Experimental analysis of the correlation between bending strength and SMFL of corroded RC beams

Measuring the bearing capacity is critical for assessing the safety and durability of civil engineering structures. However, the existing non-destructive testing (NDT) techniques cannot estimate the bending strengths of corroded reinforced concrete (RC) beams easily. Thus, the correlation between self-magnetic flux leakage (SMFL) and bending strength of corroded RC beams was investigated in this study to estimate the bending strength. First, a theoretical model was established based on the physical properties of ferromagnetic materials and engineering mechanics. Preliminary research found that the peak-to-valley differences of the SMFL curves of corroded RC beams were strongly correlated with the bending strength. The normalized peak-to-valley differences NBP(x) and normalized bending strength NBS were defined based on this correlation. NBS of corroded RC beams can be evaluated using NBP(x) of SMFL curves. The data from 18 corroded RC beams and the theoretical model were analyzed and employed to verify the correlation between NBP(x) and NBS. The experimental results were consistent with those predicted by theory and showed the semi-quantitative correlation that NBP(x) was related to NBS exponentially (without stirrups) or approximate linearly (with stirrups). Therefore, the bending strength can be estimated semi-quantitatively via the SMFL curves. In this work, a novel correlation between the SMFL and bending strengths of corroded RC beams was established. The SMFL technique can be regarded as a new effective NDT technique for estimating the bending strength of corroded RC beams.