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Concrete Decor - Index

Concrete Decor - Concrete Decor Magazine, The Journal for Decorative Concrete - Index

high humidity — the Great Lakes area
— or in the West, say Denver, it comes
with low humidity, so you can have
shrinkage cracking. Protect against that
and make sure it doesn’t craze on you.”
Also, be aware of freeze-thaw
cycles, Paine says. If the ground freezes
and thaws during the 28-day curing
time, that’s pretty tough on the concrete.
“There, the only approach is to make
sure you get it done as early as you can.”
Because new concrete loses heat
and moisture fast in cold weather,
heated insulating blankets can keep
the concrete moist and the temperature
60 | www.ConcreteDecor.net | Dec. ’07/Jan. ’08
above 50 degrees for proper curing. For
the concrete to keep gaining strength,
it needs to stay at 50 degrees or higher.
According to the American Concrete
Institute, concrete must be protected
against early freezing until it has
attained at least 500 psi.
Customer satisfaction is critically
important when you’re dealing with
decorative concrete and the look and
quality of the fi nished product is
weighted above the schedule, Paine
says. Cold-weather conditions increase
your risk. “If you do force people to wait
for the correct conditions, you’re much
better off in the long run,” he says.
For Dale Mizer, there was no talking
Cleveland State University out of a huge
stamped sidewalk project planned for
the 2004 winter break, where freezing
rains, snowstorms, gusty winds and
subzero temperatures presented a horror
show for contractors.
Mizer, a representative for the
project’s decorative concrete supplier,
Chas. E. Phipps Co., worked closely
with the concrete subcontractor, Union
Industrial Contractors. Because concrete
cannot be placed on frozen subgrade,
it had to be thawed fi rst using a heated
tubing system. Workers also needed
to erect a movable shelter to stamp
300 square feet of sidewalk at a time.
Shelters can be made simply with PVC
piping and plastic sheeting — the key is
to keep the weather off the project and
the workers. Also, Mizer says to use a
nonchloride accelerator so the concrete
will not take forever to set. (Chlorides
will leave white marks.)
Mizer recalls that the buildings
created a wind tunnel. “I felt bad for the
guys out there,” he says, “but Cleveland
State University wanted it done, so it
got done.” He says the workers were
bundled in layers of clothes. “Morale
isn’t ever as high on a 15-degree day
as it is on a 75-degree day, but a cup of
coffee goes a long way.”
It was 34 degrees and snowing
when Mizer spoke with Concrete
Decor magazine, and he was heading
to a stamping project in downtown
Cleveland that workers were rushing to
fi nish. “Take every precaution to protect
your project and protect your workers,
and try to give the owners the best job
you possibly can.”
For more information on coldweather
stamping, refer to ACI’s 306.1-
90, “Standard Specifi cation for Cold
Weather Concreting.” The specifi cation
covers prep work, temperature, and
protection after a pour. The guidelines
apply when the air temperature is 50
degrees or less for at least 12 hours
during any 24-hour period, and when
the average daily air temperature is less
than 40 degrees.
Want to learn more? Search online at
www.concretedecor.net
cold weather