Performance of bacterial mediated mineralization in concrete under carbonation and chloride induced corrosion

Abstract

Prevention of concrete structures from early deterioration under aggressive environments is a major challenge. The present study investigated the performance of bacterial-treated concrete structures under harsh conditions such as carbonation and chloride exposure. Improvement in the mechanical strength and reduction in penetration properties was recorded in bacterial-treated specimens. The maximum carbonation depth of 18.27 mm and reduction of pH (8.6) were recorded in control specimens during carbonation exposure (5% CO2) for 120 days, whereas significant resistance against CO2 diffusion and much-reduced carbonation depth was observed in BAC specimen (9.28 mm) and BSC (11.13 mm) specimens. Due to accelerated carbonation conditions, further increment in mechanical strength and reduced penetration was observed in control and bacterial treated specimens due to microstructure densification caused by carbonation reaction products. During chloride exposure (5% NaCl) for 120 days, the control specimen showed the initiation of rebar corrosion with Ecorr and Icorr values of −522.2 mV/SCE and 0.34 μA/cm2, respectively. However, bacterial-treated reinforced specimens (BARC and BSRC) significantly resisted the penetration of chloride ions. At the end of chloride exposure, BARC and BSRC specimens showed lower Ecorr values of −203.4 mV/SCE and −301.4 mV/SCE and Icorr values of 0.03 μA/cm2 and 0.02 μA/cm2, respectively. These results suggested that the biogenic treated concrete specimens resisted from the deterioration effects of chloride and carbonation exposure and improved their durability properties.