Acoustic characterization for quality or damage evaluation in concrete structures

Abstract

Concrete structures such as building columns, parking platforms, concrete highways, and bridges are under continuous action of two major types of cyclic stresses. First, thermal stress cycles due to seasonal temperature variations, resulting in cyclic thermal expansion and contraction. Second, mechanical stress cycles due to cyclic load variations; for example, resulting from the passage of a vehicle on a concrete platform. The cyclic stress, after a certain number of cycles, causes damage in concrete by fatigue. In this study, fatigue damage in concrete is evaluated by acoustic techniques, using wave speed and attenuation. Acoustic sensors of 50-kHz center frequency are coupled to the concrete, as transmitter and receiver, to evaluate concrete quality after concrete samples are subjected to thermal stress cycles. Results obtained in the laboratory will be presented, showing a significant weakening of the concrete strength after only a few stress cycles. The cyclic stress causes a significant drop in acoustic wave speed of the concrete, represented by a low value of its Youngs modulus. A quantitative relationship between fatigue damage and acoustic characteristics of concrete can be established, to evaluate the quality of the concrete structures.