Experimental study on acoustic emission sensing and vibration monitoring of corroding reinforced concrete beams

Reinforcement corrosion is a major issue in reinforced concrete structures with severe societal and economic consequences if not detected and treated in time. This paper presents an elaborate experimental study to effectively monitor chloride-induced corrosion damage in reinforced concrete beams. A combined method of acoustic emission sensing and vibration-based monitoring is developed to detect, characterise and localise damage. Additionally, crack measurements on the concrete surface are performed as a reference technique. Four beams are corroded with an accelerated corrosion set-up while two additional beams are used as reference specimens. Whereas these monitoring techniques have already been applied individually to assess corrosion in reinforced concrete beams, they are here combined, in order to verify their complementarity. This results in an elaborate and innovative data-set which allows us to draw new conclusions on the way the techniques provide information on the evolution of corrosion damage in time and space. It was found that acoustic emission sensing can accurately detect and localise damage before cracking of the concrete, especially after dedicated noise filtering through clustering of the AE signals. Vibration-based monitoring is less sensitive to early damage, yet natural frequencies contain absolute information about the stiffness decrease due to corrosion damage, and strain mode shapes can localise damage on a larger scale. In addition, results from both techniques are in line with the crack measurements. As a result, the combination of these various monitoring methods offers valuable and complementary insights about the corrosion process.