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Evaluation of Fine Graded Polymer Asphalt Mixture
Produced Using Foamed Warm Mix Asphalt Technology
Munir D. Nazzal, PhD., P.E. (Corresponding Author)
Assistant Professor,
Civil Engineering Department,
Ohio University,
Athens, OH 45701
Shad Sargand, Ph.D.
Russ Professor,
Civil Engineering Department,
Ohio University,
Athens, OH 45701
David Powers, P.E.
Asphalt Materials Engineer
Ohio Department of Transportation
Columbus, OH 43223
Edward P. Morrison
Quality Control Manager
Shelly & Sands, Inc. / Mar-Zane Materials Inc.
&
Abdalla Al-Rawashdeh
Graduate Research Assistant,
Civil Engineering Department,
Ohio University,
Athens, OH 45701
Submitted to:
2nd International Warm-Mix Conference
October 11-13, 2011
St. Louis, Missouri
No. of text words =3100
No. of Figures= 5
No. of Tables=2
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Evaluation of Fine Graded Polymer Asphalt Mixture
Produced Using Foamed Warm Mix Asphalt Technology
Abstract
Fine graded polymer asphalt mixture has been used in the past few years in the
construction of the thin overlays in Ohio. This mixture is produced at temperatures that are
higher than those typically used for other types of Hot Mix Asphalt (HMA). This paper presents
the results of a field demonstration project in Ohio in which a fine graded polymer asphalt
mixture was produced using foamed Warm Mix Asphalt (WMA) technology. Laboratory and
field testing programs were conducted to evaluate the produced mixture. The laboratory testing
program included performing modified Lottman, flow number, Asphalt Pavement Analyzer
(APA), and dynamic modulus tests on plant mixed laboratory compacted samples to evaluate the
performance properties of the produced WMA mixture. In addition, the field testing program
included measuring the initial surface roughness as well as conducting Light Falling Weight
Deflectometer (LFWD) and Portable Seismic Pavement Analyzer (PSPA) tests to evaluate the
in-situ stiffness properties of the constructed mixtures. The results of this project showed that the
fine graded polymer asphalt mixture could be produced and compacted using the foamed WMA
technology at a lower temperature than that typically used for a similar HMA mix. In addition,
the laboratory test results indicated that the considered WMA mixture had acceptable resistance
to moisture induced damage but did not have a good rutting performance. Finally, the field test
results showed that the considered WMA mixture had good initial field performance.
Keywords: Thin Overlay, Foamed WMA, Field Trials, PSPA
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Introduction
Thin overlays with thickness of 1½ inch or less are gaining considerable attention as one of the
most effective preventative maintenance techniques performed to extend the service life of the
existing pavements. Those overlays have several benefits that include protecting the pavement
structure, reducing the rate of pavement deterioration, correcting surface deficiencies, reducing
permeability and improving the ride quality of the pavement, particularly when accompanied by
surface milling (1).
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In Ohio, fine graded polymer asphalt mixture has been used in the construction of the thin
overlays. This mixture consists of fine aggregates with a maximum nominal size of 9.5 mm and a
relatively high content of 76-22m polymer modified asphalt binder. It is produced at
temperatures that are relatively higher (350-370 °F) than those typically used for other types of
Hot Mix Asphalt (HMA).
Recently, the foaming WMA technologies produced via a foaming nozzle have been gaining
popularity among asphalt mix producers. The main advantage of those systems is that they allow
the production of WMA with a standard grade asphalt binder through a one-time mechanical
plant modification minimizing the impact of increased material costs identified with other WMA
technologies. The use of foamed WMA to produce fine graded polymer asphalt mixture can
result in several benefits by allowing the asphalt mixture to be produced and compacted at lower
temperatures. Utilizing Reclaimed Asphalt Pavement (RAP) in that mixture can add further
benefits by reducing their cost and enhancing their rut performance.
Despite the advantages of producing fine graded polymer asphalt mixture with foaming WMA
technology, there are some concerns regarding its performance and durability. This paper
presents the results of a field project in Ohio where a fine graded polymer asphalt mixture
containing RAP and produced with the foamed WMA technology was used in construction of a
thin overlay. Laboratory and field testing programs were conducted to evaluate the WMA
mixture. The field testing program included measuring the initial surface roughness as well as
conducting Light Falling Weight Deflectometer (LFWD) and Portable Seismic Pavement
Analyzer (PSPA) in-situ tests. In addition, modified Lottman, flow number, Asphalt Pavement
Analyzer (APA), and dynamic modulus tests were conducted on plant mixed laboratory
compacted samples to evaluate the performance properties of the considered WMA mixture.
TESTING PROGRAM
Description of Field Project and Evaluated Mixture
The field test section was part of a rehabilitation project on State Route 146 (SR 146) near
Zanesville and Chandlersville Counties. The rehabilitation project in this study consisted of the
placement of a thin overlay layer with thickness of 1 inch. The overlay placed on SR 146
consisted of a fine graded polymer asphalt mixture with a 3/8 inch nominal maximum aggregate
size (NMAS) designed to meet ODOT specification for Item 424B for medium traffic roads. The
mixture included 10 percent RAP. The optimum asphalt binder content for this mixture was 7.5
percent (6.9 percent virgin binder and 0.6 percent from the RAP). The asphalt binder used was
an SBS elastomeric polymer-modified PG 76-22M binder. This mixture was produced using the
foamed WMA technology. Table 1 presents the Job Mix Formula of the considered mixture.
The average mixing temperature that was recorded in the asphalt plant was also included in this
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table. It is worth noting that this temperature is about 30 °F less than the average temperature
typically used for this mixture when produced as a HMA.
TABLE 1 Job Mix Formula for Considered Mixtures
Mixture Designation
424B
11% No.8 Gravel, 18% No.9 Gravel,
Aggregate blend
20% Limestone ,40% Natural Sand,
1% Bag House Fines, 10% RAP
Binder type
PG76-22M
Binder content, %
7.5 (6.9 Virgin binder)
Mixing Temperature (°F)
325
Sieve Size
Gradation (% passing)
1/2"
100
3/8"
99
#4
83
#8
53
#16
39
#30
25
#50
10
#100
4
#200
3.2
Description of Laboratory Testing Program
Sufficient loose mixture was secured within the paver extensions and at the plant and sent to the
laboratory. The foamed WMA mixture samples were prepared in this study in accordance with
the AASHTO T 312-04 procedure. Samples were compacted using the Superpave Gyratory
Compactor (SGC) to an air void of 7%. Various laboratory tests were performed to examine the
mechanical properties of the mixture that was used in the construction of the field test section.
Triplicate samples were tested. Table 2 presents a list of the mixture performance tests that were
conducted in this study. Moisture susceptibility was evaluated using the modified Lottman test.
In addition, flow number and Asphalt Pavement Analyzer (APA) tests were used to assess high
temperature permanent deformation resistance. Finally, the dynamic modulus test was used to
characterize the visco-elastic behavior of the asphalt mixture at different temperatures and
loading frequencies.
TABLE 2 Asphalt Treated Mixture Performance Test Conditions
Laboratory Test
Performance Indication Test Temperature
Test Protocol
Modified Lottman moisture susceptibility
77 º F
AASHTO 283
Asphalt Pavement
Resistance to
130 º F
ODOT Specification (2)
Analyzer (APA)
permanent deformation
Resistance to
Flow Number
130 º F
NCHRP 513 (3)
permanent deformation
Dynamic Modulus Visco-elastic properties
Various
AASHTO TP 62-03 (4)
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Description of Field Testing Program
The field testing program in this study included taking roughness measurements of the test
section immediately after construction as well as conducting Light Falling Weight Deflectometer
(LFWD) and Portable Seismic Pavement Analyzer (PSPA) tests at the thirty points along the test
section to characterize the in-situ properties of fine mixtures. The LFWD is a portable device that
is designed for estimating the elastic modulus of pavement materials. The Prima 100 LFWD was
used in this study. This device consists of a 22 lbs drop weight that falls freely onto a loading
plate that has a 5.9 in diameter, producing a load pulse. During any test operation, the Prima 100
device measures both the applied force and center deflection, utilizing a velocity transducer. The
measured load and deflection are used to compute the LFWD elastic modulus.
The PSPA is a device designed to determine the average modulus of the top layer of pavements.
It consists of two receivers (accelerometers) and a source packaged into a hand-portable system,
which can perform high frequency seismic tests. The operating principle of the PSPA is based on
generating and detecting stress waves in a medium. The Ultrasonic Surface Wave (USW)
method, which is an offshoot of the Spectral Analysis of Surface Wave (SASW) method (5), is
used to determine the modulus of the material. It is noted that the loading frequency of this
device is approximately 49,500 Hz.
RESULTS AND ANALYSIS
Compaction and Field Density Results
The overlay layer in the test section was compacted using the same rolling pattern typically used
for HMA mixtures with similar gradation. In general, the selected pattern included first
performing four compaction passes using a vibratory breakdown roller; followed by four
compaction passes of an oscillatory finish roller. The average maximum compaction temperature
was 310 °F. In addition, the average relative density obtained for the cores obtained from the test
section was 95.6%. This indicates that although the WMA mixture was produced and compacted
at a temperature lower than that typically used for similar HMA mixtures, it achieved the density
that is required in the Ohio Department of Transportation (ODOT) specifications.
Results of Laboratory Tests
Modified Lottman Test Results
This test was used to quantify the asphalt treated mixtures’ sensitivity to moisture damage, which
is necessary to assure its durability. Moisture sensitivity is measured by the percentage of
retained tensile strength ratio (TSR) of the conditioned samples compared to the control samples.
The conditioned samples are samples that have been subjected to the required freeze/thaw cycle.
In this study, triplicate samples were tested for foamed WMA fine polymer asphalt mixture
produced during the six days of construction. Figure 1 presents the average TSR values for the
samples prepared in the second, third, and sixth day of construction. It is noted that the average
TSR values were greater than 0.7; thus the mixture met the minimum TSR requirement specified
by ODOT for medium traffic mixtures. Furthermore, the average TSR value of samples obtained
from the different days construction were similar. This indicates that there was no variation in
the produced WMA mixture.
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Asphalt Pavement Analyzer (APA)Test Results
This test was conducted according to the ODOT standard test procedure to determine the rutting
characteristics of the mixture. Superpave Gyratory compacted cylindrical samples 6 inch in
diameter were prepared at an air void content of 7% and used in the APA tests. As per ODOT
Supplement 1057, the APA samples were preheated to the test temperature of 130F for a
minimum of 12 hours prior to testing. Upon testing, the APA samples were subjected to repeated
wheel loading of 115 lbf using a hose pressure of 100 psi. Rut depth measurements were
recorded at 5, 500, 1000, and 8000 cycles. For each APA sample, a total of four rut depth
readings were used to calculate the average rut depth value within the specimen. The total rutting
within the sample was calculated as the difference between the rut depth readings at the 8000th
cycle and the 5th cycle. Based on the APA test results, the average total rut depth for the tested
samples was 0.35 in. This value is greater than the maximum acceptable rut depth of 0.2 in that
ODOT specifies for heavy traffic mixtures. The relatively lower rutting resistance is mainly
attributed to the substantial amount of natural sand in the mixture. The use of foamed WMA
technology could also be a contributing factor since it reduces binder aging during the mixing.
TSR
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
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Day-2
Day-3
Day-6
FIGURE 1 Modified Lottman test results
Flow Number Test Results
The flow number test is a laboratory approach to determine the permanent deformation
characteristic of paving materials by applying a repeated dynamic load for 10,000 repetitions on
a cylindrical asphalt sample. This test was conducted according to the Annex B of the NCHRP
Report 513. The average flow number value for the considered foamed WMA mixture used to
construct the field section was less than 200 cycles. This low flow number value is consistent
with APA test results, which suggests that the mixture does not have a high rutting resistance.
Dynamic Modulus (E*) Test Results
The E* test was used to characterizes the viscoelastic properties of the asphalt mixtures at
different loading times and temperatures. This test was conducted on unconfined cylindrical
samples in accordance with AASHTO Standard TP 62-03. Figures 2a-c show the dynamic
modulus isotherms for considered foamed WMA mixture at different temperatures and
frequencies. The dynamic modulus isotherms for Evotherm WMA and HMA mixtures used in an
overlay layer in another pavement section on State Route 541 (SR 541) near Guernsey and
Coshocton Counties were also presented for comparison. The E* values for all mixtures
increased with an increase in frequency and a decrease in temperature. At low temperatures
(40°F), the E* isotherms maintained the pattern of an inclined straight-line, which indicated that
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the mixture behavior was in the linear viscoelastic region at those temperatures. However, at
intermediate and high temperatures (70°F and 130°F), the E* isotherms gained a concave shape
(Figure 2b,c) which represents the non-linear behavior of the mixtures under compression. The
424B mixture consistently had the lowest E* values at the 40°F and 70°C temperatures.
However, it had similar E* values to the HMA control mix at the 130°F. This is also
demonstrated in Figure 3, which presents the master curve for each of the considered mixtures. It
is worth noting that the mixture in SR 541 had coarser aggregate gradation than that of the
mixture evaluated in the study, which might explain the differences obtained in the E* values.
1200
3000
E* (ksi)
a.
E* (ksi)
2000
1000
800
b.
400
HMA-SR541
Foamed WMA
Evotherm-SR 541
0
0
1
10
Frequency (Hz)
E* (ksi)
0.1
100
140 c. 120
100
80
60
40
20
0
0.1
1
10
Frequency (Hz)
100
Control HMA-SR541
Foamed WMA
0.1
9
10
Foamed WMA
HMA-SR541
Evotherm-SR 541
1
10
Frequency (Hz)
100
FIGURE 2 E* Test results: (a) E* isotherms at 40°F (b) E* isotherms at 70°F (c) E*
isotherms at 130°F.
7.0
6.5
Reference Temperature=77°F
log E (psi)
6.0
5.5
5.0
HMA (SR 541)
Foamed WMA
Evotherm WMA (SR 541)
4.5
4.0
3.5
3.0
-6
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-4
-2
0
2
log fr (1/sec)
FIGURE 3 Master curve
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Results of In-Situ Tests
The mechanistic properties from field tests included the LFWD and PSPA moduli. It is noted
that the field test results were corrected to 25 °C using the following equation (6):
E 25 
ET
1.35  0.014  T
(1)
where,
E25 : modulus at 25°C, ksi
ET : modulus at test temperature T, ksi
T : pavement mid depth temperature, °C
The pavement mid depth temperature was obtained using BELLS3 model (7) as shown in
the following equation:
T = 0.95 + 0.892 × IR + {log (d) – 1.25}{-0.448 × IR + 0.621 × (1-day)+ 1.83 × sin (hr18 –
15.5)} + 0.042 × IR×sin (hr18- 13.5)
(2)
where,
T : Pavement temperature at depth d, °C
IR : Infrared surface temperature, °C
Log : Base 10 logarithm
d
: Depth at which mat temperature is to be predicted, mm
1-day : Average air temperature the day before testing, °C
sin : Sine function on an 18-hr clock system, with 2π radians equal to one 18-hr cycle
hr18 : Time of day, in 24-hr clock system, but calculated using an 18-hr asphalt concrete
PSPA Test Results
Figure 4 presents the variation of the PSPA moduli along the test section. The moduli in this
figure were corrected to a temperature of 25°C using Equations 1 and 2. The PSPA modulus
varied between 1950 and 1228 ksi with a mean value of 1499 ksi and coefficient of variation of
13.5%. The mean PSPA modulus value is similar to those reported for a well a performing HMA
mixture ((8),(9)). Furthermore, the percent coefficient of variation of the PSPA modulus is lower
than those observed when testing HMA sections (9). It is worth noting that the PSPA modulus is
higher than that obtained in the laboratory or other in-situ tests as the test is conducted at a very
high frequency of 49,500 Hz.
LFWD Test Results
Figure 5 shows the variation of the corrected LFWD modulus along the test section. It is noted
that LFWD modulus values varied widely, as it may be affected by the underlying pavement
structure. The mean value of LFWD modulus was 108.2 ksi, which is similar to those of good
performing HMA mixtures that were reported in previous studies ((8),(9) ). The coefficient of
variation of the LFWD modulus was 21.2%, which is higher than that of PSPA. This indicates
the LFWD test had more variability than the PSPA test.
Results of Roughness Measurements
Roughness measurements of the SR 146 section were conducted after the placement of the
overlay. The results of the roughness measurement were expressed as International Roughness
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Index (IRI) for every 0.1 mile segment. IRI simulates a standard vehicle traveling down the
roadway and is equal to the total anticipated vertical movement of this vehicle accumulated over
the length of the section. The average initial IRI value was 59.2 in/mile with a coefficient of
variation of 20%. It is worth noting that according to FHWA standards, pavements with IRI less
than 60 in/mile are classified to have very good riding quality.
PSPA Modulus (ksi)
2500
2000
1500
1000
500
0
0
7
8
20
Test points
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ELFWD (ksi)
FIGURE 4 PSPA test results
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20
Test points
FIGURE 5 LFWD test results
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CONCLUSIONS:
This paper presented the results of a field and laboratory testing programs that were
conducted to evaluate a fine graded polymer asphalt mixture produced using foamed WMA
technology. Based on the results of this paper, the following conclusions can be drawn:

Although the WMA mixture was produced and compacted at lower temperature than that
typically used for similar HMA mixture, it achieved the required in-place density.
 The foamed WMA mixture showed acceptable resistance to moisture induced damage as
indicated by the modified Lotmman test.
 The evaluated mixture did not exhibit good rutting performance in the APA and flow
number tests.
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ACKNOWLEDGEMENT
The authors would like to express thanks to ODOT personnel that helped in this research study,
particularly Roger Green. We thank Dan Radanovish of ODOT for taking the IRI measurements.
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REFERENCES
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K.T. Hall, C.E. Correa, and A.L. Simpson, “Performance Of Flexible Pavement
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Ohio Department of Transportation, Construction And Material Specifications, Ohio
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R. Bonaquist, NCHRP Report 513: Simple Performance Tester for Superpave Mix
Design: First-Article Development and Evaluation, National Cooperative Highway
Research Program (NCHRP), 2003.
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AASHTO TP62-03, “Determining the Dynamic Modulus of Hot-Mix Asphalt Concrete
Mixtures,” 2006.
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S. Nazarian, D. Yuan, and V. Tandon, “Structural Field Testing of Flexible Pavement
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E. Lukanen and R. Stubstad, Temperature Predictions and Adjustment Factors for Asphalt
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L. Mohammad and S. Saadeh, “Comparative Study of the Mechanical Properties of HMA
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C. Zhang, “Comparative Study of the Physical and Mechanistic Properties of HMA
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University, 2005.


The foamed WMA mixture had similar LFWD and PSPA moduli as those of good
performing HMA mixtures.
The PSPA test exhibited better repeatability and lower variability compared to the LFWD
test.
The foamed WMA test section showed very good riding quality as indicated by the IRI
values that were obtained directly after the placement of thin overlay.
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