Weber, Brian W.

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.

Instrumented dry-cast reinforced concrete pipe (DC-RCP) specimens in which
corrosion of the reinforcing steel had initiated were selected to accelerate the corrosion.
Type C and type F DC-RCP were used. An anodic current density of various magnitudes
(0.5 μA/cm2, 1 μA/cm2 and 2.5 μA/cm2) was applied during the corrosion propagation
stage. The specimens were placed in high humidity and selected specimens were later
covered with wet sand. Selected specimens were terminated for visual examination and
gravimetric analysis. Typically, the reinforcement potentials during the accelerated
corrosion period were more negative for F specimens compared to C specimens. The C
specimens experienced ~2× more corrosion than the F specimens. The accumulated
corrosion products did not cause cracks. A method was developed that allows for modest
corrosion acceleration during the corrosion propagation stage of DC-RCP.