University of Texas at El PasoDigitalCommons@UTEP
Open Access Theses & Dissertations
2018-01-01
Utilization Of Digital Image Correlation TechniqueIn Asphalt TestingAlejandra EscajedaUniversity of Texas at El Paso, [email protected]
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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
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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
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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.