The RCP Advantage
Engineered Integral Structure Proven 100-Year Lifecycle
Reinforced concrete pipe is made by a machine the same way, time and again, in a controlled environment. RCP is a constant product, manufactured with certified materials according to ASTM C76 and ASTM C443 standards. Each reinforced concrete pipe is a high-strength structure, ensuring the majority of the design parameters are present post-installation. The RCP advantage is that when the product is delivered, it has already passed rigorous tests that ensure its durability over many decades. In that sense, it is already a structure when it is delivered, with a known outcome.
Design engineers want ease of design for every project. LRFD design tables are created based upon minimum allowable D-Load values in a positive projecting embankment condition per the AASHTO LRFD Bridge Design specifications at the surface. Proper class determination of RCP takes less than one minute using the design tables.
The SDDOT independently load tests all pipe runs, confirming that RCP meets or exceeds ASTM C76 standards and specifications. Only pipe that meets ASTM C76 may ship. Results are posted regularly on the SDDOT Pipe Release web page.
Benefits of RCP
- SDDOT Manning’s Value of .012, used in design, is present following installation
- Structure delivered encompasses up to 90% of the soil-pipe structure
- 100 year proven lifespan
- 13 psi waterproof gasket
- NO DEFLECTION
- Affords contractor greatest margin for error
- Lowest risk to design engineer
- Lowest cost to owner
Case Study: What Went Wrong
This photo illustrates what goes wrong when flexible pipe is installed the same way that RCP is installed. In the field, flexible pipe requires much more preparation, inspection and post-installation testing, as well as extensive bedding materials and contractor attention to detail to avoid issues.
- Flexible pipe relies on proper installation and properly compacted aggregate backfill to provide its structure in the soil/pipe envelope. This flexible pipe installation was “faster,” because it was installed as if it had the same structural properties as reinforced concrete pipe. Only a scant amount of sand backfill is visible in this installation – fine for RCP, but a big problem for flexible pipe.
- Flexible connectors were not used. When the flexible material deflects, the void created between the flexible pipe and the rigid concrete structure will leak.
- Three feet of cover is required above the top of this pipe to support a 60,000-pound load. During surfacing operations, neither a ready-mix truck nor a loaded asphalt truck may pass over this pipe without violating the manufacturer’s guidelines and potentially damaging the installation.
This installed “smooth wall” flexible pipe actually possesses SDDOT corrugated wall Manning’s Value closer to .024, versus RCP installed value of .012. Furthermore, RCP is not subject to corrugation growth.
What went wrong…
- Engineered design not created
- No inspection
- Improper backfill methods
- Improper backfill materials and thicknesses
- Lack of flexible covers
- Three feet of cover above the pipe, necessary for surfacing operations, is not present
- No post installation testing performed with a 9-point mandrel or laser profiling
THE CEMCAST PLEDGE
- You can expect a guaranteed outcome with the installation of our product
- We will produce it and test it so you will never need to worry about it
- We will deliver a competitive price and exceptional product value
- Our product will perform according to ASTM standards
- We will be adaptive to our customer’s needs and wants
- We deliver a structure that eliminates most field variables
In today’s market, there is more and more pressure to save money in construction. Owners are requesting products they have heard are cheaper. This puts design engineers in a very difficult position. To ensure the characteristics used in design exist following installation, we recommend all thermoplastic pipe be installed according to AASHTO Section 30. This test ensures the plastic sleeve is installed correctly.
At the jobsite, all flexible pipe installation assurance should follow industry standards such as those laid out by The American Association of State Highway and Transportation Officials or AASHTO. Flexible pipe installation standards are addressed in Section 30 and state that the overall performance of the flexible pipe is highly dependent on installation handling, backfill material, and methods used to place and compact the backfill.
Plastic pipe is manufactured by a variety of methods and different profiles, but satisfactory performance of the culverts requires proper control of construction procedures at all times regardless of profile or manufacture method. Section 30 requires a mandrel test be performed a minimum of 30 days after installation once the pipe has settled. Mandrel testing, or deflection testing, is used to determine that the ovality of flexible sewer pipe meets design specification. This testing is critical to the long-term performance of flexible lines being installed today. According to Section 30.7.2, if a mandrel is used for testing purposes, it shall be a nine (or greater odd number) arm mandrel and will be sized and inspected by the Engineer prior to testing. In locations where the pipe deflection exceeds 5% of the inside diameter the Contractor must have an evaluation performed by a Professional Engineer; all installed pipe deflections that exceed 5% of the inside diameter potentially indicate the installation was substandard. If the deflection exceeds 7.5% remediation or replacement of the pipe is required.
A result from deflection testing is to ensure the ability of flexible pipe to withstand soil load without exceeding maximum deflection limits. If the flexible pipe cannot withstand the soil load it could be directly related to the quality of the installation and compaction of the embedment material around the pipe.
With concrete pipe you have a single point of testing. Independently, the DOT tests all pipe ensuring it meets the proper classification. It is not necessary to test and verify in the field every lineal foot of pipe backfill with concrete pipe as it is with a flexible sleeve. This greatly reduces the risk to the contractor and to the engineer. Give us a call at 605.528.3530. We would be glad to discuss any of our products with you.