Concrete NDT & Civil Engineering

Non Destructive Testing (NDT) professionals routinely use GPR for a number of applications. Prior to the evolution of high frequency GPR transducers of 1 GHz and above the primary tool for imaging structural embedment’s in concrete was x-ray methods. GPR is replacing the x-ray method in many instances as the preferred approach for a number of reasons. The x-ray method is expensive, time consuming, poses major health risks during operation and suffers limitations on what surfaces can be imaged. For example slabs on grade or other surfaces where both sides cannot be accessed may not be scanned with x-ray. GPR on the other hand requires minimal training, poses no health risks from emissions, and can be used on any surface. Also, results such as with MALÅ’s CX series are obtained in real time in the field.

GPR as an imaging tool allows the operator to gather the following information:

• Rebar and tension cable location and depth
• Slab thickness on grade and suspended
• Location of non-metallic and metallic conduits and other embedded non-structural features such as fiber networks, in-floor heating elements, and plumbing
• Detection of voids and variations in the concrete matrix

Condition assessment is a growing field with GPR. Bridge decks, parking decks, and other structures may be scanned to non-destructively evaluate the amount of deterioration of these structures. Areas of degraded or compromised concrete from corroded rebar and delamination are detectable with GPR as areas of low propagation velocity due to the higher dielectric properties from infiltrated water and chlorides.