Study On Microcapsule Self-repairing Cement-based Materials By Electrochemical Impedance Spectroscopy

The durability of concrete is a problem that has received extensive attention in the field of civil engineering.Microcapsule technology as an emerging self-repairing technology provides a feasible way to improve the durability of concrete.The mechanical and durability properties of microcapsule cement-based materials have been studied in the existing literature.However,there are still some problems to be solved in the research of microcapsules,including the rupture detection of microcapsules in cement-based materials and the non-destructive repair rate detection of microcapsules.In order to solve the above two practical problems encountered in the research,this paper quotes the electrochemical impedance spectroscopy method to provide a feasible idea.Firstly,the influence of different content and particle size of UF resin microcapsules on the overall impedance of cement-based materials was studied,which fills in the blank of basic research on electrochemical impedance spectroscopy in the field of UF resin microcapsules cement-based materials.In order to obtain the rupture rate of the capsule by the non-destructive testing microcapsule cement-based material,microcapsules with conductive core can be used for testing,the damage and integrity of the conductive microcapsules were simulated by using graphite and cured epoxy.The impedance spectrum data and equivalent circuit parameters of the specimens under different damage rates were obtained.The damage rate detection model was established by using the equivalent circuit parameters,and the macroscopic experimental simulation method was used to conduct a more in-depth study.In order to obtain the method of non-destructive detection of microcapsule repair rate,a single crack test piece and multi-fracture test piece were prepared.The damage repair rate detection model was established through the data of crack damage and repair,and verification by dynamic modulus of elasticity method.The main conclusions are as follows:?1?The influence of the basic parameters of microcapsules on the electrochemical impedance spectroscopy of cement-based materials was studied.It is found that with the increase of microcapsule content,the compactness of cement-based specimens increases first and then decreases,and the impedance semi-circle radius of the impedance spectrum increases first and then decreases.When the microcapsule particle size is small,20%is different.The addition of the microcapsules has little effect on the impedance.When the particle size of the microcapsules reaches a certain limit,the influence on the compactness of the test piece is intensified,and the impedance radius of the test piece is reduced.?2?The effects of different rupture rate of conductive microcapsules in cement-based materials on the electrochemical impedance spectroscopy of the specimens were investigated.As the rupture rate increases,the impedance semicircle radius of the test piece gradually decreases.It is found that R_p and R_ct in the circuit will have strict monotonous changes with the change of rupture rate.The two parameters are used to establish the detection model of the damage rate of conductive microcapsules.?3?A macroscopic simulation test was established to study the possible phenomena of particles in cement-based materials.It is found that the influence of the addition of a certain amount of insulating particles on the impedance of the material is very small,and the same amount of conductive graphite particles have a greater influence on the material impedance,and the influence amplitude increases as the number of particles increases;the same amount of graphite particles,The difference in arrangement has a great influence on the impedance,and the longer the transmission path is formed along the electrode direction,the smaller the impedance.?4?The effect of crack damage on the materials was studied.As the degree of damage increases,the semi-circle of the specimen impedance gradually decreases.Through the fitting of the equivalent circuit,the two parameters R_C and C_C in the equivalent circuit show a linear correlation between the damage degree.The damage degree and impedance parameter model are established.?5?Through the impedance test data and model of the specimens after repair,the repair rate of the specimens at different repair ages was obtained.With the increase of repair age,the repair rate of specimens with different degree of damage increases gradually.Within the same repair age,the higher the degree of damage,the higher the repair rate.Similar laws are obtained by dynamic modulus of elasticity test,which proves that the calculation model is reliable.