Above-ground construction work begins on 35W bridge

Covering the concrete
Workers cover freshly poured concrete with plastic thermal blankets, to keep the concrete at the required 40-degree temperature that's needed for it to cure properly.
MPR Photo/Dan Olson

Workers Monday began the first above-ground phase of construction on the I-35W bridge project, as construction workers began pouring concrete for the first of five bridge abutments.

Even with above normal temperatures predicted for Monday, construction workers are using cold weather construction methods.

Minnesota Department of Transportation spokesman Kevin Gutknecht says after state inspectors test the concrete to ensure the formula is correct, it is poured, covered with thermal plastic blankets and kept warm for proper curing.

Metal reinforcements
Workers on the north side of the Mississippi River guide tall columns of reinforcing bar, often called rebar, into 80-ft. deep holes, into which concrete is being poured for the new 35W bridge footings.
MPR Photo/Dan Olson

"The concrete is tested to make sure it's the right mix for this particular purpose," says Gutknecht. "There's a great deal of science into pouring concrete, actually, so there's a lot of quality control on this."

"You see a couple of large square trailers on either end of the site, those are heaters," describes Gutknecht. "The workers -- after the concrete has been poured, they're covering it with plastic. What they're doing is making sure the temperature stays at or above 40 degrees because that's what the concrete needs to cure."

Federal investigators and consultants hired by MnDOT are still inspecting debris from the old bridge that collapsed on Aug. 1 to determine a cause, with no word on when a final report will be issued.

Gutknecht says the $234 million I-35W bridge project is on schedule, with opening set for Dec. 24, 2008.

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