Pouring Concrete At Ashton SouthEnd
Kannapolis, North Carolina-based Wayne Brothers, Inc. is pouring the concrete for Ashton Southend, a 635,000-square-foot, 11-story building under construction in Charlotte, N.C. In addition to the concrete, there are 1,500 tons of reinforcing steel, 500,000 pounds of post-tension cables andapproximately 460,000 square feet of slab formwork on the project, which is on a fast 10-month schedule on a logistically challenging site.
Wayne Brothers started the foundation work in November 2007. Since vertical construction has started, Wayne Brothers has used an RCS Self-Climbing System, the SKYDECK Aluminum Slab Formwork System, and a UNIPORTAL table system — all from PERI Formwork Systems — along with a Putzmeister concrete pumping boom and three towers to pour each floor.
While there is a tower crane on site, it is kept so busy that the RCS system is needed to subsidize the tower crane. "The RCS is a self-climbing system that hangs off the side of the building and rises up with jacks," says Scott Ashworth, project superintendent. "Once a floor is poured, you raise it up and remove the formwork from that level. A crane on the (RCS) brings the formwork up to the next level."
Each floor of the building is being poured in thirds, and a floor is completed every 14 working days. Wayne Brothers is using two forming systems on each floor. The SKYDECK system is used on the interior. It is lightweight and can be handset. The UNIPORTAL table system is used around the perimeter of each floor for safety.
Once the forms are in place, the concrete is pumped from a central pump using one of two Putzmeister booms. Having three towers and two booms allows Wayne Brothers to jump the boom from tower to tower in order to pour each section of floor.
The floor is allowed to cure 24 hours to 36 hours before the post-tension cables are stressed. The forms are then stripped and moved to repeat the process for the next level.
Wayne Brothers is also using a PERI system for the vertical forms. The columns and walls are poured separately, the day after the floor has been poured. Although the tower crane is used to fly rebar and cable, according to Isaiah Wayne, project manager, "We don't use the tower crane to set our rebar cages. We use a special tool to set our column cages."
Even using the various PERI form systems, the tower crane is in operation 16 hours a day. Wayne Brothers makes more efficient use of the crane by splitting the crew. "Our vertical crew comes in at 4 a.m. and then the regular crew comes in at 7 a.m. This schedule allows the vertical crew to get its work done until 8 a.m. while the regular crew gets its safety briefing," says Wayne.
The drywall and exterior skin subcontractors are following close behind each completed pour, usually with two floors. Another subcontractor will begin erection of the precast parking deck in two weeks. The parking deck goes to the sixth level of the condominium tower, and Wayne Brothers has just finished pouring the seventh level. "We have to be completely above them because they'll stack the precast all at one time,"says Ashworth.
The Ashton SouthEnd project is a typical job for Wayne Brothers, although it is a larger project for the company. "Probably most challenging is the amount of formwork and the heavy foundations," says Ashworth. "With residential — condos and apartments — the challenge is the change in the slab edge for the balconies. You can't get the geometry of the building in your head from one floor to the next. There's no consistency. So, we use our own surveyor and a total station to do our layout."
Wayne Brothers has done 17 elevated pours since January 16 of this year. Although they are contracted for 11 months, they plan to finish the project in 10 months on a five-day schedule. The project is scheduled for completion this September.