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Central Ready Mixed Pours New Milwaukee Landmark |
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| Rising like an elegant bird in flight, the new winged expansion of the Milwaukee Art Museum, designed by Santiago Calatrava, has become an icon for the city. The concrete reinforced structure is a testimony to the flexibility, fluidity and beauty of concrete. And Central Ready Mixed of Milwaukee, a Prairie Materials subsidiary, provided all the concrete. The $100-million 142,050 sq. ft. addition is made up of three major components: a central building; a movable, winglike sunscreen-the Burke Brise-Soleil-composed of 72 steel fins and resting atop a vaulted 90 ft. high glass-enclosed reception hall; and a cable-stayed suspended pedestrian bridge, which links downtown Milwaukee directly to the lakefront and the museum. There are four elements of the main building: the parking garage, the gallery space, the pavilion (the ring beam), and the south terrace. All parts of the buildings are of reinforced concrete, except the steel A-frames which support the Burke Brise-Soleil. Beauty and elegance come at a price. Some jobs are about brute strength, but this job was all in the delicate nature of the building. The design with its curved walls and changing radii used a mix of standard and custom formwork and the concrete mix was specially designed to work with the congested rebar within the forms. Working closely with the contractor, C.G. Schmidt, Central developed a high slump, rapid setting, high performance concrete mix that would allow a very high degree of workability. "Since there was so much rebar in the forms, we used a finer 65-35 fine to coarse aggregate mix with super plasticizers and accelerators that would produce the spec'd 6,000 psi", reports Jack Gibbons, Director of Technical Services for Central Ready Mixed concrete. "The forms were closer to cabinet making than rough carpentry and the rebar congestion made for an incredibly challenging pour." For example, the ring beam that supports the central atrium and the Burke BriseSoleil used only 280 cubic yards of concrete, but it took more than 13 hours to pour, with critical consolidation procedures during each lift to prevent bug holes and honeycombing. Specific form release agents were developed to minimize discoloration and to prevent unsightly surface problems. Perhaps the most important factor in the success of the project was the close collaboration of the contractor, the masons, the form makers and the concrete company. All worked together as a team, staying in constant communication and attending joint planning meetings to ensure that the work went smoothly. Central was a full partner in that success, routinely maintaining 4-5 people on site throughout the project. |
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