Detecção da exsudação do concreto autoadensável através do comportamento de ondas ultrassônicas

Abstract

Self-compacting concrete (SCC) represents a breakthrough in concrete technology as it is capable of unite performance, uniformity and requirements that are not found in vibrated concrete. The main characteristic of this concrete is its high workability that was only made possible thanks to the development of superplasticizing additives, however, a major challenge is the proper dosage of this component, because if improperly added, the mixture is susceptible to changes in its properties, including the phenomena of segregation and exudation. Currently, in civil engineering, the applicability of non-destructive tests (NDT) has been a subject of great interest, due to its ability to evaluate the physical and mechanical properties of concrete without causing damage to the analyzed element. Among the NDT methods, ultrasonography stands out, which is possible to evaluate the homogeneity of the concrete through the ultrasonic pulse velocity. However, recent studies show that the waveform can bring potentially more effective parameters in the analysis of damaged or non-homogeneous concrete. At this perspective, an experimental program was carried out aiming to investigate the properties of a self-compacting concrete trace with three different superplasticizer additive dosages, and also to evaluate the ability of parameters derived from the ultrasonic waveform in the investigation of the exudation state of the SCC. The results showed that the pulse velocity, the group velocity and the energy propagated by the material are presented as sensitive parameters to the internal variations of the concrete, demonstrating their ability to detect and evaluate exuded concrete.