Influence of in-Service Cracks on Chloride Penetration Resistance of Concrete Samples

Chloride-induced corrosion of steel rebars embedded in concrete is one of the major concerns affecting the durability of reinforced concrete structures. The major degradation mechanism in civil engineering concrete structures is corrosion of reinforcement due to chloride penetration. Corrosion reduces serviceability and safety due to cracking and spalling of concrete and loss of steel cross section. It is widely recognised that in-service cracks in concrete affects the chloride diffusivity and accelerates the chloride-induced rein-forcement corrosion. However, most of the previous studies on the chloride-induced corrosion have focused on the uncracked concrete samples. This study considers the impact of structural cracks caused by service loading on the depth of chloride penetration into concrete. Concrete prisms with four different crack widths were utilized, and the chloride penetration depth and concentration profiles were determined using an accelerated environment test program. The impact of replacing Ordinary Portland Cement by pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS) on the chlo-ride penetration in cracked concrete was also examined. The results show a considerable influence of crack width on the depth of chloride penetration. Furthermore, the penetration of chloride were found to concentrate at crack locations, and the chloride penetration depths at other uncracked locations were found to be less than the chloride penetration depth in the un-cracked concrete samples. The results also demonstrate that the PFA and GGBS re-duce considerably the chloride penetration depth; the percentage reduction in value in un-cracked samples relative to reference mix were 35% and 38% re-spectively. This reduction is due to the refinement of the concrete pore struc-ture and an increased chloride binding capacity.