"Strict Strength Tests Pave Way for New Runway at Denver Airport"

Sunday, July 28, 2002

Strict Strength Tests Pave Way for New Runway at Denver Airport
The Denver (CO) Post


Just west of where contractors are paving the sixth runway at Denver
International Airport, a pickup truck races up to a trailer and workers
quickly unload a half-yard of concrete from a tub on the truck bed.

The trailer is a laboratory for testing samples of the 430,000 cubic
yards of concrete that are being poured for the north-south runway.

At three miles long and 200 feet wide, it will be the largest commercial
runway in the country when it opens in about 13 months.

To help guarantee the quality of the concrete on the new runway, workers
make up to 100 test beams of concrete a day.

They have only 15 minutes to capture a sample of concrete as it's being
poured on the runway construction site and get it to the nearby lab for
molding into beams.

After drying for 24 hours, the 18-by-6-by-6-inch concrete beams are
dunked in water tanks, where they sit for four weeks.

When a beam is 28 days old, it's pulled from the tank. Lab workers set
it into a beam breaker, apply a load of more than 7,000 pounds and test
its strength, said Warren Simmons, lead inspector for the sixth runway's
concrete plants.

Contractors also are cracking beams when they're three and seven days
old so they'll know whether the concrete is likely to pass the
all-important 28-day strength test, said program manager Brooks
Allshouse.

Workers are using between 4,000 and 5,000 cubic yards of concrete a day
on the $166 million runway, Allshouse said. About a third of the runway
is paved now and paving operations should be complete by the end of the
year.

>From January through August, DIA will be testing lighting and other
electrical systems on the new runway, and the first commercial flights
should begin in September 2003, Allshouse said.

When DIA's first five runways were built about a decade ago, problems
with the quality of the concrete developed quickly and contractors were
forced to remove and replace about 1,000 25-by-25-foot sections.

Chunks of clay the size of footballs were found in the runways.

Lawsuits followed, alleging that contractors short-changed the amount of
cement in concrete mixes and falsified data on moisture content.

DIA officials vowed that it would be different with the sixth runway.

"The airport wanted to make sure that this one is done right,"said
Allshouse, of DMJM Aviation, the engineering consulting firm hired by
DIA to oversee the runway project.

DIA is spending $20 million on quality control and has tripled the
number of inspectors on site, Allshouse said.

The Federal Aviation Administration is paying 75 percent of the cost of
the runway, and if test results show the runway contains under-strength
concrete, the government will reduce its payment to the airport, said
Jack Scott, an FAA paving engineer.

So far, none of the 100,000 cubic yards of concrete poured so far has
failed to meet engineers' specifications for strength, Allshouse said.


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