Builders are turning to RFID technology to set the foundation for the Freedom Tower that is being erected where the World Trade Center's Twin Towers had stood in New York City prior to September 11, 2001.
The construction project, which includes five new skyscrapers, is already underway at the site of the September 11 terrorist attacks where more than 2,500 people died. The centerpiece Freedom Tower will stand 1,776 feet tall on the site of the former World Trade Center.
Builders are using RFID tags in an effort to ease the formidable job of laying the concrete for the giant structures, according to Peter Linke, CEO and president of Lustenau, Austria-based Identec Solutions, which is supplying its RFID-based iQ32 Temperature Tracking Tags for the project. It's often difficult to know exactly when the newly laid concrete is cured, or hardened. That's where RFID comes into play, he said.
"When you pour concrete, it takes a sufficient amount of time for the concrete to cure properly to put a load on it," said Linke. "It needs a specific amount of time to harden [and] it's difficult to know what that time is." He said the hardness of the concrete depends on several factors - "temperature, humidity and how the concrete mixture has been engineered."
He said the contractors could measure hardness using a mathematical formula that's prone to error, or take test cylinders back to a lab for measuring, a time consuming and expensive process.
Linke explained that with RFID technology, construction workers simply toss in an active tag with a temperature sensor as they're pouring the concrete. An active tag is battery powered so it can be read from much farther away than with a passive tag. Linke noted that the active tags can be read from 1,500 feet away, and construction crews can check the temperature readings from the tag's sensor through up to 20 feet of concrete.
"You can determine how concrete hardens depending on the temperature profile that the concrete goes through as it hardens," explained Linke. "With one of our tags in it, it's really very convenient. You just go up with a reader and you can wirelessly tell the temperature at any given time, and you can download the temperature changes over time."
About 20,000 RFID tags will be used during construction of the 1,776-foot tall Freedom Tower and its surrounding structures .Any time a wall or a floor slab is poured, an RFID tag will be dropped in, he said.
The new center includes a retail complex, a performing arts center, a transportation hub and a Sept. 11 memorial and museum, which are slated for completion in 2011 or 2012.
"Personally, I find it extremely exciting. It's going to be the signature building of the United States," said Linke. "It will be a very important building for a very long time. And because it's so big, it will have engineering challenges. Some of the walls are 20 feet thick. We're pretty proud we can get our radio signal through 20 feet of concrete. For us, we're happy that we were able to help solve some of these problems."