RFID tags at the base of NYC's Freedom Tower

Computerworld - Builders are turning to RFID technology to set the foundation for the Freedom Tower, which is being erected where the World Trade Center's twin towers had stood in Manhattan prior to Sept. 11, 2001.

The construction project, which includes five new skyscrapers, is already underway at the site of the 9/11 terrorist attacks, which killed more than 2,500 people. The centerpiece Freedom Tower will stand 1,776 feet tall.

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 AG, 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 the temperature-tracking RFID tags come 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 they could take test cylinders to a lab for measuring -- but that's a time-consuming and expensive process.

Linke explained that construction workers can now simply toss an active RFID tag with a temperature sensor into concrete that's being poured, and they can then read temperature data from the tag's sensor through up to 20 feet of concrete. Moreover, active tags are battery-powered, so they can be read from distances of up to about 1,500 feet, meaning they can be read from much farther away than passive tags can.

"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 Freedom Tower and its surrounding structures. Whenever a wall or a floor slab is poured, an RFID tag will be dropped in, Linke said.

The new center will include 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."

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