Development of the corrosion-filled paste and corrosion layer at the steel/concrete interface

• Total corrosion-induced crack area increases linearly with corrosion growth.
• Inner cracks cause a sudden increase in corrosion-filled paste (CP) thickness.
• CP thickness initially increases with the development of corrosion layer (CL).
• CP thickness remains unchanged after CL thickness is larger than 180 μm.

This study investigated four types of concrete that had deteriorated by wet–dry cycles coupled with DC power. The thicknesses of the corrosion-filled paste, TCP, and the corrosion layer, TCL, were measured by SEM in backscattered electron mode. A sudden increase of TCP near the inner crack is observed. As TCL grows, TCP develops gradually until TCL reaches a certain value, afterwards TCP remains nearly unchanged. Considering the inner cracks, which reflects the actual situation, kT and TCPmax in the TCP − TCL model grow with increase of recycled aggregates replacement; while the rule is contrary if excluding the inner cracks.