Ultrasonic fatigue testing of concrete.

Cyclic compression fatigue properties of concrete are studied with the ultrasonic fatigue testing method with cycling frequency 19 kHz and are compared to servo-hydraulic tests performed at 60 Hz. Ultrasonic testing was found applicable for rapid generation of very high cycle fatigue (VHCF) data of concrete. Fatigue cracks can be initiated, however specimens do not rupture, since cyclic stresses decrease with increase of compliance in displacement controlled ultrasonic tests. Observation of resonance frequency, analysis of higher order harmonics of vibration, and computed tomography of specimens are successful methods to analyse fatigue damage. Calorimetric evaluations can be used to calculate the cyclic irreversible strain, which is about 1% of the elastic strain in the ultrasonic VHCF test.