| Concrete in the environment of chloride salts and other environmental erosion can corrode reinforcement and produce rust expansion cracks,eventually damaging or even destroying the structure,making it fail prematurely and thus unable to reach its design service life.In order to solve the corrosion problem and improve the durability of building structures,scholars at home and abroad have proposed a variety of repair methods.Among them,electrochemical repair methods have attracted widespread attention and research in academia because of their advantages of nondestructive removal of chloride ions from concrete and elimination of potential differences in steel reinforcement.However,the electric field during the electrochemical treatment accelerates the migration of ions in concrete,which makes the microstructure and macroscopic properties of concrete subject to various complex effects.At present,most of the domestic and international studies on electrochemical technology have focused on the exploration of chloride ion removal efficiency,and lack of quantitative and comprehensive studies on the changes of concrete properties under the action of the electric field.In this paper,the microscopic material properties,micromechanical properties,macroscopic material properties and macroscopic mechanical properties of concrete under the action of different electrical parameters and electric fields are investigated.The main research contents are as follows.(1)The microscopic material properties of concrete specimens before and after the action of the electric field were studied.Through microscopic morphological observation,thermogravimetric analysis and bubble characteristic parameters testing of the samples under different electric parameters and unenergized conditions,it was found that the porosity in the anodic region decreased and the structure was more dense,while the porosity in the cathodic region increased and the structure was loose under the action of electric field.With the increase of the energizing time,the air content of the concrete in the cathode zone increased,and the bubble spacing coefficient and the average bubble radius decreased and then increased;the air content of the concrete in the anode zone decreased with the increase of the energizing time,and the bubble spacing coefficient and the average bubble radius continued to decrease.A large amount of calcium hydroxide was produced in the concrete cathode area after energization,and the amount of calcium hydroxide increased with the increase of current density.(2)The micromechanical properties of concrete under the action of electric field were studied,and microhardness tests were performed.The aggregate-mortar interface and mortar-reinforcement interface of concrete specimens with different electrical parameters were electrochemically treated,the microhardness was measured,and the average hardness loss was calculated.It was found that the hardness of the interfacial transition zone phase and the mortar phase of the aggregate-mortar interface and the reinforcement-mortar interface of concrete showed a decreasing trend after energization,and the decrease increased with the increase of energization time and current density.After linear fitting of the experimental results with the electric flux as the independent variable,the fitting results were good,and the R-square reached 0.9856.(3)To study the macroscopic mechanical properties and macroscopic material properties of concrete under the action of electric field,the bond strength of concrete,compressive strength and impermeability of concrete cathode and anode regions were measured under different electric parameters,and it was found that with the increase of electric time and current density,the impermeability of concrete cathode region decreased and the impermeability of anode region increased;the bond performance at the interface of steel and concrete became worse;the cathode and anode regions the compressive strength of concrete decreases,but within the permissible range of the code.The effect of degradation can be kept at a low level with appropriate electrical parameters.Figure [84] table [20] reference [94]... |
PDF Full Text Request