Cathodic protection of reinforced concrete structures in objects of water-supply and sewage systems

Abstract

Concrete is a widely used material in the construction industry. It is obtained by mixing cement as a binding agent and inert or only partly reactive aggregates as fillers. In order to increase its bearing power concerning extension it is fitted with steel elements as armature. It is usually believed that the concrete provides the steel armature, embedded into it, with the protection against the corrosion regarding the high alkalinity that takes place during the hydration reactions and which retains as the solution in the concrete pores. Regardless of the aforesaid the corrosion of the steel armature in the concrete occurs due to the effect of a number of factors including the contamination of the concrete by chlorine ions, carbonation of the concrete and the like. As a consequence of this corrosion the formation of corrosion products that are in terms of volume much bigger than the in-built metal takes place and that results in the additional stress to extension of the material of the concrete. As the concrete is weak to strains by extension these forces lead to the occurrence of cracks, detachment and braking away of the concrete cover layer from the armature. Further corrosion that can endanger the lifetime of the entire structure develops on the in-built armature. This problem occurs with the reinforced concrete constructions such as bridges, dams and suchlike. Therefore it is by all means necessary to protect additionally the steel armature in the concrete against the effects of the corrosion. .

Beton je veoma raširen kao materijal u građevinarstvu. Dobija se mešanjem cementa kao vezivnog sredstva i inertnih ili samo delimično reaktivnih agregata kao punila. Za povećanje njegove nosivosti s obzirom na istezanje u njega se ugrađuju čelični elementi kao armatura. Normalno se smatra da beton pruža zaštitu čeličnoj armaturi koja je u njega ulivena od korozije s obzirom na jaku alkalnost do koje dolazi u toku hidratacionih reakcija i koja se zadržava kao rastvor u porama betona. Bez obzira na izloženo do korozije čelične armature u betonu dolazi usled delovanja više faktora, uključujući kontaminaciju betona hlornim ionom, karbonacijom betona i sl. Usled ove korozije dolazi do stvaranja korozionih produkata koji su zapreminski mnogo veći od ugrađenog metala što dovodi do dodatnog naprezanja na razvlačenje materijala betona. Kako je beton slab na opterećenja, razvlačenjem ove sile dovode do pojave naprslina, odvajanja i otpadanja betonskog prekrivnog sloja sa armature. Na izloženoj armaturi dolazi do dalje korozije, koja može ugroziti vek trajanja cele strukture. Ovaj problem se javlja kod armirano-betonskih konstrukcija kao što su mostovi, brane i sl. .