Fundamental Properties of Asphalts and Modified Asphalts, III

Fundamental Properties of Asphalts and
Modified Asphalts, III
Quarterly Technical Progress Report
April 1-June 30, 2008
June 2008
Prepared for
Federal Highway Administration
Contract No. DTFH61-07-D-00005
By
Western Research Institute
www.westernresearch.org

TABLE OF CONTENTS
TASK 1. COORDINATION ........................................................................................................1
TASK 2. CONTINUED RESEARCH.........................................................................................3
Subtask 2-1. Moisture Damage.................................................................................................3
Subtask 2-2. Aging....................................................................................................................7
Subtask 2-2.1. Impact of Water on Aging ..........................................................................7
Subtask 2-2.2. Support of the Mechanistic-Empirical Pavement Design Guide ..............11
Subtask 2-3. Nanotechnology: AFM Analysis of Asphalt Thin-Film Microstructure
Phenomenology..................................................................................................................45
Subtask 2-4. Low-Temperature Properties .............................................................................55
Subtask 2-5. Modified Asphalts..............................................................................................57
Subtask 2-6. Validation Site Monitoring ................................................................................71
TASK 3. OTHER RESEARCH ACTIVITIES (IDIQ)............................................................73
TASK 4. INFORMATION DEPLOYMENT ...........................................................................75
Subtask 4-1. Publications, Presentations, Newsletters, Flyers and Brochures .......................75
Subtask 4-2. Website Maintenance.........................................................................................77
Subtask 4-3. Research Database—Contractor Team Activities .............................................79
Subtask 4-4. Research in Progress Database ..........................................................................81
Subtask 4-5. Support of the Mechanistic-Empirical Pavement Design Guide .......................85
Subtask 4-6. Semi-Annual Meetings ......................................................................................87
i

TASK 1. COORDINATION
The goals of this task are to maintain contact with current State-of-the-Art and State-of-the-
Science in fundamental research on asphalts and modified asphalts, to keep abreast of current
and on-going science and technology in asphalt research, and to learn the needs of the asphalt
technical community.
During this quarter, WRI hosted a four-day RHEOBIT asphalt rheology course taught by Dr.
Geoffrey Rowe and Dr. David Anderson. Course topics ranged from basic asphalt properties to
master curve principles and from basic testing techniques to sources of measurement error.
Hands-on sessions were conducted with spreadsheets and RHEA analysis software, and with
laboratory instrumentation.
During this quarter, WRI welcomed a two-day visit with Dr. Ernest Bastian and Dr. Terry
Arnold, both of FHWA and co-COTRs for the Fundamental Properties of Asphalts and Modified
Asphalts contract with WRI. Ongoing research was discussed with individual researchers and
the project status was discussed with Ray Robertson, Fred Turner, and Mike Harnsberger, WRI.
Next quarter WRI will host the 2008 Petersen Asphalt Research Conference (July 14-16) and the
Pavement Performance Prediction (P3) Symposium (July 16-18). Details can be obtained at
www.westernresearch.org.
1

SUBTASK 2-1. MOISTURE DAMAGE
Statement of Problem
TASK 2. CONTINUED RESEARCH
Asphalts and aggregates demonstrate different performance characteristics, especially in the
presence of moisture. Moisture damage mechanisms are poorly understood. From a chemical
standpoint, the question is: How are moisture damage of asphalt concrete and the chemistry of
the asphalt and aggregate materials related?
Approach
The work described below represents an attempt to gain insight into moisture damage using the
Hamburg Wheel Test to subject asphalt concrete specimens to stress under a steel wheel in a
water bath. The damage that occurs to the specimen results in the loss of material from the
sample into the water bath. This material is both inorganic (aggregate) and organic (asphalt)
and, when properly sampled, the chemical make-up of each can be determined. This chemical
characterization can then be used to establish correlations, or lack there of, between pavement
failures due to the presence of moisture and chemical make-up of the asphalt and aggregate.
Another approach can be taken using theoretical calculations that represent interactions between
asphalt and aggregate to help define what chemical characteristics of each material will result in
favorable interactions. In other words, this method theoretically predicts what types of
molecules in asphalt will interact favorable with certain aggregate molecules. These predictions
eventually require a proof-of-concept experiment in the laboratory. Therefore, based on theory,
certain types of molecules can be added into or removed from an asphalt to test for changes in
adhesion characteristics that could support or disagree with the predictive calculations. This
requires complex separations of asphalt into various fractions that are based on the overall,
chemical make-up of the material.
Goal
The goal of this research is to definitively determine how the chemistry of asphalt and aggregate
affect roadway performance in the presence of moisture. To do this, a better fundamental
understanding of asphalt chemistry and aggregate material properties and their relationship to
pavement performance is needed. Understanding their fundamental properties makes it possible
to decipher and better define the phenomena that occur at the asphalt-aggregate interface and
truly predict the performance of the pavement. The ultimate goal for the body of this work is to
eventually develop the material science for asphalt pavements.
3

Support of FHWA Strategic Goals
The work conducted in this subtask is in support of the FHWA strategic goal that pertains to the
optimization of pavement performance. There is a broad-based need for a better understanding
of the mechanisms of moisture damage and advanced methods for the detection and mitigation of
moisture damage. Progress in these areas will lead to improved material selection for new
pavements as well as enhanced capability for maintenance of existing roads.
Work Conducted this Quarter
Work this quarter has involved advancing our capabilities on the Hamburg Wheel Tracking
(HWT) Device and developing our know-how on the Gyratory Compactor for the experimental
work of the “Fines and Organics” project. This study is designed to fully characterize the
inorganic and organic material generated during HWT testing. The primary aim of this project is
to eventually determine whether the material liberated from a failing core sample can be
correlated with the failure of a mix design and, furthermore, whether these results correlate with
previous moisture damage studies as well as concurrent studies of asphalt-aggregate interfacial
phenomena. To date, testing of numerous road cores obtained from various sites has occurred.
Because of the varying depths of the road cores used, shims of different thicknesses were
designed and built in the shape of the test specimens from aluminum. The shims were built in
the shape of test specimens because prototype versions of the same width as the wheel resulted in
rutting of the bottom of the sample. Aluminum was the material of choice because it was readily
available, does not react with water, is durable and non-compressive, is relatively inexpensive in
comparison to other materials, and is easy to work with. Our system is now capable of rut
testing cores at a wide variety of depths.
During testing it has become increasingly apparent that the inorganic and organic sample
collections from HWT may be troublesome. First, the material is generated slowly in the water
bath during an extended time span. It was originally thought that it might be possible to collect
the fines as the experiment progressed, however that my not be the case. Additionally, it is not
yet clear by what method samples can be collected in the case of a major failure that involves
adherence of a large amount of material to the wheel and yields very large aggregate samples.
Most likely, useful information cannot be obtained from these mixes since they appear to be a
representation of the entire mix. At this point it is believed that collecting two samples at the end
of the test will be sufficient. Both a coarse and a fine sample will then be isolated for further
testing. The results of the initial mineral analyses of these samples will guide further sample
collection method development. If, for example, both the course and fine material are
representative of the entire mix design the sample collection method will have to be redeveloped.
This brings the discussion to another possible sampling issue: collecting material that is smaller
than 30 microns. This would prove to be very challenging and might require distillation of water
away from the fine material rather than filtration to remove the fines from water.
Finally, after several trials, it is evident that there will be enough organic material to extract from
the aggregate for spectroscopic analysis. If the method of sample collection is altered, this may
also cease to be the case.
4

In other work, the Superpave Gyratory Compactor is now being brought on line to produce
samples for the fines and organics project. A visit to the Wyoming Department of Transportation
was taken by Ryan Boysen, Mike Farrar, and Eric Kalberer to get familiarized with the process
as it is being utilized in the field. Since then, numerous, additional components for mixing,
compacting, and characterizing gyratory compacted samples have been purchased. Current
efforts are being directed at developing simple mix designs to evaluate the fines and organics
project.
Another project that is being developed under the moisture damage task is to revisit the use of
chromatography to separate asphalt into fractions that could prove useful for the study of
moisture damage. Chemical functional groups have been identified through past work at WRI as
being strong or weak binders to aggregate in the presence of water. Current research on
interfacial properties of asphalt and aggregate are starting to provide detailed information on
what might truly be binding to the rock. The use of high performance liquid chromatography
(HPLC) will be a useful tool in isolating pinpointed fractions of the asphalt that could be used as
a proof-of-concept for the surface studies. This work relates to some of the initial size exclusion
chromatography and ion exchange chromatography that was developed at WRI during the SHRP
program. Other recent developments at WRI have involved automating the SARA (saturates,
aromatics, resins, asphaltenes) separation. New methods incorporating past and current
developments can be used to isolate subfractions of particular interest to moisture damage
studies for doping experiments among other things. For example, if theoretical or interfacial
studies attribute good binding characteristics to an acidic fraction of the aromatics fraction in
asphalt, it would then be possible to isolate assorted acidic fractions of aromatics from asphalt
and to eventually perform doping experiments.
Work to be Conducted Next Quarter
• Continue with the optimization of the Hamburg Wheel Tracking Device and begin full
utilization of the Gyratory Compactor to test mixes with varying compositions from the
SHRP material database. Initial extractions of organics from the fines and subsequent
spectroscopic studies will be initiated. Additionally, mineral analyses of samples will
begin to determine whether proper sample collection methods are being utilized.
• An HPLC instrument will be ordered to begin work on isolating asphalt fractions of
interest for proof of concept studies.
Problems and Solution to Problems
Some minor details during process development occurred. These centered on being able to
incorporate cores of varying depths for testing. It is believed that the core-mold and shim have
effectively alleviated these difficulties. The lack of manpower has been essentially alleviated by
the hiring of Ryan Boysen. A full-time technician may still be needed for the operation of both
the Hamburg and Gyratory Compactor as the project progresses. No further problems were
encountered this past quarter.
5

SUBTASK 2-2. AGING
SUBTASK 2-2.1. IMPACT OF WATER ON AGING
Statement of Problem
The presence of moisture has been shown to increase the rate at which aging progresses in
paving asphalts. Since aging ultimately leads to embrittlement and pavement failure,
determining and modeling the influence of moisture is important to the prediction of pavement
performance.
Approach
The sensitivity of asphalts to environmental factors is being determined using laboratory PAV
aging tests on unmodified asphalts with and without moisture in the oven. Analytical tests
applied include spectroscopic (FTIR) and rheologic (DSR) of the aged materials. Master curve
and shift factors are used to quantify changes.
Goal
Develop relationships that predict the long-term aging of asphalts in the presence of moisture.
Support of FHWA Strategic Goals
The ability to reliably reproduce in the laboratory the aging that occurs in-sevice is vital to the
highway community. With the development of a correlation between laboratory aging data and
field pavement performance, an agency may be able to predict the advent of distresses in the
field, therefore, improving the cost effectiveness of the preventative maintenance and/or
rehabilitation measures that are commonly used. This subtask supports the FHWA Strategic
Goal of Optimizing Pavement Performance.
Work Conducted This Quarter
To evaluate the impact of moisture on the aging characteristics of asphalt binders in terms of
physical chemical relationships, previously collected data including the rheological and chemical
properties of eight RTFO- and RTFO/PAV-aged SHRP asphalts were analyzed extensively. The
RTFO-aged asphalts were PAV aged for different lengths of time in the absence and presence of
water. To further develop an understanding of the relationship between rheological properties
and chemical properties mathematically, the complex modulus was plotted against carbonyl
content for different aging times, 140, 240, and 480 hours for eight asphalts. The detailed results
were presented in previous quarterly reports (December 31, 2007 and March 31, 2008). It was
reported that both the complex modulus and carbonyl content increase with increasing aging
time and that different asphalts have different sensitivities to aging. The complex modulus
increases more sharply with increasing carbonyl content for some asphalts than for others. A
statistical model, logistic with two parameters, was applied to describe the relationship. This
equation is shown as follows:
7

G
b*
Carbonyl
* = a exp
(2-2.1.1)
Where G* = complex modulus, Pa
a and b = coefficients,
Carbonyl = carbonyl content in infrared absorption units.
It was reported earlier that parameter “a” appears to be primarily a function of frequency and
parameter “b” is related to asphalt source.
To determine whether parameter “b” is related to material compatibility, the parameter “b” was
plotted against a compatibility parameter, the Gaestel Index, for eight asphalts as shown in figure
2-2.1.1. It is evident from this figure that the parameter “b” is related to asphalt compatibility in
a monotonic, but non-linear relationship. Detailed information regarding how group
compositions relate to their performance characteristics will be presented at the 45 th annual
Petersen Asphalt Research Conference in Laramie, July 14-16, 2008.
An abstract entitled “Relationship between Group Composition of Asphalts and Their
Performance Characteristics” has been submitted to the “Geohunan International Conference on
Challenges and Recent Advances in Pavement Technologies and Transportation Geotechnics
(www.geohunan.org)” for consideration for presentation and publication.
b-Value
50
40
30
20
AAA-1
AAB-1
AAC-1
AAD-1
AAF-1
AAG-1
AAK-1
AAM-1
ABD
Y=3.351*exp (5.269X) , R 2 =0.81
AAF
AAC
10
AAM
AAK
ABD
AAG
Frequency= 10 rad/s, R
0
0.0 0.1 0.2 0.3 0.4 0.5 0.6
2 =0.81
Gaestel Index
Figure 2-2.1.1. Relationship between b-value and Gaestel index for eight different asphalts.
8
AAA
AAD
AAB

To further evaluate how water influences the relationship between complex modulus and
carbonyl content, the complex modulus was plotted against carbonyl content with respect to
different aging times in the PAV in the presence of water for different asphalts, as shown in
figure 2-2.1.2. It appears that the same model, a logistic function with two parameters, can be
applied for the wet oxidized samples. The relationship between the complex modulus and
carbonyl content for wet oxidized samples is similar to those of dry oxidized samples, where the
complex modulus and carbonyl content increase with increased aging time, and different asphalts
have different sensitivities to oxidative aging.
Complex Modulus, G*, Pa
5e+5
4e+5
3e+5
2e+5
1e+5
0
Control
AAA-1
AAB-1
AAC-1
AAD-1
AAF-1
AAG-1
AAK-1
AAM-1
ABD
Wet Oxidation
AAD-1
AAA-1
0.0 0.1 0.2 0.3 0.4 0.5
Carbonyl Content, a.u.
9
480 hrs
PAV at 80°C
ABD
AAG-1
Figure 2-2.1.2. Relationship between complex modulus and carbonyl content for different
asphalts before and after PAV aging in the presence of water.
Work to be Conducted Next Quarter
● Prepare the manuscript entitled “Relationship between Group Composition of Asphalts
and Their Performance Characteristics” for the conference.
● The same approach used for dry oxidized samples will be continually employed to the
wet oxidized samples, and parameter values will be compared to determine how water
influences oxidative aging.
● Correlate oxidation master curve parameters (i.e., shift factor and rheological index) to
chemical parameters (i.e., FTIR and compatibility parameters, Corbett fractions) as well
as low temperature properties (i.e., data from DSC) on the aged asphalts.

● Construct oxidation master curves for asphalts recovered from field core samples and
correlate master curve parameters (i.e., shift factor and rheological index) to chemical
parameters (i.e., carbonyl content and compatibility parameters).
● Prepare samples with different levels of asphalt film thickness (from thin film of 50
microns to standard film thickness of 1/8 inches) and subject to PAV aging at pavement
service temperature in the presence and absence of water to investigate the relationship
between oxidation and diffusion.
Problems and Solution to Problem
None
10

SUBTASK 2-2.2. SUPPORT OF THE MECHANISTIC-EMPIRICAL PAVEMENT
DESIGN GUIDE
Statement of Problem
The global aging system is a series of models that attempt to predict the change in binder
viscosity in hot-mix asphalt (HMA) pavement with time and depth. These models are an integral
part of the NCHRP 1-37A Mechanistic-Empirical Pavement Design Guide. The models were
developed from an extensive database consisting of capillarity viscosity, and penetration and
softening point measurements converted to viscosity, over a broad range of temperatures [Mirza
and Witczak 1995]. Christensen and Bonaquist [2006] modified the global aging system models
to make use of rational rheological measurements and binder master curve parameters while
maintaining consistency with the original models. They noted in regard to a part of their study,
which employed the global aging system, that the results should be considered approximate,
since “there are many questions concerning the accuracy of the global aging system.”
WRI, also in 2006, evaluated how well the GAS models predicted the actual aging that occurred
at the FHWA/WRI Arizona validation site [Farrar et al. 2006]. One of the main findings of the
study was that oxidative aging occurring at the Arizona site was substantially greater than
predicted by the GAS models, particularly in the top 13 mm of the pavement. Al-Azri et al.
[2006] in an extensive investigation of selected Texas highway pavements concerning
unmodified binder aging reported the level of hardening reached in pavement binders
significantly exceeded estimated values calculated by the global aging system both at the
pavement surface and at 125 mm below the surface.
More specifically, the global aging system was developed based on laboratory tests of
conventional “S” binders. These linear or straight-line Class “S” asphalts were non-modified,
and the authors of the global aging system (Mirza and Witczak) advised the global aging models
should not be used for modified asphalts, Class “W” (waxy) or Class “B” (blown) asphalts. The
S, B, and W designations were originally developed by Heukelom [1973] who observed the
linear and nonlinear relationships of asphalts using the Bitumen Test Data Chart developed in the
1960’s.
In addition: (1) the global aging system does not address photo-oxidation effects on the surface,
(2) the air void adjustment factor is based on limited data and considered “optional,” (3) the
global aging system does not take into account sealer/rejuvenator, chip seals, or open graded
friction course effects on pavement aging, and (4) the global aging system is not based on
“fundamental” binder properties.
Approaches
The accuracy and possible modifications to the global aging system are being studied at WRI by
analyses of data and materials from the FHWA/WRI validation sites and laboratory aging
(RTFO and PAV). Analytical tests applied include infrared spectroscopy and dynamic shear and
bending beam rheometry of unaged and aged materials. Master curves of unaged and aged
asphalts and age based shift factors are being studied to quantify age related changes.
11

Goals
The purpose of this subtask is twofold: (1) to improve the general understanding of the
physicochemical changes that occur with time and depth in asphalt pavement due to aging, and
(2) to recommend specific modifications to the global aging system to improve its accuracy and
expand its application to modified asphalts.
Support of FHWA Strategic Goals
The work conducted in this subtask supports FHWA’s ultimate pavement research and
development goal of providing performance-based models and tools to facilitate effective
management of the national highway infrastructure. Expanding our understanding of how
pavements age in terms of time and depth is critical to developing accurate models to predict
rutting and cracking in rehabilitation and new construction projects, and to allow better timing of
preventive maintenance strategies that are cost effective in mitigating pavement aging.
Background
Over the last several decades, there have been many studies on oxidative aging in asphalt
pavements; however, very few have dealt with how oxidative aging varies with depth. Of the
few studies available on the subject, perhaps the most well known is by Coons and Wright
[1968]. In this study and other related studies [Mirza and Witczak 1995; Houston et al. 2005;
Farrar et al. 2006; Al-Azri et al. 2006], the method used to make the evaluation involved slicing
the cores parallel to the pavement surface. In these studies the thickness of the slices varied from
as little as 1.6 mm (1/16 inch) in the upper 6.3 mm (1/4 inch) of the core in the Coons and
Wright study, to 25 mm (1 inch) in the upper area of the core in the Houston et al. study. How
the cores were sliced may have determined the conclusions reached. For example, the Coons
and Wright study showed an increase of roughly 50% in the viscosity of asphalt recovered from
the top 6.3-mm slice versus asphalt recovered from the next lower 6.3-mm slice. In addition, a
very fine film at the surface of the core had a higher viscosity than the average viscosity in the
top 6.3 mm. On the other hand, the Houston et al. study found that the viscosity did not vary
significantly with depth. Since different pavement designs, binders, and ages were used in these
studies, the results for both may be valid. However, it is also possible that the 25 mm thickness
of the slices used in the Houston et al. study masked a viscosity profile that would have been
apparent if thinner slices had been examined.
The opposing conclusions are not surprising and point out the difficult nature of not only
measuring aging in HMA, but developing a global aging system to predict aging. An extensive
literature review indicates the global aging system as developed by Mirza and Witczak is the
only system or set of models attempting to predict binder aging in HMA pavement on a “global”
basis. Research to date suggests that while the system is an excellent starting point it is at best
“semi-global” and given that it is an integral part of the MEPDG, research to improve its
predictive capability is clearly warranted.
12

Work Conducted This Quarter
Introduction
Both liquid-cell and photoacoustic (PA) infrared spectroscopy experiments are described for
aged and unaged asphalt samples. In addition, aggregates and mixed aggregate-asphalt samples
(mastics) are examined using PA spectroscopy. PA spectroscopy is unique in several ways to
other more traditional infrared sampling techniques such as attenuated total reflectance (ATR).
For example, the PA technique requires little sample preparation and has low sensitivity to
surface condition [McClelland et al. 2002]. This is a very important concept that makes it
possible to examine photo-oxidation of the pavement surface without use of solvents.
Also, an evaluation of pavement distress at the FHWA/ WRI Arizona validation site and related
rheological parameters is presented.
Data presented here were collected under the Fundamental Properties of Asphalts and Modified
Asphalts, III, FHWA project (DTFH61-07-D-00005) and to a small extent under the Asphalt
Surface Aging Prediction (ASAP) project (DTOS59-07-H-0006) for the Research and Innovative
Technology Administration (RITA). The projects are complimentary in terms of achieving a
better understanding of how asphalt pavement ages, but the ASAP project is specifically directed
towards providing a tool and methodologies for determining the appropriate time for the
preemptive application of rejuvenating surface treatments.
Experimental
Asphalt Aging
Aging protocols, for this project, included the rolling-thin-film oven (RTFO, AASHTO T-240)
method and the pressurized aging vessel (PAV, AASHTO R28) method.
Rheology
The complex shear modulus and phase angle of the original and laboratory aged asphalts were
measured using a Rheometrics Model RDA II Dynamic Analyzer (a research-grade dynamic
shear rheometer, DSR). DSR measurements for the SHRP asphalts were performed at 25˚C and
60˚C and a frequency range of 0.1 to 100 radians/sec at each temperature. DSR measurements
for the Arizona validation site asphalts were performed at 10 degree intervals over a temperature
range of 0 to 80°C and a frequency range of 0.1 to 100 radians/second.
FTIR Instrument
The infrared spectrometer used for this survey was a Perkin-Elmer Spectrum One ® equipped
with a deuterated triglycine sulfate (DTGS) detector. The spectrometer was controlled by a
desktop PC running Spectrum v5.0.1 software. Available optical path difference (OPD)
velocities were 0.1, 0.2, 0.5, 1.0 and 2.0 cm/sec.
13

Transmission – liquid-cell technique
Liquid-cell samples were prepared as solutions (50 mg asphalt per one ml solvent) and placed
into a 0.99-mm (path length) KBr cell before infrared spectra collection. A single beam
background spectrum of the liquid cell with solvent was acquired daily prior to acquiring single
beam sample spectra. The solvent used was carbon disulfide (CS2). All data were collected at a
resolution of 4 cm -1 , spectral range 600 – 4000 cm -1 , and each spectra was derived from 32 coadded
scans.
Photoacoustic technique
An MTEC Model 300 photoacoustic detector (acquired under RITA contract) coupled to the
Spectrum One FTIR spectrometer as shown in figure 2-2.2.1 was used to acquire absorption
spectra. All data were collected in rapid-scan (non-phase modulation) mode at a resolution of
8 cm -1 and the spectral range was 600–4000 cm -1 . The number of scans co-added depended on
scanning speed. To improve the signal-to-noise ratio, in some cases a series of spectra were
obtained and averaged where each spectrum corresponded to a relatively short measurement
time. OPD velocity, amplifier gain setting, and number of scans are reported with each
spectrum. Carbon black (MTEC Photoacoustics) was used as the normalization reference. The
PA detector was purged with helium. A 1-mm deep sample cup and brass sample holder (MTEC
Photoacoustics) were used to contain and insert the samples into the MTEC acoustic chamber.
Photoacoustic - background
Figure 2-2.2.1. MTEC 300 Photoacoustic spectrometer coupled to a
Perkin Elmer FTIR Spectrum One.
Since PA spectroscopy is a somewhat uncommon FTIR technique a more detailed description
has been included in this report PA spectroscopy can probe surface composition over a range of
selectable sampling depths from several micrometers to more than 100 micrometers (samples
14

greater than 100 micrometers are considered “thermally thick”). PAS directly measures IR
absorption by sensing absorption induced heating of the sample within an experimentally
controllable sample depth below the samples surface [McClelland et al. 2002].
The PA sampling (thermal diffusion) depth for a homogeneous sample is conventionally
expressed as [Rosencwaig and Gersho 1976]
L π
1
2 = ( D / f )
(2-2.2.1)
where D is the thermal diffusivity, a measure of heat propagation speed, in cm 2 /sec, and f is the
infrared-intensity modulation frequency in hertz. The equation for thermal diffusivity (D) is
D = k/ρCp (2-2.2.2)
where k is the thermal conductivity in W/mK, ρ is density in kg/m 3 , and Cp is the specific heat
in J/kg K. From the literature it is estimated for an asphalt at 25˚C, typical values for ρ, k and Cp
are 1030 kg/m 3 , 0.75 W/m K and 920 J/kg K, respectively. Frequency modulation ( f ) can be
expressed as a function of V the optical path difference (OPD) velocity of the interferometer
mirror in cm/sec and ν the wave number in cm -1 .
f = Vν
(2-2.2.3)
Combining equations 2-2.2.1 and 2-2.2.3 results in
1
2
L = ( D / πVν
)
(2-2.2.4)
The sampling depth is inversely proportional to the square root of the modulation frequency and
therefore low modulation frequency or OPD velocity will result in PA signals from within the
sample, while high OPD velocities are nearer the surface region. The dependence of the
sampling depth on wavenumber (ν) means that it varies across a spectrum. For asphalt and the
thermal diffusivity estimated above, at an OPD velocity of 0.5 cm/s the thermal diffusion length
varies from 29 µm at 600 cm -1 to 11 µm at 4000 cm -1 . Thermal diffusion lengths at various
OPD velocities and selected wave numbers from 600 to 4000 cm -1 corresponding to areas of
significant asphalt absorbance peaks are listed in table 2-2.2.1.
Depth variation across the spectrum can be overcome by using a step-scan spectrometer
employing phase modulation photoacoustic measurements [Jones and McClelland 1996;
Drapcho et al. 1997]. Step-scan, as described by Drapcho et al. is the case where the “average
optical retardation is adjusted stepwise, with a secondary, single-frequency phase (optical path
difference) modulation applied. The data are collected when the average optical retardation is
kept constant; thus the velocity and wavenumber dependence of the Fourier frequency is
removed, and a constant probing depth across the spectrum for each phase modulation (PM)
frequency is achieved.”
15

Materials
Table 2-2.2.1. Sampling depth due to varying OPD velocity at selected wavenumbers.
SHRP Asphalts
Strategic Highway Research Program (SHRP) asphalts: AAB-1, AAC-1, AAD-1, and AAM-1
were used in this study. The four asphalts were RTFO/PAV aged at 60 and 80˚C for various
times (20, 144, 240, and 480 hours).
Arizona Validation Site Asphalts
The Arizona WRI/FHWA validation site is located on the south bound lane of US 93,
approximately 50 miles north of Wickenburg, Arizona at about milepost 153. The contractor’s
asphalt and asphalt from three other sources were used to construct the site. The four asphalts
are generically identified here as AZ1-1 thru AZ1-4. AZ1-1 was produced from a West Texas
intermediate sour blend; AZ1-2 from a Venezuelan crude; AZ1-3 from a Rocky Mountain blend;
and AZ1-4 from a Canadian crude. AZ1-1, AZ1-3, and AZ1-4 were classified as performance
grade PG 76-16, and AZ1-2 as PG 76-22.
The four asphalts were analyzed for the presence of polyphosphoric acid and polymers using
nuclear magnetic resonance (NMR) spectroscopy Neither PPA nor SBS polymer was detected in
the asphalt samples as indicated by phosphorus NMR and proton NMR analyses. The detection
limits for phosphorous and polymers using this method were estimated to be 0.1 and 0.5 wt %,
respectively.
Aggregates
Wavenumber (v), cm -1
Aggregates used for PA analysis are referred in this report as RA, RD (note RA and RD are
SHRP aggregates), and Arizona aggregate. RA aggregate consists primarily of granite with a
minor amount of basalt. Major RA elemental oxides are SiO2 (71%) and Al2O3 (16%). Major
mineral components are quartz (55%), K-feldspar (25%), and plagioclase (10%). RD is a
16
Sampling Depth L, µm
OPD velocity (V), cm/s
0.1 0.2 0.5 1.0 2.0
4000 25 18 11 8 6
3000 29 20 13 9 6
1600 40 28 18 13 9
1457 42 29 19 13 9
1376 43 30 19 14 10
870 54 38 24 17 12
720 59 42 26 19 13
600 65 46 29 20 14

limestone. Major RA elemental oxides are CaO (39%), and SiO2 (17%). Major mineral
components are calcite (61 %), quartz (7.4%), and organics (5%) [Robl 1991].
FTIR-PA analysis was performed on RD and RA aggregate batched to the gradation shown in
table 2-2.2.2.
FTIR-PA analysis on the Arizona aggregate was performed on the minus 2.36 mm plus
0.425 mm aggregate from the combined Arizona plant mix aggregate. Lime (approximately 1%
by mass of the aggregate) may have been added before aggregate samples were collected on the
project.
Laboratory prepared mastic
Table 2-2.2.2. Gradation for fine, dense graded mastic.
Sieve Size, mm Percent Passing
1.19 100
0.600 75
0.300 50
0.150 30
0.075 20
Mastics were prepared by mixing aged AAD-1 asphalt (RTFO/PAV 80˚C, 480 hours) with RD
and RA aggregate (see table 2-2.2.2 for mastic gradation). Four relative concentrations of each
mastic were prepared: 20% aggregate/80% asphalt, 50% aggregate/50% asphalt, 80%
aggregate/20% asphalt, and 90% aggregate/10% asphalt.
Laboratory aged compacted specimens
Four 75-mm diameter by 120 mm tall compacted specimens were received from North Carolina
State University (NCSU, Dr. Y. Richard Kim). The specimens had been cored from larger 150mm
diameter gyratory compacted specimens. A 9.5-mm nominal maximum sized aggregate was
used to fabricate the specimens. The aggregate was a limestone obtained from a quarry in North
Carolina. SHRP AAD-1 was used as the binder (6.2% by mass of the compacted specimen).
Results and Discussion
Asphalt Aging and FTIR Spectroscopy
In this study, we report a Fourier-Transform Infrared (FTIR) spectroscopic survey of eight
asphalts in unaged and laboratory aged conditions as well as several common aggregates used in
road construction and combined asphalt/aggregate samples prepared in the laboratory. FTIR
photoacoustic (FTIR-PA), and transmission liquid-cell techniques were employed to perform the
survey. Results from the survey will be used here and in later studies to: (1) compare FTIR-PA
and liquid cell techniques; (2) explore and confirm previously observed relationships between
17

asphalt chemical composition and rheological parameters; (3) determine the feasibility of
obtaining asphalt chemical composition from infrared spectra of combined laboratory
asphalt/aggregate mastic and from the actual pavement surface;
Liquid-Cell FTIR Spectra
Traditionally, the mid-infrared carbonyl (~ 1700 cm -1 ) and sulfoxide (~ 1030 cm -1) ) absorbance
bands have been used to gage oxidation in asphalt. Although, as demonstrated last quarter, there
appear to be important areas such as the region from 1150 to 1250 cm-1 shown in figure 2-2.2.2
that appear to correlate to rheological properties.
However, until these regions of the mid-infrared spectrum of asphalt are better understood and
investigated, the key relationship that allows the complex shear modulus (G*) of the binder
component of pavement to be measured using infrared spectra is the correlation between the
change in Log G* and the change in concentration of oxidation products, measured here as the
carbonyl content. For dynamic shear rheometry tests performed at 25°C and 60°C, the qualities
of the correlations are shown in figures 2-2.2.3 and 2-2.2-4. The fit data include all aged
asphalts: RTFO, PAV at 60°C, PAV at 80°C, and PAV at 100°C. R-squared values for DSR
tests at 25°C average 0.94, and for tests at 60°C they average 0.97. In field use, it is anticipated
that rheological master curves can be applied to show the stiffness of the asphalt at all in-service
temperatures and loading frequencies.
Absorbance
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2000
Carbonyl
1800
1600
Solvent
1400
Figure 2-2.2.2. Changes in infrared spectra caused by oxidative aging.
18
1200
Wave Number, cm -1
AAB-1 neat
AAB-1 RTFO
AAB-1 PAV 100°C 20hrs
AAB-1 PAV 80°C 480hrs
1150 - 1250 cm -1 Region
1000
800
600

Log G* at 10 rad/s
8
7
6
5
25°C
y = 7.349x + 5.626
R 2 = 0.923
19
y = 3.440x + 5.645
R 2 = 0.962
y = 4.145x + 6.050
R 2 = 0.924
y = 2.202x + 6.205
R 2 = 0.946
AAB-1
AAC-1
AAD-1
AAM-1
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Carbonyl Content, au
Figure 2-2.2.3. Change in Log G* measured at 25°C as a function of carbonyl content
for SHRP asphalts.
Log G* at 10 rad/s
6
5
4
3
2
60°C
y = 10.758x + 3.214
R 2 = 0.974
y = 7.081x + 3.459
R 2 = 0.970
y = 4.430x + 3.593
R 2 = 0.972
y = 4.945x + 2.823
R 2 = 0.958
AAB-1
AAC-1
AAD-1
AAM-1
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Carbonyl Content, au
Figure 2-2.2.4. Change in Log G* measured at 60°C as a function of carbonyl content
for SHRP asphalts.

A summary of aging, FTIR, and rheology data for the SHRP asphalts is provided in tables
2-2.2.3a and 2-2.2.3b. Results for G* are reported at an angular frequency of 10 rad/s. Tables
2-2.2.4a and 2-2.2.4b contain similar data for the laboratory aged field samples.
Table 2-2.2.3a. Experiment status matrix for SHRP asphalt aging and testing.
Sample 1
Solution FTIR
Analysis
(corr. peak ht.)
PA FTIR
Analysis
(total peak ht.)
Carbonyl 2 , au 2 Carbonyl 2 , au 2
20
DSR - G*, 10 rad/s
(Pa)
DSR - δ, 10 rad/s
25°C 60°C 25°C 60°C
AAB Unaged 0.0100 0.2600 4.42E+05 1.42E+03 65.396 86.627
AAB RTFO only 0.0102 0.4600 8.71E+05 2.59E+03 62.247 84.455
AAB 100°C 20hrs 0.0675 0.7600 2.44E+06 1.13E+04 49.625 77.173
AAB 60°C 20hrs 0.0243 0.4800 1.22E+06 4.19E+03 58.791 83.008
AAB 60°C 144hrs 0.0489 0.7700 2.11E+06 7.19E+03 53.063 80.805
AAB 60°C 240hrs 0.0666 0.8000 2.64E+06 9.61E+03 51.798 79.349
AAB 60°C 480hrs 0.1057 0.9600 3.41E+06 1.38E+04 47.911 77.342
AAB 80°C 20hrs 0.0300 0.5500 1.51E+06 1.90E+04 3
57.035 81.825
AAB 80°C 144hrs 0.1255 0.8900 4.43E+06 2.23E+04 43.732 73.66
AAB 80°C 240hrs 0.1725 1.0300 4.42E+06 3.30E+04 41.255 68.246
AAB 80°C 480hrs 0.2394 1.300 1.05E+07 1.74E+05 31.707 53.048
AAC Unaged 0.0061 0.2700 1.21E+05 4.00E+02 78.400 89.106
AAC RTFO only 0.0288 0.4200 4.23E+05 8.15E+02 70.570 87.702
AAC 100°C 20hrs 0.1242 0.8100 1.43E+06 3.56E+03 54.355 82.707
AAC 60°C 20hrs 0.0370 0.4500 2.17E+06 3
1.22E+03 50.007 86.220
AAC 60°C 144hrs 0.1079 0.7700 1.15E+06 2.17E+03 59.246 85.369
AAC 60°C 240hrs 0.1384 0.8200 1.42E+06 2.60E+03 57.439 84.805
AAC 60°C 480hrs 0.1810 0.9900 1.75E+06 4.18E+03 52.582 82.285
AAC 80°C 20hrs 0.0828 0.6000 8.82E+05 1.81E+03 60.944 86.087
AAC 80°C 144hrs 0.1804 0.8800 2.06E+06 5.86E+03 49.516 80.677
AAC 80°C 240hrs 0.2340 1.0000 2.72E+06 7.27E+03 45.453 77.738
AAC 80°C 480hrs 0.3014 1.2400 4.20E+06 2.64E+04 38.004 67.481
1 All samples displaying temperatures and times are PAV aged.
2 au = absorption units

Table 2-2.2.3b. Experiment status matrix for SHRP asphalt aging and testing.
Sample 1
Solution FTIR
Analysis
(corr. peak ht.)
PA FTIR
Analysis
(total peak ht.)
21
DSR - G*, 10 rad/s
(Pa)
DSR - δ, 10 rad/s
carbonyl, au 2 carbonyl, au 2 25°C 60°C 25°C 60°C
AAD Unaged 0.0411 0.4900 1.49E+05 1.22E+03 69.344 84.784
AAD RTFO only 0.0461 0.6000 5.01E+05 3.30E+03 63.524 79.601
AAD 100°C 20hrs 0.0722 0.8300 1.82E+06 1.47E+04 52.812 69.739
AAD 60°C 20hrs 0.0457 0.6400 8.11E+05 4.13E+03 59.913 76.413
AAD 60°C 144hrs 0.0605 0.6100 1.24E+06 7.74E+03 57.096 74.954
AAD 60°C 240hrs 0.0762 0.7300 1.82E+06 1.35E+04 54.473 72.31
AAD 60°C 480hrs 0.1008 0.7900 2.70E+06 1.92E+04 51.152 70.142
AAD 80°C 20hrs 0.0571 0.6300 1.05E+06 6.65E+03 58.468 75.594
AAD 80°C 144hrs 0.1129 0.9100 3.70E+06 2.93E+04 47.444 66.497
AAD 80°C 240hrs 0.1419 1.0000 5.87E+06 6.03E+04 42.331 57.757
AAD 80°C 480hrs 0.2335 1.2000 1.60E+07 4.52E+05 30.153 40.798
AAM Unaged 0.0137 0.3300 1.06E+06 2.76E+03 60.03 85.363
AAM RTFO only 0.0353 0.5300 1.51E+06 5.08E+03 55.686 82.066
AAM 100°C 20hrs 0.1397 --- 3.88E+06 2.21E+04 41.238 71.16
AAM 60°C 20hrs 0.0580 0.6200 2.17E+06 7.01E+03 49.662 80.485
AAM 60°C 144hrs 0.1277 0.7300 3.39E+06 1.48E+04 43.456 75.459
AAM 60°C 240hrs 0.1602 0.8700 3.99E+06 2.05E+04 42.116 72.573
AAM 60°C 480hrs 0.2087 0.9600 4.52E+06 2.56E+04 39.265 70.381
AAM 80°C 20hrs 0.0865 0.6600 2.57E+06 9.40E+03 47.562 78.233
AAM 80°C 144hrs 0.2199 0.9200 4.59E+06 4.06E+04 38.106 66.248
AAM 80°C 240hrs 0.2667 1.0600 6.13E+06 4.83E+04 34.856 62.808
AAM 80°C 480hrs 0.3335 1.3100 8.05E+06 1.33E+05 29.889 52.363
1 All samples displaying temperatures and times are PAV aged.
2 au = absorption units

Table 2-2.2.4a. Experiment status matrix for laboratory aged field asphalts.
Sample 1
Solution FTIR
Analysis
(total peak ht.)
PA FTIR
Analysis
(total peak ht.)
22
DSR - G*, 10 rad/s
(Pa)
DSR - δ, 10 rad/s
carbonyl, au 2 carbonyl, au 2 20°C 60°C 20°C 60°C
AZ1-1 Unaged 0.11 0.58
AZ1-1 RTFO only
AZ1-1 100°C 20hrs
0.23 7.27e+06 25919 38.889 70.521
AZ1-1 60°C 96hrs 0.30 9.27E+06 56422 34.988 64.158
AZ1-1 60°C 192hrs 0.33 9.92E+06 64523 33.925 62.779
AZ1-1 60°C 336hrs 0.38 1.31E+07 71467 30.98 61.335
AZ1-1 60°C 504hrs 0.39 1.39E+07 87137 30.146 60.441
AZ1-1 80°C 96hrs 0.35 0.93 1.22E+07 66571 31.871 61.538
AZ1-1 80°C 210hrs 0.45 1.02 1.70E+07 1.56E+05 27.801 53.363
AZ1-1 80°C 336hrs 0.47 1.29 1.97E+07 2.03E+05 25.947 49.852
AZ1-1 80°C 504hrs 0.53 1.32 2.05E+07 3.39E+05 24.137 45.539
AZ1-2 Unaged 0.05 0.43
AZ1-2 RTFO only 0.11 6.02E+06 23590 48.359 69.509
AZ1-2 100°C 20hrs
AZ1-2 60°C 96hrs 0.15 1.05E+07 32391 42.678 66.671
AZ1-2 60°C 192hrs 0.18 1.10E+07 49491 41.997 64.307
AZ1-2 60°C 336hrs 0.21 1.19E+07 50063 41.004 64.084
AZ1-2 60°C 504hrs 0.24 1.39E+07 89396 39.185 59.675
AZ1-2 80°C 96hrs 0.21 0.54 1.17E+07 48744 40.306 63.837
AZ1-2 80°C 210hrs 0.32 0.79 2.09E+07 1.65E+05 32.224 53.32
AZ1-2 80°C 336hrs 0.45 1.07 3.09E+07 3.24E+05 27.928 46.597
AZ1-2 80°C 504hrs 0.52 1.35 4.56E+07 1.94E+06 21.097 28.292
1 All samples displaying temperatures and times are PAV aged.
2 au = absorption units

Table 2-2.2.4b. Experiment status matrix for laboratory aged field asphalts.
Sample 1
Solution FTIR
Analysis
(total peak ht.)
PA FTIR
Analysis
(total peak ht.)
23
DSR - G*, 10 rad/s
(Pa)
DSR - δ, 10 rad/s
carbonyl, au 2 carbonyl, au 2 20°C 60°C 20°C 60°C
AZ1-3 Unaged 0.04 0.43
AZ1-3 RTFO only
AZ1-3 100°C 20hrs
0.12 1.12E+07 25076 46.103 75.457
AZ1-3 60°C 96hrs 0.19 1.96E+07 67533 38.522 69.777
AZ1-3 60°C 192hrs 0.22 2.17E+07 77308 37.022 68.479
AZ1-3 60°C 336hrs 0.26 2.73E+07 1.04E+05 34.2 67.606
AZ1-3 60°C 504hrs 0.29 2.71E+07 1.52E+05 33.643 63.44
AZ1-3 80°C 96hrs 0.25 0.64 2.86E+07 90512 34.11 67.19
AZ1-3 80°C 210hrs 0.37 0.85 4.32E+07 2.40E+05 28.27 58.962
AZ1-3 80°C 336hrs 0.47 1.16 5.10E+07 4.84E+05 25.288 51.064
AZ1-3 80°C 504hrs 0.53 1.39 5.85E+07 1.54E+06 21.564 40.257
AZ1-4 Unaged 0.05 0.39
AZ1-4 RTFO only 0.11 1.40E+07 30451 44.626 77.583
AZ1-4 100°C 20hrs
AZ1-4 60°C 96hrs 0.19 2.50E+07 83266 36.66 71.775
AZ1-4 60°C 192hrs 0.23 2.73E+07 92662 35.033 70.424
AZ1-4 60°C 336hrs 0.29 3.49E+07 1.25E+05 32.66 68.536
AZ1-4 60°C 504hrs 0.32 3.78E+07 2.10E+05 30.861 64.494
AZ1-4 80°C 96hrs 0.24 0.79 2.97E+07 86300 34.134 70.153
AZ1-4 80°C 210hrs 0.39 0.88 5.22E+07 3.42E+05 27.01 58.226
AZ1-4 80°C 336hrs 0.49 1.13 5.70E+07 5.44E+05 24.19 53.537
AZ1-4 80°C 504hrs 0.52 1.31 6.60E+07 1.63E+06 20.777 41.164
1 All samples displaying temperatures and times are PAV aged.
2 au = absorption units
FTIR-PA Spectra
Since the strong C-H stretching absorption in the region from 2800 to 3100 cm -1 appeared
truncated below a velocity of 0.5 cm/sec, asphalt PA spectra were collected at an OPD velocity
of 0.5 cm/sec. All PA and liquid-cell spectra are available for review; two are shown here
(figures 2-2.2.5 and 2-2.2.6) for inspection. Functional groups apparent in the unaged and aged
liquid-cell spectra are also apparent in PA spectra as shown in figure 2-2.2.7.

(a)
(b)
PA Intensity (arbitray units)
PA Intensity (arbitray units)
7.42
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.03
4000.0 3600 3200 2800 2400 2000 1800
cm-1
1600 1400 1200 1000 800 600.0
5.00
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.03
1800.0 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700.0
cm-1
Figure 2-2.2.5. PA spectra changes on oxidation of a thermally thick (1 mm ±) sample of AAD-1
(unaged, RTFO, and various PAV aging times at 80˚C). (a) Blue: Unaged. Green: RTFO only.
Black: RTFO/PAV 20hours. Brown: RTFO/PAV 144 hours. Pink: RTFO/PAV 240 hours.
Red: RTFO/PAV 480 hours. OPD velocity 0.5 cm/sec, 512 co-added scans, gain (4).
(b) expanded view - fingerprint region.
24

(a)
(b)
PA Intensity (arbitray units)
6.64
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.06
4000.0 3600 3200 2800 2400 2000 1800
cm-1
1600 1400 1200 1000 800 600.0
PA Intensity (arbitray units)
5.00
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.06
1800.0 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700.0
cm-1
Figure 2-2.2.6. PA spectra changes on oxidation of a thermally thick (1 mm ±) sample of AZ1-4
asphalt (unaged, and various PAV aging times at 80˚C). (a) Blue: Unaged. Black: RTFO/PAV 96
hours. Brown: RTFO/PAV 210 hours. Pink: RTFO/PAV 336 hours. Red: RTFO/PAV 504 hours.
OPD velocity 0.5 cm/sec, 512 co-added scans, gain (4). (b) expanded view - fingerprint region.
25

Figure 2-2.2.7. Comparison of PA and liquid-cell spectra in the fingerprint region. Top: PA
spectra unaged AAD-1, 512 co-added scans, gain (4), and OPD velocity 0.5 cm/sec. Second from
top: PA spectra after RTFO/PAV aging (480 hours at 80˚C), 512 co-added scans, gain (4), OPD
velocity 0.5 cm/sec. Third from top: Liquid-cell transmission spectra AAD-1 after RTFO/PAV
aging (480 hours at 80˚C). Bottom: Liquid-cell transmission spectra unaged AAD-1.
Comparison (PA vs. Liquid Cell)
A comparison of carbonyl peak height from liquid cell and PA spectra of the SHRP asphalts
PAV aged at 80˚C is displayed in figure 2-2.2.8. The correlation (R 2 = 0.81) reveals a
reasonably linear relationship between the PA and liquid-cell FTIR techniques. PA signal to
noise ratio is much more sensitive to the number of co-added scans than the liquid cell technique.
A significantly higher R 2 could have likely been achieved had a greater number of co-added
scans been used to acquire the PA spectra. Time constraints limited the number of co-added
scans to 512 for this survey.
26

PA - Carbonyl total peak ht. (1700 cm-1)
1.400
1.300
1.200
1.100
1.000
0.900
0.800
0.700
0.600
0.500
y = 2.42x + 0.53
R 2 = 0.81
0.400
0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350
Liquid Cell - Carbonyl corr. peak ht. (1700 cm-1)
Figure 2-2.2.8. Comparison SHRP asphalts – Carbonyl peak height at 1700 cm -1 , PA vs. Liquid
cell, without unaged or RTFO asphalts. Note: Liquid cell carbonyl represents the corrected peak
height, and PA carbonyl represents the total peak height.
SHRP RD aggregate (limestone, CaCO3)
PA spectra of RD (limestone) aggregate at several OPD velocities are presented in figure 2-2.2.9.
Spectral artifacts seem evident at lower OPD velocity, particularly at 0.1 cm/sec, where the
broad absorbance band at 1430 cm -1 appears to have sharp side lobes not corrected by the strong
apodization function selected for this analysis. Also, the broad absorption at 1430 cm -1 appears
to be inverted.
Limestone is a sedimentary rock composed of more than 50% carbonate minerals. There are two
common, naturally occurring polymorphs of calcium carbonate (CaCO3): aragonite and calcite.
Aragonite’s crystal lattice differs from that of calcite, resulting in a different crystal shape. The
bands at 713 cm -1 , 876 cm -1 , 1075 cm -1 , and 1430 cm -1 , which appear most distinct in the top
spectrum, represent carbonate vibrations.
The bands at about 1800 cm -1 , 2510 cm -1 and 2900 cm -1 are overtone and combination bands
[Logodi et al. 2001; Vassallo et al. 1992]. The lack of a sharp band around 1070–1080 cm -1 in
27

figure 2-2.2.9 suggests that calcite is predominate in the RD aggregate since calcite is infrared
inactive in this area [Logodi et al 2001].
The band at about 2510 cm -1 has been used to quantify amounts of residual limestone in lime
[Norton and McClelland 1996] and Logodi et al. [2001] have used the out-of-plane bending band
at 876 cm -1 to quantify the amount of limestone in cement blends. Logodi mentions that the
band at 876 cm -1 has also been used to quantify the amount of CaCO3 in CaCO3 /Ca(OH)2
mixtures and to study the kinetics of the decomposition of CaCO3 to CaO. Arnold et al. [2006]
has used the band at 3640 cm -1 to evaluate the presence of lime in asphalt pavement.
Figure 2-2.2.9. PA spectra of SHRP RD (limestone) aggregate at different OPD velocities. Top:
OPD velocity 2.0 cm/sec, average of six spectra (128 co-added scans per spectrum), gain (7).
Second from top: OPD velocity 1.0 cm/sec, average of four spectra (256 co-added scans per
spectrum), gain (7). Third from top: OPD velocity 0.5 cm/sec, one spectra (256 co-added
scans), gain (7). Bottom: OPD velocity 0.1 cm/sec, one spectra (64 co-added scans).
28

SHRP RA (granite)
PA spectra of RA aggregate at two OPD velocities (1 cm/sec and 2 cm/sec) are presented in
figure 2-2.2.10. The major RA elemental oxide is SiO2 (71%), which has an intense peak around
1100 cm -1 [Smith 1996]. The major mineral component in RA aggregate is quartz (56%).
Quartz exhibits an intense broad band around 1100 cm -1 from the SiO2 and also shows sharper
bands at 795, 775 and 690 cm -1 [Jackson 1998].
Figure 2-2.2.10. PA spectra of SHRP RA (granite) aggregate at two OPD velocities. Top: OPD
velocity 1.0 cm/sec, average of 4 spectra (256 co-added scans per spectrum), gain (7). Bottom
OPD velocity 2.0 cm/sec, average of 5 spectra (128 co-added scans per spectrum), gain (7).
29

For comparison, PA spectra of RD, RA, Arizona aggregate, and reagent grade calcium carbonate
are displayed in figure 2-2.2.11. Visually the Arizona aggregate appears to be primarily
siliceous, but its exact mineralogy has not been determined. The Arizona aggregate spectrum is
not well defined, but appears to contain SiO2 based on the broad band between 1100 and 1200
cm -1 . The relatively intense peak at about 3630 cm -1 is probably OH stretching related to lime
which may have been introduced to the aggregate during construction.
Figure 2-2.2.11. PA spectra – comparison of RD, RA, Arizona aggregate and reagent grade
calcium carbonate. Top: RD aggregate, OPD velocity 2.0, average of 6 spectra (128 co-added
scans per spectrum), gain (7). Second from top: Reagent grade calcium carbonate, 0.5 OPD
velocity (32 co-added scans per spectrum), gain (4). Third from top: RA aggregate, OPD
velocity 1.0, average of 4 spectra (256 co-added scans per spectrum), gain (7). Bottom: Arizona
aggregate, OPD velocity 0.5, average of 4 spectra (256 co-added scans per spectrum), gain (7).
30

Mastics
Several asphalt mastics were prepared consisting of SHRP RD aggregate and aged AAD-1
asphalt, and SHRP RA aggregate and aged AAD-1 asphalt. The mastics were prepared with
varying relative amounts of the two components. Details on the preparation can be found in the
experimental section of this report. Figures 2-2.2.12 and 2-2.2.13 show the infrared spectra of
the two mastics.
Figure 2-2.2.12. PA spectra RD/AAD-1 asphalt mastic. Top: 20% RD/80% AAD-1. Second
from top: 50% RD/50% AAD-1. Third from top: 80% RD/20% AAD-1.
Bottom: 90% RD/10% AAD-1. Variable number of separate scans averaged
(256 co-added scans per spectrum) OPD velocity 1.0 cm/sec, gain (7).
31

Figure 2-2.2.13. PA spectra RA/AAD-1 asphalt mastic. Top: 20% RA/80% AAD-1. Second
from top: 50% RA/50%AAD-1. Third from top: 80%RA/20%AAD-1.
Bottom: 90%RA/10%AAD-1. Variable number of separate scans averaged
(256 co-added scans per spectrum), OPD velocity 1.0 cm/sec, gain (7).
Spectral subtraction can be performed to obtain the spectrum of the aged AAD-1 asphalt. An
example is illustrated in figure 2-2.2.14. The top spectrum in the figure is 20% RD
aggregate/80% aged AAD-1 asphalt mixture, the middle spectrum is pure RD aggregate, the
bottom spectra is the difference spectrum. The difference spectrum was obtained by using the
limestone band at 1800 cm -1 , which is common to both the mixed spectra and the reference
spectra, and subjectively adjusting the scaling factor (0.64 in this case) until the band appeared
flat.
32

4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600.0
cm-1
Figure 2-2.2.14. Spectral subtraction. Top: PA spectrum of the mixture of 20% RD
aggregate/80% aged AAD-1 asphalt. Middle: PA spectrum of pure RD aggregate,
OPD velocity 1.0 cm/sec, average of four spectra (256 co-added scans per spectrum), gain (7).
Bottom: The difference spectrum.
The difference spectrum from figure 2-2.2.14 is compared to the spectrum of pure aged AAD-1
asphalt in figure 2-2.2.15. The spectra are similar, but there are differences. Differences can be
attributed to a number of factors such as sample position within the acoustic chamber and band
overlap. Additional FTIR methods to separate the spectral components of mixtures are being
investigated such as measuring two component mixture spectra at different relative
concentrations, and using the ratio of the spectra to obtain subtraction coefficients [Hirschfeld
1976; Koenig et al. 1977].
33

4000.0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 600.0
cm-1
Figure 2-2.3.15. Comparison of pure asphalt PA spectrum to difference spectrum. Top: PA
spectrum of pure aged AAD-1 asphalt, OPD velocity 0.5 cm/sec, 512 co-added scans, and gain
(4). Bottom: PA difference spectrum aged AAD-1 from figure 2-2.2.14.
Laboratory aged compacted specimens
In this study, cores received from NCSU were evaluated by FTIR to determine the extent of
short- and long-term aging that had occurred in the laboratory. See the “Materials’ section of
this report for details in regard to their preparation. Dynamic modulus and direct tension tests
were performed on the specimens at NCSU before shipping to WRI.
The loose mix, prior to compaction, had been short-term aged in a forced draft oven at 135˚C for
four hours. The long-term aging was performed in a forced draft oven at 85˚C at different times
(2, 4 and 8 days). The cores were labeled as follows:
• STA (short term aging) – Loose uncompacted mixture conditioned at 135˚C for four
hours and then compacted.
34

• LTA1 (long term aging Level 1): The loose mix aging procedure was the same as STA
except the compacted specimen (75-mm diameter by approximately 120-mm tall) was
conditioned at 85˚C for two days.
• LTA2 (long term aging Level 1): The loose mix aging procedure was the same as STA
except the compacted specimen (75-mm diameter by approximately 120-mm tall) was
conditioned at 85˚C for four days.
• LTA3 (long term aging Level 1): The loose mix aging procedure was the same as STA
except the compacted specimen (75-mm diameter by approximately 120-mm tall) was
conditioned at 85˚C for eight days.
In this analysis, the effects of short- and long-term laboratory aging were measured by first
splitting open the STA and LTA3 cores and removing small samples of mastic from the edge and
center of the open face of the cores as illustrated in figure 2-2.2.16. Asphalt from the small
mastic samples was recovered and evaluated by FTIR
Figure 2-2.2.16. Core face (typical) - mastic sample locations (STA and LTA3).
The FTIR analysis was performed using PA and liquid cell infrared spectroscopy. The PA
results were inconclusive due to insufficient signal to noise ratio in the region of interest
(approximately 1680 cm -1 to 1720 cm -1 ). It appeared that the number of co-added scans (512 in
this case) at an OPD velocity of 0.5 cm/sec was insufficient. Liquid cell spectra of the extracted
asphalt is shown in figure 2-2.2.17.
35

(a)
(b)
PA intensity (arbitrary units)
2.00
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.00
2000.0 1900 1800 1700 1600 1500 1400 1300
cm-1
1200 1100 1000 900 800 700 600.0
Figure 2-2.2.17. Liquid-cell transmission spectra. (a) Red: spectrum of asphalt recovered from
the edge of LTA3. Green: spectrum of asphalt recovered from the center of LTA3.
Blue: spectrum of asphalt recovered from the center of STA. (b) expanded view 1770 cm -1 to
1840cm -1 . Spectra were normalized to the umbrella bending band at 1376 cm -1 .
36

The increase in carbonyl at the center of LTA3 compared to the center of STA suggests
significant aging occurred during the eight-day oven aging period. The apparent carbonyl
gradient from the center to the edge in LTA3 suggest the oxidation reaction is diffusion
controlled and that the core has increased anisotropy due to aging.
Since the cores were prepared using AAD-1 asphalt, the observed differences in carbonyl content
were further quantified by estimating G* as shown in figure 2-2.2.18. The asphalt at the center
of STA had a G* of 10,600 Pa (at 60˚C and 10 radians/sec). The estimated G* at the center and
edge of LTA3 was 17,000 and 27,500 Pa, respectively. The complex shear modulus of AAD-1
(at 60˚C and 10 radians/sec) after standard PAV aging (20 hours, 300 psi) was 14,700 Pa., which
is somewhat less than the G* at the center of LTA3, suggesting the eight-day oven aging effect is
more severe than the standard PAV test.
Since differences in aging in the presence of aggregate at atmospheric pressure compared to
aging without aggregate at high pressure are not well understood, these results must be
considered preliminary. Some aggregates may have a catalytic effect on oxidation that is not
currently accounted for in the standard PAV test.
Log G* , Pa, 60C, 10 rad/sec
6.00
5.50
5.00
4.50
4.00
3.50
2.75E+04 Pa
1.70E+04 Pa
1.06E+04 Pa
37
y = 6.92x + 1.74
R 2 = 0.99
Linear (PAV 60C
and 80C points)
3.00
0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6
Normalized Carbonyl (total peak ht) Absorbance
Unaged
RTFO
PAV 100C
PAV 60C
PAV 80C
STA center
LTA3 center
LTA3 edge
Figure 2-2.2.18. Estimated G* of recovered asphalt from the center of STA and the center and
edge of LTA3. Correlation plot of G* versus carbonyl peak height is based on AAD-1 60˚C and
80˚C PAV’ed asphalt. Note: the infrared spectra were normalized to the umbrella bending band
at 1376 cm -1 . Unaged, RTFO and PAV 100˚C points were not included in the linear regression.

Arizona FHWA/WRI validation site
One of the objectives of this study is to validate the accuracy of laboratory fundamental material
property tests using field performance data. Table 2-2.2.5 shows field pavement performance
data that was collected in 2006 after 5 years of service. The distress survey was performed by
using the Distress Identification Manual for the Long-Term Pavement Performance Program (1).
It can be seen that asphalts from different sources perform quite differently in the field pavement.
Asphalt AZ1-1 has developed the most cracking after 5 years of pavement service, based on nonwheel
path longitudinal cracking.
Table 2-2.2.5. Distress measurements of four asphalts after five years pavement service.
Asphalt
AZ1-1
AZ1-2
AZ1-3
AZ1-4
2006 Survey = 5 years in Service
Fatigue Cracking,
Longitudinal Cracking, m
m 2 Wheel Path Non-Wheel Path
3.9
0.0
0.0
3.3
0.0
14.5
0.4
28.1
10.0
1.80
0.6
0.0
0.0
0.0
4.4
5.7
38
120.6
275.7
59.8
32.8
6.3
4.5
111.8
22.8
Transverse
Cracking, m
In a rheological context the term “dynamic measurement” usually refers to an experiment in
which either, the stress or the strain varies harmonically with time. Materials under an action of
shear stress always produce shear strain. The phase angle and the amplitude ratio of the stress to
the strain depend on the material and can be regarded as material properties although, in general,
both will vary with frequency. These two frequency-dependent parameters are required to
determine the strain for a given stress, such as the amplitude of the component of strain which is
in phase with the stress or the amplitude of the component of strain out of phase with the stress.
Instead of investigating the conventional storage modulus (G*cosδ) and/or loss modulus
(G*sinδ), the complex modulus and phase angle were used together in a unique manner. It is
believed that the phase angle is an important parameter for characterizing the flow properties of
asphalt. The phase angle indicates the level of viscoelasticity that exists in the asphalt. It is
always prudent to have a certain level of viscous flow behavior in an oxidized asphalt to provide
for the relaxation of stress. In other words, an asphalt exhibiting a higher strain to failure after
aging is more resistant to thermal or fatigue cracking than an asphalt binder with a lower strain to
failure at the same aging condition. It is well recognized that as asphalts undergo oxidative
aging, their flow behavior becomes more complex or non-Newtonian. Since the level of age
hardening is of primary concern when comparing aged asphalts, it is reasonable to assume that
the lower the phase angle at the same stiffness, the more susceptible an asphalt becomes to
fatigue cracking. With this in mind, the complex modulus (G*) versus phase angle (δ), based on
master curve at a reference temperature of 40°C for all four asphalts with respect to different
field aging times from neat asphalt to 4 years old top half inch, are plotted and presented in
8.0
4.8
0.0
0.0
0.0
0.0
1.6
23.4

figure 2-2.2.19 to show the correlation of rheological properties to field cracking performance. It
can be seen that different asphalts oxidized to the same stiffness have different phase angles.
The higher phase angle at the same oxidation stiffness indicates the asphalt has better flow
properties. Based on figure 2-2.2.19, asphalt AZ1-1 has the lowest (smallest) phase angle at the
same oxidation stiffness, indicating this asphalt will tend to become more brittle earlier than the
other three asphalts when oxidized to the same stiffness. From this figure, one can see that the
ranking (cracking potential) from laboratory rheological data agrees well with field cracking
performance. In other words, asphalt AZ1-1 has developed the most cracking so far, followed by
asphalt AZ1-2, asphalt AZ1-4, and the least tendency to crack is asphalt AZ1-3.
Complex Modulus, G*, Pa
1e+7
8e+6
6e+6
4e+6
2e+6
0
Master Curve at 10 rad/s
4th Year
30 40 50 60 70 80
Phase Angle, degree
39
Neat
AZ1-1
AZ1-2
AZ1-3
AZ1-4
Figure 2-2.2.19. Complex modulus versus phase angle with respect to
different aging times for four asphalts.
To further elucidate how phase angle relates to the flow properties of asphalt binder, the phase
angle was plotted against with reduced frequency (master curves) (figure 2-2.2.20) and
temperature (figure 2-2.2.21) for original asphalt, asphalt extracted from 4-year pavement, and
asphalt subjected to laboratory PAV aging at different aging times. A typical phase angle master
curve plot is shown in figure 2-2.2.20. The phase angle decreases as a sigmoid shape as
frequency increases. Figure 2-2.2.21 shows a similar plot for phase angle versus temperature.
All solid symbols along with solid lines represent all laboratory aging at different aging times.
The circular solid symbol represents the control sample, neat asphalt without any aging. Square,
diamond, inverted triangle, and triangle solid symbols represent 96 hours (red), 192 hours
(green), 336 hours (orange), and 504 hours (light blue), respectively, in PAV at 60°C. The
hollow symbols along with dash lines all represent 4-year old shoulder pavement at different
slices, top half inch (dark blue), 2 nd half inch (red), 3 rd half inch (dark purple) and bottom half
inch (dark cyan). Careful examination shows that the data plotted in figure 2-2.2.21 are

essentially a mirror image of the data plotted in figure 2-2.2.20, suggesting that the high
frequency in the dynamic shear test is equivalent to the inverse of temperature, and that high
temperatures represent low frequencies.
Phase Angle, degree
90
80
70
60
50
40
30
20
10
0 hr
96 hrs
192 hrs
336 hrs
504 hrs
4 yrs/Top Slice
4 yrs/2nd Slice
4 yrs/3rd Slice
4 yrs/Bottom Slice
0
1e-8 1e-6 1e-4 1e-2 1e+0 1e+2 1e+4 1e+6 1e+8
Reduced Frequency, rad/s.
40
AZ1-1 Lab Aging at 60°C
Ref. Temp. =40C
Figure 2-2.2.20. Phase angle as a function of frequency for asphalt AZ1-1
Phase Anlge at 10 rad/s, degree
90
80
70
60
50
40
30
20
0 hr
96 hrs
192 hrs
336 hrs
504 hrs
4-Year/Top Slice
4-Year/2nd Slice
4-Year/3rd Slice
4-Year/Bottom Slice
10
AZ1-1 Lab PAV Aging at 60°C
0
-60 -40 -20 0 20 40 60 80 100
Temperature, °C
Figure 2-2.2.21. Phase angle as a function of temperature for asphalt AZ1-1
before and after lab and field aging.

The majority of the results were presented in a journal article that will be published in the
proceedings of the 52 nd annual conference of Canadian Technical Asphalt Association in
November 2008 in Saskatoon, Saskatchewan.
Conclusion
The FTIR spectroscopic survey presented here provides a framework for further FTIR analysis
of complex pavement mastics including surface samples consisting of photo-oxidized asphalt
and aggregate with varying mineralogy. The results of this analysis suggest asphalt spectral
components can be removed from combined spectra of asphalt and aggregate. Asphalt PA
spectra compared favorably to liquid-cell spectra. Signal to noise ratios were lower for the PA
technique, however the PA signal to noise ratio can be significantly improved with additional coadded
scans. It remains an open question as to whether FTIR pavement surface spectra will be
predictive of the bulk mechanical properties of the pavement.
The complex shear modulus of AAD-1 (at 60˚C and 10 radians/sec) after standard PAV aging
(20 hours, 300 psi) was significantly less than the complex shear modulus of the asphalt
recovered from the edge and center of the LTA3 core (8 days oven aging at 85˚C).
At the Arizona field validation site, after five years in-service test sections constructed with
asphalts of similar performance grade but from different sources show significant differences in
the levels of pavement distress. Asphalt AZ1-1 has developed the most cracking based on nonwheel
path longitudinal cracking.
Work to be Conducted Next Quarter
• Investigations next quarter and probably several quarters after will include:
o Continue FTIR and rheological analysis of the validation site asphalts and
validation site pavement material to investigate photo-oxidation at the surface and
the extent of oxidation below the surface.
o Evaluate the variation in carbonyl moieties between field and PAV aged asphalts
due to, for example, aggregate catalytic effects.
o Expand the chemometric calibration data set to improve and verify the strength of
the observed statistical correlations reported last quarter.
o Explore the kinetic differences observed with regard to asphalt source.
o Evaluate solvent defined fractions to assess the contribution of these components
to physicochemical changes in asphalt due to aging.
o Apply the recently developed Hirsch model to evaluate the potential for
prediction of E* from carbonyl and other infrared derived indices.
o Perform a preliminary investigation to evaluate the efficacy of infrared
spectroscopy in evaluating steric and physical hardening. Infrared analysis may
show differences in amorphous (rapidly quenched) asphalt compared to more
crystalline asphalt (cooled slowly). Infrared spectra may also show subtle
41

differences in the degree of hydrogen bonding in undisturbed asphalt at different
temperatures and time intervals.
● Construct oxidation master curves for asphalts that were laboratory aged in PAV at
different durations and correlate master curve parameters (i.e., shift factor and rheological
index) to chemical parameters (i.e., carbonyl content and compatibility parameters) and
further to the field pavement performance.
● The same samples that were laboratory aged in PAV at 60°C will be subjected to the
same PAV aging test at higher aging temperatures to develop aging kinetic master curves
to further assist the revised mechanistic empirical pavement design guide.
Problems and Solution to Problem
There were no problems under this task for this quarter.
References
Al-Azri, N. A., S. H. Jung, K. M. Lunsford, A. Ferry, J. A. Bullin, R. R. Davison, and C.
J.Glover, 2006, Binder Oxidative Aging in Texas Pavements: Hardening Rates, Hardening
Susceptibilities, and the Impact of Pavement Depth. Paper accepted for presentation at the 2006
TRB January conference, Washington, D.C., 2006.
Arnold, T. S., M. Rozario-Ranasinghe, and J. Youtcheff, 2005, Determination of Lime in Hot
Mix Asphalt. Paper submitted to Transportation Research Board, November 2005.
Bell C. A. , J. J. Fellin, and A. J. Wieder, 1994, Field Validation of Aging Procedures for
Asphalt-Aggregate Mixtures. Journal of the Association of Asphalt Paving Technologists, 63:
45-80.
Christensen, D. W., and R. F. Bonaquist, 2006, Volumetric Requirements for Superpave Mix
Design, NCHRP 567. National Cooperative Highway Research Program.
Coons, R. F., and P. H. Wright, 1968, An Investigation of the Hardening of Asphalts Recovered
from Pavements of Various Ages. Journal of Association of Asphalt Paving Technologists, 37:
510-528.
Drapcho, D. L., R. Curbelo, E. Y. Jiang, R. A. Crocombe, and W. J. McCarthy, 1997, Digital
Signal Processing for Step-Scan Fourier Transform Infrared Photoacoustic Spectroscopy.
Applied Spectroscopy, 51 (4): 453-460.
Farrar, M. J., P. M. Harnsberger, K. P. Thomas, and W. Wiser, 2006, Evaluation of Oxidation in
Asphalt Pavement Test Sections after Four Years of Service. Proc., International Conference on
Perpetual Pavement, September 2006, Columbus, Ohio.
Heukelom, W., 1973, An Improved Method of Characterizing Asphaltic Bitumens with the Aid
of their Mechanical Properties. Journal of Association of Asphalt Paving Technologists, 42: 67-
98.
42

Hirschfeld, T., 1976, Computer Resolution of Infrared Spectra of Unknown Mixtures. Analytical
Chemistry, 48 (4): 721-723.
Houston, W. N., M. W. Mirza, C. E. Zapata, and S. Raghavendra. National Cooperative
Highway Research Program. Environmental Effects in Pavement Mix and Structural Design
Systems, NCHRP 9-23 Preliminary Draft Final Report Part 1, September 2005.
Jackson, K. D. O., 1998, A Guide to Identifying Common Inorganic Fillers and Activators Using
Vibrational Spectroscopy. Accessed from The Internet Journal of Vibrational Spectroscopy, 2
(3): http://www.ijvs.com/volume2/edition3/section3.html#jackson
Jones, R. W., and J. F. McClelland, 1996, Quantitative Depth Profiling of Layered Samples
Using Phase-Modulation FT-IR Photoacoustic Spectroscopy. Applied Spectroscopy, 50 (10):
1258-1263.
Jones, R. W., and J. F. McClelland, 2002, Quantitative Depth Profiling Using Saturation-
Equalized Photoacoustic Spectra. Applied Spectroscopy, 56 (4): 409-418.
Koenig, J. L., L. D’Esposito, and M. K. Antoon, 1977, The Ratio Method for Analyzing Infrared
Spectra of Mixtures. Applied Spectroscopy, 31 (4): 292-295.
Legodi, M. A., D. de Waal, and J. H. Potgieter, 2001, Quantitative Determination of CaCO3 in
Cement Blends by FT-IR. Applied Spectroscopy, 55 (3): 361-365.
McClelland, J. F., R. W. Jones, and S. J. Bajic, 2002, FT-IR Photoacoustic Spectroscopy, chapter
from Handbook of Vibrational Spectroscopy, J. M. Chalmers and P. R. Griffiths, eds., John
Wiley & Sons, Ltd.
Mirza, M. W., and M. W. Witczak. “Development of a Global Aging System for Short and Long
Term Aging of Asphalt Cements. Journal of Association of Asphalt Paving Technologists, Vol.
64, 1995, pp. 393-431.
National Cooperative Highway Research Program. Development of the 2002 Guide for the
Design of New and Rehabilitated Pavement Structures. NCHRP 1-37A, Final Report, National
Research Council, 2004.
Norton, G. A., and J. F. McClelland, 1997, Rapid Determination of Limestone Using
Photoacoustic Spectroscopy. Minerals Engineering, 10 (2): 237-240.
Robl, T. L., D. Milburn, G. Thomas, J. Groppo, K. O’Hara, and A. Haak, 1991, The SHRP
Materials Reference Library Aggregates: Chemical, Mineralogical, and Sorption Analyses,
SHRP-A/UIR-91-509, Strategic Highway Research Program, National Research Council,
Washington, DC.
43

Rosencwaig, A., and A. Gersho, 1976, Theory of the photoacoustic effect with solids. Journal of
Applied Physics, 47 (1), 64-69.
Smith, B. C., 1996, Fundamentals of Fourier Transform Infrared Spectroscopy. CRC Press,
Boca Raton, FL.
Standard Practice for Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel
(PAV), AASHTO Designation: R28-02, America Association of State Highway and
Transportation Officials, Washington, D.C.
Strategic Highway Research Program, 1993, Distress Identification Manual for the Long-Term
Pavement Performance Project, SHRP-P-338, National Research Council, Washington, DC.
Vassallo, A. M., P. A. Cole-Clarke, L. S. K. Pang, and A. J. Palmisano, 1992, Infrared Emission
Spectroscopy of Coal Minerals and their Thermal Transformations. Applied Spectroscopy, 46
(1): 73-78.
44

SUBTASK 2-3. NANOTECHNOLOGY: AFM ANALYSIS OF ASPHALT THIN-FILM
MICROSTRUCTURE PHENOMENOLOGY
Task Manager: T. Pauli
Personal: W. Grimes, J. Miller, J. Beiswenger
Statement of Problem
Asphalt pavements are known to fail over time by a combination of different mechanisms. The
modes of failure of asphalt pavements that are commonly sited are embrittlement due primarily
to steric and oxidative aging, fatigue cracking due primarily to loading cycles and moisture
(traffic), rutting due primarily to densification and plastic flow, thermal cracking due primarily to
low temperature embrittlement, and formation of potholes due primarily to breakdown of the
sub-base structure. It is further contended in the pavement community that all of the
aforementioned modes of failure are some how influenced by environmental conditions like
seasonal temperature swings and the presence of water. Why do pavements constructed to the
same specifications and subjected to similar environmental conditions and traffic loading fail at
different rates by different failure modes when different materials (e.g., asphalts and aggregates
derived from different sources) are used to construct the pavement?
Approach
In this subtask we have asked the question why pavements constructed with asphalt derived from
different crude sources, if all other variables were to be kept the same, perform differently in
terms of moisture compounded fatigue resistance. For example, pavement cracking is often
observed to form distinct patterns during the lifespan of the pavement. In many other fields of
material science, metallurgy for example, pattern forming cracking has been successfully
correlated to the formation of microstructural grain boundaries which originate in these materials
during casting [Cappelli et al. 2008; Bian and Taheri 2008]. This same pattern cracking
phenomena can also be applied to paving materials [Robertson et al. 2005, 2006]. The approach
will be to develop quick and inexpensive experimental techniques derived from other fields of
materials nano-science. Results from these tests can then be combined with chemo-mechanical
models of asphalt-aggregate composite materials to predict pavement performance.
Goal
The goal of this work is to gain a more fundamental understanding of the composition of asphalt
concrete paving materials and how it relates to pavement performance (specifically fatigue
cracking/self healing compounded by the presence of moisture).
Support of FHWA Strategic Goals
This work plan supports the following FHWA focus areas. Pavement Design and Analysis: This
work will provide a more fundamental understanding of the physico-chemical nature of asphaltbinder
and chemo-mechanical properties of mastics as they relate to pavement performance.
Optimum Pavement Performance: A more fundamental understanding of the physico-chemical
45

nature of asphalt-binder will lead to better characterization and development of modified asphalts
based on better materials selection criteria. Environmental Stewardship: A more fundamental
understanding of the physico-chemical nature of asphalt-binder will lead to better
characterization of warm mix asphalts and recycled asphalt pavement technologies and should
ultimately result in refinement of the present technologies as well as lend insight into developing
other types of “green” technology.
Introduction/Hypotheses
Kandhal and Chakaraborty [1996] have suggested, based on calculations of gradation void-space
volumetrics of aggregate in common pavement mix designs, that the average film thickness of
asphalt in a pavement has a dramatic effect upon both the resilient modulus and viscosity of a
mix. As the average film thickness is decreased from around 15 microns to 3 microns, both the
resilient modulus and the viscosity are observed to increase almost exponentially. Kandhal and
Chakaraborty [1996] also suggest that the optimum film thickness of asphalt in a mix is between
8-10 microns with thinner films producing brittle mixes and thicker films being susceptible to
increased rutting. These observations suggest that “molecular ordering” of asphalt thin-films in
mastic occurs, and that this molecular ordering becomes more pronounced with decreasing the
asphalt film thickness. Thus, the potential for crack initiation in most “composite” materials is
shown to be related to the development of grain boundaries. These boundaries are caused by
molecular ordering phenomena corresponding to the development of individual material phases
within these types of systems [Cappelli et al. 2008; Bian and Taheri 2008]. Grain boundaries
have been observed in (1) crystals, the cutting of diamonds for example, with fracturing
occurring along lattice plane flaws of the crystal, (2) the crack-flaws that form in ice cubes as a
function of cooling rate and impurities in the water, or (3) the development of dislocations in
binary metal alloy solidification processes. Micro structuring of chemically distinct phases in
asphalt “binder”, particularly at asphalt-aggregate interfaces, which originate at the micro scale
due to the heterogeneous nature of these materials could contribute to the formation of such grain
boundaries that are crack initiation points.
Crack initiation and propagation in metals and crystalline materials generally falls within the
category of brittle fracture. However, polymers are more amorphous by nature and fracturing
becomes more ductile which renders the system more difficult to model. One may hypothesize
that the large number of different petro-organic-type molecules (asphalt) interact with
themselves and with the mineral surfaces (aggregate and fines) to form distinct chemical phases
that somehow determine the viscoelastic properties of the binder in the pavement. These
properties can then be used to determine the tendency of a pavement to fracture and self-heal,
which is further compounded by variations in temperature as well as moisture.
In this subtask, uniform asphalt films are studied at near-molecular (< 5-nm), nano (1-100-nm),
meso (10’s-100’s-nm) and microscopic (100’s-1000’s-nm) scales. Scanning probe microscopy
techniques (i.e., atomic force microscopy) are employed to correlate the kinetic and
thermodynamic processes of phase transformation phenomena of different chemical moieties
present in asphalt with the materials’ performance in roadways. Asphalts, which differ by crude
source, have historically been defined by chemists by their compositionally unique chemical
classes of molecules. This is a simplified approach given that petroleum asphalt is potentially
46

comprised of tens of thousands of different types of molecules that otherwise would need to be
characterized if a totally fundamental approach to the problem were to be considered.
It has also been observed in previous experiments [Robertson et al. 2005, 2006] that different
asphalts tend to form self-ordered microstructural “features” to different degrees with different
crude sources. This was demonstrated at the asphalt-air free surface interface when prepared as
solvent spin-cast, thin-film coatings with thicknesses ranging from 3 microns to as thin as 150
nm. Generally speaking, structures with clearer phase boundaries are observed as the thickness
of these “ultra-thin” films is decreased below 2 microns [Robertson et al. 2005]. Thicker films
tend to exhibit larger structures, particularly the bumble bee shaped structures that appear to
“grow” to a limiting size in 10’s of microns thick films with less distinguishable interface
boundaries. Inevitably, the formation of these microstructures in very thin films of asphalt leads
directly to the development of interfacial grain boundaries between chemically different phases
of materials. These interfacial grain boundaries then constitute discontinuities in the film that
could lead to fracture initiation in actual pavement structures whether they were to rapidly
develop under normal paving conditions or gradually development over time.
The current experimental approaches should not be considered a direct representation or
simulation of pavement structures. Contrarily, in the present research, asphalts are prepared as
thin-films that are similar in magnitude to the average thicknesses of asphalt films estimated for
pavements (e.g., 5-15 microns or 8 to 10-microns on average [Kandhal and Chakaraborty 1996;
Kandhal et al. 1998]). In most cases they are prepared as ultra-thin-films, representing
“theoretical” slices of asphalt very close to and in contact with an aggregate interface. These
systems are then investigated in order to determine the kinetics of microstructure formation as a
function of film-thickness, temperature fluctuation, and method of film preparation (e.g., solvent
spin-coating techniques). This approach has also been adopted due to the difficulty of
experimentally observing asphalt-aggregate interfacial interactions. As a result, thin-film
experimentation on ideal systems combined with computation simulations will be needed to
adequately study these types of systems in order to make recommendations as to how to prolong
the lifecycle of pavements due to fatigue.
Much of the motivation behind the work that has been proposed in this subtask stems from the
desire to know why and how the microstructures that have been observed in these materials, as
observed by atomic force microscopy [Loeber et al. 1996; Pauli and Grimes 2003], could
contribute to pavement performance. Consequently, it is hypothesized that the thermo-kinetic
processes of phase transformations (i.e., molecular order-disorder kinetics) are anticipated to
directly influence the rheological properties of these materials at the mastic thin-film interfaces
in actual pavement structures. These processes include; wax melting-crystallization, potential
for flocculation of asphaltenes, chromatographic interactions of polar and aromatic molecules
with mineral aggregates/filler surfaces, and others that are influenced by fluctuations in
temperature and shear rate. An improved understanding of the correlations between these phase
transformations and rheological properties will help explain the nature of fatigue damage and
subsequent self-healing phenomena brought on during rest periods. In other words, how does the
asphalt chemical composition lead to the order-disorder transitions that produce micro
structuring at interfacial boundaries and thin-film regions? Also, how does this ultimately lead
47

to crack initiation brought on by fatigue, followed by pavement failure, as a function of
environmental conditions and loading cycles?
It has also been hypothesized that the process of combining asphalt with aggregate at high
temperatures, placing this composite material in a roadway, and then allowing it to cool and cure
may be modeled as a solidification process. Solidification processes are generally considered to
be non-equilibrium thermodynamic processes where fluxes in composition and thermal gradients
are driven by both mechanical and thermodynamic forces (e.g., chemical potential, surface
tension and pressure differentials), thereby constituting mechanisms for order-disorder
transitions that result in the formation of microstructural grain boundaries. These order-disorder
transitions could also be responsible for cohesive failures when, for example, subjected to
temperature fluctuations, shear and compressive loading, and exposure to moisture. Thus, a
thorough investigation of the “chemical-action” of asphalt binder as it exists in pavements is
warranted in order to define the interfacial boundary conditions and kinetic driving mechanisms
that describe the formation and destruction of microstructural phases in asphalt when adopted by
continuum mechanical modeling approaches used to simulate fatigue damage.
Background
In this subtask a somewhat simplified view has been taken to describe the composition of asphalt
thin-films in a “pavement structure.” This is particularly true at the mastic level, which may be
viewed as if one were building sandcastles with asphalt in place of water as the binding agent to
adhere and maintain structural form to the system. While constructing such a system, many
different forces can be considered that could contribute to the strength of the system. These
forces may include the capillarity and adhesion between asphalt and aggregate fine particles, the
viscoelastic response of the asphalt thin-films between aggregate particles to compression and
shear forces, and breakdown of both the cohesive strength of the asphalt and the adhesive bonds
between asphalt and aggregate in the presence of moisture. For the sake of the present
discussion, figure 2-3.1 depicts a volume element slice of an 8-μm thick asphalt thin-film
adhering three aggregate fine particles together in a mastic sub-structure of a pavement structure.
If the presence of the aggregate particles in this system have an influence on the ordering of the
asphalt molecules at the interface (e.g., first monolayer, first 200-nm, first 1.0-μm, etc) at what
distance away from this interface would long-range molecular ordering subside? At what
effective distance away from this interface would the asphalt layer have properties similar to a
bulk phase state? In the present scenario, asphalt “molecules” present at the interface would
experience the strongest interactions with the aggregate surface. Four microns out into the film,
approximately halfway between two of these particles, the asphalt should exhibit properties more
closely resembling that of asphalt in the “bulk” state.
Based on AFM surface imaging it has been observed that thicker thin-films of asphalt (>4.0 μm)
do not differ that much in appearance from films that are 10’s of microns or even 1.0-mm in
thickness. As these films are decreased to

to the aggregate fine particle interface influence the flow properties of the molecules farther
away from the interface and the adhesive properties of the molecules in direct contact with the
interface?
Figure 2-3.1. Pictorial of a volume element slice of an 8μm thick film adhering three
Aggregate fine particles together in a mastic sub-structure of a pavement structure D > d = 8μm.
49

Work Conducted This Quarter
A Topical Report, anticipated to be delivered early in the next quarter, summarizes findings from
the past two to three years of research. This report describes the present state of practice for the
investigation of the compositional nature of asphalts and aggregates, as studied by atomic force
microscopy and presents modeling approaches for integrating asphalt/aggregate physichemical
properties into continuum-damage models of pavement performance. Finally, this report will
suggest how work elements from the ARC work plan; ARC Work Element Subtask M1b-2-
Work of Adhesion at Nano-Scale using AFM, ARC Work Element Subtask M2a-2-Work of
Cohesion Measured at Nano-Scale using AFM, Work Element Subtask F1d-7-Coordinate with
AFM Analysis, and Work Element F3a-Asphalt Microstructural Modeling [Western Research
Institute 2008], will be coordinated with this task.
Work Plan Next Quarter
• Research conducted to date in this subtask has been primarily concerned with defining
and measuring compositional properties of material thin-films which exhibit and/or cause
crazing phenomena. This is thought to be a result of material discontinuity
(heterogeneity) caused by variations in wax and asphaltene content in the film. It is
hypothesized that this heterogeneity may be considered an indicator of cracking and
embrittlement in asphaltic materials. Thus, a natural avenue for future research would
then be to conduct measurements at micron and nano-scale that focus more on
physical/rheological properties of thin films related to the stiffness and embrittlement
propensity, in addition to continuing compositional/chemical characterization of these
materials, in order to draw correlations between compositional and rheological properties.
• In the next quarter, a revised SARA separation method will be employed to separate
asphalt into saturate, aromatic, polar aromatic, and asphaltene fractions. In this
procedure, iso-octane asphaltene/maltene separations will be conducted, and the maltenes
from this separation will be further separated employing the modified SARA separation
procedure. Based on the information gained from these studies, a revised method for
ASTM 4124 will be submitted to the ASTM D4 committee for approval.
• A solidification stage is being assembled as part of the atomic force microscope by
employing both a heating stage and a cooling stage fabricated along with micrometer
positioning devices, figure 2-3.2. This apparatus will be used to impart a thermal
gradient across an asphalt thin-film resulting in a moving solidification front (liquidsolid)
interface that may be monitored in time with AFM. Furthermore, an automated
wetting apparatus will also be assembled to better control the spin casting procedure and
to observe and quantify lubrication dynamics (see figure 2-3.3). Finally, metrology and
nanoindentation accessories have been added to the existing AFM equipment to enhance
capabilities to include micro/nano-rheological testing of material thin-films.
50

a. Sample, b. cold stage, c. hot stage, d. micro positioner, e. micro positioner, ΔV- thermal
controller, ΔT-digital thermoter.
f. digital positioning stage on which the solidification stage sits
Figure 2-3.2. Diagram of a proposed solidification stage to be assembled
to work with existing AFM equipment
51

a. robotic arm and nano-syringe pump for b. digital camera microscope for imaging
precision dispensing of solutions on spinning spreading solution drop glass slides
c. Spin caster
Figure 2-3.3. Diagram of a proposed dynamic wetting apparatus to better control, measure and
quantify wetting of asphalt on glass slides.
52

Problems and Solutions to Problems
An upgrade to the present AFM equipment, which includes a solidification stage, a dynamic
wetting apparatus and metrology and nanoindentation capabilities will lead to the capability of
measuring micro and nano-rheological properties and flow properties of asphalt thin-film
materials, in addition to material composition. It is anticipated that these upgrades will lead to
very rapid methods of analysis of asphalt binders that predict, individually, compositional and
rheological properties, as well as study how these properties are intimately related to the binding
action of pavement grade asphalts.
References
ASTM D4124-01, 2002, Standard Test Method for Separation of Asphalt into Four Fractions.
Annual Book of ASTM Standards, Road and Paving Materials; Vehicle-Pavement Systems,
Section 4, vol. 04.03. ASTM International, West Conshohocken, PA, 821-829.
Bian, L., and F. Taheri, 2008, Fatigue fracture criteria and microstructures of magnesium alloy
plates. Materials Science and Engineering A, 48774–85.
Cappelli, M. D., R. L. Carlson, and G. A. Kardomateas, 2008, The transition between small and
long fatigue crack behavior and its relation to microstructure. International Journal of Fatigue,
30: 1473–1478.
Kandhal, P. S., and S. Chakaraborty, 1996, Effect of Asphalt Film Thickness on Short and Long
Term Aging of Asphalt Paving Mixtures. NCAT Report No. 96-01.
Kandhal, P. S., K. Y. Foo, and R. B. Mallick, 1998, A Critical Review of VMA Requirements in
Superpave. NCAT Report No. 98-1.
Loeber, L., O. Sutton, J. Morel, J.-M. Valleton, and G. Muller, 1996, New direct observations of
asphalts and asphalt binders by scanning electron microscopy and atomic force microscopy.
Journal of Microscopy, 182(1): 32-39.
Pauli, A. T., and W. Grimes, 2003, Surface Morphological Stability Modeling of SHRP
Asphalts. American Chemical Society Division of Fuel Chemistry Preprints, 48(1): 19-23.
Robertson, R. E., K. P. Thomas, P. M. Harnsberger, F. P. Miknis, T. F. Turner, J. F. Branthaver,
S-C. Huang, A. T. Pauli, D. A. Netzel, T. M. Bomstad, M. J. Farrar, J. F. McKay, and M.
McCann. “Fundamental Properties of Asphalts and Modified Asphalts II, Final Report, Volume
I: Interpretive Report,” Federal Highway Administration, Contract No. DTFH61-99C-00022,
Chapters 1-4 submitted for publication, November 2005.
Robertson, R. E., K. P. Thomas, P. M. Harnsberger, F. P. Miknis, T. F. Turner, J. F. Branthaver,
S-C. Huang, A. T. Pauli, D. A. Netzel, T. M. Bomstad, M. J. Farrar, D. Sanchez, J. F. McKay,
and M. McCann. “Fundamental Properties of Asphalts and Modified Asphalts II, Final Report,
53

Volume I: Interpretive Report,” Federal Highway Administration, Contract No. DTFH61-99C-
00022, Chapters 5-7 submitted for publication, March 2006.
Western Research Institute, 2008, Asphalt Research Consortium Annual Work Plan for Year 2,
April 1, 2008-March 31, 2009. Prepared for Federal Highway Administration, FHWA Contract
No. DTFH61-07-H-00009, January 2008.
54

SUBTASK 2-4. LOW-TEMPERATURE PROPERTIES
Statement of Problem
The contributions of asphalt source (or chemical composition) and environmental conditions to
pavement low-temperature performance are not completely understood. Although the current
purchase specifications seem to prevent early failure, there is little confidence in any prediction
of long-term behavior.
Approach
Use differential scanning calorimetry and stress relaxation rheometry to determine asphalt
component influences on low-temperature properties. This effort will validate the use of lowtemperature
stress relaxation tests for determining asphalt mechanical properties.
Use a similar approach to determine the influence of oxidative aging on low-temperature
properties.
Goal
The goal of this work is to provide the low-temperature information to support the development
of an advanced fundamental understanding of how chemical types, reactions, and structures
determine the physical properties of asphalts and the long-term performance of asphalt
pavements.
Support of FHWA Strategic Goals
The work conducted in this subtask to better understand low-temperature asphalt behavior
supports the FHWA strategic goal that addresses optimizing pavement performance through the
development of longer lasting asphalt pavements, thus decreasing the demand for reconstruction
of pavements.
Work Conducted This Quarter
According to the Contract DTFH61-07-D-00005 documents, Year-2 work on this topic must be
shifted to Subtask 3-7. No Task 3 research has been authorized.
55

SUBTASK 2-5. MODIFIED ASPHALTS (continuing on Year-1 funds)
Statement of Problem
Asphalt modifiers are often added to meet binder purchase specifications. Common modifiers
include polymers to improve rutting resistance, lime and antistrip additives to mitigate moisture
damage, polyphosphoric acid for rutting resistance, and reclaimed asphalt pavement (RAP) for
reducing costs. New modifiers are also being introduced to enable warm-mix asphalt (WMA)
technologies where mix and compaction temperatures can be substantially reduced. One of these
modifiers is water (typically used to foam the asphalt), which improves the workability of
binders at mixing and laydown temperatures and appears to have little effect afterwards,
although there is some evidence that entrapped moisture may increase stripping [Hurley and
Prowell 2005]. In addition, the long-term effectiveness of some modifiers under highway
conditions is not known. Often, the mechanism of action of a modifier is understood only in an
empirical sense and the effective treatment levels and economical treatment levels may differ. It
is also important to point out that modifier interactions may reduce effectiveness and waste
resources.
Approaches
The sensitivity of PPA-modified asphalts to environmental factors is being determined using
laboratory PAV aging tests on modified and unmodified asphalts in the presence and absence of
moisture in the oven. Analytical tests applied include spectroscopic (FTIR) and rheologic (DSR)
of the aged materials. Master curve and shift factors are used to quantify changes.
Nuclear magnetic resonance techniques are being applied to study the reactions between
phosphorous-containing additives including antistrips and PPA in asphalts.
Goals
The goal of this research is to develop a detailed description of the actions of modifiers in
asphalts while varying environmental conditions. Where feasible, efforts are directed toward
developing relationships for predicting long-term behavior from initial laboratory tests.
Support of FHWA Strategic Goals
The work conducted in this subtask supports the FHWA strategic goal that addresses
environmental stewardship and safety. State agencies need a better understanding of how and
when to use additives, such as recycled asphalt pavement (RAP), polymers and/or
polyphosphoric acid (PPA), to improve the performance of asphalt pavements. Obviously, better
performing and longer lasting asphalt pavements, which incorporate the use of RAP, lead to the
utilization of less asphalt, thus decreasing the demand for reconstruction of pavements and
incidentally safer roads.
57

Background
The addition of polyphosphoric acid (PPA) to asphalt binders is known to affect a number of
chemical and physical properties of the asphalts. However, the mechanisms by which this
happens are not well understood. Several possible mechanisms have been advanced, and it has
been noted that the mechanisms of action may be asphalt source related [Baumgardner et al.
2005]. In 2005, WRI initiated an investigation (subtask 14-4 of FHWA Contract DTFH61-99C-
00022) to elucidate the mechanisms of action of polyphosphoric acid (PPA) in asphalt. SHRP
asphalts ABD, AAD-1, and AAM-1 were modified with 1.5 mass percent of polyphosphoric acid
(105 percent). These modified asphalts were then used to verify observations reported by others.
These observations included: (1) an increase in the high-temperature PG grade, (2) a slow
increase in the complex modulus upon storage in a heated tank, (3) a decrease in chemical aging,
as defined by the amount of carbonyl-containing compounds produced, and (4) an increase in the
gel character of the modified asphalt, i.e. the modified asphalt becomes less compatible. The
work conducted at WRI not only confirmed these observations but also provided additional
insight into the mechanism of action of PPA. In general, it was concluded that, to a certain
extent, the impact of PPA modification on the rheological properties is related to the sol-gel
character of the asphalt. While a concentration of 1.5 wt % is considered too high for paving
applications, this was considered a reasonable concentration to look for chemical changes in
asphalt brought about by PPA. Others [Falkiewicz and Grzybowski 2004] have used up to 2 wt
% PPA to look for changes in asphalt behavior with PPA modification. Nonetheless, our study
indicates that PPA-modified asphalt binders should (1) increase early resistance of the pavement
to rutting by increasing initial stiffness and (2) extend the useful life of the pavement by
improving the low-temperature flow properties. These improved properties should result in both
reduced fatigue cracking and reduced low temperature cracking [Huang et al. 2008].
Based on current experiments and previous studies, it appears that there is a relationship between
physical properties (rheological) and a chemical property (carbonyl content) for unmodified
asphalt binders with respect to long-term oxidative aging. However, addition of PPA to asphalts
disturbs the linear relationship between physical and chemical properties of asphalt binders with
respect to their long-term aging.
Based on NMR spectroscopy and modified black plots, addition of PPA into asphalt binders does
not appear to significantly change the internal structure of asphalt binders by chemical reaction
(covalent). Another observation of the WRI work, using 31 P NMR, was the apparent hydrolysis
of polyphosphoric acid to phosphoric acid by residual water in asphalt [Miknis and Thomas
2008]. This was indicated in 31 P NMR spectra of PPA modified asphalts that showed the
disappearance of phosphorous resonances in the middle and terminal groups of phosphate chains
over time, with only a phosphoric acid resonance remaining.
Work Conducted This Quarter
During this quarter, work continued on the rheological analysis of the unmodified and acidmodified
asphalts that were PAV aged at 60°C in the presence of water.
58

Figure 2-5.1 shows the complex modulus of PPA modified asphalt ABD after PAV aging in the
presence of water as a function of frequency and a constructed oxidation master curve for the
same asphalt at 30°C. As seen from figure 2-5.1, the rheological properties of the asphalt binder
are dependent on aging time. As aging time is increased an increase in the complex modulus is
observed. This phenomenon is similar to the temperature dependency of asphalt binder, where
the complex modulus increases as temperature decreases.
Complex Modulus, Pa
1e+9
1e+8
1e+7
1e+6
1e+5
1e+4
1e+3
1e+2
0 hr
96 hrs
186 hrs
260 hrs
326 hrs
Master Curve
ABD/PPA, Moist
1e+1
PAV at 60°C
1e+0
1e-6 1e-4 1e-2 1e+0 1e+2 1e+4 1e+6 1e+8
Reduced Frequency, rad/s
59
30°C Data
Figure 2-5.1. Complex modulus as a function of frequency for different aging times along with
the constructed master curve for PPA modified asphalt ABD.
The Christensen-Anderson-Marasteanu (CAM) model used for shifting time-temperature data for
regular master curves was modified and then applied to construct the aging master curves
[Christensen and Anderson 1992; Ferry 1961; Zeng et al. 2001]. The equation is shown below.
*
Gg
G * ( ω , t)
=
(2-5.1)
ωc
k −1/
k
[ 1+
( ) ] '
ω
Where t = aging time,
G*g = glass complex modulus,
ω c = location parameter of frequency,
k = shape parameter, dimensionless,
ω’ = reduced frequency, is defined as aA(t)ω,
aA = aging shift factor, dimensionless.

All different aging times were shifted to zero aging time. The aging shift factor is the amount of
shift of the complex modulus at a given aging time to the reference aging time (zero aging time
in this case) to form a single curve. The values of these shift factors can be considered to be
modulus (stiffness) changes with respect to the modulus at the reference aging time, and give an
indication of how the properties of a material change with aging time.
Figure 2-5.1 also shows the constructed complex modulus oxidation master curve for asphalt
ABD mixed with 1.5% PPA with respect to different aging times. A well-defined curve can be
seen in the figure indicating that a similarity does exist between the effects of aging and
temperature. The logarithm of the aging shift factor is the amount of shift for the complex
modulus at a given aging time to the reference aging time to form a single curve. Figure 2-5.2
shows the shift factor as a function of PAV aging time for asphalt ABD and PPA-modified ABD
aged in the absence and presence of water.
As seen from figure 2-5.2, the curve of the aging shift factor is similar to that of viscosity-aging
kinetic curves for typical asphalts and is shear rate independent. On oxidation, asphalts show an
initial rapid rate of viscosity increase followed by a slower rate of viscosity increase. This
behavior has been attributed to the formation of sulfoxide and carbonyl products in the oxidation
process of asphalt binder when exposed to atmospheric oxygen in the pavement. As seen from
figure 2-5.2, addition of PPA to asphalts increases the amount of stiffness change with respect to
the stiffness at the reference aging time, indicating that addition of PPA has changed the aging
characteristics of asphalt binders. In addition, aging in the presence of water reduces the amount
of stiffness change with respect to the stiffness at the reference aging time for neat unmodified
asphalts. However, addition of water in the pressure aging oven increases the amount of
stiffness change for PPA modified asphalt binders.
Figures 2-5.3 and 2-5.4 show similar types of plots, aging shift factors versus PAV aging times
in the presence and absence of water, for asphalts AAD-1, AAM-1, and their PPA mixtures,
respectively. Again, it can be seen that addition of PPA to asphalts increases the amount of
stiffness change due to PAV aging. As seen from both figures 2-5.3 and 2-5.4, the aging shift
factors of PPA modified asphalts after PAV aging for 326 hours in the presence of water are
similar to those of the same PPA modified asphalts at the same aging time in the absence of
water. This suggests that PPA modified asphalts AAD-1 and AAM-1 aged at 326 hours in the
PAV in the presence of water have similar complex modulus to the same materials that were
subjected to the same aging time in the absence of water. However, it is uncertain if the reduced
complex modulus at the end of aging time of 326 hours in the presence of water is due to the
presence of moisture during PAV aging or experiment error. Nonetheless, more experiments
need to be conducted to verify this observation.
During the quarter, work also continued on the study of the behavior of phosphorous containing
additives in asphalt by using NMR techniques. In particular, NMR work continued on
characterizing the behavior of phosphate ester and amine antistrip agents in asphalt. In addition,
some exploratory measurements were made to determine the feasibility of using 31 P NMR to
determine moisture in asphalt.
60

Log a A
2.0
1.5
1.0
0.5
ABD, Dry
ABD, Moist
ABD/PPA, Dry
ABD/PPA, Moist
PAV at 60°C
0.0
0 100 200 300 400
Time in PAV, hrs
61
58°C Data
Figure 2-5.2. Aging shift factor as a function of PAV aging times for asphalt ABD and its PPA
mixtures before and after PAV aging in the presence and absence of water.
Log a A
2.5
2.0
1.5
1.0
0.5
AAD-1, Dry
AAD-1, Moist
AAD-1/PPA, Dry
AAD-1/PPA, Moist
PAV at 60°C
0.0
0 100 200 300 400
Time in PAV, hrs
58°C Data
Figure 2-5.3. Aging shift factor as a function of PAV aging times for asphalt AAD-1 and its
PPA mixtures before and after PAV aging in the presence and absence of water.

Log a A
2.5
2.0
1.5
1.0
0.5
AAM-1, Dry
AAM-1, Moist
AAM-1/PPA, Dry
AAM-1/PPA, Moist
PAV at 60°C
0.0
0 100 200 300 400
Time in PAV, hrs
62
58°C Data
Figure 2-5.4. Aging shift factor as a function of PAV aging times for asphalt AAM-1 and its
PPA mixtures before and after PAV aging in the presence and absence of water.
1H NMR of Phosphate Ester Antistrips
Additional NMR measurements were made on the phosphate ester antistrip agents that were
acquired last quarter. The phosphate ester antistrip agents were Innovalt W and KAO Gripper.
Innovalt W is a phosphated 2-ethyl hexanol antistrip (molecular formula: C8H19O4P, and
C16H35O4P2), with ingredients: phosphated 2-ethyl hexanol (C8H18O) (>82%, 2-ethyl hexanol

20
these resonances were incorrectly assigned, and now have been tentatively identified as due to
the protons in phosphoric acid. Phosphoric acid is used in preparation of the phosphate esters
and so these resonances would not be unexpected. When D2O was added, these resonances
disappeared due to rapid exchange of the OH proton with the deuterium in heavy water (D2O),
i.e.,
P-O-H + D2O P-O-D + DOH
New resonances appeared at 8.1 and 5.2 ppm. The resonance at 8.1 ppm was not identified; the
one at 5.2 ppm has been tentatively identified as water (HOD).
Innovalt W in H2O
Innovalt W in D2O
15
10
Figure 2-5.5. 1 HNMR spectra of Innovalt W and Kao Gripper in D2O and in H2O.
31 P NMR of Phosphate Ester Antistrips
5
0
-5
-10
20
In a previous quarterly report (Oct.-Dec., 2007) 31 P NMR measurements were made on binder
from four cells taken from the MN Road validation site. Three of the four cells used PPA
(115%) and a phosphate ester antistrip agent, Innovalt W. The 31 P NMR spectra did not show
the presence of the phosphate ester antistrip in the binder.
However, questions have been raised about whether PPA might react with the phosphate ester
antistrip when added to asphalt. Consequently, a NMR investigation has begun to look into this
matter. Initially, 31 P NMR spectra of the neat antistrips, and antistrips with PPA, but in the
absence of asphalt were acquired (figure 2-5.6). The spectra of the neat antistrips show a main
peak at ~0.7 ppm and a minor one at ~0.2 ppm. The minor resonance is better resolved in the
63
KAO Gripper in H2O
KAO Gripper in D2O
Innovalt W neat KAO Gripper neat
Proton Chemical Shift, ppm
15
10
Proton Chemical Shift, ppm
5
0
-5
-10

KAO Gripper. The minor resonance was not assigned, but is assumed to be due to a dimer of the
2-ethyl hexanol phosphate formed during preparation of the antistrip. The spectra of the Innovalt
W and KAO gripper show partial hydrolysis of the PPA caused by residual water which is
present in the antistrip agents. This is shown by the increase of the phosphoric acid resonance at
~1.7 ppm relative to the phosphate ester resonance at ~0.7 pm with time of setting.
There do not appear to be any reactions between the Innovalt W and KAO Gripper phosphate
ester antistrip agents and PPA. Presumably, there would not be any such reactions when the
antistrip and PPA were added to asphalt. To test this assumption, Innovalt W and KAO Gripper
antistrips were added to asphalt AAM followed by PPA (115%) addition (figure 2-5.7). Both the
antistrips and PPA were added at a level of 1 wt %. The purpose of these experiments was
twofold: (1) to determine if 31 P NMR can detect signals at the 1% level in a reasonable amount
of time, and (2) to determine if there might possibly be reactions between the PPA and antistrip
in asphalt.
In the case of the phosphate ester antistrip agents, there is a single resonance at a chemical shift
(~1.7 ppm) near that of phosphoric acid (~1.4.ppm). In both cases spectra with reasonable
signal-to-noise, S/N, ratios were obtained after 3 h of signal averaging. When added to asphalt
in the presence of PPA, the ester antistrip resonance could not be resolved from that of
phosphoric acid at the resolution of the WRI magnet. Under high resolution conditions, it is
expected that these resonances could be resolved.
Innovalt W in
PPA (115%)
At 99 h
Innovalt W in
PPA (115%)
at 0 h
Innovalt W neat
30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50
Phosphorous Chemical Shift, ppm Phosphorous Chemical Shift, ppm
Figure 2-5.6. 31 P NMR spectra of phosphate ester antistrips, neat and with PPA (115%)
at different times.
64
KAO Gripper in
PPA (115%)
At 360 h
KAO Gripper
In PPA (115%)
At 0 h
KAO Gripper neat

100
1% Innovalt W in AAM-1
1% PPA(115%) and
1% Innovalt W in AAM-1
1% PPA(115%) in AAM-1
75
50
25
Figure 2-5.7. 31 P NMR spectra of Innovalt W and KAO Gripper antistrip agents in
PPA modified asphalt AAM-1.
31P NMR Moisture determination
0
Some exploratory work was performed to determine if 31 P NMR could be used to determine the
residual moisture content of asphalt. In part, this work was initiated because previous work had
shown that PPA reacts with residual water in asphalt to form orthophosphoric acid. However,
the extent of hydrolysis cannot be predicted apriori because the amount of residual water in
asphalts is generally not known. A simple method for determining moisture may be useful in
providing more quantitative data about the reaction.
The 31 P NMR method is based on the use of phosphorous compounds that react with water to
form anhydrides. For the moisture determinations, diphenylphosphinic chloride (Ph2POCl), here
referred to as DPPC, was used as the derivatizing agent [Dadey et al. 1988; Wroblewski et al.
1991a,b]. DPPC reacts with water in the presence of base (pyridine) to form the anhydride,
Ph2P(O)OP(O)Ph2 ( 1,1,3,3-tetraphenyldiphosphoxane 1,3-dioxide) according to Scheme I,
2Ph2POCl + H2O + Ph2P(O)OP(O)Ph2 + 2
N
-25
-50
Scheme I
-75
-100
65
100
KAO Gripper in AAM-1
1% PPA(115%) and
1% KAO Gripper in AAM-1
1% PPA(115%) in AAM-1
Phosphorous Chemical Shift, ppm Phosphorous Chemical Shift, ppm
75
50
25
N +
H Cl -
0
-25
-50
-75
-100

Dadey et al. [1988] proposed Scheme II for the reaction of DPPC with water to form
diphenylphosphinic acid. We are not sure which scheme more correctly describes the reaction.
However, more recent work seems to agree with Scheme I [Hatzakis et al. 2008].
Other phosphorous compounds can be used to derivatize the labile hydrogen (OH) such as in
phenols and carboxylic acids [Wroblewski et al. 1988; Dadey et al. 1988; Lensink and Verkade
1990]. Dadey et al. [1988] also proposed Scheme III for the reaction of DPPC with phenols. We
have not yet verified the reaction with phenols.
2Ph2POCl + H2O + Ph2P(O)OH +
OH
2Ph2POCl + +
N
Scheme II
N
Scheme III
66
Ph2P(O)O +
In practice, weighed amounts of an internal standard, [MePh3P]I (methyltriphenylphosphoniumiodide),
were placed into oven dried NMR tubes. These tubes were then sealed with rubber septa
to prevent moisture intrusion. A “stock solution” was then made by dissolving Ph2POCl in
CDCl3. An exact amount of stock solution was then added to the sealed tubes via syringe. NMR
data for the stock solution in the sealed tubes was collected to determine how much water was
present in the system. Weighed samples of asphalt were then dissolved in pyridine, added to the
NMR tubes described above, and allowed to react for five minutes at which point NMR spectra
were then acquired. A blank of neat pyridine was tested for water content in the same way the
asphalt samples were tested. All solvents were dried over 4 Å sieves.
The 31 P NMR method was applied to asphalts AAB-1, AAD-1, and ABD-1. Previously, residual
moisture in these asphalts was determined by a commercial laboratory using the Karl Fischer
titration method. 31 P NMR spectra are shown in figure 2-5.8 along with a spectrum of the blank.
The spectra clearly show resonances formed by the reaction of the tagging agent with the water
in asphalt. Although the peak in the blank spectrum of the water reaction product was
subtracted, the NMR results were not in close agreement with those obtained by Karl Fischer
titration (0.46% NMR vs. 0.37% Karl Fischer for ABD; 0.88% NMR vs. 0.37 Karl Fischer for
AAD; 1.28% NMR vs. 0.31% Karl Fischer for AAB). The reasons for the discrepancies are
being investigated.
N +
H
Cl -
N +
H Cl-
L -

75
Pyridine Blank
ABD-1
AAD-1
AAB-1
Tagging Reagent
Figure 2-5.8. 31 P NMR spectra of three asphalts illustrating the use of a phosphorous tagging
agent for moisture determination.
Work to be Conducted Next Quarter
50
Water Reaction
Product
● Continue the study to elucidate the mechanism of action of PPA in asphalt. The use of
antistrip agents in conjunction with PPA modification of asphalts will be investigated.
PPA will be added to asphalt containing amine and phosphate ester antistrip agents to
determine if any reactions occur that might negate the use of PPA in combination with
the antistrips.
● NMR measurements ( 31 P, 13 C, and 1 H) will be made on asphalts containing antistrip
agents to determine the feasibility of using NMR to analyze for the antistrips in asphalt at
concentrations used in paving applications.
● Continue the study of multiple modifiers in asphalt. Changes in the rheological and
spectroscopic (FTIR and 31 P and 13 C NMR), properties on PAV aged samples will be
monitored.
● Prepare a manuscript on this topic and submit it to an international conference or journal
for consideration for presentation and/or publication.
67
25
Phosphorous Chemical Shift, ppm
Internal Standard
0

Problems and Solution to Problem
No problems were encountered during this quarter.
References
Baumgardner, G. L., J-F. Masson, J. R. Hardee, A. M. Menapace, and A. G. Williams, 2005,
Polyphosphoric Acid Modified Asphalt: Proposed Mechanisms, Proceeding of the Association
of Asphalt Paving Technologists, 74: 283-305.
Christensen , D.W., and D. A. Anderson, 1992, Interpretation of Dynamic Mechanical Test Data
for Paving Grade Asphalt. Journal of the Association of Asphalt Paving Technologists, 61: 67-
116,
Dadey, E. J., S. L. Smith, and B. H. Davis, 1988, Determination of Hydroxyl Group
Concentration in Coal Liquids by 31 P NMR. Energy and Fuels, 2: 326-332.
Falkiewicz, M., and K. Grzybowski, 2004, “Polyphosphoric Acid in Asphalt Modification.”
Presented at the Pavement Performance Prediction Symposium, Cheyenne, Wyoming, June 23-
25, 2004.
Ferry, J. D., 1961, Viscoelastic Properties of Polymers. John Wiley & Sons, New York.
Hatzakis, E., and P. Dais, 2008, Determination of Water Content in Olive Oil by 31 P NMR
Spectroscopy. J. Agric. Food Chem., 56: 1866-1872.
Huang, S-C., T. F. Turner, F. P. Miknis, and K. P. Thomas, 2008, Long-Term Aging
Characteristics of Polyphosphoric Acid Modified Asphalts. Journal of Transportation Research
Record (in press).
Hurley, G. C., and B. D. Prowell, 2005, Evaluation of Aspha-Min® Zeolite for Use in Warm
Mix Asphalt. NCAT Report 05-04, National Center for Asphalt Technology, Auburn University,
June 2005, 33 pp.
Innophos: http://www.innophos.com/msdslib.asp?sort=3&selCountry=us
Lensink, C., and J. G. Verkade, 1990, 31 P NMR Spectroscopic Analysis of Labile Hydrogen
Functional Groups: Identification with a Dithiaphospholane Reagent. Energy and Fuels, 4: 197-
201.
Miknis, F. P., and K. P. Thomas, 2008, NMR analysis of polyphosphoric acid-modified
bitumens. Road Materials and Pavement Design, 9: 59-72.
Wroblewski, A. E., C. Lensink, R. Markuszewski, and J. G. Verkade, 1988, 31 P NMR
Spectroscopic Analysis of Coal Pyrolysis Condensates and Extracts for Heteroatom
Functionalities Possessing Labile Hydrogen. Energy and Fuels, 2: 765-774.
68

Wroblewski, A. E., C. Lensink, and J. Verkade, 1991a, 31 P NMR Spectroscopy for Labile
Hydrogen Group Analysis: Toward Quantification of Phenols in a Coal Condensate. Energy and
Fuels, 5: 491-496.
Wroblewski, A., K. Reinartz, and J. G .Verkade, 1991b, Moisture Determination of Argonne
Premium Coal Extracts by 31 P NMR Spectroscopy. Energy and Fuels, 5: 786-791.
Zeng, M., B. Hussain, Z. Huachun, and P. Turner, 2001, Rheological Modeling of Modified
Asphalt Binders and Mixtures. Journal of the Association of Asphalt Paving Technologists, 70:
403-441.
69

SUBTASK 2-6: VALIDATION SITE MONITORING
Statement of Problem
Laboratory tests and/or models to predict the performance of asphalt pavement materials have
always needed a connection between the original materials and actual performance in the field,
especially comparative performance, in order to calibrate or validate the test or model results.
Approach
The approach being used is to construct field sections where different asphalt sources of the
same Performance Grade are used at the same location so that comparative pavement
performance can be directly evaluated and core samples can be obtained as the comparative
pavements age in service. Original materials were collected at the time of construction and are
available for testing. The sites being monitored, using LTPP monitoring protocols, were
constructed during the previous FHWA contract, “Fundamental Properties of Asphalts and
Modified Asphalts II”.
Goal
The goal of this subtask is to provide accurate and documented performance of different asphalt
sources that also includes asphalt-aggregate interactions, to be used to determine the chemical
and physical property differences that are important to pavement performance.
Support of FHWA Strategic Goals
This subtask supports the FHWA Strategic Goal of Optimizing Pavement Performance.
Work Conducted this Quarter
The annual monitoring of the Kansas comparative pavement validation site was conducted in
May 2008. The site is still performing rather well after six years in service; however, there is
some distress being noted. There is a small amount of fatigue cracking and longitudinal cracking
(both non-wheelpath and in the wheelpath) that is occurring in two of the sections. Two core
samples were obtained by KDOT personnel to investigate one of the fatigue cracks. The core
samples revealed that the cracking is top-down cracking and only goes through the 40 mm top
lift. The four comparative asphalt sources are located in the bottom 60 mm of the pavement with
a 60 mm binder course and a 40 mm surface course placed above. There were no apparent
indications in the two core samples that there was any problem with the bottom lift.
Work to be Conducted Next Quarter
It is planned to perform the annual monitoring of the Wyoming Highway 216 sections and the
Nevada I-15 sections in August and September 2008, respectively.
71

TASK 3. OTHER RESEARCH ACTIVITIES (IDIQ)
During this quarter the White Papers that had been prepared in the previous quarter were
approved by FHWA. A task order contract for mechanical testing of validation site cores is
awaiting final signatures and will be the first Task 3 work element approved.
73

TASK 4. INFORMATION DEPLOYMENT
SUBTASK 4-1. PUBLICATIONS, PRESENTATIONS, NEWSLETTERS, FLYERS AND
BROCHURES
Presentations
The University of Oklahoma (O.U.) and the Oklahoma Department of Transportation (ODOT).
Shin-Che Huang and Ray Robertson gave seminars to O.U. and ODOT on the FHWA research
being conducted at WRI. These were on April 9 (O.U.) and April 10 (ODOT), 2008. Shin-Che
and Ray were also asked to critique several ongoing and planned O.U. pavement performance
research projects. ODOT requested information on the toluene-ethanol asphalt extraction
method developed during SHRP and on the Modified German Rolling Flask aging method
developed by WRI and AAT. This information was sent to ODOT upon return to WRI.
Conferences and Meetings Attended
The Association of Asphalt Paving Technologists Annual Meeting, Philadelphia, April 27-30,
2008. Shin-Che Huang attended the meeting.
Training
Rheobit formal course in rheology. During the week of June 2-6, 2008, WRI employed Drs.
David Anderson and Geoff Rowe to teach the Rheobit rheology course at WRI. This was open
to all WRI Transportation Technology people and a few spaces were made available (at
appropriate share of cost) to outsiders from state DOTs.
Newsletter
Volume 3, Number 1 of the Transportation Technology e-Transfer newsletter was released in
April 2008. The next Transportation Technology e-Transfer newsletter (Vol. 3, No. 2) is
planned for August 2008. It will cover the 2008 Petersen Conference and Pavement
Performance Prediction Symposium (July 14-18, 2008), WRI’s 25 Year history, and continue to
cover WRI’s work on the MEPDG.
75

SUBTASK 4-2. WEBSITE MAINTENANCE
The Western Research Institute web site and the www.petersenasphaltconference.org site were
updated in preparation for the WRI- and FHWA-sponsored 2008 Petersen Asphalt Research
Conference and the Pavement Performance Prediction Symposium to be held in Laramie,
Wyoming, in July 2008.
77

SUBTASK 4-3. RESEARCH DATABASE—CONTRACTOR TEAM ACTIVITIES
This database is to include recent, ongoing and planned research and outreach activities. More
specifically, research problem statements, timelines, research results, contacts and relationships
to other studies are to be posted. It is to be designed in a format similar to the (portland)
concrete pavements database found at http://www.cproadmap.com//research/search.aspx. WRI
has interpreted this to mean that WRI is to develop its own such database and the COTR has
agreed to this. It is the opinion of the COTR that this database is not to have restricted access as
with the concrete pavements database. This effort is being accomplished as follows: As each set
of work plans has been accepted by FHWA (with revisions if necessary), and as quarterly reports
are submitted, each has been posted at www.asphaltmodelsetg.org . Outreach activities can be
seen at www.westernresearch.org . Click Transportation Technology and choose from among 18
outreach activities listed in the left column. Although these two sites do not exactly duplicate the
portland concrete database format, the two web sites do provide all of the information required
for this subtask.
79

SUBTASK 4-4. RESEARCH IN PROGRESS DATABASE (Two parts)
The effort in this subtask is to incorporate various types of data from this project into two
databases. The contract requires listings in the Transportation Research Board (TRB) Research
in Progress (RIP) database and the FHWA R&D Project Tracking System.
The TRB RIP Database
On the next two pages is a copy of the TRB RIP entry for this project. Note that the URL for
this project is given on the page of this entry. The general URL for the TRB RIP is
http://rip.trb.org/browse/additions.asp?days=7
The FHWA R&D Project Tracking System
Since the beginning of this project, every quarter (and sometimes more frequently) WRI has
inquired as to whether the FHWA R&D Project Tracking System was developed and ready for
use. Each time through June 20, 2008, FHWA (TFHRC) responded that the system is not yet
ready for use.
Although (obviously) WRI has not seen the format for the FHWA R&D Project Tracking
System, from the title of this part of Subtask 4-4, it appears to call for the same information that
is already reported in Subtask 4-3. If this is the case it raises the question of whether the same
information should be reported twice.
81

SUBTASK 4-5. SUPPORT OF THE MECHANISTIC-EMPIRICAL PAVEMENT
DESIGN GUIDE
In this subtask WRI is to supply relevant models, materials and materials data to the NCHRP
9-30A Project Administrator, Mr. Harold Von Quintus, to further develop or contribute to the
Mechanistic-Empirical Pavement Design Guide. This process will begin as new data and models
are available from research on the FHWA-approved work plans for this contract. Mr. Von
Quintus has requested and has been supplied with a copy of Chapters 1 and 6 of the DTFH61-
99C-00022 Final Report (which is in press). Mr. Von Quintus also requested that 600 pounds of
loose mix be shipped to him from each section of all future WRI validation sites.
85

SUBTASK 4-6. SEMI-ANNUAL MEETINGS
Work Conducted this Quarter
The topic for the 2008 P3 Symposium will be “Warm Mix and Recycled Asphalt Pavements.”
This meeting is scheduled for July 16-18, 2008 in the Washakie Center on the University of
Wyoming Campus. The Symposium links researchers, highway officials, producers and others
with a need to understand how asphalts may perform in a given application over time.
All of the preliminary reservations have been made for the venue, parking, hotel room blocks,
food, etc. The full program is set and available for viewing at
www.petersenasphaltconference.org.
Work to be Conducted Next Quarter
During the next quarter we will hold the Symposium and begin the reservation process for next
year.
Work for the 2009 Annual Project Review in Washington, DC, will not begin until September or
October of this year. It is believed that it will remain at the Marriott Wardman Park directly
following TRB 2009.
Support of FHWA Strategic Goals
The work conducted in this subtask supports the FHWA strategic goal to optimize pavement
performance.
87