Steel fibre and rebar corrosion in concrete under marine curing
Concern for durability of reinforced concrete structures has, in recent years, coincided with an increasing interest in the use of steel fibre reinforcement. In this investigation the corrosion behaviour of conventional and steel fibre reinforcement in concrete under long term marine curing have been studied. The corrosion behaviour of reinforcement has been assessed visually, and by using electrochemical techniques. Three types of steel fibre were investigated namely low carbon steel, stainless steel melt extract, and galvanised steel. Previous studies have shown that steel fibres exhibit good corrosion resistance in concrete exposed to marine curing. It has been suggested that this is due to the discrete nature of the individual steel fibres which prevents the development of electrochemical cells with large cathode/anode area ratios. In order to determine, therefore, whether a 'size-effect' phenomenon influences steel fibre corrosion rates, concrete specimens were cast with different lengths and diameters of steel wire and subsequently exposed to marine curing. Parallel concrete specimens containing samples of conventional reinforcing bar were also manufactured. Cement replacement materials such as pulverised fuel ash, ground granulated blast furnace slag and microsilica are widely used in order to enhance specific properties of fresh or hardened concrete. In this investigation durability characteristics of concrete containing cement replacement materials were studied. These characteristics, including alkalinity of pore fluid and diffusion rates of chloride ions are of importance in relation to the passivation or corrosion of steel reinforcement.