Ultrasonic tests in the evaluation of the stress level in concrete prisms based on the acoustoelasticity

The ultrasonic pulse velocity method is a nondestructive test commonly used for the determination of the elastic properties of materials and verification of non-homogeneities and damages in structural elements. Another application for the ultrasound is the measurement of the stress state in a material. However, the use of ultrasonic waves for the latter purpose has been poorly studied, mainly regarding application in concrete structures. This paper addresses the use of ultrasound for the evaluation of stresses in concrete structures. Uniaxial compression tests were performed on concrete prisms. During the tests, longitudinal and shear ultrasonic waves were emitted to specimens subjected to different compressive stress levels. The results showed the increase of compression stress leads to higher velocities of ultrasonic waves, which proved the acoustoelastic effect. Such behavior was not observed in longitudinal waves emitted perpendicularly to the direction of the stress application. The largest increase in velocity was observed for longitudinal waves propagating in the same direction of the load application (variations on the order of 1%). Acoustoelastic coefficients were determined for each tested prism, according to the change in the velocities of the ultrasonic waves. The present study contributed to the knowledge on the acoustoelastic behavior of the concrete elements and shows the potential of ultrasonic tests to evaluate the stress state in concrete structures. (C) 2017 Elsevier Ltd. All rights reserved. (AU)