Assessment of corrosion prevention methods for steel reinforcement embedded in concrete exposed to a natural marine environment

Corrosion of the steel reinforcement is a serious problem that lessens the durability of concrete structures. Numerous research studies focus on the improvement of the concrete matrix and the protection of the reinforcing bars against corrosion. Fly ash and silica fume have been used for the former and inhibitors for the latter; nevertheless, corrosion is a very complex multifactorial phenomenon because the deterioration mechanisms involved in a simulated-marine environment differ from those involved in a natural environment. Despite these facts most corrosion studies have been carried out in a laboratory under accelerated conditions and using non-destructive testing. In this research, the effects of the water-cementitious materials ratio, fly ash, and a calcium nitrite-based corrosion inhibitor, as well as their interactions, were investigated as methods to prevent the corrosion of reinforcing steel in concrete containing silica fume. Specimens were exposed to a natural marine environment for seven years and the corrosive activity was monitored annually using electrochemical techniques. At the end of the exposure period, the specimens were visually inspected, autopsied and the chloride concentrations at the steel–concrete interfaces were estimated. The steel bars were extracted and their mass losses and pitting depths evaluated and finally tested for tension. The results show the underlying performance of fly ash, alone or in combination with CNI, improves the concrete matrix and is an effective corrosion prevention method.