Quantitative Evaluation of Corrosion Degrees of Steel Bars Based on Self-Magnetic Flux Leakage

Ding Yang,Haibo Di,Jianting Zhou,Feixiong Yang,Siyu Zhao,Junli Qiu

doi:10.3390/met9090952

Abstract

Corrosion is among the most critical factors leading to the failure of reinforced concrete (RC) structures. Less work has been devoted to nondestructive tests (NDT) to detect the corrosion degree of steel bars. The corrosion degree was investigated in this paper using an NDT method based on self-magnetic flux leakage (SMFL). First, a mathematic model based on magnetic dipole model was settled to simulate the SMFL of a V-shaped defect caused by corrosion. A custom 3-axis scanning device equipped with a magnetometer was used to scan the SMFL field of the 40 corroded steel bars. Experimental data obtained by scanning the 40 steel bars showed that the BZ curve of SMFL was consistent with the theoretical model analysis. Inspired by the qualitative analysis of the results, an index “K” based on a large number of experimental data was established to characterize the corrosion degree of steel bars. The experimental index “K” was linearly related to the corrosion degree α of steel bars. This paper provides a feasible approach for the corrosion degree NDT, which is not affected by the magnetization history and the initial magnetization state of steel bars.

Highlights

The reinforced concrete (RC) structure is the most common structure in civil engineering, because steel bar and concrete can work together to fully exert their mechanical properties, forming good force-bearing members [1]
This study aims to contribute to an nondestructive testing (NDT) method to detect the corrosion degree in RC structures
Regions were in the middle of the steel bars and their widths were about 5 cm

Summary

Introduction

The reinforced concrete (RC) structure is the most common structure in civil engineering, because steel bar and concrete can work together to fully exert their mechanical properties, forming good force-bearing members [1]. Corrosion is a critical determinant of stress concentration as a consequence of the reduction of the cross-sectional region of a steel bar [2,3]. The volume expansion of the corrosion product will crack the weak part of the concrete, further weakening the bearing capacity of the RC structures [4]. Steel corrosion is a continuing concern within civil engineering and the issue of nondestructive testing (NDT) has received considerable critical attention. One of the main obstacles in detecting corrosion by a typical NDT method, visual testing (VT), is that the steel bars are usually inside the RC structures. Except for VT, studies over the past three decades have provided many practical

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Conclusion