Corrosion Propagation in Dry-Cast Reinforced Concrete Pipes

Dry-cast reinforced concrete pipes (D-C-RCP) have been used as drainage pipes by the
Florida Department of Transportation and other DOTs in the United States. Corrosion of the
steel reinforcement embedded in concrete is a major economic burden for bridges and other
structures subjected to de-icing salts, or harsh marine environments. This study investigates the
corrosion propagation of instrumented specimens obtained from segments of two types of D-CRCPs
(Types F and C). The objectives of this study are to better understand the mechanism of
corrosion propagation in D-C-RCPs and to identify the factors that affect the corrosion
propagation. Potential, depolarization, linear polarization resistance (LPR) and electrochemical
impedance spectroscopy (EIS) measurements were carried out to monitor the corrosion condition
and the mechanistic properties of the reinforcement. A galvanostatic approach was used to
accelerate the chloride transport to the steel surface until corrosion initiated. Once the specimen
was declared active, the electric field was suspended. For ~250 days, the corrosion was
monitored in the laboratory environment. The specimens were then transferred to a high
humidity chamber and anodically polarized with a galvanostat to accelerate the corrosion
propagation. The specimens were disconnected every two weeks to perform depolarization, LPR
and EIS measurements. In the high humidity environment, type F specimens are exhibiting a
higher corrosion rate most likely due to the smaller concrete cover allowing the chlorides to
reach the steel rebar surface quicker and reach a higher chloride concentration. Results will be
compared with conventional gravimetric weight loss measurements.