ASSESSMENTO ON THE DAMAGE AND STRESS STATE OF CONCRETE ELEMENTS USING ULTRASONIC MEASUREMENTS

Abstract

Concrete structures are constantly deteriorating naturally. In this sense, the use of Non-Destructive Testing (NDT) is an interesting strategy for the monitoring and evaluation of the state of these structures without harming their appearance or performance. Ultrasound is one of the most commonly used NDTs and structural evaluation through this method is advantageous due to its low cost, simplicity of execution and because it does not cause any kind of damage to the structure. The velocity of propagation of the ultrasonic wave varies according to several parameters such as heterogeneities and damages in the material beyond the stress state of the element under analysis, gives origin to the so-called acustoelastic effect. There are few studies focusing on the measurement of stresses with the use of ultrasound. Moreover, in the majority of the investigations involving the acustoelastic effect, the degradation of the material generated by the stress state is not taken into account. Thus, the general objective of this research is to study the simultaneous effect of the stress and damaging states generated by the uniaxial compression test on the velocity of propagation of ultrasonic waves in concrete elements. Thus, a large experimental program will be developed in which concrete elements with different compositions and geometries will be tested under compression and continuously monitored by the ultrasonic test during loading and unloading in order to study the variations in ultrasonic pulse propagation velocity caused by the stress state and damage of the material. As expected result of this research is the better understanding of the influence of the acustoelastic effect together with the damaging of the concrete in the velocity of propagation of ultrasonic waves, as well as to standardize test procedures for the separation of the two effects. (AU)