Investigation of rebar corrosion in plain and steel fiber reinforced concrete under flexural loading

Abstract

Corrosion of rebars is one of the main causes of poor durability for RC structures as it induces an early deterioration of concrete structures and reduces their service life. Codes state the importance of concrete quality and cover thickness to protect the reinforcement from corrosion. However, as a result of many reasons, cracks can occur unavoidably and chlorides can penetrate even through high-quality concretes and greater concrete cover thicknesses. Addition of steel fibers definitely improves mechanical strength of concrete but knowledge on its contribution on corrosion is limited. This research discusses the relationship between the half-cell potentials and corrosion rates of cracked and uncracked concrete beams with a single deformed bar with two waterto- cement ratios (0.45, 0.65), two different concrete cover thicknesses (25 mm, 45 mm) and with or without fibers. Three point flexural tests were conducted to generate crack widths of 0.4 mm as the critical crack width on the specimens and these cracks were stabilized by a bolt system. The specimens were subjected to wetting-drying cycles by using NaCl solution and in the end of each cycle half-cell potential and corrosion rate measurements were taken and continued for eight months. Results showed that 0.4 mm crack width caused quick ingress of aggressive agents into the cracked specimens and shorter corrosion initiation period and quicker corrosion propagation. Water-to-cement ratio and concrete cover thickness were also found to be other significant parameters that affect corrosion. Fiber presence was investigated deeply but a conclusive comment could not be made, but for higher quality concretes fibers seemed useful. For uncracked specimens, effect of concrete cover thickness was more evident with respect to cracked specimens where water-to-cement ratio was important for both states.