Quantitative linear correlation between self-magnetic flux leakage field variation and corrosion unevenness of corroded rebars

•The uneven cross-sectional area loss of corroded rebar can be characterized by SMFL.•Rebars’ corrosion unevenness degree is linearly related to the SMFL variation ratio.•This linear relationship is independent of rebars’ magnetization and corrosion style.•A novel SMFL-based reliability assessment approach to RC structure could be developed. The accurate uneven cross-sectional area probability distribution of corroded rebars is critical to the reliability assessment of the corroded reinforced concrete structure. The cross-sectional area and self-magnetic flux leakage variation data of 22 naturally and 6 applied current corroded rebars were obtained via 3D light measurement and micromagnetic scanning technologies. The experimental correlation of the self-magnetic flux leakage field variation ratio dH(x/z) and the corrosion unevenness degree dSn of the corroded rebar was then analyzed and verified by finite element modeling. The experimental and simulated results indicated that dSn had a quantitative linear correlation with dH(x/z) with a ratio of about 1, which was proved to be functionally equivalent to the well-established rebar cross-sectional area spatial heterogeneity factor R in the structural reliability assessment. This quantitative linear correlation is not affected by the corrosion style, the magnetization differences, and the corrosion degrees of different rebars, based on which the structural reliability assessment could have higher accuracy and better adaptability for the mutative external aggressive environment.