Locating rebar in reinforced concrete through susceptibility measurement

Abstract

The location of rebar in reinforced concrete is a major examination item in the field of architecture. As a kind of non-destructive testing method, we measure the magnetic susceptibility on the surface of reinforced concrete structures with susceptibility meter. Base on the measured susceptibility anomaly, we can calculate its first order horizontal and vertical derivative anomalies in the spatial or wavenumber domain to suppress the background effect or lateral interference anomaly. The correlation imaging method is introduced to process the measured susceptibility anomaly and the calculated first order derivative anomaly respectively. For different rebar postures, horizontal or vertical embedded in concrete, different structural index is used in the method. Both the horizontal position and center (top) depth of rebar are indicated by the position of the maximum correlation coefficient in the imaging map. This method is tested with the measured susceptibility of rebar in the laboratory and a wall under construction in Changchun City. The results show that the locating accuracy of the proposed method is better than 10%.