Long-Term Corrosion Monitoring of Bacterially Healed Concrete Using Electrochemical and Ultrasonic Techniques

Bacterial biocementation has been shown to have the unique capability of healing cracks in concrete. However, there is a concern that the materials used in biocement may cause corrosion. This paper reports the performance of bacterially healed reinforced concrete when exposed to chloride-induced reinforcement corrosion. Cracks in reinforced concrete specimens were healed using two different calcium sources. After healing, the samples were subjected to 3.5% sodium chloride exposure to salt water for 120 days. The state of corrosion was assessed through standard electrochemical techniques such as half-cell and linear polarization methods as well as ultrasonic-guided waves. After the exposure period, the bars were extracted from concrete, and mass loss and tensile tests were conducted. It was found that electrochemical measurements indicated corrosion activity in the cracked specimens, but the uncracked specimen did not indicate corrosion during the entire exposure period. The presence of electrolytes in the healing fluid seems to have influenced the electrochemical measurements and gave a misleading indication of corrosion. The ultrasonic-guided waves that assess both effects of corrosion, loss of metal and bar-concrete interfacial debonding, were found to realistically assess the state of corrosion in all the samples. The rate of corrosion had slowed down significantly as a result of healing.

Automated summary

Bacterial biocementation has the ability to heal cracks in concrete, but there is a concern about the potential corrosion caused by the materials used. This paper examines the performance of bacterially healed reinforced concrete when exposed to chloride-induced corrosion. Different calcium sources were used for the healing process, and electrochemical techniques and ultrasonic-guided waves were used to assess the state of corrosion. The study found that the presence of electrolytes in the healing fluid affected the electrochemical measurements and gave misleading results, but the ultrasonic-guided waves method provided an accurate assessment of corrosion.