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Cathodic protection (CP) is being increasingly used on reinforced concrete structures to protect steel reinforcing bars from corrosion in aggressive conditions. Due to the complexity of environmental conditions, the design specifications in national and international standards are still open to discussion to achieve both sufficient and efficient protection for reinforced concrete structures in engineering practices. This paper reports an experimental research to investigate the influence of chloride content on concrete resistivity, rebar corrosion rate and the performance of CP operation using different current densities. It aims to understand the correlation between the chloride content and concrete resistivity together with the CP current requirement, and to investigate the precision of the CP design criteria in standards.

Concrete exposed to cyclic wetting and drying in salty water conditions is thought to be subjected to an accelerated ingress of chloride from the outside environment, and prone to a worsening deterioration process inside. Additionally, there is an osmotic effect on salty water flow in porous concrete. However, so far, a fully profound understanding of the coupled cyclic wetting-drying and osmosis effects on the chloride movement in concrete is still limited. This paper reports on a comprehensive study on the topic. A series of experimental tests was conducted initially for the vapour-water sorption isotherm (VWSI) of normal concrete of different porosity and chloride content. Thereafter, a novel mathematical model was proposed and validated to characterise the effect of chloride salt on the vapour absorption and water retention behaviour of concrete. Finally, the proposed characteristic model was implemented in a numerical model to simulate chloride ingress in concrete in tidal zones. The vapour-water sorption isotherm model successfully provides an effective tool to quantify the coupled influence of cyclic wetting-drying and osmosis on chloride transportation in concrete.

In this paper, the reliability of two nondestructive corrosion detection methods, Half-Cell Potential (HCP) and Electrical Resistivity (ER), was evaluated, considering the Weight Loss (WL) as the reference method. The specimens prepared for this work were placed in Al-Nasiriya Power Station where subjected to three different exposure conditions. They were high relative humidity, high temperature T and laboratory setting R. The concrete mixes included four chloride contents, 0 %, 1.5 %, 3 % and 4 % by weight of cement to generate multiple corrosion degrees. The results showed that exposure to high temperatures has slightly increased the corrosion activity of the T specimens. While the exposure to high relative humidity has clearly increased the corrosion probability of the RH specimens, comparing with the reference R specimens. However, for such environmental conditions, it was found that the reliabilities of the HCP and the ER techniques still questionable and need further investigation.