Corrosion of steel reinforcements in concrete structures present one of the most important durability problems facing bridges and related infrastructures. Monitoring this corrosion is difficult since the embedded steel is not visible to the naked eye. Detection techniques, such as acoustic, ultrasonic and radar, have proved to be limited in this capacity. There is a need for direct measurement of corrosion using non-destructive sensors that allow multiple readouts over the long term.
Researchers at The University of Texas have developed hermetically sealed, passive (battery-less) wireless sensors that operate using magnetic coupling between an external reader coil and an embedded resonant sensor. The sensors are introduced into the concrete structures at the time of manufacture. This enables non-destructive long-term monitoring of civil infrastructure. The sensor with a transduction layer supports non-contact interaction with the resonant sensors’ circuitry and provides the most direct method to monitor corrosion. The sensor further includes a diffusion layer placed over the sacrificial transducer. This enables an even dispersion of a chemical species over the sacrificial transducer and mitigates localized corrosion, making it less susceptible to false positives.
Results from exposure tests demonstrate that the passive sensors can be interrogated multiple times in a wireless manner through concrete over the testing duration (1 year). Close proximity to reinforcement does not interfere with the signal. The sensor readings are binary (one resonant frequency indicates that corrosion is present and two resonant frequencies indicate that corrosion is not likely) and easy to interpret. The cost of the materials used to fabricate each resonant sensor was under $2.00. For additional information please see the peer reviewed publication found here.
- Battery-free and wireless
- Cost effective (~$2.00/sensor)
- High long-term durability
- Improved accuracy and reliability over similar state-of-the-art technologies