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Concrete research
Paul Spry hopes highway de-icing research will lead to tax savings.
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Every mile of highway constructed in Iowa costs approximately $1 million.
You can imagine that the Iowa Department of Transportation (DOT) is trying
to eke out every possible minute in the lifespan of a major highway in
the state.
"Anything you can do to prolong the life span of the state's highways
is a benefit to the taxpayers," said Paul Spry, professor of geological
and atmospheric sciences.
Spry, along with Robert Cody, associate professor emeritus of geological
and atmospheric sciences, has been studying de-icing effects on Iowa concrete
highways for the past decade with financial support from the Iowa DOT.
That organization recently funded a fourth study by Spry and Cody.
During winter months, the Iowa DOT and other DOTs across the Midwest apply
de-icing chemicals on roadways. The desired lifespan of a highway is as
much as 40 years. But Iowa and other midwestern states were noticing that
some concrete highways were deteriorating after just five years.
"The Iowa DOT realized that the highways were deteriorating at a
much faster rate than roads that didn't have these de-icing chemicals
applied to them," Spry said.
Spry and Cody's studies have indicated that those de-icing salts have
a definite effect on aggregate, which is used to make concrete.
The two, who were assisted in earlier studies by Anita Cody, an affiliate
instructor in the department, found in their second study that certain
minerals were growing and filling spaces within the concrete. These minerals
were having a direct effect in causing cracking in concrete paste.
"One of the minerals that had a major effect was ettringite,"
Spry said. "Some of it grew during a delayed reaction and caused
cracking in the concrete."
The Codys have tested inhibitors that limited the growth of ettringite
in concrete.
"We figured if we could limit the growth of ettringite, then we could
reduce the deterioration of the concrete, thus increasing the lifespan
of highways," Spry said.
The fourth study by Spry and Robert Cody will continue to look at the
reduction of concrete deterioration by ettringite. This time the duo will
evaluate inhibitor effectiveness using crystal growth techniques. The
Iowa DOT has funded the project at $142,000.
Long-term growth of ettringite will be simulated in the latest research
project. Core samples of Iowa highways will be placed on the roof of Science
I on the Iowa State campus, where the Iowa cold and hot temperatures will
be mimicked. They will also increase the concentration of the inhibitor
in the concrete to speed up the rate of the reaction.
The results have been so encouraging that Spry says they have gotten a
"fair amount of interest" from DOTs through the U.S., Canada
and Europe. He has met with personnel from the Federal Highway Research
Board.
"States are really concerned about the deterioration of their highways,"
Spry said. "We are one of the few geological groups that does this
type of work. We understand the materials involved and that's one of the
keys to the success we have had with this project."
Around LAS
September 23 to October 6, 2002
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