“float” of the concrete. Even having the steel galvanized to resist environmental corrosion influenced the accuracy of sizings, said Hutchins. Such precision then enabled Williams Erection of At- lanta – whose portfolio includes work on the Bank of Amer- ica connecting bridge in Charlotte plus numerous sports arenas, hotels and so on throughout the southeastern U.S. — to lift and position the steel into place smoothly. It also required corresponding precision for the concrete. “It’s not every day a project like the wind turbine site comes along and when it did we knew we wanted to be a part of it,” said John DeWitte, president of Cooper River Concrete in Charleston. “Since this had never been done before we had no historical data to draw from. Each ele- ment of the reinforcing (steel) and concrete work had to be carefully planned, step by step.” The type of concrete used was important. “Due to the congestion of multiple layers of #11 rein- forcing bars we knew that conventional concrete was not going to work,” DeWitte said. “We had worked on a num- ber of local projects using self-consolidating concrete and knew that this was the answer to ensuring that we had proper consolidation of the concrete. SCC has chemical viscosity modifiers that hold the matrix of the concrete to- gether while increasing the slump or spread of the con- crete to 24” to 28”. The high level of fluidity allows the concrete to flow throughout the rebar and formwork with- 4 – October/November 2013 — The South Carolina Construction News out the need of mechanical vibration. During the process over 4,000 cubic yards of SCC were placed on this proj- ect.” Specifically, DeWitte, said, the foundation pours for the 7.5 MW and 15 MW were 750 cubic yards and 2,000 cubic yards respectively. “One concern of placing this mass con- crete was the control of hydration heat,” he said. “Through the placement of temperature sensors in the 7.5 MW foun- dation we were able to monitor the temperature of the concrete through the curing process.” Dudas said it took months of preparation for the con- crete pours, which lasted 12 to 16 hours at a time. It was very exacting work to place and verify tolerances of the embedded materials. “This foundation was so large and needed a lot of rebar, which made it impossible for us to pump and vibrate the concrete in a traditional manner….(Self consolidating con- crete) doesn’t need vibration and consolidates completely around all of the rebar and embeds,” Dudas said. “Unlike conventional concrete mix, the self-consolidat- ing mix pours like pea soup, which allows the concrete to flow around the re-bar,” said Choate Vice President/Divi- sion Manager Matthew Brewer. Use of Building Information Modeling software was key to Choate’s ability to coordinate with subcontractors such as Cooper River and SteelFab, which began as a small handrail fabrication shop in Charlotte and now is a major supplier of fabricated structural steel. “This project was an excellent use of BIM to coordinate the massive amounts of rebar and the large number and types of structural steel that needed to be placed,” he said. A precision metrologist was used to verify details, too.