Analysis On Anti-seepage Performance And Self-healing Mechanism Of Concrete Cracks Based On Immobilizing Bacteria In Expanded Perlite

As the largest man-made material,concrete has the advantages of high compressive strength and relatively low price,making it widely used in the construction industry.However,the concrete’s inherent low tensile strength and easy cracking will cause minor damage to the concrete structure.The further development of cracks in the damaged area will develop into macroscopic cracks,which will provide passageways for aggressive materials and erode the internal structure of the concrete,eventually cause the bad affect on the durability of concrete structures.Due to the drawbacks of the traditional self-healing technology of concrete cracks,the development of a kind of new crack self-healing technology is particularly important.Based on this situation,the study of self-healing technology of concrete cracks based on microbial mineralization gradually attracted the attention of scholars.The self-healing concrete of cracks based on microbial mineralization deposits is consisted of crack self-healing mechanism(composed of mineralized microorganisms and nutrients)and concrete matrix.When the cracks are generated,the crack self-healing mechanism starts working to realize the self-diagnosis and self-healing of concrete cracks and improve the durability of the concrete structure.Based on the study of expanded perlite in the early stage of the research group,this paper used expanded perlite as a microbial carrier firstly to prepare a concrete with self-healing capacity of cracks and studied the self-healing properties of cracks about the concrete.The main work includes:(1)In this paper,the test of the mineralization performance of the adopted microorganisms was carried out,and then the porous material expanded perlite was used as a carrier to immobilize Bacteria.H1 and different types of alkali-resistant alkalis selected from soil and sludge which have the functions of mineralization and sedimentation.The bacteria particles were used to prepare the self-repairing agent particles,and the physical properties of the particles such as cylindrical compressive strength and water absorption were studied.The experimental analysis shows that the cylindrical compressive strength of the coated self-healing agent particles is increased by 2.96 times,and the water absorption rate can be reduced to 40% after an hour,the self-healing agent particles can provide better protection for the survival of microorganisms and avoid the loss of self-healing agents.(2)After preparation of self-healing agent particles,the following three factors were considered to investigate the effect on the self-healing capacity of the concrete: the microbial incorporation method,microbial type and nutrient(calcium lactate)content.Then,the method of continuous observation of crack width were used to evaluate the self-healing capacity of the concrete.The test results show that nutrients are an integral part of the self-healing concrete,and the high porosity of expanded perlite makes it possible to carry more microorganisms under vacuum adsorption and shows superiority on self-healing capacity.When using different microorganisms as mineralized microorganisms,the bacteria based self-healing concrete specimens all exhibit excellent crack repairing ability,but when Bacteria.H1 and aerobic mixed bacteria were used as mineralized microorganisms,the higher crack repair efficiency were observed.(3)Based on the study of the influence of different factors on the crack repairing performance of self-healing concrete cracks,the water permeation performance of cracks in self-healing concrete specimens was tested by self-designed water permeation device,and the self-healing capacity of cracks was further verified.The test results show that the impermeability of the self-healing concrete specimens with crack self-repairing particles is effectively improved after the self-healing concrete specimens were cured.(4)In this paper,the SEM test method was used to analyze the micro-analysis in the experiment procedure,and the XRD analysis was used to analyze the phase of the mineral precipitates formed in the self-healing concrete cracks after curing.The test results further validated the feasibility of expanded perlite as a microbial carrier,on the other hand,although the shape of mineral deposits produced by the action of microorganisms were varied,all of them were calcium carbonate.