Legislature(2005 - 2006)BUTROVICH 205
04/20/2006 01:30 PM Senate TRANSPORTATION
| Audio | Topic |
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| Start | |
| Pavement Rutting Problems in Anchorage Alaska | |
| Adjourn |
* first hearing in first committee of referral
+ teleconferenced
= bill was previously heard/scheduled
+ teleconferenced
= bill was previously heard/scheduled
| + | TELECONFERENCED | ||
ALASKA STATE LEGISLATURE
SENATE TRANSPORTATION STANDING COMMITTEE
April 20, 2006
1:37 p.m.
MEMBERS PRESENT
Senator Charlie Huggins, Chair
Senator John Cowdery, Vice Chair
MEMBERS ABSENT
Senator Gene Therriault
Senator Albert Kookesh
Senator Hollis French
OTHER LEGISLATORS PRESENT
Representative Carl Gatto
COMMITTEE CALENDAR
Pavement rutting in Anchorage, Alaska
PREVIOUS COMMITTEE ACTION
No previous committee action to consider.
WITNESS REGISTER
DR. J. LEROY HULSEY, Ph.D., P.E., S.E.
Associate Professor, Civil Engineering
Fairbanks, AK
POSITION STATEMENT: Discussed pavement rutting.
GERALD J. DESJARLAIS
Denali Materials
3815 W. 40th Avenue A.
Anchorage AK 99517
POSITION STATEMENT: Discussed pavement rutting.
REPRESENTATIVE CARL GATTO
State Capitol, Room 411
Juneau, AK 99801-1182
POSITION STATEMENT: Discussed pavement rutting.
MICHAEL SAN ANGELO
Department of Transportation & Public Facilities
3132 Channel Dr.
Juneau, AK 99801-7898
POSITION STATEMENT: Discussed pavement rutting.
ACTION NARRATIVE
CHAIR CHARLIE HUGGINS called the Senate Transportation Standing
Committee meeting to order at 1:37:41 PM. Present at the call to
order were Senator John Cowdery and Senator Charlie Huggins,
Chair.
^ Pavement Rutting Problems in Anchorage Alaska
PAVEMENT RUTTING IN ANCHORAGE, ALASKA
DR. J. LEROY HULSEY, Ph.D., P.E., S.E., University of Alaska
Fairbanks, said he is principal on a state-funded research
project to investigate pavement-rutting problems in Anchorage,
Alaska. He outlined the steps his team is taking toward
development of a testing plan to evaluate possible solutions,
and introduced Gerald Desjarlais to present their research plan
and preliminary findings.
1:42:28 PM
GERALD J. DESJARLAIS, President of Denali Materials Inc.,
presented slides from a survey on pavement rutting and stressed
that rutting is contributing to premature pavement failure; it
is expensive, a safety problem, and a public inconvenience. He
said that the scope of work on his research grant request is to:
review previous work by Alaska Department of Transportation
(DOT), solicit data from other states, identify causes of
rutting, test to identify rut-resistant paving material, and
analyze data to develop appropriate pavement sections using
those materials.
He explained that there are four possible causes of rutting:
Plastic flow, which is a function of mixed design and
constructability, or testing on the job to ensure the material
you are putting down on the grade truly reflects what was
designed in the lab; studded tire wear; base and sub-base
failures which cause the flexible pavement to deflect; stripping
and raveling.
1:44:28 PM
MR. DESJARLAIS showed a slide of Tudor Road just before
resurfacing last year, which shows no evidence of sub-grade
failure, just a fairly typical example of plastic flow in which
asphalt is flushed to the surface. He noted that the conditions
on Tudor Road were typical of what they found on the other six
highways tested. The sampling locations used were Glenn Highway
at the Muldoon exit, Diamond Boulevard, Old Seward, Tudor Road
at Tudor and Burgaw, Gambol and East Thirteenth, Benson and Old
Seward, Burgaw and East Sixth, and the new pavement on Tudor
Road. They took core samples in the travel lanes and between
them for comparison.
SENATOR COWDERY asked if heavier vehicles have a greater effect
on plastic flow.
MR. DESJARLAIS answered yes, that wheel loading is a big factor.
1:46:28 PM
CHAIR HUGGINS commented that one of the discussions the
legislature has had about the transportation of pipe for the gas
pipeline, is that moving it by truck would overload and destroy
the road structure.
MR. DESJARLAIS responded that weight is a factor, but the sub-
grade is not failing at the test sites, so the state is building
good roads; it just has mix problems.
CHAIR HUGGINS asked how much the rutting factor would be reduced
if they got the mix right.
1:47:51 PM
CHAIR HUGGINS recognized Representative Carl Gatto and invited
him to join the discussion.
MR. DESJARLAIS said that he has a lot of slides and data on that
very question, including some slides illustrating that the vast
majority of flow occurs in the top lift. On Glenn Highway
however, the second lift is deteriorating badly and they aren't
sure why. He said that a study by Barter and Johnson (1996,
1997) reported that Alaska spends $5 million annually to repair
stud-related pavement damage, but they have not found anything
that establishes studded tires are the cause.
SENATOR COWDERY asked if the mixes in use today have changed
much over the past ten years or so.
MR. DESJARLAIS replied that they are studying that now, but he
believes they will find that mixes have changed a lot.
REPRESENTATIVE CARL GATTO asked how much of the asphalt laid in
the state of Alaska is made with Alaskan oil.
MR. DESJARLAIS replied that almost all of it is now made with
Alaskan oil.
REPRESENTATIVE GATTO asked if there is any data comparing roads
that were built with asphalt made from foreign oil and those
that were built using Alaskan oil. He also asked about the
hardness of the rock that is used in the sub-grade.
MR. DESJARLAIS said that he would discuss the hardness of the
rock later, but that Alaskan oil contains significant amounts of
paraffin, which might make softer asphalt.
1:53:03 PM
SENATOR COWDERY said he understands that sweet crude makes a
better product than North Slope oil, but he isn't sure whether
it is available. He also said that he has talked to DOT about it
but his suggestions were not well received.
MR. DESJARLAIS confirmed that Senator Cowdery is correct about
the superiority of crude oil in the mix. He said they have been
working closely with Department of Transportation on this
project and that both Newt Bingham and Mike San Angelo of DOT
have been very cooperative and helpful.
He presented a slide of Glenn Highway near the Muldoon exit,
which illustrated pitting in the road, and pointed out that the
rocks are not ground down; traffic is picking out the fines
[fine, binding surface materials] around them, allowing the rock
to come out. Possibly using harder aggregate and larger stones
in the surface core could slow this process. Alaska doesn't have
a lot of large stone however, so river gravel is more commonly
used, and the harder aggregate might not help without larger
surface stone. Arizona is incorporating rubber into the surface
core and it's holding up very well, so there are other options
that might work. This study focuses on plastic flow because, of
the sites they have sampled, only the Glenn Highway exhibits
this picking phenomenon.
1:57:20 PM
CHAIR HUGGINS commented that there is a major variance in
rutting along the Glenn Highway from one area to another, and
asked what Mr. Desjarlais attributes that to.
MR. DESJARLAIS answered that he thinks it is due to different
aggregates and different mix designs. He noted that, on the new
paving on Tudor Road, they found tiny variations in asphalt and
gradations, and one side is holding up better than the other. He
thinks the answer might be modified pavement asphalt, perhaps
with more polymers, or incorporating rubber as they've done in
Arizona, rather than using harder aggregate.
CHAIR HUGGINS asked if Arizona uses any recycled rubber in the
asphalt.
MR. DESJARLAIS replied that all of it is recycled. He added that
Alaska tried using rubber in asphalt about 15 years ago, but it
wasn't very successful because the federal government was
mandating the amount of rubber that had to be incorporated into
the pavement and there was no control over the type of rubber
being used. In Arizona, they are using a pretty fine mesh that
comes from grinding off the outside of truck tires, which yield
much better rubber than other types of tires.
2:00:33 PM
SENATOR COWDERY mentioned that California has also used rubber
in asphalt successfully.
REPRESENTATIVE GATTO said he heard that California has had a
problem with oxidation in rubber from passenger car tires, so he
thinks they've shifted to butyl rubber.
MR. DESJARLAIS replied that the Manhole Adjustment Company, Inc.
in Los Angeles California provides asphalt rubber to
contractors for use in mixes and has gotten the state to write
specifications requiring that it contain a certain amount of
tennis ball rubber, which might be a factor in oxidation. The
anti-oxidizing agents in tires are actually beneficial.
Approximately 60 percent of primary roads in Arizona have a thin
layer of asphalt rubber surfacing, and they have had spectacular
results. He remarked that asphalt oxidizes too, which
contributes to failure, especially in hot countries. Seal
coating is frequently used to combat it.
2:03:00 PM
REPRESENTATIVE GATTO remarked that he heard last year that
Michelin made a tire called an Ice tire, which is as good as a
studded tire.
SENATOR COWDERY said he owns Bridgestone tires that are similar
to the Michelins and they are highly effective all-season tires.
REPRESENTATIVE GATTO added that they are not aggressively
treaded so, compared to studded tires, they have less impact on
road wear.
2:03:57 PM
MR. DESJARLAIS asked what the tires look like.
SENATOR COWDERY replied that they look like sawdust tires; they
are softer rubber and are self-cleating.
2:04:47 PM
MR. DESJARLAIS said that George Way P.E. in Arizona showed him a
slide presentation of a badly damaged intersection at 1, 5, and
10 years after paving a portion with a one-inch layer of a
mixture of 8-10 percent liquid asphalt containing 20 percent
rubber. The road has continued to deteriorate, but there is not
one reflective crack in the rubber asphalt surface after 10
years.
CHAIR HUGGINS wondered if there is a difference in braking
distance on a rubber asphalt surface.
MR. DESJARLAIS replied that he has seen a video of trucks on wet
pavement and the rubber asphalt surface does not throw up the
rain; it seems to be flowing off.
CHAIR HUGGINS asked Mr. Desjarlais to repeat his overview of
their research grant for Senator Cowdery.
MR. DESJARLAIS said that about two years ago, he and John Lu
visited the civil engineering lab at University of Alaska
Fairbanks (UAF) and decided to use it to research Alaska's
pavement rutting problem. They obtained a grant to UAF for the
study and have tried to take a fresh approach to the problem,
focusing on the actual cause of road rutting, rather than
treatment of the symptoms.
2:08:05 PM
MR. HULSEY said that Dr. Rad did a lot of the research on
rubberized asphalt in California for Manhole Adjusters. He also
mentioned that he, Dr. Rad, and John Lu obtained a grant from
DOT to compare traction on Bridgestone tires to studded tires
and were surprised to find that the Bridgestone winter tires
surpassed studded tires in tractability in almost every test.
2:09:55 PM
MR. DESJARLAIS asked Senator Cowdery how much his Bridgestone
ice tires cost.
SENATOR COWDERY could not remember.
MR. DESJARLAIS reiterated that studded tires are definitely a
factor in creating road wear, although not as great a factor as
they were previously thought to be.
REPRESENTATIVE GATTO said he assumed that studded tires would be
more effective than ice tires on wet asphalt once the tires have
locked.
MR. HULSEY replied that they tested the stopping distance of
various tires on the wet runway at Fairbanks International
Airport and did not find that to be true.
2:11:55 PM
SENATOR COWDERY said that might be due to widespread use of
antilock brakes in modern cars.
MR. DESJARLAIS showed a slide of the cores from the Stone Matrix
Asphalt (SMA) surface on Glenn Highway and pointed out that SMA
is fairly porous. The slides show that the second lift has
deteriorated almost completely and the asphalt has flushed off,
leaving uncoated aggregate. He also showed slides comparing the
depth of ruts on the Glenn Highway starting at 200 ft. distance
from the Muldoon exit, up to the exit itself. Rutting is fairly
consistent at 70 mph, but as traffic slows down nearer the exit,
the rutting becomes shallower. He said this is the exact reverse
of what happens in plastic flow.
2:13:55 PM
CHAIR HUGGINS asked if that is studded tire wear.
MR. DESJARLAIS replied yes, that the high speed is what causes
studded tire wear.
REPRESENTATIVE GATTO suggested a mechanism for the trends
exhibited in the charts.
MR. DESJARLAIS showed slides of rutting caused by plastic flow
on Dimond Boulevard, starting at a distance from the stoplight
and increasing as traffic slows to a stop.
SENATOR COWDERY said that when Dimond Boulevard was paved two
years ago, ripples formed in the road within two weeks after
paving was complete.
2:15:54 PM
MR. DESJARLAIS noted that the Stewart Highway did the same thing
when it was paved 6-8 years ago. He presented a summary of their
preliminary research results on plastic flow. None of the
sampled sites showed evidence of sub-grade deflection or surface
raveling and, of the six sites tested to date, only the Glenn
Highway showed any indication that studded tires might be the
primary contributor to rutting. They are not yet sure what
impact the failed mix on the second lift might have on rutting
at this site. Testing on the other five sites shows clearly that
rutting is the result of plastic flow. Fortunately, this can be
managed utilizing the latest technological developments in mix
design adapted to Alaska's conditions.
2:18:53 PM
MR. DESJARLAIS presented slides and information from an
extensive study conducted in Colorado in 1992, which concluded,
"when air voids in the wheel path were less than 3 percent,
there was a high probability of rutting from plastic flow." He
explained that a proper mix design is one in which there is a
skeleton of aggregate, from the largest to the smallest, and
stone-on-stone contact so that it cannot compress. Each particle
is then coated with liquid asphalt to glue it all together,
which creates what is called "maximum density." At maximum
density, there should be four percent air voids, or open areas
remaining.
He went on to say that the structure of a road is sub-grade,
granular base, and surface layer and most road rutting occurs on
the surface layer. If there are excessive air voids, it is an
unstable mix that will deteriorate and ravel. Insufficient air
voids cause plastic flow, which is exacerbated by the addition
of too much liquid asphalt. He said that these results have
caused engineers to rethink asphalt composition. He compared the
Marshall Mix Design, which accounts for most of the asphalt in
Alaska, to the Simple Performance design, and stressed that the
Marshall Mix performance test cannot predict the durability of
pavement in the lab. The Simple Performance test can do that,
but the equipment required is very expensive.
2:22:30 PM
REPRESENTATIVE GATTO asked about the susceptibility of concrete
roads to studded tire damage.
MR. DESJARLAIS said that it does occur on concrete roads and
they are more subject to picking than asphalt, but there is no
plastic flow. He speculated that building concrete roads in
Alaska would be prohibitively expensive, particularly with the
poor sub-grades used in the state. Concrete can bridge some
irregularity, but Alaskan roads would have to be prepared just
as they are for asphalt, which is not necessary in the Lower 48.
REPRESENTATIVE GATTO asked if anyone has considered using an
overlay fabric between the top lift and the next lift.
2:25:18 PM
MR. DESJARLAIS said that he has done that in Anchorage, on
Arctic Boulevard. The purpose of an overlay fabric is to prevent
reflective cracking and it has proven highly effective. Polymer
modified asphalt does the same thing, and many of the roads in
Anchorage are surfaced with it. Liquid asphalt has a Performance
Grade, or PG rating; PG 52/28 means that grade of asphalt
performs to a certain level between 52 and 28 degrees Celsius.
Because that is the only grade of asphalt available in Alaska,
polymer (styrene-butadiene-styrene [SBS]) is added to make it
more resilient in extreme temperatures.
REPRESENTATIVE GATTO asked if a driveway has the same mix as a
highway.
2:27:45 PM
MR. DESJARLAIS replied that driveway mixes are much finer and
unstable in general, and would not be suitable to use on a
highway.
He said that with regard to design vs. constructability and
quality control, it is important to realize that laboratory
simulation can only sample a very, very small part of the
overall quantity. It will cost the state and the contractors
money, but it is important to have better quality controls in
place in the plant and in the field. He also said that the focus
has been on things that are inconsequential; it is important to
focus on the composition of the blends. He emphasized that
process control is more important than composition testing.
MR. DESJARLAIS' next slides provided a comparison of the
percentage of voids in different layers of the old and new
pavements on Tudor road. They illustrate that the mix on the
top lift before re-paving was down to .02 percent. It probably
had four percent voids originally, but it kept compacting and
flowing, until there were virtually no voids left. The
westbound lanes of the new pavement contain local aggregate; the
eastbound lanes contain hard aggregate with the same broadband
mix design as that on the westbound lanes. He said that he
assumes the westbound lanes will begin to rut within a few
months but that it has nothing to do with hard or soft
aggregate, but with the mix design.
2:34:33 PM
REPRESENTATIVE GATTO suggested moving the stripe on highways to
distribute wear and reduce rutting.
MR. DESJARLAIS replied that it is a thought. He concluded that
plastic flow is a major cause of rutting due to mix design and
techniques, inadequate constructability and inadequate testing.
He again stressed that process control is of the greatest
importance.
2:37:12 PM
MR. DESJARLAIS suggested requiring 3-4 percent polymer for
roads, and making testing a priority in that process as well as
in the making of hot-mix asphalt.
2:37:49 PM
SENATOR COWDERY said that he has observed that contractors bid
on a job based on the specifications that are required, not to
do the best possible job, which creates design flaws.
2:39:14 PM
REPRESENTATIVE GATTO asked what happens on runways.
MR. DESJARLAIS replied that the construction of runways is
radically different from the construction of highways. The
standards for runways are much higher.
REPRESENTATIVE GATTO asked whether the autobahns are asphalt or
concrete.
MR. DESJARLAIS replied that most of them are asphalt, and
described the construction method used on that type of project.
2:41:10 PM
CHAIR HUGGINS asked Mr. Desjarlais to explain de-icing to
Representative Gatto, particularly as it relates to the bridges
in the MatSu.
MR. DESJARLAIS said that he has been consulting with a company
that developed a system to prevent ice from forming on bridges
and tunnel entrances and exits. There is a sensor (peltier
device) set into the pavement that detects moisture on the road
and, when the temperature drops below 39 degrees Fahrenheit, a
thermal electric heat pump warms up to two degrees Celsius over
freezing to melt any ice or snow off the road, then cools down
to as much as 25 degrees Fahrenheit below the surface
temperature of the road and records the freeze-point of moisture
on the surface. Once the freeze-point has been established, when
the temperature gets within two degrees of that point, an anti-
icing chemical is sprayed on the bridge. This technology will be
used on the Knick River Bridges.
2:45:12 PM
REPRESENTATIVE GATTO said he heard that it would be frightfully
expensive.
MR. DESJARLAIS replied that it would only cost a million dollars
for the main bridge over the Knick River, both north and south
spans, plus 200 feet on each side approaching the bridge.
SENATOR COWDERY remarked that just after adding a new runway at
the Anchorage International Airport, planes sitting on that
runway were actually turning the asphalt when they turned their
wheels to move.
MR. DESJARLAIS said he remembers that. The top lift was sliding
and completely separating from the second lift. The runway has
now been chip-sealed with polymer modified asphalt.
CHAIR HUGGINS mentioned that the committee would like to have an
asphalt summit when all of the research is complete.
MR. DESJARLAIS agreed and said that they should hold another
summary meeting for stakeholders involved in the project.
CHAIR HUGGINS asked how much longer the graduate student has
left.
MR. HULSEY said that he has at least a year. Lab work should
resume in September and they should have more faculty at the lab
at that time.
MR. DESJARLAIS said that the UAF lab could be used to solve
problems in mix design instead of just throwing money at them.
CHAIR HUGGINS asked about Billy Connor's grant and wondered
whether he will be using the UAF lab.
MR. HULSEY answered that Mr. Connor has a 5-year grant of
University Transportation Center funding to bring top
researchers in the field of transportation-related problems to
Alaska, and that he will be using the UAF lab. He commented that
the lab is fortunate to have first-rate equipment, including
environmental chambers to test samples in cold weather
conditions, but it needs funding to keep the equipment properly
calibrated.
MR. SAN ANGELO said that DOT supports the work that is being
done on this.
CHAIR HUGGINS adjourned the meeting at meeting 2:55:53 PM.
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