Microwave Thermoreflectometry for Corrosion Detection in Concrete

This SBIR project will explore innovative application of the PI's proprietary microwave imaging technology to time-resolved thermoreflectometry for non-destructive detection of rebar corrosion in concrete. This is based on the principle that a corrosion layer surronding the rebar serves as a thermal insulator and, as a result, corroded rebars cools more slowly than uncorroded ones upon heating. Therefore, the corrosion can be detected by measuring the difference in rate of cooling. Previous studies have shown advantages of using microwave reflectance to measure the cooling rate, over the conventional infrared thermography. However, poor signal-to-noise ratio due to interference from heat induction and reflection from concrete surface presents a major obstacle to this promising technology. With their significant knowledge and experience in microwave imaging of concrete, the proposal team will overcome the technical obstacle with innovative bi-focusing and other approaches. In Phase I, they will integrate their unique handheld, real-time microwave array camera with a rebar heating inductor to assemble a proof-of-concept system together with signal processing software, and perform experimental study on concrete specimens with corroded and uncorroded rebars. This project will demonstrate the feasibility of the time-resolved microwave thermoreflectometry technology for corrosion detection and establish key technical parameters and an optimum system configuration.