Title: Application of Acoustic Emission Technique to Detection of Rebar Corrosion in Concrete
Author(s): Z. Li, F. Li, A. Zdunek, E. Landis, and S. P. Shah
Publication: Materials Journal
Appears on pages(s): 68-81
Keywords: acoustic emission; concrete; infrastructure; microcrack; rebar corrosion;
Although corrosion of reinforcing steel (rebar) in concrete is held responsible for most deterioration of structural concrete, current inspection methods lack accuracy and can provide information only after significant corrosion has occurred. Along the line in searching for an effective method for early detection of rebar corrosion in concrete, the capability of acoustic emission (AE) technique in detecting a weak stress wave make it a strong candidate. The primary advantage AE offers over other conventional nondestructive evaluation (NDE) techniques is that it can directly detect the process of a flaw growth. When corrosion products are formed on a corroding rebar, they swell and apply pressure to the surrounding concrete. Microcracks will be formed and stress waves will be generated during the expansion process when the pressure is high enough to break the interface layer. The growth of the microcracks is directly related to the amount of corrosion product of a corroding rebar. Thus, by detecting the AE event rate and their amplitude, the degree of the corrosion can be interpreted. This paper explores the feasibility of using AE technique in rebar corrosion detection. It examines the correlation between the characteristics of the acoustic emission event and the behaviour of the rebar corrosion in HCl solution first. Then it investigate the possibility of the corrosion detection of rebar inside of concrete through an accelerated corrosion experimental method. The theoretical prediction and experiment results has shown that AE technique do have capability to detect rebar corrosion in an early corrosion stage. It is thus expected that the information obtained in this investigation can be used for a field application to characterize the change of a corroded rebar and to help make decisions on maintenance and repair for buildings and infrastructures. The American Concrete Institute also publishes ACI Materials Journal. This section presents brief synopses of papers, committee documents, standardizations, and Committee Actions appearing in the current issue. Xerographic copies of these items are available at $7.00 ($5.00 to ACI members). Payment must accompany order. Items related to standards are available free to ACI members for a limited time. See the specific synopsis.