Gradient domestication and selection of mineralizing microorganisms suitable for the internal environment of hydraulic concrete
The harsh alkaline conditions within the internal structure of hydraulic concrete constrain the self-heal-ing efficacy of microbial concrete.This study employs a gradient domestication method to enhance the alkaline toler-ance of mineralized microorganisms,selecting enhanced alkaliphilic microorganisms that are well-suited to the pore environment of concrete and possess a heightened capacity for inducing mineralization deposition.Initially,under high alkaline conditions in laboratory,the activity and induced mineralization deposition of four Bacillus species(B.megaterium,B.cohnii,B.subtilis,and B.pasteurii)were compared.Microorganisms exhibiting superior alkaline resistance were preliminarily selected,and an adaptive alkaline tolerance domestication process was con-ducted.Subsequently,a comprehensive investigation of the impact of domesticated microorganisms on concrete me-chanical properties,capillary water absorption,water permeability,and self-healing capability was undertaken.Scanning electron microscopy and X-ray diffraction techniques were employed for the characterization of the micro-scopic morphology and composition of mineralized products.The results indicate that,in comparison to B.megate-rium,B.cohnii,and B.subtilis,B.pasteurii demonstrates higher activity under high alkaline conditions.The gradient domestication technique further enhances the activity of B.pasteurii in high alkaline environments,confir-ming that the enhanced alkaline resistance through this method exhibits multigenerational retention characteristics.In comparison to the 28-day unmodified microbial samples,the compressive strength of concrete incorporating do-mesticated microorganisms increased by 16.59％,and water absorption decreased by 37.74％.Additionally,the maximum closed crack width was 0.57 mm,exceeding the 0.44 mm of the unmodified bacterial group.Compared to unmodified bacterial samples,the water permeability coefficient of domesticated bacterial samples decreased by 19.22％at 28 days.This research provides a viable strategy for improving the efficiency of microbial-induced calci-um carbonate precipitation in concrete.
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