Oceanfront High-rise Condos Get a Lift from Placing Booms
Oceanfront High-rise Condos Get a Lift from Placing BoomsTwin-tower solutions save contractors time and developers money
Condos keep popping up all over Florida and so do placing booms. Two recent high-rise condo projects, one near Miami and another in Key Biscayne, relied on Putzmeister equipment to pour more than 80,000 cubic yards of concrete decks, columns and walls.
In the prestigious Aventura district outside Miami, the Porta Vita oceanfront condos are expected to sell at up to $2 million each. As such, timely completion of the 31-story condo complex was one of the developer's top priorities. Because they were on a tight schedule, the developer was adamant about where to place the slab openings. The two tower holes could only be about 35 feet apart and in the least conspicuous place available, a closet and service area. This would also allow for an easier finishing task after the pipeline was removed.
After securing the contract on this job, Warren's Concrete Service selected a placing boom with a long reach, the Putzmeister 32-Meter placing boom. Without counter-weighting, the boom could be moved faster from tower to tower for reduced crane time and greater overall efficiency. This also helped meet the developer's schedule of finishing one floor a week.
Although there was a large enough crane on the job to move the boom in one pick, one advantage of Putzmeister's two-piece design is that the contractor doesn't have to spend the extra money on a larger-capacity crane for flying the boom. As many as 150 trucks and five batch plants were used to service the huge Porta Vita project. The job began with an 8,400-yard mat pour at a 9-foot thickness. To eliminate traffic congestion and have the sole use of batch plants for this large job, the first load of concrete arrived at midnight one night and the last finisher left at midnight, 24 hours later. Four truck-mounted boom pumps, two 36- and 43-Meter Putzmeister units, handled the pour.
The job faced a few other interesting hurdles. Because the job site was located in a prestigious neighborhood, truckloads of fine white sand were spread over the subdivision's special roadway. With the quarter-mile-long street constructed of expensive brick pavers, all precautions were taken to prevent the staining of these bricks from the ready-mix trucks' oil or concrete drippings. Plus, workers kept watering the sand to prevent the dust from flying onto the area's expensive cars and homes.
Once the mat pour was handled, only part of the future building could be reached with a truck-mounted pump. So a placing boom tower site was set in the northwest corner of the mat. The freestanding boom was erected 50 feet above the foundation, the highest distance available in the industry – possible only because of the square Putzmeister tower design. At this position, the MXR 32/36T boom was used to pour all the walls, columns and floor slabs.
Once several floors were poured, the tower was unbolted from the foundation and raised through the building using a crane. With the building supporting the tower, a vertical support system was utilized to hold the vertical weight of the boom, and hardwood wedges were used for lateral bracing. Re-shoring below the vertical support ensured proper load distribution.
The platform, which easily mounts to the tower, allowed the operator a bird's eye view when operating the unit. The platform also made it easier to access the four pins that attach the boom to the tower, which are removed when moving the unit from one tower to another.
After the first four floors on the south end of the building were poured by a 43-Meter truck, Warren's put a second tower into place. Once this tower was in place, they flew the Putzmeister boom from tower to tower as it climbed all 31 floors. Warren's used a high-pressure Putzmeister 12000 trailer pump to supply the concrete. With up to 160 cubic yard outputs and 1,270 psi, this unit was able to pump the concrete at these excessive heights, even with unusual mix designs.
The columns and walls were a typical 10,000-mix design. However, the slabs were a 6,500-psi mix, and the balconies were a 6,000-psi mix with DCI, a special water-reducing agent and accelerator. Begun in July 1998, the $65 million Porta Vita project used more than 80,000 yards of concrete by the time it was completed in May 1999.