Size effect of reinforcement on corrosion initiation

The excellent corrosion resistance of discrete steel fibres in concrete may be due to the small size of fibres since macrocell corrosion with large cathode, small anode effects cannot occur for discrete steel fibres as it would for continuous steel rebar. The paper addresses this hypothesis by presenting the results of experiments into the corrosion behavior in concrete of various lengths (20mm to 160mm) and diameters (0.27mm to 1.90mm) of low carbon steel wires and 12mm diameter, 300mm long conventional deformed reinforcing bar. Concrete prisms containing electrodes of different dimensions of steel wire were exposed to wet-dry cycles of sea water spray for 600 days. Corrosion potentials, E-c,E- and polarisation resistance, R-p, of the wires were monitored during the exposure period. The results show that corrosion potentials and polarisation resistance of low carbon steel wires (fibres) are not influenced by the diameter or length of steel wires (fibres). Corrosion resistance of low carbon steel fibres (wires) is superior to that of conventional rebar. Corrosion of both conventional reinforcement and steel fibres (wires) is anodically controlled.