Corrosion in cracked and uncracked concrete - influence of crack width, concrete quality and crack reopening

Cracks influence the durability of reinforced concrete (RC) structures in aggressive environments by accelerating the ingress of corrosive agents to the embedded steel. This study investigated the influence of crack width (0.7 mm, 0.4 mm and incipient cracks), binder type (100% CEM I (ordinary Portland cement - OPC) and 50/50 OPC/Corex slag blend), water-to-binder (w/b) ratio (0.40 and 0.55) and crack reopening on chloride-induced corrosion in RC specimens with constant cover of 40 mm. Over the study period (31 weeks), corrosion rates varied from passive values of 0.01 μA/cm² to active values of 1.50 μA/cm². Results indicate that corrosion rate is sensitive to crack width, concrete quality (i.e. binder type and w/b ratio) and crack reopening. For a given binder type and w/b ratio, corrosion rate increased with increasing crack width; however, this increase was smaller in Corex slag specimens (increases of 40% or more) than in OPC specimens (increases 210% or more). Corex slag specimens generally had lower corrosion rates compared to OPC specimens. For both OPC and Corex slag specimens, corrosion rate decreased with decreasing w/b ratio. Crack reopening increased the corrosion rate in the cracked specimens. This increase in corrosion rate was higher if the specimen was actively corroding prior to the crack reopening.