Abstract
Repairing reinforced concrete structures experiencing corrosion of the reinforcing bars is a problem all too common in today's climate. When corrosion is the result of chloride ion ingress the use of such patch repairs is likely to create more problems than it solves. In recent years there has been a considerable interest in the development of additives and admixtures which reduce or eliminate the ingress of chloride ions into reinforced concrete. One method of increasing the tolerance of reinforced concrete structures to the presence of chloride ions is the application of corrosion inhibitors. Corrosion inhibitors offer a potentially useful means of suppressing chloride-induced corrosion that does not involve removing the concrete. This thesis presents the results of tests on two commercial corrosion inhibitors (one organic and one inorganic) used as an admixed material to the fresh concrete mix and one commercial corrosion inhibitor used as a surface applied material to mature concrete that have been subjected to accelerated chloride-induced corrosion. Specimens of high, good and poor quality concrete made from 100%0pc, 30%GGBS and 25%PFA cement replacement blends have been manufactured in order to assess the influence of the corrosion inhibitors on the fresh and hardened properties of concrete. The corrosion behaviour of steel bars embedded in equivalent concrete mixes were also examined and the ability of both admixed and surface applied inhibitors to retard and suppress corrosion rates was investigated as a function of time, depth cover and concrete quality. It is concluded that both admixed corrosion inhibitors did not have a major effect on the fresh and hardened properties of the various concrete mixes used in this study. It was also concluded that both admixed corrosion inhibitors were successful in delaying the time to corrosion initiation in all OPC and blended cement concrete mixes to various degrees. Over the time scale of this study it was concluded that the surface applied corrosion inhibitor was able to reduce corrosion rates at the reinforcement throughout the cover depths examined. It was also concluded that the penetrating inhibitors have shown higher and faster corrosion reduction rates in poor quality concrete.