Concrete is Beautiful

After you see this place, you'll never look at your garage floor the same way again.

By Steve Schultz

Photo: Jayne Laste; Click on photo for larger image.

It looks like glop, but the stuff has soul.

Most see a concrete mixer and think "new driveway." Mark Wolf envisions the graceful lines of fine architecture.
Wolf, the project executive for C.G. Schmidt Inc.'s concrete division, studies a test pile of the gray gunk drying on a cardboard box. The Milwaukee contractor is doing its own concrete work in addition to being construction manager for the project.

As Wolf says, the Calatrava wouldn't have possible without the most common building material around. But the concrete being used to create the 125,000-square-foot addition, and the formwork it requires, is anything but mundane.

Much of that planning was left to Wolf, concrete finishers, carpenters and laborers that totaled 112 over the summer.

"I think it's really good that this project gives a chance for the Milwaukee craftsmen to prove that the skill level is comparable with, literally, some of the best concrete work in the world," said Steve Chamberlin, president of C.G. Schmidt.

And that work is truly the project's foundation. The typical office building using poured-in-place concrete will require the support of about 150 pounds of reinforced steel per cubic yard, Wolf said. In certain areas that support the museum's structure, the concrete will have about 800 pounds of steel per cubic yard. Elsewhere, about 1,200 pounds of steel will be required.

Hold the ivy

But before cement trucks began rolling in, it was the concrete work that gave project architects their first shot at creating a new language.

"From an engineering standpoint, the project is as complicated as any concrete building, probably anywhere,"

A maze of rebar supports the Calatrava's structure where concerete will soon be poured. Photo: James W. Brozek; Click on photo for larger image.

said John Kissinger, a vice president for engineer Graef, Anhalt, Schloemer & Associates Inc. and the principal engineer for the addition. "That's not an exaggeration in terms of some of the complexity of the elements, just simple things like what to call them. Normally you have beams and columns and girders. There are no such things on this job."

It took months of planning before the mixers rolled in. Architects and engineers joke that an ivy wall is where there was a design mistake, but with Santiago Calatrava's design, there will be nothing hiding the architect's vision.

"One of the biggest challenges is that there's no second chances," Chamberlin said. "If the form slips at all, you're done. It will be very noticeable and very obvious."

Wolf points to the ring beam, a 293-foot-long, 58-foot-wide (and its widest point) oblong concrete beam at the south end of the addition. In order to create it, 12 separate pours were necessary.

"There were some aspects of the ring beam that are so involved that the architect cannot even detail them," Wolf said. "Some of the different areas of the ring beam are actually handled by individuals from (Kahler Slater Architects) that come out to the job site and work directly with our foremen to try to explain, 'OK, this is what we want to create in this area.' Kahler will come back the next day and say, 'Yeah, that's what we want, just change this ..."

The right recipe

About a dozen different mixes concrete are used -- with about half in the ring beam alone - to get just the right creation at each section.

Some pours require a pump truck. Recently, a six-inch steel pipe fed concrete through a tapered 3-inch nozzle, enabling a 24-foot pour deep in the reinforced steel and post-tension concrete.

Many walls are poured in layers, about 5 feet at a time, Wolf said. Crews complete one pour and move on to the next, returning to add the next layer until the wall is finished. Engineers constantly monitor the pours and remove small samples in order to monitor how well it will cure on a particular day. As a result, cardboard boxes with globs of concrete are always nearby under careful scrutiny.

"There was a tremendous amount of quality-control work," said Bob Peters, vice president of operations for Central Ready Mixed Concrete L.P. "Basically, we had to have people on most of the pours.

Back in the office

A C.G. Schmidt CAD technician examines a computer-generated three-dimensional model of the museum.

"Our CAD technician dissected that building on 1-foot increments, so that he was able to generate a drawing showing every one of the gussets and built-forms, and how every one of those built-forms had to be cut," Wolf

Photo: Jayne Laste; Click on photo for larger image.

said. "The fact that mechanical systems and pipes are built into the concrete structures made it even more challenging, he said.

Computer-controlled lasers cut some of the plywood forms, but on-site, creative C.G. Schmidt carpenters used their own means to build forms. On the southeast side of the structure, for example, exotic-looking concrete piers are broad at bottom and narrow at the top. Carpenters created reveal designs with a homemade plastic form.
Inside the structure, 78 concrete arches branch off a structural backbone, each one a rib lending support as well as beauty. In order to create them as perfectly as possible, engineers devised a mobile pouring machine that was pulled along the floor, creating a long hall of symmetrical designs.

"It's more organic." said David Kahler, the principal in charge for the architect of record, Kahler Slater Architects. Kahler said that building itself has kind of skeletal structure. "A lot of the structural elements basically replicate the skeletal elements you find in animals. You don't have any straight lines, but compound curves."
Those curves must be duplicated exactly, he said.

The planning and craftsmanship has paid off. There are few, if any, cold joints on the structure, where concrete has hardened before the next batch was poured on top of it. And air pockets are equally hard to find. Twelve external vibrators have been used on the pours, because the mass of steel.

"It's so labor intensive to build all that formwork, I'd hate pull that all off and find that you've got one little thing (wrong)," Wolf said. "I think that just about everybody who has worked on this job has learned what little bit of effort it takes to provide higher quality."