Experimental Research Of Concrete Surface Coating And Crack Remediation Based On Microbial Mineralization

Microbial Induced Carbonate Precipitation（MICP）is a kind of bioinduced mineralization widely existing in nature.It has the advantages of great compatibility,low energy consumption and environmental protection in the field of concrete remediation.The deposit of mineralized calcium carbonate was induced by Sporosarcina pasteurii,and concrete surface coating and crack remediation tests were carried out in a dock in this paper.The main researches and results are as follows:（1）The effects of temperature,p H,types of calcium salts,concentration of bacteria and nutrient solution on the activity and mineralization of Sporosarcina pasteurii were researched in this paper.The results showed that the urease activity of Sporosarcina pasteurii was better when the temperature was 30-35℃and p H was 9.The influence of calcium source type on bacterial mineralization ability was not obvious.Considering the corrosion of steel by Cl^-,calcium acetate should be used in the remediation of reinforced concrete,and calcium chloride should be used in the repair of plain concrete.The calcium carbonate deposition in the sand column is the most uniform when the OD₆₀₀ value of bacteria solution is 0.8～1.2and the nutrient solution concentration is 1.0mol/L,which is suitable for creak remediation.（2）The effects of coating process,bacterial concentration and coating material on concrete surface were researched in this paper.The results showed that the specimen surface should be soaked and then coated with bacterial solution,and then the nutrient solution should be coated separately after standing for 1～2 hours.The capillary water absorption coefficient of the specimen coated decreased by more than92%.The chloride ion diffusion coefficient of the specimen coated with 10 times concentrated bacterial solution decreased by 60%to 70%,and the carbonization depth decreased by 92%.The remediation and protection effect was better than the specimen coated with epoxy,nano-adhesive and silicone.（3）The effects of remediation techniques,crack width and depth,proportion of quartz sand on concrete crack remediation were researched in this paper.The results showed that it was more beneficial to improve the remediation effect b y injecting bacteria solution first,then injecting nutrient solution after standing.For the crack width less than 0.5mm,the remediation effect was not obvious.For the specimens with a crack width of 0.5mm～3.0mm,the remediation effect is best when the crack width is 2.0mm.The remediation effect of length of70mm/depth of 100mm penetrating crack is better than the crack length of 50mm/depth of 50mm.Single gradation sand filling and lower bacterial concentration are more conducive to improving the crack remediation effect.The calcium carbonate crystals formed by mineralization in the crack are uniformly deposited between the surface of quartz sand particles and the specimen,and the cemented sand has a tight structure.（4）The effects of high-magnification concentrated bacterial solution coating in a dock were researched in this paper.The results showed that the coating outdoor should be wetting in advance,then coated with concentrated bacteria solution,and then coated with nutrient solution.After coated,the reduction rate of capillary water absorption coefficient J of concrete surface can reach 93%,and the adhesive strength of repairing layer is greater than 1.1MPa.By drilling core sample across the interface for observation,it is found that mineralized calcium carbonate crystals gradually develops downward from the surface of cracks with tight crystal accumulation and flower cluster morphology.With the increase of coating times or concentration of bacteria liquid,the microstructure of the sediments is more tightly.