2010 Volume 59 Issue 4 Pages 183-188
The two well known methods for measuring the covers of the reinforcing bars in concrete are the electromagnetic induction method and the electromagnetic wave radar method. The former has the problem of decreased measurement accuracy when the bars are deep or when the bars are heavily corroded. The latter utilizes the B-mode image of the received wave signals. Therefore, the accuracy is not high, although it can be used to measure the cover of bars at a wide range of depths. This paper proposes a new method to measure the cover using the signal propagation model of the electromagnetic wave (EMW), which one of the authors developed previously. The method utilizes A-mode signals to accurately measure the propagation time of the EMW under the complicated environment of receiving many unwanted reflected waves from the other reinforcing bars and then applies Snell’s law to the propagation times to measure the cover. A field test demonstrated that highly accurate measurement is achievable using the proposed method, with the average and maximum error rates as low as 1.9% and 3.5%, respectively.
