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The Worldwide Web Gets Support From Putzmeister America

The Worldwide Web Gets Support From Putzmeister America

STURTEVANT, Wis. (November 2004) – Controversy over the need for public libraries in the electronic information age has evidently surfaced. Ironically, approximately half of Americans today do not have access to the worldwide web except through libraries. It is, therefore, vital for these public institutions to provide accessibility of information in all formats.

Bearing this in mind, a Library Referendum approved on November 7, 2000, provided $110 million toward a new Minneapolis Central Library to open in 2006. In addition, $30 million was approved for a decade of library improvements for 14 neighboring libraries throughout the Minnesota city.

The new Central Library, replacing an outdated library that stood since 1961, is a joint project of the Minneapolis Public Library and the City of Minneapolis. The end result is a three-story below grade parking garage along with two five-story buildings positioned side-by-side and connected by several aerial skyways. Destined to be a Minneapolis landmark with its distinct architectural appeal, the building houses a 2.4 million-item collection making it the largest public library in Minnesota and the fourth largest central library in the nation.

As soon as the library took a temporary home in an old bank in January 2003, the existing structure was demolished. Mortenson Construction of Minneapolis, the construction manager, divided the project into three phases – the foundation, the structure and the finish work. Overcoming several obstacles, the foundation was completed in September 2003, the second phase ended in November of 2003, and the third phase begins in the winter of 2004. Upon completion of the entire job, the immense 357,000 sq. ft. project will have consumed over 30,000 yd. of concrete.

Phase I – The Foundation
Phase one of the project consisted of footings, 24 ft. high perimeter walls, slab on grade, and sub-grade foundations for the building above.

The first phase general contractor, Knutson Construction Services of Minneapolis (a Michael Curry Company), selected E-Con-Placer of Minnesota as the pumping contractor. All the foundation work was accomplished using everything in the E-Con-Placer’s fleet – from the smallest 28Z-Meter concrete boom pump to its largest 52Z-Meter, depending on pour requirements. All models effectively pumped a specially designed 6000 psi mix with anti-corrosive additives that keep rebar from corroding and assist with freeze-thaw cycles found in northern climates.

Common to many jobs today, access to the downtown Minneapolis site was a problem. The size of a square city block, the job site was not conducive to setting up construction equipment on its busy surrounding streets. As a result, equipment had to be positioned inside the perimeter of the foundation’s excavation.

For access to the site, an extremely steep 30 degree, 115 ft. long ramp was built. The ramp, while difficult to drive down and even more challenging to climb up, was the only way for boom pumps and mixer trucks to reach areas that needed to be poured. Naturally, the boom pumps worked from front to back of the site until making their way out of the enormous cavity in the ground.

Knutson’s superintendent Randy Morningstar comments, "E-Con-Placer worked with us every step of the way and provided the right pump at the right time. We were able to meet our schedule even during winter conditions and limited access."

Phase II – The Structure
Phase II consisted of the underground post tension deck parking garage and all the building’s structural concrete. The design called for an architectural concrete finish. Therefore, consistency of the finished product was an enormous issue for maintaining the desired appearance throughout the interior, which was designed to showcase concrete in its more natural state.

Because of continued non-existent access, Phase II also required the arduous task of working within the perimeter. However, E-Con-Placer developed a time and labor saving strategy for placing concrete within the structure. Putzmeister’s placing boom expertise and special documentation about a similar construction approach used in Texas assisted the plan. It was further backed by strong technical support from Advance Equipment Company of St. Paul, the authorized Putzmeister equipment dealer in the area.

This combination of information provided a certain comfort level and the desired results for Graham Penn-Co., the general contractor for Phase II. As a result, E-Con-Placer was chosen to supply all concrete placing equipment for the second phase also.

Rob Tousignant, co-owner of E-Con-Placer and project manager for this job says, "Together with Graham Penn-Co., we developed a plan of how to obtain concrete coverage on the entire job site without leaving any visible trace within the architectural concrete that concrete placing equipment was ever there.

"We achieved this by using the four main elevator shafts to position four placing boom towers. We dedicated two separate placing booms to the project and moved them from tower to tower as required." Tousignant adds, "We felt Putzmeister equipment was the best choice for this high profile project, as we have had several positive experiences using their separate placing boom systems in the past."

The unique plan called for two long reaching placing booms, four compact square shaped towers, two special mounting configurations, and a high pressure concrete boom pump.

The first challenge of Phase II was extending the placing boom towers from the footings to the roof without invading any structural floor slabs. To achieve this, the freestanding towers were anchored to each base matt slab for the four elevator shafts.

"We were able to use each shaft’s base matt as the foundation for the placing boom towers, and we did this without any modifications," says Tousignant. "This saved the expense of pouring a foundation and abandoning it when done."

Fortunately, each shaft was in a separate quadrant and E-Con-Placer had the flexibility of several Putzmeister placing boom sizes to accommodate varying reach requirements. Ultimately, models MXR 32/36 and MXR 34/38 were chosen for their 104 ft. and 111 ft. horizontal reaches respectively, providing the ultimate in coverage without the need for additional hoses.

With small shaft openings and nothing as compact on the market, the 51 in. square Putzmeister towers fit perfectly. At first, these freestanding towers climbed to 80 ft. and all work possible at this height was accomplished. The towers were then tied off to the structure at 60 ft. from the base for its eventual final height of 120 ft.

Concrete traveled over 500 ft. using 300 ft. of horizontal delivery line, 120 ft. of vertical pipe and then the boom’s outreach. From its back-end, a Putzmeister BSF 28Z .16H boom pump was used to pump concrete. The truck-mounted unit proved highly mobile for daily setup and quick removal from the one street lane available during the second phase.

The truck-mounted unit featured a .16H pump cell, capable of up to 210 yd3/hr output and a maximum hydraulic system pressure of 5075 psi (350 bar). Often, the extremely tight tolerances of the mix had the equipment performing at maximum pressure resulting in average volumes between 60 to 80 yd/hr.

Tousignant says, "The concrete was highly chemically enhanced so the pump ran at almost maximum pressure, which affected volume. We used the same amount of pressure for 500 ft. with this mix as what we have done at 1500 ft. with a more typical mix. Still, our Putzmeister equipment performed without any problems."

Job challenges continued as snowstorms and brutally cold weather this past winter threatened to hamper construction. The contractor faced the challenge of clearing 84,000 sq. ft. of work area during each snowfall, which is similar to clearing a driveway 14 ft. wide and over a mile long.

Snow removal was accomplished by using large tarps that covered the work area. The tarps had lifting loops in each corner. Once the corners were brought together in the center, the tarp was connected to a tower crane that lifted and carried away the snow to an area for stockpiling or hauling away.

To further combat the weather, large 3 to 5 million BTU heaters were placed underneath the forms. They served a dual purpose – one was to assist in melting snow and ice when inclement weather occurred and the other to help cure concrete before it could freeze.

Tousignant notes, “More than anything else, it was the frequency of the snow and freezing temperatures that proved so difficult. The snow would just get cleared off the site, and it would snow 8 to 10 in. again just days later. It seemed like a never-ending battle.”

Summing up the job, Tousignant comments, “Overall, this was not the highest or longest reaching concrete placing job we have ever tackled; however, it is definitely the most complicated as far as integrating and mobilizing all the concrete placing equipment.”

Scot Fowler, branch manager for Graham Penn-Co.’s Eagan, Minn., branch, which services the Minneapolis-St. Paul area says, “The concrete pumping and placing has been a very important process for our production goals. We put a lot of faith in E-Con-Placer’s equipment and expertise and they have exceeded our expectations.”

Denny Rosin, Graham Penn-Co superintendent, echoes this comment, “We have been extremely happy with the concrete pumping.”

A second-generation family business, E-Con-Placer is celebrating its 30th year serving the concrete placing needs within a five-state area. Co-owners and brothers Rob and Dick Tousignant along with their brother Jim Tousignant all work together in the business originally started by their parents in 1974.

In addition to their solid background and lengthy experience, the brothers attribute a great deal of their continued success to the customer-oriented people working at the company and a willingness to embrace new technology.

Rob notes, “It’s the people behind the scenes that make the difference in the final result. We feel our staff does a remarkable job working with customers to ensure the success of projects like the Central Library. This type of dedication has been instrumental to our growth.”

Phase III – The Finish Work
Phase III is scheduled to be underway in the winter of 2004 with a special topping mix to be used on the south end floors.

Also under construction review is the Minnesota Planetarium and Space Discovery Center atop the new Central Library. The completion of this project would put Minnesota in the nation’s top ten in terms of the largest planetarium.

Fortunately, construction has progressed while controversy over libraries as a valuable reference point has subsided. Today, libraries are key to providing equal access to cyberspace, and books are still one of the best sources for sustained reading and learning. According to the Minneapolis Central library, 99 percent of its valuable collection is not – and never will be – available on the worldwide web.

Architect Design Team: Cesar Pelli & Associates – New Haven, CT and New York, NY; Architectural Alliance, Michaels Associates – Minneapolis, MN; Ralph Appelbaum Associates – New York City, NY
Construction Management: Mortenson Construction – Minneapolis, MN

Phase I
General and Concrete Contractor: Knutson Construction Services – Minneapolis (a Michael Curry Company)
Pumping Contractor: E-Con-Placer of Minnesota – St Paul, MN
Concrete Supplier: Cemstone Products Company – Mendota Heights, MN
Equipment Dealer: Advance Equipment Company – St. Paul, MN
Equipment: Putzmeister 28Z-Meter, 32Z-Meter, 36Z-Meter, 42X-Meter, and 52Z-Meter

Phase II
General Contractor: Graham Penn-Co Construction, Inc. – Eagan, MN
Concrete Finishing Contractor: Stellar Concrete and Masonry – Burnsville, MN
Pumping Contractor: E-Con-Placer of Minnesota – St Paul, MN
Concrete Supplier: Cemstone Products Company – Mendota Heights, MN
Equipment Dealer: Advance Equipment Company – St. Paul, MN
Equipment: Putzmeister MXR 32/36 and MXR 34/38 separate placing booms, PM towers (4), and a Putzmeister BSF 28Z .16H concrete boom pump