Development of a laser-driven ultrasonic technology for characterizations of heated and aged concrete samples

We have demonstrated a full noncontact laser technology to measure the velocity of ultrasonic waves and their spectra propagated through concrete samples exposed to specified high-temperature conditions with specified durations as models of concrete structures in a severe accident at the Fukushima Daiichi Nuclear Power Station. The velocities and spectra of the ultrasonic waves were strongly dependent on the exposed temperature, i.e. at a high-temperature condition of 400℃, the velocity was 3700 m/s, and at room temperature, the velocity was 5000 m/s. Experimental results are almost comparable to those obtained by the contact ultrasonic technique. (author)