Effect of bio-mineralization on concrete performance: carbonation, microhardness, gas permeability and Cl- migration

Abstract A gradient microstructure in the surface layer of concrete will be formed after the addition of the carbon-fixing microorganism when exposed to the atmosphere. To study the effect of bio-mineralization on concrete performance, the carbonation depth, microhardness, gas permeability, Cl- migration coefficient, and pore structure in concrete were studied. Results showed that the optimal amount of microbe improved the carbonation resistance and enhanced the microhardness of the concrete surface with a certain thickness. The gas permeability was reduced by bio-mineralization, which was up to 34.4%. And bio-mineralization with optimal bacteria content reduced the Cl- migration coefficient of concrete by 14.4%. Bio-mineralization technology could optimize pore size distribution and reduce the porosity of concrete according to CT (X-ray tomography) and MIP (Mercury intrusion porosimetry) results. Besides, polyhedral CaCO3 precipitation by bio-mineralization was observed in the pores by SEM (Scanning electron microscope). The findings indicated a promising application of bio-mineralization technology based on carbon-fixing microorganisms in improving the performance of concrete.