By: Larry Flynn
Rideability and appearance. Aside from passing the required
tests, these two factors determine whether or not a paving
project is acceptable, according to Ted McRae, president of
Anderson Columbia Co. Inc., Lake City, Fla. Attention to these
factors on an asphalt paving project in Georgia last year made
the project more than acceptable; it made it outstanding. The
result was the company being awarded the Sheldon G. Hayes Award
for quality paving by the National Asphalt Pavement Association
(NAPA).
Anderson Columbia received the hot-mix paving
industry's highest honor for its work on I-75 in Lowndes County,
Ga., in 1996. The 10-mile project, which took place just across
the Florida border, used 146,800 tons of HMA in 61.8 lane miles
of construction.
Totaling $13 million, the project involved
milling and overlay of the highway's existing four lanes and the
addition of two 12-ft lanes inside of the existing roadway.
Inside of the new lanes a 10-ft shoulder was constructed and a
guardrail installed in the median. The project also entailed the
removal of an overpass that spanned a now abandoned railroad
right of way and the lowering of the grade of the old
approaches.
Award-winning features
Rideability and
appearance stand out as the two most striking features of the
project. Randall Marchant, technical services engineer for the
Georgia DOT, said, "The Georgia Department of Transportation has
an audit program where we go out and measure the smoothness of
pavements on a regular basis. On this project, after it had been
under traffic for six months, there were several miles of it
that showed a zero reading." A zero reading indicates the ride
meter used to gauge the rideability of the pavement was unable
to detect any roughness.
"The Mays meter [readings] were
under six for the project," Anderson Columbia's McRae told ROADS
& BRIDGES. "I understand that the project was the smoothest
Georgia had ever recorded on a similar project." Marchant
concurred, saying, "The project also had, to my knowledge, the
lowest [meaning the best] overall readings of any project of
this magnitude in the state."
According to Ken Murphy,
Anderson Columbia's bituminous engineer, the Mays meter, used to
determine the ride of the pavement, records more of what a
motorist actually feels riding in a vehicle as opposed to a
profilograph, which measures the difference in elevation between
points. "The Mays meter is trailer mounted and records the
movement of the body on the axle," he said.
Perhaps an even
more impressive display of workmanship on the project lies in
its appearance. According to McRae, in his comments about the
project, the NAPA judge who evaluated the project said that the
workmanship at the pavement joints was such that he had a
difficult time locating them.
McRae credits the success of
the project to the crew that worked on the project. "Mike
Hudson, the paving foreman, did an exceptional job," he said.
"He and his people really take pride in their work. The joints
and the rideability really made for a super project." McRae
added that while the Hayes Award is the company's first national
honor, the company, and Hudson's crew in particular, has
captured many regional and state awards.
Marchant gave kudos
to Tony Williams, Anderson Columbia's area manager, and Hudson.
"The paving crew was the best I ever worked with," he said.
"Everybody in the company really cares about quality and it
shows. The results were great. The job still looks good."
"We try on every job to go out and perform quality work, whether
it's a county road, state highway or an interstate," McRae said.
"It happened to work out that this job was abnormally good."
The project consisted of three main sections, milling and
resurfacing, new lane, shoulder and guardrail additions, and
overpass removal and grade lowering. According to McRae, a
minimal amount of milling was necessary on the pavement, which
consisted of asphalt laid over a concrete pavement. "The milling
was performed to get the road back into uniform slope," he said.
The lanes were then overlaid with a 1 1/2-in. surface mix,
topped with a 3/4-in. open-graded friction course (OGFC)
designed to provide a smooth riding surface and reduce road
spray in wet weather.
Building the two new lanes on soft
Georgia clay delayed work on the project at times because of wet
weather. A graded aggregate base material consisting of crushed
lime rock was shipped in from Anderson Columbia's mine in
Columbia City, Fla. A 3-in. HMA base was then paved over the
aggregate base, followed by leveling courses where required, a
2-in. HMA binder course and a 11/2-in. surface course. The
pavement was then topped off with a 3/4-in. OGFC.
OGFC
impresses
The contractor was as impressed with the Georgia
DOT's OGFC, as the Georgia DOT was with the contractor's work.
Known in Georgia as a D-modified OGFC, the top course includes
an SBS (styrene-butadiene-styrene) polymer modifier and
reinforcing fibers. "It was the first time we've used the mix,"
said McRae. "We were really impressed with it. I thought it made
an excellent riding surface. The texture was open and the
drainage was good. All the published data says it will not
close-up." According to McRae, Florida's experience with its
OGFC had been that in time the course would close-up hindering
the beneficial aspects of the mix.
"We knew from the start
it was going to be a good mix," said Murphy. "We even brought up
a Florida engineer to see it." Murphy is particularly impressed
by the pavement's drainability. "It can be raining really hard
and you won't even know it by looking at the pavement."
Anderson Columbia placed a test strip for the Florida DOT (FDOT)
using the Georgia OGFC mix design and it was evaluated for skid
resistance, hydroplaning and drainage. FDOT was so impressed
with the mix that it is adopting the same basic OGFC design,
called an FC5 mix, except the state is using ground tire rubber
in place of a polymer modifier.
On the I-75 project, the mix
contained 6% polymer-modified asphalt binder by weight of the
total mix and 4/10th of 1% mineral fibers. The fibers, obtained
from Fiberand Corp., South Miami, Fla., were blown into the mix.
During the project, the contractor faced another challenge
when the original U.S. polymer-modifier manufacturer's plant
burned. With all other U.S. manufacturers booked two to three
years in advance, the company turned to a broker in Connecticut
who was able to supply the project with Finaprene Vector 2411
SBS polymer modifier from a licensee in Taiwan. The modifier was
purchased truck load by truck load and blended at the plant at
4.75% by weight of the binder by Advanced Asphalt Technologies,
Sterling, Va.
According to Murphy, the OGFC course not only
helps reduce spray, but the course, as it is applied in Georgia,
also enhances the pavement ride. "Back in the late '70s, Federal
Highways came out with OGFC, but it was put down real thin,
about 1/2 in.," he said. "At that thickness it does nothing for
rideability. At 3/4 in. thick, however, it does wonders for
ride." He added that the OGFC also improves the safety aspects
of the pavement, such as skid resistance and reduced
hydroplaning.
Overpass removal
Removal of the overpass
and lowering of the grade required a great deal of coordination
because the work had to be performed in 180 days under traffic
on the highway, which carried an ADT of 39,500. To conduct this
portion of the project, three operations had to be staggered,
according to McRae.
"We had to take out one side of the
overpass, and while we were taking out the one side we ran
traffic into a lowered median," he said. According to Anderson
Columbia's Williams, the company cut down the median between the
north- and south-bound lanes 14 ft and built a roadway detour
through the median. "So the existing roads were actually higher
than the detour," he said.
"After the first 30 ft of the
overpass was removed, we encountered unsuitable material, which
resulted in a change order," McRae said. "We had to bring in
suitable material." In the end, the overpass was removed, the
grade was lowered and the highway was built straight through
where the railroad right of way had been. In addition to the
overpass removal, another bridge also was reconstructed on the
project.
