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Title |
Evaluation of Reinforcement Corrosion Levels in Concrete with Various Mix Proportions Based on Ultrasonic Energy Indicators
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Authors |
이주원(Juwon Lee) ; 이유진(Yujin Lee) ; 최하진(Hajin Choi) ; 민지영(Jiyoung Min) |
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DOI |
https://doi.org/10.11112/jksmi.2026.30.5.1 |
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Keywords |
철근 콘크리트; 합성개구집속기법(SAFT); 다중 배열 전단파; 초기 부식 평가 Reinforced concrete; Synthetic aperture focusing technique (SAFT); Multi-array shear wave; Early-stage corrosion assessment |
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Abstract |
Corrosion of reinforcement in aged concrete structures is difficult to identify visually before surface cracking develops. This study proposes an evaluation technique for quantitatively classifying damage resulting from reinforcement corrosion based on synthetic aperture focusing technique (SAFT) cross-sectional images obtained using a multi-array shear wave device. Area scans were performed in dry-coupled contact mode on 54 reinforced concrete specimens representing 17 mix types subjected to long-term outdoor exposure. To ensure the reliability of the non-destructive measurements, the actual corrosion levels were determined through destructive testing. The specimens were classified into three damage grades: Low for undamaged specimens, Medium for corrosion without surface cracking, and High for corrosion with surface cracking. The root mean square error (RMSE) of the depth-normalized intensity distribution was 8.06% for the Low grade, 8.04% for the Medium grade, and 20.96% for the High grade, indicating high sensitivity to surface cracking but limited capability for detecting early-stage corrosion. In contrast, the structural similarity index measure (SSIM) decreased by 6.3% for the Medium grade and 18.8% for the High grade relative to the Low grade, while the energy centroid increased by 2.0% and 4.9%, respectively. Furthermore, a 2D feature space analysis fusing these two indicators confirmed that they form cluster distributions corresponding to each damage grade. Therefore, the proposed technique is expected to serve as a reliable approach for the quantitative assessment of reinforcement corrosion before the onset of visually identifiable surface cracking.
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