higher temperatures allow for a longer test

time, which would show a higher quantity of cracking probability on the specimen.

28

Figure 4.10 Complete test results using DIC analysis

0

50

100

150

200

250

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05

Str

ess

(psi

)

Horizontal strain (exx)

Horizontal Extensometer Middle (4.4 °C)

IDT 1

IDT 2

IDT 3

0

10

20

30

40

50

60

70

80

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05

Str

ess

(psi

)

Horizontal strain (exx)

Horizontal Extensometer Middle (25 °C)

IDT 1

IDT 2

IDT 3

0

5

10

15

20

25

30

35

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05

Str

ess

(psi

)

Horizontal strain (exx)

Horizontal Extensometer Middle (37.8 °C)

IDT 1

IDT 2

IDT 3

29

Figure 4.11 IDT DIC results at different temperatures only for the loading portion.

y = 603,037x

R² = 0.9275

y = 706,832x

R² = 0.8166

0

20

40

60

80

100

120

140

160

180

0 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006

Str

ess

(psi

)

exx

IDT (4.4 °C)

Method I IDT 1

Method I IDT 2

Method I IDT 3

Method II IDT 1

Method II IDT 2

Method II IDT 3

y = 63,433x

R² = 0.8784

y = 89,328x

R² = 0.8734

0

20

40

60

80

100

120

140

160

180

0 0.0005 0.001 0.0015 0.002

Str

ess

(psi

)

exx

IDT (25 °C)

METHOD I IDT 1METHOD I IDT 2METHOD I IDT 3METHOD II IDT 1METHOD II IDT 2METHOD II IDT 3

y = 13,513x

R² = 0.8984

y = 22,521x

R² = 0.8933

0

10

20

30

40

50

60

70

80

0 0.0005 0.001 0.0015 0.002

Str

ess

(psi

)

exx

IDT (37.8 °C)

METHOD I IDT 1

METHOD I IDT 2

METHOD I IDT 3

METHOD II IDT 1

METHOD II IDT 2

METHOD II IDT 3

30

4.3 IDT RECOMMENDED PRACTICES

For the polyurethane grade 95A synthetic specimen, the results were more reliable than

that of the HMA mix asphalt specimen. The IDT test duration for the synthetic specimen that was

18 seconds, lead to more data that can be captured. In comparison, the testing performed with the

asphalt specimen was of shorter duration of 10 seconds with less data. The modulus for each of

the three tests, for each of the three temperatures, varied greatly from each other, as seen previously

in Figure 4.11 where the slopes of the lines represent the modulus. The values in Table 4.1 are the

moduli for the middle 5 in. extensometer, which are the slopes of the lines of Figure 4.11. For

example, for the 25 °C test, one modulus value resulted in 63,433 where the other was calculated

to be 89,328, which is approximately a 41% difference between values. Table 4.2 shows the

average (mean), standard deviation, and covariance for both the asphalt HMA mix Type-C and

synthetic Polyurethane Grade 95A specimens. Table 4.1 and Table 4.2 shows the statistics for the

results for an HMA Mix Type-C; the standard deviation shows that the values differ on a large

magnitude from each other, leading to results that may vary greatly. The averages also have a large

difference between temperatures, in which we can conclude that at higher temperature, the

modulus value is smaller. For the Polyurethane Grade 95A specimen, the average modulus (7,866

psi) is relatively close to the value specified by the manufacturer (7,300 psi).

Table 4.1 Modulus data represented by a linear fit, the modulus values are the slopes of the lines

Specimen Type Temperature Modulus (psi)

Method I Method II

HMA Mix Type-C

4.4 °C 603,037 706,832

25 °C 63,433 89,328

37.8 °C 13,513 22,521

Polyurethane Grade

95A 25 °C 6,247 9,484

31

Table 4.2 Statistics generated from the modulus values for the two methods

Specimen

Type Temperature

Average

(psi)

Standard

Deviation (psi)

Coefficient of

Variation

HMA mix

Type-C

4.4 °C 654934.5 51897.5 0.07924075

25 °C 76380.5 12947.5 0.1695132

37.8 °C 18017 4504 0.2499861

Polyurethane

Grade 95A 25 °C 7,866 1618.5 0.205772

The loading portion of the stress-strain curve is better analyzed with the IDT in conjunction

with DIC as an analysis tool. The analysis will benefit greatly by using the synthetic specimen,

due to the additional time in testing (10 seconds for the asphalt specimen and 18 seconds for the

synthetic specimen) which will yield a much clearer set of data, as seen in Figure 4.7 where the

linear model of the data is a tighter fit than that of Figure 4.11 where the data is sparser.

Taking into consideration the extensometer that is placed vertically on the specimen as

seen in Figure 4.5, and observing the strain contour generated by the Vic-3D software as seen in

Figure 4.9 Frame 5, it can be inferred that this vertical digital extensometer captures the area where

the crack in the specimen is more likely to propagate. Hence, it is advised to place the longest

extensometer in the same position where the loading is applied to capture most of the data, an

extensometer of at least 5 in. has shown to be enough to capture the data of this. Due to the

flexibility of placing as many digital extensometers as required, many extensometers can be placed

in the zones where the loading is applied and where the crack is more likely to propagate.

As seen in the strain contour of Figure 4.9, if the digital extensometers are short in length

and placed in the center, the values of strain will be very low since the region is predominantly

purple. This means slight variation to be captured until the crack is present, which will show an

instantaneous growth in strain in a small area, leading to a sparser data set as seen in Figure 4.6

32

for the strain in the y-direction, where the linear models for the 4 in. and 5 in. extensometers are

close to each other, while the 3 in. extensometer is farther from the previously mentioned

extensometers.

33

Chapter 5: Overlay Tester

In the following chapter, the Overlay Tester (OT) testing specifications will be presented.

The chapter contains results for the polyurethane specimen and the HMA specimens at 25 °C. The

chapter will present how the test is performed, as well as the steps to perform it, the results in

which parameters are obtained, and the gradual strain.

5.1 TESTING SPECIFICATIONS

The test was performed using the procedure outlined by the Texas Department of

Transportation (TxDOT), Tex-248-F. The specimen is exposed to tensile displacement in the

testing system. The specimen is mounted onto two steel plates where the left plate remains static,

whereas the right plate slides horizontally to simulate the opening and closing of a crack due to

vehicle loading and temperature change. Figure 5.1 shows the OT testing features.

Figure 5.1 OT Layout with dimensions specified as well with imagery to depict the set-up

(Ramos 2015)

This test can be performed in a cyclic or monotonic fashion; this study focused on

monotonic loading of the specimen. The movable plate displaces 0.125 in. (3.18 mm) in a time

frame of 60 seconds, then returns to its original position.

34

The gluing of the specimen is an essential part of testing to ensure proper results. The

gluing methodology employed is the one proposed by Garcia and Miramontes (2015). Figure 5.2

shows the gluing procedure. The plates are to be placed in a spacer as seen in Figure 5.2b. Figure

5.2c-d shows how a line is drawn in the middle of the specimen to place petroleum jelly, and

adhesive tape to ensure no glue gets to the gap. Equal amounts of 8 grams of epoxy are added to

each side of the specimen. The specimen is then centered at the plates and glued, to ensure the

specimen stays glued, a 5-lb weight is placed on top, as seen in Figure 5.2e-h.

Figure 5.2 OT Gluing Methodology (Ramos 2015)

35

5.2 DIC TEST RESULTS

The synthetic specimen was displaced 0.017 in. (0.43 mm) to ensure no damage was done

to the specimen. Figure 5.3a shows the strain versus time and Figure 5.3b shows the stress versus

strain of the polyurethane specimen. The use of DIC in the following test allows for the adequate

capture of the hysteresis loop of the monotonic test, and it is displayed this way due to the nature

of the test because the specimen cracks and goes back to its original position. The length of the

extensometers utilized in the OT test all measure 2 in. (51 mm), the top and bottom extensometers

are placed 0.2 in. (5 mm) from the edge, there is a 0.5 in. (13 mm) space between the bottom

extensometer to the middle extensometer, and from the middle extensometer to the top

extensometer, as seen in Figure 3.4c. In this test the stress was calculated using formula two, σ =

P/A.

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

0.004

0.0045

0.005

0 50 100

exx

Time (sec)

a) 95A

DIC TopDIC MiddleDIC Bottom

36

Figure 5.3 DIC Data obtained with extensometers for a) Strain vs Time and b) Stress vs Strain

The modulus is captured due to the clear loading portion in the hysteresis loop. Figure 5.4

shows the loading portion for the three extensometers placed in the bottom, middle, and top of the

specimen. The OT has three extensometers as mentioned before -top, middle, and bottom- and

since the crack grows from bottom to top; the bottom extensometers captures the necessary data

to be able to analyze this test using DIC. With this, we can see that the magnitude of the modulus

obtained in this test by using the bottom extensometer is closer to that of the previously obtained

modulus for the synthetic specimen (6,227x psi, in which the variable x is the strain in the test, vs.

7,300 psi of the specimen from the manufacturer’s specifications).

0

5

10

15

20

25

30

0 0.001 0.002 0.003 0.004 0.005

Str

ess

(psi

)

exx

b) 95A

DIC TopDIC MiddleDIC Bottom

37

Figure 5.4 OT Stress vs Strain

The same procedure was performed for the HMA mix. Figure 5.5 shows the loading data

for the 25 °C tests. It shows the load versus time in which we can determine that the load applied

to the specimen by the OT machine peaks at around 15 seconds. The remaining temperature tests

can be found in Appendix B. OT.

Figure 5.5 OT Machine Data

y = 21,124x

R² = 0.9807

y = 12,081x

R² = 0.9906

y = 6,227x

R² = 0.9943

0

5

10

15

20

25

30

35

0 0.001 0.002 0.003 0.004 0.005

Str

ess

(psi

)

exx

95A

DIC Top

DIC Middle

DIC Bottom

-300

-200

-100

0

100

200

300

400

500

600

0 20 40 60 80 100 120

Load

(lb

f)

Time (sec)

25 oC

OT 1

OT 2

OT 3

38

Figure 5.6 shows the gradual strain evolution during the monotonic test. Figure 5.6-1

represents the strain contour at load zero, and Figure 5.6-2 represents the load in between the

beginning of the test and where the load peaks. Figure 5.6-3 shows the specimen under the

maximum load (peak). Figure 5.6-4 is at 60 seconds, and the remaining frames (5 and 6) are once

the plates return to its original position.

Figure 5.6 OT DIC Strain Progression

Figure 5.7 shows the stress versus strain curves for all the extensometers, the dashed line

shows where the maximum load occurred during the test. At the loading portion of the strain versus

stress curve, there is not enough relevant data to collect since the strains are very minimal, and

what the DIC captures from this minimal strain is very limited to understand what happens while

testing an asphalt specimen.

Figure 5.8 shows the loading slope for all the extensometers during the loading portion of

the test. The dashed line is the regression line to fit this data, and the slope of the line is the modulus

of the material. The bottom, middle, and top extensometers for each of the three specimens are

shown in the same figure.

39

Figure 5.7 OT Type C Stress vs Strain

0

10

20

30

40

50

60

0 0.02 0.04 0.06

Str

ess

(psi

)

exx

Bottom Extensometer (25 oC)

OT 1 DIC

OT 2 DIC

OT 3 DIC

0

10

20

30

40

50

60

0 0.02 0.04 0.06

Str

ess

(psi

)

exx

Middle Extensometer (25 oC)

OT 1 DIC

OT 2 DIC

OT 3 DIC

0

10

20

30

40

50

60

0 0.02 0.04 0.06

Str

ess

(psi

)

exx

Top Extensometer (25 oC)

OT 1 DIC

OT 2 DIC

OT 3 DIC

40

Figure 5.8 OT Stress vs Strain Loading

y = 14,479x

R² = 0.3255

0

10

20

30

40

50

60

70

0 0.0005 0.001

Str

ess

(psi

)

exx

Bottom Extensometer (25 oC)

OT 1OT 2OT 3

y = 26,731x

R² = 0.3174

0

10

20

30

40

50

60

70

0 0.0005 0.001

Str

ess

(psi

)

exx

Middle Extensometer (25 oC)

OT 1OT 2OT 3

y = 60,961x

R² = 0.2721

0

10

20

30

40

50

60

70

0 0.0005 0.001

Str

ess

(psi

)

exx

Top Extensometer (25 oC)

OT 1

OT 2

OT 3

41

5.3 OT RECOMMENDED PRACTICES

For the OT, it is recommended to run the test in conjunction with DIC because of its

repeatability in the synthetic specimen. Here, it is possible to capture the loading portion of the

stress versus strain curve, due to the prolonged test duration of 120 seconds, and its loading portion

being the initial 60 seconds. In this test, the DIC was never used for the cyclic test, but for the

monotonic -which opens and closes for one cycle-, and it can be inferred that it worked exceedingly

well since there were more points of data, which yields a closer set of data which leads to a better

linear fit as regression line.

For the polyurethane grade 95A synthetic specimen, the modulus was calculated using the

top, middle, and bottom extensometers at 25 °C, and the results are presented in Table 5.1. The

results for the HMA mix type-C asphalt specimen are also included in Table 5.1 for each of the

extensometers, and the specimen was also at 25 °C.

In this test, it was observed that the crack propagates from bottom to top since the load is

being applied there. In the synthetic specimen, the value obtained that was closest to the

manufacturer’s specifications was calculated using the bottom extensometer; this is where the DIC

tool will be optimal since it displays where the contours are more likely to appear. It is also

observed, that the highest strains are concentrated at the bottom of the specimen, leading to the

amount of strain concentrated at the top being usually low compared to the amount seen at the

bottom of the specimen.

The mean, standard deviation, and coefficient of variation for the three extensometers

placed in the asphalt and synthetic specimen are shown in Table 5.2, where it is observed that the

variation of the modulus for each of the extensometers is relatively high. Using the coefficient of

variation, it can be inferred that the value of the modulus for the asphalt specimen varies at around

57%, and for the synthetic specimen it is close to 46% of variation between extensometers.

42

Table 5.1 Modulus data obtained in the OT by using the regression lines of Figure 5.4 and Figure

5.8.

Specimen Type at 25 °C Extensometer Modulus (psi)

HMA Mix Type-C

Top 60,961

Middle 26,731

Bottom 14,479

Polyurethane Grade 95A

Top 21,124

Middle 12,081

Bottom 6,227

Table 5.2 Statistics calculated for the modulus calculated with the bottom, middle, and top

extensometers

Specimen Type at

25 °C

Average

(psi)

Standard Deviation

(psi)

Coefficient of

Variation

HMA mix Type-C 60,961 26,731 0.577578

Polyurethane Grade

95A 13,144 6127.948 0.466216

Recalling from Table 5.1, it is recommended to use the bottom extensometer in the

synthetic and asphalt specimens; this in part to the modulus value of the synthetic being the closest

to the value specified from the manufacturer (6,227 psi versus 7,300 psi). This will capture the

necessary data of the loading portion in the first 60 seconds of the test since the contour shows that

most of the strain is concentrated at the bottom of the ashphalt specimen as seen in Figure 5.6.

43

Chapter 6: Semicircular Bending Test

The purpose of this chapter is to present the testing specifications and test results of the

SCB test. The chapter contains the results for the test at 25 °C, and due to the nature of the test,

some parameters were not captured in the same way as in the other tests, since the SCB is limited

to 4 seconds; although these parameters obtained outside those 4 seconds will not be as clear as

those of the IDT and OT tests.

6.1 TESTING SPECIFICATIONS

The SCB Test is a three-point bending test were a semi-circular specimen is loaded

monotonically until failure. The specimen has a diameter of 6 in. (152 mm) and a height of 2 in.

(51 mm). The test is performed with varying notch depths; in this study, the notch measures 0.6

in. (15 mm). Figure 6.1 shows the specifications, and Figure 6.2 shows the DIC set up; the speckled

pattern of the specimen was created as shown previously in the other tests. The loading rate is of

1.97 in./min (50 mm/min).

Figure 6.1 SCB Testing Schematic (Chong, Kuruppu and Kuszaul 1984)

44

Figure 6.2 SCB set-up that shows how the machine and the speckled pattern specimen are placed

(Ramos 2015).

6.2 DIC TEST RESULTS

The synthetic specimen was loaded from 100 lbf to 500 lbf in increments of 100 to avoid

breaking the specimen, and it followed the same procedure as the IDT test. Figure 6.3 shows the

machine loading data as a load versus time graph, and how it increases gradually in a linear fashion.

It is observed that the load is applied proportionally over time to the synthetic specimen. This study

will show the data of a specimen loaded at a maximum of 500 lbf.

45

Figure 6.3 SCB Machine Data

The use of the extensometers as seen in Figure 3.4b allows the user to calculate the strain;

the vertical extensometer in the SCB test is placed at the top edge of the notch measuring 2 in. (52

mm) and the horizontal extensometer measures about 5 in. (127 mm), with the use of formula 1, ε

= ΔL/L. For the SCB Test two methods where utilized to calculate the stress, the first method is

utilizing formula two, σ = P/A. Method 2 utilized the formula presented below:

𝜎𝑜 = 𝑃

2𝑟𝑡

Where P is the load, r and t are the specimen’s radius and thickness respectively (Kim et al., 2015).

Figure 6.4 shows the loading portion for the synthetic polyurethane specimen under 500-lbf load.

0

100

200

300

400

500

600

0 2 4 6 8 10

Load

(lb

f)

Time (sec)

SCB Polyurethane Machine Data

100 lbf200 lbf300 lbf400 lbf500 lbf

46

Figure 6.4 SCB Synthetic Stress vs. Strain

The same procedure was followed for the testing of the HMA specimens. Figure 6.5 shows

the strain contours in the x-direction. The major strain concentration occurs at the loading point.

Figure 6.6 simultaneously shows the strain data and loading machine data for both the vertical and

horizontal extensometers.

y = 8,309x

R² = 0.9996

y = 3,330x

R² = 0.99530

2

4

6

8

10

12

14

16

18

0 0.001 0.002 0.003 0.004 0.005

Str

ess

(psi

)

ε

SCB 500-lbf (Method I)

Horizontal

Vertical

y = 9,788x

R² = 0.9996

y = 3,923x

R² = 0.99530

2

4

6

8

10

12

14

16

18

0 0.001 0.002 0.003 0.004 0.005

Str

ess

(psi

)

ε

SCB 500-lbf (Method II)

Horizontal

Vertical

47

Figure 6.5 SCB DIC Strain Results

0

100

200

300

400

500

600

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02

0 1 2 3 4

exx

Time (sec)

SCB Horizontal Extensometer 25 oC

SCB 1 DIC SCB 2 DIC SCB 3 DICSCB 1 Machine Data SCB 2 Machine Data SCB 3 Machine Data

Load

(lbf)

48

Figure 6.6 DIC and Machine Data Results

Due to the nature of the test, no loading portion in the stress versus strain curve is able to

be capture. Even at maximum frame capturing capacity, the loading portion is not clear since the

test only lasts 4 seconds. Figure 6.7 shows the stress versus strain graphs for both extensometers.

Figure 6.7 SCB Stress vs Strain

0

100

200

300

400

500

600

-0.004

-0.0035

-0.003

-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

0 1 2 3 4ey

y

Time (sec)

SCB Vertical Extensometer 25 oC

SCB 1 DIC SCB 2 DIC SCB 3 DICSCB 1 Machine Data SCB 2 Machine Data SCB 3 Machine Data

Load

(lbf)

0

10

20

30

40

50

0 0.05 0.1

Str

ess

(psi

)

exx

Horizontal Extensometers

(25 oC)

SCB 1 (25)SCB 2 (25)SCB 3 (25)

0

10

20

30

40

50

0 0.001 0.002 0.003 0.004

Str

ess

(psi

)

eyy

Vertical Extensometers

(25 oC)

SCB 1 (25)SCB 2 (25)SCB 3 (25)

49

6.3 SCB RECOMMENDED PRACTICES

Due to the relatively short duration of this test (4 seconds) it is advised to not use the DIC

analysis in conjunction with SCB for the asphalt specimen, since the data acquired is not enough

to calculate an accurate modulus value. In comparison, the synthetic specimen was tested for 10

seconds, which proved to be enough since the modulus of 8,309 psi obtained was close to the

established 7,300 psi value from the manufacturer. Hence, it is advised to utilize the SCB test in

conjunction with DIC for a synthetic specimen.

Table 6.1 represents the values obtained for the synthetic specimen using Method I and

Method II for both horizontal and vertical digital extensometers. For more data obtained for DIC

at 100 lbf to 400 lbf for the synthetic specimen, refer to Appendix C. SCB. It is also recommended

to use the horizontal extensometers since the values are closer to the one specified by the

manufacturer.

In order to quantify the variation, statistics such as mean, standard deviation, and

coefficient of variation were calculated and are shown in Table 6.2, these values were averaged

for each method used. It can be observed that the extensometers have the same coefficient of

variation, meaning that they could be proportional to each other, yet the extensometer that yields

a value closer to that of the manufacturer is the horizontal one.

Table 6.1 Moduli values obtained for the synthetic specimen using the SCB test

Specimen Type at 25 °C Extensometer Modulus (psi)

Method I Method II

Polyurethane Grade 95A Horizontal 8,309 9,788

Vertical 3,330 3,923

50

Table 6.2 Statistics for the synthetic specimen under SCB testing

Specimen Type at 25

°C Mean Standard Deviation

Coefficient of

Variation

Polyurethane Grade 95A 9,049 739.5 0.081726

3,627 296.5 0.081759

The data for the asphalt specimen was not useful since the data was seen to be very

scattered, hence the exclusion.

51

Chapter 7: Summary and Conclusions

7.1 SUMMARY

The objective of this study was to show the capabilities with the use of the DIC technique,

in its comparability, repeatability, and overall use of the system. This was done by having a robust

testing methodology that tested at varying temperature as follows, 4.4 °C, 25 °C, and 37.8 °C. In

addition, the study presented an alternate use of the DIC post-processing tools where

extensometers were utilized to obtain unseen parameters while testing. The placement of such

extensometers was essential to adequately summarize the behavior of the specimens. The

placement is also important in the data acquisition, as seen in the results; the extensometer

placement influences the final values, since there was variability in the tests based on such

placement. Such study showed the technique capabilities in the different test and showed that the

use of DIC is more beneficial in certain tests due to testing protocols.

7.2 TEST COMPARISON FOR THE MATERIAL’S MODULUS

The performed tests with the use of DIC allowed for the capture of the material’s modulus.

Table 7.1 and Table 7.2 shows the obtained modulus values for the IDT and OT Test for the

synthetic Polyurethane grade 95A and the HMA subject to the following testing temperatures: 4.4

°C (40 °F), 21.1 °C (70 °F), and 37.8 °C (100 °F). Table 7.3 shows the results from the SCB test

for the synthetic Polyurethane grade 95A material, as previously noted, due to the nature of the

test, no loading portion of the stress versus strain curve for the SCB HMA test was captured.

Table 7.1 IDT Test Results

Test Method I - Modulus (psi) Method II - Modulus (psi)

Synthetic Polyurethane 95A IDT 6,247 9,484

HMA Type-C

IDT 4.4 603,037 706,832

IDT 25 63,433 89,328

IDT 37.8 13,513 22,521

52

Table 7.2 OT Test Results

Test

Bottom

Extensometer -

Modulus (psi)

Middle Extensometer

- Modulus (psi)

Top

Extensometer -

Modulus (psi)

Synthetic Polyurethane 95A OT 6,227 12,081 21,124

HMA Type-C

OT 4.4 175,180 222,251 315,700

OT 25 14,479 26,731 60,961

OT 37.8 4,838 8,854 20,080

Table 7.3 SCB Test Results

SCB Method I - Modulus (psi) Method II - Modulus (psi)

Synthetic Polyurethane

95A

Vertical

Extensometer

Horizontal

Extensometer

Vertical

Extensometer

Horizontal

Extensometer

3,330 8,309 3,923 9,788

Table 7.4 DM Test Results

DM 4.4 °C (40 °F) 21.1 °C (70 °F) 37.8 °C (100 °F)

HMA Type-C Averages at 0.5 Hz 1,651,333.333 531,033.333 128,300

Averages at 0.1 Hz 1,250,666.666 339 68,666.667

The testing results show promising values in the synthetic material, according to the

manufacturer’s specifications; a modulus value of 7,300 psi is expected. For both the IDT and OT

tests, there is a 16% difference between the values obtained and from the Polyurethane

specifications. For the values obtained from testing the HMA in the IDT, OT, SCB, and DM, there

was no correlation between the values obtained across all tests. Comparing the values obtained

through the DIC and those by the DM test, there was a 75% difference in the modulus between

both testing techniques.

7.3 CONCLUSION

This study showed an alternate data acquisition technique that allows the user to capture

unseen parameters to conventional testing methods. It showed a reliable testing technique where

the values obtained could then be compared to widely use measuring devices as gauges or LVDT’s.

53

Throughout the study, the use of the DIC technique was proven reliable and reputable. It showed

a non-contact testing technique with robust capabilities that allows the user to obtain unseen

parameters from an already widely utilized fracture testing technique such as the IDT, OT, and

SCB test.

7.4 RECOMMENDATIONS AND FUTURE WORK

The recommendations include a more in-depth analysis on the DIC capabilities and the use

of the data provided by the DIC. In addition, having to minimize the user and interface error by

having both the testing equipment and DIC equipment be synchronized to allow for a true capture

of the material’s behavior during the test. In the post processing of the frames, it is important to

develop a sensitivity analysis on the placement of the extensometers. A more in depth research is

to be conducted to decide on the direction and placement of the extensometer on the specimen that

truly captures the experience of the material under certain loading conditions. It is also

recommended to have a further study where the use of certain parameters captured by the DIC are

to be used in the modeling aspect where an ABAQUS model is created. This process will allow

for the validation of the DIC technique and create a bridge between the experimental techniques

and mathematical modeling.

54

References

AASHTO TP62-07. 2007. "Standard Method of Test for Determinating Dynamic Modulus of

Hot-Mix Asphalt (HMA)." Washington D.C.: American Assosiation of State Highway

and Transportation Officials.

Arjun, Neenu. n.d. Types of Failures in Flexible Pavements and their Causes and Repair

Techniques. https://theconstructor.org/transportation/types-failures-in-flexible-

pavements-repair/16124/.

ASTM International. 2017. "Standard Test Method for Indirect Tensile (IDT) Strength of

Asphalt Mixtures." IDT Standard, 5.

Bennert, Thomas, Ali Maher, and Robert Sauber. 2011. "Influence of Prodcution Temperature

and Aggregate Moisture Content on the Initial Performance of Warm-Mix Asphalt."

Transportation Research Board 97-107.

Bennert, Tom. 2009. Lab Overlay Testers for Characterizing HMA Crack Resistance. Portland:

Northeast Asphalt User Producer Group.

Chong, Ken P., Mahinda D. Kuruppu, and Joel S. Kuszaul. 1984. "Fracture Toughness

Determination of Layered Materials." Engineering Fracture Mechanics 43-54.

Correlated Solutions. 1998. VIC-3D High-Speed System. http://correlatedsolutions.com/high-

speed-imaging/.

Fidalgo, Beatriz. n.d. Crack Fillercrack. https://www.emaze.com/@ACWOROZI.

Garcia, Victor M., and Alejandro Miramontes. 2015. "Understanding Sources of Variability of

Overlay Test Procedure." Transportation Research Board 10-18.

Germann, Frederick P., and Robert L. Lytton. 1979. Methodology for Predicting the Reflection

Cracking Life of Asphalt Concrete Overlay . Austin : Texas State Department of

Highway and Public Transportation .

Gutierrez, A. 2016. "Numerical Simulation of the Overlay Tester." Masters Thesis.

Hajj, Elie Y., Peter E. Sebaaly, and Luis Loria. 2008. Reflective Cracking of Flexible Pavements

Phase I and II Recommendations. Reno : Nevada Department of Transportation.

Kim, Y, G Nsengiyumva, and T You. 2015. Development of a Semicircular Bend (SCB) Test

Method for Performance Testing of Nebraska Asphalt Institute. Lincoln : Nebraska

Department of Roads.

55

Lim, I.L., I. W. Johnston, and S.K. Choi. 1993. "Stress Intensity Factors for Semi-circular

Specimens Under Three-Point Bending." Engineering Fracture Mechanics 363-382.

Pavement Interactive. n.d. Top-Down Cracking. https://www.pavementinteractive.org/reference-

desk/pavement-management/pavement-distresses/top-down-cracking/.

Ramos, Estefany. 2015. "A Methodology for use of Digital Image Correlation for Hot Mix

Asphalt Testing." Master Thesis. The University of Texas at El Paso.

Roque, R, Buttlar W, B Ruth, and Dickison S. 1998. "Short-Loading-Time Stiffness from Creep

Resilient Modulus, and Strength Tests Using Superpave Indirect Tension Test."

Transportation Research Record 10-20.

Safavizadeh, S.A., A. Wargo, and Y.R. Kim. 2018. "Utilizing Digital Image Correlation (DIC) in

Asphalt Pavement Testing." Journal of Testing and Evaluation 984-998.

Shannon. 2015. Shannon from Scratch. February 13.

https://shannonfromscratch.wordpress.com/2015/02/13/11-tips-for-unrunners-who-just-

cant-go-another-step/.

Stewart, Calvin M., Jesus G. Reyes, and Victor M. Garcia. 2016. "Comparison of Fracture Test

Standards for a Super Pave Dense-graded Hot Mix Asphalt." Engineering Fracture

Mechanics 262-275.

Yates, J.R., Zanganeh M., and Y.H Tai. 2010. "Quantifying Crack Tip Displacement Fields with

DIC." Engineering Fracture Mechanics 14.

Yi-qiu, Tan, Zhang Lei, Guo Meng, and Shan Li-yan. 2012. "Investigation of the Deformation

Properties of Asphalt Mixtures with DIC Technique." Construction and Bulding

Materials 581-590.

Zhong, Wu, Mohammad Louay N., Wang L.B, and Mary Ann Mull. 2005. "Fracture Resistance

Characterization of Superpave Mixtures Using Semi-Circular Bending Test." Journal of

ASTM International 1-15.

Zhou, F, S Hu, and T Scullion. 2007. Development and Verification of the Overlay Tester Based

Fatigue Cracking Prediction Approach. Austin: Federal Highway Administration.

Zhou, Fujie, and Tom Scullion. 2003. Upgraded Overlay Tester and its Application to

Characterize Reflection Cracking Resistance of Asphalt Mixtures. Austin: Texas

Department of Transportation.

56

Appendix

A. SYNTHETIC IDT

-0.004

-0.0035

-0.003

-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

0 2 4 6 8 10 12 14 16 18

eyy

Time (sec)

Vertical Extensometer IDT 100 lbf

5 in4 in3 in

0

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

0 2 4 6 8 10 12 14 16 18

exx

Time (sec)

Horizontal Extensometer IDT 100 lbf

Bottom

Middle

Top

57

0

0.5

1

1.5

2

2.5

3

3.5

0 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006

Str

ess

(psi

)

exx

Horizontal Extensometer IDT 100 lbf

BottomMiddleTop

0

0.5

1

1.5

2

2.5

3

3.5

0 0.001 0.002 0.003 0.004

Str

ess

(psi

)

eyy

Vertical Extensometer IDT 100 lbf

5 in4 in3 in

58

-0.009

-0.008

-0.007

-0.006

-0.005

-0.004

-0.003

-0.002

-0.001

0

0 2 4 6 8 10 12 14 16 18 20

eyy

Time (sec)

Vertical Extensometer IDT 200 lbf

5 in4 in3 in

0

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

0.0007

0.0008

0.0009

0.001

0 2 4 6 8 10 12 14 16 18 20

exx

Time (sec)

Horizontal Extensometer IDT 200 lbf

Bottom

Middle

Top

59

0

1

2

3

4

5

6

7

0 0.0002 0.0004 0.0006 0.0008 0.001

Str

ess

(psi

)

exx

Horizontal Extensometer IDT 200 lbf

BottomMiddleTop

0

1

2

3

4

5

6

7

0 0.002 0.004 0.006 0.008 0.01

Str

ess

(psi

)

eyy

Vertical Extensometer IDT 200 lbf

5 in4 in3 in

60

-0.014

-0.012

-0.01

-0.008

-0.006

-0.004

-0.002

0

0 2 4 6 8 10 12 14 16 18 20ey

y

Time (sec)

Vertical Extensometer IDT 300 lbf

5 in4 in3 in

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0.0018

0 2 4 6 8 10 12 14 16 18 20

exx

Time (sec)

Horizontal Extensometer IDT 300 lbf

Bottom

Middle

Top

61

0

2

4

6

8

10

12

0 0.0005 0.001 0.0015 0.002

Str

ess

(psi

)

exx

Horizontal Extensometer IDT 300 lbf

BottomMiddleTop

0

2

4

6

8

10

12

0 0.005 0.01 0.015

Str

ess

(psi

)

eyy

Vertical Extensometer IDT 300 lbf

5 in4 in3 in

62

-0.016

-0.014

-0.012

-0.01

-0.008

-0.006

-0.004

-0.002

0

0 2 4 6 8 10 12 14 16 18 20

eyy

Time (sec)

Vertical Extensometer IDT 400 lbf

5 in4 in3 in

0

0.0002

0.0004

0.0006

0.0008

0.001

0.0012

0.0014

0.0016

0.0018

0.002

0 2 4 6 8 10 12 14 16 18 20

exx

Time (sec)

Horizontal Extensometer IDT 400 lbf

Bottom

Middle

Top

63

0

2

4

6

8

10

12

14

0 0.0005 0.001 0.0015 0.002

Str

ess

(psi

)

exx

Horizontal Extensometer IDT 400 lbf

BottomMiddleTop

0

2

4

6

8

10

12

14

0 0.005 0.01 0.015

Str

ess

(psi

)

eyy

Vertical Extensometer IDT 400 lbf

5 in4 in3 in

64

-0.02

-0.018

-0.016

-0.014

-0.012

-0.01

-0.008

-0.006

-0.004

-0.002

0

0 2 4 6 8 10 12 14 16 18 20

eyy

Time (sec)

Vertical Extensometer IDT 500 lbf

5 in4 in3 in

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0 2 4 6 8 10 12 14 16 18 20

exx

Time (sec)

Horizontal Extensometer IDT 500 lbf

Bottom

Middle

Top

65

0

2

4

6

8

10

12

14

16

18

0 0.0005 0.001 0.0015 0.002 0.0025 0.003

Str

ess

(psi

)

exx

Horizontal Extensometer IDT 500 lbf

BottomMiddleTop

0

2

4

6

8

10

12

14

16

18

0 0.005 0.01 0.015 0.02

Str

ess

(psi

)

eyy

Vertical Extensometer IDT 500 lbf

5 in4 in3 in

66

B. OT

-400

-200

0

200

400

600

800

1000

0 20 40 60 80 100 120

Load

(lb

f)

Time (sec)

(4.4 °C)

OT 1

OT 2

OT 3

y = 175,180x + 28.949

R² = 0.04520

10

20

30

40

50

60

70

80

90

0 0.00001 0.00002 0.00003 0.00004 0.00005

Str

ess

(psi

)

exx

Bottom Extensometer (4.4 °C)

OT 1

OT 2

OT 3

67

y = 222,251x + 35.152

R² = 0.2287

0

10

20

30

40

50

60

70

80

90

0 0.00005 0.0001 0.00015 0.0002

Str

ess

(psi

)

exx

Middle Extensometer (4.4 °C)

OT 1

OT 2

OT 3

y = 315,700x + 44.446

R² = 0.1347

0

10

20

30

40

50

60

70

80

90

0 0.00005 0.0001 0.00015 0.0002

Str

ess

(psi

)

exx

Top Extensometer (4.4 °C)

OT 1

OT 2

OT 3

68

-100

-50

0

50

100

150

0 20 40 60 80 100 120

Load

(lb

f)

Time (sec)

(37.8 °C)

OT 1

OT 2

OT 3

y = 4,837.8x + 1.4453

R² = 0.9072

0

2

4

6

8

10

12

0 0.0005 0.001 0.0015 0.002

Str

ess

(psi

)

exx

Bottom (37.8 °C)

OT 1

OT 2

OT 3

69

y = 8,853.5x + 0.9726

R² = 0.9443

0

2

4

6

8

10

12

0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012

Str

ess

(psi

)

exx

Middle (37.8 °C)

OT 1

OT 2

OT 3

y = 20,080x + 1.5715

R² = 0.863

0

2

4

6

8

10

12

0 0.0001 0.0002 0.0003 0.0004 0.0005

Str

ess

(psi

)

exx

Top (37.8 °C)

OT 1

OT 2

OT 3

70

C. SCB

y = 10591x + 1.5248

R² = 0.9034

y = 7334.6x + 0.4981

R² = 0.94180

1

2

3

4

5

6

7

0 0.0002 0.0004 0.0006 0.0008 0.001

Str

ess

(psi

)

eyy

SCB 100 lbf (Method I)

Horizontal Vertical

y = 12477x + 1.7964

R² = 0.9034

y = 8640.8x + 0.5868

R² = 0.94180

1

2

3

4

5

6

7

8

9

0 0.0002 0.0004 0.0006 0.0008 0.001

Str

ess

(psi

)

eyy

SCB 100 lbf (Method II)

Horizontal Vertical

71

y = 20,406x + 1.001

R² = 0.9713

y = 15,427x + 2.7474

R² = 0.93110

2

4

6

8

10

12

14

0 0.0002 0.0004 0.0006 0.0008

Str

ess

(psi

)

eyy

SCB 200 lbf (Method I)

Horizontal Vertical

y = 24,040x + 1.1793

R² = 0.9713

y = 18,175x + 3.2367

R² = 0.9311

0

2

4

6

8

10

12

14

16

18

0 0.0002 0.0004 0.0006 0.0008

Str

ess

(psi

)

eyy

SCB 200 lbf (Method II)

Horizontal Vertical

72

y = 23,708x - 0.2656

R² = 0.9703

y = 12,494x + 3.2662

R² = 0.96920

2

4

6

8

10

12

14

16

18

20

0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014

Str

ess

(psi

)

eyy

SCB 300 lbf (Method I)

Horizontal Vertical

y = 27,930x - 0.3128

R² = 0.9703

y = 14,719x + 3.8479

R² = 0.9692

0

5

10

15

20

25

0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012 0.0014

Str

ess

(psi

)

eyy

SCB 300 lbf (Method II)

Horizontal Vertical

73

y = 13,810x + 1.1235

R² = 0.9911

y = 6,028.5x + 1.6475

R² = 0.9965

0

5

10

15

20

25

30

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01

Str

ess

(psi

)

eyy

SCB 400 lbf (Method I)

Horizontal Vertical

y = 16,269x + 1.3236

R² = 0.9911

y = 7,102.2x + 1.9409

R² = 0.99650

5

10

15

20

25

30

35

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.01

Str

ess

(psi

)

eyy

SCB 400 lbf (Method II)

Horizontal Vertical

74

0

200

400

600

800

1000

1200

1400

1600

1800

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02

0 1 2 3 4

exx

Time (sec)

SCB 4.4 °CSCB 1 (4.4)

SCB 3 (4.4)

SCB 3 (4.4)L

oad

(lbf)

0

200

400

600

800

1000

1200

1400

1600

1800

-0.004

-0.0035

-0.003

-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

0 1 2 3 4

eyy

Time (sec)

SCB 4.4 °C

SCB 1 (4.4)

SCB 2 (4.4)

SCB 3 (4.4)

Lo

ad (lb

f)

75

0

50

100

150

200

250

300

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

0 0.5 1 1.5 2 2.5 3

exx

Time (sec)

SCB 37.8 °C

SCB 1 (37.8)

SCB 2 (37.8)

SCB 3 (37.8)

Lo

ad(lb

f)

0

50

100

150

200

250

300

-0.004

-0.0035

-0.003

-0.0025

-0.002

-0.0015

-0.001

-0.0005

0

0 0.5 1 1.5 2 2.5 3

exx

Time (sec)

SCB 37.8 °C

SCB 1 (37.8)

SCB 2 (37.8)

SCB 3 (37.8)

Lo

ad (lb

f)

76

D. MASTER CURVES DATA

Temperature

oC Specimen

25 Hz DM

(ksi)

10 Hz DM

(ksi)

5 Hz DM

(ksi)

1 Hz DM

(ksi)

0.5 Hz DM

(ksi)

0.1 Hz DM

(ksi)

4.4

1 2676 2445 2267 1862 1679 1265

2 2719 2481 2302 1895 1711 1299

3 2579 2337 2151 1743 1564 1188

Temperature oC Specimen

25 Hz DM

(ksi)

10 Hz DM

(ksi)

5 Hz DM

(ksi)

1 Hz DM

(ksi)

0.5 Hz DM

(ksi)

0.1 Hz DM

(ksi)

21.1

1 1307 1089 945.6 649.1 555 358.4

2 1300 1080 933.4 637.3 541.6 346.1

3 1230 1015 874.1 588.3 497.1 312.5

Temperature oC Specimen

25 Hz DM

(ksi)

10 Hz DM

(ksi)

5 Hz DM

(ksi)

1 Hz DM

(ksi)

0.5 Hz DM

(ksi)

0.1 Hz DM

(ksi)

37.8

1 515.8 392.6 318 181 143.1 78.4

2 493.4 371.8 298.4 165.5 129.2 69.2

3 465.4 345.3 273.9 147.3 112.6 58.4

Temperature oC Specimen

25 Hz DM

(ksi)

10 Hz DM

(ksi)

5 Hz DM

(ksi)

1 Hz DM

(ksi)

0.5 Hz DM

(ksi)

0.1 Hz DM

(ksi)

54.4

1 198.2 123.1 89.7 45.4 36.9 23.9

2 165.3 98.6 72.1 39 32 20.4

3 149 86.7 62.1 32.4 27.9 19.6

77

Vita

Alejandra Escajeda Figueroa grew up in El Paso, Texas and attended Franklin High

School before going to college. She joined The University of Texas at El Paso (UTEP) on Spring

2013 to pursue a career in Civil Engineering inspired by her sister’s words. While as an

undergraduate, she had the opportunity to intern with Freeport-McMoRan as an environmental

engineer intern during the summer of 2014, she also worked as a research assistant at the Center

for Transportation Infrastructure Systems. She also participated in a study abroad opportunity

with Global and Regional Sustainable Engineering program in Peru. She obtained her Bachelor

of Science in Civil Engineering in the Spring of 2017. She continued her education in the

master’s program under supervision from Dr. Soheil Nazarian where she focused on pavement

analysis techniques.

She was also active in registered student organizations at the university, where she had

the opportunity to act as the president of the American Society of Civil Engineers (ASCE) UTEP

Chapter, as a member of the Texas Society of Professional Engineers (TSPE), and a member of

the Civil Engineering honor society known as Chi Epsilon. She participated in volunteering

events as well as in ASCE’s concrete canoe and steel bridge competitions.

She will continue working in the transportation industry and will continue to expand her

knowledge in the Civil Engineering areas.