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I-94 concrete overlay project will act
as a durability study
By Peter Fretty
Construction on any busy interstate
is rarely ever welcomed by
over-the-road freight haulers or
daily commuters. Even though both usually
like the end result, the fact remains
that few people trying to get from one
place to another want to stomach the
unavoidable interruptions always inherent
in roadway construction operations.
This was one primary reason why Dan’s
Excavating, Inc., Ajax Paving Industries,
Inc., and the Michigan Department of
Transportation (MDOT) have worked
in conjunction to schedule and perform
the preventive maintenance needed on
I-94 in St. Clair County as a comprehensive
fast-track project. The heavily
traveled I-94 bi-way not only connects
Detroit with Chicago but also connects
to Canada by way of the Blue Water
Bridge. With the work having started in
mid-April, the schedule currently shows
a completion date of October 2006. And
according to Ajax Project Manager Pete
Mann, the crew is actually on pace to
complete the work in September.
When all is said and done, the project
will include rehabilitating roughly 5
miles of I-94 between Gratiot Avenue
(known as the I-94 Business Loop) and
Griswold Street in St. Clair, primarily
through a concrete overlay. Also included
in the project is limited repair work
to the I-94/Gratiot interchange, as well
as the replacement of the Ravenswood
Road bridge deck.
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Conquering Challenges
Understandably, coordinating the overlay
with the reconstruction, the bridge
construction, and the interchange work
does cause some hurdles. But fortunately,
the crew has been able to continue
moving forward as scheduled. But like
any job where weather and fluctuations
in traffic can wreak havoc, the demanding
schedule has definitely been one of
the most challenging aspects, explains
Mann. “Whenever you have a job of this
size, it is never easy to complete everything
in a limited amount of time,” he
says. “We are fortunate that things have
moved relatively smooth.”
One way to help limit disruptions is
to schedule the work to take place in
stages, having the westbound lanes
repaired in stage one and the eastbound
lanes in stage two. Throughout the process,
work has been conducted in effect
from daylight to sundown six to seven
days a week. The Dan’s Excavating crew
has also taken advantage of time-sensitive
traffic shifts, maintaining two lanes
eastbound and one lane westbound,
again embracing the concept that the
least amount of disruption possible is
definitely preferred.
To further facilitate this mindset, according
to MDOT Transportation Service
Center Manager Larry Young, the project
is set up as a “lane-rental” project, where
the contractor is actually charged for
every hour it is occupying a lane. “This
is a process that works well because it
almost mandates an aggressive approach
toward completion,” he says.
Lane rental is used to minimize the
impacts of a project on the traveling
public. It is a method of transferring
the roadway user costs to the contractor.
The contractor must rent a lane in
order to close it. This approach creates a
monetary incentive for the contractor to
be innovative and minimize the duration
of lane closures. The contractor makes
decisions that consider the roadway user
costs, both during the bid and as the
contract progresses. By providing a more
aggressive scheduling package, it is possible
to decrease the overall impact on
the traveling public.
Understanding Uniqueness
The simple fact that roughly 60 percent
of this project is a concrete overlay
makes it somewhat unique, explains
Young. In his roughly 22 years with the
department, Young has never before
seen a “white-topping” project within
this region. However, by looking at the
obvious time and financial savings, the
overlay makes a lot of sense, especially
in an economic environment where
funding is relatively uncertain from year
to year. Plus, leaving the underlying
concrete in place adds strength to the
road and provides a thickness that can
add to the anticipated durability of the
pavement structure.
“The existing concrete pavement, which
is about 40 years old, is first patched
with concrete to provide a solid base for
the new pavement,” Mann says. “Then,
there is a 1-inch asphalt separation
layer placed over the existing concrete.
The asphalt mix is actually a drainable
design that will allow the flow of
entrapped water away from the roadway.
There is also a new underdrain system
installed parallel to the roadway,
which will keep water from accumulating
under the pavement, preventing
damage as a result of Michigan’s
unpredictable freeze/thaw cycles. The
concrete overlay is now placed on top of
the asphalt at a thickness varying from
7 inches to 12 inches. We now have
a new concrete road that will last for
many years to come.”
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The concrete pavement is also warranted
by Ajax for five years against defects
from materials or workmanship. “Average
motorists will drive on the new,
smooth concrete pavement and may not
realize that they are actually driving on
the 40-year-old pavement that has been
given a new life,” says Mann.
One of the specific requirements of
this particular job — and to provide
desired information for future concrete-centric
construction projects — is for the
materials used on this stretch of I-94 to
be part of ongoing monitoring for their
overall durability. “There is an effort
to gather a lot of different information
that is usually not collected when using
concrete,” says Mann. “This project
has been chosen by MDOT to be one of
only two concrete paving projects in the
2006 season to include this specification
for such extensive durability testing.”
The durability testing specification,
according to MDOT Assistant Delivery
Engineer James Siler, entails the installation
of maturity meters in the pavement.
“These meters allow us to monitor
changes in concrete temperature, moisture,
and strength, among other aspects,
for many years to come,” says Siler.
According to Mann, the maturity meter
is imbedded into the wet concrete pavement,
where it will emit a signal to be
picked up by a monitoring device, such
as a PDA or laptop computer. “The
information is then compiled to understand
what atmospheric stresses the
pavement has undergone while in use,”
he says. “This nondestructive testing
method will be valuable in determining
future materials, mix designs, and
roadway design.”
But the benefits do not end there. “The
new approach also includes the use of an air void analyzing machine,
which is a little different than
what MDOT has used in
the past,” Siler says. The air
void analyzer allows for the
measurement of entrained
air versus entrapped air in
the concrete mix, which is
thought to contribute to
a more durable, long-life
concrete. This testing is yet
another tool that MDOT
will have in determining
future requirements.
Educated Decisions
The ultimate goal of incorporating
this testing aspect into
the project is to find a better
way to test for a durable concrete
section, explains Siler.
To date, monitoring concrete cylinder
compression strength has been the test
of choice. But there was some discussion
that strength alone may not determine
overall durability, since it does not
take into consideration all the other
outside conditions.
It is hoped that by accurately tracking wear
and taking note of concrete performance,
MDOT can make more educated decisions
in the future as to thicknesses,
mixtures, etc., that are appropriate for
differing surfaces and traffic patterns, as
well as weather conditions.
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