RCP

Reinforced concrete pipe (RCP) is a rigid, cylindrical conduit made from concrete with an internal steel reinforcement cage, designed to carry stormwater, sewage, or other fluids under pressure or gravity. The steel cage, typically made from welded or tied rebar, prevents the concrete from cracking under tensile loads that the concrete alone cannot withstand. RCP is manufactured by casting concrete around this reinforcement in large circular molds, then curing it to specified compressive strength before shipment.

Pipe diameters range from 150 mm to over 3600 mm, with wall thicknesses scaled to handle both internal pressure and external soil and traffic loads. The concrete mix, reinforcement spacing, and wall thickness vary by design class, which is determined by the pipe's depth of burial, soil type, and groundwater conditions. Common designs include Class 1 (shallow burial) through Class IV (deep burial in weak soil), though classification systems differ by region and standard.

Installation and failure modes

RCP is laid in trenches with bedding material supporting the bottom and sides to distribute loads evenly; poor bedding leads to cracking and infiltration. The pipe is vulnerable to infiltration at joints if gaskets or grout seals fail, and to corrosion in acidic groundwater or where hydrogen sulfide gas accumulates. Joint corrosion from internal attack is common in wastewater systems, particularly in the crown (top) of the pipe where gases concentrate.

The main advantages of RCP are durability, high compressive strength, and low permeability compared to unlined masonry; the main drawbacks are brittleness (impact damage is difficult to repair), weight (requiring heavy equipment to install), and susceptibility to chemical attack from acidic or highly saline waters. For these reasons, RCP has been partly displaced in some markets by PVC pipe for smaller diameters and by lined concrete pipes in severe corrosion environments.

RCP remains standard in large municipal drainage and sewerage systems, culverts, and pressure applications where gravity flow alone is insufficient. It is typically designed and specified in accordance with ASTM C76 (United States) or equivalent national standards, which define strength classes, joint types, and testing requirements.