Identification of corrosion process in reinforced concrete by acoustic emission: Fid-Bau Portal

Identification of corrosion process in reinforced concrete by acoustic emission

Tomoda, Yuichi / Ohtsu, Masayasu

Reinforced Concrete (RC) structures are no longer maintenance-free. Particularly, damage due to salt attack in RC structures is considered to be one of serious problems in concrete structures. A reinforcing steel-bar (rebar) in concrete normally does not corrode because of a passive film on the surface of the steel. When chloride concentration at rebar exceeds the threshold level, the passive film is destroyed. The electrochemical reaction continues with supplying oxygen and water. As a result, corrosion of rebar is nucleated and expansion of corrosion products develops cracks in RC members. To identify the deterioration of RC structures due to salt attack at an early stage, nondestructive evaluation (NDE) of corrosion is a key issue for diagnosis. To this end, NDE methods are recently applied to estimate the corrosion in RC. However, such electrochemical methods as the half-cell potential and the polarization resistant are marginally successful. Recently, it is found that acoustic emission (AE) could evaluate the corrosion process at rust collapse (onset of corrosion) and at nucleation of concrete cracks due to expansion of corrosion products. In the present study, AE parameter analysis is applied to identify the onset of corrosion in rebar and the nucleation of cracking in concrete. It is demonstrated that both the onset of corrosion and the nucleation of cracking are clearly observed as two periods of high AE activity. Results show a great promise for AE technique to monitor salt damage in the concrete structures.