DON MARSH, EDITOR
If height records, early commercialization of high strength and ternary-blend mixes, and other concrete building achievements could be measured by World Series titles, Chicago would be home to the Yankees. Three weeks before hosting the 2005 Fall Classic opener, the city observed another industry milestone as two of the best players in production and practice Û Prairie Material Sales and McHugh Construction Û placed a record volume of self consolidating concrete (SCC) mixes.
The Sept. 30-Oct. 1 pour netted a mat foundation for the 92-story Trump International Hotel and Tower along a prime downtown Chicago site (shown on this month's cover and page 6). It demonstrated productivity gains and improved safety prospects that can be achieved with cast-in-place SCC. The 24-hour event also showed how Prairie Material, a top independent operator, is equal to rigid quality control standards dictated by the world's foremost high rise architectural/engineering firm, Chicago-based Skidmore, Owings & Merrill LLC.
Prairie dispatched 600 loads of SCC mixes to form a 10-ft.-thick, 198- _ 60-ft. mat foundation for the hotel and condominium. At 5,000 yd., the pour marked North America's largest self consolidating mix placement to date. The material required minimal vibration and helped lower the amount of finishing labor needed in a confined, subgrade area. Skidmore, Owings & Merrill had originally called for SCC due to congestion factors from helix-style reinforcement. Staff kept the mix spec, with a 24- to 30-in. target spread, despite a switch to less congested rebar.
Prairie and Degussa Admixtures formulated a 10,000-psi (56-day design strength) mix from the manufacturer's Rheodynamic SCC technology. Specifications capped mix temperatures at 80_F during placement and 170_F in forms. The use of fly ash and slag cement helped offset the heat of a Type I/II powder. Orders were delivered from Prairie's massive Yard 32, a central mixed plant located about 1.5 miles from the site. Each load was placed on belt conveyors staged by McHugh Construction, whose superintendents questioned pumping an SCC mix.
The foundation will support the center of a 1,125-ft. structure scheduled for completion in 2009. Trump International will consume more than 180,000 yd. of concrete, which was chosen as the primary structural material due to its ability to impart stiffness in the slender tower. Columns will be cast from 10,000-, 12,000- and 16,000-psi design strength mixes, optimizing support in minimal footprints.
The tower stands to be the tallest building completed in North America this decade. It occupies a Chicago River front plot within two blocks of one-time concrete building-height record holders, the Executive House (1959, 371 ft.) and Marina City (1965, 588 ft.). One of the world's most recognizable concrete icons, the latter project rose on the shoulders of Material Service, whose ready mixed plant assets Prairie acquired in 1995, and James McHugh, an enterprising contractor with keen insight on mix placement and concrete forming methods.
Since Marina City, Chicago has had five other reinforced concrete buildings soar to world-record height. Within the Western Hemisphere, Trump International will become the new top gun. Over the next two to three years, it will rank among the country's highest profile jobs, thanks partly to its publicity-wise developer.
Donald Trump featured the tower plan on the first season of his NBC program, The Apprentice. Before perfecting the You're fired line, he made an observation on prime time television regarding construction quality in the post-September 11 world. With a new landmark rising under the Trump banner, it's worth repeating a Donald quote we ran here in November 2001: You can build a great building a lot tougher than the World Trade Center turned out to be ÷ [with] different materials, more concrete. Regardless of the building in question, Concrete Products concurs. From our office, located next to the Trump International site, we see the work of a first-rate developer who puts his money where his mouth is, and hires concrete professionals long past their apprenticeships.
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