NYSDOT specifies CCCP for challenging culvert rehabilitation
New York Interstate 684 connects Connecticut with New York City, and is one of the state’s busiest thoroughfares. Near the border, its six lanes of traffic are nearly always busy, so shutting down 684 for culvert rehabilitation isn’t really an option. When Arold Construction Co. won a bid to apply centrifugally cast concrete pipe (CCCP) to 300 ft of 36-in. CMP culvert running under I-684, it expected that traffic logistics would be difficult. But even so, it was surprised by the amount of driving on this project.
“This was 65-mph traffic, and it never really let up,” said Arold Construction President Ryan Arold. “It made everything more tedious. Often, to get somewhere just 60 ft away, we’d have to crawl through the pipe, or get in the truck and drive 20 minutes to an exit and back.”
But this was an emergency project: The culvert’s invert was rotted out, and there was rust everywhere. Arold Construction had to be efficient and work fast in a very cold New York December.
The CCCP solution that was chosen—CentriPipe from AP/M Permaform—is a fast, efficient process, and the culverts were repaired, despite challenges, in about two weeks.
The New York State Department of Transportation (NYSDOT) has used CentriPipe on several projects, and it specified it for this emergency project.
CentriPipe is based on technology developed for manhole repair. It is built around a high-pressure spin-caster that is drawn through failing pipes while applying thin layers of high-strength cementitious grouts developed by AP/M Permaform. It has several advantages:
• CentriPipe is a structural solution. The layers of grout build up a brand-new concrete pipe inside the old sewer or culvert, and the new pipe does not rely on the old substrate for support.
• The new pipe is smooth and seamless from end to end, with no joints, even at bends. So the rehabilitated pipe is likely to last indefinitely. If needed, the grouts applied can be mixed with waterproofing or antimicrobial admixtures that make the new pipe intrinsically resistant to hydrogen sulfide and freeze/thaw cycles.
• Because CentriPipe rehabilitations are thin—just 1 in. in this case—and adhere tightly to the substrate, they do not significantly reduce culvert capacity. The annular space between the old and new pipes is completely sealed, eliminating water flow around the new pipe.
• CentriPipe can be applied to curved or bent pipe. In this case, some culvert sections had bends, including a 45-degree bend in the middle of one section.
• CentriPipe is trenchless, and it requires minimal staging areas compared to CIPP or slip-lining.
• CentriPipe is cost-effective for large-diameter pipe. Dozens of projects have shown CentriPipe to cost significantly less per foot than CIPP or slip-lining.
Arold began the I-684 project by pouring new inverts in the failing CMP—this gave a smooth surface to facilitate withdrawal of the CentriPipe spin-caster. The spin-caster was then used as a high-pressure washer and pulled through pipes to clear out debris. A few spot repairs were made to provide a good surface for the sprayed grout.
The cold was a consideration, but Arold says that it was not too big a problem.
“We heated the mix water, and we certainly had some heaters around,” he said. “But we found that cure times were not affected, and we were still able to do one pull per section, per day.”
This was important. CentriPipe is applied in thin layers—about ½ in.—and cures quickly, so that layers can be applied on successive days.
Arold was able to break up the 300 ft of culvert into five sections, working from manhole to manhole, with staging areas in the median and adjoining land. Two passes were enough for most sections. To ensure that the specified thickness of 1 in. (from the top of corrugation) was being met uniformly, interior diameter measurements were taken at spots along each section, and then the spots were re-measured after each pass. The material used was PL-8,000, a fiber-reinforced, engineered grout from AP/M Permaform. For the new inverts, Arold used PL-12,000, a self-leveling grout also made by AP/M Permaform.
Despite the extra driving and the cold, the project went smoothly—nearly routinely.