In Miami, Skanska just successfully executed one of the world’s most unusual concrete pours: creating a martini glass-shaped 500,000-gallon seawater aquarium tank through a non-stop 25-hour, 1,200-cubic-yard placement.
The stakes were very high for this aspect of our new $101 million Patricia and Phillip Frost Museum of Science project: The tank can’t have any cracks large enough to let water pass through, which essentially means no cracks at all, and certainly not any construction joints. Yet concrete, as we all know, is prone to cracking. When the science museum opens as expected in summer 2016, visitors will be able to walk below the suspended, conical tank and view sharks and other aquatic life through a 30-foot-diameter, up to 18-inch-thick acrylic lens at the center of the base.
Fireworks didn’t distract our team from their 25-hour assignment.
To enable a successful pour, the project team – including program manager Hill International and trade contractor Baker Concrete – took every precaution to guard against potential issues. This meticulous planning dates back to when we joined the project this past May, taking over the work at about 30 percent completion. For the last three months, this effort included a daily 2 p.m. planning meeting. Our team considered nearly everything:
• Multiple mock-up pours were done to ensure the proper concrete mix. The concrete needed to work with the tank’s challenging geometry, including angles of up to nearly 44 degrees that could cause concrete to slide. The mix also had to fit between dense layers of hefty rebar and post-tensioning cables to create sections up to nearly five feet thick.
• Mechanics were on site should one of the three concrete pumps break down, and also at the concrete plant. Both a concrete pump and a conveyor belt at the plant went down for 30 minutes during the overnight pour, but our team didn’t break a sweat. “Those were hiccups that we had anticipated and that we had back-up plans for,” said Scott Davis, senior superintendent. Even more, if one of the pumps had failed beyond repair, a wrecker truck was on site to tow it out of position so a replacement could be brought in.
• Fire department rescue teams came to the project on three days the week ahead of the pour to do drills with the project team, in case there would be a catastrophic form or shoring failure that trapped workers. Six concrete columns and a myriad of shoring supported the suspended tank during the pour.
Ready to go
But whether this pour – requiring 150 people for each of two shifts and 131 concrete trucks – should go ahead came down to an afternoon meeting the day before the scheduled event: Was everything – including the weather – ready for the pour to proceed? The team decided that it was.
At 4:35 p.m. on Friday, December 12, our team proceeded with their approach: Beginning the pour at the base and proceeding both clockwise and counterclockwise, they worked as the arms of the concrete pumps reached out like praying mantises above them. The collaborative quality assurance/quality control process that had been integral to all aspects of preparing for the pour continued, with our team checking every truckload of concrete that arrived on site, even tracking graphically where in the tank each load was placed should any issues be identified during ongoing testing.
“This is a remarkable team that volunteered when called upon and not only helped but succeeded in performing an extremely difficult coordination between the pump trucks, the work in the tank and documenting each and every truck load placement,” said Frank Longo, project director.
As the pour progressed, cruise ships docked in the adjacent Biscayne Bay, and fireworks exploded ahead from nearby South Beach. Not that our team had time to notice. This great time-lapse video shows the pour as it unfolded:
At 5:25 p.m. that Saturday, the pour was done.
“All in all, it was a great day and night, with no safety issues,” said Nicole Heran, senior project manager.
Our team is already onto its next unusual and significant challenge: erecting a spherical planetarium made out of precast concrete segments shaped like orange peels. These significant lifts require a 550-ton crane.
Besides the aquarium and planetarium, the 250,000-square-foot museum will include exhibition halls and indoor and outdoor science exhibits. The museum – in downtown Miami’s Museum Park – is targeting LEED Platinum certification.
Visitors will be able to walk below the conical tank and view the aquatic life through a 30-foot-diameter, up to 18-inch-thick acrylic lens.