Performance Evaluation And Efficiency Research Of 3D Printing Pipeline In Self-repairing Of Concrete Cracks

Concrete materials will inevitably produce cracks in the process of use,thus affecting the durability of the structure.Self-repairing concrete imitates the principle of self healing of organism damage,so that the composite material can self control and repair the internal or external damage,so as to eliminate the hidden danger,enhance the strength of the material and prolong the service life.In this paper,the common concrete cracks and traditional crack repair methods are introduced in detail,based on the self-repairing theory of concrete cracks,this paper puts forward the self-repairing theory of concrete cracks,c50 reinforced concrete is used as the base material of the system,supported by 3D printing technology,the mechanical properties of the self-healing system composed of 3D printing pipeline and substrate with builtin adhesive were tested,and the self-repairing efficiency of adhesive to reinforced concrete cracks has been tested and studied,and the following work has been completed:(1)On the basis of microcapsules and hollow glass fiber,which are commonly used as repair carriers in cement-based materials self-healing concrete test,and combined with 3D printing technology,3D printing PLA(polylactic acid)pipeline is selected as the carrier of concrete crack self repair,and the feasibility of this kind of repair carrier is discussed in detail.(2)According to the requirements of repairing adhesive for concrete cracks,polyurethane adhesive,acrylate adhesive and epoxy resin adhesive were introduced in detail,in this paper,two-component epoxy resin is selected as the repair adhesive of the concrete crack self repair test.Through the flexural test of cement mortar,the flexural strength,viscosity and curing time are analyzed,finally,the proportion of two-component epoxy resin is E51 epoxy resin: 692diluent: low molecular weight 650 polyamide curing agent: acetone solution is 100g: 20g: 110g:30g.(3)Based on the mixing law of composite materials,the stress model of 3D printed pipematrix is established,and the formula of bionic self repairing concrete composite before cracking is introduced according to the equilibrium condition.The critical volume ratio is introduced to determine the range of 8% pipe content by considering the factors of pipe orientation,interface bonding and pipe length.Based on the analysis of cracks in reinforced concrete specimens under four point bending test,the maximum crack volume after cracking is obtained after simplified calculation,which accounts for 1.5% to 2.2% of the total volume of this group of concrete specimens.(4)C50 reinforced concrete is selected as the sample,and three different volume ratios are designed,which are 1%,2% and 3% respectively.Firstly,four point bending tests with different pipe content were carried out to determine the appropriate pipe volume ratioof 2%.After the pipe volume ratio is determined,two different arrangements are adopted to embed the pipe containing repair adhesive into the concrete.Two four point bending tests were carried out on the concrete specimen.After cracks were found in the first test block,it was allowed to stand for one week for self repair.After the repair,the second bending strength test was carried out.The test records include crack initiation load,crack number,mid span deflection,maximum crack width and maximum crack extension height.(5)Based on the data of two four point bending tests of concrete self repairing system,t Through comparative analysis and demonstration,the performance evaluation and effectiveness of the self repairing system for concrete cracks are studied.It is found that the bionic self-healing concrete with 3D printing pipeline as the repair carrier has achieved certain crack repair effect.