Date of Award

6-2003

Document Type

Thesis

Degree Name

Master of Science in Material Science Engineering (MSMatSE)

Department

Materials Science

First Advisor

Abdullah M Al Shamsi

Second Advisor

Dr. Ahmed S. Alshamsi

Abstract

The Arabian Gulf is considered to be one of the world's most aggressive environments for reinforced concrete. Traditional methods of corrosion protection may not be enough to provide the required level of corrosion control for the design life of concrete structures in such environments.

Cathodic protection has been found as a viable technique of inhibiting chloride induced corrosion of steel in concrete structures. As an alternative to impressed current cathodic protection ICCP a remarkable developments recently have been made in the application of sacrificial anode cathodic protection as a means of enhancing the performance of patch repair.

The main objective of this thesis is to study the effectiveness of application of sacrificial anode cathodic protection (SACP) in preventing or reducing corrosion of steel reinforcement in the reinforced concrete in aggressive environments.

Various experimental settings are considered to account for the effectiveness of the sacrificial anodes (SA) locally and globally, immersed and atmospherically exposed, in relatively small and large patch repairs and in both old and new construction.

The experiment program was divided into two parts; in-situ and laboratory.

In the in-situ program, three columns with significant corrosion were selected, evaluated, repaired and monitored for about one year. Local and global sacrificial anodes were used. In the laboratory part, six slabs were cast; they were designed to simulate old repaired concrete with relatively small and large area of repairs, and new construction.

The results of in-situ program demonstrated that sacrificial anodes were working. Protection from corrosion in the columns that were treated by means of local SA was apparent relative to the control. The global SA effect was not equally apparent in such a short period. The results of SACP in new constructed slab showed positive effect in preventing steel from corrosion. Even though the average current density recorded in the slabs was appropriate for CP, the mean depolarsation potentials considerably short of the required level. It should be stated, however, that the intention was not to install sacrificial CP system but to study the performance of the sacrificial anodes in conditions where corrosion of steel reinforcement may be occurring nearby. This reflects the fact that electrochemical equilibration under polarizing conditions requires a considerable period of time to be established, particularly in the case of passive steel

The use of SACP in patch repairs has been proved to give cathodic protection to concrete. An electrochemical cell was formed in which SA was anode and surrounding steel was cathode as was seen from the potential results. This was clearer in the 20-year-old column than in newly cast laboratory slabs. Throughout the tests to date, the anodes have been found to be an effective method for controlling the problems associated with incipient anode generation and the premature failure of areas surrounding repairs in concrete, which are suffering from chloride, related corrosion.

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