Prescription for Performance
- Published: Thursday, 15 August 2013 09:32
- Written by CP Staff
Breckenridge Material leverages technical capabilities to gain a seat at design team table.
As the leader in one of few major markets not controlled by integrated operators, St. Louis-based Breckenridge Material Co. is on the path to becoming a regional ready mixed producer, with scale and technical competency to pace larger metro area peers.
Now under fourth generation management, the family-owned producer has extended a market radius to more than 100 miles beyond its home turf, running 250 mixers across more than 30 Missouri and Illinois plants, many acquired during the past decade. It has concurrently beefed up technical services with the opening of a Missouri Department of Transportation-certified testing lab, the first for a ready mixed producer, and embraced the National Ready Mixed Concrete Association’s Prescriptive to Performance (P2P) initiative.
Ironically, the project Breckenridge Material CEO Nathan McKean told the St. Louis Post-Dispatch was “hands down” the most challenging in the company’s 87-year history was the ultimate exercise in prescriptive methods. Yet the St. Louis Art Museum East Building, opened in June 2013, likely wouldn’t exhibit one of the best examples of self-consolidating concrete absent a P2P-driven producer.
Breckenridge Material delivered SCC forming the museum’s massive ceiling, a grid of 698 coffers, 9- x 4-ft. with 12-in. solid cross section—all bearing on concrete shear walls and columns. Architectural cast-in-place at its finest, the ceiling becomes part of the show in a wing dedicated to contemporary art. Lead designer, David Chipperfield Architects of London, stipulated that St. Louis-based McCarthy Building Companies Inc. attain concrete surfaces with “near drywall” smoothness, color uniformity and a 52 percent light reflectance factor. That target was determined as part of an East Building illumination scheme blending skylights and recessed fixtures above coffer beams.
“We were the only producer capable of achieving the architect and contactor specifications for the ceiling mix production and pours,” notes Breckenridge Material Senior Vice President Jeff Whidden. “Ceiling construction took place in 11 pours over a five-month period. On all pours, we limited ourselves to 8-yard loads, each truck delivering one load only in order to attain the utmost consistency.”
Expectations were clear, he adds: Trucks were loaded and staged so they would arrive at the site on four-minute intervals, mixes pumped 2 yd./minute. Slumps were checked at the plant and site, with a ±1-inch tolerance in advance of a spread measurement at the pump, the target 34 in. Failure at any one point meant the load was rejected. Of the approximately 200 trucks on the 11 ceiling pours, no loads failed the stringent requirements.
“The architect and contractor approached the job knowing you only have one shot at placement,” Whidden recalls. “We put in place an inspection process for each truck to ensure drum interiors were free of debris and contaminants. Mixes were inspected at every transfer point—plant, pump and end of hose. Our quality control staff and contractor and architect representatives inspected most all of the ceiling mixes. The delivery schedule was set with a 30-minute, plant-to-site truck target time. The ceiling pours were typically completed in 90 minutes.”
Chipperfield Architects and McCarthy representatives also determined that the coffer ceiling beams would carry epoxy-coated rebar and warrant single-use of Peri form board to maintain finish consistency, eliminate camber and spalling, and impart hard 90-degree effect on the grids’ most visible portions.
“At one point in the specification phase, the word ‘flawless’ came up for the coffer finish. American Concrete Institute guidelines for architectural cast-in-place do not define that level of quality,” says Adam Knoebel, vice president of operations for McCarthy, an ENR 400 general contractor that performs its own concrete work. “Concrete team members agreed instead that the coffers would have no bug holes, patching be limited to one square foot per 1,000 square feet of surface, and the finished structure would be as close to dry wall in appearance as possible.
“That meant no cold or vertical joints, and joints from one pour to the next placed over a wall or out of view from the museum floor. The architect had final say on the surfaces, inspecting the face of every beam prior to indicating acceptance.”
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