CHARACTERIZATION OF LOUISIANA ASPHALT MIXTURES USING SIMPLE
PERFORMANCE TESTS
Louay N. Mohammad 1 , Ph.D., Corresponding Author
Shadi Saadeh 2 , Ph.D.
Sandeep Obulareddy3
Sam Cooper4 , P.E.
Submitted to:
86th Transportation Research Board Annual Meeting
January 21-25, 2007
Washington, D.C.
Submission Date: July 31, 2006
Word Count
Abstract
Text
183
5022
FIGURES (7 x 250)
TABLES (2 x 250)
Total
1750
500
7498
1
Professor, Department of Civil and Environmental Engineering and Louisiana Transportation
Research Center, Louisiana State University, 4101 Gourrier Ave, Baton Rouge, LA 70808,
Email” [email protected], Tel: 225-767-9105, Fax: 225-767-9018
2
Materials Research Associate, Louisiana Transportation Research Center, 4101 Gourrier Ave,
Baton Rouge, LA 70808.
3
Graduate Research Assistant, Louisiana Transportation Research Center, 4101 Gourrier Ave,
Baton Rouge, LA 70808.
4
Senior Asphalt Research Engineer, Louisiana Transportation Research Center, 4101 Gourrier
Ave, Baton Rouge, LA 70808.
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Mohammad, et. al.
2
ABSTRACT
The main objective of this study was to characterize the performance of HMA mixes based on
four laboratory tests, including three simple performance tests (SPTs) dynamic modulus |E*|,
flow time (Ft ), flow number (FN ), and a loaded wheel tracking test (LWT). In addition, two
dynamic modulus prediction models, namely Witczak and Hirsch, were evaluated. Thirteen
plant-produced HMA mixtures were selected in this study. Laboratory characterization tests
included the dynamic modulus |E*|, flow number (FN ), and Hamburg -type loaded wheel tracking
tests (LWT).
Test results indicated that the |E*| test was sensitive to the nominal maximum aggregate size
(NMAS) in HMA mixture. Larger aggregates combined with recycled asphalt (RAP) tended to
have high |E*| values at high temperatures. Both the Witczak and Hirsch models could predict
the dynamic modulus |E*| values with a reasonable reliability. However the Witczak model
reliability increases for higher NMAS. On the other hand the Hirsch model reliability increases
for lower NMAS. The general ranking of the SPTs and LWT test was similar. In addition, this
ranking was consistent with the field use of those mixtures in terms of their design traffic
volume.
KEYWORDS: Hot mix asphalt, Permanent deformation, Dynamic modulus, Flow number,
loaded wheel tracking, Mechanistic-Empirical pavement design
TRB 2007 Annual Meeting CD-ROM
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Mohammad, et. al.
3
CHARACTERIZATION OF LOUISIANA ASPHALT MIXTURES USING SIMPLE
PERFORMANCE TESTS
INTRODUCTION
Permanent deformation or rutting is a common problem in asphalt pavements, particularly in hot
regions such as Louisiana [1]. Rutting is the result of a complex combination of densification and
shear flow. The primary mechanism of rutting is shear deformation (flow), which is caused by
large stresses in upper portions of asphalt concrete. Shear deformation is affected primarily by
temperature. Studies have shown that rutting in asphalt pavement is proportional to the number
of load cycles and the permanent deformation is limited to the upper 100 mm (4 in.) of the
asphalt concrete layer [2]. While significant rutting may be interpreted as a major structural
failure, it is also a serious safety issue for road users because there is a potential for hydroplaning
when water accumulates in the ruts.
The SHRP program concluded with the introduction of the Superpave (Superior
Performing Asphalt Pavements) mix design and analysis system. As part of Superpave, a series
of mechanical testing procedures using the Superpave Shear Tester (SST) were developed for
advanced mixture performance analysis [3]. Those mechanical testing procedures were adopted
by the American Association of State Highway and Transportation Officials (AASHTO) as
provisional standards AASHTO Designation TP7-94 [4]. However, since the original Superpave
Performance Models were determined to contain critical errors [3, 5], AASHTO TP-7 was not
widely used in the Superpave analysis system. On the other hand, the mechanical property tests
and associated analyses are still being used by at least 10 research and state agencies in the
United States [3]. In the past few years, major research was conducted under the National
Cooperative Highway Research Program (NCHRP) Project 9-19 “Superpave Support and
Performance Models Management” [6], which aimed to recommend a “Simple Performance Test
(SPT)” to complement the Superpave volumetric mixture design method. The results from
NCHRP Project 9-19 recommended three candidate SPTs: flow time (F T), flow number (FN ),
and dynamic modulus |E*| tests. In addition, the dynamic modulus test was selected for the HMA
materials characterization input utilized in the Mechanistic and Empirical (M-E) Guide for
Design of New and Rehabilitated Pavement Structures , developed under NCHRP Project 1-37A.
Recently, both NCHRP Projects 9-19 [6] and 9-29 [7] have reported the use of SPTs to
complement the Superpave mix design method. However, it is anticipated that more efforts need
to be made when implementing those SPT tests at a state level. This paper presents the findings
of a study conducted at the Louisiana Transportation Research Center (LTRC) to characterize
commonly used HMA mixtures for their permanent deformation as measured by dynamic
modulus |E*|, flow time (Ft ), flow number (FN ), and Hamburg-type loaded wheel tracking test
(LWT).
OBJECTIVE AND SCOPE
The main objective of this study was to evaluate the performance of HMA mixes based on four
laboratory tests, including three simple performance tests (SPTs) dynamic modulus |E*|, flow
time (Ft ), flow number (FN ), and a loaded wheel tracking rut test (LWT). In addition, two
dynamic modulus prediction models, namely Witczak and Hirsch, were evaluated. Thirteen
plant-produced HMA mixtures were selected in this study. Laboratory characterization tests
included the dynamic modulus |E*|, flow number (FN ), and Hamburg -type loaded wheel tracking
tests (LWT).
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Original paper submittal - not revised by author.
Mohammad, et. al.
4
PROJECTS OVERVIEW
Thirteen asphalt concrete mixtures were included in this study. The selection of those projects
was coordinated with the Louisiana Department of Transportation and Development (LADOTD)
construction and research personnel. Figure 1 show the locations of the projects selected. Table
1 (a) presents project and mixture designations as well as general information about each
mixture.
Asphalt Binder
Three types of asphalt binders meeting LADOTD specification, PG 76-22M, PG 70-22M and PG
64-22, were used in this study, Table 1(b). It is noted that PG 76-22M and PG 70-22M were
SBS elastomeric polymer-modified binders.
Mixture Design
The design of mixtures used in this study was performed by contractors of the selected pavement
rehabilitation projects. Table 1(c) presents the job mix formula for the selected asphalt mixtures.
Mixtures 1-3, 4-8, 9 and 13, were Superpave mixtures designed for low, medium, and high
volume roads, respectively as per the LADOTD specifications for Roads and Bridges [8].
Mixture 10 was a typical high-volume Stone Matrix Asphalt (SMA) mixture used in Louisiana
whereas, both Mixtures 11 and 12 were conventional Marshall mixtures designed for high traffic
volume [8]. Various types of aggregates and aggregate structures were part of the mixture
design, Table 1a and 1C, respectively . It is further noted that various percentages of reclaimed
asphalt pavement (RAP) were used in some of the mix designs, Table 1(c).
Sample Preparation
Two sizes of specimens were fabricated for the laboratory tests considered. These include 150
mm (5.91 inch) diameter by 170 mm (6.69 inch) high cylindrical specimens and 80 x 260 x 320
mm (3.2” x 10.2” x 12.6”) beam specimens. The cylindrical specimens were prepared for
dynamic modulus, flow time, and flow number tests, whereas the beam samples were prepared
for the loaded wheel tracking test. The cylindrical specimens were compacted with the
Superpave Gyratory Compactor (SGC), while the beam samples were compacted using a
kneading compactor. A 100mm (3.94 inch) diameter specimen was cored from the 150 mm (6
in.) in diameter by 170 mm (6.8 in.) in height sample. The height was further trimmed to 150
mm (5.91 inch) to comply with the dynamic modulus, flow time, and flow number test specimen
requirements (AASHHO TP 62) [9]. The target air void for all specimens characterized in this
study was 7.0 ± 0.5%.
PREDICTION EQUATIONS OF THE DYNAMIC MODULUS |E*|
Several regression models for predicting asphalt concrete modulus have been developed over a
number of years. Among them, the model developed by Witczak and his collaborators [10] has
been reported to be reasonably accurate [11]. This model, though empirical, is based on a large
set of data - more than 2,800 points on 200 asphalt mixtures [10]. Witczak’s model used a
symmetrical sigmoidal function, which is expressed as follows:
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Original paper submittal - not revised by author.
Mohammad, et. al.
5
LogE = - 1.249937 + 0.029232. p 200 - 0.001767.( p 200 ) 2 - 0.002841. p 4 - 0.058097. Va
- 0.8022.
Vbeff
(Vbeff + Va)
+
3.87197 - 0.0021. p 4 + 0.003958. p 38 - 0.000017.( p 38 ) 2 + 0.00547. p 34
1 + e (-0.603313- 0.31335.log ( f ) - 0.393532.log(η ))
(2)
Where:
E
= asphalt mix dynamic modulus, in 105 psi
η
= binder viscosity in 106 poise
F
= load frequency in hz
Va
= % air voids in the mix, by volume
Vb eff = % effective binder content, by volume
P34
= % retained on the ¾ inch sieve, by total aggregate weight (cumulative)
P38
= % retained on the 3/8-inch sieve, by total aggregate weight (cumulative)
P4
= % retained on the no. 4 sieve, by total aggregate weight (cumulative)
p200 = % passing the No. 200 sieve, by total aggregate weight.
Recently, Christensen et al. [12] developed another dynamic modulus prediction model
for asphalt concrete modulus. Christensen’s model, which is called the Hirsch model, was based
on an existing version of the law of mixtures that combines series and parallel elements of
phases. More details of this model can be found elsewhere. The current version of the Hirsch
model for pred icting the dynamic modulus of asphalt concrete mixtures is presented by the
following expressions:
1 −VMA/ 100

VMA
 VFA×VMA
VMA 
*
*

E = Pc 4,200,000(1 −
) + 3G

 + (1 − Pc ) 
+
*
binder
100
 4,200,000 3VFAG

 10,000 


binder
−1
0 .58
*


 20 + VFA × 3 G binder 


VMA


Pc =
0 .58
*
 VFA × 3 G

binder 
650 + 


VMA


(3)
where:
|E* |
|G* |binder
Pc
VMA
VFA
= Dynamic Modulus for the asphalt mixture, in psi
= Complex Shear Modulus for the binder, in psi
= Contact Factor
= Void in the mineral aggregate, percent
= Void filled with asphalt, percent.
LABORATORY TEST METHODS
Four laboratory tests were conducted including, Dynamic Modulus |E*|, Flow Time (F T), Flow
Number (FN ), and Hamburg-Type Loaded Wheel Tracking test (LWT). The procedures for
conducting these tests are explained briefly in the following subsections. Triplicate specimens
were used for each test, except for the LWT test where two specimens were tested.
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Mohammad, et. al.
6
Dynamic Modulus Test
This test consists of applying a uniaxial sinusoidal (i.e., haversine) compressive stress to an
unconfined or confined HMA cylindrical test specimen. The stress-to-strain relationship under a
continuous sinusoidal loading for linear viscoelastic materials is defined by a complex number
called the “complex modulus” (E*). The absolute value of the complex modulus, |E*|, is defined
as the dynamic modulus. The dynamic modulus is mathematically defined as the maximum (i.e.,
peak) dynamic stress (s 0 ) divided by the peak recoverable axial strain (e0 ):
σ
| E * |= 0
(4)
ε0
The dynamic modulus test consists of testing samples at –10, 4.4, 20, 37.8, and 54.4o C
(14, 40, 70, 100 and 130o F) at loading frequencies of 0.1, 0.5, 1.0, 5, 10, and 25 Hz at each
temperature for the development of master curves for use in pavement response and performance
analysis. The haversine compressive stress was applied on each SPT sample to achieve a target
vertical strain level of 100 microns in an unconfined test mode.
Flow Time/Static Creep Test
This test was conducted in accordance with the test method of the NCHRP Report 513 [14]. A
cylindrical sample is subjected to a rapid static axial load. The load is held on the specimen for
10,000 seconds or until tertiary flow occurs, which ever comes first. The test is conducted at an
effective temperature and stress level of 54.4o C (130°F) and 207 kPa (30 psi), respectively. The
“Flow Time” is defined as the time when shear deformation, under constant volume, starts.
Figure 3a presents a typical response curve from this test. Flow time, slope, and intercept are
presented in the analysis.
Flow Number/ Repeated Loading Test
The flow number test uses a loading cycle of 1.0 second in duration, and applies a 0.1 second
haversine load followed by 0.9 second rest period [7]. The specimen is tested for 10,000 cycles
or until tertiary flow, whichever occurs first. Permanent axial strains are recorded throughout the
test. The test is conducted at an effective temperature and stress level of 54.4o C (130°F) and 207
kPa (30 psi), respectively. The “Flow Number” is defined as the starting point, or cycle number,
at which tertiary flow occurs on a cumulative permanent strain curve obtained during the test.
Figure 3b presents a typical response curve from this test.
Hamburg-Type Loaded Wheel Tracking Device Test
A Hamburg type of Loaded Wheel Tracking (LWT) tester manufactured by PMW, Inc. of
Salina, Kansas was used in this study. This test is considered a torture test that produces damage
by rolling a 703N (158 lb) steel wheel across the surface of a slab that is submerged in 50° C
(122° F) water for 20,000 passes at 56 passes a minute. A maximum allowable rut depth of 6 mm
at 20,000 passes is used in LADOTD Specifications [8].
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Mohammad, et. al.
7
DISCUSSION OF TEST RESULTS
Dynamic Modulus Test Results
Figure 3 presents the average dynamic modulus test results at five different temperatures and six
frequencies. It is noted that the coefficients of variation of the |E*| values are generally less than
20 percent for the three test samples of each mixture. The dynamic modulus value decreases,
with an increase in temperature and decrease in the loading frequency for each mixture
considered. Figure 3(b) shows the |E*| master curve for each mixture. The complex modulus
master curve possessed a general “S” shape. It can be observed that all master curves clusters to
each other at the two ends, except for Mix 1, at low and high frequencies with the largest
separation existing in the middle portion between each mixture. Figure 3(a) shows typical
isotherms of the dynamic modulus test for medium traffic volume mixtures.
Figure 3(c) presents a summary of the dynamic modulus |E*| parameters, namely,
dynamic modulus at 54.4o C and rut factor for permanent deformation analysis, |E*|/sind|0.5hz &
54.4C. Two clustering of those parameters were observed, one for low volume traffic mixtures
and another for medium and high traffic volume mixes. The low volume mixtures possessed
lower values of dynamic modulus than the other mixtures. Furthermore, among the low volume
mixes, Mix 2 showed the highest |E*|, whereas Mix 1 exhibited the lowest |E*|. It is noted that
Mix 2 had larger aggregate size (NMAS=25mm) than Mix 1 (NMAS=12.5mm). Large
aggregates could form a stronger stone-to-stone contact in |E*| test and result in high stiffness. In
addition, apart from Mix 5 (NMAS= 25mm) and Mix 9 (NMAS=12.5) medium-traffic designed
mixes showed lower parameter than high-traffic designed mixes. It is observed that Mix 5 had a
higher NMAS and contained RAP than Mix 9 that did not contain RAP.
Mix 4 and 7 presented lower values of dynamic modulus than the other medium traffic
volume mixtures (Mix 5, Mix 6, Mix 8). It is noted that Mix 4 and Mix 7 did not include RAP
and Mix 4 had smaller aggregate size than the other mixtures. The higher |E*| at high
temperatures may be attributed to the larger aggregate size (NMAS =25 mm) and possibly the
RAP contents. RAP materials are known to contain aged binders. The aged binder with high
stiffness could also contribute to a high |E*| value for a mixture at high temperatures. Similar
observations were noted for high volume mixtures (Mix 9 – Mix 13).
The variation of the phase angles with the dynamic modulus is shown in Figure 3(d) for
the six frequencies and five temperatures for each mixture tested in this study. This figure can
also be used to illustrate the phase angle response to frequency. The phase angle increased with
increasing frequency; reached a peak, and then decreased. This response is different from the
asphalt binder in that the phase angle for an asphalt binder generally decreases with increasing
frequency. The reason for this is that, at high frequency (low temperature), the asphalt binder
primarily affects the phase angle of asphalt mixtures, i.e., binder viscoelastic behavior is
dominant. Hence, the phase angle of the asphalt binder and asphalt mixture follows similar
trend. However, at low frequency (high temperature), it is predominantly affected by the
aggregate, and therefore, the phase angle for asphalt mixtures decreases with decreasing
frequency or increasing temperature because of the aggregate influence. It was also found that
the sensitivity of phase angle to frequency is dependent upon the mixture type. Low volume
mixtures tended to separate themselves from the other mixtures in the low frequency region.
Similar observations were reported by other researchers (15, 16).
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8
In summary, the two parameters, namely, |E*|, and |E*|/sind5hz & 25°C were observed to be
sensitive to the aggregate nominal maximum size in a mixture. Larger aggregates combined with
RAP materials could result in high |E*| values at high temperatures.
Prediction of the Dynamic Modulus
Witczak’s Prediction Model Figure 4(a) presents a comparison of the measured and the
predicted dynamic modulus values using Witczak’s model for dynamic modulus prediction. In
general, a good agreement was observed between the measured and predicted modulus values
with an R-square greater that 0.90. Overall, the predicted modulus value was equal to 0.75, 0.93,
and 1.01 of the measured values for the 12.5 mm, 19.0 mm, and 25.0 mm NMAS mixtures,
respectively. It is noted that at high temperature and low frequency, the predicted modulus
values were higher than the measured ones. The reverse was true at intermediate temperature and
high frequency, Figure 4(a).
Hirsch Prediction Model Figure 4(b) presents a comparison of the measured and predicted
dynamic modulus values using the Hirsch dynamic modulus model. In general, a good
agreement was also observed between the predicted and measured modulus values with an Rsquare of greater than 0.87. Overall, the predicted modulus value was equal to 0.93, 0.93, and
0.89 of the measured values for the 12.5 mm, 19.0 mm, and 25.0 mm NMAS mixtures,
respectively. It is noted that the predicted dynamic modulus values were generally under
predicted at all tested temperatures with some exceptions at an intermediate temperature. The
overall prediction using the Hirsch model appears fairly consistent with most of data points
equally distributed along the predicted lines, Figure 4(b).
The results presented above are considered promising in terms of being able to, within a
reasonable reliability, predict the dynamic modulus values from mixtures properties, using either
the Witczak’s or Hirsch models. In particular, these models are valuable for agencies that are
evaluating the Mechanistic-Empirical design guide. Recognizing that the dynamic modulus test
is laborious, time consuming, expensive, and requires skilled personnel, the use of these
prediction models can be a valuable alternative tool for estimating the dynamic modulus value of
asphalt mixtures.
Flow Time Test Results (Ft)
Figure 2(a) shows a typical result of the flow time test. It is noted that the primary region
of the creep response curve, figure 2(a), is associated with a densification type of permanent
deformation. This behavior continues until the mixture reaches an optimum density level that is
followed by the secondary region of the curve. The slope of this region is the one that relates to
the mixture’s resistant to the applied load. As loading continues within the secondary region,
densification will continue until a point is reached where the mixture becomes unstable and
significant deformation occurs reaching the tertiary region of the creep response curve, Figure
2(a). The a-value (intercept) and b -value (slope) were obtained between 1,000 and 3,000
repetitions of the permanent strain – time of loading curve, Figure 2(a), using classical power
mode – ep = a (time)b . This loading period was considered because it provides a constant
platform for comparison of different mixtures, where the cumulative permanent curve is
generally in its second zone (after the primary, rapidly increasing zone and before the tertiary
flow zone). The b -value, or the slope of the curve, represents the rate of change in permanent
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Mohammad, et. al.
9
deformation as a function of the change in loading time. High flow times and low slopes are
desired properties for run resistant mixtures.
Figure 5(a) presents the mean flow time. The coefficients of variation of the Ft values
are generally less than 22 percent for the three test samples of each mixture. Among low traffic
volume mixtures, Mix 1 showed the lowest Ft value and Mix 3 presented highest one.
Furthermore, among medium traffic mixtures, Mix 7 had the lowest and Mix 6 obtained the
highest flow time value. In addition, comparing high volume mixture, both the Mix 9 and Mix 10
possessed the best Ft value while Mix 12 had the lowest one. Pooling all the mixtures together,
Mix 9 and Mix 10 were the least performer, wh ereas Mix 1 and Mix 7 showed the least resistant
to rutting.. Interestingly the Ft values are generally associated fairly well with both a-values and
b-values. For example, a pair of high a-value and low b-value results in a high Ft value, and vice
versa is shown in Figure 5(b). This observation is considered useful because it complements the
analysis of a flow time test, especially when the tertiary flow zone is not reached. In addition,
these parameters have potential to be used in rutting prediction models in pavement performance
analysis.
In summary, rutting resistance of mixtures measured from this test was not sensitive to
the NMAS or RAP content for the mixtures evaluated. Both mixtures (Mix 9, Mix 10) that
performed well had 12.5 NMAS, no RAP content. However, these mixtures were both coarse
graded, Figure 5(a).
Flow Number (FN ) Test Results
Figure 6(a) presents the mean flow number. The coefficients of variation of the Fn values was
higher that the Ft and are generally less than 35 percent for the three test samples of each
mixture. The response curve for this test was similar to the flow time test, except it was
generated from dynamic type of loading, Figure 2(b). In general the ranking of flow number and
slopes of mixtures amongst each traffic level was similar to the flow time test. Furthermore, the
flow number was able to rank the high volume mixtures amongst the top performer of all mixes,
except for Mix 11 and Mix 6. In Summary, the ranking of this test generally followed the
ranking of the flow time test.
Hamburg-Type Loaded Wheel Tracking (LWT) Test (Results
Figure 7 presents the rut depth measured at 20,000 passes for the mixtures considered. It is
noted that low volume mixtures were not available to include in the analysis. All the mixtures
evaluated performed well with a rut depth of less than 6.0 mm except for Mix 5 and Mix 8. No
explanations can be offered on why these two mixtures responded as such to this test. It is noted
that those two mixtures are within the medium volume mixtures. The high volume mixtures
performed very well with a maximum rut depth of 5.0 mm for Mix 12. It was observed that Mix
10 (SMA) received the smallest average rut depth of all the mixtures.
PERMANENT DEFORMATION ANALYSIS
Statistical analyses of the test results were carried out using the Statistical Analysis System
(SAS) software. A multiple comparison procedure, Tukey’s, was carried out with a 95 percent
confidence interval. The multiple comparison procedure ranked the mean test results and placed
them in groups designated by “A”, “B”, “C”, “A/B,” etc. The letter “A” is used to rank the group
with the most desired values, e.g. high |E*| values or low Hamburg rut depths, followed by the
other letter grades in the appropriate order. A multiple letter designation, such as “A/B,”
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Mohammad, et. al.
10
indicates that the mean permanent deformation factor of that group is not significantly different
from either of the groups “A” or “B.”
A rut factor defined as |E*|/sind|0.5hz & 54.4C was computed and used in statistical analysis
as the permanent deformation factor for an asphalt mixture. Table 2 presents the statistical
grouping for |E*|/sind |0.5hz & 54.4C, flow time, flow number and LWT rut depth. Table 2 also
shows the statistical ranking of mixtures based on the average test values of each parameter
analyzed.
Test results of |E*|/sind|0.5Hz & 54.4C were clustered in seven statistic groups: “A”, “A/B”,
“A/B/C”, “B/C”, “B/C/D”, “C/D”, and “D.” The “A” group included only the Mix 13 mixture;
the “A/B” group contained two mixtures, namely Mix 10 and Mix 5; the “A/B/C” group
consisted of Mix 6, Mix 8, Mix 11, Mix 12; the B/C group included Mix 4 and Mix 7; the group
B/C/D contained Mix 2 and Mix 9; the C/D group consisted of Mix 3; and group D included Mix
1, Table 2. The “A” group mixture had statistically higher |E*|/sind|5Hz & 54.4C values than the “D”
group mixture, whereas the values for the “A/B” group mixtures were not significantly different
from either of the groups “A” or “B.” Since the high rut factor was considered as the desired
value for a rut-resistant mixture, the |E*| test results implied the “A” group mixture had better
rut-resistance than the “D” group mixture. The low volume mixtures were ranked in the lower
tier of groupings: “B/C/D”, “C/D”, and “D,” whereas the medium traffic volume mixture had
ranking of “A/B/C” and “B/C” except for Mix 5 where it had a ranking of “A/B.” This is
consistent with observation reported earlier where larger NMAS combined with RAP materials
could result in high rut factor of Mix 5. High volume mixtures had the highest ranking of “A”,
“A/B”, and “A/B/C,” except for Mix 9, where it had a ranking of “B/C/D.”
Statistical analyses on flow time test values resulted in four groups: “A”, “B”, “B/C”, and
“C.” Mixtures in “A”, “B”, and “C” groups are statistically different from each other in terms of
flow time values with a statistical ranking order (from high to low) of Mix 9 and Mix 10; Mix 6;
and Mix 12, Mix 7, Mix 4, Mix 2, and Mix 1. Meanwhile, the flow time of Mix 13, Mix 11, Mix
8, Mix 5, and Mix 3 are not statistically different from either mixtures in group “B” and “C”
mixtures. In general, the grouping for most of the mixtures followed the traffic volumes ranking
from high, medium, to low.
The statistical analyses on the flow number tests result ed in nine groups, Table 2.
Mixtures in “A” and “f” groups are statistically different from each other in terms of flow
number values with a statistical ranking order (from high to low) of Mix 9 and Mix 10; and Mix
7 and Mix1. It is noted that the ranking for Mix 9, Mix 10, and Mix 1 was similar to that of the
flow time test.
Statistical analyses on of LWT test resulted in two groups: “A”, and “B.” Mixtures in
“A” and “B” groups are statistically different from each other in terms of rut depth at 20,000
passes. It is noted that the high traffic volumes mixtures were in group “A,” where as the
medium traffic volume mixture were within groups “A” and “B.”
In summary, the general ranking of the SPTs and LWT test was similar. In addition, this
ranking was consistent with the field use of those mixtures in terms of their design traffic
volume.
SUMMARY AND CONCLUSIONS
The performance characteristics of thirteen plant-produced HMA mi xtures were evaluated
through four laboratory tests: three SPTs that included dynamic modulus |E*|, flow number (FN ),
flow time (F T), and Hamburg-Type LWT test. In addition, two dynamic modulus prediction
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Mohammad, et. al.
11
models, Witczak’s and Hirsch, were evaluated. The general ranking of the SPTs and LWT test
was similar. In addition, this ranking was consistent with the field use of those mixtures in terms
of their design traffic volume. The following observations were made from this study:
• The dynamic modulus test |E*| was sensitive to nominal maximum aggregate size
(NMAS) of a mixture. Larger aggregate size in combination with recycled asphalt (RAP)
tended to have high |E*| values at high temperatures.
• The Witczak and the Hirsch model were able to predict the dynamic modulus for
Louisiana mixes used in this study with a reasonable reliability. However, the reliability
increases for the Witczak model as NMAS increases. On the other hand the reliability of
the Hirsch model increases as the NMAS decreases. The use of these prediction models
can be a valuable alternative tool in approximately estimating the dynamic modulus |E*|
value of asphalt mixtures.
• The rut factor |E*|/Sind |54.4°C & 0.5Hz was able to cluster the low traffic mixtures from the
medium and high traffic mixtures.
• The average ranking of the rut resistance parameters from the dynamic modulus test, flow
time, and flow number were able to distinguish between mixes based on their design
traffic. In addition, all the parameters had a comparable ranking for the mixes.
• The average ranking of Hamburg wheel tracking test was able to distinguish between
medium and high traffic mixes. However, the ranking of the mi xes from this test were
slightly different from the others.
ACKNOWLEDGEMENT
This study was supported by the Louisiana Transportation Research Center (LTRC) and the
Louisiana Department of Transportation and Development (LADOTD). The authors would like
to express thanks to all those who provided valuable help in this study.
REFERENCES
[1]
SHRP. Permanent Deformation Response of Asphalt Aggregate Mixes (SHRPA-415). Final Report. Strategic Highway Research Program, National
Research Council, 1994.
[2]
OECD. Heavy trucks, climate and pavement damage, prepared by an OECD
scientific experts group. Organization for Economic Co -operation and
Development, Paris, France; OECD Publications and Information Center
[distributor], Washington, D.C., 1998.
[3]
Andeson, R. M. and McGennis, R. “Ruggedness Evaluation of the Shear
Frequency Sweep Test for Determining the Shear Modulus of Asphalt
Mixtures,” Journal of the Association of Asphalt Paving Technologists,
Volume 72, 2003.
[4]
“Standard Test Method for Determining the Permanent Deformation and
Fatigue Cracking Characteristics of Hot Mix Asphalt (HMA) Using the
Simple Shear Test (SST) Device”, American Association of State Highway
and Transportation Officials, AASHTO Designation TP7, Gaithersburg, MD,
1994.
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
[5]
[6]
[7]
[8]
12
Witczak M.W., Von Quintus, H.L. and McCuen, R. “Calibration and
Validation Plan for the Superpave Models,” Report prepared for the Federal
Highway Administration, FHWA Contract DTFH-61-94-R-00045, May 1998.
Witczak, M.W., K. Kaloush, T. Pellinen, and M. El-Basyouny. Simple
Performance Test for Superpave Mix Design. National Cooperative Highway
Research Program (NCHRP) Report 465, Transportation Research Board,
National Research Council, Washington, D.C., 2002.
Bonaquist, R.F., D.W. Christensen and W. Stump, III. Simple Performance
Tester for Superpave Mix Design: First-Article Development and Evaluation.
National Cooperative Highway Research Program (NCHRP) Report 513,
Transportation Research Board, National Research Council, Washington,
D.C., 2003
Louisiana Standard Specifications for Roads and Bridges,” State of Louisiana,
Department of Transportation and Development, Baton Rouge, 2000 Edition.
[9]
AASHTO, “Standard Method of Test for Determining Dynamic Modulus of
Hot-Mix Asphalt Mixtures,” AASHTO Designation: TP 62-03. Washington,
D.C., 2004.
[10]
Witczak M.W., Von Quintus, H.L. and McCuen, R. “Calibration and
Validation Plan for the Superpave Models,” Report prepared for the Federal
Highway Administration, FHWA Contract DTFH-61-94-R-00045, May 1998.
Andrei, D., M.W. Witczak, and M.W. Mirza, “Development of a Revised
Predictive Model for the Dynamic (Complex) Modulus of Asphalt Mixtures,”
National Cooperative Highway Research Program (NCHRP) 1-37A InterReport, University of Maryland, March (1999).
[11]
[12]
Christensen, D.W., T. Pellinen and R.F.Bonaquist, “Hirsch Model for
Estimating the Modulus of Asphalt Concrete,” Journal of the Association of
Asphalt Paving Technologists, Vol.72, 2003, pp.121-151.
[13]
Witczak, M.W., Kaloush, K.E. and Von Quintus, H. “Pursuit of the Simple
Performance Test for Asphalt Mixture Rutting.” Journal of the Association of
Asphalt Paving Technologists, Volume 71, 2002.
Bonaquist, R.F., D.W. Christensen and W. Stump, III, “Simple Performance
Tester for Superpave Mix Design: First-Article Development and Evaluation,”
National Cooperative Highway Research Program (NCHRP) Report 513,
Transportation Research Board, National Research Council, Washington,
D.C., 2003.
Mohammad, L.N., Huang, B., and Zhang, X., “Laboratory Performance
Evaluation of SMA, CMHB, and Dense Graded Asphalt Mixtures.” Journal
of the Association of Asphalt Paving Technologist, Volume 68, 1999, pp.
252-283
[14]
[15]
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
[16]
13
Pellinen, T.K., M.W. Witczak, “Stress Dependant Master Cu rve Construction
for Dynamic (Complex) Modulus,” Journal of the Association of Asphalt
Paving Technologists, Volume 71, 2002.
List of Tables
TABLE 1 (a) Project and Mixtures Designations (b) LADOTD Performance Graded Asphalt
Cement Specification (c) Job mix formula for the selected asphalt mixtures
TABLE 2 Statistical Ranking of Test Results
List of Figures
FIGURE 1 Locations of the projects selected in this study
FIGURE 2(a) Typical flow time test results
FIGURE 2(b) Typical flow number test results
FIGURE 3(a) Dynamic modulus- Typical test results
FIGURE 3(b) Dynamic modulus- Master curves for all mixtures
FIGURE 3(c) Dynamic modulus- |E*| and |E*|/Sind test results
FIGURE 3(d) Dynamic modulus- Variation of Phase Angle with Dynamic Modulus
FIGURE 4(a) Measured and predicted dynamic modulus values – Witczak model
FIGURE 4(b) Measured and predicted dynamic modulus values – Hirsch model
FIGURE 5(a) Flow time test results — Flow Time
FIGURE 5(b) Flow time test results
FIGURE 6 (a) Flow number test results — Flow Number
FIGURE 6 (b) Flow number test results
FIGURE 7 -Type Loaded Wheel Tracking Test Results -- Rut Depth at 20,000 passes
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
14
TABLE 1 (a) Project and Mixtures Designations
Mix
Name
Field Project Name
Mix Course
NMAS
(mm)
Design
Aggregate
Structure
Traffic
Level
Mix Type
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Mix 10
Mix 11
Mix 12
Mix 13
LA9
Lapalco
US90
ALF
US190
US190
US190SL
US190
I-10 Egan
I-10 Vinton
LA964
LA964
I-10 Egan
Wearing
Binder
Binder
Wearing
Binder
Binder
Binder
Base
Wearing
Wearing
Wearing
Binder
Binder
12.5
25
25
19
25
25
25
25
12.5
12.5
19
25
25
Fine (F)
Interm. (I)
Fine (F)
Interm. (I)
Coarse (C)
Interm. (I)
Fine (F)
Interm. (I)
Coarse (C)
Coarse (C)
Interm. (I)
Fine (F)
Coarse (C)
Low
Low
Low
Medium
Medium
Medium
Medium
Medium
High
High
High
High
High
Superpave
Superpave
Superpave
Superpave
Superpave
Superpave
Superpave
Superpave
Superpave
SMA
Marshall
Marshall
Superpave
TABLE 1 (b) LADOTD Performance Graded Asphalt Cement Specification
PG 76-22M
Test Property
Spec
Original Binder
Rotational Viscosity @135ºC Pa-s
3.0-
PG 64-22
Spec
PG 70-22M
Spec
3.01.30+
@64ºC
232
99.0+
3.0-
Dynamic Shear, 10rad/sec G*/ Sin d, Kpa 1.00+ @76ºC
Flash Point ºC
232 +
Solubility %
99.0+
Force Ductility Ratio (F2/ F1, 4ºC,
.30+
5cm/min, F2 @30cm Elongation
Tests on Rolling Thin Film oven (RTFO) Residue
Mass Loss %
1.001.00Dynamic Shear, 10 rad/sec G*/Sin d, Kpa
2.2+ @76ºC 2.2+ @64ºC
Elastic Recovery, 25ºC, 10 cm Elongation
%
60+
Tests on Pressure Aging Vessel (PAV) Residue
Dynamic Shear, 10 rad/sec, G* Sin d, KPa,
5000400025ºC
Bending Beam Creep Stiffness, Smax,
Mpa, Tested at –12ºC
300300Bending Beam Creep Slope m Value, Min
Tested at -12ºC
TRB 2007 Annual Meeting CD-ROM
0.300+
0.300+
1.00+@76ºC
232+
99.0+
0.30+
1.002.2+@76ºC
40+
50003000.300+
Original paper submittal - not revised by author.
Mohammad, et. al.
15
TABLE 1 (c) Job mix formula for the selected asphalt mixtures
Mixture name
Mix type
Aggregate Type
(in the blend)
Binder type
% Gm m at NI
% Gm m at ND
% Gm m at NM
Design binder content, %
Design air void, %
VMA, %
VFA, %
Metric (U.S.)Sieve
37.5 mm (1½ in)
25 mm (1 in)
19 mm (¾ in)
12.5 mm (½ in)
9.5 mm (? in)
4.75 mm (No.4)
2.36 mm (No.8)
1.18 mm (No.16)
0.6 mm (No.30)
0.3 mm (No.50)
0.15 mm (No.100)
0.075 mm (No.200)
TRB 2007 Annual Meeting CD-ROM
Mix 1
12.5 mm
Superpave
Mix 2
25 mm
Superpave
Mix 3
25 mm
Superpave
18% Rhyolite
37% Gravel
15% L.S.
15% Sand
15% RAP
73.5% L.S.
7.3% .Sand
19% RAP
73.5 % L.S.
7.3% Sand
19.3% RAP
Mix 4
19mm Superpave
45.4%Granite
10.3% Sand
17.1% L.S.
12.9% Gravel
14.3% RAP
PG 70-22M
PG 70-22M
PG 70-22M
PG 76-22M
Design AC content, volumetric properties, and densification
89.5
87.3
86.2
88.4
96.5
96.4
95.7
96.1
97.3
95.2
-96.8
4.9
4.2
4
4.4
3.5
3.6
4.3
3.9
13.2
13
13.1
13.8
73.5
72
67.4
71
Gradation, (% passing)
100
100
100
100
100
94
95.3
100
100
87
89.8
97
92
75
80.6
83
82
67
69.1
73
53
44
46.9
49
37
26
30
33
27
19
21.7
24
24
15
16.8
18
17
10
10.9
10
9
7
7.5
5.7
5.2
5.5
5.6
4.6
Mix 5
25 mm
Superpave
Mix 6
25 mm
Superpave
64.8% L.S.
8% Sand
8.1% Gravel
19.1% RAP
64.8% L.S.
8.1% Sand
8. 1% Gravel
19% RAP
PG 76-22M
PG 76-22M
87.9
96
97.1
3.6
4
11.8
67
88.2
96.4
97.1
3.8
3.6
11.5
69
100
97
84
65
52
32
24
20
15
8
4.9
3.6
100
95
86
67
53
35
27
21
16
9
6
4.5
Original paper submittal - not revised by author.
Mohammad, et. al.
16
TABLE 1 (c) Job mix formula for the selected asphalt mixtures (Continued)
Mixture name
Mix 7
25 mm
Superpave
Mix 8
25 mm
Superpave
Aggregate blend
85% L.S.
15% Sand
60.4% L.S.
1% Sand
9.7% Gravel
19.4% RAP
Binder type
PG 76-22M
Mix type
% Gm m at NI
% Gm m at ND
% Gm m at NM
Design binder
content, %
Design air void, %
VMA, %
VFA, %
Metric (U.S.)Sieve
37.5 mm (1½ in)
25 mm (1 in)
19 mm (¾ in)
12.5 mm (½ in)
9.5 mm (? in)
4.75 mm (No.4)
2.36 mm (No.8)
1.18 mm (No.16)
0.6 mm (No.30)
0.3 mm (No.50)
0.15 mm (No.100)
0.075 mm (No.200)
Mix 9
12.5 mm
Superpave
45% S.S.
55% L.S.
Mix 10
Mix 11
Mix 12
12.5 mm SMA
19mm Superpave
25mm Marshall 8
50% SS
50% L.S.
44.2% Granite
24.7% L.S.
10.1% Sand
6% Gravel
15% RAP
54.3% L.S.
12.1% Sand
14.6% Gravel
19% RAP
89.4
96.5
97
PG 64-22
PG 76-22M
PG 76-22M
PG 76-22M
Design AC content, volumetric properties, and densification
89
84.1
N/A
N/A
96.4
95.9
N/A
N/A
97
97
N/A
N/A
3.8
3.5
11.8
70
3.3
3.6
11.1
67
5
4
14.5
72
100
98
87
72
62
49
42
28
22
13
5
4
100
98
88
65
53
37
27
22
17
9
5
4.2
100
100
100
98
89
50
29
19
13
10
6.5
TRB 2007 Annual Meeting CD-ROM
6
4.4
4
4
16.6
13.8
76
71
Gradation, (% passing)
100
100
100
100
100
98
93
83
71
73
30
50
20
35
25
15
18
12
12
6
8
4.5
Mix 13
25 mm
Superpave
92% L.S.
8% Sand
PG 76-22M
PG 76-22M
N/A
N/A
N/A
85.4
96.1
97.1
4
4
12.7
69
4
4
12.8
69.5
100
96
83
65
59
47
35
26
20
11
6
4.1
100
96
87
68
59
35
23
17
13
7
4
3.6
Original paper submittal - not revised by author.
Mohammad, et. al.
17
TABLE 2 Statistical Ranking of Test Results
|E*|/Sind
|E*|54.4°C,0.5hz
FT
FN
LWT
54.4°C,0.5hz
Mix
Mix
12
Mix
13
Mix
11
Mix
10
Mix
9
Mix
8
Mix
6
Mix
5
Mix
7
Mix
4
Mix
3
Mix
2
Mix
1
Traf.
Rank
High
A
High
A/B
High
A/B
High
A/B
High
A/B
Med
A/B
Med
A/B
Med
A/B
Med
A/B/C
Med
B/C
Low
B/C
Low
B/C
Low
C
Mix
Mix
13
Mix
10
Mix
5
Mix
12
Mix
11
Mix
8
Mix
6
Mix
7
Mix
4
Mix
9
Mix
2
Mix
3
Mix
1
Traf.
Rank
High
A
High
A/B
Med
A/B
High
A/B/C
High
A/B/C
Med
A/B/C
Med
A/B/C
Med
B/C
Med
B/C
High
B/C/D
Low
B/C/D
Low
C/D
Low
D
Mix
Mix
9
Mix
10
Mix
6
Mix
13
Mix
11
Mix
8
Mix
5
Mix
3
Mix
12
Mix
7
Mix
4
Mix
2
Mix
1
Traf.
Rank
High
A
High
A
Med
B
High
B/C
High
B/C
Med
B/C
Med
B/C
Low
B/C
High
C
Med
C
Med
C
Low
C
Low
C
Mix
Mix
9
Mix
10
Mix
6
Mix
12
Mix
11
Mix
13
Mix
8
Mix
5
Mix
2
Mix
3
Mix
4
Mix
7
Mix
1
Traf.
Rank
High
A
High
A
Med
A/B
High
A/B/C
High
B/C/D
High
B/C/D
Med
C/D/E
Med
C/D/E/F
Low
D/E/F
Low
D/E/F
Med
Med
Low
Mix
Mix
13
Mix
12
Mix
11
Mix
10
Mix
9
Mix
7
Mix
6
Mix
4
Mix
8
Mix
5
Traf.
High
High
High
High
Rank
A
A
A
A
High
A
Med
A
Med
A
Med
A
Med
B
Med
B
E/F
F
N/A
F
N/A: Not Available
FT: Flow Time
FN : Flow Number
LWT: Loaded Wheel Tester Rut Depth
Traf.: Traffic Volume Level
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
18
LA9
US190
Vinton
LA964
Egan
US190SL ALF
Lapalco
LA1
US90
Sasobit
FIGURE 1 Locations of the projects selected in this study
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
19
FIGURE 2(a) Typical flow time test results
FIGURE 2(b) Typical flow number test results
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
20
3500
4500
Dynamic Modulus (Ksi)
Dynamic Modulus (Ksi)
4000
3500
3000
2500
2000
1500
-10 °C
1000
500
0
3000
2500
2000
1500
4 °C
1000
500
0
0
5
10
15
20
25
30
0
5
10
1800
700
1600
600
1400
1200
1000
800
600
15
20
25
30
25
30
Frequency (Hz)
Dynamic Modulus (Ksi)
Dynamic Modulus (Ksi)
Frequency (Hz)
25 °C
400
200
0
500
400
300
38 °C
200
100
0
0
5
10
15
20
25
30
0
5
10
Frequency (Hz)
Mix 7
Mix 8
Dynamic Modulus (Ksi)
Mix 6
20
Frequency (Hz)
250
Mix 4
Mix 5
15
200
150
100
54 °C
50
0
0
5
10
15
20
25
30
Frequency (Hz)
FIGURE 3 (a) Dynamic modulus- Typical test results
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
Mix 1
Mix 11
21
Mix 2
Mix 12
Mix 3
Mix 13
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Mix 10
Log Dynamic Modulus (Ksi)
4
3.5
3
2.5
2
1.5
1
-6
-4
-2
0
2
Log Reduced Frequency (Hz)
4
6
8
FIGURE 3 (b) Dynamic modulus- Master curves for all mixtures
Dynamic Modulus, Parameter
(Ksi)
E*, 54.4C, 0.5hz
E*/Sind, 54.4C, 0.5hz
250
200
150
100
50
0
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Rap/ No RAP
RAP
RAP
RAP
RAP
RAP
RAP
No RAP
RAP
Traffic Volume
Low
Low
Low
Med
Med
Med
Med
Med
High
NMAS
Design Agg.
Structure
12.5
25
25
19
25
25
25
25
F
I
F
I
C
I
F
I
Mix 10 Mix 11 Mix 12 Mix 13
No RAP No RAP
RAP
RAP
No RAP
High
High
High
High
12.5
12.5
19
25
25
C
C
I
F
C
FIGURE 3 (c) Dynamic modulus- |E*| and |E*|/Sind test results
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
22
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 9
Mix 10
Mix 11
Mix 12
Mix 13
Mix 6
Mix 7
Mix 8
40.0
35.0
Phase Angle (Deg.)
30.0
25.0
20.0
15.0
10.0
5.0
Low Frequency
High Temperature
0.0
1
High Frequency
Low Temperature
10
100
1000
10000
Log E* (Ksi)
FIGURE 3 (d) Dynamic modulus- Variation of Phase Angle with Dynamic Modulus
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
23
(c) 12.5mm
y = 1.0054x
1000
R = 0.9247
Log Predicted E* (Ksi)
Log Predicted E* (Ksi)
(a) 25 mm
10000
2
100
10
10
100
1000
Log Measured E* (Ksi)
10000
1000
y = 0.7498x
2
R = 0.9294
100
10
10000
10
100
1000
Log Measured E* (Ksi)
(d) All
Log Predicted E*
(Ksi)
Log Predicted E*
(Ksi)
(b) 19mm
10000
y = 0.9249x
2
1000
R = 0.9867
100
10
10
10000
100
1000
Log Measured E* (Ksi)
10000
y = 0.9335x
1000
R2 = 0.9157
100
10
10000
10
100
1000
Log Measured E* (Ksi)
10000
FIGURE 4 (a) Measured and predicted dynamic modulus values – Witczak model
10000
y = 0.886x
2
R = 0.9285
(a) 25mm
1000
Log Predicted E* (ksi)
Log Predicted E* (ksi)
10000
100
10
1
y = 0.9264x
2
R = 0.8654
(c) 12.5mm
1000
100
10
1
1
10
100
1000
10000
1
10
Log Measured E* (Ksi)
1000
10000
1000
10000
10000
10000
y = 0.932x
2
R = 0.9866
(b) 19mm
1000
Log Predicted E* (ksi)
Log Predicted E* (ksi)
100
Log Measured E* (Ksi)
100
10
1
y = 0.9241x
2
R = 0.9251
(d) All
1000
100
10
1
1
10
100
Log Measured E* (Ksi)
1000
10000
1
10
100
Log Measured E* (Ksi)
FIGURE 4 (b) Measured and predicted dynamic modulus values – Hirsh model
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
24
Flow Time (seconds)
Ft
12000
10000
8000
6000
4000
2000
0
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
RAP/No RAP
RAP
RAP
RAP
RAP
RAP
RAP
No RAP
RAP
Traffic Level
Low
Low
Low
Med
Med
Med
Med
Med
High
12.5
25
25
19
25
25
25
25
F
I
F
I
C
I
F
I
NMAS
Agg. Structure
Mix 9
Mix 10
Mix 11
Mix 12
Mix 13
RAP
RAP
No RAP
High
High
High
High
12.5
12.5
19
25
25
C
C
I
F
C
Mix 10
Mix 11
Mix 12
Mix 13
RAP
RAP
No RAP
No RAP No RAP
FIGURE 5 (a) Flow time test results — Flow Time
Normalized Ft
Normalized Ft Intercept
Normalized Ft Slope
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Rap/ No RAP
RAP
RAP
RAP
RAP
RAP
RAP
No RAP
RAP
Traffic Volume
Low
Low
Low
Med
Med
Med
Med
Med
High
High
High
High
High
NMAS
12.5
25
25
19
25
25
25
25
12.5
12.5
19
25
25
Agg. Structure
F
I
F
I
C
I
F
I
C
C
I
F
C
No RAP No RAP
FIGURE 5 (b) Flow time test results
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Flow Number (cycles)
Mohammad, et. al.
25
FN
12000
10000
8000
6000
4000
2000
0
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
RAP
RAP
RAP
RAP
RAP
RAP
No
RAP
No
No
RAP
RAP
No
Traffic Level
Low
Low
Low
Med
Med
Med
Med
Med
High
High
High
High
High
NMAS
12.5
25
25
19
25
25
25
25
12.5
12.5
19
25
25
F
I
F
I
C
I
F
I
C
C
I
F
C
RAP/No RAP
Agg. Structure
Mix 9 Mix 10 Mix 11 Mix 12 Mix 13
FIGURE 6 (a) Flow number test results — Flow Number
Normalized FN
Normalized FN Intercept
Normalized FN Slope
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Mix 1
Mix 2
Mix 3
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Mix 10
Mix 11
Mix 12
Mix 13
RAP
RAP
No RAP
Rap/ No RAP
RAP
RAP
RAP
RAP
RAP
RAP
No RAP
RAP
Traffic Volume
Low
Low
Low
Med
Med
Med
Med
Med
High
High
High
High
High
NMAS
12.5
25
25
19
25
25
25
25
12.5
12.5
19
25
25
Agg. Structure
F
I
F
I
C
I
F
I
C
C
I
F
C
No RAP No RAP
FIGURE 6 (b) Flow number test results
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.
Mohammad, et. al.
26
HWT
Rut Depth (mm)
25
20
15
10
5
0
Mix 4
Mix 5
Mix 6
Mix 7
Mix 8
Mix 9
Mix 10
Mix 11
Mix 12
Mix 13
Rap/ No RAP
RAP
RAP
RAP
No RAP
RAP
No RAP
No RAP
RAP
RAP
No RAP
Traffic Volume
Med
Med
Med
Med
Med
High
High
High
High
High
NMAS
19
25
25
25
25
12.5
12.5
19
25
25
Agg. Structure
I
C
I
F
I
C
C
I
F
C
FIGURE 7 Hamburg-Type Loaded Wheel Tracking Test Results -- Rut Depth at 20,000 passes
TRB 2007 Annual Meeting CD-ROM
Original paper submittal - not revised by author.