Crack healing in concrete by microbially induced calcium carbonate precipitation as assessed through electromechanical impedance technique

In the present study, Electromechanical Impedance (EMI) technique is utilized to assess the application of the microbially induced calcium carbonate precipitation (MICCP) to restore the integrity of cracked concrete. The artificial crack width of approximately 0.5 mm is healed autonomously using a bacteria-based healing agent, using flyash (FA) as a carrier material. Lead Zirconate Titanate sensors were bonded on the cracked specimen to monitor the continuous healing process. The EMI signatures were captured over the healing period using an impedance analyser in the frequency range of 100 to 250 kHz. Statistical crack healing indicator, root mean square deviation (RMSD) was employed for evaluating crack efficiency based on extracted signatures. Results revealed that the RMSD values were effective in quantifying the progressive healing achieved due to MICCP precipitation. This is the first study with a successful implementation of the EMI technique to monitor the crack sealing in concrete through MICCP. Healing capacity was also correlated with the crack width reduction that was evaluated by optical imaging of repaired cracked surface. Also, the bacterial mineralization products were analyzed by FESEM, EDX, XRD and TGA. The results give clear proof that the FA-based carrier material can be effectively used in healing the cracks.