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Scranton Gillette Communications3030 W. Salt Creek Lane, Suite 201 Arlington Heights, IL 60005-5025
Phone: 847/391-1000 • Fax: 847/390-04083 Call to re-action
Stimulus is no substitute for reauthorization; new revenues are critical to success of highway program
4 Thin smoothieWith the right mix, thin-lift overlays can yield
cost effectiveness and an excellent ride
8 Cracking the caseInvention pinpoints when asphalt
binder will crack at low temperature
10 Examining asphalt techs A national certifi cation for binder technicians might standardize lab results
12 Warm Pacifi c breezeCaltrans is hot on warm-mix
asphalt along the Pacifi c coast
15 Indiana towns go microMicrothin overlays extend pavement life
�
2 March 2009 • Asphalt Today
EDITORIALBill Wilson [email protected] Zeyher [email protected] VanTimmeren [email protected] Lynn Duffer [email protected]
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CORPORATEChairman Emeritus (1922-2003): H.S. GilletteChairperson: K.A. GillettePresident, CEO: E.S. GilletteSr. Vice President: Ann Fallon O’NeillVice President of Custom Publishing & Creative Services: Diane VojcaninVice President of Events: Harry UrbanChief Financial Officer: David Shreiner
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By the time the readers of ROADS & BRIDGES magazine see
this article, Congress should have enacted the largest pub-
lic works bill since the 1956 legislation that established the
Interstate Highway System. The bill I refer to is the Economic
Recovery and Jobs Creation Act, which includes a substantial
new chunk of federal funds to begin reconstructing our na-
tion’s roads and bridges.
As important as this short-term stimulus legislation is,
however, the future of the transportation construction indus-
try truly rests with the reauthorization of our nation’s surface
transportation program. Some have already suggested that
enacting such a large economic stimulus bill will allow Con-
gress to defer action to reauthorize the federal-aid highway
program. The sad truth is that if this happens, the risk to the
federal-aid highway program would be great.
First, most highway projects, by their very nature, are built
over multiple construction seasons. State transportation de-
partments and local governments need a multiyear reautho-
rization to prioritize and plan projects. For the transportation
construction industry, a multiyear reauthorization bill allows
for better market forecasting and anticipation of business cy-
cles. Putting the federal-aid highway program funding levels
on a year-by-year cycle—subject to an acrimonious budget
debate in Washington, D.C., every year—would result in very
little confi dence in highway funding beyond one year for both
state departments of transportation and the industry.
However, there is even a greater risk. While the stimulus bill
is largely a blank check to create jobs and restore confi dence
in the American economy, the programs authorized by the
surface transportation legislation are signifi cantly larger and
must be paid for. Many fi nancial experts are already predict-
ing that because of slumping gas tax receipts, the Highway
Trust Fund will again run out of revenues to fully pay for the
fi scal 2009 highway program at the SAFETEA-LU-guaranteed
funding level of $42 billion.
Simply extending the federal-aid highway program with-
out Congress enacting new revenues to even maintain the
program’s current funding levels risks a substantially smaller
highway program in 2010 and beyond. That is why NAPA is
urging Congress to pass and the president to sign into law
Stimulus is no substitute for reauthorization; new
revenues are critical to success of highway program
Call to re-action
VIEWPOINT
a fuel-tax increase with 100% of the revenues applied to the
Highway Trust Fund.
Congress must not be allowed to delay the debate beyond
2009 on funding the next surface transportation legislation.
Given the huge need to rehabilitate our highways and bridges
across the nation and the lack of funding (even if one counts
the highway funding in the economic stimulus bill) to bring
our surface transportation infrastructure up to even a good
state of repair, it is in the best interest of the country to have
this debate now. Otherwise, the 44% share that the federal
government provides for capital highway and bridge construc-
tion is at great risk. Delaying legislation that would increase
revenues to pay for rebuilding and constructing highways and
bridges would certainly lead to a smaller program and per-
haps eliminate the federal share altogether.
NAPA has worked hard with our industry partners to sup-
port enactment of an economic stimulus bill. Implementing
the surface transportation reauthorization legislation also is a
top industry priority. NAPA and the transportation construction
industry must now turn our advocacy efforts to enacting in
a timely fashion a multiyear, well-funded surface transporta-
tion reauthorization bill. This will require the full involvement
of our industry grassroots as well as our partner associations
in Washington, D.C.
Congress has an opportunity to instill a great deal of con-
fi dence into the transportation construction marketplace by
passing this legislation, but the industry will have to work as
never before to make sure the job gets done. Go to http://
legislative.hotmix.org to see how you can be an effective ad-
vocate for the highway program in 2009. Together, we can
make a difference.
By Jay Hansen
Asphalt Today • March 2009 3
Hansen is vice president of government affairs at the National Asphalt Pavement Association, Lanham, Md. He can be reached at jhansen@ hotmix .org.
Thin-lift asphalt mixes are making a resurgence in Ohio. A
Federal Highway Administration (FHWA) emphasis on pre-
ventive maintenance, the need to use paving dollars judi-
ciously and the drive to deliver better pavement conditions for
the public have caused engineers to look to thin asphalt over-
lays as a rehabilitation strategy. And what they are seeing are
advances in thin-lift mixes that lead to improved performance
and sound economics.
Ever since the 1980s, Ohio engineers have given serious
consideration to thin asphalt surfaces for major roadway proj-
ects. Back then the driving force for placing thin lifts was eco-
nomics. Engineers were hard-pressed and looking for ways
to stretch a buck. Having never lost that element of frugality,
Ohio engineers have found that thin asphalt mixes are a use-
ful tool to economically extend pavement life.
Ohio engineers have turned to Smoothseal for preventive
maintenance. Making its debut in 1992, Smoothseal is offi-
cially listed in the Ohio Department of Transportation (ODOT)
Construction & Materials Specifi cation (C&MS) book as Item
424, Fine Graded Polymer Asphalt Concrete. The name
Smoothseal is borrowed from an old Rockville, Md., preven-
tive maintenance strategy. Smoothseal gained popularity
beginning in 2002 when the FHWA placed an emphasis on
preventive maintenance. From that point on, thin-lift asphalt
overlays of Smoothseal have become a favorite of engineers
looking for an economical preventive-maintenance treatment,
one that yields excellent ride characteristics and adds some
structure too.
Smoothseal was developed primarily by a designer dream
team of three talented men: Gary Cobb, Bob Bailey and Pat
Welsh. Their goal was to give Ohio’s asphalt paving industry a
cost-competitive alternative to surface treatments. They knew
the advantages of using polymers to “stretch” the perfor-
mance of hot-mix asphalt (HMA) even further. And it worked
better than anyone expected.
Designed for preventive maintenanceAsphalt overlays of various thicknesses are commonly
used in Ohio. As a consequence, they were in many cases
considered a minor rehabilitation strategy, and their useful-
ness as a preventive-maintenance tool was often overlooked.
Smoothseal has changed that. This asphalt mix is specifi cally
intended for preventive-maintenance applications.
There are two types of Smoothseal: Types A and B. The dif-
ference between the two is largely in particle size and binder
content. Type A is a sand asphalt mix with 8.5% binder con-
tent. Type B is a blend of 0.5-in.-maximum-size coarse aggre-
gate and sand-size particles with a minimum asphalt binder
content of 6.4%. A silicon dioxide requirement for both mix
types ensures good friction characteristics. Type B requires
100% two-faced crushed coarse aggregate for mixes used
in heavy traffic conditions. The crushed aggregate provides
By Cliff Ursich
4 March 2009 • Asphalt Today
With the right mix, thin-With the right mix, thin-lift overlays can yield lift overlays can yield
cost effectiveness and cost effectiveness and an excellent ridean excellent ride
Asphalt Today • March 2009 5
Pavement Type
Pavement Condition
Traffic Level:
Flexible Composite
Fair Good Fair Good
Low High Low High Low High Low High
Control (non-PM) $ 23.44 $ 26.61 $ 23.44 $ 26.61 $ 22.88 $ 30.27 $ 22.88 $ 30.27
Chip Seal $ 21.49 $ 22.97
Single Microsurfacing $ 22.35 $ 23.47 $ 21.64 $ 23.92
Double Microsurfacing $ 23.07 $ 25.67 $ 24.28 $ 27.40 $ 22.31 $ 29.58 $ 24.73 $ 32.18
NovaChip $ 22.60 $ 23.60 $ 24.28 $ 26.92 $ 23.75 $ 28.60 $ 26.92 $ 31.16
Smoothseal $ 21.39 $ 22.73 $ 22.92 $ 25.89 $ 21.03 $ 25.92 $ 23.77 $ 28.24
HMA Overlay < 2” thick with No Repairs
$ 22.68 $ 25.06 $ 23.47 $ 27.88 $ 22.28 $ 28.55 $ 24.75 $ 30.41
HMA Overlay < 2” thick
with Repairs$ 22.24 $ 23.61 $ 23.90 $ 26.99 $ 21.75 $ 26.30 $ 24.69 $ 28.75
internal mix friction, leading to greater stability. Complementing
the mixture’s stability is its use of SBR latex-rubber polymer, or
PG 76-22M—SBS polymer-modifi ed asphalt binder. The syner-
gy of using crushed aggregate and a polymer-modifi ed binder
results in durability superior to conventional fi ne-graded HMA.
“It’s a very attractive mix,” said Cobb of Shelly Materials,
one of Smoothseal’s co-developers. “We relied upon the Mar-
shall mix method back then to develop the product and that
continues to this day. No. 8s, 9s, 50% manufactured sand and
latex-modifi ed binder comprises the mix—no big secret. Binder
contents run in the high 6% range. With those materials we’re
able to place the material at 3⁄4-in. thick with no problems and
get very nice aesthetics.”
Dave Powers, ODOT asphalt materials engineer, remarked,
“What’s attractive about Smoothseal is its smoothness and du-
rability. We have a lot of experience in Ohio with using latex-
modifi ed asphalt. That experience goes all the way back to the
mid-1960s when Firestone Tire and Rubber championed the
use of rubber in asphalt mixes.”
Indeed, having Firestone’s home base in Akron, Ohio, made
it opportune for experimentation on Ohio’s roadways. Harold
Carlson, Firestone scientist and head of the company’s Syn-
thetics Division, fi rmly believed that rubber in asphalt would
pay for itself in greater pavement life. History has validated that
belief, and the asphalt industry has wholly embraced polymer-
modifi ed asphalt as a means of extending pavement life and
improving performance.
Cycle of life consideredBailey, president of Kokosing Materials, another co-develop-
er of Smoothseal, commented, “To be competitive in a market
dominated by surface treatments, we needed a hot-mix prod-
uct that was not proprietary.
“Agencies prefer to buy generic, locally available aggregates,
especially the abundant natural sand found in many of Ohio’s
gravel deposits. We also needed a mix that could be placed in
thin lifts to reduce cost per square yard and that could outper-
form the competition.”
ODOT undertook a study to ascertain whether the benefi ts of
applying preventive-maintenance treatment to a roadway justify
the costs associated with the treatment and to identify the fac-
tors for which an individual preventive-maintenance treatment
can be considered cost-effective. In its most current fi ndings,
2007 data indicate that Smoothseal provided the best life-cycle
cost of all preventive-maintenance treatments evaluated. The
study, titled “Preventive Maintenance Process Analysis,” is yet
to be fi nalized. The results received to date are preliminary and
may change with the next round of updates. Thus far, HMA
treatments have demonstrated an ability to be cost competitive
both in life-cycle cost and cost-benefi t analyses.
Table 1 provides a summary of cost-effectiveness as mea-
sured by life-cycle cost. Included is a “control” option, a non-
preventive-maintenance strategy. It serves as a benchmark
by which comparisons can be made of the cost-effectiveness
of the various preventive-maintenance treatments. The costs
shown in the tables are in dollars per square yard. The lower
the cost per square yard, the greater the savings in dollars and
the more preferred the alternative. Highlighted cells in the table
are the costs per square yard associated with treatments hav-
ing the lowest life-cycle cost.
Observations we can make from Table 1 are:
The Smoothseal treatment provided the lowest life-cycle •
cost for all pavement types, conditions and traffic levels ex-
cept composite pavements in good condition having low traf-
fi c levels;
The control option (nonpreventive maintenance) provided •
the lowest life-cycle cost for the composite pavement in good
condition having low traffic; and
The life-cycle costs of Smoothseal and chip seals placed on •
low-volume fl exible pavements in both fair and good condi-
tion were nearly equivalent.
When to thin itNot every distressed pavement is a good candidate for
Smoothseal. Experience has taught us that thin-lift asphalt
Table 1: Summary of Cost-Effectiveness ($/sq yd) as Measured by Life-Cycle Cost
overlays work well on pavements that show the following char-
acteristics:
Dry-looking, “bony” pavements that are porous or perme-•
able;
Pavements that have begun to ravel;•
Pavements with extensive cracking too fi ne for crack seal-•
ing; and
Pavements with cracking of the surface too extensive for •
crack sealing alone.
The pavement should have no fatigue damage. Also, it is
important that the pavement should have sufficient remaining
structural capacity to last the expected life of the preventive-
maintenance treatment. Rapidly deteriorating projects are not
good candidates for preventive maintenance, because the
rapidly declining condition may indicate structural inadequacy.
In summary, Smoothseal should be used wherever pavement
preservation is the objective of a treatment. It should be placed
on structurally sound pavements that are exhibiting only sur-
face distress. Smoothseal is ideal when raveling and minor
cracking caused by oxidation are the main distresses.
If signifi cant rutting (greater than 1⁄4 in.) is present, the cause
must be determined and corrected. Pavement layers exhibiting
plastic deformation must be removed and replaced with mate-
rials having sufficient stability to resist the stress being applied.
Structural or base deformation is an indicator of the need for
a structural overlay (in other words, thick overlay) or pavement
reconstruction.
A Smoothseal overlay will generally consist of a single-
course overlay. Type A is placed 0.625 to 3⁄4-in. thick, and Type
B is placed 3⁄4 to 1 in. thick. Sufficient thickness must be speci-
fi ed to permit placement and compaction of the overlay over
the existing pavement irregularities without exceeding the ma-
terial’s minimum or maximum layer thickness. Uniform courses
are best for optimum compaction. The overlay should be at
least 1.5 times the largest aggregate particle size over high
spots, and not more than three times in the low spots. Pave-
ment surfaces having greater variation will require planing or a
leveling course prior to placement of Smoothseal.
The mix specifi ed must be appropriate for the traffic con-
ditions to which it will be subjected; that is, light, medium,
heavy or high stress. Type A
is suitable for medium traf-
fi c and urban applications.
The high binder content
and fi ne gradation make it
exceptionally durable for ap-
plications where light traffic
and tree canopy can oxidize
pavement or accelerate de-
terioration. Type B mix may
be specifi ed for any and all
applications. It has proven
itself stout enough for even
heavy-duty and high-speed
applications.
The preventive-mainte-
nance concept does not
necessarily preclude the
use of pavement planing or
a leveling course, which can
provide the advantages of
a smoother ride, achieving
greater density in a uniform
thickness, or being able to
maintain curb exposure,
etc. If a leveling course is
desired, a “scratch course”
of conventional surface mix
may be specifi ed.
Modifi ed mixingThe manufacturing process for Smoothseal is similar to
any HMA mixture using polymer-modifi ed binder. In general,
polymer-modifi ed mixes require greater heat during production,
resulting in mixtures arriving at the project site with elevated
temperatures when compared with conventional mixes. Tem-
perature should not be so high as to cause the binder to drain
off the aggregate. Warm-mix asphalt technologies can be used
to reduce temperatures while still retaining the ability to com-
pact the mix.
ODOT undertook a study to ascertain whether the benefi ts of applying preventive-maintenance treatment to a roadway justify the costs associated with the treatment and to identify the factors for which an individual preventive-maintenance treatment can be considered cost effective. In its most current fi ndings, data indicate that Smoothseal provided the best life-cycle cost.
6 March 2009 • Asphalt Today
Asphalt Today • March 2009 7
The paving process differs from conventional methods only
in that using polymers requires increased attention to factors
affecting pavement smoothness. In any asphalt paving job,
obtaining a high-quality, smooth asphalt pavement requires
the contractor to observe all matters affecting mix manufactur-
ing, placement and compaction. With polymer-modifi ed mixes,
heightened sensitivity to these factors is necessary. Uniform
mix production, uniform mix temperature, uniform delivery of
material to the project, uniform head of material in front of the
screed and uniform compaction all become critically impor-
tant.
Handling and raking should be minimized when Smoothseal
or any other polymer-modifi ed mix is placed. The high binder
and polymer content of Smoothseal causes it to be very, very
sticky. Handwork is not easily accomplished and may harm the
aesthetics of the mat. The same stickiness that causes diffi-
culty in handling also may cause material to accumulate in de-
livery truck beds. However, this same material quality is what
provides the extended pavement life desired from preventive-
maintenance treatments.
For joint construction, butt joints are preferred. Keep hand-
work and feathering areas off public road surfaces, especially
for polymer-modifi ed materials that are more difficult to work
by hand. Consider using conventional mixes for driveways and
approaches where handwork or feathering is necessary.
What started out to be a mix used only by the Ohio DOT
is now moving into local markets. Indeed, one municipality
has switched from a slurry seal preventive-maintenance pro-
gram to a Smoothseal program. Eric Smith, city manager for
Englewood, Ohio, remarked that one of the few times he ever
received a resident’s phone call complimenting him on his per-
formance as city manager was when they called about their
newly Smoothsealed street. Now Englewood can boast that
with the completion of the 2008 construction season, all resi-
dential streets are paved with Smoothseal.
Thin asphalt overlays continue to grow in popularity. Their
cost-effectiveness and ability to enhance pavement longevity
and ride quality make them a very attractive strategy for high-
way engineers. Enhanced mixes like Smoothseal have long
been an integral part of thin-lift mix success. Their use will con-
tinue to fl ourish as the industry advances new materials and
new strategies.
Ursich is president and executive director of Flexible Pavements of Ohio, Dublin, Ohio.
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By Spencer Elliott
8 March 2009 • Asphalt Today
Invention pinpoints when asphalt binder will crack at low temperature
Every winter, we feel them on the highway. Every summer, the
acrid smell of road tar reminds us of their presence: cracks
in the road. When the temperatures drop, thermal contraction
puts stress on paved roads. When that stress becomes too
much, the pavement cracks.
Low-temperature cracking is one of the four major failure
modes for asphalt pavement, along with high-temperature rut-
ting, fatigue cracking and moisture damage. While easier to
repair than concrete, cracked roadway asphalt is inconvenient
and costly to repair or maintain. Other types of stress often ex-
acerbate the problem; once cracks appear in road asphalt, it is
only a matter of time before it must be replaced. Sang-Soo Kim,
associate professor of civil engineering in the Russ College
of Engineering and Technology at Ohio University, estimates
that the cost of repairing such damage on roads each year is
in the billions of dollars. Part of the problem, he thinks, is the
lack of a reliable method to test the cracking temperature of the
asphalt binder, and in response he has invented an innovative
new technology.
The current industry standard for estimating cracking tem-
peratures, the American Association of State Highway & Trans-
portation Officials (AASHTO) M320 tests, relies on two types of
equipment measuring different properties of the binder. Creep
stiffness is determined by a bending beam rheometer (BBR)
used to calculate thermal stress, and a direct tension tester
(DTT) is used to fi nd the tensile strength. The problem, said
Kim, is that this type of test does not actually measure the
cracking temperature of the material.
Asphalt Today • March 2009 9
Kim’s answer to the problem took the shape of a small metal
ring, which he dubbed the Asphalt Binder Cracking Device,
or ABCD. The ABCD offers much simpler, more accurate and
more reliable test results because it directly measures the
cracking temperature of the asphalt binder, said Kim.
“What the ABCD does is simulate fi eld conditions. ABCDs
can approach the problem a different way and give us the infor-
mation that we need,” he said.
The device consists of a silicone mold and a metal ring with
temperature and strain gauges attached. The ring, 2 in. in di-
ameter and made of the low-thermal-expansion alloy Invar, fi ts
inside the mold, and binder material is poured in between the
two. When cooled at a steady rate to simulate fi eld conditions,
the asphalt binder will contract at least 100 times more than the
ring it surrounds, putting strain on the ring. The strain is mea-
sured by a strain gauge. In addition, the binder temperature
is measured: When the asphalt binder cracks, the binder im-
mediately ceases to contract, the
impact of which is manifested as
a sudden change in strain. The
temperature at the time of the
sudden change in strain is the
cracking temperature.
It’s all insideAccording to Kim, the ABCD’s method of determining the
cracking temperature eliminates many of the assumptions and
detailed calculations that are the essence of the current meth-
ods of fi nding binder cracking temperatures.
“We don’t need to know the material’s physical properties.
We don’t need to know about the stiffness. We don’t need to
know about the strength. We don’t need to know the thermal
expansion coefficient. We don’t need to know about the tem-
perature shift function, because all those are automatically fac-
tored in the ABCD test process itself,” he said.
The key is the ring’s circular shape. There is no end, as op-
posed to the typical prismatic and cylindrical column shapes.
The circular shape reduces many of the difficulties associated
with stress testing, Kim said.
“To perform a test with a prismatic, linear shape of an as-
phalt binder specimen, one has to have something to grab at
both ends. Or, the specimen may be glued to end fi xtures. Ei-
ther case will cause a complicated stress pattern development
at the ends of test specimens and may signifi cantly affect test
results,” he explained.
Though the ABCD is simple in design, it was not without
complexities during development. Early on, Kim had trouble
with inconsistent results. The temperatures at which the binder
samples would crack varied widely. The location of the failures
did, too.
“The locations of cracking always changed, so we could not
measure reliably the strength value,” he said. “Even more im-
portant was that the variability of the test was so high. You pre-
pare four samples—same binder prepared the same way—you
put it in the freezer, you run the test, and some samples crack
at minus 30°C, while other samples crack at minus 60°C.”
Zeroing inTo correct this, he added a small cylindrical protrusion onto
the inside of the silicone mold, creating a hole in the sample
ring of the asphalt binder. This gave the stress a place to con-
centrate and crack consistently.
“Since we introduced the protrusions and created a hole in
the test specimen, the average standard deviation went from
more than fi ve degrees to less than one degree. So there was
enormous improvement in the test,” Kim said.
With the kinks worked out, Kim’s hope is that a simple and
reliable test that accurately mirrors fi eld conditions will encour-
age the development of better road materials, thereby reducing
the large amounts of money and man-hours spent each year
on repairs.
“Those saved resources can be used for some other bene-
fi ts for the general public
and taxpayers, and also
we could reduce some
inconvenience caused
by construction projects,”
he said.
The National Cooper-
ative Highway Research
Program (NCHRP) seemed to agree and granted the initial
funding for the ABCD concept through their Innovations De-
serving Exploratory Analysis (IDEA) program. The success of
his design led to a patent in August 2007, and a year later Ohio
University’s Technology Transfer Office licensed the technol-
ogy back to Kim and his new company, EZ Asphalt Technology
LLC, for further development and marketing.
Last year, the Federal Highway Administration’s (FHWA)
Highways for Life program selected the ABCD to receive sup-
port and funding in a technology partnership. With Highways
for Life, Kim plans to make improvements to the ABCD system
(including a smaller, more efficient cooling chamber and analy-
sis software that will automatically process the raw data) and
begin sending his invention out to be tested more thoroughly.
“We’re completing phase one now. Two ABCD units were
sent to North Central Superpave Center, and the University of
Madison just completed the ruggedness test. Next year, we’ll
be looking at interlaboratory studies,” he said.
In addition to EZ Asphalt, more than 30 laboratories, includ-
ing more than 20 state departments of transportation, have
been slated to participate in the studies beginning in early
2009. They will be getting their fi rst look at the ABCD in action
and evaluating its suitability for more widespread use.
One key feature the labs will examine is the ABCD’s ability to
measure the cracking temperature in chemically or physically
modifi ed binders. Many types of asphalt produced today have
polymers added to them to enhance their properties. While the
tests employed in AASHTO M320 have proved useful for grad-
ing unmodifi ed asphalt binder, they have not done as well with
these newer types.
“I am convinced that this test will contribute to “I am convinced that this test will contribute to
the savings of billions of dollars annually.”the savings of billions of dollars annually.”
—Sang-Soo Kim—Sang-Soo Kim
Continued on p 18
By Mike Beavin
10 March 2009 • Asphalt Today
A national A national certifi cation certifi cation
for binder for binder technicians technicians might stan-might stan-dardize lab dardize lab
resultsresults
In 1898, just two years after the American automobile industry
began modestly with the sale of 13 identical gasoline-powered
vehicles by the Duryea Motor Wagon Co. of Springfi eld, Mass.,
A.W. Dow designed the fi rst asphalt penetrometer. This device
was used for the fi rst physical-properties test of liquid asphalt.
A metronome was used to time the test. Dow had no way of
knowing it would be nearly 100 years before the system based
on his invention would begin to fade in the face of new tech-
nology. And as a tribute to his work, his original penetrometer
currently resides at the Asphalt Institute headquarters in Lex-
ington, Ky.
In recent history, the conclusion of the Strategic Highway
Research Project (SHRP) in 1993 heralded a comprehensive
change in the methods used to characterize the physical prop-
erties of asphalt binders. The metronomes of the past and
graph paper were replaced with very sophisticated technology.
One of the products of SHRP was a new binder character-
ization system that relied heavily on computer-data acquisition
from precision instruments operated by a new class of techni-
cians. The Superpave performance-graded (PG) binder sys-
tem evaluated asphalt binders in an entirely original way. It was
performance-related, grounded in actual in-service conditions,
and it dramatically improved our ability to characterize this
complex and versatile material.
Now designated as a standard specifi cation (AASHTO
M-320), the PG system must have been a shock to the system
for acceptance-testing personnel and bituminous engineers.
Historically, change happened slowly in asphalt binder test-
ing laboratories. Soon after the conclusion of SHRP, centers of
excellence, including the Asphalt institute (AI), were selected
to provide a coordinated training effort to expose the asphalt
industry to the new system. Binder technicians descended on
Lexington, Ky., in record numbers and returned to their facili-
ties still processing all the new information. They practiced and
passed the knowledge on to new technicians and, in some
cases, developed customized techniques that worked best for
them and their facilities.
In 2006, when California incorporated PG specifi cations, the
PG system officially became adopted nationwide. By this time,
the prolifi c use of modifi ers posed new challenges that techni-
cians had adapted to meet. With this proliferation and a decade
separating many testing personnel from the initial training push
of the 1990s, practices contrasted from lab to lab and region to
region. Single-laboratory variability continued to improve, but
interlaboratory variability began to plateau. In effect, a commu-
nication barrier had developed across state lines.
Asphalt Today • March 2009 11
Program promotedRecently, the membership of AI recognized a need to devel-
op a certifi cation program that, in conformance with the AASH-
TO Materials Reference Laboratory (AMRL) and the published
standards, promoted a national standard best practice.
So, why certify? And what is “certifi cation?” It is simply a way
of providing official recognition that a certain set of standard
qualifi cations has been met—indicating that a professional has
successfully demonstrated knowledge and profi ciency in the
certifi cation area. A person who is a certifi ed public accountant
is just one example of a professional that has demonstrated
profi ciency and knowledge of proper accounting practices.
It may be easy to understand why you
need to be certifi ed to be an accountant.
But a construction materials technician?
Is certifi cation important for construction
materials like asphalt? To answer that
question, we need to look at the Code of
Federal Regulations. Issued in June 1995,
23 CFR, Part 637, Quality Assurance (QA)
Procedures for Construction, states:
“After June 29, 2000, all sampling and
testing data to be used in the acceptance
decision or independent assurance pro-
gram will be executed by qualifi ed sam-
pling and testing personnel.”
The key word in this statement is “quali-
fi ed.” What does “qualifi ed” mean to the
asphalt industry? To some, it means at-
tending a training course and receiving a
professional development certifi cate. To
others, it means taking and passing an
examination that tests the person’s knowl-
edge and profi ciency.
It was this latter interpretation that
was adopted by the Northeast Asphalt User Producer Group
(NEAUPG) in the late 1990s for the certifi cation of PG asphalt
binder laboratory technicians. By resolution, both users and
producers of the NEAUPG agreed that technicians responsible
for PG asphalt binder testing were required to attend a certifi -
cation course administered by the New England Transportation
Technician Certifi cation Program (NETTCP) and pass a certi-
fi cation exam consisting of written and laboratory profi ciency
parts.
It was the success of this program in the NEAUPG coupled
with the Asphalt Institute’s own success in technology transfer
that led to the development of the National Binder Technician
Certifi cation (NBTC) program. Through the NBTC program,
AI’s goal is to improve testing reproducibility for asphalt binders
so there is better confi dence in test results and fewer disputes
between asphalt suppliers and user agencies. We believe that
by ensuring that technicians responsible for the testing of PG
asphalt binders have been suitably trained—and have dem-
onstrated this understanding by achieving certifi cation—the
result will be lessened testing variability.
The fi rst steps in tearing down the testing language barrier
and improving the published precision estimates started Jan.
8-10, 2008, in Salt Lake City and March 18-20 in Lexington,
Ky. Twenty technicians from both user agencies and producers
attended the two courses. Each course consisted of approxi-
mately 11⁄2 days of lecture followed by written and laboratory
profi ciency exams. The written exam included approximately 50
multiple-choice questions covering the entirety of the course
text, AI’s MS-25, “Asphalt Binder Testing: Technician’s Manual
for Specifi cation Testing of Asphalt Binders.”
The test was an open-book exam that had to be completed
within two hours. The laboratory profi ciency exam covered
hands-on demonstrations of the test pro-
cedures for the dynamic shear rheom-
eter (DSR) and bending beam rheometer
(BBR). Although other test procedures are
part of AASHTO M-320, it was decided
that if a technician could perform these
two procedures, with their detailed calibra-
tion and specimen preparation elements,
then the technician could reasonably be
expected to perform some of the other,
less-complicated procedures.
To be certifi ed, the technician needs
to pass the written exam with a minimum
score of 80% and both parts of the labo-
ratory profi ciency exam (DSR and BBR)
with minimum scores of 85% on each.
This is not a rubber-stamp course, even
for experienced technicians. At the con-
clusion of the fi rst two classes, the pass-
ing rate was approximately 60%, which
means that three out of fi ve technicians
achieved certifi cation in their fi rst time tak-
ing the exams.
Examining toughnessDoes this mean the exams are too tough? As a guide, we
looked at the success rate of engineers taking the professional
engineering (PE) exam in civil engineering. In October 2007,
the passing rate of fi rst-time takers of the PE exam was 64%.
Since both programs represent professional certifi cations, we
feel these passing rates are comparable and that the exams
are challenging but not unduly difficult. As an additional indica-
tor of success, feedback from course participants has been
very positive.
Seasoned technicians expressed they were pleasantly sur-
prised to learn something new and gain a greater understand-
ing of the product they work with each day.
Certifi cation is truly a professional accomplishment. As such,
technicians should understand that the exam covers more than
simple “how-to” questions. It requires that they understand the
purpose and impact of the test and procedural details.
The success of the NEAUPG and the Asphalt Institute led to the development of the National Binder Techni-cian Certifi cation program. To be certifi ed, a techni-cian needs to score 80% on the written exam.
Continued on p 18
By Tom Kuennen
12 March 2009 • Asphalt Today
Caltrans is hot on warm-mix asphalt along
the Pacifi c coast
California’s State Rte. 1, also
known as the Pacifi c Coast
Highway, Cabrillo Highway
and Shoreline Highway, runs
some 655 twisting miles
along California’s scenic and rugged coast. It encompasses extraordinary, unspoiled views
of the Pacifi c Ocean, shore and mountains.
But because Rte. 1 runs through remote terrain on the west side of the coastal ranges
that separate the wild Pacifi c Coast from California’s more populated interior, much of the
roadway lies far from the hot-mix asphalt (HMA) plants needed for overlays and repairs
from storms off the Pacifi c that lash the coast during winter.
Rte. 1 paving projects can be a three- to four-hour drive from the HMA plants typically
used to produce mix in the region. After a lengthy, slow drive over switchback mountain
roads, mixes would arrive lukewarm, to be further cooled in the chilly, foggy ocean air along
the coast.
If mix temperatures were ramped up at the plant to arrive with enough residual heat to
provide workability, the producer risked binder degradation. But if they were shipped at
conventional temperatures, then attainment of onsite density would be threatened.
Warm-mix asphalt offers the California Department of Transportation (Caltrans) an alter-
native that has received rapt attention in 2008.
In May 2008, a warm-mix workshop and demonstration project on Rte. 1 in Morro Bay,
Calif., between Monterey and Santa Barbara, generated excitement in the California engi-
neering community. The demonstration included MeadWestvaco’s (MWV) Evotherm prod-
uct and two other warm-mix additives.
Then, in September 2008, Evotherm was chosen for a long-haul Caltrans demonstration
project, in which both dense-graded and open-graded asphalt mixes were produced at
conventional hot-mix temperatures at the Syar Industries Inc. plant at Santa Rosa. The mix
was hauled to Rte. 1 at Point Arena on the coast north of San Francisco, a four-hour drive
through the mountains.
High-quality airLike any other industrial facility, an asphalt plant emits fumes that are an issue for re-
gional air quality in areas that are not in compliance with federal air-quality standards. How-
ever, plentiful research indicates there is no evidence that these fumes are harmful to either
workers or nearby residents.
Nonetheless, use of today’s
warm mixes has the potential
to all but eliminate such emis-
sions, giving a plant owner a
powerful tool to use in the
permitting process. Warm
asphalt mixes produce emis-
sions at a greatly reduced
level from conventional HMA plants, thus potentially enabling
the permitting of asphalt plants in air pollution nonattainment
areas or where there is local opposition.
While they come at a cost-premium, warm asphalt mixes
can save money in the plant through reduced energy costs.
While energy cost historically has been less of an issue in the
U.S. than it is in Europe, with its higher-cost energy sources,
in 2007 and 2008 skyrocketing energy costs in the U.S. have
made this aspect even more of a benefi t.
Similarly, and of interest to Caltrans, warm mixes may allow
construction of pavements in cooler environments and follow-
ing long hauls, because contractors need to no longer fear criti-
cal loss of temperature in the cold.
Warm mixes also can allow faster construction of pave-
ments made up of deep lifts of asphalt, for example intersec-
tions, which need to be opened as soon
as possible. Because the mix is not as hot
to begin with, less time is required to cool
the mix before the next lift is placed.
These benefi ts have been noted over-
seas. In its February 2008 report, FHWA’s
Warm-Mix Asphalt European Scanning
Tour reported warm-mix asphalt enabling
paving in cooler temperatures and still ob-
taining density, hauling the mix longer dis-
tances and still have workability to place
and compact, enabling the ability to com-
pact the mixture with less effort, and the
ability to incorporate higher percentages
of reclaimed asphalt pavement (RAP) at
reduced temperatures.
To MorroCaltrans has been evaluating Evotherm
and other warm-mix asphalt (WMA) tech-
nologies since 2006. The 2008 study of WMA at Point Arena
and Morro Bay results from Caltrans’ need for confi dence in
specifi cation of any new technology.
“Warm-mix asphalt is a set of technologies that reduces the
temperature needed to heat hot-mix asphalt during the com-
paction process,” said Caltrans’ Division of Research and Inno-
vation in its “Annual Accomplishment Report 2008.” “It offers the
potential to reduce energy use, reduce air emissions, reduce
cost and improve the quality of construction.”
Use of WMA in California is especially attractive because of
its intrinsically lower emissions, thus smaller carbon footprint,
compared with conventional HMA. As such it fi ts into California
Gov. Arnold Schwarzenegger’s green initiatives for state build-
ing and procurement.
However, the Division of Research and Innovation identifi ed
several questions regarding the risks of increased rutting and
moisture damage when WMA is used. As a result, Caltrans
funded laboratory and heavy vehicle simulator (HVS) testing to
address those issues for warm mixes.
HVS test sections were built in Watsonville, Calif., in August
2007 in cooperation with the Graniterock Co. and three WMA
technology providers, including MWV.
As a result of the tests, Caltrans determined that WMA pave-
ments were not intrinsically prone to rutting.
“Results of [the] HVS testing have been completed and in-
dicate that there is no increased risk of rutting in warm-mix
asphalt sections compared to the conventional hot-mix asphalt
pavement,” Caltrans Division of Research and Innovation re-
ported in early 2008. “HVS testing for moisture sensitivity is
currently under way. Plans for repeating this testing using HMA
with rubberized asphalt binders are under development.”
Following this research, Caltrans’ District 5 held the Morro
Bay warm-mix open house in May 2008, where three types of
warm-mix—including Evotherm—were placed on Rte. 1. Morro
Bay was followed by the Point Arena project in September.
Get to the PointThe Rte. 1 project at Point Arena involved thin-lift asphalt
resurfacing of the two-lane highway to a depth of 11⁄4 in.
“Caltrans has been actively studying warm mix,” said Bran-
don Milar, pavement technology engineer, Telfer Oil Co., Mar-
tinez, Calif., and supplier of Evotherm for this project. “For the
last year they have been looking for candidate projects, and for
us they’ve picked the toughest project. District 1 has been very
interested in utilizing warm-mix technology because they have
a lot of projects along the coast, with long hauls associated
with the mix. They wanted to fi nd a better way of paving and so
they were interested in Evotherm chemistry.”
Due to local conditions on Rte. 1 near Point Arena, both
dense-graded and open-graded warm asphalt mixes were
used. For the dense-graded portion—to be placed in a por-
tion of the road subject to local fl ooding—the grade of asphalt
binder was specifi ed at PG 64-16, with aggregate complying
with Caltrans’ 1⁄2-in. top-size grading.
And on the open-graded friction course section, which con-
stituted the largest part of the project, the grade of asphalt
Asphalt Today • March 2009 13
The Rte. 1 project at Point Arena involved thin-lift asphalt resurfacing of the two-lane highway to a depth of 1¼ in. Due to the conditions near Point Arena, both dense-graded and open-graded warm asphalt mixes were used.
14 March 2009 • Asphalt Today
binder mixed with aggregate was specifi ed at PG 58-34, poly-
mer modifi ed.
The aggregate for open-graded friction course had to com-
ply with the 1⁄2-in. grading, and the binder for aggregate had to
be treated with liquid antistrip. The mix consisted of anywhere
from 15 to 24% air voids to permit drainage of water through
the thin lift.
Both dense- and open-graded friction courses were be-
ing placed at 11⁄2-inches and compacted to 11⁄4-in. depth from
downtown Point Arena north about fi ve miles. A total of 4,000
tons of Evotherm chemistry warm-mix asphalt were placed.
For both mixes, a material transfer vehicle (MTV) was speci-
fi ed to receive mix from haul trucks and feed to the paver. The
MTV was intended to remix the WMA before loading the paver,
be self-propelled and independent of the paver and have suf-
fi cient capacity to prevent stopping the paver, according to Cal-
trans’ contract addendum.
At the plant, the Evotherm chemistry was introduced to the
drum mixer via an injection system.
“From the delivery totes, the water-soluble chemistry fi rst
passed through a fi lter and the fl ow could be calibrated,” said
Michael Plouff, applications engineer, MWV. “Then a mass fl ow
meter measured the material in pounds per minute before it
was injected into the asphalt line.”
Check valves keep material from backing up into the supply
feed.
“The mass fl ow meter checks the validity of calibration for
chemical additives,” Plouff said. “The meter is operated by a
programmable controller, and a speed controller manages the
pump.”
The ability to be fl ow-metered gives liquid Evotherm an ad-
vantage over wax-bead additives, he said.
“Because wax additives come in bead form, it’s more chal-
lenging to get precise meter readings which are required by
California.” Plouff said.
“With a powdered zeolite warm-mix additive, meter reading
precision is even worse,” he continued. “The supplier will have
to take a quantity of liquid asphalt into a separate tank, mix it
with the dry additive and pump that mixture out to the plant.
Suppliers may prefer to do this at the terminal; however, Cali-
fornia wants metering monitored at the plant.”
“We were using a dosage of Evotherm H5 DAT at 5% by
weight of the asphalt binder content,” said Hans Ho, technical
and environmental director, Telfer Oil Co. “For this open-graded
friction course, the mix design called for 5.8% asphalt binder,
so the Evotherm H5 DAT was 5% of that, or 0.29% of the total
mix.”
Because of the long haul, the mix was being made at tem-
peratures higher than would be normal for warm mix.
“Warm mix would normally be made at 230 to 275°F,” Ho
said. “For this particular project, we were making it at 300 to
305°F so that we could haul it for three hours and still have a
workable mix.”
Typically the mix was leaving the hot-mix plant at Santa
Rosa at just above 300°F, and was arriving at the jobsite at
about 260°F, where it was placed by contractor North Bay Con-
struction Inc. of Petaluma, Calif. After transition in the MTV, the
mix was being placed on the roadway at temperatures from
220 to 240°F. But with Evotherm, the temps can go lower. “We
placed WMA as low as 180°F without any workability issues,”
Plouff said
Stock up on WMAUse of Evotherm in California is not confi ned to Caltrans. In
September 2007, the city of Stockton, Calif., sponsored a dem-
onstration of warm-mix asphalt paving using Evotherm on city
streets, in which mix production temperatures were lowered by
100°F.
“The immediate benefi t to producing warm-mix asphalt is
the reduction in energy consumption required by burning fuels
to heat traditional hot-mix asphalt to temperatures over 300°,”
said Christine Tien, deputy city manager for Stockton. “Euro-
pean countries have already been using this technology for
some time as a method to reduce greenhouse gas emissions.
Continued use of this technology could have a signifi cant im-
pact on transportation construction projects in the San Joaquin
Valley where air quality is very poor.”
“We are very pleased with the successful results of this proj-
ect,” said Gordon McKay, Stockton deputy public works director
for operations and maintenance, in a press release. “This is the
fi rst time we have tried warm-mix asphalt in Stockton. It is a
next-generation technology that produces durable roads while
signifi cantly reducing the environmental impact of construction
on our community, something that we are striving to do as part
of Mayor Chavez’s commitment to the U.S. Mayors Climate
Protection Agreement of 2005.”
“With the sensitivity to greenhouse gases and other harm-
ful emissions,” said Telfer’s Ho, “one can argue that working
with hydrocarbon material at reduced temperatures makes a
positive change to environment impact. With the reduction of
fuel consumption and the subsequent reduction of harmful
emissions, warm-mix technology is a giant step forward for the
future. I envision the day in the future when all asphalt pave-
ments will be constructed using warm-mix technology.”
Kuennen is the principal of ExpressWaysOnline.com, Buffalo Grove, Ill. He can be reached at 847/229-1839; [email protected].
LEARNMORE For more information related to this article, go to:www.roadsbridges.com/lm.cfm/rb030905
“I envision the day in the future when all “I envision the day in the future when all
asphalt pavements will be constructed using asphalt pavements will be constructed using
warm-mix technology.”warm-mix technology.”
Microthin overlays extend pavement life
Asphalt Today • March 2009 15
Rockport, Ind., is a small, quiet city surrounded by beautiful
foliage and gently rolling hills. To mirror that attractiveness, it
is important to the city and its residents to have aesthetically
pleasing roads. State Road 70 (between U.S. 231 and State
Road 66 outside of town), which is about 10 minutes away
from the city of Rockport, recently had some minor rutting
and asphalt deterioration problems. As material, fuel and la-
bor prices have continued to rise, the need for cost-effective
road maintenance also has increased. So, the state decided
to use microsurfacing on an 8.5-mile stretch of the two-lane
state road. A microsurface layer over the top of the existing
asphalt not only fi xed those problems, but also improved skid
resistance, increased the road’s wear life and provided a bet-
ter aesthetic look.
Strawser Inc., a pavement preservation contractor based
in Columbus, Ohio, won the bid to microsurface that stretch
of road. The company is enjoying a recent upward turn to-
ward pavement preservation. It also seems that the rest
of the state is paying attention. During the six-day job near
Rockport, more than 20 state and county representatives
came to see the job and analyze if it could be a cost-effective
alternative for them.
“With asphalt prices being so high, states don’t have the
money to do as much hot mix,” said Chauncey Nance, direc-
tor of fi eld operations for Strawser. “This year, we’ll do about
8,000-10,000 tons of microsurfacing in Indiana, which is as
much as I can remember doing in one year. It’s good to see
preservation becoming something that the states really want
to focus on, because it can truly benefi t a state’s budget and
the overall appearance of its roads.”
The Rockport job required 131,000 sq yd of microsurfacing
to be laid over the two-lane road with a continuous microsur-
facing paver. The material mix consisted of 2,036 tons of Type
A (comparable to Type II) aggregate, 58,026 gal of asphalt
emulsion, 427 bags of cement and about 10% water to lay
a ½-in.-thick layer using two coats over the entire project. To
determine the mix, Strawser worked with its asphalt emulsion
supplier, which performed a full-mix design consisting of all
16 March 2009 • Asphalt Today
of the ingredients. The supplier tested it thoroughly to make
sure it would hold up to the standards expected by the state
and then sent it off to them for approval. In doing so, the mix
was made specifi cally to fi t the road and surrounding environ-
ment to ensure a longer wear life. Once the mix was approved,
the continuous paver was calibrated and set with material ra-
tios according to the mix design.
To apply the mix, Strawser used a Bergkamp Inc. M1 full-
size continuous microsurfacing paver, variable-width spreader
box and fi ve mobile support units. The variable-width spreader
box was connected to the back of the paver, using four augers
to maintain the mix and evenly distribute it across the pave-
ment. The box can expand and contract while paving to adjust
to varying pavement widths. The mobile support units held and
transported aggregate, asphalt emulsion and water to the con-
tinuous paver as it moved down the road.
Each morning the paving crew started at its staging area, lo-
cated approximately 10 minutes from the paving site. The stag-
ing area housed all of the materials that were used on the job.
The continuous paver and mobile support units were fi lled with
the necessary materials and then commuted to the paving site.
The crew blocked off a 1- to 2-mile area, removed the pave-
ment markers and cleaned the road using a street sweeper.
Then they applied a tack coat made of three parts water and
one part asphalt emulsion, which was put down on the road
to better adhere the microsurface to the existing asphalt. The
tack dried for about 30 minutes, and then the continuous paver
applied the fi rst coat of the new microsurfacing layer. The mo-
bile support units, located in different spots farther down the
road, slowly backed up to
the continuous paver one
at a time as it was paving to
refi ll the material compart-
ments as needed. Continu-
ous paving eliminated the
number of construction
joints—or small bumps—
left in the road, increased
worker efficiency and left
a nice-looking smooth sur-
face.
Seconds and thirdsMost of the job required
two coats of microsurfacing
to equal 32 lb/sq yd of ma-
terial for a ½-in.-thick layer.
The fi rst coat, called the
“scratch coat,” consisted of
14 lb/sq yd of material and
acted as a leveling surface
to fi x the minor rutting. The
No. 1 objective with this
coat was to get the road
level and provide a solid
base for the second coat
to adhere to. A stiff rubber
strike-off, connected to
the back of the spreader
box, was used to level the
surface without wiping
The Rockport job required 131,000 sq yd of microsurfacing to be laid over the two-lane road with a continuous microsurfacing paver. A variable-width spreader box was connected to the back of the paver, using four augers to maintain the mix.
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out the ruts.
During the scratch-coat process, only one lane of traffic was
blocked off, so traffic could drive on the other lane while the
road was being preserved. Because microsurfacing sets so
quickly, the road crew never had to shut down the entire road,
so there was only a short delay for motorists. After fi nishing
with the scratch coat, the crew waited about 30 minutes and
then re-opened it to traffic and blocked off the other side so a
scratch coat could be placed on it as well.
After laying the scratch coat on both sides, the crew went
back to work on the second coat. The surface coat consisted of
18 lb/sq yd of material. The purpose of this coat was to provide
a skid-resistant and aesthetically pleasing fi nish. The stiff rub-
ber strike-off on the spreader box was replaced with a more
fl exible and smooth rubber strike-off to provide the fi nal fi nish.
Like most projects, this one presented an obstacle to over-
come. Strawser assessed the road before doing the project, but
there was more signifi cant deterioration to about 7,500 sq yd of
the road than originally thought. That section had more traffic
and a higher volume of large trucks than the other parts, caus-
ing more deterioration and minor delamination that required
a third microsurfacing coat. Strawser put down 46 lb/sq yd of
material in that 7,500-sq-yd area. The fi rst two coats consisted
of 14 lb/sq yd each, and the third coat required 18 lb/sq yd.
Preserving a trendStrawser started in the pavement preservation business in
1977 and works in Indiana, Michigan, Ohio, Tennessee and
Kentucky with multiple preservation methods. Other than mi-
crosurfacing, Strawser also provides slurry seal, crack seal
and chip seal.
“We’ve defi nitely seen an increase in the popularity of pave-
ment preservation over the last few years,” said Nance. “Like
all of our preventive maintenance methods, microsurfacing is
more cost-effective for the budgeted dollars if the road doesn’t
have major structural damage. A microsurfacing job can cost
approximately 65% less than a new hot-mix overlay, so putting
a pavement preservation program into place can free up a lot
of money to fi x more roads. I like to equate it to a house that
needs new windows. You would replace the windows, not build
a new house. Then use that money to buy other things.”
Though microsurfacing is not a replacement for an asphalt
overlay, it can be used to extend the overall life of the pave-
ment and delay the need for asphalt overlays or major recon-
struction. Untreated roads are adequate for many years of
use. However, the longer they go untreated, the more they
deteriorate under the surface. Microsurfacing leaves a new
skid-resistant surface that is free of cracking and raveling and
protects against weathering. Oxidation, loss of oils and loss of
matrix also are minimized. The waterproof surface prevents
further deterioration, provides an appearance that is appeal-
ing and can increase property values.
“Microsurfacing technology is relatively inexpensive when
compared with other methods to remediate these types of
problems,” said Bill Cooper, Bergkamp’s director of sales and
marketing. “And if applied as part of a comprehensive pave-
ment maintenance program, it will result in extended service
life with lower costs and improved safety. The right contractor,
applying the right treatment to the right road, can make all the
difference when determining where to spend limited dollars on
transportation infrastructure maintenance.”
A few weeks after the job was completed, Nance went back
over the surface with members from the Indiana DOT. They
drove on it and examined it for all of the qualities mentioned
before. Final inspection showed that they passed all require-
ments. To insure the job, Strawser provides a two-year warran-
ty on the fi nish. The warranty protects against any premature
wear or delamination, meaning Strawser would come out and
fi x that part of the road if there were any kind of a problem.
“We have the utmost confi dence in this process and can
easily provide a warranty to back it,” said Nance.
Information for this article provided by Strawser Inc., Columbus, Ohio.
Asphalt Today • March 2009 17
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Adapting to polymersKim said that tests of polymer-modifi ed asphalts using the
BBR test showed higher cracking temperatures with increased
polymer concentrations despite large amounts of evidence
from the fi eld that suggests the modifi ed asphalts perform
much better in cold conditions than their unmodifi ed counter-
parts. The same tests using the ABCD showed results much
closer to fi eld data.
Kim said he did not have to look far to affirm that polymer-
modifi ed asphalt binders were becoming more widely used.
“A few years ago, the state of Ohio mandated that all the
surface courses of the asphalt pavement must be polymer
modifi ed,” he said. “The demand for the modifi ed pavement is
getting much bigger because of large volumes of traffic.”
More new pavement means more new materials to be tested.
Hoping that demand for his ABCD also increases, Kim is still
improving and refi ning his design. This includes not only mak-
ing the device more portable and efficient, but also allowing a
larger number of tests to be conducted simultaneously.
“The models we’re developing can test up to 16 ABCD rings
at one time,” he said.
Kim hopes that positive results from the interlaboratory stud-
ies may lead to the wider adoption of the ABCD as the indus-
try standard for measuring asphalt binder’s low-temperature
cracking potential.
“We hope that this test will be adopted as the specifi cation
test,” he said. “I’m convinced that this test will contribute to the
savings of billions of dollars annually across the nation . . . and
to providing long-lasting pavement. That will be the benefi t for
the general public and taxpayers.”
David Powers, of the Ohio Department of Transportation’s
Office of Materials Management, said the approval of the fed-
eral body will be key to the ABCD’s success. The success of
such inventions often depends on how much the FHWA and
their Experts Task Group (ETG) champion them to standards-
setting bodies and the state departments of transportation, he
said. But Powers went on to say that the ABCD has “high po-
tential” and credited its basic engineering as the reason why.
“I think this is mainly due to its simplicity of design, sound
engineering basis, high correlations with actual fi eld measures
and high repeatability,” he said.
With such a propitious outlook for the ABCD, Kim is now
looking to take his concept a step further. He is currently devel-
oping a larger device that could measure the cracking strength
of whole asphalt mixes. He has completed an initial design with
encouraging results and is currently working on peer-reviewed
papers to widen its exposure.
Elliott is an external relations assistant in the Russ College of Engineering and Technology at Ohio University.
18 March 2009 • Asphalt Today
ABCD—Continued from p 9
LEARNMORE For more information related to this article, go to:www.roadsbridges.com/lm.cfm/rb030903
LEARNMORE For more information related to this article, go to:www.roadsbridges.com/lm.cfm/rb030904
BINDER TEST—Continued from p 11
For instance, what would you expect to happen to BBR esti-
mated stiffness and m-value data if a sample was accidentally
left in an oven or aged too long? What impact does an im-
properly placed RTFO air jet have on DSR data? The certifi ca-
tion course and exams are intended for experienced asphalt
binder technicians who understand the importance of these
questions.
Qualifi ed certifi cation candidates must have at least six
months of binder testing experience or two months’ training
directly under a certifi ed technician.
So what’s next? The NBTC program is designed to be of-
fered and implemented nationally to ensure a consistent un-
derstanding of the standards and laboratory best practices
across state lines. In addition to offerings in Kentucky, AI is ex-
ploring partnerships to offer the certifi cation course and exams
in other locations throughout the U.S. beginning this winter.
AI believes that its NBTC program is an important part of the
effort to reduce asphalt binder testing variability. In our opinion,
it is a strong complement in this purpose to the AASHTO Ac-
creditation Program.
If you are interested in the NBTC program, we need your
help. While AI can offer standardized certifi cation courses and
exams across the nation, the real goal of reducing testing vari-
ability will be more readily achieved by following the path of the
NEAUPG in the late 1990s. This group required technicians re-
sponsible for PG asphalt binder testing to attend a course and
pass a certifi cation exam. In other words, the NBTC program
is the vehicle for ensuring that we have a consistent national
certifi cation that allows technicians to “take it to the next level,”
but the implementation decision (and the associated specifi c
details) belongs to the individual user-producer groups.
For additional insight into the NBTC program content or for
a stand-alone instructional companion to the published PG
standards, we suggest you review the newly revised manual,
MS-25, “Asphalt Binder Testing: Technician’s Manual for Speci-
fi cation Testing of Asphalt Binders,” 2nd Edition, which is now
available from AI.
For more information on the NBTC program, please visit
www.asphaltinstitute.org/NBTC.
Beavin is the technical training coordinator for the Asphalt Institute, Lex-ington, Ky. He can be reached at [email protected].
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To sponsor these events, please contact Ryan Hanson of Roads & Bridges at 847/391-1059 or by e-mail at [email protected].
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