The accuracy of the Born Approximation as a forward model of elastic wave scattering in the context of simulating Impact Echo tests of reinforced of concrete is investigated in this paper. The ability of a forward model to realistically simulate the physics of a system can be important when such a model is used as part of an inverse solution. Synthetic data of scattering by air void defects that are typically present in damaged civil engineering structures is generated by a two-dimensional Finite Difference in Time Domain (FDTD) model for elastic wave propagation in an infinite, homogeneous and isotropic concrete medium. Horizontal elongated cracks and air voids with compact shapes are considered in this study for comparison between the synthetic and the Born approximated data. It is observed that the Born Approximation simulates a compact air void better than a horizontal elongated one. This knowledge provides insight on Born Approximation as part of an inverse solution towards imaging of air voids of various shapes in a damaged civil engineering structure.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.