Abstract
Reinforced concrete structures in marine and saline environments can be very durable and may not necessarily suffer significant chloride-induced corrosion of steel reinforcement even when well beyond their design lives. Several condition surveys of reinforced concrete marine structures and coastal bridges up to 100+ years of age have identified chloride levels at reinforcement depth of up to 0.6% by weight concrete (~4% by weight cement) but with no significant reinforcement corrosion propagation occurring (or duly diagnosed as occurring). The reasons for this are contemplated via deliberations on corrosion mechanistic considerations including exploration as to why “active corrosion/pit propagation” does not necessarily progress despite what should be sufficient chloride at the reinforcement surface to result in propagation. It is surmised that several mechanisms may explain this effect including cement chloride binding and adsorption, the presence of a sound portlandite rich layer around reinforcement and the “active corrosion model” and “metastable pitting and pit growth mechanistic considerations”. An understanding of these mechanisms and models results in long-life durable structures in chloride environments with minimal maintenance expenditure (including not having to waste monies on electrochemical treatment technologies) as well as improved assurance of chloride durability in the design of new structures.
