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When Size Matters: CCCP Solution For Large Inverted Siphons Rehab
It’s important to keep in mind that several factors -- size, heat, equipment availability and staging area requirements -- combined to make CIPP impractical on this project. “Linings this big can be installed,” explains Meyer & Associates Project Manager Wayne Harris, P.E., “but the necessary equipment is hard to find and lease -- there just aren’t that many set-ups available.”
Harris says that heat was a major factor. “It was the middle of July when it's very hot, and it was extremely difficult to keep the lining cool until it was in place and ready to be cured.” Staging, too, was a consideration. For linings this size, several cranes are needed along with other bulky equipment, which means that very large pads are needed at both ends of the siphons. Sometimes, the necessary space simply isn’t available.
For all these reasons plus the fact that CIPP is proportionally more expensive at larger diameters, Harris realized that there were very good reasons to look into CentriPipe. If it could overcome the challenges that made cured lining impractical, it could solve a very real problem for the Sabine River Authority.
Centrifugally cast concrete pipe
CentriPipe, from AP/M Permaform, is a process also known as centrifugally cast concrete pipe (CCCP). This system was initially developed for manhole rehabilitation and other vertical uses, but improvements in materials and casting control have made CCCP effective for large horizontal pipes. For example, the Florida Department of Transportation has used CentriPipe to line a 13-foot diameter culvert near Jacksonville, FL.
Basically, the CentriPipe system uses an automated retrieval system and spincaster to apply thin, precisely-calculated layers of high strength cementitious grout to pipe interiors. The spincaster is inserted into the pipe and pulled back slowly as the structural liner is applied.
The cementitious grout applied was PL-8000 from AP/M Permaform. PL-8000 is a fiber reinforced high-strength cementitious grout that can be mixed onsite and used with the CentriPipe spincaster. It can be applied to most substrates (brick, concrete, metal, etc.) and it is waterproof, corrosion-resistant and structurally sound even in relatively thin layers. It also adheres extremely well, even when the substrate is damp as was the case with the SRA siphons. Since flows were active in the parallel siphons while the by-passed siphons were being repaired, serious infiltration from the saturated soils was occurring.