Corrosion of Reinforced Concrete Pipes: an Accelerated Approach

Dry-cast Reinforced concrete pipes (RCP) are frequently used as drainage pipes by several state departments of transportation (DOTs) across the United States. Corrosion has been found on culverts at locations close to the ocean where they experience wet/drying cycles of chloride rich solution. However, modest or no corrosion of RCPs have been observed on RCPs placed in soils and exposed at sites with known high chloride concentration and high moisture content. It is frequently assumed that this good performance is due to oxygen concentration limitations at the reinforcement. Another factor contributing to this observation is that on those dry-cast RCPs in which corrosion had initiated the high porosity of dry-cast RCP allows the corrosion products to move through the pore structure without causing cracks or spalls. This paper presents preliminary results of an investigation being carried out to better understand and characterize on-going corrosion on RCP exposed to relevant conditions (concrete in a high moisture content state and/or exposed to low oxygen concentration at the rebar). The results presented here correspond to the methodology developed to accelerate chloride transport as to initiate corrosion within a short period of time (a few days to a few months instead of a several years).