New research methods of electro-corrosion processes in concrete structures

The paths of electric currents flowing through sleepers and traditional methods of corrosion under the influence of leakage currents are analysed. Based on the results of this analysis, a new method of studying the processes occurring in concrete under the influence of electrical potentials is proposed for comparative studies of the electro-corrosion behaviour of sleepers and other structures with steel and composite reinforcement. The method involves the application of electric potentials, constant or pulsating unidirectional, to the sleeper models and the study of samples extracted from the models using nanoindentation. By means of nanoindentation it is possible to obtain the values of the micromechanical properties of the cement paste, the modulus of elasticity E and the hardness H, which depend on the degree of its electromigration leaching. It is experimentally proved that due to electromigration leaching, E and H decrease, starting from the face of the model, for which a negative potential is applied. The values of unleached and maximally leached cement paste with W/C = 0.35, which is characteristic of concrete sleepers, are determined. It is found that the nature of these dependencies and, consequently, the intensity of electro-corrosion processes in concrete, depends on the nature of the applied electrical potential (constant or pulsating unidirectional) and the type of reinforcement (steel or composite).