Viable FA based bacterial cells as sustainable solution for corrosion prevention in RC structures

Reinforcement corrosion is one of the biggest challenges faced by the construction industry, with billions of dollars spent on corrosion remediation and prevention. Recently, microbially induced calcium carbonate pre-cipitation (MICCP) has been considered a novel method in corrosion mitigation of reinforced concrete (RC) structures. In the current investigation, fly ash (FA) based inoculum for construction industry was developed and tested for cell viability to define the shelf life of the carrier product. The results indicated that FA-based inoculum possessed a shelf life of 180 days with an effective cell count required to induce MICCP in reinforced concrete. FA-based inoculum was immobilized in fresh concrete supplemented with nutrients to study the corrosion mitigation potential. The prepared specimens were cured for 28 days and then subjected to impressed current -induced chloride corrosion. For corrosion assessment, well established electrochemical technique and a newly emerged electromechanical impedance (EMI) technique were employed separately on different RC specimens. In the electrochemical technique, open circuit potential (OCP), corrosion potential (Ecorr), corrosion current density (Icorr) were obtained over the test exposure; whereas in EMI technique, admittance signatures were acquired for the entire testing duration at an interval of 7 days. Further to examine the changes in admittance signatures, root mean square deviation (RMSD) was used to quantify the corrosion process. Results indicated that Icorr and RMSD were linearly increasing over the test exposure. The results clearly prove that the FA-based carrier material can be effectively used for the corrosion prevention and the emerging EMI technique can efficiently monitor the corrosion process.