By: Bill Wilson
A new, permanent, ultra-fast-setting concrete repair material
now available in the U.S. helped a contractor speed through multiple concrete
slab repairs at Colorado Springs Airport late in 2001.
The repairs, done at night and under stiff penalties for
failure to vacate the work area by 5 a.m. for air traffic, addressed serious
spalling of concrete on runways and taxiways.
The airport’s elevation is 6,183 ft (1.2 miles) above
sea level. Because of the thinner atmosphere at this height, aircraft must take
longer runs for takeoff, especially in summer when the air is warmer and less
dense.
As a result, the airport has the longest runway in Colorado,
13,500 ft (2.5 miles). In fact, Boeing Co. regularly uses Colorado Springs
Airport to conduct high-altitude landing and takeoff performance testing of its
commercial aircraft, including the newest 757 and 777 models. There are three
runways at the airport, dual parallel and one crosswind runway, which occupies
7,135 acres southeast of the city.
In 2000, the last year for which firm figures are available,
some 2.4 million passengers arrived on approximately 100 daily arrivals and
departures, part of a total of 220,739 aircraft operations. Owned and operated
by the city of Colorado Springs, the facility opened in October 1994 and
features multiple sites available for commercial lease and development, some
including runway access.
Done by dawn
With all this activity, it’s little wonder the city
wanted concrete repairs executed at night, when the slower pace allowed one
runway to handle traffic while others were shut down for repairs.
The contractor, T.L. Smith Inc., Tucson, Ariz., agreed to
undertake the work at night during certain hours when aircraft operations were
slowed.
“Work areas had to be opened up to aircraft in the
morning,” said Thomas L. Smith, vice president, T.L. Smith. “So the
time period of cutting spalls, chipping them out and filling them in was
critical.”
T.L. Smith specializes in concrete sawing and sealing, spall
repair, drilling and epoxy injection for runways, highways and bridges. At
Colorado Springs, Smith’s crews worked weeknights, under flood lights,
for just under three weeks for this project, repairing over 200 sq yd of
airfield. Work began at 7 p.m. when air traffic was shifted to one runway, and
the crews would work through to 5 a.m. the next morning.
The new material, a fast-setting, proprietary product called
TechCrete (Circle 922), enabled the contractor to speed up the process and do
more repairs in one shift in the limited hours before dawn. TechCrete is
marketed by Crafco Inc., Chandler, Ariz. The material effects a full permanent
repair in less than an hour, but typically sets up much faster than that.
A small patch of time
“It’s a very simple product, and that is one of
its greatest attributes, we found,” said Bret Andreasen, project manager
and secretary/treasurer of T.L. Smith. “Everything is premeasured. You
put it in a machine, the ‘pot,’ which heats and stirs it up; and
you dump it in the ground and walk away.
“The other great attribute is that it sets rapidly.
You can get traffic on it literally 15 minutes after placement. We witnessed
this; it worked for us.”
The simplicity of application at night, and the speed of set
time under these time-critical constraints, meant money to T.L. Smith.
“It was invaluable,” Andreasen said. “It
allowed us to work throughout the whole shift. Products with two-hour curing
windows would require a whole crew to work six hours, and then be sent home,
but be paid for eight. With a 10- or 12-man crew you can be throwing hundreds
of dollars away per shift in labor costs. But while you’re waiting for
this material to cure, you can be sure that it will set up before you have to
get off the runway.”
“We were allowed six hours each night in which to
work, including set time, so it was important that the patch would set up fast
and be able to take the traffic right away,” Smith said.
Quick pay
For this spall repair work, Smith’s crews would do a
squared edge saw cut to 1 in. depth about 3 in. around the spall. Using 60-lb
air hammers, the crews would chip out the damaged concrete down to sound
material. The patch would be cleaned out and air blasted to remove moisture and
fines.
At the same time, the premeasured units of TechCrete would
have been melting in the pot, Andreasen said. Then, a supplied primer would be
placed on the patch area, and after a five- to 10-minute wait, the material
would be spread in the patch with buckets or, for larger patches, placed in the
patch directly from the pot.
No vibration or floats are required, but Andreasen’s
crews used a hot iron to minimally flatten or move the patch material for final
finish. Finally, a specified, high-performance aggregate would be placed over
the patching material before the material had cooled down to a firm consistency.
There was little margin for error under the time constraints
of the night-work project, but the proprietary product eliminated much of the
guesswork and opportunity for problems, Andreasen said. “It’s
error-proof and easy to use for your employees,” he said.
“Error-proof products are valuable to a contractor.”
“You can put traffic on it so soon. Even if a plane
had to land in an emergency, we could have sprayed water on the material and it
would have set up within 10 minutes,” said Smith.
The airport authority was so pleased with the outcome of the
work that it released T.L. Smith’s 10% retention fee from progress
payments only 60 days after completion. “They can hold it for a year to
ensure performance, but released it after only two months,” Smith said.
“They were very good people to work for.”
While the product is ideal for time-sensitive jobs like
airfield repairs, T.L. Smith acknowledges that it’s applicable for
time-critical night work on expressways or interstate highways as well.
“For major freeways in our state, all of the work has
to be done at night,” Smith said. “You have to have a material
which sets up quickly because your time frame only will be six to eight
hours.” The firm is familiarizing the Arizona Department of Transportation
with the product’s performance and hopes to have a demonstration
application there later in 2002.
Information for this article submitted by Crafco Inc.,
Chandler, Ariz.
