Reinforced concrete pipe, or RCP, is one of the standard materials used in storm sewer systems, sanitation systems, and large irrigation projects. Reinforced concrete offers high strength and durability at competitive costs and is the primary alternative to high-density polyethylene (HDPE) plastic pipe in many applications. One benefit of concrete is its inherent strength, which simplifies installation and backfilling procedures. On the other hand, RCP is very heavy and must be handled carefully during transportation and installation.
Handling Reinforced Concrete Pipe
Reinforced concrete pipes must be handled and moved carefully to prevent damaging the bell (the wide or flared end of the pipe sections) and the spigot (the narrow end that is inserted into the bell of an adjoining pipe). RCP should never be dragged to the site. It is best if the pipes are unloaded with the use of a nylon sling or other certified material that can support the weight of the pipe. The pipe must be balanced precisely in the sling for safety and to prevent damage.
Excavating for Reinforced Concrete Pipe
Trenches for RCP should be wide enough to accommodate at least two pipes. This provides sufficient room to verify the required slope, and it helps ensure that any subsequent trenching will not impact the pipe installation or compromise worker safety. The grade (pipe slope) is established during trenching, followed by laying down a bedding material. The bedding should be free of debris and must provide a uniformly level surface. When setting RCP into the trench prior to installation, the pipes should not be supported on their bells, as this can damage them.
Preparing Joining Surfaces of RCP
Just before installation, each RCP section is cleaned to remove all dirt from the pipe's bell. If the surface is not properly cleaned, it may prevent proper homing of the pipe. After cleaning, workers apply a lubricant to the pipe bell, using a brush or gloves. Lubricant should be sufficient to prevent the gasket from rolling away and damaging the bell end. Next, the spigot or tongue end of the adjoining pipe is also cleaned and lubricated to ensure a good seal with the joint gasket.
Installing each section of RCP requires at least two workers to manage the pipe. The large pipe is lowered into the trench with a crane or backhoe, while the workers guide the pipe section into place. The smaller pipe may be set by hand. Typically, the spigot end of the new pipe is inserted into the bell of the pipe at the end of the installed pipeline, then the new section is pushed into place with a crowbar, pipe pullers, or other means.
Some RCP must have its bell gasket stretched, using a rounding device. The device is passed several times along the circumference of the gasket to make sure everything is in place. If the gasket is not stretched, the pipe could leak at the joint or the bell can crack.
Once the new section is fully seated, workers make sure it is properly aligned, using surveying or leveling instruments.
Backfilling Reinforced Concrete Pipe
The final step of installing RCP is to add backfill material and compact it thoroughly. The backfill material is placed evenly in lifts on both sides of the pipe until the trench is filled about one foot above the top of the pipe.
It is important that the material is not be bulldozed into the trench or dropped directly onto the pipe. The backfill material must not contain large boulders, which do not compact and could damage the pipe. The material also should be free of roots and other organic material.
Once the pipe is adequately backfilled and compacted, the trench can be filled up to grade, per the project specifications. At any stage during the backfilling process, heavy construction equipment should not drive over the pipe until adequate backfill is in place or the pipe is deep enough that it will not be damaged.