Crack shape and rust distribution in corrosion-induced cracking concrete

► The total circumferential crack width is linearly proportional to the radius. ► Rust does not penetrate into the cracks before concrete surface cracking. ► Rust lines the edges of the crack after concrete surface cracking. ► A schematic diagram is proposed to describe crack propagation and rust development. This study investigated a reinforced concrete specimen that had deteriorated in an artificial environment for 2years. The crack width and the rust distribution were observed by digital microscopy. The variation of the total circumferential crack width along the radial direction is presented using a linear function. Observation reveals that rust does not penetrate into the corrosion-induced cracks before concrete surface cracking. After concrete surface cracking, rust fills the cracks, lining the edges of the cracks due to the circulation of the outer solution. A schematic diagram is proposed to describe crack propagation and rust development.