A Confinement-Sensitive Crack-Width Model for Bond Deterioration in Marine-Corroded Reinforced Concrete: Calibration, Thresholds, and Residual-Capacity Screening

Bond degradation at the steel–concrete interface is a primary driver of serviceability loss and capacity reduction in marine-exposed reinforced concrete (RC), and it can become critical even when the reduction in steel area remains comparatively moderate. While accelerated-corrosion pull-out experiments have established strong empirical correlations between bond strength and corrosion-induced cracking, engineering practice still lacks a simple and actionable inspection-to-capacity mapping that converts measurable surface crack width into bond retention and residual-capacity screening. This paper develops a confinement-sensitive, crack-width–based bond deterioration model calibrated from reported pull-out test data for RC cube specimens with deformed bars of 16–25~mm diameter under severe simulated marine corrosion, considering both unconfined and stirrup-confined detailing. We propose (i) an exponential crack-width law for unconfined members, (ii) a piecewise “no-loss” regime followed by exponential decay for confined members, and (iii) practical crack-width thresholds corresponding to target bond-retention levels (90%, 70%, and 50%). A simple residual-capacity screening relationship is then introduced to translate bond retention into residual strength ratio for preliminary assessment and maintenance prioritization. The resulting framework enables transparent, inspection-driven decision support for corroded marine RC elements, and it is readily extensible to field monitoring and reliability-based updating as new data become available.