USE OF ELECTROCHEMICAL (CATHODIC) PROTECTION OF REINFORCED CONCRETE STRUCTURES IN BUILDINGS AND CONSTRUCTIONS

Abstract

The article summarises the first domestic experience in designing and implementing electrochemical (cathodic) protection against corrosion of reinforcement in reinforced concrete structures exposed to aggressive environments. It considers examples of such protection for structures of many buildings and constructions with different operation conditions.

The study examines the first instance in the domestic practice of testing electrochemical (cathodic) protection against reinforcement corrosion in concrete columns. The reinforcement of reinforced concrete structures in the lower part of the columns underwent corrosion due to frequent spills of aggressive solutions from the floor. There were drainage trays on the floor located near the columns that need protection, parallel to their transverse rows, to collect and remove these spills. These trays served to house linear anodes of cathodic protection. Anodes made of individual metal rods were placed on the bottom of the trays and covered with an electrically conductive solution.

After determining the anodic areas on the reinforced concrete floor beams, they developed a project for cathodic reinforcement protection. Coating the reinforced concrete beams with polymer paints during the repair works did not lead to a decline in corrosion processes on their fittings in some areas. Given the initial conditions, the decision was to adopt an electrochemical protection scheme with selective distribution of metal foil anodes on conductive paint on the surface of the beams.

The conducted examination of the concentrated sulfuric acid shop showed that reinforcement corrosion in reinforced concrete structures occurs under the action of solutions of acid spills and their steam. Corrosion intensifies in some parts of structures. In the columns, such places appear in the lower sections, where the structures are in contact with the environment (spills). In the proposed cathodic protection system, a regulated current source allowed for obtaining a constant current of up to 10 A. A 1–2 cm thick layer of electrically conductive solution was applied to the lower part of the columns under restoration. Lead anodes were embedded into the conductive solution.

A working project was developed for cathodic protection of the reinforced concrete deck of the bridge in its reconstruction on the highway. The bridge suffered significant damage primarily due to corrosion in the reinforced concrete deck. In the existing conditions, active methods of protecting reinforced concrete structures have proven more profitable. The structural solution of the bridge facilitates the use of electrochemical protection. The concrete protective layer of the roadway includes reinforcing metal grids that serve as anodes. All reinforcement of reinforced concrete structures is a part of a single electrical circuit.

The research goal is to improve the technological properties of the reinforcement electrochemical protection installation in reinforced concrete slabs. The installation solves the task of reducing labour costs and material consumption of protection systems. A solution to this task is freeing the seam between the plates from filling materials and laying a flexible electrical insulating tape in the formed gap, which has a longitudinal perforated surface in the form of a reach-through in the middle. When laying, the tape receives a U-shaped cross-section, creating a trough in the gap between the plates that has a perforated bottom. A wire anode fits into the created trough.

The proposed device is easy to implement and replace elements during operation. The galvanic anode, which simultaneously serves as a reinforcing element of the stretched zone in reinforced concrete beams, is characterised by its versatility. The reinforcing element is made in the shape of a tape, while the metal has a higher electrochemical potential than the reinforcing metal. This metal tape is placed on the conductive solution and connected to the reinforcing frame of the beam.

Further improvement of the cathodic protection systems of the reinforced concrete structures needs to draw on the accumulated practical experience of its application.