"If we can get a product that lasts a long time - even though it
may cost more - it makes sense to use it. We won't need the labor and equipment
out there repairing it more than once."
 Michael
Zadel
Road Maintenance Manager
Illinois State Toll Highway
Authority
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DOTS
Say Quick-Setting Concrete Patches Play a Key Role in Keeping Winter Roads Open
in North Central States
But
Not All Products Perform Alike, Making Thorough Testing a Necessity
Ask a
Department of Transportation official about the process of keeping roads fit -
about keeping traffic flowing - and you realize the assignment is difficult.
Roadways take a beating in winter, and money is wasted when repair crews
revisit patches that haven't held. The traveling public has little patience for
traffic backups, and vendors of road repair products often make promises they
can't keep.
What's a highway official to do?
"We conduct
tests," says Michael Zadel, roadway maintenance manager for the Illinois State
Toll Highway Authority. "We ask the vendors to supply an amount of their
product, come out to our job site and work with our own crews."
Since
testing is important, how do states determine which products make the grade? Is
product durability what earns approval? Or, does fast application matter most
to state DOTs?
Fast-Setting Repairs
Road workers have long
had quick-curing cement materials and other speedy road repair products at
their disposal. But recently, new cold-weather, all-surface road repair
products have hit the market. They offer quick, one-step solutions for
repairing highways, bridge decks, parking lots and other asphalt, concrete and
masonry surfaces during cold temperatures and numerous freeze/thaw cycles.
Normal concrete cures to about 900 psi bonding, but that can take days.
Quick-setting concrete and asphalt repair products, on the other hand, can
achieve compressive strengths of between 2,000 to 2,500 psi - some setting at
between 3,500 to 4,000 psi in just a few hours. That being the case, fast-set
products can eliminate the need to use asphalt as a temporary fix and minimize
callbacks and follow-up repairs.
"That's the big kicker for us," says
Larry Cooper, a Minnesota highway official. "We like it when we can put traffic
back on a road in a few hours."
Cooper, who is responsible for 250
bridges in Minnesota's Mankato District in the south central portion of the
state, believes in testing road repair products because performance among
products varies widely. In one Minnesota comparison, for instance, two
quick-setting repair products were poured into separate test cylinders. Both
products set relatively quickly to equally compressive strengths. But according
to Cooper, one brand "set at a distinctly faster rate." And that, he says,
means road repair crews can patch more holes.
"You're out there in
traffic, and you don't have all day for this stuff to set," says Cooper. "You
want to put it in and get out."
Jim Parry, an official with the
Wisconsin DOT, feels the same way. He says Wisconsin uses quick-setting road
repair products to save time. In fact, Wisconsin product guidelines require
that quick-setting concrete repair products develop at least a 2,000-psi
compressive strength rating within two hours of being poured.
"We're
looking at a repair crew going out after the morning rush hour, closing down a
lane and having it back open to traffic by the afternoon rush," says Parry.
Favorable Cost Benefits
Although fast-set road repair
products may get approved for a state's highways and bridges, most DOT
officials note that field performance can vary widely. Much depends on the
prevailing temperature and humidity at the time of installation.
But
other factors also affect product performance. They include the type of
installation - whether it's a small patch or a large one, a shallow repair or a
deep one, and bridge repair or standard roadway maintenance - and the way
workers handle each patch. Saw cutting to the appropriate depth, removing
broken concrete, having the proper amount of water, using the right aggregate
and proper screeding all play a role in whether a patch holds.
Dan
Sipes, a bridge maintenance specialist in Indiana's Greenfield District, says
most quick-setting products are cementicious and restore at least some of the
structural integrity of a roadway needing repair. He looks for fast-set
products to hold for several seasons.
"You don't want to be going out
and repairing the same patch year after year. It's counter-productive and
costly to go back," says Sipes, who is responsible for 1,100 bridges from
Indianapolis to the Ohio state line. "However, I do not consider a repair with
a quick-setting patching material to be a permanent repair. We just want it to
hold until the bridge can be rehabilitated."
Zadel, with the Illinois
State Toll Highway Authority, agrees.
"My key grading point is how long
they last," says Zadel. "Obviously, the more often we have to return to the
same repair, the more costly it is for us. If we can get a product that lasts a
long time - even though it may cost more - it makes sense to use it. We won't
need the labor and equipment out there repairing it more than once."
It's all about balancing the tradeoffs. Blocking lanes for days on end
allows time for crews to pour high early strength concrete - a durable choice.
The problem is the traveling public won't have it, which is why DOT officials
often requisition quick-setting repair products.
"Our job is to keep
traffic moving and flowing," says Indiana's Sipes. "That's the main reason we
use fast-set patching materials."
Chemical Differences
But
often, performance variances among products come from differences in their
chemical make-ups. Some products feature chemical agents designed to bond the
material to the road substrate. Others require crews to mix up a mortar, which
then has to be scrubbed into the road substrate.
"We try to avoid those
materials, because it's just a lot of extra intense labor," says Sipes. "We try
to use the materials with the bonding agents, because they work well."
Sipes says Indiana has approved four quick-setting repair products.
Self-level MONO-PATCH™ Cold Set All-Surface Repair and SET 45 road repair
have a higher slump, making them easy to work with minimal screeding. The two
non-self-leveling products - DURACAL® Cement and THOROC 10-60
repair - play a role when grades are steep and require low-slump patching.
In the state of Tennessee, which experiences bursts of warm weather
followed by deep freezes, quick-setting concrete repair products must have a
specific chemical composition. Tennessee civil engineer Steve Hall says that
winter-formulated repair materials must contain magnesium phosphate. The
requirement helps ensure that quick-setting materials will work effectively in
temperatures of 32 degrees F or less, according to Hall.
Of course,
finding and approving the right materials involves some trial and error. But
Minnesota's Cooper says alternatives to cold-weather fast-set repair products
are not acceptable. He says Minnesota highway repair crews often throw down a
bituminous winter mix, but frequently return to the same holes three, four and
sometimes five times during the season.
"If you want to compare putting
down a fast-set concrete product versus these bituminous mixtures," says
Cooper. "I'd say we're saving money by going with the quick-setting product."
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