| ASPHALT IN-PLACE RECYCLING
ORLANDO RECYCLES ITS WAY TO THE TOP
Hot in-place recycling helps keep
Orlando-area roads among nation’s best.
 This
year Orlando and Orange County, Florida drivers are driving on one of the
best-kept road systems in the United States.
Orlando and Orange County civil engineers credit meticulous pavement
preservation techniques — and pavement management — with the superior
showing.
Orlando/Orange County drivers were also able to enjoy the fact that
extra vehicle operating costs per driver in their area due to
pavement-related wear-and-tear amounted to $97 per vehicle. The national
average was nearly five times higher, at $396 per vehicle, and a
worst-case urban area was Los Angeles, with a rough-road-induced wear and
damage averaging $706 per vehicle.
Federal Highway Administration pavement condition data in Orlando’s
urbanized area indicated that 17% of Orlando/ Orange County arterial roads
were rated “good”, with only 2% rated “poor”. Another 20% were
rated “acceptable”. Only Atlanta and Phoenix were rated ahead of
Orlando in the FHWA’s statistics, which were analyzed and released as a
special report by The Road Information Program.
“Perfection would be 100% good and zero poor,” says Richard M.
Howard, P.E., city engineer, Orlando Engineering/Streets & Drainage
Bureaus. “We’re not quite there yet.”
Nearly all asphalt streets
 Nearly
all of Orlando’s streets are asphalt-surfaced, and the city attempts to
apply rejuvenating treatment to every asphalt surface after six years,
followed by an asphalt overlay or hot in-place recycling every 11 or 12
years on the average, Howard said.
“Larger volume streets receive hot in-place recycling or overlay,
depending on the structural condition,” Howard said. “It’s a very
systematic approach, based on our pavement management system, which was
instituted in 1985.”
Remarkably, this general improvement has taken place against the
context of enormous growth in the Orlando area. Metro population grew by
34% in the 1990s alone, to 1.6 million.
“Our network has increased because we’ve annexed portions outside
the city,” Howard said. “What it’s shown us is that some of the
things we’ve been doing right we have continued; we’ve put a lot of
money into overlays. And some of the newer techniques that have come along
after 1985 we’ve adopted as we’ve seen the need, like hot in-place
recycling.”
Orange county uses HIR
Orange County, in which Orlando is situated, also is using hot in-place
recycling to keep its asphalt pavements smooth and free-flowing.
“We’ve got everything from four-lane to six-lane arterials, all the
way down to cul-de-sacs in subdivisions,” said Carl Landon, highway
coordinator, Roads and Drainage Division, Orange County. Currently the
county has 2,538 centerline miles to maintain, of which one-quarter is
arterial.
“Orange County probably has been the most aggressive of those I’ve
seen in trying new strategies to maintain its pavements,” said Howard F.
Russell, P.E., then Orange County chief engineer. “We’re on a quest to
find the most cost-effective means of preserving pavements. As fast as we’re
building around here, we need faster ways and cheaper ways to maintain
pavements while incorporating recycling.”
Using repaving process
To keep their pavements smooth and trouble-free, both Orlando and
Orange County have used a distinctive, one-pass hot in-place recycling
process that reuses the existing deteriorated asphalt as a leveling
course, and on it places a fresh layer of virgin hot-mix asphalt.
That HIR process, called Repaving, is provided by Cutler Repaving,
Inc., Lawrence, Kansas. This exclusive process heats the existing pavement
to 300 degrees F. When in a softened, pliant condition, the pavement is
scarified to a depth of 1 inch and a recycling agent that restores the
viscosity of the aged asphalt is mixed into the scarified, reclaimed
asphalt. This material is then reapplied and distributed with a screed as
a 1-inch leveling course. Then, while that material remains at a minimum
225 degrees F, a virgin hot-mix asphalt overlay is placed over the
recycled leveling course.
Cutler’s unique Repaving machine scarifies, applies recycling agent,
places the leveling course, and applies the new overlay simultaneously in
one pass. That benefits road users because there is no delay between the
time the pavement is recycled and the time a riding or friction course is
placed, resulting in a safer work zone for road users and for contractor
personnel.
Also, because the hot virgin mix is placed over the heated, recycled
leveling course, the process achieves a thermal bond between the recycled
layer and the new layer. “From an engineering point of view, there is no
delamination between the recycled layer and the new overlay,” says
Cutler vice president John Rathbun. “That’s very important in
predicting life cycle performance. The same heat that’s used to take the
road apart is used to put it back together, and the two layers are
effectively compacted into one lift.”
Repaving also reheats the edge of adjacent repaved lanes, resulting in
a more durable, higher-density seam between the driving lanes, Rathbun
says.
The entire machine moves forward at a rate of 18 to 25 feet per minute.
The virgin surface is applied by a four-section vibratory screed no more
than 3 feet behind the leveling course screed. It’s fed from a hopper at
the front of the Repaver via a drag/slat conveyor chain which brings the
hot-mix asphalt through a tunnel along the length of the machine, to the
paving screed. The result is a monolithic, 2-inch, finished pavement that
is equivalent in ride to a 2-inch mill and overlay.
The complete HIR Repaving pass takes place in minutes, meaning traffic
barricades can come down quickly, with all reclaimed material used on the
spot without hauling, so user delays are kept at a minimum compared to
conventional mill-and-fill recycling projects.
Traffic can drive on the new pavement as quickly as with conventional
paving, while driveways and intersections are blocked for about 15
minutes. And the objectionable tack coat ahead of HMA paving is
eliminated, meaning Orlando and Orange County enjoy cleaner sidewalks,
curb cuts and automobiles.
“The process can be invasive, because people are not used to seeing
the machine coming down the road,” Howard says. “But the entire method
is accomplished at one time, and then they’re gone. So it’s very
appropriate for urban areas.”
Suited for Orange County
The Repaving process is particularly suited for certain high-profile
arterial projects which Orange County has faced.
“On International Drive — in the heart of the convention center and
tourist entertainment district — they wouldn’t let us mill-and-fill
because it was too dusty, with the ongoing PGA convention and too many
tourists traveling through,” Orange County’s Landon said. “We had to
come up with something else, and that’s when we brought the Cutler
Repaving process in.”
As a result of that high-profile project, the county gained confidence
in the HIR method.
“International Drive is in excellent condition after seven years,”
Landon said. “HIR is quicker, suppresses reflective cracking, and
eliminates dust in construction. Lane closures are minimized, and because
it’s a rolling procedure, no one lane is closed for a long period. And
less material and trucks come out and go in so there is less traffic
disruption.”
In fact, Orange County has steadily increased its utilization of HIR
Repaving since International Drive. “We use it mainly for our heavily
traveled arterials,” Landon said. “We look for pavements that are
raveled or have slippage. We don’t use it on pavements with heavy
alligator cracking because that indicates big base problems. If a pavement
is due for an overlay, and we don’t want to increase its elevation, it’s
a candidate for HIR.”
Reusing what’s there
 Besides
its engineering characteristics, the concept of HIR appeals to Orlando’s
Howard in a more thoughtful way. “At the city we try to reuse what’s
there,” he said. “We want to extend the life of the structure we have,
rather than create a new one. There is a lot of value there, and Repaving
is a major component in making the most efficient expenditure of our
budget.”
“In the past, if we had to resurface a road, we had to rip up the
surface, haul it away, come back in, and place a new surface,” said
Deodat Budhu, P.E., manager, Roads and Drainage Division, Orange County.
“Now we have a way to recycle the pavement, providing a better base,
with fresh asphalt on top. It is a one-pass mechanism which helps us with
traffic control. It’s a cost savings for us, and that helps us do much
more work with that money.”
More information about Orlando is available at www.cityoforlando.net;
about Orange County, at www.ocfl.net;
about FP2 at http://fp2.org; and Cutler
Repaving, Inc. at www.cutlerrepaving.com.
Reprinted from Better Roads Magazine
July 2003 |
