Mian Luo;Ruiyang Li;Chunxiang Qian;
<正>The aim of this study was to improve the capacity for crack-repair in concrete by developing a new way.The self-healing agent based on Bacterially induced calcium carbonate precipitation was development.Crack-healing capacity of the cement paste specimens with this biochemical agent was researched.Scanning electron microscopy (SEM) and X-ray diffraction(XRD) were used to characterize the precipitation in cracks.The healing efficiency was evaluated by measuring the water permeability after crack healing as well. The results show that the applied biochemical agent can successfully improve the self-healing capacity of the cement paste specimens as larger cracks can be healed The cracks with a width of 0.48 mm in the specimens with the biochemical agent are nearly fully healed by the precipitation after 80d repair.SEM and XRD analysis results demonstrate that the white precipitation in cracks is calcium carbonate,which appear spherical crystal morphology.Meanwhile,The water permeability test result shows that the biochemical agent can significantly decrease the water permeability of the cement paste specimens,the water permeability of specimens with the biochemical agent respectively decrease 84%and 96%after 7d and 28d immersion of water,however the control specimens only respectively decrease 41%and 60%,which indicate the bacteria-based concrete appears to be a promising approach to increase concrete durability. Originality The phenomenon of self healing in concrete has been known for many years. Precipitation of calcium carbonate has been reported to be the most significant factor influencing the autogenous healing of concrete.However,the capacity for crack-healing in most common types of concrete appears to be limited to cracks with widths up to 0.1-0.2mm.Bacterially induced calcium carbonate precipitation has been proposed as an alternative and environmental crack repair technique in recent years.Microbial carbonate deposition,a type of biomineralization,occurs constantly in diverse ecosystems as part of biogeochemical cycling.Many bacteria in nature have the ability to precipitation calcium carbonate.So the utilization of bacterially induced calcium carbonate precipitation to heal cracks in concrete is originality.
crack-healing capacity;;concrete;;bacteria;;self-healing agent;;water permeability
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