Effect of Acoustoelasticity on Ultrasonic Pulses and Damage of Concrete Under Tensile Stresses

Longitudinal and transverse ultrasonic pulse velocities were used to assess acoustoelastic effect and damage in concrete under tensile stresses. In the experimental program, six concrete mixtures (16 specimens) were tested using third-point loading tests. During stress application, longitudinal and transverse ultrasonic pulses were transmitted perpendicularly to the applied stresses; transverse pulses were polarized in the tensile stress field direction and normal to stress field; and Murnaghan acoustoelastic parameters were calculated. After separating the acoustoelastic effect and obtaining net pulse velocities, two scalar damage models were used to evaluate degradation due to loading. One damage model assumed elastic modulus degradation alone, while the second model was based on both shear and elastic moduli. The high magnitudes of the third-order Murnaghan parameters indicate the strong influence of the acoustoelastic effect in ultrasonic testing of concrete. Results also showed that both moduli degrade at the same rate when concrete is loaded under tensile stresses.