By: Bill Wilson, Editor
Northstar Asphalt Inc. had a suggestion, but didn't quite
have the experience to make it. Nobody in the state of Ohio did.
When the Ohio Department of Transportation worked out
designs for the expansion of a 2.3-mile stretch of I-77, it originally wanted a
131/4-in. asphalt pavement over an asphalt free-draining base and 6-in.
aggregate base. Northstar Asphalt, however, believed more resilience was needed
to cover a seven-year warranty, and convinced officials to go with the state's
first section of perpetual pavement. The North Canton, Ohio-based contractor
recommended 171/4 in. of asphalt which included a 4-in. fatigue-resistant
layer, a 10-in. rut-resistant base course and a Superpave intermediate and
surface course. The design-bid-build job, which started in the spring of 2002,
is worth $16 million.
"Warranties are relatively new, and our philosophy
always is to make pavements that last," Bryan Shaw, I-77 project manager
for Northstar Asphalt, told Roads & Bridges. "The pavement will be
evaluated on a yearly basis, and there's a set of criteria which will be used.
If cracking and rutting exceeds a certain dimension we're going to be called
out to fix it.
"We wanted to make sure we were utilizing the best
materials and using the best mix and methods. By applying this perpetual
pavement we think we're dealing with a sound concept. We're hoping it exceeds
seven years. I'm thinking it will last 10, 11 or even 12 years."
Heading north
Total construction on I-77 will certainly last 10 years. The
2.3-mile segment under the direction of prime contractor The Ruhlin Co., Sharon
Center, Ohio, and Northstar Asphalt is part of a massive widening effort, which
spans from Akron to Canton. The I-77 corridor was built to hold four lanes of
traffic, but the traveling public is now demanding six. A number of asphalt
overlays extended the life of the section which, according to Shaw, is 6 in. of
asphalt over 9-10 in. of concrete base.
Managing the daily commuters called for immediate and
temporary action. To accommodate two lanes of northbound traffic, Northstar
Asphalt paved 18 ft of temporary pavement on the inside of the southbound
portion and used concrete to extend the outside shoulder 8-10 ft.
After old asphalt was removed, Ruhlin rubblized the sub-base
and fixed the subgrade. A three-sided impactor--the Thumper (Model 2000) by IRT
Technologies--broke up the sub-base. The new gravel (ODOT 304) foundation
contains aggregate no greater than 2 in. According to Ruhlin Project Manager
Doug Hartz, 70-100% of sub-base material had to pass through a 1-in. sieve;
50-90% had to pass a 3/4-in. sieve; 30-60% had to pass a No. 4 sieve; 9-33% had
to pass a No. 30 sieve; and 0-13% had to pass a No. 200 sieve.
Ruhlin also installed new under drains (perforated pipe
trenched with filter fabric wrap) and median drainage (catch basins and points
to tie in all under drains). The original pavement did not have median
drainage, which Hartz believed led to its destruction. "It just didn't
have enough drainage," he said.
Ruhlin handled a small amount of excavation work.
Caterpillar 345B L and 330C L excavators handled about 106,000 cu yd, and a CMI
TR-2503 trimmer was used to trim both the subgrade and base.
"The biggest thing is meeting the fast-paced
schedule," said Hartz on what was a smooth production until work stopped
for the winter. "It's been a dawn-to-dusk effort."
Northstar Asphalt has followed Ruhlin with the actual paving
portion of the job from dusk-to-dawn. The 171/4-in. perpetual pavement is made
up of four layers. The first is a 4-in. fatigue-resistant layer (ODOT 302)
which is made up of coarse aggregate (No. 57 crushed gravel/No. 4 limestone),
fine aggregate (manufactured/natural sand) and a performance-graded liquid
asphalt cement (PG 58-28). Maximum aggregate size is 2 in. and nominal size is
11/2 in. Asphalt cement content is 4.3%. Northstar Asphalt tweaked the
gradation and added more asphalt cement to lower the air void content to 3% in
the base layer.
The second layer--a 10-in. high-stability and rut-resistant
layer (ODOT 302)--was done in two lifts. The mix is almost identical to the
fatigue-resistant base with the exception of the air void content (4%) and
asphalt cement content (4%).
At the surface are two Superpave layers. The first layer is
a 13/4-in., 19-mm Type A Superpave design (ODOT 442). The maximum aggregate
size in the 19 mm is 1 in., the nominal aggregate size is 3/4 in. and the
asphalt cement (PG 76-22) content is 5.2%. Capping the road is a 11/2-in.,
12.5-mm Superpave design (ODOT 442) which contains slag coarse aggregate for
skid resistance. The maximum aggregate size in this lift is 1/2 in., the
nominal aggregate size is 3/8 in. and the asphalt cement (PG 76-22) content is
6.5%.
A CMI asphalt plant located on site cranked out mixes at
2,000-2,500 tph during work on the northbound lanes.
The big-stone content, however, didn't cooperate at the
beginning.
"They're typically pretty hard to handle," said
Shaw. "They are prone to segregation and we did have some difficulty up
front."
Northstar's segregation solver was a Barber Green MTD 3000
(Circle 926) material transfer vehicle (MTV) with a hopper capacity of 25-30
tons. A Cedarapids MS4 (Circle 927) also worked well on the job. Northstar
Asphalt initially used the string line Ruhlin worked off of during the
installation of the aggregate base. According to Shaw, using that string line
established lift elevation. From there, the combination of the Topcon Sonic
Grade Control System (Circle 928) and a ski helped with consistency. The 60-ft
ski was positioned in front of the screed. The device signaled back to the tow
arm of the paver to make slight adjustments en route to maximum
smoothness.
The MTVs fed into a Cedarapids CR561R rubber-tracked paver
(Circle 929) with solid screed extensions. "We've gone away from the
hydraulically extended screeds and have been using solid extensions," said
Shaw. "We felt that would be a more stable screed arrangement."
Forming the roller path were Hypac C778B (Circle 930) and
C766C (Circle 931) double-drum vibratory rollers capable of producing 3,000 vpm
and a Dynapac CP21 pneumatic tire roller (Circle 932). The density requirement
for the 2.3-mile section is 94-97%, and during northbound construction crews
were achieving 97% density. Field densities were determined by in-place nuclear
gauge testing every 300-500 ft. Core samples also were taken. Asphalt was
placed at 290-300°F.
Time to regroup
Most of the work on the northbound section is now complete.
Shaw estimated that 90,000 tons of asphalt is currently in place. Another 60,000
tons will be used when southbound construction starts again in March.
"At times this project has been a little intimidating,
but we have to look at it from the perspective that it was important to us to
build a good pavement that would last," said Shaw. "Hopefully, this
is a good exercise to where we want to be in the future. We've worked a lot of
bugs out of our laydown and plant operations, and hopefully it will run just as
smooth (in March)."
In addition to work on the aggregate base, Ruhlin is expanding
four bridges--two overpass spans and two mainline bridges--along the 2.3-mile
site. It was decided to remove the existing concrete decks and steel beams, and
save the old substructures. The northbound mainline bridge and an overpass
south of the project are already upgraded.
"We'll do the southbound bridge this year and the
overpass bridge that leads to the Akron-Canton Airport," said Hartz.
Ruhlin wants to finish the southbound mainline bridge before
Northstar makes too much progress on the paving end.
