Design of Long-lasting Discrete Sacrificial Anode for Corrosion Mitigation of Reinforcement in Chloride Contaminated Concrete
Dr. Xianming Shi, Washington State University
Reinforcement corrosion induced by chloride contamination is a leading cause of structural damage and premature degradation in reinforced concrete (RC) structures, with significant implications for safety, reliability, economics, and environmental performance. Discrete sacrificial anode (DSA) is one tool used for corrosion mitigation of steel reinforcement in chloride contaminated concrete, particularly through embedment in repair mortar to reduce the detrimental “ring effect”. Our recent study revealed that the commercial DSA products actually have much shorter service life than expected, because zinc corrosion products accumulate at the interface between zinc core and the packaged mortar, reduce the current supply to steel reinforcement, crack the encased mortar, and finally lead to the complete failure of the DSA. In this context, the overarching goal of this project is to design long-lasting DSA to prolong its service life and reduce the costs associated with the need for frequent replacements. To achieve the goal, this study aims to:
1) design conductive and porous foamed cement paste as the encasing material for DSA, and
2) characterize the effects of different components of the paste on the life-cycle performance of newly-designed DSA and assess its effectiveness on the rehabilitation of salt-contaminated RC.
Specifically, carbon fibers will be incorporated into the foamed cement paste to increase its electrical conductivity. Light weight aggregates with water or saturated calcium hydroxide (Ca(OH)2) encapsulated inside will be used in the paste to maintain a sufficient level of moisture. Electrochemical tests will be conducted to study the corrosion performance of steel bars and zinc anodes as well as evaluate the effectiveness of DSAs. Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction analysis (XRD) will be employed to investigate the mechanisms related to how the foamed microstructure and different components of the paste enhance the longevity and performance of DSAs.
Dr. Xianming Shi