Self-healing Performance Of Concrete Cracks Based On Fiber-loaded Microorganisms

In recent years,with the development of the domestic construction field,concrete materials have been widely used.However,due to the low flexural strength of concrete materials,cracking and structural damage often occur in concrete buildings,which in turn leads to damage to the building.The service life and the environment bring serious problems,which hinder the development and utilization of concrete materials.Therefore,providing a new direction for crack repair in terms of structural characteristics,traffic characteristics,and environmental resource requirements is a key research goal in the field of modern architecture.The self-repairing technology of concrete cracks based on microbial mineralization deposits is a self-repairing mechanism with mineralization and nutrients added to the concrete.When the concrete cracks,the microbial spores are activated and begin to induce the production of calcium carbonate crystals.The cracks are actively repaired to further improve the durability of the concrete structure and other issues.However,under the influence of the high alkaline environment inside the concrete,if microorganisms are directly mixed into the concrete,its activity will be significantly reduced.Therefore,the immobilization of microorganisms in porous materials provides protection for the survival and reproduction of microorganisms,thereby enhancing their mineralization.However,due to the influence of factors such as the material and performance of the carrier,the existing carrier materials have certain shortcomings.Therefore,this article On the basis of consulting a large number of documents and related research,using plant fiber as a carrier to load microorganisms,a concrete crack repair material has been developed.At the same time,the repair effects of self-healing materials are explored from different directions,and the following conclusions are mainly obtained:(1)Through previous tests,we have verified that the Bacillus pasteurianus used in this paper has a good mineralization and deposition function.At the same time,this paper selects fiber as a carrier for fiber-loaded microbial materials.For the water absorption and other physical and mechanical properties of the carrier,it is selected The nutrients of the microorganisms are calcium nitrate,urea and culture medium,and the carrier is wrapped by water glass.The length of sisal fiber is 12-16 mm,and the mixing amount is 0.5% of the mass fraction of the gelling material for subsequent tests.It is more suitable,and the best adsorption efficiency is 2h when the carrier is adsorbing the microbial liquid.(2)The surface observation method and the maximum crack width and crack repair rate method are used to study the repair performance of concrete cracks.The research results show that the concrete mixed with microorganisms in the form of carriers exhibits a good crack repair effect.After 28 days of repair and maintenance,the highest repair efficiency of the fiber-loaded microbiome was 0.65 mm,and the repair rate of cracks within0.4mm basically reached 80%.At the same time,when exploring the influence of different fly ash content on the restoration effect,the general rule is that 30% fly ash content>20%fly ash content>10% fly ash content>0% fly ash content the amount.(3)By exploring the impact of the mechanics and durability of concrete materials when microorganisms are added,we found that organic substances have a certain impact on the compressive,flexural and frost resistance of concrete materials.Among them,the direct addition of bacteria liquid to concrete has the greatest impact.Among them,the compressive strength of the DC2 group was 19% lower than that of the DC1 group,and the flexural strength was reduced by 1.6%.Compared with the DC1 group,the number of freeze-thaw cycles in the DC2 group was reduced by 15 times and 21.4%.However,due to the addition of fiber,the compressive strength of the HC2 group is 7.8% higher than that of the HC1 group during the curing age,but the flexural strength of the HC4 group is 6.9%higher than that of the HC1 group in the flexural strength.(4)Through microscopic analysis,we found that microorganisms can adhere to the surface of fiber materials,and fibers can also provide a good living and reproduction space for microorganisms.This provides a basis for the repair of concrete cracks.At the same time,we conduct research on the white crystals produced at the cracks.Microscopic and phase analysis,the main component of the white crystals is calcium carbonate crystals of the type of calcite.At the same time,we also found the existence of microbes and mineralized crystals at the edges and inside of the cracks,which will provide a follow-up study on the repair of the inside of the concrete cracks the theoretical basis.