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Concrete Pavement Progress
www.acpa.org12
W e s t D e s M o i n e s
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400 pounds minimum cement per cubic
yard of concrete was specified to address
challenges presented by cold weather pav-
ing, such as delayed set times that increase
risk of early-age cracking.
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Well-graded, durable aggregates as well
as admixtures such as air-entraining ad-
mixtures, all specified in accordance with
special provisions developed from the Iowa
DOT, Minnesota DOT, and Iowa’s Standard
UrbanDesign and Specifications guidelines,
as well as with advice from local contractors
and the Iowa Concrete Paving Association.
Construction techniques that were used to fur-
ther ensure the durability of the pavement in-
cluded providing good drainage and protecting
the concrete fromwater and de-icing chemicals.
A 12-inch subgrade was installed throughout
the project and 6-inch subbase along with a
subdrain was installed in certain sections to
evaluate the use of rock. The paving contractor,
Concrete Technologies, Inc. (CTI), an ACPA
member company, also used a surface sealer in
and around the joints before applying joint filler.
Because this was the first time the mixture had
beenused, CTI occasionallyhad to adjust thewater
content to improve the workability of themixture.
While the pavements associated with the
Microsoft project handle light traffic, with only
about 1,000 workers traveling the roads, West
Des Moines has a higher traffic volume project
underway—widening of South 50th Street, which
handles over 12,000 vehicles per day.
“It will be nine to 10 years before we know the
results of the new mixture, but we are positive,”
Wittstock said.
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