New York City’s subway is big, with nearly 450 miles of underground track. And New York City Transit, which manages the subway system, had a big – as in billion dollar – problem. As part of a public safety upgrade, the agency was blocking openings from one subway track to another. However, the traditional material of choice to do so, precast concrete, was degrading critical radio communications following installation.
If the precast concrete approach continued, a new radio system antenna would be required at an estimated cost of $1 billion. A much less expensive solution was a proprietary cast polymer that met mechanical and fire-resistance requirements. The second remedy is the one currently being implemented.
While the unit price of cast polymer materials are higher than conventional precast concrete, the installed cost of cast polymer can actually result in significant job cost savings. It weighs 75 percent less than concrete and is easier to work with. That was evident when the contractor did the first trial installation. “He did in a two-day weekend as many closures as it would have taken him 10 two-day weekends to do with concrete,” says Tom Lamb, chief of innovation and technology for New York City Transit.
The ease of installation benefited the installer and the transit agency. Closing the connecting openings between tunnels requires the subway to be shut down, which disrupts passengers and costs money. Being able to complete the project in a shorter time and for less labor saves money and reduces customer disruptions.
None of that would matter, though, if the material didn’t meet basic specifications. It had to offer negligible interference to radio waves, be fire resistant to meet safety standards, not emit toxic gases when exposed to flames, withstand pressure loads due to passing trains and not absorb moisture. The agency looked at four or five different materials as a replacement to concrete.
While in private industry, Lamb had worked with materials from Advantic. The Dayton, Ohio-based company leverages advanced materials for use in civil engineering and infrastructure construction. “The material systems that we commonly work in are unique proprietary polymers as well as polymers and composite systems produced by material manufacturers,” says President Brad Doudican.