A Study on the Wave Dispersion in Concrete Due to Damage; Numerical Observations and Theoretical Predictions

Experimental results have shown that waves propagating in nonhomogeneous and composite materials exhibit dispersive behavior even in cases where they are characterized by isotropic effective properties. Concrete is such a material and at both its fresh and hardened state wave dispersion is observed. The dispersion becomes more pronounced when microdefects like microcracks and air voids appear in the main body of the concrete. The goal of the present work is threefold: first to examine numerically the contribution of various defects to the wave dispersion in concrete, second to show through numerical experiments that circular voids embedded in a concrete matrix is a good approximation for simulating wave dispersion in damaged concrete and third to capture the dispersive behavior of a longitudinal plane wave propagating in damaged concrete with the aid of two theories, namely the multiple wave scattering model of Waterman and Truell and the generalized elastic theory of a strain gradient elastic material. Numerical, experimental and theoretical results are compared and discussed throughout the paper.