Simulation tank to aid interpretation of radar results on concrete

Abstract

Subsurface scanning impulse radar has grown in popularity in recent years, especially for the location of reinforcing bars and voids within concrete. The interpretation of results is often subjective and based on previous experience. However, there is a lack of detailed published data from systematic studies to assess objectively the capabilities of radar. The propagation and reflection of radar signals are governed by the dielectric constantsand conductivities of the materials involved. A simulation tank has been developed which utilizes an oil-water emulsion which may be modified to match both the dielectric and conductivity properties of a range of concretes. This enables a wide selection of features to be modelled in the laboratory, either singly or in combination, to provide characteristic responses. Initial attention has been concentrated on the presence of reinforcing bars and air voids, with results compared with those from laboratory and on-site concrete specimens. The development and capabilities of the approach are described, and illustrated by some typical results. These are found to resemble closely those obtained on concrete, and there is considerable scope for usage of this facility to aid the understanding and interpretation of results from concrete elements in the field.