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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

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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


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


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.



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


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.


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


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.


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


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


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.


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].


“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


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


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.



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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.


ABCD—Continued from p 9



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].

STATE OF THE INDUSTRY – FUNDING

Future Roads & Bridges Live events include:Paving Innovations September 22-24, 2009, Chicago, Ill.Bridge Infrastructure November 4-6, 2009, New Orleans, La.

To sponsor these events, please contact Ryan Hanson of Roads & Bridges at 847/391-1059 or by e-mail at [email protected].

REGISTER NOW

You are invited to join a diverse group of transportation industry professionals for Roads

& Bridges Live: State of the Industry – Funding Conference. The educational sessions will

focus on the impact of industry funding, including SAFETEA-LU reauthorization and economic

stimulus funding.

Recent Schedule Additions Include:

opportunity, with preference given to the fi rst 48 conference registrants.

For additional information, visit www.roadsbridgeslive.com.

Butch Sebers

Roadtec offers reliable, productive Cold Planers, Pavers, Shuttle Buggy® MTV’s, and Reclaimer/Stabilizers combined with excellent local, factory-supported service, and great parts availability.

Building and servicing reliable, productive roadbuilding equipment. That’s all we do, and we know how to do it. Count on Us. We’re Ready Now.

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ROADTEC an Astec Industries Company800 MANUFACTURERS RD • CHATTANOOGA, TN 37405 USA • 423.265.0600 • FAX 423.267.7104 • roadtec.com

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