Quantitative Assessment of Chloride-Induced Corrosion in Concrete Bridge Decks Using Ground-Penetrating Radar

Accurate assessment of corrosion in concrete bridge decks is essential for ensuring structural safety and guiding long-term maintenance strategies. Ground-penetrating radar (GPR), as a widely adopted nondestructive testing technique, offers significant advantages in detecting chloride-induced rebar corrosion. However, conventional GPR-based assessment methods predominantly rely on qualitative analysis of reflection amplitudes and lack clearly defined corrosion thresholds, thereby limiting their ability to perform quantitative evaluations. To address these limitations, this study proposes an automated quantitative corrosion assessment framework based on GPR data. The method introduces corrosion grading thresholds of [−0.6 dB/cm, −1.5 dB/cm], a Bridge Deck Corrosion Index (BDCI) derived from the amplitude attenuation rate of rebar reflections, and a set of corrosion condition rating criteria that incorporate maintenance recommendations. The assessment process encompasses four key steps. Initially, the raw GPR data underwent preprocessing to optimize and calibrate the data set. Subsequently, rebar was identified from the GPR B-scan to extract the positions of the rebar and the associated reflection amplitude information, which provided essential data for corrosion analysis. Following this, a qualitative analysis of the rebar’s corrosion status was conducted based on the amplitude attenuation rate, leading to the generation of a corrosion map of the bridge deck. Finally, a quantitative corrosion assessment of the bridge deck was performed, utilizing the corrosion threshold and the BDCI calculation method. To demonstrate the applicability and effectiveness of the proposed method, case studies were conducted using GPR data from three in-service bridges. The results confirmed that the method enables accurate and efficient identification of corrosion conditions, providing a reliable basis for targeted maintenance and bridge management decisions.