Nondestructive Method to Detect Corrosion of Steel Elements in Concrete: Fid-Bau Portal

Nondestructive Method to Detect Corrosion of Steel Elements in Concrete

M. DaSilva / S. Javidi / A. Yakel / A. Azizinamini

This report provides an outline of a novel approach, methodology, and equipment needed to detect corrosion of any steel element that is embedded in the concrete bridges. Further, within this project, a complete non-destructive system is developed that can detect the presence and extent of corrosion in any steel elements in concrete bridges. Possible applications include: a) Detecting corrosion of reinforcing bars in concrete deck b) Detecting corrosion of prestressing strands in prestressed girders c) Detecting corrosion of prestressing strands in post tensioned concrete bridges and placed in steel or plastic duct d) Evaluating the condition of bridge deck with respect to corrosion The method is specifically developed for post tension concrete bridges, which is the most challenging condition. Application to other conditions will be an easy transition. The method is referred to as non-destructive since it can detect the presence of corrosion without drilling holes or similar approaches for visual inspection. It is in that sense a blind technique, where condition of the embedded steel is assessed similar to taking x-ray or having an MRI on human body. The foundation of the method is based on a simple concept in physics called The Hall effect. The principle is based on creating a magnetic field around the embedded steel element and studying the resulting magnetic field changes using Hall-effect sensors. The idea is that the magnetic field will change in the presence of corrosion. The development of the concept and non-destructive equipment started with a very primitive device and evolved into a system that can be applied to field conditions. A series of laboratory tests were carried out to develop the methodology and the non-destructive device itself. An extensive amount of numerical analyses were carried out to comprehend the meaning of different signal types that were being obtained from the non-destructive device. Finally, limited field studies were carried out to develop a comprehensive methodology adoptable to field conditions. Corrosion of steel reinforcing bars or strands in concrete bridges present a great challenge for inspection and safety evaluation of these structures. The non-destructive equipment and associated methodology developed in this project allows effective and rapid assessment of bridges for the presence of corrosion.