A moment of stainless steel at one startup could change the way bridges are built

The scourge of modern concrete is, perhaps surprisingly, rust.

Most concrete structures are laced with steel reinforcement so as to add strength, but if the metal bends, it might cause the concrete to collapse prematurely. Bridges that are exposed to water and salt are some of the most sensitive. About one-third of bridges in the United States have to be repaired or replacedwhich could cost nearly $400 billion over the next decade.

There are many ways engineers deal with rust, from coating reinforcement with epoxy to pouring extra concrete to purchase some time before the water reaches the waterways. Ultimately, these measures will even fail. The only way to actually prevent problematic rust is to make use of stainless steel reinforcement, which is not low-cost.

“It’s too expensive to use on every bridge,” Steven Jepeal, co-founder and CEO of w Allium Engineeringhe told TechCrunch. So cities and states will turn to it only for the most crucial spans.

But Allium offers something of a compromise, covering the regular reinforcement with a thin layer of stainless steel to increase the bridge’s intended lifespan from 30 to 100 years.

“As long as we get full surface coverage, there is enough thin layer of stainless steel where it will resist corrosion for hundreds or thousands of years,” said Samuel McAlpine, co-founder and CTO at Allium.

A conditional stainless steel deck was recently used to interchange a bridge deck on U.S. Highway 101 in Mendocino County, California, and one other is planned for Interstate 91 in Massachusetts. He also contributed to a business boatyard in Key West, Florida, Allium told TechCrunch exclusively.

For critical bridges that carry heavy traffic, engineers sometimes specify stainless steel, which costs about five times greater than regular reinforcement. Governments imagine the additional costs are value it if they do not have to shut a major artery.

But for most other bridges they have a tendency to specify epoxy coated strips, which is only about 25% to 50% More than simply uncoated reinforcement. Epoxy-coated built-ins should be placed in storage, and any welded spots or cuts in the deck should be easy, each of which add additional indirect costs.

Allium decomposes the tinned stainless steel reinforcement as a substitute for the epoxy coated one. The company goals to match the price of epoxy coating and possibly undercut it in the future. Jepeal said that once installed, wun allium should cost less because it doesn’t have to be handled as fastidiously. The startup factor will even not need the additional concrete that is sometimes added to bridges to forestall rust.

“This extra layer of concrete is not structural. It’s just there to try to isolate the rebar and delay how long it takes for the salt to reach the rebar,” Jepeal said. Eliminating this could cut cement use by as much as 20%. And because the reinforcement is not as vulnerable to corrosion, it should allow transportation departments to specify the use of green cements, which are typically less alkaline than standard mixes, McAlpine said.

The Allium process coats 7,000 kilos of steel with a layer of stainless steel, essentially welded wires on the outside, until it is fully covered. This billet, which is typically six to eight inches square and 40 feet long, is then fed through a series of rollers until it reaches the desired thickness, which ranges from about one-third of an inch to several inches in diameter.

“By reducing the surface area with a thicker layer and integrating with the Mills process, we can make something that is much cheaper, much more scalable, much easier to control quality,” Jepeal said.

As the billet is thinned, growing as much as 150 times longer, so does stainless steel. Ultimately, each piece of reinforcement ends with roughly 0.2 mm of stainless steel cladding.

Even with such a small amount: “You’re basically not going to corrode that stainless steel in the concrete,” McAlpine said.