Quantitative detection of local corrosive conditions in reinforced concrete using an embedded, structurally optimized electromagnetic sensor

Purpose This study aims to propose an embedded, structurally optimized electromagnetic sensor for quantitatively detecting local corrosive conditions in reinforced concrete by correlating its magnetic response with the corrosion-induced mass loss of the sensor steel shell. Design/methodology/approach A square hollow steel shell sensor integrating a permanent magnet and Hall elements was designed as an embedded detection component. The sensor forms a stable, short-range and repeatable magnetic response channel, allowing local corrosion severity to be quantified from magnetic-field variations caused by sensor steel shell corrosion. Two shell corrosion models were established to reveal the corrosion-response mechanism, and three sensor-structure models were compared to optimize the shell cavity and sensitive detection region. An equivalent magnetic circuit model was developed to relate magnetic flux density to shell mass loss, and accelerated corrosion tests were conducted for validation. Findings The proposed sensor showed strong correlations between magnetic response and the mass loss ratio of the sensor steel shell. The coefficients of determination were 0.9972 and 0.9932 under uniform and nonuniform corrosion, respectively, supporting quantitative assessment of local corrosion severity under controlled accelerated-corrosion conditions. Research limitations/implications This study was validated through modeling and accelerated corrosion tests. Further long-term field studies under different concrete environments and service conditions are needed to verify the sensor performance in practical reinforced concrete structures. Practical implications The proposed embedded electromagnetic sensor provides a feasible method for local and quantitative detection of corrosive conditions in reinforced concrete. It may support early warning of potential reinforcement-corrosion risks and durability assessment of reinforced concrete structures. Social implications Reliable detection of locally corrosive conditions can help improve the safety, durability and maintenance efficiency of reinforced concrete infrastructure by providing early warning of potential reinforcement-corrosion risks and helping extend service life. Originality/value This work introduces an embedded electromagnetic sensor for quantitative characterization of sensor steel shell corrosion. The sensor steel shell acts as a corrosion-sensitive element whose mass loss reflects local corrosive conditions in reinforced concrete.