Accelerated AC impedance testing for prequalification of marine construction materials

The AC impedance technique was used in this study for the evaluation and prequalification of concrete materials prepared with chemical corrosion inhibitors and pozolanic admixtures of GGBS slag. In the Arabian Gulf region, marine seawater corrosion has caused severe concrete deterioration over the past decades. Major industrial buildings such as power generation plants, desalination plants and off-shore structures, and oil or water piers deteriorate severely in the marine industrial seawater environment due to the deleterious effect of chloride ions and CO, gas. It has only recently been appreciated in this difficult region that concrete with supplementary cementing materials exhibit a very significant reduction in permeability and corrosion effects. Assessment of the corrosion condition of steel rebar in concrete for newly proposed projects can be carried out with different techniques. Most of the testing methods suggested are based on the ASTM standards G-109, ASTM C876, and ASTM C1202. The duration for ASTM testing requires at least a minimum of 1 to 3 years of exposure in simulated weathering conditions before any reliable conclusion can be drawn. In the present study, accelerated AC impedance measurements were carried out over a wide frequency range on reinforced Lollipop specimens of GGBS slag with different degrees of compaction of the concrete mix. The AC impedance technique allows detection of the breakdown of passivity and performance of the steel reinforcement in concrete within a much shorter time than with other tests. The correlation between the AC impedance technique and traditional ASTM standards indicated concurring results of the benefit of the application of multicomponent corrosion protection systems under the prevailing conditions of the marine environment in the Arabian Gulf region.