Reinforced Concrete Foundation Remote Monitoring

BDV34-977-09Date on cover: January 2019This project investigated whether it is possible to remotely monitor reinforced concrete foundations for the purpose of corrosion detection. The focus of the project was on identifying and investigating a technology that could provide both the delivery of energy to, and communications with, embedded sensors without the additional installation of wiring. A radio frequency propagation technique that uses the reinforcing steel as a single wire transmission line was identified as the most appropriate candidate, and experiments were designed to determine its usefulness. Baseline experiments conducted at 2.4 GHz in air were successful and demonstrated that the designed interfacing couplers and impedance matching circuits were adequate. However, when the medium was changed to concrete, the attenuation was too severe to support either energy harvesting or communications. Reducing the operating frequency to 8 kHz and modifying the interface provided only slight improvement. Given the successful results when operated in air, it may be possible to transfer the technology to monitoring existing open-air steel structures such as bridges and towers. In addition, it may be possible to adapt the approach for use in reinforced concrete foundations that include concentric reinforcing steel structures that could be used as a two-wire circuit for both energy harvesting and communications