Unorthodox construction approach challenges concrete placement
The Darla Moore School of Business broke ground September 23, 2011, on a building that’s revolutionary in more ways than one. The structure, being built on the University of South Carolina (USC) campus, has an iconic design with “green” features that are testing the capabilities of Putzmeister truck-mounted boom pumps to place concrete for one of the most intricate construction feats underway in the Southeastern U.S.
“This is not any run-of-the-mill job. The construction process is highly technical, the job site difficult to access, and the concrete extremely harsh,” says Curtis Miles, general manager of Concrete & Materials Placement, LLC. (CMP) of Charlotte, North Carolina. CMP was called upon for its expertise as well as its equipment’s innovative features to intelligently pump concrete for a building that is not following the typical sequence of construction steps.
“Most contractors could not have handled such a complicated job,” notes Miles. The multi-prime group of general contractors responsible for bringing the building design of Rafael Viñoly Architects to life is BL Harbert International; Gilbane Co., Cumming and Brownstone Construction Group; and Loveless Commercial Contracting, Inc.
The school, recognized for the nation’s top undergraduate international business program over the past 16 years, is named for Darla Moore—distinguished businesswoman, first female member admitted to the Augusta National Golf Club, and generous contributor of more than $70 million to the university.
The new facility, upon completion, will further transform the way business education is conducted, serve as the front door to the university’s Innovista research district, and usher in a new era of “green” building in the state.
Inspiration for the building’s design is the state tree, the Sabal Palmetto, with the concept described as a natural structure that appears to grow naturally out of the ground. Construction crews describe it as one of the most complex and difficult to build.
Driven by Design
The construction process was dictated by the design, with the site location and LEED certification contributing factors in its approach. The rectangular footprint of the facility is 200-foot by 240-foot (60.96m x 73.15m) with a 100-foot by 180-foot (30.48 x 54.86m) wide opening in the center that will feature a landscaped courtyard with a grove of Palmetto trees reaching to the sky. Numerous windows encompass the 120-foot (35.58m) tall building that will overlook the courtyard and offer natural lighting. Meanwhile, inside the facility, there are an abundance of curved walls, which adds to the complexity of the concrete formwork.
The school is also being built into a hill so there are varying elevations, and access is available on only one side of the job site, with a steep hill and its 50-foot (15.24m) drop on one side, a busy road on another and the Carolina Coliseum on the third side. This left only one side for equipment setup, resulting in extensive job site congestion.
The 250,000-square-foot (23,225 sq m) project, being built to LEED Platinum standards, has the goal of being the largest Net-Zero (generating as much energy as consumed) building in the world. Achieving this objective puts even greater demands on the construction process.
“Hands down, this is the most challenging project we’ve ever undertaken,” notes Kevin Quinn, project manager of Loveless, a 25-year-old company focused on the job’s concrete work. “The project required the structural steel frame to be constructed in its entirety before placing concrete. Steel was placed on 24 piers starting at -24 elevations and rising seven levels; and the slab-on-grade concrete work had to be accomplished after the fact, which is highly unusual and also highly difficult.”
More than 90 percent of the concrete is to be pumped, with the majority of the concrete placement performed by a 56Z-meter truck-mounted concrete boom pump—a model introduced by Putzmeister America at the 2013 World of Concrete trade show and the latest addition to CMP’s fleet this past spring.
“We bought the 56Z because it offered a versatile five-section Z-Fold boom, reduced unit weight and five-inch boom pipe—important aspects that are on a long-reaching boom, too,” said Doug Doggett, owner of CMP.
Recognizing the equipment is only as good as the people involved with its use, Doggett says, "At CMP, it's a team effort, as sales knows how to choose the right piece of equipment for the job; operations coordinates these efforts; and our operators, who are ACPA-certified and experienced in operating our pumps, know how to maximize each unit’s special capabilities.”
“For pumping concrete at the business school, the operator knew how to articulate the 56Z boom into areas where other booms couldn't reach, which made the boom pump perfect for the application,” notes Doggett.
Quinn concurs, “The 56Z had the boom section breaks at the precise heights we needed, so it could break over the roof and extend its boom to place concrete for floor slabs. We could reach more area with the 56Z (181 foot vertical reach) than with a longer 200-foot reaching boom pump (with a four-section boom) that we had originally considered using.”
Back to Step One
Smaller boom pump models and a Telebelt® conveyor were also called upon for their special characteristics; because due to the unique structure design, after the steel frame was erected, crews had to go back to what typically would have been the first steps in the construction process. They brainstormed ingenious ways to backfill sand, stone and dirt as well as place concrete for areas now under roof, starting with the basement.
To place backfill under the structure, the Telebelt® TB 110 conveyor set up under a low 16-foot (4.88m) height and extended its telescopic conveyor belt through an 80-foot (24.38m) long tunnel, which offered a clever and resourceful solution to backfilling.
“The Telebelt was the only way to place 2,000 tons (1,814 metric tons) of backfill, as there was absolutely no access for dump trucks or loaders,” notes Quinn. “At times, the conveyor would shoot the material in place without further handling; and at other times, we dropped compact equipment into a hole to help place the materials where needed.”
“Without the Telebelt, this backfill work would have been extremely time- and labor-intensive," says Miles. “With the conveyor, it took about two-thirds less time to complete.”
Once the backfill was placed, both the conveyor and a 32Z-meter boom pump placed concrete for the basement slabs.
Boom Pumps on Stage
Even the smallest truck-mounted concrete boom pump, the 20Z-Meter, showcased its talents in the 500-seat auditorium under the second level of the building. “The 20Z could drive through the low doorway entrance and unfold its boom under 13 feet (3.96m), which made the model ideal for this job,” says Miles.
With an outrigger spread of only 11'2" (3.40m), it could setup inside the tight confines while reaching 63'10" (19.46m) vertically and 53'11" (16.43m) horizontally to pump concrete for the bowl and stairs.
The 40Z and 47Z-meter boom pumps were also called upon to assist with the unorthodox construction approach. The models, specifically chosen for their Z-folding booms, could snake their boom in-between already completed steel framed floors to place concrete. This meant greater efficiency in placing concrete, especially for the upper levels.
Concrete Supply Co., a Charlotte-based company in partnership with CMP, will supply a total of 18,000 cubic yards (13,762m³) of concrete upon completion of the school, which encompasses two levels built into the hillside and five stories above street level.
“For the slab-on-deck concrete work, we used a lightweight mix combined with lightweight aggregate, which is already a tough-to-pump mix; but when we added steel fiber to it, it made it an even tougher mix to pump,” notes Quinn. “However, the pumps had no difficulty pumping.”
The remainder of the concrete used on the project contained coarse crushed blue granite, which is notorious to the Carolinas, also makes it difficult to pump and places excessive wear on a boom pump.
“We had no hiccups placing any of these tough mixes, as we ran the concrete through five-inch boom pipe that is found on all our boom pumps,” says Miles. This includes the new 56Z model, which debuts its five-inch Esser 900 pipe, along with a more robust RS 909 hopper and high-pressure S-Valve.
Energy Efficiency Ahead
Once USC broke ground for the new $106 million project, construction began in December 2011, and the facility is expected to be complete in May 2014.
Prominent features include 35 classrooms, 136 faculty offices, 40-plus meeting rooms and 79,000 square feet of public space. One of the school’s myriad sustainable features is the landscaped roof, featuring green turf to reduce heat and improve energy efficiency; this design will maximize natural light and shade for cooling. Overall, the facility will feature energy performance targeted to be 50 percent more efficient than code, solar panels for electricity production, and cloud computing to reduce electricity consumption.
Putzmeister America, Inc. manufactures a complete line of truck-mounted concrete boom pumps, separate placing booms, truck-mounted telescopic belt conveyors, ready mix trucks and trailer-mounted concrete pumps as well as mortar, grout, shotcrete, plaster and fireproofing pumps and mixers, industrial pumps, tunneling machinery and pipeline systems. Some of the industry’s best known brands, such as Telebelt®, Thom-Katt®, and Tommy Gun®, are part of the Putzmeister America family. The company’s workforce is dedicated to hands-on customer support and advancing the industry in design and technical innovation.
Architect: Rafael Viñoly Architects—New York
General Contractors: BL Harbert International—Birmingham, Alabama; Gilbane Co., Cumming and Brownstone Construction Group—Columbia, South Carolina
General Contractor (Concrete): Loveless Commercial Contracting, Inc.—Cayce, South Carolina
Ready Mix Supplier: Concrete Supply Co.—Charlotte, North Carolina
Placing Contractor: Concrete & Materials Placement, Inc.—Charlotte, North Carolina
Equipment: Putzmeister 56Z-Meter, 47Z-Meter, 40Z-Meter, 32Z-Meter and 20Z-Meter truck-mounted concrete boom pumps; and a Telebelt® TB 110 truck-mounted telescopic belt conveyor