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Airfield and Highway Pavements 2017
119
Effects of RAP Sources for Performance Testing of Asphalt Concrete
Hasan M. Faisal1; Umme A. Mannan2; A. S. M. Asifur Rahman3; Md. Mehedi Hasan4; and
Rafiqul A. Tarefder5
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1
Ph.D. Candidate, Dept. of Civil Engineering, Univ. of New Mexico, MSC01 1070, 1 University
of New Mexico, Albuquerque, NM 87131. E-mail: hfaisal@unm.edu
2
Ph.D. Candidate, Dept. of Civil Engineering, Univ. of New Mexico, MSC01 1070, 1 University
of New Mexico, Albuquerque, NM 87131. E-mail: arahman@unm.edu
3
Ph.D. Candidate, Dept. of Civil Engineering, Univ. of New Mexico, MSC01 1070, 1 University
of New Mexico, Albuquerque, NM 87131. E-mail: uam@unm.edu
4
Ph.D. Student, Dept. of Civil Engineering, Univ. of New Mexico, MSC01 1070, 1 University of
New Mexico, Albuquerque, NM 87131. E-mail: mehedihasan@unm.edu
5
Professor, Dept. of Civil Engineering, Univ. of New Mexico, MSC01 1070, 1 University of
New Mexico, Albuquerque, NM 87131. E-mail: tarefder@unm.edu
Abstract
The use of reclaimed asphalt pavement (RAP) has become relatively common practice in all over
the world because it is an environmentally and economically attractive proposition. The primary
reason for limited use is the uncertainty and variability of the RAP material performance.
Understanding the response of RAP source and its variability are important to the selection of
virgin and RAP material. Five different percentages (0%, 15%, 25%, 35% and 40%) of RAP
included asphalt concrete (AC) were designed to compare the effects of two RAP source on hot
mix asphalt (HMA). Gradation of all the HMA were remained fixed and checked for volumetric
requirements. To assess the effect of RAP source on AC, the samples were tested for dynamic
modulus characterization, rutting characterization and beam fatigue characterization. Results
show RAP in HMA material increases the complex modulus of all the samples irrespective of
RAP sources. In addition, rutting resistance of the material increases with increase in RAP
percentage in HMA. However, high RAP in HMA materials show lower fatigue life compared to
low percentage RAP in HMA.
INTRODUCTION
Reclaimed Asphalt Pavement (RAP) is defined as the old asphalt pavement materials that are
milled up or ripped off the roadway. RAP material can be reused in new asphalt mixtures
because it contains old asphalt binder and durable aggregate. Use of RAP in Hot Mix Asphalt
(HMA) mixture can reduce the amount of new material that has to be added, saving money and
natural resources.
When RAP is reused in a new mixture, it is necessary to properly account for the old
material in the mix design. The aggregate from the RAP has to blend with the new aggregate,
and the resulting blend of aggregate has to meet certain physical properties (preferably
Superpave (SP) aggregate criteria). The old binder usually reduces the need for new binder to be
added. The old binder from the RAP has to blend with the virgin binder and the resulting target
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Airfield and Highway Pavements 2017
120
binder has to meet SP criteria. During the construction and service life of the roadway, the RAP
asphalt binder becomes aged or hardened by reacting with oxygen in the air. In addition, the
variability of aging and old pavement gradation makes use of RAP a challenging task. However,
different transportation agencies using RAP with taking account of source, variability and aging
of RAP material. Current study investigates the effects of RAP source on stiffness and
performance of HMA with laboratory testing.
In 2002, a regional study was conducted by the North Central Super Pave (SP) Center to
verify if the findings of NCHRP 9-12 were valid for Midwestern materials and to expand the
NCHRP findings to include higher RAP contents (McDaniel et al. 2002). Three sources of RAP
(Indiana, Michigan, and Missouri) with a percentage up to 50% were mixed with the same virgin
binder and virgin aggregate, and tested. Laboratory mixes were compared with the plant
produced mixes for RAP content 15-25%. Results showed that with up to 50% RAP, the mixture
can be designed according to SP design method. In some cases, to meet the SP volumetric and
compaction requirements, the RAP aggregates limited the amount of RAP. The aggregate was
the same for all mixtures and the optimum asphalt content of the mix was determined by SP mix
design. RAP mix showed higher variability than the virgin mixture.
Western Regional SP Center (WRSC) evaluated the performance of HMA containing 0,
15 and 30% RAP from three different source to measure the moisture damage using AASHTO
T283, rutting using asphalt pavement analyzer (APA), fatigue using flexural beam fatigue test
and thermal cracking using thermal stress restrained specimen test (TSRST) (Hajj et al. 2009).
Results from the moisture damage tests show that mixtures with 15 or 30% RAP had acceptable
resistance to the moisture damage regardless of the RAP source and had a reduction in
conditioned and unconditioned tensile strengths. A laboratory-based research was project
conducted evaluate the impact of RAP source and content on the mechanical properties of the
final mix (McDaniel et al. 2007). In this study, three sources of RAP, one source of virgin
aggregates, and one source of virgin asphalt binders were used to design HMA mixes with two
target asphalt binder grades. Three levels of RAP content (0, 15, and 30%) were used to estimate
the moisture sensitivity, resistance to rutting, resistance to fatigue cracking, and resistance to
thermal cracking. RAP mixtures with unmodified virgin binder show a better or worse fatigue
resistance depending on the RAP source. However, for the modified virgin binder, the addition
of RAP decreases the fatigue resistance. University of Minnesota conducted a study to
investigate the effect of RAP in the asphalt mixture properties (Li et al. 2009). In this study, two
different RAP source, three RAP percentages (0, 20 and 40%) and two virgin asphalt binder (PG
58-28 and PG 58-34) were used. Dynamic modulus and SCB fracture test were performed to
evaluate the properties. The dynamic modulus test results indicate that with the addition of RAP
the dynamic modulus value increases. Data shows that RAP source does not affect the dynamic
modulus value at low temperature, however, it affects the significantly at high temperature.
Therefore, current study has investigated the effects of RAP source on high temperature, rutting
as well as fatigue life of HMA samples.
OBJECTIVE
The current study determines the effects of for RAP sources for five different levels of RAP
percentages in HMA. To evaluate the effects of RAP sources virgin aggregate source, design
gradation and design traffic level were remained same.
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121
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TEST MATRIX
The study is subdivided into two major tasks. First one covers mix design of HMA mixes with
five different percentages of RAP content, i.e. 0%, 15%, 25%, 35% and 40% for same gradation
from same virgin aggregate and two different RAP sources, same target binder PG grade.
Secondly, performance testing of RAP blender HMA samples, dynamic modulus testing,
Hamburg Wheel Tracker testing (HWTT) and beam fatigue test. However, this study did not
investigate low temperature cracking performance of the HMA samples due to extend of test
matrix.
MATERIAL SELECTION & SAMPLE PREPARATION
Sample Preparation for different percentage of RAP material in HMA with same aggregate and
RAP source and binder grade was done by implementing following steps:
Selection of Aggregate:
Mix design of asphalt concrete (AC) is greatly influenced by the quality and variability of virgin
and RAP aggregates. This part of the study shows the evaluation of virgin aggregate gradation
and physical properties. It can be noted that the five different virgin aggregates fractions are
collected from I-40 instrumented construction site at New Mexico. The aggregate fractions are
7/8 inch, 5/8 inch, 3/8 inch, crushed fines and sand.
Selection of RAP Material:
The RAP samples were collected from West Central and Budaghar area pavements of
Albuquerque, New Mexico. However, the age information of the collected RAP samples were
not available for proper documentation, as proper documentation of pavements were introduce
after 2011 in New Mexico Department of Transportation (NMDOT). Afterwards, the RAP
binders of two sources were extracted from collected RAP sources using ASTM D2172 (2013)
(Standard Test Methods for Quantitative Extraction of Bitumen from Bituminous Paving
Mixtures) and recovered using ASTM D5404 (2013) (Standard Practice for Recovery of Asphalt
from Solution Using the Rotary Evaporator). DSR and BBR were used to determine the
rheological properties, shown in Table 1. Results from DSR and BBR are used to get the PG
grade and blending chart of the RAP binders. According to SP criteria the performance grades of
the RAP source 1 binder is PG 82-16 and RAP source 2 binder is PG 82-22.
© ASCE
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122
TABLE 1 Rheological properties of RAP asphalt binder.
RAP Source 1
Properties
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Temperature ( °C)
G*/sinδ (kPa)
G*sinδ (kPa)
Stiffness, S (MPa)
m-value
G*/sinδ (kPa)
G*sinδ (kPa)
Stiffness, S (MPa)
m-value
Values
82
25
-6
-6
2.42
4590
68.4691
0.32552
RAP Source 2
Temperature ( °C)
Values
82
2.22
22
3662.33
-12
134.331
-12
0.33305
Grade
PG 82-16
Grade
PG 82-22
Selection of Binder:
Performance grade (PG) 76-22 was selected as the target binder. As, selected RAP binders PG
grades are much higher than the target binder grade, two blending charts have been created to
select the virgin binder grade. Blending chart calculations show virgin PG 70-22 binders fulfil all
the Super Pave criteria requirements.
Selection of Gradation:
To compare the structural properties of the material, the asphalt binder and gradation of the
materials were remained same. In the asphalt mixes the gradation were remained same by taking
required amount of material needed retained in specific standard sieves. Figure 1 shows the
gradation that has examined for the current study. The mixtures were designed for nominal
maximum aggregate size of 19 mm SP gradation- III (SP-III). In figure 1 red squares indicates
the control points for SP-III gradation. It can be noted that the green gradation curve followed all
the control point requirements. The straight line indicates the maximum density line, with
theoretical zero air void. Non Linear Least Square technique was used to produce trial blends
with same gradation and mix design volumetric were matched with NMDOT specifications
(NMDOT 2015).
© ASCE
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Airfield and Highway Pavements 2017
123
100
90
Percent Passing (%)
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80
70
60
50
40
Maximum Density Line
Gradation
Upper Limits
Lower Limits
30
20
10
0
0.075 0.3 0.6 1.18 2.36
4.75
9.5 12.5
Sieve Opening (mm)
19
25
FIGURE 1 Combined aggregate gradation
Mix Design of the RAP Mixed HMA Samples
Design of RAP incorporated (0%, 15%, 25%, 35% and 40%) HMA mixes stated with design of
virgin asphalt binder from blending chart, as the target binder grade as well as the percentage of
RAP in HMA is known. Followed by determination of bulk specific gravity of RAP. The
optimum asphalt content in each percentage of RAP in HMA was determined from four trial
percentages of asphalt content. Table 2 shows the volumetric properties determined from loose
HMA sample for the determination of maximum specific gravity (Gmm) and from compacted
cylindrical sample for the determination of bulk specific gravity (Gmb) of the samples. The
volumetric properties were compared with NMDOT Specification (2015), Table 423.2.8:1.
TABLE 2 Optimum Asphalt Content and Volumetric Properties.
RAP source 1
RAP
(%)
0
15
25
35
40
RAP
(%)
15
Virgin
PG
Binder
Used
70-22
70-22
70-22
70-22
70-22
Virgin
PG
Binder
Used
70-22
Binder
Replacement
Ratio (%)
0
14.5
23.9
34.1
38.9
Binder
Replacement
Ratio (%)
18.3
AC
(%)
4.7
4.7
4.6
4.4
4.5
Gmm
Gmb
Air
Voids
(%)
VMA
(%)
VFA
(%)
Dust to
binder
Ratio
4.0
4.1
4.2
3.8
3.6
14.5
14.4
13.8
13.2
13.8
73.1
72.1
73.5
72.8
75.5
1.02
1.04
1.06
1.25
1.29
VFA
(%)
Dust to
binder
Ratio
73.2
1.08
2.560 2.438
2.559 2.453
2.579 2.471
2.553 2.486
2.510 2.424
RAP source 2
AC
(%)
Gmm
Gmb
4.6
2.570
2.468
Air
VMA
Voids
(%)
(%)
© ASCE
Airfield and Highway Pavements 2017
4.0
14.39
Airfield and Highway Pavements 2017
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25
35
40
70-22
70-22
70-22
31.7
42.7
51.8
124
4.7
4.6
4.6
2.576
2.553
2.522
2.470
2.455
2.418
4.1
3.9
4.1
14.45
14.20
14.15
72.1
71.6
71.5
1.02
1.12
1.11
Complex Modulus Testing
The |E*| with phase angles (φ) testing was conducted on cylindrical AC specimens according to
the AASHTO T 342 test standard. In short, each of the test samples was tested for |E*| and φ at
five different test temperatures, 14, 40, 70, 100, and 130 °F and six different frequencies, 25, 10,
5, 1, 0.5, and 0.1 Hz. Finally, time-temperature superposition principle (TTSP) was applied to
develop average |E*| and φ mastercurves for each AC sample at 21.1 °C reference temperature.
Following equation (1) has been introduced to fit the mastercurves at 21.1 °C reference
temperature.
log |
∗|
=
+
(1)
Here, | ∗ | is dynamic modulus; is reduced frequency;
of modulus values; , are shape parameters.
is minimum modulus value;
is span
Hamburg Wheel Tracker Test
The HWTT test is conducted on a pair of samples simultaneously. The air voids of the samples
ranges 5.0% to 6.0%. A total of four samples were tested. The test was at 50 ˚C. Wheels of 158
lbs. weight rolled over the sample for 20000 cycles. The resulting deflections were recorded at
equidistance 10 intervals of loading, which mean the instrument records the deflection data at 11
equidistance points. The testing of one set of samples (2 pairs) is shown in figure 2. It shows the
rutting after the test is completed.
150 mm
a) Wheel tracking test (before)
FIGURE 2 Hamburg Wheel Tracking Tests
b) Wheel tracking test (after)
Fatigue Characterization
Fatigue damage occurs in asphalt pavement due to repeated tensile strain at the bottom of AC
under traffic loading. In the current study, the beam fatigue tests were done only at 600 µε and
0%, 25% and 40% RAP in HMA samples. In the study, fatigue failure calculated after a sample
© ASCE
Airfield and Highway Pavements 2017
Airfield and Highway Pavements 2017
125
RESULTS AND DISCUSSIONS
Dynamic Modulus
Figure 3 represents the dynamic modulus master curve comparison for five different percentages
of RAP in HMA and two different RAP sources. The master curves comparison have been
shown in log-log scale. Figure 3(a) and 3(b) show irrespective of aging levels E* of the material
increases with increase in RAP percentages. Each curve in the figure represents average of three
replicated samples. However, the variation of complex modulus showed cluttered modulus for
low frequency region of RAP source 1. The variation between different percentages of RAP
mixes HMA samples dynamic modulus are further investigated with statistical analysis. Analysis
of variance on RAP source 1 and 2 dynamic modulus show p-value of 0.0013 and 0.0000069 for
an α-value of 0.005. Therefore variability of dynamic modulus is higher in RAP source 2
samples. However, RAP source 2 samples master curves comparison shows increasing stiffness
pattern with increase RAP in HMA. To understand the performance response the rutting
performance and fatigue performance were investigated in the following sections.
100000
10000
10000
No RAP
15% RAP
25% RAP
35% RAP
40% RAP
1000
100
0.000001 0.001
1
1000 1000000
Frequency (Hz)
E* (MPa)
100000
E* (MPa)
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achieved 50% reduction in stiffness. Beam samples are prepared in the laboratory using HMA
mixture collected from the field. HMA mixtures are heated to 162°C for no more than one hour
(to avoid aging) and are then compacted using a GCTS kneading beam compactor. The
compactor is capable of fabricating two test specimens (18″ x 6″ x 3″) in less than five minutes.
1000
100
0.00001
No RAP
15% RAP
25% RAP
35% RAP
40% RAP
0.01
10
10000 10000000
Frequency (Hz)
(a) RAP Source 1 Samples
(b) RAP Source 2 Samples
FIGURE 3 Dynamic Modulus Master Curve Comparison as a Function of RAP
Percentages in HMA Samples
Rutting
Figure 4 presents comparison of HWTT data. It’s a common practice to use smooth HWTT data
as a Weibull distribution. The Weibull distribution is widely used in reliability engineering and
elsewhere due to its versatility and relative simplicity. Weibull function is given by Eq. (2):
β N −γ 
F (r ) N = 
η  η 
β −1
(2)
where
Fr(N) = deformation rate at different cycles
β = shape parameter
© ASCE
Airfield and Highway Pavements 2017
126
η = scale parameter
γ = location parameter
Shape Parameter (β) shows the effect of how deformation rate increases or decreases in the
function. Weibull function with β < 1 has a deformation rate that decreases with time, also
known as early-life failures. Weibull function with β close to or equal to 1 has a constant
deformation rate. After post-compaction phase, rutting have a tendency to creep with a constant
deformation rate until stripping phase is reached. For this study, it was found that shape
parameters are close to 1. Otherwise, Weibul function with β > 1 has a deformation rate that
increases with time. In the past years, the application of Weibull distribution to predict pavement
performance was studied. Coleri et al. (2008) demonstrated the application of the integrated
Weibull approach to observe in-situ rutting performance of AC. Results showed that integrated
Weibull approach was successful and it is a reliability method to predict in-situ rutting. Peng et
al. (2013) showed the application of Weibull distribution in pavement performance. First, the
application of the distribution was performed to simulate the pavement performance. Secondly, a
prediction model was constructed to observe pavement performance. Results showed a good
performance of the distribution model. Yin et al. (2014) used a Novel method for rutting
evaluation using HWTD. Three new parameters to evaluate rutting were proposed and good
correlation was found when rutting was the only distress in the test.
Nonlinear least square function has been used to fit the HWTT test data. Figure 4 shows
comparison of five different percentages of RAP material and two different sources. Though all
the mixes are designed for same target binder grade all the RAP mixed HMA samples showed
higher resistance to rutting compared to zero RAP HMA samples irrespective of RAP source.
However, for RAP source 1, 15% and 25% RAP in HMA samples showed discrepancy
compared to RAP source 2 samples. RAP source 2 samples shows lower deformation or increase
in rutting resistance with increase in RAP in HMA.
8
8
0% RAP
15% RAP
25% RAP
35% RAP
40% RAP
6
5
0% RAP
15% RAP
25% RAP
35% RAP
40% RAP
7
Deformation (mm)
7
Deformation (mm)
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Airfield and Highway Pavements 2017
4
3
2
1
6
5
4
3
2
1
0
0
5000
10000
No of Passes
15000
20000
0
0
5000
10000
15000
No. of Passes
20000
(a) RAP Source 1 Samples
(b) RAP Source 2 Samples
FIGURE 4 HWTT result Comparison as a Function of RAP Percentages in HMA Samples
Fatigue
Figure 5(a) reports all the initial modulus as well as the fatigue life for each percentage of RAP
mixed HMA beam sample for RAP source 1. The figure shows as the incorporation of RAP
increases the initial stiffness of the materials, the fatigue life decreases as well. However,
inclusion of 25% RAP decreases fatigue life of HMA only 15% in compare to the control mix of
zero percent, however, fatigue life decreased by 62.5 percent compare to that of zero percent, as
© ASCE
Airfield and Highway Pavements 2017
Airfield and Highway Pavements 2017
127
6000
Initial Modulus, MPa
Initial Modulus, MPa
6000
5000
4000
3000
2000
1000
5000
4000
3000
2000
1000
0
0%
25%
40%
Percentage of RAP in HMA
0
0%
25%
40%
Percentage of RAP in HMA
(a) Initial Modulus vs. RAP percentage in
HMA for RAP source 1
50000
(b) (a) Initial Modulus vs. RAP Percentage in
HMA for RAP Source 2
No of Cycles to Failure
35000
30000
40000
Nf at 600 µε
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shown in figure 5(b) Therefore, for RAP source 1, it can be seen higher incorporation of RAP
decreases higher fatigue life compared to 25% RAP in HMA. Figure 5(c) reports all the initial
modulus as well as the fatigue life for each percentage of RAP mixed HMA beam sample for
RAP source 2. Similar trend was found for RAP source 2 as well. Increase in RAP in HMA
increases the initial stiffness. However, the fatigue life decrease shows 76 percent decrease for
40% RAP inclusion, where as it is only 15% for 25% RAP in HMA, shown in figure 5(d).
25000
30000
20000
20000
15000
10000
10000
0
0%
25%
40%
Percentage of RAP in HMA
5000
0
0%
25%
40%
Percentage of RAP in HMA
(b) No of Cycles to Failure vs. RAP
(a) No of Cycles to Failure vs. RAP
Percentage in HMA for RAP Source 1 Percentage in HMA for RAP Source 2
FIGURE 5 Beam Fatigue Characterization for increasing number of RAP percentages in
HMA for two RAP Sources
CONCLUSION
Current study investigated the effects of RAP sources on RAP mixed HMA samples. Five
different percentages of RAP material and two different sources of RAP material were
investigated to find the effect of RAP sources. The following conclusions can be made from the
current study:
© ASCE
Airfield and Highway Pavements 2017
Airfield and Highway Pavements 2017
•
•
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•
128
The stiffness of the RAP blended HMA mix increases with an increase in the percentage
of the RAP binder in HMA.
Irrespective RAP sources rutting resistance of RAP blended mixes with RAP increases
with the increase in RAP percentages.
Fatigue testing on the HMA mix shows that the higher the RAP content, the lower the
fatigue life. For the higher RAP percent (40%) the decrease in fatigue life of mix is more
than that lower RAP in HMA.
ACKNOWLEDGEMENTS
The authors would like to express their sincere gratitude and appreciation to the New Mexico
Department of Transportation for funding this project.
REFERENCES
ASTM Standard D2172, (2013). "Standard Test Methods for Quantitative Extraction of Bitumen
from Bituminous Paving Mixtures." ASTM.
ASTM Standard D5404, (2013). "Standard Practice for Recovery of Asphalt from Solution
Using the Rotary Evaporator." ASTM.
Hajj, E. Y., P. E. Sebaaly, and Raghubar Shrestha. "Laboratory evaluation of mixes containing
recycled asphalt pavement (RAP)." Road Materials and Pavement Design 10, no. 3
(2009): 495-517.
Li, J., L. M. Pierce, and J. Uhlmeyer. “Calibration of the Flexible Pavement Portion of the
Mechanistic-Empirical Pavement Design Guide for the Washington State Department of
Transportation” TRB 2009 Annual Meeting CD-ROM." Transportation Research Board,
Washington DC, 2009.
McDaniel, R. S., H. Soleymani, and A. Slah. "Use of reclaimed asphalt (RAP) under Superpave
specifications." Final Report, a Regional Pooled Fund Project (2002).
McDaniel, R. S., A. Shah, G. Huber, and V. Gallivan. "Investigation of properties of plantproduced RAP mixtures." Transportation Research Record: Journal of the
Transportation Research Board 1998 (2007): 103-111.
NMDOT Bridge and Pavement Design Specification, 2015.
Coleri, E., Tsai, B., and Monismith, C. (2008). “Pavement Rutting Performance Prediction by
Integrated Weibull Approach.” In Transportation Research Record: Journal of the
Transportation Research Board, No. 2087, Transportation Research Board of the
National Academies, Washington, D.C., 2008, pp. 120–130.
Peng, T., Wang, X., and Chen, S. Pavement Performance Prediction Model Based on Weibull
Distribution. In Applied Mechanics and Materials, 378, (2013). pp. 61-64.
Yin, F., Arambula, E., Lytton, R., Martin, A., and Garcia, L. (2014). “Novel Method for
Moisture Susceptibility and Rutting Evaluation Using Hamburg Wheel Tracking Test.”
2446, Transportation Research Board of the National Academies, Washington, D.C.,
2014, pp. 1–7.
© ASCE
Airfield and Highway Pavements 2017
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