Title: Studies on Corrosion and Carbonation Resistance by Bacteria-Mediated Mineralization in Concrete
Author(s): Vishakha Bisht, Leena Chaurasia, and L. P. Singh
Publication: Materials Journal
Appears on pages(s): 13-25
Keywords: bacteria; biodeposition; biomineralization; carbonation; corrosion; durability; interfacial transition zone; non-ureolytic; ureolytic
This paper investigates and compares the potential of ureolytic and non-ureolytic bacteria in resisting corrosion due to chloride penetration and carbonation. The concrete specimens with and without reinforcement were treated with ureolytic and nonureolytic bacterial strains and exposed to 3.5% NaCl and 2% CO2, respectively, for 90 days. The bacteria-treated reinforced concrete (RC) specimens showed approximately 32% lower corrosion rate, more positive value of Ecorr, and an approximately 26% increase in pullout strength than the control. Field emission scanning electron microscopy (FESEM) of the treated RC revealed thick mineral deposition by bacteria at interfacial transition zone (ITZ), leading to overall densification of the concrete. Moreover, ureolytic and non-ureolytic bacteria-treated concrete showed approximately 60% less carbonation. X-ray diffraction (XRD) revealed additional formation of hydration products and quantification by thermogravimetric (TG) analysis, validating approximately 40% higher CH in carbonated bacterial concrete. Besides calcite, the bacteria mediated additional formation of hydration product (CH) instead of reduction during carbonation, which is believed to be the definite reason of improved ITZ and thus the durability of treated concrete.