A review on corrosion detection and protection of existing reinforced concrete (RC) structures

Performance deterioration of existing reinforced concrete (RC) structures due to corrosion of inside steel reinforcement has been a worldwide issue for long, in particular for RC structures in aggressive environments. Although extensive research on steel corrosion has been carried out over past decades, it is still a challenging problem in civil engineering. Starting from a brief introduction on corrosion mechanism of steel in concrete, this paper presents a comprehensive review on corrosion detection techniques and protection methods for existing RC structures where corrosion has already occurred. Direct detection methods based on electrochemical and physical principles related to the steel corrosion process, and indirect methods based on measurement of corrosion-induced damages in reinforced concrete are critically reviewed, with the basic working mechanism and state of the art of each method given. According to protecting mechanism, corrosion protection methods are categorized into “prevention solutions” and “therapy solutions”, with the former including high-performance fiber-reinforced cementitious composite (HPFRCC) overlay, anti-corrosion coating and corrosion inhibitor while the latter including cathodic protection (CP) and electrochemical chloride extraction (ECE). Among them, HPFRCC overlay is regarded as effective in corrosion prevention due to its high durability although it is mainly used for strengthening because of its excellent mechanical properties, while carbon fiber reinforced polymer (CFRP) can be acted as both strengthening material and anode in CP and ECE. The dual functions of these materials make them very promising in protecting corrosion-damaged RC structures. The paper aims to not only provide useful information to researchers working on detection and protection of steel corrosion, but also shed lights on the advanced strengthening strategies for corrosion-damaged structures.