ABSTRACT
Radar method has a potential of being a powerful and effective tool of nondestructive testing (NDT) of concrete structures. Yet, not all of the available features of the method have been fully explored and current applications to civil engineering problems are limited to simplified systems. The advancement of the method can be achieved through the understanding of electromagnetic properties of concrete and the identification of optimum radar measurement parameters. For identifying optimal solution parameters for a given problem, radar measurements in parallel with accurate theoretical modeling of wave propagation and scattering are needed as well as implementation of signal processing schemes for imaging.
This paper presents a part of current research conducted at the Massachusetts Institute of Technology (MIT) as an interdisciplinary effort. The research work aims at the development of an effective methodology using radar as a tool for NDT of concrete structures and to develop specifications for radar equipment for this purpose.
The paper presents results of parametric studies to investigate the detectability of delaminations inside concrete through computer simulations and remote wideband radar measurements. Emphasis is given to the significance of transmitting waves over a wide frequency bandwidth. Two different frequency ranges have been used for the simulation; 3.4 to 5.8 GHz and 2.2 to 7.0 GHz, which have bandwidths of 2.4 GHz and 4.8 GHz, respectively. Detectability of 3.2 mm (1/8 in.) to 25.4 mm (1 in.) thick delaminations embedded at different depths inside concrete has been studied through simulation. For the comparison with simulation results, radar measurements are made at 3.4 to 5.8 GHz using a wideband inverse synthetic aperture radar on laboratory size concrete specimens with delaminations.
