Evaluation on Effect of Internally Crack and Defect on Crack Propagation due to Corrosion of Reinforcing Bar Embedded in Mortar using X-ray Tomography

Corrosion of reinforcing steel bars poses a serious challenge in concrete structure maintenance. This corrosion causes not only surface cracks but also internal cracks in the concrete owing to the expanding pressure caused by corrosion. Several studies have focused on the relationship between surface cracks and the mass loss of steel bars, seeking to establish practical inspection methods that can predict the mass loss of steel on the basis of surface cracks. However, the effects of internal cracks, or the fragile portions previously formed in concrete, on the surface cracks and corrosion of steel bars have not been sufficiently investigated. This study evaluated these effects by using X-ray technology. Mortar specimens with both axial and transverse steel bars were prepared, and one of the steel bars were corroded using the impressed current technique. X-ray imaging was used to visualize the internal cracks in the specimens. Consequently, it was revealed that the propagation of surface cracks may be diminished because of internal cracks and fragile portions in the concrete.