Replacing rusted-out culverts can be quite a project. To start, there’s the excavation. Then demolishing and rebuilding any headwalls. Major traffic disruptions. And possibly replacing nearby sidewalks and pavement damaged by the excavation work.

But thanks to a product called Storm Seal, fixing failing culverts isn’t a hassle for Nashville-based C. K. Masonry Co., which primarily does culvert and manhole rehabilitation work throughout Tennessee, plus pipe lining and grouting. The cementitious lining product from The Strong Company enables C. K. Masonry to take the easy way out — in the best possible sense.

“With Storm Seal, we can fix culverts at a fraction of the cost of digging it up and replacing it,” says company owner Kurt Koehn. “It requires no road or headwall replacement or traffic disruption.

“In fact, we can rehabilitate pipes while people are driving over the culvert. This product solves problems and saves money at the same time.”

Made with Portland cement, Storm Seal is a specially formulated, fiber-reinforced cementitious mixture that effectively forms a pipe within a pipe. It can also be used to rehab concrete pipes, catch basins and other stormwater structures.

The product features a compressive strength of 9,000 psi, a tensile strength of 800 psi and a flexural strength of 1,200 psi. Moreover, it’s resistant to freeze/thaw cycles and is suitable for a variety of structure shapes.

Shining example

A good example of the convenience and efficiency benefits Storm Seal offers occurred in 2015, when the company was hired to replace a 60-inch-diameter, 65-foot-long corrugated pipe that ran under McGavock Pike, a busy Nashville thoroughfare.

“The pipe was collapsing and as a result, the roadbed above it was, too,” Koehn explains. “Digging it out would’ve been difficult because there also was a gas line, a waterline and a fiber optic cable running on top of the pipe and below the road surface, plus sidewalks and headwalls that would need to be rebuilt.

“Plus, McGavock Pike is a pretty big artery in Nashville and we didn’t want to create traffic problems for days on end. So we used Storm Seal and saved the city a lot of money and aggravation. And it’s held up quite well, too.”

Storm Seal can be either centrifugally cast using the Strong-Seal Systems mixer, pump and spinner or sprayed onto structures manually.

“You effectively use the pipe as your (concrete) form,” he says. “After you apply the Storm Seal, you really don’t need the outer pipe anymore. But it still provides additional strength.”

Systematic process

The first step in applying Storm Seal is cleaning the culvert walls with a strong pressure washer. And if the culvert invert is rusted out, Koehn says his company uses another Strong Company product, Grout 12,000, to rebuild it prior to Storm Seal application.

The spin-casting machine is pulled by a winch connected to a control panel. The speed at which the winch travels and how much product it dispenses depends on factors such as the diameter of the pipe and the load the culvert was designed to carry; an operator uses tables supplied by the manufacturer to determine those calculations and input them into the control unit, he says.

The Storm Seal is applied in 1/4-inch-thick layers with the spin-casting unit, with four to five passes required per job; the layers are about 1/2 inch thick per pass when done with manual spraying.

“When we do it manually, we like to fill between the (corrugated) ridges and then put about another inch on top of that,” Koehn says.

“When you spin-cast it, there’s no troweling or brushing required. The machine provides the finish, though you sometimes have to do a little bit of finishing if it goes on too thick and sags a bit.

“You can get picky and find a few warts here and there — it doesn’t look like a shiny new nickel. But it’ll last a long time.”

It typically takes about eight hours to dry.

Solid investment

C. K. Masonry crews can typically apply Storm Seal at about half a foot per minute, so a 50-foot section of culvert would take about 100 minutes for each pass. At that rate most culvert pipes can be repaired in four days: one day to clean it, one day to re-establish a rusted-out invert and about two days to apply the Storm Seal, Koehn says.

The Storm Seal system costs about $200,000, but Koehn says it’s been a great acquisition with a solid return on investment.

“It’s a very practical alternative (to culvert replacements) — an elegant solution that saves customers a lot of money. It’s self-supporting, engineered to work in various applications and avoids traffic and utility line disruptions and conflicts. And it can improve the hydraulics of pipes, too.”

Looking ahead, Koehn sees even more market potential for the product because many culvert pipes have already exceeded their life cycles.

“Most culvert pipes are good for about 30 years and a lot of them are 60 years old or older,” he says. “Our biggest market for Storm Seal is failing corrugated metal pipes.

“We probably do one or two a month and we expect the business to continue to grow. Right now, I think we’re only at the tip of a very large iceberg.”