EFFECT OF TEST ACCURACY AND AXIAL STRAIN STATE ON SOUND SPEED IN CONCRETE

Abstract

When we must assess the characteristics of concretes inreal structures, it is necessary to know that, contrary tolaboratories, concrete is under an existing state of stress,also with significant dimensions. In this work, we havestudied the effect of the variation of the axial load as wellas the effect of the accuracy of tests on the ultrasonicvelocity. In homogeneous materials, when they were sub-mitted to axial load, the volume decrease thus means thematerials are more compact and the velocity may increasetoo. Contrary to what we have seen in concrete, the veloc-ity of ultrasonic wave decrease when the load rises, thisphenomenon is more complicated as a result of interactionbetween cement and aggregate which is more complex. Theinterface between these components remains the key of thiseffect. It is known that when the concrete is subjected tohigh axial loads a large crack spread appears in the inter-face, for stress rate about 60% of failure the ultrasonicvelocity decrease around 10%, this reduction was morepronounced at 90% of the strength, up to 50%. The errorscommitted on the position of the transducers shown thattheir effects become significant beyond a particular limit,allowing us to conclude that non-destructive method canbe used without a high accuracy, and also to check thequality of the concrete in situ without considering the axialstresses, also to follow the evolution of damage caused bythe spread of crack.