Some call it "steel-belted duct tape." Inspired by a rebar cage, an inventor in 2000 began tinkering in his garage with ultrahigh-strength twisted steel wires, attempting to replicate the structure in miniature. Now it is being used for structural upgrades and to increase blast resistance. The Army and the Navy are testing it for possible use in low-weight armor-plating for vehicles. And it has even been used to strengthen plywood.

The material, called Hardwire, comes in various configurations, but all resemble duct tape in being thin and shipped on a spool. All are composed of ultrahigh-tensile-strength twisted steel cords. It is the same steel-belt technology used in radial tires, say officials of Hardwire LLC, Pocomoke City, Md., the maker.

Hardwire occupies an empty niche between rebar and fiber. "Carbon fiber is as fine as baby hair, strong, expensive and hard to work," says George Tunis, the inventor and Hardwire LLC president. But it costs too much for general structural reinforcement. "Rebar is crude and strong," Tunis says. One day he noticed a rebar cage and said, "If you could ever miniaturize that, you could probably put it in plastic." He pursued the idea.

In the last year, Hardwire has begun to fulfill a need for inexpensive structural repairs and upgrades. The Structural Group, Hanover, Md., an equity partner in Hardwire LLC, has installed Hardwire in half a dozen "big-box" stores to retrofit reinforced slabs on concrete piles where misplaced or inadequate reinforcing steel had allowed cracks to develop, says Jay Thomas, vice president of subsidiary Structural Preservation Systems. Another half-dozen public buildings threatened with terrorist attacks have received applications to improve their blast-resistance. And "for literally one-quarter of the cost of replacing them, we've gone in to some of these smaller bridges [in Missouri, North Carolina and Kansas], repaired deteriorated concrete and applied externally bonded systems to upgrade the bridge. They're load-tested, certified and unposted to allow truck traffic again," says Thomas. Depending on the level of upgrade required, costs run from $10 to $20 per sq ft, he adds.

Hardwire is applied in 12-in.-wide bands on a bed of epoxy, urethane, polyurea, vinylester or cement-based adhesive and sealed with another layer of the same material. It can be applied to vertical or horizontal surfaces or molded to nonplanar shapes as necessary. Workers can install it with minimal training because it works with common construction materials.

The material comes in low-, medium- and high-density tapes, with densities ranging from four wires per in. up to 23. The steel reinforcing is Pearlite, a very fine steel with high carbon content, which Tunis describes as "the pinnacle of steel technology." Long used exclusively in tire manufacturing, "it's the Budweiser of carbon fiber," he says.

Army combat engineers can use Hardwire to repair and strengthen damaged bridges, says Maj. Gen. (ret.) Norman Delbridge, former Deputy Chief of Engineers. "You can wrap it around damaged pillars and then just use a roller on it, or apply it to bridge stringers along the bottom." He was so impressed that a few months ago he brought Hardwire to the attention of the Army Engineer Research & Development Center, Vicksburg, Miss., where it now is being studied.