RADAR INSPECTION OF STRUCTURES

During the past few years, surface scanning impulse radar systems have begun to achieve popularity in the UK for a wide range of civil engineering applications. Investigation of the structural details and of the integrity of both concrete and masonry structures has proved to be a particularly fruitful field of application. The fundamental background is outlined briefly and a wide range of reported usage on a worldwide basis is reviewed. Features of currently available equipment are described, with particular emphasis on the factors that influence reproducibility and interpretation of results, including the use of colour displays and computerized signal enhancement procedures. Advantages and limitations of the technique are examined critically, and areas for future study and development are identified. Some fundamental factors which are particularly relevant to the inspection of concrete structures are examined in detail and are illustrated by the results of laboratory studies. These include the influence of moisture and its effect on the location and sizing of reinforcing bars, delaminations and voids, and the assessment of element thicknesses. It is concluded that the technique offers considerable potential as a non-damaging investigative tool where only one surface is accessible, but it is subject to a number of practical limitations at present. Some suggestions are made as to how these may be overcome.