Protection Against Electrical Corrosion of Railway Constructions by Grounded Screens from Silicate Compositions

Abstract

Research is devoted to the development of an electrically conductive silicate composition and the improvement of screen protection against electrical corrosion of reinforced concrete and concrete structures, in particular high passenger platforms, overpasses, and bridges operated on sections of railways electrified with direct current. Theoretical and experimental investigations of electrical corrosion of concrete supports of passenger platforms have been carried out. It was found that under the influence of the pulsating unidirectional electric potential, which occurs during the passing of the trains, a stray current, carrying Ca2+ and OH- anions, flows through the concrete supports of the passenger platforms. On the supports, zones of neutralization and concrete leaching are created, where destruction takes place. These processes can be prevented by eliminating the electric current through the concrete of the support or by reducing its density. The dependence of efficiency of grounded screen-coatings Ep of electric conductor compositions based on mineral compositions on the frequency of contact of the steel grounding electrode with the screen X has been investigated. It was found that with increasing of X efficiency of protection increases. For the grounded screen-coat composition based on Portland cement optimum protective effect of 0.92 is achieved at a fraction of the contact area of the electrode with the screen X = 6.9 %. For the grounded screen-coating with a composition based on sodium silicate the optimum protective effect of 0.59 is achieved in case X = 5.9 %. According to the results of investigations ordering measures of repair and protection of concrete supports of passenger platforms is in dependence on the degree of their deterioration. The structural and technological solution for the protection of concrete supports of passenger platforms by grounded screen-coating from electric conductive compositions is developed, which provides an optimum part of the contact area of steel electrode of grounding with screen-coating of 6-7 %.